US4481664A
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Process for inspecting objects showing patterns with dimensional tolerances and reject criteria varying with the locations of said patterns and apparatus and circuits for carrying out said process
Assignee: International Business Machines Corp
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Filing: 1981-12-11
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Granted: 1984-11-06
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Expires: 2001-12-11
Abstract
Abstract First of all, this invention relates to a process based on the comparison of the image of a reference object I ref with the image of an object to be inspected I exa . Images I ref and I exa are picked-up, sampled, discretized and thresheld to produce electronic or binary images I REF and I EXA , respectively. These images are cleaned, then centered, I REF is adjusted to the minimum dimensional tolerances and becomes (I REF ) min . For each image point (pixel), the adjustment is performed by using a structuring element of variable size, the size of which is controlled by a bus from the data contained in a memory unit which take the location of the pixel on the reference object, into account. (I REF ) min is compared to I EXA which ensures the following function: [(I.sub.REF).sub.min OR I.sub.EXA ]EXCL. OR I.sub.EXA. The resulting image is the image of the "lack" type defects (which does not appear in I exa with respect to I ref ). Each defect is studied in a defect analysis unit which computes the dimensions of the defect and compares these dimensions with the maximum allowed size of the defect in this location. For this purpose, this circuit uses the reject criteria for this location, which are contained in a memory unit. The processing operations (adjustment and analysis) and the production of the corresponding data contained in the memory, are synchronized by count and delay circuits. The binary result (accepted/rejected) is available on a line. The defects of the "spreading" type are processed in the same way. The logic level of the line which is connected to a computer, determines the final decision (accepted/rejected). This invention also relates to an apparatus and circuits for carrying out the described process. This invention can be more particularly used in manufacturing semiconductors (masks, modules, chips, . . . ).
Inventors
- 👤 Claude J. A. Linger
- 👤 Gisele C. Locicero
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 13:01
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70483; G03F7/70605; G03F7/70616; B; B07; B07C; B07C5/00; B07C5/04; B07C5/10; G01; G01R; G01R31/00; G01R31/28; G01R31/302; G01R31/308; G06; G06T; G06T7/00; G06T7/0002; G06T7/0004; G06T7/001; G06T2207/00; G06T2207/30; G06T2207/30108; G06T2207/30141; G06T2207/30148
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
220 words
A process for inspecting objects showing patterns with dimensional tolerances and reject criteria varying in accordance with the location of said patterns, of the type including the comparision of image I ref of a reference object with image I exa of an object to be inspected, the latter being liable to show geometrical defects with respect to the reference object, characterized in that in includes the following steps; Step 1--elaborating binary electronic images I REF and I EXA from images I ref and I exa , Step 2--defining a structuring element B for each image point (pixel) the size of said structuring element being able to vary for each pixel in function of predetermined data and adjusting I REF to the maximum and minimum dimensional tolerances by expanding and eroding said image by structuring element B, which provides (I REF ) max and (I REF ) min , Step 3--forming images of the "spreading" and "lack" type defects by respectively carrying out the following logical operations: [(I.sub.REF).sub.max OR I.sub.EXA ] EXCL. OR (I.sub.REF).sub.max and [(I.sub.REF).sub.min OR I.sub.EXA ] EXCL. OR I.sub.EXA' and Step 4--measuring the size of the defects on the defect images and comparing said defects with respect to reject criteria which define, for each pixel, the dimensions of the defects which can be accepted according to predetermined data.
Claim 2
Dependent Claim
220 words
A process for inspecting objects showing patterns with dimensional tolerances and reject criteria varying in accordance with the location of said patterns, of the type including the comparision of image I ref of a reference object with image I exa of an object to be inspected, the latter being liable to show geometrical defects with respect to the reference object, characterized in that in includes the following steps; Step 1--elaborating binary electronic images I REF and I EXA from images I ref and I exa , Step 2--defining a structuring element B for each image point (pixel) the size of said structuring element being able to vary for each pixel in function of predetermined data and adjusting I REF to the maximum and minimum dimensional tolerances by expanding and eroding said image by structuring element B, which provides (I REF ) max and (I REF ) min , Step 3--forming images of the "spreading" and "lack" type defects by respectively carrying out the following logical operations: [(I.sub.REF).sub.max OR I.sub.EXA ] EXCL. OR (I.sub.REF).sub.max and [(I.sub.REF).sub.min OR I.sub.EXA ] EXCL. OR I.sub.EXA' and Step 4--measuring the size of the defects on the defect images and comparing said defects with respect to reject criteria which define, for each pixel, the dimensions of the defects which can be accepted according to predetermined data.
Claim 3
Dependent Claim
104 words
A process as set forth in claim 1 characterized in that the step 1 provided for elaborating images I REF and I EXA includes the following operations: picking-up images I ref and I exa of the reference object and of the object to be inspected in analog form, in black and white, with all the grey levels, sampling images according to a determined frame chosen in the group including the hexagonal frame, the square frame, . . . , quantizing the image to retain only a number 2 N of grey levels with 2≦N≦6, and thresholding the images to obtain said electronic binary images.
Claim 4
Dependent Claim
40 words
A process as set forth in claim 2 characterized in that the thresholding operation includes the determination of the threshold of images I ref and I exa , which is carried out from the frequency curve of the pixel intensities.
Claim 5
Dependent Claim
17 words
A process as set forth in claim 3 characterized in that the threshold determination is program controlled.
Claim 6
Dependent Claim
41 words
A process as set forth in claim 4 characterized in that it further includes a step for centering electronic images I REF and I EXA , said step corresponding to the optical centering of images I ref and I exa .
Claim 7
Dependent Claim
112 words
A process as set forth in claim 1 characterized in that the step 1 provided for elaborating binary electronic images I REF and I EXA includes the following operations: picking-up image I exa of the object to be inspected in analog form, in black and white, with all the grey levels, sampling this image according to a determined frame chosen in the group including: the hexagonal frame, the square frame, . . . , quantizing the image to retain only a number 2 N of grey levels with 2≦N≦6, thresholding the image to obtain I EXA and elaborating directly I REF either from a digital pattern generator or from a data bank.
Claim 8
Dependent Claim
70 words
A process as set forth in claim 1 characterized in that it further includes a step for cleaning images I REF and I EXA (noise suppression) carried out prior to the dimensional tolerance adjustment step and consisting either in an opening operation, or in a closing operation, or in a combination of both, the size of the erosion being lower than the size of the smallest defect to be detected.
Claim 9
Dependent Claim
28 words
A process as set forth in claim 1 characterized in that the structuring element of step 2 has the approximate shape of a circle with a variable diameter.
Claim 10
Dependent Claim
56 words
A process as set forth in claim 8 characterized in that the structuring element of step 2 is comprised of a plurality of concentric rings which are developed from the central pixel which is the pixel under analysis, these rings being separated one from the others by an interval equal to the interval separating two pixels.
Claim 11
Dependent Claim
41 words
A process as set forth in claim 1 characterized in that the size of each defect in step 4 is determined by computing the horizontal and vertical projections along at least, a pair of axes perpendicular along directions θ and θ+90°.
Claim 12
Dependent Claim
24 words
A process as set forth in claim 10 characterized in that direction θ corresponds to the direction of the pattern which contains the defect.
Claim 13
Dependent Claim
34 words
A process as set forth in claim 11 characterized in that reject criteria are deduced from the dimensions and direction of the pattern and appear as terms which can be compared with said projections.
Claim 14
Dependent Claim
30 words
A process as set forth in claim 12 characterized in that the reject criteria, the dimensional tolerance and direction θ are common to all the pixels of a same region.
Claim 15
Dependent Claim
48 words
A process as set forth in claim 13 characterized in that the reject criteria, the dimensional tolerance and direction θ are automatically generated for each region by a computer after scanning of I REF along the possible directions of the configuration patterns through the use of a program.
Claim 16
Dependent Claim
41 words
A process as set forth in claim 1 characterized in that said predetermined data of step 4 are provided in two data tables No. 1 and No. 2, respectively; for the defects of the "lack" type and of the "spreading" type.
Claim 17
Dependent Claim
35 words
A process as set forth in claim 15 characterized in that, for each pixel, the corresponding data include dimensional tolerances N, pattern direction θ and the reject criteria which define one or several analysis windows.
Claim 18
Independent Claim
191 words
An apparatus for inspecting objects showing patterns with dimensional tolerances and reject criteria varying with the location of said patterns, of the type comparing image I ref of a reference object with image I exa of an object to be inspected liable to show geometrical defects with respect to the reference object, characterized in that it includes: means for picking-up at least I exa , means for elaborating binary electronic images I REF and I EXA , processing means including means for adjusting I REF by expanding and eroding it to the maximum and minimum tolerances, by a structuring element B the size of which can vary for each pixel, in function of predetermined data, compare means for forming images of the defects of the "spreading" and "lack" types by respectively carrying out the following logic operations: [(I.sub.REF).sub.max OR I.sub.EXA ] EXCL. OR (I.sub.REF).sub.max and [(I.sub.REF).sub.min OR I.sub.EXA ] EXCL. OR I.sub.EXA, and means for analysing defects, including means for measuring the size of the defects and means for comparing said defects with reject criteria defining for each pixel, the defect dimensions which can be accepted, in accordance with predetermined data.
Claim 19
Independent Claim
191 words
An apparatus for inspecting objects showing patterns with dimensional tolerances and reject criteria varying with the location of said patterns, of the type comparing image I ref of a reference object with image I exa of an object to be inspected liable to show geometrical defects with respect to the reference object, characterized in that it includes: means for picking-up at least I exa , means for elaborating binary electronic images I REF and I EXA , processing means including means for adjusting I REF by expanding and eroding it to the maximum and minimum tolerances, by a structuring element B the size of which can vary for each pixel, in function of predetermined data, compare means for forming images of the defects of the "spreading" and "lack" types by respectively carrying out the following logic operations: [(I.sub.REF).sub.max OR I.sub.EXA ] EXCL. OR (I.sub.REF).sub.max and [(I.sub.REF).sub.min OR I.sub.EXA ] EXCL. OR I.sub.EXA, and means for analysing defects, including means for measuring the size of the defects and means for comparing said defects with reject criteria defining for each pixel, the defect dimensions which can be accepted, in accordance with predetermined data.
Claim 20
Dependent Claim
40 words
An apparatus as set forth in claim 17 further characterized in that it includes: synchronizing and addressing means which, for each pixel which is analysed, fetch said predetermined data out of a memory into which they have been previously charged.
Claim 21
Dependent Claim
34 words
An apparatus as set forth in claim 18 characterized in that the picking-up means are chosen from the group including the electron microscopes, the TV cameras, the photodiodes arrays and the coupled charge devices.
Claim 22
Dependent Claim
37 words
An apparatus as set forth in claim 18 characterized in that said means for elaborating electronic images I REF and I EXA include a unit for detecting a threshold and for thresholding at least I EXA .
Claim 23
Dependent Claim
19 words
An apparatus as set forth in claim 18 characterized in that I REF is stored in a buffer memory.
Claim 24
Dependent Claim
26 words
An apparatus as set forth in claim 18 characterized in that it further includes computing means for recentering electronic images I REF and I EXA .
Claim 25
Dependent Claim
126 words
A circuit for adjusting an electronic reference signal I REF to minimum dimensional tolerances by using a structural element of circular shape and variable size, formed of a plurality of concentric rings characterized in that it includes: means for storing all the pixels of I REF constituting said structuring element, into memory cells, a plurality of AND gates respectively forming each of said rings, the inputs of each AND gate being constituted by the contents of the cells corresponding to the constitutive pixels of the ring under consideration, decoding means for selecting the number and rank of the rings to be considered, and an AND gate for integrating said selected rings so that signal (I REF ) min is obtained at the output of said gate.
Claim 26
Dependent Claim
126 words
A circuit for adjusting an electronic reference signal I REF to minimum dimensional tolerances by using a structural element of circular shape and variable size, formed of a plurality of concentric rings characterized in that it includes: means for storing all the pixels of I REF constituting said structuring element, into memory cells, a plurality of AND gates respectively forming each of said rings, the inputs of each AND gate being constituted by the contents of the cells corresponding to the constitutive pixels of the ring under consideration, decoding means for selecting the number and rank of the rings to be considered, and an AND gate for integrating said selected rings so that signal (I REF ) min is obtained at the output of said gate.
Claim 27
Dependent Claim
78 words
A circuit as set forth in claim 23, characterized in that: said storing means include on the one hand, n shift registers, the cell number of which corresponds to the pixel number of each line of I REF , and n corresponds to the line number of the structuring element, and on the other hand, n shift registers comprised of cells with parallel outputs, the number of cells corresponding to the number of columns of the structuring element.
Claim 28
Dependent Claim
133 words
A circuit for adjusting an electronic reference signal I REF to maximum dimensional tolerances by using a structuring element of circular shape and variable size, comprised of a plurality of concentric rings, characterized in that it includes: means for storing all the pixels of (I REF ) constituting said structuring element into memory cells, a plurality of AND gates respectively constituting each of said rings, the inputs of each AND gate constituted by the contents of the cells corresponding to the constitutive pixels of the ring under consideration, decoding means for selecting the number and rank of the rings to be considered, and an AND gate (69) followed by an invert circuit (71) for integrating said selected rings so that signal (I REF ) max is obtained at the output of this gate.
Claim 29
Dependent Claim
133 words
A circuit for adjusting an electronic reference signal I REF to maximum dimensional tolerances by using a structuring element of circular shape and variable size, comprised of a plurality of concentric rings, characterized in that it includes: means for storing all the pixels of (I REF ) constituting said structuring element into memory cells, a plurality of AND gates respectively constituting each of said rings, the inputs of each AND gate constituted by the contents of the cells corresponding to the constitutive pixels of the ring under consideration, decoding means for selecting the number and rank of the rings to be considered, and an AND gate (69) followed by an invert circuit (71) for integrating said selected rings so that signal (I REF ) max is obtained at the output of this gate.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-11-06 | 1988-05-07 | 1988-11-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-11-06 | 1992-05-07 | 1992-11-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-11-06 | 1996-05-07 | 1996-11-06 | $7700.00 | Window Closed / Lapsed |