Grinding method and grinding apparatus

Abstract

A substrate grinding method including: lowering a grinding wheel onto a first substrate that is held by a substrate holding part, and grinding the first substrate with the grinding wheel; adjusting a reference position of the grinding wheel with respect to the substrate holding part at the time of grinding a second substrate that is to be ground after the first substrate is ground; and setting an upper limit and a lower limit for moving the reference position when adjusting the reference position.

Description

[Technical Field]

[0001] This disclosure relates to a grinding method and a grinding apparatus. [Background technology]

[0002] Patent Document 1 discloses a grinding machine for grinding wafers with a grinding wheel. In the grinding machine, the spindle feed mechanism is controlled to bring the grinding wheel closer to the wafer by an amount equal to the wear of the grinding wheel, which is calculated by subtracting the amount of grinding of the wafer from the displacement of the spindle relative to the processed wafer. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-155488 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The technology described herein appropriately controls the position of the grinding wheel when grinding a substrate with the grinding wheel. [Means for solving the problem]

[0005] One aspect of the present disclosure is a method for grinding a substrate, comprising lowering a grinding wheel onto a first substrate held in a substrate holder, grinding the first substrate with the grinding wheel, and grinding the substrate after the first substrate has been ground. Before grinding the second substrate, This includes adjusting the reference position of the grinding wheel with respect to the substrate holding portion when grinding the second substrate, and setting upper and lower limits for the movement of the reference position when adjusting the reference position. [Effects of the Invention]

[0006] According to this disclosure, the position of the grinding wheel can be appropriately controlled when grinding a substrate with the grinding wheel. [Brief explanation of the drawing]

[0007] [Figure 1] This is a plan view showing a schematic configuration of the grinding apparatus according to this embodiment. [Figure 2] This is a side view showing an example of the configuration of the grinding section and chuck. [Figure 3] This is a flowchart illustrating the entire process of wafer processing using a grinding machine. [Figure 4] This is an explanatory diagram showing the rough grinding process in the rough grinding section. [Figure 5] This is an explanatory diagram showing how to calculate the setup position. [Figure 6] This is an explanatory diagram showing how the setup position is updated. [Figure 7] This is an explanatory diagram showing the upper limit and lower limit of the setup position after updating the setup position. [Figure 8] This is an explanatory diagram showing the upper limit and lower limit of the setup position after updating the setup position. [Modes for carrying out the invention]

[0008] In the semiconductor manufacturing process, the back surface of a semiconductor substrate (hereinafter referred to as a wafer) is ground to thin it.

[0009] Wafer grinding is performed, for example, by lowering a grinding wheel onto a wafer held in a chuck and rotating the grinding wheel while bringing it into contact with the back surface of the wafer. In this process, the grinding wheel wears down and becomes thinner as the wafer is repeatedly ground. Therefore, in the grinding machine disclosed in Patent Document 1, for example, the spindle feed mechanism is controlled so that the grinding wheel approaches the wafer by an amount equal to the amount of wear of the grinding wheel.

[0010] Further, when grinding a wafer, the reference position of the grinding wheel relative to the chuck, for example, the setup position, is adjusted. The setup position is a height position at which the position of the upper surface of the chuck and the position of the grinding surface of the grinding wheel coincide with each other, or a position separated from the height position by a set distance. As described above, grinding a wafer wears the grinding wheel, so the setup position is adjusted and updated every time a wafer is ground. Specifically, the position of the grinding wheel when grinding of the wafer is completed (spark-out, which will be described later) and the thickness of the ground wafer are measured, and the setup position is updated based on the measured position of the grinding wheel and the measured thickness of the wafer. Then, based on the setup position, an air cut start position, which will be described later, is determined before starting grinding of the wafer.

[0011] However, for example, if the thickness measurement of the wafer is not appropriately performed, the setup position cannot be updated appropriately. For example, if the thickness of the wafer is erroneously measured to be larger than the actual thickness, the length of the grinding wheel is calculated to be shorter than the actual length, so the setup position for the next wafer becomes lower than the actual position, which may cause collision between the next wafer and the grinding wheel. Further, for example, if the thickness of the wafer is erroneously measured to be smaller than the actual thickness, the length of the grinding wheel is calculated to be longer than the actual length, so the setup position for the next wafer becomes higher than the actual position, which may reduce the throughput for the next wafer.

[0012] The technology according to the present disclosure has been made in view of the above circumstances, and appropriately controls the position of a grinding wheel when grinding a substrate with the grinding wheel. Hereinafter, a grinding apparatus and a grinding method according to the present embodiment will be described with reference to the drawings. In the present specification and the drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and overlapping descriptions are omitted.

[0013] In the grinding apparatus 1 shown in Figure 1, a wafer W, which serves as a substrate, is thinned by grinding. The wafer W is a semiconductor wafer, such as a silicon wafer or a compound semiconductor wafer. The surface Wa is the holding surface that is held by the chuck 42, which will be described later, in the grinding apparatus 1. The back surface Wb, opposite to the surface Wa of the wafer W, is the grinding surface that is ground in the grinding apparatus 1.

[0014] The grinding apparatus 1 has a configuration in which an input / output station 2 and a processing station 3 are integrally connected. At the input / output station 2, for example, a cassette C capable of accommodating multiple wafers W is input and output to and from the outside. The processing station 3 is equipped with various processing devices that perform desired processing on the wafers W.

[0015] A cassette mounting platform 10 is provided at the loading / unloading station 2. A wafer transport area 20 is also provided adjacent to the cassette mounting platform 10 on the positive Y-axis side.

[0016] The wafer transport area 20 is provided with a wafer transport device 22 that is configured to move freely on a transport path 21 extending in the X-axis direction. The wafer transport device 22 has a transport fork 23 that holds and transports the wafer W. The transport fork 23 is configured to move freely in the horizontal direction, vertical direction, around the horizontal axis, and around the vertical axis. The wafer transport device 22 is configured to transport the wafer W to the cassette C of the cassette mounting table 10, the alignment section 50 described later, and the first cleaning section 60 described later.

[0017] At processing station 3, the wafer W is subjected to processes such as grinding and cleaning. Processing station 3 includes a transport unit 30 for transporting the wafer W, a grinding unit 40 for performing grinding on the wafer W, an alignment unit 50 for adjusting the horizontal orientation of the wafer W, and a first cleaning unit 60 and a second cleaning unit 70 for cleaning the wafer W after grinding.

[0018] The transport unit 30 is a multi-joint robot equipped with multiple, for example, three, arms 31. Each of the three arms 31 is configured to rotate freely. A transport pad 32 for adsorbing and holding wafers W is attached to the tip arm 31. The base arm 31 is attached to a lifting mechanism 33 that raises and lowers the arm 31 vertically. The transport unit 30 is configured to transport wafers W to the grinding unit 40, the alignment unit 50, the first cleaning unit 60, and the second cleaning unit 70.

[0019] The grinding unit 40 has a rotary table 41. Four chucks 42 are provided on the rotary table 41 as substrate holders for adsorbing and holding the wafer W. Porous chucks, for example, are used for the chucks 42. The surface of the chuck 42, i.e., the wafer W holding surface, has a convex shape in which the central part protrudes more than the edges when viewed from the side. Although this central protrusion is minute, in the following explanation, the central protrusion of the chuck 42 will be shown enlarged for clarity.

[0020] As shown in Figure 2, the four chucks 42 are each held by four chuck bases 43. The chuck bases 43 are provided with a tilt adjustment mechanism 44 that adjusts the relative inclination between each grinding section (rough grinding section 90, medium grinding section 100, and finish grinding section 110, described later) and the chuck 42. The tilt adjustment mechanism 44 has a fixed shaft 45 provided on the lower surface of the chuck base 43 and multiple, for example, two, lifting shafts 46. Each lifting shaft 46 is configured to be extendable and retractable, raising and lowering the chuck base 43. This tilt adjustment mechanism 44 tilts the chucks 42 and chuck bases 43 by raising and lowering the other end of the outer circumference of the chuck base 43 vertically using the lifting shaft 46, with one end (corresponding to the fixed shaft 45) as the pivot point. This allows adjustment of the relative inclination between the grinding surface of each grinding section at processing positions A1 to A3 and the upper surface of the chuck 42. The configuration of the tilt adjustment mechanism 44 is not limited to this; it is sufficient if it can adjust the relative angle (parallelism) of the surface (holding surface) of the chuck 42 with respect to the grinding surface of each grinding section.

[0021] As shown in Figure 1, the four chucks 42 can move to the transfer position A0 and the machining positions A1 to A3 as the rotary table 41 rotates. In addition, each of the four chucks 42 is configured to rotate around a vertical axis by a rotation mechanism (not shown).

[0022] At the transfer position A0, the wafer W is transferred by the transport unit 30. A thickness measuring unit 80 is provided at the transfer position A0 to measure the thickness of the wafer W before or after grinding. The thickness measuring unit 80 measures the thickness of the wafer W at multiple points, for example, three points equally spaced in the radial direction (center point, midpoint, and outer edge point). The thickness measuring unit 80 also acquires the in-plane distribution of the wafer W's thickness and calculates the flatness (TTV: Total Thickness Variation) of the wafer W. The configuration of the thickness measuring unit 80 is arbitrary, but for example, it may include a non-contact sensor (not shown) and a calculation unit (not shown).

[0023] In this embodiment, the explanation will be given using the case where the thickness measuring unit 80 is provided at the handover position A0 as an example, but the arrangement of the thickness measuring unit 80 is not limited to this. For example, the thickness measuring unit 80 may be arranged independently of the grinding unit 40.

[0024] A rough grinding section 90 is located at processing position A1 to roughly grind the wafer W. A medium grinding section 100 is located at processing position A2 to medium grind the wafer W. A finish grinding section 110 is located at processing position A3 to finish grind the wafer W.

[0025] As shown in Figure 2, the rough grinding section 90 at machining position A1 includes an annular rough grinding wheel 91, a rough grinding wheel 92 supporting the rough grinding wheel 91, a mount 93 supporting the rough grinding wheel 92, a spindle 94 that rotates the rough grinding wheel 92 via the mount 93, and a drive unit 95 supporting the spindle 94. The drive unit 95 incorporates, for example, a motor (not shown) to rotate the spindle 94. Furthermore, as shown in Figure 1, the rough grinding section 90 is configured to be movable vertically along the support column 96 by the drive unit 95. In this embodiment, the drive unit 95 and the support column 96 constitute the moving mechanism of this disclosure that moves the rough grinding wheel 91. The drive unit 95 also includes a measuring unit (not shown) that measures the position of the rough grinding wheel 91 during spark-out, which will be described later, and specifically the boundary position between the lower surface of the mount 93 and the upper surface of the rough grinding wheel 92, thereby constituting the first measuring unit of this disclosure.

[0026] As described above, the holding surface of the chuck 42 has a convex shape. Therefore, when grinding the wafer W using the rough grinding section 90, a portion of the annular rough grinding wheel 91 comes into contact with the wafer W. More specifically, the annular rough grinding wheel 91 comes into contact with the wafer W in an arc shape from the center to the outer edge. By rotating the chuck 42 and the rough grinding wheel 92 in this state, the entire back surface Wb of the wafer W is ground.

[0027] Furthermore, a thickness measuring unit 97, which is a second measuring unit in this disclosure, is provided at the processing position A1 for measuring the thickness of the wafer W. The configuration of the thickness measuring unit 97 is arbitrary, but for example, it may include a non-contact sensor (not shown) and a calculation unit (not shown).

[0028] The intermediate grinding section 100 at processing position A2 has the same configuration as the rough grinding section 90. That is, as shown in Figure 2, the intermediate grinding section 100 includes an annular intermediate grinding wheel 101, an intermediate grinding wheel 102, a mount 103, a spindle 104, a drive unit 105, and a support column 106. The abrasive grain size of the intermediate grinding wheel is smaller than that of the rough grinding wheel.

[0029] Furthermore, as shown in Figure 1, a thickness measuring unit 107, which is a second measuring unit in this disclosure for measuring the thickness of the wafer W, is provided at the processing position A2. The configuration of the thickness measuring unit 107 is arbitrary, but for example, it may include a non-contact sensor (not shown) and a calculation unit (not shown).

[0030] The finishing grinding section 110 at processing position A3 has the same configuration as the rough grinding section 90. That is, as shown in Figure 2, the finishing grinding section 110 has an annular finishing grinding wheel 111, a finishing grinding wheel 112, a mount 113, a spindle 114, a drive unit 115, and a support column 116. The abrasive grain size of the finishing grinding wheel is smaller than that of the intermediate grinding wheel.

[0031] Furthermore, as shown in Figure 1, a thickness measuring unit 117, which is a second measuring unit in this disclosure for measuring the thickness of the wafer W, is provided at the processing position A3. The configuration of the thickness measuring unit 117 is arbitrary, but for example, it may include a non-contact sensor (not shown) and a calculation unit (not shown).

[0032] The grinding apparatus 1 described above is equipped with a display panel 120. The display panel 120 may be, for example, a monitor or a touch panel, and may be directly attached to the grinding apparatus 1 or may be remotely accessible. The display panel 120 displays a selection screen for enabling or disabling the updating of the setup position, which will be described later, and the operator can set it to enable or disable from the selection screen on the display panel 120. The display panel 120 may also display an input screen for the upper and lower limits of the setup position, or an input screen for the upper and lower limits of the movement amount from the setup position, which will be described later. The upper and lower limits of the setup position can also be controlled by information set by the control unit 130 based on the grinding amount, and this set information may be input from the input screen on the display panel 120.

[0033] The grinding apparatus 1 described above is provided with at least one control unit 130. The control unit 130 processes computer-executable instructions that cause the grinding apparatus 1 to perform the various processes described herein. The control unit 130 may be configured to control each element of the grinding apparatus 1 to perform the various processes described herein. In one embodiment, some or all of the control unit 130 may be included in the grinding apparatus 1. The control unit 130 may include a processing unit, a storage unit, and a communication interface. The control unit 130 is implemented, for example, by a computer. The processing unit may be configured to read a program from the storage unit that provides logic or routines that enable various control operations, and to perform various control operations by executing the read program. This program may be stored in the storage unit in advance, or it may be retrieved via a medium when needed. The retrieved program is stored in the storage unit and read from the storage unit and executed by the processing unit. The medium may be various storage media readable by a computer, or it may be a communication line connected to a communication interface. The storage medium may be temporary or non-temporary. The processing unit may be a CPU (Central Processing Unit), or it may be one or more circuits. The storage unit may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface may communicate with the grinding device 1 via a communication line such as a LAN (Local Area Network).

[0034] Next, a series of wafer processing operations performed in the grinding apparatus 1 configured as described above will be explained.

[0035] First, a cassette C containing multiple wafers W is placed on the cassette platform 10 of the loading / unloading station 2. Next, the wafers W in the cassette C are removed by the transport forks 23 of the wafer transport device 22 and transported to the processing station 3. The wafers W transported to the processing station 3 are then handed over to the alignment unit 50. In the alignment unit 50, the horizontal orientation of the wafers W is adjusted by adjusting the position of the notches (not shown) formed on the wafers W (S1 in Figure 3).

[0036] Next, the wafer W is transported by the transport unit 30 from the alignment unit 50 to the grinding unit 40 and then handed over to the chuck 42 at the handover position A0. At the handover position A0, the thickness of the wafer W before grinding is measured at multiple points by the thickness measuring unit 80 (S2 in Figure 3). The measured thickness is output to, for example, the control unit 130.

[0037] Next, the wafer W held in the chuck 42 is moved to the processing position A1. At the processing position A1, first, the air cut start position, which will be described later, is adjusted in the rough grinding section 90 (S3 in Figure 3). Alternatively, the air cut start position may be adjusted based on the thickness of the wafer W before grinding, which was measured in S2, or the thickness of the wafer W before rough grinding may be measured by the thickness measuring section 97 in S3, and the air cut start position may be adjusted based on the measured thickness. Details of this method for adjusting the air cut start position will be described later.

[0038] Next, the back surface Wb of the wafer W is roughly ground by the rough grinding section 90 (S4 in Figure 3). The detailed method of rough grinding the wafer W at processing position A1 will be described below with reference to Figure 4. The left figure in Figure 4 is an explanatory diagram showing the positional relationship between the rough grinding wheel 91 and the wafer W during rough grinding. The right figure in Figure 4 is a graph showing the time-series change in the height position of the rough grinding wheel 91, where the vertical axis shows the height position of the grinding surface 91a of the rough grinding wheel 91 and the horizontal axis shows time.

[0039] First, the rough grinding wheel 91 (and rough grinding wheel 92) is lowered at high speed from the standby position H1 to the air cut start position H2 (time T0 to T1). At this time, it is lowered at high speed from the viewpoint of improving throughput. However, if the rough grinding wheel 91 is brought into contact with the wafer W at high speed, the rough grinding wheel 91 may break or the wafer W may be damaged. For this reason, the rough grinding wheel 91 is then decelerated and lowered at a low speed to the contact position H3 with the wafer W (time T1 to T2: air cut).

[0040] When the coarse grinding wheel 91 is lowered and comes into contact with the wafer W, the coarse grinding wheel 91 is then lowered further to grind the wafer W to the grinding end position H4 in the coarse grinding section 90 (the target thickness of the wafer W in the coarse grinding section 90) (times T2 to T5: grinding step). In the grinding step, the lowering speed of the coarse grinding wheel 91 may be changed in steps between times T2 and T5 (for example, between times T3 and T4), or the lowering speed may be controlled to be constant.

[0041] When the rough grinding wheel 91 reaches the grinding end position H4 and stops descending, the height position of the rough grinding wheel 91 is kept at the grinding end position H4 for a certain period of time (time T5 to T6: spark-out). During the spark-out state, the rotation of the rough grinding wheel 91 continues. At this time, the position of the rough grinding wheel 91, more specifically the boundary position between the lower surface of the mount 93 and the upper surface of the rough grinding wheel 92 (hereinafter referred to as the Z position), is measured from the Z-axis position of the motor of the drive unit 95 (S5 in Figure 3). The measured Z position is output to, for example, the control unit 130.

[0042] Once the spark-out is complete, the rough grinding wheel 91 is then started to rise while continuing to rotate (time T6-T7: escape cut). During the escape cut phase, the rough grinding wheel 91 is raised at a low speed to suppress the retention of wheel marks on the back surface Wb of the wafer W when the wafer W and the rough grinding wheel 91 come into contact.

[0043] When the wafer W and the rough grinding wheel 91 move away from each other, the rough grinding wheel 91 is then accelerated to move it to the standby position H1 (after time T7), and the rough grinding of the back surface Wb of the wafer W in the rough grinding section 90 is completed.

[0044] Next, the thickness measuring unit 97 measures the thickness of the wafer W after rough grinding (S6 in Figure 3). The measured thickness is output to, for example, the control unit 130. Note that the thickness measuring unit 97 also measures the thickness of the wafer W during the rough grinding process.

[0045] Next, based on the thickness of the wafer W after rough grinding measured in S6, the reference position of the rough grinding wheel 91 relative to the chuck 42, the so-called setup position, is adjusted (S7 in Figure 3). In S7, the setup position for grinding the next wafer W in the rough grinding section 90 is adjusted. The setup position is a height position where the position of the upper surface of the chuck 42 coincides with the position of the grinding surface of the rough grinding wheel 91. Alternatively, the setup position may be a position at a predetermined distance from the aforementioned height position. The predetermined distance can be set arbitrarily. Details of the method for adjusting the setup position will be described later. The adjustment of the setup position is performed before grinding the next wafer W which will be processed at the same chuck 42 and the same processing position A1.

[0046] Next, the wafer W held in the chuck 42 is moved to the processing position A2. At the processing position A2, first, the air cut start position is adjusted in the intermediate grinding section 100 (S8 in Figure 3). At this time, the thickness of the wafer W before intermediate grinding is measured by the thickness measuring section 107, and the air cut start position is adjusted based on the measured thickness.

[0047] Next, the intermediate grinding section 100 performs intermediate grinding on the back surface Wb of the wafer W (S9 in Figure 3). Intermediate grinding in the intermediate grinding section 100 is performed in the same manner as rough grinding by the rough grinding section 90 shown in Figure 4. That is, by controlling the height position of the intermediate grinding wheel 101, air cut, grinding step, spark out, and escape cut are performed sequentially. Also, the Z position is measured during spark out (S10 in Figure 3). The measured Z position is output to the control unit 130, for example.

[0048] Next, the thickness measuring unit 107 measures the thickness of the wafer W after intermediate grinding (S11 in Figure 3). The measured thickness is output to, for example, the control unit 130. Note that the thickness measuring unit 107 also measures the thickness of the wafer W during the intermediate grinding process.

[0049] Next, based on the thickness of the wafer W after intermediate grinding measured in S6, the reference position of the intermediate grinding wheel 101 relative to the chuck 42, the so-called setup position, is adjusted (S12 in Figure 3). In S12, the setup position for grinding the next wafer W in the intermediate grinding section 100 is adjusted.

[0050] Next, the wafer W held in the chuck 42 is moved to the processing position A3. At the processing position A3, first, the air cut start position is adjusted in the finish grinding section 110 (S13 in Figure 3). At this time, the thickness of the wafer W before finish grinding is measured by the thickness measuring section 117, and the air cut start position is adjusted based on the measured thickness.

[0051] Next, the back surface Wb of the wafer W is finished grinding by the finish grinding unit 110 (S14 in Figure 3). Finish grinding in the finish grinding unit 110 is performed in the same manner as rough grinding by the rough grinding unit 90 shown in Figure 4. That is, by controlling the height position of the finish grinding wheel 111, air cut, grinding step, spark out, and escape cut are performed sequentially. Also, the Z position is measured during spark out (S15 in Figure 3). The measured Z position is output to the control unit 130, for example.

[0052] Next, the thickness measuring unit 117 measures the thickness of the wafer W after finish grinding (S16 in Figure 3). The measured thickness is output to, for example, the control unit 130. Note that the thickness measuring unit 117 also measures the thickness of the wafer W during the finish grinding process.

[0053] Next, based on the thickness of the wafer W after finish grinding measured in S16, the reference position of the finish grinding wheel 111 relative to the chuck 42, the so-called setup position, is adjusted (Figure 3). S17 In S17, the finishing grinding section 110 adjusts the setup position for grinding the next wafer W.

[0054] Next, the wafer W held in the chuck 42 is moved to the transfer position A0. At the transfer position A0, the thickness measuring unit 80 measures the thickness of the wafer W after finish grinding at multiple points, obtains the in-plane thickness distribution of the wafer W, and obtains the flatness of the wafer W (S18 in Figure 3). The obtained thickness distribution and flatness are output to, for example, the control unit 130.

[0055] Next, the wafer W is transported by the transport unit 30 from the transfer position A0 to the second cleaning unit 70, where the surface Wa and / or back surface Wb are cleaned while being held on the transport pad 32 (S19 in Figure 3).

[0056] Next, the wafer W is transported by the transport unit 30 from the second cleaning unit 70 to the first cleaning unit 60, where the surface Wa and / or back surface Wb are further cleaned using a cleaning liquid nozzle (not shown) (S20 in Figure 3).

[0057] Subsequently, the wafers W, after all processing has been performed, are transported to the cassette C on the cassette stand 10 by the transport fork 23 of the wafer transport device 22. This completes the series of wafer processing. In the grinding device 1, a series of wafer processing is performed continuously on multiple wafers W housed in the cassette C.

[0058] Next, the methods for adjusting the air cut start position (S3, S8, S13) and the setup position (S7, S12, S17) described above will be explained. Below, the methods for adjusting the air cut start position (S3) and the setup position (S7) in the rough grinding section 90 will be explained, but the methods for adjusting the air cut start position and setup position (S8, S13, S12, S17) in the intermediate grinding section 100 and the finish grinding section 110 are similar.

[0059] First, let's explain how to adjust the setup position. In the following example, we will explain how to adjust and update the third setup position P3 for the third wafer W3 using the first setup position P1 for the first wafer W1 and the second setup position P2 for the second wafer W2.

[0060] Figure 5 is an explanatory diagram illustrating the method for calculating the setup position. Figure 5(a) shows the spark-out state during rough grinding of the first wafer W1, and Figure 5(b) shows the spark-out state during rough grinding of the second wafer W2. In Figure 5, Z1 and Z2 are the Z positions (the position of the rough grinding wheel 91 calculated from the Z-axis position of the motor of the drive unit 95, specifically the boundary position between the lower surface of the mount 93 and the upper surface of the rough grinding wheel 92). D1 and D2 are the lengths of the rough grinding wheel 91 including the rough grinding wheel 92. T1 and T2 are the thicknesses of wafers W1 and W2 after rough grinding, respectively. The distance from the home position at the upper end of the Z position to the holding surface of the chuck 42 is constant, and the following equation (1) holds true. Z1 + D1 + T1 = Z2 + D2 + T2 ... (1)

[0061] Figure 6 is an explanatory diagram showing how the setup position is updated. Figure 6(a) shows the second setup position P2, and Figure 6(b) shows the third setup position P3. The amount of movement M from the second setup position P2 to the third setup position P3 is the amount of wear (D1-D2) when the rough grinding wheel 91 wears down due to the rough grinding of the second wafer W2. That is, the amount of movement M of the setup position is calculated by rearranging the above equation (1) into the following equation (2). M=D1-D2=(Z2-Z1)+(T2-T1) ···(2)

[0062] As described above, the third setup position P3 for the third wafer W3 is adjusted and updated based on the Z positions Z1 and Z2 of wafers W1 and W2 measured in S5 at the time of sparkout, and the thicknesses T1 and T2 of wafers W1 and W2 measured in S6 (S3).

[0063] Next, we will explain how to adjust the air cut start position. In the following example, we will explain how to adjust the air cut start position for the second wafer W2 based on the first setup position P1 for the first wafer W1.

[0064] The air cut start position is the height of the grinding surface 91a of the rough grinding wheel 91 when air cut is started, and is the air cut start position H2 shown in Figure 4. The air cut start position is set by adding the thickness of the second wafer W2 before rough grinding and the amount of air cut to the first setup position P1. At this time, the amount of air cut start position is set to be as small as possible without the rough grinding wheel 91 colliding with the second wafer W2. The thickness of the second wafer W2 before rough grinding may be measured by the thickness measuring unit 80 in S2 or by the thickness measuring unit 97 in S3. The amount of air cut is set in advance in the recipe and is the descent distance when the rough grinding wheel 91 descends from the air cut start position H2 to the contact position H3 shown in Figure 4.

[0065] In addition, there are cases where S2 is omitted and the thickness measurement of the second wafer W2 before rough grinding by the thickness measuring unit 80 is not performed, or where the thickness measurement of the second wafer W2 before rough grinding in S3 is not performed. In this case, when the setup position is adjusted and updated after rough grinding of the first wafer W1 (S7), the air cut start position of the second wafer W2 is adjusted based on the thickness of the second wafer W2 that is assumed in advance.

[0066] As described above, the setup positions in the rough grinding section 90, the intermediate grinding section 100, and the finish grinding section 110 are adjusted. By appropriately adjusting the setup positions, the grinding wheels can be properly positioned before grinding, even if the grinding wheels are worn. Therefore, the back surface Wb of the wafer W can be properly ground (rough grinding, intermediate grinding, and finish grinding).

[0067] Furthermore, as described above, the air cut start position is adjusted in each of the rough grinding section 90, the intermediate grinding section 100, and the finish grinding section 110. For example, when the grinding wheel wears down, the air cut start position rises, so it takes longer for the grinding wheel to reach the wafer W. In this respect, according to this embodiment, even if the grinding wheel wears down, the time required for air cut can be shortened and throughput can be improved by appropriately adjusting the air cut start position.

[0068] Here, for example, in S6, the thickness measurement of the wafer W after rough grinding may not be performed properly. For example, if the thickness measurement of the wafer W measured in S6 differs from the set thickness, a warning (alarm) is issued. In addition, if the thickness measurement differs from the set thickness in this way, upper and lower tolerance ranges are set relative to the set thickness, and if the thickness measurement falls outside the tolerance range, rough grinding of the next wafer W is stopped.

[0069] Furthermore, for example, if the thickness measurement of the wafer W measured in S6 is the same as the set thickness but differs from the actual thickness, it may not be possible to properly adjust and update the setup position of the rough grinding unit 90 in S3.

[0070] For example, if the actual thickness of the wafer W after rough grinding is 700 μm, but the thickness measuring unit 97 mistakenly measures the wafer W thickness as 900 μm, the length of the rough grinding wheel 91 will be calculated to be 200 μm shorter than the actual length. In this case, the setup position will be set lower than it actually is, which may cause the rough grinding wheel 91 to collide with the wafer W, potentially damaging the rough grinding wheel 91 or the wafer W.

[0071] Furthermore, if, for example, the actual thickness of the wafer W after rough grinding is 700 μm, but the thickness measuring unit 97 mistakenly measures the wafer W thickness as 500 μm, the length of the rough grinding wheel 91 will be calculated to be 200 μm longer than the actual length. In this case, the setup position will be set higher than it actually is, which may increase the time required for air cut-off, potentially reducing throughput.

[0072] Therefore, in this embodiment, when updating the setup position, upper and lower limits are set for the movement of the setup position. The upper and lower limits for the movement of the setup position are set in the rough grinding section 90, the intermediate grinding section 100, and the finish grinding section 110, respectively. The method for setting the upper and lower limits for the movement of the setup position in the rough grinding section 90 will be described below, but the same method applies to the intermediate grinding section 100 and the finish grinding section 110.

[0073] Figure 7 shows the upper limit position P after updating the setup position P when updating the setup position P. U And, the lower limit position P after updating the setup position P. L This is an explanatory diagram showing the upper limit M of the amount of movement from the setup position P. U The upper limit position P is the position moved upward by (the upper threshold). U Furthermore, the lower limit M of the amount of movement from the setup position P is also specified. L The lower limit position P is the position moved downward by the amount of (lower limit threshold). L That is the case.

[0074] Upper limit M of the amount of movement of the setup position P Uis set based on the rough grinding amount of the wafer W. For example, the upper limit M is obtained by multiplying the rough grinding amount of the wafer W set by a recipe by an arbitrarily set percentage (%). U is calculated. Although the method for setting the percentage is arbitrary, for example, an allowable range of 0% to 200% may be provided and set arbitrarily by an operator. For example, when the rough grinding amount of the wafer W is 30 µm and the set percentage is 10%, the upper limit M U is set to 3 µm.

[0075] The lower limit M of the movement amount of the setup position P L is also set based on the rough grinding amount of the wafer W, similarly to the upper limit M U . For example, the lower limit M is obtained by multiplying the rough grinding amount of the wafer W set by a recipe by an arbitrarily set percentage (%). L is calculated.

[0076] As described above, when the setup position P is automatically updated in S3, the movement amount M of the setup position is calculated from the above formula (2) based on the Z-position at the time of spark-out of the wafer W measured in S5 and the thickness of the wafer measured in S6. When the upward movement amount M during this automatic update is larger than the upper limit M U twist or when the downward movement amount M during automatic update is smaller than the lower limit M L big a warning is issued. Then, in response to this warning, rough grinding of subsequent wafers W is stopped.

[0077] In such a case, the update of the setup position P can be appropriately performed between the upper limit position P U and the lower limit position P L . As a result, collision between the rough grinding wheel 91 and the wafer W caused by a large erroneous measurement of the thickness of the wafer W can be avoided. Further, a decrease in throughput caused by a small erroneous measurement of the thickness of the wafer W can be avoided.

[0078] Note that, as shown in FIG. 8, the setup position P has the upper limit position P below the setup position P​U and lower limit position P L In some cases, this may be set. Even in such cases, the update of the setup position P is to the upper limit position P. U and lower limit position P L This can be done appropriately during that time, and the effects described above can be enjoyed.

[0079] Here, if the wafer W is abnormal before grinding and has a large thickness, for example, in the air cut range, there is a risk of collision between the rough grinding wheel 91 and the wafer W. In particular, if the setup position is updated in S3, that is, if the setup position is moved downward in response to wear of the rough grinding wheel 91, the likelihood of the rough grinding wheel 91 and the wafer W colliding increases.

[0080] Therefore, if it is known that the thickness of the wafer W before grinding is large, the update of the setup position of the rough grinding unit 90 in S3 is disabled. Whether to enable or disable the update of the setup position may be determined by the operator, or the control unit 130 may determine it based on the wafer W thickness known in advance. By disabling the update of the setup position in this way, the collision between the rough grinding wheel 91 and the wafer W described above can be suppressed.

[0081] Furthermore, enabling or disabling the update of the setup position may be done by comparing the thickness of the wafer W before grinding with the amount of air cut. If the surface height of the wafer W before grinding (height of the back surface Wb) is expected to be higher than the height of the rough grinding wheel 91 in the air cut start position or air cut range (contact position H3 shown in Figure 4), the update of the setup position is disabled.

[0082] Although the grinding apparatus 1 described above had a three-axis configuration comprising a rough grinding section 90, an intermediate grinding section 100, and a finish grinding section 110, it may also have a one-axis or two-axis configuration. Even with a one-axis or two-axis configuration, the technology of this disclosure can be applied to each grinding section.

[0083] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. For example, the constituent elements of the embodiments described above can be combined in any way. Such any combination will naturally yield the functions and effects of each constituent element in the combination, as well as other functions and effects that will be apparent to those skilled in the art from the description herein.

[0084] Furthermore, the effects described herein are merely descriptive or illustrative and not limiting. In other words, the technology relating to this disclosure may produce other effects that are obvious to those skilled in the art from the description herein, in addition to or instead of the effects described herein. [Explanation of Symbols]

[0085] 1. Grinding device 42 Chuck 91 Coarse grinding wheel 95 Drive unit 96 Pillar 101 Medium Grinding Wheel 105 Drive unit 106 Post 111 Finishing grinding wheel 115 Drive unit 116 Post 130 Control Unit W wafer

Claims

1. A method for grinding a substrate, The first substrate held in the substrate holder is lowered by a grinding wheel, and the first substrate is ground with the grinding wheel. Before grinding the second substrate, which is to be ground after grinding the first substrate, the reference position of the grinding wheel relative to the substrate holding portion during grinding of the second substrate is adjusted. A grinding method comprising setting upper and lower limits for the movement of the reference position when adjusting the aforementioned reference position.

2. The grinding method according to claim 1, wherein the upper limit and the lower limit are set based on the amount of grinding of the second substrate.

3. The grinding method according to claim 1, wherein the reference position is a height position where the position of the upper surface of the substrate holding portion and the position of the grinding surface of the grinding wheel coincide, or a position located a set distance away from said height position.

4. The position of the grinding wheel at the end of grinding and the thickness of the first substrate after grinding are measured, This includes calculating the amount of movement of the reference position based on the measured position of the grinding wheel and the thickness of the first substrate, The grinding method according to claim 1, wherein a warning is issued if the calculated upward movement of the reference position is greater than the upper limit threshold, or if the calculated downward movement of the reference position is greater than the lower limit threshold.

5. The grinding method according to claim 1, further comprising adjusting the air cut start position for the second substrate based on the reference position and the thickness of the second substrate before grinding.

6. To determine whether the adjustment of the aforementioned reference position is effective or ineffective, The grinding method according to claim 1, further comprising grinding the second substrate based on the determined valid or invalid information.

7. The grinding method according to claim 6, wherein if the surface height of the second substrate before grinding is higher than the air cut start position or air cut range relative to the second substrate, the adjustment of the reference position is disabled.

8. A device for grinding a substrate, A substrate holding portion for holding the substrate, A moving mechanism for moving a grinding wheel relative to the substrate held in the substrate holding part, A grinding apparatus comprising: a control unit capable of setting upper and lower limits to the movement of the reference position of the grinding wheel relative to the substrate holding part when adjusting the reference position of the grinding wheel with respect to the substrate holding part during the grinding of the second substrate, before grinding the second substrate which is to be ground after grinding the first substrate; and a control unit capable of setting upper and lower limits to the movement of the reference position.

9. The grinding apparatus according to claim 8, wherein the control unit sets the upper limit and the lower limit based on the amount of grinding of the second substrate.

10. The grinding apparatus according to claim 8, wherein the control unit sets the reference position to a height position where the position of the upper surface of the substrate holder and the position of the grinding surface of the grinding wheel coincide, or to a position a set distance away from said height position.

11. A first measuring unit for measuring the position of the grinding wheel at the end of grinding, It has a second measuring unit for measuring the thickness of the substrate after grinding, The control unit, Based on the position of the grinding wheel measured by the first measuring unit and the thickness of the first substrate measured by the second measuring unit, the amount of movement of the reference position is calculated. The grinding apparatus according to claim 8, which performs control to issue a warning if the calculated upward movement of the reference position is greater than the upper limit threshold, or if the calculated downward movement of the reference position is greater than the lower limit threshold.

12. The grinding apparatus according to claim 8, wherein the control unit performs control to adjust the air cut start position for the second substrate based on the reference position and the thickness of the second substrate before grinding.

13. The control unit determines whether the adjustment of the reference position is enabled or disabled. The grinding apparatus according to claim 8, which performs control to grind the second substrate based on the determined valid or invalid information.

14. The grinding apparatus according to claim 13, wherein the control unit determines to invalidate the adjustment of the reference position if the surface height of the second substrate before grinding is higher than the air cut start position or air cut range relative to the second substrate.

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