Stock material or miscellaneous articles – Nonparticulate element embedded or inlaid in substrate and...
Reexamination Certificate
1999-09-08
2001-01-16
Speer, Timothy (Department: 1775)
Stock material or miscellaneous articles
Nonparticulate element embedded or inlaid in substrate and...
C428S457000, C428S698000, C428S699000, C264S642000, C269S013000, C279S128000
Reexamination Certificate
active
06174583
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an aluminum nitride sintered body and a method of producing the same, and to a metal including member used as a function gradient member in which a metal member is embedded in an aluminum nitride sintered body. Moreover, the present invention especially relates to an electrostatic chuck preferably used in a semiconductor manufacturing apparatus.
2. Related Art Statement
Generally, an electrostatic chuck is used for chucking a semiconductor wafer in film forming steps of transferring, exposing, chemical vapor depositing, and spattering the semiconductor wafer, or in steps of micro-machining, washing, etching, and dicing. As a substrate member of the electrostatic member, a densified ceramics is sometimes used. Particularly, in a field of semiconductor manufacturing apparatuses, a halogen corrosive gas such as CIF is frequently used as an etching gas or a cleaning gas. Moreover, in order to rapidly heat or cool the semiconductor wafer while the semiconductor wafer is chucked, it is desirable that the substrate member of the electrostatic chuck has a high thermal conductivity. Further, in order not to fracture the substrate member due to a rapid temperature variation, it is desirable that the substrate member has a thermal shock resistivity. A densified aluminum nitride has a high corrosion resistivity with respect to the halogen corrosive gas mentioned above. Moreover, it is known that aluminum nitride has a high thermal conductivity and its volume resistivity is greater than 10
14
&OHgr;·cm. Further, it is known that aluminum nitride has a high thermal shock resistivity. Therefore, it is preferred to form the substrate member of the electrostatic chuck for the semiconductor manufacturing apparatus using an aluminum nitride sintered body.
On the other hand, in the semiconductor manufacturing apparatus, in order to use the electrostatic chuck as a suscepter for holding the semiconductor wafer, it is necessary to decrease the resistivity of the substrate member. For example, in Japanese Patent Publication No. 7-19831, in order to improve a chucking property of the electrostatic chuck, the volume resistivity of an insulation dielectric layer of the electrostatic chuck is decreased to smaller than 10
13
&OHgr;·cm by mixing a conductive material or a semiconductive material into an insulation member having a high volume resistivity. Moreover, in Japanese Patent Laid-Open Publication No. 2-22166, ceramic raw materials made of alumina as a main ingredient are sintered under a reduction atmosphere to produce a dielectric ceramic for the electrostatic chuck. In this case, 1-6 wt % of alkali earth metal and 0.5-6 wt % of transition metal, both shown as a weight of oxide, are included in the ceramic raw materials. In this method, for example, a dielectric rate is improved by mixing TiO
2
into alumina ceramics and a volume resistivity is decreased to 10
12
-10
18
&OHgr;·cm, to obtain a high chucking property.
However, the volume resistivity of a highly purified alumina nitride sintered body is greater than 10
14
&OHgr;·cm, and thus it is too high to use as the substrate member of the electrostatic chuck for the semiconductor manufacturing apparatus. In this case, in order to obtain a sufficient chucking property, it is necessary to form an extremely thin insulation dielectric layer having a thickness smaller than 300 &mgr;m. However, if the insulation dielectric layer is thin as mentioned above, there is a possibility of generating an insulation fracture and so on from one of the reaction layers in a surface of the insulation dielectric layer. From this point of view, we understand that it is preferred to make the thickness of the insulation dielectric layer greater than 500 &mgr;m.
However, in the known electrostatic chuck made of aluminum nitride, if the insulation dielectric layer is made thick as mentioned above, a chucking property of the electrostatic chuck is decreased, and thus it is difficult to obtain a sufficient chucking property particularly in a low temperature region in which a volume resistivity is high. Usually, a dry etching process is performed under a low temperature of −50° C.~−60° C., and a highly densified plasma CVD process is performed at about 100° C. In these low temperature processes, it is difficult to obtain-a predetermined chucking property stably.
In the electrostatic chuck in which aluminum nitride is used for a material of the substrate member, we think it is effective to add a metal member having a low resistivity in the substrate member as shown in Japanese Patent Publication No. 7-19831. However, in the electrostatic chuck mentioned above, the metal member having a low resistivity and so on is detached from a surface of the substrate member, and thus there is a possibility of being a cause of semiconductor pollution. Therefore, it is not preferred to use the electrostatic chuck mentioned above for a highly purified semiconductor process such as a process for 8 inch wafer.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electrostatic chuck that can be used under a wide temperature range from a low temperature of −60° C. to a Os high temperature of over 300° C., that has a stability with respect to a corrosive substance such as halogen corrosive gas or plasma, and that can minimize a removal of metal and so on from a substrate member thereof.
Another object of the present invention is to provide a metal including member that can be preferably used as an electric apparatus in a process i.e. a semiconductor manufacturing process using an electrostatic chuck and so on which requires use of highly purified substrate members.
Still another object of the present invention is to provide an aluminum nitride sintered body in which the amount of metal impurities is small and a volume resistivity thereof is low.
According to the invention, an aluminum nitride sintered body comprises characteristics such that an amount of total metal elements other than aluminum is smaller than 100 ppm, and a volume resistivity at room temperature is greater than 1.0×10
9
&OHgr;·cm and is smaller than 1.0×10
13
&OHgr;·cm.
Moreover, according to the invention, an aluminum nitride sintered body comprises characteristics such that an amount of total metal elements other than aluminum is smaller than 100 ppm, and a g-value of unpaired electrons is smaller than 2.0000 on a spectrum of aluminum nitride measured by an electron spin resonance method.
Moreover, according to the invention, an aluminum nitride sintered body comprises characteristics such that an amount of total metal elements other than aluminum is smaller than 100 ppm, and an amount of spin per unit mg of aluminum obtained from a spectrum on an electron spin resonance method is greater than 5×10
12
spin.
Moreover, according to the invention, an aluminum nitride sintered body comprises characteristics such that an amount of total metal elements other than aluminum is smaller than 100 ppm, and a main peak of a spectrum measured by a cathode luminescence method exists in a wavelength region from 350 nm to 370 nm.
Further, according to the invention, a metal including member comprises a construction such that a metal member is embedded in a substrate member made of an aluminum nitride sintered body, said metal member and said substrate member are integrally sintered, and a part of said substrate member is made of the aluminum sintered body mentioned above.
The inventors performed an examination having the steps of forming highly purified aluminum nitride powders in which a metal member is included to obtain a formed body, and sintering integrally the thus obtained formed body by means of a hot press method. During this examination, we found that a volume resistivity of the substrate member made of aluminum nitride, to which at least one side of the metal member is contacted, is extremely decreased, and the phenomena lead to the present invention. The phenomena are not known
Bessho Yuki
Kobayashi Hiromichi
Mori Yukimasa
Yamada Naohito
NGK Insulators Ltd.
Parkhurst & Wendel L.L.P.
Speer Timothy
Young Bryant
LandOfFree
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