Wafer processing method

Abstract

To provide a processing method of a wafer, capable of effectively performing a plasma etching.SOLUTION: A processing method of a wafer includes: a mounting step 1002 of mounting the wafer in which a division groove is formed along a division schedule line so as to be supported via a supporting member to an open of a frame onto a holding surface of a holding table in a chamber; a fixing step 1003 of fixing an outer peripheral region containing at least one of the supporting member or the frame exposed between an outer periphery of the wafer and an inner periphery of the frame to the holding surface by a fixing unit while being nipping; an air supplying step 1004 of supplying an air from the holding surface into an inner peripheral region from the outer peripheral region, expanding the inner peripheral region to a direction separated from the holding surface, and pumping a width of the division groove; and an etching step 1005 of supplying a plasma gas into the chamber, and removing a damage by etching the division groove by immersing the plasma gas into the division groove.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer by processing it along a planned dividing line.

Background Art

[0002] In a processing method for processing a wafer along a planned dividing line, damage due to processing remains in the dividing grooves and processing grooves formed along the planned dividing line.

[0003] Therefore, after forming the dividing grooves and processing grooves (including half cuts), there is a process of supplying an etching gas, allowing it to penetrate into the dividing grooves and processing grooves, and removing the damage on the side surfaces of the dividing grooves and processing grooves (see, for example, Patent Document 1 and Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, if the width of the dividing grooves and processing grooves is narrow, it is difficult for the etching gas to penetrate, the etching rate becomes low, and productivity is low. When the width of the dividing grooves and processing grooves is narrow and deep, it becomes even more difficult for the gas to penetrate, resulting in a problem that the time required for removing the damage becomes long.

[0006] An object of the present invention is to provide a method for processing a wafer that can perform plasma etching efficiently.

Means for Solving the Problems

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides a wafer processing method for processing a wafer along a planned division line, comprising: a placement step of placing a wafer, which is supported by a support member in an opening formed in a frame and has a division groove formed along the planned division line, on the holding surface of a holding table in a chamber; a fixing step of clamping and fixing an outer peripheral region, including at least one of the support member or the frame that is exposed between the outer peripheral of the wafer and the inner peripheral of the frame, between the holding surface and a fixing unit; a gas supply step of supplying gas from the holding surface to an inner peripheral region inside the outer peripheral region fixed in the fixing step, causing the inner peripheral region to bulge into a convex shape away from the holding surface and widening the width of the division groove; and after the gas supply step, Maintain the inner circumferential region in a convex shape, bulging away from the holding surface. The invention is characterized by comprising an etching step of supplying plasma gas into the chamber, allowing the plasma gas to penetrate the divided grooves, and etching the divided grooves to remove damage. The wafer processing method described above may include a modified layer formation step in which, before performing the placement step, a laser beam with a wavelength that is transparent to the wafer is positioned inside the wafer and irradiated to form a modified layer inside the wafer along the planned division line, and a thinning step in which, before performing the placement step and after performing the modified layer formation step, the wafer is ground to propagate cracks from the modified layer and form the division groove along the planned division line.

[0008] In the wafer processing method described above, the gas supply step may be carried out while controlling the flow rate and pressure of the supplied gas such that the space formed between the holding surface and the support member is higher than the pressure in the chamber space.

[0009] In the wafer processing method described above, the gas supply step may involve supplying the gas through ejection holes formed on the holding surface. [Effects of the Invention]

[0010] This invention widens the width of the dividing groove by making the inner circumferential region of the support member convex in the direction away from the holding surface. This allows etching gas to easily penetrate into the dividing groove, resulting in the effect of efficiently performing plasma etching. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view of the wafer to be processed in the wafer processing method according to Embodiment 1. [Figure 2] Figure 2 is a schematic side view showing a partial cross-section of the configuration of an etching apparatus used to implement the wafer processing method according to Embodiment 1. [Figure 3] Figure 3 is a flowchart showing the flow of the wafer processing method according to Embodiment 1. [Figure 4] Figure 4 is a schematic cross-sectional view of a holding table illustrating the fixing step of the wafer processing method shown in Figure 2. [Figure 5] Figure 5 is a cross-sectional view of an etching apparatus schematically showing the gas supply step of the wafer processing method shown in Figure 2. [Figure 6] Figure 6 is a cross-sectional view of an etching apparatus schematically showing the etching step of the wafer processing method shown in Figure 2. [Figure 7] Figure 7 is a flowchart showing the flow of the wafer processing method according to Embodiment 2. [Figure 8] Figure 8 is a schematic perspective view showing the wafer held on the holding table of the laser processing apparatus during the modified layer formation step of the wafer processing method shown in Figure 7. [Figure 9] Figure 9 is a schematic side view showing a partial cross-section of the state in which a laser processing apparatus forms a modified layer on a wafer during the modified layer formation step of the wafer processing method shown in Figure 7. [Figure 10] Figure 10 is a schematic side view showing a partial cross-section of the frame support step of the wafer processing method shown in Figure 7. [Figure 11] Figure 11 is a schematic side view showing a partial cross-section of the thinning step of the wafer processing method shown in Figure 7. [Figure 12] Figure 12 is a schematic side view showing a partial cross-section of the cleaning step of the wafer processing method shown in Figure 7. [Figure 13] Figure 13 is a flowchart showing the flow of the wafer processing method according to Embodiment 3. [Figure 14]FIG. 14 is a side view schematically showing in a partial cross-section a state where an expandable tape is attached to the back surface of a wafer in the expandable tape attachment step of the wafer processing method shown in FIG. 13. [Figure 15] FIG. 15 is a side view schematically showing in a partial cross-section a state where a support member is peeled off from the front surface of a wafer in the expandable tape attachment step of the wafer processing method shown in FIG. 13. [Figure 16] FIG. 16 is a side view schematically showing in a partial cross-section a state where a wafer is supported by an expanding device in the expanding step of the wafer processing method shown in FIG. 13. [Figure 17] FIG. 17 is a side view schematically showing in a partial cross-section a state where an expandable tape is expanded in the expanding step of the wafer processing method shown in FIG. 13.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] A 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.

[0013] 〔Embodiment 1〕 A wafer processing method according to Embodiment 1 of the present invention will be described based on the drawings. FIG. 1 is a perspective view of a wafer to be processed in the wafer processing method according to Embodiment 1. FIG. 2 is a side view schematically showing in a partial cross-section the configuration of an etching apparatus for carrying out the wafer processing method according to Embodiment 1. FIG. 3 is a flowchart showing the flow of the wafer processing method according to Embodiment 1.

[0014] The wafer 1 to be processed in the wafer processing method according to Embodiment 1 is a disc-shaped semiconductor wafer or optical device wafer with a substrate 2 made of silicon, sapphire, gallium arsenide, or SiC (silicon carbide), etc. Devices 5 are formed in each region of the wafer 1, which is partitioned by a plurality of division lines 4 formed in a grid pattern on the surface 3.

[0015] Device 5 is, for example, an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), or a memory (semiconductor memory device).

[0016] In one embodiment, the wafer 1 is supported by a support member 10 in an opening 12 formed on the inside of a frame 11. In Embodiment 1, the frame 11 is formed in an annular shape, and its inner diameter is larger than the outer diameter of the wafer 1. In Embodiment 1, the support member 10 has an outer diameter that is larger than the outer diameter of the wafer 1 and the inner diameter of the opening 12, and smaller than the outer diameter of the frame 11.

[0017] Furthermore, in Embodiment 1, the support member 10 may be an adhesive tape having a base layer that is flexible and non-adhesive, and an adhesive layer laminated on the base layer that is flexible and adhesive, or it may be a sheet made of a thermoplastic resin without an adhesive layer. In the case of a sheet without an adhesive layer, for example it may be attached to a wafer by heat pressing, and the material of the base layer is preferably polyethylene, polypropylene, polystyrene, etc. In Embodiment 1, the wafer 1 is attached to the center of the support member 10 with the surface 3 on which the device 5 is formed attached, and the outer edge of the support member 10 is attached to the frame 11 and supported in the opening 12 of the frame 11.

[0018] Furthermore, in Embodiment 1, the wafer 1 has a division groove 6 formed along the division line 4. In Embodiment 1, the division groove 6 comprises a modified layer formed inside the wafer 1 along the division line 4, and a crack extending from the modified layer to at least one of the surface 3 or the back surface 7 on the back side of the surface 3. However, in the present invention, the division groove 6 may be a groove formed by cutting or laser ablation that penetrates the wafer 1 across the surface 3 and the back surface 7 to divide the wafer 1 (a so-called full-cut groove), or it may be a groove formed by cutting or laser ablation that is concave from one of the surface 3 or the back surface 7 and does not divide the wafer 1 (a so-called half-cut groove).

[0019] The modified layer refers to a region whose density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding area. Examples include melted regions, cracked regions, dielectric breakdown regions, refractive index change regions, and regions where these regions are mixed. The gaseous strength of the modified layer is lower than the mechanical strength of the areas of wafer 1 other than the modified layer.

[0020] The wafer processing method according to Embodiment 1 is carried out using the etching apparatus 20 shown in Figure 2.

[0021] (Etching equipment) Next, an etching apparatus 20 for carrying out the wafer processing method according to Embodiment 1 will be described. As shown in Figure 2, the etching apparatus 20 comprises a chamber 21, a holding table 30, a plasma introduction unit 40, and a control unit (not shown).

[0022] The chamber 21 has a processing space inside. The chamber 21 is made of, for example, a conductive metal material and is grounded. An inlet / outlet 22 is provided in a part of the side wall of the chamber 21, which allows wafers 1 to be inserted and removed. The inlet / outlet 22 is opened and closed by a sliding door 29 that is slidably mounted on the outside of the side wall of the chamber 21. The door 29 is slid open and closed by, for example, an air cylinder or the like.

[0023] Furthermore, an exhaust pipe 24 to which an exhaust unit 23 is connected is connected to the side wall of the chamber 21. The exhaust unit 23 includes an exhaust valve 25, such as a solenoid valve, connected to the exhaust pipe 24, and an exhaust pump 26 connected to the exhaust valve 25. In addition, a pressure sensor 27 for measuring the pressure in the processing space inside the chamber 21 is connected to the side wall of the chamber 21. The pressure sensor 27 measures the pressure in the processing space inside the chamber 21 and outputs the measurement result to the control unit.

[0024] The holding table 30 holds the wafer 1 within the chamber 21. The holding table 30 comprises a table base 31 fixed to the bottom surface of the chamber 21, a disc-shaped electrostatic chuck 32 installed on the table base 311, and a fixing unit 33. As shown in Figure 2, the electrostatic chuck 32 comprises a bottom surface 321, a holding surface 34, and a side surface 322. A through hole 323 is provided on the outer circumference of the electrostatic chuck 32, penetrating in the vertical direction (thickness direction), and a lifting unit 37 for raising and lowering the fixing member 36 is installed in the through hole 323.

[0025] The electrostatic chuck 32 has a holding surface 34 formed in the center of its upper surface, which is flat horizontally and holds the wafer 1 via a support member 10. The electrostatic chuck 32 also has multiple electrodes embedded inside that are electrically insulated from each other. Each of these electrodes is connected to a DC power supply (not shown) capable of generating high voltage.

[0026] In Embodiment 1, the electrostatic chuck 32 is a bipolar electrostatic chuck and has a first electrode to which a positive potential is supplied and a second electrode to which a negative potential is supplied. For example, in the electrostatic chuck 32, a high voltage of +3kV is applied to the first electrode from a DC power supply, and a high voltage of -3kV is applied to the second electrode from a DC power supply.

[0027] Furthermore, a flow path (not shown) for supplying a refrigerant is formed inside the electrostatic chuck 32. A refrigerant controlled to a predetermined temperature is supplied to the flow path from a refrigerant circulation device (not shown). As a result, the temperature of the electrostatic chuck 32 is maintained at a predetermined temperature (for example, 35°C). The electrostatic chuck 32 holds the wafer 1 on the holding surface 34 by electrostatic attraction force due to the polarization of electric charge when a voltage is applied to the electrodes from a DC power supply.

[0028] Furthermore, the electrostatic chuck 32 is provided with a bias electrode (not shown) to which a high-frequency voltage is applied, in a manner electrically isolated from the multiple electrodes. A high-frequency voltage application unit 35 is connected to the bias electrode. The high-frequency voltage application unit 35 includes, for example, a high-frequency power supply 351 capable of applying a high-frequency voltage of 13.56 MHz to the bias electrode, and a DC blocking capacitor 352 provided between the bias electrode and the high-frequency power supply 351.

[0029] Furthermore, the electrostatic chuck 32 has a stepped portion 341 extending around its entire circumference, located on the outer circumference of the holding surface 34 and closer to the bottom surface of the chamber 21 than the holding surface 34. In addition, the electrostatic chuck 32 has one or more ejection holes 342 formed on the holding surface 34.

[0030] The ejection holes 342 are connected to a supply pipe 344 which is connected to a gas supply source 343. The electrostatic chuck 32 ejects gas supplied from the gas supply source 343 from a plurality of ejection holes 342 which are uniformly distributed throughout the region corresponding to the inner circumference region 15 of the holding surface 34. In Embodiment 1, the gas supplied to the holding surface 34 by the gas supply source 343 is preferably an inert gas, for example, at least one of helium, nitrogen, or argon. The supply pipe 344 is also equipped with a pressure sensor 345 that measures the pressure inside the supply pipe 344. The pressure sensor 345 outputs the measurement result to the control unit.

[0031] The fixing unit 33 clamps and fixes the outer peripheral region 14, which includes at least one of the annular region 13 of the support member 10 that is exposed between the outer peripheral region of the wafer 1 and the inner peripheral region of the frame 11, between itself and the holding surface 34. In Embodiment 1, the outer peripheral region 14 includes only the annular region 13 of the support member 10, and the annular region 13 is fixed by the fixing unit 33. However, in the present invention, the outer peripheral region 14 may include only the frame 11, and the frame 11 may be fixed by the fixing unit 33, or it may include both the annular region 13 of the support member 10 and the frame 11, and the annular region 13 and the frame 11 may be fixed by the fixing unit 33.

[0032] The fixing unit 33 comprises a fixing member 36 and a lifting unit 37 that allows the fixing member 36 to move up and down above the electrostatic chuck 32. The fixing member 36 is formed in a hollow annular shape and houses the annular region 13 of the support member 10 attached to the wafer 1 and the frame 11 on its inside. The outer diameter of the fixing member 36 is equal to the outer diameter of the electrostatic chuck 32, and in Embodiment 1, the fixing member 36 is positioned coaxially with the electrostatic chuck 32.

[0033] The fixing member 36 integrally comprises a bottom wall portion 361 located below the annular region 13 of the support member 10 attached to the wafer 1 and the frame 11, an upper wall portion 362 covering the top of the bottom wall portion 361, and a connecting portion 365 connecting the bottom wall portion 361 and the upper wall portion 362. The bottom wall portion 361 is formed flat in the horizontal direction. When the fixing member 36 is lowered by the lifting unit 37, the bottom wall portion 361 is superimposed on the stepped portion 341 of the electrostatic chuck 32.

[0034] The upper wall portion 362 is provided with a slit 363 in a part of its outer edge, which allows wafers 1 to be easily inserted into and removed from the processing space in the chamber 21 through the loading / unloading port 22 using the fixing member 36. The inner edge portion 364 of the upper wall portion 362, when the fixing member 36 is lowered by the lifting unit 37, sandwiches and fixes the annular region 13 of the support member 10 between itself and the holding surface 34 of the electrostatic chuck 32. A sealing member made of an elastic material such as an O-ring is fixed to the inner edge portion 364, sealing the space between the annular region 13 of the support member 10 and the inner edge portion, and preventing gas supplied between the holding surface 34 and the support member 10 from leaking. Alternatively, a sealing member made of an elastic material such as an O-ring may also be installed on the holding surface 34 facing the inner edge portion 364, sealing the space between it and the support member and preventing gas leakage.

[0035] The plasma introduction unit 40 supplies plasma-generated etching gas 47 (shown in Figure 6, corresponding to plasma gas) to the processing space within the chamber 21. The plasma introduction unit 40 comprises a gas supply unit 41, a gas introduction pipe 45 connected to the upper part of the chamber 21, and an applicator 46.

[0036] The gas supply unit 41 includes an inert gas supply source 42, a fluorine-based gas supply source 43, and an oxygen gas supply source 44. The inert gas supply source 42 supplies inert gases such as helium (He), argon (Ar), and nitrogen (N2) into the processing space in the chamber 21 through a gas introduction pipe 45 via a first valve 421, a first flow controller (not shown), etc. The inert gas is used, for example, as a carrier gas to transport other gases. However, the inert gas may also be used for the purpose of stabilizing the discharge.

[0037] The fluorine-based gas supply source 43 supplies fluorine-based gases such as sulfur hexafluoride (SF6) and tetrafluoromethane (CF4) into the processing space within the chamber 21 via a gas introduction pipe 45, through a second valve 431, a second flow controller (not shown), etc. The fluorine-based gas is, for example, a gas used for plasma etching of the wafer 1.

[0038] The oxygen gas supply source 44 supplies oxygen (O2) gas into the processing space within the chamber 21 through the gas introduction pipe 45 via a third valve 441, a third flow controller (not shown), etc. The oxygen gas is used, for example, to control the etching rate of wafer 1. In the process of fluorine-containing gas molecules being oxidized, active species of fluorine atoms (fluorine radicals, fluorine ions, etc.) that contribute to plasma etching are generated, which may increase the etching rate of wafer 1.

[0039] The gas supply unit 41 supplies multiple types of gas to the gas inlet pipe 45 at predetermined flow rates, with the first, second, and third flow controllers controlled by the control unit. The number of gas supply sources, the types of gases, and the flow rates of each gas can be appropriately changed depending on the type of wafer 1, etc.

[0040] The gas inlet tube 45 is made of a material that allows microwaves to pass through (such as sapphire, quartz, or ceramics).

[0041] The applicator 46 is attached to the gas inlet tube 45 in a manner that surrounds the gas inlet tube 45 and includes a housing made of a conductive material such as metal. The housing of the applicator 46 includes, for example, a waveguide for irradiating the gas inlet tube 45 with microwaves generated by a high-frequency source such as a magnetron.

[0042] Microwaves are electromagnetic waves with a frequency between 300 MHz and 300 GHz (for example, 2.45 GHz). The applicator 46 irradiates multiple types of gases flowing through the gas introduction tube 45 via a waveguide with microwaves, thereby plasma-generating the etching gas supplied from the gas supply unit 66.

[0043] Furthermore, the etching apparatus 20 according to Embodiment 1 is provided with a plasma diffusion member 28 made of metal inside the chamber 21 and above the holding table 30. The plasma diffusion member 28 has a mesh-like region, which divides the processing space inside the chamber 21 into a first region on the upper side and a second region on the lower side that houses the holding table 30.

[0044] However, the mesh-like region has multiple through-openings that spatially connect the first region and the second region. The plasma diffusion member 28 has the function of supplying the etching gas 47, which has been plasma-activated (i.e., radicalized, ionized, etc.) and supplied to the first region, to the second region in order to disperse it.

[0045] Furthermore, in the etching apparatus 20, plasma-generated etching gas 47 is supplied from the gas introduction pipe 45 to a first region of the processing space within the chamber 21, and then supplied to a second region of the processing space via the plasma diffusion member 28. When a wafer 1 is placed in the processing space, the wafer 1 is plasma-etched with the plasma-generated etching gas 47 outside the chamber 21 (remote plasma etching).

[0046] Furthermore, when the etching apparatus 20 does not irradiate the gas supplied from the gas supply unit 66 with microwaves (i.e., the applicator 46 is in the off state), the etching gas, which has not been plasma-formed, is supplied from the gas introduction pipe 45 to the first region of the processing space.

[0047] In this case, when the high-frequency voltage application unit 35 connected to the bias electrode is activated, the etching gas supplied from the gas introduction tube 45 is plasma-generated in the chamber 21. If a wafer 1 is placed in the processing space, the wafer 1 is etched with the plasma-generated etching gas in the chamber 21 (direct plasma etching).

[0048] The control unit controls each component of the etching apparatus 20 to cause the etching apparatus 20 to perform plasma etching on the wafer 1. The control unit is a computer having an arithmetic processing unit with a microprocessor such as a CPU (central processing unit), a storage device with memory such as ROM (read-only memory) or RAM (random access memory), and an input / output interface device. The arithmetic processing unit of the control unit performs calculations according to the computer program stored in the storage device and outputs control signals for controlling the etching apparatus 20 to each component of the etching apparatus 20 via the input / output interface device.

[0049] The control unit is connected to a display unit, which consists of a liquid crystal display device that shows the status of machining operations and images, and an input unit used by the operator to register machining information. The input unit consists of a touch panel provided on the display unit.

[0050] (Wafer processing method) The wafer processing method according to Embodiment 1 is a method of processing the wafer 1 having the above-described configuration along the planned division line 4. As shown in Figure 3, the wafer processing method according to Embodiment 1 comprises a loading step 1001, a placement step 1002, a fixing step 1003, a gas supply step 1004, and an etching step 1005.

[0051] (Loading Steps) Next, the loading step 1001 will be described. The loading step 1001 is the step of placing the wafer 1, which is supported by a support member 10 in the opening 12 of the frame 11 in which the opening 12 is formed, and which has a dividing groove 6 formed along the dividing line 4, onto the holding surface 34 of the holding table 30 in the chamber 21. In the loading step 1001, the etching apparatus 20 opens the loading / unloading entrance 22 with the door 29 and raises the fixing member 36 of the fixing unit 33 of the holding table 30, so that the wafer 1 is housed in the processing space in the chamber 21 and the frame 11 is inserted into the fixing member 36 through the slit 363.

[0052] In loading step 1001, as shown in Figure 3, the etching apparatus 20 is supported by the annular region 13 and frame 11 of the support member 10 on the bottom wall portion 361 of the fixing member 36 of the fixing unit 33. When the wafer 1 is loaded into the processing space in the chamber 21, the etching apparatus 20 closes the loading / unloading entrance 22 with the door 29.

[0053] (Placement step and fixing step) Next, the placement step 1002 and the fixing step 1003 will be described. Figure 4 is a schematic cross-sectional view of a holding table showing the fixing step of the wafer processing method shown in Figure 2. The fixing step 1003 is a step in which the outer peripheral region 14 is clamped and fixed between the fixing unit 33 and the holding surface 34. In the fixing step 1003, the etching apparatus 20 lowers the fixing member 36 using the lifting unit 37 of the fixing unit 33.

[0054] In the placement step 1002, as shown in Figure 4, the etching apparatus 20 places the bottom wall portion 361 of the fixing member 36 on the stepped portion 341 of the electrostatic chuck 32 and places the surface 3 of the wafer 1 on the holding surface 34 via the support member 10. In Embodiment 1, simultaneously with the placement step 1002, a fixing step 1003 is performed in which the annular region 13 of the support member 10 is sandwiched between the inner edge portion 364 of the upper wall portion 362 of the fixing member 36 and the holding surface 34 to fix it in place.

[0055] (Gas supply step) Next, the gas supply step will be explained. Figure 5 is a schematic cross-sectional view of an etching apparatus showing the gas supply step of the wafer processing method shown in Figure 2. The gas supply step 1004 is a step in which gas is supplied from the holding surface 34 to the inner peripheral region 15 to which the wafer 1 is attached, inside the annular region 13 of the support member 10 fixed in the fixing step 1003, causing the inner peripheral region 15 to bulge into a convex shape away from the holding surface 34 and widening the width of the dividing groove 6.

[0056] In the gas supply step 1004, the etching apparatus 20 applies a voltage to the electrodes inside the electrostatic chuck 32 from a DC power supply connected to the electrostatic chuck 32, generating an electrostatic attraction force between each electrode and the wafer 1, thereby attracting and holding the surface 3 side of the wafer 1 onto the holding surface 34 of the electrostatic chuck 32 via the support member 10.

[0057] In the gas supply step 1004, the etching apparatus 20 opens the exhaust valve 25 and operates the exhaust unit 23 to exhaust the gas in the processing space within the chamber 21. This reduces the pressure in the processing space within the chamber 21 to a predetermined pressure (for example, 50 Pa). During the gas supply step 1004 and the etching step 1005, the pressure in the chamber 21 is maintained at the predetermined pressure.

[0058] In the gas supply step 1004, the etching apparatus 20 operates the gas supply source 343 to supply the aforementioned gas between the holding surface 34 and the support member 10 from the ejection holes 342 formed in the holding surface 34. Then, in the gas supply step 1004, as shown in Figure 5, the inner circumferential region 15 on the holding surface 34 of the support member 10 bulges out in a convex shape away from the holding surface 34, and as the inner circumferential region 15 of the support member 10 bulges, the width of the dividing groove 6 of the wafer 1 widens.

[0059] In the gas supply step 1004 and etching step 1005, the etching apparatus 20 controls the gas supply source 343 based on the measurement results of the pressure sensors 27 and 345, and performs the work while controlling the flow rate and pressure of the supplied gas so that the space formed between the holding surface 34 and the inner circumferential region 15 of the support member 10 is at a predetermined pressure higher than the pressure of the processing space in the chamber 21. In the gas supply step 1004 and etching step 1005, the etching apparatus 20 controls the gas supply source 343 based on the measurement results of the pressure sensors 27 and 345, and maintains the support member 10 in an expanded state on the holding surface 34.

[0060] (Etching step) Next, the etching step 1005 will be described. Figure 6 is a cross-sectional view of an etching apparatus schematically showing the etching step of the wafer processing method shown in Figure 2. The etching step 1005 is a step in which, after the gas supply step 1004 is performed, plasma-formed etching gas 47 is supplied into the chamber 21, the plasma-formed etching gas 47 is introduced into the divided grooves 6, and the divided grooves 6 are plasma-etched to remove damage.

[0061] In the etching step, the etching apparatus 20 supplies, for example, 3000 sccm of He gas from the inert gas supply source 42, 165 sccm of SF6 gas from the fluorine-based gas supply source 43, and 55 sccm of O2 gas from the oxygen gas supply source 44 to the processing space of the chamber 21. In the etching step 1005, the etching apparatus 20 generates microwaves at a high frequency power of 2.45 GHz and 2000 W in the waveguide of the applicator 46, and irradiates the etching gas supplied in the gas introduction tube 45 from the gas supply unit 41 with the generated microwaves, thereby plasmaizing the etching gas in the gas introduction tube 45.

[0062] In etching step 1005, the etching gas 47, which has been plasmaized outside the chamber 21, is supplied from the gas introduction pipe 45 to the first region of the processing space, and further supplied to the second region of the processing space via the plasma diffusion member 28. The plasmaized etching gas 47 is supplied to the back surface 7 side of the wafer 1 for a predetermined time, and the etching gas 47 penetrates into the division groove 6, removing at least a portion of the damage to the inner surface of the division groove 6, namely the modified layer and the crystal strain caused by the cracks.

[0063] In this invention, damage refers to the area around the divided groove 6 of wafer 1 where chipping, cracks, or crystal distortion have occurred, if the divided groove 6 is a full-cut groove or a half-cut groove formed by cutting. In etching step 1005, at least a portion of the chipping, cracks, or crystal distortion around the divided groove 6 is removed. Furthermore, in this invention, damage refers to the area around the divided groove 6 of wafer 1 where it has been heated and altered by the laser beam, if the divided groove 6 is a full-cut groove or a half-cut groove formed by laser ablation. In etching step 1005, at least a portion of the area around the divided groove 6 where it has been heated and altered by the laser beam is removed.

[0064] Generally, when the divided groove 6 consists of a modified layer and cracks, as in Embodiment 1, the width of the divided groove 6, especially the cracks, is very narrow, several hundred nanometers. For this reason, in plasma etching, the plasma-treated etching gas 47 has difficulty penetrating into the cracks of the divided groove 6. Consequently, the etching rate within the cracks is lower than that of the surface 3 or the back surface, resulting in poor productivity.

[0065] Furthermore, generally, the etching rate within a crack depends on the aspect ratio, which is the ratio of the crack's depth to its width. As the crack deepens, the etching rate decreases further. Therefore, to remove damage at a location far from the back surface 7 of the segmented groove 6 (high aspect ratio location), the etching gas 47 must penetrate deep into the segmented groove 6 to process it, which increases processing time and further reduces productivity.

[0066] Therefore, the wafer processing method according to Embodiment 1 described above expands the inner circumferential region 15 of the support member 10 into a convex shape away from the holding surface 34, thereby widening the width of the dividing groove 6. This makes it easier for the etching gas 47 to enter the dividing groove 6, improving the etching rate within the dividing groove 6 and increasing productivity. As a result, the wafer processing method according to Embodiment 1 has the effect of enabling efficient plasma etching.

[0067] Furthermore, the wafer processing method according to Embodiment 1 widens the width of the dividing groove 6 and performs plasma etching, so plasma etching can be efficiently performed even at deep positions of the dividing groove 6, thus expanding the options for the position in which the dividing groove 6 is formed.

[0068] [Embodiment 2] Next, the wafer processing method according to Embodiment 2 will be described based on the drawings. Figure 7 is a flowchart showing the flow of the wafer processing method according to Embodiment 2. Figure 8 is a schematic perspective view showing the wafer held on the holding table of the laser processing apparatus in the modified layer formation step of the wafer processing method shown in Figure 7. Figure 9 is a schematic side view showing a partial cross-section of the state in which the laser processing apparatus forms a modified layer on the wafer in the modified layer formation step of the wafer processing method shown in Figure 7. Figure 10 is a schematic side view showing a partial cross-section of the frame support step of the wafer processing method shown in Figure 7. Figure 11 is a schematic side view showing a partial cross-section of the thinning step of the wafer processing method shown in Figure 7. Figure 12 is a schematic side view showing a partial cross-section of the cleaning step of the wafer processing method shown in Figure 7. Note that Figures 7, 8, 9, 10, 11, and 12 use the same reference numerals for the same parts as in Embodiment 1, and their descriptions are omitted.

[0069] As shown in Figure 7, the wafer processing method according to Embodiment 2 includes a modified layer formation step 1006, a frame support step 1007, a thinning step 1008, and a washing step 1009, prior to the loading step 1001.

[0070] The modified layer formation step 1006 is a step in which the laser processing apparatus 50 (shown in Figure 8) positions the focal point 54 of a laser beam 53 (shown in Figure 9) with a wavelength that is transparent to the wafer 1 inside the wafer 1 and irradiates it to form a modified layer 8 inside the wafer 1. In the modified layer formation step 1006, a protective tape 16 is attached to the surface 3 of the wafer 1, and then, as shown in Figure 8, the laser processing apparatus 50 holds the surface 3 side of the wafer 1 by suction to the holding surface 52 of the holding table 51 via the protective tape 16.

[0071] In the modified layer formation step 1006, the laser processing apparatus 50 positions the focal point 54 of a laser beam 53 with a wavelength that is transparent to the wafer 1 inside the wafer 1, as shown in Figure 9, and moves the holding table 51 and the laser beam irradiation unit 55 relatively along the division line 4 from the position shown by the dashed line in Figure 9 to the position shown by the solid line, while irradiating the wafer 1 with a pulsed laser beam 121 from the back surface 7 side of the wafer 1 along the division line 4.

[0072] As a result, because the wavelength of the laser beam 53 is transparent to the wafer 1, a modified layer 8 is formed inside the wafer 1 along the division lines 4. In Embodiment 1, in the modified layer formation step 1006, the laser processing apparatus 50 shines the laser beam 53 from the back surface 7 side of the wafer 1 along all the division lines 4 to form a modified layer 8 inside the wafer 1 along all the division lines 4.

[0073] (Frame support step) The frame support step 1007 is the step of attaching the surface 3 of the wafer 1 on which the modified layer 8 is formed to the support member 10 and supporting it with the frame 11. In the frame support step 1007, the protective tape 16 is peeled off from the surface 3 of the wafer 1, and the back surface 7 of the wafer 1 and the frame 11 are held on the holding surface 62 of the holding table 61 of a well-known mounter 60.

[0074] In the frame support step 1007, as shown in Figure 10, the mounter 60 moves a roller 63 along the holding surface 62 to press and adhere the support member 10 to the surface 3 of the wafer 1, thereby adhering the support member 10 to the frame 11 and the surface 3 of the wafer 1. In the frame support step 1007, the mounter 60 cuts the support member 10, which is adhering to the frame 11 and the surface 3 of the wafer 1, between the inner and outer edges of the frame 11, thereby supporting the wafer 1 within the opening 12 of the frame 11 via the support member 10.

[0075] (Thinning step) The thinning step 1008 is a step in which the wafer 1 supported by the frame 11 is thinned from the back surface 7 side, and cracks are propagated along the modified layer 8 from the modified layer 8 toward the front surface 3 and back surface 7. In the thinning step 1008, the grinding device 70 holds the front surface 3 of the wafer 1 to the holding surface 72 of the holding table 71 by suction via the support member 10, and clamps the frame 11 with clamping parts 73 provided around the holding table 71.

[0076] In the thinning step 1008, as shown in Figure 11, the grinding device 70 rotates the grinding wheel 75 for grinding around its axis using the spindle 74 and rotates the holding table 71 around its axis, supplying grinding fluid from a grinding fluid nozzle (not shown), and bringing the grinding wheel 76 of the grinding wheel 75 into contact with the back surface 7 of the wafer 1 and approaching the holding table 71 at a predetermined feed rate, thereby grinding the back surface 7 of the wafer 1 with the grinding wheel 76. In Embodiment 1, in the thinning step 1008, the grinding device 70 grinds the back surface 7 of the wafer 1 until the wafer 1 reaches a predetermined finished thickness. Also in Embodiment 1, in the thinning step 1008, due to the pressing force from the grinding wheel 75, cracks extend from the modified layer 8 to at least one of the surface 3 and back surface 7 of the wafer 1, forming the aforementioned dividing groove 6 on the dividing line 4.

[0077] (Washing step) The cleaning step 1009 is a step in which the wafer 1, which has undergone the thinning step 1008, is cleaned. In the cleaning step 1009, the cleaning device 80 holds the surface 3 side of the wafer 1 by suction to the holding surface 82 of the spinner table 81 via the support member 10. In the cleaning step 1009, as shown in Figure 12, the cleaning device 80 rotates the spinner table 81 around its axis and supplies cleaning water 84 (pure water in Embodiment 2) from the cleaning nozzle 83 to the center of the back surface 7 of the wafer 1.

[0078] The supplied cleaning water 84 then flows from the center to the outer edge of the back surface 7 of the wafer 1 due to the centrifugal force generated by the rotation of the spinner table 81, cleaning the entire back surface 7 of the wafer 1 and removing foreign matter from the back surface 7. The cleaned wafer 1 is then subjected to the same steps as in Embodiment 1: the placement step 1002, the fixing step 1003, the gas supply step 1004, and the etching step 1005.

[0079] Generally, in a process in which a modified layer 8 forming a segmented groove 6 is formed inside the wafer 1 by irradiation with a laser beam 53, and the back surface 7 is ground after the formation of the modified layer 8, plasma etching is performed from the ground back surface 7 side after grinding, thereby simultaneously removing the grinding damage formed on the back surface 7 side and the damage around the segmented groove 6, and increasing the bending strength of the individually segmented devices 5.

[0080] However, after grinding, the wafer 1 is divided into individual devices 5 by cracks that have extended from the modified layer 8, and the width of these dividing grooves 6 is narrow, only a few hundred μm. For this reason, in plasma etching, the plasma-generated etching gas 47 has difficulty penetrating into the cracks of the dividing grooves 6. Consequently, the etching rate within the cracks is lower than that of the surface 3 or back surface 7, resulting in poor productivity.

[0081] Furthermore, generally, the etching rate within a crack depends on the aspect ratio, which is the ratio of the crack's depth to its width. As the crack deepens, the etching rate decreases further. Therefore, to remove damage at a location far from the back surface 7 of the segmented groove 6 (high aspect ratio location), etching gas must penetrate deep into the segmented groove 6 to process it, which increases processing time and further reduces productivity.

[0082] While it is possible to shorten processing time by placing the modified layer 8 near the back surface 7, which is the grinding surface, changing the position of the modified layer 8 may worsen the divisibility of wafer 1 in subsequent expansion processes or narrow the range of process options. Thus, conventional processing methods have had challenges in terms of productivity and process margins.

[0083] Therefore, in the wafer processing method according to Embodiment 2, the inner circumferential region 15 of the support member 10 is made to bulge in a convex shape away from the holding surface 34, thereby widening the width of the dividing groove 6. This makes it easier for the etching gas 47 to enter the dividing groove 6, improving the etching rate in the dividing groove 6 and increasing productivity, thus enabling efficient plasma etching.

[0084] [Embodiment 3] Next, the wafer processing method according to Embodiment 3 will be described based on the drawings. Figure 13 is a flowchart showing the flow of the wafer processing method according to Embodiment 3. Figure 14 is a schematic side view in partial cross-section showing the state in which the expandable tape is attached to the back surface of the wafer in the expandable tape attachment step of the wafer processing method shown in Figure 13. Figure 15 is a schematic side view in partial cross-section showing the state in which the support member is peeled off from the surface of the wafer in the expandable tape attachment step of the wafer processing method shown in Figure 13. Figure 16 is a schematic side view in partial cross-section showing the state in which the wafer is supported by the expansion device in the expansion step of the wafer processing method shown in Figure 13. Figure 17 is a schematic side view in partial cross-section showing the state in which the expandable tape is expanded in the expansion step of the wafer processing method shown in Figure 13. Note that in Figures 13, 14, 15, 16, and 17, the same reference numerals are used for the same parts as in Embodiment 1, and their descriptions are omitted.

[0085] As shown in Figure 13, the wafer processing method according to Embodiment 3 includes an etching step 1005, followed by an expanded tape application step 1010 and an expansion step 1011.

[0086] (Step for applying expandable tape) The expandable tape application step 1010 is a step in which an expandable tape 17 is applied to the back surface 7 of the wafer 1 after the etching step 1005 has been performed. In the expandable tape application step 1010, the surface 3 and frame 11 of the wafer 1 are held on the holding surface 92 of the holding table 91 of a well-known mounter 90 via the support member 10.

[0087] In the expandable tape application step 1010, as shown in Figure 14, the mounter 90 presses the expandable tape 17 against the back surface 7 of the wafer 1 and moves a roller 93 along the holding surface 92 to adhere the expandable tape 17 to the frame 11 and the back surface 7 of the wafer 1, thereby adhering the expandable tape 17 to the frame 11 and the back surface 7 of the wafer 1. In the expandable tape application step 1010, the mounter 90 cuts the expandable tape 17 that has been adhered to the frame 11 and the back surface 7 of the wafer 1 between the inner and outer edges of the frame 11, inverts the wafer 1 on the holding surface 92, and then, as shown in Figure 15, peels the support member 10 from the surface 3 of the wafer 1 and the frame 11.

[0088] (Extension step) The expansion step 1011 is a step performed after the expansion tape application step 1010 to expand the expand tape 17 and widen the width of the dividing groove 6. In the expansion step 1011, as shown in Figure 16, the expansion device 100 holds the frame 11, which supports the wafer 1 in the opening 12, and the outer edge of the expand tape 17 by clamping them with the frame clamping portion 101, and a roller member 103 provided at the upper end of the cylindrical expansion drum 102 is brought into contact with the outer edge of the wafer 1 of the expand tape 17 and the inner edge of the frame 11.

[0089] Thus, in expansion step 1011, as shown in Figure 16, the expansion device 100 holds the frame 11 supporting the wafer 1 with the frame clamping portion 101, with the expanded tape 17 flat across the outer edge and the central portion. In expansion step 1011, the expansion device 100 moves the frame 11 and the wafer 1 relative to each other along a direction that intersects (orthogonal in Embodiment 3) with respect to the surface 3 of the wafer 1. In Embodiment 3, in expansion step 1011, the expansion device 100 raises the expansion drum 102 to move the frame 11 and the wafer 1 relative to each other along a direction that intersects (orthogonal in Embodiment 1) with respect to the surface 3 of the wafer 1, as shown in Figure 17.

[0090] Then, the roller member 103 presses from below upward between the outer edge of the wafer 1 and the inner edge of the frame 11 of the expanded tape 17, causing the expanded tape 17 to expand in the planar direction. As a result of the expansion of the expanded tape 17, tensile forces act radially on the expanded tape 17. When tensile forces act radially on the expanded tape 17 attached to the back surface 7 of the wafer 1, the wafer 1 forms a dividing groove 6 along the planned dividing line 4, and as shown in Figure 17, the width of the dividing groove 6 widens. Subsequently, in the expansion step 1011, the slack portion between the outer edge of the wafer 1 and the inner edge of the frame 11 of the expanded tape 17 is heated and contracted, and the wafer 1 maintains the widened width of the dividing groove 6.

[0091] The wafer processing method according to Embodiment 3, similar to Embodiments 1 and 2, involves expanding the width of the dividing groove 6 by making the inner circumferential region 15 of the support member 10 convex in the direction away from the holding surface 34. This makes it easier for the etching gas 47 to enter the dividing groove 6, improving the etching rate within the dividing groove 6 and increasing productivity, thus enabling efficient plasma etching.

[0092] In addition, in Embodiment 3, similar to Embodiment 2, the modified layer forming step 1006, the frame support step 1007, the thinning step 1008, and the cleaning step 1009 may be included before the placement step 1002. Furthermore, in the present invention, if the width of the dividing groove 6 after the expandable tape application step 1010 is sufficient, the expansion step 1011 is unnecessary. Also, in the expandable tape application step 1010, other frames may be applied together with the expandable tape 17.

[0093] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention. [Explanation of Symbols]

[0094] 1 wafer 4 planned division lines 6 dividing groove 10 Support member 11 frames 12 aperture 14 Outer area 15 Inner region 21 Chambers 30 Holding Tables 33 Fixed Unit 34 Holding surface 47 Plasma-treated etched gas (plasma gas) 342 Spout hole 1002 Placement step 1003 Fixed step 1004 Gas supply step 1005 Etching Step

Claims

1. A wafer processing method for processing a wafer along a planned splitting line, A mounting step involves placing a wafer, which is supported by a support member in the opening of a frame in which an opening has been formed, and which has a dividing groove formed along the planned dividing line, onto the holding surface of a holding table in the chamber, A fixing step of clamping and fixing an outer peripheral region, including a support member or at least one of the frame that is exposed between the outer peripheral of the wafer and the inner peripheral of the frame, between the fixing unit and the holding surface, A gas supply step involves supplying gas from the holding surface to the inner circumferential region inside the outer circumferential region fixed in the fixing step, causing the inner circumferential region to bulge in a convex shape away from the holding surface, thereby widening the width of the dividing groove, After the gas supply step is performed, the inner circumferential region is maintained in a convex shape bulging away from the holding surface, and plasma gas is supplied into the chamber, allowing the plasma gas to penetrate the divided grooves and etching the divided grooves to remove damage; A method for processing wafers, characterized by having [a certain feature].

2. A modified layer formation step, wherein, before performing the mounting step, the focal point of a laser beam with a wavelength that is transparent to the wafer is positioned inside the wafer and irradiated to form a modified layer inside the wafer along the planned division line, A wafer processing method according to claim 1, characterized by comprising a thinning step of grinding the wafer before performing the placement step and after performing the modified layer formation step to propagate cracks from the modified layer and form the division grooves on the planned division lines.

3. The wafer processing method according to claim 1 or 2, characterized in that the gas supply step is carried out while controlling the flow rate and pressure of the supplied gas such that the space formed between the holding surface and the support member is higher than the pressure in the chamber space.

4. The wafer processing method according to claim 1 or claim 2, characterized in that the gas supply step is supplied from an ejection hole formed on the holding surface.

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