CN101567301B - Method for forming adhesive crystal grains separated from wafer - Google Patents

Abstract

The invention discloses a method for forming adhesive crystal grains separated from a wafer. The method comprises the following steps: forming cutting gaps among the crystal grains of the wafer; transferring an adhesive layer formed on an expandable film to the wafer; forming a presplitting guide groove on the adhesive layer without penetrating through the adhesive layer corresponding to the cutting gap; then, stretching the expandable film to split the adhesive layer along the lines of the pre-splitting guide groove; the die to which the adhesive layer has been attached is removed from the expandable film. Therefore, cutting burrs protruding out of the bonding crystal surface can not be generated at the edge of the bonding layer, the problems of bonding crystal inclination and clearance caused by the known cutting burrs are solved, and improper solidification of the edge of the bonding layer can be avoided when the bonding layer is separated at low temperature.

Description

Formation method of cohesive die separated from wafer

technical field

The invention relates to a manufacturing technology of a semiconductor device, in particular to a method for forming sticky grains separated from wafers.

Background technique

When the wafer (wafer) has gone through dozens or even more semiconductor processes, two or more integrated circuits or micro-electromechanical systems (MEMS) structures arranged in an array can be produced, and the cutting process will be used. The wafer is cut into two or more dies for subsequent semiconductor packaging and assembly processes. However, the surface of the conventional die is not sticky, and a die-bonding material needs to be coated on the substrate. It is necessary to develop a sticky die formation technology to control the sticky die characteristics, dosage and make the subsequent semiconductor packaging/assembly process more efficient.

Please refer to FIG. 1 , which is a cross-sectional view of a partial component during the formation process of a conventional sticky die being separated from a wafer. As shown in Figure A of FIG. 1 , a wafer 110 to be diced is provided, and the wafer 110 includes two or more integrated and unseparated crystal grains 111 . In addition, the wafer 110 may have an integrated circuit forming surface 112 and a back surface 113 , and the wafer 110 may also have two or more bonding pads 114 on the integrated circuit forming surface 112 (as shown in FIG. 2 ). Next, as shown in FIG. 1 , a backgrind tape 120 is pasted on the integrated circuit forming surface 112 of the wafer 110 , thereby covering and protecting the integrated circuit forming surface 112 of the wafer 110 . Afterwards, as shown in Figure C of FIG. 1 , the back surface 113 of the wafer 110 is ground to reduce the thickness of the wafer 110 to a predetermined thickness. Afterwards, as shown in FIG. 1 , a carrier film 140 with an adhesive layer 130 is pasted on the back surface 113 of the wafer 110 . Afterwards, as shown in Figure D in FIG. 1 , the crystal backgrinding tape 120 that was previously pasted on the integrated circuit formation surface 112 is separated in the direction of the arrow with a peeling jig (not shown in the figure) to reveal the The integrated circuit forms surface 112 (shown in Figure E in FIG. 1 ). Afterwards, as shown in Figure F in FIG. 1 , the wafer 110 is aligned using a wafer cutting machine (not shown in the figure), and a cutting tool (such as a diamond scriber) is used according to the preset A scribe line is used to cut the wafer 110 into two or more separated crystal grains 111 , and not only cut through the adhesive layer 130 , but also cut into the carrier film 140 a little. Finally, as shown in diagram G of FIG. 1 , a subsequent die picking process is performed with a vacuum nozzle (not shown in the figure).

Please refer to Figure F in FIG. 1 and shown in FIG. 2, in the above cutting step, when cutting the wafer 110 and the adhesive layer 130 to the carrier film 140 from top to bottom by using the cutting tool 160, the adhesive layer 130 will produce a downward curved burr 131 (as shown in FIG. 2 ), so that the adhesive layer 130 forms an uneven die-bonding surface, which will cause the adhesive layer 130 to be attached to another chip or substrate to produce a sticking tilt and Die sticking clearance problem. The adhesive layer 130 cannot form a good bonding area with the chip (or substrate) to be attached, resulting in easy delamination, thus affecting the quality of semiconductor packaging/assembly.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a method for forming sticky crystal grains separated from the wafer, avoiding cutting burrs protruding from the sticking surface at the edge of the adhesive layer, and further solving the known cutting burrs that cause the sticking die to be inclined. Problems with backlash.

The purpose of the present invention and the solution to its technical problems are achieved by adopting the following technical solutions. A method for forming cohesive grains separated from wafers according to the present invention mainly includes the following steps. First, a wafer is provided that contains two or more integrated, unseparated dies. Next, cutting gaps are formed between these grains. Afterwards, an adhesive layer is transferred on the wafer, wherein the adhesive layer is formed on the expandable film. Afterwards, a pre-splitting guide groove is formed on the adhesive layer, the pre-splitting guide groove is aligned with the cutting gap and does not penetrate the adhesive layer. Afterwards, the expandable film is stretched so that the adhesive layer is split along the lines of the pre-split channels. Finally, the die attached with the split adhesive layer are removed from the expandable membrane.

The purpose of the present invention and its technical problems can also be further realized by adopting the following technical measures.

In the aforementioned method of forming the sticky die separated from the wafer, the wafer may have an integrated circuit forming surface and a back surface, and the wafer may also have two or more bonding pads located on the integrated circuit forming surface.

In the aforementioned method of forming adhesive die separated from a wafer, the adhesive layer may be transferred to the integrated circuit forming surface of the wafer.

In the aforementioned method for forming the adhesive die separated from the wafer, the adhesive layer may be transferred to the backside of the wafer.

In the aforementioned method of forming the sticky die separated from the wafer, the step of forming the dicing gap between the dies includes the step of wafer half-dicing.

In the aforementioned method for forming sticky grains separated from a wafer, the cutting gap formed in the wafer half-cutting step may have a cutting depth smaller than the thickness of the wafer, and further includes a crystal back grinding step, so that these Grain separation.

In the aforementioned method for forming sticky die separated from the wafer, before the back grinding step, a back grinding tape may be attached to the wafer and cover the dicing gap.

In the aforementioned method of forming the adhesive die separated from the wafer, the backgrind tape can be removed after the step of transferring the adhesive layer.

In the aforementioned forming method of separating the sticky die from the wafer, the dicing gap and the pre-cracking guide groove can be formed by a dicing tool in the same step.

In the aforementioned method of forming sticky dies separated from the wafer, after stretching the expandable film, an additional step may be included: losing or reducing the stickiness of the expandable film to the adhesive layer, so as to facilitate the removal of the dies. grain.

In the aforementioned method of forming sticky grains separated from a wafer, the method of losing or reducing the stickiness of the expandable film may include ultraviolet light irradiation.

In the aforementioned method for forming the sticky die separated from the wafer, the pre-cracking groove may have a U-shaped cross section.

In the aforementioned method for forming the sticky grains separated from the wafer, the pre-cracking groove may have a V-shaped cross section.

As can be seen from the above technical solutions, the method for forming sticky grains separated from wafers of the present invention has the following advantages and effects:

1. When individual sticky grains are formed by separating the wafer with the sticky layer attached, no cutting burr protruding from the sticky surface will be produced at the edge of the sticky layer, thereby solving the known cutting burr that causes sticky sticky sticking tilt and residual gap problem.

Second, it will not damage the structure of the expandable film to ensure good tensile properties and avoid improper curing of the edges of the adhesive layer when the adhesive layer is separated at low or normal temperature.

3. Using the wafer half-cutting step and the crystal back grinding step before the step of transferring the adhesive layer to separate the crystal grains, thereby avoiding the curing of the adhesive layer during the formation of cutting gaps.

Description of drawings

FIG. 1 is a cross-sectional view of a partial element during the formation process of known sticky grains being separated from a wafer;

2 is a partially enlarged schematic diagram of a cross-section of adjacent crystal grains in the known step of cutting a wafer with a dicing tool to separate sticky crystal grains;

Fig. 3 is a flow chart of forming a cohesive crystal grain separated from a wafer according to the first embodiment of the present invention;

4 is a cross-sectional view of a partial component during the process of separating a viscous die from a wafer according to the first embodiment of the present invention;

5 is a partially enlarged schematic diagram of a cross section of adjacent crystal grains in the step of forming pre-cracked guide grooves in the adhesive layer according to the first specific embodiment of the present invention;

6 is a partially enlarged schematic diagram of a cross section of adjacent crystal grains in the step of stretching an expandable film according to the first embodiment of the present invention;

7 is a cross-sectional view of a partial component during the process of separating a viscous die from a wafer according to a second embodiment of the present invention;

8 is a partially enlarged schematic diagram of a cross section of adjacent crystal grains in the step of forming a pre-cracked guide groove in an adhesive layer according to a second specific embodiment of the present invention;

9 is a partially enlarged schematic diagram of a cross section of adjacent crystal grains in the step of stretching an expandable film according to a second embodiment of the present invention.

Explanation of reference signs

D1 Thickness D2 Cutting Depth

1 provides wafer

2 Formation of cutting gaps between grains

3 Transfer the adhesive layer to the wafer

4 Form the pre-splitting guide groove in the adhesive layer

5 Stretch Expandable Membrane

6 Extraction of grains by expandable membrane

110 wafers 111 grains

112 integrated circuit forming surface 113 back side

114 pads

120 crystal back grinding tape

130 Adhesive layer 131 Burr

140 carrier film 160 cutting tool

210 Wafer 211 Die

212 integrated circuit forming surface 213 back

214 Welding Pads 215 Cutting Gap

220 crystal back grinding tape

230 Adhesive layer 231 Pre-cracked guide groove 232 Cracks

240 Expandable Membrane 251 Fixing Fixture 252 Stretching Platform

260 cutting tool

310 Wafer 311 Die

312 integrated circuit forming surface 313 back

314 Welding Pads 315 Cutting Gap

330 Adhesive layer 331 Pre-cracked guide groove 332 Cracks

340 expansion film 351 fixed fixture 352 stretching platform

360 cutting tool

Detailed ways

First specific embodiment

According to the first embodiment of the present invention, a method for forming sticky grains separated from wafers is specifically disclosed. FIG. 3 is a flow chart of forming a sticky die separated from a wafer, and FIG. 4 is a cross-sectional view of a partial component during the process of separating the sticky die from a wafer.

As shown in Figure 3, the method of the present invention includes the following steps: step 1, providing a wafer; step 2, forming a cutting gap between crystal grains; step 3, transferring an adhesive layer on the wafer; step 4, forming a pre- cleaving guide grooves on the adhesive layer; step 5, stretching the expandable film; and step 6, taking out the die from the expandable film.

First, step 1 of FIG. 3 can be referred to as shown in FIG. 4 , providing a wafer 210 to be diced, and the wafer 210 includes two or more integrated unseparated crystal grains 211 . In addition, the wafer 210 may have an integrated circuit formation surface 212 and a back surface 213 . The wafer 210 also has two or more bonding pads 214 (as shown in FIG. 5 ) located on the integrated circuit formation surface 212 . The base material of the wafer 210 is usually semiconductor materials such as silicon, silicon germanide, and gallium arsenide. These pads 214 are usually made of aluminum.

Step 2 in FIG. 3 is a step of half-cutting the wafer in this embodiment. First, as shown in Figure B in FIG. 4 , step 2 includes forming dicing gaps 215 between the dies 211 according to a preset scribe line. The cutting gap 215 may have a cutting depth D2 less than the thickness D1 of the wafer 210 so as not to cut through the wafer 210 . The dicing void 215 extends downward from the integrated circuit formation surface 212 of the wafer 210 . Specifically, the wafer half-cutting step can be performed using an existing cutting tool, such as a diamond scriber (diamond scriber) high-speed abrasive cutting. In detail, although the thickness D1 of the wafer 210 is not particularly limited, it is usually between 350 microns and 800 microns. Wherein the cutting depth D2 is properly adjusted to meet the predetermined chip thickness, usually between about 20 microns and 500 microns. In addition, the width of the dicing gap 215 is equal to the width of the dicing blade used, which is generally about 10 microns to 100 microns.

In this embodiment, step 2 may further include a crystal back grinding step, which is performed after the cutting gap 215 is formed, so as to separate the crystal grains 211 . As shown in Figure C of FIG. 4 , before performing the back grinding step, a back grinding tape 220 may be attached to the integrated circuit formation surface 212 of the wafer 210 and cover the dicing gap 215 . As shown in Figure D in Figure 4, the back surface 213 of the wafer 210 can be ground using a wafer back grinding tool (not shown), so that the thickness of the wafer 210 is reduced, wherein the wafer The reduced thickness of 210 is greater than the difference between the thickness D1 of the wafer 210 minus the cutting depth D2 , so that the dies 211 are divided into individual chips with cutting gaps 215 between the dies 211 . Specifically, the shape of the wafer 210 is roughly the same as that of the wafer 210 or slightly larger than the wafer 210, which can provide support for the wafer 210 during grinding without causing the die 211 to fall, and can protect the wafer 210. The integrated circuit formation surface 212 of the wafer 210 is not damaged and absorbs the impact force during grinding to ensure that the wafer 210 will not break.

Afterwards, step 3 can be referred to as shown in Figure E in FIG. 4 . An adhesive layer 230 is attached or transferred on the backside 213 of the wafer 210 . The adhesive layer 230 can be a double-sided adhesive tape or a B-stage adhesive layer. Wherein the adhesive layer 230 is formed on the expandable membrane 240 . The expandable film 240 has the property of being stretchable and can be selected from one of UV tape, thermal tape or blue tape.

Preferably, the step 3 of transferring the adhesive layer 230 (see the E diagram in FIG. 4 ) can be implemented after the above-mentioned wafer half-cutting step (see the D diagram in FIG. 4 ), so as to avoid The formation of the void 215 causes the curing of the adhesive layer 230 .

In addition, as shown in Figure E in Figure 4, the crystal backgrinding tape 220 can be removed after the transfer step of the adhesive layer 230, and a peeling tool (not shown) can be pasted in the direction of the arrow. The adhesive layer 230 of the integrated circuit forming surface 212 of the wafer 210 is separated, so that the originally covered bonding pads 214 are exposed (as shown in FIG. 4 and FIG. 5 ). Wherein, the method for making the crystal back grinding tape 220 lose its adhesiveness and be easily torn off may be ultraviolet (UV) irradiation.

Afterwards, step 4 of FIG. 3 can refer to diagram G in FIG. 4 and FIG. 5 , aligning the cutting gap 215 with the cutting tool 260 and forming the pre-cracking guide groove 231 in the adhesive layer 230 . Specifically, the pre-cracking guide groove 231 is aligned with the cutting gap 215 and does not penetrate through the adhesive layer 230 . That is, the depth of cutting the adhesive layer 230 by the cutting tool 260 is not greater than the thickness of the entire adhesive layer 230 . Specifically, as shown in FIG. 5 , the pre-splitting guide groove 231 may have a U-shaped cross section.

Afterwards, step 5 in FIG. 3 is performed. As shown in Figure H in FIG. 4 , the expandable membrane 240 can be stretched by using a fixing fixture 251 and a stretching platform 252 to generate a horizontal expansion tension so that the adhesive layer 230 can follow the lines of the pre-cracking guide groove 231 be split. As shown in Figure I in FIG. 4 , after stretching the expandable film 240 , the adhesive layer 230 is separated into two or more pieces attached to the dies 211 . Specifically, as shown in FIG. 6, after the adhesive layer 230 is split along the lines of the pre-cracking guide groove 231, a crack 232 will be formed. Although the crack 232 may be uneven, it will not form a protruding downward direction. Cut rough edges. Therefore, tearing the adhesive layer 230 can eliminate the dicing burrs protruding from the bonding surface, thereby solving the known problem of sticking inclined dies caused by dicing burrs formed by cutting the adhesive layer 230 once with a dicing tool. In addition, the structure of the expandable film 240 will not be damaged, so as to ensure good tensile properties, and can achieve the effect of avoiding improper curing of the adhesive layer 230 at the edge after step 5 when the adhesive layer 230 is split at low or normal temperature.

In addition, after stretching the expandable film 240 , an additional step may be included: losing or reducing the stickiness of the expandable film 240 to the adhesive layer 230 , so as to facilitate the removal of the dies 211 . Specifically, the method of losing or reducing the viscosity of the expandable film 240 may include ultraviolet light irradiation or heating process, so that the viscosity of the expandable film 240 is reduced, so that the expandable film 240 can be peeled off and separated from the expandable film 240. The adhesive layer 230 is detached.

Finally, go to step 6 in FIG. 3 . As shown in diagram J of FIG. 4 , the dice 211 attached with the split adhesive layer 230 are taken out from the expandable film 240 with a vacuum nozzle (not shown in the figure). These individual die 211 can be fixed and bonded to a designated substrate (not shown in the figure) through the adhesive layer 230 for semiconductor packaging; or fixed and bonded to the designated die 211 to form a multi-chip stack package.

Second specific embodiment

The second embodiment of the present invention discloses another method for forming sticky grains separated from wafers. As shown in Figure 3, the process of the present invention also includes the following steps: Step 1, providing a wafer; Step 2, forming a cutting gap between the crystal grains; Step 3, transferring the adhesive layer to the wafer; Step 4, forming a pre- cleaving the guide groove in the adhesive layer; step 5, stretching the expandable film; and step 6, taking out the die from the expandable film. Among them, step 2 can be implemented after step 3 and simultaneously with step 4.

First, step 1 of FIG. 3 can be referred to as shown in Figure A of FIG. 7 , and a wafer 310 is provided, and the wafer 310 includes two or more integrated and unseparated crystal grains 311 . In addition, the wafer 310 may have an integrated circuit formation surface 312 and a back surface 313 , and the wafer 310 may also have two or more bonding pads 314 located on the integrated circuit formation surface 312 (as shown in FIG. 8 ).

Next, go to step 3. As shown in FIG. 7B and FIG. 8 , an adhesive layer 330 is provided and attached or transferred to the integrated circuit formation surface 312 of the wafer 310 , wherein the adhesive layer 330 is formed on the expandable film 340 . The expandable membrane 340 is stretchable. And in this embodiment, the adhesive layer 330 can expose the solder pads 314 located on the integrated circuit forming surface 312 , so as to prevent the adhesive layer 330 from flowing at high temperature and pollute the solder pads 314 by overflowing glue.

As shown in Figure C of FIG. 7 , after step 3 , a backgrinding step may be performed to make the wafer 310 reach a predetermined thickness. Specifically, the shape of the adhesive layer 330 is substantially the same as that of the wafer 310 or slightly larger than that of the wafer 310 . In this embodiment, when the adhesive layer 330 is applied to the grinding step, it can replace the known wafer backgrinding tape, which can provide good fixation of the wafer 310 without peeling off, and can protect the integration of the wafer 310. The circuit forming surface 312 is not damaged and absorbs the impact of grinding to ensure that the wafer 310 will not break.

Afterwards, step 2 and step 4 in FIG. 3 are performed. Referring to Figure D in FIG. 7 and FIG. 8 , according to a preset dicing line, a dicing tool 360 is used to extend downward from the back surface 313 to cut through the wafer 310 to form a dicing gap 315 to separate the wafer. The circle 310 separates it into two or more grains 311 . At the same time, the cutting tool 360 cuts down to the adhesive layer 330 , but does not cut through the adhesive layer 330 , so as to form the pre-cracking groove 331 . Specifically, the cutting gap 315 and the pre-splitting guide groove 331 can be formed at the same time by using the cutting tool 360 through the same action. The step of cutting the wafer 310 and the adhesive layer 330 to form the pre-cracking guide groove 331 can be completed in one cutting step, which can be omitted in the first embodiment of the present invention. Preferably, as shown in FIG. 8 , the cutting tool 360 has a V-shaped blade, so that the pre-splitting guide groove 331 has a V-shaped cross section, so as to facilitate tearing off the adhesive layer 330 in step 5 .

Afterwards, step 5 in FIG. 3 is performed. As shown in Figure E and Figure 9 in Figure 7, the expandable film 340 can be stretched by using the fixing fixture 351 and the stretching platform 352, so that it can generate horizontal expansion tension so that the adhesive layer 330 can be stretched along the pre-split guide. The texture of the groove 331 is split, as shown in the F diagram of FIG. 7 and FIG. 9 . In this specific embodiment, after the adhesive layer 330 is split along the lines of the pre-cracked guide groove 331, a crack 332 will be formed, and the tearing action will not cause the adhesive layer 330 to form a cutting burr protruding downward. Furthermore, the known problem of the burrs formed by completely cutting the adhesive layer 330 with a dicing tool and causing the sticking inclination of the die-bonding and the die-bonding clearance is solved. In addition, after stretching the expandable film 340 , an additional step may be included: losing or reducing the stickiness of the expandable film 340 to the adhesive layer 330 , so as to facilitate the removal of the dies 311 .

Finally, go to step 6 in FIG. 3 . As shown in diagram G of FIG. 7 , the dice 311 attached with the split adhesive layer 330 are taken out from the expandable film 340 with a vacuum nozzle (not shown in the figure).

Therefore, the adhesive crystal grain provided by the present invention is separated from the wafer by the method for forming a single adhesive crystal grain when the wafer with the adhesive layer attached is separated to form a single adhesive crystal grain. Cutting burrs further solve the known problem of die sticking tilt and clearance caused by cutting burrs. In addition, the present invention does not damage the structure of the expandable film to ensure good tensile properties and avoid undue curing of the edges of the adhesive layer when the adhesive layer is separated at low or normal temperature.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. The scope of the technical solutions of the present invention should be determined by the appended claims. Any person skilled in the art can use the technical content disclosed above to make some changes or modify equivalent embodiments with equivalent changes, but as long as they do not deviate from the content of the technical solution of the present invention, the above embodiments shall be modified according to the technical essence of the present invention. Any simple modifications, equivalent changes and modifications still fall within the scope of the technical solution of the present invention.

Claims (10)

1. A method for forming sticky grains separated from a wafer, characterized in that it mainly comprises the following steps: providing a wafer comprising two or more integrated, unseparated dies; forming cutting voids between the grains; transferring an adhesive layer to the wafer, wherein the adhesive layer is formed on the expandable film; forming a pre-splitting guide groove on the adhesive layer, the pre-splitting guide groove being aligned with the cutting gap and not penetrating through the adhesive layer; stretching the expandable film to split the adhesive layer along the lines of the pre-split channels; and The die to which the split adhesive layer is attached is removed from the expandable membrane. 2. The method for forming sticky dies separated from a wafer as claimed in claim 1, wherein the wafer has an integrated circuit forming surface and a back surface, and the wafer also has two or more integrated circuits located on the integrated circuit. The circuit forms the solder pads on the surface. 3 . The method for forming adhesive die separated from a wafer as claimed in claim 2 , wherein the adhesive layer is transferred to the back side of the wafer. 4 . 4. The method for forming sticky dies separated from wafers as claimed in claim 1, wherein the step of forming the cutting gap between the dies comprises a step of half-cutting the wafer. 5. the method for forming that sticky grains are separated from wafers as claimed in claim 4, wherein the cutting gap formed in the wafer half-cutting step has a cutting depth less than the thickness of the wafer, and additionally comprises A crystal backgrinding step to separate the crystal grains. 6 . The method for forming sticky die separated from a wafer as claimed in claim 5 , wherein before the step of back grinding, a back grinding tape is attached to the wafer and covers the dicing gap. 7 . 7. The method for forming adhesive die separated from a wafer as claimed in claim 6, wherein the die backgrind tape is removed after the step of transferring the adhesive layer. 8. The method for forming sticky grains separated from a wafer as claimed in claim 1, further comprising the step of: losing or reducing the stretchable film to the adhesive layer after stretching the expandable film. of stickiness, remove the grains. 9. The method for forming sticky die separated from a wafer as claimed in claim 8, wherein the method for losing or reducing the stickiness of the expandable film comprises ultraviolet light irradiation. 10 . The method for forming cohesive grains separated from wafers according to claim 1 , wherein the pre-cracking guide groove has a U-shaped cross section. 11 .

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