Compositions: ceramic – Ceramic compositions – Refractory
Reexamination Certificate
1999-07-08
2001-05-01
Group, Karl (Department: 1755)
Compositions: ceramic
Ceramic compositions
Refractory
C264S653000
Reexamination Certificate
active
06225249
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an aluminum nitride sintered body, a method of producing thereof, electrostatic chuck, susceptor, dummy wafer, clamp ring and particle catcher using the same.
2. Background of the Invention
Since aluminum nitride has excellent thermal conductivity and electric insulating property, sintered bodies thereof have been employed as materials for multilayer interconnection substrates.
But, aluminum nitride has recently been appraised in plasma resistibility; application of aluminum nitride has been advanced for relative products of semiconductor producing apparatus of electrostatic chuck, susceptor or dummy wafer.
Description of the Related Art
Conventionally known is such aluminum nitride sintered body of high thermal conductivity (100 W/mK) which is composed of aluminum nitride (AlN) phase and yttrium aluminum oxide phase of mainly YAG (3Y
2
O
3
·5Al
2
O
3
or Y
3
Al
5
O
12
), where yttrium aluminum oxide phase catching impure oxygen is formed at grain boundary of aluminum nitride (see JP-A-62-171964).
This aluminum nitride sintered body is produced by granulating a mixture of aluminum nitride powder and yttrium oxide (Y
2
O
3
) powder, forming, dewaxing, and then sintering the dewaxed body in non oxidizing atmosphere. Yttrium oxide and aluminum-oxygen element contained in crystal of aluminum nitride are reacted during sintering to cause to generate yttrium aluminum oxide in liquid phase, so that oxygen element in crystal of aluminum nitride is trapped in grain boundary, and oxygen content in crystal of aluminum nitride is controlled to be very low level so as to make an aluminum nitride sintered body of high thermal conductivity and high insulating property.
However, in the conventional aluminum nitride sintered body, electric resistance is too high as around 10
15
&OHgr;·cm in volume resistivity at room temperature (20° C.±2° C.) or higher than it, and therefore when applying it to electrostatic chuck, susceptor, clamp ring, dummy wafer or particle catcher, the following inconvenience will arise. For example, in the electrostatic chuck, inconveniences are shortage of holding force by high resistance of a dielectric layer, and remaining holding force when dichucking (when stopping impression of voltage). In the dummy wafer, inconvenience is failure of holding at the electrostatic chuck. In the susceptor and clamp ring, it is a disorder of a wafer assumed to be due to static electricity. In the particle catcher, it is shortage in capture force of particles by high resistance of the dielectric layer.
Desirous electric resistance value of aluminum nitride sintered body in these applications is assumed to be around 10
10
to 10
14
&OHgr;·cm as the volume resistivity of room temperature. For removing these inconveniences, there are attempts to reduce the volume resistivity of an aluminum nitride crystal formed by a chemical vapor deposition method by making elements of IIb, IVb and VIb or oxygen solute in the aluminum nitride crystal (see JP-A-8-153603, JP-A-8-78202, JP-A-8-157263 and JP-A-8-51001).
However, since these arts introduce defects or strains into the aluminum nitride crystal, it is considered that they bring about lowering of thermal conductivity resulting in phonon scattering, and predominance of the high thermal conductivity of aluminum nitride is difficult to keep. Further, the chemical vapor deposition method is a suitable instrument for producing film like products, but has a defect not practical for producing bulk like products.
SUMMARY OF THE INVENTION
Thus, it is an object of the invention to provide an aluminum nitride sintered body having a thermal conductivity (100 W/mK or more) equivalent to high purity aluminum nitride and a volume resistivity at room temperature of 10
14
&OHgr;·cm or less, and a production method therefor as well as an electrostatic chuck, susceptor, dummy wafer, clamp ring and particle catcher using the same.
For solving the problems involved with the related prior art, according to the invention, an aluminum nitride sintered body composed of an aluminum nitride phase and an yttrium aluminum oxide phase formed at grain boundary of an aluminum nitride phase, is characterized in that the yttrium aluminum oxide phase is 0.5 to 10 wt % in extremes for the aluminum nitride phase, and contains at least one kind of lanthanoid element 0.1 to 20 atom % in extremes for an yttrium element.
On the other hand, a method of producing the aluminum nitride sintered body is characterized in that an aluminum nitride powder is added with an yttrium compound powder and at least one kind of lanthanide compound powder so as to form mixed powders, and the mixture is dewaxed, and subsequently the dewaxed body is sintered at temperature between 1600 and 2000° C. in a non oxidizing atmosphere, thereby to produce an aluminum nitride sintered body where the yttrium aluminum oxide phase is 0.5 to 10 wt % in extremes for the aluminum nitride phase, and contains at least one kind of lanthanide element 0.1 to 20 atom % in extremes for the yttrium element.
With respect to the mixed powder, it is preferable that the aluminum nitride powder is added with yttrium compound powder in such a manner that the yttrium aluminum oxide phase to be generated by sintering is 0.5 to 10 wt % in extremes for the aluminum nitride phase, and contains at least one kind of lanthanide element 0.1 to 20 atom % in extremes for yttrium element.
In addition, it is characterized that the electrostatic chuck, susceptor, dummy wafer, clamp ring and particle catcher use the aluminum nitride sintered body, respectively.
REFERENCES:
patent: 5063183 (1991-11-01), Taniguchi et al.
patent: 5314850 (1994-05-01), Miyahara
patent: 5500395 (1996-03-01), Ueno et al.
patent: 5744411 (1998-04-01), Zhao et al.
patent: 5767027 (1998-06-01), Sakon et al.
patent: 5773377 (1998-06-01), Harris et al.
patent: 5874378 (1999-02-01), Ishida et al.
patent: 5958813 (1999-09-01), Aida et al.
patent: 5993699 (1999-11-01), Katsuda et al.
patent: 6001760 (1999-12-01), Katsuda et al.
patent: 62-171964 (1987-07-01), None
patent: 406191953 (1994-07-01), None
patent: 8-51001 (1996-02-01), None
patent: 8-78202 (1996-03-01), None
patent: 8-157263 (1996-06-01), None
patent: 8-153603 (1996-06-01), None
Aonuma Shinichiro
Fujita Mitsuhiro
Muramatsu Shigeko
Sano Kouji
Foley & Lardner
Group Karl
Toshiba Ceramics Co. Ltd.
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