Semiconductor device manufacturing: process – Manufacture of electrical device controlled printhead
Reexamination Certificate
2002-04-18
2004-11-16
Mulpuri, Savitri (Department: 2812)
Semiconductor device manufacturing: process
Manufacture of electrical device controlled printhead
C438S479000, C438S044000
Reexamination Certificate
active
06818463
ABSTRACT:
RELATED APPLICATION DATA
The present invention claims priority to Japanese Patent Document No. P2001-120615 filed on Apr. 19, 2001 herein incorporated by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
The present invention relates to a vapor-phase growth method for a nitride semiconductor, which can be adapted to form a nitride semiconductor, such as a gallium nitride based compound semiconductor, on a base body by vapor-phase growth, and to a nitride semiconductor device, such as a nitride semiconductor light emitting diode, a nitride semiconductor laser, a suitable nitride semiconductor electron device formed by using the vapor-phase growth method or the like. More specifically, the present invention relates to a vapor-phase growth method for a nitride semiconductor, which can be adapted to form an anti-surfactant film on a base body and form a nitride semiconductor layer by crystal growth from an opening portion formed in the anti-surfactant film, and a nitride semiconductor device formed by using the vapor-phase growth method.
In recent years, nitride based III-V compound semiconductors, such as GaN, AlGaN and GaInN, have become a focus of attention. This is because such a semiconductor has a forbidden band width ranging from 1.8 eV to 6.2 eV, and therefore, the semiconductor theoretically allows realization of a light emitting device enabling emission of light ranging from red light to ultraviolet light.
In the case of fabricating a light emitting diode (LED) or a semiconductor laser by using a nitride based III-V compound semiconductor, it is required to form a structure in which multi-layers, such as a GaN layer, an AlGaN layer, a GaInN layer, and the like, are stacked such that a light emitting layer (active layer) is sandwiched between an n-type cladding layer and a p-type cladding layer. In some cases, such a light emitting diode or a semiconductor laser includes a light emitting layer having a quantum well structure composed of GaInN/GaN or GaInN/AlGaN.
A vapor-phase growth technique for a nitride semiconductor, such as a gallium nitride based compound semiconductor, can be problematic because it can be difficult to obtain a substrate that is lattice matched with a nitride semiconductor or a substrate having a low density of dislocations. To solve such a problem, there is known a technique of depositing a low temperature buffer layer made from AlN or Al
x
Ga
1-x
N (0≦x<1) at a low temperature of 900° C. or less on a surface of a substrate made from sapphire or the like, and then growing a gallium nitride based compound semiconductor thereon, thereby reducing dislocations due to lattice mismatching between the substrate and the compound semiconductor. Such a technique has been disclosed, for example, in Japanese Patent Laid-open No. Sho 63-188938 and Japanese Patent Publication No. Hei 8-8217. By using such a technique, it is possible to obtain a gallium nitride based compound semiconductor with improved crystallinity and morphology.
Another technique of obtaining a high quality crystal structure at a low density of dislocations has been disclosed, for example, in Japanese Patent Laid-open Nos. Hei 10-312971 and Hei 11-251253. This method involves depositing a first gallium nitride based compound semiconductor layer, forming a protective film made from a material capable of inhibiting growth of a gallium nitride based compound semiconductor, such as silicon oxide or silicon nitride, in such a manner as to selectively cover the first gallium nitride based compound semiconductor, and growing a second gallium nitride based compound semiconductor in an in-plane direction (lateral direction) from regions, not covered with the protective film, of the first gallium nitride based compound nitride layer, thereby preventing propagation of through-dislocations extending in the direction perpendicular to the interface of the substrate.
A further technique of reducing a density of through-dislocations has been disclosed, for example, in a document (MRS Internet J. Nitride Semicond. Res. 4S1, G3.38 (1999)). This method involves growing a first gallium nitride based compound semiconductor, selectively removing the thus formed semiconductor film by using a reactive ion etching (hereinafter, referred to as “RIE”) system, and selectively growing a second gallium nitride based compound semiconductor from the remaining crystal in the growth apparatus. According to this method, it is possible to obtain a crystal film having a density of dislocations, which is reduced to about 10
6
/cm
2
, and hence to realize a high life semiconductor laser using the crystal film formed according to this method.
By the way, in the case of growing a gallium nitride based compound semiconductor layer by such a selective growth technique, a selective growth portion has a three-dimensional structure called “facet” having a tilt plane which is a stable plane growing at a low crystal growth. For example, in the case of forming an underlying layer on a sapphire substrate with a C-plane of sapphire taken as a principal plane of the substrate, covering the surface of the underlying layer with a silicon oxide film as an anti-surfactant film (growth-inhibiting film), and selectively growing a gallium nitride layer from an opening portion provided in the silicon oxide film by supplying a source gas, crystal growth portion has a pyramid shape, for example, a hexagonal pyramid shape having a tilt plane covered with a crystal plane, such as an S-plane.
In this case, however, since a crystal growth rate is generally low at the tilt plane, a supplied source of a group III element is not deposited but migrated at the tilt plane. On the contrary, at a top portion of the pyramid shaped crystal growth layer, since the supplied amount of the source becomes excessively large, the crystal growth rate becomes significantly high. As a result, the top portion of the crystal growth layer contains a number of defects such as point defects, that is, has poor crystallinity. Further, crystal growth at the top portion of the crystal growth layer does not result in a smooth surface, and accordingly, in the case of fabricating a semiconductor device having an active layer or a pn-function particularly on the top portion, performances of the semiconductor device are significantly degraded.
A need, therefore, exists to provide improved nitride semiconductors that can be readily made and effectively used in a variety of applications.
SUMMARY OF THE INVENTION
An advantage of the present invention is to provide a vapor-phase growth method for a nitride semiconductor, which does not cause an excessive supply of a source at a top portion of a crystal growth layer formed by selective growth, thereby fabricating a nitride semiconductor device excellent in characteristics, such as a light emission characteristic.
Another advantage of the present invention is to provide an improved nitride semiconductor device fabricated by a vapor-phase growth method according to an embodiment of the present invention.
In an embodiment, the present invention provides a method of vapor-phase growth of a nitride semiconductor including the steps of supplying a first amount of a source material to a base body of the nitride semiconductor during a first time period; selectively growing a first portion of a nitride semiconductor layer on the base body during the first time period wherein the first portion is grown over a first area along a plane that is substantially parallel to a principle plane of the base body; supplying a second amount of the source material to the base body during a second time period; selectively growing a second portion of the nitride semiconductor layer on the base body during the second time period wherein the second portion is grown over a second area along the plane that is substantially parallel to the principle plane; and forming the nitride semiconductor wherein the second area of the selectively grown nitride layer is equal to or less than the first area of the selectively grown nitride layer and wherein the
Biwa Goshi
Doi Masato
Okuyama Hiroyuki
Oohata Toyoharu
Bell Boyd & Lloyd LLC
Mulpuri Savitri
Sony Corporation
LandOfFree
Vapor-phase growth method for a nitride semiconductor and a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vapor-phase growth method for a nitride semiconductor and a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vapor-phase growth method for a nitride semiconductor and a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3361447