Stacked substrate for laser lift-off, substrate processing method, and substrate processing apparatus

Abstract

To provide a technique for suppressing irradiation of a device layer with a laser beam through a discharge path and suppressing damage to the device layer.SOLUTION: A laminated substrate for laser lift-off includes a first substrate transparent to a laser beam, an insulating layer that absorbs the laser beam, a polysilicon layer transparent to the laser beam, and a first device layer in this order. The laminated substrate includes a first electrode that penetrates the insulating layer and electrically connects the first substrate and the polysilicon layer. The first electrode includes a material that reflects the laser beam.SELECTED DRAWING: Figure 3

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 Art

[0002] When forming a device layer on a substrate such as a silicon wafer, plasma CVD (Chemical Vapor Depositon), plasma ALD (Atomic Layer Deposition), or plasma etching is 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 that the device layer is not damaged (see, for example, Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One aspect of the present disclosure provides a technique for suppressing irradiation of a laser beam onto a device layer through a discharge path and suppressing damage to the device layer.

Means for Solving the Problems

[0005] A stacked substrate for laser lift-off according to one aspect of the present disclosure is Used for the laser lift-off comprised of, in this order, a first substrate that transmits a laser beam, an insulating layer that absorbs the laser beam, a polysilicon layer that transmits the laser beam, and a first device layer. The stacked substrate includes a first electrode that electrically connects the first substrate and the polysilicon layer through the insulating layer. The first electrode contains a material that reflects the laser beam.

Advantages of the Invention

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

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same reference numerals, and the description thereof may be omitted.

[0009] Referring to FIG. 1, a stacked substrate 1 for laser lift-off according to an embodiment will be described. The stacked substrate 1 includes, for example, a first substrate 11, an insulating layer 12, a polysilicon layer 13, and a first device layer 16 in this order. Laser lift-off, which will be described in detail later, is a technique for peeling the first substrate 11 from the first device layer 16 using a laser beam LB that passes through the first substrate 11, as shown in FIGS. 2 to 4.

[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, an insulating layer 12, a polysilicon layer 13, and a first device layer 16 are formed in this order. Thereafter, a first bonding layer 17, which will be described later, may be formed.

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

[0012] The insulating layer 12 has insulating properties. The insulating material is excellent in absorbability of the laser beam LB. The insulating layer 12 is, for example, an oxide layer. Specific examples of the oxide layer include a silicon oxide layer. The oxide layer is formed by a thermal oxidation method, a CVD (Chemical Vapor Depositon) method, an ALD (Atomic Layer Deposition) method, or the like. When forming a silicon oxide layer by the CVD method, TEOS (Tetra Ethoxy Silane) or the like is used as a raw material for the silicon oxide layer. Note that the insulating layer 12 may be a silicon nitride layer, a silicon carbonitride layer, or the like.

[0013] A through-hole is formed in the insulating layer 12. The first electrode 18 is provided in the through-hole. The first electrode 18 penetrates the insulating layer 12 and electrically connects the first substrate 11 and the polysilicon layer 13. The first electrode 18 is used as part of a discharge path that discharges charged particles (for example, electrons or holes) accumulated in the first device layer 16 to the first substrate 11 during the formation of the first device layer 16.

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

[0015] The polysilicon layer 13 is part of the above discharge path. The polysilicon layer 13 has an impurity concentration of, for example, 1.0×10 19 / cm 3 or more and less than 3.0×10 20 / cm 3 . The impurity (dopant) may be a donor that provides electrons or an acceptor that provides holes. If the impurity concentration is 1.0×10 19 / cm 3 or more, the discharge property is good. If the impurity concentration is less than 3.0×10 20 / cm 3 , the polysilicon layer 13 has a high transmittance to the laser beam LB.

[0016] 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.

[0017] By the way, if the first electrode 18 contains a material that transmits the laser beam LB, the laser beam LB will pass through the first electrode 18 and the polysilicon layer 13 and be directly irradiated onto the first device layer 16. Since the first device layer 16 is irradiated with a high-intensity laser beam LB, the first device layer 16 will be damaged.

[0018] The first electrode 18 of this embodiment contains a material that reflects the laser beam LB. Therefore, as indicated by the dashed arrow in FIG. 3, the laser beam LB is reflected by the first electrode 18. Thus, irradiation of the high-intensity laser beam LB onto the first device layer 16 can be suppressed, and damage to the first device layer 16 can be suppressed. Note that outside the first electrode 18, the laser beam LB is absorbed by the insulating layer 12 as indicated by the solid arrow in FIG. 3, so the first device layer 16 is not damaged. The reflectivity of the laser beam LB in the first electrode 18 is, for example, 70% to 100%.

[0019] The first electrode 18 contains, for example, a transition metal, a conductive oxide, or polysilicon having an impurity concentration higher than that of the polysilicon layer 13. The transition metal contains, for example, at least one selected from the group consisting of Cu, Co, Ru, Mo, W, and Ti. The conductive oxide contains, for example, IGZO (oxide containing indium, gallium, and zinc), ITO (indium tin oxide), or the like. The polysilicon contained in the first electrode 18 has an impurity concentration of, for example, 3.0×10 20 / cm 3 or more and 3.0×10 21 / cm 3 or less. The impurity (dopant) may be a donor that provides electrons or an acceptor that provides holes. If the impurity concentration is 3.0×10 20 / cm 3 or more, the discharge property is good and the reflectivity of the laser beam LB is high.

[0020] 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 side opposite to the first substrate 11 with respect to the first device layer 16. The first substrate 11 and the second substrate 21 are bonded via the first device layer 16 and the second device layer 26.

[0021] 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 for electrically connecting 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, and may be further hydrophilized by the supply of water or water vapor before the first bonding layer 17 and the second bonding layer 27 are bonded face to face.

[0022] 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. On the surface of the second substrate 21 facing the first substrate 11, the second device layer 26 and the second bonding layer 27 are formed in this order.

[0023] The second device layer 26 includes, for example, semiconductor elements. The second device layer 26 is electrically connected to the first device layer 16. The second device layer 26 has a function different from that of the first device layer 16. For example, the second device layer 26 includes a CMOS (Complementary Metal Oxide Semiconductor) logic circuit, and the first device layer 16 includes 3D NAND cells.

[0024] Similar to the first bonding layer 17, the second bonding layer 27 is an insulating layer such as a silicon oxide layer. The second bonding layer 27 may include wiring for electrically connecting the first device layer 16 and the second device layer 26. The second bonding layer 27 has a bonding surface 27a that contacts the first bonding layer 17. The bonding surface 27a may be activated by plasma or the like, and may be further hydrophilized by the supply of water or water vapor.

[0025] 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. A covalent bond may be formed by a dehydration condensation reaction of the hydrogen bond. Since solids are directly bonded to each other without using a liquid adhesive, displacement due to deformation of the adhesive can be prevented. In addition, generation of inclination due to uneven thickness of the adhesive can be prevented.

[0026] Note that the laminated substrate 1 may include a first substrate 11, an insulating layer 12, a polysilicon layer 13, and a first device layer 16 in this order. The laminated substrate 1 may not include a first bonding layer 17, a second bonding layer 27, a second device layer 26, and a second substrate 21.

[0027] Next, with reference to FIGS. 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 peels the first substrate 11 from the first device layer 16 using a laser beam LB that passes through the first substrate 11. 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.

[0028] As shown in FIG. 2, the first substrate holding unit 31 holds the laminated substrate 1. The first substrate holding unit 31 holds the laminated substrate 1 horizontally from below with the first substrate 11 facing upward, for example. 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 move the first substrate holding unit 31 in the vertical direction.

[0029] The irradiator 32 irradiates the laminated substrate 1 held by the first substrate holding unit 31 with the laser beam LB. The laser beam LB is, for example, infrared light and has a wavelength of, for example, 8.8 μm to 11 μm. The silicon wafer that is the first substrate 11 has high transparency to infrared light, and the insulating layer 12 has high absorbency to infrared light. A peeling starting point 12a is formed at the irradiation point of the laser beam LB in the insulating layer 12.

[0030] The irradiator 32 includes an oscillator that oscillates the laser beam LB. The oscillator oscillates the laser beam LB in pulses. 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.

[0031] The irradiator 32 may include a galvanometer scanner or a polygon scanner to move the irradiation point of the laser beam LB on the stacked substrate 1. Note that 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 stacked substrate 1. In this case, a galvanometer scanner or the like is not necessary.

[0032] As shown in FIG. 4, the second substrate holding unit 34 holds the stacked substrate 1. The second substrate holding unit 34 holds the stacked substrate 1 from the side opposite to the first substrate holding unit 31 (for example, 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 move the second substrate holding unit 34 in the vertical direction.

[0033] 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. A program for controlling various processes executed in the substrate processing apparatus 3 is stored in the storage medium 392. The control unit 39 controls the operation of the substrate processing apparatus 3 by causing the CPU 391 to execute the program stored in the storage medium 392.

[0034] The control unit 39 controls the irradiator 32 and the first driving unit 33 to form peeling start points 12a at the interface between the first substrate 11 and the insulating layer 12. A plurality of peeling start points 12a are formed at intervals in the radial direction and the circumferential direction of the first substrate 11. The plurality of peeling start points 12a may be arranged concentrically or spirally. Note that the peeling start points 12a may be formed inside the insulating layer 12 as described above.

[0035] Thereafter, the control unit 39 controls the second driving unit 35 to perform control to peel the first substrate 11 from the first device layer 16. For example, in a state where 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 that connect a plurality of peeling starting points 12a in a planar shape are formed, and the first substrate 11 and the first device layer 16 are peeled off.

[0036] Note that the control unit 39 may lower the first substrate holding unit 31 instead of raising the second substrate holding unit 34, or in addition to raising the second substrate holding unit 34. The control unit 39 only needs to relatively move the first substrate holding unit 31 and the second substrate holding unit 34 away from each other in the vertical direction. The control unit 39 may rotate the first substrate holding unit 31 or the second substrate holding unit 34.

[0037] Next, with reference to FIG. 5, a laminated substrate 1 for laser lift-off according to the first modification will be described. Hereinafter, the differences between the above-described embodiment and the first modification will be mainly described. As shown in FIG. 5, the laminated substrate 1 may have a conductive layer 41 that reflects the laser beam LB between the insulating layer 12 and the polysilicon layer 13. The reflectance of the laser beam LB in the conductive layer 41 is, for example, 70% to 100%.

[0038] The conductive layer 41 is a part of the above-described discharge path. The conductive layer 41 contains, for example, a transition metal, a conductive oxide, or polysilicon. The transition metal contains, for example, at least one selected from the group consisting of Cu, Co, Ru, Mo, W, and Ti. The conductive oxide contains, for example, IGZO or ITO. The polysilicon contained in the conductive layer 41 has an impurity concentration higher than that of the polysilicon layer 13, for example, 3.0×10 20 / cm 3 above 3.0×10 21 / cm 3 and has the following impurity concentration.

[0039] By reflecting the laser beam LB, the conductive layer 41 can reduce the intensity of the laser beam LB reaching the first device layer 16 and can surely suppress damage to the first device layer 16.

[0040] As described above, 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. However, the present disclosure is not limited to the above embodiments. Within the scope described in the claims, various changes, modifications, substitutions, additions, deletions, and combinations are possible. Naturally, they also belong to the technical scope of the present disclosure.

Description of Reference Numerals

[0041] 1 Laminated substrate 11 First substrate 12 Insulating layer 13 Polysilicon layer 16 First device layer 18 First electrode LB Laser beam

Claims

1. A laminated substrate for laser lift-off, comprising: a first substrate that transmits a laser beam used for the laser lift-off; an insulating layer that absorbs the laser beam; a polysilicon layer that transmits the laser beam; and a first device layer, provided in this order, and a first electrode that electrically connects the first substrate and the polysilicon layer through the insulating layer. The first electrode contains a material that reflects the laser beam, and is a laminated substrate for laser lift-off.

2. The laminated substrate for laser lift-off according to claim 1, wherein the first electrode contains a transition metal, a conductive oxide, or polysilicon having an impurity concentration higher than that of the polysilicon layer.

3. The laminated substrate for laser lift-off according to claim 1 or 2, further comprising a conductive layer that reflects the laser beam between the insulating layer and the polysilicon layer.

4. The laminated substrate for laser lift-off according to any one of claims 1 to 3, wherein the insulating layer is a silicon oxide layer.

5. A second device layer electrically connected to the first device layer, and a second substrate on which the second device layer is formed, wherein the first substrate and the second substrate are joined via the first device layer and the second device layer, and is a laminated substrate for laser lift-off according to any one of claims 1 to 4.

6. Preparing a laminated substrate for laser lift-off according to any one of claims 1 to 5, and forming a peeling starting point at an interface between the first substrate and the insulating layer or inside the insulating layer by irradiating the insulating layer with the laser beam through the first substrate, which is a substrate processing method.

7. A substrate holding part that holds a laminated substrate for laser lift-off according to any one of claims 1 to 5, an irradiator that irradiates the laminated substrate held by the substrate holding part with the laser beam, and a control part that controls the irradiator, wherein the control part controls to form a peeling starting point at an interface between the first substrate and the insulating layer or inside the insulating layer by irradiating the insulating layer with the laser beam through the first substrate, and is a substrate processing apparatus. ​

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