TWI827701B - Wafer processing methods - Google Patents

Abstract

[Problem] Provide a wafer processing method that will not degrade the quality of components even if the backside of the wafer is processed. [Solution] According to the present invention, there is provided a wafer processing method in which the back surface 10b of the wafer 10 is divided into a plurality of elements 11 by the planned division line 12 and formed on the front surface 10a. The wafer processing method at least includes the following The step consists of: a wafer arrangement step in which a polyolefin-based sheet or a polyester-based sheet having a size equal to or greater than the shape of the wafer 110 is laid on the upper surface 22 of the support table 20 formed into a flat surface. The sheet 14 is laid on the upper surface of the sheet 14 with a peeling layer 16 smaller than the diameter of the wafer 10, and the front side 10a of the wafer 10 is positioned on the upper surface of the sheet 14; in the sheet hot pressing step, through the sheet 14 and peeling The layer 16 decompresses the wafer 10 disposed on the support table 20 in a closed environment, heats the sheet 14, and presses the wafer 10 to heat-press the outer periphery of the wafer 10 to the sheet 14; the processing steps include: The backside 10b is processed; and a peeling step peels the wafer 14 from the wafer 10 .

Description

Wafer processing methods

The invention is a wafer processing method for processing the back side of a wafer.

A wafer divided by planned division lines and with multiple components such as ICs and LSIs formed on the front side is processed to a predetermined thickness by grinding the back side with a grinding device, and is then divided into individual component wafers by a cutting device and used in mobile applications. Electronic equipment such as phones and computers.

The grinding device is composed of at least the following components to process the wafer to a desired thickness: a chuck table, which has a holding surface for holding the wafer; a grinding means, which has a rotatable grinding wheel, which grinds the chuck table. The upper surface of the held wafer is ground; and a feeding means grinds and feeds the grinding stone (for example, see Patent Document 1).

When grinding the wafer in the above-mentioned grinding device, a protective adhesive film with an adhesive layer is pasted on the front side of the wafer, so that the multiple components formed on the front side of the wafer will not be affected by the holding surface of the chuck table and the Damage occurs due to contact with the front side of the wafer. [Known technical documents] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2005-246491

[Problem to be solved by the invention] As mentioned above, by sticking a protective adhesive film with an adhesive layer on the front side of the wafer, the problem of damaging the front side of the wafer when grinding the back side of the wafer is avoided, but it will peel off from the front side of the wafer after grinding. When protecting the adhesive film, part of the adhesive layer (adhesive chips) adheres and remains, causing a problem of reduced component quality after the wafer is divided into individual wafers.

In view of the above facts, the present invention takes this as its main technical subject to provide a wafer processing method that will not degrade the quality of components even if the back side of the wafer is processed.

[Technical means to solve the problem] In order to solve the above-mentioned main technical problems, according to the present invention, a wafer processing method is provided. The back side of the wafer is divided into a plurality of elements by the planned division line and formed on the front side. The wafer processing method at least consists of the following steps. : A wafer arrangement step in which a polyolefin-based sheet or a polyester-based sheet having a size equal to or greater than the shape of the wafer is laid on the upper surface of a support platform with a flat upper surface, and the sheet is A peeling layer smaller than the diameter of the wafer is laid on the upper surface, and the front side of the wafer is positioned on the upper surface of the sheet; in the sheet hot pressing step, the wafer arranged on the support table is placed on the supporting platform through the sheet and the peeling layer. The sheet is heated under reduced pressure in a closed environment, and the wafer is pressed to heat-press the outer periphery of the wafer to the sheet; the processing step is to process the back side of the wafer; and the peeling step is to peel the sheet from the wafer.

The release layer may include at least any one of paper, cloth, wax paper, or polyimide sheets.

Preferably, the support platform includes a heating means, and the support platform is heated by the heating means during the sheet thermal pressing step. Preferably, the upper surface of the support platform is covered with fluororesin. Furthermore, in this processing step, a grinding process for grinding the back surface of the wafer can be performed.

Preferably, the polyolefin-based sheet is composed of any one of a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet. Preferably, in the sheet hot pressing step, the heating temperature for the polyethylene sheet is 120 to 140°C, the polypropylene sheet is selected for the heating temperature to be 160 to 180°C, and the polystyrene is preferably selected. In the case of thin sheets, the heating temperature is 220 to 240°C.

Preferably, the polyester-based sheet is composed of either a polyethylene terephthalate sheet or a polyethylene naphthalate sheet. Preferably, in the sheet hot pressing step, the heating temperature for the polyethylene terephthalate sheet is 250 to 270° C., and the heating temperature for the polyethylene naphthalate sheet is 250 to 270° C. The heating temperature is 160 to 180°C.

Preferably, in the sheet hot pressing step, the sheet surrounds the wafer and presses the wafer in a raised manner.

[Invention effect] The wafer processing method of the present invention at least consists of the following: a wafer arrangement step in which a polyolefin-based sheet or polyester of a size equal to or greater than the shape of the wafer is laid on the upper surface of a support table with a flat upper surface. It is any kind of thin sheet, and a peeling layer smaller than the diameter of the wafer is laid on the upper surface of the thin sheet, and the front side of the wafer is positioned on the upper surface of the thin sheet; in the hot pressing step of the thin sheet, through the thin sheet and the peeling layer The layer decompresses the wafer arranged on the support table in a closed environment to heat the sheet, and presses the wafer to heat-press the outer periphery of the wafer to the sheet; the processing step is to process the back side of the wafer; and a lift-off step to peel the sheet from the wafer. Thereby, after the processing step of processing the back surface is completed, even if the sheet is peeled off from the front surface of the wafer, the problem of part of the adhesive layer adhering to the protruding electrodes and degrading the quality of the device can be solved. In addition, because a peeling layer is placed between the chip and the wafer, the heat-pressed chip can be easily peeled off from the front side of the wafer.

The following describes in detail the embodiments of the wafer processing method of the present invention with reference to the accompanying drawings.

FIG. 1( a ) shows a wafer 10 divided into a plurality of elements 11 by planned dividing lines 12 and formed on a front surface 10 a. In this embodiment, the back surface 10b of the wafer 10 is processed.

When implementing the wafer processing method of this embodiment, first, the wafer 10 and the sheet 14 are prepared, as well as the release layer 16 provided between the wafer 10 and the sheet 14 . The sheet 14 has a size equal to or larger than the diameter of the wafer 10 and is selected from a polyolefin sheet or a polyester sheet. In this embodiment, a polyethylene (PE) sheet is selected. The peeling layer 16 is a circular sheet with a smaller diameter than the wafer 10 and is made of a non-adhesive film material, such as selection paper. Furthermore, the release layer 16 is not limited to paper, and can also be selected from cloth, waxy rice paper, and polyimide sheets.

(Wafer allocation step) When performing the wafer placement step, first, the sheet 14 is placed in the center of the upper surface 22 of the support table 20 as a holding means for the thermocompression bonding device 30 (see FIG. 2( a )) that performs the thermocompression bonding step described below. The upper surface 22 of the support base 20 is covered with fluororesin and formed into a flat shape. Furthermore, as shown in FIG. 2( a ), an electronic heater 24 including a temperature sensor (not shown) as a heating means is built into the support stand 20 .

Returning to FIG. 1( a ) to continue the explanation, the peeling layer 16 is laid on the upper surface of the sheet 14 laid on the upper surface 22 of the support base 20 . When laying the release layer 16 on the sheet 14, it is preferable to align the center of the sheet 14 with the center of the release layer 16. As described above, the sheet 14 is formed to have a diameter equal to or greater than that of the wafer 10 . Since the peeling layer 16 is formed to have a smaller diameter than the wafer 10 , the outer periphery of the sheet 14 is exposed outside the peeling layer 16 .

When the release layer 16 is laid on the sheet 14, the front surface 10a of the wafer 10 is positioned on the upper surface of the sheet 14 on which the release layer 16 is laid, and the back surface 10b is exposed upward. Through the above, the wafer configuration step is completed (see Figure 1(b)).

(Thin sheet heat pressing step) After the above-mentioned wafer arrangement step is completed, the sheet thermocompression bonding step is performed next. The sheet hot pressing step is to depressurize the wafer 10 arranged on the support table 20 in a closed environment through the sheet 14 and the peeling layer 16 to heat the sheet 14, and press the wafer 10 to heat press the outer periphery of the wafer 10 Step 14 of the sheet. Referring to FIG. 2 , the function and function of the thermocompression bonding device 30 that performs the sheet thermocompression bonding step will be described.

The thermocompression device 30 is provided with: a support base 20 which has the above-mentioned electronic heater 24 built in; a support base 32 on which the support base 20 is mounted and fixed; a suction hole 34 formed in the support base 32; and a sealing cover member 36. It is used to treat the space S on the support base 32 including the support base 20 as a closed space. In addition, although the sealing cover member 36 is a box-shaped member that covers the entire upper surface of the support base 32, in FIG. Cross section of the sealing cover member 36 .

An opening 36 b is formed in the center of the upper wall 36 a of the sealing cover member 36 . The opening 36 b allows the support shaft 38 a of the pressing member 38 to pass through and move forward and backward in the up and down direction indicated by arrow Z. A sheet structure 36c is formed around the opening 36b in order to move the support shaft 38a up and down, and to block the space S of the airtight cover member 36 from the outside as a sealed environment. A pressing plate 38b is provided at the lower end of the support shaft 38a. The pressing plate 38 b is formed in a disc shape with a diameter at least larger than that of the wafer 10 , and is preferably set to have a diameter approximately the same as that of the support table 20 . On the lower end surface of the sealing cover member 36, a sheet member (not shown) having appropriate elasticity may be disposed over the entire outer circumference. In addition, a driving means (not shown) for moving the pressing member 38 forward and backward in the vertical direction is arranged above the pressing member 38 .

Through the above-mentioned wafer arrangement steps, the wafer 10 is placed on the support base 32 including the support table 20, and the sealing cover member 36 is lowered to make the space S a sealed environment. At this time, as shown in FIG. 2 , the pressing plate 38 b is pulled up to a position above the upper surface of the wafer 10 without contacting it.

If the space S formed inside the airtight cover member 36 is a sealed environment, a suction means (not shown) is activated to suck air in the space S through the suction holes 34 to depressurize the area including the wafer 10 to a state close to vacuum. . At the same time, the electronic heater 24 built in the support table 20 is activated to control the temperature of the upper surface 22 of the support table 20 . Specifically, the polyethylene sheet constituting the sheet 14 is heated to 120 to 140° C., which is close to the melting temperature. Furthermore, a driving means (not shown) is actuated to lower the pressing plate 38b in the direction indicated by arrow Z, thereby pressing the entire upper surface of the wafer 10 with a uniform force. The space S accommodating the wafer 10 is decompressed to a state close to a vacuum, and air is appropriately suctioned and removed from the alignment surfaces of the wafer 10 , the peeling layer 16 and the sheet 14 . Then, the sheet 14 is softened by heating to near the melting temperature of the sheet 14 (120 to 140° C.), and the adhesiveness is exerted, so that the wafer 10, the peeling layer 16 and the sheet 14 are in the cross-section of Figure 2(b) It is hot pressed in the state shown in the picture. The release layer 16 is made of a material (paper) that does not exhibit adhesiveness even when heated. The release layer 16 is disposed in a substantially vacuum state and is thermally pressed with the wafer 10 and the sheet 14 in the outer peripheral area. Furthermore, at this time, the wafer 10 is pressed by the pressing plate 38 b . As shown in FIG. 2( b ), the pressing plate 38 b is arranged directly below the wafer 10 and bulges on the outer periphery of the softened sheet 14 to form a thin film surrounding the wafer 10 . The outer peripheral bulge 14a. In this way, the hot pressing step is completed, and the wafer 10 , the sheet 14 , and the peeling layer 16 are integrated to form an integrated wafer W.

(processing steps) After the above-mentioned thermal bonding step is completed and the integrated wafer W is formed, a processing step of processing the back surface of the wafer 10 is performed. The processing step of this embodiment is a step of grinding the back surface 10b, and will be described in detail with reference to FIGS. 3 and 4 .

In FIG. 3 , the chuck table 52 of the grinding device 50 (only part of it is shown) is shown. The upper surface of the chuck table 52 is composed of an adsorption chuck 54 composed of porous ceramics with air permeability. On the suction chuck 54, the integrated wafer W is placed with the sheet 14 side facing down. When the integrated wafer W is placed on the suction chuck 54, a suction means (not shown) connected to the chuck table 52 is actuated to suck and hold the integrated wafer W.

As shown in FIG. 4 , the grinding device 50 includes a grinding means 60 for grinding and thinning the back surface 10 b of the wafer 10 held by suction on the chuck table 52 . The grinding means 60 is equipped with: a rotating spindle 62 rotated by a rotation drive mechanism not shown; a placement machine 64 installed at the lower end of the rotating spindle 62; and a grinding wheel 66 installed on the lower surface of the placement machine 64 ; A plurality of grinding grindstones 68 are annularly arranged on the lower surface of the grinding wheel 66.

When the integrated wafer W is held and attracted to the chuck table 52, the rotating spindle 62 of the grinding means 60 is rotated at, for example, 6000 rpm in the direction indicated by the arrow R1 in FIG. 4, and the chuck table 52 is rotated in the direction shown by the arrow R1 in FIG. 4. Rotate at, for example, 300 rpm in the direction indicated by arrow R2. Then, grinding water is supplied to the wafer 10 exposed on the upper surface of the integrated wafer W by a grinding water supply means (not shown), and the grinding grindstone 68 is brought into contact with the back surface 10 b of the wafer 10 to grind the support. The grinding wheel 66 of the grindstone 68 grinds downward at a grinding feed speed of, for example, 1 μm/second. At this time, grinding can be performed while measuring the thickness of the wafer 10 with a thickness detection device (not shown), grinding the backside 10b of the wafer 10 by a predetermined amount until the predetermined thickness of the wafer 10 is reached (for example, 50 μm), and then stopping. Grinding means 60. In this way, the processing step of grinding the back surface 10b of the wafer 10 is completed. As described above, in this embodiment, the wafer 10 is thermally pressed to the sheet 14 and supported. Thereby, the sheet 14 functions as a protective film to prevent damage to the front surface 10 a of the wafer 10 . Furthermore, the sheet 14 exerts sufficient holding force with respect to the wafer 10, and even if the back surface 10b of the wafer 10 is grinded, the wafer 10 will not move.

After the processing step of processing the back surface 10 b of the wafer 10 is completed, the integrated wafer W is unloaded from the grinding device 50 . As described above, the upper surface 22 of the support table 20 of the grinding device 5 is covered with fluororesin. Even if the sheet 14 exerts adhesive force by performing the sheet hot pressing step, it can still be easily removed from the upper surface 22 of the support table 20 Integrated wafer W.

(peeling step) When the integrated wafer W is unloaded from the support table 20, it is transferred to the holding means 70 for performing the peeling step as shown in FIG. 5(a). The upper surface of the holding means 70 is formed of a breathable suction chuck 72 similar to the above-mentioned chuck table 52, and is connected to a suction means (not shown).

The integrated wafer W transported to the holding means 70 is placed on the suction chuck 72 of the holding means 70 with the back surface 10 b side of the wafer 10 facing downward and the sheet 14 side facing upward. When the integrated wafer W is placed on the suction chuck 72, a suction means (not shown) is activated to attract and hold the integrated wafer W.

When the integrated wafer W is attracted and held by the holding means 70, as shown in FIG. The sheet 14 and the release layer 16 are peeled off. At this time, it is preferable to heat or cool the integrated wafer W. The sheet 14 is softened by heating as described above, and is in a state in which it can be easily peeled off from the wafer 10 even if there is adhesive force. In addition, by cooling, the sheet 14 is hardened and its adhesive force is reduced, so that it can be easily peeled off even if it is cooled. When performing the peeling step, which one of heating and cooling should be performed can be selected taking into account the material constituting the sheet 14 or the adhesive force of the sheet 14 . With the above, the peeling step is completed.

In this embodiment, liquid resin, wax, double-sided tape, etc. are not used, but the sheet 14 that exerts adhesive force by heating is adhered to the wafer 10 . Thereby, even if the sheet 14 is peeled off from the wafer 10 , there will be no problem that adhesive scraps such as liquid resin, wax, double-sided tape paste, etc. adhere and remain around the bumps constituting the protruding electrodes, and the device will not be damaged. 11 quality reduction. Furthermore, between the wafer 10 and the sheet 14, the peeling layer 16, which is smaller in diameter than the wafer 10, is placed in a vacuum state and is thermally pressed only on the outer periphery. Therefore, during the process of peeling the sheet 14 from the wafer 10, the air Entering the area of the peeling layer 16 allows the thermally pressed sheet 14 to be peeled off from the wafer 10 more easily, thereby improving workability.

Furthermore, in the above embodiment, although the sheet 14 is made of polyethylene, the present invention is not limited thereto. The sheet 14 that can be thermally bonded to the wafer 10 without using liquid resin, double-sided tape, wax, or the like can be appropriately selected from polyolefin-based sheets and polyester-based sheets. As the polyolefin-based sheet, other than the above-mentioned polyethylene sheet, for example, polypropylene (PP) sheet or polystyrene sheet (PS) can be selected. Examples of polyester-based sheets include polyethylene terephthalate (PET) sheets and polyethylene naphthalate (PEN) sheets.

In the above-described embodiment, the temperature at which the sheet 14 is heated in the sheet thermocompression bonding step is set to a temperature near the melting point of the polyethylene sheet (120 to 140°C). However, as mentioned above, other sheets may be selected. When forming the sheet 14, it is preferable to heat it to a temperature near the melting point of the selected sheet material. For example, when the sheet 14 is made of a polypropylene sheet, the temperature during heating is preferably set to 160 to 180° C., and when the sheet 14 is made of a polystyrene sheet, the temperature during heating is preferably set to 220 to 240° C. ℃. In addition, when the sheet 14 is composed of a polyethylene terephthalate sheet, the temperature during heating is preferably set to 250 to 270° C., and when the sheet 14 is composed of a polyethylene naphthalate sheet, it is preferable to set the temperature during heating to The temperature during heating is set to 160 to 180°C.

In the above-described embodiment, although the peeling layer 16 is formed in a circular shape, it does not necessarily have to be a circular shape. As long as it is smaller than the diameter of the wafer 10 , the peeling layer 16 can be in a shape that can be bonded to the outer peripheral area of the wafer 10 and the sheet 14 .

In the above-mentioned embodiment, as the processing step of processing the back surface 10 b of the wafer 10 , the case where the grinding process of grinding the back surface 10 b of the wafer 10 is performed is explained. However, the present invention is not limited to this. Any technique is applicable as long as the polishing step of polishing the backside 10b of the wafer 10 is performed.

In addition, in the above-mentioned embodiment, although the thermal pressing is performed by the device shown in FIG. 2, the present invention is not limited to this, and a roller equipped with a heating means not shown can also be used to press the wafer. While heating the sheet to a desired temperature on the entire surface of side 10, a sheet thermocompression step is performed in which the sheet 14 is thermocompressed on the wafer 10. Furthermore, in this case, it is preferable to cover the surface of the drum with fluororesin.

10:wafer 11:Component 12: Split scheduled line 14: thin slices 16: peeling layer 20:Support platform 22: The upper surface of the support table 24: Electronic heater (heating means) 30:Hot pressing device 32:Support abutment 34:Suction hole 36: Sealing cover component 38: Press component 38b: Press plate 50:Grinding device 52:Chuck table 60:Grinding means 66:Grinding wheel 68:Grinding stone 70:Keep your means

FIG. 1 is a perspective view showing an implementation mode of the wafer arrangement step. Figure 2(a) is a side view of a thermocompression device that performs the sheet thermocompression step, and Figure 2(b) is a cross-sectional view of an integrated wafer formed through the sheet thermocompression step. FIG. 3 is a perspective view showing an integrated wafer placed on a chuck table of a grinding device for performing a processing step. FIG. 4 is a perspective view showing an embodiment of grinding processing using a grinding device. FIG. 5( a ) is a perspective view showing a state in which the integrated wafer is placed on the holding means for separation, and FIG. 5( b ) is a perspective view showing a state in which the peeling step of peeling off the sheet from the wafer is carried out.

10:wafer

10b: Backside of wafer

14: thin slices

14a: bulge

16: peeling layer

20:Support platform

24: Electronic heater (heating means)

32:Support abutment

34:Suction hole

36: Sealing cover component

36a:Upper wall

36b:Open your mouth

36c: Thin sheet structure

38: Press component

38a:Support shaft

38b: Press plate

S: space

W: Integrated wafer

Claims (9)

A wafer processing method that processes the back side of a wafer divided into a plurality of components by planned division lines and formed on the front side. The wafer processing method at least consists of the following steps: a wafer arrangement step, forming a wafer on the upper surface; On the upper surface of the flat support base, a polyolefin-based sheet or a polyester-based sheet that is larger than the shape of the wafer is laid, and on the upper surface of the sheet, a smaller diameter than the wafer is laid. The non-adhesive circular sheet, that is, the peeling layer, directly positions the outer periphery of the front side of the wafer on the upper surface of the sheet; in the sheet hot pressing step, through the sheet and the peeling layer, the components arranged on the support table are The wafer is decompressed in a closed environment and the sheet is heated to a temperature near the melting temperature that softens and exhibits adhesiveness, and the wafer is pressed to heat-press the outer periphery of the wafer to the sheet; the processing step involves the backside of the wafer. applying processing; and a peeling step to peel the thin sheet from the wafer. In the hot pressing step of the thin sheet, the thin sheet surrounds the wafer and presses the wafer in a raised manner. For example, in the wafer processing method described in item 1 of the patent application, the peeling layer includes at least any one of paper, cloth, glutinous rice paper, or polyimide sheets. For example, in the wafer processing method described in Item 1 or 2 of the patent application, the support table includes a heating means, and during the sheet hot pressing step, the support table is heated by the heating means. For example, in the wafer processing method described in item 3 of the patent application, the upper surface of the support platform is covered with fluororesin. For example, in the wafer processing method described in Item 1 or 2 of the patent application, in this processing step, a grinding process of grinding the back side of the wafer is performed. For example, in the wafer processing method described in Item 1 or 2 of the patent application, the polyolefin sheet is composed of any one of polyethylene sheet, polypropylene sheet or polystyrene sheet. For example, in the wafer processing method described in item 6 of the patent application, in the heat pressing step of the sheet, the heating temperature of the polyethylene sheet is 120 to 140°C, and the heating temperature of the polypropylene sheet is 160 to 140°C. 180℃, the heating temperature of the polystyrene sheet is 220 to 240℃. For example, the wafer processing method described in item 1 or 2 of the patent application, wherein the polyester sheet is made of any one of polyethylene terephthalate sheet and polyethylene naphthalate sheet. composed of. For example, in the wafer processing method described in item 8 of the patent application, in the step of hot pressing the sheet, the heating temperature of the polyethylene terephthalate sheet is 250 to 270°C, and the polynaphthalene sheet is The heating temperature of the ethylene glycol diformate flakes is 160 to 180°C.