`
`
`United States Patent 19
`
`Negoro
`
`CARAA
`US005411921A
`
`
`
`
`[11] Patent Number:
`
`
`
`[45] Date of Patent:
`
`
`5,411,921
`
`
`May 2, 1995
`
`[54] SEMICONDUCTOR CHIP DIE BONDING
`
`
`
`
`
`USING A DOUBLE-SIDED ADHESIVE TAPE
`
`
`
`
`
`
`
`
`
`
`Inventor: Atsuhito Negoro, Kyoto, Japan
`[75]
`
`
`
`
`
`
`
`[73] Assignee: Rohm Co., Ltd., Kyoto, Japan
`
`
`
`
`[21] Appl. No.: 218,764
`[22] Filed:
`Mar.28, 1994
`
`
`
`
`
`4,590,667 5/1986 Simo cseesssseccsesseeceeee 148/DIG.28
`
`
`
`
`
`.
`4,667,402
`5/1987 Wilde.....
`sesees 437/224
`
`
`
`
`
`
`5,110,388
`5/1952 Komiyamaet
`.. 156/249
`
`
`
`
`
`
`
`5,270,260 12/1993 Scheunenpflug .casenstensesensess 437/212
`
`
`
`
`
`
`
`Primary Examiner—Brian E. Hearn
`Assistant Examiner—Kevin M.Picardat
`
`
`
`
`
`
`
`Attorney, Agent, or Firm—Brambaugh, Graves,
`
`
`Donohue & Raymond
`
`
`ABSTRACT
`[57]
`
`
`
`
`Related U.S. Application Data
`
`
`
`
`
`
`A semiconductor wafer is stuck on an expandable tape
`Division of Ser. No. 13,754, Feb. 4, 1993.
`{62]
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`via a double-sided adhesive tape, and the semiconductor
`
`
`
`
`
`
`
`
`
`
`
`
`
`Foreign Application Priority Data
`[30]
`wafer is diced into semiconductor chips such that the
`
`
`
`
`
`
`
`
`double-sided adhesive tape is also cut into tape sections.
`Feb. 10, 1992 [JP]Japanwaccsccsscsscssssescssssccssssens 4.023731
`Japan ......
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Then, the expandable tape is expanded to deform plasti-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`FSU] Mint, CLS ccccccceccccsessssssssssssesseevesssens HO1L 21/60
`cally to thereby part the semiconductor chips from each
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`TS2] US. CL. cessccccsccscsssssecessesesseseees 437/217; 437/209:
`other. Then, the semiconductor chip and the tape sec-
`437/215; 437/219; 437/220
`
`
`
`
`
`
`
`
`
`
`
`tion stuck thereto is removed from the expandabletape,
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`[58] Field of Search .............. 437/209, 211, 212, 213,
`in which the semiconductor chip is pushed by a bar
`437/214, 215, 216, 217, 218, 219, 220; 156/247,
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`having a pointed tip while the expandable tape is vacu-
`248, 249, 250; 148/DIG. 28
`
`
`
`
`
`
`
`
`
`
`um-sucked. Finally, the semiconductor chip is bonded
`
`
`
`
`
`
`
`
`
`
`to a die pad of a lead frame via the tape section stuck to
`References Cited
`
`
`
`
`
`the semiconductor chip.
`U.S. PATENT DOCUMENTS
`
`
`
`
`
`
`6/1975 Hartleroad et al... 437/209
`5 Claims, 2 Drawing Sheets
`
`
`
`
`
`[56]
`
`
`3,887,996
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
` ELLEA
`ALLLD
`
`
`
`
`
`
`
`
`
`
`
`MICRON 1031
`
`MICRON 1031
`
`

`

`U.S. Patent
`
`
`
`
`May 2, 1995
`
`
`
`
`Sheet 1 of 2
`
`
`5,411,921
`
`
`
`
`
`FIG.
`7
`.
`Eee
`
`
`
`
`
`
`
`
`
`FIG. 2
`
`EtenLAnaaLALVlLLLLLhha9
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`MICRON 1031
`
`MICRON 1031
`
`

`

`U.S. Patent
`
`
`
`
`May 2, 1995
`
`
`
`
`Sheet 2 of 2
`
`
`
`
`
`
`
`
`5,411,921
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`FIG. 6 PRIOR ART
`
`4
`
`MICRON 1031
`
`MICRON 1031
`
`

`

`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`This application is a division of application Ser. No.
`08/013,754, filed on Feb. 4, 1993.
`
`
`
`
`BACKGROUND OF THE INVENTION
`
`
`
`
`
`
`
`
`The present invention relates to an improvement of
`
`
`
`
`
`
`bonding of a semiconductor chip to a die pad of a lead
`frame.
`
`
`
`
`
`Conventionally, a semiconductor device is produced
`
`
`
`
`
`
`
`by first bonding a semiconductor chip to a die pad of a
`
`
`
`
`
`
`
`
`lead frame (whatis called the die bonding), performing
`
`
`
`
`
`
`electrical connections such as wire bonding to the re-
`
`
`
`
`
`
`
`
`spective leads, and finally sealing this structure by form-
`
`
`
`
`
`
`
`ing a resin (hereinafter called molding). As shown in
`
`
`
`
`
`
`FIG.6, in the die bonding of a semiconductorchip 4, a
`
`
`
`
`
`
`preform material 10 that is a bonding material such as
`
`
`
`
`
`
`
`Au, Au—Si, a solder ora paste is applied to a die pad 8
`
`
`
`
`
`
`
`
`
`of a lead frame that is a metal thin plate madeof, e.g., a
`
`
`42—Nialloy.
`
`
`
`
`
`Where the preform material 10 is a metallic material,
`
`
`
`
`
`
`
`it needs to be heated to a high temperature in the bond-
`25
`
`
`
`
`
`
`
`
`
`ing process. For example, in the case of the Au—Si
`
`
`
`
`
`
`
`preform material, the die pad 8 is pre-heated at about
`300° C.for several seconds, further heated to 500°-600°
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`C. at
`the time of the bonding, and then gradually
`cooled.
`
`30
`
`
`
`
`
`
`
`
`In the case of metallic preform materials, such as Au,
`
`
`
`
`
`
`Au—Si and a solder, which need to be heated to a high
`
`
`
`
`
`
`temperature in the bonding process, a thermal stress is
`
`
`
`
`
`
`
`exerted on the semiconductor chip to affect the semi-
`
`
`
`
`
`conductor characteristics. Further,
`several heating
`35
`
`
`
`
`
`
`
`
`stages, for instance, stages for pre-heating at 300° C.,
`
`
`
`
`
`
`
`
`bonding at 500-600° C., gradual cooling at 300° C., 100°
`
`
`
`
`
`
`
`C. and 25° C. (ordinary temperature), should be pre-
`
`
`
`
`
`
`pared, which causesan increase of costs of manufactur-
`
`
`ing equipment.
`40
`
`
`
`
`
`
`
`
`Since the paste preform material is made, for instance,
`
`
`
`
`
`
`
`of an epoxy resin that is made conductive by adding a
`
`
`
`
`
`
`
`
`silver powder etc., the bonding process itself can be
`
`
`
`
`
`
`performedat the ordinary temperature. However, to set
`
`
`
`
`
`
`
`
`the resin, a large number of bondedstructures are col-
`45
`
`
`
`
`
`
`
`lected and subjected to aging in an oven at about 170°
`C. for 10-20 hours.
`
`
`
`
`
`
`
`
`
`
`
`
`However, the existence of the aging step lowers the
`
`
`
`
`
`
`
`
`efficiency of the bonding process and causes a cost
`increase. Further, there exist some factors of deteriorat-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`ing the semiconductor characteristics: for instance, the
`
`
`
`
`semiconductor device is placed in an environmentof a
`
`
`
`
`
`
`
`
`relatively high temperature of about 170° C., and a
`
`
`
`
`
`
`
`
`
`volatile organic gas generated from the paste may cor-
`rode the solder.
`
`
`
`In addition, since MOS semiconductor devices need
`
`
`
`
`
`
`
`
`
`
`
`
`verylittle current, it is becoming less importantto dissi-
`
`
`
`
`
`
`
`pate heat through the semiconductor substrate and the
`
`
`
`
`
`
`
`
`die pad, and to make a current flow through the back
`face of the semiconductor substrate. Thatis, it is now
`
`
`
`
`
`
`
`desired that adverse influences on the semiconductor
`
`
`
`
`
`
`
`
`
`
`
`
`characteristics be prevented and the efficiency of the
`
`
`
`
`
`
`die bonding process be improved, rather than consider-
`
`
`
`
`
`
`ing such properties as electrical conduction and thermal
`
`
`
`
`
`conduction of the die bonding material.
`SUMMARYOF THE INVENTION
`
`
`
`
`
`
`
`
`
`In view of the above circumstances, an object of the
`
`
`
`
`present invention is to provide a semiconductor device
`
`
`
`
`
`
`
`
`
`
`60
`
`
`
`
`
`65
`
`
`
`
`1
`
`
`SEMICONDUCTOR CHIP DIE BONDING USING A
`
`DOUBLE-SIDED ADHESIVE TAPE
`
`
`
`
`
`
`5,411,921
`
`
`
`2
`
`
`
`
`
`
`
`
`
`in which the die bonding can be performed easily with-
`
`
`
`
`
`
`out a heating process. Another object of the invention is
`
`
`
`
`
`
`to provide a manufacturing method of such a semicon-
`ductor device.
`
`
`
`
`
`
`According to the invention, in a semiconductor de-
`
`
`
`
`
`
`vice of a type in which a semiconductorchip is bonded
`
`
`
`
`
`
`
`
`
`
`to a die pad and the semiconductor chip and wires for
`
`
`
`
`
`
`electrical connection between the semiconductor chip
`
`
`
`
`
`
`
`
`and leads are molded by a resin, the semiconductor chip
`is bonded to the die pad via a double-sided adhesive
`
`
`
`
`
`
`
`
`
`tape.
`
`
`
`
`
`
`According to a second aspect of the invention, a
`
`
`
`
`
`method of manufacturing a semiconductor device com-
`
`
`
`
`prises the steps of:
`
`
`
`
`
`
`sticking a semiconductor wafer on an expandable
`
`
`
`
`
`tape via a double-sided adhesive tape;
`
`
`
`
`
`
`dicing the semiconductor wafer into semiconductor
`
`
`
`
`
`
`
`chips such that the double-sided adhesive tape is
`
`
`
`
`
`
`
`
`cut into tape sections together with the semicon-
`
`
`ductor wafer;
`
`
`
`
`
`
`
`expanding the expandable tape to part the semicon-
`
`
`
`
`
`ductor chips from each other;
`
`
`
`
`
`
`
`
`removing the semiconductor chip and the tape sec-
`
`
`
`
`
`
`
`
`tion stuck thereto from the expandable tape; and
`
`
`
`
`
`
`
`bonding the semiconductorchip to a die pad of a lead
`
`
`
`
`
`
`
`
`frame via the tape section stuck to the semiconduc-
`’
`
`
`tor chip.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`
`
`
`
`
`
`
`
`
`
`FIGS. 1-5 are views showing manufacturing steps of
`
`
`
`
`
`a semiconductor device according to an embodimentof
`
`
`
`
`the present invention; and
`
`
`
`
`
`
`FIG.6 is a view showing a conventional die bonding
`method.
`
`DESCRIPTION OF THE PREFERRED
`
`
`EMBODIMENT
`
`
`
`
`
`A manufacturing method of a semiconductor device
`
`
`
`
`
`according to the present invention is described hereinaf-
`
`
`
`
`
`
`ter with reference to the accompanying drawings.
`
`
`
`
`
`
`
`FIGS. 1-5 show respective steps of a die bonding pro-
`
`
`
`
`
`
`
`cess, which is the main process of the manufacturing
`method of the invention.
`
`
`
`First, as shown in FIG. 1, a double-sided adhesive
`
`
`
`
`
`
`
`
`
`
`
`
`tape 2 is stuck on the surface of an expandable tape 1
`
`
`
`
`
`
`
`made of, e.g., a polyvinyl chloride film. Then, a semi-
`conductor wafer3 is stuck on the double-sided adhesive
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`tape 2 such that the back surface of the formerfaces the
`
`
`
`
`
`
`
`latter. The double-sided adhesive tape 2 is formed, for
`
`
`
`
`
`
`instance, by applying an ordinary adhesive to a resin
`
`
`
`
`
`
`
`
`film such as a polyimide film, and should havea size
`
`
`
`
`
`larger than the semiconductor wafer3.
`Then, as shown in FIG.2, to divide the semiconduc-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`tor wafer 3, which has onits front surface a large num-
`
`
`
`
`
`ber of identical semiconductor circuits arranged in ma-
`
`
`
`
`
`
`
`trix, into semiconductor chips 4, cutting lines 5 are
`
`
`
`
`
`
`
`formed at the boundaries between the adjacent semi-
`
`
`
`
`
`
`
`conductor circuits with a diamond cutter. The cutting
`
`
`
`
`
`
`
`lines 5 are formed so as to reach the expandable tape 1
`
`
`
`
`
`
`
`through the semiconductor wafer 3 and the double-
`
`
`
`
`
`
`
`
`sided adhesive tape 2. Since the cutting lines 5 are
`
`
`
`
`
`
`
`formed in the expandable tape 1 only slightly, the re-
`
`
`
`
`
`
`
`spective semiconductor chips 4 thus cut remain to stick
`
`
`
`
`
`
`
`
`to the expandable tape 1 via the double-sided adhesive
`
`
`
`
`
`
`
`tape 2, so that the semiconductorchips do not part from
`
`
`
`
`each other in this step.
`
`
`
`
`
`
`Then, the expandable tape 1 is expanded byattaching
`its outer frame (not shown) to a container and vacuum-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`MICRON 1031
`
`MICRON 1031
`
`

`

`3,411,921
`
`_ 0
`
`
`
`
`
`
`
`
`
`
`4
`3
`
`
`
`
`
`
`
`
`
`occurno adverse influences, such as a thermalstress, on
`sucking the tape 1 or applying pressureto it. Asaresult,
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`the expandable tape 1 deformsplastically, and the semi-
`the semiconductor characteristics, and there are gener-
`
`
`
`
`
`
`
`conductorchips 4 are parted from each other as shown
`
`
`
`
`
`
`
`ated no volatile gasses harmful to the semiconductor
`in FIG.3.
`
`
`
`
`
`
`
`
`chip. Thus, it becomes possible to produce semiconduc-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`In this state, the outer frame of the expandable tape 1
`tor devices having high reliability and superior charac-
`
`
`
`
`
`
`
`
`is again attached to the vacuum sucking device, and
`
`
`
`
`
`
`
`teristics at a high yield. Further, since the semiconduc-
`
`
`
`
`
`
`
`while the bottom surface of the expandable tape 1 is
`
`
`
`
`
`
`
`
`tor chip is completely secured to the die pad by the
`
`
`
`
`
`
`sucked, a semiconductor chip 4 to be picked up is
`
`
`
`
`
`
`
`
`
`resin, no problems will occur with the passage of time
`
`
`
`
`
`
`pushed upward by a push-up bar6 (see FIG.4). At the
`
`
`
`
`
`
`
`with respect to the bonding characteristic of the semi-
`
`
`
`
`
`
`
`
`same time, the front surface of the semiconductor chip
`
`
`conductor chip.
`
`
`
`
`
`
`4 is vacuum-sucked upward through a collet 7. Since
`
`
`
`
`
`
`Further, according to the invention, the double-sided
`
`
`
`
`
`
`
`the bottom surface of the expandable tape 1 is vacuum-
`
`
`
`
`
`
`
`adhesive tape is easily stuck on the semiconductor
`
`
`
`
`
`
`sucked, when the tape 1 1s pushed upwardby a pointed
`
`
`
`
`
`
`
`
`
`wafer having a large size, and is cut at the same time as
`
`
`
`
`
`
`
`
`
`tip of the push-up bar 6, its portion around the pointed
`
`
`
`
`
`
`
`
`the wafer dicing. Therefore, the increase of the number
`
`
`
`
`
`
`
`
`
`
`tip of the bar 6 is kept sucked to peel off from the dou-
`
`
`
`
`
`
`
`of manufacturing steps that is caused by the addition of
`
`
`
`
`
`
`
`ble-sided adhesive tape 2 and goes down. Asa result,
`
`
`
`
`
`
`
`the double-sided adhesive tape is negligible. The num-
`
`
`
`
`
`
`
`the expandable tape 1 is stuck to the double-sided adhe-
`
`
`
`
`
`
`
`
`ber of the entire steps rather decreases very much be-
`
`
`
`
`
`
`
`
`
`
`sive tape 2 only at its very small portion that is on the
`
`
`
`
`
`
`
`
`cause there are needed no heating, gradual cooling and
`
`
`
`
`
`
`
`
`pointedtip of the push-up bar 6, or, exactly as shown in
`
`
`
`
`
`
`
`
`aging in the die bonding process. In addition, since no
`
`
`
`
`
`
`
`
`FIG.4, the bar 6 breaks through the expandable tape 1
`
`
`
`
`
`
`equipment for heating is necessary, the manufacturing
`
`
`
`
`
`
`
`while lifting the semiconductor chip 4. Thus, when the
`
`
`
`cost is reduced greatly.
`
`
`
`
`
`
`
`semiconductorchip4is furtherlifted while being vacu-
`Whatis claimedis:
`
`
`
`
`
`
`
`
`
`um-sucked through the collet 7, the semiconductorchip
`
`
`
`
`1. A method of manufacturing a semiconductor de-
`
`
`
`
`
`
`
`
`4 having the double-sided adhesive tape 2 is easily re-
`
`
`
`
`
`25
`vice comprising the steps of:
`
`
`
`
`
`
`
`moved from the expandable tape 1. The semiconductor
`
`
`
`
`
`providing a double-sided adhesive tape having first
`
`
`
`
`
`
`
`chip 4 as picked up is then carried to a die pad 8 of a lead
`
`
`
`
`
`
`
`and second adhesive surfaces on opposite side. S;
`
`
`
`
`
`
`
`frame by the collet 7, and can be bondedthereto simply
`
`
`
`
`
`applying a semiconductor wafer to an expandable
`
`
`
`
`by pushing (see FIG.5).
`
`
`
`
`
`
`
`tape using the double-sided adhesive tape by adher-
`
`
`
`
`
`
`
`
`It may be the case that when the semiconductor chip
`ing the semiconductor wafer to the first adhesive
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`4is removed from the expandable tape 1, peeling occurs
`
`
`
`
`
`
`
`surface and adhering the expandable tape to the
`
`
`
`
`
`
`
`between the semiconductor chip 4 and the double-sided
`second adhesive surface;
`
`
`
`
`
`
`
`
`
`
`
`adhesive tape 2. This can be avoided,i.e., peeling occurs
`
`
`
`
`
`
`
`dicing the semiconductor wafer into a plurality of
`
`
`
`
`
`
`
`between the double-sided adhesive tape 2 and the ex-
`
`
`
`
`
`
`semiconductor chips such that
`the double-sided
`
`
`
`
`
`
`
`pandable tape 1 in a positive manner where the push-up
`w 5
`
`
`
`
`
`
`
`
`adhesive tape is cut into tape sections together with
`
`
`
`
`
`
`
`
`bar 6 breaks through the expandable tape 1 while lifting
`the semiconductor wafer;
`
`
`
`the semiconductor chip 4 as shown in FIG. 4. Even
`
`
`
`
`
`
`
`
`
`
`
`
`
`expanding the expandable tape to part the semicon-
`
`
`
`
`
`
`
`
`
`where the push-up bar 6 does not break through the
`ductor chips from each other;
`
`
`
`
`
`
`
`
`
`
`
`
`expandable tape 1, the double-sided adhesive tape 1 that
`
`
`
`
`
`
`removing each of the plurality of semiconductor
`has been cut into a small section hardly continues to
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`chips and the double-sided adhesive tape section
`
`
`
`
`
`
`stick to the angle-bracket-like deformed portion of the
`
`
`
`
`
`
`
`adhered thereto from the expandable tape; and
`
`
`
`
`
`
`
`expandable tape I (that is being sucked) around the
`
`
`
`
`
`bonding each of the plurality of semiconductor chips
`
`
`
`
`
`
`
`
`push-upbar6, to assure that the peeling occurs between
`
`
`
`
`
`
`
`to a die pad of a lead frame by adhering the second
`
`
`
`
`
`
`
`the double-sided adhesive tape 2 and the expandable
`
`
`
`
`
`adhesive surface of the double-sided adhesive tape
`
`
`
`
`
`
`
`tape 1. The peeling occurrence at this location can be
`
`
`
`
`
`section adhered to the semiconductor chip to the
`
`
`
`
`
`
`
`moreassured byadjusting the adhesion of the surface of 45
`
`
`die pad.
`the double-sided adhesion tape 2 to be stuck to the
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`2. The method ofclaim 1, wherein in the expanding
`expandable tape 1 to be stronger than the ether surface
`
`
`
`
`
`
`step the expandable tape is expanded to deform plasti-
`
`
`
`
`
`to be stuck to the semiconductor chip 4.
`
`cally.
`
`
`
`
`
`
`Subsequently, electrical connections, ie., wire bond-
`
`
`
`
`
`
`
`
`
`
`
`
`
`3. The method of claim 1, wherein in the expanding
`ing between bonding pads on the semiconductor chip 4
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`step the expandable tape is expanded by vacuum-suck-
`and respective leads of the lead frame are made using,
`
`
`
`
`
`
`
`
`ing it.
`e.g., a gold wire 11 (alternatively, bumps may be used),
`
`
`
`
`
`
`
`
`and the resultant structure is molded by a resin 9. Fi-
`4. The method of claim 1, wherein the removing step
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`nally, the lead frame is cut at connecting portions of the
`comprises pushing the semiconductor chip to be re-
`
`
`
`
`
`
`
`
`
`
`
`
`
`moved fromafirst side opposite to the semiconductor
`respective leads, and forming is performed. Thus, a
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`semiconductor device is produced (see FIG. 5 ).
`chip by a bar having a pointed tip while sucking the
`
`
`
`
`
`
`
`
`
`
`
`
`
`expandable tape from thefirst side.
`As described above, according to the invention, the
`
`
`
`
`
`
`
`
`
`
`
`
`double-sided adhesive tape is used to bond the semicon-
`5. The method of claim 4, wherein in the removing
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`ductor chip to the die pad of the lead frame. Therefore,
`step the semiconductor chip is pushed bythe bar until
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`neither heating to a high temperature nor aging over a
`the bar breaks through the expandable tape.
`*
`*
`*
`*
`*
`
`
`
`
`
`
`
`
`long period is needed in the die bonding process. There
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`40
`
`
`
`
`
`
`
`65
`
`
`
`MICRON 1031
`
`MICRON 1031
`
`

`

`UNITED STATES PATENT AND TRADEMARKOFFICE
`
`
`
`
`
`
`
`CERTIFICATE OF CORRECTION
`
`
`
`:
`
`97 421,921
`PATENTNO.
`
`
`
`
`
`DATED
`> May 2, 1995
`
`INVENTOR(S) :
`
`
`Atsuhito Negoro
`
`
`
`
`
`
`
`
`
`
`
`
`
`itis certified that error appears in the above-indentified patent and that said Letters Patentis hereby
`corrected as shown below:
`
`
`
`
`
`
`
`
`Column 3, line 47 "ether" should read -~other--;
`
`
`
`
`
`
`
`
`
`
`
`
`
`Column 4,
`line 26 "side. S;" should read --sides;--.
`
`
`
`
`
`
`
`
`
`Signed and Sealed this
`
`
`
`
`Twenty-second Day ofAugust, 1995
`Attest:USnce lh
`
`
`
`
`Attesting Officer
`
`
`
`
`Commissioner of Patents and Trademarks
`
`
`
`
`
`
`BRUCE LEHMAN
`
`
`
`
`
`
`
`MICRON 1031
`
`MICRON 1031
`
`