JP7665142B2 - Semiconductor chip manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor chip on which a semiconductor element is formed.

A method for manufacturing a semiconductor chip in which a semiconductor element is formed on a substrate containing gallium nitride (hereinafter also simply referred to as GaN) has been proposed (see, for example, Patent Document 1). Specifically, in this manufacturing method, first, an epitaxial film made of GaN is laminated on a substrate such as sapphire, and a semiconductor element is formed on the epitaxial film. Then, in this manufacturing method, a laser beam is irradiated to the interface between the substrate and the epitaxial film to peel off the substrate and the epitaxial film, thereby manufacturing a semiconductor chip.

Publication No. 2007-299935

However, in the above-mentioned semiconductor chip manufacturing method, a sapphire substrate is used as the substrate, and since the composition of the substrate and the epitaxial film are different, defects are likely to occur in the epitaxial film. As a result, the characteristics of the semiconductor chip manufactured by the above-mentioned semiconductor chip manufacturing method may be degraded.

In view of the above, the present invention aims to provide a method for manufacturing semiconductor chips that can prevent the deterioration of characteristics.

In order to achieve the above object, claims 1 and 3 provide a method for manufacturing a semiconductor chip having a semiconductor element formed thereon, comprising the steps of: preparing a GaN wafer (1) made of GaN and having one surface (1a) and another surface (1b) opposite to the one surface; forming an epitaxial film (3) containing GaN on one surface of the GaN wafer, so that the surface facing the epitaxial film is the one surface (10a) and the surface facing the GaN wafer is the other surface (10b), thereby forming a processed wafer (10) having a plurality of chip formation regions (RA) on one surface side; forming one surface side element constituent parts (11) of the semiconductor element in the plurality of chip formation regions; By irradiating the inside of the processed wafer with laser light (L1) from the GaN wafer, an altered layer (15) is formed inside the processed wafer along the surface direction of the processed wafer, the processed wafer is divided at the altered layer as a boundary, and the processed wafer is divided into a chip configuration wafer (30) on one side of the processed wafer and a recycled wafer (40) on the other side of the processed wafer, and a semiconductor chip (S1) is taken out from the chip configuration wafer. Before forming the altered layer, an absorption increased portion (3, 16, 17) having a higher absorption rate of the laser light than a GaN wafer is formed, and forming the altered layer forms an altered layer in the absorption increased portion.
In claim 1, forming the absorption increase portion means forming an epitaxial film having a portion with a higher impurity concentration than a GaN wafer when forming the epitaxial film, and forming the altered layer means forming an altered layer in the portion of the epitaxial film that constitutes the absorption increase portion.
In claim 3, forming the absorption increase portion comprises forming an absorption increase portion by arranging a high concentration layer (16) having an impurity concentration higher than that of the GaN wafer and the epitaxial film on the GaN wafer before forming the epitaxial film, and forming the altered layer comprises forming an altered layer in the high concentration layer.

By forming an epitaxial film containing GaN on a GaN wafer, it is possible to prevent defects from occurring in the epitaxial film. Therefore, when manufacturing a semiconductor chip, it is possible to prevent the characteristics of the semiconductor chip from deteriorating.

In addition, in claim 1, before forming the altered layer, an absorption increase section is formed that has a higher absorption rate of laser light than the GaN wafer, and the altered layer is formed in the absorption increase section. This allows the altered layer to be formed appropriately, and prevents problems such as variations in the thickness of the semiconductor chip and difficulty in separating the chip-composing wafer and the recycled wafer from each other.

The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below.

3A to 3C are cross-sectional views showing a manufacturing process of the semiconductor chip in the first embodiment. 1B is a cross-sectional view showing a manufacturing process of the semiconductor chip subsequent to FIG. 1A. 1C is a cross-sectional view showing a manufacturing process of the semiconductor chip subsequent to FIG. 1B. 1C is a cross-sectional view showing a manufacturing process of the semiconductor chip following FIG. 1C. 1D; FIG. 1E is a cross-sectional view showing a manufacturing process of the semiconductor chip subsequent to FIG. 1C is a cross-sectional view showing a manufacturing process of the semiconductor chip subsequent to FIG. 1E. 1C is a cross-sectional view showing a manufacturing process of the semiconductor chip following FIG. 1F. 1C is a cross-sectional view showing a manufacturing process of the semiconductor chip subsequent to FIG. 1G. 1C is a cross-sectional view showing a manufacturing process of the semiconductor chip following FIG. 1H. 1I is a cross-sectional view showing a manufacturing process of the semiconductor chip following FIG. 1C is a cross-sectional view showing a manufacturing process of the semiconductor chip following FIG. 1J. 10A to 10C are cross-sectional views showing a manufacturing process of a semiconductor chip according to a second embodiment. 2B is a cross-sectional view showing a manufacturing process of the semiconductor chip subsequent to FIG. 2A. 2C is a cross-sectional view showing a manufacturing process of the semiconductor chip following FIG. 2B. 11A to 11C are cross-sectional views showing a manufacturing process of a semiconductor chip according to a third embodiment. 3B is a cross-sectional view showing a manufacturing process of the semiconductor chip subsequent to FIG. 3A.

The following describes embodiments of the present invention with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals.

First Embodiment
A first embodiment will be described with reference to the drawings. Hereinafter, a method for manufacturing a semiconductor chip S1 made of GaN will be described.

First, as shown in FIG. 1A, a GaN wafer 1 having one surface 1a and the other surface 1b and in the form of a bulk wafer is prepared. The GaN wafer 1 of this embodiment is an undoped wafer that is not doped with impurities. The thickness of the GaN wafer 1 is optional, but for example, a thickness of about 300 to 500 is used. In this embodiment, the GaN wafer 1 has one surface 1a that is a gallium surface and the other surface 1b that is a nitrogen surface. After the manufacturing process of the semiconductor chip S1 described below is performed, this GaN wafer 1 is prepared by reusing a recycled wafer 40 shown in FIG. 1K, which will be described later.

Next, as shown in FIG. 1B, an epitaxial film 3 made of GaN having a thickness of about 30 to 100 μm is formed on one surface 1a of the GaN wafer 1 to prepare a processed wafer 10 having a plurality of chip formation regions RA. That is, in this embodiment, the epitaxial film 3 is formed on the GaN wafer 1 having the same composition as the epitaxial film 3 to be formed. In this embodiment, the epitaxial film 3 is formed by hydride vapor phase epitaxy (i.e., HVPE). The epitaxial film 3 is doped with at least one impurity such as silicon, oxygen, and carbon, and has an impurity concentration of, for example, 1×10 ¹⁷ cm ⁻³ or more. That is, the epitaxial film 3 has a higher impurity concentration than the GaN wafer 1. The upper limit of the impurity concentration of the epitaxial film 3 is determined according to the characteristics of the semiconductor element described later. In this embodiment, the epitaxial film having a higher impurity concentration than the GaN wafer 1 corresponds to the absorption increase portion.

In the following, the surface of the processed wafer 10 facing the epitaxial film 3 is referred to as one surface 10a of the processed wafer 10, and the surface of the processed wafer 10 facing the GaN wafer 1 is referred to as the other surface 10b of the processed wafer 10. Each chip formation region RA is configured on the one surface 10a side of the processed wafer 10.

Next, as shown in FIG. 1C, a surface side process, which is a process for the one surface 10a side of a typical semiconductor manufacturing process, is performed to form the one surface side element component 11. Specifically, as the surface side process, ion implantation, deposition, wet processes, etc. are appropriately performed to form the one surface side element component 11 of the semiconductor element, such as the diffusion layer 12, gate electrode 13, surface electrodes (not shown), wiring patterns, passivation films, etc., in each chip formation area RA. Note that various configurations of semiconductor elements are used here, such as power devices such as vertical MOS transistors, optical semiconductor elements such as light-emitting diodes, semiconductor lasers, etc. Thereafter, a surface protection film made of resist or the like is formed on the one surface 10a side of the processed wafer 10 as necessary.

Next, as shown in FIG. 1D, a holding member 20 is placed on one surface 10a of the processed wafer 10. For example, a dicing tape having a support base 21 and an adhesive 22 is used as the holding member 20. The support base 21 is made of a material that is not easily warped during the manufacturing process, such as glass, a silicon substrate, or ceramics. The adhesive 22 is made of a material that can change its adhesive strength, such as a material whose adhesive strength changes depending on temperature or light. In this case, the adhesive 22 is made of, for example, an ultraviolet curing resin, wax, or double-sided tape. However, the adhesive 22 is made of a material that maintains its adhesive strength even when forming the other surface side element component 60 in FIG. 1G, which will be described later.

Next, as shown in FIG. 1E, laser light L1 is irradiated from the other surface 10b of the processed wafer 10 to form an altered layer 15 along the surface direction of the processed wafer 10 at a position at a predetermined depth D from the one surface 10a of the processed wafer 10.

Specifically, a laser device (not shown) is prepared, which includes a laser light source that oscillates laser light L1, a dichroic mirror arranged to change the direction of the optical axis of the laser light, i.e., the optical path, a focusing lens for focusing the laser light, and a displaceable stage. When forming the altered layer 15, the position of the stage, etc. is adjusted so that the focusing point of the laser light L1 is scanned relatively along the surface direction of the processed wafer 10. As a result, an altered layer 15 is formed on the processed wafer 10 along the surface direction. More specifically, by irradiating the laser light L1, nitrogen evaporates as a gas and gallium is precipitated to form the altered layer 15.

The predetermined depth D for forming the altered layer 15 is set according to the ease of handling and pressure resistance of the semiconductor chip S1, but in this embodiment, it is set inside the epitaxial film 3. That is, in this embodiment, the impurity concentration of the epitaxial film 3 is higher than the impurity concentration of the GaN wafer 1. Therefore, the epitaxial film 3 is darker in color than the GaN wafer 1 (i.e., has a lower transparency) and has a higher absorption rate of the laser light L1. Therefore, in this embodiment, the altered layer 15 is formed inside the epitaxial film 3. As a result, the altered layer 15 is formed at a position where the laser light L1 is easily absorbed, and the altered layer 15 is preferably formed.

In this embodiment, the laser light L1 used to form the denatured layer 15 is a solid-state laser light, and a green laser with a wavelength of 532 nm is used, although this is not particularly limited. The laser light L1 is irradiated with a processing point output of 0.1 to 0.3 μJ, a pulse width of 500 ps, and a processing speed of 50 to 500 mm/s. However, these conditions are only an example, and the inventors have confirmed that the denatured layer 15 is properly formed even when the processing point output of the laser light is lower or the pulse width is shorter. The inventors have also confirmed that the denatured layer 15 is properly formed even when the processing point output of the laser light L1 is higher or the pulse width is longer. Furthermore, although a green laser is given as an example of the laser light L1 here, the laser light L1 may be an ultraviolet laser with a wavelength of 355 nm, a YAG (yttrium, aluminum, garnet) laser with a wavelength of 1064 nm, a carbon dioxide gas laser with a wavelength of 10.6 μm, etc.

In the following, the portion of the processed wafer 10 on the side 10a of the altered layer 15 will be referred to as the chip configuration wafer 30, and the portion of the processed wafer 10 on the side 10b of the altered layer 15 will be referred to as the recycled wafer 40.

Next, as shown in FIG. 1F, an auxiliary member 50 is placed on the other surface 10b of the processed wafer 10. The auxiliary member 50 is composed of, for example, a base material 51 and an adhesive 52 whose adhesive strength can be changed. In this case, the base material 51 in the auxiliary member 50 is composed of, for example, glass, a silicon substrate, ceramics, etc., and the adhesive 52 in the auxiliary member 50 is composed of, for example, ultraviolet curing resin, wax, double-sided tape, etc. Then, the support base 21 and the auxiliary member 50 are held and a tensile force or the like is applied in the thickness direction of the processed wafer 10, and the chip configuration wafer 30 and the recycled wafer 40 are separated with the altered layer 15 as the boundary (i.e., the starting point of the branching).

In the following description, the side of the chip configuration wafer 30 on which the one-side element configuration portion 11 is formed is referred to as one side 30a, the divided side of the chip configuration wafer 30 is referred to as the other side 30b, and the divided side of the recycled wafer 40 is referred to as one side 40a. In addition, in each of the figures from FIG. 1F onwards, the altered layer 15 remaining on the other side 30b of the chip configuration wafer 30 and the one side 40a of the recycled wafer 40 are omitted as appropriate.

Then, as shown in FIG. 1G, the remaining semiconductor manufacturing process involves a backside process for forming the backside element component 60 of the semiconductor element, such as the metal film 61 that constitutes the backside electrode, on the other side 30b of the chip configuration wafer 30.

Note that, prior to the step of forming the other surface side element component 60, a step of planarizing the other surface 30b of the chip configuration wafer 30 by a CMP (short for chemical mechanical polishing) method or the like may be performed as necessary. Figure 1G shows a diagram of the other surface 30b of the chip configuration wafer 30 after it has been planarized. In addition, after the step of forming the other surface side element component 60, a heat treatment such as laser annealing may be performed as necessary to make ohmic contact between the metal film 61 and the other surface 30b of the chip configuration wafer 30.

Next, as shown in FIG. 1H, a holding member 70 is placed on the other surface 30b of the chip configuration wafer 30, that is, on the metal film 61 side. For example, a dicing tape having a base material 71 and an adhesive 72 is used as the holding member 70. Note that the adhesive 72 is made of a material whose adhesive strength can be changed, and for example, one whose adhesive strength changes depending on temperature or light is used.

Then, as shown in FIG. 1I, the support base 21 attached to one surface 30a of the chip configuration wafer 30 is peeled off. Here, a process is performed to reduce the adhesive strength of the adhesive 22 that attaches the support base 21 to the chip configuration wafer 30, for example, UV irradiation is performed if the adhesive 22 is made of a UV resin adhesive.

Next, as shown in FIG. 1J, the chip configuration wafer 30 is diced into individual chip units using a dicing saw or laser dicing, to form each semiconductor chip S1. At this time, it is preferable to adjust the dicing depth so that the holding member 70 remains connected without being cut while the chip configuration wafer 30 is divided into chip units.

Subsequent steps for the semiconductor chip S1 are not shown, but for example, the following steps are performed. That is, the holding member 70 is expanded, and the spacing between each semiconductor chip S1 is increased in the diced cut portions. After that, the adhesive strength of the adhesive 72 is weakened by heating or irradiating light, and the semiconductor chip S1 is picked up. In this way, the semiconductor chip S1 is manufactured.

As shown in FIG. 1K, one surface 40a of the recycled wafer 40 constructed as shown in FIG. 1F is planarized by performing a CMP method using a polishing device 80 or the like. The planarized recycled wafer 40 is then made into a GaN wafer 1, and the steps from FIG. 1A onwards are carried out again. This allows the GaN wafer 1 to be used multiple times to construct a semiconductor chip S1.

According to the present embodiment described above, an epitaxial film 3 containing GaN is formed on a GaN wafer 1. Therefore, the composition of the GaN wafer 1 as the base substrate and the epitaxial film 3 are the same, and the occurrence of defects in the epitaxial film 3 can be suppressed compared to the case where a sapphire substrate or the like is used as the base substrate. Therefore, when the semiconductor chip S1 is manufactured, the characteristics of the semiconductor chip S1 can be suppressed from deteriorating.

In addition, in this embodiment, the impurity concentration of the epitaxial film 3 is made higher than that of the GaN wafer 1, so that the epitaxial film 3 functions as an absorption increase portion that is more likely to absorb the laser light L1 than the GaN wafer 1. When forming the altered layer 15, the epitaxial film 3 is irradiated with the laser light L1 so that the altered layer 15 is formed inside the epitaxial film 3. This allows the altered layer 15 to be formed favorably, and prevents problems such as variations in the thickness of the semiconductor chip S1 and difficulty in separating the chip configuration wafer 30 and the recycled wafer 40 from occurring.

(1) In this embodiment, when forming the epitaxial film 3, the epitaxial film 3 is doped with at least one impurity selected from silicon, oxygen, and carbon. This makes it easy to make the epitaxial film 3 n-type, which makes it easy to form n-type semiconductor elements.

(2) In this embodiment, the epitaxial film 3 is formed by hydride vapor phase epitaxy. Therefore, the deposition time required to form the epitaxial film 3 can be shortened, and productivity can be improved, compared to forming the epitaxial film 3 by metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).

(3) In this embodiment, the recycled wafer 40 is reused as the GaN wafer 1. Therefore, there is no need to prepare a new GaN wafer 1 each time a semiconductor chip S1 is manufactured, and the GaN wafer 1 can be used effectively. Therefore, the productivity of the semiconductor chip S1 can be improved.

(Modification of the first embodiment)
In the above first embodiment, the GaN wafer 1 is described as being undoped, but the GaN wafer 1 may be doped with impurities such as silicon. However, when the GaN wafer 1 is doped with an impurity, it is preferable that the impurity concentration of the GaN wafer 1 is lower than the impurity concentration of the epitaxial film 3 and that the impurity concentration of the epitaxial film 3 is four or more times higher than the impurity concentration of the GaN wafer 1.

Second Embodiment
A second embodiment will be described. In contrast to the first embodiment, this embodiment forms a high concentration layer before forming the epitaxial film 3. As the rest is similar to the first embodiment, a description thereof will be omitted here.

In this embodiment, after the process of FIG. 1A and before the process of FIG. 1B, a high-concentration layer 16 that is sufficiently thinner than the GaN wafer 1 and the epitaxial film 3 and has a higher impurity concentration than the GaN wafer 1 and the epitaxial film 3 is formed on one surface 1a of the GaN wafer 1, as shown in FIG. 2A.

In this embodiment, the high concentration layer 16 is, for example, about 100 nm thick and is made of a III-V group semiconductor such as GaN or AlGaN doped with silicon, oxygen, or carbon. In this embodiment, the high concentration layer 16 is darker in color than the GaN wafer 1 and the epitaxial film 3, and corresponds to the absorption increase portion.

Next, as shown in FIG. 2B, the process of FIG. 1B is performed to form an epitaxial film 3 on the high-concentration layer 16.

Then, the steps from FIG. 1C onwards are carried out, and in the step of FIG. 1E in which the altered layer 15 is formed, the altered layer 15 is formed by irradiating the high concentration layer 16 with laser light L1 as shown in FIG. 2C. In other words, the altered layer 15 is formed at a position on the processed wafer 10 where the laser light L1 is easily absorbed. Therefore, the altered layer 15 is preferably formed.

According to the present embodiment described above, the semiconductor chip S1 is manufactured by forming an epitaxial film 3 containing GaN on a GaN wafer 1, so that, as in the first embodiment, the characteristics of the semiconductor chip S1 can be prevented from deteriorating.

(1) In this embodiment, a high-concentration layer 16 having a higher impurity concentration than the GaN wafer 1 and the epitaxial film 3 is formed, and the high-concentration layer 16 functions as an absorption increase portion that is more likely to absorb laser light L1 than the GaN wafer 1 and the epitaxial film 3. When forming the altered layer 15, the high-concentration layer 16 is irradiated with laser light L1 so that the altered layer 15 is formed. This allows the altered layer 15 to be formed favorably, and prevents problems such as variations in the thickness of the semiconductor chip S1 and difficulty in separating the chip configuration wafer 30 and the recycled wafer 40 from occurring.

(2) In this embodiment, since an altered layer 15 is formed in the high concentration layer 16, when the chip configuration wafer 30 is separated from the processed wafer 10, the chip configuration wafer 30 is configured to include the entire epitaxial film 3 that has been formed. This makes it easier to manage the thickness of the semiconductor chip S1, etc., and improves productivity.

(Modification of the second embodiment)
In the second embodiment, the high concentration layer 16 may be appropriately patterned so as to expose a predetermined portion of the one surface 1a of the GaN wafer 1. In this way, compared to the case where the high concentration layer 16 is formed over the entire surface of the one surface 1a of the GaN wafer 1, the epitaxial film 3 also grows from the one surface 1a of the GaN wafer 1, so that it is possible to suppress a decrease in the crystallinity of the epitaxial film 3. Furthermore, when the high concentration layer 16 is appropriately patterned, a predetermined alignment mark may be formed in the patterned portion.

Third Embodiment
A third embodiment will be described. In contrast to the first embodiment, this embodiment forms a damaged layer in the GaN wafer 1 before forming the epitaxial film 3. As the rest is similar to the first embodiment, a description thereof will be omitted here.

In this embodiment, after the step of FIG. 1A and before the step of FIG. 1B, as shown in FIG. 3A, one surface 1a of the GaN wafer 1 is irradiated with laser light L2 to form a damaged layer 17 with broken crystallinity along the surface direction of the GaN wafer 1. Note that in this step, a laser device similar to that in the step of FIG. 1E is used. However, the irradiation of the laser light L2 in this step is for breaking down the crystallinity to form the damaged layer 17, and is not for decomposing nitrogen and gallium to form the altered layer 15 as in the step of FIG. 1E. For this reason, the irradiation of the laser light L2 in this step is performed, for example, with a lower energy density than in the step of forming the altered layer 15.

In this process, the damage layer 17 is formed on the one surface 1a of the GaN wafer 1. In this case, by irradiating the laser light L2 from the one surface 1a of the GaN wafer 1, the distance of the laser light L2 passing through the inside of the GaN wafer 1 to the portion where the damage layer 17 is to be formed can be shortened compared to the case where the laser light L2 is irradiated from the other surface 1b of the GaN wafer 1. Therefore, the focal point of the laser light L2 when forming the damage layer 17 is less likely to shift, and the position where the damage layer 17 is formed can be prevented from shifting from the desired position. In this embodiment, the damage layer 17 is darker in color than the GaN wafer 1 and the epitaxial film 3, and corresponds to the absorption increase portion.

After that, the steps from FIG. 1B onwards are carried out, and in the step of FIG. 1E in which the altered layer 15 is formed, the damaged layer 17 is irradiated with laser light L2 to form the altered layer 15, as shown in FIG. 3B. In other words, the altered layer is formed in a position where the laser light L1 is easily absorbed. This allows the altered layer 15 to be formed in an optimal manner.

According to the present embodiment described above, the semiconductor chip S1 is manufactured by forming an epitaxial film 3 containing GaN on a GaN wafer 1, so that the same effect as in the first embodiment can be obtained.

(1) In this embodiment, a damage layer 17 is formed in the GaN wafer 1, and the damage layer 17 functions as an absorption increase portion that is more likely to absorb the laser light L1 than the GaN wafer 1 and the epitaxial film 3. When forming the altered layer 15, the laser light L1 is irradiated to the damage layer 17 so that the altered layer 15 is formed in the damage layer 17. This allows the altered layer 15 to be formed favorably, and prevents problems such as variations in the thickness of the semiconductor chip S1 and difficulty in separating the chip configuration wafer 30 and the recycled wafer 40 from occurring.

(2) In this embodiment, the laser light L2 is irradiated from the one surface 1a side of the GaN wafer 1, and the damage layer 17 is formed on the one surface 1a side of the GaN wafer 1. Therefore, compared to the case where the laser light L2 is irradiated from the other surface 1b side of the GaN wafer 1, the distance of the laser light L2 passing through the inside of the GaN wafer 1 to the part where the damage layer 17 is to be formed can be shortened. Therefore, the focal point of the laser light L2 when forming the damage layer 17 is less likely to shift, and the position where the damage layer 17 is formed can be prevented from shifting from the desired position. In addition, since the damage layer 17 is formed on the one surface 1a side of the GaN wafer 1, the thickness of the recycled wafer 40 can be prevented from becoming thin, and the number of times the recycled wafer 40 is used can be prevented from decreasing.

Other Embodiments
Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also encompasses various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

For example, in each of the above embodiments, the epitaxial film 3 may be configured by stacking an n ⁺ type epitaxial layer and an n ⁻ type epitaxial layer in this order from the GaN wafer 1 side. In this case, for example, when the altered layer 15 is formed in the n ⁺ type epitaxial layer, it is sufficient that the impurity concentration of the n ⁺ type epitaxial layer is higher than the impurity concentration of the GaN wafer 1.

Furthermore, in each of the above embodiments, in the step of FIG. 1G, the metal film 61 may be formed without polishing the other surface 30b of the chip configuration wafer 30. For example, when forming an optical semiconductor element as a semiconductor element, forming an uneven structure on the other surface side of the semiconductor chip S1 makes it possible to effectively extract light from the other surface side. Then, immediately after dividing the processed wafer 10 into the chip configuration wafer 30 and the recycled wafer 40, the other surface 30b of the chip configuration wafer 30 has the altered layer 15 remaining thereon, and minute irregularities are formed. Therefore, when forming an optical semiconductor element, the other surface 30b of the chip configuration wafer 30 may not be polished, and the unevenness of the altered layer 15 may be utilized.

In addition, in the second and third embodiments, the GaN wafer 1 may be doped with impurities, as described in the modified example of the first embodiment.

Furthermore, in each of the above embodiments, in the step of forming the epitaxial film 3 in FIG. 1B, an epitaxial film may also be formed on the other surface 1b of the GaN wafer 1. This makes it easier to leave a predetermined thickness or more as a recycled wafer 40, particularly when an altered layer 15 is formed in the GaN wafer 1 as in the third embodiment, and increases the number of times the wafer can be reused.

1a one side 1b other side 1 GaN wafer 3 epitaxial film 10 processed wafer 10a one side 10b other side 11 one side element component 15 affected layer 30 chip component wafer 40 recycled wafer S1 semiconductor chip

Claims (5)

A method for manufacturing a semiconductor chip having a semiconductor element formed thereon, comprising the steps of:
Preparing a gallium nitride wafer (1) made of gallium nitride and having one surface (1a) and another surface (1b) opposite to the one surface;
forming an epitaxial film (3) containing gallium nitride on the one surface of the gallium nitride wafer, the surface on the epitaxial film side being one surface (10a) and the surface on the gallium nitride wafer side being the other surface (10b), thereby forming a processed wafer (10) having a plurality of chip formation areas (RA) on the one surface side;
forming one-surface-side element constituent parts (11) of the semiconductor element in the plurality of chip formation regions;
By irradiating the inside of the processed wafer with laser light (L1) from the other surface side of the processed wafer, an affected layer (15) is formed inside the processed wafer along a surface direction of the processed wafer;
Dividing the processed wafer at the deteriorated layer as a boundary, thereby dividing the processed wafer into a chip configuration wafer (30) on one side of the processed wafer and a recycled wafer (40) on the other side of the processed wafer;
and extracting a semiconductor chip (S1) from the chip configuration wafer;
Before forming the affected layer, an absorption increase portion (3, 16, 17) having a higher absorptance of the laser light than the gallium nitride wafer is formed;
The forming of the altered layer includes forming the altered layer in the absorption increasing portion ,
The formation of the absorption increase portion includes forming the epitaxial film having a portion with a higher impurity concentration than the gallium nitride wafer when forming the epitaxial film, thereby forming the absorption increase portion;
The forming of the altered layer is a method of manufacturing a semiconductor chip, the method comprising forming the altered layer in a portion that constitutes an absorption increase portion of the epitaxial film . 2. The method for manufacturing a semiconductor chip according to claim 1 , wherein the epitaxial film is doped with at least one impurity selected from the group consisting of silicon, oxygen, and carbon. A method for manufacturing a semiconductor chip having a semiconductor element formed thereon, comprising the steps of:
Preparing a gallium nitride wafer (1) made of gallium nitride and having one surface (1a) and another surface (1b) opposite to the one surface;
forming an epitaxial film (3) containing gallium nitride on the one surface of the gallium nitride wafer, the surface on the epitaxial film side being one surface (10a) and the surface on the gallium nitride wafer side being the other surface (10b), thereby forming a processed wafer (10) having a plurality of chip formation areas (RA) on the one surface side;
forming one-surface-side element constituent parts (11) of the semiconductor element in the plurality of chip formation regions;
By irradiating the inside of the processed wafer with laser light (L1) from the other surface side of the processed wafer, an affected layer (15) is formed inside the processed wafer along a surface direction of the processed wafer;
Dividing the processed wafer at the deteriorated layer as a boundary, thereby dividing the processed wafer into a chip configuration wafer (30) on one side of the processed wafer and a recycled wafer (40) on the other side of the processed wafer;
and extracting a semiconductor chip (S1) from the chip configuration wafer;
Before forming the affected layer, an absorption increase portion (3, 16, 17) having a higher absorptance of the laser light than the gallium nitride wafer is formed;
The forming of the altered layer includes forming the altered layer in the absorption increasing portion ,
The step of forming the absorption increase portion includes forming the absorption increase portion by disposing a high concentration layer (16) having a higher impurity concentration than the gallium nitride wafer and the epitaxial film on the gallium nitride wafer before forming the epitaxial film;
The forming of the altered layer is a method for manufacturing a semiconductor chip, the method comprising the steps of: forming the altered layer in the high concentration layer ; 4. The method for manufacturing a semiconductor chip according to claim 1, wherein the step of forming the epitaxial film comprises forming the epitaxial film by a hydride vapor phase epitaxy method. 5. The method for manufacturing a semiconductor chip according to claim 1, wherein in preparing the gallium nitride wafer, the recycled wafer is prepared as the gallium nitride wafer.

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