Substrate Processing Method and Substrate Processing System

Abstract

In the present invention, determining an optimum etching condition includes: acquiring training data that includes an etching quantity distribution in the radial direction of an etching object having undergone etching on a surface thereof under a plurality of different etching conditions; and optimizing, by using the least-squares method, so as to minimize a first residual distribution between a first target etching quantity distribution and a first etching quantity distribution predicted from the following formulae (1)-(6) using the training data, a first etching condition in the first etching quantity distribution. (1): ERscan(R)=ERref(R)×Ratioscan(R) (2): Ratioscan (R)=b0×exp(b1×T+b2)+C (3): b0=f(S,V) (4): b1=f(S,V) (5): b2=f(S,V) (6): T=(L-R) / V

Description

Technical Field

[0001] The present disclosure relates to a substrate processing method and a substrate processing system.

Background Art

[0002] Patent Document 1 discloses a substrate processing method including a grinding step of grinding the surface of a substrate, a measuring step of measuring the thickness of the ground substrate, a condition determination step of determining the processing conditions of a wet etching process performed on the substrate based on the measured thickness of the substrate, and a step of supplying a processing liquid to the ground substrate and performing a wet etching process based on the determined processing conditions.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technology according to the present disclosure appropriately controls the surface shape of an object to be etched after the etching process.

Means for Solving the Problems

[0005] One aspect of the present disclosure is a substrate processing method for processing a substrate, including determining optimal etching conditions, and based on the optimal etching conditions, rotating an etching target on the substrate and reciprocatingly moving an etching liquid supply unit in a radial direction through above the rotation center of the etching target while supplying an etching liquid from the etching liquid supply unit to the surface of the etching target to etch the surface. Determining the optimal etching conditions includes obtaining learning data including a radial etching amount distribution of the etching target when etching the surface of the etching target under a plurality of different etching conditions, and using the least squares method to optimize a first etching condition in the first etching amount distribution such that a first residual distribution between a first etching amount distribution predicted from the following formulas (1) to (6) and a first target etching amount distribution is minimized. ER scan (R)=ER ref (R)×Ratio scan (R) ···(1) Ratio scan (R)=b0×exp(b1×T+b2)+C ···(2) b0=f(S,V) ···(3) b1=f(S,V) ···(4) b2=f(S,V) ···(5) T=(L-R) / V ···(6) However, ER scan : The etching amount when the etching liquid supply unit reciprocates. ER ref : The etching amount when the etching liquid supply unit does not reciprocate. Ratio scan : The scan ratio. R: The position from the center of the etching target. T: The non-discharge time when the etching liquid is not supplied. C: A constant. S: The rotation speed when rotating the etching target. V: The scan speed when reciprocally moving the etching solution supply unit. L: The scan width when reciprocally moving the etching solution supply unit.

Effect of the Invention

[0006] According to the present disclosure, the surface shape of the object to be etched after the etching process can be appropriately controlled.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] In the manufacturing process of semiconductor devices, a semiconductor substrate (hereinafter referred to as "wafer") on which a plurality of devices such as electronic circuits are formed on the surface is ground and thinned, and further, the ground surface of the wafer is smoothed. The smoothing of the ground surface is performed by, for example, so-called spin etching in which an etching solution is supplied from above the ground surface of the wafer while rotating the wafer.

[0009] Patent Document 1 described above discloses that a wet etching process is performed on the ground wafer to remove the damage layer formed on the surface of the wafer by the grinding process. In the condition determination process described in Patent Document 1, based on the thickness of the wafer obtained in the measurement process, as conditions for the wet etching process, the operation of the nozzle for supplying the treatment liquid, the rotation speed of the wafer, the supply amount of the treatment liquid, the supply time of the treatment liquid, the type of the treatment liquid, etc. are determined.

[0010] However, when spin etching in which the treatment liquid is supplied while rotating the wafer is performed as in the method disclosed in Patent Document 1, it is difficult to perform precise etching control because the treatment liquid supplied to the wafer surface flows radially outward due to centrifugal force. More specifically, it is difficult to appropriately control the surface shape of the wafer after the etching process, particularly at the center of the wafer.

[0011] Therefore, it has been proposed to supply the etching solution from the nozzle to the surface of the wafer and etch the surface while rotating the wafer and reciprocatingly moving (scanning) the nozzle in the radial direction passing through the center of the wafer. Hereinafter, such etching may be referred to as "scan etching". In scan etching, while supplying the etching solution to the center of the wafer, a flow of the etching solution is generated on the surface of the wafer at the center portion to control the surface shape of the wafer.

[0012] Here, in order to control the surface shape of the wafer after the etching process, it is crucial to appropriately control the etching amount distribution (etching profile) in the wafer diameter direction. The control of the etching amount distribution is performed by adjusting the etching conditions (etching recipe) such as the rotation speed (number of revolutions) of the wafer, the scan speed and scan width in the reciprocating movement of the nozzle, so that the target etching amount distribution can be obtained.

[0013] However, conventionally, the control of the etching amount distribution is mainly performed in a so-called trial-and-error method in which an engineer predicts the variation of the etching amount distribution, sequentially acquires data regarding the etching amount distribution, and adjusts it to the target etching amount distribution. In such a case, the control of the etching amount distribution depends on the ability of the engineer, and individual differences may occur in the working time required for control and the degree of completion of control.

[0014] The technology according to the present disclosure appropriately controls the surface shape of the object to be etched after the etching process. Hereinafter, a wafer processing system as a substrate processing system according to the present embodiment and a wafer processing method as a substrate processing method will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0015] In the wafer processing system 1 according to the present embodiment described below, as shown in FIG. 1, processing is performed on a polymerized wafer T as a substrate in which a first wafer W and a second wafer S are joined. Hereinafter, in the first wafer W, the surface on the side joined to the second wafer S is referred to as the front surface Wa, and the surface on the side opposite to the front surface Wa is referred to as the back surface Wb. Similarly, in the second wafer S, the surface on the side joined to the first wafer W is referred to as the front surface Sa, and the surface on the side opposite to the front surface Sa is referred to as the back surface Sb.

[0016] The first wafer W is a semiconductor wafer such as a silicon substrate, and a device layer Dw including a plurality of devices is formed on the surface Wa side. Further, a bonding film Fw is formed on the device layer Dw, and the first wafer W is bonded to the second wafer S via the bonding film Fw. As the bonding film Fw, for example, an oxide film (THOX film, SiO2 film, TEOS film), SiC film, SiCN film, or an adhesive is used.

[0017] The second wafer S has, for example, the same configuration as the first wafer W, and a device layer Ds and a bonding film Fs are formed on the surface Sa. Note that the second wafer S does not necessarily have to be a device wafer on which the device layer Ds is formed, and may be, for example, a support wafer that supports the first wafer W. In such a case, the second wafer S functions as a protective material that protects the device layer Dw of the first wafer W.

[0018] As shown in FIG. 2, the wafer processing system 1 has a configuration in which a loading / unloading station 2 and a processing station 3 are integrally connected. In the loading / unloading station 2, for example, a cassette C capable of accommodating a plurality of polymer wafers T is loaded and unloaded to and from the outside. The processing station 3 is provided with various processing apparatuses that perform desired processing on the polymer wafer T.

[0019] The loading / unloading station 2 is provided with a cassette mounting table 10 on which a plurality of, for example, three cassettes C are mounted. Further, on the negative X-axis side of the cassette mounting table 10, a wafer transfer device 20 is provided adjacent to the cassette mounting table 10. The wafer transfer device 20 is configured to be movable on a transfer path 21 extending in the Y-axis direction. Further, the wafer transfer device 20 has, for example, two transfer arms 22, 22 that hold and transfer the polymer wafer T. Each transfer arm 22 is configured to be movable in the horizontal direction, vertical direction, around the horizontal axis, and around the vertical axis. Note that the configuration of the transfer arm 22 is not limited to this embodiment and can take any configuration. Then, the wafer transfer device 20 is configured to be able to transfer the polymer wafer T to the cassette C on the cassette mounting table 10 and a transition device 30 described later.

[0020] On the negative X-axis side of the wafer transfer device 20, adjacent to the wafer transfer device 20, a transition device 30 for transferring the stacked wafer T between the processing station 3 is provided in the loading / unloading station 2.

[0021] For example, three processing blocks B1 to B3 are provided in the processing station 3. The first processing block B1, the second processing block B2, and the third processing block B3 are arranged in this order from the positive X-axis side (the loading / unloading station 2 side) to the negative direction side.

[0022] An etching device 40, a thickness measuring device 41, and a wafer transfer device 50 are provided in the first processing block B1. The etching device 40 and the thickness measuring device 41 are arranged in a stacked manner. Note that the number and arrangement of the etching device 40 and the thickness measuring device 41 are not limited to this.

[0023] The etching device 40 etches the back surface Wb (grinding surface) of the first wafer W after grinding in the processing device 80 described later, further thins the first wafer W (stacked wafer T) after grinding, and smoothes the grinding surface by removing the grinding marks generated by the grinding process. The detailed configuration of the etching device 40 will be described later.

[0024] The thickness measuring device 41 includes a measuring unit (not shown) and a calculating unit (not shown) in one example. The measuring unit includes a sensor that measures the thickness of the first wafer W after etching at a plurality of points. The calculating unit obtains the thickness distribution of the first wafer W from the measurement results (thickness of the first wafer W) by the measuring unit, and further calculates the flatness (TTV: Total Thickness Variation) of the first wafer W. Note that the calculation of the thickness distribution and flatness of the first wafer W may be performed by the control device 90 described later instead of the calculating unit. In other words, a calculating unit (not shown) may be provided in the control device 90 described later. Note that the configuration of the thickness measuring device 41 is not limited to this and can be arbitrarily configured.

[0025] The wafer transfer device 50 is disposed on the negative X-axis side of the transition device 30. The wafer transfer device 50 has, for example, two transfer arms 51, 51 that hold and transfer the polymerized wafer T. Each transfer arm 51 is configured to be movable in the horizontal direction, vertical direction, around the horizontal axis, and around the vertical axis. And the wafer transfer device 50 is configured to be able to transfer the polymerized wafer T to the transition device 30, the etching device 40, the thickness measurement device 41, the cleaning device 60 described later, the thickness measurement device 61 described later, and the buffer device 62 described later.

[0026] In the second processing block B2, a cleaning device 60, a thickness measurement device 61, a buffer device 62, and a wafer transfer device 70 are provided. The cleaning device 60, the thickness measurement device 61, and the buffer device 62 are arranged in a stacked manner. Note that the number and arrangement of the cleaning device 60, the thickness measurement device 61, and the buffer device 62 are not limited to this.

[0027] The cleaning device 60 cleans the back surface Wb (grinding surface) of the first wafer W after grinding in the processing device 80 described later. For example, a brush is brought into contact with the back surface Wb to scrub and clean the back surface Wb. Note that, for cleaning the first wafer W, a pressurized cleaning liquid may be used. Also, the cleaning device 60 may be configured to be able to simultaneously clean the back surface Sb of the second wafer S when cleaning the first wafer W.

[0028] In one example, the thickness measurement device 61 includes a measurement unit (not shown) and a calculation unit (not shown). The measurement unit includes a sensor that measures the thickness of the first wafer W after grinding at a plurality of points. The calculation unit acquires the thickness distribution of the first wafer W from the measurement results (the thickness of the first wafer W) by the measurement unit, and further calculates the flatness (TTV) of the first wafer W. Note that the calculation of the thickness distribution and flatness of such a first wafer W may be performed by a control device 90 described later instead of the calculation unit. In other words, a calculation unit (not shown) may be provided in the control device 90 described later. Note that the configuration of the thickness measurement device 61 is not limited to this and can be arbitrarily configured.

[0029] The buffer device 62 temporarily holds the pre-process polymerization wafer T that is transferred from the first processing block B1 to the second processing block B2. The configuration of the buffer device 62 is arbitrary. Note that the buffer device 62 may have an alignment mechanism (not shown) that adjusts the center position of the polymerization wafer T with respect to the chuck 83 described later and / or the horizontal orientation of the polymerization wafer T.

[0030] The wafer transfer device 70 is disposed, for example, on the positive Y-axis side of the cleaning device 60, the thickness measurement device 61, and the buffer device 62. The wafer transfer device 70 has, for example, two transfer arms 71, 71 that adsorb and hold the polymerization wafer T by an adsorption holding surface (not shown) and transfer it. Each transfer arm 71 is supported by an articulated arm member 72 and is configured to be movable in the horizontal direction, the vertical direction, around the horizontal axis, and around the vertical axis. The wafer transfer device 70 is configured to be able to transfer the polymerization wafer T to the etching device 40, the thickness measurement device 41, the cleaning device 60, the thickness measurement device 61, the buffer device 62, and the processing device 80 described later.

[0031] The third processing block B3 is provided with a processing device 80. The processing device 80 grinds and thins the first wafer W and functions as a thinning device in the present disclosure.

[0032] The processing device 80 has a rotary table 81. The rotary table 81 is configured to be rotatable about a vertical rotation center line 82 by a rotation mechanism (not shown). Two chucks 83 for adsorbing and holding the polymerization wafer T are provided on the rotary table 81. The chucks 83 are evenly arranged on the same circumference as the rotary table 81. The two chucks 83 are movable to a delivery position A0 and a processing position A1 when the rotary table 81 rotates. Further, each of the two chucks 83 is configured to be rotatable about the vertical axis by a rotation mechanism (not shown).

[0033] At the delivery position A0, the polymerization wafer T is delivered. At the processing position A1, a grinding unit 84 is arranged, and the first wafer W is ground while the second wafer S is sucked and held by the chuck 83. The grinding unit 84 has a grinding part 85 provided with a grinding wheel (not shown) that is rotatable in an annular shape. Further, the grinding part 85 is configured to be movable in the vertical direction along the support column 86.

[0034] Note that the configuration of the processing apparatus 80 is not limited to this. For example, four chucks 83 may be provided on the rotary table 81, and the four chucks 83 may be configured to be movable between the delivery position of the polymerization wafer T, a rough grinding part (not shown) that performs rough grinding of the first wafer W, a semi-finishing grinding part (not shown) that performs semi-finishing grinding of the first wafer W, and a finish grinding part (not shown) that performs finish grinding of the first wafer W. Further, for example, the processing apparatus 80 may be provided with a thickness measuring device (not shown) that measures the thickness of the first wafer W after grinding at a plurality of points.

[0035] The above wafer processing system 1 is provided with a control device 90. The control device 90 is a computer including, for example, a CPU, a memory, etc., and has a program storage part (not shown). A program for controlling the processing of the polymerization wafer T in the wafer processing system 1 is stored in the program storage part. Note that the above program may have been recorded on a computer-readable storage medium H and installed from the storage medium H into the control device 90. Further, the storage medium H may be temporary or non-temporary.

[0036] Next, the configuration of the etching apparatus 40 described above will be explained. As shown in FIG. 3, the etching apparatus 40 has a wafer holding part 100 as a substrate holding part, a rotation mechanism 101, and an etching solution supply part 102.

[0037] The wafer holding part 100 holds the outer edge part of the polymerized wafer T at a plurality of points, in this embodiment, at three points. Note that the configuration of the wafer holding part 100 is not limited to the illustrated example. For example, the wafer holding part 100 may include a chuck that adsorbs and holds the polymerized wafer T from below. The rotation mechanism 101 rotates the polymerized wafer T (the first wafer W) held by the wafer holding part 100 about the vertical rotation center line 100a.

[0038] The etching solution supply part 102 has, as an example, a nozzle that supplies the etching solution E to the back surface Wb of the first wafer W held by the wafer holding part 100. The etching solution supply part 102 is provided above the wafer holding part 100 and is configured to be movable in the horizontal and vertical directions by the movement mechanism 103. In one example, the etching solution supply part 102 is configured to be reciprocally movable (scan movable) through the rotation center line 100a of the wafer holding part 100, that is, through the center part above the first wafer W as shown in FIG. 4. In the following description, one reciprocating movement of the etching solution supply part 102 is defined as one loop.

[0039] The etching solution E contains at least hydrofluoric acid, nitric acid, or a mixed acid in order to appropriately etch the silicon of the first wafer W that can be an etching target. Further, the etching solution E may contain phosphoric acid or sulfuric acid. Note that the etching target is not limited to the first wafer W. For example, it may be amorphous silicon. Further, the etching target of this embodiment is not limited to the back surface Wb of the first wafer W. For example, it can also be applied to the case of processing a wafer on which no processing by the processing apparatus 80 is performed. For example, when a film is formed on the back surface Wb, the film also becomes an etching target.

[0040] In the above etching apparatus 40, scan etching is performed in which the first wafer W is rotated and the etching solution is supplied from the etching solution supply part 102 to the back surface Wb of the first wafer W while the etching solution supply part 102 is reciprocally moved. In this embodiment, the etching amount distribution in the scan etching is predicted using a prediction model.

[0041] The prediction model of the etching amount distribution is for the case of performing scan etching under the etching conditions of a constant scan speed and symmetric scan as shown in FIG. 5. That is, the scan speed V when the etching liquid supply unit 102 is reciprocated is constant. Also, the scan width L of the etching liquid supply unit 102 is symmetric with respect to the center of the first wafer W, and the etching liquid supply unit 102 reciprocates between the scan one end “+L” and the scan other end “-L”. Hereinafter, this scan etching sequence may be referred to as a “constant speed scan sequence”, and the derived prediction model may be referred to as a “constant speed scan model”.

[0042] The constant speed scan model consists of the following formulas (1) to (6). ER scan (R)=ER ref (R)×Ratio scan (R) ···(1) Ratio scan (R)=b0×exp(b1×T+b2)+C ···(2) b0=f(S,V) ···(3) b1=f(S,V) ···(4) b2=f(S,V) ···(5) T=(L - R) / V ···(6) However,[[]] ER scan : The etching amount when the etching liquid supply unit 102 is reciprocated, ER ref : The etching amount when the etching liquid supply unit 102 is not reciprocated, Ratio scan : The scan ratio, R: The position from the center of the first wafer W, T: The non-discharge time when the etching liquid E is not supplied, C: A constant, S: The rotation speed when the first wafer W is rotated, V: The scan speed when the etching liquid supply unit 102 is reciprocated, L: The scan width when the etching liquid supply unit 102 is reciprocated.

[0043] The functions in each of the above formulas (3) to (5) are determined by analyzing learning data. For example, etching of a constant-speed scan sequence is performed on a dummy wafer under a plurality of different etching conditions to obtain learning data regarding the etching amount distribution. Specifically, the rotation speed S of the dummy wafer, the scan speed V when reciprocally moving the etching liquid supply unit 102, and the scan width L of the etching liquid supply unit 102 are changed to perform etching of the dummy wafer. At this time, the processing time for etching each dummy wafer is the same.

[0044] Etching of the dummy wafer under each etching condition is carried out for a predetermined desired time. Then, the etching amount distribution of the dummy wafer is acquired and output to the control device 90. Further, in the control device 90, the etching amount distribution under each output etching condition is compressed into an etching amount distribution (etching rate) per unit time or per unit loop, and each of the compressed etching amount distributions is stored as learning data.

[0045] FIG. 6 is an example of the acquired learning data. The rotation speed S of the dummy wafer was changed to S1 to S5. The scan speed V of the etching liquid supply unit 102 was changed to V1 to V3. The scan width L of the etching liquid supply unit 102 was changed to L1 to L4. In this way, the etching amount distribution was acquired for a plurality of, in this example, 60 types of etching conditions. In the graph of each learning data, the horizontal axis indicates the radial position from the center of the dummy wafer (0 (zero) on the horizontal axis) to one outer end, and the vertical axis indicates the etching amount (etching rate).

[0046] In the above description, the case where the learning data is obtained by etching a dummy wafer has been described as an example. However, the etching target when obtaining the learning data is not limited to the dummy wafer. Specifically, for example, the etching processing result of the first wafer W actually processed in the wafer processing system 1 may be stored as the above learning data. Further, for example, when a film is formed on the back surface Wb of the first wafer W, the film may be set as the etching target, and the etching processing result of the film may be stored as the above learning data.

[0047] Next, a detailed derivation method of the above-described constant-speed scan model will be described.

[0048] First, the present inventors grasped the etching amount distribution in scan etching. Then, it was found that when the etching liquid supply unit 102 is fixed and does not reciprocate (hereinafter, sometimes referred to as "no scan"), the etching amount distribution becomes the reference etching amount distribution of the etching amount distribution predicted by the constant-speed scan model.

[0049] FIG. 7 shows the etching amount distribution when the rotation speed S is S5, the scan speed V is V3, and the scan width L is changed from L1 to L4 among the learning data shown in FIG. 6 above. FIG. 7 also shows the reference etching amount distribution in the case of no scan. Referring to FIG. 7, in scan etching, only the etching amount distribution on the inner peripheral side starting from the scan width L fluctuates, and the etching amount distribution on the outer peripheral side does not fluctuate. In other words, in scan etching, only the etching amount distribution on the inner peripheral side of the scan width L fluctuates from the reference etching amount distribution in the case of no scan, and the etching amount distribution on the outer peripheral side of the scan width L shows the same behavior as the reference etching amount distribution. Therefore, the etching amount distribution in the case of no scan can be used as a reference.

[0050] Next, the inventors separated the variation in the etching amount distribution in scan etching. Specifically, from the concept that there is a reference etching amount distribution without scanning, the ratio of the etching amount distribution of scan etching to the reference etching amount distribution was defined as the scan ratio Ratio scan by the following formula (7). This scan ratio Ratio scan enables the quantitative separation of the effect of scan etching. FIG. 8 shows the scan ratio Ratio scan when the rotation speed S is S5, the scan speed V is changed from V1 to V3, and the scan width L is changed from L1 to L4. The horizontal axis in FIG. 8 indicates the radial position from the center (0 (zero) on the horizontal axis) of the first wafer W to one outer end, and the vertical axis indicates the scan ratio Ratio scan . Referring to FIG. 8, Starting from the scan width L the scan ratio Ratio scan on the inner peripheral side varies, and the variation in the etching amount distribution in the scan etching can be quantitatively separated and grasped. Then, from the following formula (7), the following formula (1) in the constant-speed scan model is derived. Ratio scan (R) = ER scan (R) / ER ref (R) ···(7) ER scan (R) = ER ref (R)×Ratio scan (R) ···(1) However, Ratio scan : Scan ratio, ER scan : Etching amount when the etching liquid supply unit 102 is reciprocally moved, ER ref : Etching amount when the etching liquid supply unit 102 is not reciprocally moved.

[0051] Further, the non-discharge time T was defined by the following formula (6). The non-discharge time T is the time during which the etching solution E is not supplied to the inner peripheral side due to the movement of the etching solution supply unit 102. During this non-discharge time T, the etching amount decreases. FIG. 9 shows the non-discharge time T when the rotational speed S is S5, the scan speed V is changed from V1 to V3, and the scan width L is changed from L1 to L4. The horizontal axis in FIG. 9 indicates the radial position from the center (0 (zero) on the horizontal axis) of the first wafer W to one outer end, and the vertical axis indicates the non-discharge time T. Referring to FIG. 9, Starting from the scan width L it is possible to grasp the variation of the non-discharge time T on the inner peripheral side. T = (L - R) / V ···(6) However, T: Non-discharge time during which the etching solution E is not supplied, V: Scan speed when reciprocally moving the etching solution supply unit 102, L: Scan width when reciprocally moving the etching solution supply unit 102.

[0052] Next, the inventors examined the relationship between the scan ratio Ratio scan and the non-discharge time T. FIG. 10 shows the relationship between the scan ratio Ratio scan and the non-discharge time T when the rotational speed S is S5 and the scan speed V is changed from V1 to V3. The horizontal axis in FIG. 10 indicates the non-discharge time T, and the vertical axis indicates the scan ratio Ratio scan . Referring to FIG. 10, the scan ratio Ratio scan decreases exponentially with respect to the non-discharge time T and can be defined by the decay curve model of the following formula (2). This decay curve model is also suitable for explaining the behavior of the actual physical phenomenon that the etching amount decreases as the time during which the etching solution E is not supplied becomes longer. Ratio scan (R) = b0 × exp(b1 × T + b2) + C ···(2) However, b0: Scale (intercept), b1: Decay rate (slope), b2: Decay delay value, C: Asymptote.

[0053] The above b0 is the scale (intercept) of the attenuation curve, and b1 is the attenuation rate (slope) of the attenuation curve. b2 is the attenuation delay value of the attenuation curve. For example, b2 is used when the amount of the etching solution E is large and the residual liquid on the first wafer W is large, and the influence such as the attenuation not occurring immediately is significant. C is the asymptote of the attenuation curve. For example, when C does not exist, the scan ratio Ratio scan mathematically approaches 0 (zero). However, in reality, once the etching solution E is supplied, the first wafer W is always etched, so the scan ratio Ratio scan will not become 0 (zero). C is a correction term for correcting this phenomenon. Also, C can be determined, for example, after once analyzing with the above formula (2), if C < 0, then set C = 0, and if C > 0, then leave C as it is.

[0054] In addition, when b2 and C are determined to be practically unnecessary, it is possible to omit them by setting b2 = 0 and C = 0.

[0055] Also, the scale b0, the attenuation rate b 1、 and the attenuation delay value b2 depend on the rotation speed S and the scan speed V, and can be defined by the following formulas (3) to (5) respectively. b0 = f(S, V) ···(3) b1 = f(S, V) ···(4) b2 = f(S, V) ···(5) However, S: The rotation speed when rotating the first wafer W, V: The scan speed when reciprocally moving the etching solution supply unit 102.

[0056] Here, in FIG. 10, the thick line is the measured value obtained by experiment, and the thin line is the calculated value calculated by the above formula (2) of the constant speed scan model. The measured value and the calculated value are substantially in agreement, and it is confirmed that the attenuation curve model of the above formula (2) is appropriate.

[0057] From the above, a constant-speed scan model (prediction model of etching amount distribution) consisting of the following formulas (1) to (6) is derived. ER scan (R)=ER ref (R)×Ratio scan (R) ···(1) Ratio scan (R)=b0×exp(b1×T+b2)+C ···(2) b0=f(S,V) ···(3) b1=f(S,V) ···(4) b2=f(S,V) ···(5) T=(L-R) / V ···(6)

[0058] Figure 11 is a graph comparing the measured values of the etching amount distribution obtained by experiments (thick line in Figure 11) with the calculated values of the etching amount distribution calculated from the constant-speed scan model (thin line in Figure 11). The rotation speed S was changed from S1 to S4, the scan speed V was changed from V1 to V3, and the scan width L was changed from L1 to L4. The measured values and the calculated values are substantially in agreement, and it was confirmed that the constant-speed scan model of the above formulas (1) to (6) is appropriate.

[0059] Next, the wafer processing performed using the wafer processing system 1 configured as described above will be described. In this embodiment, a polymerized wafer T is formed in an external bonding device (not shown) of the wafer processing system 1 in advance. Also, a range of 0.5 mm to 3 mm in the radial direction from the outer end of the first wafer W, for example, the peripheral portion of the first wafer W, may be removed in advance.

[0060] First, a cassette C containing a plurality of polymerized wafers T is placed on the cassette mounting table 10 of the loading / unloading station 2. Next, the polymerized wafer T in the cassette C is taken out by the wafer transfer device 20 and transferred to the transition device 30. The polymerized wafer T transferred to the transition device 30 is transferred to the buffer device 62 by the wafer transfer device 50. Note that in the buffer device 62, the center position of the polymerized wafer T with respect to the chuck 83 and / or the horizontal direction of the polymerized wafer T may be adjusted.

[0061] Next, the polymerized wafer T is transported to the processing device 80 by the wafer transfer device 70 and delivered to the chuck 83 at the delivery position A0. At the chuck 83, the back surface Sb of the second wafer S is adsorbed and held. Next, the chuck 83 is moved to the processing position A1, and the back surface Wb of the first wafer W is ground by the grinding unit 84. By such grinding treatment, the thickness of the first wafer W (polymerized wafer T) is reduced to a desired grinding target thickness (step S1 in FIG. 12).

[0062] Next, the polymerized wafer T is transported to the thickness measuring device 61 by the wafer transfer device 70. At the thickness measuring device 61, the thickness distribution of the first wafer W after grinding is obtained by measuring the thickness of the first wafer W (polymerized wafer T) after grinding at a plurality of points, and further the flatness of the first wafer W is calculated (step S2 in FIG. 12). The calculated thickness distribution and flatness of the first wafer W are output to, for example, the control device 90. In addition, when the processing device 80 is provided with a thickness measuring device, the thickness of the first wafer W after grinding may be measured by the thickness measuring device of the processing device 80.

[0063] The control device 90 determines the optimum etching conditions in the subsequent etching process from the output thickness distribution and flatness of the first wafer W (step S3 in FIG. 12). The detailed method for determining the optimum etching conditions in the control device 90 will be described later.

[0064] The measured thickness of the polymerized wafer T of the first wafer W is then transported to the cleaning device 60 by the wafer transport device 70 or the wafer transport device 50. In the cleaning device 60, the back surface Wb, which is the ground surface of the first wafer W after grinding, is cleaned (step S4 in FIG. 12). Further, in the cleaning device 60, the back surface Sb of the second wafer S may be cleaned as described above. When measuring the thickness after grinding with the thickness measuring device 61 as in the present embodiment, the order of step S2 and step S3 and step S4 may be reversed. That is, after cleaning the back surface Wb of the first wafer W with the cleaning device 60, the thickness of the first wafer W may be measured with the thickness measuring device 61, and the optimum etching conditions in the etching process may be determined.

[0065] Next, the polymerized wafer T is transported to the etching device 40 by the wafer transport device 50. In the etching device 40, the back surface Wb, which is the ground surface of the first wafer W, is etched with the etching solution E under the optimum etching conditions (step S5 in FIG. 12).

[0066] When etching the first wafer W, first, the wafer holding portion 100 (the first wafer W) is rotated about the vertical rotation center line 100a, and the supply (discharge) of the etching solution E from the etching solution supply portion 102 is started to start etching the back surface Wb.

[0067] Furthermore, when etching the first wafer W, while continuing to supply the etching solution E from the etching solution supply portion 102, as shown in FIG. 4, the etching solution supply portion 102 is reciprocally moved (scanned) with the rotation center line 100a passing through the rotation center of the first wafer W, that is, with the rotation center line 100a as an intermediate point above the rotation center of the first wafer W. Details of the method for determining etching conditions such as the rotation speed of the first wafer W, the scan speed when reciprocally moving the etching solution supply portion 102, and the scan width of the etching solution supply portion 102 will be described later.

[0068] When the desired etching amount is obtained on the first wafer W, the supply of the etching solution E from the etching solution supply unit 102 is stopped, the back surface Wb of the first wafer W is rinsed with pure water, and then spin-dried. Thereafter, the rotation of the wafer holding unit 100 (the first wafer W) is stopped, and the etching of the first wafer W is completed.

[0069] Here, the optimum etching conditions for the first wafer W are determined based on the thickness distribution and flatness of the first wafer W after grinding as described above. Specifically, the optimum etching conditions are determined based on the difference between the actually measured values of the thickness distribution and flatness of the first wafer W in the thickness measuring device 61 and the thickness distribution and flatness in the target surface shape (hereinafter referred to as the "target shape") of the first wafer W after etching. In step S5, by etching the first wafer W under the optimum etching conditions, the difference between the actually measured value and the target value of the thickness of the first wafer W is removed by etching, and the surface of the first wafer W is processed into the target shape. According to this embodiment, the target surface shape of the first wafer W can be appropriately obtained regardless of the surface shape of the first wafer W after grinding.

[0070] Next, the polymerized wafer T is transported by the wafer transport device 50 to the thickness measuring device 41. In the thickness measuring device 41, the thickness distribution after etching of the first wafer W is obtained by measuring the thickness of the first wafer W (polymerized wafer T) after etching at a plurality of points, and further the flatness of the first wafer W is calculated (step S6 in FIG. 12). The calculated thickness distribution and flatness of the first wafer W are output to, for example, the control device 90, and as an example, are used for the processing of other polymerized wafers T to be processed in the wafer processing system 1 next. When measuring the thickness of the first wafer W after grinding with the thickness measuring device of the processing device 80, the thickness of the first wafer W after etching may be measured in the thickness measuring device 61.

[0071] Thereafter, the polymerized wafer T that has been subjected to all the processes is transported to the cassette C on the cassette mounting table 10 via the transition device 30. Thus, a series of wafer processes in the wafer processing system 1 is completed.

[0072] Next, a detailed method for determining the above-described optimum etching conditions (step S3 in FIG. 12) will be described.

[0073] First, when determining the optimum etching conditions, prior to the treatment of the polymerization wafer T in the wafer processing system 1, learning data is acquired (step S3-1 in FIG. 13). A prediction model of the etching amount distribution is derived from the learning data (step S3-2 in FIG. 13).

[0074] In step S3-1, as described above, for example, etching of a constant-speed scan sequence is performed on a dummy wafer, and learning data regarding the etching amount distribution shown in FIG. 6 is acquired.

[0075] In step S3-2, as described above, a prediction model of the etching amount distribution, that is, a constant-speed scan model, which consists of the following formulas (1) to (6), is derived. At this time, the functions in each of the following formulas (3) to (5) are determined by analyzing the learning data acquired in step S3-1. ER scan (R) = ER ref (R) × Ratio scan (R) ···(1) Ratio scan (R) = b0 × exp(b1 × T + b2) + C ···(2) b0 = f(S, V) ···(3) b1 = f(S, V) ···(4) b2 = f(S, V) ···(5) T = (L - R) / V ···(6) However, ER scan : The etching amount when the etching liquid supply unit 102 is reciprocally moved, ER ref : The etching amount when the etching liquid supply unit 102 is not reciprocally moved, Ratio scan : The scan ratio, R: The position from the center of the first wafer W, T: Non-discharge time when etching solution E is not supplied C: Constant S: Rotation speed when rotating the first wafer W V: Scan speed when reciprocating the etching solution supply unit 102 L: Scan width when reciprocating the etching solution supply unit 102

[0076] Here, FIG. 14 is a graph showing the etching amount distribution for each when performing steps S3-3 to S3-8 described later in order to determine the optimum etching conditions. The horizontal axis of FIG. 14 indicates the radial position from the center (0 (zero) on the horizontal axis) of the first wafer W to one outer end, and the vertical axis indicates the etching amount (etching rate).

[0077] In parallel with steps S3-1 and S3-2, the first target etching amount distribution in the etching process of step S5 above is acquired (step S3-3 in FIG. 13). The first target etching amount distribution is acquired based on the thickness distribution (hereinafter referred to as the "target thickness distribution") in the target shape of the first wafer W after etching and the thickness distribution (hereinafter referred to as the "measured thickness distribution") in the surface shape of the first wafer W after grinding acquired in step S2 above. The first target etching amount distribution can be acquired, for example, by calculating the difference between the target thickness distribution and the measured thickness distribution of the first wafer W. This first target etching amount distribution is shown by the solid line in FIG. 14. Also, in this example, the first target etching amount distribution is flat within the wafer surface.

[0078] Next, the first etching condition in the first etching amount distribution is optimized using the least squares method so that the first residual distribution between the first etching amount distribution calculated using the constant speed scan model of step S3-2 and the first target etching amount distribution obtained in step S3-3 is minimized (step S3-4 in FIG. 13). The first etching condition to be optimized includes the rotation speed S of the first wafer W, the scan speed V of the etching liquid supply unit 102, and the scan width L of the etching liquid supply unit 102. Note that the first etching amount distribution corresponding to the optimized first etching condition is indicated by a one-dot chain line in FIG. 14.

[0079] Next, the first residual distribution in step S3-4 is set as the second target etching amount distribution (step S3-5 in FIG. 13).

[0080] Next, the second etching condition in the second etching amount distribution is optimized using the least squares method so that the second residual distribution between the second etching amount distribution calculated using the constant speed scan model of step S3-2 and the second target etching amount distribution set in step S3-5 is minimized (step S3-6 in FIG. 13). The second etching condition to be optimized includes the rotation speed S of the first wafer W, the scan speed V and the scan width L of the etching liquid supply unit 102. Note that the second etching amount distribution corresponding to the optimized second etching condition is indicated by a two-dot chain line in FIG. 14.

[0081] Next, the first etching amount distribution and the second etching amount distribution are connected according to the time ratio (loop count ratio) (step S3-7 in FIG. 13). The time ratio (loop count ratio) is the ratio between the time (loop count) for performing the constant speed scan sequence 1 under the first etching condition and the time (loop count) for performing the constant speed scan sequence 2 under the second etching condition. The connected etching amount distribution (hereinafter referred to as "connected etching amount distribution") is indicated by a dotted line in FIG. 14.

[0082] In this example, the connected etching amount distribution substantially coincides with the first target etching amount distribution. Therefore, the etching conditions corresponding to the connected etching amount distribution are determined as the optimal etching conditions. Specifically, the first etching condition and the second etching condition are combined according to the time ratio to determine the optimal etching conditions (step S3-8 in FIG. 13).

[0083] Thereafter, in step S4, after the back surface Wb of the first wafer W is cleaned, in step S5, the back surface Wb of the first wafer W is etched under the optimal etching conditions. That is, in the etching apparatus 40, the polymerization wafer T (the first wafer W) is rotated at the rotation speed determined by the optimal etching conditions, and while moving the etching liquid supply unit 102 at the determined scan speed and scan width, the etching liquid E is supplied to the first wafer W.

[0084] The determination of the optimal etching conditions according to this embodiment and the etching process for the first wafer W based on the optimal etching conditions are performed as described above.

[0085] According to the above embodiment, the etching amount distribution can be appropriately predicted using the constant speed scan model composed of the above formulas (1) to (6). Therefore, when controlling the etching amount distribution, it is possible to suppress the working time required for control and improve the degree of completion of control without depending on the ability of engineers as in the prior art. In addition, it is possible to suppress the variation in man-hours when determining the optimal etching conditions in step S3 and improve the accuracy of the optimal etching conditions.

[0086] In step S3, the optimal etching conditions are determined using the least squares method. Subsequently, in step S5, the first wafer W can be etched under the optimal etching conditions. As a result, the etching amount distribution in the etching process can be made closer to the first target etching amount distribution, and thus, the surface shape of the first wafer W after etching can be made into the target shape. In other words, the optimal etching conditions can be determined from indefinite etching conditions, and the surface shape of the first wafer W after etching can be appropriately controlled.

[0087] When the inventors actually performed simulations, in any of the cases where the first target etching amount distribution was V-shaped, A-shaped, M-shaped, or W-shaped, the variation in the thickness distribution of the first wafer W after etching could be kept within the allowable range. Also, the flatness (TTV) of the first wafer W after etching was improved compared to the prior art. The V-shaped distribution is a distribution that has a substantially V-shaped in a graph with the horizontal axis representing the wafer position and the vertical axis representing the etching amount, where the etching amount at the center of the first wafer W is smaller than the etching amounts at both ends. The A-shaped distribution is a distribution that has a substantially A-shaped in the above graph, where the etching amount at the center of the first wafer W is larger than the etching amounts at both ends and has a shape opposite to the V-shaped distribution. The M-shaped distribution is a distribution that has a shape formed by arranging two A-shaped distributions with the center of the first wafer W in between in the above graph and has a substantially M-shaped as a whole. The W-shaped distribution is a distribution that has a shape formed by arranging two V-shaped distributions with the center of the first wafer W in between in the above graph and has a substantially W-shaped as a whole.

[0088] Also, since steps S1 to S6 are performed for each stacked wafer T, even if the surface shape before etching (after grinding in this embodiment) is different for each wafer, the surface shape of the first wafer W after etching can be controlled for each wafer to the target shape.

[0089] In the above embodiment, the optimization of the etching conditions using the least squares method was performed twice in steps S3-4 and S3-6, but the number of times of this optimization is not limited to this.

[0090] For example, the optimization calculation by the least squares method may be performed once. For example, if as a result of optimizing the first etching condition in step S3-4, the first etching amount distribution corresponding to the first etching condition substantially coincides with the first target etching amount distribution, the first etching condition may be determined as the optimal etching condition. In such a case, steps S3-5 to S3-8 can be omitted.

[0091] For example, the optimization calculation by the least squares method may be performed three or more times. For example, if the combined etching amount distribution in step S3-8 does not substantially coincide with the first target etching amount distribution, the third residual distribution between this combined etching amount distribution and the first target etching amount distribution is set as the third target etching amount distribution. Then, steps S3-6 to S3-8 are performed to substantially match the combined etching amount distribution and the first target etching amount distribution. In this way, the residual distribution between the combined etching amount distribution and the first target etching amount distribution is sequentially reduced, and the optimization calculation by the least squares method is repeatedly performed until the combined etching amount distribution and the first target etching amount distribution substantially coincide. Then, the etching conditions at the time when the combined etching amount distribution and the first target etching amount distribution substantially coincide are combined and determined as the optimal etching conditions.

[0092] In the above embodiments, in the polymer wafer T in which the first wafer W and the second wafer S are bonded, the case of performing various processes on the back surface Wb of the first wafer W has been described as an example, but the processing target is not limited to this. For example, a thinning process or an etching process may be performed on a single wafer. The processing target may be a film formed on the surface of the wafer, such as an oxide film or a titanium nitride film. In such a case, the etching liquid supply unit 102 in the etching apparatus 40 may be configured to be arbitrarily switchable to supply different types of etching liquid E according to the etching target. Further, for example, when the film formed on the wafer surface is the etching target, the etching processing result of the film is the above Learning dataIt may be configured to be memorized. In the thickness measurement device 61, the thickness of the film is measured. Further, when a protective tape is attached to the device surface of the wafer, a thinning process or an etching process may be performed on the surface opposite to the protective tape. Furthermore, a thinning process or an etching process may be performed on a wafer that is cut out from an ingot by a wire saw or the like and lapped. Regardless of the object to be processed, the etching process can be performed under the optimum etching conditions of the above-described embodiment.

[0093] Also, for example, when a film is formed on the back surface Wb of the first wafer, the film may be an etching target. In such a case, for example, the thickness measurement device 61 measures the thickness of the film. In step S2, instead of the thickness of the first wafer W, the thickness of the film is measured, and further, the film thickness distribution and the film flatness are calculated. Then, in step S3, based on the calculated film thickness distribution and flatness, the optimum etching conditions are determined.

[0094] The wafer processing system 1 includes various devices other than the etching device 40, but the device configuration to which the present disclosure is applied is not limited to this. For example, the processing device 80 which is a thinning device may be omitted. In such a case, the etching target is not limited to the wafer after the thinning process. Also, for example, the technology of the present disclosure can be applied even when etching a wafer in a single etching device.

[0095] In the above embodiment, the first wafer W is thinned by the processing device 80, but the thinning method is not limited to this. For example, the thinning process of the first wafer W includes polishing the back surface Wb of the first wafer W. Alternatively, for example, it may be thinned by separation based on a modified layer (not shown) formed by laser processing inside the first wafer W. In such a case, instead of the processing device 80, a laser processing device (not shown) for forming the modified layer (not shown) is provided in the wafer processing system 1.

[0096] The embodiments disclosed this time should be considered illustrative in all respects and not restrictive. The above embodiments may be omitted, substituted, or changed in various forms without departing from the scope and gist of the appended claims.

Explanation of Reference Numerals

[0097] 1 Wafer processing system 40 Etching apparatus 90 Control apparatus 102 Etching solution supply unit E Etching solution T Polymerized wafer W First wafer S Second wafer

Claims

1. A substrate processing method for processing a substrate, comprising: determining optimal etching conditions; rotating an etching target on the substrate based on the optimal etching conditions, and supplying an etching liquid from an etching liquid supply unit to the surface of the etching target while reciprocating the etching liquid supply unit in a radial direction passing above the rotation center of the etching target to etch the surface; Determining the optimal etching conditions includes: acquiring learning data including a radial etching amount distribution of the etching target when etching the surface of the etching target under a plurality of different etching conditions; optimizing a first etching condition in the first etching amount distribution by using the least squares method so that a first residual distribution between a first etching amount distribution predicted from the following formulas (1) to (6) using the learning data and a first target etching amount distribution is minimized. A substrate processing method, comprising: ER ｓｃａｎ (R) = ER ｒｅｆ (R) × Ratio ｓｃａｎ (R) ··· (1) Ratio ｓｃａｎ (R) = b ０ × exp(b １ × T + b ２ ) + C... (2) b ０ = f(S, V) ... (3) b １ = f(S, V) ... (4) b ２ = f(S, V) ... (5) T = (L - R) / V... (6) However, ER ｓｃａｎ : Etching amount when the etching solution supply unit is reciprocated, ER ｒｅｆ : Etching amount when the etching solution supply unit is not reciprocally moved, Ratio ｓｃａｎ : Scanning ratio, R: Position from the center of the etching target T: Non-discharge time when the etching liquid is not supplied C: Constant S: Rotation speed when rotating the etching target V: Scan speed when reciprocating the etching liquid supply unit L: Scan width when reciprocating the etching liquid supply unit

2. The substrate processing method according to claim 1, wherein the optimal etching conditions include the rotation speed, the scan speed, and the scan width.

3. setting the first residual distribution to a second target etching amount distribution; optimizing a second etching condition in the second etching amount distribution by using the least squares method so that a second residual distribution between a second etching amount distribution predicted from the following formulas (1) to (6) using the learning data and the second target etching amount distribution is minimized; combining the optimized first etching condition and the optimized second etching condition according to a time ratio to determine the optimal etching condition. The substrate processing method according to claim 1 or 2, comprising:

4. The substrate processing method according to claim 1 or 2, wherein each function of the above formulas (3) to (5) is determined based on an analysis of the learning data.

5. Before etching the surface of the object to be etched, measuring the thickness of the object to be etched to obtain the thickness distribution in the radial direction of the object to be etched; Predicting the first etching amount distribution based on the obtained thickness distribution of the object to be etched, the substrate processing method according to claim 1 or 2, comprising:

6. Before etching the surface of the object to be etched, measuring the thickness of the object to be etched to obtain the thickness distribution in the radial direction of the object to be etched, The first target etching amount distribution is obtained based on the obtained thickness distribution of the object to be etched and the target thickness distribution of the object to be etched, the substrate processing method according to claim 1 or 2.

7. Thinning the substrate before measuring the thickness of the object to be etched, the substrate processing method according to claim 5.

8. A substrate processing system for processing a substrate, An etching apparatus that rotates the object to be etched on the substrate and supplies etching liquid from the etching liquid supply unit to the surface of the object to be etched to etch the surface while reciprocating in the radial direction through above the rotation center of the object to be etched; A control device that controls the etching of the surface of the object to be etched in the etching apparatus based on the optimum etching conditions, The control device, Obtaining learning data including the etching amount distribution in the radial direction of the object to be etched when etching the surface of the object to be etched under a plurality of different etching conditions; Optimizing the first etching condition in the first etching amount distribution by using the least squares method so that the first residual distribution between the first etching amount distribution predicted from the following formulas (1) to (6) and the first target etching amount distribution is minimized, the substrate processing system that executes. ER ｓｃａｎ (R) = ER ｒｅｆ (R) × Ratio ｓｃａｎ (R) ··· (1) Ratio ｓｃａｎ (R) = b ０ × exp(b １ × T + b ２ ) + C... (2) b ０ = f(S, V) ... (3) b １ = f(S, V) ... (4) b ２ = f(S, V) ... (5) T = (L - R) / V... (6) However, ER ｓｃａｎ : Etching amount when the etching solution supply unit is reciprocated, ER ｒｅｆ : Etching amount when the etching solution supply unit is not reciprocated, Ratio ｓｃａｎ : Scanning ratio, R: The position from the center of the object to be etched; T: The non-discharge time when the etching liquid is not supplied; C: A constant; S: The rotation speed when rotating the object to be etched; V: The scan speed when reciprocating the etching liquid supply unit; L: The scan width when reciprocating the etching liquid supply unit.

9. The substrate processing system according to claim 8, wherein the optimum etching conditions include the rotation speed, the scan speed, and the scan width.

10. The control device sets the first residual distribution to a second target etching amount distribution, using the learning data, the second etching amount distribution predicted from the following formulas (1) to (6) and the second target etching amount distribution, and using the least squares method to optimize the second etching conditions in the second etching amount distribution so that the second residual distribution is minimized, combining the optimized first etching conditions and the optimized second etching conditions according to a time ratio to determine the optimum etching conditions, the substrate processing system according to claim 8 or 9.

11. The control device determines each function of the above formulas (3) to (5) by analyzing the learning data, the substrate processing system according to claim 8 or 9.

12. having a thickness measurement device for measuring the thickness of the etching target before etching, The control device predicts the first etching amount distribution based on the thickness distribution of the etching target obtained from the thickness of the etching target measured by the thickness measurement device, the substrate processing system according to claim 8 or 9.

13. having a thickness measurement device for measuring the thickness of the etching target before etching, The control device obtains the first target etching amount distribution based on the thickness distribution of the etching target obtained from the thickness of the etching target measured by the thickness measurement device and the target thickness distribution of the etching target, the substrate processing system according to claim 8 or 9.

14. having a thinning device for thinning the substrate, The thickness measurement device measures the thickness of the etching target in the substrate after thinning, the substrate processing system according to claim 12.

Images