Method of wet-cleaning sintered silicon carbide

Details Method of wet-cleaning sintered silicon carbide Method of wet-cleaning sintered silicon carbide

2000-05-26

2002-04-23

Markoff, Alexander (Department: 1746)

Cleaning and liquid contact with solids

Processes

Including application of electrical radiant or wave energy...

C134S002000, C134S003000, C134S026000, C134S027000, C134S028000

Reexamination Certificate

active

06375752

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of wet-cleaning a sintered silicon carbide, which can be applied to various members of semiconductors and to electronic parts. More particularly, the present invention relates to a method of removing organic contaminants, metal element contaminants, particle contaminants and the like from a sintered silicon carbide which is used for dummy wafers, targets, heating elements and the like, which is parts of semiconductors, and which is required to have a high purity.
2. Description of the Related Art
A silicon carbide is a substance with strong covalent bonds, and has conventionally been put to many uses which take advantage of its excellent characteristics, such as excellent strength at high temperatures, heat resistance, wear resistance, resistance to chemicals, and the like. These advantageous characteristics have attracted attention, and recently expectations have been placed on the application of silicon carbides to the fields of electronics, information and semiconductors.
As the degree of integration in semiconductor integrated circuits using silicon substrate increases and the line width of the circuits becomes correspondingly smaller, various members of semiconductors and electronic parts used in these fields are required to have a higher purity and a higher density. Therefore, methods of hot press sintering and methods of reaction sintering using nonmetallic auxiliary sintering agents have been extensively researched. However, while the sintered silicon carbides obtained through these sintering methods have a high level of purity and a high density, the surfaces and the vicinities of the surfaces of the sintered silicon carbides become contaminated during processes before and after manufacture, such as sintering, working, handling, and the like.
Therefore, in order to apply a sintered silicon carbide to various parts of semiconductors and electronic parts, i.e., in order to prevent particle and other forms of contamination, achieving a level of surface purity as high as that of silicon wafers by cleaning the surface of the sintered silicon carbide is essential.
Disclosed methods of cleaning sintered silicon carbides are as follows: (1) in the method disclosed in Japanese Patent No. 181841, a sintered silicon carbide is cleaned with an acid, subjected to an oxidation treatment at a temperature of 1200° C. or higher, and is thereafter surface-treated in an atmosphere of nitrogen; (2) in the method disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-17229, a sintered silicon carbide is blast-cleaned with silica abrasive grains, and is then wet-cleaned with a mixed acid containing hydrofluoric acid and nitric acid; (3) in the method disclosed in JP-A No. 6-77310, a sintered silicon carbide is cleaned by dipping it into an aqueous solution of hydrofluoric acid, rinsed with ultrapure water, dry-cleaned with oxygen and a halogen gas, and is then treated with oxygen; and (4) in methods disclosed in JP-A Nos. 55-158622, 60-138913 and 64-72964, a porous silicon carbide is cleaned with a hydrogen halide gas and an inorganic acid to increase the purity, and then the purified silicon carbide is subjected to secondary sintering because achieving a high level of purity is extremely difficult once the sintering has been conducted.
Because the aforementioned methods require not only simply wet-cleaning the sintered silicon carbide but also such treatments as oxidation, blast cleaning, and secondary sintering, the entire process becomes complicated and it is difficult to regard them as satisfactory cleaning methods.
SUMMARY OF THE INVENTION
The present invention was created in consideration of the above facts. An object of the present invention is to provide a method of wet-cleaning a sintered silicon carbide to, easily and within a short period of time, remove organic and inorganic impurities which are present on the surface and in the vicinity of the surface of the sintered silicon carbide so that the sintered silicon carbide can be used in various parts of semiconductors and electronic parts.
As a result of their extensive research, the present inventors noted that, even when a sintered silicon carbide is of a high purity, a high density, and is applicable to various parts of semiconductors and electronic parts, concentrations of organic and inorganic impurities on the surface and in the vicinity of the surface markedly increase due to contamination in succeeding steps, thus making it difficult to apply the obtained sintered silicon carbide to various parts of semiconductors and electronic parts. The present inventors therefore devised a method which cleans and removes organic and inorganic impurities easily and within a short period of time.
That is, the present invention is a method of wet-cleaning a sintered silicon carbide, comprising the steps of: dipping a sintered silicon carbide into a quasi-aqueous organic solvent; and dipping the sintered silicon carbide into an aqueous solution of an inorganic acid, wherein at least one of the step of dipping the sintered silicon carbide into a quasi-aqueous organic solvent and the step of dipping the sintered silicon carbide into an aqueous solution of an inorganic acid is conducted while ultrasonic waves are applied.
The method of wet-cleaning a sintered silicon carbide of the present invention can clean, easily and within a short period of time, a sintered silicon carbide such that the resultant sintered silicon carbide has a degree of surface cleanliness (amount of impurities adhering thereto) less than 1×10
11
atoms/cm
2
and can be applied to various members of semiconductors and electronic parts.
The method of wet-cleaning a sintered silicon carbide of the present invention has an advantage in that, since the cleaning liquids (solvents and aqueous solutions) are all composed of agents which are soluble in water or can be rinsed with water, no drying process is required in the step of cleaning and, therefore, the entire process can be simplified.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A method of wet-cleaning a sintered silicon carbide of the present invention includes a step of dipping a sintered silicon carbide (hereinafter occasionally referred to as a material to be cleaned) into a quasi-aqueous organic solvent, and a step of dipping the material to be cleaned into an aqueous solution of inorganic acid. At least one of these steps is conducted while ultrasonic waves are applied.
In the method of wet-cleaning a sintered silicon carbide of the present invention, by dipping the sintered silicon carbide into a quasi-aqueous organic solvent, organic substances on the surface of the sintered silicon carbide, such as oil film, fingerprints and wax, are removed by the quasi-aqueous organic solvent. Moreover, by dipping the sintered silicon carbide into the aqueous solution of inorganic acid, metal elements on the surface and in the vicinity of the surface of the sintered silicon carbide are removed by the aqueous solution of inorganic acid.
In the method of wet-cleaning a sintered silicon carbide of the present invention, at least one of the steps is conducted while ultrasonic waves are applied, so that physical vibrations are applied to the material to be cleaned or the cleaning liquid (the solvent and/or the aqueous solution), and an active radicals are generated in the cleaning liquid, whereby impurities present on the surface and in the vicinity of the surface of the sintered silicon carbide can easily be removed. As a result, the cleaning effect can be improved remarkably, and the process can be conducted simply and efficiently with a small number of steps. Moreover, the time required for the process can be drastically reduced compared to cases in which ultrasonic waves of low frequency are applied.
In the method of wet-cleaning a sintered silicon carbide of the present invention, it is preferable, from the standpoint of the cleaning effect and process simplification, that ultrasonic waves are applied only during the s

Affiliated with

Also associated with

Rating

Method of wet-cleaning sintered silicon carbide does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of wet-cleaning sintered silicon carbide, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of wet-cleaning sintered silicon carbide will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2891189