LAMINATED SUBSTRATE FOR LASER LIFT-OFF, SUBSTRATE PROCESSING METHOD, AND SUBSTRATE PROCESSING APPARATUS

Abstract

This laminated substrate for laser lift-off comprises, in the following order, a first substrate through which a laser beam is transmitted, a first insulating layer which absorbs the laser beam, a first polysilicon layer through which the laser beam is transmitted, a second insulating layer which absorbs the laser beam, a second polysilicon layer through which the laser beam is transmitted, and a first device layer. The laminated substrate comprises: a first electrode penetrating the first insulating layer to electrically connect the first substrate and the the first polysilicon layer; and a second electrode penetrating the second insulating layer to electrically connect the first polysilicon layer and the second polysilicon layer. The first electrode and the second electrode include a material through which the laser beam is transmitted. The first electrode and the second electrode are separated from each other without overlapping in a plan view.

Description

[Technical field]

[0001] The present disclosure relates to a laminated substrate for laser lift-off, a substrate processing method, and a substrate processing apparatus. [Background technology]

[0002] When forming device layers on a substrate such as a silicon wafer, plasma CVD (Chemical Vapor Deposition) is used. i For this purpose, plasma deposition (plasma ALD), plasma atomic layer deposition (ALD), plasma etching, etc. are used. If charged particles accumulate due to plasma irradiation, the device layer will be damaged. Therefore, it has been proposed to form a discharge path so as to prevent the device layer from being damaged (for example, see Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Z. Wang, A. Scarpa, S. Smits, C. Salm, F. Kuper, "Temperature Effect on Antenna Protection Strategy for Plasma-Process Induced Charging Damage," International Symposium on Plasma and Process-Induced Damage, pp. 134-137, 2002. Summary of the Invention [Problem to be solved by the invention]

[0004] One aspect of the present disclosure provides a technique for suppressing irradiation of a laser beam to a device layer via a discharge path, thereby suppressing damage to the device layer. [Means for solving the problem]

[0005] A laminated substrate for laser lift-off according to one embodiment of the present disclosure includes a first substrate that transmits a laser beam, a first insulating layer that absorbs the laser beam, a first polysilicon layer that transmits the laser beam, a second insulating layer that absorbs the laser beam, a second polysilicon layer that transmits the laser beam, and a first device layer, in this order. The laminated substrate includes a first electrode that penetrates the first insulating layer to electrically connect the first substrate and the first polysilicon layer, and a second electrode that penetrates the second insulating layer to electrically connect the first polysilicon layer and the second polysilicon layer. The first electrode and the second electrode contain a material that transmits the laser beam, and are separated from each other without overlapping in a planar view. Effect of the Invention

[0006] According to one aspect of the present disclosure, irradiation of the device layer with a laser beam via a discharge path can be suppressed, and damage to the device layer can be suppressed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing a laminated substrate according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing formation of a peeling starting point by the substrate processing apparatus according to an embodiment. [Diagram 3] FIG. 3 is a cross-sectional view showing an example of the arrangement of peel start points. [Figure 4] FIG. 4 is a cross-sectional view showing separation by the substrate processing apparatus according to an embodiment. [Diagram 5] FIG. 5 is a cross-sectional view showing a multilayer substrate according to a first modified example. [Figure 6] FIG. 6 is a diagram showing an example of the relationship between the thickness of the first insulating layer and the energy of the laser beam required to form the peeling starting point. [Figure 7] FIG. 7 is a cross-sectional view showing a multilayer substrate according to a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding configurations are denoted by the same reference numerals, and the description may be omitted. In this specification, "plan view" means a view from a direction perpendicular to the surface of the laminated substrate 1 that is irradiated with the laser beam LB.

[0009] A laminated substrate 1 for laser lift-off according to one embodiment will be described with reference to Fig. 1. The laminated substrate 1 includes, for example, a first substrate 11, a first insulating layer 12, a first polysilicon layer 13, a second insulating layer 14, a second polysilicon layer 15, and a first device layer 16, in this order. Laser lift-off is a technique for peeling off the first substrate 11 from the first device layer 16 using a laser beam LB that transmits through the first substrate 11, as shown in Figs. 2 to 4, which will be described in detail later.

[0010] The first substrate 11 is, for example, a silicon wafer. The first substrate 11 is not limited to a silicon wafer, and may be a compound semiconductor wafer or a glass substrate. On one side of the first substrate 11, a first insulating layer 12, a first polysilicon layer 13, a second insulating layer 14, a second polysilicon layer 15, and a first device layer 16 are formed in this order. After that, a first bonding layer 17, which will be described later, may be formed.

[0011] As shown in Fig. 3, the first insulating layer 12 absorbs the laser beam LB and forms a peeling starting point 12a. A crack is formed at the peeling starting point 12a due to shear stress or the like. A modified layer obtained by modifying the first insulating layer 12 may be formed at the peeling starting point 12a. The peeling starting point 12a is formed at the interface between the first substrate 11 and the first insulating layer 12, but may also be formed inside the first insulating layer 12.

[0012] The first insulating layer 12 has insulating properties. An insulating material has excellent absorptivity for the laser beam LB. The first insulating layer 12 is, for example, an oxide layer. A specific example of the oxide layer is a silicon oxide layer. The oxide layer can be formed by a method such as thermal oxidation, CVD (Chemical Vapor Deposit), etc.i The first insulating layer 12 is formed by a CVD method, an ALD (Atomic Layer Deposition) method, or the like. When forming a silicon oxide layer by a CVD method, TEOS (Tetra Ethoxy Silane) or the like is used as a raw material for the silicon oxide layer. The first insulating layer 12 may be a silicon nitride layer, a silicon carbonitride layer, or the like.

[0013] A through hole is formed in the first insulating layer 12. A first electrode 18 is provided in the through hole. The first electrode 18 penetrates the first insulating layer 12 to electrically connect the first substrate 11 and the first polysilicon layer 13. The first electrode 18 is used as a part of a discharge path that discharges charged particles (e.g., electrons or holes) that accumulate in the first device layer 16 when the first device layer 16 is formed, to the first substrate 11.

[0014] The first device layer 16 is formed by plasma CVD, plasma ALD, plasma etching, or the like. If charged particles accumulate due to plasma irradiation, the first device layer 16 will be damaged. According to the present embodiment, the first electrode 18 and the like form a discharge path, so that damage to the first device layer 16 can be suppressed.

[0015] The first electrode 18 includes, for example, polysilicon and has a thickness of, for example, 1.0×10 19 / cm 3 Above 3.0×10 20 / cm 3 The impurity (dopant) may be a donor that provides electrons or an acceptor that provides holes. 19 / cm 3 If the impurity concentration is 3.0×10 or more, the discharge property is good. 20 / cm 3 If it is less than this, the first electrode 18 has a high transmittance for the laser beam LB.

[0016] The first polysilicon layer 13 is a part of the discharge path. The first polysilicon layer 13 has a thickness of, for example, 1.0×10 19 / cm 3Above 3.0×10 20 / cm 3 The impurity may be a donor or an acceptor. 19 / cm 3 If the impurity concentration is 3.0×10 or more, the discharge property is good. 20 / cm 3 If it is less than this, the first polysilicon layer 13 has a high transmittance for the laser beam LB.

[0017] The second insulating layer 14 absorbs the laser beam LB. The absorption rate of the laser beam LB in the second insulating layer 14 is, for example, 70% to 100%. This can prevent the first device layer 16 from being irradiated with a high-intensity laser beam LB, thereby preventing damage to the first device layer 16. The second insulating layer 14 has the same thickness as the first insulating layer 12, but may have a different thickness as described below.

[0018] The second insulating layer 14 has insulating properties similar to the first insulating layer 12. Insulating materials have excellent absorptivity for the laser beam LB. The second insulating layer 14 is, for example, an oxide layer. A specific example of the oxide layer is a silicon oxide layer. The oxide layer is formed by a thermal oxidation method, a CVD method, an ALD method, or the like. The second insulating layer 14 may be a silicon nitride layer, a silicon carbonitride layer, or the like.

[0019] A through hole is formed in the second insulating layer 14. A second electrode 19 is provided in the through hole. The second electrode 19 penetrates the second insulating layer 14 to electrically connect the first polysilicon layer 13 and the second polysilicon layer 15. The second electrode 19 is a part of the above-mentioned discharge path. The second electrode 19 includes, for example, polysilicon and has a thickness of, for example, 1.0×10 19 / cm 3 Above 3.0×10 20 / cm 3 The impurities may be donors or acceptors.

[0020] The second polysilicon layer 15 is a part of the discharge path. The second polysilicon layer 15 has a thickness of, for example, 1.0×10 19 / cm 3 Above 3.0×10 20 / cm 3 The impurity may be a donor or an acceptor. 19 / cm 3 If the impurity concentration is 3.0×10 or more, the discharge property is good. 20 / cm 3 If it is less than this, the second polysilicon layer 15 has a high transmittance for the laser beam LB.

[0021] The first device layer 16 includes, for example, a semiconductor element. The first device layer 16 includes, for example, a 3D NAND cell, a logic cell, or a DRAM cell.

[0022] However, if the laminated substrate 1 did not have the second insulating layer 14, the laser beam LB would be transmitted through the first electrode 18 and then directly irradiated onto the first device layer 16 without being absorbed by the second insulating layer 14. Since the high-intensity laser beam LB is irradiated onto the first device layer 16, the first device layer 16 would be damaged.

[0023] The laminated substrate 1 of this embodiment includes a second insulating layer 14. Therefore, the laser beam LB is absorbed by the second insulating layer 14 after passing through the first electrode 18, as shown by the two-dot chain arrow in Fig. 3. This makes it possible to prevent the high-intensity laser beam LB from being irradiated onto the first device layer 16, and to prevent damage to the first device layer 16. Outside the first electrode 18, the laser beam LB is absorbed by the first insulating layer 12, as shown by the solid arrow in Fig. 3, and therefore does not damage the first device layer 16.

[0024] Incidentally, the first polysilicon layer 13, the second polysilicon layer 15, the first electrode 18, and the second electrode 19 contain a material (e.g., polysilicon) that transmits the laser beam LB. If the first electrode 18 and the second electrode 19 overlap in a plan view (viewed from above in FIG. 3), the laser beam LB will transmit through the first electrode 18, then the second electrode 19, and reach the first device layer 16 as it is.

[0025] In this embodiment, the first electrode 18 and the second electrode 19 are separated from each other without overlapping in a plan view. Therefore, the laser beam LB is absorbed by the second insulating layer 14 after passing through the first electrode 18, as shown by the two-dot chain arrow in Fig. 3. This makes it possible to prevent the first device layer 16 from being irradiated with a high-intensity laser beam LB, and to prevent damage to the first device layer 16.

[0026] The laminated substrate 1 may include a first bonding layer 17, a second bonding layer 27, a second device layer 26, and a second substrate 21, in this order, on the opposite side of the first device layer 16 to the first substrate 11. The first substrate 11 and the second substrate 21 are bonded via the first device layer 16 and the second device layer 26.

[0027] The first bonding layer 17 is formed on the surface of the first device layer 16. The first bonding layer 17 is an insulating layer such as a silicon oxide layer. The first bonding layer 17 may include wiring that electrically connects the first device layer 16 and the second device layer 26. The first bonding layer 17 has a bonding surface 17a that contacts the second bonding layer 27. The bonding surface 17a may be activated by plasma or the like before the first bonding layer 17 and the second bonding layer 27 are bonded face to face, and may further be made hydrophilic by supplying water or water vapor.

[0028] The second substrate 21 is, for example, a silicon wafer. The second substrate 21 is not limited to a silicon wafer, and may be a compound semiconductor wafer or a glass substrate. A second device layer 26 and a second bonding layer 27 are formed in this order on the surface of the second substrate 21 facing the first substrate 11.

[0029] The second device layer 26 includes, for example, a semiconductor element. The second device layer 26 is electrically connected to the first device layer 16. The second device layer 26 has a different function from the first device layer 16. For example, the second device layer 26 includes a complementary metal oxide semiconductor (CMOS) logic circuit, and the first device layer 16 includes a 3D NAND cell.

[0030] The second bonding layer 27 is an insulating layer such as a silicon oxide layer, similar to the first bonding layer 17. The second bonding layer 27 may include wiring that electrically connects the first device layer 16 and the second device layer 26. The second bonding layer 27 has a bonding surface 27a in contact with the first bonding layer 17. The bonding surface 27a may be activated by plasma or the like, and may further be made hydrophilic by supplying water or water vapor.

[0031] The first bonding layer 17 and the second bonding layer 27 are bonded by van der Waals forces (intermolecular forces) and hydrogen bonds between OH groups. Covalent bonds may be generated by a dehydration condensation reaction of hydrogen bonds. Since solids are directly bonded together without using a liquid adhesive, it is possible to prevent misalignment due to deformation of the adhesive. It is also possible to prevent tilting due to uneven thickness of the adhesive.

[0032] It is sufficient that the laminated substrate 1 includes, in this order, the first substrate 11, the first insulating layer 12, the first polysilicon layer 13, the second insulating layer 14, the second polysilicon layer 15, and the first device layer 16. The laminated substrate 1 does not necessarily include the first bonding layer 17, the second bonding layer 27, the second device layer 26, and the second substrate 21.

[0033] 2 to 4, a substrate processing apparatus 3 according to an embodiment and a substrate processing method using the substrate processing apparatus 3 will be described. The substrate processing apparatus 3 uses a laser beam LB that transmits through the first substrate 11 to peel the first substrate 11 from the first device layer 16. The substrate processing apparatus 3 includes, for example, a first substrate holding unit 31, an irradiator 32, a first driving unit 33, a second substrate holding unit 34, a second driving unit 35, and a control unit 39.

[0034] The first substrate holding unit 31 holds the laminated substrate 1 as shown in FIG. 2. The first substrate holding unit 31 holds the laminated substrate 1 horizontally from below, for example, with the first substrate 11 facing upward. The first substrate holding unit 31 is, for example, a vacuum chuck. The first driving unit 33 moves the first substrate holding unit 31 in the horizontal direction and rotates it about a vertical rotation axis. The first driving unit 33 may also move the first substrate holding unit 31 in the vertical direction.

[0035] Irradiator 32 irradiates laser beam LB onto laminated substrate 1 held by first substrate holding part 31. Laser beam LB is, for example, infrared light and has a wavelength of, for example, 8.8 μm to 11 μm. First substrate 11, which is a silicon wafer, is highly transparent to infrared light, and first insulating layer 12 is highly absorptive of infrared light. Peeling starting point 12a is formed at the point on first insulating layer 12 where laser beam LB is irradiated.

[0036] The irradiator 32 includes an oscillator that oscillates the laser beam LB. The oscillator oscillates the laser beam LB in a pulsed manner. The oscillator is, for example, a CO2 laser. The wavelength of the CO2 laser is about 9.3 μm. The irradiator 32 may include a condenser lens. The condenser lens condenses the laser beam LB toward the laminated substrate 1.

[0037] The irradiator 32 may include a galvanometer scanner or a polygon scanner to move the irradiation point of the laser beam LB on the laminated substrate 1. The first driving unit 33 may move the first substrate holding unit 31 in the horizontal direction or rotate it about a vertical rotation axis to move the irradiation point of the laser beam LB on the laminated substrate 1. In this case, a galvanometer scanner or the like is not required.

[0038] The second substrate holding unit 34 holds the laminated substrate 1 as shown in FIG. 4. The second substrate holding unit 34 holds the laminated substrate 1 from the side opposite to the first substrate holding unit 31 (e.g., from above). The second substrate holding unit 34 is, for example, a vacuum chuck. The second driving unit 35 moves the second substrate holding unit 34 in the horizontal direction and rotates it about a vertical rotation axis. The second driving unit 35 may also move the second substrate holding unit 34 in the vertical direction.

[0039] The control unit 39 is, for example, a computer, and includes a CPU (Central Processing Unit) 391 and a storage medium 392 such as a memory. The storage medium 392 stores programs for controlling various processes executed in the substrate processing apparatus 3. The control unit 39 controls the operation of the substrate processing apparatus 3 by causing the CPU 391 to execute the programs stored in the storage medium 392.

[0040] The control unit 39 controls the irradiator 32 and the first driving unit 33 to perform control for forming peeling starting points 12a at the interface between the first substrate 11 and the first insulating layer 12. A large number of peeling starting points 12a are formed at intervals in the radial and circumferential directions of the first substrate 11. The multiple peeling starting points 12a may be arranged in a concentric pattern or in a spiral pattern. Note that the peeling starting points 12a may be formed inside the first insulating layer 12, as described above.

[0041] Thereafter, the control unit 39 controls the second driving unit 35 to peel the first substrate 11 from the first device layer 16. For example, in a state in which the first substrate holding unit 31 adsorbs the second substrate 21 and the second substrate holding unit 34 adsorbs the first substrate 11, the second driving unit 35 raises the second substrate holding unit 34. Cracks are formed that connect the multiple peeling starting points 12a in a planar manner, and the first substrate 11 and the first device layer 16 are peeled off.

[0042] Note that the control unit 39 may lower the first substrate holding unit 31 instead of or in addition to raising the second substrate holding unit 34. The control unit 39 may relatively separate the first substrate holding unit 31 and the second substrate holding unit 34 in the vertical direction. The control unit 39 may rotate the first substrate holding unit 31 or the second substrate holding unit 34.

[0043] Next, a laminated substrate 1 for laser lift-off according to a first modified example will be described with reference to FIG. 5. Differences between the above embodiment and the first modified example will be mainly described below. As shown in FIG. 5, the thickness t1 of the first insulating layer 12 may be larger than the thickness t2 of the second insulating layer 14. The thickness t1 of the first insulating layer 12 is, for example, more than 1.0 μm. The thickness t2 of the second insulating layer 14 is, for example, 0.5 μm to 1.0 μm.

[0044] Fig. 6 shows an example of the relationship between the thickness t1 of the first insulating layer 12 and the energy E of the laser beam LB required to form the peeling starting points 12a. As shown in Fig. 6, the greater the thickness t1 of the first insulating layer 12, the smaller the required energy E. This is because the greater the thickness t1 of the first insulating layer 12, the higher the absorption rate of the laser beam LB by the first insulating layer 12 and the easier it is to generate heat, so that a desired shear stress can be obtained with a small energy E.

[0045] If the thickness t1 of the first insulating layer 12 is greater than the thickness t2 of the second insulating layer 14, not only can a peel starting point 12a be formed in the first insulating layer 12 using a laser beam LB with a small energy E, but the formation of a peel starting point in the second insulating layer 14 can be suppressed, and peeling can be suppressed from occurring at an unintended position.

[0046] The magnitude relationship between the thickness t1 of the first insulating layer 12 and the thickness t2 of the second insulating layer 14 may be reversed, and the thickness t2 of the second insulating layer 14 may be greater than the thickness t1 of the first insulating layer 12. In this case, the peeling starting points 12a are formed at the interface between the first polysilicon layer 13 and the second insulating layer 14, or inside the second insulating layer 14.

[0047] Next, a laminated substrate 1 for laser lift-off according to a second modified example will be described with reference to Fig. 7. The differences between the above embodiment and the second modified example will be mainly described below. As shown in Fig. 7, the laminated substrate 1 may have a conductive layer 41 that reflects the laser beam LB between the second insulating layer 14 and the second polysilicon layer 15. The reflectance of the conductive layer 41 to the laser beam LB is, for example, 70% to 100%.

[0048] The conductive layer 41 is a part of the discharge path. The conductive layer 41 includes, for example, a transition metal, a conductive oxide, or polysilicon. The transition metal includes, for example, at least one selected from the group consisting of Cu, Co, Ru, Mo, W, and Ti. The conductive oxide includes, for example, IGZO (oxide containing indium, gallium, and zinc) or ITO (indium tin oxide). The polysilicon included in the conductive layer 41 has a higher impurity concentration than the second polysilicon layer 15, and is, for example, 3.0×10 20 / cm 3 Above 3.0×10 21 / cm 3 The impurity concentrations are as follows:

[0049] The conductive layer 41 can reflect the laser beam LB, thereby reducing the intensity of the laser beam LB that reaches the first device layer 16, and can reliably suppress damage to the first device layer 16.

[0050] Although the embodiments of the laminated substrate for laser lift-off, the substrate processing method, and the substrate processing apparatus according to the present disclosure have been described above, the present disclosure is not limited to the above-mentioned embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure.

[0051] This application claims priority based on Patent Application No. 2021-142969 filed with the Japan Patent Office on September 2, 2021, and the entire contents of Patent Application No. 2021-142969 are incorporated by reference into this application. [Explanation of symbols]

[0052] 1. Laminated substrate 11 First board 12 First insulating layer 13 First polysilicon layer 14 Second insulating layer 15 Second polysilicon layer 16 First Device Layer 18 1st electrode 19 2nd electrode LB Laser beam

Claims

1. A laminate substrate for laser lift-off, comprising: a first substrate that transmits a laser beam, a first insulating layer that absorbs the laser beam, a first polysilicon layer that transmits the laser beam, a second insulating layer that absorbs the laser beam, a second polysilicon layer that transmits the laser beam, and a first device layer, in this order; a first electrode penetrating the first insulating layer and electrically connecting the first substrate and the first polysilicon layer, and a second electrode penetrating the second insulating layer and electrically connecting the first polysilicon layer and the second polysilicon layer, A laminated substrate for laser lift-off, wherein the first electrode and the second electrode contain a material that transmits the laser beam and are separated from each other without overlapping in a planar view.

2. The laminate substrate for laser lift-off according to claim 1 , wherein the first electrode and the second electrode comprise polysilicon.

3. 3. The laminated substrate for laser lift-off according to claim 1, wherein one of the first insulating layer and the second insulating layer has a thickness greater than the other.

4. 3. The laminated substrate for laser lift-off according to claim 1, further comprising a conductive layer between the second insulating layer and the second polysilicon layer, the conductive layer reflecting the laser beam.

5. 3. The laminated substrate for laser lift-off according to claim 1, wherein the first insulating layer and the second insulating layer are silicon oxide layers.

6. a second device layer electrically connected to the first device layer, and a second substrate on which the second device layer is formed; 3 . The laminated substrate for laser lift-off according to claim 1 , wherein the first substrate and the second substrate are bonded via the first device layer and the second device layer.

7. Preparing a laminated substrate for laser lift-off according to claim 1 or 2; A substrate processing method comprising: irradiating the first insulating layer with the laser beam through the first substrate, thereby forming a peeling starting point at an interface between the first substrate and the first insulating layer, inside the first insulating layer, at an interface between the first polysilicon layer and the second insulating layer, or inside the second insulating layer.

8. A substrate holder for holding the laminated substrate for laser lift-off according to claim 1 or 2; an irradiator that irradiates the laser beam onto the laminated substrate held by the substrate holding unit; A control unit that controls the irradiator; Equipped with The control unit of the substrate processing apparatus controls the formation of a peeling starting point at the interface between the first substrate and the first insulating layer, inside the first insulating layer, at the interface between the first polysilicon layer and the second insulating layer, or inside the second insulating layer by irradiating the laser beam onto the first insulating layer through the first substrate.

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