JP6653055B2 - Wafer dividing method and wafer dividing apparatus - Google Patents

Description

  The present invention relates to a wafer dividing method and a wafer dividing apparatus.

  The wafer having the semiconductor elements formed on its surface is subjected to cutting such as cutting or grooving by a dicing device. The dicing apparatus includes a thin disk-shaped blade that is rotated at a high speed by a spindle, and a table that holds the wafer by suction. The wafer that is suction-held on the table is formed into a lattice by the blade that rotates at a high speed. Cutting along the divided line. The blade and the table are relatively moved by X, Y, Z, and θ moving units provided in the dicing apparatus. As a result, the wafer is cut along the dividing line.

  2. Description of the Related Art In recent years, in the field of semiconductor manufacturing, wafers tend to increase in size year by year, and wafers are becoming thinner in order to increase mounting density. In order to make the wafer thinner, back grinding (back grinding) for grinding the back surface of the wafer is performed.

  For example, Patent Document 1 proposes a DBG (Dicing Before Grinding) method (also referred to as a pre-dicing method) as a method of dividing a wafer having a semiconductor element formed on a surface into individual chips. In the DBG method, a cutting groove of a predetermined depth is formed (half cut) from a surface of a wafer (a surface on which devices are formed) along a line to be divided, and a protective tape is attached to the surface of the wafer. This is a method of dividing the wafer into individual chips by grinding the back surface of the wafer until the wafer reaches the cutting groove. According to the DBG method, it is possible to suppress breakage at the time of dividing the wafer, as compared with a method of performing dicing after grinding the back surface of the wafer.

JP-A-9-213662

  However, the above-mentioned DBG method has the following problems.

  In other words, the blade changes its cross-sectional shape into an R shape (arc shape) with wear, but when cutting is performed using a blade with an R shape formed at the tip, the blade tip shape changes to the shape of the cutting groove. It is transferred as it is, and the corner at the bottom (lower end side) of the cutting groove does not become vertical but becomes R-shaped. The R-shaped portion formed at the bottom of the cutting groove is a weak portion in terms of strength, and is easily chipped easily when a small impact is applied when grinding the back surface of the wafer. For this reason, after the wafer is divided into individual chips, defects such as chipping easily occur in the obtained chips. On the other hand, in order to prevent such inconvenience, it is conceivable to reduce the impact applied at the time of grinding the back surface of the wafer by lowering the grinding speed of the back surface of the wafer, but this will reduce the overall throughput. Would.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a wafer dividing method and a wafer dividing apparatus that can prevent problems such as chipping without lowering throughput.

  In order to achieve the above object, the wafer dividing method according to the first aspect of the present invention forms a cutting groove by a blade from a front surface side of a wafer along a planned dividing line of a wafer having a semiconductor element formed on the surface, A wafer dividing method in which a protective tape is adhered to a surface of a wafer on which a cutting groove is formed, and the back surface of the wafer is ground to expose the cutting groove on the back surface of the wafer and separate the wafer into individual chips. Or, an inspection groove forming step of forming an inspection groove by a blade on a dummy wafer, and an inspection groove for acquiring shape information of the inspection groove based on an image of a wafer or a dummy wafer on which the inspection groove is formed. The method includes a shape detection step and a grinding speed control step of controlling the grinding speed of the back surface of the wafer based on the shape information of the inspection groove.

  In the wafer dividing method according to the second aspect of the present invention, in the first aspect, the grinding speed control step may include setting a grinding speed of the back surface of the wafer to a first thickness until the wafer has a first thickness corresponding to a cutting depth of a blade. One grinding speed, and thereafter, a second grinding speed lower than the first grinding speed until the wafer has a second thickness smaller than the first thickness.

  In the wafer dividing method according to the third aspect of the present invention, in the first aspect or the second aspect, a blade diameter calculating step of calculating a blade diameter of a blade based on shape information of the inspection groove, and forming a cutting groove in the wafer A cutting depth control step of changing the cutting depth of the blade when performing the cutting based on the blade diameter calculated in the blade diameter calculating step.

  The wafer dividing apparatus according to the fourth aspect of the present invention forms a cutting groove by a blade from a front surface side of a wafer along a line to be divided of a wafer having a semiconductor element formed on the surface, and forms a cutting groove on the wafer. A wafer dividing device that applies a protective tape to the front surface, grinds the back surface of the wafer, exposes the cutting grooves on the back surface of the wafer, and separates the wafer into individual chips. Imaging means for imaging the inspection groove, inspection groove shape detection means for acquiring shape information of the inspection groove based on the image taken by the imaging means, and a back surface of the wafer based on the shape information of the inspection groove. Grinding speed control means for controlling the grinding speed of the workpiece.

  In the wafer dividing apparatus according to a fifth aspect of the present invention, in the fourth aspect, the grinding speed control means sets the grinding speed of the back surface of the wafer to a first thickness until the wafer reaches the first thickness corresponding to the cutting depth of the blade. One grinding speed, and thereafter, a second grinding speed lower than the first grinding speed until the wafer has a second thickness smaller than the first thickness.

  A wafer dividing apparatus according to a sixth aspect of the present invention, in the fourth aspect or the fifth aspect, wherein blade diameter calculating means for calculating a blade diameter of the blade based on shape information of the inspection groove, and forming a cutting groove in the wafer. Cutting depth control means for changing the cutting depth of the blade at the time of cutting based on the blade diameter calculated by the blade diameter calculating means.

  According to the present invention, it is possible to prevent problems such as chipping without lowering the throughput.

Flow chart showing a wafer dividing method according to an embodiment of the present invention External view showing the configuration of a dicing apparatus used in the present embodiment FIG. 2 is a plan view showing an example of a wafer to be diced by the dicing apparatus shown in FIG. Schematic diagram showing how inspection grooves are formed Schematic diagram showing a state where the surface of the wafer is imaged by the imaging means Block diagram showing the configuration of the controller The figure which showed the inspection groove | channel formed in the wafer W. Enlarged plan view in which a part of FIG. 7 is enlarged. Schematic diagram showing the positional relationship between the blade and the wafer Sectional view of inspection groove formed in wafer viewed from the side (X direction) Schematic diagram showing the cutting grooves formed on the wafer by the dicing process Schematic showing protection tape attached to wafer surface Schematic diagram showing the configuration of the back surface grinding device used in the back surface grinding step according to the present embodiment Diagram for explaining back grinding process

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a flowchart illustrating a wafer dividing method according to an embodiment of the present invention.

  As shown in FIG. 1, the wafer dividing method according to the present embodiment forms a cutting groove with a blade from a front surface side of a wafer along a planned dividing line of a wafer having a semiconductor element formed on the surface. A wafer dividing method in which a protective tape is attached to the surface of the wafer, and the back surface of the wafer is ground to expose a cut groove on the back surface of the wafer and separate the wafer into individual chips. (Step S10), a dicing step (Step S12), a tape attaching step (Step S14), and a back surface grinding step (Step S16). Hereinafter, before describing each step, an outline of the configuration of a dicing apparatus used in the present embodiment will be described.

  FIG. 2 is an external view showing the configuration of the dicing apparatus used in the present embodiment. FIG. 3 is a plan view showing an example of a wafer to be diced by the dicing apparatus shown in FIG.

  As shown in FIG. 2, the dicing apparatus 10 includes a load port 12 for transferring a cassette containing a plurality of wafers W to and from an external device, and a transfer unit having a suction unit 14 and transferring the wafer W to each unit of the apparatus. Means 16, a table 18 on which the wafer W is placed, a processing section 20 where the processing of the wafer W is performed, an imaging means 26 for imaging the surface of the wafer, and a spinner 22 for cleaning and drying the processed wafer W; It has. The operation of each part of the dicing apparatus 10 is controlled by a controller 24 as control means.

  The processing unit 20 is provided with an air-bearing spindle 32 with a built-in high-frequency motor and two blades 28 attached to the tip of the processing unit 20 so as to rotate at high speed at a predetermined rotation speed and to be independent of each other. Then, index feed in the Y direction and cut feed in the Z direction are performed. Further, the table 18 on which the wafer W is mounted by suction is configured to be rotatable around the axis in the Z direction, and is configured to be ground and fed in the X direction in FIG. .

  As the blade 28, an electrodeposition blade in which diamond abrasive grains or CBN abrasive grains are electrodeposited with nickel, a metal resin bond blade in which a resin mixed with metal powder is bonded, and the like are used.

  The controller 24 controls the X, Y, and θ movement axes (not shown) based on the image captured by the imaging unit 26 to perform alignment (alignment) between the wafer W and the blade 28.

  In the dicing apparatus 10 configured as described above, first, a cassette storing a plurality of wafers W is placed on the load port 12 by a transfer device (not shown) or manually. The wafer W is taken out from the loaded cassette and is placed on the table 18 by the transport means 16.

  Here, as shown in FIG. 3, the surface of the wafer W to be diced is divided into a plurality of regions by lattice-like planned dividing lines (streets) L. A device (semiconductor element) S having a predetermined thickness is formed in each of the divided regions. The wafer W is placed on the table 18 with the surface of the wafer W facing upward.

  The surface of the wafer W placed on the table 18 in this way is imaged by the imaging means 26, and the position of the dividing line L formed on the surface of the wafer W and the position of the blade 28 are not shown. The table 18 can be adjusted and adjusted according to the X, Y, and θ moving axes.

  When the alignment is completed and dicing is started, the spindle 32 starts rotating, the blade 28 rotates at high speed, and a cutting fluid is supplied from a nozzle (not shown). In this state, the wafer W is processed and fed in the X direction shown in FIG. 1 by a moving shaft (not shown) together with the table 18, and the spindle 32 is lowered to a predetermined height in the Z direction to perform dicing.

  In the dicing apparatus 10 of the present embodiment, the cutting depth of the blade 28 in the dicing step (step S12) and the grinding speed of the back surface of the wafer W in the back surface grinding step (step S16) according to the tip shape (R shape) of the blade 28. Prior to these steps, a blade shape recognition processing step (step S10) described below is performed in order to control the process.

  In the blade shape recognition processing step, the wafer W to be diced is placed on the table 18 and the wafer W and the blade 28 are aligned with each other. Then, as shown in FIG. At the same time, the blade 28 is moved to a predetermined height position (Z-direction position) to perform the cutting and feeding in the Z-direction. Thereby, as shown in FIG. 5, an inspection groove (micro kerf) 50 having a predetermined depth is formed on the surface of the wafer W.

  Further, in the blade shape recognition processing step, as shown in FIG. 5, the surface of the wafer W is imaged by the imaging means 26, and the shape of the inspection groove 50 is detected from the image captured by the imaging means 26. Based on this, control of the cutting depth of the blade 28 in the dicing step (step S12) and the grinding speed of the back surface of the wafer W in the back surface grinding step (step S16) are performed.

  FIG. 6 is a block diagram showing the configuration of the controller 24. As shown in FIG. 6, the controller 24 includes an inspection groove shape detection unit 40, a blade diameter calculation unit 42, a groove depth calculation unit 44, a storage unit 46, And a depth control unit 48.

  The inspection groove shape detection unit 40 is a detection unit that acquires shape information of the inspection groove 50 formed on the surface of the wafer W by the blade 28 based on the image captured by the imaging unit 26.

  FIGS. 7A and 7B are views showing the state of the inspection groove 50 formed on the wafer W, FIG. 7A is a plan view of the inspection groove 50 formed on the wafer W as viewed from above, and FIG. 5 is a cross-sectional view of the inspection groove 50 formed in the wafer W as viewed from a side surface (Y direction). FIG. 8 is an enlarged plan view in which a part of FIG. 7A is enlarged. In each drawing, the inspection groove 50 is exaggerated for easy understanding.

  The inspection groove shape detection unit 40 performs image processing on the captured image captured by the imaging unit 26 by a known method, and performs inspection as shape information of the inspection groove 50 as illustrated in FIGS. 7 and 8. The length (kerf length) a of the inspection groove 50 and the length d of the straight portion (the portion excluding the tip portion where the R shape is formed) of the inspection groove 50 are detected and acquired. The shape information of the inspection groove 50 acquired by the inspection groove shape detection unit 40 is given to the blade diameter calculation unit 42 and the groove depth calculation unit 44.

  The blade diameter calculation unit 42 is a calculation unit that calculates the blade diameter (diameter) of the blade 28 in order to control the cutting depth of the blade 28 in the cutting depth control unit 48 described below. The blade diameter calculated by the blade diameter calculation unit 42 is used for obtaining groove depth information of the inspection groove 50 in a groove depth calculation unit 44 described later. The blade diameter calculator 42 is an example of a blade diameter calculator.

  The blade diameter calculation unit 42 calculates the shape information of the inspection groove 50 acquired by the inspection groove shape detection unit 40 and the height position (Z direction position) of the blade 28 detected by the blade height detection unit 34. Based on this, the blade diameter of the blade 28 is calculated. The blade height detection unit 34 is configured by known position detection means such as a linear scale, for example, and detects the distance from the surface of the wafer W to the rotation center of the blade 28 as the height position of the blade 28. The blade diameter calculated by the blade diameter calculation unit 42 is given to the groove depth calculation unit 44 and the cutting depth control unit 48.

  FIG. 9 is a schematic diagram showing a positional relationship between the blade 28 and the wafer W. As shown in FIG. 9, the inspection groove 50 cuts and feeds the blade 28 in the Z direction with respect to the wafer W without rotating the blade 28 and relatively moving the wafer W in the X direction while rotating the blade 28. It is formed by doing. At this time, the length (X-direction length) of the inspection groove 50 formed in the wafer W by the blade 28 is a, the blade diameter of the blade 28 is R, and the blade height detection unit 34 determines the height of the blade 28. When the distance from the surface of the wafer W to the rotation center of the blade 28 is detected as the height position (Z direction position) h, the blade diameter R is obtained by the following equation.

  The groove depth calculation unit 44 acquires the groove depth information of the inspection groove 50 so that the cut depth control unit 48 controls the cut depth of the blade 28. The groove depth information of the inspection groove 50 acquired by the groove depth calculation unit 44 is given to the cut depth control unit 48.

  FIG. 10 is a cross-sectional view of the inspection groove 50 formed in the wafer W as viewed from a side surface (X direction). 10, C1 indicates the cutting depth of the blade 28, and C2 indicates the depth of the R-shaped portion at the bottom of the inspection groove 50 (the groove formed by the R-shaped portion at the tip of the blade 28). . In the drawings, the inspection groove 50 is exaggerated for easy understanding.

  The groove depth calculation unit 44 is formed on the wafer W based on the blade diameter R calculated by the blade diameter calculation unit 42 and the shape information of the inspection groove 50 obtained by the inspection groove shape detection unit 40. The cut depth C1 in the inspection groove 50 and the depth C2 of the R-shaped portion at the bottom of the inspection groove 50 are calculated and obtained. Specifically, the cutting depth C1 of the blade 28 and the depth C2 of the R-shaped portion can be obtained by the following equations (2) and (3).

  After the blade shape recognition processing step (Step S10) is performed as described above, a dicing step (Step S12) is performed as shown in FIG. In the dicing process, a plurality of cutting grooves 54 are formed on the wafer W along the planned dividing line on the wafer W while the cutting depth of the blade 28 is controlled by the cutting depth control unit 48 as shown in FIG.

  The cutting depth control unit 48 is a control unit that controls the cutting depth of the blade 28 in the dicing process, and includes the groove depth information of the inspection groove 50 calculated by the groove depth calculating unit 44 and the blade diameter calculating unit 42. Based on the calculated blade diameter R, the cutting depth of the blade 28 is controlled.

  As shown in FIG. 11, the cutting depth of the blade 28 in the dicing step is set to N1, and the cutting depth (initial cutting depth) of the blade 28 when the blade 28 is new (not worn) is set to N0. When the wear amount of the blade 28 is Δe and the finished thickness of the chip is D, the cutting depth control unit 48 controls the cutting depth N1 of the blade 28 so as to satisfy the following equation.

N1 = N0 + Δe
= D + C2 + Δe (4)
The amount of wear Δe of the blade 28 can be obtained by the following equation, where R ₀ is the blade diameter of the blade 28 when the blade 28 is in a new state.

Δe = (R ₀ −R) / 2 (5)
Further, the cutting depth N1 of the blade 28 calculated by the cutting depth control unit 48 is stored in the storage unit 46. The cutting depth N1 of the blade 28 stored in the storage unit 46 is referred to by a control unit 74 (see FIG. 13) of the back surface grinding device 60 described later.

  As described above, in the dicing step in the present embodiment, a plurality of cutting grooves 54 are formed on the wafer W along the planned dividing line while the cutting depth of the blade 28 is controlled by the cutting depth control unit 48. Specifically, control is performed such that the cutting depth of the blade 28 increases as the blade diameter R decreases due to wear of the blade 28. Thus, even if the blade diameter R changes due to the wear of the blade 28, the cutting groove 54 is always formed by the blade 28 at a constant cutting depth from the surface of the wafer W without being affected by the change. And the reliability of the cutting depth of the blade 28 is improved.

  In the dicing step in the present embodiment, the R-shaped portion at the bottom of the cutting groove 54 is formed at a position deeper than the finished thickness D of the chip by controlling the cutting depth of the blade 28 by the cutting depth control unit 48. Therefore, the occurrence of chipping can be effectively suppressed in combination with the control of the back surface grinding speed described later.

  After the dicing step (Step S12) is performed, a tape attaching step (Step S14) is performed. In the tape attaching process, a protective tape (BG tape) 66 is attached to the surface of the wafer W by a tape attaching device (not shown) as shown in FIG. 12 in order to protect the devices S formed on the surface of the wafer W. Can be The protective tape 66 is made of a base material such as PET or polyolefin and an adhesive such as an acrylic synthetic resin, and the adhesive is adhered to the semiconductor element. The pressure-sensitive adhesive has a property that the bonding state in the resin is changed by irradiation with ultraviolet light, and the adhesive strength is reduced.

  The wafer W having the protective tape 66 adhered to the front surface is transferred to the back surface grinding device 60 by a transfer device (not shown). In the back surface grinding device 60, the back surface grinding step (Step S16) shown in FIG. 1 is performed.

  FIG. 13 is a schematic diagram showing a configuration of a back surface grinding device used in the back surface grinding step according to the present embodiment. As shown in FIG. 13, the back surface grinding device 60 includes a table 62 for holding the wafer W and a back grinder 64 for grinding the back surface of the wafer W.

  The wafer W is suction-held on the upper surface of the table 62 via a protective tape 66. The table 62 is rotated at a predetermined number of rotations around a rotation shaft 68.

  The back grinder 64 is provided above the table 62. The main body 70 of the back grinder 64 has a rotation shaft 72 arranged at a position eccentric with respect to the rotation shaft 68 of the table 62, and is rotated around the rotation shaft 72 at a predetermined rotation speed. A plurality of grindstones (not shown) are fixed to the lower surface of the main body 70 at predetermined intervals, and these grindstones are lowered together with the main body 70 toward the table 62. Accordingly, the grindstone is pressed against the back surface of the wafer W, and the back surface of the wafer W is ground. Then, the back surface of the wafer W is ground until the wafer W has a predetermined thickness (a thickness corresponding to the finished thickness of the chip). Thereby, the wafer W is separated into individual chips.

  The control unit 74 controls the operation of each unit such as the table 62 and the back grinder 64 of the back surface grinding device 60.

  The control unit 74 according to the present embodiment is an example of a grinding speed control unit. In order to prevent the R-shaped portion formed at the bottom of the cutting groove 54 from being chipped when grinding the back surface of the wafer W, the inspection groove shape is used. The grinding speed of the back surface of the wafer W by the back grinder 64 is controlled based on the shape information of the inspection groove 50 acquired by the detection unit 40.

  Specifically, the control unit 74 acquires the cutting depth N1 of the blade 28 with reference to the storage unit 46 illustrated in FIG. 6, and based on the cutting depth N1, the back surface of the wafer W by the back grinder 64. To control the grinding speed. As a detailed control method, the grinding speed of the back surface of the wafer W is set to the first thickness until the thickness of the wafer W reaches the first thickness (thickness corresponding to the cutting depth N1) shown in FIG. The grinding speed is set to V1, and thereafter, the thickness of the wafer W is changed from the first thickness shown in FIG. 14A to the second thickness (thickness corresponding to the finished thickness D of the chip) shown in FIG. 14B. Until the second grinding speed V2 is lower than the first grinding speed V1.

  In the back surface grinding step in the present embodiment, the above-described control is performed by the control unit 74, so that the grinding process is performed at a high speed (the first grinding speed V1) until the cutting groove 54 appears on the back surface of the wafer W. In the R-shaped portion of the cutting groove 54, the grinding process is performed at a low grinding speed (second grinding speed V2) on the back surface of the wafer W. Therefore, the occurrence of chipping can be prevented without chipping the R-shaped portion at the bottom of the cutting groove 54 when grinding the back surface of the wafer W, and the overall throughput can be improved.

  In the present embodiment, the wafer W is placed on the table 18 and the inspection groove is formed in the wafer W. However, the present invention is not limited to this, and the same material as the wafer W is used on the table 18. The configured dummy wafer may be mounted and an inspection groove may be formed in the dummy wafer.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said example, Of course, various improvement and modification may be performed in the range which does not deviate from the summary of this invention. It is.

  Reference Signs List 10 dicing device, 18 table, 24 controller, 26 imaging means, 28 blade, 32 spindle, 34 blade height detecting section, 40 groove detecting section for inspection, 42 blade diameter calculating section, 44 ... groove depth calculation unit, 46 ... storage unit, 48 ... cutting depth control unit, 50 ... inspection groove, 54 ... cutting groove, 60 ... back surface grinding device, 62 ... table, 64 ... back grinder, 66 ... protective tape

Claims (4)

A cutting groove is formed by a blade from the front surface side of the wafer along a scheduled dividing line of the wafer on which the semiconductor element is formed, and a protective tape is attached to the surface of the wafer on which the cutting groove is formed, A wafer dividing method for grinding the back surface of a wafer to expose the cut groove on the back surface of the wafer and separating the wafer into individual chips,
An inspection groove forming step of forming an inspection groove by the blade on the wafer or dummy wafer,
An inspection groove shape detection step of acquiring shape information of the inspection groove based on an image of the wafer or the dummy wafer on which the inspection groove is formed,
A blade diameter calculation step of calculating a blade diameter of the blade based on the shape information of the inspection groove,
A groove depth calculating step of calculating groove depth information including a cutting depth of the inspection groove and a depth of an R-shaped portion at the bottom of the inspection groove based on the blade diameter and the shape information of the inspection groove; When,
Based on the blade diameter and the groove depth information, a cutting depth control step of controlling the cutting depth of the blade when forming the cutting groove in the wafer,
A grinding speed control step of controlling the grinding speed of the back surface of the wafer based on the cutting depth of the blade ,
A wafer dividing method comprising: The grinding speed control step sets the grinding speed of the back surface of the wafer to a first grinding speed until the wafer has a first thickness corresponding to a cutting depth of the blade, and thereafter, the wafer has the first thickness. A second grinding speed lower than the first grinding speed until the second thickness is smaller than
The wafer dividing method according to claim 1. A cutting groove is formed by a blade from the front surface side of the wafer along a scheduled dividing line of the wafer on which the semiconductor element is formed, and a protective tape is attached to the surface of the wafer on which the cutting groove is formed, A wafer dividing apparatus for grinding the back surface of a wafer to expose the cut grooves on the back surface of the wafer and separating the wafer into individual chips,
Imaging means for imaging the inspection groove formed in the wafer or dummy wafer by the blade,
Inspection groove shape detection means for acquiring shape information of the inspection groove based on the image captured by the imaging means,
Based on the shape information of the inspection groove, blade diameter calculating means for calculating the blade diameter of the blade,
A groove depth calculating means for calculating groove depth information including a cutting depth of the inspection groove and a depth of an R-shaped portion at the bottom of the inspection groove based on the blade diameter and the shape information of the inspection groove; When,
Based on the blade diameter and the groove depth information, a cutting depth control means for controlling the cutting depth of the blade when forming the cutting groove in the wafer,
Based on the cutting depth of the blade, grinding speed control means for controlling the grinding speed of the back surface of the wafer,
A wafer dividing device comprising: The grinding speed control means sets the grinding speed of the back surface of the wafer to a first grinding speed until the wafer has a first thickness corresponding to a cutting depth of the blade, and thereafter, the wafer has the first thickness. A second grinding speed lower than the first grinding speed until the second thickness is smaller than
The wafer dividing apparatus according to claim 3 .

Images