A High Sensitivity and Compact Real Time Gas Concentration Sensor for Semiconductor and Electronic Device Manufacturing Process

Abstract

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.

A high-sensitivity compact gas concentration sensor using ultraviolet light absorption with a heating function for a high-precision trimethyl aluminum gas supply system

“…6. 17,18) Differential signal voltages from switching two LEDs with different wavelengths with and without light absorption are amplified by a differential amplifier and sampled by a 16 bit analog/digital (A/D) converter. A 330 pF charge capacitor was used and the integration time was measured under the condition of 495 ms light irradiation at both 252 nm and 368 nm.…”

“…On the other hand, various MO gases have relatively high light absorbance in the UV waveband. [17][18][19][20][21] Focusing on this characteristic, we have been researching the development of a high-sensitivity MO gas concentration sensor using a timesharing dual-wavelength UV light absorption method. [17][18][19] The Lambert-Beer law (Eq.…”

“…[17][18][19][20][21] Focusing on this characteristic, we have been researching the development of a high-sensitivity MO gas concentration sensor using a timesharing dual-wavelength UV light absorption method. [17][18][19] The Lambert-Beer law (Eq. 1) relates attenuation and concentration when a target gas is irradiated with light:…”

“…By using a charge amplifier circuit to integrate photo charge for a higher SN ratio, a detection limit of the order of 10 ppm has been achieved for several MO gases. 17,18) Since the concentration of TMA gas in the bubbling method is generally about 1%, the detection accuracy of the gas concentration sensor needs be 100 ppm or better. The shortest wavelength LED we used was 252 nm, but even with this we could not obtain a detection limit of more than 100 ppm.…”

Induced Start Dynamic Sampling for Wafer Metrology Optimization

“…In some of the aforementioned production steps, such as Chemical Vapor Deposition (CVD), the step quality is assessed by measuring a set of, so-called, critical dimensions at several sites on the wafer surface, with consequent time-consuming procedures needed to allow the metrology tool to visit all the required sites. In fact, in the example case of CVD, a process widely employed for altering the chemical composition of wafers, the quality is assessed by measuring the height of the 'deposited' layer [10]. The challenge for CVD and similar spatial processes is measuring a sufficient number of sites to allow the complete wafer profile to be reconstructed.…”