JP2018018999A - Substrate separation method and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate separation method capable of separating a substrate having a strong cleavage surface such as a Ga2O3 system substrate at high speed without generating cleavage, and a semiconductor element obtained by separating the substrate by the method. To do. SOLUTION: In one embodiment, a light condensing point of laser light is scanned along a planned separation surface 11 inside a substrate 10 on which an element unit 20 is mounted on a first surface 10a, and the planned separation surface 11 A step of forming the altered region 12 which is continuous along the substrate 10 and reaches the second surface 10b of the substrate 10, and a step of selectively removing the altered region 12 from the substrate 10 by wet etching to form a void 15. After forming the void 15, the step of scanning the condensing point of the laser beam in the region between the first surface 10a and the void 15 to remove the region, and the surface to be separated after removing the region. Provided is a method for separating a substrate, which comprises a step of separating the substrate 10 along the line 11. [Selection diagram] Fig. 2

Description

  The present invention relates to a substrate separation method and a semiconductor device.

Since the β-Ga ₂ O ₃ crystal has a (100) plane as a very cleaved cleavage plane, the Ga ₂ O ₃ substrate made of β-Ga ₂ O ₃ crystal is separated from this (100 ) It has the property that cleavage is likely to occur along the surface.

In general, measures can be taken to reduce the cutting rate in order to prevent the occurrence of cleavage, but in order to prevent the cleavage of the Ga ₂ O ₃ substrate, the cutting rate is very small (for example, 0.1 to 0.3 mm / sec). ) It is necessary to set, and a very long time is spent in the cutting process.

  Conventionally, a method is known in which a modified region is formed and separated inside a substrate by laser light (see, for example, Patent Documents 1 and 2). The modified region is a region that is formed by moving the condensing point of the laser light along the planned cutting line of the substrate. When the modified region is appropriately formed, an external force is applied to the substrate. Thus, the substrate can be divided along the cutting line.

JP 2008-68319 A International Publication No. 2008/146744

However, when separating a substrate having a strong cleaved surface such as a Ga ₂ O ₃ based substrate, the method described in Patent Documents 1 and 2 separates when separating by applying an external force. There is a high possibility that a surface different from the surface will cleave.

One of the objects of the present invention is a method for separating a substrate capable of separating a substrate having a strong cleavage plane such as a Ga ₂ O ₃ based substrate at a high speed without causing cleavage, and the substrate by the method. Another object is to provide a semiconductor element obtained by separation.

  In order to achieve the above object, one embodiment of the present invention provides the following methods [1] to [5] for separating a substrate. In order to achieve the above object, another aspect of the present invention provides the following semiconductor elements [6] to [9].

[1] A condensing point of laser light is scanned along a planned separation surface inside the substrate on which the element portion is mounted on the first surface, and is continuously along the planned separation surface, and the first of the substrate Forming a modified region reaching the second surface opposite to the first surface, forming a void by selectively removing the modified region from the substrate by wet etching, and forming the void. Thereafter, a step of scanning a condensing point of a laser beam in a region between the first surface and the gap to remove the region, and after removing the region, along the planned separation surface Separating the substrate. A method for separating the substrate.

[2] The method for separating a substrate according to [1], wherein the altered region is formed such that a region between the first surface and the altered region has a thickness of 20 μm or more and 50 μm or less.

[3] The method for separating a substrate according to [1] or [2], wherein the substrate is a Ga ₂ O ₃ -based substrate.

[4] The substrate separation method according to [3], wherein the wet etching is performed using hydrofluoric acid or an alkali etchant as an etchant.

[5] The condensing point of the laser beam is scanned along the planned separation surface inside the Ga ₂ O ₃ based substrate having the element portion mounted on the first surface, and is continuously along the planned separation surface, Selectively forming the altered region from the Ga ₂ O ₃ based substrate by forming a modified region reaching at least a _second surface opposite to the first surface of the Ga ₂ O ₃ based substrate and wet etching; And forming a void, and after forming the void, separating the Ga ₂ O ₃ -based substrate along the planned separation surface, the main of the Ga ₂ O ₃ -based substrate A method for separating a substrate, wherein the plane and the plane to be separated are planes other than the (100) plane.

[6] a substrate made of Ga ₂ O ₃ single crystal, has an element portion formed on said substrate, said substrate having no cleavage plane of the exposed Ga ₂ O ₃ single crystal, A semiconductor element in which irregularities due to continuous laser processing exist on the entire side surface of the substrate.

[7] The semiconductor element according to [6], wherein the maximum height difference of the unevenness is 3 μm or less.

[8] The semiconductor element according to the above [6] or [7], wherein the striped unevenness is formed in a region excluding a region having a thickness of 20 μm or more and 50 μm or less from an upper end of a side surface of the substrate.

[9] a substrate made of Ga ₂ O ₃ single crystal, has an element portion formed on said substrate, said substrate having no cleavage plane of the exposed Ga ₂ O ₃ single crystal, A semiconductor element having no chipping of 5 μm or more from the edge on the surface of the substrate.

According to one embodiment of the present invention, a substrate separation method capable of separating a substrate having a strong cleavage surface such as a Ga ₂ O ₃ -based substrate at a high speed without causing cleavage, and the substrate by the method. A semiconductor element obtained by separation can be provided.

FIG. 1 is a plan view schematically showing the position of the planned separation surface of the substrate according to the first embodiment. 2A to 2F are vertical sectional views showing a method for separating a substrate according to the first embodiment. FIGS. 3A to 3C are vertical sectional views of the substrate for explaining the formation of the altered region in detail. 4A to 4G are vertical sectional views showing a method for separating a substrate according to the second embodiment. FIG. 5 is an optical micrograph of a cross section of the substrate after cleaving according to the example. FIG. 6A is a top view photograph before the break of the substrate from which the altered region has been removed by wet etching, and FIG. 6B is a top view photograph after the break and the expansion. FIG. 7A is an SEM image of the side surface of the substrate that has been subjected to the wet etching to remove the altered region according to the embodiment. FIG. 7B is an SEM image in which the periphery of the upper end of the gap in FIG. FIG. 8A is a photograph of the top surface of the substrate immediately after the wet etching when the thickness of the region between the first surface and the altered region is 15 μm according to the example. FIG. 8B is a photograph of the top surface of the substrate immediately after the wet etching when the thickness of the region between the altered regions is 20 μm.

[First Embodiment]
In this embodiment, a method for separating a substrate having a strong cleavage surface such as a Ga ₂ O ₃ -based substrate at high speed without causing cleavage is described.

Here, the Ga ₂ O ₃ based substrate is a β-type (Al _x Ga _y In _z ) ₂ O ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1) single A substrate made of a β-Ga ₂ O ₃ single crystal having a crystal as a mother crystal, and includes impurities such as Cu, Ag, Zn, Cd, Al, In, Si, Ge, Sn, Mg, Nb, and Fe. May be.

The Ga ₂ O ₃ -based substrate has a strong cleaving property on the (100) plane and is likely to cleave on the (100) plane regardless of the plane orientation of the main surface. Therefore, the substrate separation method according to the present embodiment is effective regardless of the plane orientation of the main surface of the Ga ₂ O ₃ -based substrate, but when the main surface is a surface other than the (100) surface. This is particularly effective because cleavage is particularly likely to occur during separation.

  FIG. 1 is a plan view schematically showing the position of the planned separation surface 11 of the substrate 10 according to the first embodiment. The scheduled separation surfaces 11 are typically surfaces parallel to the thickness direction of the substrate 10 and are arranged to form a lattice in the substrate 10 as shown in FIG. Element portions such as LEDs are respectively formed on the area of the surface of the substrate 10 that is divided into a lattice pattern. After the substrate 10 is separated along the planned separation surface 11, the substrate 10 and the element portions thereon are separated from each other. A plurality of semiconductor elements can be obtained.

(Substrate separation method)
2A to 2F are vertical sectional views showing a method for separating the substrate 10 according to the first embodiment.

  First, as shown in FIG. 2A, the element portion 20 is formed on the first surface 10 a of the substrate 10 partitioned by the planned separation surface 11. Here, the element portion 20 is a portion excluding a substrate of a semiconductor element such as a light emitting element, a diode, a transistor, and other circuit elements.

  Next, as shown in FIG. 2B, the altered region 12 is formed by scanning the condensing point of the laser light along the planned separation surface 11 inside the substrate 10.

  3A to 3C are vertical sectional views of the substrate 10 for explaining the formation of the altered region 12 in detail. 3A and 3B show a cross section of the substrate 10 along the planned separation surface 11.

  As shown in FIG. 3A, the laser beam 13 condensed by a condenser lens or the like is scanned so that the condensing point 14 moves on the planned separation surface 11, and continuously along the planned separation surface 11. The altered region 12 is formed.

In addition, when the substrate 10 is a Ga ₂ O ₃ based substrate, the (100) plane has a strong cleaving property, so that the cleavage is a problem when the planned separation surface 11 is a plane other than the (100) plane. There are many. For this reason, when the substrate 10 is a Ga ₂ O ₃ based substrate, the substrate separation method according to the present embodiment is particularly effective when the planned separation surface 11 is a surface other than the (100) surface.

The altered region 12 is a region in which a crystal constituting the substrate 10 irradiated with the laser beam 13 has been altered through a multiphoton absorption process. Here, if the energy applied to the crystal is too small, the altered region 12 is not formed. On the other hand, if the energy is too large, the crystals constituting the substrate 10 are removed (ablated), and the substrate 10 having a strong cleavage surface such as a Ga ₂ O ₃ -based substrate is likely to be cleaved simultaneously with the ablation.

The laser beam 13 for forming the modified region 12 is ultrashort pulse laser beam, for example, when the substrate 10 is a _Ga 2 _{O 3} based substrate, the scanning speed (scanning speed) of 100 mm / sec, the frequency is 200kHz, The center wavelength is 1030 nm and the pulse width is 10 ps or less, preferably several hundred fs to 10 ps.

  Then, as shown in FIG. 3B, the scanning of the condensing point 14 along the planned separation surface 11 is continued, and the planned separation surface 11 reaching the first surface 10 a and the second surface 10 b of the substrate 10. A continuous altered region 12 is formed along the line. Note that the scanning path of the condensing point 14 shown in FIGS. 3A and 3B is an example, and the scanning path of the condensing point 14 is not limited.

  FIG. 3C is a vertical cross-sectional view of the substrate 10 perpendicular to the separation scheduled surface 11, and shows that the formed altered region 12 has reached the first surface 10 a and the second surface 10 b of the substrate 10. Show.

  Since it is necessary to remove the altered region 12 in the subsequent wet etching process, the altered region 12 must reach the second surface 10b in order to secure an entrance for the etchant. In order to etch, it must be continuous along the planned separation surface 11. Details of the wet etching process will be described later.

  After forming the altered region 12, as shown in FIG. 2C, a support substrate 22 such as a sapphire substrate is attached to the element portion 20 side of the substrate 10 using an adhesive 21 such as wax.

Next, as shown in FIG. 2D, the altered region 12 is selectively removed from the substrate 10 by wet etching to form the void 15. The etchant 23, for example, when the substrate 10 is a _Ga 2 _{O 3} based substrate, can be used hydrofluoric acid and, KOH, an alkaline etchant such as NaOH.

  Next, as shown in FIG. 2 (e), a dicing sheet 24 having an organic solvent resistance property and a heat resistance property is attached to the second surface 10 b side of the substrate 10, and the substrate 10 is held in a bonded state. The support 21 is peeled off by removing the agent 21.

  For example, when the adhesive 21 is a wax, it can be removed by dissolving with an organic solvent such as acetone after being softened by heating. Note that the substrate 10 may be held using a member other than the dicing sheet 24.

  Next, as shown in FIG. 2 (f), after an external force is applied to the substrate 10 to completely separate the substrate 10 along the planned separation surface 11 (break process), a plurality of semiconductor elements 1 are obtained. The interval between the semiconductor elements 1 is increased (expanding process).

  2E, the substrate 10 is not completely separated along the planned separation surface 11, and a small portion of the substrate 10 remains on the planned separation surface 11. Even if the altered region 12 is appropriately formed and removed by wet etching, the substrate 10 is separated along the planned separation surface 11 by the above-described breaking step without causing cleavage.

[Second Embodiment]
In the embodiment of the present invention, a new process is added to the substrate separation process of the first embodiment in order to prevent damage to the element portion in the wet etching process. Note that the description of the same points as in the first embodiment will be omitted or simplified.

(Substrate separation method)
4A to 4G are vertical sectional views showing a method for separating the substrate 10 according to the second embodiment.

  First, as shown in FIG. 4A, the element portion 20 is formed on the first surface 10 a of the substrate 10 partitioned by the planned separation surface 11.

  Next, as shown in FIG. 4B, the altered region 16 is formed by scanning the condensing point of the laser light along the planned separation surface 11 inside the substrate 10. Unlike the altered region 12 of the first embodiment, the altered region 16 is formed so as not to reach the first surface 10a of the substrate 10. The formation method using laser light and the conditions of laser light are the same as those in the altered region 12 of the first embodiment.

  Next, as illustrated in FIG. 4C, a support substrate 22 such as a sapphire substrate is attached to the element portion 20 side of the substrate 10 using an adhesive 21 such as wax.

  Next, as shown in FIG. 4D, the altered region 16 is selectively removed from the substrate 10 by wet etching to form a void 17. At this time, since the gap 17 does not reach the first surface 10 a of the substrate 10, the etchant 23 that has entered the gap 17 enters the interface between the substrate 10 and the adhesive 21 from the gap 17 and damages the element portion 20. There is no risk of giving.

  In this step, in order to effectively prevent the etchant 23 from entering from the gap 17, the thickness of the region between the first surface 10 a of the substrate 10 and the gap 17 is preferably 20 μm or more. For this reason, it is preferable to form the altered region 16 so that the thickness of the region between the first surface 10a and the altered region 16 is 20 μm or more.

  Although the etchant 23 may enter the interface between the substrate 10 and the adhesive 21 on the side (outer peripheral portion) of the substrate 10, there is a big problem even if the element portion 20 located in the outer peripheral portion is damaged. Don't be.

  Next, as shown in FIG. 4 (e), a dicing sheet 24 having an organic solvent resistance property and a heat resistance property is attached to the second surface 10 b side of the substrate 10. The support 21 is peeled off by removing the agent 21.

  Next, as shown in FIG. 4 (f), the condensing point of the laser beam 18 that is an ultrashort pulse laser beam is scanned in the region between the first surface 10 a of the substrate 10 and the gap 17, The area is removed (ablated). In this step, the crystal constituting the substrate 10 is not altered but removed, so that the condition of the laser beam 18 is different from the condition of the laser beam for forming the altered region 16.

For example, when the substrate 10 is a Ga ₂ O ₃ based substrate, the scanning speed of the laser light 18 is 10 mm / sec, and the frequency is 200 kHz. In this case, although the frequency is the same as the laser beam for forming the altered region 16, the energy applied by the laser beam per unit volume increases because the scanning speed is slow.

  In this step, in order to effectively prevent the cleavage from occurring on the cleavage surface, the thickness of the region between the first surface 10a of the substrate 10 and the gap 17 is preferably 50 μm or less, and is 30 μm or less. It is more preferable. There is also a problem that laser ablation can be performed only to a depth of about 50 μm. Therefore, the altered region 16 is preferably formed so that the thickness of the region between the first surface 10a and the altered region 16 is 50 μm or less, and the altered region 16 is formed so as to be 30 μm or less. More preferred.

  Next, as shown in FIG. 4G, after external force is applied to the substrate 10 to completely separate the substrate 10 along the planned separation surface 11 (break process), a plurality of semiconductor elements 1 are obtained. The interval between the semiconductor elements 1 is increased (expanding process).

  In addition, when the ablation process shown in FIG. 4 (f) is omitted and the break process shown in FIG. 4 (g) is performed, there is a high possibility that cleavage will occur.

(Effect of embodiment)
According to the first embodiment, a substrate having a strong cleavage plane such as a Ga ₂ O ₃ -based substrate can be separated at high speed without causing cleavage. Furthermore, according to the second embodiment, it is possible to prevent the element portion from being damaged in the wet etching process of the first embodiment.

  Further, according to the first and second embodiments, the thicknesses (the width in the lateral direction in FIG. 3C) of the altered region 12 and the altered region 16 can be made extremely thin, approximately 2 to 3 μm. it can. For this reason, the space | interval of the element part 20 adjacent on both sides of the scheduled separation surface 11 on the board | substrate 10 can be made small (for example, 30 micrometers). On the other hand, when the substrate is cut by dicing, the distance between the element portions is required to be about 200 μm in consideration of the width of the dicing blade. For example, in the case where 300 μm × 300 μm element portions are arranged in a lattice pattern on a 2-inch substrate, according to the method of the present embodiment, about four times from one substrate as compared with the case of dicing. A number of semiconductor elements can be obtained.

Further, according to the methods of the first and second embodiments, almost no time is required except for the wet etching process, and the wet etching process can simultaneously process a plurality of substrates 10. Therefore, the processing time per sheet can be shortened. For this reason, according to the method of the first and second embodiments, for example, when the substrate 10 is a Ga ₂ O ₃ -based substrate having a diameter of 2 inches, the substrate 10 is substantially taken in about one hour per substrate. Can be separated. On the other hand, when cutting a Ga ₂ O ₃ -based substrate by dicing, it is necessary to set the cutting rate very low (for example, 0.1 to 0.3 mm / sec) in order to prevent cleavage from occurring. It takes approximately 7.5 hours to cut a 2 inch diameter Ga ₂ O ₃ based substrate.

As a substrate 10 according to the above embodiment, a Ga ₂ O ₃ substrate made of a β-Ga ₂ O ₃ crystal having a (−201) plane as a main surface is used to separate the substrate 10 without causing cleavage. The condition was verified.

  First, when the pulse width of the laser beam for forming the altered region 12 was set to 20 ps or more, cleavage occurred starting from the altered region 12 in the step of forming the altered region 12.

  Next, when the pulse width of the laser beam was set to 1 to 2 ps, it was confirmed by observation with an optical microscope that the altered region 12 was appropriately formed without cleavage. At this time, the thickness of the altered region 12 was 2 to 3 μm.

  Next, after forming the altered region 12, the wet etching step in the above embodiment was omitted, and an attempt was made to separate (break) by applying external force to the substrate 10 without removing the altered region 12. Cleavage occurred along the (100) plane, and separation along the planned separation surface 11 was not possible.

FIG. 5 is an optical micrograph of a cross section of the substrate 10 after cleavage has occurred. Cleavage occurs when an external force is applied to the substrate 10 without removing the altered region 12, in addition to the strength of the cleavage property of the β-Ga ₂ O ₃ crystal, the property of the altered region is other than Si substrate and the like. This may be caused by a difference from the substrate. That is, in the case of a Ga ₂ O ₃ substrate, compared to a Si substrate or the like, even if the crystal is altered, the decrease in strength is small and it may be difficult to separate. For this reason, it can be said that the above-described embodiment is particularly effective for separating a substrate made of a crystal whose strength is not easily lowered due to alteration by laser processing.

  FIG. 6A is a top view before the break of the substrate 10 from which the altered region 12 has been removed by wet etching according to the above embodiment, and FIG. 6B is a top view after the break and expansion. .

  FIGS. 6A and 6B show that the substrate 10 is separated without cleavage. Further, in the vicinity of the edge of the substrate 10 after the break, almost no chipping (peeling of the surface) as seen during cutting by dicing was observed. At least chipping with a length from the edge of 5 μm or more does not occur.

  FIG. 7A is an SEM (Scanning Electron Microscope) image of the side surface of the substrate 10 that has been broken by removing the altered region 12 by wet etching according to the first embodiment. The linear gap along the thickness direction in the vicinity of the center of the substrate 10 in FIG. 7A is a gap 15 extending in a direction perpendicular to the paper surface, and no break along the gap 15 is performed. FIG. 7B is an enlarged SEM image around the upper end of the gap 15 in FIG.

  As shown in FIGS. 7A and 7B, on the side surface of the substrate 10 of the semiconductor element 1 after separation, continuous fine stripe-like irregularities by laser processing are seen over almost the entire surface. The striped irregularities appear on the side surface of the substrate 10 by the break of the substrate 10 along the gap 15 and are characteristic when separating using laser processing. . In this striped pattern, the black portion is a depressed portion, and the central portion of the laser condensing point 14 is a scanned portion.

  In the substrate 10 shown in FIGS. 7A and 7B, the pitch in the in-plane direction of the substrate 10 of the condensing points 14 on the planned separation surface 11 is longer than the pitch in the thickness direction of the substrate 10. . For this reason, linear voids 15 along the thickness direction are formed side by side on the planned separation surface 11, and striped irregularities are formed on the side surface of the substrate 10.

  The maximum height difference of the unevenness on the side surface of the substrate 10 after such separation is smaller than the spot diameter of the condensing point 14 (the thickness of the altered region 12). Since the spot diameter of the condensing point 14 is 2 to 3 μm, the maximum height difference of the unevenness is 3 μm or less, usually 1 μm or less. Since the substrate 10 is separated after removing the altered region 12, the uneven side surface of the substrate 10 of the semiconductor element 1 is not altered and is made of a single crystal.

  When the substrate 10 is separated using the method of the second embodiment, the region in the vicinity of the upper surface of the substrate 10 is separated by laser ablation. Therefore, the stripe shape shown in FIGS. The unevenness is formed in a region excluding the vicinity of the upper end of the side surface of the substrate 10. For example, when the region to be separated by laser ablation is a region having a thickness of 20 μm or more and 50 μm or less from the upper surface of the substrate 10, the striped unevenness shown in FIGS. It is formed in a region excluding the region having a thickness of 20 μm or more and 50 μm or less from the upper end of the side surface.

  In the case where the altered region 12 is formed discontinuously in the thickness direction of the substrate 1, striped irregularities are not formed in the region where the altered region 12 on the side surface of the substrate 10 after separation is not formed. However, when the altered region 12 is discontinuous, only a part of the altered region 12 can be removed by wet etching, so that cleavage occurs along the (100) plane which is a cleavage plane at the time of separation, It cannot be separated along the planned separation surface 11.

  Further, when the substrate is separated by blade dicing, horizontal stripes appear on the cross section of the substrate (side surface of the substrate after separation) according to the number of passes of the blade. Further, the cross section becomes tapered depending on the thickness of the blade.

Next, the relationship between the thickness of the region between the first surface 10a and the altered region 16 and the ease of intrusion from the gap 17 of the etchant 23 when the altered region 16 of the second embodiment is formed is verified. did. Here, as a substitute for the element portion 20, a SiO ₂ film is formed on the first surface 10a of the substrate 10 for verification, and an interval between the SiO ₂ films adjacent to each other with the altered region 16 interposed is 40 μm. The thickness of the wax was 5 μm.

FIG. 8A is a top view photograph of an example of the substrate 10 immediately after the wet etching when the thickness of the region between the first surface 10a and the altered region 16 is 15 μm. This indicates that there is a case in which the SiO ₂ film as the element portion 20 may be damaged by entering the interface between the substrate 10 and the adhesive 21.

FIG. 8B is a top view photograph of the substrate 10 immediately after the wet etching when the thickness of the region between the altered regions 16 is 20 μm. The etchant 23 has not entered the gap 17 and the element portion This shows that the SiO ₂ film as 20 is not damaged. When the thickness of the region between the altered regions 16 was 20 μm, no damage was confirmed on the SiO ₂ film as the element portion 20 in any of the substrates 10 that were verified.

Further, even when the thickness of the region between the first surface 10a and the altered region 16 was set to 22.5 μm and 25 μm, no damage was confirmed on the SiO ₂ film as the element portion 20.

  Table 1 below shows the evaluation results of the relationship between the processing conditions of the ablation process shown in FIG. 4F in the second embodiment and the state of the substrate 10 after ablation.

  “Thickness” in Table 1 refers to the thickness of the region between the first surface 10 a of the substrate 10 and the gap 17. “Pulse width”, “energy”, and “scanning speed” are laser light output conditions in the ablation process, respectively. The “pass” is the number of times laser processing is performed in the ablation process.

  “Evaluation” is an evaluation of the state of the substrate 10 after ablation. “◯” indicates that the state is good, “◎” indicates that the state is particularly good, and “△” indicates that the state is relatively separable. Indicates that is not good.

  In the ablation according to condition 3, the dicing sheet 24 holding the substrate 10 was burned during laser processing, and the back surface of the substrate 10 was soiled. This is probably because the energy of the laser beam is too high.

  In the ablation under condition 6, a relatively large external force was required to separate the substrate 10 after ablation. This is presumably because the scanning speed of the pulsed laser beam was too high, and the interval in the direction parallel to the surface of the substrate 10 in the ablated region was widened.

  The evaluation results shown in Table 1 show that the “pulse width”, “energy”, and “scanning speed” of the laser light in the ablation process are 1.1 to 1. 5 ps, 2.5 to 5 μJ, preferably 10 mm / s or less, and “thickness” is preferably 25 μm or less. In order to shorten the time spent in the ablation process, the “pass” is preferably 2 or less.

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the spirit of the invention.

  The embodiments and examples described above do not limit the invention according to the claims. It should be noted that not all combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention.

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor element 10 ... Board | substrate 10a ... 1st surface, 10b ... 2nd surface, 11 ... Plane separation surface 12, 16 ... Alteration area | region, 13, 18 ... Laser beam, 14 ... Condensing point, 15 , 17 ... air gap, 20 ... element part, 23 ... etchant

Claims (9)

The condensing point of the laser beam is scanned along the planned separation surface inside the substrate on which the element portion is mounted on the first surface, and the first surface of the substrate is continuous along the planned separation surface. Forming an altered region reaching the second surface on the opposite side of
A step of selectively removing the altered region from the substrate by wet etching to form a void;
After forming the gap, scanning the laser light focusing point in the area between the first surface and the gap, and removing the area;
Separating the substrate along the planned separation surface after removing the region;
A method for separating a substrate. Forming the altered region such that the thickness of the region between the first surface and the altered region is 20 μm or more and 50 μm or less;
The method for separating a substrate according to claim 1. The substrate is a Ga ₂ O ₃ based substrate;
The method for separating a substrate according to claim 1 or 2. The wet etching is performed using hydrofluoric acid or an alkali etchant as an etchant.
The method for separating a substrate according to claim 3. The condensing point of the laser beam is scanned along the planned separation surface inside the Ga ₂ O ₃ based substrate having the element portion mounted on the first surface, and is continuously along the planned separation surface, and at least the Ga Forming an altered region that reaches a second surface opposite to the first surface of the ₂ O ₃ -based substrate;
A step of selectively removing the altered region from the Ga ₂ O ₃ based substrate by wet etching to form a void;
After forming the gap, separating said Ga ₂ O ₃ based substrate along said predetermined separation surface,
Including
The method for separating a substrate, wherein the main surface and the scheduled separation surface of the Ga ₂ O ₃ -based substrate are surfaces other than the (100) surface. A substrate made of a Ga ₂ O ₃ based single crystal;
An element portion formed on the substrate;
Have
The substrate does not have an exposed Ga ₂ O ₃ single crystal cleavage plane;
Striped irregularities exist on the side surface of the substrate,
Semiconductor element. The maximum height difference of the striped irregularities is 3 μm or less;
The semiconductor device according to claim 6. The striped unevenness was formed in a region excluding a region having a thickness of 20 μm or more and 50 μm or less from the upper end of the side surface of the substrate,
The semiconductor element according to claim 6 or 7. A substrate made of a Ga ₂ O ₃ based single crystal;
An element portion formed on the substrate;
Have
The substrate does not have an exposed Ga ₂ O ₃ single crystal cleavage plane;
There is no chipping with a length of 5 μm or more from the edge on the surface of the substrate.
Semiconductor element.