Multiprocesses in a single plasma process chamber with high throughput require precise, sequential, high-speed alteration of partial pressures of multiple gas species. A conventional gas-distribution system cannot realize this because the system seriously overshoots gas pressure immediately following valve operation. Furthermore, chamber volume and conductance of gas piping between the system and chamber should both be considered because they delay the stabilizing time of gas pressure. Therefore, the authors proposed a new gas-distribution system without overshoot by controlling gas flow rate based on pressure measurement, as well as a method of pulse-controlled gas injection immediately following valve operation. Time variation of measured partial pressure agrees well with a calculation based on an equivalent-circuit model that represents the chamber and gas piping between the system and chamber. Using pulse-controlled gas injection, the stabilizing time can be reduced drastically to 0.6s for HBr added to pure Ar plasma, and 0.7s for O2 added to Ar∕HBr plasma; without the pulse control, the stabilizing times are 3 and 7s, respectively. In the O2 addition case, rapid stabilization can be achieved during the period of line/space pattern etching of poly-Si on a thin SiO2 film. This occurs without anomalous etching of the underlying SiO2 film or the Si substrate near the sidewall, thus obtaining a wide process margin with high throughput.

The precise and high-speed alteration of various gas species is important for realizing precise and well-controlled multiprocesses in a single plasma process chamber with high throughput. The gas replacement times in the replacement of N 2 by Ar and that of H 2 by Ar are measured in a microwave excited high-density and low electron-temperature plasma process chamber at various working pressures and gas flow rates, incorporating a new gas flow control system, which can avoid overshoot of the gas pressure in the chamber immediately after the valve operation, and a gradational lead screw booster pump, which can maintain excellent pumping capability for various gas species including lightweight gases such as H 2 in a wide pressure region from 10 À1 to 10 4 Pa. Furthermore, to control the gas flow pattern in the chamber, upper ceramic shower plates, which have thousands of very fine gas injection holes (numbers of 1200 and 2400) formed with optimized allocation on the plates, are adopted, while the conventional gas supply method in the microwave-excited plasma chamber uses many holes only opened at the sidewall of the chamber (gas ring). It has been confirmed that, in the replacement of N 2 by Ar, a short replacement time of approximately 1 s in the cases of 133 and 13.3 Pa and approximately 3 s in the case of 4 Pa can be achieved when the upper shower plate has 2400 holes, while a replacement time longer than approximately 10 s is required for all pressure cases where the gas ring is used. In addition, thanks to the excellent pumping capability of the gradational lead screw booster pump for lightweight gases, it has also been confirmed that the replacement time of H 2 by Ar is almost the same as that of N 2 by Ar.

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To realize precise and high-throughput multiprocesses in a single plasma process chamber with a rapid alternative of multiple gases, gas flow characteristics in a plasma process chamber are investigated and a pulse-controlled gas injection method is developed. It is found that gas replacement characteristics greatly depend on the gas supply method used. An upper shower plate has a great advantage in realizing a rapid gas replacement over the case without using the upper shower plate, resulting from the realization of the down flow pattern of feed gas in the chamber. The pulse-controlled gas injection method employs the intentional overshoot pulse at the beginning of gas supply to rapidly stabilize gas pressure. Interference matrix operation is newly introduced to determine the pulse size for the arbitrary gas flow pattern in the chamber. The optimum pulse size can be successfully obtained in the case of HBr addition to a pure Ar plasma.

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