Substrate processing method and substrate processing system

Abstract

This substrate processing method includes: forming, on a second surface of a first substrate having a first surface on which a laminated film including a device layer is formed and the second surface that is a surface opposite to the first surface, a coating film that generates stress for deforming the first substrate such that the first substrate approximates a predetermined target shape; and bonding the first surface of the first substrate and a surface of a second substrate to form a stacked substrate. The device layer includes at least a part of a NAND memory cell array.

Description

Substrate Processing Method and Substrate Processing System 【0001】 The present disclosure relates to a substrate processing method and a substrate processing system. 【0002】 Patent Document 1 discloses modifying the shape of a wafer by forming an actuator film on a first surface of the wafer and generating stress in the actuator film. 【0003】 Japanese Patent Application Laid-Open No. 2024-530861 【0004】 The technology according to the present disclosure appropriately joins a first substrate having a device layer including at least a part of a NAND memory cell array to a second substrate. 【0005】 One aspect of the present disclosure is a substrate processing method, in a first substrate having a first surface on which a laminated film including a device layer is formed and a second surface opposite to the first surface, forming a coating film that generates a stress for deforming the first substrate so that the first substrate approximates a predetermined target shape with respect to the second surface, and joining the first surface of the first substrate and the surface of the second substrate to form a polymerized substrate, wherein the device layer includes at least a part of a NAND memory cell array. 【0006】 According to the present disclosure, a first substrate having a device layer including at least a part of a NAND memory cell array can be appropriately joined to a second substrate. 【0007】 It is a flowchart showing the main steps of wafer processing. It is an explanatory diagram showing a state of joining a first wafer and a second wafer. It is an explanatory diagram showing a state of irradiating a laser beam on a laser absorption layer. It is an explanatory diagram showing a state of separating the first wafer and the second wafer. It is a flowchart showing the main steps for forming a coating film on the second surface of the first wafer. It is a plan view schematically showing a configuration example of a wafer processing system. It is a plan view schematically showing a configuration example of a laser processing apparatus. It is a side view schematically showing a configuration example of a laser processing apparatus. 【0008】The substrate processing method according to this embodiment will be described below with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant explanations will be omitted. 【0009】 In the substrate processing method of this embodiment, first, a first wafer W is prepared as the first substrate (St1 in Figure 1), and a second wafer S is prepared as the second substrate (St2 in Figure 1). The preparation of the first wafer W and the second wafer S may be carried out in parallel. Hereinafter, as shown in Figure 2, on the first wafer W, the side that is joined to the second wafer S is called the first surface Wa, and the side opposite to the first surface Wa is called the second surface Wb. Similarly, on the second wafer S, the side that is joined to the first wafer W is called the first surface Sa, and the side opposite to the first surface Sa is called the second surface Sb. 【0010】 The first wafer W prepared in St1 is a semiconductor wafer such as a silicon substrate. In one embodiment, the first wafer W has a substantially disc shape. In St1, a laminated film is formed on the first surface Wa of the first wafer W, in which multiple films are stacked, as shown in Figure 2(a). 【0011】 The multilayer film includes, in order from the first surface Wa side, a laser absorption layer P, a device layer Dw, and a surface film Fw. These laser absorption layer P, device layer Dw, and surface film Fw are formed on the first surface Wa of the first wafer W by processes including, for example, CVD (Chemical Vapor Deposition) in a film deposition apparatus (not shown) or RIE (Reactive Ion Etching) in an etching apparatus (not shown). The multilayer film may include a wiring layer containing a conductive material that constitutes a signal network or a power supply network. 【0012】 The laser absorption layer P is not particularly limited and can be any material that absorbs the laser light L described later. For example, when the wavelength of the laser light L is 8.9 μm to 11 μm, the laser absorption layer P may be, for example, an oxide film (SiO ２It is composed of one or more of the following: a film, a TEOS film, a ThOx film, or a polysilicon film. As another example, when the wavelength of the laser light L is 1.3 μm to 2.5 μm, the laser absorption layer P is composed of one or more of the following: a metal, a metal oxide, or a metal nitride. 【0013】 The device layer Dw in this embodiment includes at least a portion of the memory cell array of a NAND flash memory. However, the technology of this disclosure is not limited thereto and can also be applied to the manufacture of other semiconductor devices by joining substrates having other desired devices. In one embodiment, the device layer Dw includes at least a portion of the memory cell array of a DRAM. In another embodiment, the device layer Dw includes at least a portion of peripheral circuits for controlling the memory cell array of a NAND flash memory or the memory cell array of a DRAM. Note that no devices are formed on the device layer Dw at the time of preparation in St1, and devices may be formed in subsequent processes. In other words, the device layer Dw may be a device formation area in which devices are planned to be formed in processes after St1. 【0014】 For example, the surface film Fw can be an oxide film (THOX film, SiO ２ Examples include films, TEOS films, SiC films, SiCN films, or adhesives. In one embodiment, the surface film Fw includes a copper pad that constitutes part of the wiring layer. 【0015】Furthermore, other desired films may be formed between the laser absorption layer P, the device layer Dw, and the surface film Fw, respectively, as components of the laminated film. An example of such other films is a separation-promoting film. The separation-promoting film is a film provided adjacent to either the top or bottom of the laser absorption layer P, which undergoes thermal expansion, vaporization, or ablation due to heat transfer from the laser absorption layer P, thereby creating separation points within the film or at the interface between the film and other films. Another example of such other films is a sacrificial film. The sacrificial film is a film provided between the laser absorption layer P and the second surface Wb, or between the laser absorption layer P and the device layer Dw, which protects the second surface Wb or the device layer Dw from damage due to heat transfer from the laser absorption layer P. Another example of such other films is a reflective film. The reflective film is a film provided between the laser absorption layer P and the device layer Dw, which reflects laser light L. 【0016】 In St1 according to this embodiment, a coating film Q is formed on the second surface Wb of the first wafer W, as shown in Figures 2(a) and (c). 【0017】 In this embodiment, the coating film Q is transparent to laser light L. In other words, the combination of the wavelength of the laser light L and the film material constituting the coating film Q is predetermined so that the coating film Q is transparent to the laser light L. Such a combination is not particularly limited, as long as the coating film Q is transparent to the laser light L. As an example of a combination, when the wavelength of the laser light L is 8.9 μm to 11 μm, the coating film Q is composed of one or more of SiN, PolySi, or an organic film. As another example of a combination, when the wavelength of the laser light L is 1.3 μm to 2.5 μm, the coating film Q is composed of one or more of SiN, PolySi, an organic film, or SiOx. 【0018】In one embodiment, when transferring the device layer Dw to the second wafer S as described later, if irradiation with laser light L as exemplified by St4 is not performed, it is not essential that the coating film Q be transparent to the laser light L. However, if irradiation with laser light L is not performed, the device layer Dw to the second wafer S is transferred by removing the second surface Wb side of the first wafer W, for example, by mechanical or chemical methods. In this case, the first wafer W cannot be reused. Separation of the first wafer W using laser light L is preferable because it makes the first wafer W reusable through the reuse process of the first wafer W described later. 【0019】 Furthermore, the coating film Q is formed with a predetermined film material or thickness so as to have one or more of the following effects, which will be described in detail later: shape correction effect, unevenness repair effect, and reflection suppression effect. Details of the method for forming the coating film Q will be described later. 【0020】 The second wafer S prepared in St2 is, for example, a semiconductor wafer such as a silicon substrate. In one embodiment, the second wafer S has a substantially disc shape. As shown in Figure 2(b), a laminated film Ms is formed on the first surface Sa of the second wafer S. The laminated film Ms has a device layer Ds and a surface film Fs in that order from the first surface Sa side. These device layer Ds and surface film Fs are formed on the second wafer S, for example, by a process including CVD in a film deposition apparatus (not shown). 【0021】The device layer Ds and surface film Fs are the same as the device layer Dw and surface film Fw of the first wafer W, respectively. The device layer Ds according to this embodiment includes at least a portion of peripheral circuits for controlling the memory cell array of a NAND flash memory. In one embodiment, if the device layer Dw of the first wafer W includes at least a portion of the memory cell array of a DRAM, the device layer Ds includes at least a portion of peripheral circuits for controlling the memory cell array. In another embodiment, if the device layer Dw of the first wafer W includes at least a portion of peripheral circuits for controlling the memory cell array, the device layer Ds includes at least a portion of the memory cell array of a NAND flash memory. In yet another embodiment, if the device layer Dw of the first wafer W includes at least a portion of peripheral circuits for controlling the memory cell array, the device layer Ds includes at least a portion of the memory cell array of a DRAM. 【0022】 After preparing the first wafer W and the second wafer S as described above, the first wafer W and the second wafer S are joined together as shown in Figure 2(c) to form a polymerized wafer T as a polymerization substrate (St3 in Figure 1). In St3, the surface film Fw of the first wafer W and the surface film Fs of the second wafer S are joined together. The method of joining the first wafer W and the second wafer S is arbitrary, but one example is a hybrid bonding method that includes fusion bonding between the surface films Fw and Fs and bonding between copper pads formed on the surface films Fw and Fs, respectively. In this disclosure, the joining of the surface film Fw of the first wafer W and the surface film Fs of the second wafer S may be referred to as the joining of the surface of the first wafer W (first surface Wa) and the surface of the second wafer S (first surface Sa). 【0023】Next, as shown in Figure 3, the laser absorption layer P is irradiated with laser light L (St4 in Figure 1). In St4, for example, in the laser processing apparatus 50 described later, the laser light is pulsed onto the laser absorption layer P, which is the target of irradiation, or onto the interface between the laser absorption layer P and the second surface Wb of the first wafer W, or onto the interface between the laser absorption layer P and another layer. The laser light L may be irradiated in a spiral pattern over the entire surface of the target in a plan view, or it may be irradiated in a concentric ring pattern over the entire surface of the target. Alternatively, the laser light L may be pulsed onto the target while moving the lens 111 included in the laser irradiation device 50 in a linear direction. In this case, for example, the lens 111 may be provided with a linear movement mechanism (transporter) to move the lens in a horizontal direction, or the laser light from the lens 111 may be scanned by a galvanometer scanner (not shown). The laser light L passes through the coating film Q and the first wafer W from the second surface Wb side of the first wafer W and is absorbed by the laser absorption layer P. Then, this laser light L reduces the bonding strength at the laser absorption layer P, the interface between the laser absorption layer P and the wafer W, or the interface between the laser absorption layer P and other layers. 【0024】 In St4, the laser light L is irradiated from the second surface Wb side of the first wafer W. As described above, the coating film Q is transparent to the laser light L. Therefore, the attenuation of the laser light L in the coating film Q is suppressed. Furthermore, if the coating film Q has the surface irregularity repair effect or reflection suppression effect described later, the energy absorption efficiency of the laser light L in the laser absorption layer P can be improved. From another point of view, since the coating film Q is transparent to the laser light L, it does not need to be removed prior to St4. Therefore, the cost of the coating film Q removal process can be reduced. 【0025】Next, as shown in Figure 4, the first wafer W is separated from the second wafer S in the polymerized wafer T (St5 in Figure 1). In St5, for example, in the separation apparatus 60 described later, the first wafer W is separated using the interface between the laser absorption layer P and the second surface Wb of the first wafer W as the starting point, based on the irradiated object whose bonding strength was reduced in St4 (in the example shown in Figure 4). In this specification, the second wafer S after at least a portion of the layers formed on the first wafer W have been transferred and the first wafer W has been separated is referred to as "the second wafer S with the transferred layers" or simply "the second wafer S". In the example in Figure 4, the one including the device layer Dw, surface films Fw and Fs, device layer Ds and the second wafer S is referred to as "the second wafer S with the transferred device layer Dw" or simply "the second wafer S". 【0026】 The method for separating the first wafer W is arbitrary. As an example, as shown in Figure 4(a), the suction chuck 210 adsorbs and holds the second surface Sb or coating film Q of the second wafer S, and further adsorbs and holds the second surface Wb of the first wafer W. Then, as shown in Figure 4(b), with the suction pad 211 adsorbing and holding the first wafer W, the suction pad 211 is raised to separate the first wafer W. At this time, as described above, the bonding strength is reduced at the interface between the irradiated object (in the example shown in Figure 4) and the laser absorption layer P and the first surface Wa of the first wafer W due to irradiation with laser light L, so the first wafer W can be separated without applying a large load. 【0027】 In one embodiment, the coating film Q may be removed from the second surface Wb of the first wafer W after irradiation with laser light L at St4 and before separation at St5. 【0028】 The first wafer W separated at St5 is reused (St10 in Figure 1). In the reuse process for the first wafer W, as an example, the laser absorption layer P and coating film Q remaining on the first wafer W are etched and removed in an etching apparatus (not shown). The etching of the laser absorption layer P and coating film Q may be done by dry etching or wet etching. 【0029】The first wafer W, from which the laser absorption layer P and coating film Q have been removed, is then subjected to the same process as in St1, and a separation layer Mw, a device layer Dw, and a surface film Fw are formed on the first surface Wa. In this way, the first wafer W is reused for the next second wafer S. Note that the first wafer W from which the laser absorption layer P has been removed is a bare wafer with no film formed on the first surface Wa, so it may be reused as the second wafer S. 【0030】 The following describes the shape correction, surface repair, and reflection suppression effects that the coating film Q may have. 【0031】 The shape-correcting effect of the coating film Q is an effect that generates stress that deforms the first wafer W so that it approximates a predetermined target shape. The target shape includes, for example, a flat shape or the initial shape of the first wafer W before the device layer Dw is formed. 【0032】 A coating film Q having a shape-correcting effect according to one embodiment may be an organic film formed by a process including the application of a film material. The application method can be carried out by supplying a liquid film material and curing it by heat treatment, as exemplified in St103 described later, but is not limited thereto, and any desired known method can be used. 【0033】The organic film is not particularly limited, as long as it is capable of changing the stress at specific locations within its plane by a patternable stress-inducing treatment. According to the stress-inducing treatment exemplified in St104 described later, the stress at specific locations within the plane of the organic film is changed so that the shape of the first wafer W approximates the target shape. The stress-inducing treatment includes, for example, exposure by irradiating with light in a frequency band that causes a chemical reaction (crosslinking) of the film material. In this case, a resist containing a photosensitive epoxy resin can be used as the film material, and ultraviolet light can be used as the light for exposure. Furthermore, the exposure may be direct writing exposure (maskless exposure). Maskless exposure can be performed by a known process using a known maskless exposure machine such as the DLP (Digital Light Processing) method. In addition, the stress-inducing treatment includes methods that change the stress by causing physical changes in the film material at specific locations within the plane of the organic film, such as stretching, shrinking, bending, changing the crystal orientation or chemical configuration. As for the combination of such organic film and the stress application treatment applicable to the organic film, known combinations can be used. For example, various actuator films and activation methods for such actuator films described in Patent Document 1 can be used. 【0034】 In one embodiment, the coating film Q having a shape-correcting effect may be an inorganic film formed by a process including the deposition of a film material by CVD. The inorganic film is, as an example, a silicon nitride film (SiN film). The SiN film imparts stress to the first wafer W during deposition. Further, specific portions of the SiN film are removed by lithography patterning, and the stress is relieved so that the shape of the first wafer W approximates the target shape as a result of this removal. 【0035】As described above, the first wafer W in this embodiment has a device layer Dw, and the device layer Dw includes at least a part of the memory cell array of a NAND flash memory. In particular, the device structure or pattern of memory cells in recent 3D NAND may generate stress that deforms the first wafer W as the number of stacks in the direction perpendicular to the surface of the first wafer W increases. Such deformation of the first wafer W may cause misalignment or bonding defects in the overlay when bonding the first wafer W and the second wafer S. 【0036】 In contrast, the coating film Q, which has a shape-correcting effect, generates stress that deforms the first wafer W so that it approximates a predetermined target shape. This solves the above-mentioned problems caused by deformation of the first wafer W, for example, by making the first wafer W a flat shape. 【0037】 The unevenness repair effect of the coating film Q is to cover the uneven areas of the second surface Wb of the first wafer W, thereby suppressing the scattering or refraction of the laser light L at the incident interface of the laser light in the uneven areas. 【0038】 The incident interface of the laser beam L at the uneven portion Wr of the second surface Wb, where the coating film Q having an unevenness repair effect is not formed, is not perpendicular to the direction of incidence of the laser beam L. Therefore, relatively large scattering or refraction of the laser beam L may occur at this incident interface. Such scattering or refraction may prevent the laser beam L from reaching the laser absorption layer P, leading to a loss of energy of the laser beam L that should be absorbed by the laser absorption layer P. 【0039】In contrast, the coating film Q, which has a surface irregularity repair function, covers the irregularities on the second surface Wb of the first wafer W. The laser light L irradiated onto the irregularities first enters the coating film Q from the external atmosphere, and the interface at which it enters is nearly perpendicular to the direction of incidence of the laser light L. Therefore, scattering or refraction at the interface is reduced. From this viewpoint, "covering the irregularities" of the coating film Q refers to a configuration of the coating film Q such that the interface between the coating film Q formed on the irregularities and the external atmosphere becomes nearly flat, regardless of the shape of the irregularities. The laser light L that enters the coating film Q then enters the irregularities, but because the difference between the refractive index of the coating film Q and the refractive index of the irregularities (second surface Wb) is adjusted, scattering or refraction at the interface from the coating film Q to the irregularities is reduced. From another viewpoint, the improved processing efficiency due to the irradiation of laser light L makes it possible to apply a wider range of laser processing recipes. 【0040】 As the material constituting the coating film Q having a surface irregularity repair effect according to this embodiment, a material can be used such that the difference in refractive index between the coating film Q and the second surface Wb is smaller than the difference in refractive index between the external atmosphere and the second surface Wb. As such a material, for example, a material having a refractive index approximately equal to that of the material constituting the second surface Wb of the first wafer W is selected. This further suppresses scattering or refraction at the interface where the laser light L is incident on the uneven portion. As the material constituting the coating film Q having a surface irregularity repair effect, for example, when the second surface Wb is made of silicon, one or more of organic films, amorphous silicon, polysilicon, etc. can be used. 【0041】Also, in order to improve the unevenness correction effect by sufficiently covering the uneven portions with the coating film Q, it is preferable that the thickness of the coating film Q is optimized. Here, the uneven portions include, for example, non-uniform unevenness such as scratches and dents formed on the second surface Wb, and artificial unevenness such as grooves formed by imprinting an identification number (ID) individually assigned to each wafer. Therefore, the thickness of the coating film Q can be optimized in consideration of the sizes of these unevenness. For example, since scratches and ID imprinting grooves may be formed to be about 1 μm to 100 μm, the thickness of the coating film Q is preferably formed to be about 1 μm to 100 μm so that the coating film Q can sufficiently cover the uneven portions. 【0042】 The reflection suppression effect of the coating film Q is an effect such that the reflectance of the laser beam L in the coating film Q is smaller than the reflectance of the laser beam L on the second surface Wb when there is no coating film Q. 【0043】 At the incident interface of the laser beam L on the second surface Wb where the coating film Q having the reflection suppression effect is not formed, a relatively large reflection of the laser beam L can occur. Such reflection prevents the laser beam L from reaching the laser absorption layer P and causes a loss of the energy of the laser beam L to be absorbed by the laser absorption layer P. 【0044】 On the other hand, the coating film Q having the reflection suppression effect is formed such that the reflectance of the laser beam L in the coating film Q is smaller than the reflectance of the laser beam L on the second surface Wb when there is no coating film Q. Thereby, the loss of the energy of the laser beam L due to the above reflection is reduced. From another viewpoint, the processing efficiency by the irradiation of the laser beam L is improved, so that a wider range of laser processing recipes can be applied. 【0045】The reflectance in the coating film Q of the laser beam L is calculated based on the sum of two reflections: the reflection at the incident interface of the coating film Q from the external atmosphere and the reflection at the incident interface of the coating film Q from the second surface Wb of the first wafer W to the second surface Wb. In other words, the total reflectance when the above two reflections occur when the coating film Q is provided is smaller than the reflectance when one reflection occurs at the second surface Wb when there is no coating film Q. The total reflectance is considered to depend on the refractive index and thickness of the film material constituting the coating film Q. Therefore, by optimizing the refractive index and thickness of the film material, the total reflectance can be reduced and the reflection suppression effect can be improved. The optimization of the refractive index and thickness of the film material can be performed by various film materials and thicknesses through verification by experiments or simulations or machine learning based on measured data. As an example, as the film material constituting the coating film Q having a reflection suppression effect, a film material having a refractive index smaller than the refractive index of the material constituting the second surface Wb of the first wafer W is selected. As the material constituting the coating film Q having a reflection suppression effect, for example, when the second surface Wb is made of silicon, one or more of an organic film, SiN, etc. can be used. 【0046】 The coating film Q as described above may include a single film having a plurality of the above functions, or may include a plurality of films each having one of the above functions. For example, an organic film material capable of a patternable stress application process and having a refractive index of 2.0 to 10 can be formed with a thickness of 1 μm to 100 μm to form a coating film Q having all of a shape correction function, an unevenness correction function, and a reflection suppression function. 【0047】 In one embodiment, when a plurality of coating films Q are stacked, the coating film Q having an unevenness correction function is preferably provided in the innermost layer adjacent to the second surface Wb. Also, the coating film Q having a reflection suppression function is preferably provided in the outermost layer adjacent to the external atmosphere. 【0048】The following describes in detail the method for forming a coating film Q on the second surface Wb of the first wafer W in the preparation of St1. The coating film Q formed by the following method has at least a shape correction effect, but by selecting the film material and adjusting the film thickness, it can further have an unevenness repair effect and a reflection suppression effect. 【0049】 First, the shape of the first wafer W is measured (St101). The shape of the first wafer W may include out-of-plane distortions such as overall warping and localized wrinkles. In one embodiment of St101, the height from the reference plane at predetermined measurement points on the periphery of the first wafer is measured, and the overall warping amount of the first wafer W is obtained from the difference between the highest measurement value and the lowest measurement value among the measurement results. In another embodiment of St101, the height from the reference plane at predetermined measurement points across the entire surface of the first wafer W is measured, thereby obtaining the height profile of the shape of the first wafer W. Note that the height measurement in St101 may be performed on the first surface Wa of the first wafer W. In this case, after the measurement with the first surface Wa facing upwards, the first wafer W is inverted so that the second surface Wb faces upwards, and the process proceeds to film formation (St103) described later. 【0050】 Next, based on the height difference between the identified shape of the first wafer W and a predetermined target shape of the first wafer W, the amount of correction to the processing conditions is determined to reduce the height difference (St102). The amount of correction includes the amount of variation in the parameters of the processing conditions in at least one of the film formation in St103 or the stress application in St104, as described below. 【0051】 In St102 according to one embodiment, a first stress distribution that causes out-of-plane strain in the first wafer W can be determined from the height difference. After the first stress distribution is determined, a second stress distribution is determined that includes a stress distribution that relaxes, cancels out, or reverses at least a portion of the stress in the first stress distribution. Furthermore, the amount of correction for the processing conditions is determined so that the coating film Q generates the stress of the second stress distribution. 【0052】Next, a film is formed on the second surface Wb of the first wafer W by coating it with a film material that constitutes the coating film Q (St103). Specifically, a liquid film material is supplied onto the second surface Wb and coated uniformly. Subsequently, the coated film material is heat-treated to form a film. In one embodiment, the thickness of the film formed in St103 is adjusted by a correction amount determined in St102. In this case, for example, the amount of liquid film material supplied to the second surface Wb is varied by the correction amount as a parameter of the film formation processing conditions. 【0053】 In one embodiment, St103 may be used to form an inorganic film by depositing a film material using CVD, instead of forming an organic film by coating. 【0054】 Next, stress is applied to the film after it has been formed (St104). The stress application according to this embodiment includes exposure, which involves irradiating the film formed in St103 with light in a frequency band that causes a chemical reaction (crosslinking). However, it is not limited to this, and a desired stress application treatment can be selected depending on the selected film material. In one embodiment, the exposure target position and range are adjusted as parameters of the stress application treatment conditions by the correction amount determined in St102. Specifically, the exposure target position and range are adjusted so that the coated film Q has a second stress distribution. 【0055】 Next, the film after the stress has been applied is subjected to heat treatment and then developed (St105). 【0056】 By the above steps St101 to St105, a coating film Q having at least a shape-correcting effect is formed. In one embodiment, after St105, the shape of the first wafer W on which the coating film Q has been formed may be measured in the same manner as in St101 to evaluate whether the shape of the first wafer W sufficiently approximates the target shape. The evaluation result may be used to correct the parameters of the processing conditions for other first wafers W to be processed next. 【0057】In the above embodiment, an example of forming a coating film Q at St1 was described, but the technology of this disclosure is not limited thereto, and the following modifications are possible. In one modification, the coating film Q is formed not when preparing the first wafer W at St1, but between joining the first wafer W and the second wafer S at St3 and irradiating the laser absorption layer P with laser light L at St4. In this case, the coating film Q is formed on the second surface Wb of the first wafer W in the polymerized wafer T formed at St3. In another modification, one coating film Q is formed at St1, then the polymerized wafer T is formed at St3, and then another coating film Q is formed on top of that coating film Q. 【0058】 In other modifications, instead of using laser irradiation for separation when transferring the device layer Dw to the second wafer S, the device layer Dw may be transferred to the second wafer S by removing the second surface Wb side of the first wafer W by mechanical and / or chemical methods. Also, the coating film Q may be removed between the time the polymerized wafer T is formed in St3 and the time the second surface Wb side of the first wafer W is removed. Furthermore, after St3, the polymerized wafer T may be annealed, but the coating film Q may be removed before the annealing process. By removing the coating film Q before the annealing process, it becomes possible to select a film material that is not resistant to the heat treatment temperature of the annealing process as the film material constituting the coating film Q. This improves the degree of freedom in the composition of the coating film Q. 【0059】 Below, a wafer processing system 1 will be described as an example of a substrate processing system capable of bonding and separating the first substrate and the second substrate in the wafer processing method described above. 【0060】 As shown in Figure 6, the wafer processing system 1 has a configuration in which an loading / unloading station 2 and a processing station 3 are integrally connected. At the loading / unloading station 2, for example, cassettes C capable of accommodating multiple polymerized wafers T are loaded and unloaded to and from the outside. The processing station 3 is equipped with various processing devices for performing desired processing on the polymerized wafers T. 【0061】The loading / unloading station 2 is provided with a cassette mounting table 10 on which a cassette C capable of accommodating multiple polymerized wafers T is placed. Adjacent to the cassette mounting table 10, on the positive X-axis side, is a wafer transport device 20. The wafer transport device 20 moves along a transport path 21 extending in the Y-axis direction and is configured to transport polymerized wafers T between the cassette C on the cassette mounting table 10 and the transition stage 30 described later. 【0062】 At the loading / unloading station 2, a transition stage 30 is provided adjacent to the wafer transport device 20 on the positive X-axis side of the wafer transport device 20 for transferring the polymerized wafer T between the loading / unloading station 2 and the processing station 3. 【0063】 Processing station 3 is equipped with a wafer transport device 40, a laser processing device 50, a separation device 60, and a cleaning device 70. 【0064】 The wafer transfer device 40 is located on the positive X-axis side of the transition stage 30. The wafer transfer device 40 is configured to move freely along a transfer path 41 extending in the X-axis direction and is capable of transporting polymerized wafers T to the transition stage 30, laser processing device 50, separation device 60, and cleaning device 70 of the loading / unloading station 2. 【0065】 The laser processing apparatus 50 irradiates the laser absorption layer P of the first wafer W in the polymerized wafer T with laser light L to form a bonding force reduction region where the first wafer W and the second wafer S are separated. The laser processing apparatus 50 has a control device 51, which will be described later. 【0066】As shown in Figures 7 and 8, the laser processing apparatus 50 has a chuck 100 that holds the polymerized wafer T on its upper surface. The chuck 100 holds the back surface Sb of the second wafer S by suction when the first wafer W is positioned on top and the second wafer S is positioned on the bottom. The chuck 100 is supported by a slider table 102 via an air bearing 101. A rotation mechanism 103 is provided on the lower surface of the slider table 102. The rotation mechanism 103 incorporates, for example, a motor as a drive source. The chuck 100 is configured to rotate freely around a vertical axis via the air bearing 101 by the rotation mechanism 103. The slider table 102 is configured to move freely on a rail 106 that extends in the Y-axis direction on a base 105 via a moving mechanism 104 provided on its lower surface. The drive source for the moving mechanism 104 is not particularly limited, but for example, a linear motor can be used. 【0067】 A laser head 110 is provided above the chuck 100. The laser head 110 has a lens 111. The lens 111 irradiates the laser absorption layer P of the polymerized wafer T held by the chuck 100 with laser light L. This separates the first wafer W and the laminated film in the area irradiated with laser light L, forming a bonding force reduction region where the first wafer W and the second wafer S are separated. The location where the bonding force reduction region is formed is not particularly limited, as long as separation occurs at the interface between the first wafer W and the second wafer S and the bonding force is reduced. That is, the separation of the first wafer W and the second wafer S may occur at the interface between the first wafer W and the laminated film as shown in the figure, or at the interface between the laser absorption layer P and other laminated films, or at the interface between the laser absorption layer P and the device layer Dw. 【0068】 The laser head 110 is supported by a support member 112. The laser head 110 is configured to move up and down along a vertically extending rail 113 by a lifting mechanism 114. The laser head 110 is also configured to move in the Y-axis direction by a moving mechanism 115. The lifting mechanism 114 and the moving mechanism 115 are each supported by a support column 116. 【0069】In the illustrated example, the chuck 100 is configured to rotate relative to the laser head 110 and move horizontally using the rotation mechanism 103 and the movement mechanism 104. However, the laser head 110 may be configured to rotate relative to the chuck 100 and move horizontally. Alternatively, both the chuck 100 and the laser head 110 may be configured to rotate relative to each other and move horizontally. 【0070】 The separation device 60 includes a suction chuck 210 and a suction pad 211 as shown in Figure 4. Then, using the method described above, the first wafer W is separated from the second wafer S, with the bonding force reduction region as the starting point. 【0071】 The cleaning device 70 performs a cleaning process on the first wafer W and the second wafer S after they have been separated by the separation device 60, removing particles from these wafers. The cleaning method can be arbitrarily selected. 【0072】 The wafer processing system 1 described above is equipped with a control device 51 and at least one control device 90. The control device 51 individually controls the operation of the laser processing device 50. The control device 90 oversees the control of a series of wafer processing operations in the wafer processing system 1. 【0073】 Control devices 51 and 90 each process computer-executable instructions that cause the laser processing apparatus 50 and the wafer processing system 1 to perform the various processes described herein. Control devices 51 and 90 may each be configured to control the elements of the laser processing apparatus 50 and the wafer processing system 1 to perform the various processes described herein. In one embodiment, some or all of the control device 51 may be included in the laser processing apparatus 50, and some or all of the control device 90 may be included in the wafer processing system 1. 【0074】The control device 51 and the control device 90 may each include a processing unit, a storage unit, and a communication interface. The control device 51 and the control device 90 may each be implemented, for example, by a computer. The processing unit may be configured to read a program from the storage unit that provides logic or routines that enable various control operations, and to perform various control operations by executing the read program. This program may be stored in the storage unit in advance, or it may be obtained via a medium when needed. The obtained program is stored in the storage unit and read from the storage unit and executed by the processing unit. The medium may be various storage media readable by a computer, or it may be a communication line connected to the communication interface. The storage medium may be temporary or permanent. The processing unit may be a CPU (Central Processing Unit), or it may be one or more circuits. The memory unit may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface may communicate between the laser processing device 50 and the wafer processing system 1 via a communication line such as a LAN (Local Area Network). 【0075】 In this embodiment, the control device 51 is installed separately from the laser processing device 50, but the control device 51 may be configured as an integral part of the control device 90. In other words, the operation of the laser processing device 50 may be controlled by the control device 90. 【0076】The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. For example, the constituent elements of the embodiments described above can be combined in any way. Such any combination will naturally yield the functions and effects of each constituent element in the combination, as well as other functions and effects that will be apparent to those skilled in the art from the description herein. 【0077】 Furthermore, the effects described herein are merely descriptive or illustrative and not limiting. In other words, the technology relating to this disclosure may produce other effects that are obvious to those skilled in the art from the description herein, in addition to or instead of the effects described herein. 【0078】 P: Laser absorption layer Q: Coating film S: Second wafer T: Polymerized wafer W: First wafer

Claims

1. A substrate processing method comprising: forming a coating film on the second surface of a first substrate having a first surface on which a laminated film including a device layer is formed, and a second surface which is the surface opposite to the first surface, such that the coating film generates stress that causes the first substrate to deform so that the first substrate approximates a predetermined target shape; and joining the first surface of the first substrate and the surface of the second substrate to form a polymerized substrate, wherein the device layer includes at least a portion of a NAND memory cell array.

2. The substrate processing method according to claim 1, wherein the coating film is transparent to laser light of a predetermined wavelength, the laminated film includes a laser absorption layer that absorbs the laser light, and the substrate processing method comprises irradiating the laser absorption layer with the laser light from the second surface side of the first substrate in the polymerized substrate, and transferring the device layer from the first substrate to the second substrate by separating the first substrate from the second substrate in the polymerized substrate.

3. A substrate processing method according to claim 1, comprising: measuring the shape of the first substrate in forming the coating film; determining the difference between the measured shape of the first substrate and the target shape, determining a correction amount for the parameters of the processing conditions for forming the coating film based on the difference; and forming the coating film using the processing conditions corrected by the correction amount.

4. The substrate processing method according to claim 2, wherein, in forming the coating film, at least one of the coating films is formed to cover the top of the uneven portion of the second surface of the first substrate, thereby suppressing the scattering or refraction of the laser light at the incident interface of the laser light in the uneven portion.

5. The substrate processing method according to claim 4, wherein the coating film formed to suppress the scattering or refraction of the laser light in the uneven portion has a refractive index that is substantially equal to the refractive index of the second surface of the first substrate at the wavelength of the laser light.

6. The substrate processing method according to claim 2, wherein, in forming the coating film, the coating film is formed with a predetermined refractive index and thickness such that the reflectance of the laser light in the coating film is less than the reflectance of the laser light on the second surface.

7. The substrate processing method according to claim 1, wherein the coating film includes a coating film formed by a step including the application of a film material.

8. The substrate processing method according to claim 7, wherein the coating film includes an organic film.

9. The substrate processing method according to claim 1, wherein the coating film includes a deposited film formed by a process including the deposition of a film material by CVD.

10. The substrate processing method according to claim 9, wherein the coating film includes an inorganic film.

11. A substrate processing method according to any one of claims 1 to 10, comprising making the first substrate reusable by removing the coating film from the second surface of the first substrate separated from the second substrate in the polymerization substrate.

12. A substrate processing method according to any one of claims 1 to 10, comprising: annealing the polymer substrate after forming the polymer substrate; and removing the coating film from the second surface of the first substrate on the polymer substrate after forming the polymer substrate and before annealing the polymer substrate.

13. A substrate processing system comprising: a laser processing apparatus configured to irradiate a polymerization substrate with laser light of a predetermined wavelength to form a bonding force reduction region; and a control device, wherein the polymerization substrate is formed by bonding the first surface of a first substrate having a laminated film including a laser absorption layer and a device layer that absorbs the laser light, and a second surface which is the surface opposite to the first surface, and one or more coating films that are transparent to the laser light are formed on the second surface of the first substrate, at least one of the coating films is formed to generate stress that deforms the first substrate so that it approximates a predetermined target shape, the device layer includes at least a part of a NAND memory cell array, and the control device executes control including irradiating the laser absorption layer with laser light from the second surface side of the first substrate, and transferring the device layer from the first substrate to the second substrate by separating the first substrate from the second substrate in the polymerization substrate.

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