KR20040078246A - Silicon crystallization system and silicon crystallization method - Google Patents

Abstract

Laser generating device; A plurality of light systems for controlling the laser beam generated in the laser generating device; A stage capable of mounting an insulating substrate on which an amorphous silicon layer crystallized into a polysilicon layer is deposited by irradiation of a laser beam passing through a light system, wherein any one of the plurality of light systems rotates by rotating the laser beam by 180 °. Photonic silicon crystallization system.

Description

Silicon crystallization system and silicon crystallization method

The present invention relates to a system and method for forming polysilicon, and more particularly, to a system and method for forming a polycrystalline silicon layer of a thin film transistor array panel.

Generally, silicon may be classified into amorphous silicon and crystalline silicon according to the crystal state. Amorphous silicon can be deposited at a low temperature to form a thin film, and is mainly used for switching elements of liquid crystal panels using glass having a low melting point as a substrate.

However, the amorphous silicon thin film has difficulty in large area of the display device due to problems such as low field effect mobility. Therefore, there is a demand for the application of polycrystalline silicon having high field effect mobility (30 cm 2 / VS), high frequency operating characteristics, and low leakage current electrical characteristics.

In particular, the electrical properties of the polycrystalline silicon thin film are greatly influenced by the grain size. That is, as the grain size increases, the field effect mobility also increases.

Therefore, the method of polycrystallization of silicon has become a big issue in consideration of this point, and in recent years, the sequential lateral solidification (SLS) (sequential lateral solidification) which induces lateral growth of silicon crystal by using an energy source as a laser to produce huge polycrystalline silicon Lateral solidification techniques have been proposed.

This SLS technology takes advantage of the fact that silicon grain grows in the direction perpendicular to the interface between the liquid silicon and the solid silicon, and controls the size of the laser energy and the shift of the irradiation range of the laser beam accordingly. The silicon grains are laterally grown by a predetermined length to crystallize the amorphous silicon thin film.

In this case, the laser beam passes through the transmission region of the slit-shaped mask to completely dissolve the amorphous silicon to form a slit-shaped liquid region in the amorphous silicon layer. Subsequently, the liquid crystal silicon is cooled and crystallized. The crystal grows in a direction perpendicular to the interface from the boundary of the solid region where the laser is not irradiated, and the growth of grains stops when they meet at the center of the liquid region. This process proceeds while moving the slit pattern of the mask perpendicular to the growth direction of the grain and the sequential side solid crystals proceed through the entire area, where the grain size grows by the width of the slit pattern. To this end, the slit patterns formed perpendicular to the grain growth direction are arranged to be offset by the width of the slit patterns in two or more regions.In the unit scanning process, the mask is moved while moving in the direction in which the slit patterns are formed in the sequential side solid crystal process. Irradiate the laser.

However, in this conventional technique, the non-uniformity of the laser beam itself is an inevitable problem, thereby leaving a serious mark that causes deterioration of image quality. That is, the microstructure of the crystallized portion is changed according to the energy uniformity in the laser beam, which creates a laser mark. In particular, when the laser beam has a rectangular shape, it is difficult to eliminate unevenness in the laser beam. In addition, the laser mark is more prominent when there is a difference in the laser intensity in the longitudinal direction of the rectangle. In the first scanning and the second scanning, the laser marking is particularly close to the areas where the high laser intensity and the weak portion are adjacent to each other. It stands out.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a silicon crystallization system and method for reducing the appearance of laser marks on the screen.

1 is a view showing a silicon crystallization system according to an embodiment of the present invention,

2 is a view showing a rotating light system of the silicon crystallization system according to an embodiment of the present invention,

FIG. 3 is a schematic diagram schematically illustrating a sequential lateral solid phase crystallization process of crystallizing amorphous silicon into polycrystalline silicon by irradiation with a laser;

4 is a view showing a microstructure of polycrystalline silicon in the process of crystallizing amorphous silicon into polycrystalline silicon through a sequential side solid phase crystallization process,

FIG. 5 is a diagram illustrating a moving position of a mask and a corresponding irradiation area in a sequential side solid phase determination process according to an embodiment of the present invention.

6A is a view showing a laser mark formed in a polycrystalline silicon layer according to an embodiment of the present invention,

6B is a view showing a laser mark formed on a polycrystalline silicon layer according to the conventional art,

7 is a cross-sectional view illustrating a structure of a thin film transistor completed through a sequential solid-state crystallization process according to an embodiment of the present invention.

8A through 8E are cross-sectional views illustrating a method of manufacturing a polysilicon thin film transistor according to an embodiment of the present invention in the order of their processes.

<Description of the symbols for the main parts of the drawings>

210; Liquid phase region 220; Solid zone

300; Mask 310; Slit pattern

In order to achieve the above object, the silicon crystallization system of the present invention comprises a laser generator; A plurality of light systems for controlling the laser beam generated by the laser generating device; And a stage capable of mounting an insulating substrate on which an amorphous silicon layer crystallized into a polysilicon layer is deposited by irradiation of a laser beam passing through the light system, wherein any one of the plurality of light systems rotates the laser beam by 180 °. It is preferable that it is a rotating light system.

Also, in the sequential solid-state crystallization process in which crystallization is performed using a mask having a slit pattern defining a transmission region through which the laser beam is transmitted, the laser beam is moved in the horizontal direction and the laser beam is moved in the vertical direction. In the stepping, the laser beam is scanned and irradiated to crystallize one horizontal line of the amorphous silicon layer with a polysilicon layer, and then stepping, and the rotation when the other horizontal line is crystallized with a polycrystalline silicon layer. Preferably, the light system is located on the optical path of the laser beam.

In addition, the rotating light system includes a first focusing lens for focusing the laser beam emitted through the laser generating device, and a second focusing lens for focusing the laser beam which is dispersed again and rotated 180 ° after focusing. desirable.

In order to achieve the above object, the silicon crystallization system of the present invention comprises the steps of depositing an amorphous silicon layer on an insulating substrate; In the sequential solid-state crystallization process in which crystallization is performed using a mask having a slit pattern defining a transmission region through which the laser beam is transmitted, the movement of the laser beam in the horizontal direction is referred to as scanning and the movement of the laser beam in the vertical direction is referred to as stepping. And when N and M are odd and even, respectively, crystallizing one horizontal line of the amorphous silicon layer into a polysilicon layer by irradiating an N-th order laser beam and irradiating the laser beam; Rotating the laser beam by 180 ° when stepping after the N-th order scanning of the laser beam; And irradiating the 180 ° rotated laser beam with the Mth order to crystallize another horizontal line adjacent to the horizontal line crystallized with the polycrystalline silicon layer by the Nth order scanning to crystallize the polycrystalline silicon layer. Do.

In addition, the sequential solid phase determination process preferably uses the mask having at least two slit regions in which the slit patterns are arranged to be offset from each other.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a portion of a layer, film, region, plate, etc. is said to be "on top" of another part, this includes not only when the other part is "right on" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A silicon crystallization system according to an embodiment of the present invention will be described in detail with reference to the drawings.

1 shows a silicon crystallization system according to an embodiment of the present invention. As shown in FIG. 1, a silicon crystallization system according to an exemplary embodiment of the present invention includes a laser generator 10 and a plurality of laser beams 1 that control the shape and energy of the laser beam 1 generated by the laser generator 10. The light system 20 is included. The insulating substrate 110 includes an amorphous silicon layer 150 on which the laser beam 1 that has passed through the plurality of light systems 20 is irradiated. The insulating substrate 110 is disposed on the stage 30.

An amorphous silicon layer 150 is formed on the insulating substrate 110 mounted on the stage 30. The amorphous silicon layer 150 is irradiated with the laser beam 1 generated by the laser generator 10 to crystallize into a polycrystalline silicon layer.

In order to control the shape of the laser beam, a plurality of light systems 20 are positioned between the path between the laser beam generator and the amorphous silicon layer.

One of the plurality of light systems is the rotating light system 22 which rotates the laser beam by 180 degrees. As shown in FIG. 2, the rotating light system 22 includes a primary focusing lens 53 for focusing the laser beam emitted through the laser generator 10 and a laser beam that is dispersed and rotated 180 ° after focusing. And a second focusing lens 54 for refocusing the light.

The process light system 21, which is the remaining light system except the rotating light system 22, performs a sequential side crystallization process by controlling the shape and energy of the laser beam.

This will be described in detail. In the sequential side crystallization process in which crystallization is performed using a mask having a slit pattern defining a transmission region through which the laser beam is transmitted, movement of the laser beam in the horizontal direction is referred to as scanning and movement of the laser beam in the vertical direction is referred to as stepping. define. In this case, the laser beam is scanned and irradiated to crystallize one horizontal line of the amorphous silicon layer to the polycrystalline silicon layer. In this case, the process light system 21 controls the shape and energy of the laser beam.

After the stepping, the other horizontal line is crystallized into a polycrystalline silicon layer. In this case, the rotating light system 22 is located on the optical path of the laser beam. That is, the rotating light system 22 and the process light system 21 are positioned on the optical path of the laser beam to irradiate the amorphous silicon layer with the laser beam rotated 180 degrees.

This position selection of the light system uses the light system position controller 40.

Silicon crystallization method according to an embodiment of the present invention will be described in detail with reference to the drawings.

First, an amorphous silicon layer 150 is deposited on the insulating substrate 110. The laser beam is irradiated to crystallize the amorphous silicon layer 150 into the polycrystalline silicon layer 150. This silicon crystallization process is described in detail below.

FIG. 3 is a schematic diagram illustrating a sequential side solid phase crystallization process of crystallizing amorphous silicon into polycrystalline silicon by irradiation with a laser; FIG. A diagram showing the microstructure of the mask and the movement of the mask.

As shown in FIG. 3, the sequential side solid phase crystal process is formed on the insulating substrate 110 by irradiating a laser beam using a mask 300 having a transmission region 310 formed of a slit pattern 310. The amorphous silicon layer 150 is locally completely melted to form the liquid region 210 in the amorphous silicon layer 150 corresponding to the transmission region 310. At this time, grains of the polycrystalline silicon grow in the direction perpendicular to the boundary surface (see FIG. 4, A direction) at the boundary surface 230 of the liquid region 210 irradiated with the laser and the solid state region 220 not irradiated with the laser, respectively. do. Growth of the grains stops when they meet at the center 231 of the liquid region 210.

Figure 4 shows the grain structure of the polycrystalline silicon when the slit pattern is formed in a horizontal direction using a mask formed in the horizontal direction, it can be seen that the grain is grown in the vertical direction with respect to the slit pattern.

3 and 4, in order to grow the grain size by the width W of the slit pattern using a mask having a slit pattern extending in the horizontal direction, the slit defining the transmissive region 310 is shown. A mask in which the pattern is staggered by the width of the slit pattern in the direction of grain growth is used. When the laser is irradiated to the amorphous silicon layer using such a mask, the mask is moved in the longitudinal direction (B direction) of the slit pattern, and at this time, the laser is irradiated to the adjacent amorphous silicon layer in the width direction of the slit pattern so that The growth is continuously performed in the width direction (A direction) of the slit pattern, so that the size of grain can be grown by the width of the slit pattern.

In this case, a unit process of irradiating a laser beam once is called a shot. As shown in FIG. 4, all portions of the amorphous silicon layer are uniformly crystallized by moving the mask partly and then proceeding the second shot after the first shot.

In addition, the laser beam and the mask 300 are horizontally moved in the longitudinal direction B of the slit pattern by repeatedly performing such shots. Then, moving the laser beam in the vertical direction at the last point of the scanning in the horizontal direction is called stepping. After this stepping, scanning is resumed in the direction opposite to the B direction.

FIG. 5 is a view illustrating a mask movement process in a sequential side solid phase determination process according to an exemplary embodiment of the present invention.

First, as shown in FIG. 5, the mask 300 for polycrystalline silicon has first and second slit regions G and H made of slit patterns defining the transmission region 310. In this case, the slit patterns 310 formed in the first and second slit regions G and H are all formed to extend in the horizontal direction, and are arranged in the vertical direction at uniformly equal intervals in each region G and H. The slit patterns 310 of the two regions G and H are arranged to be offset by a predetermined interval from each other.

In the sequential solid phase determination process according to the embodiment of the present invention using such a mask, as shown in FIG. 5, when the first shot process is performed, the mask 300 is moved to the mask position of the first shot. Irradiate the laser beam. Subsequently, when the second shot process is performed, the mask 300 is moved to the mask position of the second shot to irradiate a laser. At this time, the mask 300 is moved to overlap the second slit region H of the mask of the first shot and the first slit region G of the mask of the second shot.

This shot is repeated several times, scanning in the right direction, and irradiating a laser beam to crystallize one horizontal line of the amorphous silicon layer to the polycrystalline silicon layer. The laser beam is then stepped downward at the last right point of the first order scanning of the laser beam. In this case, the laser beam is rotated 180 degrees.

As shown in Fig. 2, rotating the laser beam by 180 ° is possible by forming a rotating light system on the optical path of the laser beam.

The 180 ° rotated laser beam is then irradiated from the right to the second scanning. Thus, another horizontal line adjacent to the horizontal line crystallized into the polycrystalline silicon layer by primary scanning is crystallized into the polycrystalline silicon layer.

In this case, nonuniformity of the polycrystalline silicon layer occurs due to energy nonuniformity of the laser beam itself during the first scanning. As shown in Fig. 6A, a dark portion is formed in the lower portion 57b in the rectangle 57, which is a polycrystallized region by primary scanning, and an upper portion 57a in the rectangle 57, which is a polycrystallized region. The bright part is formed in. After the first scanning, the laser beam is rotated 180 ° so that a dark portion is formed in the upper portion 58a of the rectangle 58, which is a polycrystallized region, in the rectangle 58, which is a polycrystallized region. The bright part is formed in the lower part 58b.

Therefore, the brighter and darker portions adjacent to each other can reduce the marked laser marks.

6B shows a laser trace of a conventional polycrystalline silicon layer. As shown in FIG. 6B, the bright and dark portions are adjacent between the first and second scanning, and the bright and dark portions are adjacent between the secondary scanning and the third scanning. It stands out.

Therefore, the silicon crystallization method according to an embodiment of the present invention can reduce the difference in the degree of crystallization between each scanning, reduce the laser mark on the screen to improve the image quality.

Next, a method of manufacturing a thin film transistor using a sequential solid-state crystal process according to an embodiment of the present invention will be described.

FIG. 7 is a cross-sectional view illustrating a structure of a polysilicon thin film transistor according to an embodiment of the present invention, and FIGS. 8A to 8E illustrate a method of manufacturing a polysilicon thin film transistor according to an embodiment of the present invention according to a process sequence thereof. It is sectional drawing. Here, although the thin film transistor has been exemplified as a structure having a pixel electrode, the manufacturing method of the thin film transistor of the present invention is also applied to the manufacturing method of a semiconductor device for designing a driving integrated circuit on the liquid crystal panel.

As shown in FIG. 7, a semiconductor layer made of polycrystalline silicon having source and drain regions 153 and 155 formed on both sides of the channel region 154 and the channel region 154 on the insulating substrate 110, respectively. 150 is formed. Here, the source and drain regions 153 and 155 may be doped with an n-type or p-type impurity and include a silicide layer. A gate insulating layer 140 made of silicon oxide (SiO ₂ ) or silicon nitride (SiNx) covering the semiconductor layer 150 is formed on the insulating substrate 110, and the gate insulating layer 140 is formed on the channel region 154. ), A gate electrode 123 is formed on the upper portion. A first interlayer insulating layer 601 is formed on the gate insulating layer 140 to cover the gate electrode 123, and the gate insulating layer 140 and the first interlayer insulating layer 601 are the source and drain regions of the semiconductor layer 150. It has first and second contact holes 161 and 162 exposing 153 and 155. The upper portion of the first interlayer insulating layer 601 faces the source electrode 173 centering on the source electrode 173 and the gate electrode 123 connected to the source region 153 through the first contact hole 161. The drain electrode 175 is connected to the drain region 155 through the second contact hole 162. The first interlayer insulating film 601 is covered with a second interlayer insulating film 602, and a third contact hole 163 exposing the drain electrode 175 is formed in the second interlayer insulating film 602, and the second interlayer insulating film 602 is formed. A pixel electrode 190 made of indium tin oxide (ITO), indium zinc oxide (IZO), or a conductive material having a reflectance is formed on the upper portion 602, and the drain electrode 175 is formed through the third contact hole 163. It is connected.

In the method of manufacturing a thin film transistor according to the embodiment of the present invention, first, as shown in FIG. 8A, amorphous silicon is deposited and patterned on the upper portion of the substrate 110 by low pressure chemical vapor deposition or plasma chemical vapor deposition or sputtering. A silicon thin film is formed. Subsequently, in the sequential solid-state crystal process using a mask having a slit pattern, the laser beam is rotated 180 ° between the front and rear scanning processes to irradiate the laser to crystallize the amorphous silicon thin film into the polycrystalline silicon layer 150. This reduces the difference in the degree of crystallization of the polysilicon layer due to the nonuniformity of the laser beam itself and reduces the laser marks on the screen.

Subsequently, as shown in FIG. 8B, the polysilicon layer 150 is patterned by a photolithography process using a mask to form the semiconductor layer 150.

Subsequently, as shown in FIG. 8C, a gate insulating layer 140 is formed by depositing silicon oxide (SiN ₂ ) or silicon nitride, and then a gate material including a gate electrode 123 is formed by depositing and patterning a conductive material for gate wiring. Form the wiring. Subsequently, an n-type or p-type impurity is ion-implanted and activated in the semiconductor layer 150 using a gate wiring including the gate electrode 123 or a photosensitive film pattern for the gate wiring as an ion implantation mask, thereby activating the source and drain regions 153. , 155). At this time, between the source and drain regions 153 and 155 is defined as a channel region 154.

Subsequently, as shown in FIG. 8D, the first insulating interlayer 601 covering the gate electrode 123 is formed by stacking silicon nitride or silicon oxide on the gate insulating layer 140, and then the gate insulating layer 140 and the gate insulating layer 140. Patterned together, first and second contact holes 161 and 162 exposing the source and drain regions 153 and 155 of the semiconductor layer 150 are formed.

Subsequently, as shown in FIG. 8E, the metal for data wiring is deposited and patterned on the insulating substrate 110, and the source and drain regions 153 and 155 are formed through the first and second contact holes 161 and 162. A data line including source and drain electrodes 173 and 175 connected to each other is formed.

Subsequently, as shown in FIG. 7, the second insulating interlayer 602 is formed by stacking silicon nitride or an organic insulating material having a low dielectric constant or a low dielectric constant material using chemical vapor deposition, and patterning the drain electrode. Form a contact 163 exposing 175. Subsequently, the pixel electrode 190 is formed by stacking and patterning a transparent conductive material such as ITO or IZO or a conductive material having excellent reflectivity.

The silicon crystallization system and method thereof according to the present invention reduce the difference in the degree of crystallization of the polysilicon layer due to nonuniformity of the laser beam itself by rotating the laser beam by 180 ° between the primary scanning and the secondary scanning. It has the advantage of reducing marks.

Claims (5)

Laser generating device; A plurality of light systems for controlling the laser beam generated by the laser generating device; A stage capable of mounting an insulating substrate on which an amorphous silicon layer is crystallized into a polycrystalline silicon layer by irradiation of a laser beam passing through the optical system; Including, One of the plurality of light systems is a silicon crystallization system of a rotating light system for rotating the laser beam 180 °. In claim 1, In the sequential solid-state crystallization process in which crystallization is performed using a mask having a slit pattern defining a transmission region through which the laser beam is transmitted, the movement of the laser beam in the horizontal direction is referred to as scanning and the movement of the laser beam in the vertical direction is referred to as stepping. when doing, When the laser beam is scanned and irradiated to crystallize one horizontal line of the amorphous silicon layer with a polycrystalline silicon layer, and then stepped, and the other horizontal line is crystallized with a polycrystalline silicon layer, the rotating light system is a laser beam. Silicon crystallization system located on the optical path. In claim 2, The rotating light system includes a first focusing lens for focusing a laser beam emitted through the laser generator, and a second focusing lens for focusing a laser beam that is dispersed again after being focused and rotated by 180 °. . Depositing an amorphous silicon layer on the insulating substrate; In the sequential solid-state crystallization process in which crystallization is performed using a mask having a slit pattern defining a transmission region through which the laser beam is transmitted, the movement of the laser beam in the horizontal direction is referred to as scanning and the movement of the laser beam in the vertical direction is referred to as stepping. And when N and M are odd and even, respectively, crystallizing one horizontal line of the amorphous silicon layer into a polysilicon layer by irradiating an N-th order laser beam and irradiating the laser beam; Rotating the laser beam by 180 ° when stepping after the N-th order scanning of the laser beam; Irradiating the 180 ° rotated laser beam with the Mth order to crystallize another horizontal line adjacent to the horizontal line crystallized by the Nth order scanning to the polycrystalline silicon layer Silicon crystallization method comprising a. In claim 4, And the sequential solid phase crystallization step uses the mask having at least two slit regions in which the slit patterns are arranged to be offset from each other.