Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
2001-07-13
2003-09-02
Tran, Khoi H. (Department: 3651)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C901S046000, C414S935000, C414S941000
Reexamination Certificate
active
06615113
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to article handling, and more particularly to article holders that handle semiconductor wafers and other articles.
During fabrication of integrated circuits from semiconductor wafers, the wafers are stored and transported in cassettes.
FIG. 1
illustrates a cassette
110
holding a number of wafers
120
. Each wafer rests on shoulders
130
A,
130
B formed on cylindrical cassette walls
140
A,
140
B. A robot (not shown) transports the wafers between the cassette and wafer processing equipment. An article holder (“end effector”) mounted on a robot arm holds the wafers by vacuum or electrostatic forces, or using a gas vortex, or by other means.
When a wafer is thin (below 100 &mgr;m), the wafer is difficult to store in a cassette. The wafer sags under its own weight, and can fall off the cassette shoulders
130
A,
130
B. A thin wafer can also be warped due to the internal stresses caused by the presence of different materials (semiconductor materials, metals, dielectrics) which constitute the wafer circuitry. Therefore, thin wafers have been stored in horizontal wafer shipment containers (“pods”), such as pod
210
in FIG.
2
. Wafers
120
are stacked in the pod on top of each other, with paper or plastic inserts
220
separating the wafers. Foam
230
is provided at the top and bottom of the stack (the top piece of foam is not shown). The foam and the paper or plastic inserts have roughly the same shape as the wafers, and most or all of the bottom surface of each wafer is in physical contact with the paper inserts above and below the wafer. The wafer circuitry is protected however. A typical fabrication process starts with fairly thick wafers (e.g. 600 to 800 &mgr;m for silicon wafers) which are stored in a cassette. When the wafer circuitry has been fabricated and a protective passivation layer has been formed on the circuitry side of the wafer, the wafer is thinned down from the other side to a final thickness (which may be 100 &mgr;m or less), and is stored in a pod. At this stage, the wafer circuitry is protected by the passivation layer, so the physical contact between the wafer
120
and the paper or plastic
220
is acceptable.
It is desirable to provide wafer handling techniques suitable for storage of wafers in pods.
SUMMARY
The present invention provides end effectors suitable for handling of wafers stored in pods such as pod
210
of FIG.
2
. The end effectors have sensors that allow automatic detection of whether an article held by the end effector is a wafer or a piece of packaging material, e.g. paper or plastic, or foam. Some embodiments can handle wafers stored in pods as well as wafers stored in cassettes.
The invention is not limited to thin wafers, and is applicable to thick wafers stored in pods or cassettes. The invention is also applicable to containers other than pods and cassettes.
The invention is not limited to semiconductor wafers. Some embodiments include article holders that handle glass or polymer wafers, or wafers made from other materials. In some embodiments, the articles handled by the end effector are multiple wafers bonded together. Such articles can be formed in the process of manufacture of vertically integrated circuits. See U.S. Pat. No. 6,184,060 issued Feb. 6, 2001 to O. Siniaguine and incorporated herein by reference. An article may include a combination of semiconductor and non-semiconductor wafers. See U.S. patent application Ser. No. 09/791,977 filed on Feb. 22, 2001 by O. Siniaguine and incorporated herein by reference. In other embodiments, the articles are flat-panel displays or other types of articles extending generally along a plane. Packaging materials other than paper or foam can be used.
The invention is not limited to article holders that are part of a robot. Some embodiments include hand-held article holders, or article holders mounted on non-electronically-controlled machinery. The invention is defined by the appended claims.
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Berger Alexander J.
Casarotti Sean A.
Kretz Frank E.
MacPherson Kwok & Chen & Heid LLP
Shenker Michael
Tran Khoi H.
Tru-Si Technologies Inc.
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