Method and apparatus for increased workpiece throughput

TLDR: In this paper, a method for speeding workpiece thoughput in a low pressure, high temperature semiconductor processing reactor was described, which includes loading a workpiece into a chamber at atmospheric pressure, bringing the chamber down to an intermediate pressure, and heating the wafer while under the intermediate pressure (115, 230).

Abstract: A method is disclosed for speeding workpiece thoughput in a low pressure, high temperature semiconductor processing reactor. The method includes loading (100, 200) a workpiece into a chamber at atmospheric pressure, bringing the chamber down to an intermediate pressure (110, 210, 225), and heating the wafer while under the intermediate pressure (115, 230). The chamber is then pumped down to the operating pressure (125, 235). The preferred embodiments involve single wafer plasma ashers, where a wafer is loaded (100) onto lift pins at a position above a wafer chuck, the pressure is rapidly pumped down (110) to about 40 Torr by rapidly opening and closing an isolation valve, and the wafer is simultaneously lowered (115) to the heated chuck. Alternatively, the wafer can be pre-processed to remove (220) an implanted photoresist crust at a first temperature and the chamber then backfilled (225) to about 40 Torr for further heating (230) to close to the chuck temperature. At 40 Torr, the heat transfer from the chuck to the wafer is relatively fast, but still slow enough to avoid thermal shock. In the interim, the pump line is further pumped down to operating pressure (about 1 Torr) behind the isolation valve. The chamber pressure is then again reduced (235) by opening the isolation valve, and the wafer is processed (240).