| Nitride-based semiconductor device and method of fabricating the same -> Monitor Keywords |
|
|
 
Nitride-based semiconductor device and method of fabricating the sameRelated Patent Categories: Semiconductor Device Manufacturing: Process, Making Device Or Circuit Emissive Of Nonelectrical SignalNitride-based semiconductor device and method of fabricating the same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070077669, Nitride-based semiconductor device and method of fabricating the same. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a nitride-based semiconductor device and a method of fabricating the same, and more particularly, it relates to a nitride-based semiconductor device having an electrode and a method of fabricating the same. [0003] 2. Description of the Background Art [0004] A nitride-based semiconductor laser device has recently been expected as a light source for an advanced large capacity optical disk, and actively developed. [0005] In general, an insulating sapphire substrate is employed for forming a nitride-based semiconductor laser device. When a nitride-based semiconductor layer is formed on the sapphire substrate, however, a large number of defects (dislocations) are disadvantageously formed in the nitride-based semiconductor layer due to large difference between the lattice constants of the sapphire substrate and the nitride-based semiconductor layer. Consequently, the characteristics of the nitride-based semiconductor laser device are disadvantageously reduced. [0006] In this regard, a nitride-based semiconductor laser device employing a nitride-based semiconductor substrate such as a GaN substrate having small difference in lattice constant with respect to a nitride-based semiconductor layer is proposed in general. [0007] FIG. 7 is a sectional view showing a conventional nitride-based semiconductor laser device employing an n-type GaN substrate 101. Referring to FIG. 7, nitride-based semiconductor layers (102 to 110) are grown on a Ga face ((HKLM) plane: M denotes a positive integer) to be improved in crystallinity in a process of fabricating the conventional nitride-based semiconductor laser device. A nitrogen face ((HKL-M) plane: M denotes a positive integer) of the n-type GaN substrate 101 having a wurtzite structure is employed as the back surface, so that an n-side electrode 112 is formed on this back surface of the n-type GaN substrate 101. The fabrication process for the conventional nitrlde-based semiconductor laser device is now described in detail. [0008] As shown in FIG. 7, an n-type layer 102 consisting of n-type GaN having a thickness of about 3 .mu.m, an n-type buffer layer 103 consisting of n-type In.sub.0.05Ga.sub.0.95N having a thickness of about 100 nm, an n-type cladding layer 104 consisting of n-type Al.sub.0.05Ga.sub.0.95N having a thickness of about 400 nm, an n-type light guide layer 105 consisting of n-type GaN having a thickness of about 70 nm, an MQW (multiple quantum well) active layer 106 having an MQW structure, a p-type layer 107 consisting of p-type Al.sub.0.2Ga.sub.0.8N having a thickness of about 200 nm, a p-type light guide layer 108 consisting of p-type GaN having a thickness of about 70 nm, a p-type cladding layer 109 consisting of p-type Al.sub.0.05Ga.sub.0.95N having a thickness of about 400 nm and a p-type contact layer 110 consisting of p-type GaN having a thickness of about 100 nm are successively formed on the upper surface (Ga face) of the n-type GaN substrate 101 having a thickness of about 300 .mu.m to about 500 .mu.m. [0009] Then, a p-side electrode 111 is formed on a prescribed region of the upper surface of the p-type contact layer 110. The back surface of the n-type GaN substrate 101 is polished until the thickness of the n-type GaN substrate 101 reaches a prescribed level of about 100 .mu.m, and an n-side electrode 112 is thereafter formed on the back surface (nitrogen face) of the n-type GaN substrate 101 . Finally, the n-type GaN substrate 101 and the layers 102 to 110 are cleft thereby performing element isolation and forming a cavity facet. Thus, the conventional nitride-based semiconductor laser device shown in FIG. 7 is completed. [0010] In the conventional nitride-based semiconductor laser device shown in FIG. 7, however, the n-type GaN substrate 101 is so hard that it is difficult to excellently perform device isolation and form the cavity facet by cleavage. In order to cope with such inconvenience, a method of mechanically polishing the back surface of the n-type GaN substrate 101 before the cleavage step for reducing irregularity on the back surface thereby excellently performing element isolation and forming the cavity facet is proposed. This method is disclosed in Japanese Patent Laying-Open No. 2002-26438, for example. [0011] In the aforementioned conventional method disclosed in Japanese Patent Laying-Open No. 2002-26438, however, stress is applied in the vicinity of the back surface of the n-type GaN substrate 101 when the back surface of the n-type GaN substrate 101 is mechanically polished. Therefore, microscopic defects such as cracks are disadvantageously formed in the vicinity of the back surface of the n-type GaN substrate 101 . Consequently, contact resistance between the n-type GaN substrate 101 and the n-side electrode 112 formed on the back surface (nitrogen face) thereof is disadvantageously increased. [0012] Further, the nitrogen face of the n-type GaN substrate 101 is so easily oxidized that the contact resistance between the n-type GaN substrate 101 and the n-side electrode 112 formed on the back surface (nitrogen face) thereof is disadvantageously increased also by this. SUMMARY OF THE INVENTION [0013] An object of the present invention is to provide a method of fabricating a nitride-based semiconductor device capable of reducing contact resistance between the back surface of a nitride-based semiconductor substrate or the like and an electrode. [0014] Another object of the present invention is to reduce the number of defects in the vicinity of the back surface of the nitride-based semiconductor substrate or the like in the aforementioned method of fabricating a nitride-based semiconductor device. [0015] Still another object of the present invention is to provide a nitride-based semiconductor device capable of reducing contact resistance between the back surface of a nitride-based semiconductor substrate or the like and an electrode. [0016] In order to attain the aforementioned objects, a method of fabricating a nitride-based semiconductor device according to a first aspect of the present invention comprises steps of etching the back surface of a first semiconductor layer consisting of either an n-type nitride-based semiconductor layer or a nitride-based semiconductor substrate having a wurtzite structure and thereafter forming an n-side electrode on the etched back surface of the first semiconductor layer. [0017] In the method of fabricating a nitride-based semiconductor device according to the first aspect, the back surface of the first semiconductor layer consisting of either an n-type nitride-based semiconductor layer or a nitride-based semiconductor substrate having a wurtzite structure is etched as hereinabove described, whereby a region including defects in the vicinity of the back surface of the first semiconductor layer resulting from a polishing step or the like can be removed for reducing the number of defects in the vicinity of the back surface of the first semiconductor layer. Thus, an electron carrier concentration can be inhibited from reduction resulting from trap of electron carriers by defects, so that the electron carrier concentration can be increased on the back surface of the first semiconductor layer. Consequently, contact resistance between the first semiconductor layer and the n-side electrode can be reduced. Further, the back surface of the first semiconductor layer is so etched that flatness thereof can be improved as compared with that of a mechanically polished back surface. Thus, the n-side electrode formed on the back surface of the first semiconductor layer can also be improved in flatness, whereby adhesion between the n-side electrode and a radiator base can be improved when the former is mounted on the latter. Consequently, excellent radiability can be attained. Further, the n-side electrode formed on the back surface of the first semiconductor layer can be so improved in flatness that wire bondability with respect to the n-side electrode can be improved when the n-side electrode is wire-bonded. [0018] In the aforementioned method of fabricating a nitride-based semiconductor device according to the first aspect, the back surface of the first semiconductor layer preferably includes a nitrogen face of the first semiconductor layer. The term "nitrogen face" denotes a wide concept indicating not only a complete nitrogen face but also a surface mainly formed by a nitrogen face. More specifically, the term nitrogen face, includes a surface having a nitrogen face of at least 50% in the present invention. When formed by a nitrogen face, the back surface of the first semiconductor layer is so easily oxidized that the oxidized portion of the back surface can be removed by etching. Thus, contact resistance between the first semiconductor layer and the n-side electrode can be further reduced. [0019] In the aforementioned method of fabricating a nitride-based semiconductor device according to the first aspect, the etching step preferably includes a step of etching the back surface of the first semiconductor layer by dry etching. According to this structure, the back surface of the first semiconductor layer can be easily improved in flatness and the number of defects can be reduced in the vicinity of the back surface due to the dry etching. [0020] In the aforementioned method of fabricating a nitride-based semiconductor device including the step of etching the back surface of the first semiconductor layer by dry etching, the step of etching the back surface of the first semiconductor layer by dry etching preferably includes a step of etching the back surface of the first semiconductor layer by reactive ion etching with Cl.sub.2 gas and BCl.sub.3 gas. According to this structure, the back surface of the first semiconductor layer can be easily improved in flatness and the number of defects can be easily reduced in the vicinity of the back surface. In this case, the ratio of the flow rate of BCl.sub.3 gas to the flow rate of Cl.sub.2 gas in the step of etching the back surface of the first semiconductor layer by the reactive ion etching is preferably at least 30% and not more than 70%. It has been experimentally confirmed that the back surface of the first semiconductor layer can be improved in flatness in this range of the ratio of the flow rate of BCl.sub.3 gas to that of Cl.sub.2 gas, and hence the back surface of the first semiconductor layer can be reliably improved in flatness by setting the ratio within this range. [0021] In the aforementioned method of fabricating a nitride-based semiconductor device including the step of etching the back surface of the first semiconductor layer by dry etching, the etching depth and the etching time in the step of etching the back surface of the first semiconductor layer by dry etching are preferably proportional to each other. According to this structure, the etching depth can be accurately controlled by adjusting the etching time. [0022] In the aforementioned method of fabricating a nitride-based semiconductor device according to the first aspect, the etching step preferably includes a step of etching the back surface of the first semiconductor layer thereby converting the back surface of the first semiconductor layer to a mirror surface. According to this structure, the back surface of the first semiconductor layer can be further improved in flatness. Continue reading about Nitride-based semiconductor device and method of fabricating the same... Full patent description for Nitride-based semiconductor device and method of fabricating the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Nitride-based semiconductor device and method of fabricating the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Nitride-based semiconductor device and method of fabricating the same or other areas of interest. ### Previous Patent Application: Light-emitting device and manufacturing method thereof Next Patent Application: Super bright light emitting diode of nanorod array structure having ingan quantum well and method for manufacturing the same Industry Class: Semiconductor device manufacturing: process ### FreshPatents.com Support Thank you for viewing the Nitride-based semiconductor device and method of fabricating the same patent info. IP-related news and info Results in 0.15672 seconds Other interesting Feshpatents.com categories: Computers: Graphics , I/O , Processors , Dyn. Storage , Static Storage , Printers 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
