Browse Prior Art Database

A UNIVERSAL WAFER FLAT FINDER

IP.com Disclosure Number: IPCOM000006150D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Dec-07
Document File: 1 page(s) / 55K

Publishing Venue

Motorola

Related People

Josephine Harbarger: AUTHOR

Abstract

Silicon crystals as used throughout the semi- conductor industry have portions of their outer surfaces ground to SEMI standard dimensions and locations thereby creating so-called "flats" (both primary and secondary) on wafers sliced from the crystals. These "flats" should directly correspond to the conductivity type of the crystal (Positive or Negative) and are used also for purposes of alignment and orientation during subsequent wafer processing steps. These "flat" dimension and tolerance specifi- cations also vary as a function of the crystal and wafer diameters.

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MOIOROLA INC. Technical Developments Volume 12 April 1991

A UNIVERSAL WAFER FLAT FINDER

by Josephine Harbarger

THE PROBLEM

   Silicon crystals as used throughout the semi- conductor industry have portions of their outer surfaces ground to SEMI standard dimensions and locations thereby creating so-called "flats" (both primary and secondary) on wafers sliced from the crystals. These "flats" should directly correspond to the conductivity type of the crystal (Positive or Negative) and are used also for purposes of alignment and orientation during subsequent wafer processing steps. These "flat" dimension and tolerance specifi- cations also vary as a function of the crystal and wafer diameters.

  During the wafer shaping processes, wafers are often inspected for the correct flat locations to avoid the inadvertent mixing of unwanted wafer con- ductivity types.

  It is common to use an apparatus or carrier to reduce the time necessary to align the "flats" of many wafers at once so that the required alignment time is minimized. A roller is used that is turned manually. This roller in turn rotates the wafers which stop at the "flat" due to a conveniently placed groove in the base, thus accomplishing the desired alignment.

Past practice was to use a different apparatus or "flat finder" for each different wafer diameter. This

could mean, for example, four separate "flat finders" for wafers of 75mm, lOOmm, 125mm and 150mm, etc. This is costly and also can be inefficient from a m...