Evaluation Using a Noncontact Laser Beam Induced Conductivity/Current Method for the Silicon-on-Insulator Made by Wafer
- PDF / 1,625,930 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 121 Downloads / 178 Views
EVALUATION USING A NONCONTACT LASER BEAM 1NDUCED CONDUlCTIVIrY/CURRENT METHOD FOR THE SILICON-ON-INSULATORl MADE BY WAFER BONDING A.USAMI,
T.NAKAI, H.FUJIWARA, S.ISHIGAMI*, K.MATSUKI** AND T.TAKEUCHI..
T.WADA,
Nagoya Institute of Technology, Nagoya 466, Japan. *Mitsubishi Material Co.,Ltd., Omiya 330, Japan a*DAINIPPON SCREEN Mfg. Co.,Ltd, Kyoto 612, Japan ABSTRACT In this study, we evaluate the electrical characteristics of the silicon on insulator (SOI) layer made by the wafer bonding method using a photoconductivity modulation method, in other words, noncontact laser beam induced conductivity/current (LBIC) method. The He-Ne laser pulse (K = 633nm, pulse width=2ms) is used as the carrier-injection light source. The detected signal intensity decreases at the void area as compared with at the center area of the SOI layer where there are no voids. The positions of the voids revealed by the proposed method are in good agreement with those by X-ray topography. We also measure the lifetime using the photoconductivity decay method using the laser diode. The lifetime at the void area is much shorter than that at the center area. It is considered that the decrease in the detected signal intensity at the void area is due to reduction in the minority carrier lifetime. I.
INTRODUCTION
In recent years, many investigations for a SOI structure have been reported. It is a very attractive technique in the very large scale integration (VLSI) fabrication, because it has many interesting features, for example, absence of the latch-up. There are several popular approaches for obtaining a SOI structure such as zone melt recrystallization (ZMR) [1], separation by implanted oxygen (SIMOX) (2,3] and a wafer bonding method. However ZMR and SIMOX exhibit certain drawbacks. The SOI layer made by the wafer bonding method [4-7] is not degraded from its original bulk quality, and this technique has an advantage of crystal perfection as compared with other SOI techniques. However, there are several problems in fabrication of the SOI layer by the wafer bonding method. One of the most important problems faced by bonding technique is the presence of a void at the bonded interface. [5,7] To solve these problems, it is very important to evaluate the SOI layer and/or the interface. Then the methods for evaluating the SOI layer separately from the substrate are desired. Conventional X-ray transmission topography is generally used to evaluate the quality of the SOI layer, but it produces a projected image of all defects present in the SOI layer and in the substrate. Thus, it is impossible to evaluate only the SOI layer by this method. In this study, we show a contactless and nondestructive method for evaluating the SOI layer based on a noncontact LBIC method. [8,9] A He-Ne laser (x = 633nm) is used for carrier injection. The penetration depth of this laser for Si is about 3 1m. Hence, the detected microwave signal intensity is closely related to surface conditions and to the minority carrier lifetime near the surface. Therefore, w. apply this met
Data Loading...
