Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1998-11-17
2001-07-31
Yoon, Tae (Department: 1714)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C528S308000, C528S308600, C206S562000, C206S833000
Reexamination Certificate
active
06268030
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a silicon wafer carrier and its production process, more particularly, to a silicon wafer carrier having little surface-staining tendency and permanent antistaticity and its production process.
BACKGROUND ARTS
Polyesters are widely used owing to their excellent moldability, mechanical properties, heat-resistance, chemical resistance, creep resistance, impact resistance, rigidity, etc. Silicon wafers composed of polytetramethylene terephthalate (which may be abbreviated hereafter as PBT) are already in use.
Polyester is easily electrified by rubbing, peeling, etc. Various troubles may take place by the static charge accumulated on a molded article by electrification. For example, accumulated static charge may cause the generation of electric shock in use and the deposition of dust on the surface of the article.
It is known that a polyester can be imparted with antistaticity by the addition of an antistatic agent.
The antistatic treatment by the addition of an antistatic agent can be carried out by coating or internal addition. The coating process necessitates an additional step and, accordingly, the internal addition is preferable from the view point of production process.
Kneading of a low-molecular ionic surfactant such as an alkylsulfonic acid salt or an alkylbenzenesulfonic acid salt into a polymer is known as an internal addition process. A process to use a phosphonium salt is disclosed in the JP-A 62-230835 (hereunder, JP-A means “Japanese Unexamined Patent Publication”).
Although high initial antistatic effect can be attained by the method using a low-molecular ionic surfactant because of the bleeding of the surfactant on the surface of the molded article, the process has a problem of losing the antistatic effect by the wiping or washing of the article.
A silicon wafer carrier composed of polytetramethylene terephthalate and carbon fiber is disclosed in the JP-A 8-88266 as a silicon wafer carrier having antistaticity, describing that the silicon wafer carrier has static charge dissipating property, i.e. antistaticity and gives little generation of particulate contaminant caused by friction.
A silicon wafer carrier is used after various treating procedures comprising an annealing step to remove the strain of the silicon wafer carrier, a degassing step to remove the residual volatile components, a washing step to remove attached contaminant and a subsequent drying step.
The silicon wafer carrier is used for the transportation and storage of a silicon wafer in the heat-treating step and the washing step of the silicon wafer under various conditions.
A polyether ester amide is known to have good antistaticity, however, the use of the polymer together with other thermoplastic resin causes laminar peeling and the production of a molded article having desirable mechanical properties is difficult.
A polyester composition composed of a polyester, a polyether ester amide and a modified vinyl polymer is disclosed in the JP-A 9-12844 as a composition having excellent impact resistance.
DISCLOSURE OF THE INVENTION
A large amount of volatile gases composed of organic gases are generated during the transportation and storage of a silicon wafer in the case of using a silicon wafer carrier made of conventional polytetramethylene terephthalate (which may be abbreviated as PBT hereafter) resin for the transportation and storage of a silicon wafer, and the generated gases are condensed on the silicon wafer to cause the contamination of the surface of the wafer. In such a case, the surface contamination of the silicon wafer takes place by the transfer of an impurity from the surface of the silicon wafer carrier to the silicon wafer.
Further, metals are dissolved from the silicon wafer carrier in the washing of the silicon wafer and attached to the surface of the silicon wafer to effect the contamination of the silicon wafer surface.
Such contamination causes the defects and the lowering of electrical properties of a semiconductor device using the silicon wafer and gives a silicon wafer having qualities unsuitable for use.
The use of a compatibilizing agent for imparting a silicon wafer carrier with antistaticity improves the compatibility problem, however, the impurity content in the resin composition increases by the addition of a large amount of the compatibilizing agent to cause the problem of surface contamination, etc., in the case of using the resin as a silicon wafer carrier.
An object of the present invention is to provide a silicon wafer carrier having suppressed bleeding tendency of impurities, especially alkali metals, to the surface of the silicon wafer carrier in heat-treatment to a level not to cause the trouble of the surface contamination of a silicon wafer and, furthermore, having excellent permanent antistaticity.
Another object of the present invention is to provide a silicon wafer carrier having an impurity bleeding tendency suppressed to an extent not to cause the trouble of the surface contamination of a silicon wafer and exhibiting excellent permanent antistaticity, wherein said permanent antistaticity is characterized by the surface resistivity of 1×10
14
to 1×10
11
&OHgr;/□ (measuring voltage: 500V).
Another object of the present invention is to provide a silicon wafer carrier having especially low bleeding of impurities and generation of volatile gases.
Another object of the present invention is to provide a silicon wafer carrier having hydrolysis resistance as well as the above characteristics.
Another object of the present invention is to provide a process for producing the silicon wafer carrier having the above properties.
Another object of the present invention is to provide a process for producing the silicon wafer carrier while suppressing the Barus effect occurring in the case of kneading a polyether ester amide with a polyester in molten state and improving the productivity of a silicon wafer carrier compounded with a large amount of a polyether ester amide.
The other object and advantage of the present invention will be clarified by the following explanations.
The present invention comprises the following constitution.
1. A silicon wafer carrier consisting of a composition composed of (a) 100 parts by weight of a polyester, (b) 5 to 100 parts by weight of a polyether ester amide. (c) 10 to 2,500 ppm (based on the polyether ester amide) of an alkaline metal and (d) 0 to 40 parts by weight of a modified polyolefin, generating not more than 10 ppm of volatile gas by the heat-treatment at 150° C. for 60 minutes, and eluting not more than 10 ppm of the alkaline metal by the immersion in pure water at 80° C. for 120 minutes:
2. A silicon wafer carrier consisting of a composition composed of (a) 100 parts by weight of a polyester, (b) 5 to 30 parts by weight of a polyether ester amide and (c) 10 to 2,500 ppm (based on the polyether ester amide) of an alkaline metal, containing a polyether ester amide phase having an aspect ratio of 3 or more, a minor diameter of 1 &mgr;m or less and a major diameter of 1 &mgr;m or more in a polyester phase in the range from the surface of the silicon wafer carrier to the depth of 20 &mgr;m, generating not more than 10 ppm of volatile gas by the heat-treatment at 150° C. for 60 minutes, and eluting not more than 10 ppm of the alkaline metal by the immersion in pure water at 80° C. for 120 minutes:
3. A silicon wafer carrier consisting of a composition composed of (a) 100 parts by weight of a polyester, (b) 31 to 100 parts by weight of a polyether ester amide, (c) 10 to 2,500 ppm (based on the polyether ester amide) of an alkaline metal and (d) 1 to 40 parts by weight of a modified polyolefin, containing a polyether ester amide phase having an aspect ratio of 3 or more, a minor diameter of 1 &mgr;m or less and a major diameter of 1 &mgr;m or more in a polyester phase in the range from the surface of the silicon wafer carrier to the depth of 20 &mgr;m, generating not more than 10 ppm of volatile gas by the heat-treatment at 150° C. for 60 minutes, and eluting not
Numata Takayoshi
Sugie Kiyoshi
Yamamoto Satoshi
Zhang En Lai
Rader Fishman & Grauer
Teijin Limited
Yoon Tae
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