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Recursive calibrationRelated Patent Categories: Data Processing: Measuring, Calibrating, Or Testing, Calibration Or Correction SystemRecursive calibration description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060142965, Recursive calibration. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] Calibration of measurement tools and scientific instrumentation typically involves the use of another tool that has a higher degree of precision than the tool(s) or instrument(s) to be calibrated. Using such a "reference", "standard" or "gold standard" tool of higher precision, measurements taken by the tool or instrument to be calibrated can be compared with measurements of the reference tool that has a higher degree of precision, and adjusted accordingly, to match the measurements of the higher precision tool as closely as possible. This not only increases the precision of each tool or instrument compared to and adjusted according to the reference tool, but it also standardizes the measurements of the tools and instruments so adjusted, so that they produce measurement results similarly to one another. However, for tools and instruments on the cutting edge of the limits of precision, this approach is no longer possible, since a tool having greater precision does not exist, and therefore some other technique, tool and/or method is needed to calibrate such tools and instruments. This need arises, among other areas, in areas where the discipline requires the ability to measure smaller and smaller units, such as distance, volume, or other unit of measurement, as the discipline progresses over time. Examples of such disciplines include semiconductor technologies, such as VLSI design and manufacturing, transistor design and manufacturing etc. A discipline that has been immediately faced with such need is the field of nanotechnology. [0002] Nano-machines are typically at the limits of technology with regard to the units of measurement that can be detected and worked with by such machines. Therefore, it is impossible to provide a "reference" tool of the type described above, that could be used to calibrate such nano-machines. [0003] An example of a conventional self-calibration technique useful for improving accuracy in the alignment of masks used in making integrated circuits via electron beam lithography is disclosed in U.S. Pat. No. 4,583,298 to Raugh, which is incorporated herein, in its entirety, by reference thereto. Raugh uses the concept of symmetry to calibrate a rigid plate by first placing the rigid plate in a reference orientation and measuring the locations of points in a grid on the calibration plate to establish reference measurements. After that, the rigid plate is repositioned into "non-reference" orientations, and for each non-reference orientation, the locations of the points in the grid are again measured. A calibration map is used to determine calibrated measured values for each orientation for each grid point. Numerical values are then set for parameters to minimize deviation from the congruence of each orientation of the rigid plate with all other orientations measured. Raugh determined that single or multiple rotations of the rigid plate about a single point cannot give complete self-calibration, since a rotationally symmetric distortion would look the same in all rotated orientations, and therefore would not be detectable as an error. The same holds for translations which, alone, are ineffective in identifying translationally invariant distortions. However, using rotational displacement of the rigid plate and a translation displacement, or another rotation about a different point, makes it possible to self-calibrate according to Raugh's technique. [0004] Ye et al., in U.S. Pat. No. 5,798,947, which is incorporated herein in its entirety, by reference thereto, also addresses self-calibration of lithography stages. A mapping of a two-dimensional array of stage positions to corresponding positions in a Cartesian coordinate grid is made to determine distortion therebetween. The mapping function is performed by a series of orthogonal Fourier series functions to decouple the determination of a pivoting point and a rotation angle from the determination of the distortion function. An operation is performed to determine complete non-four-fold rotationally symmetric distortion between the two-dimensional array of stage positions and the Cartesian coordinate grid from measured locations of marks in an original orientation to locations having been rotated by ninety degrees. A translation operation is also performed to take further distortion measurements and to determine incomplete non-four-fold rotationally symmetric distortion. [0005] However, when applying the above self-calibration techniques, the rotations and translations required introduce errors themselves, as the amount of rotation and/or translation is not exact at the level of precision of the tool. Therefore replicate symmetry operations of the object in the input field of the tool are required to reduce error of its mean symmetrical locations. The object must span the entire input field of the tool to assure complete calibration. This is a requirement that must be met by Design Of Experiments (DOE) in order to leverage all possibilities of the domain of the application, wherein, in this case, the domain is the device input field for machines. SUMMARY OF THE INVENTION [0006] Methods, systems and computer readable media are provided for calibrating a device for which it is not possible to provide another device having a higher degree of precision to be used as a standard against which the device to be calibrated can be compared to perform the calibration. Such methods, systems and computer readable media may include performance of comparing machine instructions used by the device to reproduce a current input as a current output, with machine instructions that were used by the device to reproduce the current input as the previous output, based on a previous input; determining error based upon results from the comparison, and determining whether calibration of the device has been successfully completed, based on errors determined by the determination of error, wherein if errors between the machine instructions used to produce the current output and the machine instructions used to produce the previous output are within predetermined thresholds, then it is determined that the calibration has been successfully completed, and wherein if it is not determined that the calibration has been successfully completed, adjustment of one or more operational parameters of the device is performed, and the current output is used as an input to iterate the comparison of machine instructions. [0007] Methods, systems and computer readable media are provided for calibrating a device that replicates and reduces an input to a scale for which it is not possible to provide another device having a higher degree of precision to be used as a standard against which the device to be calibrated can be compared to perform the calibration, including: using a metrology system to measure an error pattern of a current output produced as a nano-scale reproduction of a current input by the device based on inputting the current input to the device; transforming the error pattern back to a scale equal to a scale of the current input; comparing a pattern of the current input with the transformed error pattern; aligning the error pattern with the pattern of the current input by linear regression; and determining whether calibration has been successfully completed, wherein if all errors within the error pattern are less than or equal to one or more predetermined error thresholds, then it is determined that successful calibration has been completed. [0008] Methods, systems and computer readable media are provided for calibrating a device for which it is not possible to provide another device having a higher degree of precision to be used as a standard against which the device to be calibrated can be compared to perform the calibration. In one embodiment performance of such calibration includes: inputting a representative sample as a current input to the device to be calibrated; converting the current input to machine instructions used by the device to reproduce the current input as an output; outputting the reproduction of the current input as a current output; adjusting one or more operational parameters of the device with at least one adjustment to attempt to reduce recursive errors in the machine instructions; inputting the current output from said outputting the reproduction as a current input to the device to be calibrated; repeating the converting and outputting steps based upon the current input; comparing the machine instructions from the current converting step to machine instructions produced by the most recent previous converting step; and determining that the calibration of the device has been successfully completed when errors between the machine instructions from the current converting step and the machine instructions produced by the most recent previous converting step are within predetermined error tolerances, or adjusting one or more operational parameters of the device, and then repeating the inputting the current output, and repeating the converting and outputting, and comparing steps when the errors are not within said predetermined error tolerances. [0009] Methods, systems and computer readable media are provided for calibrating a device that replicates and reduces an input to a scale for which it is not possible to provide another device having a higher degree of precision to be used as a standard against which the device to be calibrated can be compared to perform the calibration, including: inputting a representative sample as a current input to the device to be calibrated; converting the current input to a current output based on current machine settings of the device to reproduce the current input as an output and wherein the output is scaled down to nano-dimensions; outputting a nano-scale reproduction of the current input as a current output; measuring an error pattern of the current output with a metrology system; transforming the error pattern back to a scale equal to a scale of the current input; comparing a pattern of the current input with the input pattern; aligning the error pattern with the pattern of the current input by linear regression; if one or more errors within the error pattern are greater than predetermined error thresholds, adjusting one or more machine settings of device to be calibrated to form current machine settings for a next recursive cycle; repeating the inputting, converting, outputting, measuring, transforming, comparing, aligning and adjusting steps to perform additional recursive cycles until current errors are all within the predetermined error thresholds or until a predetermined recursion cycle limit has been met. [0010] Forwarding, transmitting and/or receiving a result obtained from any of the methods described herein are also disclosed. [0011] These and other advantages and features of the invention will become apparent to those persons skilled in the art upon reading the details of the methods, systems and computer readable media as more fully described below. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1 is a block diagram representing a device being used to take an input from an input field 1 and to produce an output at output field 1' that is theoretically identical to the input in input field 1. [0013] FIGS. 2A and 2B are flow diagrams illustrating recursive processing for carrying out calibration as one embodiment of the present invention. [0014] FIG. 3 is a flow chart illustrating event that may be carried out for calibration by a recursive technique, at least a portion of which may be automated, as one example of the present invention. [0015] FIG. 4 is a block diagram illustrating an example of a generic computer system which may be used in implementing the present invention. [0016] FIG. 5A is a schematic representation of hardware for carrying out stepper-repeater recursive calibration according to the present invention. [0017] FIG. 5B is a schematic representation of an error diagram produced by comparing an original circuit layout with an error pattern. [0018] FIG. 5C is a schematic representation of an original reticle pattern used as the original input on the reticle of the hardware of FIG. 5A. [0019] FIG. 5D is a schematic representation of a nano-scale image fo the pattern of FIG. 5C that was produced on a wafer as an output from the hardware of FIG. 5A. [0020] FIG. 5E shows an error diagram produced in the manner described above, where crosshairs indicate the relative locations of the points on the reticle pattern, and dots indicate the relative locations of the points on the outputted image, after transforming to the same scale as the reticle pattern. DETAILED DESCRIPTION OF THE INVENTION Continue reading about Recursive calibration... Full patent description for Recursive calibration Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Recursive calibration 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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