STOP MECHANISM WITH BERNOULLI PAD

Abstract

Holding mechanism (2) with a Bernoulli pad (18a, 18b) which holds a plate-shaped body (11) by the effect of a negative pressure generated by blowing air towards the plate-shaped body (11), wherein the holding mechanism (2) comprises: a transfer device (16) at which the Bernoulli pad (18a, 18b) is arranged; a sensor (22) which is arranged at the transfer device (16) and detects that the plate-shaped body (11) is held under suction by the Bernoulli pad (18a, 18b); a section for restricting lateral movement (20) which is arranged at the transfer device (16) and restricts lateral movement of the plate-shaped body (11); a conduit (26) connecting an air source that supplies air to the Bernoulli pad (18a, 18b) and the Bernoulli pad (18a, 18b); an adjusting valve (26a) arranged in the line (26) which adjusts the flow rate of air supplied to the Bernoulli pad (18a, 18b); and a control section (32) that controls the operation of the adjusting valve (26a), wherein the control section (32) gradually increases the flow rate of the air supplied from the adjusting valve (26a) to the Bernoulli pad (18a, 18b) and sets the flow rate of the air when the sensor (22) detects that the plate-shaped body (11) has been held under suction by the Bernoulli pad (18a, 18b) by receiving the effect of the negative pressure.

Description

TECHNICAL BACKGROUNDTechnical field

[0001] The present invention relates to a holding mechanism comprising a Bernoulli pad that holds a plate-shaped body by an action of negative pressure generated by blowing air to the plate-shaped body. Description of related technology

[0002] Component chips are mounted on electronic devices such as mobile phones and personal computers. The component chips are obtained by grinding a back surface of a wafer, which is formed on a front surface thereof with a plurality of components such as integrated circuits (ICs) and large-scale integrations (LSIs), as a whole by a grinder to make the wafer thin, and dividing the thinned wafer by a dicing device or a laser machining device. Before dividing, a plurality of streets are defined in a lattice pattern on the front surface of the wafer, and the above-described components are formed in a plurality of regions divided by the streets. On the front surface of the wafer, an annular peripheral edge region in which components are not formed is provided in a periphery of a component region in which the plurality of components are formed.

[0003] Incidentally, during component chip manufacturing, there is a technique in which a central portion on the rear side corresponding to the component region is ground without grinding a peripheral portion on the rear side corresponding to the peripheral edge region, in order to thin the rear side and form a recess. In this case, the peripheral portion acts as a thick reinforcement portion, thus achieving effects of reducing wafer warpage, increasing wafer strength, and the like. However, if a wafer thickness in the portion corresponding to the component region is reduced to a thickness on the order of, for example, 30 μm, there is a risk of damaging the wafer when the wafer is conveyed by disposing a suction pad at the component region.Against this background, a holding mechanism was developed which has a Bernoulli pad that holds the wafer without coming into contact with the device area (see, for example, Japanese Laid-Open Patent Application JP 2005 - 142 462 A). PRESENTATION OF THE INVENTION

[0004] A Bernoulli pad holds a wafer under suction by utilizing negative pressure created by blowing air toward the wafer. Increasing the pressure of the supplied air can create a greater negative pressure; however, increasing the air pressure also increases the collision force exerted on the wafer by the air blown toward the wafer, causing the wafer to vibrate and resulting in wafer damage. Note that the problem of wafer vibration resulting in wafer damage can also occur in an ordinary wafer that is not formed with a recess on the back side. The present invention was made in consideration of such a problem.Accordingly, it is an object of the present invention to hold a plate-shaped body such as a wafer under suction using a Bernoulli pad in such a manner that the plate-shaped body is not damaged.

[0005] According to one aspect of the present invention, there is provided a holding mechanism comprising: a Bernoulli pad that holds a plate-shaped body by an action of negative pressure generated by blowing air to the plate-shaped body.The holding mechanism includes: a transfer device on which the Bernoulli pad is arranged, a sensor arranged on the transfer device and detecting that the plate-shaped body is held under suction by the Bernoulli pad, a lateral movement restricting section arranged on the transfer device and restricting lateral movement of the plate-shaped body, a conduit connecting an air source that supplies air to the Bernoulli pad and the Bernoulli pad, an adjusting valve arranged in the conduit and adjusting a flow rate of air supplied to the Bernoulli pad, and a control section that controls an operation of the adjusting valve.The control section gradually increases the flow rate of the air supplied from the adjusting valve to the Bernoulli pad, and, when it is detected by the sensor that the plate-shaped body has been held under suction by the Bernoulli pad by receiving the effect of the negative pressure, sets the flow rate of the air.

[0006] Preferably, the sensor is a proximity sensor, and when the sensor detects that a distance between the sensor and the plate-shaped body has reached a predetermined length, the control section determines that the plate-shaped body has been held under suction by the Bernoulli pad, and sets the flow rate of air supplied from the adjusting valve to the Bernoulli pad.

[0007] Preferably, the sensor is a vibration sensor, and when it is detected by the sensor that a vibration amplitude of the plate-shaped body, which gradually increases with an increase in the flow rate of the air, has reached a predetermined amount, the control section decides that the plate-shaped body has been held under suction by the Bernoulli pad, and sets the flow rate of the air supplied from the adjusting valve to the Bernoulli pad.

[0008] The above and other objects, features and advantages of the present invention and the modes for carrying them out will become more apparent and the invention itself will be best understood by studying the following description and the appended claims with reference to the accompanying drawings which show some preferred embodiments of the invention. SHORT DESCRIPTION OF THE FIGURES Fig. 1 is a perspective view of a holding mechanism and the like; Fig. 2 is an enlarged perspective view of a surface side of a transfer device; Fig. 3 is a diagram illustrating a manner in which a flow rate of air is adjusted to keep a wafer under suction; and Fig. 4 is a flow chart when the flow rate of air is adjusted to keep the wafer under suction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment according to one mode of the present invention will be described with reference to the accompanying drawings. First, a description will be given of a holding mechanism 2 that is attached to a processing device (not shown) such as a cutting device, a grinding device, a laser processing device, and a tape fixing device, and that conveys a wafer (plate-shaped body) 11 as a processing target or the like. Fig. 1 is a perspective view of the holding mechanism 2 and the like. The holding mechanism 2 includes a first drive section 6. The first drive section 6 includes a motor or the like (not shown) so that a cylindrical support member 8 connected to an upper portion of the first drive section 6 can be moved vertically along a Z-axis direction and rotated about a rotation axis substantially parallel to the Z-axis direction.

[0010] An end portion of a first connector 10 is connected to an upper portion of the support element 8 such that it is rotatable about a rotational axis substantially parallel to the Z-axis direction. A lower portion of an end portion of a second connector 12 is connected to an upper portion of another end portion of the first connector 10 such that it is rotatable about a rotational axis substantially parallel to the Z-axis direction. A lower portion of a second drive portion 14 is connected to an upper portion of another end portion of the second connector 12 such that it is rotatable about a rotational axis substantially parallel to the Z-axis direction. A transfer device 16 is connected to a lateral portion of the second drive portion 14 such that it is rotatable about a predetermined straight line substantially parallel to an XY plane.

[0011] Here, a structure of the transfer device 16 according to a first embodiment is described with reference to Fig. 2 described. Fig. 2 is an enlarged perspective view of one side of a surface 16d of the transfer device 16. The transfer device 16 includes a rectangular plate-shaped base portion 16a, one end portion of which is connected to the second drive portion 14. To another end portion of the base portion 16a, an arc-shaped tip portion 16b formed of a metal such as the same stainless steel as the base portion 16a or the like is connected. The arc formed by the tip portion 16b has a central angle equal to or more than 270 degrees. The tip portion 16b of this example has, on the side opposite the center of the arc from the other end portion of the base portion 16a, a cutout 16c having substantially the same width as the width of the base portion 16a.

[0012] On the side of one surface 16d of the tip portion 16b, a plurality of Bernoulli pads 18a and 18b are provided. Specifically, with a virtual straight line connecting the cutout 16c and the base portion 16a as a center, three Bernoulli pads 18a are arranged on one side and three Bernoulli pads 18b are arranged on the other side in line symmetry. Each of the Bernoulli pads 18a and 18b expels air, so that a swirling flow is generated in one direction from another surface 16e to the one surface 16d of the tip portion 16b. The Bernoulli pads 18a and 18b are substantially the same, but in order to prevent rotation of an object to be sucked, for example, the rotation direction of the swirling flow is set to be reversed.

[0013] In the vicinity of a rotation axis of the vortex flow, the pressure is reduced according to the Bernoulli principle, so that a negative pressure is generated. The wafer 11 arranged in the vicinity of the transfer device 16 is supported by the Bernoulli pads 18a and 18b through a balance between an upward force caused by an effect of the negative pressure and a downward force caused by a collision force of air and the weight of the wafer 11. Between the three Bernoulli pads 18a, a rubber pad (lateral movement restriction portion) 20 formed of, for example, a rubber sheet is arranged. Note that a rubber pad 20 is also arranged similarly between the three Bernoulli pads 18b.

[0014] The rubber pads 20 each protrude further than a projection amount of the Bernoulli pads 18a from one surface 16d. The projection amount of the rubber pads 20 is set so that they can contact the wafer 11 when the wafer 11 is sucked by the Bernoulli pads 18a and 18b. Therefore, when the wafer 11 is held under suction by the Bernoulli pads 18a and 18b, the movement (lateral movement) of the wafer 11 in a lateral direction parallel to the XY plane is restricted. Note that, instead of the rubber pads 20, guides, pins, or the like (lateral movement restricting portion) for restricting lateral movement of the wafer 11 may be provided on the transfer device 16.

[0015] Between the Bernoulli pads 18a and 18b, each arranged at a position closest to the base portion 16a, a sensor 22 is arranged, which detects that the wafer 11 has been held under suction by the Bernoulli pads 18a and 18b. The sensor 22 in the present embodiment is a capacitive proximity sensor capable of measuring a distance between a probe of the sensor 22 and the wafer 11. The capacitance of the sensor 22 varies according to the distance A (see Fig. 3) between the probe of the sensor 22 and the wafer 11. The capacitance detected by the sensor 22 is output to a control section 32 described later and converted into the distance A by the control section 32.

[0016] Here, with reference to Fig. 1, the wafer 11 and the like are described. The wafer 11 is formed, for example, from a semiconductor material such as silicon. On a front surface 11a of the wafer 11, a plurality of streets are defined in a grid pattern. In each of a plurality of regions divided by the plurality of streets, a device 13 such as an integrated circuit (IC) is formed. Note that a material, shape, configuration, size, and the like of the wafer 11 are not limited. For example, the wafer 11 could be formed from a material other than silicon, such as a semiconductor, a ceramic, a plastic, a metal, and the like. Likewise, a type, number, shape, configuration, size, arrangement, and the like of the devices 13 are not limited.

[0017] A plurality of wafers 11 are accommodated in a cassette 24. The cassette 24 has a pair of side surfaces 24a. An inner surface of each side surface 24a is formed with a plurality of support grooves 24b at a predetermined pitch along a height direction of the cassette 24. A wafer 11 is accommodated with respect to each pair of opposing support grooves 24b. Upper portions of the pair of side surfaces 24a are connected by an upper plate 24c, and lower portions of the pair of side surfaces 24a are connected by an elongated, plate-shaped connecting portion 24d. In addition, an opening 24e is formed at an end portion (front portion) in a lateral direction of the pair of side surfaces 24a.

[0018] The transfer device 16 is caused to enter the cassette 24 through the opening 24e, and one surface 16d of the transfer device 16 is placed on an upper side of the wafer 11, whereupon air is blown from the Bernoulli pads 18a and 18b to the wafer 11, so that the wafer 11 is sucked to the one surface 16d (see Fig. 3). As in Fig. As shown in Figure 3, an air supply source (air source) 28 is connected to the Bernoulli pads 18a and 18b via an air line 26. The air supply source 28 includes a compressor that compresses air and discharges the compressed air, a tank that stores the compressed air, and the like.

[0019] An electropneumatic regulator (adjustment valve) 30 is arranged in the air line 26. The electropneumatic regulator 30 is a proportional control valve capable of continuously controlling the pressure of the discharged air according to an input signal, and includes a controller (not shown) for controlling operations of an exhaust valve and an air supply valve (both not shown). The controller controls opening and closing of the exhaust valve and the air supply valve, thereby controlling the air pressure at an output port of the electropneumatic regulator 30. Note that air is supplied to the air supply valve from the air supply source 28 through the air line 26, and the air adjusted to a predetermined pressure is supplied from the output port of the air line 26 on a downstream side.

[0020] The electropneumatic regulator 30 is equipped with a pressure sensor (not shown) that monitors the air pressure at the discharge port. When an input signal indicating a pressure value of air discharged from the discharge port is input to the controller, the controller controls the discharge valve and the air supply valve according to the input signal and receives feedback from the pressure value received from the pressure sensor. Based on the feedback of the pressure value, the controller controls the discharge valve and the air supply valve so that the air pressure value at the discharge port becomes the specified pressure value. The air pressure at the discharge port is corrected accordingly.

[0021] The air pressure at the discharge port is adjusted by the input signal input to the controller, so that a flow rate (namely, a flow rate per unit time) of the air supplied to the Bernoulli pads 18a and 18b is adjusted. For example, by continuously varying the air pressure at the discharge port, the flow rate of air at the discharge port can be continuously varied. Specifically, when the air pressure at the discharge port is set to be higher, the flow rate of air discharged from the discharge port can be increased, and when the air pressure at the discharge port is set to be lower, the flow rate of air discharged from the discharge port can be reduced.

[0022] A shutoff valve 26a, such as a manual valve, is arranged between the air supply source 28 and the electropneumatic regulator 30. When the shutoff valve 26a is in an open state, air at a pressure of, for example, about 0.3 MPa is supplied from the air supply source 28 to an air supply port of the electropneumatic regulator 30. The operation of the electropneumatic regulator 30 is controlled by the control section 32. The control section 32 is a main body of a controller of the above-described machining apparatus and also controls components of the holding mechanism 2, such as a link mechanism 4, the Bernoulli pads 18a and 18b, and the sensor 22.

[0023] The control section 32 includes a computer including, for example, a component such as a processor represented by a central processing unit (CPU), a main storage device such as dynamic random access memory (DRAM), static random access memory (SRAM), and read-only memory (ROM), and an auxiliary storage device such as flash memory, a hard disk drive, and a solid-state drive. Software including a predetermined program is stored in the auxiliary storage device. By operating the processing device and the like according to this software, the functions of the control section 32 are realized. Next, a method will be described in which the wafer 11 is held under suction by the Bernoulli pads 18a and 18b by adjusting the flow rate of the air by the control section 32.

[0024] Fig. Fig. 3 is a diagram illustrating the manner in which the flow rate of air is adjusted to keep the wafer 11 under suction, and Fig. 4 is a flow chart when the air flow rate is adjusted to keep the wafer 11 under suction. Note that in Fig. 3, the Bernoulli pads 18a and 18b and the rubber pads 20 are omitted. At the time of holding the wafer 11 under suction, first, the link mechanism 4 is operated to arrange the transfer device 16 on the upper side of a wafer 11 housed in the cassette 24. In the present embodiment, one surface 16d of the transfer device 16 is formed to face the front surface 11a of the wafer 11, but in a case where a rear surface 11b of the wafer 11 faces upward, the one surface 16d may be formed to face the rear surface 11b.

[0025] Next, an input signal to the electropneumatic regulator 30 is controlled to gradually increase the air flow rate supplied from the electropneumatic regulator 30 to the Bernoulli pads 18a and 18b from zero (air flow rate increase step S10). The control section 32 monitors the capacitance of the sensor 22, thereby monitoring the distance A between the probe of the sensor 22 and the wafer 11 in real time. If the distance A has not reached a predetermined length, the control section 32 determines that the wafer 11 is not being held under suction (NO at S20) and continues to increase the air flow rate.

[0026] On the other hand, when the sensor 22 detects that the distance A has reached the predetermined length, the control section 32 determines that the wafer 11 has been held under suction (YES at S20). Note that the predetermined length of the distance A varies depending on the diameter, thickness, material, and the like of the wafer 11. For example, in the case of a silicon wafer 11 having a diameter of 300 mm, a thickness of a peripheral portion corresponding to a peripheral edge area of ​​100 µm, and a thickness of a portion corresponding to a device area of ​​30 µm, the predetermined length of the distance A is 0.5 mm.

[0027] When the distance A has reached the predetermined length, the control section 32 determines that the wafer 11 has been suctioned by the Bernoulli pads 18a and 18b and sets the flow rate of air supplied from the electropneumatic regulator 30 (air flow rate setting step S30). In the present embodiment, when the distance A has reached the predetermined length, the control section 32 determines that the wafer 11 is suctioned by the Bernoulli pads 18a and 18b and sets the flow rate. This prevents the collision force of air against the wafer 11 from becoming excessive, so that the wafer 11 can be properly suctioned with such a suction force that the wafer 11 is not damaged.

[0028] Meanwhile, when the distance A reaches the predetermined length, the wafer 11 is in the state of being held under suction with a minimum suction force, and the wafer 11 may fall from the transfer device 16 for some reason. However, if the air amount is excessively increased, there is still a risk of damaging the wafer 11. Since the collision force of the air increases as the air flow rate is increased, the wafer 11 in the suction state is vibrated in a wave-like manner in a thickness direction of the wafer 11. An amplitude of this vibration increases with the increase of the collision force of the air, possibly resulting in damage to the wafer 11.

[0029] In view of this, in a second embodiment, a capacitive type vibration sensor is used as the sensor 22. Furthermore, the control section 32 monitors the vibration amplitude of the wafer 11, which gradually increases with increasing air flow rate. Also in the second embodiment, the wafer 11 is vibrated by a method similar to that described in Fig. 4 is held under suction. First, the connecting mechanism 4 is actuated to cause one surface 16d of the transfer device 16 to face a wafer 11 housed in the cassette 24.

[0030] Next, the input signal to the electropneumatic regulator 30 is controlled, and the flow rate of air supplied from the electropneumatic regulator 30 to the Bernoulli pads 18a and 18b is gradually increased from zero (air flow rate increasing step S10). The control section 32 monitors the distance A using the sensor 22 on a real-time basis, thereby monitoring the amplitude of the vibration of the wafer 11. If the amplitude has not reached a predetermined amount, the control section 32 determines that the wafer 11 was not held under suction (NO at S20) and continues to increase the air flow rate.

[0031] When the air flow rate is increased, the wafer 11 is lifted and held under suction by the Bernoulli pads 18a and 18b. In this case, the flow rate is the same as the flow rate set in the air flow rate setting step S30 in the first embodiment. However, in this step, essentially no vibration is generated, and even if vibration is generated, it is not so strong that it damages the wafer 11.

[0032] The air flow rate is further increased, and when the sensor 22 detects that the amplitude has reached the predetermined value, the control section 32 determines that the wafer 11 has been held under suction (YES at S20). The predetermined amplitude value varies depending on the diameter, thickness, material, and the like of the wafer 11. For example, in the case of a silicon wafer 11 having a diameter of 300 mm, a thickness of a peripheral portion corresponding to a peripheral edge area of ​​100 µm, and a thickness of a portion corresponding to a device area of ​​30 µm, the predetermined amplitude value is 1.0 µm.

[0033] When the amplitude of the wafer 11 reaches the predetermined value, the control section 32 determines that the wafer 11 has been properly suctioned by the Bernoulli pads 18a and 18b and sets the air flow rate (air flow rate setting step S30). In the present embodiment, even when the wafer 11 is suctioned by a greater suction force than in the first embodiment, it is possible to prevent the wafer 11 from being damaged by excessive vibration. Apart from the above points, structures, methods, and the like according to the above-described embodiments can be implemented with appropriate modifications, as long as the modifications do not depart from the scope of the present invention.

Claims

[1] A holding mechanism (2) comprising a Bernoulli pad (18a, 18b) which holds a plate-shaped body (11) by the action of a negative pressure generated by blowing air to the plate-shaped body (11), the holding mechanism (2) comprising: a transfer device (16) on which the Bernoulli pad (18a, 18b) is arranged; a sensor (22) arranged on the transfer device (16) and detecting that the plate-shaped body (11) is held under suction by the Bernoulli pad (18a, 18b); a lateral movement restricting portion (20) disposed on the transfer device (16) and restricting lateral movement of the plate-shaped body (11); a conduit (26) connecting an air source supplying air to the Bernoulli pad (18a, 18b) and the Bernoulli pad (18a, 18b); an adjusting valve (26a) arranged in the line (26) and adjusting a flow rate of air supplied to the Bernoulli pad (18a, 18b); and a control section (32) which controls an operation of the adjustment valve (26a), wherein the control section (32) gradually increases the flow rate of the air supplied from the adjusting valve (26a) to the Bernoulli pad (18a, 18b) and sets the flow rate of the air when it is detected by the sensor (22) that the plate-shaped body (11) has been held under suction by the Bernoulli pad (18a, 18b) by receiving the effect of the negative pressure. [2] Holding mechanism (2) according to claim 1, wherein the sensor (22) is a proximity sensor, and wherein the control section (32), when it is detected by the sensor (22) that a distance between the sensor (22) and the plate-shaped body (11) has reached a predetermined length, determines that the plate-shaped body (11) has been held under suction by the Bernoulli pad (18a, 18b) and sets the flow rate of the air supplied from the adjusting valve (26a) to the Bernoulli pad (18a, 18b). [3] Holding mechanism (2) according to claim 1, wherein the sensor (22) is a vibration sensor, and wherein the control section (32), when it is detected by the sensor (22) that a vibration amplitude of the plate-shaped body (11), which gradually increases with an increase in the flow rate of the air, has reached a predetermined amount, decides that the plate-shaped body (11) has been held under suction by the Bernoulli pad (18a, 18b) and sets the flow rate of the air supplied from the adjusting valve (26a) to the Bernoulli pad (18a, 18b).

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