High-Resolution Temperature Measurement Using Phase-Compensating Interferometer and Frequency-Monitoring Interferometer

Matsudo

et al. 2010

Appl. Phys. Express

We performed real-time non-contact monitoring of temperatures of a silicon wafer and chamber parts in plasma etching processes using optical fiber-based low-coherence interferometry. The measurements were performed in dual-frequency capacitively coupled Ar/C4F8/O2 plasma processes. The temperature of a 780-µm-thick Si wafer was measured with a deviation of 0.11 K. Comparison between in-situ measurement results of an on-wafer temperature sensor and an optical-fiber type fluorescence temperature sensor confirmed that the low-coherence interferometry had superior performance in monitoring the temperature of the Si wafer in real-time. This method will enable better control of etching performance with improved process reproducibility.

mentioning

confidence: 99%

Low-Coherence Interferometry-Based Non-Contact Temperature Monitoring of a Silicon Wafer and Chamber Parts during Plasma Etching

Matsudo

et al. 2010

Appl. Phys. Express

“…10) Many noncontact optical techniques have been developed for monitoring substrate temperature. [11][12][13][14][15][16][17][18][19][20][21] However, these are not suitable for application to commercial reactors, especially capacitively coupled plasma reactors, because of the large-size optical system, cost, limited measurement condition, and so on. We previously demonstrated the noncontact measurement of the temperature of a Si wafer itself by using low-coherence interferometry (LCI) during SiO 2 plasma etching in a dual-frequency capacitively coupled Ar/C 4 F 8 / O 2 plasma.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous In situ Measurement of Silicon Substrate Temperature and Silicon Dioxide Film Thickness during Plasma Etching of Silicon Dioxide Using Low-Coherence Interferometry

Matsudo

et al. 2012

Jpn. J. Appl. Phys.

We have successfully performed real-time noncontact monitoring of substrate temperature and thin film thickness during plasma etching using optical-fiber-based low-coherence interferometry. The simultaneous measurement of the silicon (Si) substrate temperature and the etching depth of the silicon dioxide (SiO2) thin film on this substrate was performed in a dual-frequency capacitively coupled Ar/C4F8/O2 plasma. The SiO2 film thickness was deduced from the ratio of the interference intensity at the SiO2/Si interface to that at the Si/air interface. The measurement error in the SiO2 film thickness was less than 11 nm. The temperature variation of the Si wafer was derived from the temperature change of its optical path length. The temperature measurement error, caused by the shift in optical path length due to the change in SiO2 film thickness, was reduced from 7.5 to 0.6 °C by compensating for the shift using the SiO2 thickness data. This method enables precise control of etching performance and improves process reproducibility.

Simultaneous measurement of substrate temperature and thin-film thickness on SiO2/Si wafer using optical-fiber-type low-coherence interferometry

Journal of Applied Physics

Kawasaki

et al. 2009

This paper proposes a technique for simultaneously monitoring the thickness of a SiO2 thin film and the temperature of a Si substrate. This technique uses low-coherence interferometry and has the potential to be used for online monitoring of semiconductor manufacturing processes. In low-coherence interferometry, when the optical path length of a layer is shorter than the coherence length of the light source, the two interference at the top and bottom interfaces of the layer overlap each other. In this case the detected peak position of the interference is shifted from the actual interface, resulting in an error in the temperature measurement, since the temperature is derived from the optical path length of the layer. To improve the accuracy of the temperature measurement, the effect of the overlapping interference was compensated by measuring the SiO2 thickness. The thickness of the Si substrate was 750 μm and the thickness of the SiO2 film was varied between 0 and 2 μm. The SiO2 thickness, which is shorter than the coherence length of the light source, was measured from the ratio of interference intensities of two superluminescent diodes (wavelengths: 1.55 and 1.31 μm). The measured ratio corresponded well with the theoretical one for SiO2 film thicknesses between 0 and 2 μm, and the error was less than 25 nm. The Si temperature was measured from the optical path length. In order to compensate for the overlapping interference, the shift in the peak position of the interference at the SiO2/Si interface was estimated from the measurement results of the SiO2 thickness. This improved the accuracy of the temperature measurement from 5.3 to 3.5 °C.