JP2020188130A - Thickness measurement method for coated body, and grinding method - Google Patents

Abstract

To provide a thickness measurement method for a coated body capable of stably measuring a thickness of a coated body, and a grinding method capable of improving thickness precision of a wafer having been ground.SOLUTION: The present invention relates to a thickness measurement method for a coated body comprising: laminating a long-sized film, 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 having a coated body including the film and the resin and having a flat surface, and the wafer laminated; and measuring, by an optical sensor, a thickness of the coated body at a plurality of measurement places in at least one diameter direction on the wafer, wherein the thickness measurement method for the coated body measures the thicknesses of the coated body such that the at least one diameter direction on the wafer in which the thicknesses of the coated body are measured is different from an MD direction and a TD direction of the long-sized film.SELECTED DRAWING: Figure 4

Description

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, wax, etc. is applied to one side of the wafer, and this resin, etc. is pressed and cured on a flat surface plate on which a long film is placed to form a coating with a flat surface on the wafer. A surface grinding method for removing undulations and warpage of a wafer by grinding the wafer with a flat surface of an object as a reference surface is known (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, and for this purpose, a light-transmitting film is generally used. Further, conventionally, the wafer is formed so that the vertical direction (longitudinal direction, MD: Machine Direction) of the long film and the straight line connecting the notch formed in the wafer and the center of the wafer form an angle of 90 °. It was installed on a long film to form a coating. Then, the thickness of the coating is measured by using an interference type optical sensor so as not to damage the wafer and the coating, for example, along a straight line connecting the center of the wafer and the notch or a straight line orthogonal to this straight line. , Non-contact measurement in the radial direction.

JP-A-2009-148866

However, the present inventor has found that when the thickness of the coating is measured along a specific direction of a long film, the measured values may vary and may not be stable. In particular, it has been found that it is difficult to stably measure the coating thickness with high accuracy in the MD direction and the TD (Transverse Direction) direction of a long film. FIG. 7 shows an example of conventional coating thickness measurement. The upper view of FIG. 7 shows a state in which the wafer is placed on the long film as viewed from the wafer side, and the lower figure of FIG. 7 shows a view as seen from the film side. The arrow in the wafer surface shown in the lower part of FIG. 7 indicates the thickness measurement direction of the coating, and means that the thickness measurement accuracy of the coating deteriorates in the order of “〇”, “Δ”, and “×”. To do. As described above, conventionally, there is a problem that the measurement accuracy of the coating is low, and the data in which the thickness of the wafer including the coating is not included is used for grinding while the thickness is unclear. There is a problem that the thickness accuracy of the wafer from which the coating material has been removed after grinding deteriorates.

The present invention has been made to solve the above problems, and is a method for measuring the thickness of a coating that can stably measure the thickness of the coating with little variation, and the accuracy of the thickness of the wafer after grinding. It is an object of the present invention to provide a grinding method capable of improving the above.

The present invention has been made to achieve the above object, and a long film, a resin, and a wafer are laminated in this order, and the film and a platen having a flat surface are pressed so as to be in contact with each other. By curing the resin, a laminate containing the film and the resin and having a flat surface and the wafer is laminated is formed, and a plurality of measurements are taken in at least one radial direction on the wafer. A method of measuring the thickness of the coating at a location with an optical sensor, wherein at least one diameter direction of measuring the thickness of the coating on the wafer is the MD direction of the long film and the MD direction of the long film. Provided is a method for measuring the thickness of a coating film, which measures the thickness of the coating film so as to be in a direction different from the TD direction.

According to such a coating thickness measuring method, it is possible to eliminate variations in the coating thickness measurement value due to the influence of the refractive index of a long film, and it is possible to measure the thickness with high accuracy.

At this time, a wafer having a notch or an orifra is used as the wafer, and the thickness of the coating is measured by N wafers (where N is an integer of 1 or more) that evenly divides the region included in the wafer surface. Of the N number of diametrical directions, the diametrical direction passing through the center of the wafer and the notch or the central portion of the olifra is set as the first diametrical direction, and the first diametrical direction and When the minimum value of the angle formed by the TD direction of the long film is θ (°), θ = 45 / N (°) when the N is an odd number, and θ = when the N is an even number. The thickness of the coating material forming the laminate can be measured by setting the positional relationship between the long film and the wafer so as to be 90 / N (°).

As a result, the thickness of the coating can be measured with higher accuracy.

At this time, it is a method of grinding the wafer with the flat surface of the surface of the coating as a reference surface, the thickness of the coating is measured by the method of measuring the thickness of the coating, and the measured coating is measured. A grinding method can be used in which grinding is performed by using the sum of the thickness and the finished thickness of the wafer as the end point value of grinding.

As a result, the error of the wafer thickness after grinding from the target value can be reduced, and the grinding process can be performed with high accuracy.

As described above, according to the coating thickness measuring method of the present invention, it is possible to eliminate the variation in the coating thickness measurement value due to the influence of the refractive index of the long film, and to perform the thickness measurement with high accuracy. Is possible. Further, the wafer grinding method using the coating thickness measuring method of the present invention makes it possible to reduce the difference between the thickness of the wafer after grinding and the target value.

The process flow of the thickness measurement and grinding method which concerns on this invention is shown. An example of the manufacturing process of the laminated body is shown. The conceptual diagram of the thickness measurement of a covering is shown. An example of setting the thickness measurement direction of the covering is shown. Another setting example in the thickness measurement direction of the covering is shown. The wafer thickness (difference from the target value) after grinding of Examples 1 and 2 and Comparative Example is shown. An example of conventional coating thickness measurement is shown.

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 coating thickness measuring method capable of stably measuring the coating thickness with little variation.

As a result of diligent investigation on the above-mentioned problems, the present inventors have not stabilized the thickness measurement result in the MD direction and the TD direction of the long film because the refractive index of the film is not stable, and the thickness measurement is performed. The present invention has been completed by finding that the accuracy is lowered. That is, the present inventors stack a long film, a resin, and a wafer in this order, press the film so that the surface plate having a flat surface is in contact with the film, and cure the resin to cure the film. To form a laminate in which a coating film containing the resin and a flat surface and the wafer are laminated, and the thickness of the coating film is measured at a plurality of measurement points in at least one radial direction on the wafer. In the measuring method, the diameter direction of at least one film for measuring the thickness of the coating film on the wafer is set to be different from the MD direction and the TD direction of the long film. By the coating thickness measuring method for measuring the coating thickness, the coating thickness can be measured with high accuracy, and by adopting this thickness measuring method, the wafer is ground. The present invention was completed by finding that the error from the target value can sometimes be reduced.

Hereinafter, description will be made with reference to the drawings.

First, a method for measuring the thickness of the coating material according to the present invention will be described. This thickness measurement is a measurement performed before grinding the wafer. First, as shown in S01 of FIG. 1, a long film, a resin, and a wafer are laminated in this order, and the film and a surface plate having a flat surface are pressed so as to be in contact with each other to cure the resin. A laminate containing a film and the resin and having a flat surface and a wafer are laminated to form a laminate.

To give an example of a manufacturing process of a laminate in which a coating material containing a film and a resin and having a flat surface and a wafer are laminated, as shown in FIG. 2, first, a surface plate having a flat surface (lower surface plate) A light-transmitting and long film 2 is laid on top of 1, and a plastic state, for example, a liquid resin 3 is supplied and coated on the film 2. Further, the wafer 4 is placed on the resin and pressed by using the surface plate (upper surface plate) 5 so that the surface of the film 2 is flat. After that, a curing treatment is performed according to the type of resin 3 used. In the example shown in the figure, a UV curable resin is used as the resin 3, and the film is cured by irradiating the film 2 with UV light 6. In this way, the laminated body 10 can be obtained.

As a type of long film, as will be described later, since the thickness of the coating film containing the film and the cured resin is optically measured, any material that transmits the light of the thickness measurement is particularly suitable. Not limited. For example, a PET film or the like can be preferably used.

The resin is not particularly limited as long as it can be integrated with the film and the wafer to form a laminate after curing. For example, a thermosetting resin, a photocurable resin, a thermoplastic resin that becomes solid at room temperature, and the like can be used. The resin referred to here also includes wax. Of these, it is preferable to use a photocurable resin such as a UV curable resin. This is because the curing process 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 having a notch or an orientation flat, it becomes easy to adjust the mounting position of the wafer on the film and set the measurement point of the film thickness.

Next, as shown in S02 of FIG. 1, the thickness of the coating material containing the film and the resin in the laminate 10 is measured. The thickness of the coating is measured by an optical method. For example, as shown in FIG. 3, an interference type optical sensor 7 is used to irradiate light from the film 2 side for measurement. Conditions such as light having an appropriate wavelength according to the coating material, such as the material of the film 2 and the type of resin, 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 of the in-plane thickness can be obtained.

The film thickness is preferably measured at as many points as possible within the surface of the laminate, but in the present invention, a plurality of points are measured in at least one radial direction. This is because the distribution in the plane of the laminated body can be easily measured.

At this time, the present invention is characterized in that the diameter direction in which the measurement is performed is different from the MD direction and the TD direction of the long film. As described above, when the present inventor measures the coating in the direction along the MD direction or the TD direction of the long film, the measurement accuracy is lowered due to the influence of the refractive index of the film, and the obtained measurement result is obtained. We found that the variation became large. In particular, in the direction along the MD direction, the thickness measurement accuracy is significantly reduced. Therefore, the accuracy of measuring the thickness of the coating can be improved by setting the diameter direction in which the measurement is performed to be different from the MD direction and the TD direction of the long film.

The setting of the measurement direction when measuring the thickness of the coating is, for example, using a wafer in which a notch or an orifra is formed, and measuring the radial direction passing through the center of the notch or the orifla and the center of the wafer. By adjusting the position (rotation direction) of the wafer when the wafer is placed on the film and resin, the position relative to the measurement location (diameter direction) of the wafer and the MD direction or TD direction of the long film. Examples thereof include a method of adjusting the relationship and a method of changing the measurement location (diameter direction) at the time of measurement without changing the positional relationship (rotation direction) when the wafer is placed on the film and the resin.

The former, that is, the position (rotation direction) of the wafer when the wafer is placed on the film and resin is adjusted so that the measurement location (diameter direction) of the wafer is relative to the MD direction or TD direction of the long film. When a method of adjusting the positional relationship is adopted, as shown in FIG. 4, the wafer is rotated by a predetermined angle with respect to the conventional wafer position ((A) in FIG. 4) with respect to the center of the wafer. Is placed on the film ((B) in FIG. 4), and the thickness of the coating can be set in the radial direction. In this case, if the apparatus for forming the laminate is provided with a detection mechanism for detecting the notch or the orientation flat of the wafer and a rotation angle adjusting mechanism for the notch or the orientation flat, and the rotation angle of the wafer is adjusted, the position adjustment can be performed with high accuracy. it can.

The measurement accuracy can be improved by increasing the number of measurements in the radial direction. In particular, the measurement accuracy can be further improved by performing the measurement in a plurality of diameter directions such that the region included in the wafer surface is evenly divided. The plurality of diametrical directions that evenly divide the region included in the wafer surface means, in other words, that the intersecting angles of the plurality of adjacent diametrical directions are all equal.

Further, the diameter direction passing through the center of the wafer and the notch or the center of the orientation flat is defined as the first diameter direction, and the minimum value of the angle formed by the first diameter direction and the TD direction of the long film is θ (°). ), The positional relationship between the long film and the wafer is such that θ = 45 / N (°) when N is an odd number and θ = 90 / N (°) when N is an even number. When the above is set to form a laminated body, the variation in the measurement results obtained by the thickness measurement becomes very small, and more accurate measurement can be performed.

For example, the example shown in FIG. 4 is the case where N = 2. When the wafer is placed on the film, the wafer is rotated by θ = 90/2 = 45 ° around the center, so that the wafer is placed in the first diametrical direction and in the second diametrical direction orthogonal to the first diametrical direction. When the thickness of the coating is measured with, the measurement accuracy becomes high. As in the explanation of FIG. 7, in FIG. 4 and FIG. 5 described below, the measurement directions indicated by “◯” are the measured values in the order of high accuracy of the measured values, “Δ”, and “×”. Indicates the direction in which the accuracy of

FIG. 5 shows an example when N = 4. Conventionally, as shown in FIG. 5A, the positional relationship between the wafer and the film is set so that the first diameter direction and the TD direction of the long film coincide with each other, so that the thickness is measured. Two of the four radial directions coincide with the TD and MD directions.

On the other hand, as shown in FIG. 5B, the angle θ formed by the first diameter direction and the TD direction of the long film is θ = 90/4 = 22.5 ° (clockwise in the example of FIG. 5). 22.5 °) to form a laminate and measure the thickness of the coating, all four radial directions are different from the TD direction and the MD direction.

However, as shown in FIG. 5C, the angle θ formed by the first radial direction and the TD direction of the long film is θ = 45 ° (in the example of FIG. 5, 45 ° clockwise). When the thickness of the coating is measured by forming the laminate in this way, two of the four radial directions coincide with the TD direction and the MD direction. Therefore, in FIG. 5 (A). As in the case, the measurement accuracy of the coating is reduced.

Therefore, as described above, the diametrical direction passing through the center of the wafer and the notch or the central portion of the orientation flat is set as the first diametrical direction, and the minimum angle formed by the first diametrical direction and the TD direction of the long film is the minimum. When the value is θ (°), when N is odd, θ = 45 / N (°), and when N is even, θ = 90 / N (°). When the laminated body is formed by setting the positional relationship with the wafer, the variation in the measurement results obtained by the thickness measurement becomes very small, and more accurate measurement can be performed.

The larger the number of N in the diameter direction for measurement, the better the measurement accuracy, but the longer the time required for measurement, so N is preferably 10 or less. When N is set to 6 or less, it is possible to both shorten the time required for measurement and improve the thickness measurement accuracy, which is preferable.

After measuring the thickness of the coating in this way, as shown in S03 of FIG. 1, the end point value in the grinding process of the wafer is set using the measurement result. Specifically, "grinding end point value = measured coating thickness + wafer finished thickness (target value)". By doing so, it is possible to reduce the deviation (error) of the thickness of the wafer after grinding from the target value.

After that, as shown in S04 of FIG. 1, the wafer is ground. For the grinding process, for example, a known grinding method as described in Patent Document 1 can be adopted.

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

First, the conditions for forming a coating material containing a resin and a film on a wafer to obtain a laminate will be described. In Comparative Examples and Examples 1 and 2 described below, the measurement locations in the laminate including the coating material and the wafer were fixed at preset N = 4 measurement locations (diameter direction), and the film and the film. Adjust the position (rotation direction) of the wafer when mounting the wafer on the 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. Adopted the method of

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

First, a PET film was laid on a flat stone surface plate (lower surface plate), and 10 ml of a UV curable resin was dropped on the PET film. After that, when the wafer is integrated with the long film, the diametrical direction (first diametrical direction) passing through the center and the notch of the wafer is parallel to the MD direction of the long film (TD direction). The wafer was rotated around the center and held by the ceramic platen (upper platen) so as to have the rotation angle shown below, based on the case where the wafer was in the parallel direction (0 °).

(Comparison example)
The first radial direction of the wafer is perpendicular to the MD direction of the long film (the direction parallel to the TD direction), that is, the angle formed by the first radial direction of the wafer and the TD direction is 0 °. A laminated body was formed by adsorbing and holding it on a ceramic surface plate (upper surface plate) so as to be.

(Example 1)
The wafer is rotated so that the minimum value of the angle between the first diameter direction of the wafer and the TD direction of the long film is 10.0 °, and the wafer is attracted and held on the ceramic surface plate (upper surface plate). , A laminate was formed.

(Example 2)
The wafer is rotated so that the minimum value of the angle formed by the first diameter direction of the wafer and the TD direction of the long film is 22.5 °, and the wafer is attracted and held on the ceramic surface plate (upper surface plate). , A laminate was formed.

The wafer adsorbed and held on the ceramic surface plate (upper surface plate) was pressed and bonded so that the dropping point of the resin and the center of the wafer were the same. The pressure was controlled by driving a servomotor holding a ceramic surface plate, and the pressure was increased until the pressure reached 2000 N. Then, ultraviolet rays were irradiated from the film side using a UV-LED having a wavelength of 365 nm to cure the resin to obtain a laminate.

After the resin was cured, the wafer portion of the laminate was held and transported to a measuring machine for measuring the thickness of the coating. The SI-T80 manufactured by Keyence Corporation was used as the optical sensor for measuring the thickness of the coating. The thickness profile was measured by fixing the sensor and scanning the laminate of the covering and the wafer in a straight line.

Further, in the measurements of Comparative Examples and Examples 1 and 2, 1160 points were measured at a pitch of 0.25 mm per one measurement line with four measurement lines in the diameter direction in the wafer surface. The four measurement lines were set so as to divide the inside of the wafer plane into equal regions. That is, the measurement lines are the diametrical direction (first diametrical direction) passing through the center and the notch and the diametrical direction (second to fourth diametrical directions) rotated by 45 ° with respect to the wafer center from the first diametrical direction. And said. The average value of the coating thickness profile obtained by measuring in this manner was taken as the coating thickness.

After measuring the thickness of the coating, the laminate was transferred to a grinding apparatus and subjected to grinding. As the grinding apparatus, DFG8360 manufactured by DISCO was used. The grinding wheel used was one in which diamond abrasive grains were combined. The coating side was vacuum-adsorbed, and grinding was performed with "measured coating thickness + target finished thickness" as the end point value of grinding. The target finished thickness here was 820 μm.

After grinding, the thickness of the wafer was measured. For the measurement, SBW-330 manufactured by Kobelco Kaken Co., Ltd. was used. The thickness of the wafer was measured at four measurement lines in the diameter direction in the wafer surface, and 290 points were measured at a pitch of 1 mm per measurement line. The four measurement lines were the same as the measurement points for the coating thickness. The average value of the obtained measured values was taken as the wafer thickness after grinding.

FIG. 6 shows a comparison of the evaluation results of the ground wafer. The vertical axis of FIG. 6 shows 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 conventional case, the first radial direction is attracted to the upper surface plate so as to be orthogonal to the MD direction of the film to form a laminated body. , Two of the four diameter directions for measuring the thickness of the coating are in directions that coincide with the TD direction and the MD direction of the long film. For this reason, the accuracy of measuring the thickness of the coating is low and the variation becomes large, and when the grinding end point is set using this measurement result, the error from the target thickness becomes large.

On the other hand, in Examples 1 and 2, since all four diameter directions for measuring the thickness of the coating do not match the TD direction and MD direction of the long film, the target thickness is higher than that of the comparative example. I was able to get something close to. In particular, in the second embodiment, the minimum value θ (°) of the angle formed by the first radial direction, which is the radial direction passing through the center and the notch of the wafer, and the TD direction of the long film is set to θ = 90 /. 4 = 22.5 (°), and a wafer closer to the target value could be obtained.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any object having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. Is included in the technical scope of.

1 ... Surface plate (lower surface plate), 2 ... Film, 3 ... Resin, 4 ... Wafer,
5 ... Surface plate (upper surface plate), 6 ... UV light, 7 ... Optical sensor, 10 ... Laminate.

Claims (3)

By laminating a long film, a resin, and a wafer in this order and pressing the film so that a surface plate having a flat surface is in contact with the resin to cure the resin, the surface containing the film, the resin, and the surface is formed. A method of forming a laminate in which a flat coating and the wafer are laminated, and measuring the thickness of the coating with an optical sensor at a plurality of measurement points in at least one radial direction on the wafer. hand,
The thickness of the coating is adjusted so that at least one diameter direction for measuring the thickness of the coating on the wafer is different from the MD direction and the TD direction of the long film. A method for measuring the thickness of a coating, which comprises measuring. A wafer having a notch or an orientation flat is used as the wafer.
The thickness of the coating is measured in the diameter direction of N lines (where N is an integer of 1 or more) that evenly divides the region included in the wafer surface.
Of the N radial directions, the radial direction passing through the center of the wafer and the notch or the central portion of the orientation flat is defined as the first radial direction, and the first radial direction and the TD direction of the long film. When the minimum value of the angle formed by and is θ (°),
The positional relationship between the long film and the wafer is set so that θ = 45 / N (°) when the N is an odd number and θ = 90 / N (°) when the N is an even number. The method for measuring the thickness of a coating material according to claim 1, wherein the laminate is formed. A method of grinding the wafer using the flat surface of the surface of the coating as a reference surface.
The thickness of the coating is measured by the method for measuring the thickness of the coating according to claim 1 or 2.
A grinding method characterized in that grinding is performed with the sum of the measured thickness of the covering and the finished thickness of the wafer as the end point value of grinding.

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