JP2011165691A - Reduced pressure drying method and reduced pressure drying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reduced pressure drying device, which performs drying processing on a coating film formed on a substrate to be processed, reduces within-wafer nonuniformity of the coating film after the drying processing, and improves uniformity of the remaining film thickness and line width of the coating film in a wiring pattern forming process. <P>SOLUTION: A process, in which the substrate G having the coating film formed thereon is put in a chamber 2 and a pressure-reduced environment is created in the chamber, includes: a step of reducing the pressure in the chamber at a first pressure reducing speed v1 to a first pressure value P1 which is higher than vapor pressure Pe of a solvent and at which at least the solvent never vaporizes in a bumping state; and a step of slowly reducing the pressure from the first pressure value to at least the vapor pressure of the solvent at a second pressure reducing speed v2 lower than the first pressure reducing speed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reduced-pressure drying method and a reduced-pressure drying apparatus that apply a drying process to a coating film on a substrate by placing the substrate to be processed coated with a coating solution in a reduced-pressure environment.

For example, in manufacturing an FPD (flat panel display), a circuit pattern is formed by a so-called photolithography process.
Specifically, the photolithography process is performed as follows.
First, after forming a predetermined film on a substrate to be processed such as a glass substrate, a photoresist (hereinafter referred to as a resist) as a coating solution is applied to form a resist film. Then, the resist film is exposed corresponding to the circuit pattern and developed.

  In such a photolithography process, as shown in FIG. 8A, the resist pattern R has different film thicknesses (thick film portion R1 and thin film portion R2), and this is used to perform multiple etchings. By performing the treatment, the number of photomasks and the number of steps can be reduced. In addition, such a resist pattern R can be obtained by a half (halftone) exposure process using a halftone mask having a portion with different light transmittance.

A circuit pattern forming process using the resist pattern R to which the half exposure is applied will be specifically described with reference to FIGS.
For example, in FIG. 8A, on a glass substrate G, a Si composed of a gate electrode 200, an insulating layer 201, an a-Si layer (non-doped amorphous Si layer) 202a and an n + a-Si layer 202b (phosphorus-doped amorphous Si layer). A layer 202 and a metal layer 203 for forming an electrode are sequentially stacked.
A resist pattern R obtained by the half exposure process and the development process is formed on the metal layer 205.

After the formation of the resist pattern R (thick film portion R1 and thin film portion R2), as shown in FIG. 8B, the metal film is etched (first etching) using the resist pattern R as a mask.
Next, the entire resist pattern R is subjected to ashing (ashing) in plasma. As a result, as shown in FIG. 8C, a resist pattern R3 having a film thickness reduced to about half is obtained.
Then, as shown in FIG. 8D, using this resist pattern R3 as a mask, etching (second etching) is performed on the exposed metal film 203 and Si layer 202, and finally FIG. 8E. As shown in FIG. 4, a circuit pattern is obtained by removing the resist R3.

By the way, in the pre-process of the half exposure process for forming the resist pattern R, after applying the resist solution to the substrate surface, a reduced pressure drying process for drying the applied resist film in a reduced pressure environment is performed.
In this vacuum drying process, the substrate coated with the resist solution is accommodated in the chamber, the inside of the chamber is reduced to the vapor pressure of the solvent in the resist solution, and the solvent in the resist is evaporated for a predetermined time. Thus, a drying process is performed.
A reduced pressure drying apparatus for drying a coating solution such as a resist solution applied to a substrate under reduced pressure is disclosed in Patent Document 1.

JP 2004-47797 A

However, when the pressure in the chamber is reduced to the vapor pressure of the solvent at the start thereof, as in the conventional vacuum drying process, the inventors of the present application remove the solvent from the resist film as shown in the measurement results of FIG. It has been found that it evaporates suddenly (around 25 seconds), which adversely affects the uniformity of the resist film after drying under reduced pressure.
Further, as described above, when the resist pattern R having the thick film portion R1 and the thin film portion R2 is formed by the half exposure process and the ashing process is performed as shown in FIG. It has been found that the resist pattern R3 (FIG. 8C) varies due to the non-uniformity of the resist film.
Specifically, in the substrate surface, a portion where the film thickness and line width of the remaining film pattern are too small as shown in FIG. 10A and a portion where it is too large as shown in FIG. There was a problem.

  The present invention has been made in view of the above-described problems of the prior art, and in a reduced-pressure drying apparatus that performs a drying process on a coating film formed on a substrate to be processed, the in-plane of the coating film after the drying process Provided are a reduced pressure drying method and a reduced pressure drying apparatus capable of improving uniformity and improving uniformity of the remaining film thickness and line width of the coating film in a wiring pattern forming process.

In order to solve the above-described problems, the reduced-pressure drying method according to the present invention includes a substrate to be processed on which a coating film is formed in a reduced-pressure environment to evaporate a solvent in the coating film, thereby drying the coating film. A method of drying under reduced pressure, wherein the substrate on which the coating film is formed is housed in a chamber, and in the step of setting the inside of the chamber to a reduced pressure environment, the pressure in the chamber is reduced at a first reduced pressure rate, A first pressure value that is higher than the vapor pressure of the solvent and at least the solvent does not evaporate suddenly, and from the first pressure value to at least the vapor pressure of the solvent. And a step of gently depressurizing at a second depressurization rate lower than the depressurization rate.
In addition, after the step of setting the pressure in the chamber to the vapor pressure of the solvent, a step of further reducing the pressure at the second pressure reduction rate to a second pressure value lower than the vapor pressure of the solvent is performed. It is desirable.

According to such a method, the pressure in the chamber is higher than the vapor pressure of the solvent, and at least from the point of the first pressure value at which the solvent does not evaporate suddenly, the second speed is gradually lowered. The pressure is reduced at a reduced pressure rate of
By this control, the pressure value in the vicinity of the substrate surface is gradually reduced while maintaining a uniform state in the surface without variation, and reaches the vapor pressure of the solvent.
As a result, sudden evaporation of the solvent from the coating film is suppressed, the solvent can be evaporated at a low speed, and the dry state of the resist can be made uniform.
In addition, since the dried state of the resist becomes uniform, the uniformity of the pattern residual film thickness and the line width in the wiring pattern formation process when, for example, half exposure processing is used can be improved.

In order to solve the above-described problem, the reduced-pressure drying apparatus according to the present invention places a substrate to be processed on which a coating film is formed in a reduced-pressure environment to evaporate a solvent in the coating film, A vacuum drying apparatus that performs a drying process, the chamber accommodating the substrate on which a coating film is formed, an exhaust unit that exhausts the inside of the chamber, an exhaust amount adjusting unit that adjusts an exhaust amount from the chamber, Pressure detecting means for detecting the pressure in the chamber; and control means for controlling an exhaust adjustment amount by the exhaust amount adjusting means based on a detection result of the pressure detecting means. The displacement adjustment means is controlled so that the pressure is reduced at a first pressure reduction rate until the pressure is higher than the vapor pressure of the solvent and at least reaches a first pressure value at which the solvent does not evaporate suddenly. ,in front From the first pressure value to at least the vapor pressure of the solvent, the exhaust amount adjusting means is controlled so that the pressure is gradually reduced at a second pressure reduction speed lower than the first pressure reduction speed. .
The control means controls the displacement adjustment means so that the pressure in the chamber is gradually reduced at the second pressure reduction speed until the pressure in the chamber reaches a second pressure value lower than the vapor pressure of the solvent. It is desirable.

According to such a configuration, the sudden evaporation of the solvent from the coating film is suppressed, the solvent can be evaporated at a low speed, and the dry state of the resist can be made uniform.
In addition, since the dried state of the resist becomes uniform, the uniformity of the pattern residual film thickness and the line width in the wiring pattern formation process when, for example, half exposure processing is used can be improved.

  According to the present invention, in a reduced-pressure drying apparatus that performs a drying process on a coating film formed on a substrate to be processed, the in-plane uniformity of the coating film after the drying process is improved, and the coating film remains in the wiring pattern formation process. A vacuum drying method and a vacuum drying apparatus that can improve the uniformity of the film thickness and the line width can be obtained.

FIG. 1 is a sectional view showing an overall schematic configuration of an embodiment according to the present invention. FIG. 2 is a flowchart showing the operation of the embodiment according to the present invention. FIG. 3 is a graph showing pressure reduction control in the chamber in one embodiment of the present invention. FIG. 4 is a graph showing the pressure change in the chamber in Example 1-4 according to the present invention. FIG. 5 is a graph showing changes in the evaporation rate of the resist solvent in Examples 1-4 according to the present invention. FIG. 6 is a graph showing the pressure change in the chamber in Example 5-7 according to the present invention. FIG. 7 is a graph showing changes in the evaporation rate of the resist solvent in Examples 5-7 according to the present invention. 8A to 8E are cross-sectional views for explaining a series of steps for forming a wiring pattern using a half exposure process. FIG. 9 is a graph showing measurement results when using a conventional vacuum drying method and showing changes in pressure in the chamber and changes in the evaporation rate of the resist solvent. FIGS. 10A and 10B are cross-sectional views for explaining variations in the resist pattern remaining film in the wiring pattern forming process using the half exposure process.

Hereinafter, an embodiment according to a vacuum drying method and a vacuum drying apparatus of the present invention will be described with reference to FIGS. 1 to 3.
As shown in FIG. 1, this reduced pressure drying apparatus 1 includes a chamber 2 for keeping the internal space hermetically sealed. The chamber 2 is provided so as to be movable up and down so as to cover the lower chamber 2a. And an upper chamber 2b.

  The lower chamber 2a is provided with a stage 4 for placing a glass substrate G, which is a substrate to be processed, and this stage 4 is supported by a shaft 6 that can be raised and lowered to facilitate loading and unloading of the substrate. Yes. A plurality of fixing pins 5 for placing the substrate G are provided on the stage 4, and the plurality of fixing pins 5 are distributed on the stage 4. The fixing pin 5 is preferably made of substantially the same material as the substrate G (in this embodiment, glass).

  Further, four exhaust ports 10 (two of which are shown in FIG. 1) are provided at each corner of the lower chamber 2a. An exhaust pipe 11 communicates with each exhaust port 10, and the exhaust pipe 11 is connected to an exhaust pump 17 (exhaust means). That is, the upper chamber 2b is brought into close contact with the lower chamber 2a so that the inside of the chamber 2 is airtight, and exhausted through the exhaust pipe 11 by the exhaust pump 17, so that the inside of the chamber 2 is decompressed to a predetermined vacuum state. It is configured.

A flow rate adjusting valve 15 (exhaust amount adjusting means) and a main valve 16 are provided in the middle of the exhaust pipe 11. The flow rate adjusting valve 15 is controlled by a control unit 20 comprising a computer, and the opening degree of the flow rate adjusting valve 15 is determined according to the opening degree.
Further, the exhaust pipe 11 is provided with a pressure detector 18 (pressure detector) for detecting the pressure in the chamber 2, and the controller 20 controls the flow rate adjusting valve 15 based on the detection result of the pressure detector 18. The valve opening is set.
Further, the control unit 20 stores a predetermined control program in order to perform decompression in the chamber 2 based on constant control, and this control program is executed at the start of the decompression drying process.
Note that this control program performs control so that the pressure in the chamber 2 changes with time as shown in FIG. Further, in the pressure line indicated by the solid line in FIG. 3, the pressure is assumed to change linearly, but the present invention is not limited to this, and control to change in a curve as indicated by a one-dot chain line may be performed.

Subsequently, the reduced-pressure drying process using the control program will be described.
When a resist solution, which is a coating solution, is applied to the surface to be processed of the substrate G in the previous step, the substrate G is loaded into the reduced pressure drying apparatus 1 and placed on the stage 4.
Further, the upper chamber 2b is closed with respect to the lower chamber 2a, and the substrate G is accommodated in the airtight chamber 2 (step S1 in FIG. 2).

When the inside of the chamber 2 is brought into an airtight state, the exhaust pump 17 is driven and the main valve 16 is opened, and the exhaust in the chamber 2 is started from the time t0 in FIG.
Here, first, the control unit 20 adjusts the opening of the flow rate adjusting valve 15 to reduce the pressure in the chamber 2 at the first pressure reducing speed v1 as shown in FIG. A first pressure value P1 (for example, 400 Pa at time t1 in FIG. 3) higher than the vapor pressure Pe of the solvent (for example, PGMEA) is set (step S2 in FIG. 2). The first pressure value P1 is higher than the pressure value at which the solvent evaporates suddenly, and the solvent does not evaporate suddenly, for example, when the solvent does not evaporate at all or when it evaporates somewhat. The pressure value includes (for example, the case of the evaporation rate in the vicinity of 30 sec in FIG. 5). Moreover, the vapor pressure of the solvent here refers to the value of the vapor pressure in a reduced pressure environment.

  When the pressure in the chamber 2 reaches the first pressure value P1, the control unit 20 adjusts the opening degree of the flow rate adjustment valve 15 in the closing direction and reduces the exhaust amount, thereby reducing the first depressurization speed v1. The pressure is gradually reduced at the slower second pressure reduction speed v2 (step S3 in FIG. 2).

The gentle pressure reduction control at the second pressure reduction speed v2 is performed from the time point t1 of the first pressure value P1 to the time point t3 of the second pressure value P2 (for example, 250 Pa) as shown in FIG.
The second pressure value P2 is lower than the vapor pressure Pe of the solvent of the resist, and when the pressure is gradually reduced by the second pressure reduction speed v2, the evaporation of the solvent in the resist is completed. The pressure value at the time point t3. Said 1st pressure value P1 and 2nd pressure value P2 are preset according to various conditions, such as a kind of solvent.

Here, while the pressure in the chamber 2 is reduced from the first pressure value P1 to the second pressure value P2, the controller 20 reduces the pressure reduction speed in the chamber 2 based on the detection result of the pressure detector 18. Is monitored in the vicinity of the second deceleration speed v2 (within a predetermined range) (step S4 in FIG. 2).
When the pressure reduction speed in the chamber 2 is smaller than the predetermined range (step S5 in FIG. 2), the opening degree of the flow rate adjustment valve 15 is increased so that the exhaust flow rate increases (step S6 in FIG. 2). On the other hand, when the pressure reduction speed in the chamber 2 is larger than the predetermined range (step S5 in FIG. 2), the opening degree of the flow rate adjusting valve 15 is decreased so as to reduce the exhaust flow rate (step S7 in FIG. 2).

Also, as shown in FIG. 3, at time t2 during which the pressure in the chamber 2 is gradually reduced from the first pressure value P1 to the second pressure value P2, the pressure in the chamber 2 is the vapor pressure of the solvent. Reach Pe.
For this reason, the evaporation of the solvent starts at a low speed (without bumping) slightly before the time point t2 when the pressure in the chamber 2 gradually reaches the vapor pressure Pe, and further until the second pressure P2 is reached. The evaporation of the solvent proceeds at a stable evaporation rate over time.

  When the pressure in the chamber 2 is reduced to the second pressure value P2 (step S8 in FIG. 2), the evaporation of the solvent in the resist is substantially completed, and the control unit 20 stops driving the exhaust pump 17, The reduced-pressure drying process is terminated (step S9 in FIG. 2).

As described above, according to the embodiment of the present invention, the pressure in the chamber 2 is higher than the vapor pressure of the resist solvent, and at least the first pressure value P1 at which the solvent does not evaporate suddenly. From time t1, the pressure is reduced at a slower pressure reduction speed v2.
By this control, the pressure in the vicinity of the substrate surface is gradually reduced while maintaining a uniform state in the surface without variation, and reaches the vapor pressure of the solvent.
As a result, sudden evaporation of the solvent from the resist film is suppressed, the solvent can be evaporated at a low speed, and the dry state of the resist can be made uniform.
Further, since the dried state of the resist becomes uniform, it is possible to improve the uniformity of the remaining film thickness and line width of the resist pattern in the wiring pattern forming process when, for example, half exposure processing is used.

In the embodiment described above, the flow rate adjusting valve 15 is provided as the exhaust gas amount adjusting means in the vacuum drying apparatus 1 and the exhaust amount from the chamber 2 is controlled by adjusting the opening degree. The invention is not limited to the configuration.
For example, instead of the flow rate adjustment valve 15, an air introduction means (not shown) for flowing air into the exhaust pipe 11 may be provided, and the exhaust amount may be controlled by adjusting the air introduction amount.

Further, as described with reference to FIG. 3, in the pressure control, the first pressure value P1 and the second pressure value P2 are set, and the pressure reduction speed until the pressure values are reached is controlled. However, the pressure reduction rate may be controlled more finely by increasing the set number of pressure values.
For example, as shown in FIG. 3, a third pressure value P3 and a fourth pressure value P4 are further added in the vicinity of the first pressure value P1, and the pressure reduction control until reaching the first pressure value P1 is further performed. You can go finely. Further, for example, a fifth atmospheric pressure value P5 and a sixth atmospheric pressure value P6 are provided between the first atmospheric pressure value P1 and the second atmospheric pressure value P2, and the decompression control near the vapor pressure Pe is performed more finely. Also good.

  In the above embodiment, the substrate G is placed on the stage 4 in the chamber 2. However, the present invention is not limited to this configuration. For example, a support pin or a transport roller (roller) is used. The structure mounted on top may be sufficient.

Next, the coating film forming direction and the coating film forming apparatus according to the present invention will be further described based on examples.
[Example 1-4]
In Example 1-4, the resist-coated glass substrate is housed in an airtight chamber, and the pressure is reduced to a pressure value (400 Pa) corresponding to the first pressure value P1 in the above embodiment, and a predetermined time is taken. The pressure was reduced to a predetermined pressure value corresponding to the second pressure value P2. Then, it was verified how the evaporation rate of the solvent changed while the pressure was reduced from 400 Pa to the second pressure value P2.
In addition, AZ-SR210 (AZ company) was used for the resist, PGMEA was used for the solvent, and the coating thickness of the resist film was 1.5 μm.
The pressure value corresponding to the second pressure value P2 was 250 Pa in Example 1, 200 Pa in Example 2, 150 Pa in Example 3, and 100 Pa in Example 4.

FIG. 4 shows the pressure change in the chamber in each of Examples 1-4. FIG. 5 shows the change in the evaporation rate of the resist solvent at that time.
From FIG. 5, it was confirmed that Example 1 (400 Pa → 250 Pa), which has the slowest pressure reduction rate, had the smallest change in the evaporation rate of the solvent and was preferable because no sudden evaporation occurred.

[Example 5-7]
In Example 5-7, the pressure value corresponding to the first pressure value P1 in the embodiment is set to 400 Pa, the predetermined pressure value corresponding to the second pressure value P2 is set to 250 Pa, and the pressure is reduced from 400 Pa to 250 Pa. It was verified how the evaporation rate of the solvent changed with the time of the above.
The resist, solvent, and coating thickness were the same as those in Example 1-4.
The time until the pressure was reduced from 400 Pa to 250 Pa was set to 35 sec in Example 5, 25 sec in Example 6, and 15 sec in Example 7.

FIG. 6 shows the pressure change in the chamber in each Example 5-7. FIG. 7 shows the change in the evaporation rate of the resist solvent at that time.
From FIG. 7, it was confirmed that in Example 5 where the pressure reduction rate was slow by taking the longest time, the change in the evaporation rate of the solvent was the smallest and no sudden evaporation occurred, which was preferable.
From the results of Examples 1-7 above, the solvent from the resist film is gradually reduced over time from the first pressure value P1 at which the solvent of the resist solution does not evaporate suddenly. As a result, it was confirmed that the solvent could be evaporated at a low speed.

[Example 8]
In Example 8, the pressure value corresponding to the first pressure value P1 in the embodiment was set to 400 Pa, the predetermined pressure value corresponding to the second pressure value P2 was set to 250 Pa, and the pressure was reduced from 400 Pa to 250 Pa.
Using the resulting resist film, half exposure processing is performed, and the pattern line width and remaining film thickness of the obtained resist pattern are measured at 25 points in the substrate surface, and the fluctuation width (variation) is determined. Asked. Further, at each measurement point, the taper angle (inclination angle with respect to the substrate surface: θ angle shown in FIG. 8C) of the resist pattern cross section was measured, and the average value thereof was obtained.

Further, as Comparative Example 1, a conventional reduced-pressure drying method, that is, a substrate subjected to a drying process by rapidly reducing the inside of the chamber to the vapor pressure of the resist solvent and maintaining the pressure is the same as in Example 8. The fluctuation range and the taper angle were obtained.
In Example 8 and Comparative Example 1, AZ-SR210 was used as the resist, PGMEA was used as the solvent, and the coating thickness of the resist film was 2.2 μm.
The results of Example 8 and Comparative Example 1 are shown in Table 1.

As shown in Table 1, according to Example 8 to which the reduced-pressure drying method according to the present invention was applied, both the remaining film thickness and the line width of the resist pattern varied (variation) than the result of Comparative Example 1 to which the conventional method was applied. It was confirmed that the uniformity in the substrate surface was improved as compared with the prior art.
Further, the taper angle in Example 8 is smaller than that in Comparative Example 1. From this verification result, the taper angle of the resist pattern is controlled by controlling the slope (evaporation rate) of the first pressure value P1 to the vapor pressure Pe. It was confirmed that it can be controlled arbitrarily.

DESCRIPTION OF SYMBOLS 1 Vacuum drying apparatus 2 Chamber 2a Lower chamber 2b Upper chamber 4 Stage 5 Fixing pin 6 Lifting shaft 10 Exhaust port 11 Exhaust pipe 15 Flow rate adjusting valve (exhaust amount adjusting means)
16 Main valve 17 Exhaust pump (exhaust means)
20 Control unit G Glass substrate (substrate to be processed)
P1 First pressure value P2 Second pressure value Pe Vapor pressure of solvent v1 First decompression speed v2 Second decompression speed

Claims (4)

A reduced-pressure drying method in which a substrate to be processed on which a coating film is formed is placed under a reduced pressure environment to evaporate a solvent in the coating film and to perform a drying process on the coating film,
In the step of accommodating the substrate on which the coating film is formed in a chamber and setting the inside of the chamber to a reduced pressure environment,
Depressurizing the pressure in the chamber at a first depressurization rate to a pressure value higher than the vapor pressure of the solvent and at least preventing the solvent from evaporating suddenly;
And a step of gradually reducing the pressure from the first pressure value to at least the vapor pressure of the solvent at a second pressure reduction rate lower than the first pressure reduction rate. After the step of setting the pressure in the chamber to the vapor pressure of the solvent,
2. The method of forming a coating film according to claim 1, further comprising the step of reducing the pressure at the second pressure reduction rate to obtain a second pressure value lower than the vapor pressure of the solvent. A reduced-pressure drying apparatus that places a substrate to be processed on which a coating film is formed in a reduced-pressure environment to evaporate a solvent in the coating film and performs a drying process on the coating film,
A chamber containing the substrate on which the coating film is formed, an exhaust means for exhausting the interior of the chamber, an exhaust amount adjusting means for adjusting the exhaust amount from the chamber, and a pressure detecting means for detecting the pressure in the chamber And control means for controlling the exhaust adjustment amount by the exhaust amount adjustment means based on the detection result of the pressure detection means,
The control means includes
The displacement adjustment is performed so that the pressure in the chamber is higher than the vapor pressure of the solvent and at least a first pressure value at which the solvent does not suddenly evaporate is reduced at a first pressure reduction rate. Control means,
From the first pressure value to at least the vapor pressure of the solvent, the exhaust amount adjusting means is controlled so as to gradually reduce the pressure at a second pressure reduction speed lower than the first pressure reduction speed. A vacuum drying device. The control means includes
The exhaust amount adjusting means is controlled so that the pressure in the chamber is gradually reduced at the second pressure reduction rate until the pressure in the chamber reaches a second pressure value lower than the vapor pressure of the solvent. The vacuum drying apparatus described in 3.

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