Laser processing apparatus, laser stripping method, and semiconductor device manufacturing method

Abstract

To improve the manufacturing efficiency of semiconductor memory devices and to improve the reuse efficiency of substrates.SOLUTION: A laser processing device in one embodiment has a stage that holds a substrate and rotates, and a laser irradiation device that is movable in a radial direction of rotation and has a control unit that controls the output of an infrared pulse laser so that L1 / L2 is 1.2 or more and 10 or less when an interval between laser spots adjacent to the stage in a direction of rotation is L1 and an interval between laser spots adjacent in the radial direction of rotation is L2.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a laser processing apparatus, a laser peeling method, and a method for manufacturing a semiconductor device.

Background Art

[0002] A NAND flash memory is known as a semiconductor storage device. This NAND flash memory includes a memory cell array and its control circuit. As a method for manufacturing a semiconductor storage device, a method is known in which a memory cell array chip and a control circuit chip are respectively formed on separate substrates and then bonded together later. In this case, the substrate on which the memory cell array chip is formed can be reused by performing laser peeling.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0004] Embodiments relating to this disclosure provide a laser processing apparatus, a laser stripping method, and a method for manufacturing a semiconductor device that improve the manufacturing efficiency of semiconductor memory devices and improve the recycling efficiency of substrates. [Means for solving the problem]

[0005] The laser processing apparatus according to this embodiment includes a stage that holds a substrate and rotates, and a laser irradiation device that is movable in the radial direction of rotation and has a control unit that controls the output of an infrared pulse laser such that L1 / L2 is between 1.2 and 10 when the distance between adjacent laser spots in the rotational direction of the stage is L1 and the distance between adjacent laser spots in the radial direction of rotation is L2. [Brief explanation of the drawing]

[0006] [Figure 1] This figure shows the overall configuration of the semiconductor memory device (laminated substrate) according to this embodiment. [Figure 2] This is a cross-sectional view showing the configuration of a semiconductor memory device (laminated substrate) according to this embodiment. [Figure 3] This figure shows the overall configuration of the semiconductor memory device according to this embodiment. [Figure 4] This is a top view showing the basic configuration of the laser processing apparatus according to this embodiment. [Figure 5] This is a side view showing the basic configuration of the laser processing apparatus according to this embodiment. [Figure 6] This is a top view showing the laser irradiation area (laser spot) of the semiconductor memory device (laminated substrate) 1 according to this embodiment. [Figure 7] This is an enlarged top view showing the laser irradiation area (laser spot) of the semiconductor memory device (laminated substrate) 1 according to this embodiment. [Modes for carrying out the invention]

[0007] Hereinafter, the laser processing apparatus, laser stripping method, and semiconductor device manufacturing method according to this embodiment will be specifically described with reference to the drawings. In the following description, elements having substantially the same function and configuration are denoted by the same reference numeral or by an alphabet letter added to the same reference numeral, and will be described redundantly only when necessary. The embodiments shown below illustrate apparatuses and methods for realizing the technical idea of ​​this embodiment. Various modifications can be made to one embodiment without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims.

[0008] While drawings may schematically represent the width, thickness, shape, etc., of each part compared to the actual embodiment in order to clarify the explanation, these are merely examples and do not limit the interpretation of the present invention. In this specification and in each drawing, elements having the same function as those described in previously shown drawings are denoted by the same reference numerals, and redundant explanations may be omitted.

[0009] In each embodiment, the direction from each substrate toward the memory cell or control circuit is referred to as "upward." Conversely, the direction from the memory cell or control circuit toward each substrate is referred to as "downward." Thus, for the sake of explanation, the terms "upward" and "downward" are used, but for example, the up-down relationship between the substrate and the memory cell may be reversed from that shown in the diagram. Also, in the following explanation, for example, the expression "memory cell on the substrate" merely describes the up-down relationship between the substrate and the memory cell as described above, and other components may be placed between the substrate and the memory cell.

[0010] In this specification, expressions such as "α includes A, B, or C" do not exclude cases where α includes multiple combinations of A, B, and C unless otherwise specified. Furthermore, these expressions do not exclude cases where α includes other elements.

[0011] The following embodiments can be combined with each other, provided that no technical inconsistencies arise.

[0012] <First Embodiment> [Semiconductor memory device (bonded substrate)] The configuration of the semiconductor memory device (bonded substrate) 1 according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a diagram showing the overall configuration of the semiconductor memory device (bonded substrate) 1. FIG. 2 is a cross-sectional view showing the basic configuration of the semiconductor memory device (bonded substrate) 1. FIG. 3 is a diagram showing the overall configuration of the semiconductor memory device 2. As shown in FIG. 1, the semiconductor memory device (bonded substrate) 1 includes a memory cell array chip 100 as a first circuit layer, and a control circuit (CMOS circuit) chip 200 as a second circuit layer. The memory cell array chip 100 and the control circuit chip 200 are connected at a connection surface C1. The first circuit layer and the second circuit layer are not particularly limited. Therefore, the semiconductor memory device of the embodiment may be referred to as a "semiconductor device".

[0013] [Structure of memory cell array chip] As shown in FIG. 2, the memory cell array chip 100 has a substrate 10, a laser absorption layer 14, a plurality of electrode layers 16, a plurality of semiconductor pillars 15, and a memory-side wiring layer 17. The plurality of electrode layers 16 are alternately stacked with a plurality of insulating layers on the substrate 10 via the laser absorption layer 14. Each semiconductor pillar 15 is arranged to penetrate the stacked plurality of electrode layers 16 in a direction perpendicular to the substrate 10. Each semiconductor pillar 15 functions as a plurality of transistors including memory cells by being combined with the plurality of electrode layers 16 via the insulating layer. That is, in the memory cell array region 11 (the upper left portion of FIG. 2), a plurality of transistors including memory cells are three-dimensionally arranged. The semiconductor pillar 15 is electrically connected to a source line at one end (on the substrate 10 side), and is electrically connected to the memory-side wiring layer 17 at the other end (on the side opposite to the substrate 10). Connection terminals for connecting to the control circuit chip 200 are arranged on the connection surface C1 of the memory-side wiring layer 17 on the side opposite to the substrate 10.

[0014] On the substrate 10, a lead-out region 12 (the upper right portion in FIG. 2) is arranged side by side with the memory cell array region 11. In the lead-out region 12, the terminal portions of the plurality of electrode layers 16 are each led out in a stepped shape. Each terminal portion is connected to a wiring arranged in the vertical direction via a contact hole opened in an insulating film. These vertical wirings are electrically connected to the memory-side wiring layer 17, and connected to the control circuit chip 200 via connection terminals.

[0015] The substrate 10 may be a semiconductor wafer such as a silicon substrate or a glass substrate. A laser absorption layer 14 is disposed between the substrate 10 and the plurality of electrode layers 16. As shown in FIG. 3, the substrate 10 and the laser absorption layer 14 of the semiconductor memory device (bonded substrate) 1 according to the present embodiment are finally removed from the semiconductor memory device 2 by irradiating the laser absorption layer 14 with a laser in the manufacturing process of the semiconductor memory device. The laser absorption layer 14 is preferably, for example, a silicon oxide film. The semiconductor memory device 2 may be singulated into semiconductor chips after the substrate 10 and the laser absorption layer 14 are removed. The substrate 10 peeled off by the laser treatment may be reused.

[0016] [Structure of Control Circuit Chip] As shown in FIG. 2, the control circuit chip 200 includes a substrate 20, a plurality of transistors 26 constituting a control circuit, and a circuit-side wiring layer 27. The plurality of transistors 26 are formed on the substrate 20, and are electrically connected to the circuit-side wiring layer 27 on the side opposite to the substrate 20. Connection terminals for connecting to the memory cell array chip 100 are arranged on the connection surface C1 of the circuit-side wiring layer 27 on the side opposite to the substrate 20. The substrate 20 may be a semiconductor wafer such as a silicon substrate.

[0017] [Laser Processing Apparatus] The laser processing apparatus 300 according to the present embodiment will be described with reference to FIG. 4 and FIG. 5.

[0018] Figure 4 is a top view showing the basic configuration of the laser processing apparatus. Figure 5 is a side view showing the basic configuration of the laser processing apparatus. As shown in Figures 4 and 5, the laser processing apparatus 300 comprises a stage 32 and a laser irradiation device 35.

[0019] The stage 32 is circular and holds a wafer-shaped (disk-shaped) semiconductor memory device (bonded substrate) 1. Preferably, the center of the semiconductor memory device (bonded substrate) 1 is positioned at the center C of the stage 32. The semiconductor memory device (bonded substrate) 1 is arranged with the substrate 20 facing downwards (towards the stage 32) and the substrate 10 facing upwards (opposite side from the stage 32).

[0020] Stage 32 includes a rotation mechanism 33 and a control unit 39. Stage 32 rotates around a vertical axis containing the center C by the rotation mechanism 33. In Figure 4, the direction of rotation of Stage 32 is shown clockwise (arrow), but it may also rotate counterclockwise. As Stage 32 rotates, the semiconductor memory device (bonded substrate) 1 held by Stage 32 rotates around the center C. The rotational movement and rotational speed of Stage 32 driven by the rotation mechanism 33 are controlled by the control unit 39.

[0021] Stage 32 may include a holding mechanism 34. The holding mechanism 34 can hold the substrate 10, which has been peeled off from the semiconductor memory device (bonded substrate) 1 by laser processing, on the stage 32. In Figure 4, two holding mechanisms 34 are placed at the edge of the semiconductor memory device (bonded substrate) 1. However, the number and location of the holding mechanisms 34 per semiconductor memory device (bonded substrate) 1 are not particularly limited. The holding mechanism 34 only needs to not interfere with the laser processing and be able to recover the peeled substrate 10. The substrate 10 recovered without damage by the holding mechanism 34 can be reused.

[0022] A laser irradiation device 35 is positioned above the stage 32. The laser irradiation device 35 irradiates the laser absorption layer 14 of the semiconductor memory device (laminated substrate) 1 with a laser. The laser irradiation device 35 irradiates with a high-frequency pulsed laser emitted from a laser oscillator (not shown). The laser is transparent to the substrate 10. Therefore, by irradiating the semiconductor memory device (laminated substrate) 1 with a laser from the substrate 10 side, the laser can be focused and irradiated onto the laser absorption layer 14 located beneath the substrate 10. The laser is preferably an infrared pulsed laser, and preferably a carbon dioxide laser (CO2 laser). The laser irradiation causes ablation of the laser absorption layer 14.

[0023] The laser irradiation device 35 includes a moving mechanism 36 and a control unit 38. The laser irradiation device 35 moves radially above the stage 32 by the moving mechanism 36. In Figures 4 and 5, the direction of movement of the laser irradiation device 35 is shown (arrow) from the edge of the stage 32 toward the center C, but it may also move from the center C toward the edge of the stage 32. The laser irradiation device 35 can move at least from the edge to the center (within a radius) of the semiconductor memory device (bonded substrate) 1. As the laser irradiation device 35 moves while the stage 32 rotates, the laser irradiation device 35 irradiates the stage 32 with a laser along a spiral trajectory. That is, the laser irradiation device 35 irradiates the semiconductor memory device (bonded substrate) 1 placed on the stage 32 with a laser along a spiral trajectory. The movement operation and speed of the laser irradiation device 35 driven by the moving mechanism 36, and the laser output of the laser irradiation device 35 are controlled by the control unit 38.

[0024] [Laser peeling method] This invention describes a laser delamination method for removing a substrate 10 and a laser absorption layer 14 from a semiconductor memory device (bonded substrate) 1 using a laser processing apparatus 300 according to this embodiment. The semiconductor memory device (semiconductor device) of this embodiment is manufactured using the laser delamination method described below.

[0025] As shown in Figures 4 and 5, the semiconductor memory device (laminated substrate) 1 is placed on the stage 32 with the substrate 20 facing downwards (towards the stage 32) and the substrate 10 facing upwards (opposite side of the stage 32). By moving the laser irradiation device 35 while rotating the stage 32, the laser irradiation device 35 irradiates the stage 32 with a laser along a spiral trajectory. The laser is focused and irradiated onto the laser absorption layer 14 of the semiconductor memory device (laminated substrate) 1. The laser irradiation device 35 is moved at least from the edge to the center (within the radius) of the semiconductor memory device (laminated substrate) 1.

[0026] Figure 6 is a top view showing the laser irradiation area of ​​the semiconductor memory device (laminated substrate) 1. Figure 7 is an enlarged top view showing the laser irradiation area of ​​the semiconductor memory device (laminated substrate) 1. Figure 7 is an enlarged top view of the top surface of the laser absorption layer 14 in Figure 2 (area a in Figure 4). As the stage 32 rotates, the continuously irradiated laser spots S move in the opposite direction (arrow) to the rotation direction of the stage 32. That is, the two continuously irradiated laser spots S are adjacent in the direction of rotation of the stage 32. The distance L1 between the two continuously irradiated laser spots S is the linear velocity / frequency of the pulsed laser. Here, the distance L1 between the two laser spots S indicates the distance between the centers of the two laser spots S. The linear velocity of the pulsed laser is the moving speed (rotation speed) of the stage 32 at the position of the laser irradiation device 35, and is controlled by the control unit 39. The position of the laser irradiation device 35 and the frequency of the pulsed laser are controlled by the control unit 38.

[0027] In this embodiment, for example, the distance L1 between two consecutively irradiated laser spots S may be greater than the diameter x of the laser spot S (L1 > x). That is, two adjacent laser spots S in the rotational direction of the stage 32 may be spaced (L1 - x) apart. Here, the diameter x of the laser spot S represents the full width at half maximum of the laser spot S on the upper surface of the laser absorption layer 14. For example, the diameter x of the laser spot S may be defined by observing the laser trail. The diameter x of the laser spot is controlled by the control unit 38.

[0028] It is preferable that the spacing L1 of the laser spots S be substantially the same across almost the entire surface of the substrate 10. That is, it is preferable that the spacing L1 of the laser spots S be substantially the same in the central part of the substrate 10 and in the outer peripheral part located outside the central part. For this reason, it is preferable to increase the rotation speed of the stage 32 as the position of the laser irradiation device 35 approaches the center C. It is also preferable to decrease the frequency of the pulsed laser (increase the pulse period) as the position of the laser irradiation device 35 approaches the center C.

[0029] While the stage 32 rotates approximately once, the laser irradiation device 35 moves toward the center C. That is, the lapped laser spot S is adjacent to the laser spot S of the previous rotation in the radial direction of the stage 32. The distance L2 between two adjacent laser spots S in the direction of movement of the laser irradiation device 35 is the distance the laser irradiation device 35 moves while the stage 32 rotates once. Here, the distance L2 between two laser spots S represents the distance between the centers of the two laser spots S. The distance the laser irradiation device 35 moves while the stage 32 rotates once is controlled by the control unit 38 by the movement speed of the laser irradiation device 35.

[0030] In this embodiment, for example, the distance L2 between two adjacent laser spots S in the direction of movement of the laser irradiation device 35 may be greater than the diameter x of the laser spots S (L2 > x). That is, two adjacent laser spots S in the radial direction of the stage 32 may be spaced (L2 - x) apart.

[0031] It is preferable that the spacing L2 of the laser spots S be substantially the same across almost the entire surface of the substrate 10. That is, it is preferable that the spacing L2 of the laser spots S be substantially the same in the center of the substrate 10 and in the outer peripheral area located outside the center. For this reason, it is preferable that the moving speed of the laser irradiation device 35 be constant. However, it is not limited to this, and if the rotation speed of the stage 32 is increased in order to keep the spacing L1 of the laser spots S constant, the moving speed of the laser irradiation device 35 may also be increased.

[0032] In the present embodiment, the interval L1 between two consecutively irradiated laser spots S is larger than the interval L2 between two adjacent laser spots S in the moving direction of the laser irradiation device 35 (L1>L2). The interval L1 between two consecutively irradiated laser spots S is preferably in a range of 1.2 times or more and 10 times or less the interval L2 between two adjacent laser spots S in the moving direction of the laser irradiation device 35 (1.2<L1 / L2<10). When the interval L1 between two consecutively irradiated laser spots S is less than 1.2 times the interval L2 between two adjacent laser spots S in the moving direction of the laser irradiation device 35, the bonding of the laser absorption layer 14 between the two adjacent laser spots S in the moving direction of the laser irradiation device 35 cannot be sufficiently reduced, and the peeling behavior of the laser absorption layer 14 becomes non-uniform when separating the substrate 10 from the semiconductor memory device (bonded substrate) 1. When the interval L1 between two consecutively irradiated laser spots S is larger than 10 times the interval L2 between two adjacent laser spots S in the moving direction of the laser irradiation device 35, the manufacturing efficiency of the semiconductor memory device 2 decreases. Further, the interval L1 between two consecutively irradiated laser spots S is more preferably in a range of 1.2 times or more and 2.3 times or less the interval L2 between two adjacent laser spots S in the moving direction of the laser irradiation device 35 (1.2<L1 / L2<2.3). It is preferable that the ratio (L1 / L2) of the interval L1 of the laser spots S to the interval L2 of the laser spots S is substantially constant over substantially the entire surface of the substrate 10. That is, the central portion of the substrate 10 and the outer peripheral portion located outside the central portion each satisfy 1.2<L1 / L2<10, and more preferably satisfy 1.2<L1 / L2<2.3.

[0033] In the laser delamination method according to this embodiment, the spacing L1, L2 and the diameter x of the laser spots S can be appropriately adjusted by controlling the rotation speed of the stage 32 of the laser processing apparatus 300, the movement speed of the laser irradiation device 35, and the laser output of the laser irradiation device 35 (frequency of the pulsed laser, diameter of the laser spot) using control units 38 and 39. By controlling the spacing L1, L2 and the diameter x of the laser spots S within the above range, the effect of heat accumulation from two continuously irradiated laser spots S can be suppressed, and the bonding force of the laser absorption layer 14 can be uniformly reduced, thereby separating the substrate 10 from the semiconductor memory device (bonded substrate) 1. Therefore, the laser delamination method according to this embodiment can improve the manufacturing efficiency of the semiconductor memory device 2 and improve the reuse efficiency of the substrate 10.

[0034] In this embodiment, the rotational speed of the stage 32 of the laser processing apparatus 300, the movement speed of the laser irradiation device 35, and the laser output of the laser irradiation device 35 (pulse laser frequency, laser spot diameter) are shown to be controlled by two control units 38 and 39, respectively. However, the embodiment is not limited to this configuration, and the rotational speed of the stage 32 of the laser processing apparatus 300, the movement speed of the laser irradiation device 35, and the laser output of the laser irradiation device 35 (pulse laser frequency, laser spot diameter) may be integrated and controlled by a single control unit.

[0035] Furthermore, the laser irradiation device 35 is shown as having a configuration that oscillates a single laser beam. However, it is not limited to this, and the laser irradiation device 35 may also have a configuration that oscillates multiple laser beams. In this case, the multiple laser beams may be arranged at a distance L2 apart in the radial direction of the stage 32, or they may be arranged at a radial distance of the semiconductor memory device (bonded substrate) 1 in the radial direction of the stage 32. By controlling the intervals L1 and L2 of the laser spots S to the above range, the laser can be irradiated more efficiently.

[0036] 1 Semiconductor memory device (bonded substrate), 2 Semiconductor memory device, 10 Substrate, 11 Memory cell array area, 12 Extraction area, 14 Laser absorption layer, 15 Semiconductor pillar, 16 Electrode layer, 17 Memory-side wiring layer, 20 Substrate, 26 Transistor, 27 Circuit-side wiring layer, 32 Stage, 33 Rotation mechanism, 34 Holding mechanism, 35 Laser irradiation device, 36 Moving mechanism, 38 Control unit, 39 Control unit, 100 Memory cell array chip, 200 Control circuit (CMOS circuit) chip, 300 Laser processing device

Claims

1. A rotating stage for holding a bonded substrate in which a first silicon substrate and a second silicon substrate are bonded together via a laser absorption layer, A laser irradiation device having a control unit that is movable in the radial direction of the rotation, and when the distance between adjacent laser spots in the rotational direction of the stage is L1, the distance between adjacent laser spots in the radial direction of the rotation is L2, and the diameter of the laser spot is x, controls the frequency of the infrared pulsed laser so that L1 > L2, L1 > x, and L2 > x in the central part of the bonded substrate and the outer peripheral part located outside the central part of the bonded substrate, controls the frequency of the infrared pulsed laser so that 1.2 < L1 / L2 < 10 is satisfied in the central part of the bonded substrate, and controls the frequency of the infrared pulsed laser so that 1.2 < L1 / L2 < 10 is satisfied in the outer peripheral part of the bonded substrate, A holding mechanism for holding the second silicon substrate, which has been peeled off from the bonded substrate by laser processing, on the stage, A laser processing device having the following features.

2. The laser processing apparatus according to claim 1, wherein L1 is the linear velocity / frequency of the infrared pulsed laser, and the linear velocity of the infrared pulsed laser is the rotational speed of the stage at the irradiation position of the infrared pulsed laser.

3. The laser processing apparatus according to claim 1, wherein the control unit further controls the diameter of the laser spot.

4. The laser processing apparatus according to claim 1, wherein the infrared pulsed laser includes a carbon dioxide laser.

5. A laminated substrate, in which a first silicon substrate and a second silicon substrate are bonded together via a laser absorption layer, is placed on the stage. The aforementioned stage is rotated, When the distance between adjacent laser spots in the rotational direction of the stage is L1, the distance between adjacent laser spots in the radial direction of the rotation is L2, and the diameter of the laser spot is x, the frequency of the infrared pulsed laser is controlled in the central part of the second silicon substrate and the outer peripheral part located outside the central part to satisfy L1 > L2, L1 > x, and L2 > x, the frequency of the infrared pulsed laser is controlled in the central part of the bonded substrate to satisfy 1.2 < L1 / L2 < 10, and the frequency of the infrared pulsed laser is controlled in the outer peripheral part of the bonded substrate to satisfy 1.2 < L1 / L2 < 10, and the laser irradiation device that irradiates the laser absorption layer with the infrared pulsed laser is moved in the radial direction of the rotation. A laser delamination method comprising a holding mechanism that holds the second silicon substrate, which has been delaminated from the bonded substrate by irradiating the laser absorption layer with the infrared pulsed laser, on the stage.

6. The laser stripping method according to claim 5, wherein L1 is the linear velocity / frequency of the infrared pulsed laser, and the linear velocity of the infrared pulsed laser is the rotational speed of the stage at the irradiation position of the infrared pulsed laser.

7. The laser peeling method according to claim 5, wherein the laser irradiation device further controls the diameter of the laser spot.

8. The laser stripping method according to claim 5, wherein the infrared pulsed laser includes a carbon dioxide laser.

9. A laminated substrate, in which a first silicon substrate and a second silicon substrate are bonded together via a laser absorption layer, is placed on the stage. The aforementioned stage is rotated, When the distance between adjacent laser spots in the rotational direction of the stage is L1, the distance between adjacent laser spots in the radial direction of the rotation is L2, and the diameter of the laser spot is x, the frequency of the infrared pulsed laser is controlled in the central part of the second silicon substrate and the outer peripheral part located outside the central part to satisfy L1 > L2, L1 > x, and L2 > x, the frequency of the infrared pulsed laser is controlled in the central part of the bonded substrate to satisfy 1.2 < L1 / L2 < 10, and the frequency of the infrared pulsed laser is controlled in the outer peripheral part of the bonded substrate to satisfy 1.2 < L1 / L2 < 10, and the laser irradiation device that irradiates the laser absorption layer with the infrared pulsed laser is moved in the radial direction of the rotation. The holding mechanism holds the second silicon substrate, which has been detached from the bonded substrate by irradiating the laser absorption layer with the infrared pulsed laser, A method for manufacturing a semiconductor device, comprising reusing the second silicon substrate.

10. The method for manufacturing a semiconductor device according to claim 9, wherein the laser absorption layer includes a silicon oxide film.

11. The method for manufacturing a semiconductor device according to claim 9, wherein the bonded substrate includes a CMOS circuit, a memory cell array, and the laser absorption layer between the first silicon substrate and the second silicon substrate, and the infrared pulsed laser is irradiated from the second silicon substrate side.

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