JPS6021522A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To form efficiently and quickly a high precision resist pattern by executing at least either one of the the baking and cooling of resist at a pressure which is lower than the atmospheric pressure. CONSTITUTION:A resist film is applied on a substrate to be processed (step 1) and such substrate with resist film is housed in a reduced pressure vessel at a pressure lower than the atmospheric pressure, it is then subjected to the resist baking for the specified period at the specified temperature Tb (step 2). Next, the resist film is uniformly cooled for the entire part until the final cooling temperature Tc while the cooling period or cooling speed are controlled in a reduced pressure vessel (step 3). Thereafter, this resist is irradiated selectively with an electromagnetic wave in the specified wavelength or particle beam having the specified energy (step 4). Such irradiated area is developed and rinsed (step 5). Thereby, a resist pattern can be formed. Where the baking is carried out under a reduced pressure condition, vaporization of resist solvent can be accelerated and the time required for resist baking can be curtailed and where the resist is cooled under the reduced pressure condition, dispersion of cooling speed resulting from natural circulation of ambient can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of forming highly accurate resist lines.

[Technical background of the invention and its problems]

As the degree of integration of flat conductor elements increases, including super I and 8 I, techniques for forming fine and highly accurate patterns are being developed. For this reason, the permissible dimensional accuracy is extremely strict, and in the most advanced fields, 3σ≦0.1 [μm] (
However, a dimensional accuracy of σ (σ indicates variation with respect to the average dimensional value of the wafer) is required. In addition, in order to be used on a mass production line, it is necessary to suppress the dimensional variation between masks or between wafers to 3σ (0.15 Cμm).
On the other hand, in order to increase the effectiveness of mass production, high sensitivity resists are required. However, in general, high-sensitivity resists have poor resolution, making it difficult to obtain the desired P-turn dimensional accuracy; conversely, high-resolution resists have low sensitivity, making it difficult to achieve high throughput on mass production lines. There were problems such as not being able to obtain

FIG. 1 is a flowchart showing a resist layer formation process according to the prior art. First, a resist is applied to a predetermined thickness on a substrate to be processed by a well-known spin coating method. Next, in order to remove the coating solvent and improve the adhesion between the resist and the substrate, the resist is baked (silibake) at a predetermined temperature and degree (T) depending on the resist using an open method or the like. Thereafter, the resist film-coated substrate taken out from the opening is allowed to cool naturally on a support stand in the atmosphere, and is cooled to room temperature over 20 to 30 minutes. For the processed substrate with resist film that has been completely cooled,
Electromagnetic waves in a predetermined wavelength range, such as ultraviolet light, or particle beams with a predetermined energy, such as electron beams, are selectively irradiated with a predetermined dose depending on the type of resist. Thereafter, a desired resist pattern is formed through a development and rinsing process.

By the way, regarding the resist film on the substrate to be processed during the natural cooling described above, the temperature of the entire film surface at a certain point is 4.
When the misfired EllJ was examined using a 11-cell infrared radiation thermometer, the results shown in Figure 2 were obtained. In addition, in this case, prior to natural cooling (the temperature T at the time of cooling is
-16'0 [°C]. In FIG. 2, the temperature is high (cooling is slow) at the center of the resist film-coated substrate 21 (point A), and moves downward (point C) through the center region (point B). As the temperature increases, the temperature becomes lower (cooling speed becomes faster). Note that each curve in the figure is an equicross line. Figure 3 shows A and R in Figure 2.

C shows the temperature change over time at each point,
Curve 3 Z, ,'? 2. and 33 are A- and B, respectively.

This is the cooling characteristic corresponding to point C. The maximum temperature difference between points A and B is about 15 [℃], and the maximum temperature difference between points A and C is 3o
cc: It was about +. These hot water temperature measurements were carried out by attaching a thermocouple to the part to be measured of the resist film.The cause of this temperature distribution (uneven cooling rate) is that the partially damaged substrate is left to cool naturally. Because the board is placed on a support stand, etc., natural convection of the atmosphere due to heat dissipation tends to occur upward along the board surface, and the lower part of the board is likely to lose heat due to the support stand. In addition, the present inventors focused on the relationship between the temperature distribution during cooling of the resist film coated substrate and the dimensional accuracy of the resist pattern after irradiation and development processing, and determined the temperature measurement point A in FIG. ,B,C
When we measured the dimensions of the formation/zooturn in the area,
B to a pattern that should originally have the same size of, for example, 2 [μm]
0.1 [μm) at point C, 0.2 [μm] at point C
It was confirmed that the temperature distribution during cooling of the resist film-coated substrate and the size distribution of the formed resist pattern completely corresponded to each other through the sensitivity distribution of the resist.

Therefore, no! It has been found that in order to obtain highly accurate resist/f and turns with uniform turn dimensions, extremely uniform cooling is essential, which causes temperature distribution within the substrate surface after resist baking.

On the other hand, the inventors focused on the relationship between the cooling rate of the resist after baking and the sensitivity of the resist, and after conducting various experiments and research, they found Although the sensitivity is low, it has been found that when the resist is beta-ized and then rapidly cooled, the sensitivity of the resist increases dramatically. Furthermore, we have also discovered that by controlling the cooling process of the resist film after baking, it is possible to change the sensitivity of the resist to any desired value with good reproducibility. The resolution of the resist that has gone through these processes is the same as the resist itself! We have also confirmed that there is no deterioration in the slightest compared to the turn resolution. Furthermore, since conventional resist baking was performed in the atmosphere, it was found that it took a long time to evaporate the resist solvent, which is the main purpose of baking.

[Purpose of the invention]

An object of the present invention is to provide a resist pattern/forming method that can efficiently and quickly form a highly accurate resist/arm turn, and that can contribute to improving the throughput of forming the arm turn.

-6= [Summary of the Invention] The gist of the present invention is to perform at least one of baking and cooling the resist under a pressure lower than normal pressure (less than 1 atmosphere 9 ).

FIG. 4 shows an outline of the basic process of forming a resist pattern according to the present invention. First, a resist film is applied and formed on a substrate to be processed. Next, this resist film coated substrate was
The resist is stored in a reduced pressure container under a pressure lower than atmospheric pressure, and resist baking is performed at a predetermined temperature T for a predetermined time. Next, the final cooling temperature T is achieved while controlling the cooling time or cooling rate in the vacuum vessel. Uniform cooling is performed over the entire resist film. Thereafter, this resist is selectively irradiated with electromagnetic waves of a predetermined wavelength or particle beams of a predetermined energy, and is developed and rinsed to form a resist pattern.

That is, the present invention applies a resist onto a substrate to be processed,
In a method of forming a resist pattern by baking and cooling the resist, selectively irradiating the resist with electromagnetic waves of a predetermined wavelength or particle beams of a predetermined energy, and performing a development process, the above resist is baked and cooled. This is a method in which at least one of the steps is carried out under a pressure lower than normal pressure.

〔Effect of the invention〕

According to the present invention, by baking the resist under reduced pressure, evaporation of the resist solvent can be promoted,
This can significantly reduce the time required for resist baking. In addition, by cooling the resist under reduced pressure, it is possible to significantly reduce the occurrence of uneven cooling rate due to natural convection of the surrounding air, and thereby it is possible to improve the precision of resists and master turns. Furthermore, by baking and cooling the resist under reduced pressure, dust adhesion to the resist film surface is reduced, and as a result, a desired resist pattern can be obtained with a high yield.

Also, while controlling the cooling time or cooling rate, the temperature can be changed from the bake temperature T to the final cooling temperature T. By uniformly cooling the resist up to this point, the sensitivity of the resist to electromagnetic waves or particle beam irradiation can be greatly increased without deteriorating its resolution. Therefore, even a low-sensitivity resist can be made highly sensitive by the method of the present invention without deteriorating its resolution, and the time for irradiation treatment with electromagnetic waves or particle beams can be shortened.

Moreover, according to the present invention, the resist film after baking is cooled uniformly over the entire film, and the resist film surface is not roughened, so that it can be processed with very little dimensional variation over the entire substrate to be processed. High precision resist lean can be formed.

[Embodiments of the invention]

<Example 1> In this example, a method for forming a resist pattern using a positive electron beam sensitive resist such as poly(2,2,2-t!j fluoroethyl-α-chloroacrylate) will be described. First, the resist described above is applied onto the substrate to be processed 9- by a well-known spin coating method. At this time, the coating film thickness is 0.3 to 1 [μm]
It may be about 0.8 [μm] here.

Although there are many types of substrates to be processed, such as flat conductor wafers and glass substrates, a glass substrate with a metal film was used here. next,
The resist film was baked and cooled using a resist processing apparatus as described below. The baking temperature T may be approximately 140 to 190 (°C), which exceeds the glass transition temperature T, (~133°C) of the above resist, but here it is 180°C.
The temperature was set to 0 [°C]. Further, the pressure surrounding the substrate to be processed with the resist film during baking was approximately 0.1 atm, and resist baking was performed in this state for approximately 10 minutes. Although the baking time can be further shortened, it was set to 10 minutes in this example. Next, cooling was performed from the plate temperature Tb to the final cooling temperature Tc while changing the cooling time (cooling rate). In this example, the temperature Tc was set to room temperature. The cooling time from the baking temperature Tb to the room temperature To is, for example, 030 minutes, 05 minutes,
The cooling process was operated so that the time was 01 minutes, 010 seconds, and 05 seconds. FIG. 5 shows changes in substrate temperature during these cooling steps. In both cooling treatments, the resist film was cooled uniformly over the entire film surface. Note that the pressure surrounding the resist film-coated substrate during cooling was 0.0001 atm. As a result of examining the electron beam sensitivity characteristics of each of the resist samples subjected to these baking and cooling processes, sensitivity curves corresponding to the respective resist samples shown in FIG. 6 were obtained.

The characteristics shown in FIG. 6 are as follows: After irradiating the resist film that has undergone the respective baking and cooling processes with an electron beam at an accelerating voltage of 20 [keV], methyl isobutyl ketone (MIBK) is heated at room temperature.
Isonorovir alcohol (IPA) = 7:1 with 3 developer
This was obtained by developing for 0 minutes and then rinsing with IPA solution for 30 seconds. Resist sensitivity (corresponding to each baking and cooling process with Tc from ■ to ■)
Electronic irradiation dose when the film thickness residual rate is zero) is ■4
10-6(ni/y++" ], ■2 X 10-'
[:φ2], ■9 X 10-' (07m”), ■
5×10-6 [C/crn2], ■3 X 10-'
(C/2m2). In addition, conventional bake (180
℃) → Natural cooling (to room temperature) process, followed by electron beam irradiation, development, and rinsing treatment as above, the sensitivity of the above resist is ~4 x 10-6 [C/cvn"J
It is.

On the other hand, 20' [lc・■
] Using an electron beam lithography system, selective 4-turn irradiation was performed at the irradiation dose corresponding to each of the above cases ① to ②, and B I BK7I PA (7/3) development and TP at room temperature were performed.
A resist pattern was formed by performing A rinsing treatment.

The resolution of these resist patterns was all good. Furthermore, as a result of measuring and evaluating the dimensional accuracy of resist patterns in the line width range of 05 to 2.0 [μm], the resist patterns in either case were all highly accurate and had a dimensional variation error of 3σ (0, 1 (μm).

<Example 2> In this example, polymethyl methacrylate was used as the resist. Other conditions are substantially the same as in Example 1 described above. The bake temperature Tb is 180 [:°C] which exceeds the glass transition temperature Tg of this resist ~110 [°C]
It was set to The pressure around the substrate during resist baking is 0.
The pressure was 3 atm, and the resist bake time was 10 minutes. The pressure around the substrate during cooling of the resist film was approximately 0.0002 atm, and the cooling was performed in the same manner as in Example 1, with cooling times of 030 minutes, 05 minutes, 01 minutes, and 010 minutes to reach ']['b-+T.
I chose 5 seconds. After irradiating these resist samples with an electron beam at an accelerating voltage of 20 (keV), M was applied at room temperature for 13 minutes.
IBK development and IPA rinsing for 30 seconds were performed to examine the sensitivity characteristics of each. As a result, the resist sensitivity corresponding to the cooling process is 9 x 10-' [C/m2
: ], (i) 6.5 X 10-'(C7j'z"
), ■5 X 10-6 (07m”), ■3.5
X 10-'(C/rnZ), ■2.5 X 1 o-
6[:c/crn”).In addition, conventional baking (
When the same irradiation, development, and rinsing effects as above are applied after allowing the resist to cool naturally (to room temperature) (160°C), the sensitivity of the resist is approximately 1×10 −5 [C/rn2].

On the other hand, a 20 (k@y) electron beam lithography system was applied to the entire surface of the resist film-coated substrate (6-inch glass substrate with metal film), which had been subjected to vacuum baking and vacuum cooling in the same manner as in the process described above, except for the peripheral area. Selective master turn irradiation was carried out using the above-mentioned irradiation dose corresponding to each of cases ① to ②, MIBK development at room temperature and IPA Linne treatment were performed to form a resist pattern. The resolution of the resist pattern was good over all the substrates. In addition, as in Example 1, as a result of measuring and evaluating the dimensional accuracy of the resist pattern in the line width range of 0.5 to 2.0 [μm], all of the resist patterns in the range of 0.5 to 2.0 [μm] had high precision in all cases. All in-plane dimensional variation errors were 3σ (0.1 (μm)).

The main focus of the present invention is to control the cooling time from the bake temperature Tb of the resist film to around room temperature (not only to uniformly control the cooling speed button, but also to perform at least one of the baking and cooling under reduced pressure). The reason why the resist baking and cooling process is performed under reduced pressure = 14 - is to suppress dust adhesion to the substrate as much as possible, as well as to prevent rapid evaporation of the resist irradiation during baking and to reduce the pressure during baking and cooling. This is to prevent uneven temperature distribution on the resist film surface caused by thermal convection and to ensure uniform baking and cooling over the entire film surface.

Further, by using the method of the above embodiment, the sensitivity of the resist can be arbitrarily and uniformly set to match the performance of, for example, a resist irradiation (exposure) device. According to the research results of the present inventors, it has been found that the shorter the cooling time from the bake temperature Tb to around room temperature (the higher the cooling rate), the more the sensitivity of the resist improves. On the contrary, it is known that the sensitivity of the resist decreases when the cooling time is increased (the cooling rate is decreased). Therefore, it goes without saying that depending on the situation, the sensitivity of the resist can be set to a desired value by setting a cooling time (cooling rate) different from that of the above embodiment. In addition, in the above embodiment, an example of resist pattern formation regarding two types of resists was described, but the type of resist, the substrate material to which the resist film is attached, the solvent of the resist, the developer, and even the baking temperature, etc. It has been confirmed that the effects of the present invention are not limited to the above-mentioned embodiments, and that the effects of the present invention can be achieved using various known materials, developing solutions, and baking temperatures.

Furthermore, as for the resist exposure method, in addition to the above-mentioned electron beam, electromagnetic waves in a predetermined wavelength range such as light beams, X-rays, and ion beams, or particle beams with a predetermined energy can be used to obtain the effects intended by the present invention.

However, the setting of the ambient pressure surrounding the substrate during baking and cooling is not limited to the values described in the above embodiments. The pressure during baking should be set as low as possible so that the solvent in the resist does not bump or protrude during beta, and the pressure during cooling should be set even lower to reduce thermal convection caused by residual gas in the processing container. Desirable for suppression.

<Embodiment 3> Next, an example of a resist processing apparatus suitable for carrying out the method of the present invention will be described with reference to FIG. 7. The device shown in FIG. 7 is a part of a device that fully automatically processes a series of steps from, for example, resist application to a substrate to before exposure, and is responsible for baking and cooling the resist. In the figure, reference numeral 71 denotes a baking/cooling treatment container, and opening/closing pulps 72a and 72b are provided on opposite side walls of this container 7), respectively.

A support stand 73 is provided at the bottom of the processing container 71, and a substrate 75 with a resist film 74 is placed on this support stand 73. A plurality of cooling refrigerant passage holes 76 are uniformly provided inside the support base 73, and a heater 77 is placed above the support base 73.

Further, a pressure control pipe 77 is provided in the clay wall of the processing container 71.

A substrate to be processed 7 on which a resist film 74 has been applied and formed in the previous process.
5 is placed on the support stand 73 in the container 71 via the openable pulp 7-2g. Next, the pressure inside the container 71 is set to a predetermined pressure lower than 1 atmosphere through the pressure control pipe 78, and the resist is baked at a predetermined temperature T for a predetermined time using the heater 17-77. After baking, the pressure inside the container 71 is further lowered, and a refrigerant whose flow rate and temperature are controlled is circulated through the refrigerant passage 76 to uniformly cool the substrate 75 of the support base 73-F from its lower surface. In this case, it is necessary that the substrate 75 and the support base 73 have good thermal contact. After the cooling process is finished,
The pressure inside the container 71 is returned to atmospheric pressure, and the substrate 75 is taken out into the container 71 via the opening/closing pulp 7Zb. Thereafter, the substrate 75 is transported to a processing section for the next step.

Please note that this device uses a single-wafer processing method, so
Depending on the situation, the processing time in the vacuum baking/boosting cooler section may become long, which may upset the balance of processing times with other sections, making it impossible to achieve a high throughput. In such a case, arrange multiple decompression baking/boosting coolers, for example in a circle or in parallel, and set an appropriate delay time that takes into account the processing time of other parts and the baking/cooling processing time. By performing the baking and cooling processes in cycles or in parallel, it is possible to increase the throughput of the entire apparatus. Furthermore, it is also possible to increase the size of the vacuum bake/boost cooler within a predetermined allowable range and apply a patch processing method to only this part. Furthermore, as a cooling means after baking the resist film, cold air whose temperature and flow rate are uniformly controlled may be blown onto the entire surface of the resist film. Cooling in this case can be combined with a process of returning the pressure inside the reduced pressure container 7Z to the atmosphere.

In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

Figure 1 is a flowchart schematically showing a conventional resist pattern forming process, Figure 2 is a schematic diagram showing isothermal curves of temperature changes at various points on the substrate after resist baking in the conventional process; 3 is a characteristic diagram showing the state of the temperature change as a time vs. temperature curve, FIG. 4 is a flow chart schematically showing the resist pattern forming process according to the present invention, and FIG. 5 is a characteristic diagram showing the resist cooling rate. FIG. 6 is a characteristic diagram showing resist sensitivity, and FIG. 7 is a sectional view showing an example of a resist processing apparatus suitable for the method of the present invention. 7I...Processing container, 12m, 72b...Opening/closing pulp, 73...Support stand, 74...Regis) [,7,5...
...Substrate, 76...1 medium hole, 7r...heater, 7
8...Pressure control pipe. Applicant's agent Patent attorney Suzue Takehiko Go 1 1-4 Me@Tsuboshi

Claims (3)

[Claims] (1) A resist pattern is formed by applying a resist onto a substrate to be processed, baking it, cooling it, selectively irradiating the resist with an electromagnetic wave of a predetermined wavelength or a particle beam of a predetermined energy, and performing a development process. A method for forming a resist glossy turn, characterized in that at least one of baking and cooling the resist is performed under a pressure lower than normal pressure. (2) As for cooling the resist, the baking temperature T is controlled while controlling the cooling time or cooling rate. A method for forming billed turns, characterized in that the process is carried out uniformly from to a final cooling temperature T. (3) The resist pattern forming method according to claim 1, wherein the resist is cooled by rapid cooling.