Quantitative Characterization of Plasma-Induced Defect Generation Process in Exposed Thin Si Surface Layers

Abstract

The defect generation process in Si surface layer induced by plasma exposures is studied by two optical analyses, spectroscopic ellipsometry (SE) and photoreflectance spectroscopy (PR). Two plasma sources with Ar-gas mixtures are employed; one is DC plasma and the other, electron cyclotron resonance (ECR) plasma. In the case of Ar-DC plasma exposure with 300 V bias, the SE analysis with an optimized optical model determines 1-nm-thick interfacial layer (IL) between the surface layer and the substrate, while in the case of the ECR, approximately 0.5-nm-thick interfacial layer is identified. This difference is attributed to that in self-bias voltages (Vdc) between two plasma sources. In order to quantify the damage, we have modified the PR analysis technique in order to evaluate the plasma-induced carrier trap site density, by correlating the Si surface potential change to the trapped carrier density. Combined with the results by plasma diagnostics, we found that the calculated defect generation probabilities by an impinging ion were the orders of 10-2 and 10-5 in the present DC and ECR plasma conditions, respectively, and that the probability depends on the Vdc. The obtained results enable us to predict the plasma-induced physical damage to the devices in advance at the stage of plasma process designs.

Micro-photoreflectance spectroscopy for microscale monitoring of plasma-induced physical damage on Si substrate

“…The result is shown in Fig. 18 translate to defect densities of over 10 12 cm ¹2 . The decrease in V s is attributed to charge trapping sites in the damaged layer.…”

“…If we fit the spectrum obtained experimentally to Eq. [18][19][20] This is caused by the prevention of the diffusion or drift of photogenerated carriers, due to recombination centers and/or changes in the surface potential. Of these, E g can be used as a measure of strain.…”

“…(1), we obtain the values of the four parameters: C, , E g , and À. 11,17,18) 3. µ-PRS setup Figure 1 shows an overview of our system for µ-PRS. 12,18) Meanwhile, in applying PRS to PPD measurements, the amplitude factor C is focused on.…”

“…5,6) For this reason, it has become crucial to accurately measure PPD as the wafers are being processed (in situ) in the production line. [12][13][14] Since the first attempts in 1997, 15,16) a number of reports have focused on the usage of PRS to characterize the surfaces of semiconductor wafers bombarded with ions, [17][18][19][20] but PRS has not yet achieved wide use. 7) Photoreflectance spectroscopy (PRS) is one of such optical techniques, which has been used to understand the fundamental characteristics of semiconductor materials, [8][9][10] and to measure gate oxide charging damage 11) as well as strain/stress on the wafer.…”

Characterization of Plasma Process-Induced Latent Defects in Surface and Interface Layer of Si Substrate

“…The processing time of 30 s was chosen as a saturation value in terms of the damaged-layer formation process according to the previous results. 46,47 Table I shows process conditions employed in this study. RF biasing at 13.56 MHz was applied to the wafer stage 120 mm in diameter with powers ranging from 50 to 200 W in the ICP or with a power of 10 W in the CCP, respectively.…”