Integrated measurement system

Abstract

An integrated measurement system configured for integration with a processing apparatus for optical measurement of a structure is presented. The measuring system comprises: a support assembly; an optical system; the support assembly comprises a supporting unit used for bearing 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, the path extending along the second transverse axis perpendicular to the first transverse axis; and an optical window arrangement comprising at least three optical windows formed in a panel located between the optical head and the measurement plane at a distance from the measurement plane, the windows being arranged in spaced parallel relationship and extending parallel to the path, the optical windows being aligned with the illumination and collection light channels, and light propagating means for propagating light irradiated from the optical head and light returned from the irradiated area to the optical head, respectively, according to normal and oblique optical schemes.

Description

[0001] This application is a divisional application of the Chinese national phase application with an international filing date of November 17, 2019, an international application number of PCT / IL2019 / 051253, and an invention title of "Integrated Measurement System". The entry date of this Chinese national phase application into the national phase is July 16, 2021, the application number is 201980089433.X, and the invention title is "Integrated Measurement System". Technical Field

[0002] 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

[0003] The manufacture of semiconductor devices involves a multi-stage process in which wafers, which are required to be measured between successive manufacturing steps on a production line, are involved. The current trend of size reduction in the semiconductor industry and the dynamics of semiconductor manufacturing processes have increased the demand for precise 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 met by offline ("stand-alone") measurement systems that do not provide real-time responses, and cannot be provided by in-situ inspection devices such as endpoint detection devices because their performance is not precise enough.

[0004] Integrated measurement / monitoring technologies have been developed to provide a physical implementation of monitoring tools with full metrology capabilities within the production lines of semiconductor manufacturing plants. An integrated measurement system is a system that is physically installed inside a processing tool or attached to a processing tool and dedicated to a specific process.

[0005] An integrated measurement system has to be considered from several aspects and meet specific requirements in order to be feasible. Such requirements particularly include the following: a small footprint, i.e., the integrated measurement system should have as small a footprint as possible in order to physically fit inside a processing tool such as a CMP tool (e.g., installed inside the processing tool or connected to an equipment front end module (EFEM) via a load port), e.g., to isolate the measurement unit from the environment of the processing tool (e.g., using a sealed enclosure); a high-speed measurement unit (e.g., fast positioning, auto-focusing, and measurement); the ability to be bypassed by the production process and operate in an offline mode; etc.

[0006] Various integrated measurement / metrology systems have been developed and widely used and are commercially available from the assignee of the present application, such as 3090Next, etc. Summary of the Invention

[0007] There is a need in the art for a novel integrated measurement system for optical measurement of patterned structures, especially complex structures, which enables optical critical dimension (OCD) measurements to be performed using both vertical and tilted measurement schemes.

[0008] In many cases, it is advantageous to perform optical wafer metrology measurements using both normal and oblique schemes to increase the number of measurement channels. In fact, measurements using normal and oblique measurement schemes can provide more complete information about the structure being measured.

[0009] Considering metrology systems, especially OCD measurements for complex patterned structures, it is important to provide this additional information from different measurement schemes. This is because measurements using normal and oblique measurement schemes may have different sensitivities to different structural parameters and thus increase the amount of information about the structure being measured when used in combination. Additionally, combining vertical and tilted measurement schemes, for example using different orientations of the polarization plane of light with respect to the pattern in the vertical incidence scheme, and / or using different azimuths of light incidence, helps to increase further measurement channels.

[0010] The present invention provides a novel optical integrated metrology system mainly for OCD measurements, whose design / configuration is optimized such that it is on the one hand compact enough (with a small footprint) to be used with processing equipment, and on the other hand, is configured with normal and oblique measurement schemes and can be effectively switched between these two operating schemes, thereby enabling measurements under different measurement conditions. As described above, these different measurement conditions can include, for example, azimuth angle variations in the oblique incidence scheme and / or polarization variations in the vertical incidence scheme.

[0011] The integrated metrology system of the present invention can be advantageously used for the measurement of symmetric structures, i.e., structures having a geometric profile with a symmetry axis, such as a disk-shaped structure, which can be measured half by half by implementing a 180-degree rotation of the structure-carrying stage relative to the measurement optics.

[0012] Thus, according to a broad aspect of the present invention, there is provided a measurement system comprising:

[0013] 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;

[0014] An optical system defining illumination and collection light channels for normal and oblique optical schemes; the optical system includes an optical head, and the optical head includes at least three lens units located in the illumination and collection light channels;

[0015] The support assembly includes: a support unit for carrying an optical head; and a guiding 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

[0016] An optical window arrangement includes at least three optical windows formed in a panel located between the optical head and a measurement plane at a certain distance from the measurement plane. The windows are arranged in a spaced-apart parallel relationship and extend parallel to the path. The optical windows are aligned with the illumination and collection light channels for propagating the light irradiated from the optical head according to the normal and oblique optical schemes respectively and propagating the light returned from the irradiated area to the optical head.

[0017] The measurement system may further include a controller configured and operable to controllably move the operation of the optical system between the normal and oblique optical measurement schemes.

[0018] In some embodiments, the measurement system includes a navigation motion system configured and operable to drive the rotational motion of the support assembly respectively, and drive the support unit of the support assembly and the support unit of the support assembly to move along the first transverse axis and the second transverse axis respectively.

[0019] In some embodiments, the optical system includes a common illumination assembly optically coupled to the illumination channels of the normal and oblique optical measurement schemes, and separate detection devices accommodated in the respective collection light channels of the normal and oblique optical measurement schemes.

[0020] In some embodiments, each collection light channel is configured to guide the collected specularly returned light to spatially separated imaging and measurement channels. For example, each collection light channel includes a pinhole mirror device for spatially splitting the collected light into imaging and measurement light portions and guiding them to propagate through the imaging and measurement channels.

[0021] The imaging and measurement channels are optically coupled to imaging and measurement detection devices. Alternatively, the measurement channel may include an optical fiber. 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.

[0022] In some embodiments, the optical head of the optical system includes at least three objective lens units located in the normal and oblique optical schemes respectively. The objective lens units are preferably configured to have low chromatic aberration.

[0023] 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. Description of the Drawings

[0024] 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:

[0025] Figure 1 is a schematic diagram of an example of an integrated measurement / metrology system and a processing apparatus;

[0026] Figure 2 schematically shows the configuration of an integrated measurement / metrology system according to the present invention;

[0027] Figures 3A to 3C shows a specific, non-limiting example of the configuration of a bracket assembly for holding an optical head in the optical system of the present invention;

[0028] Figures 4A to 4D shows the principle of a standard wedge design used in a Z stage to convert X-axis movement into Z-axis movement ( Figures 4A to 4B ), and a specific, non-limiting example of the configuration of a Z stage using a dual-wedge actuator suitable for the measurement system of the present invention ( Figures 4C to 4D );

[0029] Figure 5 shows the light propagation scheme in the optical system of the integrated measurement / metrology system of the present invention, which is configured to operate the optical system in normal and oblique operating modes;

[0030] Figure 6A schematically shows a top view of an exemplary integrated measurement system of the present invention, which shows the travel ranges of the optical window and the wafer (support assembly) within the coverage area of the system;

[0031] Figure 6B shows the typical geometry of a complex patterned structure being measured in a wafer, showing that the system configuration of the present invention is capable of making measurements with a greater number of available azimuth angles (per pattern) for the tilt mode and with polarization azimuth for the normal mode. Detailed Description

[0032] As described above, the present invention provides a measurement system configured to be integrated with a processing apparatus for optically measuring a structure before or after being processed by the processing apparatus. The processing apparatus may include one or more processing tools, and the structure advances through successive stages of the processing apparatus while 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 apparatus, and in some other cases, the integrated measurement system is connected to an Equipment Front End Module (EFEM) via a load port. In the following description, the integrated measurement / metrology system is described as being integrated with or integrated within the processing apparatus to cover any such possible configurations.

[0033] In this regard, reference is made to Figure 1 , which illustrates by block diagram the integration of a measurement system 10 with a processing apparatus PE (e.g., a material removal (CMP, etching) or deposition (CVD) apparatus). In this example, the processing apparatus PE includes a processing / fabrication tool and its associated EFEM. The EFEM typically has a plurality of load ports LP associated with a corresponding number of cassette units, and a robot R (or robots) for transporting a structure / wafers W from the load port of the cassette unit to the processing tool. The integrated measurement system 10 is housed within the processing apparatus, e.g., within a processing tool station, and / or on the EFEM side (similar to a cassette station with a load port), and the same robot can be used to transport the wafer via the respective load port LP to a holder or support stage of the measurement system 10. Typically, the holder (or chuck / gripper) is part of the structure processing assembly.

[0034] The structure and operation of the processing apparatus and the structure and operation of the structure transport and holding means do not form part of the present invention and thus do not need to be specifically described other than to note the following. To control the processing of the structure in the processing apparatus PE, the structure is measured after and / or before being processed 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 thus be used in closed-loop process control to provide feedback results for a specific processing tool if the measurement is made after processing, and / or to provide feed-forward results for a specific processing tool if the measurement is applied to the structure before being processed by the said tool, e.g., to define initial conditions at the start of the process. For example, the processing apparatus PE may be a Chemical Mechanical Polishing (CMP) apparatus, and the integrated metrology system 10 may perform post-CMP measurements and may also perform pre-CMP measurements.

[0035] Now reference is made to Figure 2 , Figure 2FIG. 0 schematically shows, in block diagram form, a measurement system 100 of the present invention, which is configured and operative such that it can be integrated with a processing apparatus (e.g., similar to Figure 1 the example) for applying OCD measurements to a structure before and / or after processing by a processing tool of the processing apparatus. The measurement system 100 includes a structure support assembly 102 for holding a structure W (i.e., a semiconductor wafer) to be measured and defining a measurement plane MP, an optical system 104, and a support assembly for holding a movable part of the optical system 104.

[0036] The support assembly 102 may include a moving stage configured to move along one or more axes within the measurement plane and a rotatable chuck mounted on the moving stage. Thus, generally speaking, the support assembly may be configured as an r, θ stage, which is driven by a suitable driver / motor 105 for rotation within a plane parallel to the measurement plane MP and movement along a first transverse axis, the X-axis, within that plane. Such movement can be used to navigate over the structure (wafer) to reach a measurement location.

[0037] The support assembly 102 is also configured to adjust the z-axis position of the measurement plane MP. As will be described further and more specifically below, the z-axis positioning of the stage is preferably achieved using a double-wedge actuator.

[0038] 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 a light guiding assembly (e.g., folding mirrors, lenses, etc.) defining illumination and collection light channels. The optical system may also include a polarization assembly (not shown here), which enables measurements to be made under different polarization conditions.

[0039] It should be noted that one or both of the light source system 108 and the light detection system 110, as a construction (internal) part of the optical system 104 within the integrated measurement system 100, may be constituted by a light output port and a light input port, respectively, while the illumination / detection assembly or parts thereof may be housed outside the integrated measurement system 100 and may be optically coupled to the light input and output ports (e.g., via an optical guiding element such as a fiber). Thus, each of the blocks 108 and 110 respectively indicating the light source system 108 and the light detection system 110 should be interpreted broadly and not necessarily include a light emitter and a photosensitive detector.

[0040] The support assembly 112 includes a support unit (slider) 112A configured to hold the optical head 106, and a guiding unit 112B including a guide rail (not shown here) extending along a second transverse axis Y-axis perpendicular to the X-axis. The slider 112A is mounted on the guiding unit 112B and is driven by a driving unit / mechanism 111 to slide along the guide rail.

[0041] Thus, the support assembly 112 is actually configured and operable as a Y-stage for moving the optical head 106 (as a movable part of the optical system 104) along the Y-axis. The structure (wafer) moves on the x-θ stage 102. As will be described further more specifically below, the Y-stage 112 operates to move the optical head 106 including a set of objective lenses and possibly a polarizer and a bending mirror to bring the light beam from the light source to the objective lens and the wafer and back.

[0042] In some embodiments, the structure to be measured may be a symmetric structure having a certain lateral dimension, such as a disc-shaped structure (e.g., a semiconductor wafer) having a certain diameter. The travel distance y of the optical head 106 along the Y-axis can reach the size of the structure, such as the diameter of the wafer, e.g., 300 mm. The travel distance along the x-axis (i.e., during the navigation movement) can be approximately half the size of the structure, such as the radius of the wafer, e.g., 150 mm; and the stage rotation angle θ is in the range of 0 to 180 degrees. This will be described below with reference to Figure 6A Further description.

[0043] The system 100 further includes an optical window arrangement 114, which is appropriately configured for light to propagate from and to the optical head 106. Such an 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 having the optical window arrangement 114 presents the input / output light plane of the optical head.

[0044] The optical window arrangement 114 is designed to seal the moving part (optical head 106) from 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 window has a length corresponding to the travel distance along the y-axis, which corresponds to the size of the structure, such as a wafer with a diameter of 300 mm.

[0045] 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.

[0046] 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.

[0047] It should also be noted that an integrated measurement system 100 integrated with a processing equipment PE is considered, e.g. Figure 1 As shown, it may be necessary to maintain a certain environment near the measurement plane, i.e., near the structure being measured. This may be some desired environment such as N2 or vacuum or CO2. For this purpose, the present invention provides the use of a gas supply used in a processing device (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. For this purpose, 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.

[0048] 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 .

[0049] For example, the optical system 104 may utilize illumination channels IC with normal and oblique optical schemes. nor and IC oblA common light source system 108 for optical coupling, and separate detection devices D1 and D2 can be accommodated in the corresponding collection channels of the normal and oblique optical schemes.

[0050] In some embodiments, the measurement system 100 is configured to perform both imaging and measurement of a structure. Accordingly, the optical system 104 is configured such that the collection channels DC nor and DC obl at least one of which 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 (measurement detector). To this end, the collection channels DC nor and DC obl at least one of which includes a splitting device, such as a pinhole mirror device, for spatially separating the collected light into imaging and measurement light portions and guiding them to propagate through the 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 more specifically below.

[0051] As Figure 2 further shown, the measurement system 100 is configured for data communication with the control system 120 via wired and / or wireless signal transmission of any suitable technology. The control system 120 includes data input and output utilities 120A, 120B, a memory utility 120C, and a measurement data analyzer 120D.

[0052] Various controllers for controlling the operation of the control 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 / switch between the normal and oblique measurement modes; and can also be configured to control varying conditions such as polarization and / or wavelength and / or azimuth angle. The navigation motion controller 120F is configured and operable to operate the drivers 105 and 111 to control the rotational movement of the structure support assembly 102 (e.g., a chuck) and the X-axis movement of the structure support assembly 102 (e.g., a stage), respectively, and the movement of the optical head 106 along the Y-axis.

[0053] As described above, the rotational movement of the support assembly 102 (e.g., a chuck) can be performed to achieve first and second consecutive measurement sessions corresponding to first and second relative angular positions of the stage 102, the first and second relative angular positions bringing the first and second halves H1 and H2 of the structure W into the measurement position, respectively. While controlling the lateral movement of the support assembly 102 and the optical head 106 along the X-axis and the Y-axis, each of the first and second measurement sessions can be achieved in sequence, thereby navigating the measurement of a plurality of measurement positions on the respective halves of the first and second halves of the structure W. As described above, considering measurements on such a disk-shaped 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.

[0054] Generally, an integrated measurement / metrology system typically performs measurements at a plurality of measurement positions 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-described two-half measurement mode is a non-limiting example that can be used when the selected measurement positions are symmetrically positioned / oriented (assuming 180-degree symmetry). When measuring other orientations of the wafer / measurement positions, a situation may arise. In that case, the navigation (rotation and / or X-axis movement and / or Y-axis movement) can be optimized due to the plurality of measurement positions and their orientations. It should also be noted that the above-described translation scheme is not the minimized movement 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.

[0055] Reference Figures 3A to 3C , Figures 3A to 3C shows the configuration of the support assembly 112 of the optical head portion 106 (movable portion) carrying the optical system 104.

[0056] As Figure 3A shown, the optical head 106 has three light-guiding optical units (focusing optics) L1, L2, L3, and the three light-guiding optical units L1, L2, L3 define irradiation channels IC obl respectively corresponding to an oblique scheme, an irradiation-and-collection channel IC nor -and-DC nor of a normal optical scheme, and a detection channel DC oblThree associated light propagation paths. The optical units L1, L2, L3 include objective lenses OL1, OL2, OL3 (and possibly other optical elements), which define corresponding optical paths aligned with optical windows OW1, OW2, and OW3 (e.g., holes) in the panel 115 between the support assembly 112 and the 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 such that the light output / input of the optical units L1, L2, L3 is aligned with the optical windows OW1, OW2, and OW3, respectively. It should be noted that the inclined orientation of the optical window provides 90 degrees between the optical axis of the corresponding lens unit and the window surface.

[0057] As Figure 3A and Figure 3C 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 with appropriate angles corresponding to the optical scheme. The support unit 112A that holds the optical head 106 is mounted on the guiding unit 112B for sliding movement along a guide rail 112C that defines a sliding movement path along which the support unit 112A reciprocates.

[0058] As described above, the support assembly 112 (support unit 112A and guiding unit 112B) presents a Y-stage for the moving part (optical head) of the optical system 104. The optical window arrangement 114 (e.g., a three-window arrangement formed on the 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 inclined relative to the horizontal plane and are 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.

[0059] In some embodiments, the Y-stage driver 111 includes a linear magnetic motor. Preferably, the linear magnetic motor is configured such that the magnet 111A moves and the coil assembly 111B is stationary. This configuration provides a relatively constant drive current and heat transfer from the coil to the system boundary for heat dissipation via the heat dissipation interface 111C. Such a requirement may be associated with the need for the stage to be very close to the optical head environment that requires temperature stability.

[0060] As described above, the objective lens should be positioned as close as possible to the measurement plane, and thus 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 the aperture variation (e.g., 2 mm), where the window thickness is substantially uniform along the window (±1 μm tolerance), and the window length is at least two orders of magnitude higher than the thickness, e.g., a length of approximately 300 mm. Additionally, as described above and further exemplified more specifically below, the optical system 106 may include polarizers (e.g., in the optical units L1, L2, and L3). Accordingly, the optical windows OW1, OW2, and OW3 are configured to maintain (i.e., not affect) the polarization of the light passing through them. For example, the medium of the optical window may be birefringent.

[0061] 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 measurements to be made within an elongated region along the Y-axis of the structure W located in the measurement plane MP. After the stage 102 has stepped a predetermined distance along the X-axis within the range (0 to r), for example, while the optical head moves a distance of up to 2r along the Y-axis, measurements 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 measurements to be performed at multiple positions on the wafer. For example, the first half H1 of the structure W can be inspected first using the x and y movements of the stages 102 and 112, and then the stage 102 can be rotated 180 degrees, thereby bringing the second half H2 of the structure to the measurement position and repeating the process to perform measurements on this half of the structure.

[0062] 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 double-wedge actuator. In this regard, reference Figures 4A to 4B and Figures 4C to 4D . Figure 4A and Figure 4B show a standard wedge design used in a Z-stage configuration to convert X-axis movement into Z-axis movement in the z-up position (x-closed position) and the z-down position (x-open position), respectively. When in the open position, this configuration suffers from a relatively large asymmetric coverage area in the x-dimension. Figure 4C and Figure 4D show a specific example of the z-stage 102 utilizing a double-wedge configuration formed by two relatively symmetric wedges W1 and W2 in the z-up, x-closed position ( Figure 4C ) and the z-down, x-open position ( Figure 4D ). This configuration reduces the x-dimensional footprint of the system.

[0063] Now referring to Figure 5 , Figure 5 illustrates the configuration and operation of the optical system 104 and the light propagation scheme therein. 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.

[0064] Additionally, in this example, switching / shifting between normal and oblique operating modes (i.e., shifting between light propagation in normal and oblique schemes) is achieved by controlling the position of the shutter 136 (i.e., the so-called jump mirror). Further, in this example, the detection system 110 includes two detection components associated with the normal and oblique collection channels DC nor and DC obl Each of the two detection components is configured to operate in parallel with imaging and measurement modes and includes a corresponding imaging detector unit D1 and D2 (e.g., CCD), and either includes corresponding measurement detectors D1' and D2', or a common measurement detector (spectral detector) for both normal and oblique schemes. The system operates with broadband illumination, for example, in the range of 210 nm to 2500 nm. Additionally, in this non-limiting example, a polarizer assembly is used. In the figure, the polarizer / analyzer is shown as 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 within the movable part of the optical system, i.e., within the optical head 106 carried by the bracket assembly 112.

[0065] Thus, the illumination beam LB1 propagates from the light source system 108 and is guided by light guiding elements (e.g., illumination relay lens unit and tubular lens unit) to propagate along the input optical path 134 towards the mode shift position 135. For this purpose, a redirecting element 136, such as a mirror, is provided to be controllably movable (e.g., by the measurement mode controller 120E) between its operative state when located at the position 135 and its inoperative state outside the optical path 134.

[0066] When the mirror 136 is in its operative position, the illumination beam LB1 interacts with the mirror 136 and is reflected by the mirror 136 to propagate along the illumination channel IC obl of the oblique scheme, and thus the system operates in the oblique mode. The illumination channel IC obl is optically coupled to the corresponding optical component L1 of the optical head 106. As shown in the specific non-limiting example of Figure 5 the illumination channel IC oblmay include one or more light guiding (light path bending) elements, such as mirrors - three such light guiding elements (mirrors) LD1, LD2, and LD3 are shown in this example. As further shown in the figure, the optical assembly / unit L1 includes a lens unit (one or more lenses), and also includes a polarizer P1, and thus the polarizer P1 is located in the obliquely oriented illumination channel IC obl therein. The resulting obliquely incident polarized illumination beam LB1 (obl) is focused via a corresponding optical window OW1 onto an illumination area on the structure. The light LB2 (obl) returning from the area illuminated by the beam LB1 (obl) is collected by the optical assembly L3 via the optical window OW3, where the polarization of the light is adjusted by a corresponding polarizer P3, and the collected returned light is guided to propagate along the obliquely oriented detection channel DC obl similarly, the detection channel DC obl may include one or more light guiding elements (such as mirrors) - five such elements LD4 to LD8 are shown in this schematic diagram. The element LD8 may be configured as a wedge prism having two reflecting surfaces, and the two reflecting surfaces redirect the light incident thereon according to the light incident position. Thus, the element LD8 guides the obliquely reflected beam LB1 (obl) towards the obliquely oriented detection assembly to interact with a beam splitting element 164 (e.g., a pinhole mirror), where the beam is split into an imaging and a measuring component to propagate along two spatially separated imaging and detection channels C (obl) imag and C (obl) meas associated with an imaging and measuring detector (or respective light input ports) D1 (e.g., a CCD) and D'1 (a spectrometer).

[0067] When the element 136 is in a non-operating position (moved outside the optical path 134), the illumination beam LB1 passes through the position 135 and interacts with a beam splitter 160, which guides (reflects in this example) the illumination beam LB1 to propagate along the illumination channel IC in the normal orientation nor and thus the system operates in the normal mode. The illumination channel IC nor is optically coupled to a corresponding optical assembly / unit L2 (objective lens unit OL2) of the optical head 106. The normal illumination channel IC nor may include light guiding elements, such as mirrors. As shown in the figure, this configuration enables the normal illumination beam LB1 to interact successively with light guiding elements (mirrors) LD9 and LD6 and enter the optical unit L2, which includes an objective lens and a polarizer P2, to focus the polarized normally incident beam LB1 (nor) via the optical window OW2 onto the same area on the structure. The light LB2(nor) Light LB2 returned from the irradiated area (nor) Collected by the optical window OW2 to pass through the optical unit L2 and be guided along the normal scheme collection optical channel DC nor Propagates along the same path, where the light beam is guided through successive interactions with the light guiding elements (mirrors) LD6, LD9, and LD8, and the latter direct the light beam LB2 (nor) Towards the beam splitting element (pinhole mirror) 162, which directs the two beam splitting portions of the light beam LB2 (nor) Towards the normal scheme imaging detector / light input port D2 (e.g., CCD) and the light input port D2 optically coupled to the measurement detector along spatially separated imaging and measurement detection channels. As described above, the same measurement detector (spectrometer) can be used to detect light for both the normal and the oblique optical schemes.

[0068] It should be noted that the measurement system of the present invention is not limited to splitting both the normal and the 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 the oblique scheme collection channels can include two different detection schemes while the other does not. Additionally, the different detection schemes can differ in the type of detection (e.g., for detecting imaging and non-imaging data as described above); and / or can differ in the detection of different spectral ranges.

[0069] Reference Figure 6A and Figure 6B , Figure 6A and Figure 6B show some other features of the present invention. As described above, in some embodiments, the integrated measurement system has a small coverage area, e.g., less than 500 mm 2 ,which does not allow scanning a 300 mm wafer in the X and Y directions. On the other hand, the patterned structures measured on the wafer (as Figure 6B shown) do not have rotational symmetry with respect to the tilted channels. Thus, the structure can be measured at multiple positions by displacing the optical head along the Y-axis (via the movement of the support unit 112A of the support assembly 112), and displacing the structure along the X-axis and rotating the structure in the measurement plane (via the corresponding movements of the support assembly 102). This is exemplified in Figure 6A , Figure 6A which schematically shows a top view of the integrated measurement system of the present invention, showing the travel ranges of the optical window 114 and the structure / wafer W within the coverage area FP of the system. Figure 6A shows the structure W, which has a radius r at its loading position x(e.g., 150 mm for a wafer with a diameter of 300 mm), and two displacement positions W′ and W″, which respectively 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. The travel distance Y of the optical head along the Y-axis W within the Y-axis coverage dimension Y FP reaches the diameter 2r of the structure x (e.g., 300 mm, considering a semiconductor wafer or a slightly larger distance, e.g., 302 to 304 mm). The travel distance along the X-axis can be approximately half the size of the structure, e.g., the radius of the wafer, e.g., 150 mm (or a slightly larger distance, e.g., 154 mm). The support assembly 102 of the structure rotates the structure W in the measurement plane by a rotation angle θ within the range of 0 to 180 degrees. Thus, as described above, by moving the optical head along the Y-axis and moving the support assembly of the structure along the X-axis, and rotating the support assembly, the structure can be measured in half at multiple positions using one or both of the normal and oblique measurement schemes via the optical window arrangement 114.

[0070] Reference Figure 6B , schematically shows a combination of the normal and oblique measurement schemes applied to the complex patterned structure W. Due to the above system configuration, i.e., the processing, transfer, and rotation of the structure to be measured and the movement range of the optical head, the present invention allows for more available azimuths (per pattern) for measurement in the oblique mode and polarization azimuth for measurement in the normal mode. This figure exemplifies the illumination and detection channels IC nor and DC nor defining the normal measurement scheme for the propagation of the illumination and specular reflection beams LB1 (nor) and LB2 (nor) . This figure also shows two different oblique measurement schemes respectively defined by the illumination and detection channels (IC obl ) 1 -(DC obl ) 1 and (IC obl ) 2 -(DC obl ) 2 , and the corresponding two 0-degree and 90-degree azimuth angles are obtained by rotating the structure in the measurement plane relative to the optical system. Except for the angle range of 0 to 180, the structure / pattern on the wafer breaks the azimuth symmetry.

[0071] Therefore, the present invention provides a new and relatively simple solution for an optical measurement system, which can operate in both normal and oblique optical schemes, and enables a system configuration with a reduced coverage area to 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 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 illumination and collection optical channels for normal and oblique optical schemes; The optical system includes an optical head, the optical head including at least three lens units located in the illumination and collection optical channels; A bracket assembly including: a support unit for carrying the optical head; and a guiding 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 An optical window arrangement including at least three optical windows formed in a panel located between the optical head and the measurement plane at a distance from the measurement plane, the windows being arranged in a spaced parallel relationship and extending parallel to the path, the optical windows being aligned with the illumination and collection optical channels for propagating the light irradiated from the optical head and the light returned from the irradiated area to the optical head according to the normal and oblique optical schemes, respectively.

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

3. The measurement system according to claim 1 or 2, further comprising a navigation motion system configured and operable to drive the rotational movement of the support assembly and the movement of the support assembly and the support unit of the bracket assembly along the first transverse axis and the second transverse axis, respectively.

4. The measurement system according to any one of the preceding claims, wherein, The optical system includes 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 optical channels of the normal and oblique optical measurement schemes.

5. The measurement system according to any one of the preceding claims, wherein, Each of the collection optical channels is configured to direct the collected specularly returned light to spatially separated imaging and measurement channels.

6. The measurement system according to claim 5, wherein, Each of the collection optical channels includes a pinhole mirror device for spatially separating the collected light into imaging and measurement light portions and guiding them to propagate through the imaging and measurement channels.

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

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 measurement system according to any one of the preceding claims, wherein, The optical head includes at least three objective lens units located in the normal and oblique optical schemes, respectively.

10. 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 the structure to be measured in the measurement plane, the support assembly being configured and operable as an x-θ stage; An optical system, configured with normal and oblique optical measurement schemes, and including an optical head and a light guiding element for guiding incident light from a light source to the optical head and guiding 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 An optical window arrangement, including at least three optical windows formed in a panel located between the optical head and the measurement plane at a certain distance from the measurement plane, the windows being arranged in a spaced parallel relationship and extending along the y-axis such that irradiation light from the optical head is propagated and light returning from the irradiated area is propagated to the optical head according to the normal and oblique optical schemes of the optical head.

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