JPS63259560A - Organic alkali developer for positive type photoresist - Google Patents

Abstract

PURPOSE:To improve the developability of a positive type photoresist exposed by projection on a reduced scale by using an aq. soln. contg. a specified amt. each of specified tetramethylammonium hydroxide, polyhydric alcohol and a solvent for a sensitizer in the positive type photoresist. CONSTITUTION:This developer is an aq. soln. contg. 0.5-3.5wt.% tetramethylammonium hydroxide represented by formula, 0.2-10wt.% polyhydric alcohol and 0.001-0.1wt.% solvent for a sensitizer in a positive type photoresist. Di- or trihydric alcohol is suitable for use as the polyhydric alcohol from the viewpoint of dissociation inhibiting effect and ethylene glycol or glycerol is preferably used. The solvent for the sensitizer may be aliphat. ketone, cyclic ether or tert. amine. The developer maintains a developing speed close to that of a conventional developer even when a positive type photoresist exposed by projection on a reduced scale is developed, and the developer ensures improved dimensional accuracy, dimensional stability and a fine pattern profile.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an organic alkaline developer for positive photoresists.

More specifically, the present invention relates to an organic alkaline developer that improves the development performance of positive photoresists subjected to reduction projection exposure.

<Conventional Technology> In recent years, photolithography technology has undergone major changes as semiconductor integrated circuits become finer.

In terms of materials, there has been a shift from cyclized rubber-based negative photoresists to novolak resin and naphthoquinone diazide-based positive photoresists, and in exposure technology, there has been a shift from contact exposure to reduced projection exposure.

Positive photoresist is used to form fine patterns of 1.6 μm or less, and transfer is performed by reduction projection exposure.
The reality is that due to miniaturization and differences in exposure methods, sufficient performance cannot be obtained using conventional developing solutions.

Against this background, there has been a demand for a developer suitable for new exposure methods.

The two characteristics required of conventional developers are development speed and dimensional accuracy (including development unevenness and the presence or absence of undissolved residue). Improvements in impression, resolution, and residual film rate are mainly focused on the resist side. I was asked. However, when developing a pattern of 2 μm or less, the required characteristics extend to the pattern profile in addition to development speed and dimensional accuracy.

Currently, commercially available positive photoresists are mainly composed of a novolac resin and a naphthoquinonediazide-based photosensitizer. Further, a reduction projection exposure method is indispensable to form a pattern of 2 μm or less.

In the conventional contact exposure method, since a mixed wavelength of 845 to 4801 m was used, there was little light interference between the incident light and the reflected light, and the change in light intensity was small in the depth direction of the resist layer. Furthermore, since the irradiation intensity was weak, the exposure of unexposed areas due to light scattering could be almost ignored.

On the other hand, in the reduction projection exposure method, 405 or 486n
As a result of using a single wavelength of m, the interference between the incident light and the reflected light is large, and areas of strong and weak light intensity occur alternately in the resist depth direction, and even in the photosensitive area, there are semi-photosensitive areas. It turns out. Furthermore, since the irradiation intensity is strong, even if the irradiation is performed for a short time, the vicinity of the irradiated area becomes partially exposed due to scattering.

For these reasons, conventional tetramethylammonium hydroxide aqueous solutions alone gave essentially poor results in development speed, dimensional accuracy, and pattern profile, and sufficient development performance could not be obtained.

For example, JP-A-58-5712 discloses a method of improving developing performance by adding 1 to 50% by weight of an organic solvent or surfactant to a positive photoresist developer to lower surface tension and improve wetting. Proposed.

In this case, some organic solvents include alcohol, ketone,
Examples include esters, cellosolves, hydrocarbons, and aromatic types.

However, although this method improves uneven development, it does not essentially improve the dimensional accuracy of the pattern.

Also, this method does not improve the pattern profile.

On the other hand, JP-A No. 58-9148 proposes a method of adding a surfactant consisting of a quaternary ammonium salt and a polyhydric alcohol wetting agent to a positive photoresist developer, but it requires a special compound. Because of this, it is expensive, and because of its high boiling point, it has the problem of causing contamination if cleaning is insufficient. Nor does it essentially improve dimensional accuracy and pattern profile.

<Problems to be Solved by the Invention> The problems to be solved by the present invention, that is, the purpose of the present invention is to maintain the same development speed as before even in reduction projection exposure, and to greatly improve dimensional accuracy and pattern profile. The purpose is to provide a developer.

Means for Solving the Problems> The present inventors have worked diligently to solve the above-mentioned problems, and have solved the ion dissociation of tetramethylammonium hydroxide by allowing a small amount of polyhydric alcohol to coexist in an aqueous solution of tetramethylammonium hydroxide in a narrow concentration range. We discovered the fact that by partially suppressing the effects of oxidation, and by adding a very small amount of a good solvent for positive photoresist photosensitizers, it is possible to improve dimensional accuracy, that is, good dimensional stability, and greatly improve the pattern profile at the same development speed as before. The present invention has now been completed.

To explain the present invention, general chemical formulas are shown below.

The part irradiated with light becomes indenecarboxylic acid and becomes alkali-soluble through the reaction of equation (1), but the part that is not irradiated with light reacts with naphthoquinone diazide and novolac in the presence of an alkali, as shown in equation (2). A coupling reaction occurs to form a substance that is insoluble in alkali. These are well known facts.

However, when a single wavelength is used in the reduction projection exposure method, it is thought that the reaction of formula (1) will mostly proceed in the light irradiated area, and the reaction of formula (2) will also partially proceed. Therefore, if the alkali temperature is increased to 11 degrees to suppress the dissociation of the alkali,
It is thought that as a result of suppressing the OH ion concentration, the reaction of equation (2) should be suppressed as much as possible. Furthermore, it is assumed that the development speed remains unchanged because the alkali has a buffering effect and OH ions are supplied even if they are consumed.

In reality, development speed is maintained and dimensional accuracy is maintained due to the behavior of lowering the alkali concentration, the effect of maintaining a constant OR ion concentration, and the effect of the presence of a very small amount of a good solvent for positive resist photosensitizer. Moreover, it seems to exhibit developing performance with a good profile.

The present invention will be specifically explained below.

The present invention contains 0.5 to 8.5% by weight of tetramethylammonium hydroxide represented by the general formula (A) and polyhydric alcohol-/I/OQ.
, 2 to 1% ONi and 0.001 to 0.1% by weight of a positive photoresist photosensitive agent solvent.

The tetramethylammonium hydroxide represented by the general formula (4) in the present invention is required not to contain impurities such as metal ions.

The concentration of tetramethylammonium hydroxide in the developer is preferably 0.5 to 8.5% by weight, more preferably 2.38 to 2.50% by weight. If the concentration is less than 0.5% by weight, the development speed will be slow and it is not practical.
On the other hand, if it is 8.5% by weight or more, the development speed is too fast, resulting in poor dimensional stability.

The polyhydric alcohol in the present invention refers to an alcohol having a valence of two or more, including dihydric alcohols such as ethylene glycol and propylene glycol, octahydric alcohols such as glycerin and pentaglycerol, and tetrahydric alcohols such as pentaerythritol. It is selected from a wide group of alcohols, including pennuts (pentahydric alcohols) and hexites (hexahydric alcohols).

Dihydric to octavalent polyhydric alcohols are preferably used from the viewpoint of dissociation suppressing effect, and among these, ethylene glycol and glycerin are preferable.

The concentration of the polyhydric alcohol is selected to be 0.2 to 10% by weight, preferably 1.0 to 4.0% by weight. If it is less than 0.2% by weight, the effect of suppressing dissociation is small, and if it is more than 10% by weight, the resist dissolving effect of the polyhydric alcohol becomes large, which is not preferable. The content of the dissociation inhibitor should be appropriately adjusted depending on the alkali concentration.

Further, representative photosensitive aliphatic ketones for positive photoresists in the present invention include acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, etc., all of which are suitable.

Representative examples of cyclic ethers include trimethylene oxide, butylene oxide, amylene oxide, dioxane,
1,8.5-trioxane, etc., and among these, dioxane is extremely preferred.

Typical examples of the tertiary amine include trimethylamine and triethylamine, both of which are suitable.

Among them, it contains one or more of acetone, dioxane, and ethyl cellosolve, and has a total concentration of 0.001 to 0.
．． 1% by weight, preferably 0.002-0.022% by weight
Certain organic alkaline developers are preferably used. concentration is o
, oot% by weight or less, phase opening effects in development such as dimensional stability and profile cannot be obtained. On the other hand, the concentration is 0.1% by weight
Above this, the dissolution effect of the resist is too large, resulting in poor dimensional stability.
The profile etc. becomes bad.

On the other hand, as water, which is the main component of the aqueous solution, ultrapure water purified by a reverse osmosis membrane or the like is used.

<Examples> The present invention will be specifically explained below using Examples and Comparative Examples, but the present invention is not limited to these in any way.

The development characteristics were measured as follows.

(1) Method for Measuring Film Thickness Film thickness was measured using Talystep manufactured by Rank Taylor Pobson.

(2) Measurement method of dimensional stability Akashi Seisakusho Scanning Electron Microscope 8 HI GMA-■
The line width was measured from the SEM photograph taken.

(3) Method for measuring pattern inclination and S/L The pattern inclination was calculated from the 8EM cross-sectional photograph of the pattern using the following formula. The larger this value is, the better the pattern profile is.

Pattern inclination=tanθ=-～---(L-b)/2 Here, a, L and b indicate the following values.

a: height of the pattern L: lower line width of the pattern (line width) b = upper line width of the pattern On the other hand, the 8/L ratio is read from the SEM photograph and is expressed as (space width)/(line width), The closer this value is to 1.0, the better the dimensional accuracy is.

An overview of these is shown in Figure 1.

(4) Resist coating and blebake conditions resist 0
FPRJOO (Tokyo Ohka ■, trade name) was dropped onto a silicon wafer several meters thick, and Mikasa's Mikasa Binner I was used.
Using H-860 type, spin coating at 500 rPnl for 5 seconds and then 4000-5000 rpm for 20 seconds, then brebake at 90°C for 20 minutes in a clean oven to form a film with a thickness of 1.28-1.30 μm. I let it happen.

(5) Development conditions Contact mask aligner (Kasper model 2001
After UV exposure using a reduction projection exposure machine (stepper DSW4800 type) or a reduction projection exposure machine (stepper DSW4800 type), develop at 28℃7 with a developer adjusted to various concentrations.
Development was performed by a 0-second dipping method or a meniscus method.

Example 1 and Comparative Examples 1 to 3 Developers of various concentrations were adjusted and resist 0FPR-800 was prepared.
A silicon wafer coated to a thickness of 1.25 to 1.80 ttm is exposed to UVg light using a contact mask aligner.
Table 1 shows the residual film rate and sensitivity after color development by dipping at 28°C for 70 seconds.

Table 1 When the alkali concentration of tetramethylammonium hydroxide is 2.5% by weight, by adding a small amount of ethylene glycol and acetone, which is a good solvent for positive photoresist photosensitizers, the remaining film can be reduced while maintaining high sensitivity. We were able to improve the rate.

On the other hand, when the alkali concentration was as low as 0.8% by weight, although the residual film rate was very high, the development speed became extremely slow and development became impossible.

On the other hand, when the alkali concentration was as high as 4.0% by weight, the sensitivity was high, but the remaining film rate was low, and the upper part of the pattern was partially dissolved and rounded, resulting in a poor profile.

Examples 2 to 4 and Comparative Example 4 The dimensional stability of the developer of the present invention and a developer containing no polyhydric alcohol or photosensitizer solvent was compared using a reduction projection exposure method.

Resist: 0FPR-800 to 1.25 to 1.80μm
The film was coated to a thickness of 28° C. and developed by the meniscus method at 28° C. for 70 seconds. Note that a mask line width of 1.8±0.2 μm was used. Fifty measurement points were selected and the average values are shown in Table 2.

Examples 5 and 6 and Comparative Examples 5 to 7 According to Examples 2 to 4, dimensional stability was compared at an alkali concentration of 2.5 wt96.

The results are shown in Table 8.

By adding dioxane or acetone, which are good solvents for positive photoresist photosensitizers, favorable results were obtained synergistically with the effect of adding polyhydric alcohol.

On the other hand, the system in which 2.0% by weight of alethanol was added as a -hydric alcohol did not give good results and was almost the same as the system without the addition.

Example 7 and Comparative Example 8.9 1.2μ when the alkaline concentration of the developer is 2.4wt4
Table 4 shows the pattern inclination and 87L ratio when m-wide line and space patterns were subjected to reduction projection exposure using a stepper.

The resist was coated with PF-8200 to a thickness of 1.28 to 1.27 μm, and developed by the meniscus method at 28° C. for 70 seconds.

Table 4 Example 8 and Comparative Example 10 Table 5 shows the 8/L ratio when reduction projection exposure was performed using a line and space pattern 't stepper with various line setting widths when the alkali concentration was 2.45 wt%.

Ly'; Stoha0FPR-8QQ from 1.25 to 1.
It was coated to a thickness of 80/jm and developed by dipping at 28°C for 70 seconds.

Table 5 The 8/L ratio shows that when the alkali concentration of tetramethylammonium hydroxide is 2.46% by weight, 8.0% by weight of ethylene glycol and 0.004% of acetone, which is a good solvent for positive photoresist photosensitizers, are By adding %, we obtained good results with stable dimensional accuracy even when the line settings changed.

This effect was particularly remarkable in fine patterns with line settings of less than 2.0 μm.

<Effects of the Invention> Even in the reduction projection exposure method, the present invention maintains the same development speed (sensitivity) as the conventional developer using only an aqueous tetramethylammonium hydroxide solution, and also maintains dimensional accuracy and
To provide a developer for positive photoresist which has significantly improved dimensional stability and turn profile.

[Brief explanation of the drawing]

FIG. 1 shows an outline of a cross-sectional SEM photograph of the pattern. Here, a, L, b and S represent the following values. a: Height of the pattern L: Lower line width of the pattern (line width) b: Upper line width of the pattern S space width 1 Figure

Claims (5)

[Claims] (1) General formula (A) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (A) 0.5 to 3.5% by weight of tetramethylammonium hydroxide and 0.2 to 3.5% of polyhydric alcohol
10% by weight and 0% of the solvent of the positive photoresist photosensitizer.
An organic alkaline developer comprising an aqueous solution containing 0.001 to 0.1% by weight. (2) The organic alkaline developer according to claim 1, wherein the content of tetramethylammonium hydroxide is 2.38 to 2.50% by weight. (3) Claim 1 characterized in that the polyhydric alcohol is ethylene glycol and/or glycerin.
The organic alkaline developer described in Section 1. (4) The organic alkaline developer according to claim 1, wherein the polyhydric alcohol is contained in an amount of 1.0 to 4.0% by weight. (5) The organic alkaline developer according to claim 1, wherein the solvent of the positive photoresist photosensitizer is one or more of acetone, dioxane, and ethyl cellosolve.