JPH0234858A - Preparation of developing solution for photoresist - Google Patents

Abstract

PURPOSE:To stabilize an etching speed and developing speed of a developing soln. for photoresist by charging a soln. of ethylene oxide and an aq. soln. of trimethylamine contg. >=1 mole trimethylamine per 1 mole ethylene oxide to a reaction vessel at a time, mixing both solns. quickly so as to attain a uniformly dispersed state, and allowing the ethylene oxide to react with trimethylamine. CONSTITUTION:For example, an aq. soln. contg. 17.2wt.% trimethylamine and an aq. soln. contg. 11.6wt.% ethylene oxide are charged to a reaction vessel installed with a stirrer having a baffle board in a proportion of 1.10 mole trimethylamine to 1 mole ethylene oxide, and trimethylamine is allowed to react with ethylene oxide by mixing both solns. In this case, both solns. should be charged to the reaction vessel at a time, and should be mixed so as to attain quickly a uniformly dispersed state. Namely, it is preferred that the time for mixing is within 1/5 as compared to the time until the temp. of the mixture attains the highest temp. of the reaction, and the time is preferred to be as short as possible. Thus, a developing soln. for photoresist having a stable etching speed and developing speed is obtd.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for producing a photoresist developer, and more specifically, the present invention relates to a method for producing a photoresist developer, and more specifically, a method for producing a photoresist developer, in which the titer is effectively controlled, and The present invention relates to a method for producing an aqueous choline solution that is highly pure and has excellent operational and storage stability.

(Prior art) It is already known that quaternary ammonium hydroxide, which has strong basicity, is useful as a semiconductor processing agent for cleaning semiconductor surfaces, etching, developing photosensitive resins, etc.
-40181, Special Publication No. 55-40183, Special Publication No. 55
5-41529), the method for producing most quaternary ammonium hydroxides is to first obtain a halide salt of a quaternary ammonium base, a vA salt, or a salt with other acid groups, and then add silver to the salt. Traditionally, it has been generally produced by reacting barium, oxides, hydroxides, etc. of other metals to replace acid groups with hydroxyl groups, or by treating the salts with hydroxyl groups. This is the method that has been used in the past. However, in the method of substituting acid radicals with hydroxyl groups, it is inevitable that metal ions having a solubility product or less are mixed in as impurities, and in the FM electrolysis method, there is a risk that dissolved substances from the anode may be mixed in.

However, it is desirable for a semiconductor processing agent to contain as few impurities as possible, and an especially important condition is that it should contain almost no inorganic elements. At this point, choline (2-oxyethyltrimethylammonyl hydroxide [HOCH, -C
H2-N"÷CH3), ]OH-3 can be easily produced by adding ethylene oxide to an aqueous trimethylamine solution in the form of a gas, liquid or aqueous solution,
Since the above raw materials can also be obtained with high purity, Na, Cu
, A(1, etc.) has the advantage of providing a semiconductor processing agent with very few impurities. In addition, the pH of a 0.1N aqueous solution of choline at 25°C is 12.8, and the pH of a 0.1N aqueous solution of caustic soda at 25°C It has almost the same level of basicity as DH in (
(See Japanese Patent Publication No. 53-20376 and Japanese Patent Publication No. 53-20377).

However, when the aqueous choline solution produced as described above is diluted to maintain a constant choline concentration and used for cleaning semiconductor surfaces, etching, developing photosensitive resins, etc., the amount of choline produced is There was a problem that there were variations in engraving speed, developing speed, etc., and that it lacked operational and storage stability as a semiconductor processing agent.

Note that choline aqueous solution is used as a photoresist developer.

Although it is known that it is used as
No. 71), it is not known that choline side reaction products are involved in development, and known matters regarding side reaction products of choline reaction are disclosed in Japanese Patent Publication No. 37-9558. There is no suggestion that photoresist developer is involved.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to ensure that an aqueous choline solution as a semiconductor processing agent does not contain harmful impurities such as metal ions, and that it remains stable under certain conditions as a semiconductor processing agent. It is an object of the present invention to provide a simple and inexpensive method for producing a photoresist developer capable of obtaining etching and developing speeds of .

[Structure of the Invention] (Means and Effects for Solving the Problem) As a result of various studies on this problem, the present inventors found that the reaction between trimethylamine and ethylene oxide is expressed by the following formula (
Considering that it consists of the main reaction of I) and the side reactions of the following formulas (II) and (III), (HOC82CH2N" (CH,
)) It has been found that the development rate can be controlled by increasing the choline content relative to the total solutes in the OH choline aqueous solution and allowing side reaction products to coexist.

In addition, by charging both reaction solutions into the reactor at once and mixing them quickly and uniformly, and by reacting trimethylamine with ethylene oxide in an amount of 1 mole or more, side reaction products can be reduced and stabilized. The inventors have discovered that this increases the potency of the photoresist developer to an unexpectedly stable level, leading to the present invention.

That is, in the method for producing a photoresist developer of the present invention, a trimethylamine aqueous solution containing 1 mole or more of trimethylamine per 1 mole of ethylene oxide, and an ethylene oxide aqueous solution or liquid ethylene oxide are both charged into a reactor at once, and then It is characterized by mixing and reacting so as to obtain a uniformly dispersed state.

The manufacturing method of the present invention will be explained below.

Trimethylamine used in the choline production reaction is used as an aqueous solution. The concentration is not limited, but 15-35
The purpose can be sufficiently achieved using a concentration of % by weight. Similarly, there is no limit to the concentration of the ethylene oxide aqueous solution, and a concentration of 10 to 20 ff% can be used. The boiling point of ethylene oxide is 10.7°C, and liquid ethylene oxide can also be used without any problem.

It is necessary to charge both the trimethylamine aqueous solution and the ethylene oxide reaction solution into the reactor at once. This means dropping one reaction solution into the other reaction solution over time, or adding a portion of the other reaction solution to one reaction solution, and then adding the remainder of the other reaction solution after the reaction. If one reaction solution is added gradually, the other reaction solution should be added gradually so as to always maintain a predetermined molar ratio to one reaction solution. number 5
In addition, both liquids introduced into the reactor must be quickly mixed to become a homogeneous dispersion state. A homogeneous dispersion state is the usual meaning, for example, when the tracer solution is substantially It is used to mean a state of uniform distribution. To quickly achieve this state means to raise the maximum temperature of the mixing reaction (usually 30 to 60°C by mixing both liquids at room temperature).
It is preferable that the mixing time is within 115 hours of the time it takes to reach 115 minutes, and that time should be as short as possible.Such a rapid mixing state can be easily achieved using a propeller type stirrer with a baffle for low viscosity. Furthermore, if a cylindrical static mixer is provided with an inlet for each of the two liquids and the two liquids are introduced and mixed at a predetermined ratio, the desired mixed state can be instantaneously achieved.

(Example) To specifically describe the above input mixing method, 17.
A trimethylamine aqueous solution with a concentration of 2% by weight and an aqueous solution of ethylene oxide with a concentration of 11.6% by weight were mixed in a ratio of 1.10 moles of trimethylamine to 1 mole of ethylene oxide, and both solutions were mixed in a reactor equipped with a stirrer with a baffle plate or a static mixer. The mixture was added and mixed under the conditions shown in Table 1, and the weight percentage of the reacted choline to the solute was determined.

As shown in Table 1, by adding both solutions at once and mixing them remotely, the proportion of choline in the solute can be reduced to 99%.
, a stable aqueous solution with extremely high purity of 6% or more and little variation can be obtained.From the perspective of side reaction products other than choline, even though both solutions were added at once and mixed quickly, , the side reaction products in a 6 wt % choline aqueous solution are in the range of 100 to sooppm.

Here, the concentration of this side reaction product is the difference between ethylene glycol and polyoxyethylene glycol obtained by removing the alkaline content from the reaction product aqueous solution using a cation exchange resin and performing gas chromigraph analysis. The concentrations of side reaction products shown below are all based on this method.

The development time A, which is the developer titer of the obtained reaction solution, is the development time A when the choline concentration is 4.6% by weight, its variation, and the development time is changed to 40 seconds to make the variation easier to understand The investigation was made from two points: the variation in development time B when the choline concentration was adjusted so that That is, after the reaction solution was heated and suctioned to remove excess trimethylamine after the reaction, the choline concentration was adjusted, and a resist in which quinone azide was bonded to a carbonic acid-formalin condensate via a sulfone group was used for development for a period of A. and B
was measured. The results show that a photoresist developer in which side reaction products coexist can speed up the development time, and that the development time can be controlled by the amount of side reaction products. In addition, as shown in Table 1, the development time fluctuates greatly when stirring is insufficient or when stirring is carried out dropwise. Both solutions exhibited stable performance with development times A and B of 40±0.5 seconds.

Next, those with a high choline content, reduced side reaction products, and stable developer titer are 1 mole or more of trimethylamine per 1 mole of ethylene oxide, more preferably 1 mole or more of trimethylamine.
．． It was obtained by mixing and reacting at a ratio of 0.05 to 1.10 moles. If ethylene oxide is in excess relative to trimethylamine, side reaction products such as ethylene glycol will become unstable. On the other hand, if the amount of trimethylamine is 1 mole or more and is in excess, it can be easily removed by volatilization by keeping the liquid at 40 to 70°C and blowing N2 gas without suctioning it after the reaction is completed. This has the advantage that a more stable photoresist developer can be obtained. The ethylene oxide aqueous solution used in the reaction is preferably used within 1 hour after preparation, as side reaction products such as ethylene glycol are gradually generated. Adjust to a 4.6 wt% choline aqueous solution!1) The weight percentage of choline in the solute, the amount of side reaction products in the 4.6 wt% choline aqueous solution, the variation in the development time A of the 4.6 wt% choline aqueous solution, and The relationship with the variation in the development time B when the choline concentration is approximately adjusted to a development time of 40 seconds is shown.

As shown in Table 2, when trimethylamine is mixed at a ratio of 1 mole or more to 1 mole of ethylene oxide, a highly purified product with a choline content of 99.3% or more can be obtained, especially from 1.05 to 1.05%. When mixed at a ratio of 1.10 mol, the purity is as high as 9965% or more.

This is caused by the variation in the development times A and B, and in particular, the variation in the development time B when the development time is adjusted to 40 seconds is extremely stable at 1 mole or more of trimethylamine. Especially trimethylamine 1.05-1.
In the range of 10, the development time B is in the range of ±0.5 seconds.

On the other hand, when the amount of trimethylamine is less than 1 mole, as in Experiment No. 11, there is a variation of 40±10 seconds, which is such that process control is impossible.

Next, to explain in detail the photoresist developer obtained by the production method of the present invention, an aqueous solution of 2-oxyethyltrimethylammonium hydroxide (choline) obtained by mixing and reacting a trimethylamine aqueous solution and an ethylene oxide aqueous solution or liquid ethylene oxide is as follows: Contains side reaction products specific to this reaction. The side reaction products of this reaction include:
As mentioned above, the side reaction product contains ethylene glycol and its polymers, and although the amount thereof is extremely small, it is extremely effective in controlling the development time, which is the titer of the photoresist developer. . The photoresist developer of the present invention is based on this knowledge.

In addition, as shown in Tables 1 and 2 above, all experiments with experiment numbers in which 1 mole of ethylene oxide was reacted with 1 mole or more of trimethylamine and the variation in development time B was ±3.0 seconds or less , side reaction products are 100~
5001)l)l, and the side reaction product is 1
In all cases outside the range of 00 to 500 ppm, the variation in development time B is ±10 seconds or more. Therefore, when 1 mole of ethylene oxide is mixed with 1 mole or more of trimethylamine and the two are reacted, and the amount of side reaction products in a 4.6% choline aqueous solution is set at a ratio of 100 to soo ppn, the photoresist developer will certainly be Time variations can be significantly reduced.
Then, set the choline concentration to a value other than 4.6% by weight, for example ×
When expressed as weight percent, the side reaction products are added in the same ratio (X
/4.6) X1001)I)II ~(x/4.6
) The amount of side reaction products can be determined by measuring the amount of choline in the solute and calculating the amount of solutes other than choline as ppm (weight) of an aqueous solution with a choline concentration of 4.6% by weight. It is something.

It should be noted that the harmful metal ions contained in the 4.6% by weight choline aqueous solution obtained by the production method of the present invention include 0 silver, cadmium, copper, calcium, potassium, magnesium, and lead.
．． 005 ppn or less, iron, sodium, zinc 0.0
It was extremely low, less than 1 pp11.

[Effects of the Invention] As explained above, according to the method for producing a photoresist developer of the present invention, it does not contain metal ions harmful to semiconductors, the development time is effectively controlled, and a stable development rate can be maintained. A choline-containing resist developer can be obtained easily and inexpensively, and can have immeasurable effects on the manufacturing of semiconductor devices.

Claims (1)

[Claims] 1. A trimethylamine aqueous solution containing 1 mole or more of trimethylamine per 1 mole of ethylene oxide, and both the ethylene oxide aqueous solution or liquid ethylene oxide are put into a reactor and quickly become uniformly dispersed. A method for producing a photoresist developer, characterized by mixing and reacting as follows. 2. Photoresist development according to claim 1, characterized in that both the liquids are brought into a uniformly dispersed state within 1/5 of the time required for the mixing reaction of these two liquids to reach the maximum temperature. Method of manufacturing liquid.