WO2009010983A2

WO2009010983A2 - Method and system for measuring a height of a protuberance on a surface of an electric circuit

Info

Publication number: WO2009010983A2
Application number: PCT/IL2008/001003
Authority: WO
Inventors: Meir Ben Levy; Zehava Ben Ezer
Original assignee: Camtek Ltd
Priority date: 2007-07-19
Filing date: 2008-07-20
Publication date: 2009-01-22
Also published as: WO2009010983A3

Abstract

A system for measuring a height of a protuberance on a surface of an electric circuit, the system includes optics and a processor that are adapted to generate height estimations by applying a triangulation process and select a selected protuberance in response to a selection rule.

Description

METHOD AND SYSTEM FOR MEASURING A HEIGHT OF A PROTUBERANCE ON A SURFACE OF AN ELECTRIC CIRCUIT

Related applications [001] This application claims priority from US provisional patent 60/950634 filed on July 19 2008, and incorporates its content by inference.

Field of the invention

[002] The invention relates to methods and systems for measuring a height of a protuberance, on a surface of an electric circuit.

Background of the invention

[003] During the manufacturing of electric circuits, and especially of printed circuit boards and of wafers, the use of solder bumps has become conventional. Conveniently, the solder bumps are small spheres of solder that are bonded to contact areas or pads of semiconductor devices and which are used for minimizing the length of the electrical connections between the electric circuit and the substrate, and to facilitate more efficient a use to the silicon area, increasing the maximum number of interconnects, and shortening signal interconnections, resulting from distributing the contact pads over the entire electric circuit surface rather than being confined to the periphery, as in wire bonding and in most tape automated bonding technologies. A typical height of a solder bump used in the manufacturing of wafers is 100μm, and that of a solder bump used in the manufacturing of printed circuit board is 300 μm, though considerable deviations from the stated numbers are not uncommon. Although most of the bumps in fabrication today are spherical shaped solder bumps, there are other types of bumps including coined bumps, gold bumps, pillar bumps and stud bumps.

[004] The physical attributes of the bumps, such as physical dimensions and conductivity are of significant impact on the facilitation of the bumps, and thus are of great importance. Multitudinous amount of bumps is produced and used in electric circuit factories every day, and it is essential to assure that all of those bumps will have controlled physical attributes, and specifically controlled physical dimensions. It is highly desirable to develop reliable and simple systems and methods for measuring a height of a protuberance on a surface of an electric circuit.

[005] Common optical technologies for measuring the height of protuberances include triangulation, confocal, interferometer and Moire techniques. These prior art optical technologies provide fast metrology tools for automatic machines that can be integrated in production lines.

[006] Although fast, the accuracy of these prior art techniques is limited by the optical characteristics of the objects to be measured, which are mainly the shape of the feature to be measured, the surface roughness and the existence of transparent layers. The ball shape of solder bumps can offset the result of measurement especially in triangulation configurations. The height of gold bumps characteristically varies between the center of a bump to the edges, thus creating an ambiguity of the true height.

[007] Transparent layers, such as dielectric layers, passivation layers and even photo-resists allow light to penetrate to lower layers; these lower layers, having different heights, which eventually lead to metrology error. Surface roughness, which typically characterizes gold bumps but is also frequently encountered in solder bumps and especially in lead free solder bumps, creates noise in measurements and result in low repeatability.

[008] It is therefore clear to any person skilled in the art, that the accuracy of the existing metrology techniques is limited and, furthermore, rather depends on the optical characteristics of the objects to be measured. Especially, it is clear to any person skilled in the art that prior art metrology techniques encounter difficulties in at least part of the shapes that are taken by protuberances on surfaces of electric circuits. [009] There is therefore a need for systems and methods for verification, and especially for measuring height of protuberances on surfaces of electric circuits. Such systems and methods could be used in conjunction with existing metrology tools, and conveniently are capable of verifying the metrology results and calibrate offsets.

[001O] It is further desired that said systems and method would clearly overcome issues of shape, roughness, transparent layers and other issues coming from the optical characteristics of the objects to be measured.

Summary of the invention

[0011] A method for measuring a height of a protuberance on a surface of an electric circuit, the method includes: generating height estimations by applying a triangulation process and selecting a selected protuberance in response to a selection rule; focusing a pattern onto a top portion of a selected protuberance while an optical parameter of an optics has a first value; focusing the pattern onto a first focusing locus defined by a bottom portion of the selected protuberance while the optical parameter of the optics has a second value; and determining a height of the selected protuberance in response to a relationship between the first value and the second value of the optical parameter.

[0012] A system for measuring a height of a protuberance on a surface of an electric circuit, the system includes optics and a processor that are adapted to generate height estimations by applying a triangulation process and select a selected protuberance in response to a selection rule; wherein the optics is further adapted to : (i) focus a pattern onto a top portion of the selected protuberance, while an optical parameter of the optics has a first value; and (ii) focus the pattern onto a first focusing locus defined by a bottom portion of the selected protuberance, while the optica! parameter has a second value; and wherein the processor is further adapted to determine a height of the selected protuberance in response to a relationship between the first and second values of the optical parameter. Brief description of the drawings

[0013] Figure 1 illustrates a protuberance on a surface of an electric circuit;

[0014] Figure 2 illustrates a system for measuring a height of the protuberance on the surface of the electric circuit, according to an embodiment of the invention;

[0015] Figure 3 illustrates a system for measuring a height of the protuberance on the surface of the electric circuit, according to an embodiment of the invention

[0016] Figure 4 presents four images acquired during a focusing of a striped pattern onto a protuberance of an electric circuit, according to an embodiment of the invention;

[0017] Figure 5 illustrates a method for measuring a height of a protuberance on a surface of an electric circuit, according to an embodiment of the invention; and [0018] Figure 6 illustrates a method for calibration of a metrology system, according to an embodiment of the system.

Detailed description of the drawings

[0019] A method and system are provided. They utilize a combination of a first and a second height measurement processes. The first height measurement process is more sensitive to a shape of a protuberance than the second process.

[0020] The first height measurement process is conveniently a triangulation process, and especially the triangulation process described in PCT patent application publication serial number WO 2005/104658A2 titled "A method and a system for height triangulation system" which is incorporated herein by reference.

[0021] Conveniently, the first height measurement process includes utilizing a system that includes : (i) illumination optics adapted to illuminate an object with a narrow strip of light; wherein the illumination optics have a large numerical aperture along a longitudinal axis of the strip and a small numerical aperture along a lateral axis of the strip; and (ii) collection optics adapted to image the narrow strip of light onto a detector; wherein the collection optics is characterized by a large numerical aperture along the longitudinal axis of the strip and a small numerical aperture along the lateral axis of the strip. [0022] It is noted that after the first height measurement process one or more protuberances can be selected. A height of each selected protuberances is then evaluated using a second measurement process. For simplicity of explanation protuberances that are subjected to the second measurement process are merely referred to as protuberances (the "selected" is omitted for simplicity of explanation).

[0023] Figure 1 illustrates protuberance 100 on surface 101 of electric circuit 102. Protuberance 100 includes top portion 103 and bottom portion 105. Surface 101 includes first focusing locus 104 which is defined by bottom portion 105. It is noted that on some situations (not shown), first focusing locus 104 is positioned on protuberance 100. First focusing locus 104 can be shaped as a plane but this is not necessarily so. Height 109 is a height of protuberance 100.

[0024] Figure 2 illustrates system 200 for measuring a height of a protuberance on a surface of electric circuit, according to an embodiment of the invention. System 200 includes: (a) opt'cs 220 that are adapted to carry out a second height measurement process, wherein optics 220 is adapted to: (i) focus pattern 110 onto top portion 103, while an optical parameter of optics 220, which according to an embodiment of the invention is the focus position of optics 220, has a first value; and (ii) focus pattern 110 onto first focusing locus 104 while the optical parameter has a second value; and (b) processor 210, that is adapted to: (i) receive or to participate in the generation of height estimations of one or more protuberances, wherein the height estimations are generated by a first height measurement process that is more sensitive to a shape of the protuberance than the second process; (ii) select protuberance 100 out of the one or more protuberances according to a selection rule; and (iii) determine height 109 in response to a relationship between the first and second values of the optical parameter. [0025] It is noted that according to an embodiment of the invention, system 200 is further adapted to generate the height estimations by carrying out the first height measurement process, whereas, according to another embodiment of the invention, system 200 receives the height estimations from an external source, which can be an external system for measuring a height of a protuberance on a surface of an electric circuit.

[0026] It is noted that conveniently, the systems for measuring a height of a protuberance on a surface of an electric circuit which are herein offered according to different embodiments of the invention, are also capable of measuring either heights or depths of other irregularities on the surface of the electric surface, and especially of holes in the surface.

[0027] According to an embodiment of the invention, processor 210 has image processing capabilities. It is noted that according to an embodiment of the invention, the determining which is conveniently carried by processor 210 could be carried out by a user of the system, in which case processor 210 is optional.

[0028] Conveniently, the optical parameter is responsive to a working distance of optics 220, but it is not necessarily so.

[0029] According to an embodiment of the invention, electric circuit 102 is positioned on mount 120. According to an embodiment of the invention, system 200 is adapted to move mount 120 within a two dimensional plain

(usually referred to as X-Y plane) or within three dimensional space, wherein the mount can also move along a vertical axis (usually referred to as Z axis) in order to facilitate the focusing. It is noted that the distance between electrical circuit 102 and optics 220 can also be altered by moving optics 220 along the

Z axis or by moving both optics 220 and mount 120 along the Z axis.

[0030] According to an embodiment of the invention, optics 220 is characterized by a high numerical aperture and high magnification factor. By way of example only, and not intending to limit the scope of the invention in any way, according to an embodiment of the invention the numerical aperture of optics 220 is 0.7, and the magnification of optics 220 is 100x. [0031] According to an embodiment of the invention, optics 220 is further adapted to focus pattern 110 on intermediate portion (not denoted) of protuberance 100, while the optical parameter has a third value.

[0032] According to an embodiment of the invention, optics 220 include patterned illumination unit 230, that includes illumination source 232, patterned filter 240 and additional optical components, some of which are described herein.

[0033] It is noted that different embodiment of the invention implement different illumination sources 232; as an example only and not intending to limit the scope of the invention in any way, according to an embodiment of the invention, illumination source 232 is a Tungsten-Halogen illumination source, and according to another embodiment of the invention, illumination source 232 is a light emitting diodes source, that includes one or more diodes.

[0034] Light that is generated by illumination source 232 is channeled by optic components such as fibers 236 and fiber guide 234 onto patterned filter 240, so as the light generated by illumination source 232 is filtered by patterned filter 240 into patterned light which is suitable to create pattern 110.

[0035] According to an embodiment of the invention, patterned filter 240 is included in patterned filtering unit (not shown) that includes multiple patterned filters. As an example only, and not intending to limit the scope of the invention in any way, different patterned filters 240 of the patterned filtering unit are adapted for generating striped patterns, gratings patterns, checkerboard patterns, and so forth.

[0036] According to an embodiment of the invention, illumination unit 230 is further adapted to enable the varying of one or more patterned filter 240, while changing grating type and pitch. It is noted that such varying of the patterned filters 240 could be obtained mechanically, by exchanging one patterned filter 240 with another, or electrically, such as by an LCD that is adapted to induce the source pattern for the patterned filter 240. [0037] System 200 can either choose patterned filter 240 autonomously, or in response to a received command, such as a command received from a user. According to an embodiment of the invention, system 200 is adapted to determine pattern 110 in response to a physical attribute of protuberance 100 and, according to another embodiment of the invention, also in response to a physical attribute of electric circuit 102 (and especially of surface 101). [0038] As examples only, and not intending to limit the scope of the invention in any way, one physical attribute of the protuberance is the physical dimensions of the protuberance (a typical height of a solder bump used in the manufacturing of wafers is 100μm, and that of a solder bump used in the manufacturing of printed circuit board is 300 μm, though considerable deviations from the stated numbers are not uncommon, and the system is capable of determining significantly smaller and larger height differences), and one physical attribute of the electric circuit is a surface pattern of the electric circuit, and especially the surface pattern of the immediate surrounding of the protuberance. It is clear for any person skilled in the art that many additional physical attributes of both the protuberance and the electric circuit are taken into consideration during the determining. Moreover, conveniently many such physical attributes are taken into consideration during the design of the system, and during the design of the possible patterns system 200 is designed to generate. [0039] According to an embodiment of the invention, filter 240 includes an unpatterned portion, adapted to provide unpatterned illumination. Such an embodiment is specified below, referring to unpatterned illumination unit 290.

[0040] The patterned light is then guided by optic components such as illumination tube 242 and beam splitter 244 to focusing unit 250. Focusing unit 250 includes lens 252 and conveniently includes focusing unit controller 264, which is adapted to focus the patterned light onto: (a) top portion 103, (b) first focusing locus 104, or, according to a previously discussed embodiment of the invention, onto (c) an intermediate portion of protuberance 100, wherein the focusing of the patterned light is carried out in response to focusing signals which are received from sensor 270. [0041] According to an embodiment of the invention, the focusing signals are provided by processor 210 that has image processing capabilities, in response to image signals received from sensor 270. Sensor 270 is adapted to provide the focusing signals or the image signals in response to light reflected from surface 101 , and especially from protuberance 100, which are guided to sensor 270 by optical components such as collection tube 262.

[0042] According to an embodiment of the invention, optics 220 is adapted to focus pattern 110 in response to a focusing input received from a user. Whereas in different embodiments of the invention the focusing is carried out autonomously by system 200 (explicitly, by optics 220, and according to an embodiment of the invention, by processor 210 which has image processing capabilities), other embodiments facilitates receiving a focusing input from a user. According to an embodiment of the invention, a focusing determination is ceded to the user, wherein system 200 only mechanically and optically facilitates the focusing. Conveniently, embodiments that are adapted to response to a focusing input provided by the user further include a display (not shown) that is adapted to display to the user a detected image of protuberance 100, in order to facilitate a focusing determining of the user.

[0043] The determination of height 109 by system 200 according to embodiments of the invention hitherto described is, as aforementioned, relatively less sensitive to the shape of the protuberance than a first height measurement process aforementioned. According to an embodiment of the invention, system 200 additionally includes height estimator 280 that is adapted to provide processor 210 with height estimations of one or more protuberances by applying the first height measurement process which is more sensitive to the shape of the protuberance. In this embodiment system

200 and especially processor 210 is generating the height estimations aforementioned. According to such embodiments of the invention, processor

210 is further adapted to select protuberance 100 out of the one or more protuberances according to a selection rule.

[0044] Conveniently, the selection rule is responsive to a physical attribute of protuberance 100 determined during the height measurement process. As examples only, and not intending to limit the scope of the invention in any way, protuberance 100 may be selected for being higher than a predefined height limit, lower than a predefined height limit, larger than predefined limits, smaller than predefined limits, or to be otherwise different from other protuberances. It is noted that many other selection rules may be applied during the selecting.

[0045] According to an embodiment of the invention, height estimator 280 is adapted to provide height estimations by applying a triangulation process. Height estimator 280 may includes: (a) laser beam source (not shown), adapted to illuminate (i) a top portion of a scanned protuberance, and (ii) a triangulation focusing locus defined by a bottom portion of the scanned protuberance with a laser beam; (b) triangulation detector (not shown), which is, conveniently, either a position-sensitive detector or a charge-coupled device, adapted to detect a reflection positions of reflected laser signals; (c) triangulation processor (not shown) adapted to (i) calculate a first triangulation distance between the top portion of the scanned protuberance and the triangulation detector; (ii) calculate a second triangulation distance between the triangulation focusing locus and the triangulation detector; and (iii) estimate the height of the scanned protuberance in response to the first triangulation distance and to the second triangulation process. It is noted that the triangulation process is prior art, and is well known and easily implemented by any person skilled in the art.

[0046] According to an embodiment of the invention, height estimator 280 does not include a standalone triangulation processor, wherein processor 210 is adapted to carry out the calculations and the estimations of the triangulation process, that were described above. Similarly, according to an embodiment of the invention, height estimator 280 does not include a stand alone laser beam source, wherein at least one of patterned illumination unit 230 and unpatterned illumination unit 290 is adapted to illuminate a top portion of a scanned protuberance and the triangulation focusing locus with a laser beam. According to another embodiment of the invention, height estimator 280 includes a standalone laser beam source, which share at least part of the optical components used by at least one of patterned iiSumination unit 230 and unpatterned illumination unit 290.

[0047] According to an embodiment of the invention, system 200 is adapted to receive height estimations of one or more protuberances from an external system, which is conveniently a scanning system; wherein the height estimations provided by the external system are generated by a first height measurement process, which is, as aforementioned, more sensitive to the shape of the protuberance than the second process. According to such embodiments of the invention, processor 210 is further adapted to select protuberance 100 out of the multiple protuberances according to a selection rule.

[0048] Conveniently, the selection rule is responsive to a physical attribute of protuberance 100 determined during the height estimating process. As examples only, and not intending to limit the scope of the invention in any way, protuberance 100 may be selected for being higher than a predefined height limit, lower than a predefined height irmit, larger than predefined limits, smaller than predefined limits, or to be otherwise different from other protuberances. It is noted that many other selection rules may be applied during the selecting. It is further noted that, according to an embodiment of the invention, system 200 is further adapted to receive the certain protuberance, wherein the selection is carried out by the external system or by another intermediate system.

[0049] According to an embodiment of the invention, system 200 further includes unpatterned illumination unit 290, which is adapted to illuminate top portion 103, first focusing locus 104 and, according to an embodiment of the invention, the intermediate portion of the protuberance. Conveniently, the unpatterned illumination provided by unpatterned illuminating unit 290 is needed in situations in which the light provided by pattern 110 is insufficient for an accurate focusing. [0050] According to an embodiment of the invention, unpatterned illumination unit 290 includes optical components (not shown) adapted to guide unpatterned light onto top portion 103, first focusing locus 104 and, according to an embodiment of the invention, the intermediate portion of the protuberance. According to another embodiment of the invention, unpatterned illumination unit 290 is connected to optics 220 by optical components such as unpatterned illumination tube 292, and optical combiner 294. According to an embodiment of the invention, a path of the unpatterned illumination at least partly coincides with a path of the patterned light.

[0051] According to an embodiment of the invention, at least a portion of the unpatterned light generated by illumination unit 230 is not filtered, and thus is being guided by the optical components of illumination unit 230 to illuminate at least a portion of protuberance 100 with unpatterned illumination.

[0052] According to an embodiment of the invention, system 200, and especially optics 220, are further adapted to focus pattern 110 onto surface of electrical circuit 102 that is at least partially transparent (not denoted). It is not uncommon for electric circuits, such as printed circuit boards and wafers, to include one or more layers which are either transparent or semi transparent. Such transparent or semi-transparent surfaces typically present significant focusing difficulties for prior art systems and methods for measuring a height of a protuberance on a surface. Focusing the pattern on such surfaces, following the teaching of the offered invention, remedies those focusing difficulties, owing to the fact that light which is reflected from such surfaces is nevertheless patterned responsively to the pattern, thus facilitating the focusing on surfaces of electrical circuit 102 that are at least partially transparent. [0053] According to an embodiment of the invention, optics 220 is imaging optics, adapted to acquire at least one focused image of at least a portion of electric circuit 102, and especially a focused image of top portion 103, of first focusing locus 104, of bottom portion 105, or, according to an embodiment of the invention, of the intermediate portion. Conveniently, optics 220 is further adapted to acquire at least one additional other image, which is not necessarily focused, of the at least portion of electric circuit 102. Conveniently, the focused image is being used by processor 210 which has image processing capabilities during the focusing determination of the first optical parameter. According to an embodiment of the invention, the focused image is presented to the user, to facilitate the focusing of the pattern onto the first focusing locus by the user. It is noted that the focused image may be used for many further additional purposes.

[0054] According to an embodiment of the invention, processor 210 is further adapted to process the focused image to provide additional metrological data pertaining to protuberance 100. According to an embodiment of the invention, processor 210 is further adapted to process multiple focused images. [0055] Figure 3 illustrates system 201 for measuring a height of a protuberance on a surface of electric circuk according to an embodiment of the invention. System 201 differs from system 200 in having autonomous unpatterned illumination unit 291 which is independent from illumination unit 230. [0056] Figure 4 presents four images acquired during a focusing of a striped pattern onto a protuberance of an electric circuit, according to an embodiment of the invention. The first image (denoted as "1 ") shows the striped pattern focused onto the top portion of the protuberance; the second image (denoted as "2") shows the striped pattern focused onto an intermediate portion of the protuberance, just below the top portion; the third image (denoted as "3") shows the striped pattern focused onto another intermediate portion of the protuberance; and the fourth image, (denoted as "4") shows the striped pattern focused on the surface of the electric circuit having the same height as the bottom portion of the protuberance. [0057] Figure 5 illustrates method 500 for measuring a height of a protuberance on a surface of an electric circuit, according to an embodiment of the invention.

[0058] Conveniently the electric circuit is either a printed circuit board or a wafer, also it is not necessarily so. Conveniently, the protuberance is a bump, which is conventionally used in the manufacturing of both printed circuit boards and wafers. [0059] It is noted that conveniently, the methods for measuring a height of a protuberance on a surface of an electric circuit which are herein offered according to different embodiments of the invention, are also capable of measuring either heights or depths of other irregularities on the surface of the electric surface, and especially of holes in the surface.

[0060] Method 500 starts with stage 501 of generating of receiving height estimations of one or more protuberances, wherein the height estimations are generated by a first height measurement process, which is more sensitive to a shape of the protuberance than the second process which includes stages 510-530.

[0061] Stage 501 includes either stage 502 or stage 504, and according to an embodiment of the invention, a combination thereof.

[0062] Stage 502 includes generating height estimations of one or more protuberances by applying a first height measurement process. Conveniently, the first height measurement process is faster and easier to implement than the second height measurement process, but it is not necessarily so. In such situations, the first height measurement process is adapted for a fast preliminary scan of at least a portion of the electric circuit.

[0063] Referring to the examples set forward in the previous drawings, stage 502 is carried out by height estimator 280.

[0064] According to an embodiment of the invention, stage 502 includes stage 503 of applying a triangulation process as the first height measurement process. Conveniently, the triangulation process includes: (a) illuminating the vicinity of a top portion of a scanned protuberance with a laser beam; (b) detecting a first reflection position of reflected laser signals by a triangulation detector which is either a position-sensitive detector or a charge-coupled device; (c) calculating a first triangulation distance between the top portion of the scanned protuberance and the triangulation detector; (d) illuminating the vicinity of a triangulation focusing locus defined by a bottom portion of the scanned protuberance with the laser beam; (e) detecting a second reflection position of reflected laser signals by the triangulation detector; (f) calculating a second triangulation distance between the triangulation focusing locus and the triangulation detector; and (g) estimating the height of the scanned protuberance in response to the first triangulation distance and to the second triangulation distance. It is noted that the triangulation process is prior art, and is well known and easily implemented by any person skilled in the art.

[0065] Alternatively, according to another embodiment of the invention, stage 501 includes stage 504 of receiving height estimations of one or more protuberances, wherein the height estimations of the one or more protuberances are provided to the system by an external system, which is conveniently a scanning system, and are generated by a first height measurement process. According to an embodiment of the invention, stage 504 further includes receiving the certain protuberance; wherein a selecting of the certain protuberance is carried out by an external system, which can be either the external system of stage 504, or an intermediate system. [0066] Stage 501 is followed by stage 505 of selecting the certain protuberance out of the one or more protuberances according to a selection rule. Conveniently, the selecting is responsive to a physical attribute of the protuberance determined during the first height measurement process. As examples only, and not intending to limit the scope of the invention in any way, the certain protuberance may be selected for being higher than a predefined height limit, lower than a predefined height limit, larger than predefined limits, smaller than predefined limits, or to be otherwise different from other protuberances. It is noted that many other selection rules may be applied during the selecting. [0067] Referring to the examples set forward in the previous drawings, the selecting is carried out by processor 210.

[0068] Stage 505 is followed by stage 510 of focusing a pattern onto a top portion of the protuberance while an optical parameter of optics has a first value. It is noted that according to different embodiments of the invention, one or more stages of method 500 precedes stage 510, wherein some of these embodiments are discussed below. [0069] Conveniently, the focusing of the pattern onto the top portion includes the following steps: (a) Projecting the pattern onto the vicinity of the top portion; (b) detecting light signals that are reflected from the electric circuit; (c) adjusting the optics, typically by mechanically moving one or more lenses of the optics, until a focusing criterion responsive to the light signals is fulfilled. Conveniently, the projecting includes illuminating a patterned filter, but it is not necessarily so.

[0070] Conveniently, the optical parameter is responsive to a working distance of the optics, but it is not necessarily so. The first value of the optical parameter is of later use during the determining of a height of the protuberance, as specified below.

[0071] Referring to the examples set forward in the previous drawings, the focusing of the pattern onto the top portion is carried out by optics 220, and especially by patterned illumination unit 230 that includes, according to an embodiment of the invention, illumination source 232, patterned filter 240, focusing unit 250 and sensor 270.

[0072] According to an embodiment of the invention, stage 510 includes stage 51 1 of determining the pattern in response to at least one physical attribute of the protuberance, and, according to another embodiment of the invention, also in response to at least one physical attribute of the electric circuit. As examples only, and not intending to limit the scope of the invention in any way, one physical attribute of the protuberance is the physical dimensions of the protuberance (a typical height of a bump used in the manufacturing of wafers is 100μm, and that of a bump used in the manufacturing of printed circuit board is 300 μm, though considerable deviations from the stated numbers are not uncommon, and the system is capable of determining significantly smaller and larger height differences); one physical attribute of the electric circuit is a surface pattern of the electric circuit, and especially the surface pattern of the immediate surrounding of the protuberance. It is clear for any person skilled in the art that many additional physical attributes of both the protuberance and the electric circuit are taken into consideration during the determining. Moreover, conveniently many such physical attributes are taken into consideration during the design of the system, and during the design of the possible patterns the system is designed to generate.

[0073] According to an embodiment of the invention, stage 511 includes determining at least one second pattern which is different from the pattern, in response to at least one physical attribute of the protuberance and, according to another embodiment of the invention, also in response to at least one physical attribute of the electric circuit. In some situations a second pattern may facilitate a more accurate focusing.

[0074] Referring to the examples set forward in the previous drawings, stage 511 is conveniently carried out by the patterned filtering unit.

[0075] According to an embodiment of the invention, stage 510 includes stage

512 of receiving a focusing input from a user. Whereas in different embodiments of the invention the focusing is carried out autonomously by the system (explicitly, by the optics, and, according to an embodiment of the invention, by the processor which has image processing capabilities), other embodiments facilitates receiving a focusing input from a user. According to an embodiment of the invention, a focusing determination is ceded to the user, wherein the system only mechanically and optically facilitates the focusing. Conveniently, stage 512 further includes displaying to the user a detected image of the protuberance, to facilitate the focusing determining carried out by the user.

[0076] According to an embodiment of the invention, stage 510 includes stage

513 of illuminating at least a portion of the electric circuit with an unpatterned illumination. Conveniently, stage 513 is implemented in situations in which the light provided by the pattern is insufficient for an accurate focusing. According to an embodiment of the invention, a path of the unpatterned illumination at least partly coincides with a path of patterned light that produces the pattern. According to another embodiment of the invention, the patterned illumination unit is also adapted to provide unpatterned illumination. [0077] Referring to the examples set forward in the previous drawings, the illuminating is carried out by unpatterned illumination unit 290, or, according to another embodiment of the invention, by patterned illumination unit 230 that is also adapted to provide unpatterned illumination.

[0078] According to an embodiment of the invention, stage 510 includes stage 514 of acquiring at least one focused image of at least a portion of the electric circuit, and especially a focused image of the top portion, of the first focusing locus, of the bottom portion, or, according to an embodiment of the invention, of an intermediate portion of the protuberance. Conveniently, stage 514 also includes acquiring one or more other images, which are not necessarily focused, of the at least portion of electric circuit 102. Conveniently, the focused image is being used during the focusing determination of the first optical parameter. It is noted that the focused image may be used for many further additional purposes.

[0079] According to an embodiment of the invention, stage 514 is followed by stage 515 of processing the focused image to provide additional metrological data pertaining to the protuberance. According to an embodiment of the invention, the processing includes processing of multiple focused images.

[0080] Referring to the examples set forward in the previous drawings, the processing of the focus image is carried out by processor 210 which has image processing capabilities. [0081] Stage 510 is followed by stage 520 of focusing the pattern onto a first focusing locus of similar height to the bottom portion of the protuberance while the optical parameter of the optics has a second value. The second value of the optical parameter is of later use during the determining of a height of the protuberance, as specified below. [0082] It is noted, that the focusing of the pattern onto the first focusing locus resembles to great details the focusing of the pattern onto the top portion. Explicitly, different embodiments of the invention facilitate the determining of the pattern in response to at least one physical attribute of the protuberance and, according to an embodiment of the invention, to at least one physical attribute of the electric circuit, the receiving of a focusing input from a user and the ceding of the focusing determination to the user, the illuminating of at .

least a portion of the electric circuit with an unpattemed illumination, the acquiring a focused image of at least a portion of the electric circuit, and the processing the focused image to provide additional metrological data pertaining to the protuberance. [0083] It is further noted that the illumination patterns used during the focusing of the pattern onto the first focusing locus may either conform or differ from the illumination patterns used during the focusing of the pattern onto the top portion. It is further noted that according to an embodiment of the invention, multiple focused images could be generated during both the focusing of the pattern onto the top portion and the focusing of the pattern onto the first focusing locus.

[0084] Referring to the examples set forward in the previous drawings, the focusing of the pattern onto the first focusing locus is carried out by optics 220, and especially by patterned illumination unit 230 that includes, according to an embodiment of the invention, illumination source 232, patterned filter 240, focusing unit 250 and sensor 270.

[0085] According to an embodiment of the invention, stage 520 includes stage 521 of processing multiple focused images to provide additional metrological data pertaining to the protuberance. According to an embodiment of the invention, stage 521 includes processing of multiple focused images that were acquired during both the focusing of the pattern onto the top portion and the focusing of the pattern onto the first focusing locus. According to another embodiment of the invention, stage 521 includes processing of multiple focused images that were acquired during both the focusing of the pattern onto the top portion, the focusing of the pattern onto the first focusing locus and the focusing of the pattern onto an intermediate portion of the protuberance, described below.

[0086] Referring to the examples set forward in the previous drawings, the processing is carried out by processor 210 which has image processing capabilities. [0087] According to an embodiment of the invention, stage 520 includes stage 522 of focusing the pattern onto a surface of the electrical circuit that is at least partially transparent. It is not uncommon for electric circuits, such as printed circuit boards and wafers, to include one or more layers which are either transparent or semi transparent. Such transparent or semi-transparent surfaces typically present significant focusing difficulties for prior art systems and methods for measuring a height of a protuberance on a surface. Focusing the pattern on such surfaces, following the teaching of the offered invention, remedies those focusing difficulties, owing to the fact that light which is either reflected from such surfaces is nevertheless patterned responsively to the pattern, thus facilitating the focusing on surfaces of the electrical circuit that are at least partially transparent.

[0088] Referring to the examples set forward in the previous drawings, stage 522 is carried out by optics 220, and especially by patterned illumination unit 230, that includes, according to an embodiment of the invention, illumination source 232, patterned filter 240, focusing unit 250 and sensor 270.

[0089] According to an embodiment of the invention, method 500 further includes stage 525 focusing the pattern onto an intermediate portion of the protuberance, while the optical parameter of the optics has a third value. Stage 525 may precede the focusing of the pattern onto the top portion, follow the focusing of the pattern onto the first focusing locus, come between the two, or alternate with one or both of the focusing of the pattern onto the top portion and the focusing of the pattern onto the first focusing locus.

[0090] It is noted, that the focusing of the pattern onto an intermediate portion of the protuberance resembles to great details the focusing of the pattern onto the top portion, and the focusing of the pattern onto the first focusing locus.

Explicitly, different embodiments of the invention facilitate the determining the pattern in response to at least one physical attribute of the protuberance and, according to an embodiment of the invention, to at least one physical attribute of the electric circuit, the receiving of a focusing input from a user and the ceding of the focusing determination to the user, the illuminating of at least a portion of the electric circuit with an unpatterned illumination, the acquiring a focused image of at least a portion of the e!ectric circuit, the processing of the focused image to provide additional metrological data pertaining to the protuberance, and the focusing the pattern onto a surface of the electrical circuit that is at least partially transparent. [0091] It is further noted that the patterns used during the focusing of the pattern onto an intermediate portion of the protuberance may either conform to or differ from the patterns used during both the focusing of the pattern onto the top portion and the focusing of the pattern onto the first focusing locus. It is further noted that according to an embodiment of the invention, multiple focused images could be generated during both the focusing of the pattern onto the top portion, the focusing of the pattern onto the first focusing locus, and the focusing of the pattern onto an intermediate portion of the protuberance.

[0092] Referring to the examples set forward in the previous drawings, the focusing of the pattern onto an intermediate portion of the protuberance is carried out by optics 220, and especially by patterned illumination unit 230 that includes, according to an embodiment of the invention, illumination source 232, patterned filter 240, focusing unit 250 and sensor 270.

[0093] Stage 520 is followed by stage 530 of determining a height of the protuberance in response to a relationship between the first value and the second value of the optical parameter. Conveniently, stage 530 is responsive to physical attributes of the system, and especially to physical attributes of the optics, and particularly to optical and dimensional attributes of the optics.

[0094] According to an embodiment of the invention, stage 530 further includes the determining of one or more additional physical attributes of the protuberance or of the electric circuit, beside the height of the protuberance.

[0095] Conveniently, stage 530 includes stage 531 of providing the height of the protuberance. Stage 531 may include, for example, the providing of the height to a user, or to an external system. It is noted that especially, according to an embodiment of the invention, the height of the protuberance is provided to a measuring system that have measured the height of the protuberance (such as, though not necessarily, the system that provided the estimations of stage 550), in order to calibrate said measuring system.

[0096] It is noted that according to an embodiment of the invention, method 500 includes the determining of the heights of multiple protuberances, by repeating the stages herein described.

[0097] Figure 6 illustrates method 600 for calibration of a metrology system, according to an embodiment of the invention. Method 600 starts with stage 610 of measuring heights of one or more protuberances on an electric circuit by a measuring system, which is adapted to measure the heights of the one or more protuberances by carrying out a first height measurement process which is more sensitive to a shape of the protuberance than the second process. According to some of the embodiments of the invention, the measuring of stage 610 is carried out by prior art techniques such as triangulation, confocal, interferometry and Moire techniques. Conveniently, the measuring of stage 610 is faster in relation to method 500.

[0098] Stage 610 is followed by stage 620 of selecting one or more protuberances out of one or more protuberances according to a selection rule.

[0099] Conveniently, the selecting is responsive to a physical attribute of the protuberances that were determined during the measuring of stage 610, or otherwise provided. As examples only, and not intending to limit the scope of the invention in any way, the certain protuberance may be selected for being higher than a predefined height limit, lower than a predefined height limit, larger than predefined limits, smaller than predefined limits, or to be otherwise different from other protuberances. It is noted that many other selection rules may be applied during the selecting.

[00100] Stage 620 is followed by stage 630 of measuring the heights of the selected protuberances by the second height measurement process. It is noted that the measuring of stage 630 includes the carrying out of at least some of the stages of method 500, and especis'ly ot stages 510, 520 and 530. [00101] Stage 630 is followed by stage 640 of calibrating the measuring system, according to differences between the heights measured is stage 610 and the heights measured in stage 630. It is noted that, according to an embodiment of the invention, stage 640 is only carried out if the difference is larger than a calibration difference threshold.

[00102] It is noted that the measuring of stage 630 could be carried out by the measuring system of stage 610 (conveniently by at least partly different components of said measuring system) or by another measuring system, such as though not limited to system 200. [00103] The present invention can be practiced by employing conventional tools, methodology and components. Accordingly, the details of such tools, component and methodology are not set forth herein in detail. In the previous descriptions, numerous specific details are set forth, in order to provide a thorough understanding of the present invention. However, it should be recognized that the present invention might be practiced without resorting to the details specifically set forth.

[00104] Only exemplary embodiments of the present invention and but a few examples of its versatility are shown and described in the present disclosure. It is to be understood that the present invention is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein.

Claims

WE CLAIM

1. A system for measuring a height of a protuberance on a surface of an electric circuit, the system comprises optics and a processor that are adapted to generate height estimations by applying a triangulation process and select a selected protuberance in response to a selection rule; wherein the optics is further adapted to : (i) focus a pattern onto a top portion of the selected protuberance, while an optical parameter of the optics has a first value; and (ii) focus the pattern onto a first focusing locus defined by a bottom portion of the selected protuberance, while the optical parameter has a second value; and wherein the processor is further adapted to determine a height of the selected protuberance in response to a relationship between the first and second values of the optical parameter.

2. The system according to any of the preceding claims, wherein the optics is further adapted to focus the pattern onto an intermediate portion of the selected protuberance, while the optical parameter has a third value.

3. The system according to any of the preceding claims, wherein the processor is adapted to determine, with a first accuracy level, the height of the selected protuberance in response to relationships between the first and second values of the optical parameter; and wherein the height estimations are characterized by a second accuracy level that is lower than the first accuracy level.

4. The system according to any of the preceding claims, wherein the selection rule is responsive to a physical attribute of the selected protuberance.

5. The system according to any of the preceding claims, wherein the optics is characterized by a high numerical aperture and high magnification factor.

6. The system according to any of the preceding claims, wherein the system is adapted to determine the pattern in response to a physical attribute of the selected protuberance and to a physical attribute of the electric circuit.

7. The system according to any of the preceding claims, wherein the optics is adapted to focus the pattern onto at least one of the top portion and the first focusing locus in response to a focusing input received from a user.

8. The system according to any of the preceding claims further comprising an un-patterned illumination unit.

9. The system according to any of the preceding claims, wherein the optics comprises a patterned illumination unit and wherein an optical path of an un-patterned illumination unit at least partly coincides with an optical path of the patterned illumination.

10. The system according to any of the preceding claims, wherein the optics is further adapted to focus the pattern onto a surface of the electrical circuit that is at least partially transparent.

11. The system according to any of the preceding claims, wherein the optics is an imaging optics.

12. The system of claim 11 , wherein the processor is further adapted to process a focused image of at least a portion of the selected protuberance; wherein the focused image is provided by the imaging optics to provide additional metrological data pertaining to the selected protuberance.

13. The system according to any of the preceding claims wherein the optics comprises illumination optics adapted to illuminate an object with a narrow strip of light; wherein the illumination optics have a large numerical aperture along a longitudinal axis of the strip and a small numerical aperture along a lateral axis of the strip; and collection optics adapted to image the narrow strip of light onto a detector; wherein the collection optics is characterized by a large numerical aperture along the longitudinal axis of the strip and a small numerical aperture along the lateral axis of the strip.

14. A method for measuring a height of a protuberance on a surface of an electric circuit, the method comprises: generating height estimations by applying a triangulation process and selecting a selected protuberance in response to a selection rule; focusing a pattern onto a top portion of a selected protuberance while an optical parameter of an optics has a first value; focusing the pattern onto a first focusing locus defined by a bottom portion of the selected protuberance while the optical parameter of the optics has a second value; and determining a height of the selected protuberance in response to a relationship between the first value and the second value of the optical parameter.

15. The method of claim 14, further comprises focusing the pattern onto an intermediate portion of the selected protuberance, while the optical parameter has a third value.

16. The method of claim 15, wherein the determination of the height of a certain selected protuberance is characterized by a first accuracy level; and wherein generating of height estimations of multiple selected protuberances is characterized by a second accuracy level that is lower than the first accuracy level.

17. The method of according to any claim of claims 14- 16, wherein the selecting is responsive to a physical attribute of the selected protuberance.

18. The method of according to any claim of claims 14- 17, wherein at least one of the focusing of the pattern onto the top portion and the focusing of the pattern onto the first focusing locus are carried out by optics characterized by a high numerical aperture and high magnification factor.

19. The method of according to any claim of claims 14- 18, further comprising determining the pattern in response to a physical attribute of the selected protuberance and to a physical attribute of the electric circuit.

20. The method of according to any claim of claims 14-19, wherein at least one of the focusing on the top portion and the focusing of the pattern onto the first focusing locus is responsive to a focusing input received from a user.

21. The method of according to any claim of claims 14-20, further comprises illuminating at least a portion of the electric circuit with an un- patterned illumination.

22. The method of claim 21 , wherein an optical path of an un-patterned illumination unit at least partly coincides with an optical path of the patterned illumination.

23. The method of according to any claim of claims 14-22, further comprises focusing the pattern onto a surface of the electric circuit that is at least partially transparent.

24. The method of according to any claim of claims 14-23, further comprises acquiring a focused image of at least one of the top portion of the selected protuberance and the first focusing locus.

25. The method of claim 24, further comprises processing the focused image of at the at least portion of the selected protuberance to provide additional metrological data pertaining to the selected protuberance.

26. The method according to according to any claim of claims 14-25 wherein the generating height estimations by applying a triangulation process comprises: illuminating an object with a narrow strip of light by illumination optics that have a large numerical aperture along a longitudinal axis of the strip and a small numerical aperture along a lateral axis of the strip; and imaging the narrow strip of light onto a detector by a collection optics that is characterized by a large numerical aperture along the longitudinal axis of the strip and a small numerical aperture along the lateral axis of the strip.