Processing method

Abstract

To provide a processing method capable of restraining a part of a protective layer from remaining on the surface of a workpiece.SOLUTION: A processing method is a method for processing a workpiece, and includes a coating step 101 of forming a protective layer made of silicon on a surface which is a first surface of a workpiece, thereby covering the surface with the protective layer, a processing step 103 of processing the workpiece after the coating step 101, and a removal step 104 of supplying a plasma-like etching gas to the protective layer after the processing step 103, and removing the protective layer. In the coating step 101, the protective layer for covering a device is formed on the surface of the workpiece, and in the processing step 103, the surface of the workpiece is irradiated with a laser beam through the protective layer.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for machining a workpiece. [Background technology]

[0002] For example, as a method for dividing a wafer into individual devices, a method has been proposed in which a sheet is attached via an adhesive layer to form a protective layer to protect the surface of the wafer from contamination and water, and then dicing is performed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-175148 A Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned protective layer is required to protect the surface of the workpiece during processing, and not to contaminate the surface of the workpiece or leave behind any residue after removal.

[0005] Conventional protection using a sheet having an adhesive layer has the risk of the adhesive remaining on the surface of the workpiece after the sheet is removed, and improvement thereto has been eagerly desired.

[0006] An object of the present invention is to provide a processing method capable of suppressing a portion of a protective layer from remaining on the surface of a workpiece. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the processing method of the present invention is a method for processing a workpiece, characterized in that it includes a coating step of forming a protective layer made of silicon on a first surface of the workpiece to cover the first surface, and a processing step of processing the workpiece after performing the coating step.

[0008] In the above processing method, the workpiece is a device wafer having a plurality of devices formed on a surface of a substrate, and in the coating step, a protective layer for covering the devices is formed on the surface of the device wafer, and in the processing step, a laser beam may be irradiated onto the surface of the device wafer through the protective layer.

[0009] In the processing method, the processing step may include forming a liquid layer on the protective layer of the device wafer and irradiating the surface of the device wafer with a laser beam through the liquid layer and the protective layer.

[0010] In the above processing method, the protective layer may be formed by sputtering in the covering step.

[0011] The processing method may further include a removal step of removing the protective layer by supplying a plasma-like gas to the protective layer after carrying out the processing step. Effect of the Invention

[0012] The present invention has an advantage that the surface of the workpiece is protected by a protective layer made of silicon, and therefore it is possible to prevent a portion of the protective layer from remaining on the surface of the workpiece. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing an example of a workpiece to be processed by the processing method according to the first embodiment. [Diagram 2] FIG. 2 is a flowchart showing the flow of the processing method according to the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view showing a schematic view of the workpiece after the coating step of the processing method shown in FIG. [Figure 4] FIG. 4 is a perspective view showing a schematic view of the workpiece after the tape adhering step of the processing method shown in FIG. [Diagram 5]FIG. 5 is a perspective view that illustrates a processing step of the processing method illustrated in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a cross-sectional view that typically illustrates a state in which a laser beam is irradiated while a liquid layer is being formed in the processing step of the processing method illustrated in FIG. [Figure 8] FIG. 8 is a cross-sectional view that typically illustrates a state in which debris is removed in the processing step of the processing method illustrated in FIG. [Figure 9] FIG. 9 is a cross-sectional view that illustrates a schematic configuration example of an etching apparatus that removes the protective layer in the removal step illustrated in FIG. [Figure 10] FIG. 10 is a perspective view illustrating a processing step of a processing method according to a modified example of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0015] [Embodiment 1] A processing method according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing an example of a workpiece to be processed by the processing method according to the first embodiment. Fig. 2 is a flowchart showing the flow of the processing method according to the first embodiment.

[0016] (workpiece) The processing method according to the first embodiment is a method for dividing a workpiece 1 shown in Fig. 1 into individual device chips 10. The workpiece 1 to be processed by the processing method according to the first embodiment is a wafer such as a disk-shaped semiconductor wafer or an optical device wafer, with a substrate 2 made of, for example, silicon, gallium arsenide, sapphire, SiC, lithium tantalate, lithium niobate, or the like.

[0017] 1, a plurality of mutually intersecting division lines 4 are set on a surface 3 (corresponding to a first surface) of a substrate 2 of the workpiece 1, and devices 5 are formed in areas defined by the division lines 4 on the surface 3 of the substrate 2. Note that in the present invention, the workpiece 1 does not necessarily have to have devices 5 formed on the surface 3 of the substrate 2.

[0018] The device 5 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), an optical element such as an LED (Light-Emitting Diode), or a memory (semiconductor memory device).

[0019] In the first embodiment, the device 5 is an integrated circuit or memory such as an integrated circuit (IC) or large scale integration (LSI), and includes a low dielectric constant insulator coating (referred to as a low-k film) made of an inorganic film such as SiOF or BSG (SiOB), an organic film such as a polymer film of a polyimide or parylene, or carbon-containing silicon oxide (SiOCH), and a circuit layer including a conductive metal pattern or metal film.

[0020] The low-k film is laminated with a circuit layer to form the device 5. The circuit layer constitutes the circuit of the device 5. For this reason, the device 5 is composed of a low-k film laminated on the substrate 2 and a circuit layer laminated between the low-k films. Note that, at the planned division lines 4, the low-k film is laminated on the substrate 2.

[0021] The workpiece 1 is divided into individual device chips 10 along the planned division lines 4. Each device chip 10 includes a part of the substrate 2 and a device 5 formed on the surface 3 of the substrate 2. Thus, in the first embodiment, the workpiece 1 is a device wafer in which a plurality of devices 5 are formed on the surface 3 of the substrate 2.

[0022] (Processing method) The processing method according to the first embodiment includes a covering step 101, a tape application step 102, a processing step 103, and a removing step 104, as shown in FIG.

[0023] (Covering step) Fig. 3 is a cross-sectional view showing a schematic diagram of the workpiece after the coating step of the processing method shown in Fig. 2. The coating step 101 is a step of forming a protective layer 11 made of silicon on a surface 3, which is a first surface of the workpiece 1, to coat the surface 3.

[0024] In the first embodiment, in the coating step 101, silicon is coated on the surface 3 of the workpiece 1 by sputtering, i.e., a dry plating method (also called vacuum plating), to form a protective layer 11 on the surface 3 of the workpiece 1 as shown in Fig. 3. The thickness of the protective layer 11 is appropriately set depending on the processing performed on the workpiece 1 in the processing step 103, and is, for example, 100 nm in the first embodiment.

[0025] In the first embodiment, if the thickness of the protective layer 11 is too thin, it will peel off from the surface 3 in the processing step 103, and if it is too thick, it will take a long time to remove it in the removing step 104. Thus, in the first embodiment, in the covering step 101, the protective layer 11 that covers the devices 5 is formed on the surface 3 of the workpiece 1, which is a device wafer.

[0026] (Tape application step) Fig. 4 is a perspective view showing a schematic view of the workpiece after the tape application step of the processing method shown in Fig. 2. The tape application step 102 is a step of applying tape 12 to the back surface 6 behind the front surface 3 of the workpiece 1 and fixing the workpiece 1 to a frame 13.

[0027] In embodiment 1, in the tape application step 102, as shown in FIG. 4, the back surface 6 of the workpiece 1 is applied to the center of a circular tape 12 having a larger diameter than the outer diameter of the workpiece 1, and an annular frame 13 having an inner diameter larger than the outer diameter of the workpiece 1 is applied to the outer edge of the tape 12, and the workpiece 1 is supported within the inner opening of the frame 13 via the tape 12.

[0028] In the first embodiment, the tape 12 is an adhesive tape including a base layer made of a non-adhesive and flexible resin and a glue layer laminated on the base layer and made of an adhesive and flexible resin, the glue layer being attached to the back surface 6 of the workpiece 1 and the frame 13. In the present invention, the tape 12 may be a sheet that does not include an adhesive layer and is made of only a base material made of a thermoplastic resin, and is attached to the back surface 6 of the workpiece 1 and the frame 13 by heating.

[0029] (Processing steps) Fig. 5 is a perspective view showing a processing step of the processing method shown in Fig. 2. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 5. Fig. 7 is a cross-sectional view showing a state in which a laser beam is irradiated while a liquid layer is being formed in the processing step of the processing method shown in Fig. 2. Fig. 8 is a cross-sectional view showing a state in which debris is removed in the processing step of the processing method shown in Fig. 2.

[0030] The processing step 103 is a step of processing the workpiece 1 after the covering step 101 is performed. In the first embodiment, in the processing step 103, the laser processing device 20 sucks and holds the back surface 6 of the substrate 2 of the workpiece 1 on the holding surface of a holding table (not shown) via the tape 12, and clamps the frame 13 with a clamp unit (not shown) around the holding table. In the first embodiment, in the processing step 103, the laser processing device 20 relatively moves the holding table and the laser beam irradiation unit 21 along the planned division line 4 as shown in FIG. 5, sets a focusing point on the front surface 3 of the substrate 2 with a focusing lens 22 shown in FIG. 6, and irradiates a pulsed laser beam 23 having a wavelength (e.g., 355 nm) that is absorbed by the workpiece 1 and the protective layer 11 from the laser beam irradiation unit 21 along the planned division line 4.

[0031] In embodiment 1, in the processing step 103, since the laser beam 23 has a wavelength that is absorbent for the workpiece 1 and the protective layer 11, the workpiece 1 is subjected to an ablation process along all of the intended dividing lines 4, thereby dividing the workpiece 1 into individual device chips 10 along the intended dividing lines 4.

[0032] In the first embodiment, in the processing step 103, the laser beam irradiation unit 21 of the laser processing device 20 includes, as shown in Fig. 6, an oscillator 24 that oscillates a pulsed laser beam 23, a reflecting mirror 25 that appropriately changes the laser beam 23 oscillated from the oscillator 24, and a condenser lens 22. The oscillator 24 oscillates the laser beam 23 having a wavelength absorbed by the workpiece 1, and includes an attenuator and the like that adjusts the output of the oscillated laser beam 23.

[0033] The laser beam 23 emitted from the oscillator 24 is reflected by the reflecting mirror 25, collected by the collecting lens 22, and irradiated onto the workpiece 1 held on the holding table. In the present invention, a polygon mirror that rotates at high speed may be disposed in place of the reflecting mirror 25. If the rotating polygon mirror reflects the laser beam 23 so as to reciprocate in the X-axis direction, which is the processing feed direction (the relative movement direction between the laser beam irradiation unit 21 and the workpiece 1 when irradiating the laser beam 23), the laser processing can be performed more efficiently.

[0034] In the first embodiment, in the processing step 103, the laser processing apparatus 20 attaches the liquid injector 30 shown in Figures 5 and 6 to the laser beam irradiation unit 21. The liquid injector 30 is attached to the lower end of the laser beam irradiation unit 21 as shown in Figures 5 and 6.

[0035] The liquid injector 30 includes a housing 31, as shown in Fig. 5 and Fig. 6. The housing 31 is substantially rectangular in plan view, and is composed of an upper housing member 32 and a lower housing member 33. The upper housing member 32 is formed in a box shape with an opening on the lower side, and a circular opening 321 for mounting the laser beam irradiation unit 21 is formed in the center of the upper surface. The upper housing member 32 also includes a transparent plate 34 that covers the opening on the lower side and transmits the laser beam 23 irradiated from the condenser lens 22. The transparent plate 34 is made of, for example, a glass plate, and is disposed in a position facing the opening 321, i.e., the condenser lens 22.

[0036] The housing lower member 33 is formed in a box shape with an opening at the top, and includes a bottom wall 331 facing the transparent plate 34, and a side wall 332 continuing to the outer edge of the bottom wall 331. The side wall 332 of the housing lower member 33 is attached to the side wall 322 of the housing upper member 32, and a space 333 is formed inside.

[0037] The housing lower member 33 has an opening 334 extending in the X-axis direction at the center of the bottom wall 331, and an inclined portion 335 formed along both sides of the opening 334 in the longitudinal direction. The width of the opening 334 is set to about 1 mm to 2 mm. The liquid supply tube 35 is connected to a side wall 332 on the front side in FIG. 5 in the Y-axis direction along the horizontal direction to which the liquid supply tube 35 is connected and perpendicular to the X-axis direction, to which the liquid 200 (pure water in the first embodiment) is supplied from a liquid supply source (not shown). The housing upper member 32 and the housing lower member 33 are joined from above and below to form the housing 31 having a space 333 formed by the transparent plate 34, the side wall 332, and the bottom wall 331.

[0038] When the laser beam irradiation unit 21 irradiates the laser beam 23, the liquid injector 30 supplies liquid 200 from a liquid supply source to a liquid supply tube 35 of the housing 31, passes through a space 333 in the housing 31, and is sprayed from an opening 334 formed in the bottom wall 331.

[0039] In the first embodiment, in the processing step 103, the laser processing device 20 positions the lower surface of the housing lower member 33 of the liquid injector 30 at a distance of, for example, about 0.5 mm or more and 2.0 mm or less from the protective layer 11 on the surface 3 of the workpiece 1 held by the holding table, and supplies the liquid 200 to the liquid supply tube 35 of the liquid injector 30. In the first embodiment, in the processing step 103, the laser processing device 20 injects the liquid 200 from the opening 334 of the housing lower member 33 of the liquid injector 30 to fill the space between the liquid injector 30 and the protective layer 11 with the liquid 200, thereby generating a liquid layer 201 as shown in FIG. 7, while irradiating the laser beam 23 while moving the holding table and the laser beam application unit 21 relatively along the planned division line 4.

[0040] In the first embodiment, in the processing step 103, the laser beam 23 passes through the transparent plate 34 of the liquid injector 30, the space 333, and the liquid layer 201, and is irradiated onto the workpiece 1 from the opening 334. Thus, in the first embodiment, in the processing step 103, the liquid layer 201 is formed on the protective layer 11 of the workpiece 1, which is a device wafer, and the laser beam 23 is irradiated onto the surface 3 of the workpiece 1 through the liquid layer 201 and the protective layer 11. Note that, in the processing step 103, a water flow is generated in the space 333, but since the transparent plate 34 is provided, the laser beam 23 irradiated from above is irradiated downward without being affected by the water flow.

[0041] In the first embodiment, in the processing step 103, when the laser beam 23 ablates the workpiece 1, minute bubbles (microbubbles) 202 are generated together with debris in the grooves 7 of the workpiece 1 irradiated with the laser beam 23, as shown in Fig. 8. The microbubbles 202 are bubbles having diameters on the order of µm, and although the diameters are not uniform, the microbubbles 202 include bubbles having diameters of, for example, 50 µm or less.

[0042] In the first embodiment, in the processing step 103, microbubbles 202 generated in the groove 7 by irradiation with the laser beam 23 agitate the inside of the groove 7, and the microbubbles 202 burst to remove debris that tends to adhere to the inner wall of the groove 7, as in cavitation. As shown in Fig. 8, liquid 200 is constantly supplied at a predetermined flow rate to the gap formed on the workpiece 1, generating a liquid layer 201. As a result, the microbubbles 202 generated near the irradiation position of the laser beam 23 are pushed out together with the liquid 200 from the groove 7 formed in the workpiece 1 to the outside.

[0043] Thus, in embodiment 1, in processing step 103, a liquid layer 201 is formed on the protective layer 11 of the workpiece 1, which is a device wafer, and a laser beam 23 is irradiated onto the surface 3 of the workpiece 1 through the liquid layer 201 and the protective layer 11.

[0044] (Removal step) Fig. 9 is a cross-sectional view showing a schematic configuration example of an etching apparatus for removing the protective layer in the removing step shown in Fig. 2. The removing step 104 is a step for removing the protective layer 11 by supplying a plasma gas to the protective layer 11 after the processing step 103 is performed.

[0045] (Etching equipment) Next, an etching apparatus 50 for performing the removal step 104 shown in Fig. 2 will be described with reference to the drawings. As shown in Fig. 9, the etching apparatus 50 includes a rectangular parallelepiped chamber 51, a holding unit 52, an upper electrode 53, and a control unit 55.

[0046] The chamber 51 has a processing space 511 formed therein where plasma etching is performed. The chamber 51 has an opening 513 for carrying in and out the workpiece 1, and an opening / closing door 514 for opening and closing the opening 513, provided on one side wall 512. The opening / closing door 514 opens and closes the opening 513 by being raised and lowered by an opening / closing mechanism 515 formed of an air cylinder or the like.

[0047] Further, an exhaust port 517 that connects the inside and outside of the chamber 51 is formed in the bottom wall 516 of the chamber 51. An exhaust mechanism 510 such as a vacuum pump is connected to the exhaust port 517.

[0048] The holding unit 52 and the upper electrode 53 are disposed opposite to each other in the processing space 511 of the chamber 51. The upper surface of the holding unit 52 is a holding surface 524 that holds the workpiece 1 via the tape 12. The holding unit 52 is also made of a conductive material and functions as a lower electrode.

[0049] The holding unit 52 includes a disk-shaped holding portion 521 and a columnar support portion 520 protruding downward from the center of the lower surface of the holding portion 521. The support portion 520 is inserted into an opening 522 formed in a bottom wall 516 of the chamber 51. In the opening 522, an annular insulating member 523 is disposed between the bottom wall 516 and the support portion 520, and the chamber 51 and the holding unit 52 are electrically insulated from each other. In addition, the holding unit 52 is connected to a high-frequency power source 56 outside the chamber 51.

[0050] An electrode 526 connected to a high-frequency power source (not shown) is provided on the holding portion 521 of the holding unit 52. When power is applied from the high-frequency power source to the electrode 526, the holding unit 52 generates a dielectric polarization phenomenon between the holding surface 524 and the workpiece 1, and attracts and holds the workpiece 1 on the holding surface 524 by electrostatic attraction force due to polarization of the electric charge.

[0051] Moreover, inside the holding part 521 and inside the support part 520 of the holding unit 52, a cooling flow path 527 through which a cooling fluid flows for cooling the holding unit 52 is formed. Both ends of the cooling flow path 527 are connected to a refrigerant circulation mechanism 528. When the refrigerant circulation mechanism 528 is operated, the cooling fluid such as water circulates through the cooling flow path 527, and the holding unit 52 is cooled.

[0052] The upper electrode 53 is made of a conductive material and includes a disk-shaped gas ejection part 531 and a cylindrical support part 530 protruding upward from the center of the upper surface of the gas ejection part 531. The support part 530 is inserted into an opening 532 formed in an upper wall 518 of the chamber 51. In the opening 532, an annular insulating member 533 is disposed between the upper wall 518 and the support part 530, and the chamber 51 and the upper electrode 53 are electrically insulated from each other.

[0053] The upper electrode 53 is connected to a high-frequency power source 57 outside the chamber 51. In addition, a support arm of a lifting mechanism 534 is attached to the upper end of the support part 530. The upper electrode 53 is raised and lowered by the lifting mechanism 534.

[0054] A plurality of ejection ports 535 are provided on the lower surface side of the gas ejection part 531. The ejection port 535 is connected to a first etching gas supply source 58 and a second etching gas supply source 59 through a flow path 536 formed in the gas ejection part 531 and the support part 530. The first etching gas supply source 58 supplies the first etching gas from the ejection port 535 through the flow path 536 into the chamber 51. In the first embodiment, when the substrate 2 of the workpiece 1 is made of silicon, the first etching gas supply source 58 supplies SF6 gas, which is a fluorine-based gas, into the chamber 51 as the first etching gas. The second etching gas supply source 59 supplies the second etching gas from the ejection port 535 through the flow path 536 into the chamber 51. In the first embodiment, the second etching gas supply source 59 supplies an oxygen-based gas into the chamber 51 as the second etching gas.

[0055] The control unit 55 controls each component of the etching apparatus 50 to cause the etching apparatus 50 to perform plasma etching on the workpiece 1. The control unit 55 is a computer having an arithmetic processing device having a microprocessor such as a CPU (central processing unit), a storage device having a memory such as a ROM (read only memory) or a RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 55 performs arithmetic processing according to a computer program stored in the storage device, and outputs control signals for controlling the etching apparatus 50 to each component of the etching apparatus 50 via the input / output interface device.

[0056] The control unit 55 is connected to a display unit configured with a liquid crystal display device or the like that displays various information and images, and an input unit that an operator uses to register processing content information, etc. The input unit is configured with at least one of a touch panel provided on the display unit and an external input device such as a keyboard.

[0057] In the first embodiment, in the removing step 104 , the etching apparatus 50 raises the upper electrode 53 by the lifting mechanism 534 , and then lowers the opening / closing door 514 by the opening / closing mechanism 515 to open the opening 513 .

[0058] In the first embodiment, in the removing step 104, in the etching apparatus 50, the workpiece 1 divided into individual device chips 10 is carried into the processing space 511 by a transport unit (not shown), and the workpiece 1 is placed on the holding surface 524 of the holding unit 52 via the tape 12. In the first embodiment, in the removing step 104, the etching apparatus 50 applies power from a high-frequency power source to the electrode 526, and adsorbs and holds the back surface 6 of the workpiece 1 on the holding surface 524 via the tape 12.

[0059] In the first embodiment, in the removing step 104, the etching apparatus 50 raises the opening / closing door 514 by the opening / closing mechanism 515 to close the opening 513, operates the exhaust mechanism 510 to reduce the pressure inside the chamber 51, places the processing space 511 in a vacuum state (low pressure state), and operates the coolant circulation mechanism 528 to circulate a cooling fluid such as water inside the cooling passage 527 to suppress an abnormal temperature rise in the holding unit 52. In the first embodiment, in the removing step 104, the etching apparatus 50 lowers the upper electrode 53 by the lifting mechanism 534, and positions the distance between the lower surface of the upper electrode 53 and the workpiece 1 held by the holding unit 52 constituting the lower electrode at a predetermined inter-electrode distance suitable for plasma etching.

[0060] In the first embodiment, in the removing step 104, the etching apparatus 50 supplies SF6 gas, which is a first etching gas, from the first etching gas supply source 58 at a predetermined flow rate and ejects it from the multiple ejection ports 535 of the gas ejection part 531 toward the workpiece 1 held on the holding unit 52. In the first embodiment, in the removing step 104, while the first etching gas is being supplied from the first etching gas supply source 58, the etching apparatus 50 applies high-frequency power from the high-frequency power source 57 to the upper electrode 53 to create and maintain plasma, and applies high-frequency power from the high-frequency power source 56 to the holding unit 52, which is the lower electrode, to attract ions.

[0061] In the first embodiment, in the removing step 104, the etching device 50 turns the first etching gas in the space between the holding unit 52 and the upper electrode 53 into plasma, and this first etching gas in a plasma state is drawn into the workpiece 1 side to etch (so-called plasma etching) the protective layer 11 of the workpiece 1. Thus, in the first embodiment, in the removing step 104, the protective layer 11 is plasma etched to remove the protective layer 11.

[0062] In the first embodiment, since the protective layer 11 is made of silicon, a fluorine-based gas such as SF6 gas is used as the first etching gas, but the first etching gas is not limited to SF6 gas.

[0063] In the first embodiment, in the removing step 104, the etching device 50 has a predetermined time for plasma etching the protective layer 11 set in advance according to the thickness of the protective layer 11. In the first embodiment, in the removing step 104, the etching device 50 applies high frequency power to the holding unit 52 and the upper electrode 53 while supplying the first etching gas for the predetermined time, thereby completely removing the protective layer 11.

[0064] In the processing method according to the first embodiment described above, the surface 3 of the workpiece 1 is protected by the protective layer 11 made of silicon, and the protective layer 11 is removed by plasma etching in the removing step 104 .

[0065] As a result, the processing method according to embodiment 1 has the advantage that the protective layer 11 made of silicon can be removed by plasma etching without leaving any residue, thereby making it possible to prevent a portion of the protective layer 11 from remaining on the surface 3 of the workpiece 1.

[0066] In particular, in the processing method of embodiment 1, when the workpiece 1 is a semiconductor wafer, using a metal as the protective layer 11, for example, may cause metal contamination of the device 5. However, since silicon, which is also used for the substrate 2, is used as the protective layer 11, there is no risk of affecting the device 5.

[0067] In addition, in the processing method according to embodiment 1, since the protective layer 11 is made of silicon and the laser beam 23 has a wavelength that is absorbed by the workpiece 1 and the protective layer 11, in the processing step 103, the protective layer 11 absorbs the scattered light of the laser beam 23 caused by bubbles generated by processing the workpiece 1, thereby preventing damage to the device 5 due to the scattered light and improving the flexural strength of the device chip 10.

[0068] Furthermore, in the processing method according to the first embodiment, since the protective layer 11 has the ability to absorb the scattered light of the laser beam 23, the risk that the device 5 will be damaged due to the scattered light being absorbed by the protective layer 11 can be reduced.

[0069] [Modifications] A processing method according to a modified example of the first embodiment will be described with reference to the drawings. Fig. 10 is a perspective view showing a schematic diagram of processing steps of the processing method according to a modified example of the first embodiment. In Fig. 10, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted. In Fig. 10, the protective layer 11 is omitted.

[0070] The processing method according to the modification of the first embodiment is the same as that of the first embodiment, except for the difference in processing step 103. In the modification of the first embodiment, in processing step 103, as shown in FIG. 10 , a cutting device 60 causes a cutting blade 61 to cut into the division lines 4 of the workpiece 1 until it reaches the tape 12, and cuts the workpiece 1 along the division lines 4 to divide the workpiece 1 into individual device chips 10.

[0071] In the processing method according to the modified example of embodiment 1, surface 3 of workpiece 1 is protected by protective layer 11 made of silicon, and protective layer 11 is removed by plasma etching in removal step 104. Therefore, protective layer 11 made of silicon can be removed by plasma etching without leaving any residue, and similar to embodiment 1, there is an effect of preventing a portion of protective layer 11 from remaining on surface 3 of workpiece 1.

[0072] In addition, in the processing method according to the modified example of embodiment 1, the protective layer 11 is made of silicon, so that it adheres more closely to the surface 3 of the workpiece 1 and is easier to process with the cutting blade 61 than when the protective layer 11 is made of a liquid water-soluble resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) (for example, HogoMax (registered trademark) manufactured by Disco Corporation).

[0073] For this reason, in the processing method according to the modified example of embodiment 1, since protective layer 11 is made of silicon, protective layer 11 is not removed by cutting fluid, and since protective layer 11 is in close contact with the upper surface of device 5, there is no peeling of the low-K film that constitutes device 5, and it is possible to suppress the occurrence of chipping.

[0074] The present invention is not limited to the above embodiment. In other words, various modifications can be made without departing from the gist of the present invention. In the present invention, the processing step 103 is not limited to the ablation process of irradiating the laser beam 23 and the cutting process by the cutting blade 61, but may be a grinding process or a polishing process on the workpiece 1. [Explanation of symbols]

[0075] 1 Workpiece 2. Board 3 Surface (first side) 5 Devices 11 Protective layer 23 Laser Beam 101 Covering Step 103 Processing Steps 104 Removal Step 201 Liquid layer

Claims

1. A method for processing a workpiece, comprising the steps of: a coating step of forming a protective layer made of silicon on a first surface of the workpiece to coat the first surface; The processing method further comprises a processing step of processing the workpiece after the coating step is performed.

2. the workpiece is a device wafer having a plurality of devices formed on a surface of a substrate; The coating step includes forming a protective layer on the surface of the device wafer to cover the device; 2. The processing method according to claim 1, wherein the processing step comprises irradiating the front surface of the device wafer with a laser beam through the protective layer.

3. 3. The processing method according to claim 2, wherein the processing step comprises forming a liquid layer on the protective layer of the device wafer and irradiating the surface of the device wafer with a laser beam through the liquid layer and the protective layer.

4. The processing method according to claim 1 , wherein in the covering step, the protective layer is formed by sputtering.

5. 2. The processing method according to claim 1, further comprising a removing step of removing the protective layer by supplying a plasma-like gas to the protective layer after the processing step is performed.

Images