Chamber pressure

About: Chamber pressure is a research topic. Over the lifetime, 2988 publications have been published within this topic receiving 30725 citations.

In situ fiber optic thermometry of wafer surface etched with an electron cyclotron resonance source

Abstract: The effect of plasma heating on wafer temperature during etching has been studied. Si and InP were etched using a high ion density discharge generated by an electron cyclotron resonance source. The wafer temperature was measured using fiber optic thermometry as microwave power, rf power, chamber pressure, and gas flow were varied. Wafer temperatures increased with both rf and microwave power, and decreased with chamber pressure. For a rf power of 50 W, chamber pressure of 1 mTorr, a source distance of 13 cm, and a 10 sccm Ar flow, an increase in microwave power from 50 to 500 W caused the temperature to increase from 62 to 186 °C. An increase in the rf power from 50 to 300 W increased the wafer temperature to 145 °C. Additionally, the effectiveness of using He flowing at the backside of the wafer for temperature control was analyzed. By setting the backside He pressure at 3 Torr, the temperature increased to only 29 °C. Time dependent etch characteristics of InP were studied and related to the in situ temperature measurements. At 100 W of microwave power, the InP etch rate increased from 100 to 400 nm/min as the wafer temperature rose from 20 to 150 °C. As the temperature increased above 150 °C, the profile became more undercut and the surface morphology improved. By setting the stage temperature to −100 °C and using 3 Torr of He pressure at the backside of the wafer, the InP etch rate remained constant during etching and undercutting was suppressed. For 500 W of microwave power, a fast InP etch rate of 2 μm/min was obtained when the wafer temperature was <110 °C, and it increased to over 4 μm/min when the temperature was ≳150 °C.

Apparatus for increased workpiece throughput

Abstract: A system is disclosed for speeding workpiece thoughput in low pressure, high temperature semiconductor processing reactor. The system includes apparatus for 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. The chamber is then pumped down to the operating pressure. The preferred embodiments involve single wafer plasma ashers, where a wafer is loaded onto lift pins at a position above a wafer chuck, the pressure is rapidly pumped down to about 40 Torr by rapidly opening and closing an isolation valve, and the wafer is simultaneously lowered to the heated chuck. Alternatively, the wafer can be pre-processed to remove an implanted photoresist crust at a first temperature and the chamber then backfilled to about 40 Torr for further heating 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 by opening the isolation valve, and the wafer is processed.

Novel Technique for Reconstructing High-Frequency Transient Rocket Chamber-Pressure Measurements

Abstract: *† ‡ , An algorithm for reconstructing transient rocket chamber pressures from attenuated time histories is presented. This method is presented as an alternative to traditional methods where motor pressures are sensed by transducers mounted in-situ to the motor casing. This in-situ installation presents several significant measurement issues including potential structural weakening of chamber walls, overheating of the pressure sensing element, motorcase strain-biasing of the sensing element, and resonance within the measurement port. A less complex, and consequently less risky, installation is to tap the case at desired locations using very small pressure ports, and then transmit pressure from the port to a pressure transducer using a significant length of pneumatic transmission tubing. This installation allows the transducer to be mounted in a controlled environment, and virtually eliminates any sensing errors due to motor case strain. Very small pressure taps are far easier to integrate with motor case walls, and allow multiple longitudinal measurements to be obtained without significantly reducing structural integrity of the motor case. The method, based on optimal deconvolution theory, amplifies attenuated pressure signals while rejecting additive noise. The method is validated using laboratory-derived data, and then applied to reconstructing transient chamber pressure for a small scale solid rocket motor.