JP5686545B2

JP5686545B2 - Cutting method

Info

Publication number: JP5686545B2
Application number: JP2010167332A
Authority: JP
Inventors: 翔平佐々木; 靖博三浦; 金子　武司; 武司金子
Original assignee: 株式会社ディスコ
Priority date: 2010-07-26
Filing date: 2010-07-26
Publication date: 2015-03-18
Anticipated expiration: 2030-07-26
Also published as: JP2012028635A; CN102347276A; CN102347276B

Description

The present invention relates to a cutting method for cutting a workpiece such as a wafer with a cutting blade along a line to be divided.

For example, in the manufacturing process of a semiconductor device or an optical device, devices are formed in each region partitioned by a plurality of scheduled division lines formed in a lattice shape on the surface of a wafer such as sapphire or silicon.

These devices and division lines are also called circuit patterns and are formed by repeating photolithography. Semiconductor wafers and optical device wafers on which circuit patterns have been formed are ground on the back and thinned to a predetermined thickness, and then the division lines are cut by a cutting machine to produce individual semiconductor devices and optical devices. The

The cutting apparatus includes a cutting blade for cutting a workpiece as disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-64828. Cutting is performed by cutting the workpiece into the workpiece while rotating the cutting blade at a high speed of, for example, 30000 rpm.

Specifically, the cutting blade that is rotated at a high speed is positioned on the planned dividing line, and the cutting planned line is cut by relatively feeding the cutting blade and the workpiece. Then, by indexing and feeding the cutting blade with a predetermined index amount, the cutting blade is positioned on the next division line and the next division line is cut.

JP 2009-64828 A

However, due to variations in the accuracy of the circuit pattern formed on the workpiece, when the cutting blade is indexed and fed with a single index amount, the cutting position gradually shifts, cutting the device outside the planned division line and cutting the device. There is a problem of causing damage.

When the workpiece is a wafer such as a semiconductor wafer or an optical device wafer, the pattern accuracy formed by reduced projection exposure is relatively poor in the outer peripheral area compared to the central area. To get bigger.

The present invention has been made in view of these points, and an object of the present invention is to provide a cutting method that does not damage the device by cutting outside the division line of the workpiece. It is.

According to the present invention, there is provided a cutting method of cutting a wafer having a plurality of division lines formed on the surface thereof with a cutting blade along the division lines, registering a predetermined area on the wafer as a key pattern, A pre-registration step of registering the distance from the key pattern to the nearest division planned line as a first distance and registering the distance between the division planned lines as an index amount , and relatively cutting and feeding the cutting blade and the wafer. the divided cutting a single planned line along the wafer and the cutting blade by relatively machining feed the said cutting blade and the wafer from the feed the index amount indexing to the plurality of division lines by A cutting step for cutting and detecting a cutting groove formed by cutting at a predetermined timing during the cutting step; A detecting step of detecting a nearest key pattern from the cutting groove and detecting a distance of the key pattern to the cutting groove as a second distance; and the registered first distance and the detected second distance. A correction index amount calculating step for calculating a correction index amount obtained by correcting the index amount so as to cancel the deviation amount; A correction cutting step for cutting a predetermined line, and after performing the correction cutting step, the cutting step is performed again , and in the outer peripheral region of the wafer compared to the central region of the wafer, the detection step, cutting method is provided, which comprises many correction index value calculation step, the frequency of performing the correction cutting step

According to the present invention, the cutting position is corrected by detecting the deviation amount of the cutting position at a predetermined timing during the cutting with the cutting blade and correcting the index amount to be indexed. Therefore, it is possible to prevent the device from being damaged by cutting outside the planned division line.

In a general wafer, the pattern accuracy in the outer peripheral region is relatively poor as compared with the central region. Therefore, by making the correction frequency in the outer peripheral area more frequent than in the wafer central area, cutting without excessive cutting time is possible without cutting the outside of the planned division line and damaging the device. It becomes.

It is a perspective view of a cutting device suitable for implementing the cutting method of the present invention. It is a surface side perspective view of the wafer supported by the annular frame via the dicing tape. It is a flowchart which shows the cutting method of this invention. It is a flowchart which shows the cutting method of this invention. It is a partial enlarged view of the wafer surface. It is explanatory drawing which shows a prior registration step. It is explanatory drawing which shows a cutting step. It is explanatory drawing which shows a detection step and a correction index amount calculation step. It is explanatory drawing which shows a preferable cutting method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an external view of a cutting device (dicing device) 2 that can divide a wafer into individual chips (devices).

On the front side of the cutting device 2, there is provided operating means 4 for an operator to input instructions to the device such as machining conditions. In the upper part of the apparatus, there is provided a display means 6 such as a CRT for displaying a guidance screen for an operator and an image taken by an imaging means described later.

As shown in FIG. 2, a plurality of planned dividing lines (streets) 13 are formed in a lattice shape on the surface of a wafer 11 to be cut, which is a kind of workpiece, and the planned division is formed in a lattice shape. A device 15 is formed in each region partitioned by the line 13.

The circuit pattern including the division lines 13 and the device 15 is formed by photolithography including reduced projection exposure, but the pattern accuracy of the outer peripheral region 21 is inferior to that of the central region 17.

The wafer 11 is attached to a dicing tape T that is an adhesive tape, and the outer peripheral edge of the dicing tape T is attached to an annular frame F. As a result, the wafer 11 is supported by the frame F via the dicing tape T, and a plurality of wafers (for example, 25 sheets) are accommodated in the wafer cassette 8 shown in FIG. The wafer cassette 8 is placed on a cassette elevator 9 that can move up and down.

Behind the wafer cassette 8, a loading / unloading means 10 for unloading the wafer W before cutting from the wafer cassette 8 and loading the wafer after cutting into the wafer cassette 8 is disposed. Between the wafer cassette 8 and the loading / unloading means 10, a temporary placement area 12, which is an area on which a wafer to be carried in / out, is temporarily placed, is provided. Positioning means 14 for positioning at a certain position is provided.

In the vicinity of the temporary placement area 12, transport means 16 having a turning arm that sucks and transports the frame F integrated with the wafer W is disposed, and the wafer W carried to the temporary placement area 12 is Adsorbed by the conveying means 16 and conveyed onto the chuck table 18 and sucked by the chuck table 18, and held on the chuck table 18 by fixing the frame F by a plurality of fixing means (clamps) 19. .

The chuck table 18 is configured to be rotatable and reciprocally movable in the X-axis direction. Above the movement path of the chuck table 18 in the X-axis direction, alignment means (detection) for detecting the street of the wafer W to be cut. Means) 20 is provided.

The alignment unit 20 includes an imaging unit (imaging camera) 22 that images the surface of the wafer W, and can detect a street to be cut by processing such as pattern matching based on an image acquired by imaging. The image acquired by the imaging unit 22 is displayed on the display unit 6.

On the left side of the alignment means 20, a cutting means 24 for cutting the wafer W held on the chuck table 18 is disposed. The cutting means 24 is configured integrally with the alignment means 20, and both move together in the Y-axis direction and the Z-axis direction.

The cutting means 24 is configured by attaching a cutting blade 28 to the tip of a rotatable spindle 26 and is movable in the Y-axis direction and the Z-axis direction. The cutting blade 28 is located on the extended line of the imaging means 22 in the X-axis direction.

Next, with reference to FIG. 3 thru | or FIG. 9, the cutting method which concerns on this invention embodiment is demonstrated in detail. Referring to FIG. 3, a flowchart of the cutting method of the present invention is shown. In the cutting method of the present invention, as a preparation process for alignment, first, as shown in step S10, a predetermined area on the workpiece is imaged by the imaging camera 22, a key pattern is determined, and this key pattern is determined by the cutting apparatus 2 Register in the controller memory.

That is, as shown in FIG. 5, the operator of the cutting device 2 operates the operation means 4 to pick up an image of the wafer 11 with the image pickup camera 22 and slowly move the image displayed on the display means 6. A key pattern 30 that is a pattern matching target is searched. The key pattern 30 uses, for example, a characteristic part of a circuit in the device 15. One key pattern 30 is included in each device 15.

Next, in step S11, as shown in FIG. 6, the distance from the key pattern 30 to the center 13a of the nearest division planned line 13 is registered in the controller memory as the first distance S1. In step S12, the distance between the lines to be divided is registered in the controller memory as the index amount Y1. Steps S10 to S12 constitute a pre-registration step.

When the pre-registration step is completed, as shown in FIG. 2, the wafer 11 supported by the annular frame F is inserted into the wafer cassette 8 via the dicing tape T and is conveyed by the loading / unloading means 10 and the conveying means 16. It is sucked and held by the chuck table 18 of the cutting device 2 (step S13).

Next, in step S14, two points on the wafer 11 are imaged by the imaging camera 22, and the key pattern 30 at the two points is detected by pattern matching with the key pattern 30 registered in advance.

Next, the process proceeds to step S15, and the chuck table 18 is rotated by θ so that the detected straight line connecting the two key patterns 30 is parallel to the X-axis direction, so that the division line 13 and the cutting blade 28 are parallel. And the θ rotation amount of the chuck table 18 is registered in the memory of the controller. Next, the chuck table 18 is rotated forward by 90 degrees, and Steps S14 and S15 are repeated.

Then, the machining start position is detected from the detected key pattern 30 and the position of the imaging camera 22, the wafer size registered in advance, and the first distance S1, and the machining start position of the division line 13 to be cut by the cutting blade 28 is determined. Position at the center 13a (step S16). Steps S14 to S15 constitute an alignment process.

When the alignment process is completed, the process proceeds to step S17, and the division line 13 is cut by relatively moving the wafer 11 and the cutting blade 28 rotating at high speed in the processing feed direction (X-axis direction).

That is, the cutting blade 28 rotating at a high speed of 30000 rpm or the like is cut into the wafer 11 and the division line 13 is cut by feeding the chuck table 18 at a predetermined speed in the X-axis direction, as shown in FIG. Thus, the cutting groove 32 is formed.

When the cutting of one division line 13 is completed, the process proceeds to step S18, and the cutting blade 28 is indexed (indexed feeding) in the Y-axis direction by the registered index amount Y1.

When the index feed is finished, the wafer 11 and the cutting blade 28 rotating at high speed are relatively moved in the machining feed direction to cut the next division line 13 (step S19). Steps S17 to S19 are repeated a plurality of times.

Next, the process proceeds to step S20, the wafer 11 is imaged by the imaging camera 22 having a microscope, and the cutting groove 32 and the nearest key pattern 30 are detected as shown in FIG. A distance (second distance) S2 to the center 32a is detected.

Then, a difference between the first distance S1 and the second distance S2 is calculated as a deviation amount D, and a corrected index amount Y2 is calculated by correcting the index amount so as to cancel the deviation amount D (step S21).

For example, assuming that the index feed direction (upward direction in FIG. 8) is the + direction in FIG. 8, the registered first distance S1 is 150 μm, and the detected second distance S2 is 140 μm, the deviation amount D is +10 μm. Therefore, if the index amount Y1 is 5.00 mm, the corrected index amount Y2 is 4.99 mm.

When the correction index amount Y2 is calculated in this way, the process proceeds to step S22, where the cutting blade 28 is indexed and fed in the Y-axis direction by the correction index amount Y2, and the center of the scheduled division line 13 to cut the cutting blade 28 is obtained. 13a. Then, the division line 13 is cut by relatively moving the wafer 11 and the cutting blade 28 rotating at a high speed in the machining feed direction (X-axis direction) (step S23).

Next, by repeating Step S18 to Step S23 a plurality of times, all of the planned division lines 13 extending in the first direction are cut. Next, the chuck table 18 is reversely rotated by 90 degrees, and the division line 13 and the cutting blade 28 are positioned in parallel based on the rotation amount θ registered in the memory of the controller in the previous step S15, and then the steps S16 to S23 are performed. By repeating the above, the dividing line 13 extending in the direction orthogonal to the first direction is cut.

As described above, the pattern accuracy of the wafer 11 is somewhat deteriorated in the outer peripheral region 21 as compared with the central region 17. Therefore, as shown in FIG. 9A, the wafer 11 is divided into three blocks (1) to (3), and step S20 is performed every time three lines are cut in the outer peripheral region 21 of (1) and (3). The correction process of Step S23 is entered, and the correction process is performed every 20 lines are cut in the central region 17 of (2).

The same applies when cutting the division line 13 extending in the second direction shown in FIG. 9B. When cutting the outer peripheral area of (1) and (3), every time three lines are cut. When the center region 17 in (2) is cut, the correction step is controlled every 20 lines.

By controlling in this way, even when the pattern accuracy is relatively poor, the correction frequency is reduced when cutting the central region 17 and the correction frequency is increased only when the outer peripheral region 19 is cut. Long processing time can be prevented.

2 Cutting machine 11 Wafer 13 Scheduled line (street)
15 Device 17 Central area 18 Chuck table 20 Alignment means 21 Outer peripheral area 22 Imaging camera 24 Cutting means 28 Cutting blade 30 Key pattern S1 First distance S2 Second distance Y1 Index amount Y2 Correction index amount

Claims

A cutting method of cutting a wafer having a plurality of division lines formed on the surface with a cutting blade along the division lines,
A pre-registration step of registering a predetermined area on the wafer as a key pattern, registering the distance from the key pattern to the nearest planned division line as a first distance, and registering the distance between the planned division lines as an index amount; ,
The cutting blade and the wafer are relatively processed and fed to cut one of the division lines, the cutting blade is indexed and fed, and then the cutting blade and the wafer are relatively fed. A cutting step for cutting the wafer along the plurality of division lines,
During the cutting step, a cutting groove formed by cutting at a predetermined timing is detected, the nearest key pattern is detected from the cutting groove, and the distance from the key pattern to the cutting groove is set as a second distance. A detection step to detect;
A corrected index amount calculating step of calculating a difference between the registered first distance and the detected second distance as a shift amount, and calculating a corrected index amount by correcting the index amount so as to cancel the shift amount; ,
A correction cutting step of indexing and feeding the cutting blade to cut the division planned line,
After performing the correction cutting step, perform the cutting step again ,
A cutting method characterized in that the detection step, the correction index amount calculation step, and the correction cutting step are performed more frequently in the outer peripheral region of the wafer than in the central region of the wafer .