Maximum Processing Time

The rapid thermal processor (RTP) uses high intensity lamps to heat up silicon wafers to over 1000 degrees C over several seconds. However, the RTP can not sustain high temperatures for lengthy processes due to limited cooling capabilities.

To characterize the maximum processing time, we performed experiments at various temperature setpoints using the following fixed/initial conditions:

The temperature of the chilled water is monitored and the process is aborted when the chilled water temperature exceeds 30 [°C].

The table below specifies that maximum process time at each temperature setpoint. Since the ramp time was fixed at 20 [s], processes that require very slow ramp rates will overheat sooner. Also, at the end of the process, the chilled water temperature is recorded. The chilled water temperature always begins at 18 [°C] and at the end of each process, the chilled water temperature is higher. This is clear evidence that the chilled water system could not keep up with the amount of heat generated by the RTP. To protect the instrument from overheating, an interlock is set at 36 [°C].

Temperature
[°C]
Maximum Time
[s]
Water Temperature
[°C]
650 900 19.3
700 900 22.0
750 600 31.4
800 450 32.6
850 360 33.7
900 270 33.8
950 180 31.1
1000 100 27.4
1050 80 27.8

Specification

From conversations with the vendor, the tool is capable of much longer processing time and higher temperature. Below is a table of the instrument's capabilities. To achieve better performance, it is recommended to upgrade the cooling capacity of the chiller from 2500 [kW] to 3000 [kW].

Figure 1: The capability of our RTP is below the specification achieved by the vendor.