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.
Gas flow control is important factor that influences the concentration of process gas and the pressure of the process chamber. In manufacturing processes that use metal organic (MO) gases, a system that controls the flow rate of MO gas must be developed to improve film performance and the reliability of film formation. We have developed a high temperature flow control system based on pressure measurements (HT-FCS) to control the flow rate of MO gas. Moreover, a liquid source control system that combines a HT-FCS and vaporizer was developed. Using this system, it was possible to control the flow rate of MO gas with high accuracy for extended periods. A flow control system that can supply MO gas with a stable flow rate by vaporizing MO material with the quantity needed at each time has been realized.
A new system for controlling gas concentration in a process chamber was developed using a combination of a new flow controller and a gas pumping system. The new flow controller does not exhibit overshooting; thus, a stable gas flow rate can be realized in a process chamber after valve operation. Furthermore, very rapid gas displacement in the chamber can be realized by combined gas flow system and pumping system. As a result, it took only 2 s to stabilize chamber pressure and gas composition from purge gas to process gases using Fourier transform infrared spectroscopy (FT-IR) method. It is possible to control process parameters such as gas concentration and working pressure during the entire process using this system.
We have been studying in-line gas concentration sensor units for various metal-organic(MO) gases used in electronic device manufacturing process. MO gases are low vapor pressure and are generally supplied by bubbling. At the time of bubbling supply, concentration control is performed by internal pressure control and feedback control by in-line gas concentration sensor units for concentration correction due to lowering of the liquid level inside the MO tank. We have evaluated a high sensitivity in-line gas concentration sensor that adopts ultraviolet absorption method and charge amplifier detection circuit and demonstrated that it is a unit with high response speed of 400 msec or less and high detection sensitivity. In this report, we confirmed that it is possible to measure the concentration of Zr, Hf type MO gas used for semiconductor gate insulating film.
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