KR20200131763A - Thickness measuring method of covering materials and grinding method - Google Patents

Abstract

The purpose of the present invention is to provide a thickness measurement method for a coating material, which can stably measure the thickness of a coating material, and a grinding method capable of improving thickness precision of a wafer having been ground. The thickness measurement method for a coating material comprising: laminating a long film, a resin, and a wafer in this order and then hardening the resin while pressing the film and a surface plate having a flat surface into contact so as to form a laminate in which a coating material including the film and the resin and having a flat surface, and the wafer are laminated; and measuring, by an optical sensor, the thickness of the coating material at a plurality of measurement places in at least one diameter direction on the wafer. The thickness measurement method for a coating material measures the thicknesses of the coating material so that the at least one diameter direction in which the thickness of the coating material is measured is different from an MD direction and a TD direction of the long film.

Description

Coating thickness measurement method and grinding method {THICKNESS MEASURING METHOD OF COVERING MATERIALS AND GRINDING METHOD}

The present invention relates to a method for measuring the thickness of a coating formed on a wafer, and a grinding method using the method for measuring the thickness.

A resin or wax is applied to one side of the wafer, and the resin is pressed on a flat surface plate on which a long film is placed, and cured to form a coating with a flat surface on the wafer. A planar grinding method is known in which a wafer is ground using the flat surface of the wafer as a reference surface to remove bending or warpage of the wafer (Patent Document 1). In this grinding method, it is necessary to measure the thickness of the coating in order to obtain a uniform thickness of the wafer after grinding, so it is common to use a light-transmitting film. In addition, conventionally, the wafer is installed on the long film so that the longitudinal direction (long direction, MD: Machine Direction) of the long film and the straight line connecting the notch formed on the wafer and the center of the wafer form an angle of 90°. It had formed a coating. In addition, for measuring the thickness of the coating, an interference type optical sensor is used so as not to damage the wafer and the coating, and for example, a straight line connecting the center of the wafer and the notch or a straight line orthogonal to this straight line is non-contact in the radial direction. I measured it.

Japanese Patent Publication No. 2009-148866

However, the inventor of the present invention discovered a problem in that when the thickness of the coating was measured along a specific direction of a long film, the measured value was uneven and may not be stable. In particular, it has been found that it is difficult to measure the coating thickness stably with high precision in the direction along the MD direction or the TD (Transeverse Direction) direction of a long film. Fig. 7 shows an example of the thickness measurement of a coating that has been performed in the past. The top view of FIG. 7 shows a view when the wafer is placed on a long film as viewed from the wafer side, and the bottom view of FIG. 7 shows a view seen from the film side. The arrows in the wafer surface shown in the bottom diagram of FIG. 7 indicate the thickness measurement direction of the coating, in the order of "○", "Δ", and "x", meaning that the thickness measurement accuracy of the coating is deteriorated. As such, conventionally, there is a problem that the accuracy of the measurement of the coating material is low, and the data of the thickness of the wafer including the coating material with non-uniformity is used, and grinding is performed with the thickness unclear. There is a problem that the thickness accuracy of the wafer from which is removed is deteriorated.

The present invention has been made in order to solve the above problem, and an object of the present invention is to provide a method for measuring the thickness of a coating capable of stably measuring the thickness of the coating with a small non-uniformity, and a grinding method capable of improving the thickness precision of a wafer after grinding. To do.

The present invention has been made in order to achieve the above object, by laminating a long film, a resin, and a wafer in this order, pressing (pressing) the film and a platen having a flat surface to contact (pressing) the resin, Forming a laminate in which a coating material containing a film and the resin and having a flat surface and the wafer is stacked, and measuring the thickness of the coating material at a plurality of measurement points in at least one radial direction on the wafer As a method, a coating for measuring the thickness of the coating by making the at least one radial direction in the wafer for measuring the thickness of the coating material different from the MD direction and the TD direction of the long film Provides a method of measuring the thickness of

According to this method of measuring the thickness of the coating, it is possible to eliminate unevenness in the thickness measurement value of the coating due to the influence of the refractive index of the long film, and thus, it is possible to measure the thickness with high precision.

At this time, a wafer having a notch or an orientation flat is used as the wafer, and the measurement of the thickness of the coating is performed in a radial direction of N (wherein N is an integer greater than 1) equally dividing the area included in the wafer surface. In the N diameter directions, the diameter direction passing through the center of the wafer and the center of the notch or the orientation flat is a first radial direction, and the first radial direction and the long length When the minimum value of the angle formed by the TD direction of the film of is θ(°), θ=45/N(°) when N is an odd number, and θ=90/N(°) when N is an even number To this end, the positional relationship between the long film and the wafer can be set, and a method for measuring the thickness of the coating forming the laminate can be used.

Accordingly, it is possible to measure the thickness of the coating with higher precision.

At this time, as a method of grinding the wafer using the flat surface of the coating as a reference plane, the thickness of the coating is measured by the thickness measurement method of the coating, and the measured thickness of the coating and the finished thickness of the wafer ( Alternatively, the total of the finished thickness) can be used as a grinding method in which grinding is performed by using the total value of the grinding end point.

Accordingly, it is possible to reduce the error of the wafer thickness after grinding from the target value, and it becomes possible to perform grinding with high precision.

As described above, according to the method for measuring the thickness of a coating according to the present invention, it is possible to eliminate unevenness in the thickness measurement value of the coating due to the influence of the refractive index of a long film, and thus it is possible to perform thickness measurement with high precision. Further, by the method of grinding a wafer using the method of measuring the thickness of the coating of the present invention, it becomes possible to reduce the difference between the thickness of the wafer and the target value after grinding.

1 shows the process flow of the thickness measurement and grinding method according to the present invention.
2 shows an example of a manufacturing process of a laminate.
3 shows a conceptual diagram of the thickness measurement of the coating.
4 shows an example of setting the thickness measurement direction of the coating.
5 shows another example of setting the thickness measurement direction of the coating.
6 shows wafer thicknesses (difference from target values) after grinding in Examples 1 and 2 and Comparative Examples.
7 shows an example of the thickness measurement of a conventional coating.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

As described above, there has been a demand for a method for measuring the thickness of a coating that can stably measure the thickness of a coating with a small non-uniformity.

The inventors of the present invention found that, as a result of careful investigation on the above problems, the MD direction and TD direction of the long film were not stable because the refractive index of the film was not stable, so that the accuracy of the thickness measurement decreased. , Completed the present invention. That is, the present inventors laminate a long film, a resin, and a wafer in this order, and cure the resin by pressing the film and a surface plate having a flat surface in contact with each other to cure the resin, thereby comprising the film and the resin, and a coating having a flat surface. And a method of forming a laminate in which the wafers are stacked, and measuring the thickness of the coating at a plurality of measurement points in at least one radial direction on the wafer, wherein the thickness of the coating is measured on the wafer. By making the at least one radial direction different from the MD direction and the TD direction of the long film, the thickness of the coating can be measured with high precision by a thickness measurement method of measuring the thickness of the coating. What can be done, by employing this thickness measurement method, it has been found that errors from the target value can be reduced when the wafer is ground, and the present invention has been completed.

Hereinafter, it will be described with reference to the drawings.

First, a method for measuring the thickness of a coating according to the present invention will be described. This thickness measurement is a measurement performed before grinding of the wafer. First, as shown in S01 of FIG. 1, a long film, a resin, and a wafer are stacked in this order, pressed so that the film and a platen having a flat surface are in contact, and the resin is cured, thereby including the film and the resin. The flat coating and the wafer are laminated to form a laminate.

For example, as shown in FIG. A transparent and elongated film 2 is laid, and a plasticized state, for example, a liquid resin 3 is supplied and applied thereon. The wafer 4 is placed on the resin again, and the surface of the film 2 is pressed using a platen (top plate) 5 so that the surface of the film 2 is flat (pressed). After that, curing treatment according to the kind of resin 3 to be used is performed. In the example shown in the drawing, a UV curable resin is used as the resin 3 and curing is performed by irradiating the UV light 6 from the side of the film 2. In this way, the laminate 10 can be obtained.

The type of the elongate (shape) film is not particularly limited as long as it is a material that transmits the light of the thickness measurement, since the thickness measurement of the coating comprising the film and the cured resin is optically performed as described later. . For example, PET film or the like can be suitably used.

The resin is not particularly limited as long as it is integral with the film and the wafer after curing to form a laminate. For example, thermosetting resins, photocuring resins, thermoplastic resins that become solid at room temperature, and the like can be used. In addition, wax is also contained in the resin mentioned here. Among these, it is preferable to use a photocurable resin such as a UV curable resin. This is because hardening treatment can be easily performed.

As the wafer, for example, a semiconductor wafer made of a single crystal material such as silicon can be used. In particular, in the case of a wafer in which notches or orientation flats are formed, it becomes easy to adjust the mounting position of the wafer on the film and to set the measurement point of the film thickness.

Next, as shown in S02 of FIG. 1, the thickness of the coating material of the laminated body 10 containing a film and a resin is measured. The thickness of the coating is measured by an optical method. For example, as shown in FIG. 3, the interference type optical sensor 7 is used, and light is irradiated from the side of the film 2, and it measures. Conditions such as light of an appropriate wavelength depending on the coating material, such as the material of the film 2 or the type of resin, etc. may be set as appropriate. By moving at least one of the wafer 4 and the optical sensor 7 in a straight line, a line profile having an in-plane thickness can be obtained.

In the measurement of the film thickness, it is preferable to measure as many locations as possible in the plane of the laminate. In the present invention, it is assumed that a plurality of locations are measured in at least one radial direction. This is because the distribution in the plane of the laminate can be measured easily.

At this time, the present invention has a characteristic in that the radial direction to be measured is a direction different from the MD direction and the TD direction of a long film. As described above, the inventors have found that when measuring the coating in the direction along the MD direction or the TD direction of the long film, the measurement accuracy is lowered and the unevenness of the obtained measurement result is increased depending on the influence of the refractive index of the film. I found it. Particularly in the direction along the MD direction, the decrease in thickness measurement accuracy is remarkable. Therefore, the measurement accuracy of the thickness of the coating can be improved by setting the radial direction to be measured in a direction different from the MD direction and the TD direction of the long film.

When measuring the thickness of the coating, the measurement direction is set, for example, by using a wafer with a notch or orientation flat, and measuring a radial direction passing through the center of the notch or orientation flat and the wafer, A method of adjusting the position (rotation direction) of the wafer when placing the wafer on the film and resin to adjust the relative positional relationship between the measurement location (diameter direction) of the wafer and the MD direction or TD direction of the long film. , A method of changing the measurement location (diameter direction) at the time of measurement without changing the positional relationship (rotation direction) when placing the wafer on the film and the resin.

In other words, by adjusting the position (rotation direction) of the wafer when placing the wafer on the film and resin, the relative positional relationship between the measurement location (diameter direction) of the wafer and the MD direction or the TD direction of the long film can be determined. In the case of adopting the method of adjusting, as shown in Fig. 4, by rotating a predetermined angle relative to the center of the wafer with respect to the conventional wafer position (Fig. 4A) and placing the wafer on the film (Fig. In (B) of 4), the diameter direction of the thickness measurement of the coating can be set. In this case, if a device for forming a laminate is provided with a detector for detecting a notch or an orientation flat of the wafer, and a rotation angle adjustment mechanism for the notch or orientation flat, and the rotation angle of the wafer is adjusted, it is highly accurate. Position adjustment is possible.

The measurement accuracy can be further improved by increasing the number of measured radially. In particular, measurement accuracy can be further improved by performing measurements in a plurality of radial directions equally dividing the area included in the wafer surface. A plurality of radial directions for equally dividing a region included in the wafer plane, in other words, means that all of the intersection angles of a plurality of adjacent radial directions are the same.

In addition, the diameter direction passing through the center of the wafer and the center of the notch or orientation flat is the first radial direction, and the minimum value of the angle between the first radial direction and the TD direction of the long film is θ (°). When N is odd, the positional relationship between the long film and the wafer is set so that θ = 45/N (°) when N is an even number, and θ = 90/N (°) when N is an even number to form a laminate. If it does, the unevenness of the measurement result obtained by the thickness measurement becomes very small, and it is possible to perform more highly accurate measurement.

For example, the example shown in FIG. 4 is a case where N=2. When placing the wafer on the film, the thickness of the coating in the first radial direction and the second radial direction orthogonal to the first radial direction by rotating the wafer θ=90/2=45° around the center When is measured, the accuracy of the measurement increases. On the other hand, as in the description of FIG. 7, in FIG. 4 or in FIG. 5 described below, the measurement direction indicated by "○" is the direction in which the precision of the measured value is high, in the order of "△" and "x", Indicates the direction in which the precision of is lowered.

In FIG. 5, an example when N=4 is shown. Conventionally, as shown in Fig. 5A, since the positional relationship between the wafer and the film is set so that the first radial direction and the TD direction of the long film coincide, two of the four diameter directions for measuring thickness. The dog coincides with the TD and MD directions.

On the other hand, as shown in Fig. 5(B), the angle θ formed by the first radial direction and the TD direction of the long film is θ = 90/4 = 22.5° (in the example of Fig. 5, 22.5° clockwise) When the thickness of the coating is measured by forming a layered product by setting it to be, all four radial directions become different directions from the TD direction and the MD direction.

However, as shown in Fig. 5(C), the angle θ formed by the first radial direction and the TD direction of the long film is set to be θ = 45° (in the example of Fig. 5, 45° clockwise). When a laminate is formed and the thickness of the coating is measured, two of the four radial directions coincide with the TD direction and the MD direction, and thus the measurement accuracy of the coating decreases as in the case of Fig. 5A.

Thus, as described above, the diameter direction passing through the center of the wafer and the center of the notch or orientation flat is the first radial direction, and the minimum value of the angle formed by the first radial direction and the TD direction of the long film When is θ (°), the positional relationship between the long film and the wafer is determined so that θ = 45/N (°) when N is an odd number and θ = 90/N (°) when N is an even number. When the laminate is formed by setting, the unevenness of the measurement result obtained in the thickness measurement becomes very small, and more highly accurate measurement can be performed.

On the other hand, the larger the number of N, which is the number in the radial direction to be measured, the higher the measurement accuracy, but since the time required for the measurement becomes longer, N is preferably 10 or less. If N is 6 or less, it is possible to achieve both reduction of the time required for measurement and improvement of the thickness measurement accuracy, which is preferable.

If the thickness of the coating is measured in this way, as shown in S03 of Fig. 1, the end point value in the grinding of the wafer is set using the measurement result. Specifically, it is set as "the end point value of grinding = thickness of the measured coating material + finish thickness of the wafer (target value)". By doing so, the deviation (error) of the thickness of the wafer after grinding from the target value can be reduced.

After that, as shown in S04 in Fig. 1, the wafer is ground. The grinding process can employ a known grinding method as described in Patent Document 1, for example.

Example

Hereinafter, the present invention will be described in detail with reference to examples, but this does not limit the present invention.

First, conditions for obtaining a laminate by forming a coating comprising a resin and a film on a wafer will be described. On the other hand, in Comparative Examples and Examples 1 and 2 described below, in a laminate comprising a coating and a wafer, the measurement points were fixed to preset N=4 measurement points (diameter direction), and the film and the resin were A method of adjusting the position (rotation direction) of the wafer when placing the wafer on top of the wafer, and adjusting the relative positional relationship between the measurement point (diameter direction) of the wafer and the MD direction or TD direction of the long film was adopted.

As the wafer, a P-type Si single crystal wafer having a diameter of 300 mm having a notch in the outer peripheral portion was used. Among the coatings, a UV-curable resin was used as a resin, and a PET film was used as a long film.

First, a PET film was laid on a flat stone platen (lower platen), and 10 ml of a UV-curable resin was dripped on the PET film. After that, when the wafer is integrated with the long film, the radial direction passing through the center of the wafer and the notch (first radial direction) is a direction perpendicular to the MD direction of the long film (a direction parallel to the TD direction) ) Was taken as a reference (0°), and the wafer was rotated around the center so as to have a rotation angle shown below, and held by adsorption on a ceramic plate (top plate).

(Comparative example)

Ceramic so that the first radial direction of the wafer is orthogonal to the MD direction of the long film (a direction parallel to the TD direction), that is, the angle between the first radial direction of the wafer and the TD direction is 0°. It was adsorbed and held on a surface plate (upper surface plate) to form a laminate.

(Example 1)

The wafer was rotated so that the minimum value of the angle formed by the first radial direction of the wafer and the TD direction of the long film was 10.0°, and adsorbed and held on a ceramic platen (upper platen) to form a laminate.

(Example 2)

The wafer was rotated so that the minimum value of the angle formed by the first radial direction of the wafer and the TD direction of the long film was 22.5°, and adsorbed and held on the ceramic platen (upper platen) to form a laminate.

The wafer held by adsorption on the ceramic platen (upper platen) was pressed (pressed) so that the dropping point of the resin and the center of the wafer were the same. The pressure control was performed by driving a servomotor holding a ceramic base, and the pressure was applied until the pressure reached 2000 N. Thereafter, using a UV-LED having a wavelength of 365 nm, ultraviolet rays were irradiated from the film side, and the resin was cured to obtain a laminate.

After curing the resin, the wafer portion of the laminate was held and transferred to a measuring device for measuring the thickness of the coating. As the optical sensor for measuring the thickness of the coating, SI-T80 manufactured by Keyence Corporation was used. The sensor was fixed, and the thickness profile was measured by scanning the laminated body of the coating and the wafer in a straight line.

In addition, in the measurement of Comparative Examples and Examples 1 and 2, 1160 points were measured at a pitch of 0.25 mm per measurement line in four measurement lines in the radial direction of the wafer surface. The four measurement lines were set so as to divide the wafer surface into even regions. In other words, the measurement line measures the radial direction passing through the center and the notch (first radial direction) and the radial direction rotated by 45° from the first radial direction to the center of the wafer (the second to fourth radial directions). I did it. The average value of the coating thickness profile obtained by measuring in this way was taken as the coating thickness.

After measuring the thickness of the coating, the laminate was conveyed to a grinding machine and subjected to grinding. For the grinding mill, DFG8360 manufactured by Disco Corporation was used. As the grinding wheel, a diamond abrasive grain bonded one was used. The coating side was vacuum-adsorbed, and grinding was performed using "measured coating thickness + target finish thickness" as the end point value of grinding. The target finish thickness here was set to 820 μm.

After grinding, the thickness of the wafer was measured. For the measurement, SBW-330 manufactured by Kobelco Overtwisted Company was used. The measurement points of the thickness of the wafer were measured at 290 points at a 1 mm pitch per measurement line in four measurement lines in the radial direction in the wafer plane. The four measurement lines were made into the same line as the measurement location of the coating thickness. The average value of the obtained measured values was taken as the wafer thickness after grinding.

A comparison of the evaluation results of the wafer after grinding is shown in FIG. 6. The vertical axis (vertical axis) in Fig. 6 represents the difference between the target thickness of the wafer after grinding and the actual thickness of the wafer after grinding. As shown in Fig. 6, in the comparative example, as in the prior art, the first radial direction is adsorbed on the upper plate so that the relationship is orthogonal to the MD direction of the film to form a laminate, so that the thickness of the coating is measured. Two of the four radial directions correspond to the TD and MD directions of the long film. Therefore, the accuracy of the measurement of the thickness of the coating material is low, the non-uniformity becomes large, and when the end point for grinding is set using this measurement result, the error from the target thickness becomes large.

On the other hand, in Examples 1 and 2, all of the four radial directions for measuring the thickness of the coating did not coincide with the TD direction and the MD direction of the long film, so that the one closer to the target thickness was obtained than the comparative example. In particular, in Example 2, the minimum value θ (°) of the angle formed by the first radial direction, which is the radial direction passing through the center of the wafer and the notch, and the TD direction of the long film, is θ = 90/4 = 22.5 ( °), it was possible to obtain a wafer closer to the target value.

In addition, this invention is not limited to the said embodiment. The above-described embodiment is an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operation and effect is included in the technical scope of the present invention.

1: platen (lower platen)
2: film
3: resin
4: wafer
5: plate (top plate)
6: UV light
7: optical sensor
10: laminate

Claims (3)

A long film, a resin, and a wafer are stacked in this order, and the resin is cured by pressing the film and a surface plate having a flat surface to contact the resin, whereby a coating material containing the film and the resin and having a flat surface is stacked. A method of forming a laminate and measuring the thickness of the coating material at a plurality of measurement points in at least one radial direction on the wafer with an optical sensor,
In the wafer, the at least one diameter direction for measuring the thickness of the coating is in a direction different from the MD direction and the TD direction of the long film, and the thickness of the coating is measured. How to measure the thickness of the coating. The method of claim 1,
As the wafer, a wafer having a notch or an orientation flat is used,
The measurement of the thickness of the coating is performed in the radial directions of N (wherein N is an integer greater than or equal to 1) equally dividing the area included in the wafer surface,
Among the N radial directions, a diameter direction passing through the center of the wafer and the center of the notch or the orientation flat is a first radial direction, and the first radial direction and the TD direction of the long film are formed. When the minimum value of the angle is θ (°),
When N is an odd number, θ = 45/N (°), and when N is an even number, set the positional relationship between the long film and the wafer so that θ = 90/N (°). Method for measuring the thickness of the coating, characterized in that to form a. A method of grinding the wafer using a flat surface of the coating material as a reference surface,
Measuring the thickness of the coating by the method for measuring the thickness of the coating according to claim 1 or 2,
A grinding method, characterized in that grinding is carried out by using a sum of the measured thickness of the coating material and the finished thickness of the wafer as an end point value of grinding.

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