JPH0241896B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming a resist pattern, and more particularly to a method for forming a resist pattern in which a cooling process of a resist film after baking treatment is improved.

[Technical background of the invention and its problems]

As the degree of integration of semiconductor devices, including VLSIs, increases, there is a need for finer and more precise pattern formation technology. For this reason, the permissible dimensional accuracy is extremely strict, and in the cutting-edge field, it is necessary to use a 6-inch mask or a 5-inch wafer.
Dimensional accuracy of 3σ≦0.1 μm (where σ indicates variation with respect to the average dimensional value of wafers, etc.) is beginning to be required. In addition, in order to be used on a mass production line, dimensional variations between masks or wafers must be reduced to 3σ≦
It is necessary to suppress the thickness to 0.15 μm. On the other hand, in order to enhance the mass production effect, a highly sensitive resist is required, and sensitivity control is also required to adjust the sensitivity to suit the exposure device (energy irradiation device) used.

Incidentally, conventionally, the following method has been adopted to form a resist pattern. First, a resist is applied onto a substrate (for example, a mask substrate) by a spin coating method or a dipping method. Next, a so-called baking process is performed in which the resist film on the substrate is heated to a predetermined temperature (Tb) using heating means such as an oven or a hot plate. After baking for a predetermined period of time, the resist film coated substrate is heated at room temperature and pressure for 20 to 30 minutes.
Cool naturally for about 30 minutes. Next, the resist film on the cooled substrate is exposed to light at a predetermined exposure amount depending on the resist, and is further subjected to predetermined development and rinsing treatments to form a resist pattern.

However, with the conventional method described above, it is difficult to uniformize the sensitivity within a delicate range using the same resist, and even if the exposure conditions are constant, each substrate
As a result, it has been difficult to stably form a highly accurate resist pattern between substrates and within a substrate because the resist sensitivity varies between sheets and sensitivity differences occur within the substrate.

For this reason, attempts have been made to improve the sensitivity of the resist by increasing the cooling rate of the resist film after baking (for example, by immersing the substrate in a fluid that does not dissolve the resist). However, in such a method, the drying process after immersion in the fluid is complicated. Moreover, although high sensitivity can be achieved, variations within the substrate surface become larger than in conventional methods using natural cooling. Therefore, with this method, it is difficult to form a resist pattern with high sensitivity and uniform in-plane dimensions using an inexpensive system.

[Purpose of the invention]

The present invention stabilizes resist sensitivity by improving the cooling process after baking.
Furthermore, the present invention aims to provide a method that can form a uniform and highly accurate resist pattern between substrates and within the plane of the substrates with good reproducibility.

[Summary of the invention]

As a result of intensive research into the differences in dimensions of resist patterns on substrates created by conventional methods, the present inventors found that during natural cooling of a substrate coated with a resist film after baking treatment, cooling when the substrate is left standing It has been found that, as shown in FIG. 7, there is an upper part that is cooled at a cooling rate such as cooling curve A, and a lower part that is cooled at a cooling rate such as cooling curve B. In fact, when we investigated the sensitivity of the resist film portion on the cooled substrate using curve A shown in FIG. 7, we found that the sensitivity characteristic of curve A' was shown in FIG. The sensitivity of the resist film portion on the substrate cooled by B shows the sensitivity characteristic of curve B' shown in Fig. 8, and there is a strong correlation between the cooling rate and the sensitivity characteristic, and this is the cause of the difference in dimensions. I found out something.

From the above, it was found that the conventional technology does not control the cooling rate during the cooling process, so the sensitivity fluctuates depending on the cooling conditions, which makes it difficult to form highly accurate resist patterns.

Therefore, the present inventors conducted a baking process on a substrate coated with a resist, and developed it based on the fact that the sensitivity characteristics of a resist are correlated with the cooling rate after baking, and that variations in sensitivity occur due to uneven cooling. By cooling the substrate and the temperature control plate in parallel and close to each other during cooling before processing and after baking, sensitivity can always be stabilized and the sensitivity conditions for the same resist can be limited. We have discovered a method that can be selected within a range, and that can form highly accurate resist patterns in mass production with good reproducibility under the most process-stable sensitivity conditions.

That is, the present invention provides a transport means for transporting a substrate coated with a resist film, a shutter disposed in the middle of the transport means and partitioning the front side of the transport means as a baking chamber and the rear side as a cooling chamber; A heating means disposed in the baking chamber divided by a shutter, a heat insulating pin disposed in the cooling chamber divided by the shutter and moving the substrate of the conveying means downward; When forming a resist pattern using a resist processing apparatus equipped with a cooling mechanism consisting of a temperature control plate facing parallel to the upper substrate, the substrate is transported to the baking chamber by the transport means and the temperature inside the baking chamber is Baking the resist film on the substrate to a desired temperature by heating means, opening the shutter, transporting the baked substrate to the cooling chamber by the transport means, and moving the substrate downward while receiving it with the heat insulating pins. and cooling the resist film on the substrate by bringing the substrate close to the temperature control plate in parallel with the temperature control plate through which the pins are passed, and irradiating the cooled resist film with electromagnetic waves of a predetermined wavelength or particle beams of energy ( After performing (hereinafter referred to as exposure),
This is a resist pattern forming method including a step of performing a development treatment.

Examples of the substrate include a mask substrate, a wafer, or a wafer coated with various semiconductor films, insulating films, or metal films.

Examples of the above-mentioned resists include photoresists, deep ultraviolet-sensitive resists, electron beam-sensitive resists, X-ray-sensitive resists, highly accelerated X-ray-sensitive resists, and ion beam-sensitive resists. In particular, positive resists made of fluorine-containing polylotyl methacrylate (PMMA)
When the method of the present invention is applied, it is suitable because it has a high sensitivity stabilizing effect.

In the process of cooling the substrate covered with the resist film and the temperature control plate in parallel and close proximity, the temperature should be kept at a temperature that does not adversely affect the dimensional uniformity of the resist pattern (specifically, lower than the glass transition temperature of the resist). It is desirable to cool the product until it reaches a temperature of at least 30°C (lower temperature). After cooling down to such a temperature, the substrate may be placed on a temperature control plate to improve cooling efficiency. In addition, in this cooling process, from the viewpoint of achieving further stabilization of sensitivity, the distance between the substrate and the temperature control board, the time until the proximity of the temperature control board, and the temperature of the temperature control board are adjusted respectively. It is preferable to perform cooling while controlling the cooling rate of the surface of the resist film on the substrate.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to FIG.

FIG. 1 is a schematic diagram showing a baking/cooling device used in the resist pattern forming method of the present invention. In the figure, 1 indicates a substrate is installed, and the direction shown by the arrow is forward and downward (position L ₂ ). It is a walking beam consisting of a pair of beam-shaped rails that drive , backward, and upward (position L ₁ ). In the middle of this walking beam 1, a heat insulating plate 2 and a double shutter 3 which can be opened and closed are provided to separate a space for baking and a space for cooling. A first heat insulating cover ₄₁ is fixed to the heat insulating plate 2 above the beam 1 on the side of the baking space, and a heating element 5 is disposed on the inner surface of the cover ₄₁ . There is. Further, a hot plate 6 for performing a baking process is arranged below the beam 1 in the baking side space. On the other hand, a second heat insulating cover 4 ₂ is arranged above the beam 1 in the cooling side space. Further, a cooling mechanism 7 is arranged below the beam 1 in the cooling side space. This cooling mechanism 7
consists of a temperature control plate 8 and four heat insulating pins 9 which are passed through the four corners of the control plate 8 to support the substrate conveyed on the walking beam 1 and move it downward. The temperature control board 8 is
As shown in FIGS. 2 and 3, a meandering heater 10 is buried near the top surface, and a meandering pipe 11 for circulating refrigerant is buried near the bottom surface. The heat insulating pin 9 is made of, for example, fluororesin, Delrin, or other heat-resistant resin. The distance between the walking beam 1 and the temperature control plate 8 is, for example, 20 mm. Also,
The beam 1 and the tip of the heat insulating pin 9 are spaced apart by 2 mm.

Next, a method of forming a resist pattern using the baking/cooling apparatus described above will be described.

First, a mask substrate coated with an EB resist having a glass transition temperature (Tg) of 133° C. was prepared, and the mask substrate 12 was placed on the walking beam 1. Next, with the double shutter 3 open, the beam 1 is driven in the direction shown by the arrow in FIG. was baked to 200°C (Tb).

Next, the walking beam 1 is driven forward and downward again to move the position of the beam 1 from L ₁ to L ₂ , and the substrate 12 on the beam 1 is set on the four heat insulating pins 9, and the two are simultaneously moved. Heavy shutter 3 was closed. Subsequently, the four heat insulating pins 9 were lowered, and the substrate 12 on the pins 9 was brought into contact with the temperature control board 8 set at 25° C. for cooling. In this cooling process, walking beams 1 to 4
It was set to take 1 minute to set on the heat insulating pins 9 of the book, and 1 minute to bring the substrate 12 on the pins 9 into contact with the temperature control board 8.
Thereafter, the walking beam 1 located below was driven 8 minutes after cooling, and the substrate 12 on the temperature control plate 8 was placed on the beam 1 and moved forward to be transported to the exposure apparatus.

Next, the resist film after cooling is accelerated at a voltage of 20 keV.
Exposure was performed using an electron beam of Furthermore
A resist pattern was formed on the mask substrate by treatment with an IPA rinsing solution (liquid temperature: 25°C) for 30 seconds.

When the temperature of the substrate (temperature at two points at the center and corner portions) was measured during the cooling process after the baking treatment in this example, the characteristic diagram shown in FIG. 4 was obtained. In addition, C ₁ in FIG. 4 is the temperature curve at the center of the substrate in this example, C ₁ ′ is the temperature curve at the corner portion in this example, and C ₂ is the substrate naturally cooled after baking treatment (conventional method). C 2 ′ shows the temperature curve at the center part of C 2 ′, and C ₂ ' shows the temperature curve at the corner part in the same conventional method. Further, P ₁ in the figure indicates the time when the substrate was moved from the walking beam onto the four heat insulating pins, and P ₂ indicates the time when the substrate was placed on the temperature control board. As is clear from FIG. 4, the method of this embodiment can make the in-plane temperature of the mask substrate more uniform than the conventional method.

In addition, regarding the resist pattern formed by the conventional method of naturally cooling after baking treatment, and the resist pattern formed by this example,
In-plane variations were investigated. As a result, the characteristic diagram shown in FIG. 5 was obtained in the conventional method, and the characteristic diagram shown in FIG. 6 was obtained in this embodiment. As is clear from these FIGS. 5 and 6, in the conventional method, the in-plane variation is 3σ≦0.15, whereas in this embodiment, the same variation is 3σ≦0.04, which is more than twice as high, resulting in a highly accurate resist pattern. It can be seen that it is possible to form

Furthermore, in the above example, when the resist pattern was formed by adjusting the temperature of the temperature control plate to, for example, 80°C or 50°C, the sensitivity of the resist film was controlled more than when the temperature control plate was set to 25°C. was completed.

In the above embodiment, the baking treatment was performed immediately after the resist film was applied, but the same effect could be achieved even if the baking treatment was performed after exposure and before development.

〔Effect of the invention〕

As detailed above, according to the present invention, sensitivity can always be stabilized, sensitivity conditions for the same resist can be selected within a limited range, and reproduction can be performed under the most stable sensitivity conditions in terms of process. The present invention can provide a method for forming highly accurate resist patterns in a mass-produced manner with ease.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a baking/cooling device used in the resist pattern forming method of the present invention, FIG. 2 is a top view of the cooling mechanism used in FIG. 1, and FIG. The bottom view of the mechanism, Figure 4 is a characteristic diagram showing the in-plane temperature at two locations on the mask substrate during the cooling process according to this example and the conventional method, and Figure 5 is the in-plane dimensions of the resist pattern formed by the conventional method. FIG. 6 is a characteristic diagram showing the in-plane dimensional variation of the resist pattern formed by this example. FIG. 7 is a cooling process when the substrate after baking is placed vertically and allowed to cool naturally. FIG. 8 is a characteristic diagram showing the relationship between the exposure amount and the film thickness remaining rate in the resist portion during different cooling processes shown in FIG. DESCRIPTION OF SYMBOLS 1... Walking beam, 3... Double shutter, 6... Heat plate, 7... Cooling mechanism, 8... Temperature control board, 9... Heat insulation pin, 10... Heater, 11...
...Refrigerant piping, 12...Mask board.

Claims (1)

[Scope of Claims] 1. A transport means for transporting a substrate coated with a resist film, and a shutter disposed in the middle of the transport means to partition the front side of the transport means as a baking chamber and the rear side as a cooling chamber. , heating means disposed in the baking chamber partitioned by the shutter;
a cooling mechanism that is disposed in the cooling chamber partitioned by the shutter and includes a heat insulating pin for moving the substrate of the conveying means downward; and a temperature control plate through which the pin is penetrated and facing parallel to the substrate on the pin; When forming a resist pattern using a resist processing apparatus comprising: a step of transporting the substrate to a baking chamber by the transport means and baking the resist film on the substrate to a desired temperature by a heating means in the chamber; , the shutter is opened, and the substrate after baking is transferred to the cooling chamber by the transfer means, and the substrate is received by the heat insulating pin and moved downward, so that the substrate is parallel to the temperature control plate through which the pin penetrates. Formation of a resist pattern, which includes the steps of: cooling the resist film on the substrate in close proximity to the substrate; and irradiating the cooled resist film with an electromagnetic wave of a predetermined wavelength or a particle beam of energy, followed by a development process. Method. 2. In the step of cooling the substrate by bringing it close to the temperature control board, adjust the distance to bring the board close to the temperature control board, the time to bring the board close to the temperature control board, and the temperature of the temperature control board, respectively. 2. The method of forming a resist pattern according to claim 1, wherein cooling is performed while controlling the cooling rate of the surface of the resist film on the substrate.