Workpiece machining method

Abstract

[Problem] To provide a workpiece machining method capable of machining a non-circular workpiece into a desired shape with high precision. [Solution] In a workpiece processing method in which the back surface 8 of a workpiece 1 is ground by a grinding wheel 33 in a state in which the front surface 3 side of the workpiece 1 having a non-circular shape is held by suction by a chuck table 31, before the workpiece 1 is held by suction by the chuck table 31, the workpiece 1 is divided into a plurality of substantially arc-shaped processing regions A in which the workpiece 1 is in contact with the grinding wheel 33. A thickness adjustment film (7) is formed on the surface (3) side of the workpiece (1), and the film thickness of the thickness adjustment film (7) is adjusted in accordance with each machining region (A) so as to reduce the change in the amount of grinding of the workpiece (1) accompanying the change in the area of each machining region (A).

Description

Technical Field

[0001] The present invention relates to a workpiece processing method for processing a workpiece. Background Art

[0002] In the field of semiconductor manufacturing, in order to form a semiconductor wafer such as a silicon wafer (hereinafter referred to as "workpiece") in a thinner manner, plunge grinding is required, in which while a chuck table for sucking and holding the workpiece and a grinding wheel are rotated respectively, the grinding wheel is pressed against the workpiece to grind the workpiece to a predetermined thickness (for example, refer to Patent Document 1). In this grinding method, when viewed from above, the processing area where the grinding wheel and the workpiece are in contact with each other forms an arc shape, so the thickness of the workpiece is ground uniformly in a concentric circle shape.

[0003] [Prior Art Documents]

[0004] [Patent Documents]

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-123666 Summary of the Invention

[0006] [Problems to be Solved by the Invention]

[0007] However, most of the semiconductor wafers with a small diameter are formed with an orientation flat indicating the crystal orientation on a part of the outer periphery. Also, in recent years, the demand for rectangular semiconductor wafers has been increasing. In the case of plunge grinding such non-circular workpieces, the area of the arc-shaped processing area where the grinding wheel and the workpiece are in contact is not fixed in the circumferential direction of the workpiece.

[0008] Moreover, in the processing area with a relatively narrow area, the surface pressure becomes too large, increasing the grinding amount, so that the workpiece after grinding becomes locally thinner. On the other hand, in the processing area with a relatively wide area, the surface pressure becomes too small, reducing the grinding amount, so that the workpiece after grinding becomes locally thicker. Thus, due to the change in the area of the processing area, there is a risk of thickness deviation in the workpiece after grinding.

[0009] Then, in order to process a non-circular workpiece into a desired shape with high precision, a technical problem to be solved has arisen, and the present invention aims to solve this problem.

[0010] [Solutions to the Problems]

[0011] In order to achieve the above object, a workpiece processing method according to the present invention is a workpiece processing method in which, while a non-circular workpiece is adsorbed and held on one side by a chuck, the other side of the workpiece is ground using a grinding wheel. The method is characterized in that, before the workpiece is adsorbed and held by the chuck, when the workpiece is divided into a plurality of substantially arc-shaped processing regions where the workpiece contacts the grinding wheel, a thickness adjustment film is formed on one side of the workpiece, and the film thickness of the thickness adjustment film is adjusted corresponding to each processing region to reduce the change in the grinding amount of the workpiece accompanying the area change of each processing region.

[0012] Further, in the workpiece processing method according to the present invention, preferably, when viewed from above, the narrower the area of the processing region overlapping with the thickness adjustment film, the thinner the film thickness of the thickness adjustment film is set.

[0013] Further, in the workpiece processing method related to the present invention, preferably, the workpiece is formed with an orientation plane, and the film thickness of the thickness adjustment film overlapping with the processing region reaching the orientation plane is set to be thinner than the film thickness of the thickness adjustment film overlapping with the processing region not reaching the orientation plane.

[0014] Further, in the workpiece processing method related to the present invention, preferably, the workpiece is formed in a rectangular shape, and the film thickness of the portion of the thickness adjustment film overlapping with the processing region having a relatively small area is set to be thinner than the film thickness of the portion of the thickness adjustment film overlapping with the processing region having a relatively large area.

[0015] Further, in the workpiece processing method related to the present invention, preferably, the thickness adjustment film is formed on the surface of a protective tape pasted so as to cover the one side.

[0016] Further, in the workpiece processing method related to the present invention, preferably, the thickness adjustment film is made of a substance that can be cured after being coated on the protective tape in a liquid state.

[0017] Further, in the workpiece processing method related to the present invention, preferably, the thickness adjustment film is made of a UV curable liquid.

[0018] Further, in the workpiece processing method related to the present invention, preferably, the thickness adjustment film is formed by laminating and coating a UV curable liquid.

[0019] [Effects of the Invention]

[0020] The present invention can reduce the change in the grinding amount of the workpiece caused by the area change of the processing region where the grinding wheel contacts the workpiece, and suppress the thickness deviation of the workpiece after grinding. [Description of the Drawings]

[0021] Figure 1A top view schematically showing the positional relationship between the grinding wheel and the workpiece.

[0022] Figure 2 A figure showing a non-circular shaped workpiece. Figure 2 (a) thereof is a top view showing a workpiece having an orientation plane. Figure 2 (b) thereof is a top view showing a state in which four rectangular shaped workpieces are held on a chuck table.

[0023] Figure 3 A flowchart showing the sequence of a workpiece machining method.

[0024] Figure 4 A schematic diagram showing the sequence of a workpiece machining method.

[0025] Figure 5 A sectional view schematically showing the main part in a workpiece machining method.

[0026] Figure 6 A top view and a side view showing the structure of a thickness adjustment film formed on the workpiece in Examples 1 and 2.

[0027] Figure 7 A figure showing the thickness distribution of the workpiece after grinding in Example 1.

[0028] Figure 8 A figure showing the thickness distribution of the workpiece after grinding in Example 2. Detailed Description of the Invention

[0029] Regarding an embodiment of the present invention, it will be described with reference to the accompanying drawings. In addition, hereinafter, when referring to the number, numerical value, quantity, range, etc. of constituent elements, unless otherwise specifically stated and in cases where it is clearly limited to a specific number in principle, it is not limited by that specific number, and it does not matter whether it is more than or less than the specific number.

[0030] Furthermore, when referring to the shape, positional relationship, etc. of constituent elements, unless otherwise specifically stated and in cases where it is considered clearly not so in principle, it substantially includes cases where it is approximate or similar to its shape, etc.

[0031] Furthermore, in order to make the features easy to understand, there are cases where the drawings exaggerate parts of the features, etc., and the dimensional ratios, etc. of the constituent elements are not necessarily the same as the actual ones.

[0032] Figure 1A schematic diagram showing the positional relationship between a workpiece 100 having a circular shape and a grinding wheel 101. In a state where the workpiece 100 and the grinding wheel 101 are respectively rotated, the grinding wheel 101 is pressed against the workpiece 100 to grind the back surface (surface to be ground) 102 of the workpiece 100. At this time, when viewed from above, the machining area A where the workpiece 100 and the grinding wheel 101 are in contact forms a substantially arc shape. The substantially arc-shaped machining area A is generally continuously formed from the rotation center O of the chuck table holding the workpiece 100 to the outer periphery of the workpiece 100. When the circular workpiece 100 is circumferentially divided into a plurality of machining areas A, the areas of all the machining areas A are substantially the same, while when a non-circular workpiece is circumferentially divided into a plurality of machining areas A, the areas of all the machining areas A are not the same.

[0033] As a non-circular workpiece, for example, it is possible to consider a workpiece 1 having an orientation plane 2 formed on a part of the outer periphery as shown in (a) of Figure 2 , or a workpiece 1 having a substantially rectangular shape as shown in (b) of Figure 2 . In addition, Figure 2 (b) of

[0034] shows a state where four rectangular workpieces 1 are held on a chuck table 102. The workpiece 1 is, for example, a silicon substrate, but the material of the workpiece 1 can be any material. Also, the workpiece 1 can be made of a single substrate, or can be a substrate made of a brittle material or a composite substrate formed by bonding a support substrate to a substrate having an extremely thin target thickness.

[0034] Moreover, in the workpiece 1 shown in (a) of Figure 2 , the area of the machining area A1 set not to reach the orientation plane 2 is compared with the area of the machining area A2 set to reach the orientation plane 2, and the former is larger than the latter. Also, when the grinding wheel 101 is pressed against the substantially flat workpiece 1 for grinding, as the contact area between the workpiece 1 and the grinding wheel 101 increases, the grinding amount of the workpiece 1 decreases, and the ground workpiece 1 becomes thicker. Therefore, in the workpiece 1 shown in (a) of Figure 2 , the thickness of the ground workpiece 1 in the machining area A1 set not to reach the orientation plane 2 is compared with that in the machining area A2 set to reach the orientation plane 2, and it is predicted that the former will be thicker than the latter.

[0035] Similarly, in the rectangular workpiece 1 shown in (b) of Figure 2 , the area of the machining area A3 set to pass through a pair of diagonals of the workpiece 1 is compared with the area of the machining area A4 set to pass through the corner and the midpoint of the side length of the workpiece 1, and the former is approximately twice that of the latter. Also, when the grinding wheel 101 is pressed against the substantially flat workpiece 1 for grinding, as the contact area between the workpiece 1 and the grinding wheel 101 increases, the grinding amount of the workpiece 1 decreases and the ground workpiece 1 becomes thicker, so in Figure 2In the rectangular workpiece 1 shown in (b), the thickness of the ground workpiece 1 in the machining area A3 set to pass through a pair of diagonals of the workpiece 1 and the machining area A4 set to pass through the corner and the midpoint of the side length of the workpiece 1 is compared, and it is predicted that the former will be thicker than the latter.

[0036] Next, a machining method for machining the non-circular workpiece 1 will be described. Figure 3 It is a flowchart showing the order of the workpiece machining method. Figure 4 It is a schematic diagram showing the order of the workpiece machining method. Figure 5 It is a cross-sectional view schematically showing the main part in the workpiece machining method. In addition, hereinafter, the case of machining the workpiece 1 formed with the orientation plane 2 will be described as an example, but the non-circular workpiece 1 is not limited to this shape.

[0037] <BG tape pasting>

[0038] First, a BG (back grinding) tape 4 as a protective tape is pasted on the surface 3 side of the workpiece 1 (step S1). Specifically, as shown in (a), the BG tape 4 continuously released above the workpiece 1 is pasted on the surface 3 side of the workpiece 1 by using a pressing roller 10. The workpiece 1 is adsorbed and held by a chuck table (not shown), and the BG tape 4 is pasted on the entire surface of the workpiece 1 by sliding the chuck table in the horizontal direction. Figure 4 As shown in (a), the BG tape 4 continuously released above the workpiece 1 is pasted on the surface 3 side of the workpiece 1 by using a pressing roller 10. The workpiece 1 is adsorbed and held by a chuck table (not shown), and the BG tape 4 is pasted on the entire surface of the workpiece 1 by sliding the chuck table in the horizontal direction.

[0039] The BG tape 4 is generally a UV curable type that is cured by irradiating UV (Ultra Violet). However, when the thickness adjustment film 7 uses the UV curable liquid 6, there is a risk that the BG tape 4 will also be cured and peeled off when the UV curable liquid 6 is irradiated with UV for curing. Therefore, when the thickness adjustment film 7 uses the UV curable liquid 6, the BG tape 4 is preferably a non-UV curable type. In addition, the BG tape 4 can be a resin film formed by spin coating or spraying, etc.

[0040] Next, the shape of the surface 5 side of the BG tape 4 is measured. Specifically, as shown in (b), the shape measuring device 11 is scanned above the BG tape 4 to measure the surface shape of the BG tape 4. The shape measuring device 11 is, for example, a stylus type step gauge, an optical surface measuring device, etc. In addition, since the surface shape of the BG tape 4 is substantially the same as the shape of the workpiece 1, if the shape of the workpiece 1 is known, the shape of the BG tape 4 is also known, so this process can be omitted. Figure 4 As shown in (b), the shape measuring device 11 is scanned above the BG tape 4 to measure the surface shape of the BG tape 4. The shape measuring device 11 is, for example, a stylus type step gauge, an optical surface measuring device, etc. In addition, since the surface shape of the BG tape 4 is substantially the same as the shape of the workpiece 1, if the shape of the workpiece 1 is known, the shape of the BG tape 4 is also known, so this process can be omitted.

[0041] <Formation of thickness adjustment film>

[0042] Next, a UV curable liquid 6 is coated on the surface 5 of the BG tape 4 to form a thickness adjustment film 7 (step S2). Specifically, since the workpiece 1 and the BG tape 4 have substantially the same shape, when the workpiece 1 is divided into a plurality of processing regions A in the circumferential direction, the surface 5 of the BG tape 4 is divided into a plurality of imaginary processing regions in the circumferential direction corresponding to each processing region A, and a thickness adjustment film 7 with an adjusted film thickness is formed for each imaginary processing region.

[0043] That is, first, using a general computer or the like, based on the surface shape of the BG tape 4 measured by the shape measuring device 11 or the surface shape of the BG tape 4 stored in advance, the BG tape 4 is divided into a plurality of arc-shaped imaginary processing regions in the circumferential direction, and the area (presumed contact area) of each imaginary processing region is calculated. At this time, each imaginary processing region set by dividing the BG tape 4 into a plurality of regions is set to correspond to each processing region A set by dividing the workpiece 1 into a plurality of regions in the circumferential direction. When viewed from above, each processing region A coincides with each imaginary processing region.

[0044] Next, the area (reference area) of the imaginary processing region that is the preset reference is compared with the presumed contact area of each imaginary processing region, and the film thickness of the thickness adjustment film 7 to be formed for each imaginary processing region is calculated. In addition, in a computer or the like, there is stored a relational expression such as the change amount of the grinding amount in the processing region A when the area of the processing region A changes from the reference area to the presumed contact area calculated in advance through experiments or the like, and the film thickness of the thickness adjustment film 7 to be formed in the processing region A to offset such a change amount of the grinding amount.

[0045] The narrower the presumed contact area, in other words, the narrower the area of the processing region A corresponding to the imaginary processing region, the thinner the film thickness of the thickness adjustment film 7 is set. That is, since the grinding amount is small in the processing region A with a relatively large area, the film thickness of the thickness adjustment film 7 in the imaginary processing region corresponding to the processing region A is set to be relatively thick. On the other hand, since the grinding amount is large in the processing region A with a relatively narrow area, the film thickness of the thickness adjustment film 7 in the imaginary processing region corresponding to the processing region A is set to be relatively thin. In addition, the film thickness of the thickness adjustment film 7 can be arbitrarily adjusted within a range of, for example, 0 to 150 μm.

[0046] For example, in the workpiece 1 having the alignment plane 2 shown in (a) where Figure 2 is formed, the thicknesses of the ground workpiece 1 in the processing region A1 set not to reach the alignment plane 2 and the processing region A2 set to reach the alignment plane 2 are compared. In the case where a thickness deviation of about 1 μm is generated such that the former is thicker than the latter, for example, a thickness adjustment film 7 with a thickness of 2 μm can be considered to be formed on the former, and a thickness adjustment film 7 with a thickness of 1 μm can be formed on the latter.

[0047] Moreover, as shown in (c) of Figure 4 Liquid UV curable liquid 6 is ejected in minute amounts from the inkjet head 21 of the UV inkjet printer 20 onto the surface 5 of the BG tape 4. CAD data including the coordinates of each imaginary processing area and the film thickness of the thickness adjustment film 7 formed within each imaginary processing area is input into the UV inkjet printer 20, and the inkjet head 21 ejects a predetermined amount of the UV curable liquid 6 into each imaginary processing area. In addition, the UV curable liquid 6 is made of a liquid UV curable resin.

[0048] Next, as shown in (d) of Figure 4 UV light is irradiated from the UV irradiation device 22 of the UV inkjet printer 20 onto the surface 5 of the BG tape 4 to cure and adhere the UV curable liquid 6. Thus, as shown in (a) of Figure 5 A layered thickness adjustment film 7 is formed on the surface 5 of the BG tape 4. The UV inkjet printer 20 has a known configuration, for example, a flatbed UV printer (model: Versa UV LEF2 300) manufactured by Roland D.G. Corporation, etc.

[0049] When the film thickness of the thickness adjustment film 7 formed by the UV curable liquid 6 that can be ejected at one time by the inkjet head 21 is lower than the film thickness of the thickness adjustment film 7 that should be formed within the imaginary processing area, by ejecting the UV curable liquid 6 again on the once-cured UV curable liquid 6 and curing it, as shown in (b) of Figure 5 The UV curable liquid 6 can be locally laminated to adjust the film thickness of the thickness adjustment film 7. Also, it is possible to measure the shape of the surface 5 of the BG tape 4 after forming the thickness adjustment film 7 and re-coat the UV curable liquid 6 as needed.

[0050] As a method of forming the thickness adjustment film 7, in addition to the UV inkjet printer 20, stereolithography that irradiates light to a liquid resin and cures only the resin at a desired portion to obtain a three-dimensional structure or various photolithography methods, etc. can also be considered. However, the advantage of the UV inkjet printer 20 is that the position where the liquid is ejected can be easily specified using CAD data, etc., and overprinting of the UV curable liquid 6 can be performed again on the once-cured UV curable liquid 6 and the surface shape of the BG tape 4 can be finely corresponded to, so it is suitable. Furthermore, in order to obtain the thickness adjustment film 7 suitable for the shape of the workpiece 1, the UV inkjet printer 20 preferably can arbitrarily adjust the type and ejection amount of the ejected liquid and the number of overprinting times.

[0051] In addition, the material of the thickness adjustment film 7 is not limited to the UV curable liquid 6. For example, it can also be a resin that rapidly cures by light irradiation or heating, a resin that slowly cures at room temperature, a silver solution, or a material having insulating properties, etc. However, a resin that rapidly cures by light irradiation or heating is suitable in terms of overprintability.

[0052] <Grinding>

[0053] Next, the workpiece 1 is ground to be thinner using the grinding device 30 (step S3 ). Specifically, first, the workpiece 1 is placed on the chuck table 31 with the surface 3 facing downward.

[0054] The upper surface of the chuck table 31 is provided with an adsorption body 32 made of a porous material such as alumina. The chuck table 31 is provided with a pipeline extending through its interior to the adsorption body 32. The pipeline is connected to a vacuum source via a rotary joint. When the vacuum source is activated, the workpiece 1 placed on the chuck table 31 is adsorbed and held on the chuck table 31 via the thickness adjustment film 7. At this time, Figure 5 As shown in (c), a portion of the back surface 8 of the workpiece 1 corresponding to the locally thickened thickness adjustment film 7 is locally raised.

[0055] Next, if Figure 4 As shown in (e), the back surface 8 of the workpiece 1 vacuum-adsorbed on the chuck table 31 is ground using the grinding wheel 33.

[0056] The grinding wheel 33 is, for example, a cup-shaped grinding wheel. It is mounted on the lower end of a grinding wheel spindle 34 located above the chuck table 31 and is driven by the grinding wheel spindle 34 to rotate about a rotation axis 35. The grinding wheel 33 is labeled, for example, #8000. The processing surface of the grinding wheel 33 is formed into a generally annular shape. The grinding wheel spindle 34 is raised and lowered vertically by a feed mechanism (not shown). The feed mechanism is, for example, a screw slide mechanism that raises and lowers the grinding wheel spindle 34.

[0057] The chuck table 31 is driven by a chuck spindle 36 to rotate about a rotation axis 37. The chuck spindle 36 is driven by a servo motor, for example. Furthermore, the chuck table 31 is equipped with a tilt mechanism that adjusts the inclination of the rotation axis 37. By adjusting the inclination of the rotation axis 37, the contact between the grinding wheel 33 and the workpiece 1 can be adjusted, thereby increasing or decreasing the thickness of the workpiece 1 after grinding.

[0058] After the grinding wheel 33 is lowered near the workpiece 1, the feed mechanism is driven while the grinding wheel spindle 34 and chuck spindle 36 are rotating. The grinding wheel 33 is pressed against the back surface 8 of the workpiece 1, thereby performing feed grinding on the back surface 8. For example, the rotation speed of the grinding wheel spindle 34 is set to 2000 rpm, and the rotation speed of the chuck spindle 36 is set to 300 rpm. Furthermore, the feed speed of the feed mechanism is set to 0.4 μm / s.

[0059] At this time, when grinding the back surface 8 of the workpiece 1 with a non-circular shape, the grinding amount of the workpiece 1 will increase or decrease locally due to the area change of the machining area A, and the ground workpiece 1 may have a thickness deviation. By forming a thickness adjustment film 7 on the surface 3 side of the workpiece 1 whose thickness increases or decreases according to the area change of the machining area A, minute unevenness will be formed on the back surface 8 of the workpiece 1 corresponding to the film thickness of the thickness adjustment film 7. The increasing trend of the grinding amount in the machining area A with a relatively narrow area will be alleviated, and the decreasing trend of the grinding amount in the machining area A with a relatively large area will also be alleviated. Since the change in the grinding amount of the workpiece 1 caused by the area change of the machining area A is reduced, the thickness deviation of the ground workpiece 1 can be suppressed.

[0060] When the measured value of the in-process gauge 38 reaches the target thickness during the process of measuring the thickness of the workpiece 1 being ground, after stopping the chuck spindle 36 and the grinding wheel spindle 34, the grinding wheel 33 is retracted upward.

[0061] <Workpiece shape measurement>

[0062] Next, the shape of the ground workpiece is measured to determine whether the grinding is appropriate (step S4). The shape measurement of the workpiece 1 is performed using, for example, an optical interference film thickness sensor that measures the thickness of the workpiece 1. The shape of the ground workpiece is compared with a predetermined determination reference (for example, TTV 1 μm). When the shape of the ground workpiece does not meet the determination reference (No in step S5), the process returns to step S2, and a UV curable liquid 6 is applied to the surface 5 of the BG tape 4 to form a thickness adjustment film 7.

[0063] On the other hand, when the shape of the ground workpiece meets the determination reference (Yes in step S4), the grinding is ended, and the BG tape 4 is removed from the workpiece 1. As a result, the thickness adjustment film 7 is removed from the workpiece 1 together with the BG tape 4, so that the thickness adjustment film 7 can be prevented from remaining in the workpiece 1.

[0064] As described above, the workpiece processing method of the present embodiment is a workpiece processing method for grinding the back surface 8 of the non-circular workpiece 1 while adsorbing and holding the surface 3 side of the workpiece 1 by the chuck table 31. This workpiece processing method is configured such that before the workpiece 1 is adsorbed and held by the chuck table 31, when the workpiece 1 is divided into a plurality of substantially arc-shaped machining areas A in contact with the grinding wheel 33, a thickness adjustment film 7 is formed on the surface 3 side of the workpiece 1, and the film thickness of the thickness adjustment film 7 is adjusted corresponding to each machining area A to reduce the change in the grinding amount of the workpiece 1 accompanying the area change of each machining area A.

[0065] According to this configuration, a thickness adjustment film 7 whose thickness increases and decreases according to the area of the machining region A is formed on the surface 3 side of the workpiece 1, and the workpiece 1 is machined in a state where the change in the grinding amount of the workpiece 1 caused by the change in the area of the machining region A is reduced. Thus, even a workpiece 1 having a non-circular shape can be machined into a substantially flat shape. Furthermore, by forming the thickness adjustment film 7 with a position and film thickness suitable for the shape of each workpiece 1, grinding with high flatness can be performed at low cost and with a high qualified rate.

[0066] [Embodiment]

[0067] Next, a case of grinding a 12-inch silicon wafer in a state where a relatively thin thickness adjustment film 7 is formed on the BG tape 4 (Embodiment 1) and a case of grinding a 12-inch silicon wafer in a state where a relatively thick thickness adjustment film 7 is formed on the BG tape 4 (Experimental Example 2) will be described. In addition, as the BG tape 4, a non-UV curable BG tape (SB-170HRA) is used, and the thickness adjustment film 7 is formed in a layered form by overprinting a UV curing liquid 6 on the BG tape 4.

[0068] In Embodiments 1 and 2, the thickness adjustment film 7 is formed in a stepped shape as shown in Figure 6 (a) and (b) thereof. Specifically, it is composed of six regions with different film thicknesses divided into "Zone1" to "Zone6". The film thickness difference between the regions constituting the thickness adjustment film 7 in Embodiment 1 is about 6 to 15 μm, with "Zone1" being the thinnest and "Zone6" being the thickest. Also, the film thickness difference between "Zone1" and "Zone6" is set to 49 μm. Also, the film thickness difference between the regions of the thickness adjustment film 7 in Experimental Example 2 is about 20 to 30 μm, and the film thickness difference between "Zone1" and "Zone6" is set to 123 μm. Then, the silicon wafers of Embodiments 1 and 2 are rough-ground and finish-ground in the same manner, and the thickness of the ground silicon wafers is measured over the entire surface.

[0069] In Embodiment 1, as shown in Figure 7 in the ground silicon wafer, the maximum film thickness of "Zone1" is 312 μm, the minimum film thickness of "Zone6" is 262 μm, and the difference between the maximum film thickness and the minimum film thickness is 50 μm, which is approximately equal to the film thickness difference between "Zone1" and "Zone6". Therefore, it is known that the grinding amount of the silicon wafer can be adjusted according to the film thickness difference between the regions of the thickness adjustment film 7. Also, no cracks occurred in the ground silicon wafer.

[0070] Also, in Embodiment 2, as shown in Figure 8As shown, in the ground silicon wafer, the maximum film thickness of "Zone1" is 351 μm, the minimum film thickness of "Zone6" is 225 μm, the difference between the maximum and minimum film thicknesses is 126 μm, which is roughly equal to the film thickness difference between "Zone1" and "Zone6". Therefore, it is known that the grinding amount of the silicon wafer can be adjusted by adjusting the film thickness difference in each region of film 7 according to the thickness. However, near the boundary between "Zone4" and "Zone5", there is a thin part due to excessive local grinding amount, and cracks are generated in this part.

[0071] In addition, the present invention is not limited to the above-described embodiments, and various changes other than the above can be made as long as the spirit of the present invention is not departed from, and of course, the present invention can be applied to such changes.

[0072] Also, in the above-described embodiment, the case where the thickness adjustment film 7 is formed on the entire surface 5 of the BG tape 4 has been described as an example, but the thickness adjustment film 7 may also be locally formed on the surface 5 of the BG tape 4.

[0073] In addition, in the above-described embodiment, the case where the thickness adjustment film 7 is formed on the surface 5 of the BG tape 4 has been described as an example, but the thickness adjustment film 7 may also be directly formed on the surface 3 of the workpiece 1, and the BG tape 4 may be pasted on the workpiece 1 so as to cover the thickness adjustment film 7.

[0074] In addition, the present invention is applicable not only to the grinding of the workpiece 1 but also to the polishing of the workpiece 1. For example, a thickness adjustment film is partially coated on the surface portion on the back side of the surface to be polished of the workpiece to form fine irregularities, and the workpiece is subjected to CMP (chemical mechanical polishing), whereby partial polishing of the workpiece can be performed. In addition, compared with the contact between the grinding wheel and the workpiece being a rigid body, since the polishing head used in CMP is a non-rigid body, the irregularities of the thickness adjustment film do not directly affect the polishing amount.

[0075] [Description of reference numerals]

[0076] 1: Workpiece

[0077] 2: Orientation plane

[0078] 3: (Surface of the workpiece)

[0079] 4: BG tape

[0080] 5: (Surface of the BG tape)

[0081] 6: UV curable liquid

[0082] 7: Thickness adjustment film

[0083] 8: (Back surface of the workpiece)

[0084] 10: Pressing roller

[0085] 11: Shape measuring device

[0086] 20: UV inkjet printer

[0087] 21: Inkjet head

[0088] 22: UV irradiation device

[0089] 30: Grinding device

[0090] 31: Chuck table

[0091] 32: Adsorbent

[0092] 33: Grinding wheel

[0093] 34: Grinding wheel spindle

[0094] 35: Rotation axis

[0095] 36: Chuck spindle

[0096] 37: Rotation axis

[0097] 38: In - process measuring instrument

[0098] A, A1 to A4: Machining areas

[0099] O: Center of rotation.

Claims

1. A workpiece processing method, which is a workpiece processing method of grinding the other side of the workpiece with a grinding wheel while adsorbing and holding one side of the workpiece having a non-circular shape by a chuck, characterized in that, Before the workpiece is adsorbed and held by the chuck, when the workpiece is divided into a plurality of substantially arc-shaped processing regions where the workpiece contacts the grinding wheel, a thickness adjustment film is formed on one side of the workpiece, and the film thickness of the thickness adjustment film is adjusted corresponding to each processing region to reduce the change in the grinding amount of the workpiece accompanying the area change of each processing region.

2. The workpiece processing method according to claim 1, characterized in that, When observed from above, the narrower the area of the processing region overlapping with the thickness adjustment film, the thinner the film thickness of the thickness adjustment film is set.

3. The workpiece processing method according to claim 2, characterized in that, The workpiece is formed with an orientation plane. The film thickness of the thickness adjustment film overlapping with the processing region reaching the orientation plane is set to be thinner than the film thickness of the thickness adjustment film overlapping with the processing region that does not reach the orientation plane.

4. The workpiece processing method according to claim 2, characterized in that, The workpiece is formed in a rectangular shape. The film thickness of the part of the thickness adjustment film overlapping with the processing region having a relatively small area is set to be thinner than the film thickness of the part of the thickness adjustment film overlapping with the processing region having a relatively large area.

5. The workpiece processing method according to claim 1, characterized in that, The thickness adjustment film is formed on the surface of a protective tape pasted in a manner covering the one side.

6. The workpiece processing method according to claim 5, characterized in that, The thickness adjustment film is made of a substance that can be cured after being coated on the protective tape in a liquid state.

7. The workpiece processing method according to claim 6, wherein The thickness adjustment film is made of a UV curable liquid.

8. The workpiece processing method according to claim 7, characterized in that, The thickness adjustment film is formed by laminating and coating a UV curable liquid.

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