Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-03-20
2002-12-10
Rose, Robert A. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S054000
Reexamination Certificate
active
06491571
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate for use in an apparatus for attracting a wafer such as a semiconductor wafer and a manufacturing method thereof
2. Description of the Related Art
Electrostatic chuck are currently used to attract and hold semiconductor wafers in conveying, exposing, film-forming such as CVD (Chemical Vapor Deposition) and sputtering, micro processing, cleaning, etching or dicing the semiconductor wafers. Attention has been much paid to dense ceramics as materials for such electrostatic chucks. Particularly in the semiconductor manufacturing apparatus, a halogenated corrosive gas such as ClF
3
is often used as an etching gas or a cleaning gas. It is desired that the substrate or susceptor for the electrostatic chuck has high thermal conductivity in order to rapidly heat and cool the semiconductor wafer while holding it. It is further desired that the substrate has such thermal shock resistance as to be broken due to rapid temperature change. For example, dense aluminum nitride and dense alumina are considered promising, because they have good corrosion resistance to the above-stated haloganated corrosive gas and thermal shock resistance.
In the semiconductor manufacturing apparatus, it is necessary to prevent the production of particles which would cause defects in semiconductors. In the actual semiconductor manufacturing apparatus, the semiconductor wafer is attracted and held at its back face by the electrostatic chuck. At that time, particles occur on the back surface side of the semiconductor wafer. If a large amount of particles occur, they spread over the front surface of the semiconductor wafer and into a chamber. As a result, the chamber is contaminated, so that semiconductor failure might occur on surfaces of other semiconductor wafers.
To prevent this problem, there have been proposed the following techniques. When the attracting surface of the ceramic electrostatic chuck comes in contact with a silicon wafer, the uneven attracting surface of the electrostatic chuck contacts with the silicon, and rubs off a part of the silicon having relatively low hardness to produce particles. Considering this, fine protrusions on the attracting surface of the electrostatic chuck are rounded by applying plasma onto this attracting surface, thereby preventing the silicon from being rubbed off and consequently decreasing the number of particles (Japanese Unexamined Patent Application Laid-open No. 7-245336).
According to Japanese Unexamined Patent Application Laid-open No. 8-55900, when a silicon wafer is to be attracted to the electrostatic chuck, voltage to be applied to the electrostatic chuck is gradually increased, thereby to mitigate any shock caused through the contact of the silicon wafer with the chuck. By so doing, the damage to the silicon wafer is suppressed, and the number of particles resulting from silicon wafer having been rubbed off is decreased.
The present inventors have been continuing the study to decrease the number of particles adhering to the back surface of a semiconductor wafer after the wafer has been attracted by the electrostatic chuck. According to prior art stated above, it is possible to decrease the number of particles down to for example, few to several thousands per 8-inch wafer. However, to further improve the yield of the semiconductor wafers in the semiconductor manufacturing process and to cope with more micro-structured semiconductors, it is required to decrease the number of particles furthermore. It has been desired, for example, to decrease the number of particles to a few to several hundreds per 8-inch wafer.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to considerably decrease the number of particles adhering to the back surface of the wafer after the wafer has been attracted to a ceramic substrate of a wafer attracting apparatus.
The present invention relates to a substrate for use in a wafer attracting apparatus which comprises a substrate made of a ceramic material and adapted to attract and hold a wafer onto an attracting surface thereof, wherein said attracting surface is constituted by a ductile worked surface, the ductile worked surface has concave portions, a diameter of each of the concave portions is 0.1 &mgr;m or less, and when the wafer is attracted onto the attracting surface of the substrate and released from the attracting surface, the number of particles adhering to that wafer is 9.3 or less per 1 cm
2
. The measurement of the particles adhering to the wafer is effected in the present invention under the following condition, that is, at an attracting force of 50 g/cm
2
at room temperature in clean air. The ductile working is a working which effects working such as polishing of particles themselves at the surface of the substrate without peeling off such particles themselves from the attracting surface of the substrate.
The present invention also relates to a wafer attracting apparatus which comprises a substrate made of a ceramic material and adapted to attract and hold a wafer onto an attracting surface thereof, wherein said attracting surface is constituted by a ductile worked surface having a center line surface roughness height Ra of 0.05 &mgr;m or less formed by etching, vertical steps are formed among ceramic particles exposed outside at the attracting surface is 0.5 &mgr;m or less, and when the wafer is attracted onto the attracting surface of the substrate, the number of particles adhering to that wafer is 9.3 or less per 1 cm
2
.
The present invention further relates to a method for manufacturing a wafer attracting apparatus having a substrate made of a ceramic material and adapted to attract and hold a wafer on an attracting surface of the substrate, said method comprising the steps of: converting the attracting surface of the substrate to a ductile worked surface, cleaning the ductile-worked attracting surface by a cleaning member in a high purity cleaning agent while rubbing the attracting surface of the substrate with the cleaning member, and conducting an ultrasonically cleaning for the attracting surface in the high purity cleaning agent. The term “rubbing” means that the attracting surface of the substrate is rubbed with the cleaning member, while the attracting surface is not substantially damaged thereby.
The present invention further relates to a method for manufacturing a wafer attracting apparatus having a substrate made of a ceramic material and adapted to attract and hold a wafer on an attracting surface of the substrate, said method comprising the steps of: converting the attracting surface of the substrate to a ductile worked surface having a center line surface roughness height of Ra=0.05 &mgr;m, cleaning the ductile-worked attracting surface by a cleaning member in a high purity cleaning agent while rubbing the attracting surface of the substrate with the cleaning member, and conducting an ultrasonically cleaning for the attracting surface in the high purity cleaning agent.
The present invention further relates to a wafer attracting apparatus which comprises a substrate made of a ceramic material and adapted to attract and hold a wafer onto an attracting surface thereof, wherein said attracting surface is constituted by a ductile worked surface, and when the wafer is attracted onto the attracting surface of the substrate, a maximum roughness Rmax of the ductile worked surface of the substrate is 0.1 &mgr;m or less, and the number of particles adhering to that wafer is 9.3 or less per 1 cm
2
.
The present inventors have conducted a detailed study as to particles generated after the semiconductor wafer was attracted and held by the ceramic electrostatic chuck. As a result, the inventors made discoveries as follows. Specifically, the mirror finished surface of an 8-inch silicon wafer was mounted and attracted onto an attracting surface of an aluminum nitride electrostatic chuck. Thereafter, the number of particles on the mirror finished surface of the silicon wafer was measured to
Inoue Takahiro
Kato Kouji
Ohno Masashi
Yamada Naohito
NGK Insulators Ltd.
Parkhurst & Wendel L.L.P.
Rose Robert A.
LandOfFree
Substrate for use in wafer attracting apparatus and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Substrate for use in wafer attracting apparatus and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Substrate for use in wafer attracting apparatus and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2972830