Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2002-06-12
2004-08-03
Jenkins, Daniel (Department: 1742)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S623000
Reexamination Certificate
active
06770379
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a susceptor for semiconductor manufacturing equipment which retains a semiconductor raw material by means of electrostatic charge, and more particularly, a susceptor for semiconductor manufacturing equipment formed by laminating plural aluminum nitride ceramic substrates with a high melting point metallic layer and an adhesive layer, the susceptor being used for a surface treatment of a silicon semiconductor wafer material.
2. Description of the Background Art
In the production of an LSI, an integrated circuit having fine wiring patterns is formed on the surface of a silicon semiconductor wafer. In order to establish an electrical insulation between the wiring patterns, an insulating film of silicon dioxide, silicon nitride or the like is formed by using various CVD means, such as plasma CVD, normal pressure CVD, etc. Hereinafter, this is referred to as “surface treatment”. In this surface treatment, the wafer is treated one by one and a susceptor for retaining the wafer is required. This will be explained about the case of an electrostatic chuck method using a ceramic susceptor (chuck) by way of example. As schematically shown in
FIG. 1
, a semiconductor wafer
2
is placed on the susceptor
1
. Reference numeral
9
denotes a thick-film electrode for endowing an electrostatic chucking function by applying an electric field to the susceptor through a direct current power source
10
. The electrode is generally composed a metallic layer of a high melting point metal such as W, Mo, etc. In general, a heater
3
for heating up the wafer
2
is provided under the susceptor. A direct current power source
7
gives an electric field to an electrode
6
and a CVD material gas
4
is supplied in a vacuum chamber
5
from an upside of the susceptor
1
, and plasma
8
is electrically generated. In such a manner, a film as mentioned above is formed on the surface of the wafer
2
. The susceptor is required to have a high thermal conductivity, so as to rapidly conduct heat from the heater, so that the wafer uniformly heated. Further, in order to retain the retaining position of the wafer with a high precision, the susceptor is required to have a high dimensional precision.
A fairly high direct current voltage (generally about 1 kV) must be applied between the electrode for chucking and the ground. For this, the aforesaid thick-film electrode is formed. A method for this film formation includes the so-called co-fire metallizing method and the so-called post-fire metallizing method. The former is a method, in which a layer of a material comprising mainly the high melting point metal is formed (generally by printing and coating a conductive paste) on a green body (green sheet) of ceramic powder, followed by laminating, and the ceramics and the high melting point metallic layer are simultaneously sintered. The later is a method, in which a layer of a raw material comprising mainly a high melting point metal is formed (generally by printing and coating a conductive paste) on a substrate composed of a sintered ceramic body and then several these sintered bodies are laminated. Further, the high melting point metallic layer is fired by sintering. The former is advantageous in producing a multilayer wiring substrate for a semiconductor device at a low cost as compared with the latter. However, in the former method, since a large number of thin sheets are laminated, the resultant sintered bodies are subjected to a large deformation. Therefore, this method is undesirable when a susceptor having a large outer diameter and a high dimensional precision is desired.
The outer diameter of a wafer to be surface-treated is rapidly becoming large. Therefore, the size of a susceptor for holding it is also required to be large and, in the case of a circular shaped susceptor, the currently required size is 200 to 300 mm in diameter and its thickness is generally about 5 to 50 mm. However, it is considered that a susceptor having a larger diameter will be demanded in the future. Also, with the increasing trend toward fine and highly dense wiring on wafers, it will be increasingly important to ensure a high precision in the arrangement of wiring patterns. Therefore, the precision of the retaining position of the wafer should be highly improved, and the dispersion of the thickness of the susceptor in the direction of the main plane and the demanded tolerance of the flatness are becoming severe. For example, there is a severe demand in that when the outer diameter is 200 mm and the thickness of 5 mm, the allowable tolerance of the thickness is plus/minus several tens &mgr;m and that of the flatness is about 100 &mgr;m. As described above, there is a strong demand for larger suceptors with a higher dimensional precision. Therefore, there are difficulties in applying conventional production processes of multilayer wiring substrates for semiconductor devices without modifications.
The mode for retaining (chucking) a wafer includes a mechanical method chucking mechanically, an electrostatic chucking method using electrostatic charge, and a vacuum suction method sucking with vacuum. Among them the mechanical method has been mainly used in which an aluminum (Al) article that has an enhanced corrosion resistance to plasma by forming an anodic oxide film is used as a susceptor. However, in recent years the spacing between wirings is narrower with rapid increase in density of an LSI. When the wafer or susceptor is corroded by plasma, they generate dusts. If the dusts are adhered on the wafer as contaminants, there is a serious problem in that the wiring patterns of an LSI is broken and forms short circuit, to decrease the yield of the wafer. In order to avoid this problem, it is required to use a susceptor having a superior corrosion resistance to a raw material gas or often clean a chamber. Cleaning means removing the dusts by using a gas, such as NF
3
, CF
4
, etc., which has a higher corrosion activity than the raw material gas and reacts with the dusts and such a gas is hereinafter referred as “reaction medium” or simply as “medium”. The above-mentioned susceptor made of aluminum is liable to be corroded by the medium. Accordingly, in order to solve the problems, an electrostatic chuck method using ceramics having excellent corrosion resistance as a susceptor has been used in recent years, as described in
Ceramics, vol.
30, No. 11, p. 999 to 1001 (hereinafter, the ceramic susceptor used in this method is called “an electrostatic chuck” or simply called “a chuck”).
As described in the foregoing article, a material suitable as such a electrostatic chuck includes ceramics composed mainly of alumina (Al
2
O
3
), aluminum nitride (AlN), boron nitride (BN), etc. Among these, aluminum nitride-based ceramics comprising mainly aluminum nitride (AlN) (hereinafter simply called “aluminum nitride” or “AlN”) is excellent in corrosion resistance to the medium and also is excellent in thermal conductivity. When aluminum nitride ceramics is sufficiently densified, for example, defects such as pores are extremely small to have a density of 98% of the theoretical density, it has a high corrosion resistance to a fluorine compound and the amount of dusts generated from the chuck can be largely decreased. Accordingly, the contamination of the wafer described above can also be prevented, and simultaneously the life of the chuck itself can be prolonged. Due to its high thermal conductivity, even when the outer diameter of a wafer becomes large, uniform heating of the wafer is relatively rapidly conducted owing to its quick uniform heating. In order to form a circuit having fine patterns with uniform quality and thickness, it is necessary to precisely control the surface temperature of a wafer. Accordingly, the electrostatic chuck made of aluminum nitride ceramics is being spread quickly.
A method for the preparation of such a ceramic substrate includes a method in which thin molded bodies (green sheets) are laminated and sintered and a method in which
Nakata Hirohiko
Natsuhara Masuhiro
Yushio Yasuhisa
Jenkins Daniel
McDermott Will & Emery LLP
Sumitomo Electric Industries Ltd.
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