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Alignment of Buried Structures in Semiconductor on Insulator Technology

IP.com Disclosure Number: IPCOM000039944D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Kern, DP: AUTHOR [+2]

Abstract

Semiconductor on insulator (SOI), for instance, Si on oxide, is a useful technology for a wide variety of applications. One technique to create Si on oxide is the so called Q-bonding approach. Here, oxidized Si wafers are brought into contact and fused together. One of the wafers is subsequently thinned down to form the Si on the oxide layer, while the other serves as the substrate. One extension of the basic approach is the possibility to have some structures already built into one, or possibly both, of the wafers to be joined. This article relates to a technique for providing alignment for the device structures already present in one of the wafers, with the structures to be built on the other.

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Alignment of Buried Structures in Semiconductor on Insulator Technology

Semiconductor on insulator (SOI), for instance, Si on oxide, is a useful technology for a wide variety of applications. One technique to create Si on oxide is the so called Q-bonding approach. Here, oxidized Si wafers are brought into contact and fused together. One of the wafers is subsequently thinned down to form the Si on the oxide layer, while the other serves as the substrate. One extension of the basic approach is the possibility to have some structures already built into one, or possibly both, of the wafers to be joined. This article relates to a technique for providing alignment for the device structures already present in one of the wafers, with the structures to be built on the other. Typically, the structures are present in the thick wafer (substrate), and they have to be located through the thin layer of Si and the insulator. Fig. 1 gives a cross- sectional view of an exemplary situation. As shown, the structure in the substrate is a shallow polysilicon-filled trench. It must be emphasized that the locating scheme to be disclosed does not depend on this specific embodiment. It is aimed at being able to discover the position of the structures in the substrate independently of the nature of the structures, or that of the insulator. The following method is employed to find the buried elements. It is done by inducing a current through the insulator with an impinging electron beam. One monitors this current as the electron beam is scanned across the wafer. A buried structure manifests itself as a change in the electron-beam-induced current. Fig. 2 shows the same structure as Fig. l, together with the electron beam and a schematic current measuring circuit. The circuit simply consists of a voltage source and a current meter. Fig. 3 shows an expec...