Workpiece processing method

Abstract

To provide a workpiece processing method that can suppress etching of the peripheral edge of a support wafer.SOLUTION: A workpiece processing method is a processing method for a workpiece in which the surface of a wafer and the surface of a support wafer are bonded via a bonding layer, and includes a trimming step 101 of removing a peripheral portion of the wafer of the workpiece in the thickness direction and removing a portion of the peripheral portion of the surface of the support wafer in the thickness direction, a protective film formation step 103 of forming a protective film on the peripheral portion of the surface of the support wafer exposed by the trimming step 101 after the trimming step 101, and an etching step 105 of etching the wafer side of the workpiece after the protective film formation step 103.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for processing a workpiece in which one surface of a wafer and one surface of a support wafer are joined via a bonding layer.

Background Art

[0002] In recent years, the number of laminated wafers (workpieces) in which a wafer is joined to a support wafer via a bonding layer has been increasing. Before thinning the wafer side of such a laminated wafer by grinding or the like, the wafer may be trimmed into a circular shape so that a sharp edge is not formed on the thinned wafer (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the method described in Patent Document 1 and the like, when trimming is performed, due to problems such as processing accuracy, trimming is not limited to the upper wafer, but the lower support wafer may also be trimmed to a certain depth in the thickness direction. In such a case, when further etching is performed on the wafer side for the purpose of removing processing damage after grinding the wafer side, the peripheral portion of the support wafer exposed by trimming is also etched.

[0005] When a device is formed on the bonding layer side of the support wafer, there is a problem that the device on the support wafer is damaged by this etching of the peripheral portion.

[0006] Therefore, when processing a laminated wafer (workpiece) in which a wafer is bonded to a support wafer via a bonding layer on the support wafer, there is a problem that the peripheral portion of the support wafer exposed by trimming should not be etched.

[0007] An object of the present invention is to provide a method for processing a workpiece that can suppress etching of the peripheral portion of the support wafer.

Means for Solving the Problems

[0008] In order to solve the above-described problems and achieve the object, a method for processing a workpiece according to the present invention is a method for processing a workpiece in which one surface of a wafer and one surface of a support wafer are bonded via a bonding layer, wherein a trimming step of removing a peripheral portion of the wafer of the workpiece in the thickness direction and removing a part of a peripheral portion of the one surface of the support wafer in the thickness direction, a protective film forming step of forming a protective film on a peripheral portion of the one surface of the support wafer exposed by the trimming step after the trimming step, and an etching step of etching the wafer side of the workpiece after the protective film forming step.

[0009] In the method for processing the workpiece, the protective film forming step may form a protective film also on a side surface of the wafer of the workpiece.

[0010] In the method for processing the workpiece, before the etching step, a grinding step of grinding the wafer side of the workpiece to thin the wafer may be further provided.

[0011] In the method for processing the workpiece, the trimming step may be performed by cutting with a cutting blade.

[0012] In the method for processing the workpiece, before the protective film forming step, a flattening step of flattening a peripheral portion of the one surface of the support wafer exposed by the trimming step may be further provided.

Advantages of the Invention

[0013] The present invention has an effect of being able to suppress etching of the peripheral portion of the support wafer.

Brief Description of the Drawings

[0014]

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Mode for Carrying Out the Invention

[0015] The mode (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0016] 〔Embodiment 1〕 The method for processing a workpiece according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing a configuration example of a workpiece to be processed in the method for processing a workpiece according to Embodiment 1. FIG. 2 is a cross-sectional view schematically showing the workpiece shown in FIG. 1. FIG. 3 is a flowchart showing the flow of the method for processing a workpiece according to Embodiment 1.

[0017] (Workpiece) The method for processing a workpiece according to Embodiment 1 is a method for processing the workpiece 1 shown in FIG. 1. In Embodiment 1, the workpiece 1 to be processed in the method for processing a workpiece includes a wafer 10 and a support wafer 20. In Embodiment 1, the wafer 10 and the support wafer 20 are wafers such as disk-shaped semiconductor wafers having silicon, gallium arsenide, or SiC (silicon carbide) or the like as substrates 11 and 21. Note that in Embodiment 1, the wafer 10 and the support wafer 20 have the same configuration.

[0018] As shown in FIG. 1, on the wafer 10 and the support wafer 20, a plurality of planned division lines 13 and 23 that intersect (orthogonal in Embodiment 1) the surfaces 12 and 22 (corresponding to one side) are set, and devices 14 and 24 are respectively formed in a plurality of regions partitioned by the planned division lines 13 and 23. The devices 14 and 24 are, for example, integrated circuits such as IC (Integrated Circuit) or LSI (Large Scale Integration), or various memories (semiconductor memory devices).

[0019] The workpiece 1 is configured by joining the surface 12 of the wafer 10 and the surface 22 of the support wafer 20. In Embodiment 1, as shown in FIG. 2, the surface 12 of the wafer 10 and the surface 22 of the support wafer 20 are joined via a resin-based adhesive or a joining layer 2 made of an oxide film (SiO2) or the like. The workpiece 1 is divided along the planned division lines 13 and 23 of the wafers 10 and 20 and separated into individual device chips having a so-called three-dimensional stacked structure. In the present invention, the joining layer 2 may be a joining layer that performs surface activation on the surfaces 12 and 22 and then joins them.

[0020] Also, in Embodiment 1, chamfered portions 16 and 26 that are parallel to each other and flat at the peripheral edge and are continuous with the back surfaces 15 and 25 (corresponding to the other side) opposite to the surface 12 and 22 side are formed on the wafer 10 and the support wafer 20. The chamfered portions 16 and 26 are formed from the surfaces 12 and 22 to the back surfaces 15 and 25, and are formed in an arc shape in cross section such that the center in the thickness direction is located on the outermost peripheral side.

[0021] Thus, in Embodiment 1, the wafer 10 and the support wafer 20 are chamfered at the chamfered portions 16 and 26, so that the outer peripheral edge is chamfered in an arc shape. In Embodiment 1, the workpiece 1 is a laminated wafer formed by bonding the wafer 10 and the support wafer 20. In Embodiment 1, the workpiece 1 has the wafer 10 and the support wafer 20 formed with the same diameter and arranged coaxially. In Embodiment 1, the wafers 10 and 20 have substrates 11 and 21 made of silicon, an outer diameter of 300 mm, and a thickness of 775 μm. In the embodiment, the bonding layer 2 is made of an oxide film (SiO2) and has a thickness of 1 μm or more and 10 μm or less.

[0022] (Method for processing a workpiece) The method for processing the workpiece according to Embodiment 1 is the method for processing the workpiece 1 shown in FIGS. 1 and 2, which is a method of removing the chamfered portion 16 at the peripheral edge of the wafer 10 and then thinning the wafer 10 to a predetermined thickness. The method for processing the workpiece according to Embodiment 1 includes, as shown in FIG. 3, a trimming step 101, a planarization step 102, a protective film forming step 103, a grinding step 104, and an etching step 105.

[0023] (Trimming step) FIG. 4 is a side view schematically showing a trimming step of the method for processing the workpiece shown in FIG. 3 in a partial cross section. FIG. 5 is a cross-sectional view schematically showing the workpiece after the trimming step of the method for processing the workpiece shown in FIG. 3. The trimming step 101 is a step of removing the peripheral edge of the wafer 10 of the workpiece 1 in the thickness direction and removing a part of the peripheral edge on the surface 22 side of the support wafer 20 in the thickness direction.

[0024] In Embodiment 1, in trimming step 101, the processing device 30 shown in FIG. 4 sucks and holds the back surface 25 of the support wafer 20 of the workpiece 1 on the holding surface 32 of the holding table 31. In Embodiment 1, in trimming step 101, as shown in FIG. 4, the processing device 30 causes the cutting blade 35, whose spindle 34 in the processing unit 33 rotates around an axis parallel to the holding surface 32, to cut into the peripheral portion of the wafer 10 until it reaches the peripheral portion of the support wafer 20, and rotates the holding table 31 at least once around an axis orthogonal to the holding surface 32.

[0025] Thus, in Embodiment 1, in trimming step 101, as shown in FIG. 4, the cutting blade 35 is cut in, and as shown in FIG. 5, the peripheral portion of the wafer 10 of the workpiece 1 is removed over the entire thickness direction, the entire chamfered portion 16 is removed, a part of the peripheral portion of the support wafer 20 is removed from the surface 22 side, a part of the surface 22 side of the chamfered portion 26 is removed, and a part of the peripheral portion on the surface 22 side of the support wafer 20 is removed in the thickness direction. In Embodiment 1, in trimming step 101, in a cross-section passing through the axis, the outer surface 17 (corresponding to the side surface) of the wafer 10 of the workpiece 1 is formed flat along a direction orthogonal to both the front surface 12 and the back surface 15. Further, in Embodiment 1, in trimming step 101, as shown in FIG. 5, an outer surface 27 on the same plane as the outer surface 17 is formed on the surface 22 side of the peripheral portion of the support wafer 20 of the workpiece 1, and a stepped surface 28 formed parallel to both the surface 22 and the back surface 25 is formed from the outer surface 27 across the outer edge of the support wafer 20.

[0026] (Planarization step) FIG. 6 is a side view schematically showing a part of the cross-section of the planarization step of the processing method of the workpiece shown in FIG. 3. FIG. 7 is a cross-sectional view schematically showing a modified example of the planarization step shown in FIG. 6 in a part of the cross-section. The planarization step 102 is a step of planarizing the peripheral portion of the surface 22 of the support wafer 20 exposed by the trimming step 101 before the protective film forming step 103.

[0027] In Embodiment 1, in the planarization step 102, the processing apparatus 40 as shown in FIG. 6 sucks and holds the back surface 25 of the support wafer 20 of the workpiece 1 on the holding surface 42 of the holding table 41. In Embodiment 1, in the planarization step 102, as shown in FIG. 6, the processing apparatus 40 causes the outer peripheral surface 46 of the annular polishing grindstone 45, whose spindle 44 of the processing unit 43 rotates around an axis parallel to the holding surface 42, to contact the stepped surface 28, and causes the flat end surface 47 in the direction orthogonal to the axis of the spindle 44 of the polishing grindstone 45 to contact the outer side surfaces 17 and 27, thereby planarizing the outer side surfaces 17 and 27 and the stepped surface 28. Note that the polishing grindstone 45 is softer than the grindstone of the cutting edge 36 of the cutting blade 35 and is configured to include a grindstone smaller than the grindstone of the cutting edge 36 of the cutting blade 35. Thus, in Embodiment 1, in the planarization step 102, the outer side surfaces 17 and 27 and the stepped surface 28 are planarized to planarize the peripheral portion on the surface 22 side of the support wafer 20.

[0028] Also, in the present invention, in the planarization step 102, as shown in FIG. 7, the processing apparatus 40 may cause the outer peripheral surface 46 of the annular polishing grindstone 45, whose spindle 44 of the processing unit 43 rotates around an axis orthogonal to the holding surface 42, to contact the end portions of the outer side surface 27 and the outer side surface 17 closer to the support wafer 20, and cause the flat end surface 47 in the direction orthogonal to the axis of the spindle 44 of the polishing grindstone 45 to contact the stepped surface 28, thereby planarizing the outer side surfaces 17 and 27 and the stepped surface 28.

[0029] (Protective film forming step) FIG. 8 is a side view schematically showing in partial cross section the protective film forming step of the processing method of the workpiece shown in FIG. 3. FIG. 9 is a cross-sectional view schematically showing the workpiece after the protective film forming step of the processing method of the workpiece shown in FIG. 3. The protective film forming step 103 is a step of forming a protective film 3 on the peripheral portion of the surface 22 of the support wafer 20 exposed by the trimming step 101 after the trimming step 101.

[0030] In Embodiment 1, in the protective film formation step 103, the workpiece 1 is carried into the processing space 512 in the chamber 51 through the opening 511 by a transfer unit (not shown) using the plasma device 50 shown in FIG. 8, and the back surface 25 side of the support wafer 20 of the workpiece 1 is placed on the holding surface 521 of the holding table 52. In Embodiment 1, in the protective film formation step 103, the plasma device 50 applies high-frequency power from the high-frequency power supply 522 to the electrode 524 in the holding table 52 via the matcher 523, generating a dielectric polarization phenomenon between the holding surface 521 and the workpiece 1, and adsorbing and holding the workpiece 1 on the holding surface 521 by the electrostatic adsorption force due to the polarization of charges.

[0031] In Embodiment 1, in the protective film formation step 103, the plasma device 50 closes the opening 511 with the gate 513 to keep the processing space 512 in the chamber 51 airtight, and the evacuation device 514 reduces the pressure in the processing space 512 to a predetermined pressure. In Embodiment 1, in the protective film formation step 103, the plasma device 50 supplies the protective film gas from the gas supply unit 531 to the gas diffusion space 532 in the gas ejection head 53 that functions as the upper electrode, and ejects the protective film gas from the gas ejection port 533 of the gas ejection head 53 toward the holding table 52, i.e., the workpiece 1.

[0032] Also, in Embodiment 1, in the protective film formation step 103, the plasma device 50 applies high-frequency power from the high-frequency power supply 534 to the gas ejection head 53 via the matcher 535, and further applies high-frequency power from the high-frequency power supply 522 to the electrode 524 of the holding table 52 via the matcher 523 to plasmaize the protective film gas, and deposits the plasmaized protective film gas on the back surface 15, the outer surface 17 of the wafer 10 of the workpiece 1, the outer surface 27 and the step surface 28 of the support wafer 20 to form the protective film 3 shown in FIG. 9 thereon. Thus, in Embodiment 1, in the protective film formation step 103, as shown in FIG. 9, the protective film 3 is also formed on the outer surface 17 of the wafer 10 of the workpiece 1.

[0033] Note that the protective film 3 has corrosion resistance against the chemical solution 74 (shown in FIG. 12) used in the etching step 105 and is composed of SiO2 or SiN. Also, in Embodiment 1, in the protective film forming step 103, the protective film 3 is formed by CVD (Chemical Vapor Deposition), but in the present invention, the protective film 3 may be formed by PVD (Physical Vapor Deposition).

[0034] (Grinding Step) FIG. 10 is a side view schematically showing a partial cross-section of the grinding step of the processing method of the workpiece shown in FIG. 3. FIG. 11 is a cross-sectional view schematically showing the workpiece after the grinding step of the processing method of the workpiece shown in FIG. 3. The grinding step 104 is a step of thinning the wafer 10 by grinding the wafer 10 side of the workpiece 1 before the etching step 105.

[0035] In Embodiment 1, in the grinding step 104, as shown in FIG. 10, the grinding device 60 sucks and holds the back surface 25 side of the support wafer 20 of the workpiece 1 on the holding surface 62 of the holding table 61, and rotates the grinding wheel 64 around the axis perpendicular to the holding surface 62 by the spindle 63 and rotates the holding table 61 around the axis perpendicular to the holding surface 62. As shown in FIG. 6, the grinding device 60 grinds the back surface 15 of the wafer 10 of the workpiece 1 with the grinding wheel 65 by bringing the grinding wheel 65 into contact with the back surface 15 of the wafer 10 of the workpiece 1 and approaching the holding table 61 at a predetermined feed rate while rotating the grinding wheel 64 and the holding table 61 around the axis. In Embodiment 1, in the grinding step 104, as shown in FIG. 11, the grinding device 110 grinds the wafer 10, removes the protective film 3 from the back surface 15 of the wafer 10, and exposes the substrate 11 of the wafer 10.

[0036] (Etching Step) FIG. 12 is a side view schematically showing in partial cross section an etching step of the method for processing a workpiece shown in FIG. 3. FIG. 13 is a cross-sectional view schematically showing the workpiece after the etching step of the method for processing the workpiece shown in FIG. 3. The etching step 105 is a step of etching the wafer 10 side of the workpiece 1 after the protective film forming step 103.

[0037] In Embodiment 1, in the etching step 105, the etching apparatus 70 shown in FIG. 12 sucks and holds the back surface 25 of the support wafer 20 of the workpiece 1 on the holding surface 72 of the spinner table 71. In Embodiment 1, in the etching step 105, as shown in FIG. 12, the etching apparatus 70 rotates the spinner table 71 around the axis perpendicular to the holding surface 72 while supplying a chemical solution 74 (in Embodiment 1, hydrofluoric acid and nitric acid) having corrosiveness to the substrate 11 of the wafer 10 from the nozzle 73 onto the center of the back surface 15 of the wafer 10 of the workpiece 1.

[0038] Then, the chemical solution 74 flows toward the outer periphery of the workpiece 1 due to the centrifugal force of the rotation of the spinner table 71, and corrodes the entire back surface 15 of the wafer 10 of the workpiece 1. In Embodiment 1, in the etching step 105, as shown in FIG. 13, the etching apparatus 70 performs so-called wet etching on the back surface 15 of the wafer 10 to thin the wafer 10 to a predetermined thickness, release the internal stress of the wafer 10 of the workpiece 1 generated during the grinding step 104, remove the damage on the back surface 15, and remove particles from the back surface 15.

[0039] As described above, the method for processing a workpiece according to Embodiment 1 is after the trimming step 101 and before the etching step 105, and includes a protective film forming step 103 of forming a protective film 3 on the stepped surface 28 of the peripheral portion on the surface 22 side of the support wafer 20 exposed by the trimming step 101, so that the peripheral portion of the support wafer 20 can be suppressed from being etched in the etching step 105.

[0040] Further, in the processing method of the workpiece according to Embodiment 1, since the protective film 3 is also formed on the outer surfaces 17 and 27 of the wafers 10 and 20 in the protective film forming step 103, it is possible to suppress the etching of the peripheral portion of the support wafer 20 in the etching step 105.

[0041] Further, the processing method of the workpiece according to Embodiment 1 includes a grinding step 104 of grinding the back surface 15 of the wafer 10 of the workpiece 1 before the etching step 105. Therefore, before the etching step 105, the back surface 5 of the wafer 10 can be exposed and etched.

[0042] Further, the processing method of the workpiece according to Embodiment 1 includes a planarization step 102 of planarizing the stepped surface 28 of the support wafer 20 and the outer surfaces 17 and 27 of the wafers 10 and 20 before the protective film forming step 103. Therefore, the protective film 3 can be formed in the protective film forming step 103.

[0043] Note that the present invention is not limited to the above embodiments. That is, various modifications can be made and implemented without departing from the gist of the present invention. In the present invention, in the trimming step 101, in addition to trimming with the cutting blade 35 as in Embodiment 1, the peripheral portion may be removed by stealth dicing in which a laser beam having a wavelength that is transmissive to the wafer 10 is irradiated, or the peripheral portion may be removed by laser ablation in which a laser beam having a wavelength that is absorptive to the wafer 10 is irradiated.

[0044] Further, in the present invention, in the etching step 105, plasma etching using a plasmaized gas may be performed. In this case, the protective film 3 may be formed by applying a liquid water-soluble resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) (for example, HogoMax (registered trademark) manufactured by DISCO Corporation) and drying it.

[0045] Further, in the present invention, instead of performing the grinding step 104, the etching step 105 may be carried out after the protective film forming step 103.

Explanation of Reference Numerals

[0046] 1 Workpiece 2 Bonding layer 3 Protective film 10 Wafer 12 Surface (one surface) 20 Support wafer 22 Surface (one surface) 35 Cutting blade 101 Trimming step 102 Planarization step 103 Protective film forming step 104 Grinding step 105 Etching step

Claims

1. A method for processing a workpiece in which one surface of a wafer and one surface of a support wafer are joined via a joining layer, comprising: a trimming step of removing a peripheral portion of the wafer of the workpiece in a thickness direction and partially removing a peripheral portion of the one surface of the support wafer in the thickness direction; a protective film forming step of forming a protective film on a peripheral portion of the one surface of the support wafer exposed by the trimming step after the trimming step; an etching step of etching the wafer side of the workpiece after the protective film forming step; The method for processing a workpiece, characterized by comprising the above steps.

2. The method for processing a workpiece according to claim 1, wherein the protective film forming step forms a protective film also on a side surface of the wafer of the workpiece.

3. The method for processing a workpiece according to claim 1 or claim 2, further comprising a grinding step of grinding the wafer side of the workpiece to thin the wafer before the etching step.

4. The method for processing a workpiece according to claim 1, wherein the trimming step cuts in a cutting blade to remove the material.

5. The method for processing a workpiece according to claim 1 or claim 4, further comprising a planarization step of planarizing a peripheral portion of the one surface of the support wafer exposed by the trimming step before the protective film forming step.

Images