JP2020061440A - Wafer processing method - Google Patents

Abstract

To provide a wafer processing method capable of performing plasma etching while holding down costs.SOLUTION: A wafer processing method for dividing a wafer in which a plurality of devices are formed on a surface of a substrate composed of gallium arsenide comprises a protection member arranging step (ST1), a cutting step (ST2), a plasma etching step (ST3), and a functional layer dividing step (ST4). The protection member arranging step arranges an adhesive tape on a functional layer side on a surface of the wafer. The cutting step forms a cut groove on a rear surface of the wafer along division schedule lines. The plasma etching step supplies a plasmatized etching gas to the rear surface side of the wafer and divides the substrate at a division groove. The functional layer dividing step divides the wafer by irradiating an exposed functional layer from the rear surface side of the wafer with a laser beam.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wafer processing method, and more particularly to plasma dicing.

  It is known that a semiconductor wafer made of a silicon substrate or the like is divided into individual device chips, and thus a processing method using a cutting blade or a laser beam is applied. In these processing methods, the planned dividing lines (streets) are processed one by one to divide the wafer into device chips. Due to the recent miniaturization of electronic devices, lighter, thinner, shorter, and smaller device chips, and cost reductions have progressed, and many device chips with a size of 2 mm or less have been produced from device chips with a size of more than 10 mm as in the past. . In particular, the tendency is remarkable in an LED (Light Emitting Diode) formed from a gallium arsenide substrate or the like. When manufacturing a small-sized device chip, the number of lines to be divided into a single wafer is drastically increased, and processing time for each line becomes long.

  Therefore, a technique called plasma dicing has been developed in which all the planned dividing lines of the wafer are collectively processed (for example, refer to Patent Document 1). In the plasma dicing shown in Patent Document 1, the area other than the area shielded by the mask is removed by plasma etching and processing is performed on a wafer-by-wafer basis, so that the processing time is dramatically increased even if the number of planned division lines increases. The effect is that it will not be long.

  However, in the plasma dicing shown in Patent Document 1, it is necessary to prepare a precise mask that matches the planned dividing line of each wafer in order to accurately expose only the region to be removed by etching (for example, Patent Document 1). Reference 2 and Patent Reference 3).

JP, 2006-114825, A JP, 2013-055120, A JP, 2014-199833, A

  However, in particular, the masks disclosed in Patent Documents 2 and 3 have a higher cost and a higher degree of difficulty than cutting processes, such as the suppression of manufacturing cost and the number of manufacturing steps, and the establishment of a technique for aligning the mask. Was left.

  The present invention has been made in view of the above problems, and an object thereof is to provide a wafer processing method capable of performing plasma etching while suppressing costs.

  In order to solve the above-mentioned problems and achieve the object, a wafer processing method of the present invention is a wafer in which a functional layer is laminated on a surface of a substrate made of gallium arsenide to form a plurality of devices. A method of processing a wafer that is divided along a dividing line that divides the wafer, including a protective member disposing step of disposing a protective member on the functional layer side of the front surface of the wafer, and a cutting blade on the back surface of the wafer. A cutting step of forming a cutting groove having a depth not reaching the functional layer on the substrate along the dividing line, and supplying a gas in a plasma state to the back surface side of the wafer to cut the cutting groove. A plasma etching step of removing the substrate remaining at the bottom by etching and dividing the substrate by dividing grooves along the dividing line, and after performing the plasma etching step A functional layer dividing step of irradiating the functional layer exposed from the back surface side of the wafer with a laser beam having a wavelength having an absorptivity with respect to the functional layer, and dividing the functional layer along a dividing line. Characterize.

  The wafer processing method may further include, after the plasma etching step, a finish grinding step of grinding the back surface of the wafer to a finished thickness of the wafer.

  The wafer processing method may further include a preliminary grinding step of previously grinding the back surface of the wafer before the plasma etching step.

  The wafer processing method of the present invention has an effect that plasma etching can be performed while suppressing cost.

FIG. 1 is a perspective view showing an example of a wafer to be processed by the wafer processing method according to the first embodiment. FIG. 2 is a flowchart showing the flow of the wafer processing method according to the first embodiment. FIG. 3 is a side view showing a partial cross section of a cutting step of the method for processing the wafer shown in FIG. FIG. 4 is a cross-sectional view of the essential part of the wafer after the cutting step of the wafer processing method shown in FIG. FIG. 5 is a sectional view showing the structure of an etching apparatus used in the plasma etching step of the wafer processing method shown in FIG. FIG. 6 is a cross-sectional view of an essential part of the wafer after the plasma etching step of the wafer processing method shown in FIG. FIG. 7 is a sectional view showing a functional layer dividing step of the wafer processing method shown in FIG. FIG. 8 is a cross-sectional view of the essential part of the wafer after the functional layer dividing step of the wafer processing method shown in FIG. FIG. 9 is a side sectional view showing a finish grinding step of the wafer processing method shown in FIG. FIG. 10 is a cross-sectional view of the wafer after the die attach film attaching step of the wafer processing method shown in FIG. FIG. 11 is a cross-sectional view showing a die attach film dividing step of the wafer processing method shown in FIG. FIG. 12 is a cross-sectional view of the essential part of the wafer after the die attach film dividing step of the wafer processing method shown in FIG. FIG. 13 is a flowchart showing the flow of the wafer processing method according to the second embodiment. 14 is a side sectional view showing a pre-grinding step of the wafer processing method shown in FIG. FIG. 15 is a cross-sectional view of the essential part of the wafer after the pre-grinding step of the wafer processing method shown in FIG.

  Modes (embodiments) 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 embodiments below. Further, the constituent elements described below include those that can be easily conceived by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Further, various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

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

  The wafer processing method according to the first embodiment is the wafer 1 processing method shown in FIG. In the first embodiment, the wafer 1 is a disk-shaped semiconductor wafer or optical device wafer having a substrate 2 made of gallium arsenide. In the wafer 1, as shown in FIG. 1, a functional layer 4 is laminated on a surface 3 of a substrate 2 and a plurality of devices 5 are formed. The functional layer 4 includes a low dielectric constant insulating film (Low-k film) made of an inorganic film such as SiOF or BSG (SiOB) or an organic film such as a polyimide or parylene polymer film. The functional layer 4 is laminated on the surface 3 of the substrate 2.

  The device 5 is formed in each area of the surface 3 which is divided by a plurality of planned dividing lines 6. That is, the planned dividing line 6 divides the plurality of devices 5. The circuit forming the device 5 is formed by the functional layer 4. In the first embodiment, the device 5 is smaller than the device divided from the wafer 1 by cutting, and has a size of, for example, about 1 mm × 1 mm, and is individually processed by plasma etching (also referred to as plasma dicing). It is suitable for being divided. At least one of a metal film (not shown) and a TEG (Test Element Group) is formed on the functional layer 4 side in at least a part of the planned dividing line 6 of the wafer 1. The TEG is an evaluation element for finding a design or manufacturing problem that occurs in the device 5.

  The wafer processing method according to the first embodiment is a method of dividing the wafer 1 into individual devices 5 along the dividing line 6 and thinning the devices 5 to a finished thickness of 100. As shown in FIG. 2, the wafer processing method includes a protection member disposing step ST1, a cutting step ST2, a plasma etching step ST3, a functional layer dividing step ST4, a finishing grinding step ST5, and a die attach film attachment. The step ST6 and the die attach film dividing step ST7 are provided.

(Protection member installation step)
The protective member disposing step ST1 is a step of disposing the adhesive tape 200 as a protective member on the surface 3 of the substrate 2 of the wafer 1 on the side of the functional layer 4. In the first embodiment, in the protection member disposing step ST1, as shown in FIG. 1, an adhesive tape 200 having a diameter larger than that of the wafer 1 is attached to the functional layer 4 side, and the annular frame 201 is provided on the outer peripheral edge of the adhesive tape 200. Affix. Although the adhesive tape 200 is used as the protective member in the first embodiment, the protective member is not limited to the adhesive tape 200 in the present invention. The processing method of the wafer proceeds to the cutting step ST2 when the adhesive tape 200 is attached to the functional layer 4 side of the wafer 1.

(Cutting step)
FIG. 3 is a side view showing a partial cross section of a cutting step of the method for processing the wafer shown in FIG. FIG. 4 is a cross-sectional view of the essential part of the wafer after the cutting step of the wafer processing method shown in FIG.

  In the cutting step ST2, the cutting blade 12 of the cutting device 10 shown in FIG. 3 is cut into the back surface 7 of the substrate 2 of the wafer 1, and the cutting groove 300 having a depth not reaching the functional layer 4 is cut along the dividing line 6. This is a step of forming on the substrate 2. In the first embodiment, in the cutting step ST2, as shown in FIG. 3, the functional layer 4 side of the wafer 1 is attached to the holding surface 14 of the chuck table 13 of the cutting device 10 having one cutting unit 11 via the adhesive tape 200. Hold by suction. In the cutting step ST2, an infrared camera (not shown) of the cutting device 10 images the back surface 7 of the wafer 1 to detect the planned dividing line 6, and performs alignment for aligning the wafer 1 and the cutting blade 12 of the cutting unit 11. To do.

  In the cutting step ST2, the cutting device 10 causes the cutting blade 12 to cut from the back surface 7 while relatively moving the wafer 1 and the cutting blade 12 of the cutting unit 11 along the planned dividing line 6, and A cutting groove 300 having a depth that does not reach the functional layer 4 is formed on the back surface 7 side.

  In the cutting step ST2, the cutting device 10 forms a cutting groove 300 having a depth that does not reach the functional layer 4 on the back surface 7 side of the wafer 1 and leaves the base material of the substrate 2 at the bottom 301 of the cutting groove 300. As shown in FIG. 4, the wafer processing method proceeds to plasma etching step ST3 when the cutting grooves 300 are formed on the back surface 7 side of all the planned dividing lines 6 of the wafer 1. In the first embodiment, in the cutting step ST2, a so-called single cut in which the wafer 1 is cut with one cutting blade 12 is performed, but after the wafer 1 is cut with one of the two thick cutting blades, You may implement what is called a step cut which cuts with the other thin cutting blade.

(Plasma etching step)
FIG. 5 is a sectional view showing the structure of an etching apparatus used in the plasma etching step of the wafer processing method shown in FIG. FIG. 6 is a cross-sectional view of an essential part of the wafer after the plasma etching step of the wafer processing method shown in FIG.

  In the plasma etching step ST3, the etching gas in the plasma state is supplied to the back surface 7 side of the wafer 1 holding the adhesive tape 200 side by the chuck table 21 in the plasma etching chamber 25 of the etching apparatus 20 shown in FIG. The substrate 2 remaining on the bottom 301 (shown in FIG. 4) of the substrate is removed by etching, and the substrate 2 is divided by the dividing groove 310 (shown in FIG. 6) along the dividing line 6. The plasma etching step ST3 is a step of plasma dicing the substrate 2 of the wafer 1.

  In the plasma etching step ST3, the control unit 22 of the etching apparatus 20 operates the gate operating unit 23 to move the gate 24 downward in FIG. 5, and opens the opening 26 of the plasma etching chamber 25. Next, the wafer 1 on which the cutting step ST2 has been performed by the loading / unloading means (not shown) is transferred to the closed space 27 in the plasma etching chamber 25 through the opening 26, and the chuck table of the workpiece holder 29 that constitutes the lower electrode 28. The functional layer 4 side of the wafer 1 is placed on 21 (electrostatic chuck, ESC: Electrostatic chuck) via the adhesive tape 200. At this time, the control unit 22 operates the lift drive unit 30 to raise the upper electrode 31. The control unit 22 applies electric power to the electrodes 32 and 33 provided in the workpiece holder 29 to suck and hold the wafer 1 on the chuck table 21.

  The control unit 22 operates the gate operating unit 23 to move the gate 24 upward, and closes the opening 26 of the plasma etching chamber 25. The control unit 22 operates the elevating and lowering drive unit 30 to lower the upper electrode 31, thereby lowering the lower surface of the gas ejection portion 34 forming the upper electrode 31 and the wafer 1 held on the chuck table 21 forming the lower electrode 28. The distance between them is set to a predetermined electrode distance suitable for the plasma etching process.

  The control unit 22 operates the gas discharge unit 35 to evacuate the closed space 27 in the plasma etching chamber 25 to maintain the pressure of the closed space 27 at a predetermined pressure and to operate the coolant supply unit 36. Helium gas, which is a coolant, is circulated in the coolant introduction passage 37, the cooling passage 38, and the coolant discharge passage 39 provided in the lower electrode 28 to suppress abnormal temperature rise of the lower electrode 28.

  Next, the control unit 22 operates the gas supply unit 40 to eject the etching gas from the plurality of ejection ports 41 of the upper electrode 31 toward the wafer 1 held on the chuck table 21 of the lower electrode 28 and perform etching. With the gas supplied, high frequency power for generating and maintaining plasma is applied from the high frequency power supply 42 to the upper electrode 31, and high frequency power for attracting ions to the lower electrode 28 is applied from the high frequency power supply 42. As a result, an etching gas in a plasma state is generated in the space between the lower electrode 28 and the upper electrode 31, the etching gas in the plasma state is drawn into the wafer 1, and the back surface 7 of the wafer 1 and the inner surface of the cutting groove 300 are drawn. The bottom 301 is etched and the cutting groove 300 is advanced toward the surface 3 of the substrate 2.

Although Cl ₂ or the like is used as the etching gas in the first embodiment, the etching gas is not limited to these. Further, in the first embodiment, the plasma etching step ST3 generates AsCl ₃ , GaCl or the like as an etching deposit, but the etching deposit is not limited to these.

  In the plasma etching step ST3, the control unit 22 presets a predetermined time for plasma etching the wafer 1 according to the depth of the cutting groove 300 and the thickness of the wafer 1. In the plasma etching step ST3, as shown in FIG. 6, the entire back surface 7 of the wafer 1 that has been plasma-etched for a predetermined time is etched and thinned by a thickness of 101. Further, as shown in FIG. 6, the substrate 1 remaining on the bottom 301 of the cutting groove 300 is etched and removed from the wafer 1 plasma-etched for a predetermined time, and the cutting groove 300 reaches the functional layer 4 and is cut. The groove 300 serves as a dividing groove 310 that divides the substrate 2. In the wafer 1, the substrate 2 is divided by the dividing grooves 310, the functional layers 4 are exposed in the dividing grooves 310, and the functional layers 4 remain on the bottoms of the dividing grooves 310. Further, in the first embodiment, the dividing groove 310 formed in the plasma etching step ST3 is formed such that the width thereof gradually becomes narrower from the back surface 7 toward the front surface 3.

  In the wafer processing method, after performing plasma etching for a predetermined time in plasma etching step ST3, the process proceeds to functional layer dividing step ST4. Note that FIG. 6 shows an example in which the substrate 2 at the bottom of the dividing groove 310 is removed from the wafer 1 after the plasma etching step ST3, but in the present invention, the substrate 2 is slightly left at the bottom 301 of the cutting groove 300. May remain. Further, in the wafer processing method of the present invention, in the plasma etching step ST3, an etching step of etching the entire back surface 7 of the wafer 1 and advancing the cutting grooves 300 toward the front surface 3 of the substrate 2 is performed. The wafer 1 may be plasma-etched by a so-called Bosch method in which a coating film deposition step of depositing a coating film on the back surface 7 of 1, the inner surface of the cutting groove 300 and the bottom 301 is alternately repeated.

(Function layer division step)
FIG. 7 is a sectional view showing a functional layer dividing step of the wafer processing method shown in FIG. FIG. 8 is a cross-sectional view of the essential part of the wafer after the functional layer dividing step of the wafer processing method shown in FIG.

  The functional layer dividing step ST4 is a function in which the laser processing apparatus 50 shown in FIG. 7 exposes the laser beam 51 having a wavelength having an absorptivity to the functional layer 4 from the back surface 7 side of the wafer 1 after performing the plasma etching step ST3. It is a step of irradiating the layer 4 and dividing the functional layer 4 along the dividing line 6.

  In the functional layer dividing step ST4, the laser processing device 50 holds the functional layer 4 side of the wafer 1 on the chuck table via the adhesive tape 200, and divides the laser beam irradiation unit 52 and the chuck table as shown in FIG. The bottom 301 of the cutting groove 300 is formed by moving the condensing point 51-1 of the laser beam 51 having a wavelength (for example, 355 nm) having an absorptivity to the functional layer 4 from the laser beam irradiation unit 52 while moving relatively along the planned line 6. The functional layer 4 exposed to the above is set and the laser beam 51 is irradiated to the functional layer 4. In the functional layer dividing step ST4, the functional layer 4 exposed at the bottom of the dividing groove 310 is ablated in each planned dividing line 6, the functional layer 4 exposed at the bottom of the dividing groove 310 is cut, and the wafer 1 Is divided into individual devices 5. In the functional layer dividing step ST4, the metal film or TEG formed on the division line 6 (not shown) is also divided. As shown in FIG. 8, the wafer processing method proceeds to finish grinding step ST5 when the functional layer 4 exposed at the bottom of the dividing groove 310 is divided in all the dividing lines 6 to be divided.

(Finishing grinding step)
FIG. 9 is a side sectional view showing a finish grinding step of the wafer processing method shown in FIG. The finish grinding step ST5 is a step in which the back surface 7 of the wafer 1 is ground and the wafer 1 has a finished thickness of 100 after the plasma etching step ST3 and the functional layer dividing step ST4.

  In the finish grinding step ST5, the grinding device 60 sucks and holds the functional layer 4 side of the wafer 1 on the holding surface 62 of the chuck table 61 via the adhesive tape 200. In the finishing grinding step ST5, as shown in FIG. 9, while the spindle 63 rotates the grinding wheel 64 for finishing grinding and the chuck table 61 is rotated about the axis, the grinding water is supplied and the grinding stone 65 for finishing grinding is used. Is brought closer to the chuck table 61 at a predetermined feeding speed, and the grinding wheel 65 for finish grinding finishes the wafer 1 or the back surface 7 of the device 5. In the finish grinding step ST5, the wafer 1 or the device 5 is ground until the finished thickness is 100. In the wafer processing method, when the wafer 1 or the device 5 is thinned to a finished thickness of 100, the process proceeds to a die attach film attaching step ST6.

(Step of attaching die attach film)
FIG. 10 is a cross-sectional view of the wafer after the die attach film attaching step of the wafer processing method shown in FIG. The die attach film attaching step ST6 is a step of attaching the die attach film 202 to the back surface 7 of the wafer 1 after the plasma etching step ST3, the functional layer dividing step ST4 and the finish grinding step ST5.

  In the die attach film attaching step ST6, the die attach film 202 for attaching the device 5 is attached to the back surface 7 of the wafer 1 that has been finish ground in the finish grinding step ST5, that is, the device 5. In the die attach film attaching step ST6, as shown in FIG. 10, the annular frame 204 is attached to the outer peripheral edge, and the die attach film 202 laminated on the dicing tape 203 is attached to the back surface 7 of the wafer 1 to function. The adhesive tape 200 is peeled off from the layer 4. In the wafer processing method, when the adhesive tape 200 is peeled from the functional layer 4, the process proceeds to the die attach film dividing step ST7.

(Die attach film dividing step)
FIG. 11 is a cross-sectional view showing a die attach film dividing step of the wafer processing method shown in FIG. FIG. 12 is a cross-sectional view of the essential part of the wafer after the die attach film dividing step of the wafer processing method shown in FIG. The die-attach film dividing step ST7 is a step of dividing the die-attach film 202 by irradiating the die-attach film 202 with the laser beam 71 along the dividing groove 310 with the laser processing device 70 shown in FIG.

  In the die attach film dividing step ST7, the laser processing device 70 holds the back surface 7 side of the wafer 1 on the chuck table via the dicing tape 203, and divides the laser beam irradiation unit 72 and the chuck table as shown in FIG. A laser beam 71 having a wavelength (for example, 355 nm) having an absorptivity for the die attach film 202 from the laser beam irradiation unit 72 is moved to the die attach film 202 exposed in the cutting groove 300 while relatively moving along the planned line 6. Irradiate. In the die-attach film dividing step ST7, the die-attach film 202 exposed in the dividing groove 310 is ablated in each division line 6 to divide the die-attach film 202 exposed in the dividing groove 310. As shown in FIG. 12, the wafer processing method ends when the die attach film 202 exposed in the dividing grooves 310 is divided in all the dividing lines 6 to be divided. In addition, after that, the device 5 is picked up from the dicing tape 203 by a not-shown pickup for each die attach film 202.

  In the wafer processing method according to the first embodiment, after the cutting groove 300 is formed from the back surface 7 along the planned dividing line 6 in the cutting step ST2, plasma cutting is performed from the back surface 7 side in the plasma etching step ST3. Since the wafer 1 is divided by advancing 300 toward the front surface 3 of the substrate 2, the cutting groove 300 etches to the back surface 7 earlier than other regions, so that plasma dicing without a mask is realized. be able to. For this reason, since the wafer processing method is smaller than the device divided by the cutting process, the wafer 1 provided with the device 5 suitable for the plasma etching does not require an expensive mask. . As a result, the wafer processing method can divide the wafer 1 into individual devices 5 by performing plasma etching on the wafer 1 while suppressing costs.

  Further, in the wafer processing method, the adhesive tape 200 is attached to the functional layer 4 side in the protective member disposing step ST1 before the cutting step ST2 and the finish grinding step ST5. For this reason, it is possible to prevent the contamination generated in the cutting step ST2 and the finish grinding step ST5 from adhering to the device 5.

  Further, in the method of processing a wafer, in the functional layer dividing step ST4, the functional layer 4 remaining on the groove bottom of the dividing groove 310 is irradiated with the laser beam 51 to divide the wafer. Even if the functional layer 4 containing a resin such as a Low-k film remains, the wafer 1 on which the functional layer 4 such as a Low-k film is laminated can be divided into individual devices 5. Further, in the wafer processing method, the adhesive tape 200 is attached to the functional layer 4 side in the protective member disposing step ST1 before the functional layer dividing step ST4, and the laser beam 51 is applied from the back surface 7 side in the functional layer dividing step ST4. Since the functional layer 4 on the bottom of the dividing groove 310 is irradiated, it is possible to prevent debris generated during ablation processing from adhering to the device 5.

  Further, in the wafer processing method, in the plasma etching step ST3, in order to divide the substrate 2 along the dividing line 6, the side surfaces of the individually divided devices 5 are removed by plasma etching. For this reason, the wafer processing method has an effect that the chip 5 due to cutting does not remain on the side surface of the individually divided device 5, and the device 5 having high bending strength can be manufactured.

  Further, since the wafer processing method includes the die attach film attaching step ST6 and the die attach film dividing step ST7, the device 5 that can be fixed to the substrate or the like can be obtained.

[Embodiment 2]
A wafer processing method according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 13 is a flowchart showing the flow of the wafer processing method according to the second embodiment. 14 is a side sectional view showing a pre-grinding step of the wafer processing method shown in FIG. FIG. 15 is a cross-sectional view of the essential part of the wafer after the pre-grinding step of the wafer processing method shown in FIG. 13, 14, and 15, the same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

  The wafer processing method according to the second embodiment is the same as that of the first embodiment except that a preliminary grinding step ST10 is provided as shown in FIG. The preliminary grinding step ST10 is a step of previously grinding the back surface 7 of the wafer 1 before the plasma etching step ST3. In the second embodiment, the wafer processing method performs the preliminary grinding step ST10 after the protection member disposing step ST1 and before the cutting step ST2, but in the present invention, if it is before the plasma etching step ST3, It may be performed before the protection member disposing step ST1 or after the cutting step ST2.

  In the preliminary grinding step ST10, the grinding device 80 sucks and holds the functional layer 4 side of the wafer 1 on the holding surface 82 of the chuck table 81 via the adhesive tape 200. In the pre-grinding step ST10, as shown in FIG. 14, while the spindle 83 rotates the grinding wheel 84 for pre-grinding and the chuck table 81 is rotated around the axis, the grinding water is supplied and the grindstone 85 for pre-grinding is used. Is brought closer to the chuck table 81 at a predetermined feed speed, so that the back surface 7 of the wafer 1 is roughly ground by the pregrinding grindstone 85.

  In the preliminary grinding step ST10, as shown in FIG. 15, the wafer 1 is ground until the finished thickness 100 and the thickness 101 removed in the plasma etching step ST3 are equal to or more than the total thickness. In the second embodiment, the wafer processing method proceeds to the plasma etching step ST3 when the wafer 1 is ground until the finished thickness 100 and the thickness 101 removed in the plasma etching step ST3 are equal to or more than the total thickness. In the present invention, in the preliminary grinding step ST10, the finished thickness 100, the thickness 101 removed in the plasma etching step ST3, and the thickness removed in the finish grinding step ST5 are set to be approximately equal to the total thickness. The wafer 1 may be thinned.

  In the wafer processing method according to the second embodiment, after the cutting groove 300 is formed from the back surface 7 along the planned dividing line 6 in the cutting step ST2, the plasma etching is performed from the back surface 7 side in the plasma etching step ST3. In this case, the etching progresses to the back surface 7 earlier than the other regions, so that plasma dicing without a mask can be realized. As a result, the wafer processing method can divide the wafer 1 into individual devices 5 by performing plasma etching on the wafer 1 while suppressing the cost, as in the first embodiment.

  Further, in the wafer processing method according to the second embodiment, since the wafer 1 is thinned by performing the preliminary grinding step ST10 before the plasma etching step ST3, the removal amount of the substrate 2 of the wafer 1 at the plasma etching step ST3. Can be reduced. As a result, the wafer processing method according to the second embodiment can reduce the amount of so-called outgas generated in the plasma etching step ST3 and the processing time.

  Further, in the wafer processing method according to the second embodiment, the backside 7 of the wafer 1 is ground by performing the preliminary grinding step ST10 before the cutting step ST2. Even on the satin surface (the surface having fine irregularities), the back surface 7 can be flattened before the cutting step ST2. As a result, in the wafer processing method according to the second embodiment, in the cutting step ST2, it is possible to take an image with the infrared camera, and the cutting blade 12 and the planned dividing line when the alignment is performed based on the taken image of the surface of the wafer 1. Positioning with 6 is possible.

[Embodiment 3]
A wafer processing method according to the third embodiment of the present invention will be described. In the method for processing a wafer according to the third embodiment, in the plasma etching step ST3, high-frequency power is not applied to the electrodes to plasma the etching gas or the like in the closed space, but the etching gas in the plasma state is used in the plasma etching chamber. A remote plasma type plasma etching apparatus for introducing into a closed space is used.

  Since the wafer processing method according to the third embodiment uses the remote plasma type etching apparatus in the plasma etching step ST3, in the etching apparatus, the ions mixed in the plasmaized etching gas collide with the inner surface of the supply pipe to perform plasma etching. Since it is possible to suppress the reaching of the closed space in the chamber and to supply the etching gas with a high concentration of radicals, the substrate 2 can be divided for each device 5 even if the cutting groove 300 has a narrower width.

  The wafer processing method according to the third embodiment may perform the preliminary grinding step ST10 as in the second embodiment.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the gist of the present invention. For example, in the present invention, the functional layer 4, the metal film and the TEG formed on the planned dividing line 6 may be removed by ablation by irradiating a laser beam from the surface before the cutting step ST2. Further, in the present invention, when an oxide film is formed on the back surface 7 of the wafer 1 in advance, plasma etching may be performed using the oxide film as a mask in the plasma etching step ST3. Further, according to the present invention, in both of the finish grinding step ST5 and the preliminary grinding step ST10, after the back surface 7 of the wafer 1 is roughly ground by using the preliminary grinding wheel 85, the finishing grinding having smaller abrasive grains than the preliminary grinding wheel 85 is performed. The back surface 7 of the wafer 1 may be finish ground by the grinding wheel 65, the back surface 7 of the wafer 1 may be only rough ground, or the back surface 7 of the wafer 1 may be only finish ground. Further, the present invention is not limited to the size of the device 5 described in the above embodiment.

1 Wafer 2 Substrate 3 Surface 4 Functional Layer 5 Device 6 Planned Division Line 7 Backside 12 Cutting Blade 51 Laser Beam 100 Finished Thickness 200 Adhesive Tape (Protective Material)
300 cutting groove 301 bottom 310 dividing groove ST1 protective member disposing step ST2 cutting step ST3 plasma etching step ST4 functional layer dividing step ST5 finishing grinding step ST10 preliminary grinding step

Claims (3)

A method of processing a wafer, in which a functional layer is laminated on the surface of a substrate made of gallium arsenide to form a plurality of devices on a wafer, and the wafer is divided along division lines that divide the plurality of devices.
A protective member disposing step of disposing a protective member on the functional layer side of the surface of the wafer;
A cutting step of cutting a back surface of the wafer with a cutting blade to form a cutting groove having a depth not reaching the functional layer on the substrate along the dividing line;
A plasma etching step of supplying a gas in a plasma state to the back surface side of the wafer, etching and removing the substrate remaining at the bottom of the cutting groove, and dividing the substrate by dividing grooves along the dividing lines.
After performing the plasma etching step, a function of irradiating the functional layer exposed from the back surface side of the wafer with a laser beam having a wavelength having an absorptivity for the functional layer, and dividing the functional layer along a dividing line. A method for processing a wafer, comprising: a layer dividing step.   The method of processing a wafer according to claim 1, further comprising a finish grinding step of grinding the back surface of the wafer to a finished thickness of the wafer after the plasma etching step.   3. The wafer processing method according to claim 1, further comprising a pre-grinding step of previously grinding the back surface of the wafer before the plasma etching step.

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