Patent ID: 12194594

DETAILED DESCRIPTION

Recently, in a manufacturing process for a semiconductor device, in a combined substrate in which a semiconductor substrate (hereinafter, referred to as “first substrate”) having devices such as a plurality of electronic circuits formed on a front surface thereof and a second substrate are bonded to each other, the first substrate is thinned by grinding a rear surface thereof.

The thinning of the first substrate is performed by bringing a grinding whetstone into contact with the rear surface of the first substrate in the state that a rear surface of the second substrate is held by a substrate holder. However, when performing the grinding of the first substrate in this way, if a thickness distribution in the diametrical direction of the second substrate held by the substrate holder is not uniform, the degree of flatness (TTV: Total Thickness Variation) of the first substrate after being ground may be degraded. Specifically, as shown inFIG.1, in a portion within a surface of a combined substrate T where a thickness of a second substrate S is small, a thickness of a first substrate W becomes large, whereas in a portion where the thickness of the second substrate S is large, the thickness of the first substrate W becomes small.

The grinding method disclosed in the aforementioned Patent Document 1 is a method for grinding the first substrate (second plate-shaped workpiece) to a uniform thickness by detecting non-uniformity in the thickness of the second substrate (first plate-shaped workpiece) and adjusting an inclination of the substrate holder (holding table). In the grinding method disclosed in Patent Document 1, the thickness of the second substrate (first plate-shaped workpiece) is directly calculated by measurement light emitted from a non-contact type thickness measuring device provided above the combined substrate (plate-shaped workpiece). Further, the measurement light penetrates the first substrate (second plate-shaped workpiece).

However, when devices are formed on the front surface of the first substrate as stated above, for example, that is, when a device layer, which is a metal film, is interposed between the first substrate and the second substrate, the thickness of the second substrate including the metal film may not be calculated properly. To elaborate, since the measurement light (for example, IR light) cannot penetrate the device layer which is the metal film, the thickness of the second substrate including the metal film can be measured properly from neither the first substrate side nor the second substrate side. Since a thickness distribution of the second substrate including the metal film cannot be measured appropriately for this reason, an inclination of the grinding whetstone to be brought into contact with the first substrate, that is, a grinding amount may not calculated appropriately, making it difficult to improve the degree of flatness of the first substrate after being ground. In this regard, there is still a room for improvement in the conventional grinding method for grinding the first substrate to the uniform thickness.

In this regard, exemplary embodiments of the present disclosure provides a technique enabling to appropriately improve flatness of a first substrate in a combined substrate in which the first substrate and a second substrate are bonded to each other. Hereafter, a processing apparatus as a substrate processing apparatus and a processing method as a substrate processing method according to an exemplary embodiment will be described with reference to the accompanying drawings. Further, in the present specification and the drawings, parts having substantially the same functions and configurations will be assigned same reference numerals, and redundant description thereof will be omitted.

In a processing apparatus1to be described later according to an exemplary embodiment, a processing is performed on a combined wafer T as a combined substrate in which a first wafer W as a first substrate and a second wafer S as a second substrate are bonded to each other as shown inFIG.2. In the processing apparatus1, the first wafer W is thinned. Hereinafter, in the first wafer W, a surface to be bonded to the second wafer S will be referred to as a front surface Wa, and a surface opposite to the front surface Wa will be referred to as a rear surface Wb. Likewise, in the second wafer S, a surface to be bonded to the first wafer W will be referred to as a front surface Sa, and a surface opposite to the front surface Sa will be referred to as a rear surface Sb.

The first wafer W is a semiconductor wafer such as, but not limited to, a silicon wafer, and has, on the front surface Wa thereof, a device layer D including a plurality of devices. Further, a surface film F is formed on the device layer D, and the device layer D is bonded to the second wafer S with this surface film F therebetween. The surface film F may be, by way of non-limiting example, an oxide film (a SiO2film or a TEOS film), a SiC film, a SiCN film, an adhesive, or the like. Further, to suppress a peripheral portion of the first wafer W from having a sharp pointed shape (a so-called knife edge shape) by a grinding processing in the processing apparatus1, the peripheral portion is previously removed. The peripheral portion may be in the range of e.g., 0.5 mm to 3 mm from an edge of the first wafer W in the diametrical direction thereof.

The second wafer S has the same configuration as that of the first wafer W, for example, and the device layer D and the surface film F are formed on the front surface Sa thereof. Further, a peripheral portion of the second wafer S is chamfered, and the thickness of the peripheral portion decreases toward a leading end thereof on a cross section thereof. The second wafer S does not need to be a device wafer on which the device layer D is formed, and it may be, for example, a support wafer configured to support the first wafer W. In this case, the second wafer S functions as a protection member configured to protect the device layer D on the front surface Wa of the first wafer W.

In addition, in the following description, in order to avoid complication of illustration, the device layer D and the surface film F may be marked together, and they may sometimes be referred to as a device layer and surface film “DF”.

As depicted inFIG.3, the processing apparatus1has a structure in which a carry-in/out station2and a processing station3are connected as one body. In the carry-in/out station2, a cassette Ct capable of accommodating a plurality of combined wafers T therein is carried to/from the outside, for example. The processing station3is equipped with various kinds of processing apparatuses each configured to perform a required processing on the combined wafer T.

The carry-in/out station2is equipped with a cassette placing table10. In the shown example, a plurality of, for example, four cassettes Ct can be arranged on the cassette placing table10in a row in the X-axis direction. Further, the number of the cassettes Ct placed on the cassette placing table10is not limited to the example of the present exemplary embodiment but may be selected as required.

In the carry-in/out station2, a wafer transfer section20is provided adjacent to the cassette placing table10on the positive Y-axis side of the cassette placing table10. Provided in the wafer transfer section20is a wafer transfer device22configured to be movable on a transfer path21which is elongated in the X-axis direction. The wafer transfer device22is equipped with a transfer fork23configured to hold and transfer the combined wafer T. The transfer fork23attracts and holds the combined wafer T with its biforked leading ends. The transfer fork23transfers the combined wafer T before and after being subjected to the grinding processing, for example. The transfer fork23is configured to be movable in a horizontal direction and a vertical direction and pivotable around a horizontal axis and a vertical axis.

Further, the configuration of the wafer transfer device22is not limited to the present exemplary embodiment, and various other configurations may be adopted. By way of example, the wafer transfer device22may be equipped with two transfer forks23respectively configured to transfer the combine wafer T before being subjected to the grinding processing and the combined wafer T after being subjected to the grinding processing.

In the processing station3, processings such as grinding and cleaning is performed on the combined wafer T. The processing station3includes a rotary table30, a transfer unit40, an alignment unit50, a first cleaning unit60, a second cleaning unit70, a rough grinding unit80, an intermediate grinding unit90, and a finishing grinding unit100as a finishing grinding device.

The rotary table30is configured to be rotated by a rotating mechanism (not shown). Four chucks31each of which serves as a substrate holder configured to attract and hold the combined wafer T are provided on the rotary table30. The chucks31are arranged on a circle concentric with the rotary table30at a regular distance therebetween, that is, at an angular distance of 90 degrees therebetween. The four chucks31are configured to be moved to a delivery position A0and processing positions A1to A3as the rotary table30is rotated. Further, each of the chucks31is configured to be rotated around a vertical axis by a rotating mechanism (not shown).

As depicted inFIG.3, in the present exemplary embodiment, the delivery position A0is a position on the positive X-axis and negative Y-axis side of the rotary table30. The second cleaning unit70, the alignment unit50, and the first cleaning unit60are disposed on the negative Y-axis side of the delivery position A0. The alignment unit50and the first cleaning unit60are stacked in this order from above. The first processing position A1is a position on the positive X-axis and positive Y-axis side of the rotary table30, and the rough grinding unit80is disposed thereat. The second processing position A2is a position on the negative X-axis and positive Y-axis side of the rotary table30, and the intermediate grinding unit90is disposed thereat. The third processing position A3is a position on the negative X-axis and negative Y-axis side of the rotary table30, and the finishing grinding unit100is disposed thereat.

The chuck31may be, for example, a porous chuck. The chuck31attracts and holds the rear surface Sb of the second wafer S that constitutes the combined wafer T. When viewed from the side, a front surface of the chuck31, that is, a holding surface of the combined wafer T has a protruding shape with a central portion thereof protruding higher than an end portion thereof. Further, since the protrusion of this central portion is minute, illustration of the protruding shape of the chuck31will be omitted in the following description.

Each chuck31is held by a chuck base32. In the following description, as shown inFIG.4, the four chuck bases positioned at the processing positions A1to A3and the delivery position A0may sometimes be respectively referred to as a first chuck base321, a second chuck base322, a third chuck base323, and a fourth chuck base324. The chuck bases321to324hold the chucks311to314, respectively.

As illustrated inFIG.5, the chuck base32is provided with an inclination adjuster33configured to adjust an inclination of the chuck31and the chuck base32from a horizontal direction. The inclination adjuster33has a fixed shaft34and a plurality of elevating shafts35provided on a bottom surface of the chuck base32. Each of the elevating shafts35is configured to be extensible/contractible, and moves the chuck base32up and down. By using the inclination adjuster33to raise or lower one end of an outer periphery of the chuck base32in a vertical direction with respect to the other end thereof (a position corresponding to the fixed shaft34), the chuck31and the chuck base32can be inclined. Thus, it is possible to adjust an inclination of the rear surface Wb of the first wafer W as a grinding surface with respect to grinding whetstones belonging to the various kinds of grinding units at the processing positions A1to A3.

Further, the configuration of the inclination adjuster33is not limited to the above-described example, and any of various other configurations may be adopted as long as it is capable of adjusting the relative angle (parallelism) of the first wafer W with respect to the grinding whetstone.

As depicted inFIG.3, the transfer unit40is a multi-joint robot equipped with a plurality of, for example, three arms41. Each of the three arms41is configured to be rotatable. The arm41at a leading end is equipped with a transfer pad42configured to attract and hold the combined wafer T. The arm41at a base end is mounted to an elevating mechanism43configured to move this arm41in a vertical direction. The transfer unit40having this configuration is capable of transferring the combined wafer T to/from the delivery position A0, the alignment unit50, the first cleaning unit60, and the second cleaning unit70.

In the alignment unit50, a direction of the combined wafer T before being subjected to the grinding processing in a horizontal direction is adjusted. By way of example, while rotating the combined wafer T held by a spin chuck (not shown), a position of a notch of the first wafer W is detected by a detector (not shown), and by adjusting the position of the notch, the direction of the combined wafer T in the horizontal direction is adjusted.

In the first cleaning unit60, the rear surface Wb of the first wafer W after being subjected to the grinding processing is cleaned, and, more specifically, cleaned by spinning. By way of example, while rotating the combined wafer T held by a spin chuck (not shown), a cleaning liquid is supplied to the rear surface Wb of the first wafer W from a cleaning liquid nozzle (not shown). The supplied cleaning liquid diffuses on the rear surface Wb, so that the rear surface Wb is cleaned.

In the second cleaning unit70, the rear surface Sb of the second wafer S is cleaned in the state that the combined wafer T after being subjected to the grinding processing is held by the transfer pad42, and, also, the transfer pad42is cleaned.

In the rough grinding unit80, the rear surface Wb of the first wafer W is roughly ground. The rough grinding unit80is equipped with a rough grinder81. As depicted inFIG.5, the rough grinder81has a rough grinding wheel82, a mount83, a spindle84, and a driver85. The rough grinding wheel82is equipped with a rough grinding whetstone on a bottom surface thereof, and has an annular shape. The rough grinding wheel82is supported on the mount83. The mount83is provided with the driver85with the spindle84therebetween. The driver85incorporates therein, for example, a motor (not shown), and serves to rotate the rough grinding wheel82and move it in a vertical direction along a supporting column86shown inFIG.3. In the rough grinding unit80, by respectively rotating the chuck31and the rough grinding wheel82while keeping the first wafer W of the combined wafer T held by the chuck31in contact with a part of an arc of the rough grinding wheel82, the rear surface Wb of the first wafer W is roughly ground.

In the intermediate grinding unit90, the rear surface Wb of the first wafer W is ground to an intermediate level. The configuration of the intermediate grinding unit90is substantially the same as the configuration of the rough grinding unit80, as shown inFIG.3andFIG.5. The intermediate grinding unit90includes an intermediate grinder91, an intermediate grinding wheel92, a mount93, a spindle94, a driver95, and a supporting column96. Further, a particle size of abrasive grains of the intermediate grinding whetstone is smaller than a particle size of abrasive grains of the rough grinding whetstone.

In the finishing grinding unit100, the rear surface Wb of the first wafer W is ground finely. The configuration of the finishing grinding unit100is substantially the same as the configuration of the rough grinding unit80and the intermediate grinding unit90, as illustrated inFIG.3andFIG.5. The finishing grinding unit100includes a finishing grinder101, a finishing grinding wheel102, a mount103, a spindle104, a driver105, and a supporting column106. Further, a particle size of abrasive grains of the finishing grinding whetstone is smaller than the particle size of the abrasive grains of the intermediate grinding whetstone.

Furthermore, the processing station3is equipped with a thickness measuring unit110configured to measure the thickness of the first wafer W upon the completion of the intermediate grinding, and a thickness measuring unit120configured to measure the thickness of the first wafer W upon the completion of the finishing grinding. The thickness measuring unit110is provided at, for example, the processing position A2or the processing position A3. The thickness measuring unit120is provided at, for example, the processing position A3or the delivery position A0. Further, a thickness measuring device (not shown) configured to detect an endpoint of the various kinds of grinding processings at the processing positions A1to A3is provided at each of the processing positions A1to A3. When the thickness of the first wafer W measured by the thickness measuring device reaches a target thickness, the rotary table30is rotated to move the first wafer W. In addition, at the processing positions A2and A3, the above-described thickness measuring units110and120may be used as the thickness measuring device for performing the endpoint detection.

The thickness measuring unit110as a first thickness distribution measuring device includes a sensor111and an operation unit112, as illustrated inFIG.4. The sensor111is, for example, a non-contact type sensor, and it measures the thickness of the first wafer W before being subjected to the finishing grinding. The sensor111measures the thickness of the first wafer W at multiple points thereof. Measurement results of the sensor111are output to the operation unit112. The operation unit112acquires a thickness distribution of the first wafer W from the measurement results (thicknesses of the first wafer W) of the sensor111at the multiple points. At this time, TTV data of the first wafer W may also be calculated. Further, the thickness of the first wafer W measured by the thickness measuring unit110is just the thickness of the silicon portion of the first wafer W, and it does not include the thickness of the device layer D and the thickness of the surface film F.

The thickness measuring unit120as a second thickness distribution measuring device has the same configuration as the thickness measuring unit110as shown inFIG.4, and it includes a sensor121and an operation unit122. In the thickness measuring unit120, the sensor121acquires the thickness of the first wafer W after being subjected to the finishing grinding, and the operation unit122calculates TTV data.

In addition, in the thickness measurement of the first wafer W using the thickness measuring units110and120, the thickness of the first wafer W is measured at a plurality of measurement points in the diametrical direction of the first wafer W. At each of the plurality of measurement points in the diametrical direction, while rotating the combined wafer T, the thickness of the first wafer W is measured at multiple points in the circumferential direction. Then, a moving average value or a moving median value of the thicknesses measured at the multiple points in the circumferential direction is calculated, and the calculated value may be used as the thickness of the first wafer W at the corresponding measurement point in the diametrical direction.

Further, instead of using the moving average value or the moving median value of the multiple points as the thickness of the first wafer W, the thickness of the first wafer W at certain designated coordinates may be measured, and the measured thickness may be used as the thickness of the first wafer W as a representative value.

In addition, the configuration of the thickness measuring units110and120are not limited to the present exemplary embodiment, and any of various other configurations may be adopted as long as the thickness distribution and the TTV data of the first wafer W can be obtained.

As depicted inFIG.3, the above-described processing apparatus1is equipped with a controller130. The controller130is implemented by, for example, a computer equipped with a CPU and a memory, and includes a program storage (not shown). A program for controlling the processing of the combined wafer T in the processing apparatus1is stored in the program storage. Further, the program storage also stores therein a program for controlling operations of the above-described various kinds of processing units and a driving system such as the transfer devices to implement a processing to be described later in the processing apparatus1. The program may be recorded on a computer-readable storage medium H and installed from the recording medium H to the controller130.

Now, a processing method performed by using the processing apparatus1having the above-described configuration will be explained. In the present exemplary embodiment, the combined wafer T is previously formed by bonding the first wafer W and the second wafer S in a bonding apparatus (not shown) outside the processing apparatus1. Further, the peripheral portion of the first wafer W is removed in advance.

First, the cassette Ct having therein a multiple number of combined wafers T is placed on the cassette placing table10of the carry-in/out station2.

Then, the combined wafer T is taken out of the cassette Ct by the transfer fork23of the wafer transfer device22, and transferred into the alignment unit50of the processing station3.

In the alignment unit50, by adjusting the position of the notch of the first wafer W while rotating the combined wafer T held by the spin chuck (not shown) as described above, the direction of the combined wafer T in the horizontal direction is adjusted.

Next, the combined wafer T is transferred from the alignment unit50to the delivery position A0by the transfer unit40, and handed over onto the chuck31located at the delivery position A0. Thereafter, the chuck31is moved to the first processing position A1. Then, the rear surface Wb of the first wafer W is roughly ground by the rough grinding unit80.

Subsequently, the chuck31is moved to the second processing position A2. Then, the rear surface Wb of the first wafer W is ground to an intermediate level by the intermediate grinding unit90.

Next, the chuck31is moved to the third processing position A3. Then, the rear surface Wb of the first wafer W is finely ground by the finishing grinding unit100. The detailed method of the finishing grinding in the present exemplary embodiment will be elaborated later.

Thereafter, the chuck31is moved to the delivery position A0. Here, by using the cleaning liquid nozzle (not shown), the rear surface Wb of the first wafer W is roughly cleaned with the cleaning liquid. In this process, the cleaning is performed to reduce the contamination of the rear surface Wb to some extent.

Then, the combined wafer T is transferred from the delivery position A0to the second cleaning unit70by the transfer unit40. In the second cleaning unit70, the rear surface Sb of the second wafer S is cleaned and dried in the state that the combined wafer T is held by the transfer pad42.

Subsequently, the combined wafer T is transferred from the second cleaning unit70to the first cleaning unit60by the transfer unit40. In the first cleaning unit60, the rear surface Wb of the first wafer W is finally cleaned with the cleaning liquid by using the cleaning liquid nozzle (not shown). In this process, the rear surface Wb is cleaned to a required level of cleanliness and dried.

Thereafter, the combined wafer T after being subjected to all the required processings is transferred to the cassette Ct of the cassette placing table10by the fork23of the wafer transfer device22. Then, upon the completion of the processings on all the combined wafers T in the cassette Ct, a series of processings in the processing apparatus1is ended. In addition, in the processing apparatus1, the processing of the combined wafers T may be performed in a single-wafer unit. That is, after the processing of one combined wafer T is finished, the processing of another combined wafer T may be started. Alternatively, the processings of the plurality of combined wafers T may be performed successively, that is, the processings of the plurality of combined wafers T in the processing apparatus1may be performed simultaneously.

In the processing apparatus1as described above, the processing is successively performed on the plurality of combined wafers T accommodated in the cassette Ct. In order to perform the grinding processing on the plurality of combined wafers T uniformly in the processing apparatus1, that is, in order to uniformly control the thickness distribution of the first wafer W in each combined wafer T after being subjected to the finishing grinding, it is necessary to consider the thickness distribution in the surface of the second wafer S as described above. Hereinafter, the finishing grinding method for the first wafer W considering the thickness distribution of the second wafer S in the processing apparatus1will be explained.

In the following description, the nthsheet of combined wafer T to be processed in the processing apparatus1may sometimes be referred to as “combined wafer Tn”. Likewise, the first wafer W and the second wafer S constituting the nthsheet of combined wafer T to be processed may sometimes be referred to as “first wafer Wn” and “second wafer Sn”, respectively.

In implementing the above-described grinding method, the processing apparatus1is equipped with, as illustrated inFIG.3andFIG.4, the thickness measuring unit110configured to acquire the thickness distribution of the first wafer W before being subjected to the finishing grinding, and the thickness measuring unit120configured to acquire the thickness distribution of the first wafer W after being subjected to the finishing grinding and calculate TTV of the first wafer W. The thickness measuring unit110(120) measures the thickness of the first wafer W at multiple points thereof by emitting, for example, IR light to the first wafer W, and acquires the in-surface thickness distribution of the first wafer W based on the measured thicknesses. Further, the thickness measuring unit120calculates the TTV of the first wafer W after being subjected to the finishing grinding processing based on the acquired in-surface thickness distribution. The IR light is emitted to the combined wafer T from above the combined wafer T held by the chuck31, that is, from the first wafer W side, for example. In addition, as stated above, the TTV of the first wafer W before being subjected to the finishing grinding processing may be calculated by using the thickness measuring unit110.

In the present exemplary embodiment, in the processing of a first sheet of combined wafer T1among the plurality of combined wafers T, the thickness of a first wafer W1before being subjected to the finishing grinding is first measured at multiple points thereof by the thickness measuring unit110, and film thickness distribution data D1as one thickness distribution is acquired, as shown inFIG.6A. The acquired film thickness distribution data D1is output to the controller130.

Subsequently, a rear surface W1bof the first wafer W1of the combined wafer T1is finely ground by the finishing grinding unit100.

In the finishing grinding of the first wafer W1in the combined wafer T1, a grinding amount in the surface of the first wafer W1is decided based on the film thickness distribution data D1such that the in-surface thickness of the first wafer W1becomes uniform, that is, the flatness of the first wafer W1detected from the film thickness distribution data D1is improved. Specifically, the finishing grinding amount is increased at a position where the thickness is found to be large in the surface of the first wafer W1, whereas the finishing grinding amount is decreased at a position where the thickness is found to be small.

Next, as shown inFIG.6B, the thickness of the combined wafer T1after being subjected to the finishing grounding is measured at multiple points thereof by the thickness measuring unit120, and film thickness distribution data DD1as a thickness distribution after the finishing grinding is acquired. The obtained film thickness distribution data DD1is output to the controller130.

Here, as the first wafer W1is finely ground based on the grinding amount decided based on the film thickness distribution data D1, it is desirable that the flatness of the first wafer W1upon the completion of the finishing grinding is improved, that is, the thickness of the first wafer W1is uniform in the surface thereof. However, depending on the wear of the finishing grinding whetstone, the parallelism between the chuck31and the finishing grinding whetstone, and other device characteristics, the flatness of the first wafer W1may not be improved as illustrated inFIG.6B.

As a resolution, in the processing according to the present exemplary embodiment, difference data a between the film thickness distribution data D1and the film thickness distribution data DD1is acquired as first difference data. The obtained difference data a is output to the controller130. Further, the difference data a is acquired based on the film thickness distribution data D1and DD1acquired at the same point in the surface of the wafer W.

The difference data a is a difference between the film thickness distribution data of the first wafer W before and after being subjected to the finishing grinding in the finishing grinding unit100. That is, tendency of deterioration of flatness due to the device characteristics in the finishing grinding unit100can be calculated based on the difference data a. In the processing according to the present exemplary embodiment, in the processing of a second sheet of combined wafer onwards (combined wafer Tn (n≥2)), the finishing grinding amount is decided based on the difference data a so as to offset the tendency of deterioration of flatness due to the device characteristics. Accordingly, in the processing of the second sheet of combined wafer T onwards, the flatness of the first wafer W can be appropriately improved.

In addition, the finishing grinding amount in the finishing grinding unit100is adjusted by adjusting the relative inclination of the chuck base32with respect to the finishing grinding whetstone by the inclination adjuster33, for example.

In the combined wafer T1from which the film thickness distribution data DD1has been acquired, the first wafer W1is re-ground based on the acquired difference data a, as shown inFIG.6C, to offset the tendency of deterioration of the flatness of the first wafer W1due to the device characteristics. This re-grinding of the first wafer W1is performed in the finishing grinding unit100. Further, when there is found no difference between the film thickness distribution data D1and the film thickness distribution data DD1, that is, when no problem is found in the device characteristics of the finishing grinding unit100, the re-grinding of the first wafer W1may be omitted.

Thereafter, the combined wafer T1upon the completion of the processing is transferred to the cassette Ct via the second cleaning unit70and the first cleaning unit60. Then, the processing on the second combined wafer T2is started.

In the processing of the combined wafer T2, the thickness of a first wafer W2before being subjected to the finishing grinding is measured at multiple points thereof by the thickness measuring unit110, and film thickness distribution data D2is acquired as one thickness distribution, as depicted inFIG.6D. The acquired film thickness distribution data D2is output to the controller130.

Here, for the first wafer W2, as a finishing grinding amount is determined based on a grinding amount decided based on difference data A, it is desirable that the flatness of the first wafer W2is improved, that is, the thickness of the first wafer W2becomes uniform in the surface thereof. However, as shown inFIG.6AandFIG.6D, when shape characteristics of a second wafer S1and a second wafer S2are different, the flatness of the first wafer W2may not be improved if the first wafer W1and the first wafer W2are ground under the same conditions. Specifically, as shown inFIG.7, when the second wafer Sn has a convex shape with a protruding center portion and the second wafer Sn+1has a concave shape with a recessed center portion, only an outer peripheral portion of the first wafer Wn+1 may be ground, leaving the center portion thereof not ground if the first wafer Wn and the first wafer Wn+1are ground under the same conditions.

As a resolution, in the processing according to the present exemplary embodiment, the difference data A between the film thickness distribution data D1and the film thickness distribution data D2is obtained as second difference data. The acquired difference data A is output to the controller130.

The difference data A is a difference in the film thickness distribution data between the first wafer W1and the first wafer W2before being subjected to the finishing grinding in the finishing grinding unit100. That is, tendency of deterioration of flatness caused by the shape characteristics of the second wafer S can be calculated based on the difference data A. In the processing according to the present exemplary embodiment, in the processing of the second sheet of combined wafer T2, the inclination of the chuck base32is adjusted based on the difference data A to offset the tendency of deterioration of flatness due to the shape characteristics, and, also, a finishing grinding amount in the surface of the first wafer W2is decided. Accordingly, in the processing of the combined wafer T2, the flatness of the first wafer W2can be appropriately improved.

As described above, in the combined wafer T2from which the film thickness distribution data D2has been acquired, a rear surface W2bof the first wafer W2is finely ground by the finishing grinding unit100. In the finishing grinding of the first wafer W2, correction of the inclination of the chuck base32is performed based on the difference data A in addition to the adjustment of the inclination of the chuck base32based on the difference data a described above, and a finishing grinding amount is decided. Accordingly, in the processing of the second sheet of combined wafer T2, the flatness of the first wafer W2may be appropriately improved.

Subsequently, for the combined wafer T2, the thickness of the first wafer W2after being subjected to the finishing grinding is measured at multiple points thereof by the thickness measuring unit120, and film thickness distribution data DD2as a thickness distribution upon the completion of the finishing grinding is obtained, as depicted inFIG.6E. The obtained film thickness distribution data DD2is output to the controller130.

Once the film thickness distribution data DD2is acquired, difference data b between the film thickness distribution data D2and the film thickness distribution data DD2is acquired as first difference data. The acquired difference data b is output to the controller130. Further, the difference data b is acquired based on the film thickness distribution data D2and DD2measured at the same point in the surface of the wafer W.

The difference data b is a difference between the film thickness distribution data of the first wafer W2before and after the finishing grinding in the finishing grinding unit100. The finishing grinding unit100repeatedly performs the finishing grinding of the first wafers W in the plurality of combined wafers T. As a result, the device characteristics due to, for example, wear of the finishing grinding whetstone change with a lapse of time. Further, the device characteristics may also change over time due to, for example, environmental factors (for example, atmosphere temperature, etc.) at the time when the finishing grinding is performed. In view of these, in the grinding processing according to the present exemplary embodiment, the inclination of the chuck base32is adjusted, following the trend of deterioration of flatness due to the device characteristics over time, to thereby decide the finishing grinding amount. Therefore, even in the processing of a third sheet of combined wafer T onwards, the flatness of the first wafer W can be appropriately improved.

The combined wafer T2from which the film thickness distribution data DD2has been acquired is transferred to the cassette Ct via the second cleaning unit70and the first cleaning unit60. Then, the third sheet of combined wafer T3is taken out from the cassette Ct, and the processing on this combined wafer T3is begun.

In the processing of the combined wafer T3, the thickness of a first wafer W3before being subjected to the finishing grinding is measured at multiple points thereof by the thickness measuring unit110, and film thickness distribution data D3is obtained as one thickness distribution, as illustrated inFIG.6F. The acquired film thickness distribution data D3is output to the controller130.

Further, in the processing of the combined wafer T3, difference data B between the film thickness distribution data D1and the film thickness distribution data D3is acquired as second difference data indicating shape characteristics of a second wafer S3. The obtained difference data B is output to the controller130. The difference data B may be a difference between the film thickness distribution data D2and the film thickness distribution data D3as long as the shape characteristics of the second wafer S3can be acquired.

In the combined wafer T3from which the film thickness distribution data D3has been acquired, a rear surface W3bof the first wafer W3is finely ground by the finishing grinding unit100. In the finishing grinding of the first wafer W3, the inclination of the chuck base32is adjusted based on the difference data b and the difference data B, and the finishing grinding amount is determined. Thus, in the processing of the third sheet of combined wafer T3, the flatness of the first wafer W3can be appropriately improved. Further, when no difference is found between the difference data a and the difference data b, that is, when no change is found in the device characteristics of the finishing grinding unit100, the inclination may be adjusted, that is, the finishing grinding amount may be decided based on the difference data a and the difference data B in the finishing grinding of the first wafer W3.

Next, as shown inFIG.6G, in the combined wafer T2, the thickness of the first wafer W3after being subjected to the finishing grinding is measured at multiple points thereof by the thickness measuring unit120, and film thickness distribution data DD3is acquired as a thickness distribution upon the completion of the finishing grinding. The obtained film thickness distribution data DD3is output to the controller130.

After the film thickness distribution data DD3is acquired, difference data c between the film thickness distribution data D3and the film thickness distribution data DD3is then acquired as first difference data. The obtained difference data c is output to the controller130. Further, the difference data c is acquired based on the film thickness distribution data D3and DD3acquired at the same point in the surface of the wafer W.

According to the above-described exemplary embodiment, the difference data A, B, . . . , which are differences in the shape characteristics of the second wafers S in the plurality of combined wafers T, are acquired based on the film thickness distribution data before being subjected to the finishing grinding obtained for each of the plurality of combined wafers T processed in the processing apparatus1. Since the finishing grinding amount of the first wafer W is determined by adjusting (correcting) the inclination of the chuck base32based on these difference data, it is possible to control the final thickness of the first wafer W uniformly. That is, the flatness of the first wafer W can be appropriately improved.

At this time, according to the present exemplary embodiment, the shape characteristics of the second wafer S can be acquired only by measuring the thickness of the first wafer W by the thickness measuring unit110and the thickness measuring unit120. That is, even when the total thickness of the combined wafer T and the thickness of the second wafer S cannot be measured because of the device layer D formed on the front surface Wa of the first wafer W, for example, the flatness of the first wafer W can be improved by appropriately acquiring the shape characteristics of the second wafer S.

Further, in the present exemplary embodiment, the difference data a as a device characteristic of the finishing grinding unit100is acquired based on the film thickness distribution data before and after the finishing grinding on the first sheet of combined wafer T1. Since the finishing grinding amount of the first wafer W is determined by adjusting (correcting) the inclination of the chuck base32based on the difference data a, the final thickness of the first wafer W can be uniformly controlled more properly. That is, the flatness of the first wafer W can be improved more appropriately.

In addition, in the present exemplary embodiment, the difference data b, c, . . . , which are device characteristics of the finishing grinding unit100, are obtained based on the film thickness distribution data before and after the finishing grinding on the second sheet of combined wafer onwards (combined wafer Tn). As a result, even if the device characteristics of the finishing grinding unit100change with a lapse of time due to various factors, the finishing grinding amount of the first wafer W can be decided by adjusting (correcting) the inclination of the chuck base32to follow the change of the device characteristics over time. Therefore, the flatness of the first wafer W can be improved more appropriately.

Here, in the finishing grinding of the second sheet of combined wafer onwards (combined wafer Tn), there is no need to perform re-grinding as in the case of the finishing grinding of the first combined wafer T1. This is because, during the finishing grinding of the first combined wafer T1, the TTV adjustment due to the device characteristics has already been performed based on the difference data A, so occurrence of TTV deterioration to such an extent that re-grinding is required is suppressed. In this way, since it is not necessary to perform re-grinding on the combined wafer T2onwards, the throughput regarding the finishing grinding of the first wafer W can be appropriately improved.

In addition, in the above-described exemplary embodiment, in the processing of the first sheet of combined wafer T1, the difference data a that is the device characteristic of the finishing grinding unit100is acquired. However, the difference data a may be acquired in advance by, for example, grinding a combined wafer T0as a dummy combined substrate. By acquiring the device characteristic in advance using the dummy substrate in this way, it is not necessary to acquire device characteristic in the processing of the first sheet of combined wafer T1in the cassette Ct. That is, since the above-described re-grinding need not be performed in the processing of the combined wafer T1, the throughput regarding the finishing grinding of the combined wafer T1can be improved.

Furthermore, in the above-described exemplary embodiment, the finishing grinding amount of the first wafer W is adjusted by inclining the chuck base32with the inclination adjuster33, to thereby improve the flatness of the first wafer W. However, the method of adjusting the finishing grinding amount is not limited thereto. By way of example, the inclination adjuster33may adjust the finishing grinding amount of the first wafer W by inclining the grinding whetstone instead. Moreover, even the inclination adjuster33may not be used as long as the finishing grinding amount of the first wafer W can be adjusted.

Additionally, in the above-described exemplary embodiment, the film thickness distribution data before and after the finishing grinding of the first wafer W1are acquired, and the flatness of the first wafer W1is adjusted based on the acquired film thickness distribution data. However, the adjustment of the flatness may be performed during the rough grinding or the intermediate grinding of the first wafer W1. That is, film thickness distribution data before and after the rough grinding or before and after the intermediate grinding are further acquired, and based on the obtained film thickness distribution data, the relative inclination of the chuck base32with respect to the grinding whetstone when performing the rough grinding or the intermediate grinding may be adjusted.

Moreover, the above exemplary embodiment has been described for the example where the thickness of the second substrate including the metal film cannot be measured due to the influence of the metal film(s) (device layer(s)) interposed between the first wafer W and the second wafer S. However, the technique of the present disclosure is not limited to being applied to the case where the combined wafer T has the metal film, but may be appropriately applied in any of various cases where the thickness of the second wafer S cannot be calculated properly.

It should be noted that the above-described exemplary embodiment is illustrative in all aspects and is not anyway limiting. The above-described exemplary embodiment may be omitted, replaced and modified in various ways without departing from the scope and the spirit of claims.

According to the exemplary embodiments, it is possible to improve the flatness of the first substrate appropriately in the combined substrate in which the first substrate and the second substrate are bonded to each other.