JP5437680B2 - Semiconductor wafer double-side grinding apparatus and double-side grinding method - Google Patents

Description

  The present invention relates to a semiconductor wafer double-side grinding apparatus and a double-side grinding method.

  2. Description of the Related Art Conventionally, a double-sided grinding apparatus has been proposed that grinds both sides while rotating a semiconductor wafer around an axis while supporting the semiconductor wafer in a vertical position (see, for example, Patent Document 1). In such a double-sided grinding apparatus, the thickness sensor is held in contact with both surfaces of the rotating semiconductor wafer, and the thickness sensor continuously monitors the thickness of the semiconductor wafer from the start to the end of the double-sided grinding process. Execute.

By the way, the semiconductor wafer subjected to the double-side grinding process is sliced to a predetermined thickness by a wire saw or the like in a slicing process as a previous process.
In this slicing step, saw marks are formed on both sides of the semiconductor wafer by a wire saw or the like. The saw mark is a cut mark such as undulations and steps remaining on both surfaces of a semiconductor wafer sliced by a wire saw or the like.

JP 2006-332281 A

  However, if the semiconductor wafer is rotated in a state where the thickness sensors are in contact with both surfaces of the semiconductor wafer set in the double-side grinding apparatus, the thickness sensors jump up when the saw marks on both surfaces of the semiconductor wafer pass through the thickness sensors. As a result, the thickness sensor vibrates slightly, and the semiconductor wafer may be scratched on both sides.

  Scratches on both sides of the semiconductor wafer due to such vibration of the thickness sensor are often so deep that they do not disappear even when the double-side grinding process is executed. Since this scratch does not disappear even in the finish grinding process in which each side is ground after the double-side grinding process, it is discovered as a product defect in the shipping process.

  The present invention has been made in view of the above-described problems, and provides a double-sided grinding apparatus and double-sided grinding method for a semiconductor wafer capable of suppressing scratches caused by a contact-type thickness sensor on both sides of a semiconductor wafer. The purpose is to provide.

  (1) A semiconductor wafer double-side grinding apparatus according to the present invention includes a rotational drive unit that supports a semiconductor wafer in a vertical position and rotates it around an axis, and a pressure of fluid supplied to both surfaces of the semiconductor wafer. A pair of static pressure pads that support both surfaces, a pair of grinding wheels that rotate around an axis parallel to the rotation axis of the semiconductor wafer to grind both surfaces of the semiconductor wafer, and contacts that contact both surfaces of the semiconductor wafer From the start of the double-sided grinding process by the grinding wheel with a thickness sensor that can move between a position and a non-contact position that is movable, and monitors the thickness of the semiconductor wafer when in the contact position. A switching unit that holds the thickness sensor at the non-contact position and holds the thickness sensor at the contact position from the predetermined stage to the end of the double-side grinding process. , Characterized in that it comprises a.

  (2) Preferably, the predetermined stage is a stage in which the saw mark substantially disappears from both sides of the semiconductor wafer.

  (3) It is preferable that the predetermined stage is a time when a preset time elapses from the start of the double-side grinding process.

  (4) The method for double-sided grinding of a semiconductor wafer according to the present invention includes a rotary drive unit that supports the semiconductor wafer in a vertical position and rotates it around an axis, and a pressure of fluid supplied to both sides of the semiconductor wafer. A pair of static pressure pads that support both surfaces, a pair of grinding wheels that rotate around an axis parallel to the rotation axis of the semiconductor wafer to grind both surfaces of the semiconductor wafer, and contacts that contact both surfaces of the semiconductor wafer A method of double-sided grinding of a semiconductor wafer using a double-sided grinding apparatus comprising a thickness sensor that can move between a non-contact position and a non-contact position and that monitors the thickness of the semiconductor wafer when in the contact position. The thickness sensor is held at the non-contact position from the start of the double-side grinding process by the grinding wheel to a predetermined stage, and the both sides of the semiconductor wafer A non-thickness monitoring grinding process for performing grinding, and a thickness monitoring grinding process for grinding both surfaces of the semiconductor wafer while holding the thickness sensor at the contact position from the predetermined stage to the end of the double-side grinding process. It is characterized by.

  (5) Preferably, the predetermined stage is a stage in which the saw mark substantially disappears from both surfaces of the semiconductor wafer.

  (6) It is preferable that the predetermined stage is a time when a preset time elapses from the start of the double-side grinding process.

  ADVANTAGE OF THE INVENTION According to this invention, the double-sided grinding apparatus and double-sided grinding method of a semiconductor wafer which can suppress that the crack resulting from a contact-type thickness sensor is attached to both surfaces of a semiconductor wafer can be provided.

It is a schematic front view which shows one Embodiment of the double-sided grinding apparatus of the semiconductor wafer by this invention. It is a schematic side view of the double-sided grinding apparatus shown in FIG. It is a schematic plan view of the principal part which shows the state which has a thickness sensor in a non-contact position. It is a schematic plan view of the principal part which shows the state which has a thickness sensor in a contact position. It is a schematic block diagram of the double-sided grinding apparatus shown in FIG. It is a flowchart which shows one Embodiment of the double-sided grinding method of the semiconductor wafer by this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, with reference to FIG.1 and FIG.2, the whole structure of the double-sided grinding apparatus 10 of a semiconductor wafer is demonstrated. The double-side grinding apparatus 10 grinds both surfaces of a silicon wafer 1 as a semiconductor wafer at the same time.

  As shown in FIGS. 1 and 2, the double-side grinding apparatus 10 of the present embodiment includes a carrier 11, a rotating roller 13 and a support roller 14 as a rotation drive unit, a pair of static pressure pads 21 and 26, and a pair of Grinding wheels 31, 36, a control device 50 (see FIG. 5), a fluid supply unit 20 (see FIG. 5), a thickness sensor 40, and a switching unit 45 (see FIGS. 3 to 5). The control device 50 performs various controls such as the rotating roller 13, the fluid supply unit 20, the grinding wheels 31 and 36, the thickness sensor 40, and the switching unit 45.

  The carrier 11 is a ring-shaped member and has one protrusion 12 on the inner peripheral portion thereof. The inner peripheral portion of the carrier 11 is filled with a thin disc-shaped silicon wafer 1. The thickness of the carrier 11 is formed thinner than the thickness of the silicon wafer 1. By filling the inner peripheral portion of the carrier 11 with the silicon wafer 1, the outer peripheral portion of the silicon wafer 1 can be protected. At that time, the silicon wafer 1 is positioned in the circumferential direction with respect to the carrier 11 by fitting the notch 2 formed on the outer peripheral portion of the silicon wafer 1 to the protrusion 12 of the carrier 11. Thereby, the silicon wafer 1 can be rotated integrally with the carrier 11 by rotating the carrier 11 around the center of the ring.

The rotation roller 13 and the support roller 14 support the silicon wafer 1 in a vertical position and rotate it around a horizontal axis 1a. Here, the “vertical direction” is typically the direction of gravity, but may be slightly inclined from the direction of gravity.
The silicon wafer 1 is disposed between the pair of static pressure pads 21 and 26. The pair of static pressure pads 21 and 26 support both surfaces 3 and 4 of the rotating silicon wafer 1 by the pressure of the fluid 25 supplied to both surfaces 3 and 4 of the silicon wafer 1.
The pair of grinding wheels 31 and 36 rotate around axes 31 a and 36 a parallel to the rotation axis 1 a of the silicon wafer 1 to grind both surfaces 3 and 4 of the silicon wafer 1.

One rotating roller 13 and three supporting rollers 14 are positioned at four locations around the carrier 11.
The rotating roller 13 is a roller that rotates around a horizontal axis 13a by a motor (not shown). The rotating roller 13 constitutes one of the two lower rollers that support the weight of the silicon wafer 1 and the carrier 11. The rotating roller 13 is connected to the control device 50 shown in FIG. 5 and is rotated through a motor in response to a command from the control device 50.

  The support roller 14 is a roller that is rotatable around a horizontal axis 14a. The support roller 14 constitutes two rollers at the top and another roller at the bottom. The two upper support rollers 14 are configured so that they can be retracted to the left and right in FIG. 2 so as not to obstruct when the silicon wafer 1 is taken in and out from above.

  The pair of static pressure pads 21 and 26 are formed to be larger in the vertical direction than the sizes of the silicon wafer 1 and the carrier 11 that are arranged in a vertical position between them. Under the static pressure pads 21 and 26, cutout portions 22 and 27 each having a diameter approximately half the diameter of the silicon wafer 1 disposed therebetween are formed.

  In the static pressure pads 21 and 26, a large number of through holes 23 and 28 are formed in a region corresponding to the silicon wafer 1 disposed between them and in a region excluding the notches 22 and 27, respectively. The through holes 23 and 28 are connected to the fluid supply unit 20 shown in FIG. 5 through pipes 24 and 29, respectively.

  The fluid supply unit 20 supplies the fluid 25. The fluid supply unit 20 is connected to the control device 50 and controls the supply of the fluid 25 according to a command from the control device 50. The fluid 25 supplied from the fluid supply unit 20 is ejected from the through holes 23 and 28 to the both surfaces 3 and 4 of the silicon wafer 1 at a required pressure through the pipes 24 and 29, respectively.

  When the silicon wafer 1 and the carrier 11 rotate while being supported by the rotating roller 13 and the supporting roller 14, the pressure of the fluid 25 ejected from the through holes 23 and 28 toward the both surfaces 3 and 4 of the silicon wafer 1 Both surfaces 3 and 4 of the wafer 1 are kept in a vertical state on the opposing surfaces of the static pressure pads 21 and 26.

  The pair of grinding wheels 31 and 36 have a substantially cylindrical shape, and are provided with annular grindstone portions 32 and 37 on tip surfaces facing each other. The grinding wheels 31 and 36 are disposed in the notches 22 and 27 of the static pressure pads 21 and 26, respectively, and are rotated around horizontal axes 31a and 36a by a motor (not shown). The rotation directions of the grinding wheels 31 and 36 may be opposite to each other or the same direction.

  The grinding wheels 31 and 36 are moved to the silicon wafer 1 by a feed motor (not shown) as the heights of the grinding stone portions 32 and 37 along the directions of the axes 31a and 36a are reduced as the double-side grinding process proceeds. Move forward gradually in the direction of approach. As a result, the grinding surfaces 33 and 38 at the tips of the grindstone portions 32 and 37 properly come into contact with both surfaces 3 and 4 of the silicon wafer 1.

The grinding wheels 31 and 36 are connected to the control device 50 and are rotated via a motor in response to a command from the control device 50.
Further, the grinding wheels 31 and 36 are controlled to be displaced in the forward direction by a command from the control device 50 via a feed motor. That is, the grinding wheels 31 and 36 advance at a relatively high feed rate at the initial stage of the double-side grinding process. Further, the grinding wheels 31 and 36 advance at a relatively slow feed rate at the end of the double-side grinding process.

  As shown in FIGS. 2 to 4, the thickness sensor 40 includes a sensor unit 41 that can contact one surface 3 of the silicon wafer 1 and a sensor unit 42 that can contact the other surface 4. The thickness sensor 40 includes a contact position (see FIG. 4) where the sensor portions 41 and 42 are in contact with both surfaces 3 and 4 of the silicon wafer 1, and a non-contact position where the sensor portions 41 and 42 are not in contact with both surfaces 3 and 4 (see FIG. 3). The thickness sensor 40 is a contact-type sensor that monitors the thickness of the silicon wafer 1 when it is at the contact position shown in FIG.

  When the thickness sensor 40 is in the non-contact position shown in FIG. 3, the distance between the sensor portions 41 and 42 is larger than the thickness of the silicon wafer 1, and the tip portions of the sensor portions 41 and 42 are the outer periphery of the carrier 11. Retreats outward in the circumferential direction from the part.

  When the thickness sensor 40 is located at the contact position shown in FIG. 4, the tip portions of the sensor portions 41 and 42 penetrate inside the outer peripheral portion of the silicon wafer 1. The sensor unit 41 contacts one surface 3 of the silicon wafer 1, and the sensor unit 42 contacts the other surface 4 of the silicon wafer 1. The thickness sensor 40 monitors the thickness of the silicon wafer 1 by sandwiching the silicon wafer 1 between the sensor unit 41 and the sensor unit 42.

  The thickness sensor 40 is connected to the control device 50 and continuously transmits the thickness data of the silicon wafer 1 to the control device 50 while monitoring the thickness of the silicon wafer 1 at the contact position.

  The switching unit 45 holds the thickness sensor 40 in the non-contact position from the start of the double-side grinding process by the grinding wheels 31 and 36 to a predetermined stage, or contacts the thickness sensor 40 from the predetermined stage to the end of the double-side grinding process. The state of the thickness sensor 40 can be switched so as to hold the position.

  Prior to the start of the double-side grinding process, the switching unit 45 moves the thickness sensor 40 from the contact position shown in FIG. 4 to the non-contact position shown in FIG. 3 according to a command from the control device 50. Then, the thickness sensor 40 is held at the non-contact position from the start of the double-side grinding process to a predetermined stage.

  When the double-side grinding process reaches a predetermined stage, the switching unit 45 moves the thickness sensor 40 from the non-contact position shown in FIG. 3 to the contact position shown in FIG. And the switching part 45 hold | maintains the thickness sensor 40 in a contact position from the predetermined | prescribed stage to the completion | finish of a double-sided grinding process.

Here, a setting method at a predetermined stage in which the switching unit 45 moves the thickness sensor 40 from the non-contact position to the contact position will be described.
For example, the stage where the saw mark substantially disappears from both surfaces 3 and 4 of the silicon wafer 1 can be set as a predetermined stage. The “stage where the saw mark substantially disappears” refers to a stage where the saw mark disappears from both surfaces 3 and 4 of the silicon wafer 1 as a semiconductor wafer to the extent that the effect of the present invention can be achieved.
Alternatively, the time when a preset time elapses from the start of the double-side grinding process can be set as a predetermined stage.

Here, the process from the start to the end of the double-side grinding process of the silicon wafer 1 is classified into four processes: rough grinding, medium 1 grinding, medium 2 grinding, and finish grinding. Spark-out after finish grinding is not considered.
The thickness of the silicon wafer 1 at the start of rough grinding is A μm, the thickness of the silicon wafer 1 at the start of medium 1 grinding is B μm, the thickness of the silicon wafer 1 at the start of medium 2 grinding is C μm, and finish grinding Let the thickness of the silicon wafer 1 at the start be D μm.

Using such a double-sided grinding process, a test was performed on the stage where the saw mark disappeared from both sides 3 and 4 of the plurality of silicon wafers 1, and the following results were obtained.
That is, saw marks remained on both surfaces 3 and 4 of many silicon wafers 1 when the rough grinding was completed. That is, at the stage where the thickness was B μm, the silicon wafer 1 in which the saw mark disappeared was very small.

At the stage of finishing the middle 1 grinding, saw marks disappeared from both sides 3 and 4 of most silicon wafers 1. That is, at the stage where the thickness was C μm, there was almost no silicon wafer 1 in which saw marks remained.
At the stage where the middle 2 grinding was completed, saw marks disappeared from both sides 3 and 4 of all the silicon wafers 1. That is, at the stage where the thickness was D μm, there was no silicon wafer 1 on which saw marks remained.

Through this test, it was found that saw marks substantially disappeared from both surfaces 3 and 4 of all silicon wafers 1 during the middle 2 grinding. Based on this knowledge, it has been found that the middle 2 grinding may be set as a predetermined stage.
Therefore, the intermediate half grinding time was set as a predetermined stage. That is, the thickness sensor 40 is held at the non-contact position from the start of rough grinding to the middle of the middle 2 grinding. Further, the thickness sensor 40 is held at the contact position from the middle 2 grinding to the end of the finish grinding and the spark-out after the finish grinding.

  Specifically, for example, by monitoring the feed amount of the grinding wheels 31 and 36 by the feed motor, the control device 50 can detect that the double-side grinding process has progressed to the middle of the middle 2 grinding. is there. Thereby, the control apparatus 50 can issue a command to the switching unit 45 to move the thickness sensor 40 from the non-contact position shown in FIG. 3 to the contact position shown in FIG.

  Further, for example, by setting in advance the time required for the double-sided grinding process to progress from the start of rough grinding to the middle 2 grinding, the control device 50 allows the double-side grinding process to proceed to the middle 2 grinding. Can be detected. Also in this case, the control device 50 can issue a command to the switching unit 45 to move the thickness sensor 40 from the non-contact position shown in FIG. 3 to the contact position shown in FIG.

  Hereinafter, an embodiment of a double-side grinding method for a semiconductor wafer according to the present invention will be described with reference to the flowchart of FIG.

  First, in step S1, the control device 50 sets the thickness sensor 40 to a non-contact position. That is, the switching unit 45 receives a command from the control device 50 and retracts the sensor units 41 and 42 of the thickness sensor 40 to the outside of the outer peripheral portion of the carrier 11 (see FIG. 3).

In step S <b> 2, the control device 50 rotates the silicon wafer 1 and the grinding wheels 31 and 36.
That is, the motor receives a command from the control device 50 and rotates the rotating roller 13 around the axis 13a. Thereby, the rotation roller 13 rotates the silicon wafer 1 and the carrier 11 around the axis 1a. The other motor receives a command from the control device 50 and rotates the grinding wheels 31 and 36 around the axes 31a and 36a.
Thereby, the double-sided grinding process in which the grinding surfaces 33 and 38 of the grinding wheels 31 and 36 simultaneously grind both the surfaces 3 and 4 of the silicon wafer 1 is started.

In step S <b> 3, the control device 50 determines whether or not the double-side grinding process has progressed from the both surfaces 3 and 4 of the silicon wafer 1 to the stage where the saw mark is substantially eliminated.
That is, it is determined whether the double-sided grinding process has progressed from the start of rough grinding to middle 1 grinding through middle 1 grinding. Alternatively, it is determined whether or not the time required for the double-sided grinding process from the start of rough grinding to middle 1 grinding through middle 1 grinding has elapsed.
If this determination is NO, the process returns to step S3, and if YES, the process proceeds to step S4.

  In addition, since there is a sufficient margin until the end of the double-sided grinding process during the period up to step S3, the double-sided grinding of the silicon wafer 1 is performed without any problem even if the thickness of the silicon wafer 1 is not monitored by the thickness sensor 40. be able to.

  In step S4, the thickness sensor 40 is set at the contact position by the control device 50. That is, the switching unit 45 receives a command from the control device 50 and causes the sensor unit 41 and the sensor unit 42 of the thickness sensor 40 to enter more inside than the outer peripheral portion of the silicon wafer 1. Then, the sensor unit 41 is brought into contact with one surface 3 of the silicon wafer 1, and the sensor unit 42 is brought into contact with the other surface 4 of the silicon wafer 1 (see FIG. 4).

  In step S5, the thickness of the silicon wafer 1 is monitored by the thickness sensor 40. That is, the thickness of the silicon wafer 1 is monitored by sandwiching both surfaces 3 and 4 of the silicon wafer 1 between the sensor unit 41 and the sensor unit 42 of the thickness sensor 40. The thickness data of the monitored silicon wafer 1 is transmitted to the control device 50 in real time.

In step S6, the control device 50 determines whether or not the double-side grinding process has been completed. That is, it is determined whether or not the double-sided grinding process is completed from the middle of the middle 2 grinding through the finish grinding to the spark-out.
If this determination is NO, the process returns to step S5, and if it is YES, the process ends.

  According to the present invention, as described above, the thickness sensor 40 is held in a non-contact position where the thickness sensor 40 is not in contact with both surfaces 3 and 4 of the silicon wafer 1 from the start of the double-side grinding process to a predetermined stage. It is possible to eliminate the jumping of the thickness sensor 40 due to the saw mark, which is a cause of scratching both surfaces 3 and 4 of the silicon wafer 1. That is, after the predetermined stage, even if the thickness sensor 40 comes into contact with both surfaces 3 and 4 of the silicon wafer 1, the saw mark has substantially disappeared, and therefore, the thickness sensor 40 jumps up almost due to the saw mark. do not do. Thereby, it is possible to suppress the scratches caused by the contact-type thickness sensor 40 on both surfaces 3 and 4 of the silicon wafer 1.

As mentioned above, although one Embodiment of the double-sided grinding apparatus and the double-sided grinding method of this invention was described, this invention is not restrict | limited to the embodiment mentioned above.
For example, in the above embodiment, the thickness sensor 40 is retracted to the non-contact position and entered into the contact position as shown in FIGS. 3 and 4, but the present invention is not limited to this. Other evacuation forms and entry forms can be employed.
The semiconductor wafer is not limited to a silicon wafer.

1 Silicon wafer (semiconductor wafer)
10 Double-side grinding machine 13 Rotating roller (Rotation drive unit)
14 Support roller (rotation drive part)
21, 26 Static pressure pad 31, 36 Grinding wheel 40 Thickness sensor 45 Switching section

Claims (2)

A rotation drive unit that supports the semiconductor wafer in a vertical position and rotates it around an axis;
A pair of hydrostatic pads that support both sides of the semiconductor wafer by the pressure of the fluid supplied to both sides;
A pair of grinding wheels that rotate around an axis parallel to the rotation axis of the semiconductor wafer to grind both sides of the semiconductor wafer;
A thickness sensor that is movable between a contact position that contacts both surfaces of the semiconductor wafer and a non-contact position that does not contact, and monitors the thickness of the semiconductor wafer when in the contact position;
A method for double-sided grinding of a semiconductor wafer using a double-sided grinding apparatus comprising:
A non-thickness monitoring grinding step for grinding both sides of the semiconductor wafer by holding the thickness sensor in the non-contact position from the start of the double-side grinding step with the grinding wheel to a predetermined stage;
See containing and a thickness monitoring grinding step for grinding of both surfaces of the semiconductor wafer while holding the thickness sensor in the contact position to the end of the double-side grinding step from said predetermined stage,
The semiconductor wafer double-side grinding method , wherein the predetermined stage is a stage in which saw marks substantially disappear from both sides of the semiconductor wafer. A rotation drive unit that supports the semiconductor wafer in a vertical position and rotates it around an axis;
A pair of hydrostatic pads that support both sides of the semiconductor wafer by the pressure of the fluid supplied to both sides;
A pair of grinding wheels that rotate around an axis parallel to the rotation axis of the semiconductor wafer to grind both sides of the semiconductor wafer;
A thickness sensor that is movable between a contact position that contacts both surfaces of the semiconductor wafer and a non-contact position that does not contact, and monitors the thickness of the semiconductor wafer when in the contact position;
A switching unit that holds the thickness sensor at the non-contact position from the start of the double-side grinding process by the grinding wheel to a predetermined stage and holds the thickness sensor at the contact position from the predetermined stage to the end of the double-side grinding process. and, with a,
2. The semiconductor wafer double-side grinding apparatus according to claim 1, wherein the predetermined stage is a stage in which saw marks substantially disappear from both sides of the semiconductor wafer.

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