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Early Emitter Pipe Detector Detection by Measuring the Light Density After Base Diffusion

IP.com Disclosure Number: IPCOM000083887D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Paz, O: AUTHOR

Abstract

Early emitter pipe detection is possible because of the correlation between light emitter spots at an emitter after base diffusion, and the probability that there are collector-to-emitter shorts after emitter diffusion.

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Early Emitter Pipe Detector Detection by Measuring the Light Density After Base Diffusion

Early emitter pipe detection is possible because of the correlation between light emitter spots at an emitter after base diffusion, and the probability that there are collector-to-emitter shorts after emitter diffusion.

Light emission can be detected by using the microplasma emission localization process. With the PN junction biased as shown in Fig. 1, the electric field excites electrons from the P side. Electron 1 acquires kinetic energy and by colliding it excites an electron from valance band 2, which frees a hole 3.

The hole wanders to the left and then recombines with an electron that falls from the conduction band 4, through the defect level 5 that exists in the band- gap. Also shown is the electron trap that is generated by the weak spot 6. The defect level makes recombination more probable; therefore, it is necessary for observable light emission.

In operation, the base diffusion is contacted by one probe as shown in Fig. 2. In order to save a probe, the other contact is made through the back of the substrate, which forward biases the substrate's epitaxial junction. Microplasma spots are observed through a microscope. (The microscope should be equipped for simultaneous probing and viewing.)

Fig. 3 shows that the probability of a pipe occurring in an emitter is related to the number of microplasma spots (weak spots) seen after base diffusion. However, not all weak sp...