Methane (CH4) concentration distribution in a semiconductor process chamber was controlled using the measurement of computed tomography-tunable diode laser absorption spectroscopy (CT-TDLAS) and the ...feedback control toward the feeding CH4 concentrations and flow rates. CH4 diluted with nitrogen was fed into the chamber through a shower head having three separate and concentric areas. Thirty-two laser paths were configured in the chamber to collect the infrared absorption spectra for the CT-TDLAS measurement. The computed tomography calculation using the 32 spectra reconstructed the two-dimensional CH4 concentration distribution in the chamber. The measured concentration distribution was updated once per second. Based on the measured concentration distribution, the feedback control algorithm determined the feeding CH4 concentration and flow rate of each shower head area. In this work, we set the target distribution as a ring shape. In the control algorithm, first the feeding CH4 flow rate of each shower head area was adjusted to match the concentration peak radius in the measured distribution to the radius in the target distribution. Then, the feeding CH4 concentration of each area was adjusted in sequence to match the measured average concentration of each area to the corresponding concentration in the target distribution. The algorithm worked successfully, and the concentration distribution reached the target distribution. The extension of the application and its limitations were also discussed.
We performed in-situ monitoring of bis-cyclopentadienyl magnesium (Cp2Mg) vapor pressure supplied into a metal-organic vapor phase epitaxy reactor. As a light source we adopted a quantum cascade ...laser (QCL) of 12.9 m, which is the wavelength of Cp2Mg infrared absorption. We directly configured a laser path in the reactor to construct the Cp2Mg in-situ monitoring system. We streamed Cp2Mg and measured the vapor pressure in the reactor to evaluate it and its saturation and purge times in comparison with their calculated values which were determined from the measured values in the supply line. Next, we streamed Cp2Mg and other gas species used in gallium-nitride processes one by one to investigate their saturation times with the same QCL. Characteristic features of Cp2Mg such as the largest saturation time ratio and its large fluctuation were observed. These results indicate the importance of Cp2Mg in-situ monitoring in the reactor.
Abstract
The behavior of the partial pressure of SiF
4
, a byproduct of fluorine-based plasma etching, has been measured in real-time using a method based on Laser Absorption Spectroscopy (LAS). The ...partial pressure of SiF
4
is highly correlated with the etch rate of SiO
2
(
R
2
= 0.999). Etch endpoints were clearly observed from the signal transitions, whose period indicate the etch rate uniformity. In addition, integrating the partial pressure of SiF
4
with respect to time is correlated with the number of Si atoms etched regardless of the composition of the etched materials. Specifically, Si, SiO
2
and Si
3
N
4
were examined in this work. Based on the strong relationship between the measured SiF
4
partial pressure and the etching profiles, real-time monitoring by LAS is useful for the prediction of etch profiles.
The behavior of the partial pressure of SiF4, a byproduct of fluorine-based plasma etching, has been measured in real-time using a method based on Laser Absorption Spectroscopy (LAS). The partial ...pressure of SiF4 is highly correlated with the etch rate of SiO2 (R2 = 0.999). Etch endpoints were clearly observed from the signal transitions, whose period indicate the etch rate uniformity. In addition, integrating the partial pressure of SiF4 with respect to time is correlated with the number of Si atoms etched regardless of the composition of the etched materials. Specifically, Si, SiO2 and Si3N4 were examined in this work. Based on the strong relationship between the measured SiF4 partial pressure and the etching profiles, real-time monitoring by LAS is useful for the prediction of etch profiles.
Methane (CH4) concentration and temperature distributions were measured in a semiconductor process chamber using computed tomography-tunable diode laser spectroscopy (CT-TDLAS). A semiconductor ...chamber was designed with 32 laser-paths to collect the infrared spectrum of CH4 with tunable diode laser absorption spectroscopy. Absorptions at wavelength of 1628.1 nm and 1653.7 nm were used to reconstruct CH4 concentration and temperature distributions using computed tomography (CT) calculations. The validity of our CT algorithm for concentration and temperature distributions was checked using computer fluid dynamics. Concentration and temperature distributions were generated by injecting CH4 with different concentrations (5% or 10%) into the four inlet ports and setting different temperatures (25 °C or 125 °C) for four heater blocks on the susceptor. The pressure in the chamber was fixed at 760 Torr. The measured distributions showed high concentrations around the port set at 10% and high temperatures around the heater blocks set at 125 °C, as expected. When all blocks were set at 125 °C, CH4 temperature around one heater block was higher than others. The temperatures were confirmed with the thermocouples when CH4 was streamed at the same conditions.
Abstract
We performed in-situ monitoring of bis-cyclopentadienyl magnesium (Cp
2
Mg) vapor pressure supplied into a metal-organic vapor phase epitaxy reactor. As a light source we adopted a quantum ...cascade laser (QCL) of 12.9
μ
m, which is the wavelength of Cp
2
Mg infrared absorption. We directly configured a laser path in the reactor to construct the Cp
2
Mg in-situ monitoring system. We streamed Cp
2
Mg and measured the vapor pressure in the reactor to evaluate it and its saturation and purge times in comparison with their calculated values which were determined from the measured values in the supply line. Next, we streamed Cp
2
Mg and other gas species used in gallium-nitride processes one by one to investigate their saturation times with the same QCL. Characteristic features of Cp
2
Mg such as the largest saturation time ratio and its large fluctuation were observed. These results indicate the importance of Cp
2
Mg in-situ monitoring in the reactor.
We measured methane (CH4) concentration distribution in a semiconductor process chamber by using the computed tomography-tunable diode laser spectroscopy (CT-TDLAS). We designed the CT-TDLAS ...measurement system with a 32-laser-path. The CH4 concentration distribution was measured by the CT-TDLAS based on the 32 absorption spectra which were collected by scanning the laser wavelength around the CH4 absorption peak of 1653.7 nm. We checked linearity of the measurement, validity of the algorithm, and resolution of the computed tomography (CT) reconstructed distribution. In the algorithm check, we measured a simple concentration distribution generated in a five-fold concentric cylinder. Next, we designed a semiconductor process chamber in which the 32-laser-path was installed. After quantitative evaluations of the CT reconstructed distributions by comparing the simulated results of computational fluid dynamics, we actually measured the CH4 concentration distribution in the chamber when we streamed 10% CH4 from one of four inlet ports and nitrogen from other three ports into the chamber. The measured distributions were obviously different in accordance with the CH4 inlet location, although all the inlet ports were located cyclic-symmetrically. Those results indicated that the flow impedances of the four exhaust holes on the susceptor were different depending their locations.
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