JP6381110B2 - Substrate processing method and substrate - Google Patents

Description

  The present invention relates to a substrate processing method for processing a silicon single crystal substrate and a substrate obtained by processing a silicon single crystal substrate.

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

  The semiconductor wafer manufactured in this way is subjected to various processes such as circuit pattern formation in the previous process in order and used in the subsequent process. In this subsequent process, the back surface is back-grinded and thinned. Accordingly, the thickness is adjusted to about 750 μm to 100 μm or less, for example, about 75 μm or 50 μm.

  In addition, instead of the wire saw, the focusing point of the laser beam is aligned with the inside of the ingot with a condensing lens, and the ingot is relatively scanned with the laser beam, so that the surface processing is performed inside the blocked ingot. There has been proposed a slicing technique in which a layer is formed, and a part of the ingot is peeled off using the processed layer as a peeling surface (see, for example, Patent Documents 1 to 3).

  Conventionally, in order to peel off such a substrate, the ingot block is temporarily fixed to another member, and can be easily removed after peeling off the substrate. An adhesive with weak adhesive strength was used.

JP 2012-169361 A JP 2012-169363 A JP 2013-161820 A

  However, if the block of the ingot is temporarily fixed to another member with an adhesive in this way, it requires a step of peeling the adhesive after the substrate is peeled off, and it is difficult to provide a base material in a field where contamination is not desired. -A separate purification step was required.

  The present invention is proposed in view of the above-described problems, and does not require a step of temporarily fixing to another member with an adhesive when the substrate is peeled off, and processing by such a method. It is an object to provide a finished substrate.

  The substrate processing method according to this application is to process a single crystal silicon substrate, and the laser condensing means irradiates the surface of the substrate with laser light to condense the laser light inside the substrate. The process of forming a processing layer inside the substrate by relatively moving the laser focusing means and the substrate, and the step of applying stress to the substrate and peeling the surface side portion from the processing layer of the substrate Including. The processed layer may have a polycrystalline structure with a predetermined thickness formed at a predetermined depth from the surface of the substrate.

  The stress may be a bending stress or a tensile stress. The stress may be applied by bending the substrate or scratching the surface of the substrate. The surface of the substrate may be scratched manually using a glass cutter or a scribing pen. The surface of the substrate may be mirror-finished.

  The method may further include a step of cutting the substrate and exposing a processed layer from the cut end surface, and the peeling step may peel the cut substrate. The step of cutting the substrate may be performed automatically or manually using a dicing apparatus or a glass cutting or scribing pen.

  The substrate according to this application is obtained by processing the single crystal silicon substrate by the substrate processing method.

  According to the present invention, it is not necessary to temporarily fix the substrate with an adhesive when peeling the substrate, and there is no contamination due to the adhesive used for temporary fixing. In addition, since there is no temporary fixing step with an adhesive, and there is no need for an adhesive peeling step or a cleaning / purifying step for removing contamination, man-hours are reduced.

It is a flowchart which shows a series of processes of a board | substrate processing method. It is a perspective view of a substrate processing apparatus. It is a perspective view explaining formation of the process layer by the scan of a laser beam. It is sectional drawing explaining formation of the process layer by condensing of a laser beam. It is an expanded sectional view which shows the processing layer which consists of many property-change parts. It is a figure which shows the specific example of a laser condensing part. It is a figure explaining dicing and slicing. It is a photograph which shows the specific example of a board | substrate processing method.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions 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.

  Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention include the material, shape, structure, The layout is not specified as follows. Various modifications can be made to the embodiment of the present invention within the scope of the claims.

  As shown in FIG. 1, the substrate processing method of the present embodiment includes a series of steps including an internal processing step (S1) of a substrate by a laser beam, a dicing step (S2), and a braking step (S3). It is configured. Below, these each process is demonstrated in order.

(Laser processing of substrate)
In the first step S1, internal processing of the substrate is performed. This step is performed by a substrate processing apparatus. In this embodiment, a silicon single crystal substrate is used as a substrate to be processed by the substrate processing apparatus. For this substrate, a block obtained by cutting a silicon single crystal ingot to an appropriate length may be used.

  FIG. 2 is a perspective view showing the configuration of the substrate processing apparatus 100. The substrate processing apparatus 100 includes a stage 110, a stage support 120 that supports the stage 110 so that the stage 110 can move in the XY directions, and a substrate fixture 130 that is disposed on the stage 110 and fixes the substrate 10. Yes.

  Further, the substrate processing apparatus 100 includes a laser light source 160 that generates pulsed laser light, and a laser condensing unit 190 that includes a condensing lens 170 and an aberration correction unit 180, and emits laser light B emitted from the laser light source 160. Irradiation is performed toward the mirror-finished surface of the substrate 10 through the laser condensing unit 190.

  The condensing point of the laser beam B which is condensed and irradiated on the substrate 10 is 2 in the horizontal direction on the surface by forming a locus of a predetermined shape in a region of a predetermined depth from the surface inside the substrate 10. A dimensionally processed layer can be formed. This processed layer includes a polycrystalline structure having a stress strain in which a portion where the laser beam B is condensed and melted is rapidly cooled later, and has a weaker structure than other single crystal portions.

  FIG. 3 is a view for explaining that the laser beam B is condensed from the surface 20t of the substrate 10 by the laser condensing unit 190 to form the processed layer 21 therein. The substrate 10 is irradiated with the adjusted laser light B on the surface 20 t of the substrate 10 by the laser condensing unit 190 to condense the laser light B inside the substrate 10.

  The condensed laser light is moved (modified) from the surface 20t into the substrate 10 by relatively moving the laser condensing unit 190 and the substrate 10 while modifying (modifying) the single crystal member in the condensing portion. A processed layer 21 extending in the horizontal direction at an arbitrary depth is formed. The condensing point moves from the surface 20t of the substrate 10 in an arbitrary depth position in the horizontal direction while being intermittently irradiated with the pitch p in the scanning direction S, and when it reaches the scanning end, it is only offset w in the offset direction F. Advance and wrap the scan.

  FIG. 4 is a schematic cross-sectional view for explaining that the processed layer 21 is formed inside the substrate 10 by irradiation with the laser beam B. FIG. The substrate 10 to be processed in the present embodiment collects the pulse laser beam B from the mirror-finished surface 20t of the substrate 10 made of silicon single crystal, so that the substrate 10 is separated from the surface 20t and arbitrarily separated from the surface 20t. A processed layer 21 extending in the horizontal direction at a depth is formed. As a result, the substrate 10 includes a processed layer 21 and a non-processed layer 22 adjacent to both sides of the processed layer 21.

  FIG. 5 is an enlarged cross-sectional view of the substrate 10 showing the processed layer 21 composed of a number of altered portions. In the processed layer 21, altered portions 21 c having a polycrystalline structure formed along the scanning direction S of the laser beam B are arranged with a pitch p.

  FIG. 6 is a diagram illustrating a specific example of the laser condensing unit 190. A specific example of this is an Olympus lens LCPLN100XIR, which is configured as an objective lens 200 with an aberration correction ring for silicon infrared light including a condenser lens 170, an aberration correction unit 180, and a correction ring 210 with NA = 0.85. Yes. In this objective lens 200 with an aberration correction ring, the aberration correction amount of the aberration correction unit 180 can be set by manual rotation of the correction ring 210.

  The laser condensing unit 190 is not limited to the specific example described above, and a laser condensing unit 190 suitable for this processing purpose may be manufactured. In this case, the laser condensing unit includes an objective lens with NA = 0.5 to 0.9 and an aberration correction unit with an aberration correction ring. By using such an aberration correction ring, the condensing point of the laser beam B in the substrate 10 can be set to a desired shape.

(Substrate dicing)
The substrate 10 on which the processed layer 21 is formed in step S1 is diced in the next step S2. FIG. 7 is a diagram schematically showing the strength of the binding force when dicing and slicing occur.

  As schematically shown in FIG. 7 (a), the substrate 10 made of silicon single crystal is composed of silicon atoms 31 arranged at a predetermined interval. However, depending on the laser internal processing conditions, there is no reaction between the silicon atoms 31. The covalent bond 32 and the bond 33 modified (modified) by laser irradiation exist. Among these, the unreacted covalent bond 32 is an original bond between the silicon atoms 31, and the bond 33 modified (modified) by laser irradiation is a bond corresponding to a weakened portion corresponding to the processed layer 21. is there.

  The bonds 33 modified (modified) by laser irradiation in the drawing extend in the direction of the processed layer 21 formed on the substrate 10 shown in FIGS. In the dicing, the substrate 10 is cut by a cutting layer 35 perpendicular to a bond that has been altered (modified) by laser irradiation extending in the direction of the processed layer 21. For this purpose, it is necessary to cleave between the silicon atoms 31 having the unreacted covalent bond 32 by applying a larger stress than the unreacted covalent bond 32 between the silicon atoms 31.

  In the substrate 10 shown in FIG. 3, the substrate 10 can be diced so as to have a predetermined dimension by cutting the substrate 10 in a direction perpendicular to the surface 20t. By the dicing, the processed layer 21 of the substrate 10 is exposed on the end surface of the substrate 10 cut by the cutting layer 35.

  Dicing is not limited to completely cutting the substrate 10. For example, a half cut in which the cut layer 35 is formed by a groove-like cut having a predetermined depth from the surface 20t of the substrate 10 may be used. The cutting layer 35 may reach the depth of the processed layer 21 from the surface 20t, and the processed layer 21 may be exposed to the end face, or the processed layer 21 may be exposed to the end face by cleaving the crystal.

  In the dicing, the substrate 10 can be automatically cut or half-cut using a dicing apparatus, for example. Further, for example, it is possible to form a groove on the surface 20t of the substrate 10 by using glass cutting, or to apply a force to cleave from the groove portion.

(Board braking)
The substrate 10 diced in step S2 is braked in the next step S3. In the substrate 10 in which silicon atoms 31 schematically shown in FIG. 7B are arranged at predetermined intervals, as described above, the silicon atoms 31 are altered (modified) by unreacted covalent bonds 32 and laser irradiation. ), And the unreacted covalent bond 32 is an original bond between the silicon atoms 31, and the bond 33 modified (modified) by laser irradiation is weakened corresponding to the processed layer 21. Corresponds to the part.

  In the breaking, the substrate 10 is divided by a horizontal cutting layer 35 along the bond 33 that has been altered (modified) by laser irradiation extending in the direction of the processed layer 21. For this purpose, it is larger than the bond 33 modified (modified) by the laser irradiation between the silicon atoms 31, but is modified (modified) by the laser irradiation by applying a stress smaller than the unreacted covalent bond 32. Only the bond 33 can be broken, leaving an unreacted covalent bond 32.

  Here, the unreacted covalent bond 32 and the bond 33 altered (modified) by laser irradiation can be controlled by the laser irradiation conditions for forming the processed layer 21 inside the substrate 10. The braking becomes easier as the bond 32 that has been altered (modified) by laser irradiation becomes weaker. For this purpose, it is advantageous that the laser beam B has a high output and the pitch p of the altered portion 21c is small.

  In the substrate 10 shown in FIG. 3, the processed layer 21 is a fragile portion where a bond 33 that has been altered (modified) by laser irradiation is formed. In addition, the substrate 10 is subjected to a predetermined process by the dicing process in step S2. Therefore, in the processed layer 21 of the substrate 10, the non-processed layer 22 from the processed layer 21 to the surface 20 t can be easily divided and separated.

  By this braking process, the processed layer 21 that is separated from the surface 20t of the substrate 10 and extends in the horizontal direction can be divided as the cutting layer 35, and the non-processed layer 22 from the processed layer 21 to the surface 20t can be peeled off. Therefore, the first substrate of the non-processed layer 22 separated from the processed layer 21 to the surface 20t and the non-processed layer from the processed layer 21 to the back side surface are sliced by this braking process. Slicing can be performed on two substrates composed of 22 second substrates.

  Such braking of the substrate 10 can be performed automatically using an appropriate device. For example, the bending stress or tensile stress applied to the substrate 10 can be gradually increased by bending or pulling the substrate 10 fixed to an appropriate fixture. When the stress applied to the processed layer 21 of the substrate 10 increases and exceeds a threshold that the processed layer 21 can withstand, the stress strain of the processed layer 21 is released and the processed layer 21 is spontaneously broken.

  The braking of the substrate 10 can also be performed manually using an appropriate tool. For example, the non-processed layer 21 on the surface 20t side can be peeled from the processed layer 21 by scratching the surface of the substrate 10 diced using a glass cutting or scribing pen. When the stress applied to the processed layer 21 of the substrate 10 by the tool exceeds a threshold that the processed layer 21 can withstand, the stress strain of the processed layer 21 is released and the processed layer 21 is broken.

  Thus, in the present embodiment, the bond 33 modified (modified) by the laser irradiation between the silicon atoms 31 extending in the direction of the processed layer 21 is weaker than the unreacted covalent bond 32 in the other direction. It is possible to obtain an isolated base material by applying a stress to the substrate 10 and directly slicing it without using a step of bonding and fixing the substrate 10 to another member.

  Therefore, this embodiment does not use an adhesive and does not cause contamination. Further, there is no need for a step of bonding the substrate 10 to another member and a step of peeling, cleaning, and drying the substrate 10 bonded to the other member, and man-hours are reduced. Furthermore, no purification step is necessary to remove contamination.

  Examples in which the substrate processing method of this embodiment is applied will be described below. In Examples 1 to 10 shown in Table 1, Examples 1 to 4 use a solid-state semiconductor laser as a laser oscillator used for the laser light source 160, Examples 5 and 6 are Q-switched lasers, and Example 7 is a first fiber. The laser, Examples 8-10 used a second fiber laser. The oscillation wavelength was 1062 ± 2 nm in all cases.

  In each of Examples 1 to 10, an objective lens having a magnification of 100 for infrared light and an NA of 0.85 was used. The pulse frequency, output, pulse width, focal position (DF), aberration correction ring, processing pitch p, and processing offset w of the laser light are as shown in the table. The thickness of the substrate 10 was 725 μm.

  In these Examples 1 to 10, the processed layer 21 was formed on the substrate 10 in step S1 according to the conditions in Table 1. Then, after dicing by half-cutting with a cutting depth of 575 μm with respect to the thickness 725 μm of the substrate 10 in step S2, the substrate is divided by the processing layer 21 by braking in step S3. The non-processed layer 22 could be peeled off. In Examples 1 to 4, the surface of the wafer was scratched using a scribing pen, and the processing traces were cut out manually to peel off the non-processed layer 22 on the surface side from the processed layer 21.

  FIG. 8 is a photograph showing the result of a specific example of slicing. In this specific example, a laser light source 160 having an oscillation wavelength of 1062 ± 2 nm, a pulse width of 190 ns, and an output of 0.9 W was used. The processed layer 21 was formed by laser processing the substrate 10 under the conditions of DF 50 μm, silicon aberration correction ring 0.3 mm, laser irradiation processing pitch 2 μm, and processing offset 2 μm. Other conditions are the same as in the above embodiment.

  Then, when the bending stress was applied to the board | substrate 10 by bending the board | substrate 10, the crack generate | occur | produced in the surface 20t. The non-processed layer 22 on the surface 20t side from the processed layer 21 could be peeled off by scratching the floating part of the surface 20t with a scribing pen or glass cutter. In the figure, the peeling surface 10a in the processed layer 21 exposed by this peeling is shown.

Comparative example

  For comparison with the example, the substrate 10 was subjected to laser processing under the conditions shown in Table 2, and then the substrate 10 was diced. Other conditions are the same as in the above embodiment. Thereafter, braking by applying a bending stress to the substrate 10 was attempted. However, all of Comparative Examples 1 to 14 failed, and the substrate 10 could not be divided by the processed layer 21. In Comparative Examples 1 to 4, the surface of the wafer was scratched using a scribing pen, and processing marks were cut out manually, but all failed, and the substrate 10 could not be divided at the processing layer 21. It was.

DESCRIPTION OF SYMBOLS 10 Substrate 20t Surface 21 Processed layer 22 Non-processed layer 100 Substrate processing apparatus 190 Laser condensing part

Claims (7)

A substrate processing method for processing a single crystal silicon substrate,
While irradiating the surface of the substrate with laser light by the laser condensing means and condensing the laser light inside the substrate, the laser condensing means and the substrate are relatively moved to move inside the substrate. Forming a processed layer;
Stress was added to the substrate, seen including a step of peeling the portion of the surface side from the processing layer of the substrate, the stress is the bending stress or tensile stress, the stress to bend the substrate, or the substrate A substrate processing method, wherein the substrate is applied by scratching the surface .   The substrate processing method according to claim 1, wherein the processed layer has a polycrystalline structure with a predetermined thickness formed at a predetermined depth from the surface of the substrate.   The substrate processing method according to claim 1, wherein the scratching of the surface of the substrate is performed manually using a glass cutter or a scribing pen.   The method further comprises a step of cutting the substrate so that a processed layer is exposed from the cut end face, and the peeling step applies a stress to the cut substrate and peels off. 4. The substrate processing method according to any one of 3 above.   5. The substrate processing method according to claim 4, wherein the step of cutting the substrate is performed automatically or manually using a dicing apparatus or a glass cutting or scribing pen.   The substrate processing method according to claim 1, wherein the surface of the substrate is mirror-finished. The board | substrate obtained by processing the said single crystal silicon substrate by the board | substrate processing method as described in any one of Claims 1-6.