JP2020061496A - 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 by a functional layer laminated on a surface comprises a protection member arranging step (ST1), a cutting step (ST2), a plasma etching step (ST3), and a functional layer cutting step (ST4). The protection member arranging step forms an adhesive tape 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. The functional layer cutting step forms a liquid column by jetting a liquid from the rear surface side of the wafer, guides a laser beam into the liquid column, cuts the functional layer exposed on a bottom of the cut groove by processing it by the laser beam, and removes a debris generated during cutting of the functional layer by flowing the debris by the liquid.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. . 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, the wafer processing method of the present invention divides a wafer in which a plurality of devices are formed by a functional layer laminated on the surface of a substrate into the plurality of devices. A method of processing a wafer that is divided along a dividing line, including a protective member disposing step of disposing a protective member on the surface of the wafer, and holding the protective member side of the wafer by a chuck table of a cutting device. Then, a cutting blade is cut into the back surface of the wafer, and a cutting step of forming a cutting groove having a depth not reaching the functional layer on the substrate along the dividing line, and the protective member side of the wafer. It is held by a chuck table of a plasma device, plasmaized gas is supplied to the back side of the wafer, the substrate remaining at the bottom of the cutting groove is removed by etching, and the substrate is divided. A plasma etching step of dividing along a fixed line, and a liquid is ejected from the back surface side of the wafer to form a liquid column, and a laser beam is guided into the liquid column to be exposed at the bottom of the cutting groove. A functional layer cutting step of processing the functional layer with the laser beam to cut the functional layer and removing the generated debris by flowing with the liquid.

  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 may further include a grinding step of grinding the back surface of the wafer after 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 cross-sectional view showing a configuration of a plasma device used in a 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 cross-sectional view showing a functional layer cutting 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 step of cutting the functional layer of the method for processing a wafer shown in FIG. FIG. 9 is a side sectional view showing a grinding step of the method for processing the wafer 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 the substrate 2 made of silicon, sapphire, gallium arsenide, or the like. As shown in FIG. 1, the wafer 1 has a plurality of devices 5 formed by the functional layer 4 laminated on the surface 3 of the substrate 2. 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. In this specification, the back surface 7 of the substrate 2 will be referred to as the back surface of the wafer 1, and the front surface 8 of the functional layer 4 will be referred to as the front surface of the wafer 1 hereinafter.

  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 cutting step ST4, a grinding step ST5, and a die attach film attaching step. ST6 and a 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 front surface 8 of the wafer 1. 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 method of processing the wafer proceeds to the cutting step ST2 when the adhesive tape 200 is attached to the front surface 8 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 adhesive tape 200 side of the wafer 1 is held by the holding surface 14 of the chuck table 13 of the cutting device 10 shown in FIG. 3, and the cutting blade 12 of the cutting device 10 is cut on the back surface 7 of the substrate 2 of the wafer 1. This is a step of forming a cutting groove 300 having a depth that does not reach the functional layer 4 on the substrate 2 along the planned dividing line 6 by inserting the cutting groove 300. 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 cross-sectional view showing a configuration of a plasma device used in a 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 adhesive tape 200 side of the wafer 1 is held by the chuck table 21 in the plasma etching chamber 25 of the plasma apparatus 20 shown in FIG. 5, and the plasma-etched etching gas is supplied to the back surface 7 side of the wafer 1. This is a step of etching and removing the substrate 2 remaining on the bottom 301 (shown in FIG. 4) of the cutting groove 300, and dividing the substrate 2 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 plasma device 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, and the etching gas in the plasma state is drawn into the wafer 1 side, so that the back surface 7 of the wafer 1 and the cutting groove 300 The inner surface and the bottom 301 are etched, and the cutting groove 300 is advanced toward the surface 3 of the substrate 2.

In the first embodiment, when the substrate 2 is made of silicon, SF ₆ , C ₄ F ₈ or CF ₄ is used as the etching gas, but the etching gas 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, that is, 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. In the wafer 1 plasma-etched for a predetermined time, as shown in FIG. 6, the substrate 2 remaining on the bottom 301 of the cutting groove 300 is etched and removed, and the cutting groove 300 reaches the functional layer 4. In the wafer 1, the substrate 2 is divided by the cutting groove 300, the functional layer 4 is exposed in the cutting groove 300, and the functional layer 4 remains on the bottom of the cutting groove 300. In the first embodiment, the width of the cutting groove 300 formed in the plasma etching step ST3 is gradually narrowed 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 cutting step ST4. Although FIG. 6 shows an example in which the substrate 2 at the bottom of the cutting groove 300 has been removed from the wafer 1 after the plasma etching step ST3, 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.

(Functional layer cutting step)
FIG. 7 is a cross-sectional view showing a functional layer cutting 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 step of cutting the functional layer of the method for processing the wafer shown in FIG.

  In the functional layer cutting step ST4, after performing the plasma etching step ST3, the laser processing apparatus 50 shown in FIG. 7 ejects the liquid from the back surface 7 side of the wafer 1 to form the liquid column 54 and functions in the liquid column 54. While guiding the laser beam 51 having a wavelength having an absorptivity to the layer 4 to process and cut the functional layer 4 exposed at the bottom of the cutting groove 300 by the laser beam 51, the generated debris is removed by flowing with a liquid. It is a step.

  In the functional layer cutting step ST4, the laser processing apparatus 50 holds the functional layer 4 side of the wafer 1 on the chuck table via the adhesive tape 200, and divides the processing head 52 and the chuck table as shown in FIG. Liquid is ejected from the processing head 52 while relatively moving along the line 6 to form a liquid column 54, and through a condenser lens 53, a wavelength (eg, 355 nm) having an absorptivity for the functional layer 4 is emitted. The laser beam 51 is guided into the liquid column 54 to irradiate the functional layer 4 exposed at the bottom 301 of the cutting groove 300. The laser beam 51 is applied to the wafer 1 in the liquid column 54. The laser beam 51 guided into the liquid column 54 is reflected by the outer peripheral surface of the liquid column 54 and is irradiated on the functional layer 4 exposed at the bottom 301 of the cutting groove 300. In the functional layer cutting step ST4, the functional layer 4 exposed at the bottom of the cutting groove 300 is ablated in each planned dividing line 6, and the functional layer 4 exposed at the bottom of the cutting groove 300 is cut, so that the wafer 1 Is divided into individual devices 5. In the functional layer cutting step ST4, the metal film and TEG formed on the planned dividing line 6 (not shown) are also divided. Further, in the functional layer cutting step ST4, the debris generated when the functional layer 4 is subjected to the ablation process is made to flow by the liquid that constitutes the liquid column 54 and removed from the inner surface of the cutting groove 300 and the like. As shown in FIG. 8, the wafer processing method proceeds to a grinding step ST5 when the functional layer 4 exposed at the bottom of the cutting groove 300 is divided on all the planned dividing lines 6.

(Grinding step)
FIG. 9 is a side sectional view showing a grinding step of the method for processing the wafer shown in FIG. The grinding step ST5 is a step of grinding the back surface 7 of the wafer 1 to make the finished thickness 100 of the wafer 1 after the plasma etching step ST3 and the functional layer cutting step ST4.

  In the 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 grinding step ST5, as shown in FIG. 9, while the spindle 63 rotates the grinding wheel 64 for finish grinding and the chuck table 61 is rotated about the axis, the grinding water is supplied and the grinding wheel 65 for finish grinding is supplied. By bringing the chuck table 61 closer to the chuck table 61 at a predetermined feeding speed, the grinding wheel 65 for finish grinding finishes the back surface 7 of the wafer 1, that is, the device 5. In the 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 cutting step ST4 and the 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 which is finish-ground in the 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 cutting groove 300 with the laser beam 71.

  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 cutting groove 300 is subjected to ablation processing in each division line 6 to divide the die-attach film 202 exposed in the cutting groove 300. As shown in FIG. 12, the wafer processing method is completed when the die attach film 202 exposed in the cutting grooves 300 is divided on all the planned dividing lines 6. 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, and realizes plasma dicing without a mask. You can 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 adhered to the functional layer 4 side in the protective member disposing step ST1 before the cutting step ST2 and the grinding step ST5. For this reason, it is possible to prevent the contamination generated in the cutting step ST2 and the grinding step ST5 from adhering to the device 5.

  Further, in the wafer processing method, in the functional layer cutting step ST4, the functional layer 4 remaining on the groove bottom of the cutting groove 300 is irradiated with the laser beam 51 to divide the wafer. Therefore, after the plasma etching step ST3, the wafer is cut to the bottom of the cutting groove 300. 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 cutting step ST4, and the laser beam 51 is applied from the back surface 7 side in the functional layer cutting step ST4. Since the functional layer 4 on the bottom of the cutting groove 300 is irradiated, debris generated during ablation processing can be suppressed from adhering to the device 5.

  Further, the wafer processing method is such that, in the functional layer cutting step ST4, the laser beam 51 is guided into the liquid column 54 to irradiate the functional layer 4 exposed at the bottom of the cutting groove 300 to remove debris generated by ablation processing. The liquid composing the liquid column 54 is flowed and removed so as not to adhere to the inside of the cutting groove 300. As a result, the wafer processing method has an effect that debris does not adhere to the inner surface of the cutting groove 300, that is, the side surface of the device 5 after division.

  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 wafer has a thickness that is substantially equal to the combined thickness of the finished thickness 100, the thickness 101 removed in the plasma etching step ST3, and the thickness removed in the grinding step ST5. 1 can 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 other regions, and 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.

  In the plasma processing step ST3, the wafer processing method according to the third embodiment uses the remote plasma type plasma apparatus. Therefore, in the plasma 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, in the present invention, in both the 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, for finishing grinding with smaller abrasive grains than the preliminary grinding wheel 85. The back surface 7 of the wafer 1 may be subjected to finish grinding with the grindstone 65, the back surface 7 of the wafer 1 may only be subjected to rough grinding, or the back surface 7 of the wafer 1 may be subjected to only finish grinding. 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 Divided Line 7 Back 8 Surface 10 Cutting Device 12 Cutting Blade 13 Chuck Table 20 Plasma Device 21 Chuck Table 51 Laser Beam 54 Liquid Column 100 Finished Thickness 200 Adhesive Tape (Protective Member)
300 cutting groove 301 bottom ST1 protective member disposing step ST2 cutting step ST3 plasma etching step ST4 functional layer cutting step ST5 grinding step ST10 preliminary grinding step

Claims (3)

A wafer processing method of dividing a wafer, in which a plurality of devices are formed by a functional layer laminated on the surface of a substrate, along a dividing line that divides the plurality of devices,
Disposing a protective member on the surface of the wafer, a protective member disposing step,
The protection member side of the wafer is held by a chuck table of a cutting device, a cutting blade is cut into the back surface of the wafer, and a cutting groove having a depth that does not reach the functional layer is formed along the division line. A cutting step to form
The protection member side of the wafer is held by a chuck table of a plasma device, plasmaized gas is supplied to the back surface side of the wafer, and the substrate remaining at the bottom of the cutting groove is removed by etching. A plasma etching step of dividing along the dividing line,
While ejecting a liquid from the back surface side of the wafer to form a liquid column and guiding a laser beam into the liquid column, the functional layer exposed at the bottom of the cutting groove is processed and cut by the laser beam. And a functional layer cutting step of removing generated debris by flowing it with the liquid.   The wafer processing method according to claim 1, further comprising a preliminary grinding step of previously grinding the back surface of the wafer before the plasma etching step.   The method of processing a wafer according to claim 1, further comprising a grinding step of grinding the back surface of the wafer after the plasma etching step.

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