Browse Prior Art Database

Detection of Contamination of Silicon Surfaces

IP.com Disclosure Number: IPCOM000087532D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 81K

Publishing Venue

IBM

Related People

Kulkarni, MV: AUTHOR [+2]

Abstract

Described is a method that can be used to detect materials and residues on top of silicon surfaces that may interfere with the diffusion of impurity elements into the silicon.

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Detection of Contamination of Silicon Surfaces

Described is a method that can be used to detect materials and residues on top of silicon surfaces that may interfere with the diffusion of impurity elements into the silicon.

It is known that gaseous mixtures of H(2)O, HF and NO or NO(2) stain clean silicon surfaces very evenly. With contaminated silicon surfaces, on the other hand, the staining is quite uneven and usually brings out many artifacts which some workers have tried to relate to the surface properties of semiconductors. One of the hypotheses is that the residues, particles (hydrophilic and hydrophobic), and scratches act as nucleating sites for the staining reaction by virtue of the condensation characteristics of moisture (H(2)O) at these sites. Advantage of this chemical reaction, for which the condensation of moisture on silicon surfaces is one of the basic requirements, can be usefully taken to measure the cleanliness of silicon surfaces in the etched-out patterns in the silicon oxide before the impurity diffusion process.

The present method was successfully applied to detect residues on the bare silicon surfaces (P type base diffused) on the wafers which were used to make devices. It was noted that with identical processing at the arsenic emitter diffusion in a closed capsule, one of the groups of wafers gave shallower emitter diffusions (and consequently lower R(DB)) than the others. When some of the wafers from this particular group were inspected with the technique outlined below, easily noticeable stains of large circular areas occurred (Figs. 1A and 1B). In contrast, the wafers from the groups that, after emitter diffusion, showed higher R(DB) (indicating deeper emitter diffusion resulting in narrower base width) did show stains, but...