A New Temperature Compensation Method For Si Wafers In Rapid Thermal Processor Using Separated SI Rings as Susceptors
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uniformity problem, a stronger radiation intensity at the perimeter of the wafer can be performed by a suitable design of the chamber reflector geometry[2], or by multiple zone lamp clusters with independent and dynamic power control[2-5]. Application of radiation shields and guard rings[6] can also lower the radiation losses from the wafer's edges. Temperature non-uniformity is also affected by the radiation properties of the pattern, film thickness, and surface roughness[7,8]. The specific geometry of the patterns and film thickness will affects the wafer's own processing uniformity. Even if one has the reactor perfectly tuned for a non-patterned test wafer, the temperature non-uniformity may be unacceptable for the patterned product wafer if the pattern size is sufficiently large (>5mm)[9]. From the above point of view, pattern effect is not good for RTP systems. However, on the contrary, one can utilize the property of pattern effect and make the semiconductor wafers have more uniform temperature distribution in a non-uniform temperature RTP system. In this work, we present a new temperature compensation method through patterned susceptors and show how this method works. EXPERIMENT Concentric Si rings, placed on the plane quartz or Si susceptor, are used as temperature compensation means to get uniform temperature distribution on Si wafers. Si rings were fabricated from 4-inch Si wafers by chemical wet etching. Each ring is 4mm in width and 30O0tm in 187 Mat. Res. Soc. Symp. Proc. Vol. 470 01997 Materials Research Society
thickness. The distance between adjacent rings is 1mm. Figure 1 shows the system configuration and the denoted number of each Si ring. Si rings are put on a plane quartz or a 4-inch Si wafer and are regarded as a patterned susceptor. The susceptor is supported by 3 quartz pins. 3-inch Si wafers are used as the monitor wafers to monitor the oxide thickness distributions after rapid thermal oxidation (RTO) processing. The RTP system is a cold wall system. The heating halogen lamps are arranged parallel to the Si wafer so that the Si wafer is front side heated. The oxidation condition is 960 °C, 500 torr in pure 02 without wafer rotation. We examine the different RTO oxide thickness distribution behaviors of monitor wafers for different patterned susceptors with different arrangement of Si rings. Halogen Lamps
MN4oritor Wafer
Si or Quartu Susceptor
Si Rings
Thermali Couple
1
2 3 4 5 6 7 8 9
et 3 Quartz Pins Susceptor
-J
Figure 1. The system configuration of the temperature compensation method using separated Si rings. RESULTS AND DISCUSSIONS Figures 2 (a),(b),(c) show the monitor wafers' oxide thickness distributions for 30 sec RTO oxidation on the quartz susceptor, 3 quartz pins susceptor and Si susceptor, respectively. No Si ring insertion was used in this case. Figure 3 shows the monitor wafers' center RTO oxide thickness with different oxidation time on the three different susceptors described above. From Figs.2 and 3, we can see that the monitor wafer on the quartz susceptor perfo
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