JP2015074003A - Internal processing layer-forming single crystal member, and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal processing layer-forming single crystal member and a manufacturing method for the same, in which a processing time is shortened, when a relatively large and thin single crystal substrate is formed by being peeled from the processing layer formed in a single crystal member.SOLUTION: A laser beam is condensed on the inside of a single crystal member of silicon to form affected zones 21c which are arranged regularly in a scan direction S of the laser beam and an off-set direction F respectively. In so doing, at least one of a crack CS straddling the affected zones 21c adjacent to each other in the scan direction S of the laser beam and a crack CF straddling the affected zones 21c adjacent to each other in the off-set direction F of the laser beam is formed.

Description

  The present invention relates to an internally processed layer-forming single crystal member in which a processed layer is formed inside a single crystal member by condensing laser light from the surface on the irradiated side of the single crystal member of silicon into the single crystal member, and its manufacture Regarding the method.

  Conventionally, when manufacturing a semiconductor wafer typified by a single crystal silicon (Si) wafer, a cylindrical ingot solidified from a silicon melt melted in a quartz crucible is cut into blocks of an appropriate length. Then, the peripheral edge is ground to a target diameter, and then the block-shaped ingot is sliced into a wafer shape with a wire saw to manufacture a semiconductor wafer.

  The semiconductor wafer thus manufactured is subjected to various processes such as formation of a circuit pattern in the previous process in order and used for the subsequent process, and the back surface is back-ground processed in the subsequent process to achieve thinning. Accordingly, the thickness is adjusted to about 750 μm to 100 μm or less, for example, about 75 μm or 50 μm.

  A conventional semiconductor wafer is manufactured as described above, and an ingot is cut by a wire saw, and a cutting allowance larger than the thickness of the wire saw is required for cutting, so a thin semiconductor wafer having a thickness of 0.1 mm or less It is very difficult to manufacture the product, and the product rate is not improved.

  On the other hand, the focusing point of the laser beam is adjusted to the inside of the ingot (wafer) with the condenser lens, and the ingot is relatively scanned with the laser beam, so that a planar modified layer by multiphoton absorption is inside the ingot. It is disclosed that a (processed layer) is formed, and a part of the ingot is peeled off using the modified layer as a peeling surface (see, for example, Patent Document 1).

  In this specification, a wafer is appropriately referred to as a substrate unless otherwise specified.

JP2011-167718A

  However, when the modified layer is formed inside the single crystal member, one laser pulse forms one (one) processing mark. Therefore, the processing pitch, which is the processing interval, is determined by the stage moving speed and the pulse frequency in the processing progress direction. Further, the number of processing marks (the number of processing) formed inside the single crystal member is determined by the processing pitch and the processing offset that is an interval in the offset direction (direction orthogonal to the processing progress direction).

  Therefore, the machining time is shortened by reducing the number of machining pitches and machining offsets.

  On the other hand, it is possible to create a new single crystal member by dividing the inner processed layer on which the single crystal member is formed. As this dividing method, a method in which a single crystal member in which an internal processing layer is formed is sandwiched and fixed by a metal plate using an adhesive, and then peeled by applying a force in a direction away from each other, a single crystal Examples include a method in which stress is applied from the side surface of a substrate to propagate a crack and peel off. However, in the method of dividing the single crystal member from the processed layer by such a conventional method, a stress or deformation is caused in the non-processed layer region of the single crystal member due to stress being applied to or applied to the single crystal member. And is likely to cause metastasis. As a result, the quality of the divided and created single crystal member is deteriorated, resulting in problems in actual use. Furthermore, it is suggested that the internally processed layer crystal member that requires these cutting methods cannot be separated unless the internal processed layer is loaded or applied with stress. Therefore, there is a need for a method for forming a processed layer that can divide and separate the single crystal member from the formed internal processed layer without applying or applying stress.

  In view of the above problems, the present invention is capable of peeling without applying stress when forming a relatively large and thin silicon single crystal substrate by peeling from a processed layer formed on a silicon single crystal member. It is an object of the present invention to provide an internally processed layer-forming single crystal member capable of reducing the processing time and a method for manufacturing the same.

  According to one aspect of the present invention for solving the above-described problem, the single crystal member is irradiated with laser light from the irradiated surface of the single crystal member of silicon via a laser condensing unit that condenses the laser light. And the laser condensing means are relatively moved to provide a processed layer formed inside the single crystal member, and a non-processed portion adjacent to both sides of the processed layer, and the processed layer In which the altered portions formed by condensing the laser light are arranged in the scanning direction and the offset direction of the laser light, respectively, and the cracks straddling the altered portions adjacent to each other in the scanning direction of the laser light, and the offset of the laser light Provided is an internally processed layer-forming single crystal member in which at least one of cracks straddling altered portions adjacent to each other is formed.

  According to another aspect of the present invention, the single crystal member and the laser condensing means are irradiated while irradiating the laser light from the irradiated surface of the single crystal member of silicon through the laser condensing means for condensing the laser light. And the relative movement of the single crystal member, forming a processed layer inside the single crystal member, and using the single crystal member as an internal processed layer forming single crystal member, At the time of forming the processed layer, at least one of the cracks straddling the deteriorated portions adjacent to each other in the laser beam scanning direction and the cracks straddling the deteriorated portions adjacent to each other in the laser beam offset direction, There is provided a method for producing an internally processed layer-forming single crystal member that is formed so as to cause the above.

  According to the present invention, when a relatively large and thin silicon single crystal substrate is formed by peeling from a processed layer formed on a silicon single crystal member, it can be peeled without applying stress, and the processing time can be reduced. An internally processed layer-forming single crystal member that can be shortened and a method for manufacturing the same can be provided.

It is a typical bird's-eye view explaining manufacturing an internal processing layer formation single crystal member by one embodiment of the present invention. It is a typical side sectional view explaining manufacture of an internal processing layer formation single crystal member by one embodiment of the present invention. It is a typical side sectional view of an internal processing layer formation single crystal member concerning one embodiment of the present invention. It is a side view explaining manufacturing an internal processing layer formation single crystal member in one embodiment of the present invention. It is a typical plane sectional view explaining an internal processing layer formation single crystal member concerning one embodiment of the present invention. It is a typical side sectional view explaining an internal processing layer formation single crystal member concerning one embodiment of the present invention. In an experiment example, it is explanatory drawing which cut | disconnected each alteration part located in a line along the process advancing direction. In an experiment example, it is the optical microscope photograph figure which cut | disconnected each alteration part located in a line along the process advancing direction.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, the same or similar components as those already described are denoted by the same or similar reference numerals, and detailed description thereof is omitted as appropriate.

  In addition, it should be noted that the drawings are schematic and the dimensional ratios and the like are different from actual ones. Therefore, specific dimensional ratios and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments are exemplifications for embodying the technical idea of the present invention, and the embodiments of the present invention are described below in terms of the material, shape, structure, arrangement, etc. of the components. It is not something specific. The embodiments of the present invention can be implemented with various modifications without departing from the scope of the invention.

  FIG. 1 shows an embodiment of the present invention (hereinafter referred to as the present embodiment), in which laser light is condensed from an irradiated surface (surface on the irradiated side) of a single crystal member 10 by laser focusing means. It is a typical bird's-eye view explaining explaining that the processing layer 21 is formed. FIG. 2 is a schematic cross-sectional view for explaining that the processed layer 21 is formed inside the single crystal member 10 by irradiation with laser light to form the internal processed layer forming single crystal member. FIG. 3 is a schematic side cross-sectional view for explaining the cross-sectional structure of the internally processed layer-forming single crystal member 20 manufactured in the present embodiment. FIG. 4 is a side view for explaining the production of the internally processed layer-forming single crystal member in the present embodiment, and also shows an overall view of an example of the laser processing apparatus in the present embodiment. FIG. 5 is a schematic plan cross-sectional view for explaining the internally processed layer-forming single crystal member in the present embodiment. FIG. 6 is a schematic side cross-sectional view for explaining the internally processed layer forming single crystal member in the present embodiment.

(Overview)
The internally processed layer-forming single crystal member 20 manufactured in the present embodiment irradiates the pulsed laser beam B from the irradiated surface 20t of the silicon single crystal member 10 and condenses it inside the single crystal member. The processing layer 21 is spaced apart from the irradiation surface 20t and extends in parallel with the irradiated surface 20t, and the non-processing layers 22 adjacent to both surfaces of the processing layer 21 are provided.

  Altered portions 21 c formed by condensing the laser beam B are regularly arranged in the processing layer 21 in the scanning direction S and the offset direction F of the laser beam, respectively. In this embodiment, the crack CS (see FIGS. 5 and 6) straddling the deteriorated portions adjacent to each other in the laser beam scanning direction S and the crack CF (see FIG. 5) straddling the deteriorated portions adjacent to each other in the laser beam offset direction. 5 and 6) are formed. These cracks CS and CF are formed so as to extend in a planar shape from the altered portion 21c formed by the laser beam B, and are formed on the laser irradiation surface side of the altered portion 21c in the cross-sectional direction, and straddle the altered portions. ing.

  As shown in FIG. 6, each crack is formed at substantially the same depth position from the irradiated surface 20 t of the single crystal member 10, whether it is a crack CS or a crack CF. Here, “substantially the same depth” refers to a difference in depth position of 3 μm or less (or 2 μm or less when the dimension of the processing layer 21 is small), although it depends on the size of the processing layer 21. When this depth position exceeds 3 μm, it is necessary to apply a stress load or application at the time of peeling, and the peeling stress increases, resulting in deterioration of the quality of the single crystal member and reduction in the flatness of the peeling surface.

  In order to obtain the single crystal substrate by manufacturing the inner processed layer forming single crystal member 20, the laser beam B is applied to the irradiated surface 20 t of the single crystal member 10 by, for example, a condenser (assembled lens) 78 as laser condensing means. While irradiating and condensing the laser beam B inside the single crystal member 10, the condenser 78 and the single crystal member 10 are relatively moved so that the single crystal member 10 is parallel to the irradiated surface 20 t. The inner processed layer forming single crystal member 20 in which the extended processed layer 21 is formed is manufactured.

  At that time, the altered portion 21c is formed so that the crack CS and the crack CF are formed. The single crystal member 10 includes an irradiated surface 20t (first surface) that irradiates laser light B, and a light emitting surface 20s that is parallel to the irradiated surface 20t and through which the laser light B irradiated to the irradiated surface 20t passes. (Second surface) is used.

(Detailed explanation)
Hereinafter, this embodiment will be described in more detail. In the present embodiment, as shown in FIG. 4, the laser processing apparatus includes a laser oscillator 71 and a condenser 78 sequentially, and also includes an XY stage 80. The concentrator 78 is a combined lens in which a plurality of lenses are combined, and has high condensing performance.

  The size of the single crystal member 10 to be irradiated with the laser light is preferably made of, for example, a thick silicon wafer E having a diameter of 300 mm, and the irradiated surface Et irradiated with the laser light B is preferably planarized in advance.

  The laser beam B is applied to the irradiated surface 20t, not the peripheral surface of the single crystal member 10, via the condenser 78. This laser beam B is composed of, for example, a pulse laser beam having a pulse width of 1 μs or less, and a wavelength of 900 nm or more, preferably 1000 nm or more is selected, and a YAG laser or the like is preferably used.

(Function, effect)
Hereinafter, manufacturing the internally processed layer-forming single crystal member 10 in this embodiment will be described. In the present embodiment, the single crystal member 10 is placed on the XY stage 80, and the single crystal member 10 is held by a vacuum chuck, an electrostatic chuck, or the like. Then, by moving the single crystal member 10 in the X direction or the Y direction on the XY stage, the laser condensing means (condenser 78) and the single crystal member 10 are parallel to the irradiated surface 20t of the single crystal member 10. The laser beam B is irradiated while being relatively moved. As a result, as shown in FIG. 5, the altered portions 21 c are regularly formed in a line along the scanning direction S of the laser light B by the laser light B condensed inside the single crystal member 10. After the altered portions 21c are formed in a row, the single crystal member 10 is moved in the offset direction F by the movement of the XY stage 80, and the altered portions 21c are similarly formed in a row in the scanning direction S. In this way, the processed layer 21 is formed.

  In this embodiment, when forming the altered portion 21c, the processing pitch p, which is the interval between the altered portions 21c adjacent to each other in the laser beam scanning direction S, is in the range of 1 to 10 μm (more preferably 1.5 to 3.5 μm). ).

  Further, the processing offset w that is the interval between the altered portions 21c adjacent to each other in the offset direction F of the laser light is set to a range of 1 to 10 μm (more preferably, a range of 1.5 to 3.5 μm).

  As a result, when the altered portion 21c is formed, as shown in FIGS. 5 and 6, a crack CS straddling the altered portions 21c adjacent to each other in the scanning direction S of the laser beam occurs, and the offset direction of the laser beam Cracks CF straddling the altered portions 21c adjacent to F occur. The altered portion 21c is formed in an elongated shape along the irradiation direction of the laser beam B (for example, the vertical direction when the laser beam B is irradiated from above to below), and the cracks CS and CF are formed from the altered portion 21c. It spreads in a planar shape.

  From the viewpoint of forming the cracks CS and CF more uniformly and stably, it is more preferable that the processing pitch p is in the range of 1.5 to 3.5 μm, and the processing offset w is also 1.5 to 3.5 μm. More preferably, it is within the range. In order to shorten the time required for forming the cracks CS and CF, the processing pitch p and the processing offset w are increased.

  As a result of forming the processed layer 21, the non-processed layer 22 exists adjacent to the processed layer 21 on the opposite side to the irradiation direction of the laser beam B across the processed layer 21. The dimensions, density, and the like of the processed layer 21 to be formed are preferably set from the viewpoint of facilitating peeling.

  In the internally processed layer forming single crystal member 20 of the present invention, the cracks CS and CF are formed so as to extend in a planar shape from the altered portion 21c formed by the laser beam B, and the laser irradiation surface side of the altered portion 21c in the cross-sectional direction. The processed layer 21 and the non-processed layer 22 can be peeled off without applying and applying stress, and only the processed layer is exposed as described above. Can be peeled off, and a new single crystal member can be created without giving an impact or the like.

At this time, the above-described processed marks 21s and the altered layer 21c can be divided or separated without applying stress. In the present invention, to make it possible to sever or peel a single crystal member without applying a stress means that it can be severed or peeled by itself after the formation of the internal processed layer, and the peel load is 10 N / cm ² or less. Say.

  Moreover, in order to make it easy to peel, you may expose the process layer 21 to the side surface of the internal processing layer formation single-crystal member 20 before peeling. For example, when the non-processed layer 22 is cleaved along a predetermined crystal plane, a structure in which the processed layer 21 is sandwiched by the non-processed layer 22 is obtained. When the processed layer 21 is already exposed, or when the distance between the peripheral edge of the processed layer 21 and the side wall of the internal processed layer forming single crystal member 20 is sufficiently short, the exposure work can be omitted. It is.

  After peeling, the peeled surface (processed layer exposed surface) is polished by lapping and polishing. The polishing process can be performed using, for example, a lapping / polishing apparatus. In lapping, a slurry obtained by mixing free abrasive grains having a particle size of 1 μm to several tens of μm as a polishing agent with a lubricant is placed between a lapping plate and the exposed surface of the processed layer. As the free abrasive grains at this time, colloidal silica, alumina, fine diamond, cerium oxide, or the like can be used. In the polishing process, a fine abrasive having a particle size of 1 μm or less is used, and the exposed surface of the processed layer is polished by attaching a polishing pad to a surface plate.

  As described above, in the present embodiment, when the processed layer 21 is formed, the crack CS straddling the deteriorated portions 21c adjacent to each other in the scanning direction S of the laser beam is generated, and the offset direction F of the laser beam is generated. The crack CF straddling the degenerated portions 21c adjacent to each other is generated. Therefore, when the processed layer 21 and the non-processed layer 22 are peeled off, they can be peeled off from the cracks CS and CF.

  Therefore, since the processing pitch p of the altered portion 21c adjacent in the scanning direction S of the laser beam and the processing offset w of the altered portion 21c adjacent in the offset direction of the laser beam can be significantly widened, The processing density of the altered portion 21c, that is, the number of formed altered portions 21c can be significantly reduced. Therefore, the processing time of the altered portion 21c is greatly shortened, and the manufacturing efficiency of the internal processed layer forming single crystal member 20 is greatly improved. Further, the force required for peeling can be reduced, and peeling can be performed without applying stress.

  Further, the depth positions of the cracks CS and CF from the irradiated surface 20t are substantially the same for each crack. Therefore, the peeling surface of the non-processed layer 22 is significantly flat compared to the conventional case.

  In the present embodiment, an example in which both the crack CS and the crack CF are formed has been described. However, only one of the crack CS and the crack CF is formed by widening one of the processing pitch p and the processing offset w. However, it can be made to peel from the crack, and this can further shorten the processing time of the altered portion 21c.

  In the present embodiment, the silicon wafer E is described as an example of the single crystal member 10. However, the single crystal member 10 has an ingot shape, and a processed layer 21 is formed to form a non-processed portion on the laser light irradiation side. The steps may be sequentially repeated, and the dimensions of the single crystal member 10 are not particularly limited.

<Experimental example>
The inventor conducted an experiment for examining a preferable range of the processing pitch p and the processing offset w in forming the processed layer 21 and peeling the non-processed layer 22. As a result, under the following experimental conditions, the formation time of the processed layer 21 was relatively short, and good flatness was obtained on the peeled surface of the peeled non-worked layer 22.

Light source (laser oscillator): Fiber laser Wavelength: 1064nm
Mode: Single mode Condenser lens NA: 0.8
Repetition frequency: 100 kHz
Pulse width: 200 ns
Output: 1W (1μJ / pulse)
Processing speed: 300 mm / sec
Processing pitch p: 3 μm
Processing offset: 3 μm
Processing procedure and evaluation:
1) Adjust the height position of the condenser so that the beam is focused on the sample wafer surface.
2) Next, the height of the collector is processed from the position toward the sample wafer by 60 μm, and the beam focus is moved into the sample wafer.
3) A laser was irradiated on a 100 mm × 100 mm portion inside a φ150 mm wafer under the above processing conditions.
4) Two samples were prepared.
5) Using one sample, cut out one side of the laser irradiated part by dicing, expose the processed layer, and determine the difference in position of the 50 processed layers using a confocal laser microscope (model name: OLS-4000 Olympus) (Measurement by Co., Ltd.) and found to be 3 μm or less. The measurement results are shown in Table 1. Table 1 shows the measurement results based on the surface of the wafer on the laser irradiation surface side.
6) The laser irradiation area portion was cut out from the remaining one sample by dicing. The cut-out wafer could be cut into two pieces and separated by the processed layer without applying stress in the cut-out state.
7) As a result of measuring the surface roughness of the peeled wafer with a non-contact three-dimensional measuring apparatus (PF-60: manufactured by Mitaka Kogyo Co., Ltd.), the surface roughness Ra = 0.84 μm.

  FIG. 7 shows an explanatory diagram in which the processed layer 21 is formed on the single crystal member 10 under the same experimental conditions, and the altered portions 21c arranged in a line along the processing progress direction (laser scanning direction S) are cut in FIG. Are shown in FIG. In FIG. 7, the crack CS is omitted for simplicity. As shown in FIG. 8, it was confirmed that the crack CS straddling the adjacent altered portions 21c was formed at substantially the same depth position.

  Further, when the processing pitch p was 2 μm and the processing offset w was 2 μm, the flatness of the peeled surface of the non-processed layer 22 was further improved.

  From this experimental example, it was found that the processing pitch p is more preferably in the range of 1.5 to 3.5 μm and the processing offset w is more preferably in the range of 1.5 to 3.5 μm.

  Since a thin single crystal substrate can be efficiently formed according to the present invention, the thinly cut single crystal substrate can be applied to a solar cell as long as it is a Si substrate (silicon substrate). For example, the present invention can be applied to SiC power devices and the like, and can be applied in a wide range of fields such as transparent electronics field, lighting field, and hybrid / electric vehicle field.

10 Single crystal member 20 Internally processed layer forming single crystal member 20t Irradiated surface 21 Processed layer 21c Altered part 22 Non-processed layer (non-processed part)
72 Zoom Expander (Laser focusing means)
73 Aperture (Laser focusing means)
78 Condenser (laser condensing means)
B Laser beam CF Crack CS Crack F Offset direction S Scanning direction p Processing pitch w Processing offset

Claims (9)

By relatively moving the single crystal member and the laser condensing means while irradiating the laser light from the irradiated surface of the single crystal member of silicon through the laser condensing means for condensing the laser light, A processed layer formed inside the single crystal member;
A non-processed part adjacent to each side of the processed layer;
With
In the processed layer, altered portions formed by condensing the laser beam are arranged in the scanning direction and the offset direction of the laser beam, respectively.
Internally processed layer forming single crystal characterized in that at least one of a crack straddling the deteriorated portions adjacent to each other in the laser beam scanning direction and a crack straddling the deteriorated portions adjacent to each other in the laser beam offset direction is formed Element.   2. The internally processed layer-forming single crystal member according to claim 1, wherein each crack is formed at substantially the same depth position from the irradiated surface.   The crack which straddles between the quality-change parts adjacent in the scanning direction of a laser beam, and the crack which straddles between quality-change parts adjacent in the offset direction of a laser beam are formed, The claim 1 or 2 characterized by the above-mentioned. Internally processed layer forming single crystal member. By relatively moving the single crystal member and the laser condensing means while irradiating the laser light from the irradiated surface of the single crystal member of silicon through the laser condensing means for condensing the laser light, A method for producing an internally processed layer forming single crystal member, wherein a processed layer is formed inside the single crystal member and the single crystal member is used as an internally processed layer forming single crystal member,
At the time of forming the processed layer, at least one of the cracks straddling the deteriorated portions adjacent to each other in the laser beam scanning direction and the cracks straddling the deteriorated portions adjacent to each other in the laser beam offset direction, A method for producing an internally processed layer-forming single crystal member, characterized by comprising forming so   5. The method for producing an internally processed layer-forming single crystal member according to claim 4, wherein each crack is generated at substantially the same depth position from the irradiated surface.   6. The method for producing an internally processed layer-forming single crystal member according to claim 4, wherein a processing pitch, which is an interval between the altered portions adjacent to each other in the laser beam scanning direction, is in a range of 1 to 10 [mu] m.   The method for producing an internally processed layer-forming single crystal member according to claim 6, wherein the processing pitch is in the range of 1.5 to 3.5 µm.   6. The method for producing an internally processed layer-forming single crystal member according to claim 4, wherein a processing offset which is an interval between the altered portions adjacent to each other in a laser beam offset direction is in a range of 1 to 10 [mu] m.   9. The method for producing an internally processed layer-forming single crystal member according to claim 8, wherein the processing offset is in a range of 1.5 to 3.5 [mu] m.