JPS60211839A - Forming method of photoresist pattern - Google Patents

Abstract

PURPOSE:To form a photoresist pattern to self-align without limiting the thickness of a thin film by emitting a long wavelength light having the specific value or higher from a transparent substrate side to photosense a photographic photosensitive material, developing and fixing it, then emitting ultraviolet ray from the side of the photosensitive material. CONSTITUTION:When a long wavelength light 11 having 500nm or longer is emitted from a substrate 9 side, it photosenses a photographic photosensitive material 13 through a thin film layer 11 and a photoresist 12. Since the photoresist 12 does not have a sensitivity for the light 11, it is not photosensed, an opaque unit 10 does not pass the light 11. Accordingly the material 13 is not photosensed. When it is developed and fixed, the portion except the unit 10 is blackened. Then, when the light 15 is emitted from the material 13 side, the blackened portion 13a does not pass the light 15, and the not blackened portion 13b passes the light 15. Therefore, the lower photoresist 12 is selectively photosensed. Then, when the material 13 is separated and the photoresist 12 is developed, a photoresist pattern is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for forming a photoresist pattern in a thin film device. Specifically, the present invention relates to a method of forming a photoresist pattern for the purpose of self-alignment of thin film semiconductor devices.

(Prior art and its problems) When manufacturing semiconductor devices, self-alignment technology is an indispensable technology for improving device performance and yield. The same is true for thin film semiconductor devices, and in recent years, as the development of thin film semiconductor devices such as flat displays and contact image sensors has become more active, recognition of its importance has increased. As a conventional self-alignment method for thin film semiconductor devices, the following methods have been reported for thin film transistors for flat panel displays.

FIG. 1 shows an example of this method. In the figure, l is a glass substrate, 2 is a metal electrode that becomes a gate, 3 is St, , 5
4 is an amorphous silicon film (a-8i:
H), 5 is a positive 7 photoresist (a photoresist that removes the areas exposed to light), 6 is ultraviolet light, 7 is 4
n”-a −8i to obtain ohmic contact between the amorphous silicon film of 8 and the source/drain electrode of A1 of 8:
It is an H' film. The process is as follows.

First, as shown in FIG. 1(a), a semiconductor thin film is formed,
A photoresist is applied, and ultraviolet light 6 is irradiated from the glass substrate 1 side. At this time, since the metal electrode 2 does not transmit the ultraviolet light 6, it serves as a mask and the photoresist 7 above it is not exposed.

Therefore, when developed, the photoresist remains only on the gate electrode as shown in FIG. 1(b). Next on top of this is 7 n+
-a-8i: H and AI are stacked in this order (FIG. 1(C)). Finally, the photoresist is lifted on to complete the thin film transistor (FIG. 1(d)).

However, this self-alignment method for forming a photoresist pattern has the following drawbacks. 1st
The drawback is that the thickness of the semiconductor thin film is severely limited. The semiconductor thin films mentioned here include single crystal silicon, polycrystalline silicon, amorphous silicon, CdS, CdSe, etc., all of which have large absorption coefficients in the ultraviolet region. For example, the absorption coefficient of amorphous silicon in the ultraviolet region is greater than lQ'L:N''. Therefore, unless the film thickness is limited, ultraviolet light will be absorbed by the semiconductor thin film and will not reach the photoresist. Second, for the same reason, ultraviolet light is absorbed by the semiconductor thin film and weakens, so a long exposure time is required.In a reported example, when the film thickness is 0.1 μm in amorphous silicon, the exposure time is 20~20 μm. It can take up to 30 minutes, which is 3 times longer than the exposure time of normal photoresist.
It corresponds to 0 times to 50 times. Thirdly, there is a risk of damaging the film by irradiating it with ultraviolet light for a long period of time. For example, in amorphous silicon, S table
It is known that the structure of a film changes due to light, called the r-Wronski effect, and when ultraviolet light is irradiated for a long time, the quality of the film deteriorates due to this effect. In addition, in the case of this thin film transistor, as mentioned in the first drawback, there is a limit to the film thickness, so normally n+-a”Si can be formed continuously.
There was also the secondary drawback of having to add the H later.

(Objective of the Invention) The object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods, and to produce a photoresist that can be applied to thicknesses up to one thickness within the practical range of thin-film semiconductor devices, and whose exposure time to ultraviolet light is the same as that of a normal process. The object of the present invention is to provide a method for forming a pattern.

(Structure of the Invention) According to the present invention, in the process of forming a photoresist pattern on an element in which a thin film including a thin film that is at least partially opaque is laminated on a transparent substrate, a photoresist pattern is formed on the thin film element.
Otoresist, a photographic photosensitive material sensitive to long wavelength light of 500 nm or more is laminated, with a distance of 500 nm from the transparent substrate side.
The photographic light-sensitive material is irradiated with the above long wavelength light, developed and fixed, and then ultraviolet light is irradiated from the side of the photographic light-sensitive material, and the photoresist is exposed using the photographic light-sensitive material as a mask. A method for forming a photoresist pattern is obtained, which is characterized by forming a photoresist pattern by developing.

(Summary of the Invention) A method for forming seven photoresist patterns according to the present invention is shown in FIG. In the figure, 9 is a transparent insulating substrate, 10 is an opaque material such as a metal, and 11 is a thin film layer containing at least a semiconductor layer.For example, in the thin film transistor shown earlier, an insulating film, an amorphous silicon/film, and a PLN diode are used. If available, they are thin films made by stacking p-type, i-type, and n-type semiconductor films, respectively. 12 is a photoresist, 13 is a photographic light-sensitive material sensitive to long wavelength light of 500 nm or more, and 13a is a blackened portion of the photographic light-sensitive material of 13 after exposure, development, and fixation;
131) is the part that went through the same process and was not blackened, 1
4 is long wavelength light of 500 nm or more, and 15 is ultraviolet light.

Hereinafter, the method for forming the seven photoresist patterns of the present invention will be explained in order.

First, a 12-7 photoresist is spin-coated on a thin film semiconductor element on which a photoresist pattern is to be formed. This photoresist can be selected as positive or negative depending on the purpose. Next, 13 photographic light-sensitive materials are formed. This photographic light-sensitive material is selected depending on the wavelength dependence of the absorption coefficient of the thin film semiconductor element. For example, the optical absorption edge of CdS is around 500 nm, and in this case, the most common photosensitive material used in the visible light range is sufficient. In the case of amorphous silicon, the optical absorption edge is around 650 nm, and in the long wavelength range above this, the absorption coefficient is less than lQ"o++-". Single-crystal silicon has an absorption coefficient that is one order of magnitude smaller than that of amorphous silicon in the visible light region, and the relationship in magnitude reverses from near the absorption edge of amorphous silicon, but the value is lQ"n-'
It is as follows. 600nm for these silicon-based semiconductors
Photosensitive materials that are sensitive to longer wavelengths than this are best. At present, photosensitive materials cover almost all wavelength ranges from ultraviolet to infrared, and for this purpose, it is sufficient to simply use photosensitive materials for infrared photography. Furthermore, since commonly used visible photographic materials are sensitive to red, this may be sufficient depending on the thickness of the semiconductor thin film. Any photographic light-sensitive material may be used as long as it satisfies this requirement and has sufficient resolution to form a pattern. A versatile emulsion is based on gelatin and contains silver halide, and is sensitized to red. Infrared sensitized products are manufactured that have maximum sensitivity at 750 nm, 850 nm, and 950 nm.

14 from the transparent insulating substrate side of the device fabricated as above.
(Figure 2 (a)
)). At this time, this long wavelength light passes through the thin film layers of 11 and 7 of 12.
It passes through the photoresist and reaches 13 photographic light-sensitive materials, which are exposed to light. Photoresist is not sensitive to long wavelength light, so it is not exposed to light. Further, since the opaque body 10 does not transmit this light, the photographic light-sensitive material thereon is not exposed.

When this is developed and fixed, the area outside the upper slope of the opaque body 10 becomes black as shown in FIG. 2(b).

Next, as shown in FIG. 2 (cl), ultraviolet light 15 is irradiated from the side of the photographic light-sensitive material.The blackened portion 13a does not transmit ultraviolet light, and the non-blackened portion 13b transmits ultraviolet light. It acts as a mask and selectively exposes the underlying photoresist.Then, the photosensitive material 13 is peeled off.
When the photoresist 12 is developed, a photoresist pattern is formed as shown in FIG. 2(e) in the case of a negative type 7 photoresist.

As is clear from the above description, in the method for forming a photoresist pattern of the present invention, restrictions on the thickness of a semiconductor thin film are much looser than in conventional methods.

For example, in the case of a silicon-based semiconductor thin film, 1 to 2 pmCa
With S, etc., it is applicable up to several tens of μm. Therefore, it can be applied to most of the thin film semiconductor devices reported to date. Furthermore, since the ray time of ultraviolet light is almost the same or shorter than that of a conventional method of forming a photoresist pattern, there is no damage caused by ultraviolet light.

(Example) Some examples of the method for forming a photoresist layer of the present invention will be described. FIG. 3 shows the process of forming a staggered thin film transistor by a self-alignment method to which the fort resist pattern forming method of the present invention is applied. In the figure, 16 is a glass substrate, 17 is a source, and MO118, which becomes a drain electrode, is a non-doped a-8i film with a thickness of 0.3 pm formed by glow discharge decomposition of SiH4: HIIK.
, 19 is SiH4°N, or SiH4,N, ,
20 is a negative photoresist, 21 is an infrared photographic material with maximum sensitivity at 750 nm, and 22 is a SiNx film with a thickness of 0.3 pm formed by glow discharge decomposition of a mixed gas of NH. 23 is ultraviolet light; 24 is Mo serving as a gate electrode; and 23 is ultraviolet light. The formation process is shown below.

1 on a glass substrate on which source and drain electrodes 17 are formed.
8 a-8i: H, 19 SiNx is continuously formed and a negative photoresist is applied thereon)20. A photosensitive material 21 is applied, and long wavelength light 22 is irradiated from the glass substrate side (FIG. 3(a)). This is developed and then irradiated with ultraviolet light 23 (FIG. 3(C)). When the photographic light-sensitive material is peeled off and the photoresist is developed, a 7-photoresist pattern is formed as shown in FIG. 3 (dl).Mo is deposited on this (FIG. 3(e)).

Finally, the photoresist is lifted on and the M and O portions on the channel other than the gate electrode are removed to complete the thin film transistor (FIG. 3(f)).

Next, a second embodiment is shown in FIG. FIG. 4 is an example in which the method for forming seven photoresist patterns of the present invention is applied to the self-alignment force of an inverted staggered thin film transistor. In the figure, 25 is a glass substrate, 26 is a gate electrode made of Cr, and 27 is 5IH4°N or S i Ha , N
, , NH, SiNx film formed by decomposing a mixed gas by a glow discharge method, 28 is a non-doped a-8i film formed by a glow discharge decomposition method of SiH4: HIII,
29 is a 0.05 pm n+-a-8i:H film formed by a glow discharge method using 5zH4 mixed with 0.1% PH, 30 is a negative type 7 photoresist, and 31 is a red film with maximum sensitivity at 750 nm. A photosensitive material for external photography, 32 is long wavelength light including light with a wavelength of at least around 750 nm, 33 is ultraviolet light, and 34 is A1 serving as a source/drain electrode. The formation process is shown below.

First, Cr is deposited on a glass substrate and patterned to form the gate electrode 26. 27 S by glow discharge method
iNx, 28 a-8t:H, 29 n+-a-
8i:H is continuously formed, a negative photoresist 30 and an infrared photosensitive material 31 are applied thereon, and long wavelength light 32 is irradiated from the glass substrate side (FIG. 4(a)). When this is developed and fixed, the photographic light-sensitive material except for the portion directly above the gate electrode turns black, as shown in FIG. 4(b). Next, ultraviolet light 33 is irradiated from the side of the photographic light-sensitive material (FIG. 4(C)).

When the photosensitive material is peeled off and the photoresist is developed, seven photoresist patterns are formed as shown in FIG. 4(d). AI is deposited on this (FIG. 4(e)).

The photoresist is lifted off to remove A1 on the channel (FIG. 4(f)). Finally n+-a on the channel
-8i:) (is etched to complete a thin 11% transistor (Fig. 4(g)).

In these examples, the thickness of the semiconductor thin film was set to 0.3/Jm, but this thickness is a practical thickness commonly used in thin film transistors using amorphous silicon, and the conventional method described above The thickness is impractical. The film thickness may become even thicker in relation to other elements. For example, this is the case when a diode and a thin film transistor are formed using the same semiconductor thin film. Also, considering how much time it actually takes in the conventional method, if it takes 20 minutes to expose the semiconductor thin film with a thickness of 0.1 μm in the second embodiment, then the n + -a-si:
Due to the formation of the H film, the light time is actually as long as 90 minutes.

This is because the attenuation of light is exponential with respect to the film thickness. In contrast, in the method for forming a photoresist pattern of the present invention, the exposure time to ultraviolet light is at most several tens of seconds.

Although the above embodiments relate to two types of thin film transistors, the steps are almost the same for other thin film transistors and diodes.

(Effects of the Invention) As is clear from the above explanation, according to the method for forming a photoresist pattern of the present invention, the method for forming a photoresist pattern in a thin film semiconductor device can be used to perform self-alignment without being limited by the thickness of the thin film. A resist pattern can be formed. Moreover, the exposure time of the photoresist to ultraviolet light is the same as in a normal process, so the film is not damaged. Therefore, it is possible to stably manufacture thin film semiconductor devices with a high yield.

[Brief explanation of the drawing]

FIGS. 1(a) to dl are diagrams for explaining a conventional example of a self-alignment method for thin film transistors; FIGS. 3(a) to 3(f) are diagrams for explaining the manufacturing process of a staggered thin film transistor to which the method of forming seven photoresist patterns of the present invention is applied, and FIG. 4(a)
) to fg) are diagrams for explaining the manufacturing process of an inverted staggered thin model transistor to which the photoresist pattern forming method of the present invention is applied. In the figure, 1...Glass substrate, 2...Metal electrode, 3...Insulating film, 4...Amorphous silicon dioxide, 5...Photoresist, 6...Ultraviolet light, 7-n "-a-8i: H film, 8. Al electrode, 9... transparent insulating substrate, 10.
... Opaque body, 11 ... Semiconductor thin ah, 12 ... Photoresist, 13 ... Photographic light-sensitive material sensitive to long wavelength light of 500 nm or more, 13a ... Blackening of photographic light-sensitive material 13b... Portion of photosensitive material that did not blacken, 14... Long wavelength light of 500 nm or more, 15... Ultraviolet light, 16.25... Glass substrate, 1
7.24.-Mo electrode, 18.28-.a-81:H
Film, I 9 , 27- SiNx film, 20.30 = -Negative type 7 photoresist, 21.31... Sensitive material for infrared photography, 22.32... Long wavelength light, 23.33...
Ultraviolet light, 34... AIl electrode attorney-1: Susumu Uchihara Figure 1 (α) Ib) (C) ((1) (α) (b) (C) (d) (e) (α ) (b) (C) (d) Figure 3 (e) (chi) (0) (b) (C) (d)

Claims (1)

[Claims] In the process of forming a photoresist pattern on an element in which a thin film including at least a partially opaque thin film is laminated on a transparent substrate, a photoresist,
Photographic light-sensitive materials sensitive to light with a wavelength of 500 nm or more are laminated, and long-wavelength light of 500 nm or more is irradiated from the transparent substrate side to expose the photographic material, developed, and fixed, and then the photographic material is 1. A method for forming a photoresist pattern, which comprises irradiating ultraviolet light from the side of a photographic photosensitive material, exposing and developing a photoresist using the photographic photosensitive material as a mask, and forming a photoresist pattern.