Apparatus for measuring thickness profile and refractive index distribution of multiple layers of thin films by means of two-dimensional refrectometry and method of measuring the same
First Claim
1. An apparatus for measuring thickness and refractive index of a single or multiple layers of thin films, said apparatus comprising;
- a substrate carrier for supporting a substrate;
an optical unit for providing a light source and a reflected light from said substrate for said measurements;
an optical filter set for filtering said reflected light by different wavelength;
a two-dimensional array type of CCD sensors;
an image grabber for capturing images generated by said CCD sensors;
a data processing unit for computing and generating one or more measurement data of thickness, thickness profile or refractive index of thin films using said image data captured by said image grabber in groups of pixels of at least (3×
3) pixels, and by means of repeated and iterative use of a nonlinear error minimization method;
means for computing theoretical values of reflectivity or refractive index;
means for finding a minimum error between a computed and a measured reflectivity or refractive index values by iterative and repeated use of a nonlinear error minimization method;
a system controller unit containing image processing, information processing and system control functions for processing said image data.
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Abstract
The present invention relates to a non-contact, non-destructive measuring apparatus that measures thickness profile and refractive index distribution of a single or multiple layers of thin films by means of the principle of reflectometry. According to the present invention, by employing more than one narrow band-pass optical filters and a two-dimensional array of CCD sensors, and by finding an optimal solution for the nonlinear functional relationship between the thickness of said thin film or thin films and the corresponding refractive indexes by using an iterative numerical computation method, said apparatus simultaneously measures local area-wise thickness profile and refractive index distribution among others of said a single layer or multiple layers of thin films on a substrate.
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Citations
20 Claims
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1. An apparatus for measuring thickness and refractive index of a single or multiple layers of thin films, said apparatus comprising;
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a substrate carrier for supporting a substrate;
an optical unit for providing a light source and a reflected light from said substrate for said measurements;
an optical filter set for filtering said reflected light by different wavelength;
a two-dimensional array type of CCD sensors;
an image grabber for capturing images generated by said CCD sensors;
a data processing unit for computing and generating one or more measurement data of thickness, thickness profile or refractive index of thin films using said image data captured by said image grabber in groups of pixels of at least (3×
3) pixels, and by means of repeated and iterative use of a nonlinear error minimization method;
means for computing theoretical values of reflectivity or refractive index;
means for finding a minimum error between a computed and a measured reflectivity or refractive index values by iterative and repeated use of a nonlinear error minimization method;
a system controller unit containing image processing, information processing and system control functions for processing said image data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method for measuring thickness and refractive index of a single or multiple layers of thin films, said method comprising the processes of:
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capturing two-dimensional images by using a two-dimensional array of CCD sensors;
discriminating said lights incident into said CCD sensors by using a narrow band-pass filter set;
measuring said thickness in two-dimensions by partitioning the pixels out of said CCD sensors in groups in order to maintain stability in measured values;
measuring said refractive index distribution as a function of position of said pixels on the surface of a substrate in two-dimensions by partitioning said pixels in groups of at least (3×
3) pixels in order to maintain stability in measured values;
finding measured values for thickness profile or refractive index distribution or both by means of iterative and repetitive use of a nonlinear error minimization method by using said data on said reflected lights captured through said two-dimensional array type of CCD sensors;
displaying the results of measuring thickness or thickness profile or refractive index distribution, or any combination of these, of a single or multiple layers of thin films, by processing said intensity of the projected lights onto said CCD sensors as a function of wavelength and also optionally the surface profiles in two-dimensional or three-dimensional representations selectively on said monitor.
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Specification