JPS6381923A - Light-sensitive polyimide resin processing method and device therefor - Google Patents

Abstract

PURPOSE:To prevent resin from being peeled and to improve cheracteristics of resin in a protective film, by performing the first baking process for smooth heat treatment prior to an exposure processing and performing the second baking process for heat treatment after the exposure process. CONSTITUTION:Respective processes of I. coating, II. exposure, V. developing, and IV. curing are performed by the conventional methods. II. Wafers 21 coated with sensitive polyimide resin films 22 in the first baking process are held in plural numbers by a jig 4. This jig 4 is suspended on a prescribed position in a processing chamber 3 and processed under the following processing conditions; a pressure condition: pressure is controlled in the range of about 500 Torr+ or - 50 Torr under a nitrogen purge, and a temperature condition: temperature is raised 3 deg.C/min from 40 deg.C to 70 deg.C. A process 2 allows light bridging reaction to advance sufficiently even on a film part large in thickness. IV. After the exposure precessing in the second baking process, the processing conditions are as follows; the pressure condition: 500-600 Torr under the nitrogen purge, the temperature condition: constant at 85+ or -2 deg.C, and a processing time: about 10 min. This processing allows the heat bridging reaction to advance on the sensitized part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to photosensitive polyimide resin processing technology, in particular, to baking and drying processing technologies. The present invention relates to a technique that is effective when performing lithography processing on polyimide resin.

[Conventional technology]

In the manufacturing process of semiconductor devices, photosensitive polyimide resin is used to form a protective film on a wafer and to punch holes (hereinafter referred to as "holes") in the protective film to expose electrode pads. It is conceivable that the lithography process can be simplified by this.

In this case, it is generally considered that the conventional photoresist processing method can be used as is as a processing method for the photosensitive polyimide resin.

That is, a photosensitive polyimide resin is applied onto a wafer using a spinner, the photosensitive polyimide resin is prebaked at a constant temperature under normal pressure, and then the photosensitive polyimide resin is exposed and developed. This is a method in which the resin is subjected to a boss bake treatment and a curing treatment at high temperatures.

An example of photoresist processing technology is
"Electronic Materials November 1984 Special Edition" published by Kogyo Kaikakai Co., Ltd., November 20, 1984, P67-P71,
There is.

[Problem that the invention seeks to solve]

However, in such a photosensitive polyimide resin processing method, the spinner coating film becomes thicker at the periphery of the wafer due to the high viscosity of the photosensitive polyimide resin solution used as the spinner coating material. The present inventor has clarified that there is a problem in that the crosslinking reaction of the photosensitive polyimide resin becomes insufficient during exposure processing, and as a result, the photosensitive polyimide resin peels off in that area. An object of the present invention is to provide a processing technique that can prevent the peeling phenomenon of photosensitive polyimide resin.

Another object of the present invention is to provide a processing technique that can improve the properties of photosensitive polyimide resin as a protective film.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Failure to solve the problem]

An overview of typical inventions disclosed in this application is as follows.

That is, the photosensitive polyimide resin coated on the substrate is subjected to a gentle heat treatment before being exposed to light.
After baking and exposure, the photosensitive polyimide resin is subjected to a heat treatment to promote a thermal crosslinking reaction, and then subjected to a second bake.

[Effect]

According to the above-described means, the light transmittance and sensitivity of the photosensitive polyimide resin are improved since the photosensitive polyimide resin is heated slowly in the first baking process. As a result, in the exposure treatment, even if the coating film is relatively thick, the photocrosslinking reaction progresses well to the lower layer portion.

On the other hand, since the solvent is effectively volatilized by gentle heat treatment, adhesion to the photomask is prevented even if the photosensitive polyimide resin film is brought into close contact with the photomask during the exposure process.

Then, since the thermal crosslinking reaction is further progressed by the second baking treatment after the exposure treatment, the insoluble strength of the remaining portion of the photosensitive polyimide resin in the developing solution is increased. As a result, upon development, the remaining portion of the photosensitive polyimide resin remains properly adhered without peeling.

〔Example〕

Fig. 1 is a process diagram showing a photosensitive polyimide resin processing method which is an embodiment of the present invention, and Fig. 2 is a longitudinal section showing a photosensitive polyimide resin processing apparatus which is an embodiment of the present invention used in the method. FIG. 3 is an enlarged vertical sectional view showing the coating process, and FIGS. 4, 5, and 6 are diagrams for explaining the operation thereof.

In this embodiment, a heat treatment apparatus 1 used in the photosensitive polyimide resin processing method is equipped with a process tube 2 made of quartz glass and formed into a substantially cylindrical shape. It essentially forms a processing chamber 3 capable of accommodating a jig 4 in which wafers are aligned parallel to each other and held horizontally. The process tube 2 is arranged so that the centering direction is vertical, and a door 6 is placed over a furnace port 5 opened at its upper end so that the furnace port 5 can be opened and closed. An exhaust lower is provided at the lower end of the process tube 2, and an exhaust device 8 including a vacuum pump or the like is connected to the exhaust lower. A drive device 9 such as a motor in the exhaust device 8 is configured to be controlled by a controller 1O consisting of a combinator or the like, and the controller 10 includes a pressure sensor 11 that detects the internal pressure of the processing chamber 3. is connected so that it can be input at any time. Further, a purge gas supply pipe 12 is inserted into the processing chamber 3 through the door 6, and this gas supply pipe 12 is connected to a supply source (not shown) that supplies nitrogen gas as a purge gas. .

A shield box 13 is installed outside the process tube 2 to surround it, and this shield box 13 is configured to shield electromagnetism. The shield box 13 is equipped with a magnetron 14, and the magnetron 14 is configured to be able to supply microwaves into the processing N3 via a waveguide 15. The magnetron 14 is configured to have its power controlled by the controller 10.
0 is connected to a temperature sensor 16 for detecting the temperature of the processing chamber 3 so as to input the detected temperature at any time.

Next, an example of the photosensitive polyimide resin processing method according to the present invention will be described in the first example. The case of forming a protective film with holes on a wafer will be explained along the process diagram shown in FIG.

■, Coating process.

First, in a coating process, a photosensitive polyimide resin is coated with a spinner onto a wafer on which integrated circuits have been fabricated and electrical wiring has been formed.

That is, as shown in FIG. 3, a wafer 21 as an object to be coated is placed on a spin head 1f and held by means such as vacuum suction, and the wafer is rotated. When this rotation becomes stable, the coating material 19 is dropped onto the center of the wafer from the dropping tube 18, and the coating material 19 is dispersed in the radial direction by centrifugal force and is coated on the surface of the wafer. A film 22 will be formed.

Here, a photosensitive polyimide resin solution is used as the coating material 19, and this solution is applied to a polyimide resin such as polyimide iso indolo quina zolinedione (PIQ) and a photosensitive polyimide resin such as amine, diazide, azide, bisazide, etc. normal methyl 2-pyrrolidone (NMP)
It is a solution obtained using a solvent for polyimide resin such as 20 to 40 voids, and has a relatively high viscosity for spinner coating.

By the way, when a photosensitive polyimide resin solution is used as a coating material to form a protective film ff1ff51 with holes on a wafer, as shown in FIG.
Y applied on top! 22 becomes thicker at its periphery. This is because it is necessary to set the viscosity of the photosensitive polyimide resin solution as a coating material to be relatively high for spinner coating in order to obtain the desired photosensitive performance and film thickness as a protective film.

For example, when a protective film with an average thickness of 7 um is coated on a wafer using a spinner using a photosensitive polyimide resin solution with 20 to 40 voids, the ratio of the film thickness B at the periphery to the film thickness A at the center is B/ A was 1.5-2°0.

In this way, the film thickness at the periphery remained large and no measures were taken to protect the photosensitive polyimide resin film on the wafer.
The present inventors have revealed that when a general lithography process is performed, crosslinking becomes insufficient in the peripheral area where the film thickness is large, resulting in a problem in that peeling occurs in that area.

Therefore, in this embodiment, as shown in FIG. 1, by setting a first baking process and a second baking process before and after the exposure process, the photosensitive polyimide resin y! The occurrence of peeling around the periphery of 22 is prevented. The first baking step and the second baking step are each carried out using the photosensitive polyimide resin processing apparatus 1 having the above configuration. However, there is no need to use the same equipment.

■, First baking step.

Here, an example of the first baking step will be described using the photosensitive polyimide resin processing apparatus. The processing conditions in this first baking step are as follows.

Pressure conditions: Reduce the pressure to about 500 Torr under a nitrogen gas barge. It is desirable to control within the range of ±50 Torr.

Temperature conditions: Raise the temperature from 40°C to 70°C at a rate of 3°C per minute.

A plurality of wafers 21 coated with the photosensitive polyimide resin film 22 in the coating process using a spinner are held in a jig 4 in parallel to each other in a line. This jig 4 is housed in the processing chamber 3 so as to be suspended from the furnace opening 5 of the process tube 2, and is suspended at a predetermined position.

When the furnace port 5 is closed by the door 6, nitrogen gas is supplied to the processing chamber 3 from the purge gas supply pipe 12, and the processing chamber 3 is exhausted by the exhaust device 8 through the exhaust lower.
The pressure is reduced to a predetermined pressure.

At this time, the internal pressure of the processing chamber 3 is detected by the pressure sensor 11 at any time and inputted to the controller IO.

Then, the controller 10 performs feedback control of the drive device 9 in the exhaust device 8 based on this detection result, thereby stably maintaining the internal pressure of the processing chamber 3 at a predetermined pressure value.

When the internal pressure of the processing chamber 3 has stabilized to a predetermined pressure, the controller 10 operates the magnetron 14 to supply microwaves to the processing chamber 3 as appropriate while gradually increasing the power, so that the jig can be heated under the above-mentioned temperature conditions. The group of 21 wafers held at 4 is heated. At this time, the temperature inside the processing chamber 3 is detected by the temperature sensor 16 at any time and inputted to the controller 10. And controller 10
The temperature conditions are appropriately created by feedback-controlling the magnetron 14 based on this detection result.

When the first baking process under the above conditions is completed, the door 6 is opened, the jig 4 is lifted up, and the group of wafers 21 is carried out from the processing chamber 3. Thereafter, the group of wafers 21 that have undergone this first baking process are sent to an exposure process.

According to the processing conditions, in the first baking step according to this example, the heat treatment is performed at a low temperature of 40 to 70 ° C., so the heat treatment is performed at a higher temperature (for example, 85 ° C.). Light transmittance and sensitivity are improved compared to the conventional case. As the light transmittance improves, the exposure light reaches deeper into the photosensitive polyimide resin film, so that the photocrosslinking reaction progresses even in the thicker parts of the film. Furthermore, the better the sensitivity is, the more the photocrosslinking reaction is promoted. As a result, the photocrosslinking reaction will proceed sufficiently even in the peripheral portion of the photosensitive polyimide resin film, which has become thicker due to spinner coating.

FIGS. 4 and 5 are diagrams comparing the light transmittance depending on the heating temperature, with the vertical axis representing the light transmittance (percentage) and the horizontal axis representing the wavelength (nm) of the test light.

FIG. 4 shows that light with a shorter wavelength can be transmitted when the baking temperature is 60° C. than when the baking temperature is 85° C., and it is understood that this shows that the light transmittance is good.

According to FIG. 5, it is understood that when the film thickness of the photosensitive polyimide resin is thin, the baking temperature does not have much effect on the light transmittance.

Table 1 is for comparing sensitivity depending on heating temperature, and Table 0 shows the results of analyzing photosensitive polyimide resin films peeled from heat-treated wafers by gas chromatography using a thermal decomposition furnace. The numbers in the middle indicate the output of gas chromatography, and the larger the number, the better.
The quantity is large.

According to this Table 1, when the baking temperature is 60°C, the
It is understood that the sensitivity is good because the amount of amine as a photosensitizer is large compared to 5°C.

Table 1 By the way, when the heat treatment temperature is lowered, the amount of solvent volatilization is suppressed. If a photomask is brought into close contact with a photosensitive polyimide resin film in which the solvent has not volatilized sufficiently during the exposure process, the photosensitive polyimide resin film will adhere to the photomask, resulting in peeling of the photosensitive polyimide resin film and contamination of the photomask. The inventor has revealed that there is a point.

However, in this example, the first baking treatment is carried out under reduced pressure and by heating at an elevated temperature, so the solvent in the photosensitive polyimide resin film is sufficiently volatilized and dried. Peeling of the photosensitive polyimide resin film and contamination of the photomask during the exposure process can be prevented. In other words, under reduced pressure, the solvent easily evaporates from the photosensitive polyimide resin film even at low temperatures, and by heating at elevated temperatures, the photosensitive polyimide resin film dries sequentially from the surface layer to the deep layer. Therefore, the solvent evaporates uniformly and effectively.

■、Exposure process.

In the exposure step, a photomask is brought into close contact with the photosensitive polyimide resin film on the wafer that has been subjected to the first baking process, and the pattern of the photomask is transferred onto the photosensitive polyimide resin film using exposure light such as ultraviolet rays. At this time,
As mentioned above, since the photosensitive polyimide resin film is sufficiently dried, it will not adhere to the photomask.

In this case, the portion of the photosensitive polyimide resin film that is exposed to light transmitted through the photomask becomes insoluble in the developing solution due to a photocrosslinking reaction (corresponding to a so-called negative photoresist). The portions that are not exposed to light because they are blocked by the photomask maintain their solubility in the developer, and these portions form the holes after development.

At this time, as described above, since the light transmittance and sensitivity of the photosensitive polyimide resin film has been increased by the treatment in the first baking step, the photocrosslinking reaction can proceed sufficiently even in the peripheral portion where the film is thick.

The wafer subjected to exposure processing in this manner is sent to a second baking process.

■Second baking step.

The second baking step is also performed using the photosensitive polyimide resin processing apparatus 1.
The process is carried out using the process, but since it is similar to the first baking process, its explanation will be omitted. The processing conditions in this second baking step are as follows.

Pressure conditions: 500-600 Torr under nitrogen gas barge
r.

Temperature conditions: constant at 85±2℃.

Processing time: about 10 minutes.

In this second baking step, by being heat-treated under predetermined conditions, the photosensitive polyimide resin film undergoes a thermal cross-linking reaction in the portion exposed to light in the exposure step, further increasing its insolubility in the developer, and First, the adhesion with Eva can be improved. At this time, it is important to be careful not to melt the photosensitive polyimide resin film by heating.

The wafer that has been subjected to the second baking process is sent to a developing process.

■, Development process.

In the development process, the non-photosensitive portions of the photosensitive polyimide resin film on the wafer are dissolved in the developer and are therefore removed from the wafer. As a result, a hole for exposing the electrode band is formed on the wafer by a development removal section provided in the photosensitive polyimide resin film itself serving as a protective film.

The developed wafer is sent to a curing process.

■, about half cured.

The curing process is also carried out using the photosensitive polyimide resin processing apparatus 1, but since it is similar to the first baking process, its explanation will be omitted. The processing conditions in this curing step are as follows.

Processing pressure 1×100-2 Torr Processing temperature: Raise the temperature from 100°C to 350°C at a rate of 10°C per minute.

By the way, if the curing treatment is carried out under normal pressure and constant high temperature after the development treatment, there is a problem that the photosensitive polyimide resin loses its transparency and the color tone becomes black.
revealed by the inventor. This is considered to be because the solvent and water are in the form of bubbles inside the photosensitive polyimide resin film.

However, in this example, since the curing treatment is carried out under reduced pressure and heating, the solvent and moisture can be effectively and slowly dissipated to the outside, and bubbles etc. are not generated inside the photosensitive polyimide. The resin film exhibits the desired transparency, that is, good light transmittance. Furthermore, since the photosensitive polyimide resin film is extremely dense, its heat resistance is improved.

FIG. 6 is a diagram comparing the light transmittance by curing treatments under normal pressure and reduced pressure, with the vertical axis representing the light transmittance (percentage) and the horizontal axis representing the wavelength of the test light.

According to FIG. 6, it is shown that light with a shorter wavelength can be transmitted under reduced pressure than under normal pressure, and it is understood that the light transmittance is better.

By going through each of the above steps, a protective film with holes made of photosensitive polyimide resin is formed on the wafer, and a protective film with good heat resistance and transparency can be obtained.

According to the embodiment described above, the following effects can be obtained.

11) By increasing the light transmittance and sensitivity of the photosensitive polyimide resin by heat treatment in the first baking step,
In the exposure process, it is possible to accelerate the photocrosslinking reaction in the thick part of the photosensitive polyimide resin.
Even if the photosensitive polyimide resin film becomes thicker in the peripheral area due to spinner coating, peeling of the area can be prevented.

(2) By heat treatment at elevated temperature under reduced pressure, the solvent in the photosensitive polyimide resin can be sufficiently volatilized even with low temperature heat treatment, so the photosensitive polyimide resin is tightly attached to the photomask during the exposure process. It is possible to prevent the photosensitive polyimide resin from peeling off or adhering to the photomask when the photosensitive polyimide resin is used.

(3) After the exposure process, by promoting the thermal crosslinking reaction of the photosensitive polyimide resin through a second baking process, even the parts of the photosensitive polyimide resin that have become thicker due to spinner coating will have sufficient insolubility in the developer. Since this can be ensured, peeling at the location can be prevented.

(4) By applying high-temperature heat treatment under reduced pressure to the photosensitive polyimide resin in the curing process after development processing, the solvent and water can be released to the outside of the photosensitive polyimide resin slowly and effectively. The transparency of the photosensitive polyimide resin can be increased by preventing air bubbles from being generated inside the polyimide resin, and the heat resistance can also be improved by increasing the density of the photosensitive polyimide resin.

(5) By providing the processing chamber with an exhaust means and a heating means configured to be able to adjust the heating temperature, temperature raising heat treatment under reduced pressure can be realized. The effect of 4) can be reasonably obtained.

(6) By realizing the formation of a protective film with holes using a photosensitive polyimide resin film, the lithography process can be completed in the process of forming a protective film using a photosensitive polyimide resin.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above-mentioned Examples, and can be modified in various ways without getting across the gist of the invention. Nor.

For example, the processing conditions in the first baking step, second baking step, and curing step are not limited to the conditions in the above examples, but it is desirable to find optimal values based on the composition of the photosensitive polyimide resin, viscosity, film thickness of the coating film, etc. .

Further, the first baking step, the second baking step, and the curing step are not limited to being carried out using the photosensitive polyimide resin processing apparatus having the above configuration, but may be carried out using another processing apparatus.

In the above explanation, we have mainly explained the case where the invention made by the present inventor is applied to the field of application which is the background of the invention, which is the technology of forming an R1 film with holes on a wafer using photosensitive polyimide resin. The invention is not limited thereto, and can also be applied to cases where an insulating film with terminals is formed on a printed circuit board using photosensitive polyimide resin.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

The light transmittance and sensitivity of the photosensitive polyimide resin can be increased by providing a first baking step in which a gentle heat treatment is performed before the exposure step. It can accelerate the reaction. Further, by providing a second baking step in which heat treatment is performed after the exposure treatment, it is possible to promote the thermal crosslinking reaction of the photosensitive polyimide resin, thereby increasing the sensitivity of the part to the developer.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing a photosensitive polyimide resin processing method which is an embodiment of the present invention, and Fig. 2 is a longitudinal section showing a photosensitive polyimide resin processing apparatus which is an embodiment of the present invention used in the method. FIG. 3 is an enlarged vertical sectional view showing the coating process, and FIGS. 4, 5, and 6 are diagrams for explaining the operation. DESCRIPTION OF SYMBOLS 1... Photosensitive polyimide resin processing device, 2... Process tube, 3... Processing chamber, 4... Jig, 5...
・Furnace mouth, 6... Door, 7... Exhaust port, 8... Exhaust device, 9... Drive device, 10... Controller, 1
1... Pressure sensor, 12... Purge gas supply pipe, 1
3... Shield box, 14... Magnetron,
15... Waveguide, 16... Temperature sensor, 17...
Spin head, 18...Dripping tube, 19...Applying material (
photosensitive polyimide resin solution), 21...tsueva, 22
...Photosensitive polyimide resin film. Figure 3 Figure 4

Claims (1)

[Claims] 1. A first baking step in which the photosensitive polyimide resin coated on the substrate is gently heat-treated, and after the exposure treatment, the photosensitive polyimide resin is heat-treated so that the thermal crosslinking reaction proceeds. A method for processing a photosensitive polyimide resin, comprising: a second baking step. 2. The photosensitive polyimide resin processing method according to claim 1, wherein the first baking step is set to perform heat treatment while increasing the temperature under reduced pressure. 3. The first baking step is performed under nitrogen gas purge for about 50 minutes.
The photosensitive polyimide resin treatment according to claim 2, characterized in that the heat treatment is performed by reducing the pressure to 00 Torr and increasing the temperature from 40° C. to 70° C. at a rate of 3° C. per minute. Method. 4. The photosensitive polyimide resin processing method according to claim 1, wherein the second baking step is set to perform heat treatment at a constant temperature under reduced pressure. 5. The second baking step is performed under nitrogen gas purge for about 5 minutes.
5. The photosensitive polyimide resin processing method according to claim 4, wherein the heat treatment is performed at a temperature of about 85° C. under reduced pressure of 00 to 600 Torr. 6. A first baking step in which the photosensitive polyimide resin coated on the substrate is gently heat-treated; and after the exposure treatment, a second baking step in which the photosensitive polyimide resin is heat-treated so that the thermal crosslinking reaction proceeds; 1. A method for processing a photosensitive polyimide resin, comprising a curing step of heat-treating the photosensitive polyimide resin at a relatively high temperature under reduced pressure after the development process. 7. Claims characterized in that the curing process is set to heat treatment at a rate of 10°C per minute from 100°C to 350°C while reducing the pressure to 1 x 100^-^2 Torr. 6. The photosensitive polyimide resin processing method according to item 6. 8. A processing chamber capable of accommodating a substrate coated with a photosensitive polyimide resin, an exhaust means for evacuating the processing chamber, and a heating means configured to adjust the heating temperature. Photosensitive polyimide resin device. 9. The photosensitive polyimide resin device according to claim 8, wherein the heating means is constituted by a magnetron electromagnetically connected to the processing chamber.