JPH0812841B2 - Resist processing method - Google Patents

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 ultraviolet irradiation, and more particularly to a method for treating a relatively thinly applied photoresist. 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 it is used, its application to a baking process, which is one of the photoresist processing processes, has recently attracted attention. The baking step is an intermediate step between the step of forming a photoresist pattern by applying photoresist, exposing and developing, and the step of performing ion implantation or plasma etching using this photoresist pattern. This is a heating step for the purpose of improving adhesion to substrates and heat resistance. 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,
This gas causes bubble generation, collapse of the photoresist pattern, and rupture of the photoresist film, such as peeling, rupture, and roughening of the photoresist film, which is a cause of defective semiconductor devices.

The cause of this gas is a rapid photochemical reaction of the exposed photo-sensitive groups of the photoresist, a photochemical reaction between the photoresist and HMDS (hexamethyldisilazane) or anti-reflective agent applied to the wafer as a pre-treatment of the photoresist application. , A photochemical reaction of a photoresist additive such as a dye, a photochemical reaction of a solvent remaining in the photoresist, and the like. These gas generating photochemical reactions have wavelengths of 300 nm.
It is significantly advanced by light in the range of up to 500 nm, particularly light having a photosensitive wavelength for exposure of photoresist.

On the other hand, when irradiated with short-wavelength ultraviolet light, especially light with a wavelength of 300 nm or less, a surface skin (polymerized surface film) is formed on the photoresist surface in the initial stage of irradiation.
Is formed. 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. When the amount of generated gas is greater than the released amount, the gas accumulates inside the photoresist, and the accumulated gas grows into bubbles and eventually destroys the photoresist. I will end up. 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 is a problem that high-speed processing cannot be performed. Then, when examining the destruction of the photoresist film in more detail, for example, in the case of a relatively thin coating film of OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd.,
HPR-118 manufactured by Fuji Hunt Electronics Technology Co., Ltd.
It was found that the state of progress of destruction differs from that of the comparatively thick coating film of 2 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 circumstances, the present invention prevents the destruction of a relatively thin photoresist film due to the radiated light from a microwave-excited electrodeless discharge lamp or a high-pressure mercury discharge lamp, thereby enabling high-speed processing of the photoresist by ultraviolet radiation. The purpose 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. In irradiating ultraviolet rays, first, of the ultraviolet rays, the ultraviolet rays in the wavelength range where gas is generated from the photoresist are reduced and then irradiated, and then all the ultraviolet rays from the ultraviolet ray radiation source are irradiated.

[Action]

In the present invention, in the initial stage of the irradiation treatment, as a pretreatment, in a strong radiated light from a microwave-excited electrodeless discharge lamp or a high-pressure mercury discharge lamp, a wavelength range in which gas is generated from the photoresist through a filter. 300nm-500nm
To reduce the ultraviolet rays and irradiate. That is, the gas is gently generated. At this time, the surface skin of the photoresist is gradually formed by light of 300 nm or less, but the gas is generated slowly, and since the photoresist film thickness is relatively thin, the gas generation amount is small, In addition, the moving distance of the gas within the film is short, and therefore, the gas generation rate is kept within the gas releasing capacity, and most of the gas escapes before the surface skin becomes thick. After that, all the radiated light from the ultraviolet radiation source is irradiated without passing through the filter, but since the gas is completely released, the photoresist film shape does not collapse even if it is irradiated with strong light, and the processing is performed in a short time. finish. 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 lamp 1 and emits 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 a larger amount of mercury is added than that disclosed in the above publication, the emitted light of 220 to 300 nm becomes strong, which is preferable. .

The radiated light from the electrodeless mercury discharge lamp 1 is radiated onto 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. As the filter 3, a filter having a characteristic of blocking or reducing emitted light in the wavelength range of 300 nm to 500 nm, which is a wavelength range including the exposure light exposure wavelength of the photoresist, is used to effectively perform the photoresist treatment by ultraviolet irradiation. You can

It is suitable to use a wavelength-selective filter in which a multilayer vapor deposition film is formed on a quartz glass plate as a material having a characteristic of blocking or reducing radiation in the wavelength range of 300 nm to 500 nm. Spectral transmittance of this filter 3 An example of characteristics is shown in FIG.

Using this equipment, the photoresists of OFPR-800 and OFPR-5000 manufactured by Tokyo Ohka Kogyo Co., Ltd. are used, and HMDS is used as a wafer pretreatment agent. Ultraviolet rays were radiated to the sample on which the film had been formed, based on the time chart shown in FIG. That is, the filter 3 is closed when the shutter 24 is first opened, and irradiation is performed through the filter 3 for, for example, 1 to 20 seconds. This state is the "pretreatment state", and since it passes through the filter 3, the intensity of the radiated light of the exposure photosensitive wavelength on the photoresist surface is small, gas is generated slowly in the suppressed state, and the resist film is thin. The amount of gas generated is small, and the moving distance of gas to the resist film surface is small. On the other hand, although a surface skin is also generated, since the amount of gas generated is gentle, the generated gas is released to the outside without staying in the film and destroying the photoresist. 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, for example, for 30 to 60 seconds with the filter 3 opened, but since the filter 3 is not passed through, the intensity of the radiated light on the photoresist surface is large, and processing can be performed in a short time. 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 relatively small film thickness can be favorably treated, and the heat resistance and the plasma etching resistance are improved. On the other hand, when the filter 3 was not used and 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, At the time of irradiation, first, of the ultraviolet rays, the ultraviolet rays in the wavelength range in which gas is generated from the photoresist are reduced and then irradiated, and then all the ultraviolet rays from the ultraviolet radiation source are irradiated, so that the heat resistance of the photoresist is improved. This can be achieved even by 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 for improving the plasma etching resistance. Since the light in the wavelength range to be introduced is controlled by the filter in the "pretreatment state", the ratio For target thin photoresist film gas exits through quick surface skin. That is, the photochemical reaction that causes a destructive action on the photoresist film is suppressed. Moreover, since the ultraviolet rays effective for improving the heat resistance and the plasma etching resistance of the photoresist are still strongly contained when the filter is open, high-speed and effective photoresist treatment is possible.

[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. 1 ... Electrodeless discharge lamp, 3 ... Filter 4 ... Photoresist, 5 ... Semiconductor wafer 6 ... Wafer processing table, 7 ... Vacuum suction 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. A resist treatment method, which comprises first irradiating with reducing and irradiating, among ultraviolet rays, ultraviolet rays in a wavelength range in which gas is generated from the photoresist, and then irradiating all ultraviolet rays from the ultraviolet ray radiation source. 2. The resist processing method according to claim 1, wherein the ultraviolet source is a microwave-excited electrodeless discharge lamp or a high-pressure mercury discharge lamp.