Grinding method and grinding device

Abstract

To properly control air cut in grinding a substrate with a grinding stone.SOLUTION: A grinding method for grinding a substrate using a grinding device provided with a grinding stone, a moving mechanism that moves down the grinding stone, and a substrate holding part that holds a substrate, includes steps of: moving down the grinding stone from a stand-by position to an air-cut start position at a first speed, when moving down the grinding stone with respect to the substrate held by the substrate holding part; setting at least two deceleration positions, between the air-cut start position and a substrate contact position; starting to move down the grinding stone from the air-cut start position, at a second speed lower than the first speed; and decreasing the moving-down speed of the grinding stone, at each deceleration position, so that the moving-down speed decreased at the last deceleration position becomes equal to a grinding-start speed predetermined as a speed at which grinding of the substrate is started from the substrate contact position.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Patent Document 1 discloses a grinding device that grinds a wafer with a rotating grinding wheel. It describes that when the grinding wheel is lowered, it descends at a first feed rate to a feed rate change position, and then descends at a second feed rate that is slower than the first feed rate but faster than the grinding feed rate from the feed rate change position until the grinding wheel rotation speed detected by the grinding wheel rotation speed detection means drops to a predetermined value. It also describes that thereafter, it descends at the grinding feed rate to a grinding end position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-052075 A Summary of the Invention [Problem to be solved by the invention]

[0004] The technology disclosed herein appropriately controls air cutting when grinding a substrate with a grinding wheel. [Means for solving the problem]

[0005] One aspect of the present disclosure is a method for grinding a substrate using a grinding device including a grinding wheel, a moving mechanism for lowering the grinding wheel, and a substrate holding part for holding a substrate, the method including: when lowering the grinding wheel relative to the substrate held by the substrate holding part, lowering the grinding wheel from a standby position to an air-cut start position at a first speed; setting at least two deceleration positions between the air-cut start position and a substrate contact position; starting a descent speed of the grinding wheel from the air-cut start position at a second speed lower than the first speed; and decelerating the descent speed of the grinding wheel at each of the deceleration positions until the descent speed after deceleration at the last deceleration position becomes a grinding start speed that is predetermined as a speed at which grinding of the substrate starts from the substrate contact position. Effect of the Invention

[0006] According to the present disclosure, it is possible to appropriately control air cutting when grinding a substrate with a grinding wheel. [Brief description of the drawings]

[0007] [Figure 1] 1 is a plan view showing an outline of a configuration of a grinding device according to an embodiment of the present invention; [Diagram 2] FIG. 4 is a side view showing an example of the configuration of a grinding unit and a chuck. [Diagram 3] FIG. 2 is a flow chart showing a series of wafer processing steps performed by the grinding device. [Figure 4] FIG. 4 is an explanatory diagram showing an example of grinding in a grinding unit. [Diagram 5] FIG. 4 is a flow chart showing a series of steps of air cutting in the grinding section. [Figure 6] FIG. 11 is an explanatory diagram showing an example of air cutting in a grinding portion. [Figure 7] FIG. 11 is an explanatory diagram showing another example of air cutting in the grinding portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 2. Description of the Related Art In a semiconductor manufacturing process, a semiconductor substrate (hereinafter, referred to as a wafer) is thinned by grinding the back surface of the wafer.

[0009] Wafer grinding is performed, for example, by lowering a grinding wheel onto a wafer held by a chuck and contacting the back surface of the wafer while rotating the grinding wheel. In this case, an air-cut lowering method has been proposed in which the grinding wheel is lowered from a safe retreat position onto the substrate at a relatively high speed on the order of mm / sec, and then the speed is changed and the wheel is lowered at a relatively low speed on the order of μm / sec until it comes into contact with the substrate. Such air-cutting is provided to prevent damage to the substrate if the grinding wheel comes into contact with the substrate while maintaining the relatively high speed on the order of mm / sec.

[0010] Patent Document 1 discloses that in such air cutting, if the grinding wheel tip descends at the same extremely slow speed as the grinding conditions immediately after reaching a predetermined air cutting start position, it takes a long time before grinding actually starts, which is problematic from the viewpoint of productivity.In addition, Patent Document 1 discloses a method for addressing such a problem, in which a rotational speed detection means is used to detect a decrease in the rotational speed of the grinding wheel when the grinding wheel descending while rotating comes into contact with grinding water supplied to the substrate surface, and the descent speed is changed before and after the detection.

[0011] However, in order to stably and accurately evaluate the decrease in rotation speed due to the resistance of the grinding water supplied to the substrate surface, there are many variables to be considered, and therefore a great deal of trial and error may be required when introducing the device or performing maintenance. The variables to be considered include the mass of the entire grinding unit, which contributes to the inertia of rotation, the torque of rotation, the rotation speed, the descending speed, the contact area between the grinding wheel tip and the grinding water, the thickness of the grinding water, or the viscosity of the grinding water. In addition, since it is not always possible to change the processing speed at the same position, the time required for the grinding process varies for each wafer, which may affect the throughput of the entire device. Thus, the method described in Patent Document 1 has room for improvement in terms of the cost and throughput associated with trial and error.

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

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

[0014] The grinding apparatus 1 has a configuration in which a loading / unloading station 2 and a processing station 3 are integrally connected. In the loading / unloading station 2, for example, a cassette C capable of accommodating a plurality of wafers W is loaded and unloaded between the loading / unloading station 2 and the outside. The processing station 3 includes various processing devices that perform desired processing on the wafers W.

[0015] A cassette mounting table 10 is provided in the carry-in / out station 2. A wafer transfer area 20 is provided adjacent to the cassette mounting table 10 on the Y-axis positive side of the cassette mounting table 10.

[0016] A wafer transport device 22 configured to be movable on a transport path 21 extending in the X-axis direction is provided in the wafer transport area 20. The wafer transport device 22 has a transport fork 23 that holds and transports a wafer W. The transport fork 23 is configured to be movable horizontally, vertically, around a horizontal axis, and around a vertical axis. The wafer transport device 22 is configured to be able to transport the wafer W to the cassette C on the cassette mounting table 10, an alignment unit 50 described below, and a first cleaning unit 60 described below.

[0017] In the processing station 3, processing such as grinding and cleaning is performed on the wafer W. The processing station 3 includes a transfer unit 30 that transfers the wafer W, a grinding unit 40 that performs a grinding process on the wafer W, an alignment unit 50 that adjusts the horizontal orientation of the wafer W, and a first cleaning unit 60 and a second cleaning unit 70 that clean the wafer W after grinding.

[0018] The transfer unit 30 is an articulated robot equipped with multiple, for example, three, arms 31. Each of the three arms 31 is configured to be freely rotatable. A transfer pad 32 that suctions and holds the wafer W is attached to the arm 31 at the tip end. The arm 31 at the base end is attached to a lifting mechanism 33 that raises and lowers the arm 31 in the vertical direction. The transfer unit 30 is configured to be able to transport the wafer 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. On the rotary table 41, for example, two chucks 42 are provided as substrate holders for suction-holding the wafer W. For example, a porous chuck is used as the chucks 42. The surface of the chucks 42, i.e., the holding surface for the wafer W, has a convex shape in which the center protrudes compared to the ends in a side view. Note that although this protrusion of the center is minute, in the following explanation, the protrusion of the center of the chuck 42 is illustrated enlarged for clarity of explanation.

[0020] As shown in FIG. 2, the two chucks 42 according to this embodiment are held by two chuck bases 43, respectively. The chuck base 43 is provided with an inclination adjustment mechanism 44 for adjusting the relative inclination between the grinding unit 90 and the chuck 42. The inclination adjustment mechanism 44 has a fixed shaft 45 provided on the lower surface of the chuck base 43 and a plurality of, for example, two, lifting shafts 46. Each lifting shaft 46 is configured to be freely expandable and contractible, and lifts and lowers the chuck base 43. The inclination adjustment mechanism 44 lifts and lowers one end of the outer periphery of the chuck base 43 (the position corresponding to the fixed shaft 45) in the vertical direction by the lifting shaft 46, thereby inclining the chuck 42 and the chuck base 43. This makes it possible to adjust the relative inclination between the grinding surface of the grinding unit 90 and the upper surface of the chuck 42. The configuration of the inclination adjustment mechanism 44 is not limited to this, but may be any configuration capable of adjusting the relative angle (parallelism) of the surface (holding surface) of the chuck 42 with respect to the grinding surface of the grinding portion 90.

[0021] 1, the two chucks 42 can be moved to a delivery position A0 and a processing position A1 by rotation of the rotary table 41. Furthermore, each of the two chucks 42 is configured to be rotatable about a vertical axis by a rotation mechanism (not shown).

[0022] At the transfer position A0, the transfer unit 30 transfers the wafer W. At the transfer position A0, a thickness measuring unit 80 is provided 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 (center point, middle point, and outer periphery point) equally spaced in the radial direction. The thickness measuring unit 80 also obtains the in-plane distribution of the thickness of the wafer W and calculates the flatness (TTV: Total Thickness Variation) of the wafer W. The thickness measuring unit 80 may have any configuration, but may include, for example, a non-contact sensor (not shown) and a calculation unit (not shown).

[0023] In this embodiment, the thickness measuring unit 80 is provided at the delivery position A0, 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] An example of the configuration of the grinding unit 90 is shown in FIG. 2. As shown in FIG. 2, the grinding unit 90 at the processing position A1 has an annular grinding wheel 91, a grinding wheel 92 that supports the grinding wheel 91, a mount 93 that supports the grinding wheel 92, a spindle 94 that rotates the grinding wheel 92 via the mount 93, and a drive unit 95 that supports the spindle 94. The drive unit 95 has, for example, a built-in motor (not shown) and rotates the spindle 94. The grinding unit is also configured to be movable vertically along a support 96 by a lift drive unit 98. In this embodiment, the support 96 and the lift drive unit 98 constitute a moving mechanism of the present disclosure that moves the grinding wheel 91. As an example, the lift drive unit 98 includes a lift motor and a guide rail provided on the support 96. In this example, the grinding unit 90 is moved so as to slide on the guide rail in the Z-axis direction by driving the lift motor. As an example, the movement mechanism is configured to be able to change the speed of movement, including the lowering of the grinding wheel, to a desired speed by receiving a control signal from the control unit 130. In one embodiment, the lifting / lowering drive unit 98 is configured to measure whether or not the lifting / lowering motor has reached a deceleration position during air cutting, which will be described later, using a measurement unit (not shown) that measures the Z-axis position of the lifting / lowering motor, and to feed this back to the control unit 130.

[0025] Here, as described above, the holding surface of the chuck 42 has a convex shape. Therefore, when the wafer W is ground using the grinding unit, a part of the annular grinding wheel 91 comes into contact with the wafer W. More specifically, the annular grinding wheel 91 comes into contact with the wafer W in an arc shape from the center to the outer peripheral edge. In this state, the chuck 42 and the grinding wheel 92 are rotated, respectively, to grind the entire back surface Wb of the wafer W.

[0026] 1, a thickness measuring unit 97 is provided at the processing position A1 to measure the thickness of the wafer W. The thickness measuring unit 97 may have any configuration, but may include, for example, a non-contact sensor (not shown) and a calculation unit (not shown).

[0027] The configuration of the grinding apparatus 1 is not limited to this. For example, four chucks 42 may be provided on the rotating table 81, and the four chucks 42 may be configured to be movable among a transfer position of the wafer W, a rough grinding section (not shown) for performing rough grinding of the first wafer W, a medium grinding section (not shown) for performing medium grinding of the first wafer W, and a finish grinding section (not shown) for performing finish grinding of the first wafer W. In addition, for example, the grinding apparatus 1 may be provided with a thickness measuring device (not shown) for measuring the thickness of the first wafer W at multiple points after grinding.

[0028] The grinding apparatus 1 described above is provided with a display panel 120. The display panel 120 is, for example, a monitor or a touch panel, and may be directly attached to the grinding apparatus 1 or may be remotely viewable. A selection screen for enabling or disabling the update of the setup position, which will be described later, is displayed on the display panel 120, and the operator can set the update to be enabled or disabled from the selection screen of the display panel 120. The display panel 120 may also display an input screen for the upper limit and lower limit positions of the setup position, which will be described later, or an input screen for the upper limit and lower limit of the movement amount from the setup position. The upper limit and lower limit positions 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 of the display panel 120.

[0029] The grinding apparatus 1 described above is provided with a control unit 130. The control unit 130 processes computer-executable instructions that cause the grinding apparatus 1 to execute various steps described in this disclosure. The control unit 130 can be configured to control each element of the grinding apparatus 1 to execute various steps described herein. The control unit 130 is, for example, a computer equipped with a CPU, a memory, and the like, and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the wafer W in the grinding apparatus 1. The program may be recorded in a computer-readable storage medium H and installed from the storage medium H to the control unit 130. The storage medium H may be temporary or non-temporary.

[0030] Next, a series of wafer processing steps performed in the grinding apparatus 1 configured as above will be described.

[0031] First, a cassette C storing a plurality of wafers W is placed on the cassette mounting table 10 of the carry-in / out station 2. Next, the wafers W in the cassette C are removed by the transport fork 23 of the wafer transport device 22 and transported to the processing station 3. The wafers W transported to the processing station 3 are delivered to the alignment section 50. In the alignment section 50, the horizontal orientation of the wafer W is adjusted by adjusting the position of a notch portion (not shown) formed in the wafer W (S1 in FIG. 3).

[0032] Next, the wafer W is transported by the transport unit 30 from the alignment unit 50 to the grinding unit 40, and is delivered to the chuck 42 at the delivery position A0. At the delivery position A0, the thickness of the wafer W before grinding is measured at multiple points by the thickness measuring unit 80 (S2 in FIG. 3). The measured thickness is output to, for example, the control unit 130.

[0033] Next, the wafer W held by the chuck 42 is moved to the processing position A1. At the processing position A1, first, the grinding unit 90 adjusts the air cut start position (S3 in FIG. 3). At S3, the air cut start position may be adjusted based on the thickness of the wafer W before grinding measured at S2. Also, at S3, the thickness measuring unit 97 measures the thickness of the wafer W before grinding, and the air cut start position may be adjusted based on the measured thickness.

[0034] Next, the back surface Wb of the wafer W is ground by the grinding unit 90 (S4 to S7 in FIG. 3). A detailed method of grinding the wafer W at the processing position A1 will be described below with reference to FIG. 4. The left diagram in FIG. 4 is an explanatory diagram showing the positional relationship between the grinding wheel 91 and the wafer W during grinding. The right diagram in FIG. 4 is a graph showing the time-series change in the height position of the grinding wheel 91, with the vertical axis representing the height position of the grinding surface 91a of the grinding wheel 91 and the horizontal axis representing time.

[0035] First, the grinding wheel 91 (and the grinding wheel 92) is lowered at a first speed from the standby position H1 to the air-cut start position H2 (time T0 to T1). At this time, the first speed is set to a relatively high speed from the viewpoint of improving throughput. In one embodiment, the first speed is, for example, 100 mm / sec. On the other hand, if the high-speed grinding wheel 91 is brought into contact with the wafer W, the grinding wheel 91 may be broken or the wafer W may be damaged. For this reason, the grinding wheel 91 is decelerated and lowered from the air-cut start position H2 to the substrate contact position H3, thereby performing air-cut (S4 in FIG. 3 and time T1 to T2 in FIG. 4). Note that the graph is shown as a straight line from T1 to T2, but this is a description for convenience in explaining the entire process, and the air-cut according to this embodiment performs a different control. Details of the air-cut according to this embodiment will be described later.

[0036] When the grinding wheel 91 is lowered, the grinding wheel 91 and the wafer W come into contact with each other at a substrate contact position H3. Thereafter, the grinding wheel 91 is further lowered to grind the wafer W to a grinding end position H4 (a target thickness of the wafer W in the grinding section 90) in the grinding section 90 (S5 in FIG. 3 and times T2 to T5 in FIG. 4: grinding step). Note that in the grinding step, the lowering speed of the grinding wheel 91 may be changed stepwise between times T2 and T5 (for example, times T3 and T4 in FIG. 4), or the lowering speed may be controlled to be constant.

[0037] When the grinding wheel 91 reaches the grinding end position H4 and stops descending, the grinding wheel 91 is made to wait at the grinding end position H4 for a certain period of time (S6 in FIG. 3 and time T5 to T6 in FIG. 4: spark out). In the spark out state, the grinding wheel 91 continues to rotate.

[0038] After the spark out is completed, the grinding wheel 91 starts to rise while continuing to rotate (S7 in FIG. 3 and time T6 to T7 in FIG. 4: escape cut). In the escape cut state, the grinding wheel 91 is raised at a low speed to prevent wheel marks from remaining on the back surface Wb of the wafer W when the wafer W and the grinding wheel 91 are separated from each other.

[0039] When the wafer W and the grinding wheel 91 are separated from each other, the grinding wheel 91 is then accelerated to move to the standby position H1 (after time T7), and grinding of the back surface Wb of the wafer W in the grinding unit 90 is completed.

[0040] Next, the thickness of the wafer W after grinding is measured by the thickness measuring unit 97 (S8 in FIG. 3). The measured thickness is output to, for example, the control unit 130. At this time, an estimated height 91b of the grinding surface 91a of the grinding wheel 91 may be determined and stored based on the thickness of the wafer W. Furthermore, the estimated height 91b may be used to adjust the air cut start position S3 for the second and subsequent wafers W. The thickness measuring unit 97 may measure the thickness of the wafer W during grinding.

[0041] The details of the air cut according to this embodiment will be described below. In the air cut according to this embodiment, the grinding surface 91a is lowered from the air cut start position H2 to the substrate contact position H3 by executing each process shown in FIG. 5 described below from time T1 to T2 in the above-mentioned wafer processing. In one embodiment, the substrate contact position H3 is a virtual position determined by the control unit 130 using a desired algorithm by taking into account the thickness of the wafer W before grinding measured by the thickness measuring unit 97 and the degree of wear of the grinding wheel 91 described later.

[0042] First, as shown in FIG. 6, at least two, in this embodiment, three deceleration positions D1, D2, and D3 are set within the total air cut section CT set from the air cut start position H2 to the substrate contact position H3 (S101 in FIG. 5). The deceleration positions D1 to D3 are virtual positions based on the grinding surface 91a. Here, the section from the air cut start position H2 to the first deceleration position D1 is defined as a first section C1. Also, the section from the first deceleration position D1 to the adjacent next deceleration position D2 is defined as a second section C2. Also, the section from the deceleration position D2 to the last deceleration position D3 is defined as a third section C3. Also, the section from the last deceleration position D3 to the substrate contact position H3 is defined as a fourth section C4. The total air cut section CT is the sum of these sections C1 to C4.

[0043] Next, the lowering speed in each of the sections C1 to C4 is set (S102 in FIG. 5). As described above, the lowering is performed at the first speed from the standby position to the air cut start position H2, but the lowering speed in each of the sections C1 to C4 is set to a value smaller than the first speed. Furthermore, the lowering speed in the first section C1 is v1, the lowering speed in the second section C2 is v2, the lowering speed in the third section C3 is v3, and the lowering speed in the fourth section C4 is v4. At this time, the lowering speed v4 in the fourth section C4 is set to be equal to a grinding start speed that is previously determined as a speed at which grinding of the wafer W is started from the substrate contact position H3. Furthermore, the lowering speeds v1 to v4 in each of the sections C1 to C4 are set to satisfy the following formula (1). v1>v2>v3>v4 Equation (1)

[0044] Next, the grinding surface 91a starts to descend from the air-cut start position H2 at a descending speed v1. Thereafter, the grinding surface 91a is lowered while being decelerated in sequence at each of the deceleration positions D1 to D3 so that each descending speed becomes the descending speed v2 to v4 set as described above (S103 in FIG. 5). In S103, after the grinding surface 91a descends at the descending speed v4 (grinding start speed) in the fourth section C4 and reaches the substrate contact position H3, grinding of the wafer W is started without changing the speed from the descending speed v4 (S5 in FIG. 3). In one embodiment, grinding of the wafer W may be performed at the descending speed v4 until time T3 in FIG. 4, and then the descending speed of the grinding wheel 91 may be changed stepwise.

[0045] According to the air cut of this embodiment as described above, the time required for air cut can be shortened and the throughput can be improved, compared to the comparative example (the straight line L shown by the dashed line in the graph of FIG. 6) in which air cut is started at the grinding start speed from the beginning of the air cut start position H2. Also, since the lowering speeds v1 to v4 in each of the sections C1 to C4 can be set based on the distance of the total air cut section CT and the grinding start speed, the air cut speed can be set simply and stably with a small number of variables. Furthermore, since the time required for air cut can be determined in the process of determining the distance and the lowering speeds v1 to v4 of each of the sections C1 to C4, the time required for the entire process including air cut (throughput) can be accurately calculated.

[0046] In one embodiment, the distance of the first section C1 is d1, the distance of the second section C2 is d2, the distance of the third section C3 is d3, and the distance of the fourth section C4 is d4. In this case, the deceleration positions D1 to D3 are set so as to satisfy the following formula (2). d1≧d2≧d3≧d4...Equation (2)

[0047] By setting the deceleration positions D1 to D3 to satisfy the above formula (2), the section with a relatively high speed can be secured longer than the section with a relatively low speed, thereby making it possible to further shorten the air cut time.

[0048] In one embodiment, as shown in FIG. 7, the fourth section C4 includes a contact margin M. That is, the final deceleration position D3 is determined as a position taking into consideration the contact margin M. The significance of the contact margin M is explained as follows. First, as a premise, in the processing of the second and subsequent wafers W, the grinding wheel 91 may be worn by the grinding performed in the previous or previous grinding. Therefore, even if the Z-axis position in the control of the lifting and lowering drive unit 98 is the same, the distance between the grinding surface 91a and the wafer W may vary depending on the degree of wear of the grinding wheel 91. In the example state shown in FIG. 7, the grinding surface 91a is worn down from the initial state to the wear surface 200 as a result of wear. The wear surface 200 is the actual grinding surface 91a in this worn state. At this time, the control unit 130 estimates and stores the distance between the wear surface 200 of the grinding surface 91a and the wafer W based on, for example, the grinding result of the previous wafer W. The grinding surface 91a estimated at this time is referred to as the estimated surface 201. The estimated surface 201 is a virtual grinding surface 91a. The control unit 130 executes control of the current grinding of the wafer W based on the estimated surface 201. In this case, the distance between the estimated surface 201 and the wafer W may cause an error E between the actual wear surface 200 and the wafer W. In the state example shown in FIG. 7, an error E occurs such that the wear surface 200, which is the actual grinding surface 91a, is closer to the wafer W than the estimated surface 201. In this case, when air cutting is performed based on the estimated surface 201, the wear surface 200 may contact the wafer W at a speed higher than a predetermined grinding start speed, for example, at a descending speed v3 of the third section C3. In contrast, by determining the deceleration position so that the fourth section C4 includes the contact margin M, it is possible to ensure that the grinding surface 91a descends through deceleration at the final deceleration position D3 even if an error E occurs, and it is possible to ensure that the grinding surface 91a contacts the substrate at a descending speed v4 equal to the grinding start speed. From this viewpoint, it is preferable to set the contact margin M to be larger than the expected error E.

[0049] In one embodiment, a preferred range of the grinding start speed at which grinding of the wafer W is started from the substrate contact position H3 is set to, for example, 0.2 μm / s or more and 2.0 μm / s or less, and the lowering speed v4 in the fourth section C4 is set similarly. Moreover, a preferred range of the lowering speeds v1 to v3 in the first section C1 to the third section is set to, for example, 0.2 μm / s or more and 10.0 μm / s or less, provided that the above formula (1) is satisfied.

[0050] In the above embodiment, three deceleration positions D1 to D3 are set, but the present invention is not limited to this, and the number of deceleration positions may be two or more. In one embodiment, a large number of deceleration positions may be provided so that deceleration is performed substantially continuously.

[0051] The following describes a generalized embodiment in which a desired number of n deceleration positions are set in the total air cut section CT and the total air cut section CT is divided into (n+1) sections. The first section is from the air cut start position H2 to the first deceleration position (first deceleration position). Sections 2 to n are from any deceleration position to the next adjacent deceleration position from the air cut start position to the substrate contact position. Sections 2 to n are from the last deceleration position (nth deceleration position) to the substrate contact position H3. Section (n+1) is from the last deceleration position (nth deceleration position) to the substrate contact position H3. In this case, the descent speed v(k) in any kth section and the descent speed v(k+1) in the next adjacent (k+1)th section are set to satisfy the following formula (3). v(k)>v(k+1) (3) Here, n≧2 and 1≦k≦n are satisfied, and v(n+1) is the grinding start speed.

[0052] In one embodiment, each deceleration position is set so that the distance d(k) in the kth section and the distance d(k+1) in the (k+1)th section satisfy the following formula (4). d(k)≧d(k+1) (4)

[0053] Furthermore, in one embodiment, when a desired number is input for the number (n) of deceleration positions, the control unit 130 determines the specific descent speed and / or the specific coordinates of the deceleration positions in each section so as to satisfy the above formula (3) and / or the above formula (4). As an example, the "specific coordinates of the deceleration positions" are the Z-axis position of the lift motor measured by the lift drive unit 98. In this case, when the coordinates are determined, the specific descent speed and / or the specific coordinates of the deceleration positions in each section may be determined based on the total time set in the total air cut section CT. This makes it possible to accurately calculate the required time for the entire process including the air cut.

[0054] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims. For example, the components of the above-described embodiments may be arbitrarily combined. From such an arbitrary combination, the actions and effects of each of the components in the combination can be obtained as a matter of course, and other actions and effects that are obvious to a person skilled in the art from the description of this specification can be obtained.

[0055] In addition, the effects described in this specification are merely explanatory or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to a person skilled in the art from the description of this specification in addition to or in place of the above effects. [Explanation of symbols]

[0056] 1 Grinding equipment 42 Chuck 91 Grinding Wheel 96 Pillar 98 Lifting drive unit H1 Standby position H2 Air cut start position H3 Board contact position D1, D2, D3 deceleration position W wafer

Claims

1. A method for grinding a substrate using a grinding device including a grinding wheel, a moving mechanism for lowering the grinding wheel, and a substrate holding part for holding a substrate, the method comprising the steps of: When the grinding wheel is lowered relative to the substrate held by the substrate holder, lowering the grinding wheel from a standby position to an air cut start position at a first speed; setting at least two deceleration positions between the air cut start position and the substrate contact position; Starting a lowering speed of the grinding wheel from the air cut start position at a second speed that is lower than the first speed; decelerating the descent speed of the grinding wheel at each of the deceleration positions, so that the descent speed after deceleration at the last deceleration position becomes a grinding start speed that is a predetermined speed at which grinding of the substrate is started from the substrate contact position; A grinding method comprising:

2. 2. The grinding method according to claim 1, further comprising the step of setting a descending speed in each section of the air-cut start position, the deceleration position and the substrate contact position that are adjacent to each other when setting the deceleration position.

3. 3. The grinding method according to claim 2, further comprising, when setting the deceleration position, setting a distance of one section so as to be equal to a distance of another section adjacent to the first section and closer to the air-cut start position, or so as to be smaller than a distance of the other section.

4. An apparatus for grinding a substrate, comprising: A grinding wheel; A moving mechanism for lowering the grinding wheel; A substrate holder for holding the substrate; A control unit, When the control unit lowers the grinding wheel relative to the substrate held by the substrate holding unit, lowering the grinding wheel from a standby position to an air cut start position at a first speed; setting at least two deceleration positions between the air cut start position and the substrate contact position; Starting a lowering speed of the grinding wheel from the air cut start position at a second speed that is lower than the first speed; decelerating the descent speed of the grinding wheel at each of the deceleration positions, so that the descent speed after deceleration at the last deceleration position becomes a grinding start speed that is a predetermined speed at which grinding of the substrate is started from the substrate contact position; A grinding apparatus that performs control including:

5. The grinding apparatus according to claim 4 , wherein when the control unit sets the deceleration position, it sets a lowering speed in each section of the air-cut start position, the deceleration position, and the substrate contact position that are adjacent to each other.

6. 6. The grinding device according to claim 5, wherein, when setting the deceleration position, the control unit sets the distance of one section so as to be equal to the distance of another section adjacent to the first section and closer to the air cut start position, or so as to be smaller than the distance of the other section.

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