Wafer clamp for a heater assembly

Details Wafer clamp for a heater assembly Wafer clamp for a heater assembly

1999-06-15

2001-02-13

Ferensic, Denise L. (Department: 3749)

Heating

Accessory means for holding, shielding or supporting work...

Support structure for heat treating ceramics

C432S253000, C432S259000, C269S021000, C204S298150

Reexamination Certificate

active

06186779

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an apparatus for semiconductor fabrication, and more particularly to a heater assembly clamp used in an Al reflow process.
BACKGROUND OF THE INVENTION
In manufacturing a semiconductor device, an Al (aluminium) reflow process provides metal with excellent step coverage for filling high aspect ratio contact openings. In performing Al reflow on a semiconductor wafer, argon (Ar) gas can be blown on the back side of the wafer to improve temperature uniformity and thermal conductivity. However, the argon gas flow can separate the wafer from a heater table on which the wafer sits for the Al reflow by creating a pressure difference between a high vacuum chamber and the backside of the wafer. Thus, a clamp is used for preventing the wafer separation.
FIG. 6
illustrates a known clamp
100
, which holds a semiconductor wafer during Al reflow. Clamp
100
includes a cap
102
, a pad
104
and a mounting plate
106
which are made of stainless steel. Cap
102
and pad
104
are fixed to mounting plate
106
by screws
110
. Clamp
100
can damage a semiconductor wafer that is fixed between pad
104
and mounting plate
106
. For example, a wafer edge section that contacts the pad
104
may crack when heating causes clamp
100
and the wafer to expand. Although slots
108
are made in clamp
100
to suppress expansion of pad
104
that may contact and damage the wafer, the expansion can still damage the wafer during an actual process. Additionally, the surface of pad
104
can become rough, due to deformation of pad
104
during multiple high temperature processes. As a result, the rough surface of pad
104
can damage a surface of the wafer.
SUMMARY OF THE INVENTION
According to an embodiment of the present invention, a heater assembly clamp includes a pad, a cap and a mounting plate which are made of a ceramic material. The pad contacts the edge of a semiconductor wafer, and the cap covers the top surface of the wafer. The mounting plate covers the side surface of the wafer. The cap, the pad and the mounting plate may be integrated in a single body or structure.
The clamp can include several additional features to improve performances. The inner surface of the cap and the pad can be polished to enhance thermal reflectivity. The surface of the pad contacting the wafer can be sloped 0.5 degree or more with respect to a horizontal plane to minimize potentially damaging contact with a wafer, and the pad can have slots outside the perimeter of the wafer to reduce heat dissipation from the wafer through the clamp.
Since the clamp is made of a ceramic material, which has less thermal deformation than stainless steels, the damage to the wafer due to the deformation of a clamp pad is reduced. In addition, the ceramic material has lower thermal conductivity than the stainless steel, and thus the heat dissipation from the wafer through the clamp is reduced. The reduction of the heat dissipation minimizes the temperature difference across the wafer during the Al reflow.


REFERENCES:
patent: 4537244 (1985-08-01), Holden
patent: 5131460 (1992-07-01), Krueger
patent: 5421401 (1995-06-01), Sherstinsky et al.
patent: 5605866 (1997-02-01), McClanahan et al.
patent: 5725718 (1998-03-01), Banholzer et al.
patent: 5842690 (1998-12-01), Lee et al.
patent: 5885428 (1999-03-01), Kogan
patent: 5969934 (1999-10-01), Larsen

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