JP6308895B2 - Wafer processing method - Google Patents

Description

  The present invention relates to a processing method for processing a wafer on which a structure to be a micromachine device is formed.

  In recent years, the demand for micromachine devices (also referred to as MEMS (Micro Electro Mechanical Systems) devices) represented by acceleration sensors and pressure sensors is increasing. A device chip including a micromachine device, for example, divides the surface of a wafer made of a material such as silicon by a plurality of division lines, and after forming a structure to be a micromachine device in each region, follows the division lines. Then, it can be manufactured by dividing the wafer (see, for example, Patent Document 1).

JP 2009-76823 A

  By the way, in the above-described method of cutting a wafer including a micromachine device with a cutting blade to divide the wafer into a plurality of device chips, a fragile structure constituting the micromachine device is generated by the impact of the cutting fluid sprayed to remove the cutting waste. It may be damaged. On the other hand, if a method of dividing a wafer using a laser beam is adopted, this problem can be avoided. However, since an expensive laser processing apparatus is required, there remains a problem in terms of introduction cost.

  It is also conceivable to divide the wafer using an etching process for forming a space called a cavity in the micromachine device. However, if the wafer is divided by etching the line to be divided at the time of forming the cavity, the position of the divided device chip is likely to shift in a subsequent processing step (additional processing step), and appropriate processing becomes difficult.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a wafer processing method capable of processing a wafer on which a micromachine device is formed appropriately and at low cost.

  According to the present invention, a plurality of scheduled division lines are formed in a lattice shape on the surface, and a movable portion and a fixed portion connected to the movable portion are provided in a plurality of regions partitioned by the plurality of scheduled division lines. A method of processing a wafer on which a micromachine device having the above structure is formed, wherein the back surface side of the wafer corresponding to the fixed portion of the micromachine device is coated with a resist film, and the back surface side of the wafer corresponding to the movable portion is coated. In addition to exposing, the back side of the wafer corresponding to the planned dividing line is intermittently covered with a resist film, and the exposed area is shorter than one side of the micromachine device where the back side of the wafer is exposed. And a resist film coating process in which regions are alternately provided along the planned dividing lines, and a back surface side of the wafer on which the resist film coating process is performed Etching step of performing plasma etching, forming a recess reaching the movable portion on the back side corresponding to the movable portion of the wafer, and forming a through hole corresponding to the exposed region along the planned dividing line, An additional process for performing a predetermined additional process on the wafer after the etching process, a resist film removing process for removing the resist film before or after the additional process, the resist film removing process, and the additional process And a wafer supporting step of attaching the back side of the wafer to a dicing tape mounted on an annular frame, and extending the dicing tape to apply an external force to the wafer along the scheduled division line. And a dividing step of dividing the wafer.

  In the present invention, the resist film in the covering region corresponding to the division line is formed thinner than the resist film covering the back side of the wafer corresponding to the fixed portion, and the covering region of the wafer after the etching step The thickness of the portion corresponding to is preferably smaller than the thickness of the portion corresponding to the fixed portion.

  In the wafer processing method of the present invention, in the etching process in which the concave portion reaching the movable part of the micromachine device is formed on the back surface side of the wafer, the through holes are intermittently formed along the planned dividing line, and external force is applied in the subsequent dividing process. In addition, since the wafer is divided, the micromachine device is not damaged due to the impact of the cutting fluid as in the case of cutting with a cutting blade.

  Further, since it is not necessary to use an expensive laser processing apparatus, the processing cost can be kept low. Furthermore, in the etching process, since the device chip is kept connected by intermittently forming through holes along the planned dividing line, the position of the device chip is not shifted in the additional process after the etching process. The wafer can be processed appropriately.

  As described above, according to the present invention, it is possible to provide a wafer processing method capable of processing a wafer on which a micromachine device is formed appropriately and at low cost.

FIG. 1A is a perspective view schematically illustrating a configuration example of a wafer, and FIG. 1B is a cross-sectional view schematically illustrating a configuration example of a wafer. FIG. 2A is a plan view schematically showing the resist film coating step, and FIG. 2B is a cross-sectional view schematically showing the resist film coating step. It is a longitudinal cross-sectional schematic diagram which shows typically the structural example of a plasma etching apparatus. 4A is a plan view schematically showing the wafer after the etching step, and FIG. 4B is a cross-sectional view schematically showing the wafer after the etching step. It is a perspective view which shows a wafer support process typically. 6A and 6B are partial cross-sectional side views schematically showing the dividing step.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The wafer processing method according to the present embodiment includes a resist film coating process (see FIGS. 2A and 2B), an etching process (see FIGS. 4A and 4B), and an additional process. , A resist film removing step, a wafer supporting step (see FIG. 5), and a dividing step (see FIGS. 6A and 6B).

  In the resist film coating process, the back surface side of the wafer corresponding to the fixed part of the micromachine device formed on the front surface of the wafer is coated with the resist film, and the back surface side of the wafer corresponding to the division line is intermittently covered with the resist film. Cover. In the etching step, the back surface side of the wafer is plasma etched to form a recess reaching the movable part of the micromachine device on the back surface side of the wafer, and through holes along the division lines are intermittently formed.

  In the additional processing step, arbitrary additional processing is performed on the wafer. In the resist film removing step, the resist film remaining on the back side of the wafer is removed. In the wafer support step, the wafer is attached to a dicing tape mounted on an annular frame, and the wafer is supported by the annular frame. In the dividing step, the dicing tape is expanded and an external force is applied to divide the wafer along the division line. Hereinafter, the wafer processing method according to the present embodiment will be described in detail.

  First, a wafer processed by the wafer processing method according to the present embodiment will be described. FIG. 1A is a perspective view schematically illustrating a configuration example of a wafer, and FIG. 1B is a cross-sectional view schematically illustrating a configuration example of a wafer.

  As shown in FIG. 1A, the wafer 11 is a substantially circular plate-like object formed of, for example, a semiconductor material such as silicon, and the surface 11a surrounds the central device region 13 and the device region 13. It is divided into an outer peripheral surplus area 15.

  The device region 13 is further divided into a plurality of regions by division lines (streets) 17 arranged in a lattice pattern, and a micromachine device 19 typified by an acceleration sensor or a pressure sensor is formed in each region. ing. The outer periphery 11c of the wafer 11 is chamfered and rounded.

  As shown in FIG. 1B, the micromachine device 19 includes a movable portion 19a that is displaced according to acceleration, pressure, and the like. A fixed portion 19b that supports the movable portion 19a is disposed around the movable portion 19a, and at least a part of the movable portion 19a is connected to the fixed portion 19b. The shape of the movable portion 19a in plan view is, for example, a circle (see FIG. 4A), but may be other shapes.

  In the wafer processing method according to the present embodiment, first, a resist film coating step of coating the back surface 11b side of the wafer 11 with a resist film is performed. FIG. 2A is a plan view schematically showing the resist film coating step, and FIG. 2B is a cross-sectional view schematically showing the resist film coating step. Note that FIG. 2B shows an AA cross section of FIG.

  In this resist film coating step, for example, a mask (not shown) in which an opening corresponding to a resist film formation region is formed is placed on the back surface 11b side of the wafer 11, and resist material resistant to later plasma etching is used. Is dropped toward the opening of the mask. Thereafter, the resist material is cured by drying and heating, and the mask is removed from the back surface 11b side of the wafer 11, whereby a desired resist film can be formed on the back surface 11b side of the wafer 11.

  As shown in FIGS. 2A and 2B, in this embodiment, a plurality of resist films 21 are formed to cover the back surface 11b of the wafer 11 corresponding to the fixing portion 19b of the micromachine device 19. Each resist film 21 is formed with a circular opening 21a corresponding to the movable portion 19a of the micromachine device 19, and the back surface 11b of the wafer 11 corresponding to the movable portion 19a is exposed.

  In the present embodiment, a plurality of resist films 23 are formed that intermittently cover the back surface 11 b corresponding to the planned division line 17 along the planned division line 17. Thereby, the back surface 11b side of the wafer 11 is divided along the planned dividing line 17 into a covered region B covered with each resist film 23 and an exposed region C where the back surface 11b of the wafer 11 is exposed. That is, the covered areas B and the exposed areas C are alternately provided along the scheduled division line 17.

  Each resist film 23 is formed at a position where two adjacent resist films 21 can be connected with the planned dividing line 17 in between. Specifically, the interval between two adjacent resist films 23 is set to be shorter than one side of the micromachine device 19. That is, the length of the exposed region C in the direction along the division line 17 is shorter than one side of the micromachine device 19.

  The resist film 23 corresponding to the planned dividing line 17 is preferably formed thinner than the resist film 21 corresponding to the fixing portion 19b. Such resist films 21 and 23 can be formed, for example, by repeating the above-described steps a plurality of times. Alternatively, the resist films 21 and 23 having different thicknesses may be formed by a method such as inkjet or photolithography using a gray tone mask.

  After the resist film coating process, an etching process for plasma etching the back surface 11b side of the wafer 11 is performed. FIG. 3 is a schematic vertical cross-sectional view schematically showing a configuration example of a plasma etching apparatus that performs an etching process.

  As shown in FIG. 3, the plasma etching apparatus 2 includes a vacuum chamber 6 that forms a processing space 4. An opening 8 for carrying in and out the wafer 11 is formed in the side wall 6 a of the vacuum chamber 6.

  A gate 10 that opens and closes the opening 8 is attached to the outside of the opening 8. An opening / closing device 12 is provided below the gate 10, and the gate 10 moves up and down by the opening / closing device 12. The gate 10 is moved downward by the opening / closing device 12 and the opening 8 is opened, whereby the wafer 11 is carried into the processing space 4 of the vacuum chamber 6 through the opening 8 or the wafer 11 is unloaded from the processing space 4 of the vacuum chamber 6. it can.

  An exhaust port 14 is formed in the bottom wall 6 b of the vacuum chamber 6. The exhaust port 14 is connected to an exhaust device 16 such as a vacuum pump. In the processing space 4 of the vacuum chamber 6, the lower electrode 18 and the upper electrode 20 are disposed so as to face each other.

  The lower electrode 18 is made of a conductive material, and includes a disk-shaped holding portion 22 and a columnar support portion 24 extending downward from the center of the lower surface of the holding portion 22. The support portion 24 is inserted through an opening 26 formed in the bottom wall 6 b of the vacuum chamber 6.

  In the opening 26, an insulating bearing 28 is disposed between the bottom wall 6 b and the support portion 24, and the vacuum chamber 6 and the lower electrode 18 are insulated. The lower electrode 18 is connected to the high frequency power supply 30 outside the vacuum chamber 6.

  A recess is formed on the upper surface of the holding unit 22, and a table 32 on which the wafer 11 is placed is installed in the recess. The table 32 is provided with a suction path (not shown), and this suction path is connected to a suction source 36 through a flow path 34 and the like formed inside the lower electrode 28.

  In addition, a cooling flow path 38 is formed inside the holding unit 22. One end of the cooling flow path 38 is connected to the circulation device 42 through a refrigerant supply path 40 formed in the support portion 24, and the other end of the cooling flow path 38 is connected through a refrigerant discharge path 44 formed in the support section 24. The circulation device 42 is connected. When the circulation device 42 is operated, the refrigerant flows in the order of the refrigerant supply path 40, the cooling flow path 38, and the refrigerant discharge path 44 to cool the lower electrode 18.

  The upper electrode 20 is made of a conductive material and includes a disk-shaped gas ejection part 46 and a columnar support part 48 extending upward from the center of the upper surface of the gas ejection part 46. The support portion 48 is inserted through an opening 50 formed in the upper wall 6 c of the vacuum chamber 6.

  In the opening 50, an insulating bearing 52 is disposed between the upper wall 6 c and the support portion 48, and the vacuum chamber 6 and the upper electrode 20 are insulated. The upper electrode 20 is connected to a high frequency power supply 30 outside the vacuum chamber 6. Further, the upper end portion of the support portion 48 is connected to a support arm 58 of the elevating mechanism 56, and the upper electrode 20 moves up and down by the elevating mechanism 56.

  A plurality of gas ejection ports 60 are formed on the lower surface of the gas ejection part 46. The gas outlet 60 is connected to a gas supply source 64 through a flow path 62 and the like. Thereby, the raw material gas for etching can be supplied to the processing space 4 in the vacuum chamber 6.

  In the etching process, first, the gate 10 is lowered by the opening / closing mechanism 12. Next, the wafer 11 is carried into the processing space 4 of the vacuum chamber 6 through the opening 8 and placed on the table 32 of the lower electrode 18. In this etching step, the wafer 11 is placed on the table 32 so that the back surface 11b side is exposed upward. Further, when the wafer 11 is carried in, the upper electrode 20 is raised by the elevating mechanism 56 to secure a loading space for the wafer 11.

  Thereafter, the negative pressure of the suction source 36 is applied to fix the wafer 11 on the table 32. Further, the gate 10 is raised by the opening / closing mechanism 12 to seal the processing space 4. Further, the upper electrode 20 is lowered by the elevating mechanism 56 so that the lower electrode 18 and the upper electrode 20 have a predetermined positional relationship suitable for plasma etching. Further, the exhaust device 16 is operated to make the processing space 4 vacuum (low pressure).

  In this state, if a predetermined high frequency power is supplied to the lower electrode 18 and the upper electrode 20 by the high frequency power supply 30 while supplying a raw material gas for etching from the gas supply source 64 at a predetermined flow rate, the lower electrode 18 and the upper electrode 20 are supplied. Plasma containing radicals and ions is generated between the two. Thereby, the back surface 11b side of the wafer 11 is etched (plasma etching). The etching source gas is appropriately selected according to the material of the wafer 11 and the like.

  4A is a plan view schematically showing the wafer after the etching step, and FIG. 4B is a cross-sectional view schematically showing the wafer after the etching step. Note that FIG. 4B shows a cross section taken along the line AA in FIG. 4A and 4B show the wafer 11 with the resist films 21 and 23 removed.

  As described above, the back surface 11 b of the wafer 11 corresponding to the fixed portion 19 b is covered with the resist film 21. Therefore, as shown in FIGS. 4A and 4B, the back surface 11b side of the wafer 11 corresponding to the fixing portion 19b remains almost unremoved in the etching process.

  On the other hand, the back surface 11b of the wafer 11 corresponding to the movable portion 19a is exposed without being covered with the resist film 21 as described above. Therefore, the back surface 11b side of the wafer 11 corresponding to the movable portion 19a is removed by etching.

  Thereby, the support part 25 which supports the fixing | fixed part 19b, and the recessed part 25a corresponding to the movable part 19a are formed. In addition, the recessed part 25a is formed in the depth which reaches the movable part 19a. That is, as shown in FIG. 4A, the movable portion 19a is exposed to the back surface 11b side of the wafer 11 through the recess 25a.

  Further, the back surface 11b of the wafer 11 corresponding to the division line 17 is intermittently covered with the resist film 23 as described above. Therefore, mainly, the exposed region C not covered with the resist film 23 is removed by etching. Thereby, the connection part 27 corresponding to the covering region B and the through hole 27a corresponding to the exposed region C are formed.

  As described above, since the resist film 23 is formed so as to connect the two resist films 21 adjacent to each other with the planned division line 17 interposed therebetween, the two support portions 25 adjacent to each other with the planned division line 17 also interposed therebetween. They are connected by a connecting part 27.

  In the present embodiment, since the resist film 23 is formed thinner than the resist film 21, the resist film 23 disappears and the coating region B is removed to some extent as the etching proceeds. As a result, a connecting portion 27 thinner than the support portion 25 is formed.

  After the etching process, an additional process and a resist film removing process are performed. In the additional process, a step of forming a reinforcing structure of the micromachine device 19 and a step of forming a cavity in the micromachine device 19 are performed. However, the content of processing is not limited to these, and can be set arbitrarily.

  In the resist film removing step, the resist film 21 remaining on the back surface 11b side of the wafer 11 is removed by a method such as ashing. When the resist films 21 and 23 are formed to have the same thickness, there is a high possibility that the resist film 23 remains. Thus, when the resist film 23 remains, the resist film 23 is also removed in the resist film removing step.

  In addition, the order of an additional process process and a resist film removal process is not specifically limited. The resist film removing process may be performed after the additional process is performed, or the additional process may be performed after the resist film removing process.

  After the additional processing step and the resist film removal step, a wafer support step is performed. FIG. 5 is a perspective view schematically showing the wafer support process. As shown in FIG. 5, in the wafer support step, a dicing tape 31 having a diameter larger than that of the wafer 11 is attached to the back surface 11 b side of the wafer 11.

  An annular frame 33 is attached to the outer periphery of the dicing tape 31. As a result, the wafer 11 is supported by the annular frame 33 via the dicing tape 31.

  After the wafer support process, a dividing process for dividing the wafer 11 along the scheduled dividing line 17 is performed. 6A and 6B are partial cross-sectional side views schematically showing the dividing step.

  As shown in FIG. 6A, the dividing step is performed by the expanding device 72. The expanding device 72 includes a support structure 74 that supports the wafer 11 and a cylindrical expansion drum 76 that expands the dicing tape 31 attached to the back surface 11 b side of the wafer 11. The inner diameter of the expansion drum 76 is larger than the outer diameter of the wafer 11, and the outer diameter of the expansion drum 76 is smaller than the inner diameter of the frame 33.

  The support structure 74 includes an annular frame support table 78 that supports the frame 33. The upper surface of the frame support table 78 is a mounting surface on which the frame 33 is mounted. A plurality of clamps 80 for fixing the frame 33 are provided on the outer peripheral portion of the frame support table 78.

  A lifting mechanism 82 is provided below the support structure 74. The lifting mechanism 82 includes a cylinder case 84 fixed to a base (not shown) and a piston rod 86 inserted through the cylinder case 84. A frame support table 78 is fixed to the upper end portion of the piston rod 86.

  The elevating mechanism 82 positions the upper surface (mounting surface) of the frame support table 78 at a reference position having a height substantially equal to the upper end of the extension drum 76 and an extension position below the upper end of the extension drum 76. The support structure 74 is raised and lowered.

  In the dividing step, first, as shown in FIG. 6A, the frame 33 supporting the wafer 11 is placed on the upper surface of the frame support table 78 positioned at the reference position, and fixed by the clamp 80. Thereby, the upper end of the expansion drum 76 contacts the dicing tape 31 positioned between the outer periphery of the wafer 11 and the inner periphery of the frame 33.

  Next, the support structure 74 is lowered by the elevating mechanism 82, and the upper surface of the frame support table 78 is positioned at the extended position below the upper end of the expansion drum 76, as shown in FIG. As a result, the expansion drum 76 rises with respect to the frame support table 78, and the dicing tape 31 expands so as to be pushed up by the expansion drum 76.

  As described above, the through holes 27 a are intermittently formed in the wafer 11 along the scheduled division lines 17. Therefore, when the dicing tape 31 is expanded and an external force is applied, the wafer 11 is divided into a plurality of device chips 35 starting from the through holes 27a.

  As described above, in the wafer processing method according to the present embodiment, in the etching process for forming the concave portion 25a reaching the movable portion 19a of the micromachine device 19 on the back surface 11b side of the wafer 11, the through hole 27a along the division line 17 is formed. Since the wafer 11 is divided by applying an external force in the subsequent dividing step, the micromachine device 19 is not damaged by the impact of the cutting fluid as in the case of cutting with a cutting blade.

  Further, since it is not necessary to use an expensive laser processing apparatus, the processing cost can be kept low. Furthermore, in the etching process, since the device chip 35 is kept connected by intermittently forming the through holes 27a along the planned dividing line 17, the position of the device chip 35 in the additional process after the etching process is maintained. Therefore, the wafer 11 can be appropriately additionally processed.

  Further, in the wafer processing method according to the present embodiment, the connecting portion 27 is formed thinner than the support portion 25 by forming the resist film 23 thinner than the resist film 21, so that the thin connecting portion is formed in the subsequent dividing step. The wafer 11 can be appropriately divided starting from 27.

  Note that the configurations, methods, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention.

DESCRIPTION OF SYMBOLS 11 Wafer 11a Front surface 11b Back surface 11c Outer periphery 13 Device area | region 15 Outer periphery excess area | region 17 Divided line (street)
DESCRIPTION OF SYMBOLS 19 Micromachine device 19a Movable part 19b Fixed part 21 Resist film 21a Opening 23 Resist film 25 Support part 25a Concave part 27 Connection part 27a Through hole 31 Dicing tape 33 Frame 35 Device chip B Covering area C Exposed area 2 Plasma etching apparatus 4 Processing space 6 Vacuum chamber 6a Side wall 6b Bottom wall 6c Top wall 8 Opening 10 Gate 12 Opening / closing mechanism 14 Exhaust port 16 Exhaust device 18 Lower electrode 20 Upper electrode 22 Holding part 24 Support part 26 Opening 28 Bearing 30 High frequency power supply 32 Table 34 Flow path 36 Suction source DESCRIPTION OF SYMBOLS 38 Cooling flow path 40 Refrigerant introduction path 42 Circulating device 44 Refrigerant discharge path 46 Gas ejection part 48 Support part 50 Opening 52 Bearing 56 Lifting mechanism 58 Support arm 60 Jet outlet 62 Channel 64 Gas supply source 72 Expanding apparatus 74 Support structure 76 Expansion drum 78 Frame support table 80 Clamp 82 Lifting mechanism 84 Cylinder case 86 Piston rod

Claims (2)

A micromachine device having a plurality of division lines formed on the surface in a lattice shape and having a movable portion and a fixed portion connected to the movable portion in a plurality of regions partitioned by the plurality of division lines. A method for processing a formed wafer, comprising:
The back side of the wafer corresponding to the fixed part of the micromachine device is coated with a resist film to expose the back side of the wafer corresponding to the movable part, and the back side of the wafer corresponding to the division line is resisted. Resist film coating in which a coating region that is intermittently covered with a film and covered with a resist film and an exposed region that is shorter than one side of the micromachine device where the back surface of the wafer is exposed are alternately provided along the division line Process,
Plasma etching is performed from the back surface side of the wafer on which the resist film coating step has been performed, and a recess reaching the movable portion is formed on the back surface side corresponding to the movable portion of the wafer, and the exposure is performed along the division line. An etching step for forming a through hole corresponding to the region;
An additional processing step for performing a predetermined additional processing on the wafer after the etching step;
A resist film removing step for removing the resist film before or after the additional processing step;
After the resist film removing step and the additional processing step are performed, a wafer supporting step of attaching the back side of the wafer to a dicing tape attached to an annular frame,
A dividing step of applying an external force to the wafer by dividing the dicing tape to divide the wafer along the scheduled dividing line. The resist film in the covering region corresponding to the division line is formed thinner than the resist film covering the back side of the wafer corresponding to the fixed portion, and the portion corresponding to the covering region of the wafer after the etching step The wafer processing method according to claim 1, wherein the thickness of the wafer is thinner than a thickness of a portion corresponding to the fixed portion.