Image inspection system for defect detection

• US 4,587,617 A
• Filed: 10/18/1983
• Issued: 05/06/1986
• Est. Priority Date: 11/02/1982
• Status: Expired due to Fees

• Current Assignee: Cambridge Instruments Limited Rustat Road Cambridge CB1 3QH England
• Original Assignee: Cambridge Engineering Incorporated
• Inventors: Barker, John C., Cruttwell, Ian A.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/543,038
• Time in Patent Office: 931 Days
• Field of Search: 364/507, 364/514, 382/8, 382/34, 382/44, 382/54, 382/55, 358/106, 358/107, 356/237
• US Class Current: 382/149
• CPC Class Codes: G01N 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10

Abstract

A defect detection system for classifying defects in reticles (such as used in the manufacture of integrated circuit wafers) is described. An inspection unit, scanning the reticle in real time, compares it with the correct form and inputs signals representing each defect and its position in a store. The stored defects are then used to direct the inspection unit to inspect each defect more slowly. The inspection unit classifies each defect as either being an "excess metal" or a "missing metal" defect, and corresponding signals are stored in respective additional stores. The signals stored in these stores are then further processed and compared with the desired form of the reticle so as to classify the "excess metal" defects as either being a "pin spot" defect, an "extension" defect or a "bridge-type" defect. Similarly, the "missing metal" defects are classified as either being a "pinhole" defect an "intrusion" defect or a "break-type" defect. A size measuring unit measures the size of each defect.

Claims

1. An image inspection system, comprising

comparison means automatically responsive to the said image and to a desired form thereof whereby to detect abnormalities in the image and to produce data relating thereto,

storage means operative to store the said data,

first classifying means responsive to the stored data to classify each abnormality represented thereby as either being an abnormality of addition or an abnormality of omission, and

second classifying means responsive to the said first classifying means and operative to classify the abnormalities of addition and the abnormalities of omission as being particular types of such abnormalities.

2. A system according to claim 1, including size measuring means responsive to the said data to automatically measure the size of the abnormalities.

3. An image inspection system, comprising

comparison means responsive to the said image and to a desired form thereof and operative to carry out a rapid inspection of the whole image so as to detect the existence of any abnormalities therein and at least the approximate position of those abnormalities by comparing the actual image with the desired form thereof,

storage means responsive to the comparison means and connected to store signals corresponding to the detected abnormalities and at least their said approximate positions, and

inspection means responsive to the stored signals and operative less rapidly to inspect the said detected abnormalities and to classify those abnormalities as to type and to measure their sizes,

the said inspection means comprising means operative to classify each abnormality as either being an abnormality of addition or an abnormality of omission, and means operative to classify the abnormalities of addition and the abnormalities of omission as being particular types of such abnormalities.

4. A system according to claim 3, in which the comparison means operates in real time.

5. A system according to claim 3 in which each said abnormality is an abnormality which is at least as great in size as a predetermined but variable limit.

6. An image inspection system for inspecting an image in the form of a desired predetermined pattern of image paths with spaces between them, comprising

comparison means for automatically inspecting the image, the comparison means comprising means for comparing the said image with the desired form of the image and producing data identifying the position and size of each abnormality of addition and of each abnormality of omission,

storage means for storing the said data,

first classifying means responsive to the data identifying each abnormality of addition for automatically classifying each such abnormality as an abnormality of addition in a said space and unconnected with any said path, an abnormality of addition in a said space and connected to one said path, or an abnormality of addition in a said space and connected to two said paths, and

second classifying means responsive to the said data identifying each abnormality of omission for automatically classifying each abnormality of omission as an abnormality of omission within a said path but not completely breaking the path, an abnormality of omission in an edge, only, of a said path, or an abnormality of omission within and completely breaking a said path.

7. A system according to claim 6, including means for measuring the size of each abnormality.

8. A system according to claim 6, in which the image being inspected is the image of a reticle and each said path is a metal path thereon.

9. A method of inspecting an image, comprising the steps of

rapidly comparing the whole image with a desired form thereof so as to detect the existence of any abnormalities therein and at least the approximate position of those abnormalities and producing data relating to the existence of those abnormalities and their said approximate positions,

storing the said data,

processing the stored data so as to carry out a less rapid inspection of those parts of the image where abnormalities have been detected by the comparing step to classify those abnormalities as to type and to measure their sizes,

classifying each detected abnormality as either being an abnormality of addition or an abnormality of omission, and

classifying the abnormalities of addition and the abnormalities of omission as being particular types of such abnormalities.

10. A method according to claim 9, in which the comparing step operates in real time but the processing and classifying steps do not.

11. A method of inspecting an image in the form of a predetermined pattern of image paths with spaces between them, comprising the steps of

automatically comparing the image with a desired form of the image whereby to produce data identifying the position and size of each abnormality of addition and of each abnormality of omission,

storing the said data,

automatically processing the said data to classify each abnormality of addition as being either an abnormality of addition in a said space and unconnected with any said path, an abnormality of addition in a said space and connected to one said path, or an abnormality of addition in a said space and connected to two said paths, and

automatically processing the said data to classify each abnormality of omission as being either an abnormality of omission within a said path but not completely breaking the path, an abnormality of omission in an edge, only, of a said path, or an abnormality of omission within and completely breaking a said path.

12. A method according to claim 11, including the step of measuring the size of each abnormality.

13. A method according to claim 11, in which the image being inspected is the image of a reticle and each said path is a metal path thereon.