Integrated measurement system

Abstract

A measurement system is proposed, which is configured to be integrated with a processing device for optical measurement of a structure. The measurement system includes: a support assembly for holding the structure to be measured in a measurement plane, the support assembly being configured and operable to rotate in a plane parallel to the measurement plane and move along a first transverse axis in the measurement plane; an optical system, defining an illumination and collection light channel of a normal and oblique optical scheme; the optical system includes an optical head, the optical head including at least three lens units located in the illumination and collection light channels; a support assembly, including: a support unit for carrying the optical head; and a guide unit, which is configured and operable to guide the support unit to slide along a path extending along a second transverse axis perpendicular to the first transverse axis, the path extending along the second transverse axis perpendicular to the first transverse axis; and an optical window arrangement, including at least three optical windows formed in a panel, the panel being located between the optical head and the measurement plane, at a distance from the measurement plane, the windows being arranged in a spaced-apart parallel relationship and extending parallel to the path, the optical windows being aligned with the illumination and collection light channels, for propagating light irradiated from the optical head and light returned from the illuminated area to the optical head according to the normal and oblique optical schemes, respectively.

Description

Technical Field

[0001] The present invention belongs to the field of measurement technology and relates to an optical measurement system for an integrated measurement / monitoring system, which is particularly useful in the semiconductor industry. Background Art

[0002] The manufacture of semiconductor devices includes a multi-stage process that requires wafers to be measured between successive manufacturing steps as they are carried out on a production line. The current trend towards reduced size in the semiconductor industry, as well as the dynamic nature of semiconductor manufacturing processes, has increased the need for accurate diagnostic tools that can provide near real-time measurements for short-time response feedback loops such as closed-loop control and feed-forward control. Such stringent requirements cannot be achieved by off-line ("stand-alone") measurement systems that do not provide real-time response, and cannot be provided by field detection devices such as endpoint detection devices because their performance is not accurate enough.

[0003] Integrated measurement / monitoring technologies have been developed to provide physical implementation of monitoring tools with full metrology capabilities within the production line of a semiconductor manufacturing plant. An integrated measurement system is a system that is physically installed within or attached to a processing tool and is dedicated to a specific process.

[0004] An integrated measurement system should be considered from several aspects and meet specific requirements in order to be feasible. Such requirements include, among others, the following: small footprint, i.e., the integrated measurement system should have as small a footprint as possible so as to be physically located within a process tool such as a CMP tool (e.g., mounted inside the process tool or connected to the tool front end module (EFEM) via a load port), such as separating the measurement unit from the environment of the process tool (e.g., using a sealed housing); high-speed measurement unit (e.g., fast positioning, automatic focusing, and measurement); the option to be bypassed by the production process and operated in an offline mode; etc.

[0005] Various integrated measurement / metrology systems have been developed and are widely used and are commercially available from the assignee of the present application, e.g. 3090Next, wait. Summary of the invention

[0006] There is a need in the art for a new integrated measurement system for optical measurement of patterned structures, especially complex structures, which enables optical critical dimension (OCD) measurement using both perpendicular and tilted measurement schemes.

[0007] In many cases, it is advantageous to perform optical wafer metrology measurements with both normal and oblique schemes to increase the number of measurement channels. In fact, measurements with normal and oblique measurement schemes can provide more complete information about the measured structure.

[0008] Providing this additional information from different measurement schemes is important when considering metrology systems, especially for OCD measurements of complex patterned structures. This is because measurements with normal and oblique measurement schemes may have different sensitivities to different structural parameters and therefore increase the amount of information about the measured structure when used in combination. Furthermore, combining normal and oblique measurement schemes helps to add further measurement channels, for example using different orientations of the polarization plane of the light relative to the pattern in the normal incidence scheme, and / or using different azimuths of light incidence.

[0009] The present invention provides a novel optical integrated metrology system primarily for OCD measurement, whose design / configuration is optimized such that it is compact enough (with a small footprint) to be used with processing equipment on the one hand, and on the other hand, is configured with normal and oblique measurement schemes, effectively switching between these two operation schemes, thereby enabling measurement under different measurement conditions. As described above, these different measurement conditions may include, for example, azimuth changes in the oblique incidence scheme and / or polarization changes in the normal incidence scheme.

[0010] The integrated metrology system of the present invention can be advantageously used for measuring symmetrical structures, i.e. structures having a geometric profile with an axis of symmetry, such as a disk-like structure, which can be measured in half by achieving a 180 degree rotation of the structure-carrying stage relative to the measuring optics.

[0011] Therefore, according to a broad aspect of the present invention, there is provided a measurement system comprising:

[0012] a support assembly for holding a structure being measured in a measurement plane, the support assembly being configured and operable to rotate in a plane parallel to the measurement plane and to translate along a first lateral axis in the measurement plane;

[0013] An optical system defining illumination and collection light paths for normal and oblique optical schemes; the optical system comprising an optical head comprising at least three lens units located in the illumination and collection light paths;

[0014] A support assembly, comprising: a support unit for carrying an optical head; and a guide unit configured and operable to guide the support unit to slide along a path extending along a second transverse axis perpendicular to the first transverse axis; and

[0015] An optical window arrangement includes at least three optical windows, the at least three optical windows are formed in a panel, the panel is located between the optical head and the measurement plane, and is a certain distance away from the measurement plane. The windows are arranged in a spaced parallel relationship and extend parallel to the path. The optical windows are aligned with the illumination and collection light channels for propagating light illuminated from the optical head and light returned from the illuminated area to the optical head according to normal and oblique optical schemes, respectively.

[0016] The measurement system may further include a controller configured and operable to controllably shift the optical system operation between normal and oblique optical measurement schemes.

[0017] In some embodiments, the measurement system includes a navigation motion system configured and operable to drive rotational motion of the support assembly and motion of the support units of the support assembly and the bracket assembly along the first and second transverse axes, respectively.

[0018] In some embodiments, the optical system includes a common illumination assembly optically coupled to illumination channels of the normal and oblique optical measurement schemes, and separate detection devices housed in respective collection light channels of the normal and oblique optical measurement schemes.

[0019] In some embodiments, each light collection channel is configured to direct the collected specular return light to spatially separated imaging and measurement channels. For example, each light collection channel includes a pinhole mirror device for spatially dividing the collected light into imaging and measurement light portions and directing them to propagate through the imaging and measurement channels.

[0020] The imaging and measurement channels are optically coupled to the imaging and measurement detection devices. Alternatively, the measurement channels may include optical fibers. In one or both of these configurations, the measurement channels of the normal and oblique optical schemes may be optically coupled to the same spectral detector.

[0021] In some embodiments, the optical head of the optical system comprises at least three objective lens units respectively located in normal and oblique optical schemes. The objective lens units are preferably configured to have low chromatic aberration.

[0022] In some embodiments, the optical system includes a polarization component including at least one polarizer located in at least one of the illumination and collection light channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to better understand the subject matter disclosed herein and to illustrate how it may be implemented in practice, embodiments will now be described by way of non-limiting examples only, with reference to the accompanying drawings, in which:

[0024] FIG. 1 is a schematic diagram of an example of integration of a measurement / metrology system with a processing device;

[0025] Figure 2 Schematically shows the configuration of an integrated measurement / metering system according to the present invention;

[0026] FIG. 3A to FIG. 3C Specific, non-limiting examples of configurations of support assemblies for holding optical heads in the optical systems of the present invention are shown;

[0027] Figure 4A to Figure 4D The principles of a standard wedge design used in a Z stage to convert X-axis motion to Z-axis motion ( FIGS. 4A-4B ), as well as a specific, non-limiting example of a configuration of a Z stage utilizing a dual wedge engine suitable for use in the measurement system of the present invention ( FIG. 4C to FIG. 4D );

[0028] Figure 5 A light propagation scheme in an optical system of an integrated measurement / metrology system of the present invention is shown, the light propagation scheme being configured for operating the optical system in normal and oblique operation modes;

[0029] Fig. 6A Schematically illustrates a top view of an exemplary integrated measurement system of the present invention showing the range of travel of the optical window and wafer (support assembly) within the footprint of the system;

[0030] Figure 6B Typical geometries of complex patterned structures measured in a wafer are shown, illustrating that the system configuration of the present invention is able to measure with a greater number of available azimuth angles (per pattern) for tilted mode and with polarization azimuth for normal mode. DETAILED DESCRIPTION

[0031] As described above, the present invention provides a measurement system configured for integration with a processing device for optically measuring a structure before or after processing by the processing device. The processing device may include one or more processing tools, and the structure advances through successive stages of the processing device, and the measurement system may measure the structure before or after at least some of the processing stages. As described above, in some cases, the integrated measurement system may be located inside the processing device, and in some other cases, the integrated measurement system is connected to an equipment front end module (EFEM) via a loading port. In the following description, the integrated measurement / metrology system is described as being integrated with or integrated within the processing device to cover any such possible configurations.

[0032] In this regard, with reference to FIG1 , the integration of a measurement system 10 with a processing equipment PE (e.g., a material removal (CMP, etching) or deposition (CVD) equipment) is illustrated by way of a block diagram. In this example, the processing equipment PE includes a processing / manufacturing tool and its associated EFEM. The EFEM typically has a plurality of loading ports LP associated with a corresponding number of wafer cassette units, and a robot R (or a plurality of robots) for transporting the structure / wafer W from the loading ports of the cassette units to the processing tool. The integrated measurement system 10 is housed within the processing equipment, such as within a processing tool station, and / or on the EFEM side (similar to a cassette station with loading ports), and the same robot can be used to transport the wafer to a support or support stage of the measurement system 10 via the corresponding loading port LP. Typically, the support (or gripper / chuck) is part of a structure handling assembly.

[0033] The structure and operation of the processing equipment and the structure and operation of the structure transport and holding means (means) do not form part of the present invention and therefore do not need to be described in detail except to note the following. In order to control the processing of the structure in the processing equipment PE, the structure is measured after processing by the processing tool and / or before processing by the processing tool, and the processing of the structure is controlled by the processing tool, i.e., the operating parameters of the processing tool are controlled. The measurement data provided by the integrated measurement system can therefore be used in a closed-loop process control, providing feedback results for the specific processing tool if the measurement is performed after processing, and / or providing feedforward results for the specific processing tool if the measurement is applied to the structure before processing by the tool, for example, to define initial conditions at the beginning of the process. For example, the processing equipment PE can be an equipment for chemical mechanical polishing (CMP), and the integrated metrology system 10 can perform post-CMP measurements and can also perform pre-CMP measurements.

[0034] Reference now Figure 2 , Figure 2 The measurement system 100 of the present invention is schematically shown in a block diagram, and the measurement system 100 is configured and operable so that it can be integrated with a processing device (e.g., similar to the example of FIG. 1 ) for applying OCD measurement to a structure before and / or after processing by a processing tool of the processing device. The measurement system 100 includes a structural support assembly 102 for holding a measured structure W (i.e., a semiconductor wafer) and defining a measurement plane MP, an optical system 104, and a bracket assembly for holding a movable portion of the optical system 104.

[0035] The support assembly 102 may include a motion stage configured to move along one or more axes in the measurement plane and a rotatable chuck mounted on the motion stage. Thus, in general, the support assembly may be configured as an r,θ stage driven by an appropriate drive / motor 105 for rotation in a plane parallel to the measurement plane MP and translation in that plane along a first transverse axis X. Such motion may be used to navigate on a structure (wafer) in order to reach a measurement location.

[0036] The support assembly 102 is also configured to adjust the z-axis position of the measurement plane MP. As will be described in more detail further below, the z-axis positioning of the stage is preferably achieved using a dual wedge engine.

[0037] The optical system 104 is configured to define normal and oblique optical schemes. The optical system 104 includes an optical head 106 optically coupled to a light source system 108 and a light detection system 110, and includes light guiding components (e.g., folding mirrors, lenses, etc.) that define illumination and collection light channels. The optical system may also include a polarization component (not shown here) that enables measurements with different polarization conditions.

[0038] It should be noted that one or both of the light source system 108 and the light detection system 110, as a constructed (internal) part of the optical system 104 within the integrated measurement system 100, can be constituted by a light output port and a light input port, respectively, while the illumination / detection components or parts thereof can be housed outside the integrated measurement system 100 and can be optically coupled to the light input and output ports (e.g., through light-conducting elements such as fibers). Therefore, each of the blocks 108 and 110, respectively indicating the light source system 108 and the light detection system 110, should be interpreted broadly without necessarily including a light emitter and a light sensitive detector.

[0039] The support assembly 112 includes a support unit (slide) 112A and a guide unit 112B, wherein the support unit (slide) 112A is configured to hold the optical head 106, and the guide unit 112B includes a guide rail (not shown here) extending along a second transverse axis Y axis perpendicular to the X axis. The slide 112A is mounted on the guide unit 112B and is driven by the driving unit / mechanism 111 to slide along the guide rail.

[0040] Thus, the support assembly 112 is actually configured and operable as a Y stage for the optical head 106 (as a movable portion of the optical system 104) to move along the Y axis. The structure (wafer) moves on the x-theta stage 102. As will be described in more detail further below, the Y stage 112 operates to move the optical head 106, which includes a set of objective lenses and possibly polarizers and bending mirrors, to bring the light beam from the light source to the objective lens and wafer, and back again.

[0041] In some embodiments, the structure being measured can be a symmetrical structure having a certain lateral dimension, such as a disk-shaped structure having a certain diameter (e.g., a semiconductor wafer). The travel distance y of the optical head 106 along the Y-axis can be up to the size of the structure, such as the diameter of the wafer, for example 300 mm. The travel distance along the x-axis (i.e., during the navigation motion) can be approximately half the size of the structure, such as the radius of the wafer, for example 150 mm; and the stage rotation angle θ is in the range of 0 to 180 degrees. This will be referred to below Fig. 6A Further description.

[0042] The system 100 further comprises an optical window arrangement 114 which is suitably configured for light propagation from and to the optical head 106. This optical window arrangement 114 is formed in a plate / housing / frame (so called panel) 115 between the support assembly 112 (on which the optical head 106 is located) and the measurement plane MP (wafer plane). The panel 115 with the optical window arrangement 114 presents the input / output light plane of the optical head.

[0043] The optical window arrangement 114 is designed to seal the moving part (optical head 106) with the structure. The optical window arrangement 114 includes three optical windows OW1, OW2, OW3, which are elongated, extend along the Y axis, and are arranged in a spaced parallel relationship in the panel 115 to be located in the illumination and collection channels. A certain distance z is maintained between the optical window arrangement 114 (i.e., the input / output light plane of the optical head) and the measurement plane MP. The optical windows have a length corresponding to the y-axis travel distance, which corresponds to the size of the structure, such as a wafer with a diameter of 300 mm.

[0044] As will be described in more detail further below, the central optical window OW2 extends in a horizontal plane and is used for normal scheme operation of the optical system, while the two other optical windows OW1 and OW3 extend along inclined planes and are used for inclined scheme operation of the optical system.

[0045] As will be further described and exemplified in more detail below, the optical head 106 includes an objective lens assembly. The distance between the optical head 106 and the measurement plane MP is selected to provide as small a distance / gap as possible between the objective lens assembly and the measurement plane, so as to meet the requirement of as small a footprint as possible for the entire integrated measurement / metrology system, and to reduce aberration effects caused by the optical device. Therefore, the objective lens is a short-focus lens.

[0046] It should also be noted that considering the integrated measurement system 100 integrated with the processing equipment PE, for example, as shown in Figure 1, it may be necessary to maintain a certain environment near the measurement plane, that is, near the structure being measured. This can be some required environment such as N2 or vacuum or CO2. To this end, the present invention provides the use of a gas supply used in the processing equipment (corresponding processing tool), thereby eliminating the need for any additional gas source. More specifically, the gas (N2) from the EFEM can be used without the need to use an additional N2 source. To this end, the interface of the integrated measurement system 100 and the EFEM is sealed, and the wafer compartment in the integrated measurement system 100 is sealed so that N2 can flow from the EFEM to the vicinity of the wafer in the system 100.

[0047] As described above, the optical system 104 is configured to define normal and oblique optical measurement schemes for directing incident (illumination) light onto the structure along normal and oblique illumination channels, and collecting light returned from the illumination area on the structure and propagating along corresponding collection channels. The return light may include specular reflections of the illumination from the structure and / or zero-order scattered light. The optical system can also be used for dark field measurements, while the illumination light and the collected light propagate along different channels, for example, the same oblique illumination channel and different collection channels are used to perform both bright field mode and dark field mode. For example, the central optical window OW2 is located in the coincidence / overlapping region of the optical paths of the normal and oblique schemes, and defines the illumination and collection channels IC. nor and DC nor , and the optical windows OW1 and OW3 are located on opposite sides of the central window and define the illumination and collection channels IC of the oblique scheme respectively obl and DC obl .

[0048] For example, the optical system 104 may utilize illumination channels IC with normal and oblique optical schemes. nor and IC obl An optically coupled common light source system 108 and separate detection devices D1 and D2 may be accommodated in the respective collection channels of the normal and oblique optical schemes.

[0049] In some embodiments, the measurement system 100 is configured to perform both imaging and measurement of a structure. Thus, the optical system 104 is configured such that the collection channel DC nor and DC obl At least one of the collection channels DC defines spatially separated imaging and measurement channels / paths associated with two different detectors D1 and D2, such as a CCD (imaging detector) and a spectrophotometer (measuring detector). nor and DC oblAt least one of the optical systems 100 includes a light splitting device, such as a pinhole mirror device, for spatially separating the collected light into imaging and measurement light portions and directing them to propagate through imaging and measurement channels / paths. For example, the measurement channels of both the normal and oblique optical schemes can be optically coupled to the same measurement detector (e.g., a spectrometer). The configuration and operation of the measurement system 100 are further exemplified in more detail below.

[0050] like Figure 2 As further shown, the measurement system 100 is configured for data communication with a control system 120 via any suitable technology of wired and / or wireless signal transmission. The control system 120 includes data input and output utilities 120A, 120B, a memory utility 120C, and a measurement data analyzer 120D.

[0051] Various controllers for controlling the operation of the system are also provided in the control system 120, including a measurement mode controller 120E and a navigation motion controller 120F. The measurement mode controller 120E is configured to control the system shift / switching between normal and oblique measurement modes; and can also be configured to control changing conditions such as polarization and / or wavelength and / or azimuth. The navigation motion controller 120F is configured and operable to operate the drivers 105 and 111 to control the rotational movement of the structural support assembly 102 (e.g., chuck) and the X-axis movement of the structural support assembly 102 (e.g., stage), respectively, and the movement of the optical head 106 along the Y-axis.

[0052] As described above, rotational movement of the support assembly 102 (e.g., a chuck) may be performed to implement first and second consecutive measurement sessions corresponding to first and second relative angular positions of the stage 102, which bring the first and second halves H1 and H2 of the structure W into measurement positions, respectively. Each of the first and second measurement sessions may be implemented sequentially while controlling lateral movement of the support assembly 102 and the optical head 106 along the X-axis and the Y-axis, thereby navigating measurements of a plurality of measurement positions on respective halves of the first and second halves of the structure W. As described above, considering measurements on such a disk-like structure, the maximum travel distance x of the support assembly 102 along the X-axis corresponds to (is equal to or slightly greater than) the radius r of the structure, and the travel distance y of the optical head along the Y-axis reaches the diameter 2r of the structure.

[0053] Typically, an integrated measurement / metrology system typically performs measurements at multiple measurement locations on a wafer. It should be understood that the manner in which the relative displacement between the wafer and the optical head is achieved depends on the sampling plan for a specific structure (e.g., for a 300 mm wafer). The above-mentioned two-half measurement mode is a non-limiting example, which can be used when the selected measurement position is symmetrically positioned / oriented (assuming 180 degree symmetry). A situation may arise when measuring other orientations of the wafer / measurement position. In that case, navigation (rotation and / or X-axis motion and / or Y-axis motion) can be optimized due to multiple measurement locations and their orientations. It should also be noted that the above-mentioned translation scheme is not a minimized motion scheme (e.g., θ / R, R) that can cover the entire wafer, but may be optimal in some applications. The principles of the present invention are not limited to the two-half measurement mode.

[0054] refer to Figure 3A To Figure 3D, Figure 3A 3D shows the configuration of the support assembly 112 that carries the optical head portion 106 (moving portion) of the optical system 104.

[0055] like Figure 3A As shown, the optical head 106 has three light-guiding optical units (focusing optical devices) L1, L2, and L3, and the three light-guiding optical units L1, L2, and L3 define the oblique illumination channels IC, respectively. obl , illumination-and-collection channel IC for normal optical scheme nor -and-DC nor And the detection channel DC of the oblique optical solution obl The optical units L1, L2, L3 include objective lenses OL1, OL2, OL3 (and possibly other optical elements) that define corresponding optical paths aligned with optical windows OW1, OW2, and OW3 (e.g., holes) disposed in a panel 115 between the support assembly 112 and a measurement plane in which the structure to be measured is located. The panel 115 has a planar (horizontal) facet 115A in which the optical window OW2 is formed, and two inclined facets 115B and 115C in which the optical windows OW1 and OW3 are formed. The optical units L1, L2, L3 are arranged relative to the panel 115 so that the light output / input of the optical units L1, L2, L3 are aligned with the optical windows OW1, OW2, and OW3, respectively. It should be noted that the inclined orientation of the optical windows provides 90 degrees between the optical axis of the corresponding lens unit and the window surface.

[0056] like Figure 3A and Figure 3CAs shown, the support assembly 112 has a support unit 112A (optical head carriage), and the focusing / objective optical units L1, L2, L3 are mounted on the support unit 112A in an appropriate angle orientation corresponding to the optical scheme. The support unit 112A holding the optical head 106 is mounted on a guide unit 112B for sliding movement along a guide rail 112C that defines a sliding motion path along which the support unit 112A reciprocates.

[0057] As described above, the support assembly 112 (support unit 112A and guide unit 112B) presents a Y stage for the moving part (optical head) of the optical system 104. An optical window arrangement 114 (e.g., a three-window arrangement formed on a panel 115) is located between the support assembly 112 and the measurement plane MP. For a normal optical scheme, one window OW2 is horizontal, while the other two windows OW1 and OW3 are tilted relative to the horizontal plane and are used for an oblique optical scheme. The Y stage is configured to move the optical head 106 (a set of three optical units, including an objective lens, and possibly also a polarizer and a bending (light-guiding) mirror, as will be further described below) to bring the illumination beam from the light source to the objective lens and the structure, and to guide the light returning from the structure to the detection system.

[0058] In some embodiments, the Y stage drive 111 includes a linear magnetic motor. Preferably, the linear magnetic motor is configured so that the magnet 111A moves and the coil assembly 111B is stationary. This configuration provides a relatively constant drive current, as well as heat transfer from the coil to the system boundary for heat dissipation via the thermal interface 111C. Such a requirement can be associated with the need for the stage to be very close to the optical head environment that requires temperature stability.

[0059] As described above, the objective lens should be positioned as close to the measurement plane as possible, and therefore the optical units L1, L2, L3 include short focus lenses. This requirement is further supported by configuring the optical window arrangement 114 with a very thin optical window to reduce aperture variation (e.g., 2 mm), wherein the window thickness is substantially uniform along the window (±1 μm tolerance), and the window length is at least 2 orders of magnitude higher than the thickness, for example, a length of about 300 mm. In addition, as described above and further more specifically exemplified below, the optical system 106 may include a polarizer (e.g., in the optical units L1, L2, and L3). Therefore, the optical windows OW1, OW2, and OW3 are configured to maintain (i.e., not affect) the polarization of the light passing therethrough. For example, the medium of the optical windows may be birefringent.

[0060] For each given position of the support assembly 102 relative to the optical head 106, the sliding movement of the optical head 106 along the guide rail 112C (along the Y axis) enables measurement to be performed in an elongated region of the structure W located in the measurement plane MP along the Y axis. After the stage 102 has been moved stepwise along the X axis by a predetermined distance within the range (0 to r), for example, while the optical head has been moved along the Y axis by a distance of 2r, the measurement can be applied to a further region of the structure W. This stepwise movement of the stage (support assembly) 102 along the X axis and the optical head 106 (i.e., the support unit 112A) along the Y axis enables measurement to be performed at multiple locations on the wafer. For example, one half H1 of the structure W can first be inspected using the x- and y-movements of the stages 102 and 112, and then the stage 102 can be rotated 180 degrees to bring the other half H2 of the structure to the measurement position, and the process is repeated to perform measurements on this half of the structure.

[0061] Furthermore, the z-axis position of the optical head 106 relative to the measurement plane MP is controlled, for example for focusing purposes. The z-axis positioning of the support assembly 102 is preferably achieved using a dual wedge engine. In this regard, reference is made to FIGS. 4A to 4B and FIG. 4C to FIG. 4D 4A and 4B illustrate a standard wedge design used in a Z stage configuration to convert X-axis motion to Z-axis motion in the z-up position (x-closed position) and z-down position (x-open position), respectively. This configuration suffers from a relatively large asymmetric footprint in the x-dimension when in the open position. Figure 4C and Figure 4D Shown in the z-up, x-closed position ( Figure 4C ) and z down, x open position ( Figure 4D ) utilizes a specific example of a z stage 102 having a double wedge configuration formed by two relatively symmetrical wedges W1 and W2. This configuration reduces the x-dimensional footprint of the system.

[0062] Reference now Figure 5 , Figure 5 The configuration and operation of the optical system 104 and the light propagation scheme therein are illustrated. In this non-limiting example, a single (common) illumination assembly (light source system) 108 is used for both normal and oblique light propagation schemes. The light source system 108 may include an illumination fiber that guides light from a light emitter to an illumination channel.

[0063] In addition, in this example, the switching / shifting between the normal and oblique operating modes (i.e., the shifting between the light propagation in the normal and oblique schemes) is achieved by controlling the position of the shutter 136 (i.e., the so-called jumping mirror). In addition, in this example, the detection system 110 includes a detection channel DC connected to the normal and oblique collection channels. nor and DC oblTwo detection assemblies associated. Each of the two detection assemblies is configured to operate in parallel with the imaging and measurement modes and includes corresponding imaging detector units D1 and D2 (e.g., CCD), and either includes corresponding measurement detectors D1' and D2', or a common measurement detector (spectral detector) is used for both normal and oblique schemes. The system operates with broadband illumination, for example in the range of 210nm to 2500nm. In addition, in this non-limiting example, a polarizer assembly is used. In the figure, the polarizer / analyzer is shown as forming part of the optical units L1, L2 and L3 of the optical head 106. However, it should be understood that the present invention is neither limited to the use of any polarizer nor to accommodating the polarizer in a movable part of the optical system, i.e., the optical head 106 carried by the support assembly 112.

[0064] Thus, the illumination beam LB1 propagates from the light source system 108 and is guided by the light guiding elements (e.g., the illumination relay lens unit and the tubular lens unit) to propagate along the input optical path 134 towards the mode shift position 135. To this end, a redirecting element 136, such as a mirror, is provided to be controllably movable (e.g., by the measurement mode controller 120E) between an operable state in which it is located in the position 135 and a non-operational state in which it is located outside the optical path 134.

[0065] When the reflector 136 is in its operating position, the illumination beam LB1 interacts with and is reflected by the reflector 136 to follow the illumination channel IC of the oblique scheme. obl propagation, and thus the system operates in oblique mode. Illumination channel IC obl The optical head 106 is optically coupled to the corresponding optical component L1. Figure 5 As shown in the specific non-limiting example, the illumination channel IC obl One or more light-guiding (light path bending) elements, such as reflectors, may be included - three such light-guiding elements (reflectors) LD1, LD2, LD3 are shown in this example. As further shown in the figure, the optical component / unit L1 includes a lens unit (one or more lenses) and also includes a polarizer P1, which is therefore located in the oblique scheme illumination channel IC obl The resulting oblique polarized illumination beam LB1 (obl) The light beam LB1 is focused onto the illumination area on the structure through the corresponding optical window OW1. (obl) The light LB2 returned from the illuminated area (obl) The light is collected by the optical component L3 via the optical window OW3, where the polarization of the light is adjusted by the corresponding polarizer P3, and the collected return light is guided along the oblique scheme detection channel DC obl Similarly, the detection channel DC oblOne or more light-guiding elements (e.g., reflectors) may be included - five such elements LD4 to LD8 are shown in this schematic. Element LD8 may be configured as a wedge-shaped prism having two reflective surfaces that redirect the light incident thereon depending on the light's incident position. Thus, element LD8 directs the obliquely reflected light beam LB1 (obl) The beam is propagated towards the oblique scheme detection assembly to interact with the beam splitting element 164 (e.g., a pinhole mirror), wherein the beam is split into imaging and measurement components along two spatially separated imaging and detection channels C associated with imaging and measurement detectors (or respective light input ports) D1 (e.g., CCD) and D'1 (spectrometer). (obl) imag and C (obl) meas spread.

[0066] When element 136 is in the non-operating position (moved outside of optical path 134), illumination beam LB1 passes through position 135 and interacts with beam splitter 160, which directs (in this example reflects) illumination beam LB1 to illuminate channel IC along the normal scheme. nor propagates, and thus the system operates in normal mode. Illumination channel IC nor Optically coupled to the corresponding optical component / unit L2 (objective lens unit OL2) of the optical head 106. Normal illumination channel IC nor A light-guiding element, such as a reflector, may be included. As shown in the figure, the configuration enables the normal incident light beam LB1 to interact with the light-guiding elements (reflectors) LD9 and LD6 successively and enter the optical unit L2, which includes an objective lens and a polarizer P2 to polarize the polarized normal incident light beam LB1 through the optical window OW2. (nor) Focusing on the same area on the structure. (nor) The light LB2 returned from the illuminated area (nor) Collected by optical window OW2 to pass through optical unit L2 and guided along the normal plan to collect light channel DC nor The light beam is guided by the continuous interaction with the light-guiding elements (reflectors) LD6, LD9 and LD8, and the latter converts the light beam LB2 (nor) The light beam LB2 is guided to the light splitting element (pinhole mirror) 162, and the light splitting element (pinhole mirror) 162 converts the light beam LB2 (nor) The two split beam portions of the optical beam are directed to propagate along spatially separated imaging and measurement detection channels toward a normal scheme imaging detector / light input port D2 (e.g., CCD) and light input port D2 optically coupled to the measurement detector. As described above, the same measurement detector (spectrometer) can be used to detect light for both normal and oblique optical schemes.

[0067] It should be noted that the measurement system of the present invention is not limited to splitting both the normal and oblique scheme collection channels into two detection channels. For example, each of these collection channels can use a single detection channel / single detector; or one of the normal and oblique scheme collection channels can include two different detection schemes while the other does not. In addition, the different detection schemes can differ in the type of detection (e.g., as described above, for detecting imaging and non-imaging data); and / or can differ in the detection of different spectral ranges.

[0068] refer to Fig. 6A and Figure 6B , Fig. 6A and Figure 6B As described above, in some embodiments, the integrated measurement system has a small footprint, for example less than 500 mm 2 , which does not allow scanning of a 300 mm wafer in both the X and Y directions. On the other hand, patterned structures measured on the wafer (e.g. Figure 6B 102) does not have rotational symmetry with respect to the tilted channel. Therefore, the structure can be measured at multiple positions thereof by displacement of the optical head along the Y-axis (via movement of the support unit 112A of the support assembly 112), and by displacement of the structure along the X-axis and rotation of the structure in the measurement plane (via corresponding movement of the support assembly 102). Fig. 6A In the example, Fig. 6A A top view of the integrated measurement system of the present invention is schematically shown, illustrating the range of travel of the optical window 114 and the structure / wafer W within the footprint FP of the system. Fig. 6A A structure W is shown having a radius r in its stowed position. x (e.g., 150 mm for a wafer with a diameter of 300 mm), and two displacement positions W′ and W″, which correspond to the displacement of the structure along the X-axis and the rotation of the structure in the measurement plane caused by the X-axis movement and rotation of the support assembly 102, respectively. The travel distance Y of the optical head along the Y-axis is W Footprint size Y on the Y axis FP The diameter of the structure is 2r x(e.g., 300 mm, considering semiconductor wafers or a slightly larger distance, such as 302 to 304 mm). The travel distance along the X-axis can be approximately half the size of the structure, such as the radius of a wafer, such as 150 mm (or a slightly larger distance, such as 154 mm). The support assembly 102 of the structure rotates the structure W in the measurement plane at a rotation angle θ in the range of 0 to 180 degrees. Therefore, as described above, by moving the optical head along the Y-axis and moving the support assembly of the structure along the X-axis, as well as the rotation of the support assembly, the structure can be measured in half in multiple positions using one or both of the normal and oblique measurement schemes via the optical window arrangement 114.

[0069] refer to Figure 6B , schematically shows a combination of normal and oblique measurement schemes applied to a complex patterned structure W. Due to the above system configuration, i.e. the handling, transfer and rotation of the structure to be measured and the range of motion of the optical head, the present invention allows for measurements with a greater number of available orientations (per pattern) for oblique modes and for measurements with polarization orientations for normal modes. The figure illustrates the combination of normal and oblique measurement schemes applied to a complex patterned structure W. Due to the above system configuration, i.e. the handling, transfer and rotation of the structure to be measured and the range of motion of the optical head, the present invention allows for measurements with a greater number of available orientations (per pattern) for oblique modes and for measurements with polarization orientations for normal modes. nor and DC nor Defined for illumination and specular reflection beam LB1 (nor) and LB2 (nor) The figure also shows the normal measurement scheme of the propagation of obl ) 1 -(DC obl ) 1 and (IC obl ) 2 -(DC obl ) 2 Two different oblique measurement schemes are defined, corresponding to two azimuthal angles of 0 and 90 degrees, obtained via a rotation of the structure in the measurement plane relative to the optical system. Except for the angle range 0 to 180, the structure / pattern on the wafer destroys the azimuthal symmetry.

[0070] The present invention thus provides a new, relatively simple solution for an optical measurement system that can operate in both normal and oblique optical schemes and enables a system configuration with a reduced footprint that can be properly integrated with processing equipment.

Claims

1. A measurement system configured to be integrated with a processing device for optically measuring a structure, the measurement system comprising: a support assembly for holding a structure being measured in a measurement plane, the support assembly being configured and operable to rotate in a plane parallel to the measurement plane and to translate along a first lateral axis in the measurement plane; An optical system defining illumination and collection light channels for normal and oblique optical measurement schemes; the optical system comprising an optical head comprising at least three lens units including a first lens unit, a second lens unit, and a third lens unit located in the illumination and collection light channels; A support assembly, comprising: a support unit for carrying the optical head; and a guide unit configured and operable to guide the support unit to slide along a path extending along a second transverse axis perpendicular to the first transverse axis; and The optical window arrangement includes at least three optical windows including a first optical window, a second optical window and a third optical window, wherein the at least three optical windows are formed in a panel, and the panel is located between the optical head and the measuring plane and is at a certain distance from the measuring plane. The first lens unit and the first optical window are associated with the illumination and collection light channels of a normal optical measurement scheme; The second lens unit and the second optical window are associated with an illumination light channel of the oblique optical measurement scheme; The third lens unit and the third optical window are associated with a collection light channel of the oblique optical measurement scheme; and The at least three optical windows are arranged in a spaced-apart parallel relationship and extend parallel to the path, and the at least three optical windows are aligned with the illumination and collection light channels for propagating light irradiated from the optical head and light returned from the illuminated area to the optical head according to the normal and oblique optical schemes, respectively.

2. The measurement system of claim 1, further comprising a controller configured and operable to controllably move the optical system operation between normal and oblique optical measurement schemes.

3. The measurement system according to claim 1 or 2 further includes a navigation motion system, which is configured and operable to drive the rotational movement of the support assembly, and drive the support units of the support assembly and the bracket assembly to move along the first lateral axis and the second lateral axis, respectively.

4. The measuring system according to claim 1 or 2, wherein: The optical system comprises a common illumination assembly optically coupled to the illumination channels of the normal and oblique optical measurement schemes, and separate detection devices housed in the respective collection light channels of the normal and oblique optical measurement schemes.

5. The measuring system according to claim 1 or 2, wherein: The light is returned, wherein each of the collection light channels is configured to direct the returned light to spatially separated imaging and measurement channels.

6. The measurement system according to claim 5, wherein: Each of the collecting light channels comprises a pinhole mirror device for spatially splitting the collected light into imaging and measuring light parts and guiding them to propagate through the imaging and measuring channels.

7. The measurement system according to claim 6, wherein: The imaging and measurement channels are optically coupled to an imaging and measurement detection device.

8. The measurement system according to claim 7, wherein: The measurement channels of the normal and oblique optical schemes are optically coupled to the same spectral detector.

9. The measuring system according to claim 1 or 2, wherein: The optical head comprises at least three objective lens units respectively located in the normal and oblique optical schemes.

10. The measurement system according to claim 9, wherein: The objective lens unit is configured to have low chromatic aberration.

11. The measuring system according to claim 1 or 2, wherein: The optical system includes a polarization component including at least one polarizer positioned in at least one of the illumination and collection light channels.

12. The measurement system according to claim 11, wherein: The polarization assembly is located within the optical head and includes three polarizers located in the illumination and detection channels of normal and oblique optical measurement schemes, respectively.

13. The measurement system according to claim 1 or 2, wherein: The at least three optical windows are configured to maintain polarization of light passing therethrough.

14. The measurement system according to claim 1 or 2, wherein: Each of the at least three optical windows has a substantially uniform thickness along the length of the optical window, the length being at least 2 orders of magnitude greater than the thickness.

15. The measurement system according to claim 14, wherein: The thickness of the at least three optical windows is several millimeters.

16. The measurement system according to claim 1 or 2, wherein: The panel has a small plane in which a central optical window among the at least three optical windows is formed, and two inclined side surfaces on opposite sides of the small plane, in which two other optical windows among the at least three optical windows are formed, so that each of the at least three optical windows is located in a plane oriented at 90 degrees to the optical axis of a corresponding one of the at least three lens units.

17. The measurement system according to claim 3, wherein: The navigation motion system includes a driving assembly configured and operable to drive the supporting unit of the bracket assembly to slide along a guide rail of the guiding unit.

18. The measurement system according to claim 17, wherein: The drive assembly includes a linear magnetic motor.

19. The measurement system according to claim 18, wherein: The linear magnetic motor includes a movable magnet and a stationary coil assembly.

20. The measurement system according to claim 1 or 2, wherein: The support assembly is configured and operable via a drive mechanism to control a position of the measurement plane relative to the optical head.

21. The measurement system according to claim 20, wherein: The drive mechanism includes a dual wedge engine, thereby reducing the size of the measurement system along the first axis.

22. A measurement system configured to be integrated with a processing device for optically measuring a structure, the measurement system comprising: a support assembly defining a measurement plane for holding a structure to be measured in the measurement plane, the support assembly being configured and operable as an x-theta stage; An optical system configured with normal and oblique optical measurement schemes and comprising an optical head and a light guide element including a first light guide element, a second light guide element, and a third light guide element, wherein the light guide element is used to guide incident light from a light source to the optical head and guide light collected by the optical head to a detection system; a support assembly configured and operable as a y-stage for guiding the optical head to slide along the y-axis; and The optical window arrangement includes at least three optical windows including a first optical window, a second optical window, and a third optical window, wherein the at least three optical windows are formed in a panel, and the panel is located between the optical head and the measuring plane and is at a certain distance from the measuring plane. The first light guiding element and the first optical window are associated with illumination and collection light channels of a normal optical measurement scheme; The second light-guiding element and the second optical window are associated with an illumination light channel of the oblique optical measurement scheme; The third light-guiding element and the third optical window are associated with a collection light channel of the oblique optical measurement scheme; as well as The at least three optical windows are arranged in a spaced-apart parallel relationship and extend along the y-axis so that illumination light from the optical head and light returned from an illuminated area are propagated to the optical head according to normal and oblique optical schemes of the optical head.

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