JP2008227077A - Laser light mask structure, laser processing method, TFT element, and laser processing apparatus - Google Patents

Abstract

Provided are a laser beam mask structure, a laser processing method, a TFT element, and a laser processing apparatus in which a high-performance semiconductor device is realized by making the crystal orientation uniform.
A linear pattern extending in a first direction is formed on a projection mask. A plurality of linear pattern rows 41 are constituted by the linear patterns 40 arranged in the first to k-th band regions 46 (1) to (k) while being shifted by a certain pitch in the second direction 140. Among the linear patterns 40 formed in the first to k-th strip regions 46 (1) to (k), the plurality of linear pattern rows 41 includes a first strip region 46 (1) and a k-th strip region 46 ( k) includes a first linear pattern row group 41 </ b> A in which the interval is set so that only the linear pattern 40 partially overlaps in the first direction 130. The plurality of linear pattern rows 41 further include a second linear pattern row group 41B disposed between the linear pattern rows 41 forming the first linear pattern row group 41A.
[Selection] Figure 3

Description

  The present invention generally relates to a laser beam mask structure, a laser processing method, a TFT element, and a laser processing apparatus. For example, an amorphous material used as a semiconductor material in a semiconductor device or the like is crystallized by laser beam irradiation. The present invention relates to a laser beam mask structure, a laser processing method, a TFT element, and a laser processing apparatus that are used in the process.

  In general, as a method for manufacturing a semiconductor device, there is a method using a single crystal silicon (Si) material. In addition to this manufacturing method, there is a manufacturing method using a silicon thin film in which a silicon thin film is formed on a glass substrate. A semiconductor device manufactured by using a silicon thin film formed on a glass substrate is used as a part of an image sensor or an active matrix liquid crystal display device.

  In a liquid crystal display device, semiconductor devices are used as TFTs (Thin Film Transistors) arranged as a regular array on a transparent substrate. Each transistor of the TFT functions as a pixel controller in the liquid crystal display device. The TFT of the liquid crystal display device is formed of an amorphous silicon film.

  However, in recent years, a polycrystalline silicon film having a high electron mobility is being used instead of an amorphous silicon film having a low electron mobility. By using a polycrystalline silicon film, a TFT liquid crystal display device with enhanced switching characteristics and increased display speed is manufactured. As a method of manufacturing a polycrystalline silicon film, for example, there is a method of crystallization by irradiating an excimer laser on an amorphous or microcrystalline silicon film deposited on a substrate (Excimer Laser Crystallization: ELC).

  In the ELC method, a sample is generally irradiated with a linear laser beam having a length of about 200 to 400 mm and a width of about 0.2 to 1.0 mm on a semiconductor film while scanning at a constant speed. is there. At this time, the portion of the semiconductor film irradiated with the laser does not melt over the entire thickness direction, but melts while leaving a part of the semiconductor film region.

  For this reason, crystal nuclei are generated everywhere on the entire surface of the unmelted region / melted region interface. Along with this, crystals grow toward the outermost layer of the semiconductor film, and crystal grains with random orientations are formed, so that the crystal grain size becomes as small as 100 to 200 nm.

  Since there are many unpaired electrons in the crystal grain boundary of the polycrystalline silicon film, it forms a potential barrier and acts as a strong carrier scatterer. Therefore, a TFT formed with a polycrystalline silicon film having a smaller crystal grain boundary, that is, a larger crystal grain size generally has higher mobility.

  However, in the conventional ELC method, as described above, since it is longitudinal crystal growth in which crystallization occurs at random positions at the unmelted region / melted region interface, it is difficult to obtain a polycrystalline silicon film having a large grain size. . For this reason, it is difficult to obtain a TFT with high mobility. In addition, since crystallization is performed randomly, in such a case, non-uniform structure occurs between the TFTs, and non-uniform switching characteristics occur in the TFT array. In addition, when such a problem occurs, in the TFT liquid crystal display device, there arises a problem that pixels having a high display speed and pixels having a low display speed coexist in one display screen.

For the reasons described above, in order to obtain a higher-performance TFT liquid crystal display device, the quality of the polycrystalline silicon film is improved, that is, the crystal grain size is increased, the orientation of the silicon crystal is controlled, etc. Is required. Therefore, many proposals have been made for the purpose of obtaining a polycrystalline silicon film having performance close to that of single crystal silicon. Among them, in particular, a laser crystallization technique classified as a “lateral growth method” has a length in which the orientation is aligned in the crystal growth direction as disclosed in, for example, JP 2000-505241 A (Patent Document 1). It is attracting attention as a technique for obtaining crystals.
Special Table 2000-505241

  FIG. 17 is a cross-sectional view showing a semiconductor device processed using a lateral growth method. FIG. 18 is a top view showing a change in the crystal structure of the semiconductor device in FIG.

  Referring to FIG. 17, in the lateral growth method, a semiconductor is irradiated with a fine-width pulse laser, and the semiconductor film is melted and solidified over the entire thickness direction of the laser irradiation region to perform crystallization. The semiconductor device 501 includes a transparent substrate 502 having optical transparency, a base film 503 and a semiconductor film 504 formed on the transparent substrate 502.

  Hereinafter, the process of the lateral growth method will be described. First, heat is induced to the region C in the semiconductor film 504 in order to form a crystal region along the extending direction of the semiconductor film 504 on the transparent substrate 502 (direction indicated by an arrow 520 in the drawing). The induction of heat is performed by masking a region other than the region C of the semiconductor film 504 and then exposing the semiconductor film 504 to laser. The energy of the laser beam 505 irradiated to the region C is converted into thermal energy. This induces heat to the region C in the semiconductor film 504 and melts the semiconductor film 504 over its thickness.

  Next, the semiconductor film 504 melted in the region C is solidified by cooling. At this time, as shown in FIG. 18A, a crystal grows from the boundaries C1 and C2 between the region C and other regions toward the center of the region C.

  Next, as shown in FIG. 18B, a new region D adjacent to the region C is set so as to include a portion where no crystal is formed in the region C, and the region D is similar to the above procedure. Melt. When the semiconductor film 504 melted in the region D is solidified, a crystal grows in the region D as shown in FIG. By repeating such a procedure and forming a desired crystal stepwise along the extending direction of the semiconductor film 504, the semiconductor crystal having a polycrystalline structure can be expanded as shown in FIG. it can. Thereby, a polycrystalline silicon film having large crystal grains can be formed.

  In such a crystallization method, since the stage speed is low and the crystallization takes time, the above-described Patent Document 1 discloses that the mask slit is divided into several blocks and the crystal is partially stretched without stretching the entire surface of the substrate. There has been proposed a method for arranging stretched crystals. In patent document 1, since it is crystallized by sequential lateral crystallization in which the melted portion is taken over and the crystal grains become large, it has very high mobility. However, the mobility is not determined only by the size of the crystal grains but also greatly depends on the crystal orientation, which causes a problem that non-uniformity occurs.

  Accordingly, an object of the present invention is to solve the above-described problems. A mask structure of a laser beam, a laser processing method, a TFT element, and a laser processing apparatus, which realize a high-performance semiconductor device by making the crystal orientation uniform. Is to provide.

  A mask structure for laser light according to one aspect of the present invention includes an irradiated object including an amorphous semiconductor layer and laser light irradiated toward the irradiated object to crystallize the amorphous semiconductor layer. A partially light-shielding mask. A plurality of linear patterns extending in the first direction and having the same shape are formed on the mask. The mask includes first to kth band-shaped regions arranged in order along the first direction. A plurality of linear pattern rows are constituted by linear patterns arranged from the first belt-like region to the k-th belt-like region while shifting by a constant pitch in the second direction orthogonal to the first direction. In each linear pattern row, a linear pattern formed in the nth band-shaped region and a linear pattern formed in the n + 1th band-shaped region (n is an integer of 1 to k−1) are partially in the first direction. Overlapping. Among the linear patterns formed in the first to k-th band regions, the plurality of linear pattern rows include a linear pattern formed in the first band region and a linear pattern formed in the k-th band region. 1st linear pattern row group in which the interval between linear pattern rows is set so that only partially overlaps in the first direction. The plurality of linear pattern rows further include a second linear pattern row group disposed between the linear pattern rows forming the first linear pattern row group. While the object to be irradiated and the mask relatively move stepwise in a direction corresponding to the first direction, laser light is irradiated toward the object to be irradiated at each stage.

  A mask structure for laser light according to another aspect of the present invention includes an irradiated object including an amorphous semiconductor layer and laser light irradiated toward the irradiated object to crystallize the amorphous semiconductor layer. A partially light-shielding mask. The mask is formed with a plurality of linear patterns extending in a second direction orthogonal to the first direction and having the same shape. The plurality of linear patterns include a first linear pattern group disposed at equal intervals in the first direction and a second linear pattern group disposed between the linear patterns forming the first linear pattern group. Including. While the object to be irradiated and the mask relatively move stepwise in a direction corresponding to the first direction, laser light is irradiated toward the object to be irradiated at each stage.

  According to the laser beam mask structure thus configured, the irradiated object and the mask move relative to each other in a direction corresponding to the first direction, and the laser beam is directed toward the irradiated object in each step. A plurality of linear patterns are formed so that the same portion of the amorphous semiconductor layer is irradiated twice or more when. Thereby, a high-performance semiconductor device can be realized by giving priority to a certain crystal orientation with respect to the crystal growth direction in the laser light irradiation region.

  Preferably, the linear pattern includes end portions at both extending ends thereof. The end has a triangular shape. According to the laser light mask structure thus configured, the crystal growth direction can be aligned between the end of the linear pattern and another position. Thereby, it can suppress that the crystal orientation of a different direction is formed in the takeover position between the edge parts of a linear pattern.

  The laser processing method according to the present invention is a laser processing method in which an amorphous semiconductor layer is crystallized by using the laser light mask structure described above. In the laser processing method, the amorphous region in the m-th region is irradiated by irradiating the m-th region (m is an integer of 1 or more) defined on the surface of the amorphous semiconductor layer through a mask. An amorphous semiconductor on which a linear pattern is projected by relatively moving the irradiated object and the mask in a direction corresponding to the first direction, by melting and solidifying the crystalline semiconductor layer to crystallize the target semiconductor layer By irradiating the (m + 1) th region with laser light through a mask and a moving step for defining the (m + 1) th region partially overlapping the mth region at a position on the surface of the layer, A m + 1 th crystallization step of melting and solidifying the amorphous semiconductor layer to crystallize it. The crystallization process and the transfer process are alternately repeated until the region where the amorphous semiconductor layer is crystallized reaches a predetermined area.

  According to the laser processing method configured as described above, the characteristics of the obtained semiconductor device can be made uniform by alternately performing the crystallization process and the movement process. Further, by increasing the moving speed while ensuring accuracy, the processing speed of crystallization can be improved.

  Preferably, during the crystallization process or immediately before the crystallization process, the surface of the amorphous semiconductor layer is irradiated with a laser beam without passing through the mask, separately from the laser beam irradiated through the mask. According to the laser processing method thus configured, the crystal grains formed in the amorphous semiconductor layer can be enlarged.

  The TFT element according to the present invention is a TFT element manufactured using any of the laser processing methods described above. The crystal orientation in the crystallized region is set so that (100) is the preferred orientation with respect to the current direction of the device. According to the TFT element configured as described above, the carrier mobility can be stabilized, and the threshold voltage (Vth) value and variations in the value can be suppressed to be small. As a result, low voltage and low power consumption can be designed.

  A laser processing apparatus according to the present invention is a laser processing apparatus using the laser light mask structure described above. The laser processing apparatus further includes a laser light source that emits laser light to the object to be irradiated, a control unit that controls emission of the laser light from the laser light source, and relative movement between the object to be irradiated and the mask. The control unit irradiates the m-th region (m is an integer of 1 or more) defined on the surface of the amorphous semiconductor layer with a laser beam through the mask, whereby the amorphous region in the m-th region is irradiated. An amorphous semiconductor layer on which a linear pattern is projected by relatively moving an object to be irradiated and a mask in a direction corresponding to the first direction by melting and solidifying the semiconductor layer to crystallize the semiconductor layer. And moving the laser beam to the (m + 1) th region via a mask and a moving step for defining the (m + 1) th region partially overlapping the mth region at a position on the surface of An m + 1th crystallization step is performed in which the crystalline semiconductor layer is melted and solidified to be crystallized. The crystallization process and the transfer process are alternately repeated until the region where the amorphous semiconductor layer is crystallized reaches a predetermined area.

  According to the laser processing apparatus configured as described above, the control unit synchronizes the emission of the laser beam and the relative movement between the irradiation object and the mask, thereby enabling high-accuracy and reliable crystallization. .

  As described above, according to the present invention, it is possible to provide a laser beam mask structure, a laser processing method, a TFT element, and a laser processing apparatus that realize a high-performance semiconductor device by making the crystal orientation uniform. .

  Embodiments of the present invention will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are denoted by the same reference numerals.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a semiconductor device irradiated with laser light. With reference to FIG. 1, a semiconductor device 21 includes a transparent substrate 22 as a substrate, and a base film 23 and a silicon film 24 sequentially stacked on the transparent substrate 22. The material used for the base film 23 is a dielectric material made of SiO ₂ , SiON, SiN, AlN or the like. In the present embodiment, the film thickness of the base film 23 is 100 nm and the film thickness of the silicon film 24 is 50 nm, but each film thickness is not limited to these values.

  The base film 23 is laminated on the transparent substrate 22 by a method such as vapor deposition, ion plating, or sputtering. The silicon film 24 is laminated on the base film 23 by a method such as plasma enhanced chemical vapor deposition (PECVD), vapor deposition, or sputtering. At this point, the silicon film 24 is in an amorphous state.

  In the present embodiment, the case where the amorphous semiconductor layer is the amorphous silicon film 24 will be described. However, the present invention is not limited to this. For example, the amorphous material layer is made of amorphous germanium or an alloy thereof. May be.

  FIG. 2 is a diagram schematically showing a laser processing apparatus for processing the semiconductor device in FIG. With reference to FIG. 2, the laser processing apparatus 10 includes a projection mask 14 and a laser light source 11. The semiconductor device 21 is mounted on the movable stage 16. The laser light emitted from the laser light source 11 passes through the variable attenuator 12, the reflection mirrors 7 and 8, the variable focus field lens 13, the projection mask 14, the imaging lens 15, and the reflection mirror 9, and the upper surface of the semiconductor device 21. Is irradiated. The laser processing apparatus 10 includes a controller 17 as a control unit. The controller 17 controls the operations of the movable stage 16 and the laser light source 11.

  In this embodiment, the excimer laser emitted from the laser light source 11 is a short pulse laser, and the excimer laser has a wavelength of 308 nm (XeCl) and a pulse width of 30 ns. The laser light emitted from the laser light source 11 is not limited to the excimer laser, and may be another laser.

  FIG. 3 is a plan view showing a projection mask to which the laser beam mask structure according to the first embodiment of the present invention is applied. With reference to FIGS. 2 and 3, the projection mask 14 is disposed on the optical path of the laser light traveling from the laser light source 11 toward the semiconductor device 21. The projection mask 14 partially shields the laser beam irradiated toward the silicon film 24 of the semiconductor device 21.

  The projection mask 14 includes a non-transmissive area 32 and a transmissive area 33. The projection mask 14 has a substantially rectangular shape. The non-transmissive area 32 is disposed in the frame portion of the projection mask 14. The non-transmissive area 32 is an area that shields laser light. A plurality of linear patterns 40 are formed in the transmission area 33. The linear pattern 40 is formed by a hole that penetrates the projection mask 14. The plurality of linear patterns 40 have the same shape. The linear pattern 40 extends along the first direction 130. The linear pattern 40 is a slit having a relatively large length along the first direction 130 and a relatively small length along a second direction 140 orthogonal to the first direction 130. The plurality of linear patterns 40 are arranged at equal pitches in the first direction 130 and the second direction 140, respectively. In the transmission area 33, the laser light is transmitted through the linear pattern 40.

  The projection mask 14 includes a first strip region 46 (1), a second strip region 46 (2),... Nth strip region 46 (n), an n + 1th strip region 46 (n + 1), a kth strip region 46 (k )including. The first to kth band-like regions 46 (1) to (k) are arranged in order in the first direction 130. The first to k-th band regions 46 (1) to (k) have the same width in the first direction 130. Each strip region extends in a strip shape along the second direction 140.

  The linear pattern 40 is formed in each of the first to kth belt-like regions 46 (1) to (k). The linear pattern 40 is arranged from the first band region 46 (1) to the k th band region 46 (k) with a certain pitch shift in the second direction 140. At this time, the linear pattern 40 formed in the n-th band region 46 (n) and the linear pattern 40 formed in the n + 1-th band region 46 (n + 1) partially overlap in the first direction 130. A linear pattern row 41 is constituted by a collection of a plurality of linear patterns 40 arranged from the first strip region 46 (1) to the kth strip region 46 (k). A plurality of linear pattern rows 41 are formed side by side in the second direction 140.

  In each linear pattern row 41, adjacent linear patterns 40 partially overlap in the first direction 130. Each linear pattern row 41 includes a plurality of linear patterns 40 arranged in an oblique direction with respect to the first direction 130. The plurality of linear pattern rows 41 are arranged at equal intervals in the second direction 140.

  The plurality of linear pattern rows 41 includes a first linear pattern row group 41A and a second linear pattern row group 41B. In the first linear pattern row group 41A, among the linear patterns 40 formed in the first to k-th band regions 46 (1) to (k), the linear shape formed in the first band region 46 (1). The interval between the linear pattern rows 41 is set so that only the pattern 40 and the linear pattern 40 formed in the k-th band region 46 (k) partially overlap in the first direction 130. That is, assuming a straight line L extending in the first direction 130 as shown in FIG. 3, the first linear pattern row group 41 </ b> A is formed in the first strip region 46 (1) of a certain linear pattern row 41. The straight line L overlaps the linear pattern 40 and the linear pattern 40 formed in the k-th band region 46 (k) of the linear pattern row 41 adjacent to the linear pattern row 41. At this time, the linear pattern 40 formed in the second strip region 46 (2) to the (k-1) th strip region 46 (k-1) does not overlap the straight line L. The linear pattern rows 41 constituting the first linear pattern row group 41 </ b> A are arranged at an equal pitch in the second direction 140.

  The linear pattern rows 41 constituting the second linear pattern row group 41B are arranged between the linear pattern rows 41 constituting the first linear pattern row group 41A. In the present embodiment, the linear pattern rows 41 constituting the second linear pattern row group 41B are arranged one by one between the linear pattern rows 41 constituting the first linear pattern row group 41A. The linear pattern rows 41 constituting the second linear pattern row group 41B are arranged at an equal pitch in the second direction 140. Not limited to this, two or more linear pattern rows 41 constituting the second linear pattern row group 41B may be arranged between the linear pattern rows 41 constituting the first linear pattern row group 41A. .

  Next, a process for crystallizing the silicon film 24 in FIG. 1 will be described. 4 is a top view showing a first crystallization step of the laser processing method using the projection mask in FIG. FIG. 5 is a top view showing the i-th crystallization step of the laser processing method using the projection mask in FIG.

  With reference to FIGS. 1 and 2, the laser beam 25 emitted from the laser light source 11 is irradiated onto the upper surface of the silicon film 24 of the semiconductor device 21 through the projection mask 14. Referring to FIG. 4, laser light 25 is applied to first region 48 (1) of silicon film 24 as a fine-width pulse laser by masking with projection mask 14. Thereby, the silicon film 24 as the semiconductor film is crystallized by melting and solidifying the entire region in the thickness direction of the first region 48 (1) (region C in FIG. 1) (first crystallization step).

  Referring to FIG. 5, next, under the control of controller 17, movable stage 16 is moved by a predetermined distance to the left in the direction indicated by arrow 120 in FIG. 1 and arrow 101 in FIG. 2. The moving direction of the movable stage 16 corresponds to the left direction along the first direction 130 on the projection mask 14. The movement of the movable stage 16 causes the silicon film 24 and the projection mask 14 to move relative to each other by the distance Y in the first direction 130. At this time, the movable stage 16 is moved so that the second region 48 (2) partially overlapping with the first region 48 (1) is defined at the position of the upper surface of the silicon film 24 onto which the linear pattern 40 is projected. Move (moving process).

  Similarly to the above, the laser beam 25 is irradiated on the upper surface of the silicon film 24, and the silicon film 24 is melted and solidified over the entire thickness direction of the second region 48 (2) to perform crystallization (second crystallization step). ).

  The moving process and the crystallization process of the movable stage 16 are alternately repeated to crystallize a predetermined area of the silicon film 24.

  By repeating the crystallization step and the moving step, the irradiation region 50A is formed by the laser light transmitted through the first linear pattern row group 41A. The irradiation region 50B is formed by the laser light transmitted through the second linear pattern row group 41B. The irradiation region 50B is formed so as to overlap the irradiation region 50A. By forming the second linear pattern row group 41B in addition to the first linear pattern row group 41A, the same portion on the upper surface of the silicon film 24 can be irradiated twice or more times in this embodiment. it can.

  FIG. 6 is a plan view showing a projection mask for comparison. FIG. 7 is a top view showing the first crystallization step of the laser processing method using the projection mask for comparison in FIG. FIG. 8 is a top view showing the i-th crystallization step of the laser processing method using the projection mask for comparison in FIG. 6, 7 and 8 correspond to FIGS. 3, 4 and 5, respectively.

  With reference to FIGS. 6 to 8, in the projection mask 114 for comparison, only the linear pattern 40 constituting the first linear pattern row group 41 </ b> A is formed. When the silicon film 24 is crystallized using the projection mask 114, only the irradiation region 50A is formed by the laser light transmitted through the first linear pattern row group 41A. In this case, the laser beam can be irradiated only once over almost the entire upper surface of the silicon film 24.

  FIG. 9 schematically shows a silicon film crystallized using the projection mask in FIG. FIG. 10 is a diagram schematically showing a silicon film crystallized using a projection mask for comparison in FIG. A line 56 in the figure indicates a protrusion formed by collision of crystals grown from the end by final irradiation.

  With reference to FIG. 9 and FIG. 10, the crystal grows in the second direction 140 in the present embodiment by repeating the crystallization process and the movement process. At this time, at the position where crystallization is started (crystallization start position), the crystal orientation is (111) or (110), but when the crystal is taken over to some extent, the crystal orientation becomes stable (100). .

  When the projection mask 14 in FIG. 3 is used, the transmitted laser beam irradiates the same portion twice or more, so there is no vicinity of the crystallization start position, and the (100) orientation is preferentially oriented with respect to the crystal growth direction. Is done. When the projection mask 14 in FIG. 3 is used, the interval between the protrusions caused by the collision of the crystal is shortened, but a certain orientation is prioritized with respect to the crystal growth direction. Can be realized. When the projection mask 14 in FIG. 3 is used, the entire region on the upper surface of the silicon film 24 is composed of crystals that have inherited a length of several tens of μm or more. On the other hand, when the projection mask 114 for comparison is used, the (111) and (110) orientations are seen up to the middle of the crystal growth direction, and the (100) orientation is not preferentially oriented over the entire surface.

  In the present embodiment, the linear pattern 40 is arranged so that the transmitted laser light is irradiated twice on the same portion, but the (100) orientation is preferentially oriented as the number of times of laser light irradiation increases. Is done.

  FIG. 11 is a plan view showing an end portion of the linear pattern formed on the projection mask in FIG. FIG. 12 is a plan view showing an end portion of a linear pattern for comparison.

  Referring to FIG. 11, the linear pattern 40 includes end portions 62 at both ends extending in the first direction 130. The end 62 is formed in a triangular shape. When the projection mask 14 having such a configuration is used, the portion where the grown crystal of the silicon film 24 collides is linear, so the crystal grain growth direction is constant. On the other hand, when the linear pattern 40 has a rectangular shape as shown in FIG. 12, the growth direction of the crystal grains is different by 90 ° at the position where the end 62 is projected. For this reason, even if crystals are taken over by repetition of the moving process and the crystallization process, crystal grains grown in different directions remain at the positions where the end portions 62 overlap.

  The laser light mask structure according to the first embodiment of the present invention is directed to the semiconductor device 21 as an irradiated object including the silicon film 24 as an amorphous semiconductor layer and the semiconductor device 21 for crystallizing the silicon film 24. And a projection mask 14 as a mask for partially shielding the laser beam irradiated. A plurality of linear patterns 40 extending in the first direction 130 and having the same shape are formed on the projection mask 14. The projection mask 14 includes first to k-th band-shaped regions 46 (1) to (k) arranged in order along the first direction 130. A plurality of linear pattern rows 41 is constituted by the linear patterns 40 arranged from the first strip region 46 (1) to the k th strip region 46 (k) with a certain pitch shift in the second direction 140 orthogonal to the first direction 130. Has been.

  In each linear pattern row 41, the linear pattern 40 formed in the nth strip region 46 (n) and the linear pattern 40 formed in the (n + 1) th strip region 46 (n + 1) (n is 1 to k−). 1), partially overlapping in the first direction 130. The plurality of linear pattern rows 41 are linear patterns formed in the first strip region 46 (1) among the linear patterns 40 formed in the first to kth strip regions 46 (1) to (k). 40 and the first linear pattern in which the interval between the linear pattern rows 41 is set so that only the linear pattern 40 formed in the k-th band region 46 (k) partially overlaps in the first direction 130. A column group 41A is included. The plurality of linear pattern rows 41 further include a second linear pattern row group 41B arranged between the linear pattern rows 41 forming the first linear pattern row group 41A. While the semiconductor device 21 and the projection mask 14 are relatively moved stepwise in a direction corresponding to the first direction 130, laser light is irradiated toward the semiconductor device 21 at each step.

  According to the laser light mask structure and laser processing method of the first embodiment of the present invention configured as described above, a transistor is formed by performing appropriate processing on the crystallized silicon film 24. It can be used as a display element such as a liquid crystal panel. At this time, the crystal orientation in the crystallized region is set so that (100) is the preferred orientation with respect to the current direction of the transistor. In this embodiment mode, the crystal grains formed in the silicon film 24 are remarkably large and the crystal orientation is aligned, so that the mobility of carriers flowing in the channel of the transistor is increased. In addition, a high-performance element having a low threshold voltage (Vth) value and small variations can be obtained.

(Embodiment 2)
FIG. 13 is a plan view showing a projection mask to which the laser beam mask structure according to the second embodiment of the present invention is applied. In the present embodiment, the description of the overlapping structure as compared with the mask structure in the first embodiment will not be repeated.

  Referring to FIG. 13, in the present embodiment, a plurality of linear patterns 70 are formed on projection mask 74. The plurality of linear patterns 70 have the same shape. The linear pattern 70 extends along the second direction 140. The linear pattern 70 is a slit having a relatively small length along the first direction 130 and a relatively large length along the second direction 140. The plurality of linear patterns 70 are arranged at intervals in the first direction 130.

  The plurality of linear patterns 70 include a first linear pattern group 71A and a second linear pattern group 71B. The linear patterns 70 constituting the first linear pattern group 71 </ b> A are arranged at an equal pitch in the first direction 130. The linear patterns 70 constituting the second linear pattern group 71B are arranged between the linear patterns 70 constituting the first linear pattern group 71A.

  FIG. 14 is a top view showing the i-th crystallization step of the laser processing method using the projection mask in FIG. With reference to FIG. 14, in the present embodiment, in the moving step, the silicon film 24 and the projection mask 74 are relatively moved by a distance Y in the first direction 130 by the movement of the movable stage 16. At this time, the movable stage 16 is moved so that the irradiation region of the laser light that passes through the first linear pattern group 71A partially overlaps before and after the moving step (moving step).

  By repeating the crystallization process and the movement process, an irradiation region 76 is formed on the upper surface of the silicon film 24 where the laser beam transmitted through the first linear pattern group 71A and the second linear pattern group 71B irradiates the same portion. Is done. By forming the second linear pattern group 71B in addition to the first linear pattern group 71A, the same portion on the upper surface of the silicon film 24 can be irradiated twice or more.

  In the present embodiment, a crystal grows in the first direction 130 by repeating the crystallization process and the movement process. At this time, by using the projection mask 74, the laser beam irradiates the same portion of the silicon film 24 twice or more, so there is no vicinity of the crystallization start position, and the (100) orientation is preferentially given to the crystal growth direction. Oriented.

  According to the laser beam mask structure and the laser processing method in the second embodiment of the present invention configured as described above, the same effects as those described in the first embodiment can be obtained.

(Embodiment 3)
FIG. 15 is a diagram schematically showing a laser processing apparatus according to Embodiment 3 of the present invention. Referring to FIG. 15, laser processing apparatus 80 crystallizes silicon film 24 of semiconductor device 21. Since semiconductor device 21 has the same structure as semiconductor device 21 in FIG. 1, description thereof will not be repeated. However, the base film 23 is formed of a material that easily absorbs the second laser light described below. Preferably, the base film 23 has a multilayer film structure to facilitate absorption of the second laser light.

  The laser processing device 80 includes a first laser light source 81 and a second laser light source 85. The first laser light 88 emitted from the first laser light source 81 passes through the variable attenuator 12, the reflection mirrors 7 and 8, the variable focus field lens 13, the projection mask 84, the imaging lens 15, and the reflection mirror 9. The top surface of the semiconductor device 21 is irradiated. The laser processing apparatus 80 includes a controller 17 that controls operations of the movable stage 16, the first laser light source 81, and the second laser light source 85. The second laser light 89 emitted from the second laser light source 85 is irradiated on the upper surface of the semiconductor device 21 via the uniform irradiation optical system 82 and the reflection mirror 83.

  In the projection mask 84, a linear pattern 40 having a slit width wider than that of the projection mask 14 in FIG. 3 is formed. In the present embodiment, since the crystal grain length is increased by simultaneously irradiating the second laser beam 89, the linear pattern 40 having a wider slit width is formed.

  The first laser beam 88 has a wavelength in a range where the absorption rate of the silicon film 24 in the solid state is higher than that of the second laser beam 89. More specifically, the first laser beam 88 preferably has an ultraviolet wavelength.

  Examples of the first laser beam 88 having such a wavelength in the ultraviolet region include an excimer laser pulse having a wavelength of 308 nm. The first laser beam 88 preferably has an energy amount for melting the silicon film 24 in a solid state. The amount of energy varies depending on the material type of the silicon film 24, the thickness of the silicon film 24, the area of the crystallization region of the silicon film 24, and the like, and cannot be uniquely determined. Therefore, it is preferable to use the first laser beam 88 having an appropriate amount of energy as appropriate in accordance with the above-described conditions in the silicon film 24. The same applies to the case where another type of semiconductor film is crystallized instead of the silicon film 24. Specifically, it is recommended to use the first laser beam 88 having an energy amount capable of heating the silicon film 24 as a semiconductor film to a temperature equal to or higher than the melting point in the entire film thickness.

  The second laser beam 89 preferably has a wavelength in a range where the absorption rate into the silicon film 24 in the liquid state is higher than that of the first laser beam 88. Specifically, the second laser beam 89 preferably has a wavelength from the visible range to the infrared range. Examples thereof include a YAG laser with a wavelength of 53/4 nm, a YAG laser with a wavelength of 1064 nm, a carbon dioxide gas laser with a wavelength of 10.6 μm, and the like. The second laser beam 89 preferably has an energy amount that does not melt the silicon film 24 in the solid state. The amount of energy varies depending on the type of material of the silicon film 24, the thickness of the silicon film 24, the area of the crystallization region, and the like, and cannot be uniquely determined. For this reason, it is preferable to use the second laser beam 89 having an appropriate energy amount in accordance with the mode of the silicon film 24. Specifically, when the second laser beam 89 is irradiated alone, it is recommended to use the second laser beam 89 having an energy amount that cannot heat the silicon film 24 to a temperature higher than the melting point. . This is the same when another type of semiconductor film is used instead of the silicon film 24.

  In the present embodiment, for example, the first laser beam 88 is incident on the upper surface of the silicon film 24 of the semiconductor device 21 from the vertical direction, and the second laser beam 89 is incident on the upper surface of the silicon film 24 from an oblique direction. Make it incident.

  FIG. 16 is a graph showing an example of output waveforms of the first laser beam and the second laser beam. Referring to FIG. 16, the relationship between the time when first laser light source 81 emits first laser light 88 and the output of first laser light 88 is shown by curve V1, and second laser light source 85 is the second laser. The relationship between the time when the light 89 is emitted and the output of the second laser light 89 is indicated by a curve V2.

  As can be seen by comparing the curves V1 and V2, the second laser beam 89 is emitted from the time t0 to t2, but the first laser beam 88 is transmitted from the time t1 after the time t0 to before the time t2. It is emitted over a period. That is, the emission period of the first laser beam 88 is shorter than the emission period of the second laser beam 89 and is about half or less. On the other hand, the peak value of the output of the first laser beam 88 is larger than the peak value of the output of the second laser beam 89 and is several times as large. The relationship between the irradiation time of the first laser beam 88 and the second laser beam 89 and the output of each laser beam is not limited to the relationship shown in FIG. 16, but is preferably in the same relationship as the characteristics shown in FIG. . The output of the second laser beam 89 may be stopped immediately before time t1.

  As described below, the silicon film 24 is in a molten state from time t1 to time t2 in FIG.

  By irradiating the silicon film 24, which is a precursor semiconductor thin film in a liquid state, with the second laser beam 89 in addition to the first laser beam 88, the temperature of the silicon film 24 that is the precursor semiconductor is lowered. The speed can be reduced and the time until solidification can be extended. For this reason, the lateral growth distance of the semiconductor polycrystal produced | generated when the silicon film 24 used as the precursor semiconductor thin film in a liquid state solidifies can be extended significantly.

  Another example of the relationship between the time when the second laser light source 85 emits the second laser light 89 and the output of the second laser light 89 is indicated by a straight line V3. In this case, since the second laser beam 89 is constantly irradiated, the output of the laser beam can be made lower than that of the curve V2. This makes it possible to reduce the size of the device.

  Subsequently, a process of forming a crystallization region in the silicon film 24 by irradiating the silicon film 24 of the semiconductor device 21 with the first laser beam 88 and the second laser beam 89 by the laser processing apparatus 80 shown in FIG. To do.

  4 and 5, first, in the first crystallization step, the first laser beam 88 emitted from the first laser light source 81 at each timing indicated by the curve V1 in FIG. The first region 48 (1) defined on the upper surface of the silicon film 24 is irradiated through the pattern 40. At the same time, the second region 89 (1) is irradiated with the second laser beam 89 emitted from the second laser light source 85 at the timing indicated by the curve V2 in FIG. By these irradiations, the silicon film 24 in the first region 48 (1) is melted, and the melted silicon film 24 in the first region 48 (1) is solidified and crystallized.

  In the moving step, the silicon film 24 and the projection mask 84 are relatively moved by the distance Y in the first direction 130 by the movement of the movable stage 16.

  Next, in the second crystallization step, the silicon film is irradiated with the first laser light 88 emitted from the first laser light source 81 through each linear pattern 40 of the projection mask 84 at the timing indicated by the curve V1 in FIG. Irradiation is performed in the second region 48 (2) defined on the upper surface of 24. At the same time, the second region 48 (2) is irradiated with the second laser light 89 emitted from the second laser light source 85 at the timing indicated by the curve V2 in FIG. By these irradiations, the silicon film 24 in the second region 48 (2) is melted, and the melted silicon film 24 in the second region 48 (2) is solidified and crystallized.

  Further, the crystallization process and the moving process involving irradiation of the first laser beam 88 and the second laser beam 89 are repeated a plurality of times until the crystallized region of the silicon film 24 reaches a predetermined area. At this time, by using the projection mask 84, the laser beam irradiates the same portion of the silicon film 24 twice or more, so there is no vicinity of the crystallization start position, and the (100) orientation is preferentially given to the crystal growth direction. Oriented.

  According to the laser beam mask structure and laser processing method in Embodiment 3 of the present invention configured as described above, the same effects as those described in Embodiment 1 can be obtained. Further, the crystal grains formed in the silicon film 24 can be enlarged by irradiation with the first laser beam 88 and the second laser beam 89. Thereby, a semiconductor device having a larger channel length can be manufactured. In addition, the crystallization time can be shortened by increasing the crystal grains, and the laser processing apparatus 80 optimal for mass production can be realized.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is sectional drawing which shows the semiconductor device irradiated with a laser beam. It is a figure which represents typically the laser processing apparatus which processes the semiconductor device in FIG. It is a top view which shows the projection mask to which the mask structure of the laser beam in Embodiment 1 of this invention was applied. It is a top view which shows the 1st crystallization process of the laser processing method using the projection mask in FIG. It is a top view which shows the i-th crystallization process of the laser processing method using the projection mask in FIG. It is a top view which shows the projection mask for a comparison. It is a top view which shows the 1st crystallization process of the laser processing method using the projection mask for the comparison in FIG. It is a top view which shows the i-th crystallization process of the laser processing method using the projection mask for the comparison in FIG. It is a figure which represents typically the silicon film crystallized using the projection mask in FIG. FIG. 7 is a diagram schematically showing a silicon film crystallized using a projection mask for comparison in FIG. 6. It is a top view which shows the edge part of the linear pattern formed in the projection mask in FIG. It is a top view which shows the edge part of the linear pattern for a comparison. It is a top view which shows the projection mask to which the mask structure of the laser beam in Embodiment 2 of this invention was applied. It is a top view which shows the i-th crystallization process of the laser processing method using the projection mask in FIG. It is a figure which represents typically the laser processing apparatus in Embodiment 3 of this invention. It is a graph which shows an example of the output waveform of a 1st laser beam and a 2nd laser beam. It is sectional drawing which shows the semiconductor device processed using a lateral growth method. FIG. 18 is a top view showing a change in the crystal structure of the semiconductor device in FIG. 17.

Explanation of symbols

  10, 80 laser processing apparatus, 11 laser light source, 14, 74, 84 projection mask, 17 controller, 21 semiconductor device, 24 silicon film, 40, 70 linear pattern, 41 linear pattern array, 41A first linear pattern array Group, 41B 2nd linear pattern row | line | column group, 46 (1) -46 (k) 1st strip | belt-shaped area | region-k-th strip | belt-shaped area | region, 48 (1) -48 (i) 1st area | region-i-th area | region, 62 edge part , 71A first linear pattern group, 71B second linear pattern group, 81 first laser light source, 85 second laser light source, 88 first laser light, 89 second laser light, 130 first direction, 140 second direction .

Claims (7)

An irradiated object including an amorphous semiconductor layer;
A mask that partially shields laser light irradiated toward the irradiated object in order to crystallize the amorphous semiconductor layer;
The mask is formed with a plurality of linear patterns extending in the first direction and having the same shape,
The mask includes first to kth band-shaped regions arranged in order along the first direction,
A plurality of linear pattern rows are constituted by the linear pattern arranged from the first band-shaped region to the k-th band-shaped region while being shifted by a certain pitch in a second direction orthogonal to the first direction,
In each of the linear pattern rows, the linear pattern formed in the n-th band region and the linear pattern formed in the n + 1-th band region (n is an integer of 1 to k−1), Partially overlaps in one direction,
The plurality of linear pattern rows are formed in the linear pattern formed in the first strip-shaped region and in the k-th strip-shaped region among the linear patterns formed in the first to k-th strip-shaped regions. Including a first linear pattern row group in which an interval between the linear pattern rows is set such that only the linear pattern partially overlaps in the first direction;
The plurality of linear pattern rows further include a second linear pattern row group disposed between the linear pattern rows forming the first linear pattern row group,
A laser beam mask structure in which the irradiation object and the mask are relatively moved stepwise in a direction corresponding to the first direction, and laser light is irradiated toward the irradiation object in each step. An irradiated object including an amorphous semiconductor layer;
A mask that partially shields laser light irradiated toward the irradiated object in order to crystallize the amorphous semiconductor layer;
The mask is formed with a plurality of linear patterns extending in a second direction orthogonal to the first direction and having the same shape,
The plurality of linear patterns include a first linear pattern group arranged at equal intervals in the first direction and a second linear pattern arranged between the linear patterns forming the first linear pattern group. A group,
A laser beam mask structure in which the irradiation object and the mask are relatively moved stepwise in a direction corresponding to the first direction, and laser light is irradiated toward the irradiation object in each step. The linear pattern includes ends at both extending ends thereof,
The laser beam mask structure according to claim 1, wherein the end portion has a triangular shape. A laser processing method for crystallizing the amorphous semiconductor layer with the laser light mask structure according to any one of claims 1 to 3,
By irradiating the mth region (m is an integer of 1 or more) defined on the surface of the amorphous semiconductor layer through the mask, the amorphous light in the mth region is irradiated. An m-th crystallization step of melting, solidifying and crystallizing the semiconductor layer;
The object to be irradiated and the mask are relatively moved in a direction corresponding to the first direction, and the mth region and a part of the surface of the amorphous semiconductor layer on which the linear pattern is projected. A movement step for defining an m + 1th region to be superimposed on
Irradiating laser beam to the (m + 1) th region through the mask to melt and solidify the amorphous semiconductor layer in the (m + 1) th region, and the (m + 1) th crystallization step for crystallization. ,
A laser processing method in which the crystallization step and the moving step are alternately repeated until a region where the amorphous semiconductor layer is crystallized reaches a predetermined area.   Irradiating the surface of the amorphous semiconductor layer without passing through the mask separately from the laser light irradiated through the mask during the crystallization process or immediately before the crystallization process. The laser processing method according to claim 4. A TFT element manufactured using the laser processing method according to claim 4 or 5,
A TFT element in which the crystal orientation in the crystallized region is set so that (100) is a preferred orientation with respect to the current direction of the device. A laser processing apparatus using the laser light mask structure according to any one of claims 1 to 3,
A laser light source for emitting laser light to the object to be irradiated;
A control unit for controlling the emission of laser light from the laser light source and the relative movement of the irradiated object and the mask;
The controller is
By irradiating the mth region (m is an integer of 1 or more) defined on the surface of the amorphous semiconductor layer through the mask, the amorphous light in the mth region is irradiated. An m-th crystallization step of melting, solidifying and crystallizing the semiconductor layer;
The object to be irradiated and the mask are relatively moved in a direction corresponding to the first direction, and the mth region and a part of the surface of the amorphous semiconductor layer on which the linear pattern is projected. A movement step for defining an m + 1th region to be superimposed on
Irradiating the m + 1st region with a laser beam through the mask to melt, solidify and crystallize the amorphous semiconductor layer in the m + 1st region, and execute the m + 1st crystallization step. And
A laser processing apparatus, wherein the crystallization step and the moving step are alternately repeated until a region where the amorphous semiconductor layer is crystallized reaches a predetermined area.

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