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  Damage evaluation method of compound semiconductor member, production method of compound semiconductor member, gallium nitride compound semiconductor member, and gallium nitride compound semiconductor membraneUSPTO Application #: 20060281201Title: Damage evaluation method of compound semiconductor member, production method of compound semiconductor member, gallium nitride compound semiconductor member, and gallium nitride compound semiconductor membrane Abstract: A method of evaluating damage of a compound semiconductor member, comprising: a step of performing spectroscopic ellipsometry measurement on a surface of the compound semiconductor member; and a step of evaluating damage on the surface of the compound semiconductor member, using a spectrum in a wavelength band containing a wavelength corresponding to a bandgap of the compound semiconductor member, in a spectrum of an optical constant obtained by the spectroscopic ellipsometry measurement. (end of abstract)
Agent: Mcdermott Will & Emery LLP - Washington, DC, US Inventors: Akihiro Hachigo, Takayuki Nishiura, Keiji Ishibashi USPTO Applicaton #: 20060281201 - Class: 438016000 (USPTO) Related Patent Categories: Semiconductor Device Manufacturing: Process, With Measuring Or Testing, Optical Characteristic Sensed The Patent Description & Claims data below is from USPTO Patent Application 20060281201. 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 damage evaluation method of a compound semiconductor member, a production method of a compound semiconductor member, a gallium nitride compound semiconductor member, and a gallium nitride compound semiconductor membrane. [0003] 2. Related Background Art [0004] Compound semiconductors have various merits in comparison with Si. For example, the compound semiconductors permit control of the bandgap through adjustment of compositions. Furthermore, the compound semiconductors have such optical properties as direct transition and wide bandgap, and are thus suitably applied to optical devices such as LEDs or LDs. Since the compound semiconductors have high carrier mobility, they are also suitably applied to high-speed devices. [0005] In producing such compound semiconductor devices as the optical devices or high-speed devices, a substrate used is a compound semiconductor substrate, or a laminated substrate in which a compound semiconductor membrane is formed on an amorphous substrate such as a glass substrate. For example, a compound semiconductor membrane or electrodes are formed on a surface of the compound semiconductor substrate or laminated substrate. The device characteristics of the compound semiconductor devices are significantly affected by an interface between the compound semiconductor substrate or laminated substrate and the compound semiconductor membrane or by interfaces between the compound semiconductor substrate or laminated substrate and the electrodes. Therefore, it is important to evaluate the interfaces in the compound semiconductor devices. [0006] In production of the compound semiconductor devices, damage occurs on the foregoing interfaces in several production processes. For example, since surface roughness of the compound semiconductor substrate or laminated substrate affects the device characteristics, the surface of the compound semiconductor substrate or laminated substrate is subjected to polishing or etching. This process produces scratches or distortion on the surface to cause damage on the surface. For example, dry etching or wet etching or the like is used in forming a thin film or fine pattern of nanometer size on the surface of the compound semiconductor substrate or laminated substrate. At this time, damage is caused on the surface of the compound semiconductor substrate or laminated substrate or on the surface of the thin film or fine pattern. [0007] When a compound semiconductor device is produced, for example, by growing an epitaxial film on the surface of the compound semiconductor substrate or compound semiconductor membrane with the surface including the damage as described above, the device characteristics are degraded by virtue of the damage existing at the interface between the compound semiconductor substrate or compound semiconductor membrane and the epitaxial film. [0008] Methods for evaluating the damage on the surface of the compound semiconductor substrate or compound semiconductor membrane include methods using X-ray diffraction, scanning electron microscope (SEM), cathodoluminescence, or the like as usually adopted methods. [0009] On the other hand, Japanese Patent Application Laid-Open No. 11-87448 discloses a method of evaluating damage on a substrate by ellipsometry. This method is to evaluate a depth of a damage layer or a level of damage from a change rate of intensity of reflected light from the substrate. [0010] Japanese Patent Application Laid-Open No. 2005-33187 discloses a method of subjecting a wafer to an etching treatment and evaluating a surface structure of the wafer after the etching treatment by ellipsometry. This method is to project polarized light onto the wafer and to evaluate the surface structure of the wafer, using polarized light reflected from the wafer. Specifically, the surface structure of the wafer is estimated from a phase difference .DELTA. and an amplitude ratio .psi. between the polarized light projected onto the wafer and the polarized light reflected from the wafer. SUMMARY OF THE INVENTION [0011] However, the methods disclosed in the foregoing Patent Applications are not satisfactory yet in accuracy of damage evaluation on a surface of a compound semiconductor member, and there are desires for further improvement in the accuracy. [0012] An object of the present invention is therefore to provide a damage evaluation method of a compound semiconductor member and a production method of a compound semiconductor member capable of evaluating a level of damage on a surface with high accuracy and to provide a gallium nitride compound semiconductor member and a gallium nitride compound semiconductor membrane with a low level of damage. [0013] In order to solve the above problem, a damage evaluation method of a compound semiconductor member according to the present invention is (1) a method of evaluating damage of a compound semiconductor member, comprising: a step of performing spectroscopic ellipsometry measurement on a surface of the compound semiconductor member; and a step of evaluating damage on the surface of the compound semiconductor member, using a spectrum in a wavelength band containing a wavelength corresponding to a bandgap of the compound semiconductor member, in a spectrum of an optical constant obtained by the spectroscopic ellipsometry measurement. Here the term "spectrum of an optical constant" refers to data of an optical constant at wavelengths, for example. [0014] Preferably, (2) the optical constant is an imaginary part of a complex index of refraction, and the step of evaluating the damage uses a maximum absolute value of a slope of the spectrum in the wavelength band. [0015] Preferably, (3) the optical constant is an imaginary part of a complex index of refraction, and the step of evaluating the damage uses an absolute value of an extremum of a first derivative of the spectrum in the wavelength band. [0016] Preferably, (4) the optical constant is an imaginary part of a complex index of refraction, and the step of evaluating the damage uses a wavelength at which an absolute value of a slope of the spectrum in the wavelength band is maximum. [0017] Preferably, (5) the optical constant is an imaginary part of a complex index of refraction, and the step of evaluating the damage uses a maximum of the spectrum in the wavelength band. [0018] Another damage evaluation method of a compound semiconductor member according to the present invention is (6) a method of evaluating damage of a compound semiconductor member, comprising: a step of performing spectroscopic ellipsometry measurement on a surface of the compound semiconductor member; and a step of evaluating damage on the surface of the compound semiconductor member, using a peak in a separate wavelength band located on a longer wavelength side than a wavelength band containing a wavelength corresponding to a bandgap of the compound semiconductor member, in a spectrum of an imaginary part of a complex index of refraction obtained by the spectroscopic ellipsometry measurement. [0019] Still another damage evaluation method of a compound semiconductor member according to the present invention is (7) a method of evaluating damage of a compound semiconductor member, comprising: a step of performing spectroscopic ellipsometry measurement on a surface of a damage layer in the compound semiconductor member having a compound semiconductor region and the damage layer provided on the compound semiconductor region; and a step of evaluating damage on the surface of the damage layer in the compound semiconductor member, using a peak appearing in a spectrum of an imaginary part of a complex index of refraction with at least one reflection of light between the compound semiconductor region and the damage layer, in the spectrum of the imaginary part of the complex index of refraction obtained by the spectroscopic ellipsometry measurement. [0020] Preferably, (8) the optical constant is an imaginary part of a complex dielectric constant, and the step of evaluating the damage uses a maximum absolute value of a slope of the spectrum in the wavelength band. [0021] Preferably, (9) the optical constant is an imaginary part of a complex dielectric constant, and the step of evaluating the damage uses an absolute value of an extremum of a first derivative of the spectrum in the wavelength band. [0022] Preferably, (10) the optical constant is an imaginary part of a complex dielectric constant, and the step of evaluating the damage uses a wavelength at which an absolute value of a slope of the spectrum in the wavelength band is maximum. Continue reading... Full patent description for Damage evaluation method of compound semiconductor member, production method of compound semiconductor member, gallium nitride compound semiconductor member, and gallium nitride compound semiconductor membrane Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Damage evaluation method of compound semiconductor member, production method of compound semiconductor member, gallium nitride compound semiconductor member, and gallium nitride compound semiconductor membrane 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. 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