JP5664171B2 - Resist adjusting method and resist adjusting apparatus - Google Patents

Description

The present invention relates to a resist adjustment of how to provide adjustment of the component variation unused resist, or once resist used for the recovered and reused.

  In the production of the color filter substrate, a colored resist is used for forming colored pixels, and a corresponding transparent resist is used for forming the spacer, the orientation control layer, and the protective layer. For resist application, spin coating, slit coating, roll coating, ink jet, etc. are selected according to the purpose. Resist scattered during substrate coating, resist remaining or staying in the ink supply pipe or coating device It is economical and preferable to recycle and reuse the recovered used resists (see, for example, Patent Document 1).

Collected used resist (hereinafter also referred to simply as “resist”) generally contains agglomerates in the apparatus, or once exposed to the air, absorbs moisture or volatilizes the solvent and becomes solid. The partial concentration is high. The degree of the dispersion varies from batch to batch, but the resist is collected in a tank after filtering the aggregated foreign matter with a filter, stirred while adding a solvent , and adjusted so that it is as close to the resist composition as possible before use. Is done.

To bring the composition of the used resist closer to the original resist composition before use, or to match the composition of the used resist belonging to different batches as much as possible, a solvent is added to the resist and its viscosity is used as an index. It is common to adjust to the same degree as the resist used or the same between different resists in a batch. If the viscosities match, it can be said that the composition is regarded as a regenerating method.

Then, it tried to collect | recover the used resist used for photospacer formation for every batch, add a solvent so that a viscosity might become a predetermined value (measurement value of a rotational viscometer), and to reproduce | regenerate as a resist. At the same time, the viscosity of the unused resist was measured and used as a comparative sample. Using these resists, photo spacers (hereinafter also referred to as PS) were formed under the same coating conditions by spin coating, and the film thickness after drying was examined.

  As shown in FIG. 1, the viscosity (Δ) of the regenerated resist was adjusted so that the viscosity was the same, so it was within the target value ± 2%, but the film thickness was unused as the target value ± 4% The variation was about twice that of the previous resist. On the other hand, the variation in the viscosity (♦) of the unused resist is larger than that of the recycled resist, but the variation in the film thickness is small and tends to converge to a constant value. Therefore, the conventional method of performing the resist regeneration based on the viscosity has a problem that the film thickness control is not stable.

By the way, in general, the viscosity of the resist solution is expected to depend on the amount of solid content dissolved in the solvent. The value was within a range of ± 0.5%, and the viscosity was almost constant within the range. Next, when the correlation between the solid content concentration and the PS film thickness was observed, it was a natural result that the PS film thickness became thicker as the solid content concentration increased as shown in FIG. The film thickness variation was larger than that of the unused resist (♦).

In general, when PS is formed using a regenerated resist obtained by adjusting the viscosity by adding a solvent to a used resist, there is a problem that the film thickness cannot be controlled sufficiently after adjusting the viscosity. This suggests that there is some difference in the composition of the regenerated resist, and it is necessary to control the composition of the resist from the viewpoint of the solid content concentration. By the way, the solid content concentration in the resist is usually calculated using a heating residue method. The residual heating method is obtained from the ratio of the weight before heating to the weight after heating, but as the name suggests, there is a problem that it is an off-line measuring means and not a method suitable for in-line measurement.

JP 2003-340354 A

To reuse the recovered already used resist after being used in different batches, when using recycled resist to form a predetermined pattern, to be smaller the variation between batches in the pattern production It is not useful because of its low nature.

Accordingly, the present invention is the used resist considered composition belonging to different batches is different, and aims to provide an adjustment of how to have the composition in different ways to play the same resist the conventional method. Of course, this is also a resist adjustment method for reducing the uniformity of the composition of the unused resist and making it uniform.

  Specifically, it introduces a new index that characterizes the resist characteristics so that the composition of the resist to be used can be considered to be consistent, and the heating residue to quickly and accurately estimate the solid content concentration in the resist. To provide an alternative to the law

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The invention according to claim 1 is a step of estimating the viscosity and solid content concentration of the collected used resist, and the viscosity of the resist is set to be higher than a target viscosity by adding a solvent . The step of diluting to the viscosity, the step of adding water until the solid content concentration of the diluted resist reaches a predetermined value, the refractive resist is measured and the viscosity is measured, while the diluted resist is the target viscosity and solid content concentration And a step of further adding a solvent until it becomes a resist adjusting method.

The present invention specifies a specific procedure for reclaiming a used resist and uses the solid content concentration as an index for component adjustment in addition to the viscosity, and has a correlation with the refractive index.

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The invention according to claim 2 is a step of estimating the viscosity and solid content concentration of an unused resist.
The step of diluting the viscosity of the resist to a predetermined viscosity set higher than the target viscosity by adding a solvent , the step of adding water until the solid content concentration of the diluted resist reaches a predetermined value, And a step of adding a solvent until the diluted resist reaches the target viscosity and solid content concentration while measuring the refractive index and measuring the viscosity. .

Further, the invention described in claim 3 is characterized in that the solid content concentration of the resist is estimated from the value of the refractive index based on a calibration curve indicating the relationship between the refractive index and the solid content concentration obtained in advance. The method for adjusting a resist according to Item 1 or Claim 2 is used.

  The present invention specifies refractive index measurement as a method for measuring the solid content concentration in a resist.

According to a fourth aspect of the present invention, there is provided a resist adjusting apparatus comprising means for performing the process according to any one of the first to third aspects .

The resist pattern formed by using the regenerated resist in which both the viscosity and the solid content concentration are adjusted by using the method of adjusting the collected used resist according to the present invention is compared with the regenerated resist in which only the viscosity is adjusted. Excellent shape stability. With respect to PS resist, there is little variation in film thickness (PS height) between different batches, and the manufacturing yield is improved.
By switching the measurement of solids concentration in the resist from the heating residue method to the refractive index measurement, the process from the recovery of the waste resist to the adjustment / regeneration of adding solvent and water is inlined, enabling high-speed processing became.
The present invention can also be used to suppress variations in the composition of unused resists.
As a result, the use efficiency of the entire resist increases, and at the same time, the productivity of the color filter substrate is greatly improved, which greatly contributes to cost reduction.

It is a figure explaining the relationship between the viscosity of PS reproduction resist and unused PS resist, and PS film thickness. Δ is a regenerated resist having a uniform viscosity, and ♦ is an unused resist. It is a figure which clarifies the relationship between the solid content density | concentration of PS reproduction | regeneration resist and unused PS resist, and PS film thickness. Δ is a regenerated resist having a uniform viscosity, and ♦ is an unused resist. It is a figure which shows the relationship between the solid content density | concentration in a reproduction | regeneration resist, and a moisture content (weight%). It is a figure which shows the change of the viscosity at the time of adding water to an unused resist and raising water content. It is a figure explaining the relationship between the solid content concentration in a resist, and a refractive index. □ indicates an unused resist, and Δ indicates a case where pure water is added to the unused resist to change the solid content concentration. It is a schematic block diagram of the resist reproduction | regeneration apparatus which performs the adjustment method of the resist which becomes this invention. It is a figure explaining the relationship between the film thickness obtained by applying this invention, and solid content concentration. □ is a uniform viscosity (invention), Δ is a uniform viscosity (conventional method), and x is an unused resist.

The present invention is based on the knowledge obtained in the process of clarifying the problems of the conventional method that has relied on viscosity adjustment by addition of a solvent to regenerate used resist or to adjust the unused resist before use. This point will be briefly described below.

  Six cans of used PS resists (acrylic) belonging to different batches collected in can units (20 liters) were prepared. The experiment was divided into three times from the same can and evaluated by collecting samples for evaluation, and the average value was taken as the value of the evaluation of the can. The same experiment was conducted with 6 unused resist cans prepared.

Next, add the specified dilution solvent to the collected used resist cans, collect the diluted resist, measure the viscosity with a rotational viscometer, and repeat this until the target viscosity is reached. Viscosity adjustment as a resist was performed. The unused product was measured using the stock solution without dilution.

Next, these PS resists are applied onto a glass substrate by a spin coat method, and the standard film thickness is 4.00 μm (rotating at 600 rpm for 10 seconds and drying at 230 ° C. for 44 minutes) ) And dried, and the film thickness was measured. The results are shown in FIG.
According to FIG. 1, the viscosity (Δ) of the regenerated resist is in the range of ± 0.02 mPa · s, but the unused product (◆) whose viscosity is not adjusted varies about ± 0.15 mPa · s. Had.

  However, the regenerated resist had a large variation in film thickness of ± 0.04 μm even though the variation was small with the same viscosity. On the other hand, there was a tendency for the unused product to vary in viscosity within the range of ± 0.02 μm, and in this range, the film thickness increased as the viscosity increased. In other words, even when the viscosity is adopted as an index for regeneration of the used resist, and this value is made uniform, the obtained film thickness is not constant and the variation is large.

This tendency is expected to become stronger as the target film thickness is made thinner by using the regenerated resist, and it can be said that it is a problem to rely on the viscosity adjustment of the solvent addition for the regeneration of the resist. The thickness of the colored resist is generally thinner than that of PS, and it is expected to become thinner in the future, so viscosity adjustment cannot be used. Even if it is limited to the regeneration of the resist for PS, it is necessary to keep the variation in film thickness to the same level as that of an unused product.

  Therefore, in order to find the cause of the variation in the film thickness of the resist whose viscosity has been adjusted, the solid content concentration and moisture concentration, which are relatively easy to measure, are measured by the residual heating method (230 ° C, held for 1 hour) and the Karl Fischer method, respectively. did. FIG. 2 shows the relationship between the solid content concentration and the PS film thickness. Both the regenerated resist (△) and the unused product (◆) have a natural result that the film thickness is thick when the solid content concentration is high, but the regenerated resist is less dependent on the film thickness with respect to the solid content concentration ( There was a tendency for variation to be small. The remaining component after heating is an acrylic resin component.

FIG. 3 shows the relationship between the solid content concentration of the regenerated resist and the amount of moisture (% by weight). The amount of water in the resist was not constant and spread from 0.5% to 1.8%. FIG. 4 shows the change in viscosity when water is increased by adding water to an unused resist in order to see the effect of moisture. It is clear that the viscosity decreases even when water is added, suggesting that the amount of water is related to viscosity variation. However, since water dissolves only about 7% by weight with respect to the solvent , it cannot be added any more.

To summarize the above results, even if a solvent is added to the used resist to make the viscosity uniform, the variation in the PS film thickness is larger than the variation in the film thickness of the unused resist. The film thickness of PS has a correlation between the viscosity and the solid content concentration in the unused resist, but in the regenerated resist, the correlation with the viscosity is weak and seems to have a good correlation with the solid content concentration. This means that the viscosity and the solid content concentration are correlated with the amount of water contained. In short, even if the viscosity is the same, there is some difference in the composition of the recycled resist.

  From these facts, although not certain, it was assumed that the variation in the shape (film thickness) at the time of applying the regenerated resist was due to variations in the amount of water in the regenerated resist even when the viscosity was constant. The moisture of the unused resist is as low as 0.2% or less, but in the used resist, the blending of the solvent and the amount of water is considered to vary from batch to batch due to moisture absorption of the resist or volatilization of moisture and solvent.

Therefore, in the present invention, the physical property value of each recovered can (batch) is adjusted not only by adding a solvent so that the viscosity is the same, but by making both the solid content concentration and the viscosity the same. Then, it was decided to eliminate the difference in composition for each can (batch) by adding and adjusting the solvent and water.

  The problem here is the method for evaluating the solid content concentration in the resist, but since the heat residue method is difficult to measure in real time and cannot be inlined, a physical quantity that correlates with the solid content concentration is an alternative. And found that there is a good correlation with the refractive index of the resist. FIG. 5 shows an example of the result of measuring the refractive index of a resist (Δ) in which pure water was added to an unused resist (□) having a water content of 0.2% by weight to change the solid content concentration. .

  The refractive index was measured with an Abbe refractometer at a light source wavelength of 589 nm (D line) and a liquid temperature of 25 ° C. The solid content concentration was measured by a heating residue method. The solid content concentration obtained by the heating residue method and the refractive index have a linear correlation as shown in FIG. 5 and can be used as a calibration curve. The refractive index of water is smaller than the refractive index of the solvent. Although there is a problem that it is difficult to apply to a combination having a small refractive index difference, the solid content concentration can be estimated from the refractive index value.

Even though the resist has the same solid content concentration, the refractive index differs depending on the mixing ratio of the solvent and the water, but the solubility of water in the solvent is about 7% by weight or less, so the difference in the refractive index due to the mixing ratio was practically ignored. However, if a calibration curve is created for each mixing ratio, the resist composition can be predicted more accurately.

  Next, a specific procedure and apparatus for adjusting the viscosity and the solid content concentration to predetermined values will be described.

  As shown in FIG. 6, the resist adjusting apparatus 1 for adjusting the above characteristics includes a liquid preparation tank 2 (about 20 liters) for preparing the collected used resist 9, and the used resist 9 collected in the tank. It consists of a collection line 3 for feeding in and a supply line 4 for delivering the regenerated resist to the coating device. The tank 2 is provided with a viscometer 5 (vibrating viscometer), a refractometer 6, a thermometer 7 and the like, and a liquid rotating mechanism 8, and can measure in real time. Of course, the tank 2 does not need to be connected to the resist collection / supply line, and may be an independent method of pouring from the collected waste liquid can. Since the figure becomes complicated, the resist and pure water addition mechanism is omitted.

  The used resist to be regenerated is collected in the liquid preparation tank 2 after filtering such as foreign matter removal and mixed well, and the viscosity and solid content concentration are measured by the attached measuring device. It is desirable to measure the amount of water at the start of blending. If the water content and the solid content concentration are known, the variation in the water content can be more effectively suppressed when bringing the viscosity and the solid content concentration to the target values. However, it is not always necessary to specify the amount of water, but in this case, there are many elements of trial and error in the following procedure.

The used resist has a higher viscosity (higher solid content ratio) due to the volatilization of the solvent component than the unused resist, but the water content is excessive due to variations in the unused resist itself and moisture absorption. Therefore, the target viscosity and solid content concentration are set in the direction in which the solvent and moisture are added based on the above-described actual measurement values. For used resists in different batches, it is preferable to adjust the amount of each additive based on the amount of water, not the amount of solvent , so that the ratio of solvent and moisture is as equal as possible. The target value is generally in the range of 5 to 6% by weight.

When the set value and the amount of solvent and water added are roughly determined, the solvent is first added to lower the viscosity. However, even if water is added later, the viscosity decreases, so the provisional target viscosity is higher than the actual target viscosity. Set. The solvent is added while referring to the scale of the viscosity measuring device. The amount added is usually less than the estimated amount added. If there is a calibration curve of refractive index for each mixing ratio of solvent and water, the amount of addition of solvent and water can be estimated more accurately. This is the same in the following.

After adding the solvent , the refractive index is measured, and the solid content concentration is estimated from a calibration curve prepared in advance. The solids concentration will be higher than the target value. Next, pure water is added until the solid content concentration is lower than the above value but slightly higher than the target value (the solid content concentration reaches the target value when the remaining solvent is added). As a result, the viscosity also decreases and approaches the target viscosity.

Finally, the addition of solvent until the viscosity and solid concentration reaches the target value. The remaining solvent will be added. If there are some mistakes and neither of the two indicators reaches the target value, it is sufficient to add a dark unused resist and start over. It is obvious that the above procedure can be used as it is for resist adjustment to reduce the variation in composition of each unused resist can (batch) or lot.

Six cans of unused PS resists (clear resists using an acrylic photo resin) and 10 cans of waste liquids of the resists were prepared. As for the waste liquid, 4 cans were regenerated by adding a resist solvent so that only the viscosity was obtained according to the conventional method. About the remaining 4 cans, the solvent and the pure water were added by the procedure as described above so that both the viscosity and the solid content concentration were prepared.

  A resist was collected from each can and applied on a glass substrate by a spin coating method under predetermined conditions (700 rpm, kept rotating for 6 seconds, dried at 230 ° C. for 44 minutes). FIG. 7 shows the relationship between the film thickness after drying and the solid content concentration, with the horizontal axis representing the solid content concentration. Δ is a uniform viscosity, □ is a uniform viscosity and solid content concentration, and x is an unused resist.

  The variation in the solid content concentration was large in the regenerated resist having the same viscosity, and the variation was more than twice as much as the others. The variation in the film thickness was greatly improved by adjusting the viscosity and the solid content concentration, and there was a tendency to be smaller than the new product (×).

The regenerated resist obtained by adding the solvent and moisture so that the viscosity and solid content concentration are equal to each of the used resists using the adjusting device according to the present invention has a composition regardless of the process leading to recovery. Becomes a regenerated resist having substantially the same value.
The used PS resist has been described above, but the present invention can also be applied to colored resists having different compositions and various unused resists.

DESCRIPTION OF SYMBOLS 1, Resist reproduction | regeneration apparatus 2, Liquid preparation tank 3, Recovery line 4, Supply line 5, Rotational viscometer 6, Refractometer 7, Thermometer 8, Liquid rotation mechanism 9, Resist

Claims (4)

A process for estimating the viscosity and solid content concentration of the collected used resist,
A step of diluting the viscosity of the resist to a predetermined viscosity set higher than a target viscosity by adding a solvent ;
Adding water until the solid content concentration of the diluted resist reaches a predetermined value;
And a step of adding a solvent until the diluted resist has a target viscosity and solid content concentration while performing refractive index measurement and viscosity measurement, and a resist adjustment method. A process of estimating the viscosity and solid content concentration of the unused resist,
A step of diluting the viscosity of the resist to a predetermined viscosity set higher than a target viscosity by adding a solvent ;
Adding water until the solid content concentration of the diluted resist reaches a predetermined value;
And a step of adding a solvent until the diluted resist has a target viscosity and solid content concentration while performing refractive index measurement and viscosity measurement, and a resist adjustment method. The solid content of the resist, the resist according to claim 1 or claim 2, wherein the estimating the value of the refractive index on the basis of a calibration curve showing the relationship between the refractive index and the solid concentration that is obtained in advance Adjustment method. A resist adjusting apparatus comprising means for performing the process according to claim 1 .

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