JP2007335458A - Wafer grinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a wafer having a target thickness surely by measuring the thickness of the wafer excepting a protective tape accurately without being affected by the thickness of the wafer, or existence of an oxide film or a nitride film on the backside of the wafer when the backside of the wafer coated with the protective film is made thin by grinding. <P>SOLUTION: At the time of rough grinding, backside of a wafer 1 is ground while measuring the thickness of the wafer as the total thickness including a protective tape 4 by means of a contact thickness gauge 43. At the time of finish grinding, grinding is performed while measuring the thickness only of the wafer 1 by means of a noncontact thickness gauge 54. Grinding is ended when a target finish thickness is reached, thus obtaining a wafer 1 having an accurate finish thickness. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a grinding apparatus that grinds and thins a wafer such as a semiconductor wafer, and in particular, when a wafer having a protective member such as a protective tape attached to the surface of a device forming surface is thickened. It is related to the technology to get accurately

  A semiconductor chip having an electronic circuit such as an IC or LSI formed on its surface is now indispensable for downsizing various electric / electronic devices. A semiconductor chip divides a grid-like rectangular area on a surface of a disk-shaped semiconductor wafer (hereinafter referred to as a wafer) with cutting lines called streets, forms an electronic circuit in these rectangular areas, and then moves the wafer along the street. Manufactured in a process of dividing.

  In such a manufacturing process, before the wafer is divided into semiconductor chips, the back surface opposite to the device surface on which the electronic circuit is formed is ground by a grinding device. The purpose of grinding the back surface is to further reduce the size and weight of the electronic device and to improve the heat dissipation and maintain the performance. For example, the initial thickness is 600 μm to 200 to 100 μm or less, or Thinning to a thickness of 50 μm or less is performed.

  Wafer grinding equipment generally has a structure in which the back side is exposed to a vacuum chuck table, the wafer is sucked and held, and the grindstone placed opposite to the chuck table is pressed against the back surface while rotating at high speed. It is. When supplying a wafer to such a grinding machine, a protective tape is applied to the surface to prevent the electronic circuit from being damaged or contaminated by grinding waste liquid due to the surface directly contacting the chuck table. is doing. The protective tape has, for example, a configuration in which an adhesive of about 10 μm is applied to one side of a polyethylene or polyolefin sheet having a thickness of about 100 to 200 μm. However, in such a protective tape, the thickness of the adhesive particularly varies. The thickness varies about ± 5%.

  When grinding a wafer, the thickness is usually controlled by the total thickness including the protective tape (the thickness of the wafer + the thickness of the protective tape). It directly affects the variation in thickness. Here, when the thickness of the wafer to be obtained by grinding is relatively large, the variation in the thickness of the protective tape has a small effect, but as the thickness becomes thinner, the effect on the wafer thickness becomes more prominent. In some cases, the thickness of the wafer alone exceeded the allowable value, and was too thick or too thin. Therefore, the thickness of only the wafer before grinding is measured with a non-contact type thickness measuring device using laser light reflection, and the target grinding amount is calculated from the thickness and the target thickness after grinding. A technique of grinding an amount corresponding to a target grinding amount while measuring a wafer thickness (thickness including a protective tape) with a contact-type thickness measuring device during grinding has been proposed (see Patent Document 1). .

JP 2006-21264 A

  However, in a non-contact type thickness measuring device using laser light reflection, it is difficult to accurately measure the thickness of a wafer having a certain thickness, for example, 700 μm or more, which is not practical. Even if the thickness is measurable, the thickness of the wafer is often not accurately measured due to the influence of an oxide film or nitride film formed on the back surface of the wafer.

  Therefore, the present invention is not affected by the thickness of the wafer and the presence or absence of an oxide film or nitride film on the back surface of the wafer when the back surface of the wafer whose surface is covered with a protective member such as a protective tape is ground and thinned. An object of the present invention is to provide a wafer grinding apparatus capable of accurately measuring the thickness of only the wafer excluding the protective member, and thereby reliably obtaining a wafer having a target thickness.

  The wafer grinding apparatus of the present invention includes at least a rough grinding part and a finish grinding part, and each of these grinding parts holds a protective member side of a wafer in which a protective member is coated on a surface on which a device is formed. A rotatable wafer holding means having a surface, a grinding means having a rotation axis parallel to the rotation axis of the holding means, and a holding means and a grinding means arranged opposite to the holding surface of the holding means. Rough grinding in a wafer grinding apparatus having a feed means that moves relative to each other along a direction in which the shaft extends to approach and separate from each other and grinds the back surface of the wafer by a grinding means to reduce the thickness of the wafer. The part is provided with a contact-type thickness measuring instrument that contacts the exposed back surface of the wafer held by the wafer holding means and measures the thickness of the wafer including the protective member. In the finish grinding part, together with a contact-type thickness measuring device similar to the contact-type thickness measuring device, the thickness of only the wafer is measured close to the exposed back surface of the wafer held by the wafer holding means. A non-contact type thickness measuring device is provided.

  As the contact-type thickness measuring instrument of the present invention, a generally known height gauge or the like that converts a swing displacement into a measured thickness by bringing a swingable measuring element into contact with the back surface of the wafer can be used. In addition, the non-contact type thickness measuring instrument of the present invention has a thickness based on the time difference when the wafer is irradiated with a laser beam from the back surface and reflected by the back surface and the front surface (interface with the protective member). The thing using the laser beam reflection which converts thickness can be used.

  According to the wafer grinding apparatus of the present invention, for example, a wafer having a thickness of about 700 μm is roughly ground to a thickness of about 100 μm by a rough grinding portion, and then the wafer is transferred to a finish grinding portion to finish grinding to a thickness of about 50 μm. Is done. In the rough grinding part, the thickness of the wafer including the protective member is measured to 100 μm while the thickness of the wafer including the protective member is measured by the contact-type thickness measuring device, but the measured value is obtained when there is an error in the thickness of the protective member. The error is included, but it is allowed because it is not finish grinding.

  Next, in finish grinding the wafer transferred to the finish grinding section, it is desirable to first confirm the thickness of the wafer again with a contact-type thickness measuring device. This is because when the wafer thickness after rough grinding is thicker than the target thickness, the grinding means of the finish grinding part is brought into contact with the wafer at a relatively high speed in consideration of the target thickness as set. In order to avoid this, the thickness of the wafer is measured again, and the grinding means is controlled based on the thickness. Prior wafer thickness measurement at the finish grinding part is difficult to measure with the non-contact type because the rough ground surface is rough, and therefore the thickness of the wafer is first measured by a contact type thickness meter. taking measurement. Furthermore, at the initial stage of finish grinding (for example, grinding a thickness of about several μm after contacting the grinding surface), it is required to control grinding while measuring the thickness with a contact-type thickness measuring device. After this, the ground surface by the grinding means of the finish grinding part becomes a mirror surface that can be measured with a non-contact type thickness measuring device, so it is ground while measuring the wafer thickness by switching to the non-contact type thickness measuring device. . In the non-contact type thickness measuring instrument, the thickness of only the wafer excluding the protective member is measured, so that the thickness of the wafer alone is accurately measured, and the target thickness, that is, the thickness without error is 50 μm. At this point, the grinding is finished.

  According to the present invention, since the contact-type thickness measuring device and the non-contact-type thickness measuring device are arranged in the finish grinding part, the wafer thickness before finish grinding by the contact-type thickness measuring device as described above. The thickness can be reconfirmed and the initial finish grinding can be performed, and the finish grinding of the wafer can be accurately set to the target thickness by performing the finish grinding with the non-contact type thickness measuring device.

  In the present invention, in order to control the apparatus as described above, measurement signals of each contact-type thickness measuring instrument and non-contact-type thickness measuring instrument are input, and the grinding means by the feeding means based on these measurement signals Control means for controlling the feed amount of the wafer and grinding the wafer to a predetermined thickness in the rough grinding section and the finish grinding section, and the control means measures the contact type thickness measuring instrument in the rough grinding section. Based on the signal, the feeding means is controlled until the thickness of the wafer including the protective member reaches a predetermined rough grinding thickness. Then, in the finish grinding part, first, based on the measurement signal of the contact-type thickness measuring device. Then, after confirming whether the thickness of the wafer including the protective member is the thickness after the specified rough grinding, finish grinding by the grinding means is started. During this final grinding, non-contact thickness measurement Protection based on the measurement signal of the instrument The thickness of only the wafer containing no wood comprises an arrangement for controlling the feeding means to a predetermined finish thickness.

  As a more specific example of this configuration, the control means includes a thickness before the rough grinding including the wafer protective member, a target thickness including the protective member after the rough grinding of the wafer, and a finish grinding of the wafer after the final grinding. Thickness from the thickness before the rough grinding including the protective member of the wafer to the target thickness including the protective member after the rough grinding of the wafer at the time of grinding in the rough grinding portion. The feed means is controlled so as to grind the region, and then, at the time of grinding in the finish grinding part, the feed means is controlled while measuring the thickness of the wafer only by the non-contact type thickness measuring device, and the thickness of the wafer only. When the target thickness after finish grinding, which is stored in advance, reaches the target thickness, a control is performed to stop the operation of the feeding means.

  According to the present invention, in the finish grinding part, by switching between a contact type and a non-contact type thickness measuring device according to the thickness of the wafer, the thickness of the wafer, the presence or absence of an oxide film or nitride film on the back surface of the wafer, Without being affected by the surface condition such as surface roughness, it is possible to accurately measure the thickness of only the wafer excluding the protective member, and the effect that the wafer having the target thickness can be obtained reliably. Play.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[1] Semiconductor Wafer Reference numeral 1 in FIG. 1 indicates a disk-shaped semiconductor wafer (hereinafter abbreviated as a wafer) that is thinned by back grinding. The wafer 1 is a silicon wafer or the like, and the thickness before processing is, for example, about 600 to 700 μm. A plurality of rectangular semiconductor chips (devices) 3 are partitioned on the surface of the wafer 1 by grid-like division planned lines 2. On the surface of the semiconductor chip 3, an electronic device (not shown) such as an IC or LSI is provided. A circuit is formed.

  The wafer 1 is ground on the back surface and thinned to a target thickness (for example, about 50 to 100 μm), and then cut and divided along the planned division line 2 to be separated into a large number of semiconductor chips 3. At the time of back surface grinding, as shown in FIG. 1B, a protective tape (protective member) 4 is attached to the surface on which the electronic circuit is formed for the purpose of protecting the electronic circuit. . For example, the protective tape 4 having a configuration in which an adhesive of about 10 μm is applied to one side of a polyethylene or polyolefin sheet having a thickness of about 100 to 200 μm is used.

[2] Wafer Grinding Device FIG. 2 shows a wafer grinding device 10 according to one embodiment. Reference numeral 11 in the figure is a base on which various mechanisms are mounted. The base 11 is mainly composed of a rectangular parallelepiped portion having a horizontal upper surface, and has one end in the longitudinal direction (the end on the back side in FIG. 2). ) Has a wall portion 12 standing vertically. In FIG. 2, the longitudinal direction, the width direction, and the vertical direction of the base 11 are shown as a Y direction, an X direction, and a Z direction, respectively. The side of the base 11 from the substantially middle portion in the longitudinal direction is the grinding area 10A, and the opposite side supplies the wafer 1 before grinding to the grinding area 10A and collects the wafer 1 after grinding. It is set as the collection area 10B.

  A shallow rectangular pit 11a is formed in the grinding area 10A on the upper surface of the base 11, and a disk-shaped turntable 13 whose rotational axis is parallel to the Z direction and whose upper surface is horizontal is formed in the pit 11a. Is rotatably provided. The turntable 13 is rotated in the direction of arrow R by a rotation drive mechanism (not shown). A plurality of (in this case, three) disk-shaped chucks having a rotating shaft extending in the same Z direction as that of the turntable 13 and an upper surface (holding surface) 14a being horizontal are provided on the outer peripheral portion of the turntable 13. A table 14 is rotatably provided at equal intervals in the circumferential direction.

  The chuck table 14 is of a generally known vacuum chuck type, and the wafer 1 is placed on the upper surface 14a and is sucked and held. Each chuck table 14 is independently rotated in one direction or both directions by a rotation driving mechanism (not shown) provided in the turntable 13.

  As shown in FIG. 2, in the state where two chuck tables 14 are arranged in the X direction on the wall 12 side, a rough grinding unit (grinding unit) is disposed immediately above the chuck table 14 in order from the upstream side in the rotation direction of the turntable 13. Means) 20A and finish grinding unit (grinding means) 20B are arranged respectively. Each chuck table 14 is closest to the supply / recovery area 10B by the intermittent rotation of the turntable 13 and the rough grinding position below the rough grinding unit 20A, the finish grinding position below the finish grinding unit 20B, and the finish grinding unit 20B. It is positioned at each of three positions with the attached / detached position. A rough grinding part is constituted by the chuck table 14 and the rough grinding unit 20A in the rough grinding position, and a finish grinding part is constituted by the chuck table 14 and the finish grinding unit 20B in the finish grinding position.

Since the rough grinding unit 20A and the finish grinding unit 20B have the same configuration, they will be described with common reference numerals.
These grinding units 20A and 20B are attached to the wall 12 of the base 11 through a slider 31 and a guide rail 32 so as to be movable up and down in the Z direction, and are fed by a feed mechanism (feed means) 33 driven by a motor 34. Can be raised and lowered. As shown in FIGS. 3 and 4, the grinding units 20 </ b> A and 20 </ b> B are fixed to the tip of the spindle 22 via a flange 24 when the spindle 22 incorporated in the cylindrical housing 21 is driven to rotate by a motor 23. The cup wheel 25 is rotated, and a large number of grindstones 26 arranged in an annular manner and fixed to the outer peripheral portion of the lower surface of the cup wheel 25 are configured to grind the workpiece. The outer diameter of the circular grinding locus of the grindstone 26 is approximately equal to the diameter of the wafer 1.

  The grinding units 20A and 20B are not coaxially arranged with respect to the chuck table 14, but are offset. In detail, as shown in FIG. 4, among the many grindstones 26 arranged in an annular shape, the most central portion of the blade thickness (the length in the radial direction) of the blade tip located most inside the chuck table 14 is The relative position is set so as to be positioned on a vertical line passing through the center. Due to this positional relationship, when the back surface of the wafer 1 is pressed with the grindstone 26 of the cup wheel 25 while rotating the wafer 1 together with the chuck table 14, the entire back surface is ground. The grindstone 26 of the rough grinding unit 20A includes, for example, those containing # 280 to # 600 diamond abrasive grains, and the grindstone 26 of the finish grinding unit 20B includes, for example, those containing # 2000 to # 8000 diamond abrasive grains. It is done.

The cup wheel 25 is provided with a grinding water supply port (not shown) for supplying grinding water for cooling or lubrication or discharging grinding scraps to the workpiece below, and the grinding units 20A and 20B have the grinding water supplied thereto. A water supply line for supplying grinding water to the supply port is provided (not shown).
In both of the rough grinding unit 20A and the finish grinding unit 20B having the above-described configuration, the housing 21 is fixed to the slider 31 via the block 27.

  As shown in FIG. 2, in the pit 11a on the base 11, around the turntable 13 and closest to the supply / recovery area 10B, the cleaning water is discharged to the chuck table 14 at the attachment / detachment position. A chuck table cleaning nozzle 15 for cleaning the chuck table 14 is provided. Further, a drain hole 16 for discharging the water in the pit 11a to the outside is provided at one corner of the pit 11a on the wall 12 side.

  The wafer 1 is roughly ground by the rough grinding unit 20A at a rough grinding position to a thickness of, for example, 30 μm thicker than the finish thickness, and then finish ground to the target finish thickness by the finish grinding unit 20B at the finish grinding position. As shown in FIG. 2, a rough grinding side thickness measuring unit 40 for measuring the thickness of the wafer 1 and finish grinding are provided around the turntable 13 in the pit 11a and in the vicinity of each grinding position. A side thickness measuring unit 50 is provided. The wafer 1 is ground to the target thickness while the thickness is measured one by one by the thickness measuring units 40 and 50 at each grinding position.

  First, the finish grinding side thickness measuring unit 50 will be described. As shown in FIG. 3, the unit 50 includes a contact type thickness measuring device 53 including a pair of height gauges 51 and 52, and a non-contact type thickness measuring device. 54 is fixed to a bracket 59 supported by the base 11.

  The height gauges 51 and 52 of the contact-type thickness measuring device 53 are generally well-known ones. The probe 51b extends horizontally from the measurement main body portions 51a and 52a fixed to the bracket 59 on the chuck table 14 and swings. , 52b, but the tip of the probe 51b always contacts the upper surface 14a of the chuck table 14 to measure the height position of the upper surface 14a, and the tip of the probe 52b is the chuck. It is divided into a variable height gauge 52 that always contacts the back surface (grinding surface) of the wafer 1 held on the table 14 and measures the height position of the back surface of the wafer 1. Each of the height gauges 51 and 52 is configured such that a coil-type sensor using electromagnetic induction built in the measurement main body portions 51a and 52a converts the swing of the probes 51b and 52b into an electric signal and outputs it as a measured value at the height position. belongs to. According to the contact-type thickness measuring device 53 composed of these height gauges 51 and 52, the total thickness (including the protective tape 4) of the wafer 1 is calculated from the difference between the measured value of the variable height gauge 52 and the measured value of the reference height gauge 51. Converted.

  The non-contact type thickness measuring device 54 irradiates the wafer 1 held on the chuck table 14 vertically with a visible light semiconductor laser beam at the tip of an arm 55 fixed to the bracket 59 and extending horizontally on the chuck table 14. And a laser head 56 that receives the reflected light from the wafer 1. The laser head 56 receives the reflected light of the laser beam reflected by the upper back surface and the lower surface (interface with the protective member) of the wafer 1 held on the chuck table 14. The non-contact type thickness measuring device 54 converts the thickness of the wafer 1 from the time difference when the laser head 56 receives the reflected light. As the non-contact type thickness measuring device 54 using such laser beam reflection, for example, a configuration described in Japanese Patent Application Laid-Open No. 2001-203249 can be used.

  Air is blown to the bracket 59 from the laser head 56 to the irradiation surface of the laser beam irradiated to the wafer 1 to remove moisture such as grinding water, and the laser beam transmits moisture, so that the measurement accuracy is lowered. An air nozzle 58 for prevention is attached via a nozzle bracket 57. A pneumatic feed line (not shown) is connected to the air nozzle 58.

  On the other hand, the rough grinding side thickness measurement unit 40 has a contact type thickness measurement unit 43 having the same configuration as the contact type thickness measurement unit 53 of the finish grinding side thickness measurement unit 50, that is, the height of the upper surface of the chuck table 14. A reference-side height gauge 41 that measures the height position and a variable-side height gauge 42 that always contacts the back surface of the wafer 1 and measures the height position of the back surface of the wafer 1 are configured. Each of the height gauges 41 and 42 has a configuration in which swinging probes 41b and 42b are attached (see FIGS. 5A and 5C).

The above is the configuration related to the grinding area 10A on the base 11. Next, the supply / recovery area 10B will be described with reference to FIG.
In the center of the supply / recovery area 10B, a two-bar link type transfer robot 60 that moves up and down is installed. Around the transfer robot 60, a supply cassette 61, an alignment table 62, a swing arm type supply arm 63, a recovery arm 64 having the same structure as the supply arm 63, a spinner A cleaning device 65 and a recovery cassette 66 are arranged.

  The cassette 61, the alignment table 62 and the supply arm 63 are means for supplying the wafer 1 to the chuck table 14, and the recovery arm 64, the cleaning device 65 and the cassette 66 are configured to remove the wafer 1 from the chuck table 14 after grinding the back surface. It is a means to collect. The cassettes 61 and 66 are for storing a plurality of wafers 1 in a horizontal posture and in a stacked state at a constant interval in the vertical direction, and are set at predetermined positions on the base 11.

  When one wafer 1 is taken out from the supply cassette 61 by the transfer robot 60, the wafer 1 is placed on the alignment table 62 with the back side to which the protective tape 4 is not attached facing up, Here, it is determined at a certain position. Next, the wafer 1 is picked up and picked up from the alignment table 62 by the supply arm 63 and placed on the chuck table 14 waiting at the attachment / detachment position.

  On the other hand, the back surface is ground by each of the grinding units 20A and 20B, and the wafer 1 on the chuck table 14 positioned at the attachment / detachment position is picked up and taken up by the recovery arm 64, transferred to the cleaning device 65, and washed and dried. . The wafer 1 cleaned by the cleaning device 65 is transferred and accommodated in the collection cassette 66 by the transfer robot 60.

  The mechanical configuration of the wafer grinding apparatus 10 has been described above. As shown in FIG. 2, the wafer grinding apparatus 10 includes the measured value of the contact-type thickness measuring device 43 of the rough grinding side thickness measuring unit 40 and the finish. It has a control means 70 to which the measured value of the contact-type thickness measuring device 53 of the grinding side thickness measuring unit 50 and the measured value of the non-contact-type thickness measuring device 54 are input. This control means 70 is based on these thickness measurements, and each motor of the motor 23 that rotates the cup wheel 25 of the rough grinding unit 20A and the finish grinding unit 20B and the feed mechanism 33 that moves the grinding units 20A and 20B up and down. 34 is controlled. In addition, the control means 70 receives, from appropriate input means, the “thickness (total thickness) of the wafer 1 including the protective tape 4 before grinding” and the target “wafer 1 including the protective tape 4 after rough grinding”. ”(Total thickness)” and a target “finished thickness of only the wafer” are input, and the storage unit 71 stores the data.

Next, the operation of grinding the back surface of the wafer 1 by the wafer grinding apparatus 10 will be described including the control by the control means 70.
First, one wafer 1 accommodated in the supply cassette 61 is moved to the alignment table 62 and positioned by the transfer robot 60. Subsequently, the supply arm 63 waits at the attachment / detachment position and is vacuum operated. The wafer 1 is placed on the chuck table 14 with the back side facing up. As a result, the protective tape 4 on the front surface side of the wafer 1 is in close contact with the upper surface 14a of the chuck table 14, and is attracted and held on the upper surface 14a with the back surface exposed. At this time, the probes 41b and 42b of the height gauges 41 and 42 in the contact-type thickness measuring instrument 43 on the rough grinding side are appropriately upward and are retracted from the upper surface 14a of the chuck table 14.

  Next, the turntable 13 rotates in the direction of arrow R in FIG. 2, and the chuck table 14 holding the wafer 1 stops at the rough grinding position. At this time, the next chuck table 14 is positioned at the attachment / detachment position, and the wafer 1 to be ground next is set on the chuck table 14 as described above.

  At the rough grinding position, the wafer 1 is rotated in one direction by rotating the chuck table 14 and, at the same time, each probe of the reference height gauge 41 and the variable height gauge 42 of the contact-type thickness measuring instrument 43 on the rough grinding side. 41b and 42b are lowered and brought into contact with the upper surface 14a of the chuck table 14 and the back surface, which is the exposed surface of the wafer 1, respectively, and the state in which the thickness of the wafer 1 including the protective tape 4 is measured is maintained. Subsequently, the rough grinding unit 20 </ b> A is lowered by the feed mechanism 33, and grinding is performed by pressing the grindstone 26 of the cup wheel 25 rotated at a high speed against the back surface of the wafer 1 while supplying grinding water. When lowering the rough grinding unit 20A, if the grindstone 26 of the cup wheel 25 is lowered at a relatively high speed until the grindstone 26 of the cup wheel 25 approaches the wafer 1 based on the measurement value by the contact-type thickness measuring device 43, the time This is preferable in terms of shortening.

  5A and 5C show the wafer 1 on the chuck table 14 before grinding. FIG. 5A shows that the protective tape 4 is relatively thick, and FIG. 5C shows that the protective tape 4 is relatively thin. Each case is shown. The contact-type thickness measuring instrument 43 measures the total thickness t (t1 + t4) of the wafer 1 and the protective tape 4. Here, the control means 70 compares the total thickness t obtained by the contact-type thickness measuring instrument 43 with the total thickness of the wafer 1 including the protective tape 4 inputted in advance, and the total thickness t of the measured value is greatly increased. When the allowable value is exceeded (for example, there is a possibility that the grindstone 26 may collide with the wafer 1), an alarm process is performed and measures such as temporarily stopping the operation are taken. 5 (a) and 5 (c) show that the thickness t4 of the protective tape 4 varies, the thickness t1 of the wafer 1 may also vary. For this reason, It is necessary to know the total thickness t.

  While the rough grinding is in progress, the thickness (total thickness t) of the wafer 1 from the contact-type thickness measuring device 43 is input to the control means 70 one by one, and the control means 70 performs the rough grinding based on the measured value. The motor 34 of the unit 20A is controlled to control the feed amount of the cup wheel 25, that is, the grinding amount. When the control means 70 determines that the measured value of the contact-type thickness measuring device 43 has reached the rough grinding thickness stored in the storage unit 71 (the thickness of the wafer 1 including the protective tape 4 after the rough grinding). Then, the lowering of the cup wheel 25 by the feed mechanism 33 is stopped and the cup wheel 25 is rotated as it is for a certain period of time, and then the rough grinding unit 20A is raised to finish the rough grinding. As described above, the rough grinding thickness is, for example, about 30 μm thicker than the finish thickness.

  Subsequently, the wafer 1 that has finished the rough grinding is transferred to the finish grinding position by rotating the turntable 13 in the R direction. Then, the wafer 1 set in advance at the attachment / detachment position is transferred to the rough grinding position, and this wafer 1 is roughly ground in parallel with the preceding finish grinding while the thickness is measured in the same manner as described above. Further, the wafer 1 to be processed next is set on the chuck table 14 moved to the attachment / detachment position.

  At the finish grinding position, the wafer 1 is first rotated together with the chuck table 14, and the thickness (total thickness t) of the wafer 1 is similarly measured by the contact-type thickness measuring device 53 of the finish grinding side thickness measuring unit 50. Is measured. The thickness measured by the contact-type thickness measuring device 53 is the same as the rough grinding thickness, but if the measured value by the contact-type thickness measuring device 43 on the rough grinding side is different from the actual thickness, the finish grinding unit When the 20B grindstone 26 is lowered at a relatively high speed until it approaches the wafer 1, the grindstone 26 may collide with the wafer 1, for example, as described above. In order to avoid such a problem in advance, it is necessary to newly measure and confirm the thickness of the wafer 1 including the protective tape 4 by the contact-type thickness measuring device 53.

  Next, the finish grinding unit 20B is lowered at a relatively high speed until the grindstone 26 of the cup wheel 25 comes close to the wafer 1 based on the measurement value of the contact-type thickness measuring device 53, and then the contact-type thickness measuring device. While measuring the thickness of the wafer 1 by 53, the back surface of the wafer 1 is ground by about several μm using the finish grinding unit 20B in the same manner as the rough grinding. As a result, the back surface of the wafer 1 becomes a mirror surface that can be measured by the non-contact type thickness measuring device 54. Therefore, the thickness measurement of the wafer 1 is switched to the non-contact type thickness measuring device 54 and the wafer 1 is ground. The finish grinding is performed while the thickness of only the wafer 1 is measured by the non-contact type thickness measuring instrument 54. From the viewpoint of accurately measuring the thickness of only the wafer 1 with the non-contact type thickness measuring instrument 54, the thickness of the wafer 1 transferred to finish grinding (rough grinding thickness) is preferably about 200 μm or less.

  While the finish grinding is in progress, the thickness of the wafer 1 by the non-contact type thickness measuring device 54 is inputted to the control means 70 one by one, and the control means 70 turns on the motor 34 of the finish grinding unit 20B based on the measured value. The feed amount of the cup wheel 25, that is, the grinding amount, is controlled. When the finish grinding advances and the control means 70 determines that the measured value of the non-contact type thickness measuring instrument 54 has reached the finished thickness stored in the storage unit 71, the feeding mechanism 33 lowers the cup wheel 25. After stopping and rotating the cup wheel 25 as it is for a certain period of time, the rough grinding unit 20B is raised and finish grinding is finished.

  Here, examples of suitable operating conditions for rough grinding and finish grinding will be given. In both the rough grinding and finish grinding grinding units 20A and 20B, the rotational speed of the cup wheel 25 is 3000 to 5000 RPM, and the rotational speed of the chuck table 14 is 100 to 300 RPM. The lowering speed, which is the feed speed of the rough grinding unit 20A, is 3 to 5 μm / second, and the lowering speed of the finish grinding unit 20B is 0.3 to 1 μm / second.

  When both finish grinding and rough grinding, which have been performed in parallel, are finished, the turntable 13 is rotated, and the wafer 1 on which finish grinding has been finished is transferred to the attachment / detachment position. As a result, the subsequent wafer 1 is transferred to the rough grinding position and the finish grinding position, respectively. The wafer 1 on the chuck table 14 positioned at the attachment / detachment position is transferred to the cleaning device 65 by the recovery arm 64, and is washed with water and dried. The wafer 1 cleaned by the cleaning device 65 is transferred and accommodated in the collection cassette 66 by the transfer robot 60.

  The above is a cycle in which one wafer 1 is washed and recovered after being thinned to a desired finish thickness. According to the wafer grinding apparatus 10 of the present embodiment, while the turntable 13 is rotated intermittently as described above, rough grinding is performed on the wafer 1 at the rough grinding position, and finish grinding is performed at the finish grinding position in parallel. As a result, the plurality of wafers 1 are efficiently ground.

  In the wafer grinding apparatus 10 of this embodiment, first, the rough grinding unit is measured while measuring the total thickness (t) of the wafer 1 including the protective tape 4 by the contact-type thickness measuring device 43 of the rough grinding side thickness measuring unit 40. The wafer 1 is roughly ground at 20 A, and the wafer 1 is thinned to about 30 μm, for example, at a finished thickness. Next, in finish grinding, the thickness of the wafer 1 is measured again by the contact-type thickness measuring device 53 and safety is confirmed, and then the thickness of only the wafer 1 is measured by the non-contact-type thickness measuring device 54. Grinding is performed, and when the wafer 1 is thinned to the finished thickness, the grinding is finished. The thickness of the wafer 1 including the protective tape 4 is measured at the time of rough grinding. However, since the measured value is not finish grinding, even if the thickness of the protective tape 4 varies, it is allowed. When the process shifts to finish grinding, the thickness of only the wafer 1 is measured by the non-contact type thickness measuring device 54. Therefore, the thickness of the wafer 1 is accurately measured, and the thickness of the protective tape 4 or the thickness of the wafer 1 itself is measured. Regardless of variation, the wafer 1 can be reliably processed to a target thickness.

  5 (b) and 5 (d) show the wafer 1 shown in (a) and (c), respectively. The thickness of the wafer 1 is determined by the contact-type thickness measuring device 53 and the non-contact-type thickness measuring device 54. It shows the state of grinding while measuring. If the thickness of the wafer 1 is measured only by the contact-type thickness measuring device 53, only the total thickness t can be controlled. If the thickness t4 of the protective tape 4 is different as shown in the figure, the grinding is performed. The thickness t1 of the wafer 1 to be used is also different. However, the non-contact type thickness measuring device 54 measures the thickness of only the wafer 1 and controls the grinding feed amount based on this fixed value, so that even if the thickness of the protective tape 4 is different, the wafer 1 The finish thickness can be made constant at all times.

  On the finish grinding side, the thickness of the wafer 1 before grinding is measured again by the contact-type thickness measuring device 53 and then the measurement is continued until the finish grinding is finished, whereby the grindstone 26 of the cup wheel 25 is worn. It is meaningful to acquire data to know the amount.

It is the (a) perspective view and (b) side view of the semiconductor wafer by which the back surface is ground by one Embodiment of this invention. 1 is an overall perspective view of a wafer grinding apparatus according to an embodiment. FIG. 2 is a perspective view of a grinding unit provided in the wafer grinding apparatus shown in FIG. 1. FIG. 2 is a side view of a grinding unit provided in the wafer grinding apparatus shown in FIG. 1. (A), (c) is sectional drawing which shows the state which is measuring the thickness of the wafer from which the thickness of a masking tape differs with a contact-type thickness measuring device, (b), (d) is (a), ( It is a side view which shows the state which grinds the wafer shown to c), measuring thickness with a contact-type thickness measuring device and a non-contact-type thickness measuring device.

Explanation of symbols

1 ... Wafer 3 ... Semiconductor chip (device)
4 ... Protective tape (protective member)
10 ... Wafer grinding device 14 ... Chuck table (Wafer holding means)
14a ... Upper surface (holding surface) of chuck table
20A: Coarse grinding unit (grinding means)
20B: Finish grinding unit (grinding means)
33 ... Feed mechanism (feed means)
43, 53 ... contact-type thickness measuring instrument 54 ... non-contact type thickness measuring instrument 70 ... control means 71 ... storage unit t ... thickness of wafer including protective tape t1 ... thickness of wafer only t4 ... thickness of protective tape The

Claims (3)

At least a rough grinding part and a finish grinding part are provided.
A rotatable wafer holding means having a holding surface for holding the protective member side of the wafer having a protective member coated on the surface on which the device is formed;
Grinding means disposed opposite to the holding surface of the holding means and having a rotation axis parallel to the rotation axis of the holding means;
The holding means and the grinding means are moved relative to each other along the direction in which the rotation shaft of the means extends to approach and separate from each other, and when approaching, the back surface of the wafer is ground by the grinding means. In a wafer grinding apparatus having a feeding means for reducing the thickness,
The rough grinding portion is provided with a contact-type thickness measuring instrument that contacts the exposed back surface of the wafer held by the wafer holding means and measures the thickness of the wafer including the protection member,
The finish grinding part has a contact thickness measuring device similar to the contact thickness measuring device and a thickness of only the wafer adjacent to the exposed back surface of the wafer held by the wafer holding means. A wafer grinding apparatus, comprising a non-contact type thickness measuring device for measuring thickness. Measurement signals of the contact-type thickness measuring devices and the non-contact-type thickness measuring device are input, and the feed amount of the grinding means by the feed means is controlled based on the measurement signals, and the rough grinding is performed. Control means for grinding the wafer to a predetermined thickness in the section and the finish grinding section,
The control means includes
In the rough grinding part, based on the measurement signal of the contact-type thickness measuring device, the feeding means is controlled until the thickness of the wafer including the protective member reaches a predetermined rough grinding thickness,
Next, in the finish grinding part, first, based on the measurement signal of the contact-type thickness measuring device, it is determined whether or not the thickness of the wafer including the protective member is a thickness after a predetermined rough grinding. After confirming, finish grinding by the grinding means is started, and at the time of finish grinding, based on the measurement signal of the non-contact type thickness measuring device, the thickness of only the wafer not including the protective member is predetermined. 2. The wafer grinding apparatus according to claim 1, wherein the feeding means is controlled until a finishing thickness is reached. The control means stores a thickness of the wafer before the rough grinding including the protective member, a target thickness including the protective member after the rough grinding of the wafer, and a target thickness of the wafer after the final grinding. Part
At the time of grinding in the rough grinding part, the feed is performed so as to grind a thickness region from a thickness of the wafer before the rough grinding including the protection member to a target thickness including the protection member after the rough grinding of the wafer. Control means,
Then, during grinding in the finish grinding section, the feeding means is controlled while measuring the thickness of only the wafer by the non-contact type thickness measuring instrument, and after the finish grinding, the thickness of only the wafer is stored in advance. 3. The wafer grinding apparatus according to claim 2, wherein control is performed to stop the operation of the feeding means when the target thickness is reached.

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