Succeeding - Silicon Wafer and SOI Wafer Temperature Uniformity Processing
SUCCEEDING in acceptable silicon wafer and soi wafer temperature uniformity during rapid thermal processing (RTP), continues to challenge the semiconductor industry.
The gradient in across-wafer temperature can lead to thermal stress, which causes plastic deformation if wafer stress levels exceed the prescribed limit. Misregistration of the wafer can occur with the occurrence of plastic deformation changing the wafer dimensions from one lithography step to the next causing the inevitable misalignment and failure. Warpage of the wafer can additionally lead to higher stress levels and defects in dielectric films, with device performance suffering thereafter. With shrinking dimensions of devices and wafers living on the edge of 300mm, with continued talk of 450mm, these challenges will become critical.
As show in Figure 1, the front side of the wafer consists of three areas. The wafer periphery with its optically smooth thin films, the die area typically rough consisting of thin film stacks on a micro-scale level, and the area between the die. These three areas are all different consisting of radiative properties challenging temperature uniformity specifications.
Solving processing problems can be answered by understanding the non-uniformity of silicon wafer processing temperatures and its effect on thermal stress. Even with RTP delivering acceptable temperature uniformity, the levels of stress for unpattered wafers can lead to uniformities being unacceptable with plastic deformation of the patterned areas (see Figure 1).
Power ratios utilizing lamps (see Figure 2) for example, are enhanced for bare silicon wafers and then are used for patterned wafers. This may not be the best way to optimize the temperature uniformity since there are three differing zones as described in figure 1.
For more information about Standard Silicon Wafers and SOI Wafers as well as improving your chamber temperature uniformity, call or email Applied Watts today. We are the leaders in providing products and helpful information to ensure your application will succeed.
