Adjustable achromatic collimator assembly for endpoint detection systems

Abstract

To provide a system having improved spectral accuracy of optical control systems, which allow real-time monitoring of various stages of device manufacturing.SOLUTION: A manufacturing machine including a broadband collimator assembly includes: a collimator housing 202 that includes an optical interface 214 optically coupling to a process chamber that has a target surface; a port to receive an optical fiber 208 to deliver, to an enclosure formed by the collimator housing, a first (second) plurality of spectral components of light belonging to a first (second) range of wavelengths; and an achromatic lens 210 located, at least partially, within the enclosure formed by the collimator housing, the achromatic lens directing the first (second) plurality of spectral components of light onto the target surface to illuminate a first (second) region on the target surface, where the second region is substantially the same as the first region.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This disclosure relates generally to the fabrication of integrated circuits and other semiconductor devices in processing chambers. More particularly, this disclosure relates to an adjustable endpoint detection system for precise product control in device manufacturing.

[0002] The fabrication of microelectronic and integrated circuit devices often requires the performance of numerous operations on semiconductor, dielectric, and conductive substrates. Examples of these operations include oxidation, diffusion, ion implantation, thin-film deposition, cleaning, etching, lithography, etc. Materials produced in this manner may include single crystals, semiconductor films, fine coatings, and many other substances used in the fabrication of electronic devices and other practical applications. When selected types of atoms are added to (e.g., by deposition) or removed from (e.g., by etching) the substrate, efficient and accurate endpoint monitoring techniques (and systems) become important. Under-etching and over-etching (and similarly, under-deposition and over-deposition) can result in substandard devices or even malfunctions. Optical control systems capable of monitoring the various stages of device fabrication in real time significantly improve product quality. This is especially useful given the ever-increasing demands on semiconductor device quality. Overview

[0003] In one embodiment, a collimator assembly is disclosed that includes a collimator housing and an achromatic lens. The collimator housing includes an interface configured to optically couple to a target surface and a process chamber having a port for receiving an optical fiber. The optical fiber transmits a first plurality of spectral components of light belonging to a first range of wavelengths and a second plurality of spectral components of light belonging to a second range of wavelengths to an enclosure formed by the collimator housing. The first range is within the 400-700 nm wavelength interval, and the second range is outside the 400-700 nm wavelength interval. The achromatic lens is at least partially disposed within the enclosure formed by the collimator housing. The achromatic lens directs the first plurality of spectral components of light onto the target surface to illuminate a first area on the target surface. Furthermore, the achromatic lens directs the second plurality of spectral components of light onto the target surface to illuminate a second area on the target surface, the second area being substantially the same as the first area.

[0004] In another embodiment, an endpoint detection system is disclosed that includes a light source, a collimator housing, an achromatic lens, a photodetector, and a processing device. The light source outputs a first plurality of spectral components of light belonging to a first range of wavelengths and a second plurality of spectral components of light belonging to a second range of wavelengths. The first range is within the 400-700 nm interval of wavelengths, and the second range is outside the 400-700 nm interval of wavelengths. The collimator housing includes an interface configured to optically couple to a process chamber having a target surface. The collimator housing also includes a port for receiving an optical fiber for transmitting the first plurality of spectral components of light belonging to the first range of wavelengths and the second plurality of spectral components of light belonging to the second range of wavelengths to an enclosure formed by the collimator housing. The achromatic lens is at least partially disposed within the enclosure formed by the collimator housing. The achromatic lens directs the first plurality of spectral components of light toward the target surface to illuminate a first area on the target surface and directs the second plurality of spectral components of light toward the target surface to illuminate a second area on the target. The second region is substantially the same as the first region. The second optical fiber collects a first plurality of spectral components of light reflected from the target surface generated by the first plurality of spectral components of light directed at the target surface. Additionally, the second optical fiber collects a second plurality of spectral components of light reflected from the target surface generated by the second plurality of spectral components of light directed at the target surface. The photodetector receives the first plurality of reflected spectral components of light and the second plurality of reflected spectral components of light via the second optical fiber. A processing device communicatively coupled to the photodetector determines the reflectivity of the target surface based on the received first plurality of reflected spectral components of light and the received second plurality of reflected spectral components of light.

[0005] In another embodiment, a method is disclosed for outputting a first plurality of spectral components of light belonging to a first range of wavelengths and a second plurality of spectral components of light belonging to a second range of wavelengths from a light source. The first range is within the 400-700 nm wavelength interval, and the second range is outside the 400-700 nm wavelength interval. The disclosed method further comprises directing the first plurality of spectral components of light to a target surface via an achromatic lens to illuminate a first region on the target surface. The disclosed method further comprises directing a second plurality of spectral components of light to the target surface via an achromatic lens to illuminate a second region on the target surface, the second region being substantially the same as the first region. The disclosed method further comprises collecting, via a second optical fiber, the first plurality of spectral components of light reflected from the target surface that are generated by the first plurality of spectral components of light directed to the target surface. The disclosed method further comprises collecting, via a second optical fiber, a second plurality of spectral components of light reflected from the target surface produced by the second plurality of spectral components of light directed toward the target surface. The disclosed method further comprises receiving, via a photodetector, the first plurality of reflected spectral components of light and the second plurality of reflected spectral components of light via the second optical fiber. The disclosed method further comprises determining, via a processing device communicatively coupled to the photodetector, a reflectivity of the target surface based on the received first plurality of reflected spectral components of light and the received second plurality of reflected spectral components of light. [Brief explanation of the drawings]

[0006] [Figure 1] 1A and 1B illustrate schematic diagrams of a manufacturing apparatus including a spatially adjustable broadband collimator assembly for accurate optical characterization of targets in a processing chamber, according to some embodiments of the present disclosure. [Figure 2] 1A and 1B illustrate schematic diagrams of an exemplary achromatic (broadband) collimator assembly for accurate optical characterization of targets in a processing chamber, according to some embodiments of the present disclosure. [Figure 3A]~ [Figure 3D] 1A-1C schematically illustrate the advantages of using an achromatic (broadband) collimator for accurate optical characterization of targets in a processing chamber compared to conventional collimators, according to some embodiments of the present disclosure. [Figure 4] 1A and 1B illustrate schematic diagrams of an exemplary collimator assembly with adjustable alignment for accurate optical characterization of targets in a processing chamber, according to some embodiments of the present disclosure. [Figure 5] 1A-1C illustrate schematic diagrams of an exemplary tilted collimator assembly with adjustable alignment for accurate optical characterization of targets in a processing chamber, according to some embodiments of the present disclosure. [Figure 6] 1A and 1B schematically illustrate side views of exemplary collimator assemblies with adjustable alignment, according to some embodiments of the present disclosure. [Figure 7] 1 is a flowchart of one possible embodiment of a method for deploying a broadband collimator assembly for accurate optical characterization of a target in a processing chamber, according to some embodiments of the present disclosure. [Figure 8] 10 is a flowchart of one possible embodiment of a method for adjusting the tilt of an adjustable collimator assembly for accurate optical characterization of a target in a processing chamber, according to some embodiments of the present disclosure. [Figure 9] 1 shows a block diagram of an exemplary processing system capable of supporting real-time detection of particulate contaminants present in a deposition chamber based on light scattering data. Detailed Description

[0007] Embodiments disclosed herein provide precise broadband optical endpoint control for semiconductor device manufacturing. The embodiments enable delivery of an optical beam into a processing chamber with a uniform spatial profile across a wide range of wavelengths. For example, the width of the beam allows the 250 nm spectral component of the beam to be the same as the 750 nm spectral component of the beam. Spatial uniformity of the beam can be achieved by sending the optical signal through a collimator equipped with a broadband achromatic lens. This enhanced uniformity allows for more accurate measurement of the optical response of a target (e.g., a substrate) within the processing chamber (compared to collimators employing conventional optics) and therefore more accurate determination of the target condition (e.g., during substrate etching or deposition processing).

[0008] Additionally, the collimator may be equipped with a precision adjustment mechanism that adjusts the alignment of the collimator's optical axis to maximize the efficiency of delivering incident light to an intended area on a target located within the processing chamber. In some embodiments, the adjustment mechanism may be used to compensate for small changes in the position of the processing tool (e.g., variations in the position of a wafer-supporting chuck) caused by tool disassembly, reassembly, and / or recalibration after maintenance on the processing chamber has been performed.

[0009] During the manufacture of electronic devices, many pattern transfer operations, including lithography and etching, are often performed. For example, in a lithography process, a photoresist layer partially protected by a photomask (containing a desired pattern) can be exposed to a light source and subsequently developed with an appropriate chemical solution to remove the exposed, unprotected portions of the photoresist. The resulting patterned photoresist layer is used as a mask to protect a substrate (e.g., a silicon wafer, etc.) that is exposed to a reactive (e.g., wet or dry etching) environment in an etching step to remove the unprotected portions of the substrate. During etching, endpoint data from the substrate (e.g., optical response data, which may include reflectivity data, polarization data, etc.) can be used to determine whether the process is operating according to specifications and whether the desired results of the etching (e.g., etch depth and uniformity) are being achieved.

[0010] Changes in the reaction environment (e.g., composition, temperature, plasma density, etc.) or differences in photomask patterns can result in changes in etch rate and uniformity. Tracking and responding to these changes can require accurate, tunable optical endpoint systems capable of collecting precise, substantial optical response data characterizing various target surfaces (wafers, photomasks, etc.) within the processing chamber. Furthermore, accuracy goals are driven by the miniaturization of microelectronic devices, increasingly complex photomask designs, and increasing demands for device uniformity. Existing optical systems for endpoint control are often unable to meet these increasing technological demands.

[0011] Aspects and embodiments of the present disclosure address this and other shortcomings of optical inspection techniques that can be used in substrate manufacturing. Described herein is a spatially tunable optical inspection apparatus that can deliver a light beam with a uniform spatial profile over a wide range of wavelengths for accurate optical characterization of substrate processing. The embodiments disclosed herein help to accurately determine the optical, physical, and / or morphological properties of a substrate (e.g., substrate uniformity, smoothness, thickness, refractive index, reflectivity, etc.), providing an efficient quality control tool without degradation of the manufacturing process.

[0012] The disclosed embodiments relate to various manufacturing techniques that use processing chambers (which may include deposition chambers, etch chambers, etc.), such as, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), plasma-enhanced CVD, plasma-enhanced PVD, sputter deposition, atomic layer CVD, combustion CVD, catalytic CVD, evaporation, molecular beam epitaxy techniques, etc. The disclosed embodiments can be employed in techniques that use vacuum deposition chambers (e.g., ultra-high vacuum CVD or PVD, low pressure CVD, etc.) and atmospheric pressure deposition chambers.

[0013] FIG. 1 schematically illustrates a manufacturing apparatus 100 including a spatially adjustable broadband collimator assembly for accurate optical characterization of targets within a processing chamber, in accordance with some embodiments of the present disclosure. In one embodiment, the manufacturing apparatus 100 includes a processing chamber 102 within a processing chamber housing 104 for processing (e.g., deposition, lithography, etching, etc.) one or more substrates 106. During processing, the substrate 106 is exposed to a plasma environment 110 for plasma-enhanced processing (e.g., etching). The substrate 106 may be supported by a chuck 108. The processing chamber 102 may include one or more process kit tools 112 (e.g., edge rings, etc.). The substrate 106 may be lifted by lift pins (not shown) to achieve a targeted exposure of the backside of the substrate 106 to the processing environment, and the substrate 106 may be heated (e.g., by applying light).

[0014] The processing of the substrate 106 in the processing chamber 102 can be optically monitored by an end-point optical system including a collimator assembly 120 and a control module 130. The collimator assembly 120 can be mechanically coupled to the processing chamber housing 104 (either rigidly or operatively, as described below) and can optically interface with the processing chamber environment (e.g., the plasma environment 110, etc.). The optical interface between the collimator assembly 120 and the processing chamber 102 can be an orifice, a converging or diverging lens, a transparent slab (which may have no optical power), a polarizer, or any other device or material capable of transmitting light between the collimator assembly 120 and the processing chamber 102. As used herein, "light" refers to electromagnetic radiation in any spectral range, including visible, near-infrared (IR), near-infrared (UV), etc. Furthermore, "light" can include unpolarized (natural) light, linearly, circularly, or elliptically polarized light, partially polarized light, focused light, diverging light, collimated light, etc.

[0015] The light beam 122 can be generated by the collimator assembly 120 from input light 124 generated by a light source 132. In some embodiments, the input light 124 is transmitted through one or more input optical fibers. The light source 132 can be a narrowband light source, such as a light emitting diode, laser, or light bulb. In some embodiments, the light source 132 is a broadband light source. In some embodiments, the light source 132 includes two or more component light sources, such as multiple narrowband light sources that (when combined) generate the broadband input light 124. The light source 132 can include additional spectrally controlling optical elements (e.g., filters, absorbers, polarizers, etc.) to control the spectral dispersion and / or polarization of the input light 124.

[0016] In some embodiments, the input light 124 is converted into a light beam 122 by the collimator assembly 120, for example, by passing the input light 124 through multiple optical elements (e.g., lenses, reflectors, filters, apertures, etc.) of the collimator assembly 120. The collimator assembly 120 may have broadband characteristics. More specifically, the collimator assembly 120 may generate a light beam 122 whose spatial extent can be the same as multiple spectral components of the beam (as described in more detail below). For example, the diameter of the generated light beam 122 may be the same within a broad band of wavelengths λ of the various spectral components contained in the input light 124, and thus within the light beam. In existing endpoint detection systems, the diameter of a conventional light beam 122-1 varies with wavelength λ. For example, a green component (λ = 550 nm) may have a diameter of 9 mm, and a red component (λ = 650 nm) may have a diameter of 13 mm. (This is shown diagrammatically in FIG. 1 by varying the shading in a conventional depiction of light beam 122-1.) As a result, different spectral components propagate along different optical paths, which can lead to significant errors in the resulting substrate reflectivity R(λ), and thus to mischaracterization of the target (e.g., the surface of substrate 106) and errors in the etching process (e.g., stopping etching too early or too late).

[0017] In contrast, embodiments of the present disclosure describe a broadband collimator assembly 120 that ensures substantially the same spatial extent of the various spectral components λ of the light beam 122. This is shown schematically in FIG. 1 with a uniformly white cross-section of the achromatic beam 122-2. To achieve such a broadband achromatic light beam output, the collimator assembly 120 can have one or more achromatic lenses, which are described in more detail below with reference to FIG. 2. More specifically, the achromatic beam 122-2 can be characterized by specifying the beam's spectral components for multiple spectral ranges Δλ, such as widths Δλ = 100 nm (or 150 nm, 200 nm, or any other wavelength range). The spectral ranges can be centered around a series of central wavelengths λ1, λ2, λ3, etc. In some embodiments, the ranges overlap with Δλ greater than the distance between adjacent central wavelengths. In some embodiments, Δλ is equal to the distance between the central wavelengths (e.g., Δλ = λ3 - λ2). In some embodiments, Δλ is greater than the distance between the center wavelengths (thus the ranges do not overlap). In some embodiments, the ranges Δλ have unequal widths. (Alternatively, the ranges can correspond to equal frequency intervals Δf.) In some embodiments, the range Δλ corresponds to the actual emission range of the various light emitters in light source 132 (e.g., the emission range of the light emitting diodes in light source 132). In other embodiments, the range Δλ is defined for characterization purposes only and may not be limited to specific physical light emitters.

[0018] λ k The range Δλ centered on k The spectral components within a certain diameter d k (For simplicity, the beams are described as having circular cross sections, but it should be understood that similar characterizations can be made for beams of other cross sections (e.g., elliptical beams or beams having some other shape, etc.). The kth spectral beam propagates through the kth region A on the target surface (e.g., the surface of the substrate 106). k It is possible to irradiate. kcan represent the area of ​​the illuminated region, or some other geometric property of the illuminated region. The diameter and / or area of ​​the kth illuminated region can be defined using any suitable scheme, as long as the same scheme is used across various spectral ranges. For example, the half-width or full-width of the continuous distribution of the kth spectral beam intensity can be used to define the diameter d k In some embodiments, the two illuminated areas A can be determined to be substantially the same. k and A m should have at least 90% (or 85%, 95%) overlap. m Area A outside k (and vice versa, area A k It should be less than 10% (or 15%, 5%) of the

[0019] In some embodiments, to have an achromatic broadband characteristic, the collimator assembly 120 generates at least two spectral beams that illuminate substantially the same area on the target surface. In some embodiments, to have an achromatic broadband characteristic, the collimator assembly 120 generates at least three spectral beams that illuminate substantially the same area on the target surface. In some embodiments, to have an achromatic broadband characteristic, the two spectral beams correspond to ranges separated by a center-to-center wavelength separation of at least 200 nm. In some embodiments, to have an achromatic broadband characteristic, the collimator assembly 120 generates at least three spectral beams that illuminate substantially the same area on the target surface. In some embodiments, the three spectral beams correspond to ranges separated by a wavelength separation of at least 400 nm between the centers of the two outermost ranges.

[0020] Light reflected from the target surface may pass back through the collimator assembly 120 and be collected by one or more second optical fibers. The second optical fibers may transmit this output light 126 to a photodetector 134 for spectral analysis. The photodetector 134 may include one or more spectrometers, spectrometers, diffraction gratings, mirrors, lenses, photodiodes, and other devices. The photodetector 134, alone or in conjunction with a processing device 136 (e.g., a central processing device (CPU), microcontroller, application specific integrated circuit (ASIC), digital signal processor (DSP), field programmable gate array (FPGA), or other type of processing device, etc.), may determine one or more optical responses of the target. The optical responses may include reflectance R(λ), refractive index n(λ), or other optical quantities that can be used to characterize the substrate (e.g., polarization dependence of reflectance, angle of rotation of the plane of polarization upon reflection, emission intensity, etc.).

[0021] The processing device 136 can be in communication with a memory device 138. In some embodiments, the memory device 138 stores instructions that the processing device 136 executes to cause the light source 132 to generate the input light 124, the light detector 134 to detect the output light 126, and to perform further operations that may be required for substrate processing. Such operations include starting, stopping, and / or restarting etching, lithography, or deposition operations. The processing device 136 may be the same processing device that controls operations within the processing chamber 102 or may be a separate, dedicated processing device of an endpoint detection system.

[0022] In some embodiments, the collimator assembly 120 includes a tilt adjustment mechanism 128 that allows adjustment of the collimator's optical axis (shown in dashed lines in FIG. 1 ) to facilitate centering (or recentering) the collimator after maintenance or to ensure chamber-to-chamber consistency when the collimator assembly 120 is moved to a different processing chamber. In some embodiments, the tilt adjustment mechanism 128 includes one or more adjustment screws to facilitate a configurable connection between the collimator assembly 120 and the processing chamber housing 104, as described below with reference to FIGS. 4-6 .

[0023] FIG. 2 schematically illustrates an exemplary achromatic (broadband) collimator assembly 200 for accurate optical characterization of targets in a processing chamber, according to some embodiments of the present disclosure. FIG. 2 is not drawn to scale and is intended as a schematic diagram only. Some additional elements known to those skilled in the art of optical detection technology may not be shown in FIG. 1 for clarity and brevity. However, these elements may actually be present in various embodiments. In some embodiments, the collimator assembly 200 corresponds to the collimator assembly 120 of FIG. 1. The collimator assembly 200 may include a collimator housing 202. The collimator housing 202 may include a chamber interface 204 for coupling the collimator assembly 200 to a processing chamber (e.g., processing chamber 102, etc.). In some embodiments, the chamber interface 204 may be permanently fused to the collimator housing 202 or may be an extension of the collimator housing 202. In some embodiments, the chamber interface 204 is removably attached to the collimator housing 202 by screws, or is retained in the collimator housing by friction or by retaining screws, pins, detents, etc. The chamber interface 204 can fit into a receiving orifice in the processing chamber housing 102 and can be sealed (by one or more gas-tight seals or gaskets) to the receiving orifice to prevent leakage of gases from the processing chamber environment. In some embodiments, the chamber interface 204 is sealed to an orifice in the processing chamber housing 102, thereby allowing the axis of the collimator housing 202 to tilt away from the vertical within set limits, but not destroying the separation of the internal atmosphere of the processing chamber from the external atmosphere of the environment.

[0024] The collimator housing 202 can define an enclosure that houses the various optical elements of the collimator assembly 200 (e.g., the achromatic (broadband) lens 210, the optical filler 212, the optical interface 214, etc.). As shown, the top of the collimator housing 202 has an opening through which one or more optical fibers 208 can be guided (to deliver the input light 124 and / or receive the output light 126) via conduits in a guide cap. In some embodiments, the optical fibers 208 can access the collimator assembly housing in different ways, for example, through a sidewall of the housing 202. The optical interface 214 can include an opening, a waveguide, a lens, etc. The optical interface 214 can be configured to allow the passage of light but prevent access of contaminants. For example, upon exiting the optical fiber 208, the input light 124 can pass through a slab (film) of optically transparent material or a diverging (converging) lens, which mechanically seals the optical fiber conduit.

[0025] The achromatic lens 210 may be a broadband lens designed to minimize chromatic aberration over a wide range of wavelengths. For example, the achromatic lens 210 may include multiple lenses made of different materials, some with higher refractive index dispersion and some with lower dispersion. In some embodiments, the achromatic lens 210 may be a doublet lens with two optical elements (e.g., a converging lens and a diverging lens). In some embodiments, as shown in FIG. 2, the achromatic lens 210 may be a triplet lens with three optical elements. In some embodiments, the achromatic lens 210 may have four or more optical elements. The achromatic lens 210 may be designed so that two, three, or more reference wavelengths Λ1, Λ2, Λ3, etc. have the same focal point (as shown in FIG. 1, some or all of the reference wavelengths may be center wavelengths used to characterize the light beam 122). This allows for minimal chromatic aberration even at wavelengths between the reference wavelengths. The focal lengths of the various elements of achromatic lens 210 can be selected so that input light delivered via optical fiber 208 becomes a parallel beam after passing through achromatic lens 210. In other embodiments, an (appropriately selected) distance between optical fiber 208 and achromatic lens 210 can be used to ensure that the output beam (e.g., beam 122-2) is collimated. In some embodiments, one or more lenses in optical interface 214 facilitate collimation.

[0026] In some embodiments, the achromatic lens 210 is held within the collimator housing 202 by a retaining ring. In some embodiments, the achromatic lens is threaded onto a threaded portion of the collimator housing 202. In some embodiments, the achromatic lens 210 is frictionally held by the collimator housing 202. For example, the diameter of the achromatic lens 210 can be precisely adjusted relative to the inner diameter of the enclosure formed by the collimator housing 202, ensuring that the lens is under sufficient lateral tension to create enough friction to hold the lens securely in place. In some embodiments, the space between the achromatic lens 210 and the optical interface 214 is filled with a transparent optical filler 212 to ensure the integrity of the optical path (e.g., minimize the presence of air, moisture, and other potential contaminants along the optical paths of the input and output optical signals).

[0027] FIG. 3 schematically illustrates the advantages of using an achromatic (broadband) collimator for accurate optical characterization of targets in a processing chamber compared to a conventional collimator, according to some embodiments of the present disclosure. FIG. 3A shows reflectance R(λ) data of a reference substrate obtained over a continuum of wavelengths λ ranging from near-UV to near-IR (e.g., the 200-800 nm range, in one example). The measurement data shown schematically in FIG. 3A is obtained using a conventional collimator without an achromatic lens. The dashed line shows the standard reflectance of the same reference substrate obtained by high-precision reflectance measurements in a laboratory setting using a high-quality light source and a light-detecting spectrometer. The solid line in FIG. 3A shows data obtained using a conventional collimator that generates uncontrolled beams (e.g., beam 122-1) for wavelengths with different spatial extents. As a comparison of the two curves shows, the measured reflectance is fairly close to the accurate standard reflectance in the UV range and the blue portion of the visible range, but with significantly less accuracy in the red portion of the visible spectrum and poorer in the IR range.

[0028] Figure 3B shows the reflectance R(λ) measured for the same standard substrate using a broadband collimator with an achromatic lens, as described above with reference to Figures 1-2. The improvement shown in Figure 3B results from illuminating the target substrate with a beam (e.g., beam 122-2) that has substantially the same spatial extent across the entire continuum of wavelengths λ used for target characterization. The table below shows the improvement in beam uniformity at several wavelengths.

[0029] [Table 1] Improved beam uniformity contributes to more accurate determination of R(λ). More accurate measurements of reflectivity enable the processing device 136 to accurately determine the current state of the processing operation (deposition, etch, etc.) being performed on the actual substrate in the processing chamber 102.

[0030] FIG. 3C is a depiction of the spatial extent of a conventional beam (e.g., beam 122-1, etc.) having two exemplary spectral components shown as visible light (e.g., 550 nm) and near-infrared light (e.g., 750 nm). The position shown on the horizontal axis may be the radial distance from the center of the beam. As shown, the spatial extents of the two spectral components (e.g., the distances corresponding to the half-widths of the beams) may be significantly different. In contrast, FIG. 3D is a depiction of the spatial extent of a beam (e.g., beam 122-2, etc.) output by a broadband collimator assembly (e.g., assembly 120) for the same two spectral components. As shown, the spatial extents of the two spectral components are substantially the same.

[0031] FIG. 4 schematically illustrates an exemplary collimator assembly 400 having adjustable alignment for accurate optical characterization of targets in a processing chamber, according to some embodiments of the present disclosure. FIG. 4 is not drawn to scale and is intended as a schematic diagram only. Some elements shown in FIG. 4 may be omitted in various embodiments. Some additional elements known to those skilled in the art of optical detection technology may not be shown in FIG. 4 for clarity and brevity, but may actually be present in various embodiments. In some embodiments, the collimator assembly 400 may be the collimator assembly 200 of FIG. 2. The collimator assembly 400 may be configured to optically couple to a processing chamber (e.g., processing chamber 102, etc.). The collimator assembly 400 may include a collimator housing 402. The collimator housing 402 may have a chamber interface 404 for coupling to the processing chamber. The chamber interface 404 may allow some variability (within set limits) in the direction of the collimator axis (which may also be the optical axis of the collimator contained within the enclosure formed by the collimator housing 402).

[0032] FIG. 5 schematically illustrates an exemplary tilted collimator assembly 500 with adjustable alignment for accurate optical characterization of targets within a processing chamber, according to some embodiments of the present disclosure. As shown in FIG. 5, the collimator axis 405 can be tilted at an angle θ from a reference axis 407 (shown as a dashed line). While FIG. 5 illustrates a vertical reference axis 407, in various embodiments, the orientation of the reference axis can have any other suitable direction. For example, in some embodiments in which the collimator assembly 400 is coupled to a sidewall of the processing chamber 102, the reference axis can be horizontal. The tilt angle shown in FIG. 5 is exaggerated for ease of illustration. In some embodiments, the maximum tilt angle can be 1° (or a fraction of 1°). In some embodiments, the tilt angle can be greater than 1° and can be limited by many factors, such as the anticipated need for a large tilt angle and the ability of a given chamber interface 404 to maintain an adequate gas seal in the processing chamber.

[0033] In some embodiments, the tilt adjustment mechanism includes one or more adjustment mechanisms 403 for controlling the tilt (alignment) of the collimator axis 405. As used herein, "adjustment mechanism" refers to any mechanical device (e.g., a screw, a bolt, a lever, a wedge, etc.) or combination of mechanical devices that can convert rotational motion of a control head (e.g., a screw head, a knob, etc.) into translational motion of a mechanical member (e.g., a screw shaft, a spring, a wedge, etc.). The mechanical member can interface between a movable portion of the collimator housing 402 and a stationary portion of the collimator housing. In some embodiments, the mechanical member directly interfaces between the movable portion of the collimator housing 402 and the process chamber housing 104 (or any portion attached thereto). In some embodiments, to precisely control the collimator tilt angle θ, the adjustment mechanism 403 can be equipped with a micrometer head or other device that provides appropriate feedback regarding the tilt angle and allows for repeatable adjustment of the collimator assembly 400.

[0034] Geometrically, any three arbitrarily positioned points define a plane, so in some embodiments, the number of adjustment mechanisms 403 is three. In some embodiments, the number of adjustment mechanisms 403 is less than three. For example, adjustment screw 403(1) can be replaced with a non-adjustable screw (or pin) that maintains fixed contact with the process chamber housing, but adjustment mechanisms 403(2) and 403(3) (not shown in FIGS. 4-5) can still allow fully adjustable tilt control. As a result, collimator axis 405 can still be tilted in two directions, allowing both a tilt θ of the collimator axis away from reference axis 407 and azimuthal rotation about the reference axis.

[0035] FIG. 6 schematically illustrates a side view 600 of an exemplary collimator assembly with adjustable alignment, according to some embodiments of the present disclosure. FIG. 6 is not drawn to scale and is intended as a schematic view only. Some elements shown in FIG. 6 may be omitted in various embodiments. Some additional elements known to those skilled in the art of optical detection technology may not be shown in FIG. 6 for clarity and brevity, but may actually be present in various embodiments. In some embodiments, the side view 600 may be of a collimator assembly whose top view 500 is shown in FIG. 5.

[0036] As shown in FIG. 6 , in some embodiments, the first housing support 602-1 can be rigidly attached to the collimator housing 602. The second housing support 602-2 can be attached to the process chamber housing (not shown). One or more tilt adjustment screws 603 can operably couple the first housing support 602-1 to the second housing support 602-2. In some embodiments, a tension spring 614 is used in conjunction with the illustrated adjustment screws 603. In some embodiments, the tension spring 614 is positioned at a different location than the adjustment screws 606. The tension spring 614 remains compressed, causing the total force applied (upward) to the first housing support 602-1 to be greater (in some embodiments, significantly greater) than the total weight of the collimator assembly. Such spring compression can stabilize the first support relative to the second support, advantageously preventing the collimator assembly from wobbling during operation of the endpoint detection device. Manipulation of one or more adjustment screws 603, similar to that described in connection with FIG. 4 above, can achieve a desired tilt of the optical axis of the collimator.

[0037] A tiltable gap 616 can be implemented to accommodate movement of the first housing support 602-1 relative to the second housing support 602-2. The tiltable gap 616 can extend symmetrically around the circumference of the housing 602 (if the housing has a cylindrical shape) or can be designed to be asymmetric. One or more tilt adjustment screws can be manipulated (e.g., by a human operator) to tilt the housing 602, allowing tilt freely until the body of the housing contacts the second housing support 602-2, preventing further adjustment. The amount of gap 616 can be set to allow a maximum predetermined tilt. For example, if the height of the second housing support 602-2 near the gap 616 is 0.3 inches, a gap of 0.005 can allow tilt of up to 1° from a reference (e.g., vertical) orientation (in addition to a full 360° azimuth tilt).

[0038] FIG. 7 is a flowchart of one possible embodiment of a method 700 for deploying a broadband collimator assembly for accurate optical characterization of a target in a processing chamber, in accordance with some embodiments of the present disclosure. In some embodiments, the broadband collimator assembly is spatially adjustable. Method 700 can be performed using the systems and components described in FIGS. 1-6 , or any combination thereof. In some embodiments, some or all of the blocks of method 700 can be performed in response to instructions from processing device 136. Processing device 136 can be coupled to one or more memory devices 138. In some embodiments, method 700 can be performed while a substrate is being processed in processing chamber 102. In some embodiments, method 700 can be performed while a calibration device or reference substrate is in processing chamber 102.

[0039] Method 700 may include outputting an optical signal with a light source (operation 710). In some embodiments, a processing device (e.g., device 136) causes the light source to output the optical signal. In other embodiments, a human operator outputs the optical signal. The optical signal may have a broad spectral distribution (or may be a collection of multiple narrow band distributions). The optical signal may have many wavelength ranges (e.g., λj-Δλj / 2, λj+Δλj / 2, where j=1, 2, 3...). Each range may be characterized by a center wavelength and a width Δλj. Each range may include multiple spectral components. Because the spectral components may represent a continuum (which may be characterized by a Fourier integral), the number of components within each range may be very large, or even infinite.

[0040] In operation 720, the method 700 may continue by directing a first plurality of spectral components of light belonging to the interval [λ1-Δλ1 / 2, λ1+Δλ1 / 2] onto the target surface to illuminate a first area on the target surface. Similarly, in operation 730, the method 700 may continue by directing a second plurality of spectral components of light belonging to the interval [λ2-Δλ2 / 2, λ2+Δλ2 / 2] onto the target surface to illuminate a first area on the target surface. The first and second plurality of spectral components may be transmitted via a first optical fiber(s) to a broadband collimator. The collimator may include an achromatic lens. After passing through the broadband collimator, the first beam (which may be a collimated beam, a converging beam, or a diverging beam) including the first plurality of spectral components may have substantially the same cross-section as the second beam including the second plurality of spectral components. As a result, a first area on a surface of a target (e.g., a substrate being etched or otherwise processed) illuminated by the first beam can be substantially the same as a second area on the target surface illuminated by the second beam. Operations 720 and 730 can be performed in any order. In some embodiments, operations 720 and 730 can be performed simultaneously. In some embodiments, operations 720 and 730 can be performed sequentially.

[0041] Each beam directed toward the target surface counter-propagates through a collimator, is received by one or more second optical fibers, and is sent to a photodetector. More specifically, in operation 740, a first reflected beam (comprising a first plurality of spectral components of the light reflected from the target surface) can be collected by a second optical fiber. Similarly, in operation 750, a second reflected beam (comprising a second plurality of spectral components of the light reflected from the target surface) can be collected by a second optical fiber. The first (second) reflected beam can be generated by the first (second) plurality of spectral components of the light incident on the target surface. Operations 740 and 750 can be performed in any order. In some embodiments, operations 740 and 750 can be performed simultaneously. In some embodiments, operations 740 and 750 can be performed sequentially, one after the other.

[0042] In operation 760, method 700 may continue with receiving, via a photodetector, the first plurality of reflected spectral components of light and the second plurality of reflected spectral components of light via the second optical fiber. In operation 770, the photodetector (in some embodiments, in conjunction with a processing device and / or memory) may determine a reflectance at the target surface based on the first plurality of reflected spectral components of light received and the second plurality of reflected spectral components of light received. In some embodiments, the reflectance may be determined across a first range of wavelengths and across a second range of wavelengths. In some embodiments, additional (e.g., third, fourth, etc.) wavelength ranges may be further used in a manner similar to that described above to obtain a more accurate characterization of the target surface. In some embodiments, the first range is within the 400-700 nm interval of wavelengths, and the second range is outside the 400-700 nm interval of wavelengths. In some embodiments, the third range is outside the 400-700 nm interval of wavelengths and is different from the second range. In some embodiments, the second (or third) range is within the interval of 100-400 nm, and the third (second) range is within the wavelength range of 700-900 nm.

[0043] 8 is a flowchart of one possible embodiment of a method 800 for adjusting the tilt of an adjustable collimator assembly for accurate optical characterization of a target in a processing chamber, according to some embodiments of the present disclosure. In some embodiments, method 800 is performed using the systems and components described in FIGS. 1-6 , or any combination thereof. In some embodiments, some or all of the blocks of method 800 may be performed in response to instructions from processing device 136.

[0044] In operation 810, method 800 can detect a processing chamber setup event. For example, a processing chamber may have been serviced (e.g., scheduled or unscheduled maintenance performed), one or more components of a processing chamber may have been replaced, or a collimator assembly may have been moved and coupled to a different chamber. In some embodiments, a "setup event" can be a setup check event that is not associated with a setup change, but may indicate a scheduled periodic checkup (or a checkup requested by a human operator).

[0045] In operation 820, the method 800 may continue by outputting an incident light beam through an (adjustable) collimator assembly onto a target. For example, one or more light sources may generate the light beam. The light beam is sent to the collimator assembly (e.g., via one or more input optical fibers) and, after passing through the optical components of the collimator assembly, is directed onto the target. The target may be a calibration device, a standard substrate with known optical properties, or a regular substrate to be processed (e.g., etched) provided that its optical properties are known.

[0046] The incident beam can cause the target to generate a reflected beam. The reflected beam can pass through the collimator optics (in the reverse direction) and be sent to a photodetector via one or more output optical fibers. In operation 830, the photodetector can determine the intensity of the reflected beam. In operation 840, a processing device in communication with the photodetector and the memory device can retrieve calibration data for the target from the memory device. In some embodiments, the calibration data can include the reflectivity of the target as a function of the angle of incidence of the incident beam. In operation 850, method 800 can continue with the processing device performing a comparison of the intensity data obtained from the photodetector with the calibration data retrieved from the memory device. As a result, the processing device can determine the degree of misalignment of the collimator assembly (e.g., due to a performed process chamber setup change). For example, the reflectivity may decrease (or increase) with the degree of misalignment.

[0047] In operation 860, the method 800 can output a tilt adjustment value to be applied to a tilt adjustment mechanism of the collimator assembly to correct the determined misalignment of the collimator assembly. The output value can be accessed by a human operator who corrects the alignment of the collimator assembly taking the output value into account.

[0048] FIG. 9 illustrates a block diagram of an exemplary processing device 900 that operates in accordance with one or more aspects of the present disclosure. In one embodiment, the processing device 900 may be the processing device 136 of FIG. 1 . The exemplary processing device 900 may be connected to other processing devices within a LAN, an intranet, an extranet, and / or the Internet. The processing device 900 may be a personal computer (PC), a set-top box (STB), a server, a network router, switch, or bridge, or any device capable of executing a set of instructions (sequential or otherwise) that specify actions to be performed by the device. Furthermore, while only a single exemplary processing device is shown, the term “processing device” is intended to include any collection of processing devices (e.g., computers) that individually or jointly execute a set (or sets) of instructions to perform any one or more of the methodologies described herein.

[0049] The exemplary processing device 900 may include a processor 902 (e.g., a CPU), a main memory 904 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM), etc.), a static memory 906 (e.g., flash memory, static random access memory (SRAM), etc.), and a secondary memory (e.g., a data storage device 918), which may communicate with each other via a bus 930.

[0050] Processor 902 represents one or more general-purpose processing devices (e.g., microprocessors, central processing devices, etc.). More specifically, processor 902 may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor executing other instruction sets, or a processor embodying a combination of instruction sets. Processor 902 may also be one or more special-purpose processing devices (e.g., an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, etc.). In accordance with one or more aspects of the present disclosure, processor 902 may be configured to execute instructions for performing method 700 of deploying a broadband collimator assembly for accurate optical characterization of a target in a processing chamber and / or method 800 of adjusting the tilt of an adjustable collimator assembly.

[0051] Additionally, the exemplary processing device 900 may include a network interface device 908 that may be communicatively coupled to a network 920. Additionally, the exemplary processing device 900 may include a video display 910 (e.g., a liquid crystal display (LCD), a touch screen, or a cathode ray tube (CRT)), an alphanumeric input device 912 (e.g., a keyboard), an input control device 914 (e.g., a cursor control device, a touch screen control device, a mouse), and a signal generation device 916 (e.g., an audio speaker).

[0052] The data storage device 918 can include a computer-readable storage medium (or, more specifically, a non-transitory computer-readable storage medium) 928 having stored thereon one or more sets of executable instructions 922. In one or more aspects of the present disclosure, the executable instructions 922 can include executable instructions for performing the method 700 of deploying a broadband collimator assembly for accurate optical characterization of a target in a processing chamber and / or the method 800 of adjusting the tilt of an adjustable collimator assembly.

[0053] Additionally, the executable instructions 922 may reside, completely or at least partially, within the exemplary processing device 900, the main memory 904, and the processor 902 during execution by the processor 902, which constitute computer-readable storage media. Additionally, the executable instructions 922 may be transmitted or received over a network via the network interface device 908.

[0054] Although computer-readable storage medium 928 is shown in Figure 9 as a single medium, the term "computer-readable storage medium" should be interpreted to include a single medium or multiple media (e.g., centralized or distributed databases, and / or associated caches and servers) that store one or more sets of operating instructions. The term "computer-readable storage medium" should also be interpreted to include any medium that can store or encode a set of instructions for execution by a machine that performs any one or more of the methodologies described herein. Accordingly, the term "computer-readable storage medium" should be interpreted to include, but is not limited to, solid-state memory, optical and magnetic media.

[0055] It should be understood that the above description is intended to be illustrative, and not limiting. Many other embodiments will become apparent to those skilled in the art upon reading and understanding the above description. While the present disclosure describes particular examples, it is recognized that the disclosed systems and methods are not limited to the examples set forth herein, but can be modified and practiced within the scope of the appended claims. Accordingly, the specification and drawings should be regarded in an illustrative, rather than a restrictive, sense. The scope of the present disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

[0056] The above method, hardware, software, firmware, or code embodiments may be implemented via instructions or code stored on a machine-accessible, machine-readable, computer-accessible, or computer-readable medium that is executable by a processing element. "Memory" includes any mechanism that provides (i.e., stores and / or transmits) information in a form readable by a machine (e.g., a computer or electronic system). For example, "memory" includes random access memory (RAM), such as static RAM (SRAM), dynamic RAM (DRAM), ROM, magnetic or optical storage media, flash memory devices, electronic recording devices, optical storage devices, acoustic storage devices, and any type of tangible machine-readable medium suitable for storing or transmitting electronic instructions or information in a form readable by a machine (e.g., a computer).

[0057] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrase "one embodiment" or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0058] In the foregoing specification, a detailed description has been given with reference to certain exemplary embodiments. However, it will be apparent that various modifications and changes can be made therein without departing from the broader spirit and scope of the present disclosure as set forth in the appended claims. Accordingly, the specification and drawings should be interpreted in an illustrative rather than a restrictive sense. Furthermore, the previous use of the terms embodiment and / or other example does not necessarily mean the same embodiment or the same example, but may potentially mean the same embodiment and different embodiments.

[0059] The terms "example" or "exemplary" are used herein to mean serving as an example, instance, or example. Any aspect or design described herein as "example" or "exemplary" should not necessarily be construed as preferred or advantageous over other aspects or designs. Rather, use of the term "example" or "exemplary" is intended to present concepts in a concrete manner. The term "or" as used herein is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless otherwise specified or clear from the context, "X includes A or B" is intended to mean any of the natural inclusive permutations. That is, if X includes A, if X includes B, or if X includes both A and B, then "X includes A or B" is satisfied by any of the aforementioned examples. Furthermore, the articles "a" and "one," as used in this application and the appended claims, should be construed generally to mean "one or more" unless otherwise specified or clear from the context to refer to the singular form. Furthermore, use of the terms "embodiment" or "one embodiment" is not intended to refer to the same embodiment or embodiments unless so described. Also, as used herein, terms such as "first," "second," "third," "fourth," etc. are intended as labels to distinguish between different elements and may not necessarily have an ordinal meaning according to their numerical designations.

Claims

[Claim 1] 1. A collimator assembly comprising: A collimator housing, an interface configured to optically couple to a process chamber having a target surface; a collimator housing having a port for receiving a first optical fiber that transmits a first plurality of spectral components of light belonging to a first range of wavelengths and a second plurality of spectral components of light belonging to a second range of wavelengths to an enclosure formed by the collimator housing, the first range being within the 400-700 nm interval of wavelengths and the second range being outside the 400-700 nm interval of wavelengths; an achromatic lens disposed at least partially within an enclosure formed by the collimator housing, directing a first plurality of spectral components of light onto a target surface to illuminate a first area on the target surface; A collimator assembly having an achromatic lens for directing a second plurality of spectral components of the light onto the target surface to illuminate a second area on the target surface, the second area being substantially the same as the first area.

Images