JP3604550B2 - Method for manufacturing nitride semiconductor device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a light emitting diode or a laser diode capable of emitting light from the ultraviolet region to the orange color, and further relates to a method for manufacturing a group 3-5 semiconductor device which can be driven even at a high temperature, and in particular, a semiconductor wafer having a nitride semiconductor laminated on a substrate. The present invention relates to a manufacturing method for dividing a nitride semiconductor device from the above.
[0002]
[Prior art]
Today, nitride semiconductors (In_XGa_YAl_1-XYN, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1) Various semiconductor devices are being developed. As an example of a device using a nitride semiconductor, a light-emitting diode capable of emitting blue, green, and ultraviolet light and a semiconductor laser capable of emitting blue-violet light have been reported. Further, various semiconductor elements which can be driven stably even at a high temperature and have high mechanical strength can be cited.
[0003]
Usually, in the case of a semiconductor wafer in which a semiconductor material such as GaAs, GaP, or InGaAlAs is used as a semiconductor element such as an LED chip capable of emitting red, orange, or yellow light, the semiconductor wafer is chipped by a dicer or a diamond scriber. It is cut out and formed. A dicer is a device that cuts a semiconductor wafer by an external force after fully cutting a semiconductor wafer by a rotating motion of a disk having a cutting edge of diamond, or by cutting a groove having a width wider than the cutting edge width (half cut). On the other hand, a diamond scriber is an apparatus for drawing an extremely thin line (scribe line) on a semiconductor wafer, for example, in a grid pattern using a needle having a diamond tip, and then cutting the semiconductor wafer with an external force. Crystals having a zinc zinc structure, such as GaP and GaAs, have cleavage in the "110" direction. Therefore, by utilizing this property, a semiconductor wafer such as GaAs, GaAlAs, or GaP can be relatively easily separated into a desired shape.
[0004]
However, a semiconductor element using a nitride semiconductor is difficult to form a single crystal unlike a semiconductor element such as GaAsP, GaP, or InGaAlAs formed on a GaP, GaAlAs, or GaAs semiconductor substrate. In order to obtain a single crystal film of a nitride semiconductor having good crystallinity, a single crystal film is formed on a sapphire, spinel substrate, or the like via a buffer using a MOCVD method, an HDVPE method, or the like. Therefore, it is necessary to cut and separate the nitride semiconductor layer formed on the sapphire substrate or the like into a desired size to form a semiconductor element such as an LED chip.
[0005]
A nitride semiconductor stacked on sapphire, spinel, or the like has a heteroepitaxial structure. A nitride semiconductor has a large lattice constant mismatch and a different coefficient of thermal expansion from a sapphire substrate or the like. In addition, the sapphire substrate has a hexagonal crystal structure, and has no cleavage property due to its properties. Further, both sapphire and nitride semiconductors are very hard substances having Mohs hardness of about 9.
[0006]
Therefore, it was difficult to cut only with a diamond scriber. In addition, when full cutting was performed with a dicer, cracks and chipping were likely to occur on the cut surface, and cutting could not be performed neatly. In some cases, the nitride semiconductor layer was partially separated from the substrate.
[0007]
Therefore, as a method for dividing a nitride semiconductor wafer into desired chips, a method using a combination of a diamond scriber and a dicer as described in JP-A-8-274371 has been considered. As a specific example, FIGS. 5A to 5D show steps of manufacturing a nitride semiconductor device. FIG. 5A shows a semiconductor wafer 500 in which a nitride semiconductor 502 is formed on a sapphire substrate 501. FIG. 5B shows a step of forming a groove 503 by a dicer (not shown) at a depth that does not reach the nitride semiconductor 502 from the lower surface side of the sapphire substrate 501. FIG. 5C shows a step of forming a scribe line 504 in the groove with a diamond scriber. FIG. 5D shows a separation step of separating the semiconductor wafer 500 into chips 510 after the scribe step. It is said that this makes it possible to cut relatively cleanly without generating cracks and chipping on the cut surface.
[0008]
[Problems to be solved by the invention]
However, when the groove 503 is formed by partially reducing the thickness of the semiconductor wafer 500 with a dicer or the like and the scribe line 504 is formed in the groove 503 with a diamond scriber, the edge of the diamond scriber contacts the bottom of the groove 503. Must.
[0009]
That is, the edge of the diamond scriber is usually larger than the disk width of the dicer. Therefore, as shown in FIG. 6, the edge 601 of the diamond scriber may not reach the bottom of the groove 503 formed in the semiconductor wafer 500 in some cases. When the scriber is driven in this state, a desired scribe line 703 is not formed on the plane of the semiconductor wafer as shown in FIG. 7, and a distorted scribe line 704 tends to be formed. In order for the cutting edge of the diamond scriber to come into contact with the bottom of the groove 503 in order to prevent them, it is necessary to increase the width of the groove 503 formed by the dicer. As the groove 503 becomes wider, the number of semiconductor devices taken from a semiconductor wafer decreases.
[0010]
On the other hand, when the width of the groove is reduced, it is necessary to reduce the depth of the groove 503 so that the cutting edge contacts the bottom of the groove. When the depth of the groove 503 is reduced, the thickness of the separation portion of the semiconductor wafer increases, and it tends to be difficult to accurately separate the semiconductor wafer. Therefore, there is a problem that a smaller nitride semiconductor device cannot be formed accurately.
[0011]
At present, when it is desired to form a smaller nitride semiconductor device accurately and with good mass productivity, the above cutting method is not sufficient, and an excellent method of manufacturing a nitride semiconductor device is required. If the semiconductor wafer can be accurately separated into chips without damaging the crystallinity of the nitride semiconductor, the electrical characteristics and the like of the semiconductor element can be improved. In addition, since many semiconductor elements can be obtained from one semiconductor wafer, productivity can be improved.
[0012]
Therefore, the present invention further reduces the occurrence of cracks and chipping on the cut surface when dividing the nitride semiconductor wafer into smaller chips. It is another object of the present invention to provide a manufacturing method capable of forming a nitride semiconductor element having a desired shape and size at a high yield without deteriorating the crystallinity of the nitride semiconductor with high productivity.
[0013]
[Means for Solving the Problems]
The present invention is a method for manufacturing a nitride semiconductor device, which divides a semiconductor wafer 100 in which a nitride semiconductor 102 is formed on a substrate 101 into nitride semiconductor devices 110. In particular, the semiconductor wafer 100 has first and second main surfaces and at least the first main surface side and / or the second main surface side.Sapphire substrateTo 101Groove by dicer (103) The groove (103) Is not less than 10 μm and not more than 35 μm, and the groove is (103) Is formed in a range of not less than 3.7 μm and not more than 100 μm.Process and break line 104 in groove 103Using a YAG laserA method for manufacturing a nitride semiconductor device, comprising a step of forming by laser irradiation and a step of separating a semiconductor wafer along a break line 104.
[0014]
In the method for manufacturing a nitride semiconductor device according to claim 2 of the present invention, the first main surface 121 isSapphire substrate 101The second main surface 111 is the side of the exposed substrate facing the semiconductor wafer 100 on which the nitride semiconductor is formed only on one of the upper sides, and the second main surface 111 is opposed to the semiconductor wafer 100 via the semiconductor wafer.
[0015]
In the method for manufacturing a nitride semiconductor device according to claim 3 of the present invention, the break lineSapphire substrateThe recess 104 is formed on the bottom surface of the groove 101.
[0016]
In the method for manufacturing a nitride semiconductor device according to claim 4 of the present invention, the break lineSapphire substrateA damaged part 204 formed inside 201.
[0018]
In the method of manufacturing a nitride semiconductor device according to a fifth aspect of the present invention, the groove 403 is formed on the surface of the first main surface side 421 where the sapphire substrate 401 is previously exposed.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
As a result of various experiments, the present inventors have manufactured a nitride semiconductor device which is excellent in mass productivity without damaging semiconductor characteristics by irradiating a laser to a specific portion of a semiconductor wafer when manufacturing a nitride semiconductor device. It has been found that the present invention can be performed and the present invention has been accomplished.
[0020]
The reason why the separation end face formed by the method of the present invention is formed flat along the break line is not clear, but internal stress occurs near the groove with the formation of the groove, and the internal stress and the break line are large in the shape of the cut end face. It seems to be related.
[0021]
That is, a groove portion mechanically cut by a dicer, a diamond scriber, or the like generates internal stress when the groove portion is formed. In particular, in the step of forming a scribe line by a diamond scriber along the bottom surface of the groove, the strain is amplified not only at the bottom of the groove but also by the load applied to the cutting edge of the scriber. For this reason, if the grooves are formed and separated by a diamond scriber, it is considered that the end face as desired is not formed due to the stress held in the semiconductor wafer, and the nitride semiconductor wafer cannot be separated more accurately.
[0022]
In the present invention, a laser scriber generates a local stress that contributes to division without depending on an internal stress generated by a dicer. It is considered that this makes it possible to manufacture a nitride semiconductor device having a clean (smooth) end surface and good mass productivity. Further, in order to separate the nitride semiconductor element, a groove part in which the thickness of the semiconductor wafer is partially thin is formed. By forming a break line narrower than the groove by laser irradiation, an extremely thin break line can be formed deeply to a desired depth, and a nitride semiconductor element having good mass productivity can be separated. Hereinafter, an example of the production method of the present invention will be described.
[0023]
As a semiconductor wafer, a nitride semiconductor layer having a structure to be an LD (laser diode) was formed on a spinel substrate. More specifically, a GaN buffer layer, an n-type GaN contact layer, an n-type AlGaN cladding layer, an n-type GaN optical guide layer, and a multi-quantum structure in which Si is doped and the composition of In is changed are formed on a spinel substrate. An InGaN active layer having a well structure, a p-type AlGaN cap layer, a p-type GaN optical guide layer, a p-type AlGaN cladding layer, and a p-type GaN contact layer are stacked. Grooves are formed vertically and horizontally on the surface of the semiconductor wafer by wet etching on the spinel substrate side of the semiconductor wafer. CO₂By irradiating the bottom of the groove with a laser, a break line was formed vertically and horizontally along the groove as a process-altered portion inside the spinel substrate. Separation as a nitride semiconductor device is performed by pressing with a roller along a break line. Each of the separated nitride semiconductor elements has a clean end face. Hereinafter, an apparatus used in the process of the present invention will be described in detail.
[0024]
(Nitride semiconductor wafer)
The nitride semiconductor wafer has a nitride semiconductor layer formed on a substrate. Examples of the nitride semiconductor substrate include sapphire, spinel, silicon carbide, zinc oxide, gallium nitride single crystal, and various other materials.In order to form a nitride semiconductor layer with good mass productivity and good crystallinity, a sapphire substrate, A spinel substrate or the like is preferably used. Since the sapphire substrate or the like has no cleavage property and is extremely hard, the present invention works particularly effectively.
[0025]
Nitride semiconductor (In_XGa_YAl_1-XYN, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1) can be variously formed by MOCVD, HVPE, or the like. A nitride semiconductor can be used as a semiconductor element by forming a PN junction, a PIN junction, and a MIS junction. The structure of the semiconductor can be variously selected such as a homo junction, a hetero junction, and a double hetero junction. In addition, a single quantum well structure or a multiple quantum well structure in which the semiconductor layer is thin enough to produce a quantum effect can be used.
[0026]
Nitride semiconductors have relatively large band gaps and are resistant to heat, so they have light emitting diodes that can emit light from the ultraviolet to red, light emitting elements such as short wavelength lasers that can be used for DVDs, optical sensors, and relatively high electromotive forces. It can be used as various semiconductor elements such as a light receiving element such as a solar cell and a transistor having heat resistance.
[0027]
The thickness of the substrate can be selected variously depending on the processing accuracy and output of the laser processing machine. However, when forming a larger groove (deep groove) in the laser, it takes more time than a dicer and a portion due to a long heating time. It is preferable not to form too large a groove or the like by laser processing from the viewpoint of permanent destruction.
[0028]
The width of the groove formed on the semiconductor wafer by a dicer or the like is preferably 35 μm or less, more preferably 30 μm or less, from the viewpoint of forming a desired shape and size with good productivity and good yield. More preferably, it is 25 μm or less. The lower limit is not particularly limited, but when formed with a dicer, if the thickness is too small, the cutting edge is shaken, and the groove tends to be thin and deep. Therefore, it is preferably at least 10 μm, more preferably at least 15 μm. Further, it is preferably at least 20 μm. The depth of the groove depends on the thickness of the semiconductor wafer, but is preferably at least 3.7 μm, more preferably at least 4.5 μm, from the viewpoint of mass productivity and ease of separation. More preferably, it is not less than 5.2 μm. The upper limit is not particularly limited, but is preferably 100 μm or less in consideration of mass productivity. Similarly, when the groove has a width of 35 μm or less and a depth of 5.2 μm or more, more preferably a width of 30 μm or less and a depth of 4.5 μm, and still more preferably a width of 25 μm or less and a depth of 3.7 μm or more, the diamond scriber has a groove in FIG. As described above, a scribe line contributing to division of a semiconductor wafer cannot be formed, so that the effect of the present invention is particularly large.
[0029]
In addition, as a method of simply forming a groove in the nitride semiconductor wafer, it can be formed by wet etching, dry etching, dicer, diamond scriber, laser processing, or a combination thereof. However, in order to partially reduce the thickness of the semiconductor wafer efficiently with a certain width, it is preferable to use a dicer. In particular, when the groove is formed using a dicer, the difference in the cleanliness (smoothness) of the end face when divided into chips tends to be remarkable. That is, when a semiconductor wafer is separated using a laser after forming a groove using a dicer, and a semiconductor wafer is separated using a diamond scriber after forming a groove using a dicer, and the concave portion is formed by the laser. The formed one tends to form the separation end face more clearly. Such smoothness may be a significant difference when performing an optical design using a sapphire substrate which is a light-transmitting insulating layer.
[0030]
When the sapphire substrate on which the nitride semiconductor is laminated is separated, the thickness of the thinnest separation portion of the nitride semiconductor wafer is preferably 100 μm or less in order to cut the cut end surface with good productivity. When the thickness is 100 μm or less, separation can be performed relatively easily with little chipping or the like. The lower limit of the thickness of the substrate is not particularly limited. However, if the thickness is too small, the semiconductor wafer itself is easily broken and mass productivity is deteriorated, so that the thickness is preferably 30 μm or more.
[0031]
When the nitride semiconductor layer includes a thin film having a single quantum well structure, a multiple quantum well structure, or the like, the nitride semiconductor layer that is irradiated with a laser in advance to prevent a semiconductor junction or damage to the semiconductor layer due to laser irradiation is etched. It can be removed in advance.
[0032]
In the case of a nitride semiconductor wafer for a light emitting diode, the substrate typically has a thickness of 200 to 500 μm, and the nitride semiconductor layer having a pn junction has a thickness of several μm to several tens μm. Therefore, most of the semiconductor wafer is occupied by the thickness of the substrate. The thickness of the substrate can be reduced by polishing in order to facilitate processing by laser. In such polishing, the nitride semiconductor may be formed and then thinned, or the nitride semiconductor may be formed on a thinly polished substrate.
[0033]
In addition, it is considered that the nitride semiconductor wafer irradiated with the laser has an irradiated portion serving as a focal point selectively fly or becomes a deformed portion which is a set of micro clocks. In the break line of the present invention, the surface of the groove of the semiconductor wafer may be removed, or a damaged portion may be formed inside the groove of the substrate. Further, in the present invention, the center of the total film thickness of the semiconductor wafer may be laser-processed in addition to the break line formed by laser processing near the groove.
[0034]
(Laser processing machine)
The laser processing machine used in the present invention may be any laser processing machine as long as it can form a concave portion serving as a break line, a deformed portion, and the like. Specifically, YAG laser, CO₂Lasers, excimer lasers and the like are preferably used. In particular, a YAG laser can form a break line with little heat deterioration. Also, CO₂Lasers have high cutting power because of their high power.
[0035]
The focus of the laser irradiated by the laser beam machine can be variously adjusted by an optical system such as a lens as desired. Therefore, it is possible to form a concave portion, a damaged portion, and the like without damaging the nitride semiconductor at an arbitrary focal point of the semiconductor wafer by laser irradiation. The laser irradiation surface can be adjusted to a desired shape such as a perfect circle, an ellipse, or a rectangle by passing through a filter.
[0036]
In forming a break line by a laser beam machine, the laser irradiation device itself may be moved, or only the irradiated laser may be scanned by a mirror or the like. Furthermore, a desired break line can be formed by variously driving the stage holding the semiconductor wafer, such as up, down, left, right, and 90 degrees rotation. Hereinafter, embodiments of the present invention will be described in detail, but it goes without saying that the present invention is not limited to only the embodiments.
[0037]
【Example】
(Example 1)
Using a sapphire substrate 200 having a thickness of 200 μm and having been cleaned, a nitride semiconductor was laminated using MOCVD to form a nitride semiconductor wafer. The nitride semiconductor was formed as a multilayer film so as to function as the light emitting element 110 after dividing the substrate. First, at 510 ° C., NH₃By flowing (ammonia) gas, TMG (trimethylgallium) gas, and hydrogen gas as a carrier gas, a buffer layer having a thickness of about 200 Å was formed.
[0038]
Next, after stopping the inflow of TMG gas, the temperature of the reactor was raised to 1050 ° C.₃(Ammonia) gas, TMG gas, SiH as dopant gas₄By flowing a (silane) gas and a hydrogen gas as a carrier gas, a GaN layer having a thickness of about 4 μm and serving as an n-type contact layer was formed.
[0039]
The active layer is temporarily made to be a carrier gas only, the temperature of the reactor is kept at 800 ° C., and NH 3 is used as a source gas.₃An undoped InGaN layer having a thickness of about 3 nm was deposited by flowing (ammonia) gas, TMG gas, TMI (trimethylindium), and hydrogen gas as a carrier gas.
[0040]
In order to form a clad layer on the active layer, the flow of the raw material gas was stopped and the temperature of the reactor was maintained at 1050 ° C.₃(Ammonia) gas, TMA (trimethylaluminum) gas, TMG gas, Cp as dopant gas₂A hydrogen gas was flowed as an Mg (cyclopentadiermagnesium) gas and a carrier gas, and a GaAlN layer having a thickness of about 0.1 μm was formed as a p-type cladding layer.
[0041]
Finally, the temperature of the reactor is maintained at 1050 ° C. and NH 3 is used as a raw material gas.₃(Ammonia) gas, TMG gas, Cp as dopant gas₂An Mg gas and a hydrogen gas were flowed as a carrier gas to form a GaN layer having a thickness of about 0.5 μm as a p-type contact layer (the p-type nitride semiconductor layer was annealed at 400 ° C. or higher).
[0042]
A semiconductor wafer is used in which a plurality of island-shaped nitride semiconductor layers are formed by etching a semiconductor wafer by RIE (Reactive Ion Etching) from a nitride semiconductor surface side until a boundary surface with a sapphire substrate on which a groove is formed is exposed. . A mask is formed so that each pn semiconductor is exposed at the time of etching, and is removed after the etching. An electrode 120 is formed on each pn semiconductor layer by a sputtering method (FIG. 1A).
[0043]
After the sapphire substrate 101 of the nitride semiconductor wafer 100 thus formed is polished to 100 μm, the sapphire substrate surface 111 of the semiconductor wafer 100 is fixed using a vacuum chuck on a table that can be freely driven in the horizontal direction so that the sapphire substrate surface 111 faces upward. Let it go. By moving the stage at a blade rotation speed of 30,000 rpm and a cutting speed of 3 mm / sec, a groove having a width of about 30 μm and a depth of about 15 μm is formed vertically and horizontally on the bottom surface of the sapphire substrate 101 to form a groove 103. The groove 103 is formed substantially parallel to the etching surface 130 when viewed from the sapphire substrate exposed surface side 111 of the nitride semiconductor wafer 100, and each is formed to have a size of 300 μm square which will later become a nitride semiconductor element. (FIG. 1 (B)).
[0044]
Next, a YAG laser irradiator capable of irradiating laser (356 nm) only on a driving unit such as a blade of a dicer was replaced (not shown). While keeping the nitride semiconductor wafer 100 fixed, the laser optical system is adjusted so that the laser focuses on the bottom of the groove 103 of the nitride semiconductor wafer. Adjusted laser beam at 16 J / cm²By moving the stage while irradiating in step (1), a concave portion 104 as a further groove having a depth of about 3 μm is formed as a break line along the bottom surface of the groove portion 103 (FIG. 1C).
[0045]
A load can be applied by a roller (not shown) along the break line to cut and separate the nitride semiconductor wafer 100. Any of the end faces of the separated nitride semiconductor element 110 can form a nitride semiconductor element without chipping or cracking (FIG. 1D).
[0046]
When power was supplied to the LED chips as nitride semiconductor elements formed in this way, all of them could emit light and almost no cracks or chippings occurred on the cut end faces. Further, the generated chipping was extremely small, and the yield was 98% or more.
[0047]
Accordingly, since the break line is formed by the laser, unlike the method using the diamond scriber, the variation in the processing accuracy due to the wear and deterioration of the cutter and the cost for replacing the cutting edge can be reduced. The manufacturing yield can be increased and the variation in shape can be reduced. In particular, it is possible to reduce the cutting margin and improve the number of semiconductor elements to be obtained.
[0048]
(Example 2)
A break line was formed in the same manner as in Example 1 except that the focal depth in the laser irradiation apparatus of Example 1 was increased by adjusting the laser optical system. In the formed break line, no concave portion is formed in the groove portion 203 serving as the surface of the substrate 201, but it is formed inside the substrate 201 as a processed deteriorated portion (FIG. 2C).
[0049]
Even if the break line is formed not on the bottom surface of the groove 203 but on the inner surface of the substrate 201, the yield similar to that of the LED chip of the first embodiment can be formed.
[0050]
(Example 3)
Using a sapphire substrate 150 having a thickness of 150 μm and cleaned as a substrate 301, a nitride semiconductor was laminated by MOCVD to form a nitride semiconductor wafer 300. The nitride semiconductor was formed as a multilayer film on a substrate. First, at 510 ° C., NH₃By flowing (ammonia) gas, TMG (trimethylgallium) gas, and hydrogen gas as a carrier gas, a buffer layer having a thickness of about 200 Å was formed.
[0051]
Next, after stopping the inflow of TMG gas, the temperature of the reactor was raised to 1050 ° C.₃(Ammonia) gas, TMG gas, SiH as dopant gas₄By flowing a (silane) gas and a hydrogen gas as a carrier gas, a GaN layer having a thickness of about 4 μm and serving as an n-type contact layer was formed.
[0052]
The active layer is temporarily made to be a carrier gas only, the temperature of the reactor is kept at 800 ° C., and NH 3 is used as a source gas.₃An undoped InGaN layer having a thickness of about 3 nm was deposited by flowing (ammonia) gas, TMG gas, TMI (trimethylindium), and hydrogen gas as a carrier gas.
[0053]
In order to form a clad layer on the active layer, the flow of the raw material gas was stopped and the temperature of the reactor was maintained at 1050 ° C.₃(Ammonia) gas, TMA (trimethylaluminum) gas, TMG gas, Cp as dopant gas₂A hydrogen gas was flowed as an Mg (cyclopentadiermagnesium) gas and a carrier gas, and a GaAlN layer having a thickness of about 0.1 μm was formed as a p-type cladding layer.
[0054]
Finally, the temperature of the reactor is maintained at 1050 ° C. and NH 3 is used as a raw material gas.₃(Ammonia) gas, TMG gas, Cp as dopant gas₂A GaN layer having a thickness of about 0.5 μm was formed as a p-type contact layer by flowing a hydrogen gas as a Mg gas and a carrier gas (FIG. 3A). (Note that the p-type nitride semiconductor layer has been annealed at 400 ° C. or higher.)
The formed semiconductor wafer 300 was fixed using a vacuum chuck on a stage capable of freely moving in the horizontal direction with the surface 321 on which the nitride semiconductor was formed facing upward. Vertical and horizontal grooves 303 are formed on the main surface of the semiconductor wafer 300 from the nitride semiconductor lamination surface side 321 to the substrate 301 by a dicer (not shown) at a blade rotation speed of 30,000 rpm and a cutting speed of 3 mm / sec. The groove 303 formed by the dicer has a width of 25 μm, and is formed so that the distance between the bottom surface of the groove 303 and the exposed surface 311 of the sapphire substrate on which the nitride semiconductor is not formed is substantially uniform at 50 μm (FIG. 3). (B)).
[0055]
Next, a YAG laser irradiator capable of irradiating laser (356 nm) only on a driving unit such as a blade of a dicer was replaced (not shown). While keeping the nitride semiconductor wafer 300 fixed, the optical system of the laser is adjusted so that the bottom of the groove 303 formed is focused. Adjusted laser beam at 16 J / cm²By moving the stage while irradiating, a recess 304 having a depth of about 3 μm is formed along the groove 303 as a break line (FIG. 3C).
[0056]
A load is applied by a roller (not shown) along the break line to cut and separate the nitride semiconductor wafer 300. Any of the end faces of the separated nitride semiconductor element 310 can form a nitride semiconductor element substantially free of chipping and cracks (FIG. 3D). Cracks and chipping hardly occurred on the cut end faces of the nitride semiconductor thus formed.
[0057]
(Example 4)
The sapphire substrate 401 of the semiconductor wafer 400 formed in the same manner as in Example 1 is further polished to 80 μm and mirror-finished. This semiconductor wafer 400 was fixedly arranged on the same stage (not shown) as in Example 3 with the nitride semiconductor laminated side 421 facing up (FIG. 4A).
[0058]
In the fourth embodiment, a groove portion 403 having a width of about 25 μm and a depth of about 10 μm is formed from the nitride semiconductor laminated surface side 421 by a dicer along the etching surface 430 which has been etched in advance (FIG. 4B).
[0059]
Next, a YAG laser irradiator capable of irradiating laser (356 nm) only on a driving unit such as a blade of a dicer was replaced (not shown). While keeping the nitride semiconductor wafer 400 fixed, the laser optical system is adjusted so that the bottom of the groove 403 formed is focused. Adjusted laser beam at 16 J / cm²By moving the stage while irradiating in step (3), a recess 404 having a depth of about 3 μm is formed as a break line along the groove 403 (FIG. 4C).
[0060]
A load can be applied by a roller (not shown) along the break line to cut and separate the nitride semiconductor wafer 400. Any of the separated end faces can form a nitride semiconductor element 410 with almost no chipping or cracking (FIG. 4D).
[0061]
When electricity was supplied to the LED chip 410, which was a separated nitride semiconductor element, any of them could emit light. When the end face of the LED chip 410 was examined, almost no chipping or cracking occurred. The yield was over 98%.
[0062]
(Example 5)
A semiconductor wafer was separated and LED chips were formed in the same manner as in Example 1 except that an excimer laser was used instead of the YAG laser irradiation in Example 1. As in the case of the first embodiment, each of the separated end faces of the formed LED chip can emit light and has a clean surface free of chipping and cracks.
[0063]
(Comparative Example 1)
A semiconductor wafer was separated in the same manner as in Example 1 except that the diamond wafer was repeatedly scribed three times along a groove instead of laser processing. The separated nitride semiconductor device of Comparative Example 1 was partially cracked or chipped. Further, a distorted scribe line as shown in FIG. 7 was formed, and the yield was about 75%.
[0064]
【The invention's effect】
According to the present invention, a groove reaching a substrate of a semiconductor wafer is formed, and a break line is formed in the groove by laser irradiation. This makes it possible to form high-precision break lines in narrower and deeper grooves without any processing variations, without causing deterioration in processing accuracy due to wear of the cutting edge, etc., and easily and accurately along the break lines. It is possible to divide the nitride semiconductor device. Therefore, it is possible to supply a product having a uniform shape and improve the product yield.
[0065]
Further, by forming a break line in a non-contact manner with respect to a semiconductor wafer by laser irradiation, it is possible to reduce the processing cost caused by deterioration and replacement of a conventional scribe cutter.
[0066]
Furthermore, by forming the groove reaching the substrate from the semiconductor layer surface side in the semiconductor wafer from which the nitride semiconductor has been removed in advance, it is possible to manufacture a highly reliable element without damage to the semiconductor due to the formation of the groove. .
[0067]
By forming the concave portion on the nitride semiconductor laminated surface side by laser irradiation, a narrower groove portion can be formed. For this reason, it is possible to improve the number of nitride semiconductor devices obtained from a semiconductor wafer.
[0068]
[Brief description of the drawings]
FIG. 1 is a schematic partial cross-sectional view illustrating a method for separating a semiconductor wafer according to a first embodiment of the present invention.
[0069]
FIG. 2 is a schematic partial sectional view illustrating a method for separating a semiconductor wafer according to a second embodiment of the present invention.
[0070]
FIG. 3 is a schematic partial sectional view showing a method for separating a semiconductor wafer according to a third embodiment of the present invention.
[0071]
FIG. 4 is a schematic partial cross-sectional view illustrating a method for separating a semiconductor wafer according to a fourth embodiment of the present invention.
[0072]
FIG. 5 is a schematic partial sectional view showing a method for cutting a nitride semiconductor wafer shown for comparison with the present invention.
[0073]
FIG. 6 is a schematic partial sectional view when the nitride semiconductor wafer is cut by a diamond scriber.
[0074]
FIG. 7 is a schematic partial plan view showing distortion generated when forming a scribe line of a nitride semiconductor wafer shown for comparison with the present invention.
[0075]
[Explanation of symbols]
100, 200, 300, 400, 700 ... semiconductor wafer
101, 201, 301, 401 ... substrate
102, 202, 402 ... island-shaped nitride semiconductor
103, 203, 303, 403 ... grooves formed on the substrate surface
104, 304, 404... Break lines formed by recesses formed in the bottom of the groove
204: Break line due to damaged part formed inside substrate
302: nitride semiconductor
110, 210, 310, 410 ... nitride semiconductor device
111, 311, 411 ... substrate exposed surface side
120, 220, 420 ... electrodes
121, 321, 421 ... nitride semiconductor laminated side
130, 430 ... etching surface
500, 600 ... semiconductor wafer
501 ... substrate
502: nitride semiconductor layer
503, 603... Groove formed in sapphire substrate
504, 604... Scribe lines formed on the bottom of the groove
510 ・ ・ ・ Nitride semiconductor device
601: Diamond scriber blade
703: Normally formed scribe line
704: scribe line formed distorted

Claims (5)

A method for manufacturing a nitride semiconductor device, comprising dividing a semiconductor wafer (100) having a nitride semiconductor (102) formed on a substrate (101) into nitride semiconductor devices (110),
The semiconductor wafer (100) has first and second main surfaces, and a groove (103) is formed by a dicer on at least the sapphire substrate (101) on the first main surface side and / or the second main surface side. Forming a groove (103) with a width of 10 μm or more and 35 μm or less and a depth of the groove (103) of 3.7 μm or more and 100 μm or less ;
Forming a break line (104) in the groove (103) by laser irradiation using a YAG laser ;
Separating the semiconductor wafer along the break line (104). The first main surface (121) is a nitride semiconductor laminated side of a semiconductor wafer (100) on which a nitride semiconductor is formed only on one side on a sapphire substrate (101), and the second main surface (111) is provided. 2. The method for manufacturing a nitride semiconductor device according to claim 1, wherein is a substrate exposed surface side opposed via a semiconductor wafer. 2. The method according to claim 1, wherein the break line is a recess formed on a bottom surface of the groove of the sapphire substrate. 3. 2. The method according to claim 1, wherein the break line is a processed part (204) formed inside the sapphire substrate (201). 3. The method according to claim 2, wherein the groove (403) is formed on a surface of the first main surface (421) where the sapphire substrate (401) is previously exposed.

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