JPH0480531B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a method for forming a resist pattern with improved pattern accuracy.

[Prior art and its problems] As the integration density of semiconductor devices, including VLSIs, increases, finer and more accurate pattern forming techniques are required. For this reason, the permissible dimensional accuracy has become very strict, and dimensional accuracy of a maximum deviation of pattern dimensions of 0.1 μm or less is now required for 6-inch masks or 5-inch wafers.

FIG. 1 is a block diagram showing a resist pattern forming process according to the prior art. First, a resist is applied to a desired thickness onto a substrate to be processed by spin coating. Next, the coating solvent is removed, and the substrate is placed in an oven and baked (prebaked) at a predetermined temperature (Tb) depending on the type of resist to improve adhesion to the substrate. Thereafter, the resist film-coated substrate taken out of the oven is allowed to cool naturally in clean air, and is cooled to about room temperature over 20 to 30 minutes. A resist film-coated substrate to be processed is exposed by selectively irradiating electromagnetic waves in a predetermined wavelength range, such as ultraviolet light, or particle beams with a predetermined energy, such as electron beams, at 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, the inventors used an infrared radiation thermometer to investigate the temperature distribution over the entire surface of the substrate to be processed (resist film) at a certain point during the natural cooling mentioned above.
It was as shown in Figure 2. That is, the substrate to be processed 1
In the upper central part (point A), the temperature is high and it is difficult to cool down.
It was found that the temperature below and around the area (points B and C) is low and is easily cooled.

Note that the curves in the figure are isothermal lines. Figure 3 further shows the state of temperature change over time at each of the points A, B, and C, and curves 1, 2, and 3 represent points A, B, and C.
This is a characteristic corresponding to B and C. The maximum temperature difference between points A and B is about 15℃, and the maximum temperature difference between points A and C is about 30℃.
It was about ℃. The reason why such a temperature distribution occurs is that the substrate to be processed is placed on a support stand during natural cooling, so natural convection due to heat dissipation tends to occur upward along the substrate surface, and the bottom of the substrate is placed on the support stand. It is thought that heat is easily taken away by this.

Furthermore, the inventors focused on the relationship between the temperature distribution of the substrate (resist film) and pattern accuracy, and measured the dimensions of the formed pattern at temperature measurement points A, B, and C, and found that they were originally the same size (2 μm). The expected pattern has an error of about 0.1 μm at point B and 0.2 μm at point C, which shows that the temperature distribution of the substrate (resist film) and the size distribution of the pattern to be formed are extremely consistent. It was confirmed that, as shown in Figure 5, if the temperature is lowered while the temperature distribution of the substrate (resist film) is uniform, there will be no variation in the cooling rate at each point, and the pattern dimensions will be less uneven and accuracy will be improved. It was.

[Purpose of the invention]

An object of the present invention is to provide a method for forming a resist pattern that is formed by electromagnetic wave or particle beam irradiation and development treatment and has excellent precision.

[Summary of the invention]

FIG. 4 shows an outline of the resist pattern forming process according to the present invention. First, a resist is applied onto a substrate to be processed, and then the resist film is baked (prebaked). The process up to this point is the same as the conventional process. Next, the resist film is cooled.
This is done by lowering the temperature of the entire resist film at a uniform cooling rate. Thereafter, the resist film is selectively irradiated with electromagnetic waves in a predetermined wavelength range or particle beams with a predetermined energy, and then developed and rinsed to form a resist pattern.

〔Effect of the invention〕

According to the present invention, dimensional variations are reduced over the entire substrate to be processed, and pattern accuracy is significantly improved.

[Embodiments of the invention]

Examples of the present invention will be specifically described below. First, the following experiment was conducted according to the resist pattern forming process according to the present invention shown in FIG.

Poly 2,2,2-trifluoroethyl-α-chloroacrylate as a resist dissolved in a solvent is dripped from a jet nozzle onto a glass substrate on which chromium is vapor-deposited and placed on a rotary table using a well-known spin coating method. The film was coated to a predetermined thickness. Thereafter, the resist film was baked (prebaked) in an oven at 200° C. for 30 minutes. After the prebaking was completed, the resist film and the substrate were immersed all at once in a water tank containing pure water at room temperature as a cooling liquid to uniformly cool the resist film through the glass transition temperature (Tg). in this case,
As shown in FIG. 5, while the temperature of the resist film decreases from the pre-bake temperature to near room temperature, A in FIG.
The temperatures at points corresponding to points B and C are curve 1,
It decreased uniformly like 2 and 3.

Next, the substrate with the resist film was placed on a rotating table and spin-dried. For a sufficiently dried resist film,
It was selectively irradiated with an electron beam at an accelerating voltage of 20 KV, and then developed with a developer of methyl isobutyl ketone:isopropyl alcohol = 7:3 at 25°C for 10 minutes, and then with isopropyl alcohol.
Rinse treatment was performed at 25°C for 30 seconds.

As a result, it was possible to form a highly accurate pattern in which the maximum deviation value of resist pattern dimensions on the substrate was 0.1 μm or less.

Even when polymethyl methacrylate is used as the type of resist, the same procedure as in the above example is applied.
It was possible to form a highly accurate pattern with a maximum deviation value of 0.1 μm or less.

Furthermore, it was confirmed that the pattern accuracy of photoresists and X-ray resists was significantly improved compared to conventional processes. The present invention can be applied not only to positive type resists but also to negative type resists.

The main purpose of the present invention is to reduce the temperature of the resist film after prebaking at a uniform cooling rate for the entire film, and the cooling rate can be selected arbitrarily, and the cooling medium, cooling means, and subsequent drying The method and the like are not particularly limited to the above-mentioned embodiments. For example, as the coolant, other than pure water, a liquid or gas that does not dissolve or react with the resist can be used. In that case, it is effective to select a material with as large a specific heat as possible. Compatible refrigerants include liquid fluorocarbon, low-temperature nitrogen gas, and fluorocarbon gas. or,
The type of resist, substrate material to which the resist film is applied, resist solvent, developer, pre-bake temperature, etc. are not limited to the above-mentioned examples, and high accuracy can be achieved with various known materials and temperatures. It was confirmed that Regarding the resist exposure method, similar results can be obtained by using a particle beam of a predetermined energy such as an ion beam or an electromagnetic wave in a predetermined wavelength range, in addition to the above-mentioned electron beam, light beam, or X-ray.

Next, an example of an apparatus suitable for carrying out the method of the present invention will be described with reference to FIG. The apparatus shown in FIG. 6 fully automatically performs a series of steps from applying resist to a substrate to before exposure.

First, a substrate 1 to be coated with a resist is placed on a rotating sample stage 3 for spin coating by means of a vacuum chuck 2 . A resist dissolved in a solvent is dropped from the upper jet nozzle 4, and the substrate is rotated to form a resist film on the substrate 1. Next, the substrate 1 is placed on a belt conveyor 5 by a vacuum chuck 2 and introduced into a pre-bake oven 6. A heater 7 for pre-baking is provided inside the oven 6, and a low-speed belt conveyor 8 for conveying the substrate 1 is also provided below the heater 7. When the substrate 1 conveyed by the belt conveyor 5 enters the oven 6, it is transferred to the belt conveyor 8. The substrate 1 is slowly passed through the oven 6 by the belt conveyor 8, and is prebaked by the heater 7 at a predetermined temperature for a predetermined time. The prebaked substrate 1 is transferred to the belt conveyor 9, further conveyed, and introduced into the cooling mechanism 10. That is, the substrate 1 conveyed by the belt conveyor 9 is transferred to a conveyance mechanism 11 that can move vertically and horizontally, and is immersed in pure water 13, which is a liquid refrigerant, in a cooling tank 12, and is uniformly cooled.
The cooled substrate 1 is transferred to a belt conveyor 14 by a transport mechanism 11, and is transferred to a rotating sample stage 1 for spin drying.
5. The substrate 1 dried by the rotation of the sample stage 15 is transferred to a belt conveyor 17 by a vacuum chuck 16 and carried out. The substrate 1 with the resist film thus obtained is subjected to a predetermined exposure process and development/rinsing process to form a pattern.
Thermocouples 40 and 41 are used to measure the temperature of the resist. An infrared radiation thermometer can also be used to measure temperature.

Note that the cooling mechanism 10 is not limited to the immersion type shown in FIG. 6, and may be modified in various ways, such as a spray type, a shower type, or a cooling plate type.

FIG. 7 shows a cooling mechanism using a spray method, in which the substrate 1 is placed on a rotating sample stage 20, and while being rotated, a liquid or gas coolant is sprayed from an upper jet nozzle 21. The cooled substrate 1 is transferred by a vacuum chuck 22.

Figure 8 shows the shower type cooling mechanism.
The substrate 1 transported by the belt conveyor 9 is transferred to the low-speed belt conveyor 25 in the cooling chamber 24 of the porous cooling device 23, and the refrigerant 27 stored in the liquid refrigerant chamber 26 is jetted out from the porous nozzle 29 of the partition wall 28. It is something to do. The cooled substrate 1 is transferred to a belt conveyor 14, dried by a rotating sample stage 15, and then transferred to a belt conveyor 17 by a vacuum chuck 16 and carried out. Gas can also be used as the refrigerant 27. In that case, rotating sample stage 1
5 becomes unnecessary.

FIG. 9 shows a cooling plate type cooling mechanism. While the substrate 1 is being conveyed by the belt conveyor 31, it is uniformly cooled by a cooling plate 32 located close to the substrate 1 above. Note that the belt conveyor 31 may be stopped and the cooling plate 32 may be brought into contact with the base body 1.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing a conventional resist pattern forming process, and FIG. 2 is an explanatory diagram showing isothermal curves of temperature changes at various points on the substrate to be processed after prebaking in the conventional process. Figure 3 is a characteristic diagram showing the same temperature change as a time vs. temperature curve.
The figure is a block diagram schematically showing the resist pattern forming process according to the present invention, Figure 5 is a characteristic diagram showing how the temperature of the substrate to be processed changes due to uniform cooling of the resist in the present invention, and Figure 6 is a diagram showing the process of the present invention. FIG. 7 to FIG. 9 are explanatory diagrams showing each modification of the uniform cooling mechanism. 1...Substrate, 4...Resist jet nozzle, 6...
…Oven, 5, 8, 9, 14, 15, 25, 3
1... Belt conveyor, 11... Conveyance mechanism, 12
...Cooling tank, 3, 15, 20...Sample rotating table, 2
1... Refrigerant jet nozzle, 23... Cooling device, 32
...cooling plate.

Claims (1)

[Claims] 1. A step of applying a resist onto a substrate, a step of baking the formed resist film, and a step of forcibly cooling the resist film one substrate at a time, and cooling the entire resist film at a uniform cooling rate, A resist pattern characterized by comprising the steps of: irradiating the resist film with electromagnetic waves in a predetermined wavelength range or particle beams with a predetermined energy; and forming a resist pattern by developing the resist film. Formation method.