JPH0812840B2 - Resist processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a photoresist applied to a semiconductor wafer by irradiating ultraviolet rays, and more particularly to a method for treating a photoresist applied relatively thickly. Is.

[Conventional technology]

Regarding the conventional treatment of photoresist by UV irradiation, UV irradiation is performed in the process of exposing the mask pattern on the photoresist applied to the semiconductor wafer, the preliminary cleaning process of decomposing and cleaning the organic contaminants adhering to the photoresist surface, etc. Although used, the application to the baking process, which is one of the resist processing processes, has recently attracted attention.

The baking step is an intermediate step between the step of forming a resist pattern by photoresist application, exposure, and development and the step of performing ion implantation or plasma etching using this resist pattern. This is a heating process for the purpose of improving the adhesiveness and heat resistance of the. Recently, a method has been investigated in which the photoresist is exposed to ultraviolet rays before the baking step after development or at the time of baking to enhance heat resistance and plasma etching resistance during baking in a shorter time.

[Problems to be solved by the invention]

As described above, recently, in the photoresist baking step, irradiation of ultraviolet rays has been studied.

However, in order to speed up the process, when the photoresist is irradiated with light with high ultraviolet intensity, such as radiated light from a microwave-excited electrodeless discharge lamp or high-pressure mercury discharge lamp, which has high ultraviolet emission efficiency, the gas from the inside of the photoresist is Occurs,
The gas causes bubbles, collapse of the photoresist pattern, and breakage of the photoresist film such as peeling, rupture, and roughening of the photoresist film, which is a cause of defective semiconductor devices.

The causes of this gas are a rapid photochemical reaction of the exposed photosensitive group of the photoresist, a photochemical reaction between the photoresist and HMDS (hexamethyldisilazane) or antireflection agent applied to the wafer as a pretreatment for resist application, A photochemical reaction of a resist additive such as a dye or a photochemical reaction of a solvent remaining in the photoresist can be considered. These gas generating photochemical reactions are significantly promoted by light having a wavelength in the range of 300 nm to 500 nm, particularly light having the exposure exposure wavelength of the photoresist.

On the other hand, when ultraviolet rays with a short wavelength, particularly light with a wavelength of 300 nm or less, are irradiated, a surface skin (polymerized surface film) is formed on the surface of the photoresist in the initial stage of irradiation. This surface skin spreads over the inside of the photoresist with the passage of time, and eventually the entire photoresist becomes polymerized, but this polymerized layer does not allow gas to easily pass therethrough, and therefore, due to the above-mentioned causes, the inside of the photoresist is blocked. The release of the gas generated in is blocked.
In particular, when the amount of gas generated is greater than the amount released, such as when the photoresist film thickness is large, the gas accumulates inside the photoresist, and the accumulated gas grows into bubbles and finally the photoresist. Will destroy. Therefore, the intensity of light cannot be increased in a photoresist processing apparatus that uses a microwave-excited electrodeless discharge lamp or a high-pressure mercury discharge lamp that emits light including these wavelength ranges. That is,
There was a problem that high-speed processing could not be performed. Then, when examining the breakdown of the photoresist film in more detail, for example, OFPR which is a novolac resist manufactured by Tokyo Ohka Kogyo Co., Ltd.
-5000 relatively thin coating film and TSMR-88 manufactured by the same company
It was found that the state of progress of destruction differs from that of the comparatively thick coating film of 00 depending on the irradiation method of ultraviolet rays. Therefore, it is necessary to devise each irradiation process according to the type of photoresist used and its film thickness.

In view of such a situation, the present invention prevents the destruction of a relatively thick photoresist film by the radiated light from a microwave-excited electrodeless discharge lamp or a high-pressure mercury discharge lamp, and thus makes it possible to process the photoresist by ultraviolet irradiation at high speed. In addition, the object is to provide a method that can be effectively performed.

[Means for solving problems]

In order to achieve this object, in the present invention, in a resist treatment method for increasing the heat resistance and plasma etching resistance of the photoresist by irradiating the photoresist forming a pattern by exposure and development with ultraviolet rays from an ultraviolet radiation source. When irradiating with ultraviolet rays, first remove the wavelength range where the photoresist is cured, and then irradiate with ultraviolet rays including the wavelength range where gas is generated from the photoresist.
Irradiates all ultraviolet rays from an ultraviolet radiation source.

[Action]

In the present invention, in the initial stage of the irradiation treatment start,
As a pretreatment, strong radiant light from a microwave-excited electrodeless discharge lamp or a high-pressure mercury discharge lamp is applied through a filter that blocks ultraviolet rays in the wavelength range that hardens the photoresist. That is, the gas generated in the photoresist is easily released to the outside while suppressing the formation of the surface skin of the photoresist. Therefore, in the case of a relatively thick photoresist film, a large amount of gas is generated and the moving distance to the surface of the photoresist film is long, but this generated gas is released to the outside without being obstructed by the surface skin. After that, all the radiation light from the ultraviolet radiation source is irradiated without passing through the filter, but since the gas is completely released, the shape of the photoresist film is not destroyed and the processing is completed in a short time. That is, predetermined heat resistance and plasma etching resistance can be obtained.

〔Example〕

The present invention will be specifically described below based on the embodiments shown in the drawings.

FIG. 1 shows a photoresist processing apparatus for explaining an embodiment of the photoresist processing method according to the present invention. A patterned photoresist 4 is formed on a semiconductor wafer 5, and the semiconductor wafer 5 is placed on a wafer processing table 6. The wafer processing table 6 is heated by the heater 10 by supplying electricity from the heater lead wire 9 or cooled by flowing cooling water through the cooling hole 11. The heating and cooling mechanism controls the temperature of the semiconductor wafer 5. Further, the wafer processing table 6 has a vacuum suction hole 7
Has a function of fixing the semiconductor wafer 5 in close contact with the wafer processing table 6 by drawing a vacuum through the communication hole 8 with a vacuum pump. Ultraviolet radiation source is electrodeless mercury discharge lamp 1, magnetron 20, power supply 2
1, a waveguide 22, and a cavity resonator 23 having a light-reflecting mirror (not shown) arranged on the inner surface thereof, and constitute an irradiation device together with an openable / closable filter 3, a shutter 24, and the like. The first
In the figure, the shutter 24 shown by the solid line shows the closed state, the shutter 24 'shown by the dotted line shows the open state, and similarly, the filter 3 shown by the solid line shows the closed state, and the filter 3'shown by the dotted line shows the open state.

The magnetron 20 supplied with power from the power supply 21 oscillates microwaves having a frequency of 2450 MHz. The generated microwave is guided to the cavity resonator 23 and forms a strong microwave magnetic field in the cavity resonator 23. The strong microwave magnetic field excites the mercury gas in the electrodeless mercury discharge lamp 1 to emit radiant light including ultraviolet rays.

It is known that a rare gas such as argon and a small amount of mercury are added as an enclosed gas of the electrodeless mercury discharge lamp 1 to emit strong ultraviolet rays. In particular, regarding an electrodeless mercury discharge lamp that strongly emits light with a wavelength of 220 to 230 nm, see JP-A-59-
It is disclosed in Japanese Patent No. 87751, and it is possible to use this, but the wavelength range of ultraviolet rays effective for improving the heat resistance and plasma etching resistance of photoresist is 22
Since it is as wide as 0 to 300 nm, an electrodeless mercury discharge lamp having a strong emitted light in this range is preferable, and when the amount of mercury added is larger than that disclosed in the above publication, the emitted light of 220 to 300 nm becomes strong, which is preferable. is there.

The radiated light from the electrodeless mercury discharge lamp 1 is applied to the photoresist 4 as radiated light containing ultraviolet rays having an appropriate wavelength by the filter 3 or the like. FIG. 2 is an example of the emission spectrum of the electrodeless discharge lamp 1 used in this example. The filter 3 has a property of transmitting radiation in a wavelength range of 300 nm to 500 nm including a photoresist exposure wavelength but blocking or reducing radiation in a wavelength range of 300 nm or less in which the photoresist is cured. By using the one, it is possible to effectively perform the photoresist treatment by ultraviolet irradiation.

Although a radiant light of 300 nm to 500 nm is transmitted, it is suitable to use a wavelength selective filter in which a multilayer vapor-deposited film is formed on a quartz glass plate as a characteristic of blocking or reducing the radiant light of 300 nm or less. An example of the spectral transmittance characteristic of the filter 3 is shown in FIG.

Using this equipment, Fuji Hunt Electronics Technology Co., Ltd. HPR-1182 and Tokyo Ohka Kogyo Co., Ltd. TSMR-8800 were used as a photoresist, and HMDS was used as a wafer pretreatment agent to obtain a thickness of 2.5 μm. The sample on which the thick photoresist film was formed was irradiated with ultraviolet rays based on the time chart shown in FIG. That is, when the shutter 24 is opened for the first time, the filter 3 is closed, and irradiation is performed through the filter 3 for 1 to 20 seconds, for example. This state is the "pretreatment state", and since it passes through the filter 3, it has a particularly large effect of forming a surface film that does not allow gas to easily pass through the photoresist. Light having a wavelength of 300 nm or less is blocked or reduced, and the surface film is not formed. Alternatively, the surface film is formed in an extremely suppressed state, and the gas generated by the light of the exposure photosensitive wavelength has a relatively large thickness due to the photoresist film being relatively thick, and the gas traveled to the surface of the photoresist film. Even if it is long, it easily comes out. Next, the shutter 24 is closed, for example, for 5 to 10 seconds. This period is a rest period, and the gas generated during this period is completely released.
Then, the shutter 24 is opened again with the filter 3 opened.
Is opened for, for example, 30 to 60 seconds, but since it does not pass through the filter 3, the intensity of radiated light having a wavelength of 300 nm or less, which is highly effective in improving heat resistance and plasma etching resistance, is large on the photoresist surface, and is processed in a short time. can do.
Further, since the gas is completely released, the photoresist film is not destroyed even if it is treated with radiation having high intensity. Thus, by providing the "pretreatment state" for a short time, the photoresist having a large film thickness can be favorably treated, and the heat resistance and the plasma etching resistance are improved. On the other hand, without using the above filter 3,
And, when the irradiation was continued, the photoresist film was destroyed.

In the above examples, argon gas to which mercury having a high ultraviolet intensity was added was used as the filling gas of the electrodeless discharge lamp, but the present invention is not limited to this, and a metal other than mercury is added in a trace amount, for example, in the form of halide. It may be one that emits ultraviolet rays of a predetermined wavelength, and further, mercury is added to a rare gas other than argon, a mixed gas of argon and another rare gas, or a mixed gas of a rare gas other than argon. It is also possible to use an added mercury rare gas electrodeless discharge lamp. The frequency of the microwave is not limited to 2450 MHz, and any microwave having another frequency may be used as long as it can efficiently excite the enclosed gas. Further, it may be a high frequency wave having a wavelength longer than that of the microwave.

Furthermore, this technique can be directly used even when a high-pressure mercury discharge lamp is used as a UV radiation source.

〔The invention's effect〕

As is clear from the above description, in the resist processing method for enhancing the heat resistance and plasma etching resistance of the photoresist by irradiating the photoresist forming the pattern by exposure and development with ultraviolet rays from the ultraviolet radiation source, When irradiating, the photoresist is first exposed to ultraviolet rays including the wavelength range in which gas is generated from the photoresist, except for the wavelength range in which the photoresist is cured, and then is irradiated with all ultraviolet rays from the ultraviolet radiation source. Using a microwave-excited electrodeless discharge lamp or a high-pressure mercury discharge lamp that strongly radiates light in the wavelength range that causes a destructive effect on the photoresist together with ultraviolet rays that are effective in improving the heat resistance and plasma etching resistance of Photoresist by the wavelength of light controlled by the filter in the "pretreatment state" Is relatively thick and a large amount of gas is generated, and even if the moving distance to the surface of the photoresist film is long, the gas has already been released from inside the photoresist, which causes a rapid destructive effect on the photoresist film. Gas generation photochemical reaction is suppressed. Moreover,
Ultraviolet rays, which are effective in improving the heat resistance and the plasma etching resistance of the photoresist when the filter is open, are still strongly contained, so that the photoresist processing can be performed at high speed and effectively.

[Brief description of drawings]

FIG. 1 is an explanatory view of an example of an apparatus for carrying out a resist processing method according to the present invention, FIG. 2 is an explanatory view showing an example of a radiation spectrum of a microwave excitation electrodeless discharge lamp used in the present invention, and FIG. Is an explanatory view showing an example of the spectral transmittance characteristic of the filter used in the present invention, and FIG. 4 is an explanatory view of a time chart. DESCRIPTION OF SYMBOLS 1 ... Electrodeless discharge lamp, 3 ... Filter 4 ... Photoresist, 5 ... Semiconductor wafer 6 ... Wafer processing table, 7 ... Vacuum adsorption hole 8 ... Communication hole, 9 ... Heater lead wire, 10 ... Heater 11 ... Cooling hole, 12 … Mirror, 13… Quartz plate 20… Magnetron, 21… Power supply, 22… Waveguide 23… Cavity resonator, 24… Shutter

Claims (2)

[Claims] 1. In a resist treatment method for enhancing the heat resistance and plasma etching resistance of a photoresist by irradiating the photoresist forming a pattern by exposure and development with ultraviolet rays from an ultraviolet radiation source, the irradiation of ultraviolet rays is performed. First, the resist is characterized by irradiating with ultraviolet rays including a wavelength range for generating gas from the photoresist except for a wavelength range for curing the photoresist, and then irradiating all ultraviolet rays from the ultraviolet radiation source. Processing method. 2. The resist processing method according to claim 1, wherein the ultraviolet radiation source is a microwave-excited electrodeless discharge lamp or a high-pressure mercury discharge lamp.