Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-09-28
2003-09-02
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S141000, C428S332000, C117S952000
Reexamination Certificate
active
06613461
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gallium nitride-based compound semiconductor chip produced by growing a gallium nitride-based compound semiconductor crystal on a gallium nitride substrate with a wurtzite type crystal structure and dividing the resulting wafer, a method for producing such a chip, and a gallium nitride-based compound semiconductor wafer.
2. Description of the Related Art
A light emitting device using a gallium nitride-based compound semiconductor is capable of emitting light with wavelengths widely ranging from blue to orange by adjusting a composition of each of the compound semiconductor layers therein. Such gallium nitride-based compound semiconductor light emitting devices have been conventionally produced by growing a gallium nitride-based compound semiconductor film on a sapphire substrate, the crystal structure of which is a rhombohedral structure, by using a metal organic chemical vapor deposition method or the like. However, a gallium nitride-based compound semiconductor crystal formed on a sapphire substrate is poor in quality because a lattice incommensurate between the sapphire substrate and the gallium nitride-based compound semiconductor crystal is significant. Therefore, a high light emission efficiency cannot be achieved. This is why attempts are being made to produce a light emitting device by producing a gallium nitride substrate and growing a gallium nitride-based compound semiconductor thereupon. However, the gallium nitride substrate has a crystal structure which is a wurtzite type structure, unlike the sapphire substrate which has a rhombohedral structure. No methods have been devised for producing a wafer by growing the gallium nitride-based compound semiconductor crystal on the gallium nitride substrate having the wurtzite type structure and forming an electrode thereon, and dividing the wafer into chips.
In a wafer produced by growing a gallium nitride-based compound semiconductor crystal on a gallium nitride substrate having a wurtzite type structure, there is no lattice incommensurate between the gallium nitride substrate and the gallium nitride-based compound semiconductor crystal. Therefore, the quality of the gallium nitride-based compound semiconductor crystal in such a wafer is satisfactory. However, with regard to producing a wafer by growing a gallium nitride-based compound semiconductor crystal on a gallium nitride substrate having a wurtzite type crystal structure and forming an electrode thereon, and dividing the wafer into gallium nitride-based compound semiconductor chips are light emitting devices, no reports have been made in relation to the following: (1) what an approximate thickness of the wafer should be and what a division facet direction of the wafer should be in order to produce satisfactory chips with no defects in the shape, such as nicks or the like; (2) how grooves for assisting chip division should be formed; and (3) how the chip division should be made.
SUMMARY OF THE INVENTION
The inventors of the present invention examined a technique in the chip division of a wafer produced by growing a gallium nitride-based compound semiconductor crystal on a gallium nitride substrate having a (0001) facet of a wurtzite type crystal structure as a principal facet. Such a technique has never been put into practice. A method has been found for producing a gallium nitride-based compound semiconductor chip as a light emitting device of a satisfactory shape without nicks or the like at a high yield, and the structure of the gallium nitride-based compound semiconductor chip also has been disclosed.
A nitride semiconductor light emitting chip is a gallium nitride-based compound semiconductor chip including a gallium nitride substrate with a (0001) facet of a wurtzite type crystal structure as a principal facet, and a gallium nitride-based compound semiconductor crystal grown on the gallium nitride substrate. The gallium nitride-based compound semiconductor chip is characterized in that at least one of the division facets thereof is a cleave facet of the gallium nitride substrate.
Cleave facets of the wurtzite type crystal in directions can be deviated by 60 degrees from one another. Division is relatively easy in the cleave facet direction, while division is difficult in a direction substantially perpendicular to the cleave facet. The ease of division in such a substantially perpendicular direction is different from that in the cleave facet direction, thereby causing defects in the shape of the chips, such as nicks or the like. The present invention decreases the number of defects in the shape of the chips, such as nicks or the like. Therefore, chips having satisfactory cross-sectional portions can be produced at a high yield.
The thickness of the gallium nitride substrate may be in the range between 50 &mgr;m or more and 250 &mgr;m or less. When the thickness of the gallium nitride-substrate is greater than 250 &mgr;m, the number of the chips having defects in the shape, such as nicks or the like, increases in the chip division step because the gallium nitride substrate is relatively hard. When the thickness of the wafer is smaller than 50 &mgr;m, the wafer becomes easy to break in wafer polishing and chip division steps. When the thickness of the gallium nitride substrate is in the range between 50 &mgr;m or more and 250 &mgr;m or less, the number of defects in the shape of the chips, such as nicks or the like, is few and the wafer substantially does not break in the polishing and chip division steps.
The nitride semiconductor light emitting chip of the present invention is characterized by having a structure such that at least one of the chip division facets is a facet substantially perpendicular to a cleave facet of the gallium nitride substrate.
According to the present invention, it is possible to prevent production yield in the chip division step from decreasing because an adjustment in direction of the grooves is made with ease and the deviations in the direction are minimized by forming the chip division facet in a direction substantially perpendicular to the cleave facet. Moreover, the grooves are formed in a direction substantially perpendicular to the cleave facet so that an angle of the chip does not become acute, thereby substantially eliminating the occurrence of nicks in a chip.
The nitride semiconductor light emitting chip of the present invention is characterized by having a structure such that the side length of the division facet in the cleave facet direction of the gallium nitride substrate is longer than that in the division facet substantially perpendicular to the cleave facet of the gallium nitride substrate.
According to the present invention, it is possible to produce a rectangular chip such that a shorter side direction thereof is a direction substantially perpendicular to a cleave facet direction and a longer side direction thereof is a cleave facet direction. A greater force is applied to the shorter side, since division is not easily made in the direction perpendicular to the cleave facet direction. Therefore, an appropriate force can be applied to a groove based on leverage so that the chips are produced at a high yield.
The nitride semiconductor light emitting chip of the present invention is characterized by having a structure such that all of the chip division facets are the cleave facets of the gallium nitride substrate. Because of this characteristic, the number of defects in the shape of the chips, such as nicks or the like, may be few. Accordingly, a chip having a satisfactory condition of the cross-sectional portions can be produced at a high yield.
The gallium nitride-based compound semiconductor chip of the present invention includes a gallium nitride substrate with a (0001) facet of a wurtzite type crystal structure as a principal facet and a gallium nitride-based compound semiconductor crystal formed on the gallium nitride substrate. The gallium nitride-based compound semiconductor chip is characterized in that at least two of th
Jones Deborah
Morrison & Foerster / LLP
Sharp Kabushiki Kaisha
Stein Stephen
LandOfFree
Gallium nitride-based compound semiconductor chip and method... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gallium nitride-based compound semiconductor chip and method..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gallium nitride-based compound semiconductor chip and method... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3046664