Patent Application
20140327906
Objects such as silicon wafers, printed circuit boards, reticules, flat panel display or other substrate shaped objects are inspected by high resolution inspection systems that include optics that have a limited depth of field.
The inspection process involves scanning the objects while the objects are supported by a chuck. The objects are not ideally flat and their deviation from flatness may exceed by magnitude the depth of field.
There is a need to provide a system with auto-focus capabilities.
According to an embodiment of the invention there is provided a system that may include a pivot chuck that may include : a lower chuck portion; an upper chuck portion; a first distance changing module that may include a pivot mechanism and an angle changing element; wherein the pivot mechanism pivotally couples the lower chuck portion to the upper chuck portion; wherein the angle changing element is coupled between the upper and lower chuck portions; wherein the upper chuck portion may be arranged to support a substrate; wherein the angle changing element may be arranged to induce a rotation of the upper chuck portion in relation to the pivot mechanism in response to first focus correction signals.
The system may include a second distance changing module that may be arranged to change a distance between the pivot chuck and optics in response to second focus correction signals.
A maximal distance correction introduced by the second distance changing module exceeds a maximal distance correction introduced by the first distance changing module.
The system may include optics and a sensor that may be arranged to (i) sense deviation of optics focus and (ii) generate the first and second focus correction signals.
The second distance changing module may be arranged to change a height of the optics.
The second distance changing module may be arranged to change a height of the optics and a height of the pivot chuck.
The joint mechanism defines a pivot point and wherein the second distance changing module may be arranged to change the distance between the pivot chuck and the optics until a point of the substrate that is immediately above the pivot point is located at a focal point of the optics.
The system may include a memory unit that may be arranged to store first focus correction signals that were generated during a certain scan of the substrate; and wherein the system may be arranged to feed the first focus correction signals to the first distance changing module during a another scan of the substrate.
The joint mechanism defines a pivot point that is positioned at a center of the upper chuck portion.
The joint mechanism defines a pivot point that is positioned outside a center of the upper chuck portion.
The joint mechanism defines a pivot point; wherein a ratio between (a) a first distance between the pivot point and a center of the upper chuck portion, and (b) a second distance between the pivot point and an edge of the upper chuck portion ranges between 0.1 and 10.
The system may include at least one additional angle changing element arranged to induce the rotation of the upper chuck portion in relation to the pivot mechanism in response to focus correction signals.
The angle changing element is a piezoelectric actuator.
An auto-focus method, the method may include : sensing, by a sensor, a deviation from focus of optics; and inducing, by an angle changing element, a rotation of an upper chuck portion in relation to a pivot mechanism that pivotally couples a lower chuck portion to the upper chuck portion; wherein the upper chuck portion may be arranged to support a substrate.
The method according to may include changing, by a second distance changing module, a distance between the pivot chuck and optics in response to second focus correction signals.
The method according to wherein a maximal distance correction introduced by the second distance changing module exceeds a maximal distance correction introduced by the first distance changing module.
The method may include sensing by a sensor deviation of optics focus and generating the first and second focus correction signals.
The method may include changing by the second distance changing module a height of the optics.
The method may include changing by the second distance changing module a height of the optics and a height of the pivot chuck.
The joint mechanism defines a pivot point and wherein the method may include changing by the second distance changing module the distance between the pivot chuck and the optics until a point of the substrate that is immediately above the pivot point is located at a focal point of the optics.
The method may include storing by a memory module first focus correction signals that were generated during a certain scan of the substrate; and feeding the first focus correction signals to the first distance changing module during another scan of the substrate.
The joint mechanism defines a pivot point that is positioned at a center of the upper chuck portion.
The joint mechanism defines a pivot point that is positioned outside a center of the upper chuck portion.
The joint mechanism defines a pivot point; wherein a ratio between (a) a first distance between the pivot point and a center of the upper chuck portion, and (b) a second distance between the pivot point and an edge of the upper chuck portion ranges between 0.1 and 10.
The method according to wherein the inducing of the rotation of the upper chuck portion is performed by the angle changing element and by at least one other angle changing element.
The angle changing element is a piezoelectric actuator.
The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:
Because the apparatus implementing the present invention is, for the most part, composed of electronic components and circuits known to those skilled in the art, circuit details will not be explained in any greater extent than that considered necessary as illustrated above, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention. The drawings may be in scale or out of scale. For example,
In the following specification, the invention will be described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended claims.
There is provided a system that may include a pivot chuck, a method and a pivot chuck.
The following description assumes that the optics are positioned above the substrate and that the distance between the optics and the substrate (or a distance between the optics and a point of interest of the substrate to be viewed by the optics) equals the height differences between the optics and the substrate. Accordingly—focus correction involves changing the relative height of the optics, the substrate (or the substrate point of interest) or both. Assuming that the substrate is located in an imaginary XY plane, the height changes may occur along the Z axis.
A pivot chuck is a chuck that includes a pivot mechanism that allows an upper portion of the chuck to pivot in relation to the pivot mechanism and thereby maintain optics in focus. A chuck includes any mechanical element, module, device capable of supporting a substrate.
The pivoting can be perform fine distance corrections. Coarser distance corrections an be provided by another mechanism such as a Z-stage. Additionally or alternatively, the Z-stage may provide finer distance changes or distance changes that are substantially equal to those provided by the pivot chuck.
It is noted that using fine and coarse distance correction mechanisms provides both fine height corrections and also a large range of height corrections.
The pivot chuck 10 includes pivot mechanism 13 that allows an upper chuck portion 12 to pivot in relation to the pivot mechanism 13 and thereby maintain optics (not shown) in focus.
The pivot mechanism 13 may be a pivot joint or any other mechanism that allows a rotation of one end of the pivot mechanism in relation to another end of the pivot mechanism.
A first distance changing module 19 is formed by the pivot mechanism 13 and the angle changing element 14.
The angle changing element 14 may change its height and thereby allow the rotation between the upper and lower chuck portions 12 and 11. It may be a piezoelectric actuator or motor or any other element with controllable height.
The rotation of the upper chuck portion changes the distance between the optics and a substrate point of interest thereby placing the substrate point of interest at the focal point of optics (not shown) thereby maintaining focus.
The upper part has a ball-shaped lower end and an lower part that has a concave upper end that matches the ball-shaped upper end.
The pivot mechanism may be integrated with one of the portions of the pivot chuck.
In
Positioning the pivoting mechanism outside the center of the substrate may reduce the weight carried by it but may reduce the distance between it and he edge of the substrate and thus result in a greater angular compensation range provided by it.
These figures provide a top view of the chuck upper portion 12. The pivot mechanism 13 and the two angle changing elements 14 and 18 are below the chuck upper portion 12 and are shown by dashed lines.
System 101 of
Sensor 40 senses deviation from focus and generates focus correction signals that may be processed by controller 60 to provide first focus correction signals to be provided to pivot chuck 10 and second focus correction signals to be provided to Z stage 51. The processing by controller 60 may include changing the format (modulation, amplitude, phase) of the focus correction signals.
The focus correction signals may be stored at memory module 70. Accordingly—focus correction signals obtained during a first scan of the substrate can be used for further scans of the substrate. Different scans can use the same optical elements of optics or may be used by different optical elements of optics 30.
Optics 30 may include light source, lenses, beam splitter, collimators or any other radiation manipulating element.
The Z stage 51 may be coarser than a first distance change mechanism formed by pivot mechanism 13 and angle changing elements. The maximal distance correction introduced by the Z stage 51 may be even reach few millimeters, few centimeters (or more) while the first distance change mechanism may introduce smaller height changes—for example it may introduce a maximal distance correction of few hundred microns (for example 400 microns).
System 102 of
System 103 of
System 104 of
Using a Z-stage and pivot stage 10 below the substrate 20 (as illustrated, for example, in
Optics 30 of
Optics 30 of
Method 200 illustrates distance corrections that are performed in response to real time distance measurements - distance corrections are made in timing proximity to the obtaining of focus parameters that trigger the distance corrections.
Method 200 may start by stage 210 of performing an initial alignment.
The height of a point (denoted 15′ in
The initial alignment 210 may include placing the alignment point at the focal length of the optics. Stage 210 may include positioning (211) a sensor at a position that allows that sensor to perform a misfocus measurement related to the alignment point, sensing (212) by the sensor deviation of optics focus (distance between the alignment point and the focal length of the optics), generating (213) second focus correction signals, and moving (214) at least one out of the substrate and the optics by a second distance changing module to correct the misfocus.
Stage 210 may be followed by stage 220 of scanning the substrate while attempting to maintain focus. The scanning includes imaging one new point (or one area) of the substrate after the other.
Stage 220 may include sensing (222) by the sensor deviation of optics focus in relation to a new point of the substrate, generating (223) first focus correction signals, and moving (224) the substrate by a first distance changing module to correct the misfocus.
The moving (224) of the substrate by the first distance changing module includes inducing (225), by one or more angle changing element of a pivot chuck that has an upper chuck portion that supports the substrate, a rotation of the upper chuck portion in relation to a pivot mechanism that pivotally couples a lower chuck portion to the upper chuck portion.
Method 300 illustrates distance corrections that are performed in response to non real time distance measurements. These non real time measurements may be obtained a long time (at least few minutes) before making the distance corrections. For example, a height map of the substrate can be generated after one or more scans of the substrate. This height map or a corresponding map of distance correction signals may be stored and used in further scans of the substrate.
Method 300 may start by stage 301 of receiving or generating height information reflecting the heights of points of the upper surface of a substrate to be inspected. The height information may be a height map and/or may include the focus correction signals to be generated when reaching the different points of the substrate.
Stage 301 may include generating the height map during an execution of method 200. It is noted that the height map may be generated by scanning the substrate while measuring misfocus but without misfocus correction. Stage 301 may be followed by stage 210 of initial alignment.
Stage 210 may be followed by stage 320 of scanning the substrate while attempting to maintain focus. The scanning includes imaging one new point (or one area) of the substrate after the other.
Stage 320 may include generating (323) first focus correction signals in response to the height information, and moving (324) the substrate by a first distance changing module to correct the misfocus.
The moving (324) of the substrate by the first distance changing module includes inducing (325), by one or more angle changing element of a pivot chuck that has an upper chuck portion that supports the substrate, a rotation of the upper chuck portion in relation to a pivot mechanism that pivotally couples a lower chuck portion to the upper chuck portion.
Methods 200 and 300 or any combination of stages of these method may be executed by any of the systems of
Furthermore, those skilled in the art will recognize that boundaries between the functionality of the above described operations are merely illustrative. The functionality of multiple operations may be combined into a single operation, and/or the functionality of a single operation may be distributed in additional operations. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments.
Thus, it is to be understood that the architectures depicted herein are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In an abstract, but still definite sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality.
However, other modifications, variations, and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.
The word “comprising” does not exclude the presence of other elements or steps then those listed in a claim. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.
Furthermore, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe.
Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.
This application claims priority from U.S. provisional patent Ser. No. 61/819694 filing date May 6 2013 which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61819694 | May 2013 | US |
