JP2000176802A - Wafer grinding device and wafer grinding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding device capable of reducing the dispersion width of thickness of a finished-ground wafer group. SOLUTION: This wafer grinding device is provided with an index tables, wafer chuck mechanisms, m-piece of grinding wheels journalled to spindle-shafts rotatably provided at the same intervals as that of the chuck mechanisms above m-piece of the chuck mechanisms, a wafer thickness measuring device, a recording part for recording the number of the chuck mechanisms and the thicknesses of the wafers, an arithmetic operating mechanism which compares the grinding speeds of the respective grinding wheels for grinding the wafers installed in the respective chuck mechanisms and the final thicknesses Ti.n of the respective ground wafers to calculate the difference between the final thickness of the wafers and the minimum thickness T0: ΔTi.n=Ti.n-T0, and to calculate the wafer grinding speed Si.n of the respective grinding wheels, and a control mechanism which transmits the number (m) of the chucks and the prolonged time t (ΔTi.n/Si.n) of the grinding wheels to finishing grinding wheels to allow the grinding wheels to prolong the grinding time for the time (t) to perform finish- grinding. (wherein, (i) is the number of the chuck mechanisms, (j) is the number of the grinding wheels).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an apparatus for grinding a surface of a wafer such as a bare wafer, a magnetic head substrate, and a magnetic disk wafer, and a method for grinding a wafer using the apparatus.

[0002]

2. Description of the Related Art As a method of grinding a substrate wafer of a semiconductor wafer, for example, a plurality of (m) wafer chuck mechanisms provided on an index table are provided with wafer loading, unloading and m-stage grinding stages. Using the n-base grindstone supported on a plurality of spindle shafts provided above this index table and this,
Wafer grinding machines with reduced wafer grinding time are known. GNX200 (trade names: m = 3, n = 2) is available from Okamoto Machine Tool Works, Ltd., and DNX is available from Disco Corporation.
FG850 (product name: m = 3, n = 2) has been sold and put to practical use. Further, as the diameter of the wafer increases from 6 inches to 8 inches and 12 inches, m = 4
Grinding apparatuses with ６6 and n = 3〜4 are also in practical use.

FIG. 1 is a top view of a grinding apparatus showing one example. In the grinding apparatus 1 shown in FIG. 1, w is a wafer, 2 is a cassette, 3 is a wafer backside cleaning mechanism, 4 is a robot for loading a wafer, 5 is an index table, 6a, 6b, 6a, 6b.
6c is a chuck mechanism, 7 is a coarse grinding wheel supported on a spindle shaft 7a, 8 is a finish grinding wheel supported on a spindle shaft 8b, 9 is a chuck cleaner, 10 is an unloading robot, and 11 is a spinner. A cleaning mechanism, 12 a cassette, and 13 a thickness measuring device.

[0004] The process of grinding a wafer using the grinding apparatus is as follows. The wafer w stored in the cassette 2 is transferred to the robot 4
Is transferred to the cleaning mechanism 3 by means of the arm, and the back surface thereof is washed with water. Thereafter, the wafer is placed on the chucking mechanism 6a of the loading / unloading zone s1 of the index table 4, and the wafer is placed thereon. Vacuum is adsorbed.

[0005] The index table is rotated clockwise by 120 degrees, and the wafer w is transferred to the coarse grinding zone s2. Next, the chuck mechanism 6a in the zone s2 is rotated, and the rough grinding wheel 7 supported by the rotating spindle shaft descends, contacts and presses the wafer, rubs the wafer surface, and rubs the wafer. Rough grinding. At the same time, the loading / unloading zone from cassette 2 is the same as in the process.
A new wafer is carried into the chuck mechanism 6b of the second s1, and the wafer is vacuum-sucked. After rough grinding, the thickness of the wafer is measured and the spindle axis is raised to move it away from the wafer

The index table is rotated clockwise by 120 degrees, and the roughly ground wafer w is transferred to the finish grinding zone s3. Next, the chuck mechanism 6a in the zone s3 is rotated, and the finishing grinding wheel 8 supported by the rotating spindle shaft descends to contact the wafer.
The wafer is pressed, and the wafer surface is rubbed, and the wafer is finished and roughly ground.
At the same time, the wafer w transferred to the coarse grinding zone s2 rotates the chuck mechanism 6b in the zone s2, and at the same time, the coarse grinding wheel 7a supported by the rotating spindle shaft descends to hit the wafer. The wafer is contacted and pressed, and the wafer surface is rubbed to roughly grind the wafer. Simultaneously, a new wafer is loaded from the cassette 2 into the chuck mechanism 6c in the loading / unloading zone s1 from the cassette 2 and vacuum-adsorbed.

The index table is rotated clockwise by 120 degrees, and the finish-ground wafer w is transferred to a loading / unloading zone s1. This zone
In step s1, the robot 10 transfers the wafer to the spinner-cleaning mechanism 11 by spin cleaning, and after the cleaning, the thickness is measured by the thickness measuring devices 13, 13,..., And then stored in the cassette 12 by the robot 10.

When the chuck mechanism 6b rotates and the chuck mechanism 6b is rotated, the finishing grinding wheel 7b supported by the rotating spindle shaft is moved down by the coarse grinding wafer adsorbed on the chuck mechanism 6b coming to the finishing grinding zone s3. Then, the wafer is brought into contact with and pressed against the wafer, and the wafer surface is rubbed, so that the wafer is subjected to finish rough grinding. At the same time, the wafer w held by the chuck mechanism 6c transferred to the rough grinding zone s2 is moved by the chuck mechanism 6c in the zone s2 and the rough grinding wheel supported by the rotating spindle shaft. 7 descends, contacts and presses the wafer, rubs the wafer surface, and roughly grinds the wafer. Hereinafter, similarly, the finish grinding of the wafer is performed.
Loading, loading, rough grinding of wafer, finish grinding,
The cleaning of the wafer is performed continuously. The index table type grinding apparatus using the plurality of chuck mechanisms and the grinding wheels has an advantage that the grinding time can be reduced because a plurality of grindings are performed simultaneously.

[0009]

In the case of a conventional 6-inch wafer, the thickness variation of the finish-ground wafer is allowed to be about 2 to 5 μm. However, an integration degree of 264 MB or more is required, and the wafer diameter is 8 inches,
As the diameter is increased to 2 inches, the thickness variation of the finish-ground wafer is required to be 1 μm or less. An object of the present invention is to provide a wafer grinding method satisfying the requirement that the variation in the thickness of the finish-ground wafer is 0.5 μm or less, and a grinding apparatus used therefor.

[0010]

According to one aspect of the present invention, there is provided (A) an index table whose center is supported by a rotatable shaft, (B) revolvable on the index table, and M (where m is an integer of 3 to 6) wafer chuck mechanisms provided equidistantly about the axis and on the same circumference, (C) above the index table N (n is an integer of 2 to 5 and is smaller than m) which is rotatably supported on a rotatable spindle shaft provided at the same interval as the chuck mechanisms above the m chuck mechanisms. ) Whetstone (of which at least 1
One is a rough grinding wheel and one is a finishing wheel. ), (D)
Wafer thickness measuring device, (E) number of chuck mechanism holding wafer, and recording unit of thickness of ground wafer attached to chuck mechanism, (F) wafer attached to each chuck mechanism The grinding speed of each grindstone for grinding the wafer, and the final thickness (T
_{i, n} ), to calculate the thickness difference (ΔT _{i, n} = T _{i, n} -T ₀ ) from the wafer having the minimum thickness (T ₀ ), and to calculate the wafer grinding speed (S _{i, n} ) of each grindstone. An arithmetic mechanism for calculating
(G) A control mechanism for transmitting the number m of the chuck and the extended time t (ΔT _{i, n} / S _{i, n} ) of the chuck to the finishing whetstone and extending the grinding at the time t to perform finish grinding. Wafer grinding device (where i is the number of the chuck mechanism, j is
An integer indicating the number of the grinding wheel. ).

According to a second aspect of the present invention, the index table of the wafer grinding apparatus is divided into a wafer loading area, a wafer rough grinding area, a wafer finish grinding area, and a wafer unloading area. It is characterized by the following. A grinding apparatus according to a third aspect of the present invention is characterized in that the index table of the wafer grinding apparatus is divided into a wafer loading / wafer unloading area, a wafer rough grinding area, and a wafer finish grinding area. And

According to a fourth aspect of the present invention, the grinding apparatus is used.
In grinding the wafer, the wafer is first held
Attached to each chuck mechanism number
The final thickness (T_{i, n})
And a grinding wheel attached to a chuck mechanism that performs finish grinding
Grinding speed (S_{i, j})
And then the ground wafer of each chuck mechanism
Final thickness (T_{i, n}) And compare the minimum thickness (T₀Ue)
Thickness difference (ΔT_{i, n}= T_{i, n}-T₀Calculate and record
After that, the number m of the chuck and the grinding
Long time t (ΔT _{i, n}/ S_{i, n}) And at that time t
Finish grinding of wafer by extending grinding time of finishing wheel
Wafer grinding method (where i
Indicates the number of the chuck mechanism, and j indicates the number of the grinding wheel.
It is an integer. ).

[0013]

The cause of the variation in the thickness of the ground wafer is caused by the chuck mechanisms provided on the index table,
It is possible to read from the thickness data of the finish-ground wafer of each chuck that the origin of the grinding stone and the material of the spindle shaft supported by each spindle and the processing accuracy can be read from the thickness data of the finish-ground wafer. A chuck mechanism that provides a wafer with the minimum thickness, grinding to compensate for variations in thickness when combining chuck mechanisms and grinding wheels to give the thickness of the combination of finishing whetstones, and to correct each habit during finish grinding By extending the time, the variation in thickness can be reduced to 0.5 μm or less.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. Grinding apparatus: The grinding apparatus for carrying out the present invention has three sets of chuck mechanisms, two sets of grinding wheels, and a wafer transfer robot shown in FIG.
Grinding devices divided into a loading / unloading zone (s1), a rough grinding zone (s2), and a finish grinding zone (s3) may be used. Alternatively, as shown in FIG. The chuck mechanism has two sets of grinding wheels, and the index table has a loading zone (s1) and a coarse grinding zone (s).
2), finishing grinding zone (s3), unloading zone
(S4).

Further, it has four sets of chuck mechanisms and three sets of grinding wheels, and the index table has a loading / unloading zone, a rough grinding zone, and a medium finishing grinding zone.
, A finishing grinding zone. Furthermore, it has five sets of chuck mechanisms and three sets of grinding wheels, and the index table has loading and coarse grinding zones.
, A medium finishing grinding zone, a finishing grinding zone, and an unloading zone.
It has a set of chuck mechanisms and three sets of grinding wheels, and the index table has a loading / unloading zone,
The grinding device may be divided into a rough grinding zone, a medium finishing grinding zone, and a finishing grinding zone.

The grinding wheels are all the same grinding number (mesh)
May be used, but it is preferable that they are different.
The finishing becomes more precise as the number of the grinding number increases to 200 mesh, 325 mesh, 500 mesh, 600 mesh, 800 mesh, 1,000 mesh, 1,200 mesh, and 2,000 mesh. Therefore, for example, rough grinding is performed using a 200-mesh grindstone, medium finish grinding is performed using a 600-mesh grindstone, finish grinding is performed using a 2,000-mesh grindstone, or coarse grinding is performed using a 32-mesh grindstone.
Finish grinding is performed with a 5-mesh whetstone and a 2,000-mesh whetstone. Which grinding wheel to use is selected depending on the material of the wafer of the object, the amount of grinding, and the throughput time.

When the grinding is performed in three stages of rough grinding, medium finish grinding and finish grinding, the rough grinding is performed by setting the number of rotations of the holder holding the rough grinding wheel to 500 to 4000 rpm and holding the wafer. Rotation speed of the chuck is 50-300r
pm, and the medium finish grinding is performed by setting the number of rotations of the holder holding the medium finish grinding wheel to 500 to 4000 rpm and the number of rotations of the chuck holding the wafer to 30 to 300 rpm.
m, and the finish grinding is performed at a rotation speed of the holder holding the finish grinding wheel at 50 to 3500 rpm and a rotation speed of the chuck holding the wafer at 50 to 200 rpm.

The grinding is performed in two stages of rough grinding and finish grinding.
In this case, the rough grinding is performed at a rotation speed of the holder holding the rough grinding grindstone at 1000 to 4000 rpm, and the rotation speed of the chuck holding the wafer is set at 50 to 300 rpm. Holder holding a grinding stone
Is performed at a rotational speed of 1500 to 4000 rpm, and a rotational speed of a chuck holding the wafer is 50 to 200 rpm.
Preferably, the grindstone and the grinding time are set so that the work in each zone is completed at the same time.

Thickness adjustment: As shown in FIG.
B - before being loading and the stearyl - after being ground with di-, the thickness (T _{i, j)} with a thickness measuring device 13 is measured, the thickness together with the chuck number _{(m) (T i, j} ),
The grinding time (t _{i, j} ) is reported to the recording unit (ROM) of the control device. In the arithmetic mechanism, the difference (ΔT _{i, n} ) between the minimum thickness To of the finish-ground wafer and the thickness (T _{i, n} ) of the finish-ground wafer and the wafer grinding speed (S _i ) of the final finish grinding wheel _{, n} ), and based on the number of each chuck mechanism, also calculates the grinding extension time t of the final finishing grinding wheel, and notifies the controller of this grinding extension time,
The control device transmits to the grinding device so as to extend the grinding time of the finishing whetstone by the time t.

In the present invention, the variation in the thickness of the obtained ground wafer is eliminated by extending the grinding time of the finishing whetstone. Although it is possible to adjust the grinding time for coarse grinding wheels and medium finishing wheels, the grinding speed is the slowest (slow) because the program software is complicated.
The thickness of the finishing whetstone is eliminated to prevent excessive cutting.

The determination of the thin thickness (To) is sufficient after the finish grinding in each chuck mechanism of the grinding device is completed in one to three times. Due to the development of the processing accuracy of the grinding apparatus, if one chuck mechanism is used, the thickness variation of the finish-ground wafer is 0.2 μm or less. However, there is a variation of 2 to 5 μm in each chuck mechanism. Therefore, the present invention can sufficiently satisfy the market requirement that the thickness variation of each finish-ground wafer is 1 μm or less.

[0022]

Embodiment 1 A grinding machine GN of Okamoto Machine Tool Works, shown in FIG.
X200 (trade name), diameter 200mm, thickness about 7
A 00 μm silicon wafer was ground under the following conditions so as to have a thickness of about 500 μm (target of an allowable variation of 0.5 μm). The finish grinding was started one minute after the start of the rough grinding.

Rough grinding Grinding wheel grinding number 325 mesh Spindle rotation speed 3000 rpm Chuck rotation speed 150 rpm Grinding amount 180 μm Grinding speed target 60 μm / min Grinding time 3 minutes Finish grinding Grinding wheel grinding number 2000 mesh Spindle rotation speed 3600 rpm Chuck rotation speed 100 rpm Grinding amount 20μm Grinding speed target 12μm / min Grinding time 1 minute 40 seconds

As shown in Table 1, the minimum value of the final thickness of the finished ground wafer that has been ground while the index table has been rotated three times (three stages) is the chuck mechanism 1 (i = 1).
) Is 498.0 μm, so this is stored in the ROM as To, and the finish grinding extension time t _{i, 2} in the chuck mechanism 2 (i = 2) and the chuck mechanism 3 (i = 3) is calculated ( (The chuck mechanism 2 is 20 seconds, the chuck mechanism 3 is 10 seconds.) Thereafter, the chuck mechanisms 2 and 3 control the finish grinding for the time t _{i, 2} by extending the finish grinding, and reduce the wafer grinding to the indexing time. -Up to 30 revolutions of the bull. Table 1 shows the finish grinding time, the thickness of the finish ground wafer, and the finish grinding extension time (seconds) for each chuck mechanism (three).

[0025]

[Table 1]

[0026]

According to the wafer grinding method of the present invention, the variation between wafers obtained by finish grinding can be made 0.5 μm or less.

[Brief description of the drawings]

FIG. 1 is a top perspective view of a grinding device of the present invention.

FIG. 2 is a top view of a grinding device showing another embodiment.

FIG. 3 is a diagram showing a control mechanism for wafer grinding according to the present invention.

[Description of Signs] 1 Grinding device w Wafer 2,12 Cassette 3 Cleaning mechanism 4,10 Robot 5 Index table 6a, 6b, 6c Chuck mechanism 7 Coarse grinding wheel 7a Spindle shaft 8 Finishing wheel 8a Spindle shaft 11 Spin cleaning mechanism 13 Thickness measuring equipment

Claims (4)

[Claims] (A) an index table whose center is supported by a rotatable shaft; and (B) a revolvable shaft around the index table and equidistant about the shaft.
And (m) a number of wafer chuck mechanisms provided on the same circumference (where m is an integer of 3 to 6), and (C) above the index table and including the m number of chuck mechanisms. N (where n is an integer of 2 to 5 and a number smaller than m) whetstones supported on a rotatable spindle shaft provided at the same interval as the chuck mechanism above. At least one is a rough grinding wheel and one is a finishing wheel.), (D) Wafer thickness measuring device, (E)
The number of the chuck mechanism holding the wafer, the recording unit of the thickness of the ground wafer attached to the chuck mechanism, (F) the grinding speed of each grindstone for grinding the wafer attached to each chuck mechanism, And the final thickness (T _{i, n} ) of each polished wafer,
₀ ), and a calculation mechanism for calculating the thickness difference (ΔT _{i, j} = T _{i, j−} T ₀ ) from the wafer, and the wafer grinding speed (S _{i, j} ) of each grindstone, and (G) the finishing grindstone To chuck number m
And the extended grinding time t (ΔT _{i, n} / S _{i, n} )
A control mechanism for extending the grinding of the time t to finish grinding,
(Where i is an integer indicating the number of the chuck mechanism and j is an integer indicating the number of the grinding wheel). 2. The wafer grinding apparatus according to claim 1, wherein the index table is divided into a wafer loading area, a wafer rough grinding area, a wafer finish grinding area, and a wafer unloading area. apparatus. 3. The index table includes a wafer loading / wafer unloading area, a wafer rough grinding area,
2. The wafer grinding apparatus according to claim 1, wherein roles are assigned to a wafer finish grinding area. 4. A method for grinding a wafer by using the grinding apparatus according to claim 1, wherein first of the number of the chuck mechanism holding the wafer, the number of the ground wafer attached to the chuck mechanism is determined. The final thickness (T _{i, n} ) and the grinding speed (S _{i, j} ) attached to each chuck mechanism of the grindstone attached to the chuck mechanism that performs finish grinding are determined. compares the final thickness (T _{i, n),} the minimum thickness difference between the wafer thickness _{(T 0) (ΔT i,} j = T i, j- T 0) is calculated and recorded,
Then, the number m of the chuck and the extension time t (ΔT _{i, n} / S _{i, n} ) of the chuck are transmitted to the finishing grindstone, and the grinding time of the finishing grindstone is extended by the time t to finish grind the wafer. (Where i is an integer indicating the number of the chuck mechanism and j is an integer indicating the number of the grinding wheel).