Method and system for machine vision-based feature detection and mark verification in a workpiece or wafer marking system

• US 20040152233A1
• Filed: 05/15/2003
• Published: 08/05/2004
• Est. Priority Date: 05/17/2002
• Status: Active Grant

• Current Assignee: Electro Scientific Industries Incorporated (MKS Instruments Incorporated)
• Original Assignee: GSI Group Corporation (Novanta Inc.)
• Inventors: Nemets, Chris, Woelki, Michael, Pukmel, Michael
• Granted Patent: US 7,119,351 B2
• Time in Patent Office: Days
• US Class Current: 438/106
• CPC Class Codes: B23K 2101/007 Marks, e.g. trade marks
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/04 Automatically aligning, aiming or focusing the laser beam, e.g. using the back-scattered light
• CPC Class Codes: B23K 26/042 Automatically aligning the laser beam
• CPC Class Codes: B23K 26/043 along the beam path, i.e. alignment of laser beam axis relative to laser beam apparatus
• CPC Class Codes: B23K 26/0853 Devices involving movement of the workpiece in at least in two axial directions, e.g. in a plane
• CPC Class Codes: B23K 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/705 Beam measuring device
• CPC Class Codes: G06K 1/126 by photographic or thermographic registration recording apparatus for measuring instruments G01D15/00
• CPC Class Codes: H01C 17/242 by laser trimming by laser in general B23K26/351
• CPC Class Codes: H01L 21/67282 Marking devices
• CPC Class Codes: H01L 21/681 using optical controlling means
• CPC Class Codes: H01L 2223/5442 comprising non digital, non alphanumeric information, e.g. symbols
• CPC Class Codes: H01L 2223/54453 for use prior to dicing
• CPC Class Codes: H01L 2223/54473 for use after dicing
• CPC Class Codes: H01L 2223/5448 Located on chip prior to dicing and remaining on chip after dicing
• CPC Class Codes: H01L 23/544 Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps test patterns for characterising or monitoring manufacturing processes H01L22/00
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 : Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A precision laser based method of marking semiconductor wafers, packages, substrates or similar workpieces is provided. The workpieces have articles which may include die, chip scale packages, circuit patterns and the like. The marking occurs in a workpiece marking system and within a designated region relative to an article position. The method includes determining at least one location from which reference data is to be obtained using (a) information from which a location of an article is defined, and (b) a vision model of at least a portion of at least one article. Reference data is obtained to locate a feature on a first side of (a second) workpiece using at least one signal from a first sensor. The method further includes positioning a marking field relative to the workpiece so as to position a laser beam at a marking location on a second side of the workpiece. The positioning is based on the feature location. A predetermined pattern is marked on the second side of the workpiece using a laser marking output beam. The workpiece is a semiconductor wafer, and the step of determining includes: measuring at least one feature in an image obtained from a first wafer portion; relating the measured feature to a wafer map; and storing the data for use when marking of wafers substantially identical to the first wafer.

Claims

1. In a precision laser based method of marking a semiconductor wafer having articles which may include die, chip scale packages, circuit patterns and the like, the marking to occur in a wafer marking system and within a designated region relative to an article position, the method comprising:

determining at least one location from which reference data is to be obtained using (a) information from which a location of an article is defined and (b) a vision model of at least a portion of at least one article;

obtaining reference data to locate a feature on a first side of the wafer using at least one signal from a first sensor;

positioning a marking field relative to the wafer so as to position a laser beam at a marking location on a second side of the wafer, the positioning being based on the feature location; and

marking a predetermined pattern on the second side of the wafer using a laser marking output beam, wherein the step of determining comprises;

measuring at least one feature in an image obtained from a first wafer portion;

relating the measured feature to a wafer map; and

storing the data for use when marking wafers substantially identical to the first wafer, and wherein the steps of measuring, relating, and storing are performed automatically.

2. The method of claim 1 wherein the step of measuring includes measuring the average pitch of a plurality of articles and relating the average pitch to a wafer map.

3. The method of claim 1 wherein the articles comprise a row-column pattern of die, and wherein the step of determining further includes:

locating a pair of orthogonal edges of the row-column pattern;

forming bounding boxes from the edges and;

defining a die pattern coordinate system from the bounding boxes.

4. The method of claim 3 wherein the relative positioning of the wafer is carried out in a primary coordinate system substantially aligned with the movement of at least one positioner, the method further comprising transforming coordinates to relate the primary coordinate system with the die pattern coordinate system.

5. The method of claim 1 wherein the step of determining further includes:

obtaining a coordinate using a wafer map to provide the information from which a location of the article is defined; and

imaging at least a portion of an article on a first wafer to generate the vision model.

6. A method for inspecting machine readable marks on one side of a wafer without requiring transmission of radiant energy from another side of the wafer and through the wafer, the wafer having articles which may include die, chip scale packages, circuit patterns and the like, the marking occurring in a wafer marking system and within a designated region relative to an article position, the articles having a pattern on a first side, the method comprising:

imaging a first side of the wafer;

imaging a second side of the wafer;

establishing correspondence between a portion of first side image and a portion of a second side image; and

superimposing image data from the first and second sides to determine at least the position of a mark relative to an article.

7. The system of claim 6 further comprising substantially matching images obtained from the first and second sides so that the superimposed image portions correspond, wherein the step of substantially matching is carried out using a calibration target and a matching algorithm.

8. The method of claim 7 further comprising providing an input using the user interface so as to cause a region of interest to be defined within at least a portion of an image of an article.

9. The method of claim 8 wherein the region of interest is operator adjustable.

10. The method of claim 7 wherein the superimposed data is used to determine the position of a mark relative to the article.

11. The method of claim 7 further comprising providing an inspection station having a wafer positioning subsystem separated from a positioning subsystem used for marking.

12. In a precision laser based system of marking semiconductor wafers, the wafer having articles which may include die, chip scale packages, circuit patterns and the like, the marking to occur in a wafer marking system and within a designated region relative to an article position, the system comprising:

means for determining at least one location from which reference data is to be obtained using (a) information from which a location of an article is defined and (b) a vision model of at least a portion of at least one article;

means for obtaining reference data to locate a feature on a first side of a wafer using at least one signal from a first sensor;

means for positioning a marking field relative to the wafer so as to position a laser beam at a marking location on a second side of the wafer, the positioning based on the feature location; and

means for marking a predetermined pattern on the second side of the wafer using a laser marking output beam, the means for determining measures at least one feature in an image obtained from a first wafer portion, relates the measured feature to a wafer map, and stores the data for use when marking wafers substantially identical to the first wafer, and wherein the measuring, relating, and storing are performed automatically by the means for determining.

13. A system for inspecting machine readable marks on one side of a wafer without requiring transmission of radiant energy from another side of the wafer and through the wafer, the wafer having articles which may include die, chip scale packages, circuit patterns and the like, the marking occurring in a wafer marking system and within a designated region relative to an article position, the articles having a pattern on a first side, the system comprising:

means for imaging the first side of the wafer to obtain an image;

means for imaging the mark on the second side of the wafer to obtain an image;

means for establishing correspondence between a portion of a first side image and a portion of a second side image; and

means for superimposing image data from the first and second sides to determine at least the position of a mark relative to an article.

14. The system of claim 13 wherein at least one of the means for imaging includes a zoom lens.

15. The system as claimed in claim 13 wherein the means for establishing correspondence includes a calibration target and an algorithm.

16. In a laser based system for laser marking of substrates such as semiconductor wafers or similar substrates with a laser marking beam, the substrates having a repetitive pattern of articles arranged in rows and columns, each of the articles having a feature detectable with an imaging subsystem, the system having a laser marking head, the imaging subsystem for imaging and measurement, a motion subsystem having a stage for positioning at least the substrate relative to the imaging subsystem, and a user interface connected at least to the imaging subsystem and motion subsystem, wherein laser marks are to be placed at predetermined locations relative to the articles, a method of laser marking with beam position control using predetermined pattern features, the method comprising:

providing, through the user interface, an input so as to cause a portion of the pattern to be identified for automatic feature detection and measurement with a machine vision algorithm;

positioning a first substrate relative to the imaging subsystem automatically to traverse the pattern along at least one of a row or column of the pattern so as to acquire image data at a first set of feature locations;

measuring a dimension using at least one detectable feature of a plurality of articles, the algorithm, and the image data;

storing dimensional data based on the measurement;

determining at least three feature locations of a second set of feature locations relative to the pattern using the dimensional data, the feature locations of the second set suitably defining a relationship between a pattern coordinate system and a stage coordinate system;

removing the first substrate;

positioning a second substrate to be marked relative to the imaging subsystem;

locating the at least three corresponding feature locations of the second set of feature locations in image data obtained from the corresponding pattern on the second substrate;

relating coordinates of the pattern on the first substrate to the corresponding pattern on the second substrate; and

positioning the substrate relative to the marking beam based on at least the three feature locations of the second set to mark the substrate.

17. The method of claim 16 wherein a first estimate of the dimension is obtained by semiautomatic relative positioning of the substrate and the imaging subsystem over a substantially small area of the pattern and further comprising:

identifying a feature in a displayed image; and

communicating the image location of the feature using the user interface.

18. The method of claim 17 wherein the substrate is a semiconductor wafer, the articles are die, and a feature is a corner of the die.

19. The method of claim 18 wherein the dimensional measurement is the average die pitch measured over a substantial number of die along at least one of a row and column.

20. The method of claim 19 wherein the average die pitch is related with a wafer map.

21. The method of claim 16 wherein the pattern coordinate system has an origin defined relative to a boundary of the pattern.

22. The method of claim 16 wherein the step of determining includes searching for pattern locations, and wherein searching is carried out controlling the stage based on pattern system coordinates.

23. The method of claim 16 wherein the step of providing further includes generating a vision model using an image of a portion of the pattern.

24. A system for carrying out the method of claim 16.