Fast Gas Replacement in Plasma Process Chamber by Improving Gas Flow Pattern

Abstract

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.

Gas Flow Characteristics in a Plasma Process Chamber and Proposal of New Pulse-Controlled Gas Injection Method Using Interference Matrix Operation for Rapid Stabilization of Gas Pressure

“…At the same time, it was reported that gas replacement time becomes shorter with the introduction of an upper shower plate that can supply gases with a uniform down flow pattern in the chamber compared with the case that gas is only introduced from the sidewall of the chamber, demonstrating that gas replacement characteristics depend on the gas supply method used. 3) It is newly found that such characteristic variations induce a deviation in the actual time variation of gas pressure from the solution of the differential equation of gas flow, contrary to our previous study. 2) Thus, the establishment of a design guide for obtaining an optimum pulse size in the pulse-controlled gas injection method that can be applied to arbitrary gas flow patterns in various chambers is strongly required.…”

“…Time variations of relative concentrations of these gases in the chamber during the plasma excitation including the transient period of the gas replacement were approximately estimated by optical emission spectroscopy (OES) using the calibration curves. 2,3) In the OES measurement, an optical fiber was set outside of a quartz window installed at the chamber wall, and the emitted light was guided to the optical spectrometer (Ocean Optics HR2000) through the optical fiber, as shown in Fig. 1.…”

“…where P 0 ¼ f =S is the steady-state Ar pressure. Equation (3) indicates that the Ar partial pressure P A ðtÞ increases with the time constant 0 and asymptotes to P 0 . Thus, in the CSTR, the gas is not replaced completely at t ¼ 0 , i.e., P A ð 0 Þ ¼ 0:63P 0 , and it requires few 0 to complete practical gas replacement, i.e., P A ¼ 0:99P 0 at t ¼ 4:6 0 .…”

“…Rapid gas replacement in a plasma process chamber is an important issue in realizing high-throughput processes and/or precise multiprocesses in a single chamber. [1][2][3] This is also a key issue for atomic layer deposition processes employing sequential reactive gas supply and gas purging 4) to improve both film quality and throughput. To realize a rapid stabilization of the gas pressure in the chamber, the pulse-controlled gas injection method was developed.…”

Effect of Process Temperature of Al2O3 Atomic Layer Deposition Using Accurate Process Gasses Supply System

“…During the dielectric formation process, gas flow control is an important factor that influences the concentration of process gas and the pressure of the process chamber (8)(9)(10)(11)(12). Additionally, controlling the gas flow accurately makes process costs lower, because the minimum necessary source gas is used at each cycle of ALD.…”