JP5554612B2 - Grinding equipment - Google Patents

Description

  The present invention relates to a grinding apparatus, and more particularly to a grinding apparatus for grinding a workpiece such as a semiconductor wafer.

  In the manufacturing process of a semiconductor device, in order to obtain a target thickness of the device, thinning is performed by back-grinding at the stage of a semiconductor wafer which is an aggregate of a large number of devices. In accordance with the remarkable thinning of devices in recent years, wafers are processed to be thinner, and higher accuracy is required in managing the thickness. Wafer grinding and polishing can be performed while measuring the thickness, but as a means of measuring the thickness in such a form, a contact type that detects the displacement of the thickness while bringing the measuring probe into contact with the work surface. There are known thickness measuring means (see, for example, Patent Document 1).

  However, in the contact-type thickness measuring means, the surface to be processed is scratched by the probe that comes into contact, and the scratch causes the wafer's bending strength to be reduced. There was a problem that only the thickness could not be measured. For this reason, the present applicant has proposed an optical non-contact type thickness measuring means capable of measuring the thickness without bringing a probe or the like into contact with the wafer. (For example, refer to Patent Document 2).

Japanese Patent Laid-Open No. 2001-9716 JP 2009-50944 A

  The non-contact type thickness measurement means solves the above-mentioned problems and enables more advanced processing. However, the thickness measurement means reflects light from other than the front and back surfaces of the wafer (reflection of the front and back surfaces of the device layer). In some cases, contamination in the machining fluid and reflection from grindstone waste) are erroneously detected. If a value smaller than the actual thickness is erroneously detected, the grinding apparatus may stop processing even though the actual thickness is not the target thickness.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a grinding apparatus capable of reducing malfunction of the apparatus in accordance with an erroneous workpiece thickness detection value.

The grinding apparatus of the present invention comprises a holding means for holding a work, a processing means for grinding the work held by the holding means, and a thickness detection means for detecting the thickness of the work held by the holding means. The thickness detection unit includes a detection unit that detects the thickness of a workpiece in a non-contact manner, a storage unit that stores the thickness detected by the detection unit, and the thickness detected by the detection unit. A lower limit value that restricts storage to the storage unit, and when a thickness equal to or lower than the lower limit value is detected, a detection thickness regulating unit that does not store in the storage unit, and the detection unit detects and detects the storage unit And a control unit that lowers the lower limit value by a predetermined amount based on the difference between the thickness stored in step 1 and the lower limit value being less than or equal to a predetermined value.

  According to the above grinding apparatus, since the thickness detection value equal to or lower than the lower limit value set by the restriction portion is restricted from being stored in the storage portion, the grinding by the processing means according to the thickness detection value equal to or lower than the lower limit value. Therefore, it is possible to reduce the malfunction of the apparatus in response to an erroneous workpiece thickness detection value.

  According to the present invention, since the thickness detection value equal to or lower than the lower limit set by the restriction unit is restricted from being stored in the storage unit, the grinding by the processing means is performed according to the thickness detection value equal to or lower than the lower limit value. Since it can be prevented from being controlled, it is possible to reduce malfunction of the apparatus in accordance with an erroneous workpiece thickness detection value.

1 is an external perspective view of a grinding apparatus according to an embodiment of the present invention. It is a figure for demonstrating the relationship between the grinding wheel at the time of the grinding process of the grinding device which concerns on the said embodiment, and a semiconductor wafer. It is a schematic diagram for demonstrating the detection result in the thickness detector of the grinding device which concerns on the said embodiment. It is a flowchart for demonstrating the grinding process of the grinding apparatus which concerns on the said embodiment. It is a schematic diagram which shows the side cross section of the semiconductor wafer which is a process target of the grinding apparatus which concerns on the said embodiment. It is a figure for demonstrating transition of the thickness of the semiconductor wafer ground with the grinding apparatus which concerns on the said embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. A grinding apparatus according to an embodiment of the present invention includes a workpiece (workpiece) thickness detector, provides an allowable range of the detection result, and grinds the workpiece while excluding the detection result outside the allowable range. By controlling the processing, it is possible to reduce the malfunction of the apparatus in accordance with the erroneous thickness detection value.

  FIG. 1 is an external perspective view of a grinding apparatus 1 according to an embodiment of the present invention. FIG. 2 is a view for explaining the relationship between the grinding wheel 61 and the semiconductor wafer W during the grinding process of the grinding apparatus 1 according to the present embodiment. FIG. 3 is a schematic diagram for explaining a detection result in the thickness detector 7 of the grinding apparatus 1 according to the present embodiment. In the following, for the sake of convenience of explanation, the lower left side shown in FIG. 1 is called the front side of the grinding apparatus 1, and the upper right side shown in FIG. 1 is called the rear side of the grinding apparatus 1. In the following, for convenience of explanation, the vertical direction shown in FIG. 1 is referred to as the vertical direction of the grinding apparatus 1.

  As shown in FIG. 1, the grinding apparatus 1 has a base 2 having a generally rectangular parallelepiped shape. On the front side of the upper surface of the base 2, an operation panel 3 that receives instructions for the grinding device 1 is provided. A table support 4 for supporting the chuck table 41 is provided on the rear side of the operation panel 3. A column portion 5 is provided on the rear side of the table support 4. A grinding unit 6 is supported on the front surface of the support column 5 so as to be movable in the vertical direction. In the vicinity of the grinding unit 6, there is provided a laser head portion 71 that constitutes a part of the thickness detector 7 that detects the thickness of the semiconductor wafer W held on the chuck table 41 before and after grinding.

  The grinding apparatus 1 according to the present embodiment having such a configuration is configured to process the semiconductor wafer W by relatively rotating the grinding unit 6 and the chuck table 41 holding the semiconductor wafer W. ing. In the grinding process, the thickness detector 7 detects the thickness of the semiconductor wafer W, and the grinding process for the semiconductor wafer W is continued or stopped. More specifically, as shown in FIG. 2, a part of a grinding wheel 61 of a grinding unit 6 to be described later is disposed so as to face the semiconductor wafer W held on the chuck table 41 and comes into contact with the semiconductor wafer W. Move to position. Then, the semiconductor wafer W is ground by rotating the chuck table 41 in the direction of arrow B and rotating the grinding wheel 61 in the direction of arrow C. And the grinding process with respect to the semiconductor wafer W is continued or stopped, detecting the thickness of the semiconductor wafer W of the area | region which is not arrange | positioned facing the grinding wheel 61 with the thickness detector 7. FIG.

  In the grinding apparatus 1 according to the present embodiment, a semiconductor wafer W such as a silicon wafer or GaAs is described as an example of a workpiece (workpiece), but the present invention is not limited to this configuration. Glass, sapphire-based inorganic material substrates, plate-like metal or resin ductile materials, and various processed materials requiring flatness on the order of micron to submicron order may be used as the workpiece.

  The table support 4 is provided in a square shape and rotatably supports the chuck table 41. The table support 4 is connected to a drive mechanism (not shown), and is slid in the front-rear direction in the opening 2 a formed on the upper surface of the base 2 by a drive force supplied from the drive mechanism. Thereby, the chuck table 41 is separated from the grinding position where the semiconductor wafer W is opposed to the grinding unit 6 and the front side from the grinding position, and the unprocessed semiconductor wafer W is supplied. Is slid to and from the repositioning position at which it is collected.

  Before and after the table support 4, a dust-proof cover 8 is provided to prevent intrusion of grinding wheel scraps generated during grinding of the semiconductor wafer W into the base 2. The dust cover 8 is attached to the front surface and the rear surface of the table support base 4, and is provided so as to be expandable / contractable according to its movement position, and is configured to cover the opening 2 a of the base 2.

  The chuck table 41 constitutes a holding unit, and is formed in a disk shape, and a holding surface 41 a on which the semiconductor wafer W is held is formed. An adsorption surface is formed of a porous ceramic material at the central portion of the holding surface 41a. The chuck table 41 is connected to a suction source (not shown) disposed in the base 2 and holds the semiconductor wafer W by suction on the suction surface of the holding surface 41a. The chuck table 41 is connected to a rotation driving mechanism (not shown), and is rotated while the semiconductor wafer W is held on the holding surface 41a by the rotation driving mechanism. The semiconductor wafer W is placed on the holding surface 41a of the chuck table 41 as indicated by an arrow A by an operator of the grinding apparatus 1, for example.

  The support column 5 is provided in a rectangular parallelepiped shape, and a grinding unit moving mechanism 51 for moving the grinding unit 6 above the chuck table 41 is provided on the front surface thereof. The grinding unit moving mechanism 51 has a Z-axis table 52 that moves in the vertical direction with respect to the support column 5 by a ball screw type moving mechanism. The grinding unit 6 is supported on the Z-axis table 52 via a support portion 53 attached to the front side thereof.

  The grinding unit 6 constitutes a processing means, and has a grinding wheel 61 that is detachably attached to the lower end of a spindle (not shown). The grinding wheel 61 is composed of, for example, a diamond grinding stone in which diamond abrasive grains are hardened with a binder such as metal bond or resin bond.

  The thickness detector 7 constitutes a thickness detection means, and a semiconductor head based on the laser head unit 71 for irradiating the semiconductor wafer W held on the chuck table 41 with laser light and the reflected light from the semiconductor wafer W. A laser unit 72 that calculates a thickness detection value of W, a storage unit 73 that stores information necessary to determine continuation or stop of grinding in the grinding apparatus 1, and a predetermined thickness detection value of the storage unit 73 It has a regulation unit 74 that regulates storage, and a control unit 75 that controls grinding by the grinding unit 6 based on the thickness detection value stored in the storage unit 73 (see FIG. 3). In the thickness detector 7, the laser head unit 71 and the laser unit 72 constitute a detection unit that detects the thickness of the semiconductor wafer W.

  The laser head portion 71 is provided at the distal end of an arm portion 76 having an inverted L-shape standing on the side of the opening 2 a of the base 2. The laser head unit 71 is disposed at a position close to the surface of the semiconductor wafer W held on the chuck table 41 so that the laser beam is irradiated perpendicularly to the upper surface of the semiconductor wafer W held on the chuck table 41. Is provided. Note that the arm unit 76 may be connected to a drive mechanism (not shown) so that the laser head unit 71 is rotated in the horizontal direction.

  For example, the laser unit 72 is disposed inside the base 2 and is connected to the laser head unit 71 by an optical fiber or the like disposed in the arm unit 76. The laser unit 72 receives an interference wave of a laser light source constituting a light source of laser light emitted from the laser head unit 71 and reflected light (first reflected light and second reflected light described later) from the semiconductor wafer W. It includes a photodiode and a detection circuit that analyzes the waveform of the interference wave received by the photodiode. In the laser unit 72, the waveform of the interference wave received by the photodiode is analyzed by the detection circuit, and a value (for example, an electric signal or the like) digitized according to the waveform is obtained as the thickness detection value.

  The storage unit 73 is a thickness detection value output from the laser unit 72 and, for example, an average thickness of the semiconductor wafer W input from the operation panel 3 as information for determining whether the grinding process 1 is continued or stopped in the grinding apparatus 1. A value (hereinafter, simply referred to as “thickness average value”), a value indicating the width of the allowable range of the thickness detection value provided from the restriction unit 74 (hereinafter, referred to as “allowable width value” as appropriate), and a control unit 75 The upper limit value and the lower limit value of the allowable range of the thickness detection value are stored.

  For example, the restricting unit 74 calculates an allowable width value from the thickness variation value (hereinafter simply referred to as “thickness variation value”) of the semiconductor wafer W input from the operation panel 3 and notifies the storage unit 73 of the allowable width value. To do. Further, the restricting unit 74 restricts the storage unit 73 from storing a thickness detection value equal to or greater than the upper limit value of the allowable range stored in the storage unit 73 and a thickness detection value equal to or less than the lower limit value of the allowable range. For example, each time the thickness detection value is output from the laser unit 72, the regulation unit 74 determines whether the thickness detection value is greater than or equal to the upper limit value of the allowable range, or less than the lower limit value. The thickness detection value is discarded.

  The control unit 75 calculates the upper limit value and the lower limit value of the allowable range of the thickness detection value from the allowable width value and the thickness average value stored in the storage unit 73 and notifies the storage unit 73 of these upper limit value and lower limit value. To do. Specifically, the upper limit value and the lower limit value of the allowable range are obtained by setting the thickness average value as the center value of the allowable width value stored in the storage unit 73. In addition, the control unit 75 updates the upper limit value and the lower limit value of the allowable range of the thickness detection value based on the comparison result between the thickness detection value stored in the storage unit 73 and a constant value within the allowable range. Further, the control unit 75 controls the grinding process in the grinding unit 6 based on a comparison result between the thickness detection value stored in the storage unit 73 and a predetermined desired value.

  Here, with reference to FIG. 3, the thickness detection result of the semiconductor wafer W in the thickness detector 7 will be described. 3A shows the state of reflected light when the thickness detector 7 detects the thickness of the semiconductor wafer W appropriately. In FIG. 3B, the thickness detector 7 shows the semiconductor wafer. It shows the state of reflected light when the thickness of W is detected by mistake.

  In the thickness detector 7 according to the present embodiment, laser light is oscillated by the laser light source in the laser unit 72 and the semiconductor wafer W is irradiated with the laser light from the laser head unit 71. As shown in FIG. 3A, interference between the first reflected light L1 reflected by the front surface W1 of the Si layer constituting the semiconductor wafer W and the second reflected light L2 reflected by the back surface W2 of the Si layer. The wave is received by a photodiode in the laser unit 72. And the waveform of the interference wave of these 1st reflected light L1 and the 2nd reflected light L2 is analyzed with a detection circuit, and an appropriate thickness detection value is obtained by digitizing into an electric signal etc. according to the waveform. It has become something that can be.

  However, when the laser light irradiated to the semiconductor wafer W from the laser head unit 71 passes through the Si layer constituting the semiconductor wafer W, as shown in FIG. 3B, a device layer under the Si layer is formed. The first reflected light L1 may be reflected by the front surface W3, and the second reflected light L2 may be reflected by the back surface W4 of the device layer. When the waveform is analyzed based on the interference wave between the first reflected light L1 and the second reflected light L2, and is digitized according to the waveform, an erroneous thickness detection value smaller than the original thickness detection value is obtained. Will be detected.

  In order to cope with such a false detection of the thickness detection value, the thickness detector 7 according to the present embodiment sets an allowable range (upper limit value, lower limit value) in the detection result of the thickness detector 7, and this allowable value. By determining the continuation or stop of the grinding process of the semiconductor wafer W while eliminating the detection result outside the range, the malfunction of the apparatus accompanying the erroneous detection of the thickness detection value is reduced. Hereinafter, the grinding process of the grinding apparatus 1 according to the present embodiment considering the erroneous detection of the thickness detection value will be described with reference to FIG. FIG. 4 is a flowchart for explaining the grinding process of the grinding apparatus 1 according to the present embodiment.

  As shown in FIG. 4, the grinding apparatus 1 is in a state of waiting for the input of the thickness variation value x and the thickness average value y via the operation panel 3 (step (hereinafter referred to as “ST”) 301). . Note that, when there is no input of the thickness variation value x and the thickness average value y, this standby state is continued.

  Here, the thickness variation value x and the thickness average value y will be described with reference to FIG. FIG. 5 is a schematic diagram for explaining the thickness variation value x and the thickness average value y of the semiconductor wafer W that is a processing target of the grinding apparatus 1 according to the present embodiment. As shown in FIG. 5, in the semiconductor wafer W, thickness variations can occur on the surface to be ground in the manufacturing process. In FIG. 5, for convenience of explanation, the case where the central portion is thinner than the outer peripheral edge of the semiconductor wafer W is shown. However, the actual thickness variation is shown in the entire semiconductor wafer W. It is what happens.

  In the semiconductor wafer W shown in FIG. 5, the thickness variation value x is specified by the thickest portion of the outer peripheral edge and the thinnest portion near the center, and the average value of the thickness of the semiconductor wafer W including the thickness variation value x is determined. The thickness average value y is specified as follows. These thickness variation value x and thickness average value y can be specified by the type of the semiconductor wafer W based on the processing results. In the grinding apparatus 1 according to the present embodiment, the thickness variation value x and the thickness average value y are input from the operation panel 3, but the present invention is not limited to this. In the following, for convenience of explanation, it is assumed that the thickness variation value x is “5 μm” and the thickness average value y is “160 μm”.

  When the input of the thickness variation value x and the thickness average value y is received from the operation panel 3, the thickness average value y is input to the storage unit 73, while the thickness variation value is input to the regulation unit 74. Storage unit 73 stores input thickness average value y (ST302). On the other hand, the restriction unit 74 calculates an allowable width value from the input thickness variation value x (ST303). Here, the reason why the allowable width value is calculated on the basis of the thickness variation value x is that the grinding process is appropriately performed in consideration of the thickness variation value x of the semiconductor wafer W to be processed. By determining the allowable width value in this way, when the semiconductor wafer W having a large thickness variation value x is ground, the allowable width value corresponding to this can be calculated. Here, it is assumed that the allowable width value is set to “4x” which is four times the thickness variation value x. In the example described above, the allowable width value is calculated as “20 μm”. The allowable width value calculated by the restriction unit 74 is input to the storage unit 73 and stored therein. Here, “4x” is used as an example of the allowable width value, but the value of the allowable width value can be appropriately changed. This allowable width value is preferably calculated according to the type of the semiconductor wafer W as the workpiece.

  Next, in the control unit 75, an allowable range that allows storage in the storage unit 73 from the thickness average value y (= 160 μm) stored in the storage unit 73 and the allowable width value 4x (= 20 μm). It is set (ST304). Specifically, the control unit 75 sets an allowable range 4x in which the thickness average value y is arranged at the center value. In this case, since the thickness average value y is “160 μm”, “170 μm” is set as the upper limit value of the allowable range, and “150 μm” is set as the lower limit value of the allowable range. The upper limit value and the lower limit value of the allowable range set in this way are input to the storage unit 73 and stored therein.

  In the processing so far, the storage unit 73 has “160 μm” as the thickness average value y, “20 μm” as the allowable width value 4x, and “170 μm” and “150 μm” as the upper limit value and the lower limit value of the allowable range. Remembered. When these values are stored in the storage unit 73, grinding of the semiconductor wafer W is started. Then, as needed, the thickness of the semiconductor wafer W is detected by the laser head unit 71 and the laser unit 72, and the detected thickness value is stored in the storage unit 73 (ST305).

  When the thickness detection value is stored in storage unit 73, restriction unit 74 determines whether or not the thickness detection value is within the allowable range set in ST304 (ST306). In this case, the regulation unit 74 determines whether the thickness detection value stored in the storage unit 73 is larger than “150 μm” and smaller than “170 μm”. That is, in ST306, it is determined whether or not the thickness detection value stored in storage unit 73 is an incorrect thickness detection value outside the allowable range.

  When the thickness detection value stored in the storage unit 73 is not within the allowable range, the regulation unit 74 discards the thickness detection value from the storage unit 73 (ST307). That is, in ST307, an erroneous thickness detection value that deviates from the allowable range is discarded so as not to be considered in the determination of continuation or stop of the grinding process described later. As a result, it is possible to reliably prevent a situation in which the grinding process is stopped based on such an erroneous thickness detection value outside the allowable range. If the corresponding thickness detection value is discarded, the process returns to ST305, and the arrival of the thickness detection value by the subsequent grinding process is awaited.

  On the other hand, when the thickness detection value stored in the storage unit 73 is a value within the allowable range, the control unit 75 has a thickness detection value equal to or smaller than a predetermined desired thickness detection value (desired value). Is determined (ST308). That is, in ST308, it is determined whether the semiconductor wafer W has been ground to a desired thickness. As described above, in ST307, the thickness detection value that deviates from the allowable range is discarded by the restricting unit 74. Therefore, the degree of grinding of the semiconductor wafer W is appropriately set based on the thickness detection value within the allowable range. Can be determined.

  In this case, when the thickness detection value stored in the storage unit 73 is equal to or less than the desired value, the control unit 75 instructs the grinding unit 6 to stop the grinding process. In response to this instruction, grinding by the grinding unit 6 is stopped (ST309).

  On the other hand, when the thickness detection value stored in the storage unit 73 is not a desired value, the control unit 75 determines that the thickness detection value is a constant value within an allowable range (here, the thickness variation value x from the thickness average value y). It is determined whether or not the value is equal to or less than (subtracted value “y−x”) (ST310). Here, before the thickness of the semiconductor wafer W reaches a desired value, it is determined whether or not the allowable range stored in the storage unit 73 should be updated. In this case, the control unit 75 determines whether the thickness detection value stored in the storage unit 73 is “155 μm” or less.

  If the thickness detection value stored in the storage unit 73 has not reached “y−x” or less, the process returns to ST305, and the arrival of the thickness detection value by the subsequent grinding process is awaited. . On the other hand, when the thickness detection value stored in storage unit 73 has reached “y−x” or less, control unit 75 replaces thickness average value y with “y−x” (ST311). In this case, the thickness average value y is replaced from “160 μm” to “155 μm”. Thereafter, the process returns to ST304, and an allowable range that allows storage in the storage unit 73 is set again from the thickness average value y (= 155 μm) and the allowable width value 4x (= 20 μm). In this case, since the thickness average value y is “155 μm”, the upper limit value and the lower limit value of the allowable range are updated to “165 μm” and “145 μm”, respectively.

  In the allowable range updated in this way, the processing from ST305 is repeated again. When the thickness detection value stored in the storage unit 73 in ST308 reaches a desired value while repeating the processes of ST304 to ST311, stop of the grinding process in the grinding unit 6 is instructed, and accompanying this, the grinding unit 6 grinding is stopped. In this way, a series of grinding processes in the grinding apparatus 1 according to the present embodiment is completed.

  Hereinafter, the transition of the thickness of the semiconductor wafer W that is ground by the grinding process shown in FIG. 4 will be described with reference to FIG. FIG. 6 is a diagram for explaining the transition of the thickness of the semiconductor wafer W that is ground by the grinding apparatus 1 according to the present embodiment. In FIG. 6, the vertical axis indicates the thickness of the semiconductor wafer W, and the horizontal axis indicates the elapsed time of the grinding process. As shown in FIG. 2, the grinding unit 6 is disposed with respect to the semiconductor wafer W, and the grinding according to this embodiment is performed in which the grinding unit 6 and the chuck table 41 are rotated relative to each other to grind the semiconductor wafer W. In the apparatus 1, the thickness of the semiconductor wafer W changes so as to draw a wave with one rotation of the semiconductor wafer W as one cycle. However, in FIG. 6, for convenience of explanation, it is assumed that such a change in the thickness of the semiconductor wafer W is omitted, and the thickness of the semiconductor wafer W to be ground is assumed to change linearly.

  In ST301 shown in FIG. 4, in the initial state in which the input of “5 μm” as the thickness variation value x and “160 μm” as the thickness average value y is accepted, as shown at time t1 in FIG. The value and the lower limit are set to “170 μm” and “150 μm”, respectively. With the allowable range set in this manner, the semiconductor wafer W is ground and the thickness is detected. In ST310, the thickness detection value reaches (y−x) or less (“155 μm” or less). If it is determined, in ST311, the thickness average value y is updated to “155 μm”.

  In ST304, a new allowable range is set based on the updated thickness average value y (155 μm) as shown at time t2. Specifically, the upper limit value and the lower limit value of the allowable range are set to “165 μm” and “145 μm”, respectively. With the allowable range set in this manner, the semiconductor wafer W is further ground and the thickness is detected. In ST310, the thickness detection value is again (y−x) or less (“150 μm” or less). In ST311, the thickness average value y is updated to “150 μm”.

  Similarly, as shown at time points t3, t4, and t5, new allowable ranges are set based on the updated thickness average values y (150 μm, 145 μm, and 140 μm, respectively). That is, in the grinding apparatus 1 according to the present embodiment, the allowable range is gradually lowered to the lower side (thin thickness becomes thinner) based on the difference between the thickness detection value and the lower limit value of the allowable range being a predetermined value or less. Has been moved to. In the process of shifting the allowable range in this way, if the thickness detection value of the semiconductor wafer W becomes equal to or less than the desired value in ST308, the grinding processing in the grinding unit 6 is stopped in ST309.

  In this case, an erroneous thickness detection value outside the allowable range set at each point in the grinding process is detected in ST306 and discarded in ST307. As described above, in the grinding apparatus 1 according to the present embodiment, since an erroneous thickness detection value outside the allowable range is restricted from being stored in the storage unit 73, according to the thickness detection value outside the allowable range. Since it is possible to reliably prevent the grinding process by the grinding unit 6 from being controlled, it is possible to reduce the malfunction of the grinding apparatus 1 according to an erroneous thickness detection value of the semiconductor wafer W.

  More specifically, in the grinding apparatus 1 according to the present embodiment, since the thickness detection value equal to or lower than the lower limit set by the regulation unit 74 is regulated to be stored in the storage unit 73, the lower limit value is set. Since the grinding process by the grinding unit 6 can be prevented from being controlled according to the following thickness detection values, the grinding process can be performed according to an erroneous thickness detection value smaller than the appropriate thickness detection value of the semiconductor wafer W. It is possible to reduce a situation in which a malfunction that is stopped occurs.

  Further, in the grinding apparatus 1 according to the present embodiment, since the thickness detection value equal to or higher than the upper limit value set by the restriction unit 74 is restricted from being stored in the storage unit 73, the thickness detection greater than or equal to the upper limit value is detected. Since it is possible to prevent the grinding process by the grinding unit 6 from being controlled in accordance with the value, the semiconductor wafer W can move to a desired location in accordance with an erroneous thickness detection value larger than the appropriate thickness detection value of the semiconductor wafer W. It is possible to reduce a situation in which a malfunction that occurs beyond grinding (overgrinding) occurs.

  Furthermore, in the grinding apparatus 1 according to the present embodiment, the allowable range is gradually lowered based on the difference between the thickness detection value stored in the storage unit 73 and the lower limit value of the allowable range being a predetermined value or less. The side has been moved. Thereby, since the allowable range of the thickness detection value allowed to be stored in the storage unit 73 can follow the current thickness average value y of the semiconductor wafer W, the erroneous thickness detection value is stored in the storage unit 73. Can be regulated with high accuracy.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the above-described embodiment, the restriction unit 74 of the thickness detector 7 sets an allowable range for limiting the storage of the thickness detection value in the storage unit 73, and the storage unit 73 for the thickness detection value outside this allowable range. Although the case of restricting the storage is described, the constituent elements that restrict the storage to the storage unit 73 are not limited to the restriction unit 74 and can be appropriately changed. For example, the control unit 75 may have such a function.

  In the above-described embodiment, all the thickness detection values (including the thickness detection values to be discarded) output from the laser unit 72 are stored in the storage unit 73, and then are regulated by the regulation unit 74 as necessary. Although the case where the storage of the predetermined thickness detection value in the storage unit 73 is regulated by discarding has been described, the method of regulating the storage in the storage unit 73 is not limited to this and is appropriately changed. Is possible. For example, the restriction unit 74 may determine whether or not storage is permitted prior to the storage process of the storage unit 73, and only the thickness detection value that is allowed to be stored according to the determination result may be output to the storage unit 73.

  As described above, the present invention reduces the malfunction of the apparatus according to the erroneous workpiece thickness detection value by preventing the grinding process from being controlled according to the thickness detection value equal to or lower than the lower limit value. In particular, the present invention is useful for a grinding apparatus that performs grinding while detecting the thickness of a semiconductor wafer.

DESCRIPTION OF SYMBOLS 1 Grinding device 2 Base 3 Operation panel 4 Table support stand 41 Chuck table (holding means)
41a Holding surface 5 Supporting part 51 Grinding unit moving mechanism 52 Z-axis table 53 Supporting part 6 Grinding unit (processing means)
7 Thickness detector (thickness detection means)
71 Laser Head Unit 72 Laser Unit 73 Storage Unit 74 Restriction Unit 75 Control Unit 76 Arm Unit 8 Dustproof Cover

Claims (2)

A grinding apparatus comprising: holding means for holding a workpiece; processing means for grinding the workpiece held by the holding means; and thickness detecting means for detecting the thickness of the workpiece held by the holding means,
The thickness detecting means limits a detection unit that detects the thickness of the workpiece in a non-contact manner, a storage unit that stores the thickness detected by the detection unit, and stores the thickness detected by the detection unit in the storage unit. A lower limit value to be set, and when a thickness equal to or lower than the lower limit value is detected, a detected thickness regulating unit that is not stored in the storage unit, a thickness detected by the detection unit and stored in the storage unit, and the lower limit And a control unit that lowers the lower limit value by a predetermined amount based on a difference from the value being equal to or less than a predetermined value. The grinding apparatus according to claim 1, wherein the detected thickness regulating unit calculates the lower limit value based on a thickness variation value specified in advance according to a type of workpiece.

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