JPH07106387A - Measurement of surface shape of cut wafer - Google Patents

Abstract

PURPOSE:To prevent a dull blade from causing reduction in the throughput, such as interruption of a cutting work. CONSTITUTION:A surface displacement measuring means 3 is provided in the middle of a transfer path that transfers a cut wafer 100 from directly under an ingot 200 to a wafer housing part 15 and the surface shape of the wafer is measured during the transfer. Thereby, a dull blade, which results in defective wafers, can be detected from the measured surface shape of the wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface shape measuring method for a cut wafer for measuring the surface shape of a wafer cut from a semiconductor ingot.

[0002]

2. Description of the Related Art A semiconductor wafer used for manufacturing a semiconductor device (hereinafter, simply referred to as a wafer) is cut from a semiconductor ingot manufactured as a single crystal body by a slicing machine, the cut wafer is lapped, and a mirror is further cut. Manufactured by polishing and polishing.

The flatness of the wafer cut by this slicing machine is achieved by finely adjusting the dressing state (polishing state) of the blade of the slicing machine and the tensioning method of the blade. If there is a problem with the adjustment of the blade at the time of this cutting, waviness and warpage will occur in the cut wafer, and the waviness and warpage etc. at the time of cutting that occurred once, the lapping afterwards, the polishing step Since it cannot be recovered even by the above, the flatness required for the product must be secured at the time of cutting.

Conventionally, in order to obtain good wafer flatness at the time of cutting with this slicing machine, Japanese Patent Laid-Open No. 861/1990 has been proposed.
Japanese Patent Laid-Open No. 43-43 discloses a method for measuring the shape of the end face of an ingot. According to this, measure the degree of warpage in the diameter of the ingot in the cutting direction of the ingot end face immediately after cutting the wafer and in the direction perpendicular to this, and adjust the blade appropriately to obtain the wafer flatness based on the result. It is said that.

[0005]

However, in order to measure the shape of the end surface of the ingot immediately after the wafer is cut, even if there is no blade dressing defect or adjustment error that causes defects such as waviness and warpage of the wafer,
The cutting operation itself has to be interrupted to measure the shape of the ingot cut surface, which makes it impossible to continuously cut the wafer from the ingot, resulting in a decrease in throughput.

Therefore, an object of the present invention is to provide a method for measuring the surface shape of a cut wafer that does not lead to a decrease in throughput such as interruption of cutting work.

[0007]

The present invention for solving the above-mentioned problems, in a slicing machine for cutting a wafer from a semiconductor ingot by a blade, the cut wafer is provided in the slicing machine directly below the ingot. In the transfer path that is transferred to the existing wafer storage unit, a surface displacement measuring unit that moves relative to the wafer being transferred is provided, and the wafer in the transfer direction of the wafer being transferred is provided by the surface displacement measuring unit. A method for measuring the surface shape of a cut wafer, which comprises measuring the displacement of the surface shape over the diameter.

Further, according to the present invention, when the surface displacement result of the wafer measured by the surface displacement measuring means exceeds a preset allowable displacement amount, the blade adjustment and the adjustment are performed based on the surface displacement measurement result. A method for measuring the surface shape of a cut wafer, which comprises determining the amount of grinding of a cut surface on the ingot side.

[0009]

The surface shape measuring method for a cut wafer according to the present invention having the above-described structure is capable of displacing the surface of the wafer during the transfer path for transferring the wafer cut by the blade of the slicing machine from immediately below the ingot to the wafer storage section. By providing the surface displacement measuring means for measuring, the wafer being transported is moved relative to the surface displacement measuring means by the wafer diameter in the cutting direction of the wafer and scanned. Thereby, the shape of the diameter of the wafer in the cutting direction is measured.

From the shape of the diameter in the cutting direction of the wafer, the cause of poor blade sharpness is found,
Adjustment of the blade, for example, the degree of tension of the blade and the dressing amount are determined, and the grinding amount of the ingot side cut surface at the time of the next cutting is determined.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a drawing showing the external appearance of a slicing machine for carrying out the present invention, and FIG. 2 is a drawing showing the main components required for cutting an ingot.

The main components required for cutting the ingot of this slicing machine are an inner peripheral blade 1 for cutting the ingot 200, a suction arm 2 for conveying the cut wafer 100, and a displacement sensor 3 for measuring the surface shape of the wafer. And the air nozzle 4. In FIG. 1, other components of this slicing machine are the main body frame 10, the cover 11, the ingot support 12, the vertical drive mechanism 13 for vertically driving the ingot 200, and the horizontal drive in the cutting direction. The mechanism 14, the position of the ingot 200, the wafer transfer rail portion 16, the wafer storage portion 15, and the like. Also, the suction arm 2
Are connected to the horizontal drive mechanism 14 on the rear surface of the apparatus and are interlocked with the horizontal movement of the ingot 200.

When cutting the ingot 200, the blade 1 which is held with a constant tension applied by the tension head 5 is rotated by the rotating shaft 51, and the ingot 200 is supplied to the blade 1 and water is supplied to the cut surface. While moving in the right direction in FIG. 2, it is cut. A slice base 210, which supports the ingot 200 and prevents cracks and chips of the wafer 100 at the cutting end point, is bonded to the ingot 200.

A wafer surface shape measuring operation to which the present invention is applied, which is carried out by this slicing machine, is shown in FIG.
3B, the wafer 100 cut from the ingot 200 is suction-supported by the suction arm, and as shown in FIG. 3B, the suction arm 2 that has suctioned the wafer 100 changes its direction to the wafer storage portion 15 direction and rises. Figure 3
As shown in FIG.
With the return to the cutting start position, the wafer is moved toward the wafer storage portion 15. At this time, the wafer transfer direction,
That is, the displacement sensor 3 measures the surface shape of the wafer in the direction coinciding with the cutting direction. Wafer 100 transferred
Are stored in a wafer cassette (not shown) in the wafer storage unit 15 by the transfer rail 16. When the wafer 100 is sucked by the suction arm 2, the distortion of the entire wafer is eliminated and only the surface shape is measured. Further, when the wafer 100 is transferred, the ingot 200 also returns to the cutting start position along with the transfer.

As described above, by measuring the surface shape of the wafer 100 by the displacement sensor 3 while the cut wafer 100 is being transferred to the wafer storage unit 15, the displacement sensor 3 scans the wafer 100 in the cutting direction. Will be. Therefore, the wafer 10 can be measured without interrupting the cutting operation for measuring the surface shape of the wafer 100.
A surface shape of 0 can be measured.

The measured displacement amount of the surface shape of the wafer 100 is determined to be defective, that is, the displacement amount which cannot be recovered in the subsequent wafer lapping and polishing processes is determined by the type of semiconductor material or the semiconductor material. In the case of silicon, it is about 20 μm, though it depends on the size and the like. When a displacement amount larger than 20 μm is measured, blade dressing (polishing) and tension adjustment are performed on the basis of the wafer surface shape pattern which is the measurement result.

Specifically, for example, when the displacement amount δ of the wafer surface shape exceeds an allowable value of 20 μm and the surface shape pattern as shown in FIG. 4 is measured, the wafer is initially thick in the cutting direction, Shows that the blade 1 becomes thinner as it advances, and in such a case, as shown in FIG. 5, the blade 1 is cut while being deformed downward. As the cause, it is determined that the upper side of the diamond grindstone portion 20 of the blade edge is defective in sharpness, and
Rotating dressing wheels 50 and 5 as shown in FIG.
The dressing of the blade 1 is carried out by 1. In that case, it is necessary to perform dressing (UP dressing) on the upper side of the diamond grindstone portion 20 of the blade edge with the dressing grindstone 50. In addition, in FIG.
Is a dressing grindstone for performing lower dressing (DOWN dress).

When the amount of displacement of the wafer surface shape exceeds the allowable value, the end face of the ingot also undergoes the same displacement. Therefore, when cutting next, as shown in FIG. Simultaneous cutting with the whetstone 40 and ingot 2
It is necessary to grind the bottom surface of No. 00. The amount of lower surface grinding at this time is obtained by adding the amount of displacement of the wafer and the mechanical precision error of the horizontal drive mechanism. The error level of the horizontal drive function is 2 to 3 μm as described later.

Displacements such as waviness and warpage of the wafer caused by poor sharpness and adjustment of the blade are deformed in the wafer cutting direction, and the surface shape of the wafer to be measured is the diameter in the cutting direction. It is sufficient if the surface shape can be measured.

The flow of operations from the measurement of the surface shape of the wafer to the blade dressing will be described with reference to the flow chart shown in FIG. 8. First, the wafer is cut from the ingot (S1), and the cut wafer is cut. The surface shape is measured along with the transportation of (S
2). It is determined whether the displacement amount is larger than an allowable value, here 20 μm (S3). If the displacement amount exceeds 20 μm, the measurement patterns of the measured surface shape are classified (S4), and the UP dress ( Dress on the upper side of the blade)
Or the DOWN dress (dress on the lower side of the blade) is determined (S5), and the dressing of the blade is performed (S5).
6). The dressing completion is confirmed (S7), and if the cutting work of all the ingots is completed, the processing is completed,
When the cutting work is not completed (S8), the lower surface grinding amount is determined (S9), and the ingot is cut again (S1).
I do. By measuring the surface shape of the wafer to be cut next time, the dressing effect can be determined from the displacement amount.

The measurement of the wafer surface shape will be described in more detail below.

First, the displacement sensor provided in the wafer transfer path for actually measuring the surface shape of the wafer is preferably a non-contact displacement gauge such as a capacitance type displacement gauge or a laser type displacement gauge. Is also used in the field of manufacturing semiconductor wafers and devices.

As shown in FIG. 9a, the capacitance type displacement meter obtains the electrode distance D by measuring the capacitance C between the opposing electrodes 31 and 32, and this capacitance C is , The opposing electrode area S, and the dielectric constant ε of the dielectric between the electrodes, C = (ε · S) / D. In actual measurement, as shown in FIG.
The electrode on the surface measurement side of 00 is called a probe 31a, and the wafer 100 itself attracted by the attraction arm 2 becomes an electrode facing the probe 31a.
The surface shape is measured by relatively moving (scanning) the wafer 100.

Further, the laser displacement meter is, as shown in FIG. 10, a measurement target surface (here, the surface of the wafer 100).
Laser light from the laser light source 35, and reflected light from the surface to be measured is passed through the condenser lens 36 to the CCD sensor 3
If the measurement target surface has a vertical displacement, C
Since the photometric point on the CD sensor 37 moves, the surface shape is measured by this.

In this example, a capacitance type displacement meter was used.

Next, regarding the correction of the measured value during the transfer movement, as described above, in the present embodiment, the suction arm 2 is used.
Since the wafer is moved during transfer, the displacement of the suction arm drive mechanism due to mechanical vibration, and the distortion of the measured value due to sludge and water droplets during cutting, and the actual wafer shape are corrected separately. There is a need.

First, among the displacements due to the mechanical vibration of the drive mechanism, the horizontal position displacements at the start point and the end point between the transfer paths are as follows. The displacement of the horizontal position due to movement is about 200 mm between the start point and the end point of the transport distance, and is 2 to 3 μm.
The one with a very high degree of accuracy has already been put into practical use,
Also in this embodiment, the scan distance for measuring the displacement amount of the wafer surface shape is the same as the wafer diameter,
The distance is about 200 mm, and the amount of displacement at the horizontal position between them is 2 to 3 μm or less. Therefore, when compared with 20 μm which is the allowable value of the displacement amount of the wafer surface shape, it is sufficiently small and does not affect the measured value of the wafer surface shape.

Even if the amount of displacement at this horizontal position is large, the amount of displacement at such a horizontal position is always constant, and whether the end point is higher or lower than the start point, which is the value of each transfer. It does not change with each move. Therefore, at regular intervals, for example, during regular inspection of the machine or before starting the cutting of the ingot, the displacement of the suction arm, which is the transport mechanism, is measured by measuring the surface shape of the flat wafer that has been mirror-polished as an initial measurement. It is possible to know the quantity, and it is also possible to obtain a more accurate surface shape by subtracting this initial measurement result from the cut wafer measurement result.

Next, among the displacement due to mechanical vibration of the drive mechanism, there are vertical vibrations during transfer and distortion of measured values due to sludge and water droplets. Since it is minute compared to the change in the measurement pattern, it can be distinguished from the measurement pattern. Specifically, as shown in FIG. 11a, the pattern of the measured actual values is such that the entire body is vertically displaced while repeating small displacements a, and large peaks b are observed in some places. This small displacement a is a vertical vibration of the drive mechanism measured by the displacement sensor 3, and a large peak b is due to sludge or water droplets.

As can be seen from this figure, the mechanical vibration is
The pattern a is such that small vibrations are repeated in the wafer diameter direction to be measured, which is clearly different from the pattern (see FIG. 4) such as warpage or undulation caused by cutting the wafer. In addition, sludge and water droplets suddenly appear as a large peak with respect to the displacement of the wafer, and thus can be distinguished.

In this embodiment, as shown in the block diagram of FIG. 12, the information processing apparatus 60 is used to first use the filter circuit 61 to remove a large peak component (waveform b in FIG. 11a) due to this sludge or water droplets. It is removed from the measured waveform, and then a small waveform a due to mechanical vibration is displayed on the display 64 as a wafer surface shape waveform by connecting its peaks with a gentle line by a waveform output circuit, as shown in FIG. 11b, for example. is doing.

Incidentally, the sludge is washed away by the water supplied during the cutting operation, and the water droplets have a hydrophobic surface on the semiconductor itself.
Although not usually attached so much, in the present embodiment, more accurate measurement is performed by removing air as much as possible from blowing air from the air nozzle 4.

[0034]

As described above, according to the method for measuring the shape of a cut wafer of the present invention, the surface displacement of the wafer is measured in the transfer path for transferring the cut wafer from immediately below the ingot to the wafer storage section. Since the surface displacement measuring means is provided and the surface shape in the wafer diameter direction of the cutting direction of the wafer being transferred is to be measured, the surface shape of the wafer can be measured online without interrupting the cutting work for cutting the wafer from the ingot. . Therefore, it becomes possible to know the flatness of the wafer without reducing the throughput of the cutting work, and when the flatness is poor, it is possible to know the blade sharpness defect that causes the defect from the measured surface shape of the wafer. Therefore, the blade can be properly adjusted, and a wafer with high flatness and less warpage can be obtained. Further, as a result, an appropriate grinding amount can be determined, so that the loss of material is small and the yield is improved.

[Brief description of drawings]

FIG. 1 is an external view of a slice machine used in an example of the present invention.

FIG. 2 is a cross-sectional view showing main components required for cutting an ingot of a slicing machine used in an embodiment of the present invention.

FIG. 3 is a diagram for explaining a wafer surface shape measuring operation according to an embodiment of the present invention.

FIG. 4 is a view showing a measurement pattern of a wafer surface shape according to an embodiment of the present invention.

FIG. 5 is a view for explaining displacement of a blade.

FIG. 6 is a diagram for explaining dressing of a blade.

FIG. 7 is a drawing for explaining an ingot lower surface grinding amount.

FIG. 8 is a flow chart for explaining the flow of operation of the embodiment according to the present invention.

FIG. 9 is a view for explaining a capacitance type displacement meter.

FIG. 10 is a diagram for explaining a laser displacement meter.

FIG. 11 is a diagram for explaining correction of a measured value of a wafer surface shape in an example according to the present invention.

FIG. 12 is a diagram for explaining an apparatus configuration for correcting a measured value of a wafer surface shape in an example according to the present invention.

[Explanation of symbols]

1 ... Blade, 2 ... Suction arm, 3 ... Displacement sensor, 4 ...
Air nozzle, 15 ... Wafer storage,
100 ... Wafer, 200 ... Ingot.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masaaki Tsuboi 3434 Shimada, Hikari City, Yamaguchi Prefecture Nittetsu Electronic Co., Ltd.

Claims (2)

[Claims] 1. A slicing machine that cuts a wafer from a semiconductor ingot with a blade, during the transfer of the cut wafer into a wafer storage section provided in the slicing machine from directly under the ingot. A surface displacement measuring means that moves relative to the wafer is provided, and the surface displacement measuring means measures the displacement of the surface shape over the wafer diameter in the carrying direction of the wafer being carried. Method for measuring surface shape of cut wafer. 2. When the surface displacement result of the wafer measured by the surface displacement measuring means exceeds a preset allowable displacement amount, the blade adjustment and ingot side cutting are performed based on the surface displacement measurement result. The method for measuring the surface shape of a cut wafer according to claim 1, wherein the grinding amount of the surface is determined.