Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
  • G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
  • G01B21/04—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness by measuring coordinates of points
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70691—Handling of masks or workpieces
  • G03F7/70716—Stages
  • G03F7/70725—Stages control
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
  • G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
  • G01B21/04—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness by measuring coordinates of points
  • G01B21/042—Calibration or calibration artifacts
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
  • G03F7/70491—Information management, e.g. software; Active and passive control, e.g. details of controlling exposure processes or exposure tool monitoring processes
  • G03F7/70516—Calibration of components of the microlithographic apparatus, e.g. light sources, addressable masks or detectors
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
  • G03F7/70605—Workpiece metrology
  • G03F7/70616—Monitoring the printed patterns

Definitions

• the invention relates to a method for determining a correction function for eliminating the coordinate-dependent measurement errors of a coordinate measuring machine by self-calibration.
• High-precision coordinate measuring machines are used in the semiconductor industry to measure the structures on masks or wafers. Precise knowledge of the coordinates of the structures on masks is imperative in order to be able to carry out a controlled manufacture of integrated circuits.
• the measured values of these high-precision coordinate measuring machines have error components which depend on the measuring location, that is to say the measured coordinate itself. There are systematic error components that result from the design and selection of the components of the coordinate measuring machine itself. So z. B. known error causes defects in the mirror orthogonality and mirror flatness, distortions in the scaling of the measuring axes (so-called cosine errors) and the deflection of the mask used for correction.
• US 4,583,298 describes the self-calibration of a coordinate measuring machine with the aid of a so-called calibration plate, on which a grating is arranged.
• the positions of the grid points are not calibrated.
• the grid plate is placed on the stage of the coordinate measuring machine and the positions of its grid points are measured.
• the same grid plate is then rotated two or more times by 90 ° around an axis of rotation and the positions of the grid points are measured in each of the set orientations.
• the measurement results are mathematically turned back and various correction factors and tables are optimized so that the turned back data records have a better match.
• the mounting mechanism In order to allow a significant displacement of the turning centers, the mounting mechanism, such as the square frame, has to be moved.
• the measuring range must also be enlarged compared to the non-displaced object.
• the measures required for this conversion of the coordinate measuring machine are associated with considerable disadvantages Is it difficult to attach a sliding holding frame for the caliber plate on the object table? If there are other mask holders on the sample table (eg vacuum chuck or special multi-point mounting), these had to be removed especially for the calf measurements Place a holding frame on existing ones
• Mask holders are also out of the question, since they can be damaged or do not provide a flat support surface for the holding frame
• the enlargement of the measuring range for measuring the caliber plate in the shifted state is also problematic. It requires costly constructive changes that go into the manufacturing costs of the machine.
• the outer dimensions of the machine are also enlarged.
• the footprint of the machine has a direct impact on its operating costs, because in the semiconductor industry, the footprint in the clean room is very expensive.
• the invention is therefore based on the object of specifying a method for determining a correction function for eliminating the coordinate-dependent measurement errors of a coordinate measuring machine, in which, during the calibration measurements using the already present, non-displaceable mask holders, rotations of the respective calibration substrate about a single center of rotation are sufficient without having to move the calibration substrate.
• an optimal error correction should be achieved.
• a continuous correction function is to be specified with which it is possible to correct any measurement locations in the entire measurement range, that is to say also between the points of a calibration grid.
• a correction function that depends on the measurement location is a two- or three-dimensional function K (r) for eliminating the coordinate-dependent measurement errors of a coordinate measuring machine.
• the correction function is always continuous and differentiable.
• the fit parameters ⁇ must therefore be determined for the fit functions k ⁇ r) in such a way that the correction is optimal, that is to say the residual error is minimal or equal to zero.
• the invention is based on the knowledge that there are special components of the correction function K (r), which are not clearly determined or have a very large error. This is mainly about
• rotationally symmetrical components in the form of the linear combination S (r) make no or a very imprecise contribution to the approximation of the ideal, ie exactly correct, correction function K (r).
• the presence of such rotationally symmetrical components can result in the fit parameters a t for the fit functions k, (r) not being able to be clearly determined. To improve the error correction, they are therefore removed from the series development of the correction function K (r) according to the invention or excluded by measurement technology.
• the invention thus specifies a method for error correction of a coordinate measuring machine which specifically disregards the rotationally symmetrical error components.
• Three different exemplary embodiments A, B and C are specified.
• a first, metrological solution consists in a method in which no rotationally symmetrical portions arise in the correction function by measurement with two differently dimensioned reference objects.
• a second solution consists in a method in which the rotationally symmetrical linear combinations S (r) of the fit functions k t (f) are determined by measurement on a single reference object and are removed from the set of fit functions. The shortened set of fit functions is then used to approximate the correction function.
• C Although the rotationally symmetrical linear combinations S (r) interfere with the determination of the fit parameters ⁇ , they are desirable for describing certain error components and are therefore originally included in the general set of fit functions.
• the correction function K (r) is optimized by one of the reference objects completely covering the measuring range of the coordinate measuring machine
• the current orientation of the reference object 1 is indicated by a marker 4. It appears in the initial orientation in the lower right corner of the reference object 1.
• the reference object 1 is chosen to be large enough to cover the entire measuring range of the coordinate measuring machine and, accordingly, almost the entire object table 3.
• a conventional mask holder which is not shown here for simplification, is used to hold the reference object 1 and is designed for the measurement of square masks. It is known, for example, to store the mask on three support points without any force. The deflection generated by the dead weight is calculated and extracted from the measured coordinates of the structures of the mask. Other mask holders suck the mask with vacuum feet. However, this creates deflections of the mask that cannot be precisely described.
• reference object 1 (as well as other reference objects later) is always placed flush against the lower edge of object table 3, which also serves as a system for the masks to be measured and for which there are movable support points for different mask sizes.
• a number j of reference structures 5 is selected on the reference object 1, the coordinates of which are to be measured in order to carry out the self-calibration.
• the reference object 1 is placed on the mask holder in the initial orientation.
• the reference structures 5 of the reference object 1 must then be measured in at least one other orientation of the reference object 1. This so-called calibration orientation must be different from the initial orientation and must have originated from the initial orientation by rotation about an axis of rotation 6. If, as in this example, a square reference object 1 is selected and this is always placed flush with the lower edge of the object table 3, an axis of rotation 6 perpendicular to the center of the reference object 1 is appropriate due to the mask holder provided.
• a complete correction function K (rA) can already be calculated.
• K (rA) it is advantageously possible to measure calibration coordinates of the reference structures 5 in at least one other of the previously used orientations of the reference object 1 different calibration orientation, as described below.
• FIG. 2a shows the second reference object 2 on the object table 3.
• the second reference object 2 is clearly selected to be smaller than the previously measured first reference object 1.
• Axis of rotation 7 passes for setting the different orientations. It can be seen that due to the different sizes of the two reference objects 1, 2, the two axes of rotation 6, 7 are at a clear distance from one another.
• the initial coordinates r 2j0 of the reference structures 5 are measured.
• the fit functions k, (r Jk ) must be specified first.
• Many complete sets of linearly independent functions are known from the mathematical literature, which can approximate a correction function K (rA as precisely as desired. The best known are, for example, polynomial and Fourier series. Certain linearly independent functions are also known which are particularly suitable for correcting certain errors From this, a set of fit functions /, (f y / is now specified which describes the correction function KirA with sufficient accuracy.
• the initial coordinates r 1v0 and the calibration coordinates r 1y1 and r y2 of the first reference object 1 as well as the initial coordinates r 2j0 and the calibration coordinates ⁇ r 2j ⁇ and r 2j2 of the second reference object 2 are now acted upon by the correction function KuA, which is approximated linearly by an approximation independent functions should be described.
• the fit parameters a t of the N predetermined linearly independent fit functions k, (r k ) are still unknown. They should now be determined.
• the calibration coordinates charged with the correction function K are rotated back into the initial orientation assigned to them by means of rotary functions D k , which describe their rotation in the initial orientation assigned to them, i.e. that the calibration coordinates r ⁇ and r 1j2 of the first reference object 1 into the Initial orientation of the first reference object 1 are rotated back, while on the other hand the calibration coordinates r 2y1 and r 2j2 of the second reference object 2 are rotated back into the initial orientation of the second reference object 2.
• the fit parameters a are now calculated such that the corrected initial coordinates associated with a specific reference structure 5 and the associated corrected and rotated calibration coordinates have the best possible match.
• a measurement with another reference object is not necessary.
• the measured initial coordinates r 1y0 and calibration coordinates 7M ⁇ 7, 2 are subjected to the mathematical correction function K (r J / t ) to be determined.
• the fit parameters a l are optimized again that the corrected and rotated calibration coordinates and the corrected initial coordinates have the greatest possible match.
• the method described in claim 3 and in the previous description part B described method steps a correction function K ⁇ ( lk ) determined and approximated by a modified set of fit functions kf M) (r jk ). From this modified set of the fit functions k [ M) (r jk ), all linear combinations S (r) that are rotationally symmetrical with respect to the rotations about the first axis of rotation 6 have been removed. For each deleted rotationally symmetrical linear combination S ( ⁇ ), the dimension of the functional space spanned by the fit functions is reduced by 1.
• the rotationally symmetrical linear combinations S (r) are removed from the original basis of the fit functions k ⁇ f jk ), because one cannot determine the fit parameters a t with the rotationally symmetrical linear combinations S (r). If the original fit function basis is selected in a targeted manner, however, the rotationally symmetrical linear combinations S (r) contain components which should be used to describe certain errors and which are therefore desired in the correction function. Now that the fit parameters a t of the first correction function K x [r lk ) have been determined in relation to the rotations of the first reference object 1, efforts have been made to get the deleted components of the original function base, i.e. the rotationally symmetrical linear combinations S (,) back into the correction function .
• the initial coordinates r 2j0 and calibration coordinates r 2j1 , r 2j2 measured in this way are all corrected with the already determined first correction function KJrA.
• a second correction function K 2 (rA is determined with the method steps of claim 3. It should also be based on the fit function basis k originally specified for the first correction function KirA. (r jk) are approximated. For this purpose, all of the on the second reference object 2 around the second rotational axis 7 carried out rotations D 2k rotationally symmetrical linear combinations S () is determined. is then For each such found rotationally symmetrical linear combination S (r) this original predetermined Fitfunktionenbasis k, (r k ) converted into a new one from linear functions of these fit functions k, (r Jk ) and the linear combination S (r deleted from it. Here too, the dimension of the functional space spanned by the fit function base is reduced by each deleted linear combination S (r) 1.
• a second correction function K 2 (rA is determined in a known manner. This now contains no rotationally symmetrical linear combinations S () with respect to all rotations D 2k about the second axis of rotation 7, which were used for the second reference object 2. However, it contains rotationally symmetrical linear combinations with respect to the first axis of rotation 6, which were used for the rotations D ⁇ k of the first reference object 1. Likewise, the correction function K rA determined first does not contain any rotationally symmetrical linear combinations with respect to the first axis of rotation 6 that was used when the first reference object 1 was rotated. However, it contains rotationally symmetrical linear combinations S (r) with respect to the rotations about the second axis of rotation 7, which were used in the measurements with the second reference object 2.
• This total correction function K Ges (rA therefore contains all rotationally symmetrical linear combinations S (r) removed to determine the fit functions, and the full function space is again spanned by the fit functions.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Length Measuring Devices With Unspecified Measuring Means (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Image Processing (AREA)

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• 1997
  • 1997-08-11 DE DE19734695A patent/DE19734695C1/de not_active Expired - Fee Related
• 1998
  • 1998-06-25 EP EP98936250A patent/EP0931241B1/de not_active Expired - Lifetime
  • 1998-06-25 JP JP11511495A patent/JP2001502433A/ja not_active Ceased
  • 1998-06-25 DE DE59809276T patent/DE59809276D1/de not_active Expired - Fee Related
  • 1998-06-25 KR KR1019997002954A patent/KR20000068713A/ko not_active Ceased
  • 1998-06-25 US US09/269,768 patent/US6317991B1/en not_active Expired - Lifetime
  • 1998-06-25 WO PCT/DE1998/001744 patent/WO1999008070A1/de not_active Ceased
  • 1998-07-17 TW TW087111708A patent/TW393564B/zh not_active IP Right Cessation

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