Browse Prior Art Database

INVENTION SUMMARY: AUTOMATION OF THE WAFER DEMOUNT PROCESS

IP.com Disclosure Number: IPCOM000007228D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2002-Mar-06
Document File: 2 page(s) / 125K

Publishing Venue

Motorola

Related People

Anthony R. Weeks: AUTHOR [+3]

Abstract

The wafer thinning process requires the front side of each wafer to be submerged in wax, wherein, the wax mechanically affixes the wafer to the stain- less steel carrier. Next, the carrier is turned wafer side down and spun on a stainless steel table. A mixture of grit (aluminum oxide) and water are dis- pensed onto the table to aid in the wafer thinning process and to eliminate wafer to table contact. The lapping process continues until the wafers are approx- imately 7 mils thick. At this point, the carriers and attached wafers are submerged in a 5:l:l acid bath to etch the wafers to a final thickness of 5 mils. Finally, the carrier is placed on a hot plate for 10 minutes in an attempt to melt the wax bond be- tween the wafer and the carrier. At the end of this time, an operator attempts to peel (like the skin off a banana) the wafers from the carrier with a hand held vacuum wand by placing the vacuum on the back side ofthe wafer and lifting in an upward motion (Figure 1).

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 50% of the total text.

Page 1 of 2

0 M

MOlOlROLA Technical Developments Volume 22 June 1994

INVENTION SUMMARY: AUTOMATION OF~THE WAFER DEMOUNT PROCESS

by Anthony R. Weeks, James Lee and Stephen Switzer

  The wafer thinning process requires the front side of each wafer to be submerged in wax, wherein, the wax mechanically affixes the wafer to the stain- less steel carrier. Next, the carrier is turned wafer side down and spun on a stainless steel table. A mixture of grit (aluminum oxide) and water are dis- pensed onto the table to aid in the wafer thinning process and to eliminate wafer to table contact. The lapping process continues until the wafers are approx- imately 7 mils thick. At this point, the carriers and attached wafers are submerged in a 5:l:l acid bath to etch the wafers to a final thickness of 5 mils. Finally, the carrier is placed on a hot plate for 10 minutes in an attempt to melt the wax bond be- tween the wafer and the carrier. At the end of this time, an operator attempts to peel (like the skin off a banana) the wafers from the carrier with a hand held vacuum wand by placing the vacuum on the back side ofthe wafer and lifting in an upward motion (Figure 1).

  CSDM's wafer demount process will be auto- mated by incorporating; a large (2") delrin vacuum chuck! The chuck is connected to a vacuum shaft: which connects the chuck to the house vacuum line! Two bushings4 connect ithe vacuum shah to a sup- port beam: which allows the vacuum shaft move vertically without obstruction. Two springs are located above6 and below' the lower bushing. A stop pin8 is inserted through the vacuum shah, above the upper spring! Therefore, when !a downward force is applied to the vacuum shah; relative to the support beam: the stop pin forces the, upper spring6 into a com- pressed state. When the downward force is removed, the compressed spring6 expands, raising the vacuum shah* to its normal un state. To ensure that the upward movement of the vacuum shaft* does not come to a sudden stop, the lower spring' provides a cushion to the upward moving vacuum chuck! To ensure proper wafer/carrier separation, the place- ment of the vacuum shaft is not located above the centroid of the wafer. With the vacuum chuck closer to the edge ofthe wafer, air will be introduced to the bonding material allowing for a smooth wafer car- rier separation.

VACUUMWAND

-7

I HOT PLATE

Figure 1

  The wafer breakage occurs when the operator either fails to let the wax melt prior to attempting to remove the wafer, or the wafer is left on the carrier too long and the wafer cracks From heat stress. In other situations, wafer breaks have been attributed to the variation in removal techniques between oper- ators, For example, opera...