JPH0677106A - Method for forming photoresist pattern - Google Patents

Abstract

PURPOSE:To form a certain overhang part for stabilizing the size of an electrode by a photoresist pattern by exposing a proper amount of exposure exceeding a proper exposure at a region which is smaller than the exposure region and then allowing a photoresist film at a site which is exposed to be insoluble to a development liquid. CONSTITUTION:A specific part of a part other than a region where an electrode is formed is exposed via a first photo mask 13. Then, a second photo mask 14 with a narrower exposure region than a first pattern is used and an exposure exceeding a proper amount of exposure is performed. Then, one part of a photoresist exposure region 22 is formed at a second photoresist exposure region 32. Then, when baking is performed in an ammonium atmosphere, the photoresist exposure region which has already been exposed changes its properties, thus becoming a photoresist exposure region 52 which is insoluble to a development liquid. Then, when an entire surface is exposed and is developed, parts excluding the overhang part of a photoresist film 12 and the photoresist film 42 other than the photoresist 52 whose properties changed are eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, it is applied to the formation of a photoresist pattern when forming an electrode by a lift-off method using an image reverse method.

[0002]

2. Description of the Related Art Electrode formation by a lift-off method is widely used in the manufacture of semiconductor devices and is one of the important techniques. When forming an electrode by the lift-off method, first, a photoresist pattern having an inverse taper shape or an eaves on the photoresist surface is formed. Next, an electrode metal layer is formed on the entire surface by vapor deposition or the like, and then the photoresist is removed, whereby the metal on the photoresist film is also removed and the electrode is formed only on a predetermined portion. Various methods of forming a photoresist pattern having an inverse taper shape or an eaves on the photoresist film surface have been proposed, but the image reverse method has a simple process and can stably obtain a photoresist pattern having an eaves. ,
It is also a method often used because a wide variety of positive type photoresists can be used. Some photoresists used in the image reversal method are insoluble in the developing solution because the exposed portion is deteriorated only by baking after the exposure. However, since the film thickness of this type of photoresist is limited, a normal positive type photoresist having flexibility in film thickness is usually used.

A lift-off process according to a commonly used image reverse method will be described with reference to FIG. A positive type photoresist 10 is formed on the substrate 101 on which the circuit is formed.
After coating 2, the photoresist of a predetermined portion is exposed through the mask 103 (FIG. 4A). Next, when baking is performed in an ammonia atmosphere, the photoresist 112 in the exposed portion becomes the altered photoresist 122 and becomes insoluble in the developing solution (FIG. 4B). Next, the entire surface is exposed and the unexposed photoresist portion 102 is also exposed to be the exposed photoresist portion 112 (FIG. 4C).
After development, only the altered portion of the photoresist 122 remains, and at this time, the photoresist has an inverse taper shape,
Eaves are formed on the photoresist surface (FIG. 5).

[0004]

In the above, the size of the eaves is mainly determined by the conditions of the first exposure.
In the image reverse method, the exposure is performed under an exposure condition that is smaller than the appropriate exposure amount for normal patterning. At this time, the smaller the exposure amount is, the larger the eaves size becomes, and the eaves cannot be provided at an appropriate exposure amount in normal use or at an exposure amount higher than that. When the thickness of the photoresist film is thin, the subsidence of the photoresist film under the eaves during vapor deposition of the electrode metal is substantially the same if the eaves have a certain size. However, when the film thickness of the photoresist is large, the submersion of the electrode metal layer under the eaves of the photoresist also becomes large. Therefore, there is a problem in that the size of the electrode differs depending on the size of the eaves, and the stable size of the electrode cannot be maintained. This is because, even if the photoresist pattern forming conditions are constant, the size of the eaves varies due to differences in the photoresist production lot and slight variations in the photoresist pattern forming conditions.

An object of the present invention is to form a constant eave portion on the photoresist pattern in order to stabilize the size of the electrode when forming the photoresist pattern for forming the electrode.

[0006]

A method of forming a photoresist pattern according to the present invention comprises a step of forming a positive type photoresist film on a substrate on which a circuit is formed, and an appropriate exposure amount in an area excluding a planned electrode formation area. A step of exposing with a smaller exposure amount, a step of exposing a region slightly smaller than the exposure region with an exposure amount of an appropriate exposure amount or more, and a photoresist film in the exposed portion is formed with an ammonia or amine compound. In an atmosphere containing, or a step of simply baking to make it insoluble in a developing solution, a step of exposing the entire surface to development, and forming a reverse taper on the photoresist film,
Alternatively, it is formed into a pattern having an eaves surface.

[0007]

In the method of forming a photoresist pattern according to the present invention, the difference between the pattern exposed at an appropriate exposure amount or more and the pattern exposed at an exposure amount less than the appropriate exposure amount becomes the size of the eaves. Therefore, a photoresist pattern having a constant eaves size is always formed without being affected by the difference in the proper exposure amount due to the difference in the photoresist manufacturing lot and the variation in the conditions for forming the photoresist pattern.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to.

After the positive type photoresist film 12 is formed on the substrate 11 on which the circuit is formed, first, a portion other than a region where an electrode is to be formed (a region where an electrode is to be formed) is passed through a first photomask 13 to a predetermined portion. Exposure (Fig. 1
(A)). The size 13a of the unexposed portion of the mask at this time is the size of the opening diameter of the photoresist, and the exposure amount is larger than the proper exposure amount (the exposure amount T) when used as a normal positive type photoresist. Also reduce. Reference numeral 22 in the drawing denotes a first photoresist exposure area which has been exposed by less than the exposure amount T.

Next, using a second photomask 14 having an exposure area narrower than that of the first pattern, an exposure amount T or more is applied to expose a part of the photoresist exposure area 22 to the second photoresist exposure area. Form in area 32 (Fig. 1
(B)).

Then, when baking is performed in an ammonia atmosphere, the photoresist exposed area which has already been exposed changes in quality and becomes a photoresist exposed area 52 which is insoluble in the developing solution (FIG. 1 (c)).

Next, the entire surface is exposed to light and developed, and the photoresist film 12 other than the photoresist 52 that has been deteriorated and the portion of the photoresist film 42 excluding the eaves portion are removed, and the photoresist having the eaves or the reverse taper shape is formed. A pattern is obtained (Fig. 2). Next, the profile of the photoresist film at this time will be described in more detail with reference to FIG.

When the first exposure condition is changed while the other conditions such as the development condition are kept constant by the image reverse method, the photoresist profile becomes as follows. When the exposure amount of the first mask is small, the profile becomes A, and as the exposure amount increases, it becomes B and C, and the exposure amount T
In the above, the profile D is almost vertical. Next, when a second mask whose exposed portion is one size smaller than that of the first mask is passed through and exposure is performed with an exposure amount T or more, a profile obtained as a result becomes as shown by E. Therefore, the photoresist profile obtained as a result of two exposures is
It is a combination of A, B or C and E. The shape of the eaves varies depending on the first exposure amount, but the size of the eaves depends on the mask size difference, that is, {(width of 14a)-(13a
Width)} / 2, so it is always constant. There is a concern that the mask alignment will be misaligned between the first exposure and the second exposure, but this is not a problem because the alignment accuracy can be set to 0.1 μm or less at present.

As described above, according to the present invention, the size of the eaves can always be made constant when forming the photoresist pattern having the inverse taper shape or the eaves on the surface of the photoresist film by the image reverse method. Therefore, after that, when an electrode metal layer is formed on the entire surface by vapor deposition or the like and the electrode is formed only on a predetermined portion by lift-off, an electrode having a constant size is always obtained.

In the above description, the order of exposure is the first mask 1
Although the process was performed in the order of 3 to the second mask 14, conversely, the same result was obtained even when the second mask 14 to the first mask 13 were exposed in this order.

In the above description, a normal photoresist was used, and after the pattern exposure, baking was performed in an ammonia atmosphere to change the quality of the photoresist in the exposed portion to make it insoluble in the developing solution. However, simply exposing the exposed portion to the exposed portion Similar results are obtained even when a photoresist that is altered and insolubilized in a developing solution is used.

[0017]

According to the present invention, in the formation of a photoresist pattern, the difference between the pattern exposed at a proper exposure dose or more and the pattern exposed at an exposure dose less than the proper exposure dose becomes the size of the eaves. Therefore, without being affected by the difference in the proper exposure amount due to the difference in the production lot of the photoresist and the variation in the conditions for forming the photoresist pattern,
A photoresist pattern having a constant eave size is always formed.

[Brief description of drawings]

1A to 1C are cross-sectional views each showing a part of a method of forming a photoresist pattern according to an embodiment of the present invention in the order of steps.

FIG. 2 is a cross-sectional view showing a part of a method for forming a photoresist pattern according to an example of the present invention.

FIG. 3 is a sectional view for explaining the present invention.

4A to 4C are cross-sectional views each showing a part of a method of forming a photoresist pattern by a conventional image reverse method in the order of steps.

FIG. 5 is a cross-sectional view showing a part of a method of forming a photoresist pattern by a conventional image reverse method.

[Explanation of symbols]

 1, 11 Substrate (on which circuits are formed) 2, 12 Positive type photoresist film 22, 32 Exposed photoresist area 42, 52 Denatured photoresist area 13, 14 Mask

Claims (1)

[Claims] 1. A step of forming a positive type photoresist film on a substrate on which a circuit is formed, a step of exposing a region excluding a predetermined electrode formation region with an exposure amount smaller than an appropriate exposure amount, A step of exposing a smaller area to an exposure amount more than an appropriate exposure amount, the photoresist film of the exposed portion is insoluble in a developing solution in an atmosphere containing ammonia or an amine compound, or simply by baking. And a step of exposing and developing the entire surface, and forming the photoresist pattern into a pattern having a reverse taper or an eaves shape on the surface.