Browse Prior Art Database

Lead Silicate Glass Isolation Technology

IP.com Disclosure Number: IPCOM000047578D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Beyer, KD: AUTHOR [+2]

Abstract

Lead silicate glasses are useful as an isolation material for deep trench isolation of semiconductor integrated circuits. Although many techniques, such as chemical vapor deposition (CVD), sputtering or paint-on coatings, are feasible for the deposition of lead silicate glasses, it is preferred to use the centrifuge sedimentation method. The centrifuge sedimentation of lead silicate glass allows the precise selection of the glass material, which matches the thermal expansion coefficient characteristics of silicon or other semiconductor in which the isolation is to be formed. In particular, the preferred material is lead silicate glass (CORNING 7723*), which has a softening temperature of approximately 770ŒC.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Lead Silicate Glass Isolation Technology

Lead silicate glasses are useful as an isolation material for deep trench isolation of semiconductor integrated circuits. Although many techniques, such as chemical vapor deposition (CVD), sputtering or paint-on coatings, are feasible for the deposition of lead silicate glasses, it is preferred to use the centrifuge sedimentation method. The centrifuge sedimentation of lead silicate glass allows the precise selection of the glass material, which matches the thermal expansion coefficient characteristics of silicon or other semiconductor in which the isolation is to be formed. In particular, the preferred material is lead silicate glass (CORNING 7723*), which has a softening temperature of approximately 770OEC. This softening temperature is higher than the common deposition temperatures of low pressure CVD polysilicon (600 to 700OEC). Therefore, polysilicon can be formed over the trench areas filled with CORNING 7723 glass. The process steps for making the glass isolation structure in a silicon substrate are shown in Figs. 1 to 6. As shown in Fig. 1, the starting structure includes P-substrate 10, N+ subcollector 12, N-silicon dioxide layer 15, silicon nitride layer 16, polysilicon layer 17, and silicon dioxide layer 18. The polysilicon layer 17 serves as an etching stop layer for the reactive ion etch (RIE) back at a later stage. Lithography and RIE etching techniques are used to form the groove 19 where the isolation is to be required, as shown in Fig. 1. A suitable masking structure is now formed on the Fig. 1 structure which consists of, for example, 50- to 100- nanometer thermal silicon dioxide, (SiO2) layer 20, 50- to 100-nanometer CVD or low pressure CVD (LPCVD) silicon nitride (Si3N4) layer 21, and 50-nanometer CVD SiO2 layer 22. This dielectric layer structure prevents the diffusion of boron or any other unwanted impurities contained in the glas...