Method for processing a workpiece

Abstract

Provided is a method for processing a workpiece, the workpiece (wafer (1)) having a division line (3) provided on a front surface (1a) and a metal film (21) stacked on a back surface (1b), the method comprising: a groove forming step of forming a groove (30) that does not reach the metal film on the front surface of the workpiece along the division line; a first protective film forming step of forming a first protective film (41) that coats the front surface of the workpiece and an inner wall surface of the groove with a first protective agent having a viscosity that allows the agent to be immersed in the groove after the groove forming step; a second protective film forming step of forming a second protective film (42) that coats at least the front surface of the workpiece with a second protective agent after the first protective film forming step; and a laser processing step of breaking the metal film by irradiating a laser beam (94) having a wavelength that is absorbed by the workpiece along the groove from the front surface side of the workpiece after the second protective film forming step.

Description

TECHNICAL FIELD

[0001] The present application relates to a processing method of a workpiece which is a semiconductor wafer provided with a division intended line on a front surface and a metal film laminated on a back surface. BACKGROUND

[0002] Conventionally, for example as disclosed in Patent Literature 1, for a semiconductor wafer on which a metal film is formed on a back surface, there is known a processing method having steps of: a cutting step of forming a cutting groove on a front surface by a cutting tool; a protective film forming step of covering the front surface and the cutting groove with a protective film; a laser processing step of irradiating a laser beam to the metal film to separate the wafer and the metal film; and a protective film removing step of removing the protective film by cleaning.

[0003] According to this processing method, metal chips generated by irradiating a laser beam to the metal film adhere to the protective film and can be removed together with the protective film, and can not remain on the device side.

[0004] Patent Literature 1: Japanese Patent Application Publication No. 2018-78162

[0005] However, it is confirmed that sometimes the protective agent does not easily sufficiently penetrate into the cutting groove and does not easily form a protective film on the inner wall surface of the cutting groove due to the narrow groove width of the cutting groove or the like.

[0006] Here, it is considered that if a protective agent with low viscosity is used, the protective agent easily penetrates into the cutting groove.

[0007] However, in the case of a protective agent with low viscosity, it is worried that it is difficult to form a protective film layer of sufficient thickness on the front surface of the wafer, and at the edge portion of the cutting groove, the protective film dissolves or peels off to expose the front surface of the wafer, and thus metal chips can adhere to the exposed portion.

[0008] And, when metal chips adhere to the exposed site like this, it is worried that the side surface (inner wall surface of the cutting groove) or the device of the front surface of the chip will be damaged. SUMMARY

[0009] The present application provides a processing method of a workpiece in view of the above problems, and proposes a new method for a technique of protecting the side surface (inner wall surface of the cutting groove) and the front surface of the chip with a protective film layer.

[0010] According to one embodiment of the present application, there is provided a method for processing a workpiece formed with a division line on a front surface and a metal film on a back surface, the method comprising: a groove forming step of forming a groove that does not reach the metal film along the division line on the front surface of the workpiece; a first protective film forming step of forming a first protective film that covers the front surface of the workpiece and an inner wall surface of the groove with a first protective agent having a viscosity that allows the first protective agent to be immersed in the groove after the groove forming step; a second protective film forming step of forming a second protective film that covers at least the front surface of the workpiece with a second protective agent after the first protective film forming step; and a laser processing step of irradiating a laser beam having a wavelength that is absorbed by the workpiece along the groove from the front surface side of the workpiece to separate the metal film after the second protective film forming step.

[0011] In addition, according to one embodiment of the present application, the second protective agent has a higher viscosity than the first protective agent.

[0012] According to one embodiment of the present application, the first protective agent and the second protective agent are the same.

[0013] According to one embodiment of the present application, the method for processing the workpiece further comprises a removing step of removing the first protective film and the second protective film after the laser processing step.

[0014] According to the structure of the present application, the front surface of the workpiece and the inner wall surface of the groove can be reliably protected with the double protective films, and the metal chips generated by the laser processing can be prevented from adhering to the front surface of the workpiece and the inner wall surface of the groove. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 FIG. 1 is a view showing a semiconductor wafer as an example of a workpiece processed by the present application.

[0016] Figure 2 FIG. 2 is a view illustrating an example of a processing device used to perform the front surface side groove forming step.

[0017] Figure 3 (A) of FIG. 4 is a cross-sectional view of the workpiece after the groove is formed, Figure 3 (B) of FIG. 4 is a view illustrating the front surface hydrophilization step.

[0018] Figure 4 FIG. 5 is a cross-sectional view of the workpiece in a state covered with the first protective film.

[0019] Figure 5 FIG. 6 is a partial side cross-sectional view of a protective film forming device.

[0020] Figure 6 (A) is a cross-sectional view of a workpiece in a state of being coated with a second protective film, Figure 6 (B) is a view illustrating a state in which a laser-processed groove is formed by a laser processing step.

[0021] Figure 7 is a view illustrating the laser processing step.

[0022] Figure 8 is a cross-sectional view of the workpiece after the protective film removal step.

[0023] Figure 9 (A) is a view showing an example in which double protective films are formed using the same protective agent, Figure 9 (B) is a view showing an example in which a laser-processed groove is formed in (A). Figure 9

[0024] Explanation of Reference Signs

[0025] 1: wafer; la: front surface; lb: back surface; lk: substrate; 3: division- scheduled line; 5: device; 21: metal film; 30: groove; 30a: inner wall surface; 30b: bottom surface; 30m: opening portion; 30n: edge portion; 32: laser-processed groove; 41: first protective film; 42: second protective film; 50: protective film forming device; 54: rotary table mechanism; 70: first protective agent ejection nozzle; 80: second protective agent ejection nozzle; 90: laser processing unit; 92: condenser; 94: laser beam. DETAILED DESCRIPTION

[0026] Hereinafter, an embodiment of the present application will be described with reference to the drawings.

[0027] Figure 1 is a view showing a semiconductor wafer as an example of a workpiece processed by the present application.

[0028] The front surface la of the wafer 1 is divided by a plurality of division-scheduled lines 3 (spacer lines) that intersect each other, and a device 5 such as an IC (Integrated Circuit) or an LSI (Large-Scale Integrated circuit) is formed in each region. The wafer 1 is scheduled to be divided along the division-scheduled lines 3 to be individualized into each device chip.

[0029] A metal film 21 formed of copper (Cu) or aluminum (Al) or the like is formed on the back surface lb of the wafer 1. The metal film 21 is used, for example, as an electrode or a heat sink.

[0030] ​The back side 1b of the chip 1 is attached to the adhesive layer on the upper side of the strip 7. In addition, a ring-shaped frame 9 is attached to the adhesive layer of the strip 7 in a manner surrounding the chip 1, and the chip unit 11 is formed by integrating the chip 1 and the frame 9.

[0031] In addition, the present invention can also be applied to situations where no devices are formed on the front side of the wafer.

[0032] The following steps are performed using the above-mentioned wafer 1 as the workpiece.

[0033] <Steps for forming the front side groove>

[0034] like Figure 2 and Figure 3 As shown in (A), a groove 30 with a depth not reaching the metal film 21 is formed along the predetermined dividing line 3 on the front side 1a of the wafer 1.

[0035] In this embodiment, as Figure 2 As shown, a groove 30 is formed by cutting along a predetermined dividing line 3 using a high-speed rotating cutting tool 66. In addition to forming the groove 30 (cutting groove) by cutting with the cutting tool 66, a groove can also be formed by irradiating a laser beam.

[0036] like Figure 3 As shown in (A), a device 5 is formed on the front side 1a of the substrate 1k of the wafer 1, and a metal film 21 is formed on the back side 1b of the substrate 1k of the wafer 1. The metal film 21 is attached to the tape 7.

[0037] like Figure 3 As shown in (A), the groove 30 is formed along the thickness direction of the substrate 1k of the wafer 1 and along the predetermined dividing line 3, and a device 5 is disposed between each groove 30.

[0038] In addition, there is no particular limitation on the thickness of the cutting residue of the substrate 1k at the bottom surface 30b of the groove 30, but considering the operability in subsequent steps, it is preferable to have a cutting residue of about 30μm to 50μm.

[0039] <Positive Hydrophilization Steps>

[0040] Preferably after the front side groove forming step, such as Figure 3The front side is hydrophilicated as shown in (B). Specifically, the front side 1a of the wafer 1 is simultaneously or sequentially irradiated with ultraviolet light of wavelengths 184 nm and 254 nm by the ultraviolet irradiator 46. The waiting oxygen is decomposed by the ultraviolet light of wavelength 184 nm to generate an ozone layer. The generated ozone is decomposed by the ultraviolet light of wavelength 254 nm to generate active oxygen. The generated active oxygen acts on the front side 1a of the wafer 1 to increase its hydrophilicity. At the same time, organic compounds such as oil adhering to the front side 1a are also volatilized and removed from the front side 1a of the wafer 1 as H2O, CO2, NO, etc.

[0041] As the ultraviolet irradiator 46, a low-pressure mercury lamp with two peaks at wavelengths of 184 nm and 254 nm, or an LED lamp with wavelengths of 184 nm and 254 nm, can be used, for example. Alternatively, hydrophilication treatment can be performed by plasma irradiation instead of ultraviolet irradiation. A mixture of argon and water vapor can be used as the plasma generating gas.

[0042] <First Protective Film Formation Steps>

[0043] Next, as Figure 4 and Figure 5 As shown, a first protective film forming step is performed to form a first protective film 41 on the front side 1a of the wafer 1.

[0044] exist Figure 4 The diagram shows that the front surface 1a of the wafer 1 and the front surface of the device 5 are covered by a first protective film 41, and the inner wall surface 30a and the bottom surface 30b of the groove 30 are also covered by the first protective film 41.

[0045] Figure 5 This is a partial side sectional view of a protective film forming apparatus 50 for forming a first protective film 41. The protective film forming apparatus 50 has a rotating table mechanism 54 and a liquid receiving mechanism 56 arranged to surround the rotating table mechanism 54.

[0046] The rotary table mechanism 54 is configured to include: a rotary table (holding table) 58 that attracts and holds the wafer 1; a support member 60 that supports the rotary table 58; and a motor 62 that drives the rotary table 58 to rotate via the support member 60.

[0047] A clamp 44 is provided on the rotary table 58. When the rotary table 58 rotates, these clamps 44 swing due to centrifugal force, which... Figure 1 The annular frame 9 shown is used to clamp and hold the object.

[0048] The liquid receiving mechanism 56 is configured with a liquid receiving container 56a configured to receive a liquid such as a cleaning liquid, and a cover member 56b mounted to the support member 60, and the liquid received in the liquid receiving container 56a is discharged as waste liquid through a discharge path not shown.

[0049] A first protective agent ejection nozzle 70 for ejecting the first protective agent 40 is provided in a space surrounded by the liquid receiving container 56a. The first protective agent ejection nozzle 70 is formed at a front end of a substantially L-shaped arm 71, and the other end of the arm 71 is oscillated by a motor 72. The arm 71 is connected to a protective film supply source 75 through a protective film supply path 73 and an on-off control valve 74.

[0050] When the wafer 1 is rotated at a predetermined speed by the protective film forming device 50 configured as described above, and the first protective agent 40 is ejected toward the central portion of the wafer 1, the first protective agent 40 spreads in the radial direction by centrifugal force, and the entire front surface la of the wafer 1 is coated (spin-coated) with the first protective agent 40.

[0051] In addition, during the spreading of the first protective agent 40, the first protective agent 40 is immersed in the groove 30, and as shown in Figure 4 the inner wall surface 30a and the bottom surface 30b of the groove 30 are coated with the first protective film 41.

[0052] The first protective agent 40 for forming the first protective film 41 is, for example, a water-soluble liquid resin such as PVP (polyvinyl pyrrolidone) or PVA (polyvinyl alcohol).

[0053] Here, the viscosity of the first protective agent 40 is preferably set to a value that enables reliable immersion in the groove 30, and for example, a value between 1 cP and 20 cP, for example, 8 cP, can be selected.

[0054] [Second protective film forming step]

[0055] Next, as shown in (A) of Figure 6 , a second protective film forming step for forming a second protective film 42 as a second layer on the first protective agent 41 formed on the front surface of the wafer is performed.

[0056] As shown in Figure 5 , in the above-described protective film forming device 50, in addition to the first protective agent ejection nozzle 70, a second protective agent ejection nozzle 80 for ejecting a second protective agent for forming the second protective film 42 Figure 6 (A) is provided.

[0057] The second protective agent ejection nozzle 80 is formed at a front end of a substantially L-shaped arm 81, and the other end of the arm 81 is oscillated by a motor 82. The arm 81 is connected to a protective film supply source 85 through a protective film supply path 83 and an on-off control valve 84.

[0058] After completing the first protective film formation step, the arm 71 is rotated by the motor 72 so that the first protective agent ejection nozzle 70 is retracted to the standby position, and the arm 81 is rotated by the motor 82 so that the second protective agent ejection nozzle 80 is positioned above the wafer 1.

[0059] Furthermore, when wafer 1 is rotated at a predetermined speed and a second protective agent is sprayed toward the center of wafer 1, the second protective agent expands radially due to centrifugal force, such as... Figure 6 As shown in (A), the surface of the first protective film 41 is covered by the second protective film 42.

[0060] The second protective agent used to form the second protective film 42 is, for example, a water-soluble liquid resin such as PVP (polyvinylpyrrolidone) or PVA (polyvinyl alcohol).

[0061] Here, it is preferable that the viscosity of the second protective agent used to form the second protective film 42 is set higher than that of the first protective agent used to form the first protective film 41. For example, a value between 40 cP and 80 cP can be selected, such as 60 cP.

[0062] In this way, when forming the second protective film 42, a high-viscosity second protective agent is used, thereby enabling a protective film of sufficient thickness to be formed on the front side of the device 5.

[0063] In addition, by increasing the viscosity of the second protective agent, thus... Figure 6 As shown in (A), the second protective agent will not penetrate into the tank 30, but the inner wall surface 30a and the bottom surface 30b of the tank 30 have been covered by the first protective film 41 and are thus protected.

[0064] <Laser Processing Steps>

[0065] Figure 7 A laser processing unit 90 is shown for performing laser processing steps, wherein the laser processing unit 90 irradiates a laser beam from a concentrator 92 along a groove 30.

[0066] like Figure 6 As shown in (B), a laser beam 94 is irradiated into the groove 30, causing the substrate 1k and metal film 21 of the wafer 1 remaining below the bottom surface 30b of the groove 30 to absorb the laser beam 94 and be destroyed, thereby forming a laser processing groove 32. The focal position of the laser beam 94 is set at a position corresponding to the substrate 1k and metal film 21 of the wafer 1 remaining below the bottom surface 30b of the groove 30.

[0067] like Figure 6As shown in (B), the second protective film 42 covering the groove 30 is also removed by irradiation with laser beam 94, and the groove 30 is opened to form an opening 30m. At this time, there is a concern that the protective film may dissolve or peel off at the edge portion 30n around the opening 30m, but the second protective film 42 has sufficient thickness to prevent the front side of the wafer or device from being exposed and causing metal debris to adhere to the exposed portion.

[0068] Furthermore, even assuming that the second protective film 42 is dissolved or peeled off, the front side of the wafer or the device can still be protected by the first protective film 41 inside the second protective film 42. In this way, the front side of the wafer or the device can be protected twice.

[0069] <Protective Film Removal Steps>

[0070] In the above Figure 5 In the protective film forming apparatus 50 shown, in addition to the first and second protective agent ejection nozzles 70 and 80, a cleaning liquid nozzle (not shown) is also provided. The cleaning liquid is ejected from the cleaning liquid nozzle toward the wafer 1, and the wafer 1 is rotated, thereby removing the first and second protective films 41 and 42 covering the wafer 1 or device 5.

[0071] As mentioned above, it is possible to... Figure 8 The wafer 1 is shown in a state where the protective film has been removed and the device 5 is exposed. Furthermore, the laser processing groove 32 formed on the substrate 1k and the metal film 21 can be used as a starting point for dicing and then monolithically formed into a chip through subsequent expansion processes.

[0072] Additionally, in the above embodiments, such as Figure 6 As shown in (A), protective agents of different viscosities are used to coat the front side of wafer 1 through the first and second protective films 41 and 42, but it is also possible to... Figure 9 (A) Figure 9 As shown in (B), the laser processing groove 32 is formed after being double-coated with the same type of protective film 43, 43.

[0073] In this case, the same protective agent is applied twice to the front side of the wafer, with both the first and second applications of the protective agent being immersed in the tank 30. This allows for double coating of the inner wall surface 30a and the bottom surface 30b of the tank 30.

[0074] As described above, the present invention can be realized.

[0075] That is, such as Figures 1 to 8 As shown, a processing method for a workpiece (wafer 1) is provided. The workpiece has predetermined dividing lines 3 on its front side 1a and a metal film 21 is laminated on its back side 1b. The processing method for the workpiece includes the following steps:

[0076] a groove 30 not reaching the metal film 21 is formed on the front surface la of the work along the division predetermined line 3;

[0077] a first protective film 41 that coats the front surface la of the work and the inner wall surface of the groove 30 is formed using a first protective agent having a viscosity that allows the agent to be immersed in the groove 30 after the groove forming step is performed;

[0078] a second protective film 42 that coats at least the front surface la of the work is formed using a second protective agent after the first protective film forming step is performed; and

[0079] a laser processing step in which the metal film 21 is broken by irradiating a laser beam 94 having a wavelength that is absorbed by the work from the front surface la side of the work along the groove 30 after the second protective film forming step is performed.

[0080] According to the above processing method, the front surface of the work and the inner wall surface of the groove can be reliably protected by the double protective films, and the metal chips generated by the laser processing can be prevented from adhering to the front surface of the work and the inner wall surface of the groove.

[0081] In addition, the viscosity of the second protective agent is higher than the viscosity of the first protective agent.

[0082] Thus, as shown in (A) of FIG. 1 and (B) of FIG. 2, the second protective film 42 having a thickness that is thick can be formed by the second protective agent having a high viscosity, and the front surface la of the wafer 1 and the device 5 as the work can be reliably protected. Figure 6 Figure 6 Thus, as shown in (A) of FIG. 1 and (B) of FIG. 2, the second protective film 42 having a thickness that is thick can be formed by the second protective agent having a high viscosity, and the front surface la of the wafer 1 and the device 5 as the work can be reliably protected.

[0083] In addition, the first protective agent and the second protective agent are the same.

[0084] Thus, as shown in (A) of FIG. 1 and (B) of FIG. 2, the second protective film 42 having a thickness that is thick can be formed by the second protective agent having a high viscosity, and the front surface la of the wafer 1 and the device 5 as the work can be reliably protected. Figure 9 Figure 9 Thus, as shown in (A) of FIG. 1 and (B) of FIG. 2, the second protective film 42 having a thickness that is thick can be formed by the second protective agent having a high viscosity, and the front surface la of the wafer 1 and the device 5 as the work can be reliably protected.

[0085] In addition, the processing method of the work further includes a removal step in which the first protective film 41 and the second protective film 42 are removed after the laser processing step is performed.

[0086] Thus, the protective films can be removed and a division process or the like can be performed.​​

Claims

1. A method for processing a workpiece, wherein the workpiece has predetermined dividing lines formed on its front side and a metal film laminated on its back side, wherein, The processing method for the workpiece includes the following steps: The groove forming step involves forming a groove on the front side of the workpiece along the predetermined dividing line that does not reach the metal film; In the first protective film forming step, after the tank forming step is performed, a first protective film is formed by using a first protective agent to cover the front surface of the workpiece and the inner wall surface of the tank, the first protective agent having a viscosity that allows it to penetrate the tank. The second protective film forming step involves forming a second protective film covering at least the front side of the workpiece using a second protective agent after the first protective film forming step has been performed. as well as In the laser processing step, after the second protective film formation step is performed, a laser beam of a wavelength that is absorbed by the workpiece is irradiated along the groove from the front side of the workpiece to break the metal film.

2. The processing method for the workpiece according to claim 1, characterized in that, The viscosity of the second protective agent is higher than that of the first protective agent.

3. The processing method for the workpiece according to claim 1, characterized in that, The first protective agent and the second protective agent are the same.

4. The processing method for the workpiece according to any one of claims 1 to 3, characterized in that, The processing method for the workpiece further includes the following removal step: after performing the laser processing step, removing the first protective film and the second protective film.

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