JPH06140296A - Pattern forming method - Google Patents

Abstract

(57) [Summary] [Objective] Regarding the pattern formation method, the purpose is to reduce the number of lithography steps and suppress the fluctuation of the side etch amount even if the film thickness of the film to be etched changes. [Structure] 1) When using a resist film as a mask to simultaneously open windows at locations with different thicknesses, the windows with thinner thicknesses are opened, and then this window is covered with resist by heat treatment, followed by etching. To open a window of a thick film thickness, 2) apply a resist having both positive and negative photosensitivity, perform near-ultraviolet light exposure and far-ultraviolet light exposure on a part of the exposed portion, and develop Then, the resist residual film is left in the opening of the deep UV exposure portion, and the film on the residual film is lifted off, 3).
The resist is applied, exposed to near-ultraviolet rays and developed to form a resist pattern, and then exposed to near-ultraviolet rays and far-ultraviolet rays on the entire surface and redeveloped. 4) Using the resist pattern having the residual film as a mask Then, the base film is etched, the residual film is removed, and etching is performed again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method in a manufacturing process of liquid crystal display elements, semiconductor elements and the like.

[0002]

2. Description of the Related Art In the case of forming various patterns on a substrate, wet etching is inexpensive, and
Isotropic dry etching is widely used according to the purpose because it has excellent selectivity with respect to the underlying layer.
Since these etching methods involve side etching, the film thickness of the film to be etched must be constant over the entire surface of the substrate in order to make the opening dimensions uniform after etching. However, depending on the film to be etched, the film thickness may be locally different due to the influence of the step of the underlying layer.

Further, there is a case where etching is performed through two films due to a request for cost reduction due to the simplification of the process. At this time, if the lower etching target film is already patterned once, the etching target film is changed depending on the pattern. It means that the film thickness of is locally changed.

The above-mentioned variation in the film thickness appears as variation in the amount of side etching during etching, and it becomes impossible to open the dimension as designed. For this reason, conventionally, when the windows of the films to be etched having different film thicknesses are simultaneously opened, the side etching progresses in the openings having a small film thickness, and the openings become large.

That is, when the film thickness of the film to be etched differs depending on the location, the pattern formation is divided into two parts for the thick part and the thin part, and each opening size is optimized or the resist is formed. The size of the mask pattern used to expose the wafer was corrected by just canceling the side etch amount. In this case, the amount of dimensional correction must be changed depending on where the film to be etched is thick or thin.

[0006]

If the pattern formation is divided according to the film thickness, the number of steps is increased and the manufacturing cost is increased, and if the dimension correction is performed on the exposure mask, the value is the entire surface of the mask. If it is not constant, there is a drawback that the man-hours of CAD for generating pattern data are increased.

It is an object of the present invention to suppress an increase in the number of steps from the lithography process, that is, from the patterning of a resist film to the etching, and to perform patterning without a large change in the side-etch amount even if the film thickness of the film to be etched changes. .

[0008]

[Means for Solving the Problems] 1)
When etching is performed with the photoresist film as a mask at the same time to open windows at different film thicknesses of the film to be etched, the film is thinned by heat treatment after the windows of the film to be etched are thinned. Pattern formation method in which the window of the thin portion of the film is covered with the resist, and then etching is performed to open the window of the portion where the film to be etched has a large film thickness, or 2) A base polymer capable of alkali development on the substrate is positively applied. A resist having both photosensitivity and negative photosensitivity is applied, near-ultraviolet light exposure for forming a positive pattern and far-ultraviolet light exposure for a portion of the exposed portion are performed, and developed to form an opening portion of the far-ultraviolet exposed portion. A pattern forming method comprising the steps of forming a resist pattern leaving a residual resist film, then depositing a film on the substrate, and lifting off the film on the residual resist film, or 3. A base polymer capable of alkali development is coated on the substrate with a resist having both positive and negative photosensitivity, exposed to near-ultraviolet light to form a positive pattern, and developed to form a resist pattern, and then the resist pattern is formed. A pattern forming method including a process of performing near-ultraviolet light exposure and far-ultraviolet light exposure on the entire surface of the substrate and performing development again, or 4) a base polymer capable of alkali development on the substrate has both positive photosensitivity and negative photosensitivity. A resist pattern is formed by applying a resist and performing near-ultraviolet light exposure to form a positive pattern and far-ultraviolet light exposure to a part of the exposed portion, and developing to form a resist residual film in the opening of the far-ultraviolet exposed portion. Then, the underlying film is etched by using the resist pattern as a mask, the residual resist film is removed, and the underlying film is etched again. It is achieved by that the pattern forming method.

[0009]

According to the first aspect of the present invention, an opening opened with a size corresponding to the film thickness of the positive photoresist film is closed by heat treatment, but an opening opened with a size sufficiently larger than the film thickness is opened. By utilizing the fact that the film is not blocked by the heat treatment, the films to be etched having different film thicknesses can be patterned at the same time, and the side etching at the thin film thickness portion is eliminated.

In inventions 2 to 4, a phenol novolac resin is used as a base polymer, naphthoquinonediazide is contained as a photosensitizer, and a photocrosslinking agent sensitive to far ultraviolet rays is used.
Add 4-4'-diazidodiphenylmethane or 4-4'-diazidodiphenyl sulfide.

FIGS. 2A to 2C are explanatory views of the principle of the invention 2. In FIG. 2 (A), the resist 22 is applied on the substrate 21, and all the openings are exposed and baked by near-ultraviolet exposure, and another opening mask 23 is used to expose far-ultraviolet rays to some of the openings 24. I do. Here, the shaded area indicates the latent image area.

In FIG. 2B, a resist pattern 25 is obtained by developing with an alkali developing solution. At this time, since the resist is cross-linked by the deep ultraviolet exposure, the resist remains in the opening 24.

In FIG. 2 (C), the film thickness of the resist remaining in the opening 24 is adjusted so that the film 26 formed thereon can be lifted off by the near-ultraviolet exposure and far-infrared exposure. To optimize.

Next, a film 26 is formed on the entire surface of the substrate,
The coating 26 is lifted off, including over the openings 24, to obtain the final pattern. 3A and 3B are explanatory diagrams of the principle of the invention 3.

In FIG. 3 (A), the resist 22 is applied on the substrate 21, all openings are exposed and baked by near-ultraviolet exposure, and developed with an alkali developing solution to obtain a resist pattern 25.

After that, the entire surface is exposed to deep ultraviolet rays to form a photocrosslinking portion 27 on the surface layer of the resist film. In FIG. 3B, a resist pattern 28 is obtained by performing sufficient near-ultraviolet exposure and developing with an alkali developing solution.

FIG. 4 illustrates the principle of Invention 4. In the figure, the above resist 22 is applied on the substrate 21, all the openings are exposed and baked by near-ultraviolet light exposure, and some of the openings 24 are exposed by far-ultraviolet light using another exposure mask 23. The resist pattern 25 is obtained by developing with a developing solution.

At this time, the exposure doses of near-ultraviolet rays and far-ultraviolet rays are optimized so that the resist film thickness of the opening 24 becomes a predetermined film thickness. After that, the film to be etched 29 is formed on the base 31 of the opening 30.
Wet or dry etch until appears. At this time, after the etching was interrupted halfway, ashing or reactive ion etching (RIE) using oxygen gas was performed until the resist in the opening 24 was exhausted, and then the etching was restarted and the underlayer 31 appeared. finish.

In the above-mentioned inventions 2 and 4, the action of the photo-crosslinking agent in the resist causes the base polymer to be crosslinked during the exposure to deep ultraviolet rays and insolubilizes it in the developing solution. Leaves a resist film. At this time, the residual film rate of the resist is determined by the concentration of the cross-linking agent, the exposure amount of near-ultraviolet rays, the exposure amount of far-ultraviolet rays, the development time, etc. Therefore, the desired remaining film thickness can be obtained by optimizing these factors. .

Further, in the invention 3, the deep ultraviolet rays do not reach the lower part of the pattern due to the absorption of the polymer in the thick resist pattern, and the deep ultraviolet rays do not reach the lower part of the pattern of the original film thickness (thin film thickness). Since it reaches all the way to the whole membrane,
When the near UV exposure is sufficiently large, the original resist pattern remains after development and the thick resist pattern is removed.

[0021]

1 (A) to 1 (E) are sectional views for explaining an embodiment of the first invention. In this example, a manufacturing process of an inverted staggered thin film transistor (TFT) substrate will be described as an example.

In FIG. 1 (A), after forming an Al / Cr film (film thickness 500 / 1000Å) 2 as a gate electrode on a glass substrate 1, a SiN film (film thickness 4000Å) as a gate insulating film 3, TFT operation Amorphous silicon (a-Si) film (film thickness 150
Å) 4, SiN film as channel protection film (thickness 1000 Å) 5
Is deposited by plasma vapor deposition (CVD) method.

In FIG. 1B, a resist is applied to the entire surface of the substrate, self-aligned with the gate electrode to leave a resist film on the gate electrode, and the SiN film is used as a mask.
To etch.

Then, an n ⁺ type a-Si / Cr film (film thickness 500 / 1000Å) 6 was deposited on the substrate as a contact layer / electrode film by plasma CVD and sputtering, respectively, and ordinary photolithography was performed. Using a-Si film 4 and n ⁺ type a-Si / Cr film 6
Etching is performed to form source and drain electrodes, and device isolation is performed.

The etching of Cr is performed by ceric ammonium nitrate, and the etching of a-Si is performed by reactive ion etching. In Fig. 1 (C), SiN film is used as a protective film.
(Thickness 3000 Å) 7 is deposited by plasma CVD method.

Then, a positive resist film having a thickness of 2.5 μm
8 is applied, and a plurality of narrow windows 9 having a diameter of 2.5 μm are formed on the source electrode, and a tab (TAB: Tape Automated Bonding) terminal is simultaneously formed with a wide window 10 having a size slightly smaller than the terminal width (100 μm).

In FIG. 1D, the SiN film 7 on the source electrode is etched with buffered hydrofluoric acid using the resist film 8 as a mask. Then, the heat treatment (200 ° C, which is a feature of the present invention,
After 5 minutes, the narrow window 9 on the source electrode is covered with resist. The resist of the window opening buried in the figure is shown by reference numeral 11.

On the other hand, although the resist on the tab terminal is rounded, the wide window 10 opened with a size sufficiently wider than the resist film thickness is not filled with the resist. In Fig. 1 (E), etching of the remaining SiN film 3 on the tab terminals is continued to expose the Al / Cr film 2 on the tab terminals, and ITO (indium oxide) for pixel electrodes and tab terminal electrodes is formed on the substrate. Tin) film 12
The TFT substrate is completed by depositing and patterning to form pixel electrodes and tab terminal electrodes.

As described above, the narrow window opened with a dimension corresponding to the film thickness of the positive type photoresist is effectively used to be closed by the heat treatment, and a window having different film thicknesses of the film to be etched is simultaneously opened. I was able to. As a result, the number of steps can be significantly reduced and the manufacturing yield can be improved compared to the conventional method.

Further, as another advantage, in order to simultaneously etch portions having different film thicknesses by the conventional example, the source electrode must be enlarged in consideration of side etching until the tab terminal portion is etched. Although the reduction of the aperture ratio of TFT was unavoidable, the reduction of the aperture ratio could be minimized by the embodiment.

FIG. 5 is a sectional view for explaining an embodiment of Invention 2. After forming a pattern on the resist film 22, an aluminum (Al) film 32 is deposited on the entire surface of the substrate and lift-off is performed. When the openings where the Al film should be left are widely separated from each other with a gap 33, if the gap 33 is too large, the penetration of the wrist-off solvent into the resist at this portion will be slowed down by the usual method, and the resist will be removed. It cannot be completely removed.

On the other hand, in the embodiment, since the side surface of the resist film of the portion 34 is exposed, the solvent penetrates from there and lift-off is easy. In addition, with the formed wiring pattern 35
Since there is no direct contact with the Al wiring 32, mutual insulation reliability is not impaired.

FIG. 6 is a sectional view for explaining an embodiment of Invention 3. When a resist is applied, if there is a foreign substance or a protrusion 36 on the base, the resist is gathered around it due to the surface tension, and a large protrusion of the resist can be formed. Since this ridge is thick, the normal exposure dose is not sufficient for complete development, and remains after development, resulting in pattern defects 37 in the film to be etched. At this time, the defect 37 can be removed by applying the present invention 3.

Next, an embodiment of the invention 4 will be described with reference to FIG. If the resist in the opening 24 has a residual film of about 1000 to 3000 Å, it has a considerable resistance to wet etching and isotropic dry etching.
It can withstand etching of about a layer. Then, even if the resist in this part is removed by ashing or RIE using oxygen gas, the resist in other parts can be left with a sufficient film thickness, so that the film to be etched left in the opening 24 can be removed. Etching can be performed. As described above, in the opening 24, the time for exposing the film to be etched is shorter than that in the opening 30, so that the side etch amount can be prevented from increasing.

[0035]

According to the first aspect of the present invention, it is possible to suppress an increase in the number of steps from the lithography process, that is, from the patterning of the resist film to the etching, and to perform the patterning without the fluctuation of the side etching amount even if the film thickness of the film to be etched changes. I can do it now.

According to the second aspect of the invention, the one-layer resist film can give different etching times to respective portions of the underlying film to be etched, and the side etch amount can be easily controlled. Further, since it is possible to automatically select a location where the resist film thickness has become abnormally large and remove it in the development process, it is possible to suppress the occurrence of pattern defects after the underlying etching. As a result, it was possible to contribute to a reduction in the number of steps for pattern formation and an improvement in processing yield.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating an embodiment of the invention 1.

FIG. 2 is an explanatory view of the principle of the invention 2.

FIG. 3 is an explanatory view of the principle of Invention 3.

FIG. 4 is an explanatory view of the principle of Invention 4.

FIG. 5 is a cross-sectional view illustrating an embodiment of invention 2;

FIG. 6 is a sectional view for explaining an embodiment of the invention 3;

[Explanation of symbols]

1 Glass substrate 2 Al / Cr film as gate electrode 3 SiN film as gate insulating film 4 a-Si film as TFT operating layer 5 SiN film as channel protective film 6 n ⁺ type a-Si / Cr film as contact layer / electrode film 7 SiN film as protective film 8 Positive resist film 9 Narrow window on source electrode 10 Wide window for tab (TAB) terminal 11 Resist for buried window opening 12 ITO film for pixel electrode and tab terminal electrode 21 Substrate 22 Resist Film 23 Mask for far-ultraviolet exposure 24 Area exposed to far-ultraviolet light in opening of resist film 25 Entire resist pattern 26 Film deposited on resist film and lifted off 27 Area photocrosslinked by far-ultraviolet exposure 28 Resist pattern Overall 29 Etched film 30 Opening of resist film 31 Underlayer film of etched film 29 Al film lifted off 33 Al pattern spacing after lifted off 34 Resist pattern with exposed side surface 35 Wiring pattern already formed 36 pattern defects resist underlayer of foreign matter or protrusions 37 to be etched film is left formed

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G03F 7/26 511 7124-2H 7/38 7124-2H 7352-4M H01L 21/30 361 K

Claims (4)

[Claims] 1. When a window is simultaneously formed in a portion having a different film thickness of the film to be etched by etching using a photoresist film as a mask, after the window having a thin film portion in the film to be etched is opened. A pattern forming method, characterized in that a window of a thin film portion is covered with the resist by heat treatment, and then etching is performed to open a window of a thick film portion of the film to be etched. 2. Near-ultraviolet light exposure for forming a positive pattern by applying a resist having both positive and negative photosensitivity to a base polymer capable of alkali development on a substrate, and deep ultraviolet light for a part of the exposed portion. Exposure and development are performed to form a resist pattern in which the resist residual film is left in the opening of the deep UV exposure part, then a film is deposited on the substrate, and the film on the resist residual film is lifted off. A method for forming a pattern, which comprises: 3. A resist pattern having a positive photosensitivity and a negative photosensitivity is applied to a substrate-developable base polymer on a substrate, exposed to near ultraviolet rays to form a positive pattern, and developed to form a resist pattern. Then, a pattern forming method comprising the steps of performing near-ultraviolet light exposure and far-ultraviolet light exposure on the entire surface of the substrate, and then performing development again. 4. Near-ultraviolet light exposure for forming a positive pattern by applying a resist having both positive and negative photosensitivity to a base polymer capable of alkali development on a substrate, and deep ultraviolet light for a part of the exposed portion. Exposure and development are performed to form a resist pattern in which the resist residual film is left in the opening of the far-ultraviolet-exposed portion, then the base film is etched using the resist pattern as a mask, and then the resist residual film is formed. And a step of etching the base film again.