JP3196963B2 - How to remove organic matter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing organic substances on a substrate such as a semiconductor wafer, a glass substrate and a ceramic substrate, and more particularly to a method for removing organic substances by oxidative decomposition of organic substances on a substrate.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device or the like, if an organic substance adheres to a substrate, a defect occurs in a formed device. Therefore, the organic substance adhering to the substrate surface is removed by sulfuric acid, ozone or the like having a large oxidizing power. That is being done. In addition, in order to form fine electrical elements and circuits on a substrate, a photoresist, which is a photosensitive organic polymer compound, is applied, and ultraviolet light is applied through a photomask on which a pattern such as a predetermined circuit is formed. After exposing the photoresist, the photoresist is developed, a circuit pattern of the photoresist is formed on the substrate, and the photoresist film on the substrate is removed after performing processing such as etching on the substrate. I have.

[0003] If the removal of organic substances or the removal of the photoresist on the substrate is incomplete, the subsequent steps are adversely affected, so that it is necessary to completely remove the photoresist. In particular, the degree of integration of semiconductor devices has increased,
When the line width of a circuit of a semiconductor device to be formed becomes thinner, the influence of a photoresist residue becomes a bigger problem than in the case where the degree of integration is low. Therefore, it is required to completely remove it.

Various methods have been adopted for removing organic substances, but a method using ozone which has a large oxidizing power and does not adversely affect semiconductor devices has been used. .

[0005]

As a method of removing organic substances using ozone, a method of immersing a substrate in water into which an ozone-containing gas is blown, a method of spraying a mixed gas of ozone and water vapor on a substrate surface, and the like are known. However, these methods have a problem that the solubility of ozone in water is low and the oxidizing power of ozone is not sufficiently exhibited, so that the removal rate of organic substances is slow and the treatment takes a long time. Was.

[0006] In order to enhance the oxidizing power of ozone, it is conceivable to increase the temperature of the liquid in which the substrate is immersed and to inject ozone to accelerate the treatment. Therefore, the decomposition temperature of ozone must be high, for example, 150 ° C. or higher, which is not practical.

[0007]

According to the present invention, an oxidative decomposition of an organic substance is produced by irradiating ozone with ultraviolet rays.
By using a hydroxyl radical generated by a reaction between a singlet excited oxygen atom and water, the rate of oxidative decomposition is increased.

That is, according to the method of the present invention, when a substrate to be processed immersed in or adhered to a liquid is treated with ozone, the substrate is irradiated with ultraviolet rays to generate a singlet excited oxygen atom generated by decomposition of ozone and water. This is to generate hydroxyl radical generated by the reaction. Ozone is considered to generate hydroxyl radicals by the following reaction.

[0009]

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When immersing in ultra-pure water for treatment, ozone is introduced into ultrapure water to use a liquid in which ozone is dissolved or present in a bubble state (hereinafter referred to as a liquid in which ozone coexists). Is preferred.

The processing liquid containing ozone is obtained by supplying ozone into ultrapure water, and the supply of ozone is performed by using gaseous ozone obtained from a generator using a silent discharge such as a surface discharge type. Electrolysis of water using high-concentration ozone water in which gaseous ozone is dissolved in ultrapure water in advance or a lead dioxide electrode as an anode and a fluoropolymer cation exchange membrane as a solid polymer electrolyte High-concentration ozone water obtained from the apparatus may be used.

In order to obtain high-concentration ozone in an ozone generator using a silent discharge such as a surface discharge type, it is preferable to supply a high oxygen concentration gas such as pure oxygen to the ozone generator.

The higher the concentration of the ozone-containing gas supplied to the ozone treatment tank is, the greater the effect is.
It is preferable to supply 000 to 100,000 ppm of ozone. Ozone is introduced into the ultrapure water from a ceramic filter or glass filter that has many fine holes to form fine bubbles to increase the contact with the ultrapure water, thereby improving the ultrapure water. By increasing gas hold-up in water and promoting dissolution of ozone, processing can be facilitated.

The ultraviolet rays to be irradiated are preferably ultraviolet rays containing a large wavelength of 253.7 nm, which is a wavelength for decomposing ozone, and such ultraviolet rays can be obtained by a low-pressure mercury lamp or the like.

The photoresist film that can be removed by the method of the present invention can be either a positive type or a negative type.

Further, the substrate is placed on a processing apparatus without immersing the substrate in a liquid, and the surface to be processed is wetted with ultrapure water. When irradiating the surface with ultraviolet rays to remove organic substances, 50,
It is preferable to supply 000 to 100,000 ppm of ozone. It is preferable to rotate the substrate to be processed so that uniform processing is performed. However, if the number of rotations is large, water that keeps the surface of the substrate in a wet state is blown to the surroundings, so that the number of rotations is about 20 rpm. Appropriate.

Since ozone has an extremely large oxidizing power and adversely affects the human body and the like, it is necessary to provide an ozone decomposing device for undecomposed ozone emitted by ozone and decompose ozone into oxygen.

[0018]

According to the present invention, there is provided a method for removing organic substances on a substrate such as a wafer for manufacturing a semiconductor device, wherein the substrate is kept in water or in a wet state and irradiated with ultraviolet rays while supplying ozone. Organic substances can be rapidly removed by the action of hydroxyl radicals generated by the irradiation of.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings.

FIG. 1 shows a method for removing organic substances from a substrate immersed in a processing tank. The processing tank 1 is filled with a processing liquid 2 made of ultrapure water, and the organic substances are removed. The substrate 3 on the surface is held by the substrate holder 4 and immersed in the processing liquid. An ozone supply device 5 made of a ceramic filter, a glass filter, or the like is provided below the substrate.
Is provided, and a high-concentration ozone-containing gas is ejected from the ozone generator 6 as fine bubbles 7 in the processing liquid. A mercury lamp 8 for irradiating ultraviolet rays is provided in the liquid, and the ultraviolet rays decompose ozone and react with water to generate hydroxyl radicals. Since the gas discharged from the processing tank contains ozone, it is decomposed and discharged by an ozone treatment device. Further, the substrate after the treatment is taken out of the liquid to be treated, rinsed with ultrapure water and dried.

FIG. 2 shows a method for processing a substrate without immersion in a processing solution.
A mounting table 23 for the substrate 22 is provided. The mounting table is provided such that the substrate to be processed can be rotated by a rotation shaft 24. The rotating shaft is required to perform high-speed rotation when removing water from the substrate surface, and thus a rotation speed control device is coupled. A supply pipe 26 for supplying an ozone-containing gas from an ozone generator 25 is attached to an upper portion of the processing apparatus, and a mercury lamp 27 for ultraviolet irradiation is provided inside the processing apparatus. Further, a perforated plate 28 made of quartz or the like is provided above the substrate to be processed so that the ozone-containing gas is uniformly supplied to the substrate surface, and the ozone-containing gas is supplied through holes of the perforated plate. Further, an ultrapure water supply nozzle 29 for supplying ultrapure water to the surface is provided above the substrate, and the substrate surface is covered with water when an organic substance on the substrate surface is treated. The substrate after processing is rotated while supplying ultrapure water to the substrate to remove residues on the surface, and further rotated at high speed to remove moisture.

Example 1 A 6-inch wafer whose surface was cleaned by a degreasing and drying treatment was mounted on a spin coater, and a positive resist (OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd.) was dropped on the wafer by a female pipette. After that, rotate at 3500 rpm,
The resist was uniformly applied. The substrate was heated and dried at 85 ° C. for 20 minutes to obtain a substrate to be processed, and the thickness of the positive resist on the substrate to be processed was accurately measured.

The substrate to be processed is suction-fixed to the substrate mounting table shown in FIG. 2, and while the mounting table is rotated at 15 rpm, ultrapure water is sprayed from the ultrapure water supply nozzle, and the surface of the substrate to be processed is treated with ultrapure water. Covered. Thereafter, an ozone concentration of 80,000 pp is supplied from an opening of an opening plate provided at a position facing the surface to be processed.
The ozone-containing oxygen of m was supplied to the surface to be processed, and at the same time, the surface to be processed was irradiated with ultraviolet light having a wavelength of 253.7 nm by an ultraviolet lamp. After processing for 1 minute, the surface to be processed is washed by rotating the mounting table at 150 rpm while supplying ultrapure water from the ultrapure water supply nozzle, and the number of rotations of the mounting table is increased to 2000 r.
Draining was performed at pm. The residual resist film thickness was measured with a film thickness meter (Nanospec 210 manufactured by Nanometrics). Table 1 shows the film thickness before and after the treatment.

Comparative Example 1 A substrate coated with a positive resist was processed in the same manner as in Example 1 except that no ultraviolet light was irradiated, and the film thickness of the positive resist before and after the treatment was measured. Table 1 shows the results.

COMPARATIVE EXAMPLE 2 A substrate coated with a positive resist on the substrate surface in the same manner as in Example 1 was fixed to a substrate holder in a processing tank filled with ultrapure water at a temperature of 25 ° C. as shown in FIG. Ozone-containing oxygen having an ozone concentration of 80,000 ppm is supplied to the surface of the substrate to be processed at a supply rate of 4 l / min through the gas-containing supply device, and at the same time, a wavelength of 253.7 nm is emitted by an ultraviolet lamp installed at a distance of 50 mm from the substrate surface. UV light was applied to the surface of the substrate to be processed. After the treatment for one minute, rinsing with ultrapure water and drying were performed, and then the residual resist film thickness was measured by a film thickness meter (Nanospec 210 manufactured by Nanometrics). Table 1 shows the film thickness before and after the treatment.

[0026]

Comparative Example 3 A substrate coated with a positive resist was treated in the same manner as in Example 1 except that no ultraviolet light was irradiated, and the thickness of the positive resist before and after the treatment was measured. Table 1 shows the results.

[0028]

Table 1 Measured value of resist film thickness (nm) Before processing speed processing After processing (nm / min) Example 1 981.8 383.4 638.4 Comparative Example 1 983.5 829.9 153.6 Comparative Example 2 976.6 384.7 591.9 Comparative Example 3 979.3 754.0 225.3

[0029]

According to the present invention, when removing an organic substance and a resist on a substrate such as a wafer for semiconductor production with ozone, the ozone-containing gas is immersed in the substrate or the surface to be treated is covered with water. Is supplied and ultraviolet light is irradiated, so that the removal rate of organic substances can be increased as compared with the case of using only ozone.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating one embodiment of the present invention.

FIG. 2 is a diagram illustrating another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Processing tank, 2 ... Processing liquid, 3 ... Substrate, 4 ... Substrate holder,
5 ozone supply device, 6 ozone generator, 7 air bubble,
8 ... Mercury lamp, 21 ... Processing device, 22 ... Substrate, 23 ... Placement table, 24 ... Rotating shaft, 25 ... Ozone generator, 26 ... Supply tube, 27 ... Mercury lamp, 28 ... Perforated plate, 29 ... Ultra pure water supply nozzle

Claims (1)

(57) [Claims] In a method for removing organic substances on a substrate, water is supplied to a surface to be processed while the substrate is rotated to make the surface to be processed wet, and an ozone-containing gas is supplied under irradiation of ultraviolet rays. A method for removing organic matter.