JPH06218677A - Low contamination shock tool for silicon breakage - Google Patents

Abstract

PURPOSE: To break silicon of semiconductor-grade into pieces without contaminating silicon by comprising a core forming a handle part and a head part, mounting a tungsten carbide striking element contacted with the head part of the core, and coating the core with a synthetic resin outer shell. CONSTITUTION: This striking tool comprises a core made out of metal, alloy, plastic or composite having the rigidity and strength sufficient for giving the impact to a surface, and having a handle part 1 and a head part 2. A striking element 4 made of tungsten, carbide alloy is contacted and fixed to the head part 2, and the core is totally coated by a cover 3 made of a synthetic resin such as urethane and the like in a state that a striking surface 5 side of the striking element 4 is partially exposed. By coating the surface excluding the striking surface with a low-contamination rigid resin, and forming the striking element 4 out of a low-contamination material, a semiconductor such as silicon and the like can be broken into pieces without contaminating the same.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is a low pollution impact tool particularly useful for breaking semiconductor grade silicon into small pieces. The low pollution impact tool comprises a core forming a handle portion and a head portion, the head portion contacting a striking element of tungsten carbide alloy. The core is encapsulated in synthetic resin.

[0002]

BACKGROUND OF THE INVENTION High density integrated electronic circuits require high purity single crystal silicon wafers. Of particular concern are transition metal impurities including copper, gold, iron, cobalt, nickel, chromium, tantalum, zinc and tungsten, and impurities such as carbon, boron, phosphorus, aluminum and arsenic. Even small amounts of these impurities introduce defect sites in semiconductor grade silicon, which ultimately degrades device performance and limits circuit density.

High purity polycrystalline silicon is typically formed by chemical vapor deposition of high purity chlorosilane gas on a heated silicon substrate. The resulting product is a rod of polycrystalline silicon. The polycrystalline silicon rod must be further processed to produce single crystal silicon that can be cut into silicon wafers.

A significant portion of the monocrystalline silicon needed for the semiconductor industry is produced by the well-known Czochski process. In a typical Choklasky process, a piece of silicon is melted in a suitable container and a seed crystal of single crystal silicon is used to pull a semiconductor grade single crystal rod from the melt. Control of this crystal growth process requires that the silicon pieces added to the vessel containing the melt be within a defined size range. Therefore, it is necessary to break the polycrystalline silicon rods formed during the chemical vapor deposition process into appropriately sized pieces.

Maeda, US Pat. No. 4,697,481, issued Oct. 6, 1987, discloses a hammer including a head core and a handle core, the head core and the handle core acting as a striking surface. It is embedded in resin except the end of the head core. Maeda describes a striking surface made of ferrous metal.

Porter (February 8, 1972)
Er., U.S. Pat. No. 3,640,324 describes a forged steel hammer head having a striking face with an electrodeposited tungsten carbide layer. That tungsten
The carbide layer is reported to provide a non-slip and wear resistant surface on the striking surface.

[0007]

The low pollution impact tool described by the present invention is particularly useful for breaking silicon into small pieces. The inventors have discovered that during the breaking process, the silicon is significantly contaminated by contact with the surface of the breaking device, including the handle and the striking surface. The present invention reduces the pollution associated with a breaking instrument by coating all surfaces except the striking surface with a low-contamination synthetic resin. The exposed striking surface is formed of a tungsten carbide alloy with low contamination.

The present invention is a low pollution impact tool that is particularly effective in breaking semiconductor grade silicon into small pieces. The low-pollution impact tool comprises a core forming a handle portion and a head portion, the head portion of which is in contact with a tungsten carbide alloy striking element. The core is encapsulated in synthetic resin material. The preferred synthetic resin is urethane.

[0009]

The present invention is a low pollution impact tool. The tool is specifically designed to break semiconductor grade silicon into small pieces without much contamination.

According to the invention, (A) a core forming a handle and a head, (B) a tungsten carbide alloy striking element whose end is in contact with the head of the core, and (C) a core are encapsulated. There is provided a low-contamination tool characterized by comprising a synthetic resin outer shell.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a sectional view of a low pollution impact tool according to an embodiment of the present invention. The low pollution impact tool is the handle 1
And a core forming the head portion 2. The core can be made of metal, metal alloys, plastics or composites with sufficient rigidity and strength to impact the surface. The core is preferably made of a metal or metal alloy, such as carbon steel, stainless steel, Inconel, Monel or Hastelloy. AISI (American Iron and Steel Institute standard) 10
More preferably, it is made of 18 cold rolled steel.

The size of the core is not critical to the invention. As is well known, the core must have a sufficient cross-sectional area to prevent bending and crushing of the core while using a low contamination impact tool as a breaking tool. The required cross-sectional area depends on the material of construction of the core as well as the length of the handle part 1. When AISI 1018 cold rolled steel is used as a constituent material of the core material and a low pollution impact tool is used for breaking silicon, the length of the handle portion 1 is about 20.3 cm (8i).
n) to 30.5 cm (12 in) and the handle portion 1 has a cross-sectional diameter of about 1.02 (0.4 in) to 1.2.
7 cm (0.5 in) is suitable.

The head part 2 can be made of the same or different material as the handle part 1. Head part 2 is handle part 1
It is desirable to make it with the same material as.

The head portion 2 and the handle portion 1 are joined together. The bonding is accomplished by molding the core as a unit, for example by molding, casting, stamping, cutting or machining, depending on the particular material of manufacture. Alternatively, the head part 2 and the handle part 1 can be made separately and the two solids can be joined, for example by edging, welding, brazing, melting, threading or other standard means. When the core is made of AISI cold-rolled steel, it is desirable that the head portion 2 and the handle portion 1 be separately made and bonded by a solvent.

The size of the head portion 2 is a manufacturing material, the size of the handle portion 1, the fixing method of the striking element 4, and the striking element 4.
Depends on the size of. When the handle portion 1 and the head portion 2 are made of AISI 1018 cold rolled steel, the head portion 2 has a length of about 2.54 to 5.1 cm and about 1.27 to.
It is desirable to have a diameter of 2.54 cm.

The head part 2 is fixed in contact with the striking element 4. Although the method of fixing the contact between the head part 2 and the striking element 4 is not critical to the invention, the striking element 4 in the preferred embodiment of the invention does not include the head part 2 during the process of molding the core with synthetic resin. It is fixed by making contact with. The synthetic resin holds the position of the striking element as shown in FIG.
The advantage of this method of fixing the striking element 4 is that the striking element can be easily retrieved and reused if the rest of the low-pollution impact tool is damaged. Also, the striking element 4 can be fixed directly to the head part 2 by standard means as described above.

The striking element 4 is made of a tungsten carbide alloy (cobalt is the alloy metal). The tungsten carbide alloy preferably contains about 8 to 15 weight percent cobalt. It is further desirable that the tungsten carbide alloy contain about 10 to 13 weight percent cobalt. In general, the shape of the striking element 4 is not important,
A cylindrical shape with a contracted central portion is desirable. The shrunken central part assists in fixing the striking element 4 when using synthetic resin as a recovery means. The shrinkage can be about 1-30% of the diameter of the striking element 4. A contraction of about 5-20% of the diameter of the striking element 4 is desirable.

The striking element 4 in the preferred embodiment of the present invention has a diameter in the range of about 1.27 to 2.57 cm.

The striking element 4 comprises a striking surface 5. Striking surface 5
The radius of curvature of the edges of is important in minimizing the destruction of particles from the striking element 4 during use. About 0.076-0.
A radius of 635 cm (0.03-0.25 in) is considered effective, but about 0.178-0.305 cm.
A radius of (0.07 to 0.12 in) is desirable.

The core is enclosed in a synthetic resin forming the cover 3. The purpose of encapsulating the core in synthetic resin is to prevent the core from coming into contact with materials that are destroyed by low-impact impact tools. The synthetic resin is selected to minimize the harmful contamination of the destroyed material. "Synthetic resin" means a highly crosslinked polymeric material that is not naturally occurring. The synthetic resin is
For example, polyurethane, polypropylene, polyethylene or polycarbonate. Desirably, the synthetic resin is polyurethane. More preferred is a polyurethane in which the synthetic resin has a Shore hardness of about 90-97.

The cover 3 is formed around the core and the striking element 4 by injecting or casting a synthetic resin into a cavity of a mold having the same shape as the outer shape. In the preferred embodiment, the core is placed in a mould, the striking element 4 is arranged as shown in FIG. 1, a synthetic resin is injected and cured to fix the striking element 4 in contact with the head part 2.

Comparative Example 1 This comparative example is outside the scope of the present invention. AISI
Silicon samples were prepared by breaking a rod of polycrystalline silicon with an impact tool that was not resin coated on a handle and head made of 1018 cold rolled steel. A tungsten carbide alloy striking element was attached to the head of the impact tool. The tungsten carbide alloy contained about 12 wt% cobalt. Care was taken that each piece of silicon adhered to the handle of the impact tool during the fracture process. Samples of silicon pieces were analyzed for iron and phosphorus surface contamination by graphite atomic absorption and autoluminescence methods, respectively. The results are shown in Table 1.

[0023]

[Table 1] Example 1 By breaking a rod of polycrystalline silicon with an impact tool whose handle and head are coated with polyurethane,
A silicon sample was prepared. AI handle and head
It was made of SI 1018 cold rolled steel. The polyurethane coating was formed from a polyether-based liquid isocyanate-terminated prepolymer using 4,4'-methylene-bis (orthochloroaniline) as a curing catalyst. The cured polyurethane had a Shore A hardness of about 95.

The tungsten carbide alloy striking element was bonded to the impact tool head by molding into polyurethane. The tungsten carbide alloy was as described in Comparative Example 1. Care was taken to contact each sample of silicon with the urethane-coated handle of the impact tool during the fracture process. Silicon samples were analyzed as described in Comparative Example 1 and the results are shown in Table 2.

[0025]

[Table 2] Comparing the data shown in Table 2 with the data in Table 1 shows that contamination of the silicon pieces occurs when they come into contact with the uncoated handle of the impact tool.

[Brief description of drawings]

1 is a cross-sectional view of an embodiment of the present invention.

[Explanation of reference numerals] 1 handle portion 2 head portion 3 cover 4 striking element 5 striking surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eldon Emery Rourig, Mount Valley, Michigan, USA 6489, E Valley Ray Road (72) Inventor John Dee Nemes, Drake Street, Midland, Michigan, USA 4907 (72) Inventor Chris Tim Schmid, 1068 N Union Road, Auburn, Michigan, USA

Claims (2)

[Claims] 1. A core forming a head portion with a handle portion; (B) a tungsten carbide striking element whose end portion is in contact with the head portion of the core; and (C) a synthetic resin encapsulating the core. A low-pollution impact tool characterized by comprising a shell. 2. The low-pollution impact tool according to claim 1, wherein the head portion is fixed in contact with the tungsten carbide alloy striking element by a synthetic resin.