JP2001068451A - Etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an etching method capable of comparatively safely forming a fine pattern with high precision on a silicon carbide substrate. SOLUTION: The etching method comprises forming a thin liq. layer contg. hydrofluoric acid between a silicon carbide substrate and a sapphire glass window member, and irradiating the silicon carbide substrate with an Xe2* excimer lamp beam and an ArF laser beam from the sapphire glass window member, thereby removing at least a part of the surface of the silicon carbide substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an etching method, and more particularly to an etching method for etching a silicon carbide substrate.

[0002]

2. Description of the Related Art Silicon carbide has characteristics such as excellent heat resistance, radiation resistance, chemical resistance, and abrasion resistance, a wide band gap, and a high reflectance in the X-ray region. ing. For this reason, silicon carbide is expected to be applied to semiconductor devices and SR light gratings.

At present, silicon carbide substrates are often processed by a physical method such as diamond engraving or laser ablation. However, in order to form a fine pattern in a short time and with high accuracy, a chemical method is used. Application is mandatory. However, there are some problems in forming a fine pattern on a silicon carbide substrate in a short time and with high accuracy using a conventional chemical method.

For example, when pattern etching is performed using a reactive ion etching (RIE) method or the like, a resist having better chemical resistance than silicon carbide is required. However, such a resist is impractical. Further, when a photoelectrochemical (PEC) method is used, a resist is not necessary, but there is a problem in processing time and processing accuracy because of the direct drawing method.

[0005] In addition to the above method, the present inventors have developed a photochemical pattern etching method using an etchant gas such as ClF ₃ gas or NF ₃ gas as a chemical method. This method uses the radicals generated by photolysis of the etchant gas, silicon carbide on the surface of the silicon carbide substrate in which sublimate as SiF _n and CF _n or CN. According to this method,
Since the sublimation occurs only in the exposed portion of the laser light that is the surface excitation light, a desired pattern can be formed with high accuracy. However, this method requires dangerous gases such as ClF ₃ gas and NF ₃ gas.

[0006]

As described above, according to the conventional method, in order to form a fine pattern on a silicon carbide substrate with high accuracy by a chemical method, ClF ₃ is required.
Dangerous gases such as gas and NF ₃ gas are required.

The present invention has been made in view of the above problems, and has as its object to provide an etching method capable of forming a fine pattern on a silicon carbide substrate relatively safely.

[0008]

To solve the above-mentioned problems, the present invention provides a sapphire glass window having a thin liquid layer containing hydrofluoric acid interposed between a silicon carbide substrate and a sapphire glass window member. An etching method characterized by removing at least a part of the surface of a silicon carbide substrate by irradiating a silicon carbide substrate with Xe ₂ ^* excimer lamp light and ArF laser light from a member side.

According to the etching method of the present invention, a highly active oxygen atom generated by photoexcitation of hydrofluoric acid, and Si and C whose bonds have been cut by photoexcitation of the surface of a substrate made of silicon carbide. Of the reaction. SiO ₂ and CO ₂ generated by this reaction
Among oxides such as, a gas such as CO ₂ diffuses into hydrofluoric acid. On the other hand, SiO _{2 and the} like remain on the substrate surface, but are easily removed by hydrofluoric acid. The etching method of the present invention is based on such a principle.

As described above, in the method of the present invention, a liquid is used as an etchant. in this case,
The contact density between the surface to be processed and the etchant can be further increased as compared with the case where a gas is used. Therefore, the etching rate can be improved.

According to the method of the present invention, a dangerous gas such as ClF ₃ gas or NF ₃ gas is not used for etching silicon carbide, but hydrofluoric acid is used instead.

Further, in the method of the present invention, the silicon carbide substrate and the sapphire glass window member are laminated via a thin liquid layer containing hydrofluoric acid. Such a structure can be formed, for example, by utilizing the capillary phenomenon. In this case, hydrofluoric acid can be uniformly supplied to the entire surface to be processed of the silicon carbide substrate. Therefore, uniform etching can be performed. Further, in this case, since the required amount of hydrofluoric acid is small, etching can be performed more safely.

In the present invention, the concentration of hydrofluoric acid in the thin liquid layer is usually in the range of 35 to 46%, preferably in the range of 10 to 30%. When the concentration of hydrofluoric acid is within the above range, a sufficient etching rate can be obtained.

In the present invention, the thickness of the thin liquid layer is usually
Within the range of 100 to 0.5 μm, preferably 50 to
It is in the range of 1 μm. When the thickness of the thin liquid layer is within the above range, a sufficient amount of the etchant can be supplied to the surface of the silicon carbide substrate, and furthermore, the absorption of ArF laser light in the thin liquid layer is suppressed and the silicon carbide is suppressed. The surface of the substrate can be sufficiently photoexcited.

In the present invention, the energy density of the Xe ₂ ^* excimer lamp light is preferably 20 mW or more. In this case, a highly active oxygen atom can be sufficiently generated. Further, in the present invention, the energy density of the ArF laser beam is preferably 100 mJ / cm ² or more, and more preferably 500 mJ / cm ² or more. In this case, a sufficient etching rate can be obtained.

[0016]

Embodiments of the present invention will be described below.

First, hydrofluoric acid was dropped on one main surface of a silicon carbide substrate. Next, a sapphire glass plate was placed on the surface of the silicon carbide substrate on which hydrofluoric acid was dropped. Drops of hydrofluoric acid present on the silicon carbide substrate are spread between the silicon carbide substrate and the sapphire glass plate by capillary action.
As a result, a very thin liquid film of hydrofluoric acid was formed between the silicon carbide substrate and the sapphire glass plate.

Thereafter, Xe ₂ ^* excimer lamp light (1) is directed from the sapphire glass plate side toward the silicon carbide substrate.
(0 mW) to excite hydrofluoric acid. At the same time, Ar is perpendicular to the substrate surface from the sapphire glass plate side.
The surface of the silicon carbide substrate was photoexcited by irradiating an F excimer laser beam in a pattern.

[0019] irradiation of these light toward the silicon carbide substrate from the sapphire glass plate side, the exposed portion of the ArF excimer laser beam, SiF _n or CF _n Strong F radicals silicon carbide active from the substrate surface
It is removed as a gas. On the other hand, such a gas is not generated in an unexposed portion of the ArF excimer laser beam. That is, only the portion of the silicon carbide substrate exposed to the ArF excimer laser light can be selectively removed.

As described above, the surface of the silicon carbide substrate was etched to form a predetermined pattern.

FIG. 1 shows that the conditions of ArF excimer laser light are 400 mJ / cm ² , 20 Hz, and 10,000 shots.
It is a graph which shows the relationship between the concentration of hydrogen fluoride in hydrofluoric acid obtained when s was set, and etching depth. In the figure, the horizontal axis indicates the hydrogen fluoride concentration, and the vertical axis indicates the etching depth.

As shown in FIG. 1, the concentration of hydrogen fluoride was set to 1
Etching was most effectively performed when the content was 5%, and an etching depth of about 75 Å was achieved.

The etching rate depends on the energy density of the ArF excimer laser light, and is 650 m
Under the conditions of J / cm ² , 20 Hz, and 10,000 shots, an etching depth of 150 Å was achieved.

[0024]

As described above, according to the method of the present invention, no dangerous gas such as ClF ₃ gas or NF ₃ gas is used for etching silicon carbide, and hydrofluoric acid is used instead. Can be Therefore, according to the method of the present invention, it is possible to form a fine pattern on a silicon carbide substrate relatively safely.

That is, according to the present invention, there is provided an etching method capable of forming a fine pattern on a silicon carbide substrate relatively safely.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the concentration of hydrofluoric acid and the etching depth obtained when the etching method according to the embodiment of the present invention is used.

Continuation of front page (72) Inventor Koichi Hirobe 1-9-3-311 Nakahara, Hiratsuka-shi, Kanagawa F-term (reference) 5F043 AA05 AA37 BB12 BB25 DD08 DD30

Claims (1)

[Claims] A thin liquid layer containing hydrofluoric acid is interposed between a silicon carbide substrate and a sapphire glass window member, and a Xe ₂ ^* excimer lamp is directed from the sapphire glass window member side toward the silicon carbide substrate. Light and A
An etching method comprising irradiating an rF laser beam to remove at least a part of the surface of the silicon carbide substrate.