JP2011189411A - Wafer grinding device, wafer grinding method, wafer grinding program and wafer grinding control device - Google Patents

Abstract

An object of the present invention is to detect wafer grinding abnormality in units of wafers regardless of the type of wafer.
A wafer grinding apparatus according to the present invention detects a spindle current value of a wheel attached to a rotating shaft, grinding a wafer, a motor for rotating the rotating shaft, and a motor after starting grinding of the wafer over time. After the detection unit, the wafer and the wheel are in contact with each other, a storage unit that stores the first peak value of the spindle current value detected by the detection unit, the first peak value stored by the storage unit, and the spindle that the detection unit detects A determination unit for comparing the current value and determining whether the spindle current value detected by the detection unit after detecting the first peak value exceeds a value determined based on the first peak value; and a determination unit And an output unit for outputting that the grinding state of the wafer is abnormal when it is determined that the spindle current value exceeds a value determined with reference to the first peak value.
[Selection] Figure 1

Description

  The present invention relates to a wafer grinding apparatus, a wafer grinding method, a wafer grinding program, and a wafer grinding control apparatus.

  As a wafer grinding device, for example, there are devices described in Patent Documents 1 to 3.

  Patent Document 1 describes a wafer grinding apparatus that detects a change in the processing strain layer depth of a wafer based on a waveform of a grinding resistance value taken during surface grinding of the wafer. In Patent Document 1, this makes it possible to grasp a more delicate grinding situation than the conventional surface grinding method in which the average value of the grinding resistance value is obtained, and thereby to detect the grinding abnormality. In addition, it is said that it is possible to detect a wide range of grinding conditions such as wafer surface roughness during grinding, processing strain layer depth abnormality due to generation of scratches on the wafer surface, clogging of the grindstone, and wear of the grindstone.

  Further, in the wafer grinding apparatus of Patent Document 2, a grindstone is connected to a grindstone shaft via an electrostrictive element or a magnetostrictive element, the grindstone shaft load current value during grinding is monitored, and the grindstone shaft load current value is determined in advance. When the value exceeds the reference value, the electrostrictive element or magnetostrictive element connected to the grindstone shaft is instantly activated, and the grindstone is moved up by 10-20 μm in the anti-cutting direction of the grindstone shaft to retract the grindstone. Yes. According to Patent Document 2, it is said that, by doing so, damage to the wafer can be remedied when an abnormal processing state including clogging of a grindstone and dropping of abrasive grains in a large unit occurs.

  Patent Document 3 describes a wafer grinding apparatus that uses a grinding resistance profile and a motor current or motor power profile to determine the similarity. In Patent Document 3, by doing this, it is possible to make a determination that does not depend on the shape of the workpiece, the grinding conditions, or the like, compared to the case where the grinding resistance or the motor current reaches a predetermined value as a criterion. It is supposed that the timing of dressing can be determined appropriately.

JP-A-9-29630 JP 2006-35406 A JP 2008-62364 A

  However, the technique described in the above document is not a method capable of detecting wafer grinding abnormality for each wafer unit, regardless of the type of wafer.

  In the techniques of Patent Documents 1 and 2, it is necessary to acquire a threshold value and a grinding profile in advance. Therefore, it is necessary to acquire these threshold values and profiles for each wafer type.

  On the other hand, in Patent Document 3, by monitoring the similarity of the grinding profile, it is possible to detect grinding abnormality regardless of the shape of the wafer. However, since it is necessary to obtain a normal motor current profile and a grinding resistance profile in advance, it is necessary to prepare at least two wafers, and it is impossible to detect wafer grinding abnormalities in units of wafers.

  As described above, with the technique of the above-mentioned document, it is difficult to detect wafer grinding abnormalities in units of wafers regardless of the type of wafer.

According to the present invention,
A grinding part attached to the rotating shaft and grinding the wafer;
A motor for rotating the rotating shaft;
A detection unit for detecting the current value of the motor after the start of grinding of the wafer over time;
A storage unit that stores an initial peak value of the current value detected by the detection unit after the wafer and the grinding unit are in contact with each other;
The first peak value stored in the storage unit is compared with the current value detected by the detection unit, and the current value detected by the detection unit after detecting the first peak value is A determination unit for determining whether or not a value determined based on the peak value is exceeded,
An output unit that outputs that the grinding state of the wafer is abnormal when the determination unit determines that the current value exceeds the value determined based on the first peak value;
A wafer grinding apparatus is provided.

Moreover, according to the present invention,
A step of grinding a wafer by a grinding unit attached to the rotating shaft by rotating a rotating shaft by a motor;
A computer detecting the current value of the motor over time after the start of grinding of the wafer;
A computer obtains a first peak value of the detected current value after the wafer and the grinding part are in contact;
The computer compares the acquired first peak value with the detected current value, and the current value detected after detecting the first peak value is a value determined based on the first peak value. Determining whether or not
When it is determined that the current value exceeds the value determined on the basis of the first peak value, a computer outputs that the grinding state of the wafer is abnormal;
A wafer grinding method is provided.

Moreover, according to the present invention,
A grinding process in which a rotating shaft is rotated by a motor and the wafer is ground by a grinding portion attached to the rotating shaft;
Detection processing for detecting the current value of the motor after grinding of the wafer over time;
A storage process for storing an initial peak value of the current value detected by the detection process after the wafer and the grinding unit are in contact with each other;
The first peak value stored by the storage process is compared with the current value detected by the detection process, and the current value detected by the detection process after detecting the first peak value is A determination process for determining whether or not a value determined based on a peak value is exceeded,
An output process for outputting that the grinding state of the wafer is abnormal when it is determined by the determination process that the current value exceeds the value determined based on the first peak value;
A wafer grinding program for causing a computer to execute is provided.

Furthermore, according to the present invention,
A wafer grinding control device for controlling a wafer grinding process, wherein a rotation shaft is rotated by a motor and a wafer attached to the rotation shaft is ground.
A detection unit for detecting the current value of the motor after the start of grinding of the wafer over time;
A storage unit that stores an initial peak value of the detected current value after contacting the wafer and the grinding unit;
The first peak value stored in the storage unit is compared with the current value detected by the detection unit, and the current value detected by the detection unit after detecting the first peak value is A determination unit for determining whether or not a value determined based on the peak value is exceeded,
An output unit that outputs that the grinding state of the wafer is abnormal when the determination unit determines that the current value exceeds the value determined based on the first peak value;
A wafer grinding control device is provided.

  According to the present invention, the current value of the motor after the start of grinding of the wafer is detected over time, the first peak value among the current values detected after the wafer and the grinding part are in contact is stored, and then the current value When the value exceeds a value determined on the basis of the first peak value, it is output that the grinding state of the wafer is abnormal. Thereby, it is possible to detect wafer grinding abnormality in units of wafers without acquiring a reference value in advance. Therefore, it is possible to detect and cope with wafer grinding abnormality regardless of the type of wafer.

  According to the present invention, it is possible to detect an abnormal grinding of a wafer in units of wafers regardless of the type of wafer.

It is a mimetic diagram showing a wafer grinding device concerning an embodiment. It is a flowchart explaining the wafer grinding method using the wafer grinding apparatus which concerns on embodiment. It is a figure explaining the wafer grinding device concerning an embodiment. It is a figure which shows the example of the time-dependent change of the spindle current which the detection part of the wafer grinding apparatus which concerns on embodiment detects. It is a figure explaining maximum height roughness (Rz).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  FIG. 1 is a diagram schematically showing a wafer grinding apparatus according to the present embodiment. This wafer grinding apparatus is attached to a rotating shaft 12, and a wheel (grinding unit) 14 for grinding the wafer W, a motor 11 for rotating the rotating shaft 12, and a spindle current value of the motor 11 after starting the grinding of the wafer W. The detection unit 17 that detects over time, the storage unit 111 that stores the first peak value of the spindle current value detected by the detection unit 17 after the wafer W and the wheel 14 contact each other, and the first that the storage unit 111 stores Is compared with the spindle current value detected by the detection unit 17, and the spindle current value detected by the detection unit 17 after detecting the first peak value is a value determined based on the first peak value. When the determination unit 112 determines whether or not the spindle current value exceeds a value determined with reference to the first peak value, Having an output unit 113 that the grinding condition of E c W outputs an abnormal, a.

  First, the wafer grinding apparatus of this embodiment will be described. This wafer grinding apparatus includes a chuck table 16 on which a wafer W is mounted. The chuck table 16 includes a chuck 15 on which the wafer W is attracted. The wafer W is a semiconductor substrate made of silicon, sapphire, or the like. Various types of wafers W can be used, such as different types of attached films on the back surface.

  The wheel 14 is connected to the rotary shaft 12 via an electrostrictive element or magnetostrictive element 19 and a flange 13. FIG. 3A is a schematic diagram showing the wheel 14 in an enlarged manner. As shown to Fig.3 (a), the wheel 14 is equipped with the grindstone 14a, and when the grindstone 14a and the wafer W contact, the wafer W is ground. The grindstone 14a can be a diamond, for example. The rotation shaft 12 is driven to rotate by the motor 11, and the rotation shaft load current value (spindle current value) to the motor 11 is input to the detection unit 17 and monitored by the detection unit 17. Since the detection unit 17 detects the spindle current value together with the load from the wafer W applied to the rotary shaft 12, it can also detect when the wafer W and the wheel 14 are in contact with each other. The moving mechanism 18 can move the rotating shaft 12 in the vertical direction (direction d). The electrostrictive element or the magnetostrictive element 19 incorporates a distortion amount feedback sensor (not shown), and a signal of the distortion amount feedback sensor is input to the control unit 114 of the wafer control apparatus 10 described later. The electrostrictive element or magnetostrictive element 19 is instantly activated by a signal from the control unit 114, and the rotary shaft 12 is raised in the anti-cutting direction −d of the rotary shaft 12 to retract the wheel 14.

  The wafer control apparatus 10 includes an input unit 110, a storage unit 111, a determination unit 112, an output unit 113, and a control unit 114. The input unit 110 receives a change with time in the spindle current value of the motor 11 detected by the detection unit 17 and stores the change in the storage unit 111. The control unit 114 controls the moving direction and moving speed of the moving mechanism 18. The determination unit 112 extracts the first peak value of the spindle current value detected by the detection unit 17 after the wafer W and the wheel 14 come into contact with each other. The storage unit 111 receives the moving speed of the moving mechanism 18 directly from the control unit 114 or via the determination unit 112 and stores it. Since the spindle current value stored in the storage unit 111 is detected together with the wafer load received by the rotating shaft, it is stored for each wafer.

  Each part of the wafer grinding apparatus of the present embodiment is realized by using various hardware as required. However, it can be realized by functioning in accordance with a computer program in which the wafer grinding apparatus is mounted.

  Such a computer program includes, for example, a grinding process in which the motor 11 rotates the rotating shaft 12 and the wafer 14 is ground by the wheel 14 attached to the rotating shaft 12, and the spindle of the motor 11 after the grinding of the wafer W is started. A detection process for detecting the current value over time, a storage process for storing the first peak value of the spindle current value detected by the detection process after the wafer W and the wheel 14 contact each other, and a first process stored by the storage process Judgment processing that compares the peak value with the detected spindle current value and determines whether the detected spindle current value after detecting the first peak value exceeds a value that is determined based on the first peak value. When it is determined by the determination process that the current value has exceeded a value determined based on the first peak value, the grinding state of the wafer W is Stored in the information storage medium such as RAM as software for executing the processing operation of the output processing such as CPU or the like for outputting be para.

  Next, the wafer grinding method of this embodiment will be described with reference to FIGS. FIG. 2 is a flowchart for explaining the wafer grinding method of the present embodiment. First, at least one wafer W is prepared on a wafer stage (not shown). And while rotating the motor 14, the detection part 17 starts the detection of a spindle electric current (S101). Next, one wafer W is picked up from the workpiece using a jig (not shown), transferred to the chuck table 16, and attracted to the chuck 15 (S102).

  Subsequently, after the moving mechanism 18 is lowered to the predetermined position in the cutting direction d, the grinding of the wafer W is started (S103). At this time, the determination unit 112 grasps that the grindstone 14 a has contacted the wafer W via the control unit 114. Thereafter, the determination unit 112 grasps that the unevenness is eliminated from the ground surface to the extent that the wafer W is stably ground. The unevenness difference of the ground surface of the wafer W at this time may be, for example, Rz (maximum height roughness): 10 μm or less. Generally, as shown in FIG. 5, Rz is represented by the sum of the maximum value of the peak height (Rp) and the maximum value of the valley depth (Rv) of the contour curve at the reference length (lr). Then, after the wafer W and the wheel 14 are in contact with each other, the spindle current value detected until the ground surface of the wafer W becomes flat enough to grind the wafer W stably (initial grinding time (t)). Among them, the highest spindle current value is acquired as the first peak value (initial peak value) (S104).

  An example of how to obtain the initial peak value will be specifically described with reference to FIG. FIG. 3 is an enlarged side view showing a contact portion between the wheel 14 and the wafer W shown in FIG. The moving mechanism 18 can bring the grinding wheel 14 a into contact with the wafer W by lowering the wheel 14 at a moving speed V (μm / second). At the beginning of contact between the grindstone 14a and the wafer W, as shown in FIG. 3A, since the surface of the wafer W has irregularities, the grindstone 14a bites into the irregularities, and the spindle current value increases. Then, after the spindle current value reaches the peak value, the spindle current value gradually decreases as the wafer is flattened. Thereafter, when the unevenness difference of the grinding surface of the wafer W becomes Rz: 10 μm or less, the grindstone 14a is placed at a position where the wafer W can be stably ground (FIG. 3B).

  In order to flatten the wafer W to some extent, it is preferable to grind the wafer surface of at least several tens of μm. In consideration of variations in the surface roughness (± 10 μm) of the protective sheet 20 attached to the side opposite to the ground surface of the wafer, variations in the thickness of the wafer W (± 15 μm), etc., the wafer W is about 100 μm. More preferably, it is ground to some extent. By doing so, the ground surface of the wafer is flattened to the extent that the wafer W is ground stably. In this case, the grinding initial time (t) can be expressed by the equation “t (seconds) = 100 / V”. Therefore, the determination unit 112 receives V from the control unit 114, grasps the passage of time after the wafer W and the wheel 14 come into contact, and determines the spindle current value with the highest spindle current value detected within t seconds. By extracting, an initial peak value can be acquired.

  Then, while grinding the wafer W, the acquired initial peak value is compared with the detected spindle current value, and the detected spindle current value after detecting the initial peak value is a value determined based on the initial peak value. It is determined whether or not (initial peak reference value) has been exceeded (S105).

  Here, as the initial peak reference value, the initial peak value itself may be used, or the initial peak value may be calculated. As the arithmetic processing, the initial peak value may be multiplied by a magnification larger than 1 time, or a value obtained by adding a predetermined value to the initial peak value may be used. When the magnification of the initial peak reference value with respect to the initial peak value is defined, the initial peak reference value can be set to 1.2 times the initial peak value, for example. When the initial peak reference value is a value obtained by adding a predetermined value to the initial peak value, the initial peak reference value can be a value obtained by adding 0.5 A to the initial peak value, for example. .

  If it is determined that the spindle current value does not exceed the initial peak reference value (S105Y), it is determined whether to continue grinding (S106). Whether to continue the grinding may be determined based on a predetermined grinding time for each wafer, or may be determined by detecting the flatness of the wafer surface. When it is determined that the grinding is continued (S106Y), the process returns to S105, and the obtained initial peak value is compared with the detected spindle current value while grinding the wafer W continuously.

  If it is determined that the grinding is not continued, that is, the grinding of the wafer W is finished (S106N), the grinding is finished (S107). If there is a wafer W on a wafer stage (not shown) (S108Y), it is set on the chuck table 16 (S102), and the subsequent operation is repeated. In this manner, all the wafers W to be ground are ground, and the grinding process of the wafers W is completed (S108N).

  FIG. 4A shows an example of a change in spindle current value with time when no abnormality is detected, that is, when the wafer W is not broken. In the example of FIG. 4A, after the initial peak value is detected at the beginning of grinding, the spindle current value does not exceed the initial peak value.

  On the other hand, when it is determined that the spindle current value exceeds the initial peak reference value (S105N), the output unit 110 outputs to the control unit 114 that the grinding state of the wafer W is abnormal. An abnormal grinding state of the wafer W means that the wafer W is cracked or the wafer W is cracked. The control unit 114 receives the abnormal signal from the output unit 110, instantly activates the electrostrictive element or the magnetostrictive element 19, moves the moving mechanism 18 in the -d direction, and retracts the wheel 14 (S109). Next, the control unit 114 stops the rotating shaft 12 and stops the motor 11 (S110). The output unit 110 may output an alarm signal to the user when an abnormality is detected. By doing so, the user can know that the wafer W is broken and can stop the grinding apparatus and check the operation of the grinding apparatus.

  FIG. 4B shows an example of the change over time in the spindle current value when an abnormality is detected, that is, when the wafer W is cracked. As shown in the example of FIG. 4B, after the initial peak value is detected at the initial stage of grinding, the spindle current value exceeds the initial peak value.

  It continues and demonstrates the effect of this embodiment. According to this embodiment, the peak value of the spindle current detected from when the wafer W comes into contact with the wheel 14 until stable grinding is stored as the initial peak value, and the stored initial peak value is stored. When the spindle current value exceeds the initial peak reference value after detection, it is output that the grinding state of the wafer W is abnormal. Thereby, it is possible to take measures such as detecting a crack in the wafer W in units of wafers without acquiring a reference value in advance and stopping the grinding apparatus. Therefore, it is possible to detect an abnormality in grinding of the wafer regardless of the type of wafer.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable. For example, in the embodiment, the wafer grinding by the infeed method in which the wafer is ground by moving the moving mechanism in the direction perpendicular to the rotation axis (direction d) has been described as an example. However, the present invention can also be applied to wafer grinding by a creep feed method in which a wafer is ground by moving a moving mechanism in a horizontal direction with respect to a rotation axis.

DESCRIPTION OF SYMBOLS 10 Wafer control apparatus 11 Motor 12 Rotating shaft 13 Flange 14 Wheel 14a Grinding wheel 15 Chuck 16 Chuck table 17 Detection part 18 Moving mechanism 19 Electrostrictive element or magnetostrictive element 20 Protection sheet 102 Rotating shaft 110 Input part 111 Storage part 112 Judgment part 113 Output Part 114 Control part

Claims (10)

A grinding part attached to the rotating shaft and grinding the wafer;
A motor for rotating the rotating shaft;
A detection unit for detecting the current value of the motor after the start of grinding of the wafer over time;
A storage unit that stores an initial peak value of the current value detected by the detection unit after the wafer and the grinding unit are in contact with each other;
The first peak value stored in the storage unit is compared with the current value detected by the detection unit, and the current value detected by the detection unit after detecting the first peak value is A determination unit for determining whether or not a value determined based on the peak value is exceeded,
An output unit that outputs that the grinding state of the wafer is abnormal when the determination unit determines that the current value exceeds the value determined based on the first peak value;
A wafer grinding apparatus.   The wafer grinding apparatus according to claim 1, wherein the value determined based on the first peak value is the first peak value.   2. The wafer grinding apparatus according to claim 1, wherein the value determined on the basis of the first peak value is a value obtained by multiplying the first peak value by a magnification larger than one time.   The wafer grinding apparatus according to claim 1, wherein the value determined based on the first peak value is a value obtained by adding a predetermined value to the first peak value.   After the wafer and the grinding part come into contact, the maximum value of the current value detected until the grinding part reaches a position where the wafer can be stably ground is determined as the first peak value. The wafer grinding apparatus according to any one of claims 1 to 4. A moving mechanism for moving the grinding unit in a direction perpendicular to the wafer to bring the grinding unit into contact with the wafer;
The time until the grinding unit reaches the position where the wafer can be stably ground after contacting the wafer and the grinding unit is t (seconds), and the moving speed of the grinding unit in the vertical direction is V. (Μm / sec), t = 100 / V,
6. The wafer grinding apparatus according to claim 1, wherein a maximum value of the current value detected for t seconds is determined as the first peak value after the wafer comes into contact with the grinding unit. A moving mechanism for moving the grinding part;
The wafer grinding apparatus according to claim 1, wherein when the output unit outputs that the grinding state of the wafer is abnormal, the moving mechanism retracts the grinding unit from the wafer. A step of grinding a wafer by a grinding unit attached to the rotating shaft by rotating a rotating shaft by a motor;
A computer detecting the current value of the motor over time after the start of grinding of the wafer;
A computer obtains a first peak value of the detected current value after the wafer and the grinding part are in contact;
The computer compares the acquired first peak value with the detected current value, and the current value detected after detecting the first peak value is a value determined based on the first peak value. Determining whether or not
When it is determined that the current value exceeds the value determined on the basis of the first peak value, a computer outputs that the grinding state of the wafer is abnormal;
A wafer grinding method. A grinding process in which a rotating shaft is rotated by a motor and the wafer is ground by a grinding portion attached to the rotating shaft;
Detection processing for detecting the current value of the motor after grinding of the wafer over time;
A storage process for storing an initial peak value of the current value detected by the detection process after the wafer and the grinding unit are in contact with each other;
The first peak value stored by the storage process is compared with the current value detected by the detection process, and the current value detected by the detection process after detecting the first peak value is A determination process for determining whether or not a value determined based on a peak value is exceeded,
An output process for outputting that the grinding state of the wafer is abnormal when it is determined by the determination process that the current value exceeds the value determined based on the first peak value;
Wafer grinding program to make computer execute. A wafer grinding control device for controlling a wafer grinding process, wherein a rotation shaft is rotated by a motor and a wafer attached to the rotation shaft is ground.
A detection unit for detecting the current value of the motor after the start of grinding of the wafer over time;
A storage unit that stores an initial peak value of the detected current value after contacting the wafer and the grinding unit;
The first peak value stored in the storage unit is compared with the current value detected by the detection unit, and the current value detected by the detection unit after detecting the first peak value is A determination unit for determining whether or not a value determined based on the peak value is exceeded,
An output unit that outputs that the grinding state of the wafer is abnormal when the determination unit determines that the current value exceeds the value determined based on the first peak value;
A wafer grinding control device.

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