JP7833985B2 - Chip manufacturing method - Google Patents

Description

This invention relates to a method for manufacturing chips.

In the semiconductor device manufacturing process, a method known as "pre-dicing" is used to divide device wafers into chips. In this method, a groove at least equivalent to the finished thickness of the device is formed on the surface of the wafer. The back surface of the device wafer is then ground while the surface is protected with protective tape, exposing the bottom of the groove and thus dividing the wafer.

After the wafers are divided in this way, a polishing process is sometimes performed to improve their flatness and chip strength. This polishing process uses a polishing apparatus that includes a chuck table for holding the wafers by suction, and a polishing head with a polishing pad that rotates while pressing the wafers held on the chuck table with a predetermined pressure (see, for example, Patent Document 1).

Japanese Patent Publication No. 2004-335668

However, when attempting to polish chips that have already been divided into individual devices using the pre-dicing method, a problem arose: the chips moved on the adhesive layer of the protective tape, making it difficult for the polishing pad to grip the wafer, resulting in a longer polishing time.

Furthermore, when polishing with a slurry containing free abrasive particles, there was a problem of the slurry getting into the sides of the chip and causing contamination.

This invention was made in view of the above facts, and aims to provide a method for manufacturing chips that shortens the polishing time when polishing the back surface of the chip after dividing the workpiece by a pre-dicing method to form chips, and also suppresses contamination of the chip's sides.

To solve the above-mentioned problems and achieve the objective, the present invention provides a chip manufacturing method for a workpiece having multiple division lines set on its surface, which is divided along these division lines to produce chips. This method comprises: a groove forming step, in which a groove is formed by processing the workpiece from its surface along the division lines to form a groove having a depth corresponding to the finished thickness of the chip; a protective member integration step, in which, after the groove forming step, a protective member containing a thermoplastic resin is heat-pressed onto the surface of the workpiece where the groove is formed, thereby allowing the thermoplastic resin to penetrate the groove and integrate the workpiece and the protective member; a grinding step, in which, after the protective member integration step, the back surface of the workpiece is ground to expose the groove and divide it into individual chips; and a polishing step, in which, after the grinding step, the back surface of each individual chip is polished with a polishing pad. The method is characterized by suppressing the setting of the storage modulus of the protective member to a range of 1 × 10⁶ (Pa) or more and 1 × 10⁹ (Pa) or less.

In the chip manufacturing method described above, the polishing pad in the polishing step may be a fixed abrasive polishing pad containing abrasive grains and a binder that binds the abrasive grains together.

This invention offers the advantage of reducing the polishing time when polishing the back surface of a chip after dividing the workpiece by a pre-dicing method to form chips, and also suppressing contamination on the sides of the chips.

Figure 1 is a perspective view showing an example of the configuration of a workpiece to be processed by the chip manufacturing method according to Embodiment 1. Figure 2 is a flowchart showing the flow of the chip manufacturing method according to Embodiment 1. Figure 3 is a schematic side view showing a partial cross-section of the groove formation step in the chip manufacturing method shown in Figure 2. Figure 4 is a schematic side view showing a modified example of the groove formation step in the chip manufacturing method shown in Figure 2, in partial cross-section. Figure 5 is a schematic side view showing a partial cross-section of the protective member integration step in the chip manufacturing method shown in Figure 2. Figure 6 is a schematic cross-sectional view showing a portion of the workpiece after the protective member integration step in the chip manufacturing method shown in Figure 2. Figure 7 is a schematic side view showing a partial cross-section of the start of the grinding step in the chip manufacturing method shown in Figure 2. Figure 8 is a schematic side view showing a partial cross-section of the end of the grinding step in the chip manufacturing method shown in Figure 2. Figure 9 is a schematic side view showing a partial cross-section of the polishing step in the chip manufacturing method shown in Figure 2.

The embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below. Furthermore, the components described below include those that are easily conceivable to those skilled in the art, and those that are substantially the same. Moreover, the components described below can be combined as appropriate. In addition, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the present invention.

[Embodiment 1]
A method for manufacturing a chip according to Embodiment 1 of the present invention will be described with reference to the drawings. Figure 1 is a perspective view showing an example of the configuration of a workpiece to be processed in the chip manufacturing method according to Embodiment 1. Figure 2 is a flowchart showing the flow of the chip manufacturing method according to Embodiment 1.

(Workpiece)
The chip manufacturing method according to Embodiment 1 is a method of dividing the workpiece 1 shown in Figure 1 into chips 10. The workpiece 1 to be processed in the chip manufacturing method according to Embodiment 1 is a wafer such as a disc-shaped semiconductor wafer or optical device wafer with a substrate 2 made of silicon, sapphire, gallium arsenide, or SiC (silicon carbide). As shown in Figure 1, the workpiece 1 has a plurality of intersecting division lines 4 set on its surface 3, and devices 5 are formed in the regions partitioned by the division lines 4.

Device 5 is, for example, an integrated circuit (IC) or LSI (Large Scale Integration), an image sensor (CCD) or CMOS (Complementary Metal Oxide Semiconductor), or a memory (semiconductor memory device). The workpiece 1 is divided into individual chips 10 along the planned division line 4. Each chip 10 comprises a portion of the substrate 2 and the device 5, and is thinned to a finished thickness 11 that is thinner than the thickness of the workpiece 1.

(Method of manufacturing chips)
The chip manufacturing method according to Embodiment 1 is a method for manufacturing a chip 10 by dividing a workpiece 1 along a planned division line 4. The chip manufacturing method according to Embodiment 1 comprises a processing groove forming step 101, a protective member integration step 102, a grinding step 103, and a polishing step 104.

(Processing groove formation step)
Figure 3 is a schematic side view showing a partial cross-section of the groove formation step of the chip manufacturing method shown in Figure 2. Figure 4 is a schematic side view showing a partial cross-section of a modified example of the groove formation step of the chip manufacturing method shown in Figure 2. The groove formation step 101 is a step in which processing is performed from the surface 3 side of the workpiece 1 along the planned division line 4 of the workpiece 1 to form a groove 13 having a depth 12 (shown in Figure 3) corresponding to the finished thickness 11 of the chip 10.

In Embodiment 1, during the groove forming step 101, a disc-shaped adhesive tape 7, shown in Figure 1, with a diameter larger than the outer diameter of the workpiece 1, is attached to the back surface 6 of the workpiece surface 3. An annular frame 8, shown in Figure 1, with an inner diameter larger than the outer diameter of the workpiece 1, is attached to the outer edge of the adhesive tape 7, and the workpiece 1 is supported within the opening of the frame 8. In Embodiment 1, during the groove forming step 101, the cutting device 20 shown in Figure 3 holds the back surface 6 of the workpiece 1 to the holding surface 22 of the chuck table 21 via the adhesive tape 7, and clamps the frame 8 with clamping portions 23 provided around the chuck table 31.

In Embodiment 1, in the groove formation step 101, the cutting device 20 uses an imaging unit (not shown) to image the workpiece 1 held on the chuck table 21. From the image acquired, the cutting device extracts the planned division line 4 and performs alignment, aligning the planned division line 4 of the workpiece 1 with the cutting blade 24. In Embodiment 1, in the groove formation step 101, as shown in Figure 3, the cutting device 20 moves the chuck table 21 and the cutting blade 24 relative to each other along the planned division line 4, causing the cutting blade 24 to cut into the planned division line 4 to a depth 12 corresponding to the finished thickness 11, thereby forming a groove 13 with a depth 12 corresponding to the finished thickness 11 in the planned division line 4 of the workpiece 1.

In Embodiment 1, the groove formation step 101 involves cutting (equivalent to machining) the workpiece 1 to form grooves 13 along all planned division lines 4 of the workpiece 1. In Embodiment 1, the depth 12 of the grooves 13 is greater than or equal to the finished thickness 11 of the chip 10.

Furthermore, in Embodiment 1, in the groove formation step 101, the cutting device 20 formed grooves 13 on all the planned division lines 4 of the workpiece 1. However, in the present invention, the laser processing device 30 shown in Figure 4 may form grooves 13 on all the planned division lines 4 of the workpiece 1. In this case, in Embodiment 1, in the groove formation step 101, the laser processing device 30 holds the back surface 6 of the workpiece 1 to the holding surface 32 of the chuck table 31 via adhesive tape 7, and clamps the frame 8 with clamping parts 33 provided around the chuck table 31.

In the groove formation step 101, the laser processing apparatus 30 uses an imaging unit (not shown) to image the workpiece 1 held on the chuck table 31. From the acquired image, the laser processing apparatus extracts the planned division lines 4 and performs alignment, aligning the planned division lines 4 of the workpiece 1 with the focusing lens 34 of the laser beam irradiation unit. In the groove formation step 101, as shown in Figure 4, the laser processing apparatus 30 moves the chuck table 41 and the focusing lens 34 of the laser beam irradiation unit relative to each other along the planned division lines 4, setting the focusing point 35 to the surface 3. The laser beam irradiation unit then irradiates the planned division lines 4 with a laser beam 36 of a wavelength absorbed by the workpiece 1, forming grooves 13 with a depth 12 corresponding to the finished thickness 11 along the planned division lines 4 of the workpiece 1. In this way, in the groove formation step 101, ablation processing (equivalent to processing) may be performed on the workpiece 1 to form grooves 13 along all of the planned division lines 4 of the workpiece 1.

(Integration step of protective component)
Figure 5 is a schematic side view showing a partial cross-section of the protective member integration step in the chip manufacturing method shown in Figure 2. Figure 6 is a schematic cross-sectional view showing a part of the workpiece after the protective member integration step in the chip manufacturing method shown in Figure 2. The protective member integration step 102 is a step in which, after performing the processing groove formation step 101, a protective member 14 containing a thermoplastic resin is heat-pressed onto the surface 3 side of the workpiece 1 in which the processing groove 13 has been formed, thereby allowing the thermoplastic resin to penetrate into the processing groove 13 and integrating the workpiece 1 and the protective member 14.

In Embodiment 1, during the protective member integration step 102, the integration device 40 shown in Figure 5 holds the back surface 6 of the workpiece 1 to the holding surface 42 of the chuck table 41 via adhesive tape 7, and places the protective member 14 on the front surface 3 of the workpiece 1. In Embodiment 1, the protective member 14 is formed in a disc shape with the same diameter as the workpiece 1 and has a uniform thickness. The protective member 14 is made of thermoplastic resin.

In Embodiment 1, the thermoplastic resin constituting the protective member 14 is specifically acrylic resin, methacrylic resin, vinyl resin, polyacetal, natural rubber, butyl rubber, isoprene rubber, chloroprene rubber, polyethylene, polypropylene, polyolefins such as poly(4-methyl-1-pentene) and poly(1-butene), polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon-6, nylon-66, and polymetaxylene adipamide, polyacrylate, polymethacrylate, polyvinyl chloride, polyetherimide, and polyacrylo Examples include one or more selected from nitriles, polycarbonates, polystyrenes, polysulfones, polyethersulfones, polyphenylenes, etherpolybutadiene resins, polycarbonate resins, thermoplastic polyimide resins, thermoplastic polyurethane resins, phenoxy resins, polyamideimide resins, fluororesins, ethylene-unsaturated carboxylic acid copolymer resins, ethylene-vinyl acetate copolymer resins, ionomers, ethylene-vinyl acetate-maleic anhydride terpolymer resins, ethylene-vinyl acetate copolymer saponified resins, and ethylene-vinyl alcohol copolymer resins.

Examples of unsaturated carboxylic acids constituting the above-mentioned ethylene-unsaturated carboxylic acid copolymer include acrylic acid, methacrylic acid, maleic acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride, and itaconic anhydride. Here, the term ethylene-unsaturated carboxylic acid copolymer includes not only binary copolymers of ethylene and unsaturated carboxylic acids, but also multi-component copolymers in which other monomers are copolymerized. Examples of other monomers that may be copolymerized in the ethylene-unsaturated carboxylic acid copolymer include vinyl esters such as vinyl acetate and vinyl propionate, and unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, methyl methacrylate, isobutyl methacrylate, dimethyl maleate, and diethyl maleate.

Furthermore, in Embodiment 1, the storage modulus of the protective member 14 is set to be in the range of 1 × ^10⁶ (Pa) or more and 1 × ^10⁹ (Pa) or less, by appropriately adjusting the components, molecular weight, etc., of the thermoplastic resin described above. If the storage modulus of the protective member 14 is less than 1 × ^10⁶ (Pa), the protective member 14 will be too soft, causing the tip 10 to move during the polishing step 104, and even if the protective member 14 is peeled off after the polishing step 104, the thermoplastic resin constituting the protective member 14 will remain on the tip 10, which is undesirable.

Furthermore, if the storage modulus of the protective member 14 is greater than 1 × ^10⁹ (Pa), the protective member 14 will not adhere to the workpiece 1 unless the heating temperature of the protective member 14 is increased in the protective member integration step 102, which may lead to damage to the device 5 and is therefore undesirable. For example, if the storage modulus of the protective member 14 is around 1 × ^10¹¹ (Pa), the protective member 14 will not adhere to the workpiece 1 unless the heating temperature of the protective member 14 in the protective member integration step 102 is increased to around 200°C.

Thus, the manufacturing method of the chip 10 according to Embodiment 1 suppresses the movement of individual chips 10 during the polishing step 104 by setting the storage modulus of the protective member 14 to a range of 1 × ^10⁶ (Pa) or more and 1 × ^10⁹ (Pa) or less. Furthermore, the manufacturing method of the chip 10 according to Embodiment 1 reduces the risk of damage to the device 5 because the protective member 14 does not need to be attached at a high temperature by setting the storage modulus of the protective member 14 to a range of 1 × ^10⁶ (Pa) or more and 1 × ^10⁹ (Pa) or less.

In Embodiment 1, during the protective member integration step 102, the integration device 40, as shown in Figure 5, heats the protective member 14, which is placed on the surface 3 of the workpiece 1, to approximately 100°C using a heat source 43 for a predetermined time, while simultaneously pressing the protective member 14 toward the workpiece 1 with a pressing member (not shown). This causes the protective member 14 to soften and adhere to the surface 3 of the workpiece 1, while a portion of the thermoplastic resin constituting the protective member 14 penetrates into the processing groove 13, as shown in Figure 6. Furthermore, in the present invention, during the protective member integration step 102, the protective member 14 may be pressed toward the workpiece 1 with a pressing member incorporating the heat source 43.

Thus, in Embodiment 1, in the protective member integration step 102, the integration device 40 heat-presses the protective member 14 containing thermoplastic resin onto the surface 3 side of the workpiece 1 where the processing groove 13 is formed, thereby allowing the thermoplastic resin to penetrate into the processing groove 13 and integrating the workpiece 1 and the protective member 14. It is desirable that in the protective member integration step 102, the protective member 14 is heated to a temperature above its softening point and below its melting point using the heat source 43. Furthermore, in Embodiment 1, in the protective member integration step 102, the adhesive tape 7 is peeled off from the back surface 6 of the workpiece 1.

(Grinding step)
Figure 7 is a schematic side view showing a partial cross-section at the start of the grinding step in the chip manufacturing method shown in Figure 2. Figure 8 is a schematic side view showing a partial cross-section at the end of the grinding step in the chip manufacturing method shown in Figure 2. The grinding step 103 is a step in which, after performing the protective member integration step 102, the back surface 6 side of the workpiece 1 is ground to expose the processing groove 13 on the back surface 6 side, and the workpiece 1 is divided into individual chips 10.

In Embodiment 1, during the grinding step 103, the grinding device 50 holds the workpiece 1 (surface 3 side) to the holding surface 52 of the chuck table 51 via a protective member 14. In Embodiment 1, during the grinding step 103, as shown in Figure 7, the grinding device 50 rotates the grinding wheel 54 around its axis using the spindle 53, and also rotates the chuck table 51 around its axis. While supplying grinding fluid from a grinding fluid nozzle (not shown), the grinding wheel 55 of the grinding wheel 54 is brought into contact with the back surface 6 of the workpiece 1 and brought closer to the chuck table 51 at a predetermined feed rate, thereby grinding the back surface 6 of the workpiece 1 with the grinding wheel 55.

In Embodiment 1, as shown in Figure 8, during the grinding step 103, when the thickness of the workpiece 1 reaches the finished thickness 11, the grinding device 50 moves the grinding wheel 54 away from the back surface 6 of the workpiece 1. This exposes the machining groove 13 to the back surface 6 of the workpiece 1, and the workpiece 1 is divided into individual chips 10.

(Polishing step)
Figure 9 is a schematic side view showing a partial cross-section of the polishing step in the chip manufacturing method shown in Figure 2. The polishing step 104 is a step in which the back surface 6 of each chip 10 is polished with a polishing pad 64 after the grinding step 103 has been performed.

In Embodiment 1, during polishing step 104, the polishing device 60 holds the workpiece 1 (surface 3) to the holding surface 62 of the chuck table 61 via a protective member 14. In Embodiment 1, during polishing step 105, as shown in Figure 9, the polishing device 60 rotates the polishing pad 64 around its axis using a spindle 63, and rotates the chuck table 61 around its axis. While supplying polishing fluid 66 from a polishing fluid supply passage 65 provided on the polishing pad 64, the polishing pad 64 is pressed against the back surface 6 of the workpiece 1, polishing the back surface 6 of the workpiece 1 for a predetermined time. In Embodiment 1, after polishing step 104, when the polishing device 60 finishes polishing the workpiece 1, the polishing pad 64 is moved away from the back surface 6 of the workpiece 1, thus ending the chip manufacturing process.

In Embodiment 1, in polishing step 104, the polishing pad 64 is a fixed abrasive type polishing pad containing abrasive grains and a binder that binds the abrasive grains, and the polishing liquid 66 is a polishing liquid that does not contain abrasive grains. Thus, in Embodiment 1, in polishing step 104, the workpiece 1 is polished with the fixed abrasive type polishing pad 64 and the polishing liquid 66 that does not contain abrasive grains. However, in the present invention, in polishing step 104, polishing may also be performed using a slurry containing abrasive grains as the polishing liquid, a so-called free abrasive slurry.

The chip manufacturing method according to Embodiment 1 described above involves forming a processing groove 13 on the surface 3 of the workpiece 1 in the processing groove forming step 101, then performing a protective member integration step 102 in which a protective member 14 made of thermoplastic resin is heated to adhere to the surface 3 of the workpiece 1 and the thermoplastic resin constituting the protective member 14 penetrates into the processing groove 13, and finally, in the grinding step 103, the workpiece 1 is ground to divide it into individual chips 10 using a so-called pre-dicing method. As a result, the chip manufacturing method according to Embodiment 1 has the effect of suppressing the movement of the chips 10 during the polishing step 104 because the thermoplastic resin constituting the protective member 14 penetrates into the processing groove 13.

Furthermore, in the chip manufacturing method according to Embodiment 1, since the thermoplastic resin constituting the protective member 14 penetrates into the processing groove 13 during the polishing step 104, even if polishing is performed with a slurry of free abrasive particles, the penetration of slurry into the processing groove 13 can be suppressed, and the adhesion of slurry to the side surfaces of the divided chip 10 can be suppressed. As a result, the chip manufacturing method according to Embodiment 1 has the effect of suppressing contamination of the side surfaces of the chip 10 even when polishing is performed with a slurry of free abrasive particles during the polishing step 104.

Furthermore, the inventors of the present invention discovered that in the polishing step 104, polishing the workpiece 1 with a fixed abrasive-type polishing pad 64 and a polishing liquid 66 that does not contain abrasive particles removes dirt from the sides of the chip 10. However, when the divided chip 10 is fixed with adhesive tape or the like for polishing, the chip 10 moves, resulting in a longer polishing time. However, in the chip manufacturing method according to Embodiment 1, the storage modulus of the protective member 14, which enters into the processing groove 13 of the workpiece 1 and integrates with the workpiece 1, is set to 1 × ^10⁶ (Pa) or higher. Therefore, movement of the chip 10 during the polishing step 104 can be suppressed, and the polishing time can be reduced.

As a result, the chip manufacturing method according to Embodiment 1 has the effect of shortening the polishing time when polishing the back surface 6 of the chip 10 after dividing the workpiece 1 by the pre-dicing method and forming the chip 10, and also suppressing contamination of the side surface of the chip 10.

Furthermore, in the chip manufacturing method according to Embodiment 1, the storage modulus of the protective member 14 integrated with the workpiece 1 is set to 1 × ^10⁶ (Pa) or higher. Therefore, even when the chip 10 is peeled off from the protective member 14, it is possible to suppress the remaining presence of the thermoplastic resin constituting the protective member 14 on the chip 10.

Furthermore, in the chip manufacturing method according to Embodiment 1, the storage modulus of the protective member 14 integrated with the workpiece 1 is set to 1 × ^10⁹ (Pa) or less, so the protective member 14 can be attached to the surface 3 side of the workpiece 1 without damaging the device 5.

Furthermore, the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention.

1 Workpiece 3 Surface 4 Planned division line 10 Chip 11 Finished thickness 12 Depth 13 Machining groove 14 Protective member 101 Machining groove formation step 102 Protective member integration step 103 Grinding step 104 Polishing step

Claims (2)

A method for manufacturing chips, which involves dividing a workpiece having multiple division lines set on its surface along the division lines to produce chips,
A machining groove forming step involves machining the workpiece from the surface side along the planned division line of the workpiece to form a machining groove having a depth corresponding to the finished thickness of the chip,
After performing the groove forming step, a protective member integration step is performed, in which a protective member containing a thermoplastic resin is heat-pressed onto the surface side of the workpiece on which the groove has been formed, thereby allowing the thermoplastic resin to penetrate into the groove and integrating the workpiece and the protective member.
After performing the protective member integration step, the back side of the workpiece is ground to expose the processing grooves and divide it into individual chips in a grinding step,
The grinding step is followed by a polishing step in which the back surface of each chip is polished with a polishing pad,
A method for manufacturing a chip, characterized in that the storage modulus of the protective member is set to a range of 1 × ^10⁶ (Pa) or more and 1 × ^10⁹ (Pa) or less. The method for manufacturing a chip according to claim 1, characterized in that, in the polishing step, the polishing pad is a fixed abrasive polishing pad containing abrasive grains and a binder that binds the abrasive grains together.