JP2023029446A - Wafer grinding method and wafer grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer grinding method and a wafer grinding device capable of thinning a wafer to a finished thickness.

SOLUTION: A wafer grinding method includes a rough grinding step of rough grinding the back surface of a wafer by rough grinding means until the thickness of the wafer reaches a second thickness that is thicker than a first thickness, which is the finished thickness, and a fine grinding step of performing fine grinding of the back surface of the wafer while gradually or continuously slowing down the feeding speed of fine grinding means after the rough grinding step has taken place, and setting the feeding speed of the fine grinding means so as to give priority to immediately stopping the fine grinding means right after grinding the back surface of the wafer until it reaches the first thickness.

SELECTED DRAWING: Figure 8

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to a wafer grinding method and a wafer grinding apparatus, and more particularly, groove processing for processing grooves shallower than the thickness of the wafer from the front surface side of the wafer along dicing lines that divide a plurality of semiconductor elements formed on the front surface of the wafer. The present invention relates to a wafer grinding method and a wafer grinding apparatus for grinding a back surface of a wafer to a finished thickness by holding the front side of the wafer with a protective tape attached to the surface after performing a process, by a table.

Patent Document 1 discloses a semiconductor device manufacturing method for separating a chip having a plurality of semiconductor elements formed thereon from a wafer, and manufacturing a semiconductor device to which a dicing method called the DBG method (Dicing Before Grinding) is applied. A method is disclosed.

The DBG method includes a dicing process, an attaching process, and a back grinding process.

In the dicing process of the DBG method, as shown in the cross-sectional view of the wafer W in FIG. A cutting groove 2 for separation shallower than the thickness of is formed. As a result, grid-shaped cut grooves 2 are formed along the dicing lines on the surface of the wafer W, as shown in the plan view of the wafer W in FIG.

Next, in the pasting step, the wafer W is turned upside down as shown in FIG. 9B, and a tape for back grinding (protective tape, hereinafter referred to as a protective tape) is applied to the surface of the semiconductor element SD (Semiconductor Device) on the lower side in the drawing. , BG tape.) 3 is attached.

Next, in the back surface grinding step, as shown in FIG. 9C, the back surface of the wafer W, which is the upper surface in the drawing, is ground by the wafer grinding device 4 until it reaches the cutting groove 2, and the wafer W is ground. Individual chips T are separated. In the back surface grinding step, the front side of the wafer W is held by the table 5 via the BG tape 3, the table 5 and the wafer grinding device 4 are rotated in the directions of arrows a and b, and the wafer grinding device 4 is rotated in the direction of the arrow c. It will be implemented while sending it to

After that, a wafer holding tape (not shown) is attached to the rear surface of the separated chip T, and the BG tape 3 is removed from the table 5. Next, after removing the BG tape 3 from the chip T, the chip is separated from the wafer holding tape. Take out the T.

Japanese Patent Application Laid-Open No. 2002-100588

However, in the wafer grinding method by the DBG method as in Patent Document 1, when the chips T are separated into individual pieces, sludge generated by the grinding process enters the gap 6 between the adjacent chips T, There was a problem that sludge adhered to the side of the T.

Such a problem can be alleviated by ending the back grinding process immediately after the back grinding by the wafer grinding device 4 reaches the cut groove 2 . Therefore, the thickness of the wafer W may be measured while the back surface of the wafer W is being ground, and the back surface grinding process may be terminated immediately after the thickness reaches the depth of the cut groove 2 .

Here, as a device for measuring the thickness of the wafer W during the backside grinding process, for example, a known contact-type thickness measuring gauge (also referred to as an electric micrometer or an in-process gauge) may be used. This contact thickness gauge has a pair of probes. With the back surface of the wafer W held by the table 5, one of the pair of probes is brought into contact with the back surface of the wafer, and the other probe is brought into contact with the top surface of the table. The thickness of the wafer W is measured.

However, since the BG tape 3 is attached to the surface of the wafer W, the contact thickness measurement gauge detects the thickness of the wafer W including the thickness of the BG tape 3, but the thickness of the BG tape 3 does not exceed the thickness of the BG tape 3. is non-uniform, it is difficult to accurately measure the thickness of the wafer W alone. In addition, there is also a problem that the rear surface of the individualized chip T is damaged due to the contact of one of the contacts.

Therefore, in place of the contact thickness measuring gauge, a known non-contact thickness gauge is used in which the thickness of only the wafer W is measured by transmitting an ultrasonic wave or a laser to the back surface of the wafer W and receiving the reflected wave. It is conceivable to use a measurement gauge (also called a non-contact in-process gauge).

However, since the back surface of the wafer W being ground is rough, the transmitted ultrasonic wave or laser is diffused on the back surface. Therefore, it is difficult to measure the thickness of the wafer W only accurately.

The present invention has been made in view of such circumstances, and a wafer grinding method capable of thinning the wafer to a finished thickness by grinding the back surface of the wafer while accurately measuring the thickness of only the wafer. and to provide a wafer grinding apparatus.

In one aspect of the wafer grinding method of the present invention, in order to achieve the object of the present invention, along the dicing line that divides a plurality of semiconductor elements formed on the surface of the wafer, from the wafer surface side, the thickness of the wafer is reduced. After the grooving process for forming shallow grooves is performed, the front side of the wafer with the protective tape attached to the surface is held by a table, and the back surface of the wafer is ground to finish the wafer to a first thickness. wherein the thickness of the wafer is measured by the contact thickness measuring means that measures the thickness of the wafer by contacting the back surface of the wafer while measuring the thickness of the wafer by the contact thickness measuring means. After the rough grinding step of rough grinding the back surface of the wafer by rough grinding means until the wafer thickness reaches a second thickness that is thicker than the first thickness based on the thickness of the wafer, and the rough grinding step, Based on the thickness of the wafer measured by the non-contact thickness measuring means while measuring the thickness of the wafer by the non-contact thickness measuring means that measures the thickness of the wafer from a position remote from the back surface of the wafer and a fine grinding step of fine grinding the back surface of the wafer by fine grinding means until the thickness of the wafer reaches the first thickness.

In one aspect of the wafer grinding apparatus of the present invention, in order to achieve the object of the present invention, from the wafer surface side along a dicing line that divides a plurality of semiconductor elements formed on the wafer surface, the thickness of the wafer is reduced from the wafer thickness. After the grooving process for forming shallow grooves is performed, the front side of the wafer with the protective tape attached to the surface is held by a table, and the back surface of the wafer is ground to finish the wafer to a first thickness. A wafer grinding apparatus that thins to a thickness of up to 100 mm, comprising rough grinding means for rough grinding the back surface of the wafer held on the table, and contact-type thickness measuring means for measuring the thickness of the wafer by contacting the back surface of the wafer held on the table. thickness measuring means, fine grinding means for finely grinding the back surface of the wafer held on the table, and non-contact thickness measuring means for measuring the thickness of the wafer from a position distant from the back surface of the wafer held on the table. and a second thickness that is thicker than the first thickness based on the thickness of the wafer measured by the contact thickness measuring means while measuring the thickness of the wafer by the contact thickness measuring means; A control means for roughly grinding the back surface of the wafer by the rough grinding means until the back surface of the wafer reaches the non-contact thickness while measuring the thickness of the wafer by the non-contact thickness measurement means after the rough grinding process is performed. a control means for causing the precision grinding means to precisely grind the back surface of the wafer until the thickness of the wafer reaches the first thickness based on the thickness of the wafer measured by the measurement means.

According to one aspect of the present invention, the wafer backside grinding process is divided into a rough grinding process with a large grinding amount per unit time and a fine grinding process with a small grinding amount per unit time. In the rough grinding process, a contact-type thickness measuring means is used that can measure the thickness of the wafer even if the surface roughness of the back surface of the wafer is rough. While measuring the thickness of the wafer by contacting the contact thickness measuring means with the back surface of the wafer, the thickness of the wafer is determined as the finished thickness based on the thickness of the wafer measured by the contact thickness measuring means. Rough grinding is performed by the rough grinding means until a second thickness thicker than the first thickness is obtained. After that, the rough grinding process is switched to the fine grinding process.

In the fine grinding step, the back surface of the wafer is finely ground by the fine grinding means, that is, the back surface of the wafer is ground so that the surface roughness of the back surface of the wafer is reduced. A contact thickness measurement means is used. Until the thickness of the wafer reaches the first thickness based on the thickness of the wafer measured by the non-contact thickness measuring means while only the thickness of the wafer is measured by the non-contact thickness measuring means without contact. Fine grinding by fine grinding means.

Thus, according to one aspect of the present invention, the wafer can be thinned to the finished thickness by grinding the back surface of the wafer while accurately measuring the thickness of only the wafer.

In one aspect of the wafer grinding method of the present invention, the rough grinding step controls the feeding speed of the rough grinding means to a first speed to rough grind the back surface of the wafer to a second thickness, and the fine grinding step comprises fine grinding. a first fine grinding step of finely grinding the wafer to a third thickness thinner than the second thickness and thicker than the first thickness by controlling the feeding speed of the means to a second speed lower than the first speed; , After the first fine grinding step is performed, a second fine grinding step of finely grinding the wafer to a first thickness by controlling the feeding speed by the fine grinding means to a third speed lower than the second speed. and preferably.

In one aspect of the wafer grinding apparatus of the present invention, the control means controls the feeding speed by the rough grinding means to a first speed to roughly grind the back surface of the wafer to a second thickness, and then feeds the wafer by the fine grinding means. The speed is controlled to a second speed that is lower than the first speed, and the wafer is precisely ground to a third thickness that is thinner than the second thickness and thicker than the first thickness, and then the feeding speed by the fine grinding means. is controlled to a third speed lower than the second speed to precisely grind the wafer to the first thickness.

According to one aspect of the present invention, the rough grinding step controls the feed speed of the rough grinding means to a first speed to rough grind the back surface of the wafer to the second thickness.

The fine grinding process is divided into a first fine grinding process and a second fine grinding process. In the first fine grinding step, the feed speed by the fine grinding means is controlled to a second speed lower than the first speed, and the wafer is thinned to a third thickness thinner than the second thickness and thicker than the first thickness. Grind finely. As a result, the back surface of the wafer W is ground to a mirror surface. Then, in the second fine grinding step, the feed speed of the fine grinding means is controlled to a third speed lower than the second speed, and the wafer is fine ground to the first thickness. As a result, the wafer W is gradually ground from the third thickness to the first thickness, so that the grinding process of the back surface of the wafer can be finished immediately after grinding to the first thickness, which is the finished thickness. . In other words, by setting the first thickness to the depth of the groove, it is possible to reduce the problem of sludge generated by grinding entering the gaps between adjacent chips and adhering to the side surfaces of the chips. .

One aspect of the wafer grinding method of the present invention preferably includes a spark-out step in which, after the fine grinding step is performed, feed of the fine grinding means is stopped and spark-out is performed by the fine grinding means.

In one aspect of the wafer grinding apparatus of the present invention, it is preferable that the control means stop feeding the fine grinding means after the fine grinding process is performed, and cause the fine grinding means to perform spark-out.

According to one aspect of the present invention, the uncut portion of the back surface of the wafer that has reached the first thickness by the fine grinding process can be removed by the spark-out process. Thereby, the quality of the back surface, which is the finished surface, can be improved.

According to the wafer grinding method and wafer grinding apparatus of the present invention, the wafer can be thinned to the finished thickness by grinding the back surface of the wafer while accurately measuring the thickness of only the wafer.

Appearance perspective view of the wafer grinding apparatus of the embodiment The top view of the wafer grinding apparatus shown in FIG. Block diagram showing the configuration of the wafer grinding apparatus shown in FIG. Block diagram showing the configuration of the IPG Block diagram showing the configuration of NCIG A flow chart showing the processes of the rough grinding section and the fine grinding section Graph showing the amount of wafer grinding in the rough grinding and fine grinding processes Explanatory drawing showing the operation of the rough grinding section and the fine grinding section Explanatory diagram showing a method for manufacturing a semiconductor device in chronological order A plan view of a wafer in which cut grooves are formed in a dicing process

Preferred embodiments of the wafer grinding method and wafer grinding apparatus according to the present invention will be described below with reference to the accompanying drawings.

[Wafer grinding device 10]
FIG. 1 is a perspective view of a wafer grinding device 10 of an embodiment, and FIG. 2 is a plan view of the wafer grinding device 10. As shown in FIG. 3 is a block diagram showing the configuration of the wafer grinding apparatus 10. As shown in FIG.

As shown in FIGS. 1 and 2, the main body 12 of the wafer grinding apparatus 10 has a cassette housing portion 14, a wafer transfer device 16, an alignment portion 18, an index table 20, a rough grinding portion 22, and a fine grinding portion 24 at predetermined positions. is provided in These devices and respective parts are centrally controlled by a controller (control means) 26 shown in FIG. The controller 26 controls these devices and each section based on information indicating the type of wafer W input from the input device 28 . The content of control will be described later. The rough grinding section 22 and the fine grinding section 24 shown in FIGS. 1 and 2 are covered with a cover (not shown) to prevent the working fluid used in the rough grinding section 22 and the fine grinding section 24 from scattering outside. are preventing.

<Cassette storage unit 14>
A cassette 30 storing a plurality of wafers W before back surface grinding and a cassette 32 storing wafers W after back surface grinding are detachably mounted in the cassette storage unit 14 .

Cut grooves 2 (see FIG. 8) for separating the semiconductor elements are formed on the front surface of the wafer W before the back surface is ground through a groove processing step using a dicing device (not shown). That is, cut grooves 2 shallower than the initial thickness of the wafer W are formed on the front surface of the wafer W from the front surface side of the wafer along dicing lines that divide a plurality of semiconductor elements. A BG tape 3 (see FIG. 8) is attached to the surface of the wafer W to protect the semiconductor elements.

The wafers W stored in the cassette 30 are held one by one by the suction section 34 of the wafer transfer device 16 and transferred to the alignment section 18 . The wafer transfer device 16 is a general-purpose 6-axis joint robot, and its configuration is well known, so the description thereof will be omitted here.

<Alignment part 18>
The alignment unit 18 is a device that aligns the wafers W unloaded from the cassette 30 to predetermined positions. The wafer W aligned by the alignment unit 18 is sucked and held again by the suction unit 34 of the wafer transfer device 16, and then transferred to the empty table 36, where the front side of the wafer W is suctioned to the suction surface on the upper surface of the table 36. retained. The table 36 is installed on the upper surface of the index table 20, and tables 38, 40 and 42 having the same function are installed on the upper surface of the index table 20. FIG.

<Index table 20>
The index table 20 has a disk shape and is rotatably supported by the main body 12 via a rotating shaft 44 indicated by a dashed line in FIG. A rotating shaft (not shown) of a motor 46 indicated by a dashed line in FIG. 2 is connected to the rotating shaft 44 . Therefore, the index table 20 is rotated by the power of the motor 46, and the motor 46 is controlled by the controller 26 of FIG. The four tables 36 to 42 described above are arranged on a concentric circle around the rotating shaft 44 of the index table 20 at intervals of 90 degrees.

<Tables 36-42>
1 and 2, the table 36 is at the wafer W receiving position, the table 38 is at the rough grinding position by the rough grinding section 22, the table 40 is at the fine grinding position by the fine grinding section 24, and the table 42 is at the wafer W receiving position. are placed at the delivery positions of

After being held by the table 36 positioned at the receiving position, the wafer W is moved to the rough grinding position by intermittent rotation of the index table 20 by 90 degrees, where it is rough ground. When the rough grinding is completed, the wafer W is moved to the fine grinding position by intermittent rotation of the index table 20 in the same direction by 90 degrees, where fine grinding and spark-out processing are performed. When the precision grinding process is finished, the wafer W is moved to the transfer position by intermittent rotation of the index table 20 by 90 degrees in the same direction, where it is held by the wafer transfer device 16 and then stored in the cassette 32. .

The tables 36 to 42 are connected to a rotating shaft of a motor (not shown) supported on the lower surface of the index table 20, and are rotated by the driving force of the motor.

The adsorption surfaces of the tables 36 to 42 are made of a porous material made of sintered bodies such as ceramics, and are connected to suction pumps (not shown). By applying the suction force of the suction pump to the suction surface, the front side of the wafer W is held by suction on the suction surface.

<Rough grinding part 22>
The rough grinding unit 22 includes a cup-shaped grindstone (rough grinding means) 48 for rough grinding the back surface of the wafer W, a motor 50, a feeding device 52, and an in-process gauge (Tokyo Seimitsu Products Co., Ltd., PULCOM series.In Process Gage.Hereinafter referred to as "IPG".

As shown in FIG. 1, the cup-shaped grindstone 48 is connected to a rotating shaft (not shown) of the motor 50 and is rotated by the driving force of the motor 50. As shown in FIG. Also, the cup-shaped grindstone 48 is attached to the feeding device 52 via a motor 50 and a motor support portion 56 .

The feeding device 52 is a device for vertically moving the cup-shaped grindstone 48 together with the motor 50 with respect to the rough grinding position. . Thereby, the back surface of the wafer W is roughly ground.

The feeding speed of the cup-shaped grindstone 48 by the feeding device 52 is set to a constant speed based on the grindstone specifications such as the grit of the abrasive grains of the cup-shaped grindstone 48 and the grinding conditions such as the material of the wafer W and the like.

In addition, the feeding amount of the cup-shaped grindstone 48 to the back surface of the wafer W by the feeding device 52 depends on the initial thickness of the wafer W, the thickness of the wafer W during rough grinding measured by the IPG 54, and the grooving process. The controller 26 in FIG. 3 controls based on the depth of the groove 2 formed in .

FIG. 4 is a block diagram showing the configuration of the IPG 54. As shown in FIG.

The IPG 54 has a pair of contacts 58 , 60 and a computing section 62 . The contactor 58 is brought into contact with the back surface of the wafer W, and the contactor 60 is brought into contact with the upper surface of the table 36 located at the rough grinding position (see FIG. 8). The calculator 62 obtains the thickness of the wafer W by subtracting the height of the top surface of the table 36 measured by the contactor 60 from the height of the back surface of the wafer W measured by the contactor 60 . The thickness of the wafer W measured by the IPG 54 is output to the controller 26 in FIG. 3, and the controller 26 controls the rough grinding section 22 based on the thickness. Note that the thickness of the wafer W measured by the IPG 54 includes the thickness of the BG tape 3 .

After the cup-shaped grindstone 48 is retracted upward from the wafer W, the wafer W subjected to the rough grinding process in the rough grinding section 22 is moved to the fine grinding section 24 by rotating the index table 20 by 90 degrees. .

<Precise grinding unit 24>
As shown in FIGS. 1 and 2, the fine grinding unit 24 includes a cup-shaped grindstone (fine grinding means) 64 for finely grinding the back surface of the wafer W, a motor 66, a feeding device 68, and a non-contact thickness measuring means. A contact in process gauge (No Contact In Process Gage, hereinafter referred to as “NCIG”) 70 is provided.

The cup-shaped grindstone 64 is connected to a rotating shaft (not shown) of a motor 66 and is rotated by the driving force of the motor 66 . Also, the cup-shaped grindstone 64 is attached to a feeding device 68 via a motor 66 and a motor support portion 72 .

The feeding device 68 is a device for vertically moving the cup-shaped grindstone 64 together with the motor 66 with respect to the fine grinding position. . As a result, the back surface of the wafer W is finely ground.

The feeding speed of the cup-shaped grindstone 64 by the feeding device 68 is set based on the grindstone specifications such as the grit of the abrasive grains of the cup-shaped grindstone 64 and the grinding conditions such as the material of the wafer W and the like.

Further, the feeding amount of the cup-shaped grindstone 64 with respect to the back surface of the wafer W by the feeding device 68 is determined by the thickness of the wafer W during the precision grinding process measured by the NCIG 70 and the groove 2 formed in the grooving process. is controlled by the controller 26 of FIG.

FIG. 5 is a block diagram showing the configuration of the NCIG 70. As shown in FIG.

The NCIG 70 includes a wave transmitting portion 76 that transmits an ultrasonic wave U such as a pulsed ultrasonic wave oscillated from an ultrasonic wave oscillating portion toward the wafer W below, and a wave transmitting portion 76 that transmits the wave and reflects it onto the wafer W. A wave receiving section 78 for receiving reflected waves of ultrasonic waves and a computing section 80 are provided.

According to the NCIG 70, the ultrasonic wave U transmitted from the wave transmitting unit 76 toward the wafer W is reflected by the back surface W1 and the front surface W2 of the wafer W, and the first reflected wave U1 and the second reflected wave U2 are generated, respectively. , is received by the wave receiving unit 78 . Since the second reflected wave U2 arrives at the wave receiving section 78 with a delay of the thickness of the wafer W from the first reflected wave U1, the calculation section 80 obtains the thickness of the wafer W only based on this time difference. The thickness of only the wafer W measured by the NCIG 70 is output to the controller 26 in FIG. 3, and the controller 26 controls the precision grinding section 24 based on the thickness. Although the NCIG 70 using ultrasonic waves has been described as a non-contact thickness measuring means, a measuring means using laser light can also be used as a non-contact type.

Further, in the fine grinding section 24 , after the fine grinding process with the cup-shaped grindstone 64 , the spark-out process with the cup-shaped grindstone 64 can be performed. The spark-out process is a process performed in the final stage of grinding, in which the feeding of the cup-shaped grindstone 64 is stopped, the cup-shaped grindstone 64 is rotated, and the back surface of the wafer W is removed until sparks and grinding noise due to grinding are eliminated. This is the process of processing.

After the cup-shaped grindstone 64 is retracted upward from the wafer W, the wafer W whose back surface has been sparked out by the fine grinding section 24 is moved to the delivery position by rotating the index table 20 in the same direction by 90 degrees. .

[Actions of Rough Grinding Section 22 and Fine Grinding Section 24]
FIG. 6 is a flowchart of a wafer grinding method including rough grinding steps (S (Steps) 10, S20) by the rough grinding section 22 and fine grinding steps (S40, S50, S60, S70) by the fine grinding section 24. FIG.

FIG. 7 is a graph showing the thickness of the wafer W that gradually decreases through the rough grinding processes (S10, S20) and the fine grinding processes (S40, S50, S60, S70) over time. That is, the vertical axis indicates the thickness of the wafer W, and the horizontal axis indicates the elapsed time of grinding.

8A to 8E are explanatory diagrams showing the grinding operations of the rough grinding section 22 and the fine grinding section 24. FIG.

In FIG. 3, the rotation speed of the motor 50 of the rough grinding section 22, the feeding speed of the feeding device 52, the feeding end position, the rotation speed of the motor 66 of the fine grinding section 24, the feeding speed of the feeding device 68, The feeding end position is controlled by the controller 26 .

Description will be made below with reference to FIGS. 3 and 6 to 8. FIG.

The controller 26 inputs from the input device 28 the initial thickness A of the wafer W, the depth d of the cutting groove 2 formed on the surface, the first thickness B (B=d) which is the finished thickness, the cup The first feed speed V1 of the die grindstone 48, the second thickness C after grinding in the rough grinding step, the third thickness D after fine grinding in the first fine grinding step, the first fine grinding The rough grinding part 22 and the fine grinding are performed based on the second feed speed V2 of the cup-shaped grindstone 64 in the process, the third feed speed V3 of the cup-shaped grindstone 64 in the second fine grinding process, and the set time S1 of the spark-out process. It controls the operation of each section of the section 24 .

First, rough grinding steps (S10, S20) and fine grinding steps (S40, S50, S60, S70) will be outlined.

<Rough Grinding Step (S10, S20)>
FIG. 8A shows the table 36 moved to the rough grinding position. Thereafter, as shown in FIG. 8B, the cup-shaped grindstone 48 is moved downward from above the wafer W, and rough grinding is started when the cup-shaped grindstone 48 comes into contact with the back surface of the wafer W (S10).

When the rough grinding is started, the thickness of the wafer W measured by the IPG 54 is measured while the IPG 54 that measures the thickness of the wafer W in contact with the back surface of the wafer W held on the table 36 is measured. Based on the thickness (including the thickness of the BG tape), the thickness of the wafer W is changed from the initial thickness A to the second thickness C, which is thicker than the first thickness B, which is the finished thickness. The back surface of the wafer W is roughly ground by (S20).

As shown in FIG. 8B, when the thickness of the wafer W reaches the second thickness C, the cup-shaped grindstone 48 is retracted upward. Thereafter, the index table 20 is rotated by 90 degrees to move the table 36 to the fine grinding position (S30).

<Precision grinding process>
After the rough grinding process is performed, as shown in FIG. 8C, fine grinding by the cup-shaped grindstone 64 is started (S40). In the fine grinding process, while the thickness of only the wafer W is measured by the NCIG 70 that measures the thickness of the wafer W from a position distant from the back surface of the wafer W, the wafer W is measured based on the thickness of the wafer W measured by the NCIG 70. The back surface of the wafer W is precisely ground by the cup-shaped grindstone 64 until the thickness of W reaches the first thickness B (S70). When the thickness of the wafer W reaches the first thickness B, the cup-shaped grindstone 48 is retracted upward. After that, the index table 20 is rotated by 90 degrees to move the table 36 to the delivery position.

According to the wafer grinding apparatus 10 of the embodiment, the back surface grinding process of the wafer W is divided into the rough grinding process (S10, S20) with a large grinding amount per unit time and the fine grinding process (S40) with a small grinding amount per unit time. , S50, S60, and S70).

In the rough grinding steps (S10, S20), the IPG 54 that can measure the thickness of the wafer W even if the surface roughness of the back surface of the wafer W is rough is used. The contactor 58 of the IPG 54 is brought into contact with the back surface of the wafer W, and while measuring the thickness of the wafer W gradually decreasing from the initial thickness A, the thickness of the wafer W is measured based on the thickness of the wafer W measured by the IPG 54. Rough grinding is performed by the cup-shaped grindstone 48 until the thickness reaches a second thickness C that is thicker than the first thickness B, which is the finishing thickness. After that, the rough grinding process is switched to the fine grinding process.

In the fine grinding steps (S40, S50, S60, S70), the back surface of the wafer W is finely ground by the cup-shaped grindstone 64, that is, the back surface of the wafer W is ground so that the surface roughness is reduced. Therefore, NCIG70 is used instead of IPG54. While only the thickness of the wafer W is measured by the NCIG 70 in a non-contact manner, the cup-shaped grindstone 64 precisely grinds the wafer W until the thickness of the wafer W reaches the first thickness B based on the thickness of the wafer W measured by the NCIG 70. do.

Thus, according to the wafer grinding apparatus 10 and the wafer grinding method of the embodiment, the back surface of the wafer W is ground while the thickness of only the wafer W is accurately measured, and the wafer is ground to the first thickness which is the finished thickness. It can be thinned to B.

Next, the rough grinding steps (S10, S20) and fine grinding steps (S40, S50, S60, S70) will be described in detail.

<<Rough Grinding Step (S10, S20)>>
In the rough grinding steps (S10, S20), the feeding speed of the cup-shaped grindstone 48 is controlled to the first feeding speed V1, and the back surface of the wafer W is roughly ground from the initial thickness A to the second thickness C.

The first feeding speed V1 is set with priority given to shortening the processing time spent in the back grinding process and efficiently performing the back grinding process without damaging the back surface of the wafer W by the cup-shaped grindstone 48. speed.

<<Precise Grinding Process (S40, S50, S60, S70)>>
The fine grinding process is divided into a first fine grinding process (S40, S50) and a second fine grinding process (S60, S70).

As shown in FIG. 8(D), in the first fine grinding step (S40, S50), the feeding speed of the cup-shaped grindstone 64 is controlled to a second feeding speed V2 lower than the first feeding speed V1, The wafer W is precisely ground to a third thickness D which is thinner than the second thickness C and thicker than the first thickness B.

The second feeding speed V2 is a speed set so as to give priority to mirror-finishing the rough back surface of the wafer W without damaging the back surface of the wafer W by the cup-shaped grindstone 64 . Therefore, the second feeding speed V2 is set lower than the first feeding speed V1 to reduce the grinding amount per unit time. Therefore, in the first fine grinding step (S40, S50), the back surface of the wafer W is ground to a mirror surface.

Then, as shown in FIG. 8(E), in the second fine grinding step (S60, S70), the feeding speed of the cup-shaped grindstone 64 is controlled to a third feeding speed V3 lower than the second feeding speed V2. The wafer W is precisely ground until the wafer W reaches the first thickness B.

The third feeding speed V3 is, of course, a speed at which the back surface of the wafer W is not damaged by the cup-shaped grindstone 64. This speed is set so as to give priority to immediately stopping the downward movement of the cup-shaped grindstone 64 by the loading device 68 . In other words, the speed is set to prevent excessive grinding of the back surface caused by a slight difference between the time required for grinding to the first thickness B and the stop time of the downward movement of the cup-shaped grindstone 64 .

Therefore, the wafer W in the second fine grinding step is gradually increased from the third thickness D to the first thickness B over time by the cup-shaped grindstone 64 whose feeding speed is controlled to the third feeding speed V3. being ground. Then, when the NCIG 70 detects the first thickness B, the controller 26 immediately stops the downward movement of the cup-shaped grindstone 64 by the feeding device 68 . As a result, an excessive amount of back grinding can be prevented.

That is, by setting the first thickness B to the depth d of the cutting groove 2, the sludge generated by the grinding process enters the gap between the adjacent chips T, and the sludge adheres to the side surfaces of the chips T. can be reduced. Moreover, since the displacement of the chips T immediately after being diced can be suppressed, damage to the chips T due to contact between the chips T can be prevented.

<<Spark Out Step (S80)>>
After the fine grinding process is performed, feeding of the cup-shaped grindstone 64 is stopped, and the cup-shaped grindstone 64 performs spark-out for S1 time.

A spark-out step (S80) can remove an uncut portion of the back surface of the wafer W that has reached the first thickness B in the second fine grinding step (S60, S70). Thereby, the quality of the back surface, which is the finished surface of the wafer W, is improved.

As described above, according to the wafer grinding method of the embodiment, when grinding the back surface of the wafer W to thin it to a predetermined thickness (finished thickness, first thickness B, target thickness of chip T), In addition to changing the type of grinding (rough grinding, fine grinding) according to the thickness of the wafer W, the means for measuring the thickness of the wafer W is also changed. Specifically, in the rough grinding process, the contact thickness measuring means IPG 54 is used, while in the fine grinding process, the non-contact thickness measuring means NCIG 70 is used.

As a result, in the rough grinding process, the approximate thickness of the wafer W (that is, the protective tape The back surface of the wafer W can be efficiently ground at a relatively high grinding speed while measuring the thickness of the wafer W including the thickness error of . In the fine grinding process, the surface roughness of the back surface of the wafer W is smaller than that in the rough grinding process. It can be measured well, and it becomes possible to manage the finished thickness of the wafer W and the thickness of the residual film in the groove.

Thus, according to the wafer grinding method of the embodiment, the thickness of the wafer W can be ground to the finished thickness while detecting the thickness of the wafer W only.

The groove residual film thickness mentioned above is the thickness from the back surface of the wafer W to the groove 2, and this groove residual film thickness can also be measured with high precision by the non-contact thickness measuring means (NCIG70). By obtaining the groove remaining film thickness, the controller 26 can control the feed speed of the cup-shaped grindstone 64 of the fine grinding section 24 to a lower speed to grind the back surface until the groove 2 is reached.

By the way, as a comparative form, when the thickness of the wafer W is measured by the thickness measuring means of the same method regardless of the type of grinding, the following problems arise. That is, when the contact thickness measuring means (NCIG70) is used not only in the rough grinding process but also in the fine grinding process, the contactor (contactor 58) of the contact thickness measuring means is used to measure the back surface of the wafer W, that is, , the back surface of the chip T is damaged. In addition, since the contact-type thickness measuring means measures the thickness of the wafer W including the thickness of the protective tape with uneven thickness, the thickness of the wafer W alone cannot be measured. It becomes difficult to properly manage the thickness and the residual film thickness of the groove.

On the other hand, when the non-contact thickness measuring means is used not only in the fine grinding process but also in the rough grinding process, the wafer W is greatly affected by the surface roughness of the back surface of the wafer W in the rough grinding process. It may not be possible to measure the thickness of As a result, the grinding amount in the rough grinding process may not be confirmed.

On the other hand, in the wafer grinding method of the embodiment, as described above, while the thickness of the wafer W is measured by the contact thickness measuring means, the thickness of the wafer W reaches the predetermined thickness (second thickness C). After roughly grinding the back surface of the wafer W while measuring the thickness of the wafer W until the thickness is Since the back surface of the wafer W is precisely ground until it reaches the thickness B) of 1, it is possible to solve the problems in the comparative embodiment described above.

Further, in the wafer grinding method of the embodiment, when the back surface of the wafer W is ground to thin it to the finished thickness (first thickness B), the cup-shaped grindstones 48 and 64 are fed according to the thickness of the wafer W. slows down the loading speed step by step. That is, in the rough grinding process, rough grinding is performed from the initial thickness A to the second thickness C at the first feeding speed V1, and in the fine grinding process, from the second thickness C to the first thickness B, the Precise grinding is performed at a feeding speed (second feeding speed V2, third feeding speed V3) lower than the first feeding speed V1. Further, in the fine grinding process, the feeding speed is divided into two stages, and from the second thickness C to the third thickness D, the second feeding speed V2, which is lower than the first feeding speed V1, is precisely used. Grinding is performed, and from the third thickness D to the first thickness B, fine grinding is performed at a third feeding speed V3 lower than the second feeding speed V2. In other words, in the wafer grinding method of the embodiment, the feeding speed is gradually decreased in three steps during grinding.

In addition, in the embodiment, as an example, a form in which the feeding speed is gradually decreased in three steps is shown, but the present invention is not limited to this, and the feeding speed may be changed in four or more steps, for example. Alternatively, the feeding speed may be continuously reduced in proportion to the thickness of the wafer W.

In this manner, by slowing down the feed speed stepwise or continuously according to the thickness of the wafer W, rough grinding is performed in which the feed speed (grinding speed) is prioritized over the measurement accuracy of the thickness of the wafer W. In the process, the wafer W having a large thickness and a large rear surface roughness can be roughly ground to the second thickness C in a short time and efficiently. Further, in the fine grinding step in which the thickness measurement accuracy of the wafer W is prioritized over the feeding speed, the wafer W having a small thickness and a small rear surface roughness can be finely ground to the finished thickness.

As a result, the wafer grinding method of the embodiment can grind the thickness of the wafer W to the finished thickness while detecting only the thickness of the wafer W, and while increasing the throughput, the finished thickness of the wafer W and the It is possible to properly manage the remaining film thickness of the groove.

Further, rough grinding conditions in the rough grinding process are set so that the machining time of the rough grinding process (S10 to S20) and the machining time of the fine grinding process (S40 to S70) including the spark-out process (S80) are substantially equal. (that is, the amount of rough grinding, feeding speed, number of revolutions, etc. of the cup-shaped grindstone 48) and fine grinding conditions in the fine grinding step (that is, the amount of fine grinding, feeding speed, number of revolutions, etc. of the cup-shaped grindstone 64) is preferably set.

That is, in the graph of FIG. 7, the machining time of the fine grinding steps (S40-S70) including the spark-out step (S80) is about three times as long as the machining time of the rough grinding steps (S10-S20). By equalizing these processing times, it is possible to eliminate the waiting time of the wafer W that has finished the grinding process. Therefore, since the grinding time can be further shortened, the throughput can be further increased.

For example, the wafer W is roughly ground from the initial thickness A to the third thickness D in the rough grinding process, and then fine ground from the third thickness D to the first thickness B in the fine grinding process. As a result, the rough grinding time is slightly longer than the grinding time shown in FIG. 7, but the fine grinding process time is greatly shortened. In addition, the feeding speed for fine grinding from the third thickness D to the first thickness B may be divided into two stages (second feeding speed V2, third feeding speed V3), and may be performed continuously. You can make it slow down.

The wafer grinding method described above is a grinding method using the wafer grinding apparatus 10 in which one rough grinding unit 22 and one fine grinding unit 24 are installed. However, when a plurality of fine grinding units 24 are installed, The wafers W, which have been roughly ground in the rough grinding section 22, may be sequentially transferred to the empty fine grinding section 24 for fine grinding. In this case, it is preferable to shorten the rough grinding time of the rough grinding section 22 and lengthen the fine grinding time of the fine grinding section 24 by the number of fine grinding sections 24 .

DESCRIPTION OF SYMBOLS W... Wafer 10... Wafer grinding apparatus 12... Main body 14... Cassette storage part 16... Wafer transfer apparatus 18... Alignment part 20... Index table 22... Rough grinding part 24... Fine grinding part 26... Controller 28 Input device 30, 32 Cassette 34 Adsorption unit 36, 38, 40, 42 Table 44 Rotary shaft 46 Motor 48 Cup-shaped grinding wheel 50 Motor 52 Feed Loading device 54 IPG 56 Motor supporting portion 58, 60 Contactor 62 Computing portion 64 Cup-type grinding wheel 66 Motor 68 Feeding device 70 NCIG 72 Motor supporting portion , 76 ... Wave transmitting section, 78 ... Wave receiving section, 80 ... Operation section

Claims (2)

A wafer grinding method for thinning the wafer to a first thickness, which is a finished thickness, by grinding the back surface of the wafer in which grooves shallower than the thickness of the wafer are formed along the dicing line on the surface of the wafer, ,
a rough grinding step of rough grinding the back surface of the wafer by rough grinding means until the thickness of the wafer reaches a second thickness that is thicker than the first thickness;
After the rough grinding step is performed, fine grinding is performed on the back surface of the wafer while the feed speed of the fine grinding means is reduced stepwise or continuously, and the feed speed of the fine grinding means is set to the first thickness. a fine grinding step in which priority is given to immediately stopping the fine grinding means immediately after grinding the back surface of the wafer until the wafer is flat;
A wafer grinding method comprising: A wafer grinding apparatus for thinning the wafer to a first thickness, which is a finished thickness, by grinding the back surface of the wafer in which grooves shallower than the thickness of the wafer are formed along the dicing line on the front surface of the wafer, ,
rough grinding means for rough grinding the back surface of the wafer;
fine grinding means for finely grinding the back surface of the wafer;
Control means for rough-grinding the back surface of the wafer by the rough-grinding means until the thickness of the wafer reaches a second thickness that is thicker than the first thickness, wherein the fine-grinding is performed after the rough-grinding is performed. The back surface of the wafer is finely ground while the feed speed of the means is gradually or continuously reduced, and the feed speed of the fine grinding means is changed to the first thickness immediately after grinding the back surface of the wafer. , a control means for giving priority to immediately stopping the fine grinding means;
A wafer grinding device comprising:

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