JP2577288B2 - Cutting method by groove alignment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a semiconductor wafer having a predetermined circuit pattern on its surface into chips by using a dicing apparatus.

[0002]

2. Description of the Related Art In general, a predetermined circuit pattern is provided on the surface of a semiconductor wafer, and the circuit pattern is defined by grid-like straight lines called streets, and cut along the streets by a rotating blade of a dicing apparatus. By doing so, a chip is formed from a semiconductor wafer. When a semiconductor wafer is cut by a dicing apparatus in this manner, it is necessary to precisely position a rotating blade on the street, and this positioning method is disclosed in, for example, JP-A-60-244803. In addition, a circuit matching method is used in which a circuit pattern is imaged by optical means and the image is processed by the image processing.

[0003]

However, depending on the type of diode or the like, a half cut (first cutting step) is first performed on a predetermined portion without cutting the semiconductor wafer into chips, and then etching and a predetermined test are performed. And the like (non-groove forming step), there is an irregular cutting method in which the half-cut portion is completely cut (second cutting step) and separated into chips. At this time, if the alignment is performed by the pattern matching method in the second cutting step, the first cutting step and the non-groove forming step cause the pattern matching due to a change in the wafer surface due to adhesion of contamination, etching, and the like. May not be performed smoothly,
Therefore, the second groove to be full-cut may deviate from the position of the first half-cut first groove, and may not be able to cut the center of the first groove. In addition, when the dicing device that forms the first groove is different from the dicing device that forms the second groove, the same problem occurs due to the peculiarity of the dicing device. Further, in the etching process,
If the first groove is unevenly etched, the rotating blade forming the second groove cannot be positioned at the center of the groove.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem. When a chip is cut from a semiconductor wafer in two steps of a first cutting step and a subsequent second cutting step, An object of the present invention is to provide a cutting method based on groove alignment, which can prevent displacement from the first groove in the second cutting step.

[0005]

As a means for technically solving this problem, the present invention provides a first cutting step for forming a first groove in a semiconductor wafer such as a diode;
In a cutting method comprising: a non-groove forming step of performing etching or the like after the first cutting step; and a second cutting step of forming a second groove by overlapping the first groove after the non-groove forming step. In forming the second groove, the gist is that alignment is performed with reference to the already formed first groove.

[0006]

[Operation] If the first and second cutting steps are aligned by the pattern matching method, the above-described problem occurs. Therefore, the second cutting step is not based on the pattern matching, but is performed by the first first cutting step. Since the method is an alignment method based on the formed first groove, the rotating blade can be accurately positioned at the center of the first groove, and the displacement from the first groove is completely prevented. can do.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
(A) is a first alignment step, in which a semiconductor wafer 2 which is an object to be ground is mounted and fixed on a wafer holding table 1 which is rotatable about its axis, and image recognition means 3 such as a CCD camera is used.
Then, a predetermined circuit pattern of the semiconductor wafer 2 is imaged,
The image processing is compared with a pattern stored in a CPU (not shown) in advance to enable precise alignment by pattern matching.

FIG. 1B shows a first cutting step for forming a first groove, which is performed after the first alignment step.
This is shown in FIG.
As shown in (1), a first groove 5 is formed along the street of the semiconductor wafer 2 by half cutting. The semiconductor wafer 2 is then subjected to processing such as etching in a non-groove forming step, and is returned to the holding table 1 again.

FIG. 1D shows a second alignment step, which is performed via the image recognizing means 3. In this case, the image recognition is performed not by a circuit pattern as described later in detail but by a first pattern. This is performed based on the first groove 5 already formed by the cutting step (b).

FIG. 1E shows a second cutting step for forming a second groove, which is performed after the completion of the second alignment step. The second cutting step is performed by a rotating blade 4 of a dicing apparatus. The second groove 6 is formed by full cutting so as to overlap the first groove 5. The semiconductor wafer 2 is completely cut by the second cutting step, and is divided into chips 7 as shown in FIG.

The second alignment step (d) will be described in more detail. At this stage, the semiconductor wafer 2 is mounted on the frame 10 via the holding tape 8 as shown in FIG. Is mounted and fixed. In the semiconductor wafer 2, first grooves 5 formed by a first cutting step are formed along streets in the x-axis direction and the y-axis direction, and a square portion surrounded by these streets is a chip 7 such as an IC. It has become. The holding tape 8 holds the chips divided in the second cutting step so as not to be scattered.

In this case, since the first groove 5 looks black and the other areas look white, it is convenient to perform image processing by the image recognition means 3 such as a CCD camera. FIG. 3 (a) shows that the first groove is already formed in the street separating the chips 7 such as ICs by the first cutting step, and the wafer is held after the semiconductor wafer 2 has gone through a non-cutting step such as etching. FIG. 3 shows a state where the image pickup device is placed on the table 1 and a part of the surface is imaged by the image recognition means 3.

The alignment reference line S shown in FIG. 1 coincides with the cutting center line of the rotary blade on which a groove is to be formed, and therefore the first groove 5 (x) already formed.
In order to form the second groove 6 so as to overlap the axial groove 5x and the y-axis groove 5y), the first groove 5 must be aligned with the alignment reference line S.
Need to be matched.

If the explanation is further continued with reference to FIG.
Assuming that the alignment reference line S and the groove 5x in the x-axis direction are in an inconsistent state at an angle of α, this angle α is determined as disclosed in JP-A-60-54454.
For example, the continuity in the x and y coordinates (eg, 10 pixels in the positive direction of the x-axis and in the positive direction of the y-axis) of the cutting area (the area recognized as black by the pixel) recognized by the CCD camera composed of 256 × 256 pixels (Like one pixel)
Is detected by If the wafer holding table 1 is rotated clockwise by the angle α based on the detected angle α, the alignment reference line S and the groove 5x in the x-axis direction become parallel.

Further, the center position of the groove 5x in the x-axis direction is x,
The wafer holding table 1 is relatively moved so as to match the alignment reference line S based on the y coordinate. By doing so, the groove 5x in the x-axis direction is aligned with the alignment reference line S as shown in FIG.

Next, the wafer holding table 1 is rotated by a required angle, that is, 90 °, and as shown in FIGS. 3 (c) and 3 (d), y
The axial groove 5y and the alignment reference line S are aligned in the same manner as described above.

The groove 5x in the x-axis direction and the groove 5y in the y-axis direction
Is stored in the CPU of the dicing apparatus, and a second cutting step for forming a second groove is performed based on the stored result. That is, as shown in FIG. This is performed by full-cutting from above, overlapping the groove 5. The rotating blade 4 at the time of this second cutting step is
The same as the rotating blade at the time of the cutting step or a slightly thinner blade is used.

As described above, when the alignment is performed based on the half-cut first grooves formed earlier on the semiconductor wafer, alignment errors can be prevented beforehand. That is, since a non-groove forming step such as etching is included between the first cutting step performed first and the second cutting step performed last, the appearance of the chip including the circuit pattern partially changes in the middle. In the case where the dicing device for forming the first groove is different from the dicing device for forming the second groove, or when the first groove is etched unevenly, a second cutting step to be performed later If the pattern matching is performed based on the circuit pattern at the time of the alignment, there may be a mistake that the rotating blade forming the second groove cannot be positioned at the center of the first groove, and the alignment is performed based on the first groove. If you do
Such mistakes can be prevented beforehand.

[0019]

As described above, according to the present invention,
In a cutting method in which a semiconductor wafer is diced, a first groove is formed by half-cutting first, and a non-groove forming step such as etching is performed, and then a second groove is formed by full-cutting to divide each chip. In forming the second groove, the alignment is performed with reference to the already formed first groove, so that the alignment can be performed accurately, and the second groove is cut from the first groove in the second cutting step. It has excellent effects such as preventing displacement.

[Brief description of the drawings]

FIGS. 1A to 1F are explanatory views showing an embodiment of cutting by the method of the present invention in the order of steps.

FIG. 2 is a top view when a second alignment step is performed.

FIGS. 3A to 3D are explanatory views sequentially showing a procedure for performing the second alignment step. FIGS.

FIG. 4 is a schematic sectional view showing a state where a second groove is formed by a second cutting step.

[Explanation of symbols]

1: wafer holding table 2: semiconductor wafer
DESCRIPTION OF SYMBOLS 3 ... Image recognition means 4 ... Rotating blade 5 ... 1st groove 5x ... groove | channel of x-axis direction 5y ... groove | channel of y-axis direction 6 ... 2nd groove | channel 7 ...
Chip 8: Holding tape 10: Frame S: Alignment reference line

Claims (1)

(57) [Claims] A first cutting step of forming a first groove in a semiconductor wafer such as a diode; a non-groove forming step of performing etching or the like after the first cutting step; In a cutting method comprising a second cutting step of forming a second groove by overlapping the first groove,
Wherein the alignment is performed with reference to the already formed first groove when forming the groove.