Adjustable achromatic collimator assembly for an end point detection system

Abstract

The disclosed embodiments disclose a collimator assembly including a collimator housing including an interface configured to optically couple to a process chamber having a target surface, a port for receiving an optical fiber that transmits a first (second) plurality of spectral components of light belonging to a first (second) range of wavelengths to an enclosure formed by the collimator housing, and an achromatic lens at least partially disposed within the enclosure formed by the collimator housing, wherein the achromatic lens directs the first (second) plurality of spectral components of light toward the target surface to illuminate a first (second) area on the target surface, the second area being substantially the same as the first area.

Description

Technical Field

[0001] This specification generally relates to the manufacture of integrated circuits and other semiconductor devices within a processing chamber. More specifically, this specification relates to an adjustable endpoint detection system for accurate product control in device manufacturing. Background

[0002] The manufacture of microelectronics and integrated circuit devices often requires performing numerous operations on semiconductor, dielectric, and conductive substrates. Examples of these operations include oxidation, diffusion, ion implantation, thin film deposition, cleaning, etching, lithography, and the like. Materials produced in this way may include single crystals, semiconductor films, fine coatings, and many other substances used in the manufacture of electronic devices and other practical applications. When selected types of atoms are added to (e.g., by evaporation, etc.) or removed from (e.g., by etching, etc.) the substrate, efficient and accurate endpoint monitoring techniques (and systems) become important. Undereetching and overetching (similarly, underdeposition and overdeposition) can cause substandard devices and even malfunction. An optical control system that can monitor various stages of device manufacturing in real time can significantly improve product quality. This is particularly useful considering that the requirements for the quality of semiconductor devices are constantly increasing. Summary

[0003] In one embodiment, a collimator assembly including a collimator housing and an achromatic lens is disclosed. The collimator housing includes an interface configured to optically couple to a processing chamber having a port for receiving the target surface and an optical fiber. The optical fiber sends 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 into an enclosure formed by the collimator housing. 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 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 and irradiates a first region on the target surface. Further, the achromatic lens directs the second plurality of spectral components of light onto the target surface and irradiates a second region of the target surface, and the second region is substantially the same as the first region.

[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 wavelength interval, and the second range is outside the 400 - 700 nm wavelength interval. The collimator housing includes an interface configured to optically couple to a processing chamber having a target surface. The collimator housing also includes a port for receiving an optical fiber for sending a first plurality of spectral components of light belonging to the first range of wavelengths and a second plurality of spectral components of light belonging to the second range of wavelengths into 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 a first plurality of spectral components of light onto the target surface, irradiating a first region on the target surface, and directs a second plurality of spectral components of light onto the target surface, irradiating a second region on the target. The second region is substantially the same as the first region. A 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 onto the target surface. Further, 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 onto the target surface. The photodetector receives a first plurality of reflected spectral components of light and a 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 other embodiments, a method is disclosed for outputting, by a light source, 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 wavelength interval, and the second range is outside the 400 - 700 nm wavelength interval. Further, the disclosed method directs, via an achromatic lens, the first plurality of spectral components of light to a target surface to irradiate a first region on the target surface. Further, the disclosed method directs, via an achromatic lens, the second plurality of spectral components of light to the target surface to irradiate a second region on the target surface, where the second region is substantially the same as the first region. Further, the disclosed method collects, by a second optical fiber, a 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. Further, the disclosed method collects, by a second optical fiber, a second plurality of spectral components of light reflected from the target surface that are generated by the second plurality of spectral components of light directed to the target surface. Further, the disclosed method is to receive, by a photodetector via the second optical fiber, the first plurality of reflected spectral components of light and the second plurality of reflected spectral components of light. The disclosed method further 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 by a processing device communicatively coupled to the photodetector.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3A

Figure 3D

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

[0007] The embodiments disclosed herein provide accurate broadband optical endpoint control in semiconductor device manufacturing. The embodiments enable sending an optical beam having a uniform spatial profile over a wide range of wavelengths into a processing chamber. For example, the width of the beam enables the 250 nm spectral component of the beam to be the same as the 750 nm spectral component of the beam. The spatial uniformity of the beam can be achieved by sending an optical signal through a collimator equipped with a broadband achromatic lens. This enhanced uniformity enables a more accurate measurement of the optical response of a target (e.g., a substrate, etc.) in the processing chamber (compared to a collimator equipped with conventional optical elements), and thus enables a more accurate determination of the target state (e.g., during etching or deposition of a substrate).

[0008] Furthermore, the collimator can be equipped with a fine adjustment mechanism that adjusts the alignment of the optical axis of the collimator to maximize the delivery efficiency of the incident light to the intended area on the target located in the processing chamber. In some embodiments, after maintenance of the processing chamber is performed, the adjustment mechanism can be used to compensate for small changes in the position of the processing tool caused by disassembly, reassembly, and / or recalibration of the tool (e.g., fluctuations in the position of the chuck for wafer support, etc.).

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

[0010] Changes in the reaction environment (e.g., composition, temperature, plasma density, etc.) or differences in the photomask pattern may cause changes in the etching rate and uniformity. Tracking and addressing such changes may require an accurate and adjustable optical endpoint system capable of collecting accurate and substantial optical response data characterizing various target surfaces (wafer, photomask, etc.) within the processing chamber. Furthermore, the goal of precision is being driven by the miniaturization of microelectronic devices, the increasingly complex design of photomasks, and the growing requirements for device uniformity. Existing optical systems for endpoint control often cannot meet such increasing technical requirements.

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

[0012] The disclosed embodiments relate to various manufacturing techniques that use processing chambers (which can include deposition chambers, etching chambers, etc.) such as, for example, chemical vapor deposition techniques (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 shows a manufacturing apparatus 100 including a spatially adjustable broadband collimator assembly for accurate optical property evaluation of a target within a processing chamber, according to 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 one or more substrates 106 (e.g., deposition, lithography, etching, etc.). During processing, the substrate 106 is exposed to a plasma environment 110 for plasma enhanced processing (e.g., etching). The substrate 106 can be supported by a chuck 108. The processing chamber 102 can include one or more process kit tools 112 (e.g., edge rings, etc.). The substrate 106 can be lifted by lift pins (not shown) to achieve targeted exposure of the backside of the substrate 106 to the processing environment and can heat the substrate 106 (e.g., by applying light).

[0014] The processing of the substrate 106 within 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 (either rigidly or operatively as described below) to the processing chamber housing 104 and can optically interface with the environment of the processing chamber (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 not have 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" means electromagnetic radiation in any spectral range, including visible, near and far infrared (IR), near and far ultraviolet (UV), etc. Further, "light" can include non-polarized (natural) light, linearly, circularly, or elliptically polarized light, partially polarized light, focused light, divergent light, collimated light, etc.

[0015] The light beam 122 can be generated by the collimator assembly 120 from the input light 124 generated by the light source 132. In some embodiments, the input light 124 is sent via one or more input optical fibers. The light source 132 can be a narrow-band light source such as a light-emitting diode, a laser, an incandescent bulb, etc. In some embodiments, the light source 132 is a broad-band light source. In some embodiments, the light source 132 includes two or more component light sources such as a plurality of narrow-band light sources that (when combined) generate the broad-band input light 124. The light source 132 includes additional optical elements (e.g., filters, absorbers, polarizers, etc.) for controlling the spectrum and can control the spectral dispersion and / or polarization of the input light 124.

[0016] In some embodiments, the input light 124 is converted by the collimator assembly 120 into the light beam 122, for example, by passing the input light 124 through a plurality of optical elements (such as lenses, reflectors, filters, apertures, etc.) of the collimator assembly 120. The collimator assembly 120 may have broadband characteristics. More specifically, the collimator assembly 120 can generate a light beam 122 whose spatial extent can be the same for a plurality of spectral components of the beam (as will be described in more detail below). For example, the diameter of the generated light beam 122 can be the same within a wide band of wavelengths λ of the various spectral components included in the input light 124, and thus can be within the light beam. In existing endpoint detection systems, the diameter of the conventional light beam 122-1 varies with the wavelength λ. For example, the green component (λ = 550 nm) can have a diameter of 9 mm, and the red component (λ = 650 nm) can have a diameter of 13 mm. (This is schematically shown in FIG. 1 with a different shading in the depiction of the conventional light beam 122-1.) As a result, different spectral components propagate along different optical paths. This can lead to significant errors in the reflectivity R(λ) of the resulting substrate, and thus can lead to an incorrect characterization of the target (e.g., the surface of the substrate 106) and errors in the etching process (e.g., the etching stops 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 for various spectral components λ of the light beam 122. This is schematically shown in FIG. 1 as having a uniformly white cross-section of the achromatic beam 122-2. To achieve the output of such a broadband color achromatic light beam, the collimator assembly 120 can have one or more achromatic lenses, which will be described in more detail below with reference to FIG. 2. More specifically, the achromatic beam 122-2 can be characterized by specifying the spectral components of the beam for a plurality of spectral ranges Δλ (or, for example, 150 nm, 200 nm, or any other wavelength range) such as a width Δλ = 100 nm. The spectral ranges can be centered about a series of central wavelengths λ1, λ2, λ3,.... In some embodiments, the ranges overlap with a Δλ that is 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 central wavelengths (and 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 emitters of the light source 132 (e.g., the emission range of the light-emitting diodes of the light source 132). In other embodiments, the range Δλ is defined only for the purpose of characterization and may not be limited to a particular physical emitter.

[0018] λ k Range Δλ centered about k The spectral components within can propagate in the form of a spectral beam of a certain diameter d k (For simplicity, the beam is described as having a circular cross-section. However, 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 k-th spectral beam can irradiate the k-th region A k on the target surface (e.g., the surface of the substrate 106). Designation A kcan represent the area of the irradiated region or some other geometric characteristic of the irradiated region. The diameter and / or area of the k-th irradiation region can be defined using any suitable scheme as long as the same scheme is used across various spectral ranges. For example, the diameter d can be determined using the full width at half maximum or the full width of the continuous distribution of the k-th spectral beam intensity. k In some embodiments, two irradiation regions A k and A m should have at least 90% (or 85%, 95%) overlap. That is, the portion of region A m that is outside region A k (and vice versa) should be less than 10% (or 15%, 5%) of region A k .

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

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

[0021] The processing device 136 can communicate with the 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, cause the photodetector 134 to perform the detection of the output light 126, and perform further operations that may be required for substrate processing. Such operations include the start, stop, and / or resumption of etching, lithography, or deposition operations. The processing device 136 may be the same processing device that controls the operations within the processing chamber 102 or may be a separate dedicated processing device for the endpoint detection system.

[0022] In some embodiments, the collimator assembly 120 includes an inclination adjustment mechanism 128 that enables adjustment of the optical axis of the collimator (shown by the dashed line in FIG. 1), facilitating centering (or re-centering) of the collimator after maintenance or ensuring chamber-to-chamber consistency when the collimator assembly 120 is moved to a different processing chamber. In some embodiments, as described below with reference to FIGS. 4-6, the inclination adjustment mechanism 128 includes one or more adjustment screws and facilitates a configurable connection between the collimator assembly 120 and the processing chamber housing 104.

[0023] FIG. 2 schematically shows an exemplary achromatic (broadband) collimator assembly 200 for accurate optical property evaluation of a target within a processing chamber, according to some embodiments of the present disclosure. FIG. 2 is not drawn to scale and is intended only as a schematic. Some additional elements known to those skilled in the art of optical detection techniques may not be shown in FIG. 1 for clarity and simplicity. However, these elements may actually exist in various embodiments. In some embodiments, the collimator assembly 200 corresponds to the collimator assembly 120 of FIG. 1. The collimator assembly 200 can have a collimator housing 202. The collimator housing 202 can have 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 held to the collimator housing by friction, or retaining screws, pins, detents, etc. The chamber interface 204 can be adapted to a receiving orifice within the processing chamber housing 102 and can seal against the receiving orifice (by one or more gas-tight seals or gaskets) to prevent leakage of gas from the environment of the processing chamber. In some embodiments, the chamber interface 204 is sealed to the orifice of the processing chamber housing 102, thereby allowing the axis of the collimator housing 202 to tilt away from the vertical within set limits, without breaking 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 various optical elements of the collimator assembly 200 (e.g., an achromatic (broadband) lens 210, an optical filler 212, an optical interface 214, etc.). As shown, the upper portion of the collimator housing 202 has an opening and can guide one or more optical fibers 208 (for sending input light 124 and / or receiving output light 126) through a conduit within the guide cap. In some embodiments, the optical fibers 208 can be accessed in different ways to the housing of the collimator assembly, for example, through the 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 while preventing the access of contaminants. For example, as the input light 124 exits the optical fiber 208, it can pass through a slab (film) of an optically transparent material or a diverging (converging) lens, which mechanically seals the connector of the optical fiber.

[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 can have a plurality of lenses formed of different materials, with some materials having a higher dispersion of refractive index and some materials having a lower dispersion. In some embodiments, the achromatic lens 210 may be a doublet lens having 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 having three optical elements. In some embodiments, the achromatic lens 210 can have four or more optical elements. The achromatic lens 210 may be designed such that two, three, or more reference wavelengths Λ1, Λ2, Λ3... have the same focal point (as shown in FIG. 1, some or all of the reference wavelengths may be the central wavelength used to characterize the light beam 122). Thereby, chromatic aberration can be kept small even for wavelengths between the reference wavelengths. The focal lengths of the various elements of the achromatic lens 210 can be selected such that the input light delivered via the optical fiber 208 becomes a parallel beam after passing through the achromatic lens 210. In other embodiments, the (appropriately selected) distance between the optical fiber 208 and the 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 of the 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 screwed into the screw portion of the collimator housing 202. In some embodiments, the achromatic lens 210 is held by friction 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 such that a lateral tension sufficient to generate enough friction to firmly hold the lens in place is applied to the lens. 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 coherence of the optical path (e.g., minimizing the presence of air, moisture, and other possible contaminants along the optical paths of the input and output optical signals).

[0027] Figure 3 schematically shows the advantages of using an achromatic (broadband) collimator for accurate optical characterization of a target within a processing chamber as compared to a conventional collimator, according to some embodiments of the present disclosure. Figure 3A shows the reflectivity R(λ) data of a reference substrate obtained for a continuum of wavelengths λ in the range from near UV to near IR (in one example, in the range of 200 - 800 nm, etc.). The measurement data schematically shown in Figure 3A was obtained using a conventional collimator without an achromatic lens. The dashed line shows the standard reflectivity of the same reference substrate obtained by high-precision reflectivity measurements in a laboratory setting using a high-quality light source and a photodetector spectrometer. The solid line in Figure 3A shows data obtained using a conventional collimator that generates a beam (such as beam 122-1) that is not controlled for different wavelengths over a spatial range. As the comparison of the two curves shows, the measured reflectivity is fairly close to the accurate standard reflectivity in the UV range and the blue part of the visible range, but the accuracy significantly degrades in the red part of the visible spectrum and is poor in the IR range.

[0028] FIG. 3B shows the result of measuring the reflectance R(λ) for the same standard substrate using a broadband collimator equipped with an achromatic lens, as described above with reference to FIGS. 1-2. The improvement shown in FIG. 3B results from irradiating the target substrate with a beam (e.g., beam 122-2) having a substantially same spatial extent over the entire continuum of wavelengths λ used for target characterization. The following table shows the improvement in beam uniformity at several wavelengths.

[0029]

Table 1

[0030] FIG. 3C depicts 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 extent (e.g., the distance corresponding to the half-width of the beam) of the two spectral components may be significantly different. In contrast, FIG. 3D depicts 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 extent of the two spectral components is substantially the same.

[0031] FIG. 4 schematically shows an exemplary collimator assembly 400 having an adjustable alignment for accurate optical characterization of a target within a processing chamber, according to some embodiments of the present disclosure. FIG. 4 is not drawn to scale and is intended only as a schematic. Some of the elements shown in FIG. 4 may be omitted in various embodiments. Some additional elements known to those skilled in the art of optical detection techniques may not be shown in FIG. 4 for clarity and brevity, but may in fact 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 can be configured to be optically coupled to a processing chamber (e.g., processing chamber 102, etc.). The collimator assembly 400 can include a collimator housing 402. The collimator housing 402 can have a chamber interface 404 for coupling to the processing chamber. The chamber interface 404 can allow for 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 shows an exemplary collimator assembly 500 with adjustable alignment for accurate optical property evaluation of a target 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). Although FIG. 5 shows 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 where the collimator assembly 400 is coupled to the sidewall of the processing chamber 102, the reference axis may be horizontal. The tilt angle shown in FIG. 5 is exaggerated for simplicity of explanation. In some embodiments, the maximum tilt angle may be 1° (or a fraction of 1°). In some embodiments, the tilt angle may 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 a proper 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, an “adjustment mechanism” means any mechanical device (e.g., screw, bolt, lever, wedge, etc.) or combination of mechanical devices that can convert the rotational movement of a control head (e.g., the head of a screw, a knob, etc.) into the translational movement of a mechanical member (e.g., the shaft of a screw, a spring, a wedge, etc.). The mechanical member can interface between a movable part of the collimator housing 402 and a stationary part of the collimator housing. In some embodiments, the mechanical member interfaces directly between a movable part of the collimator housing 402 and the processing chamber housing 104 (or any part attached thereto). In some embodiments, in order to accurately control the tilt angle θ of the collimator, the adjustment mechanism 403 can be loaded with a micrometer head or other device that provides appropriate feedback regarding the tilt angle and enables reproducible adjustment of the collimator assembly 400.

[0034] Geometrically, any three arbitrarily placed points define a plane, and thus, 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 processing chamber housing, while adjustment mechanisms 403(2) and 403(3) (not shown in FIGS. 4-5) can nevertheless enable fully adjustable tilt control. As a result, the collimator axis 405 can still be tilted in two directions, enabling both the tilt θ of the collimator axis away from the reference axis 407 and the azimuthal rotation around the reference axis.

[0035] FIG. 6 schematically shows a side view 600 of an exemplary collimator assembly having adjustable alignment, according to some embodiments of the present disclosure. FIG. 6 is not drawn to scale and is intended only as a schematic. Some of the elements shown in FIG. 6 may be omitted in various embodiments. Some additional elements known to those skilled in the art of optical detection techniques 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 that of the collimator assembly for which the 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 a processing 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 with the adjustment screw 603 shown. In some embodiments, the tension spring 614 is disposed at a location different from the location of the adjustment screw 606. The tension spring 614 remains in a compressed state, whereby all the forces applied (upward) to the first housing support 602-1 are greater than (substantially greater in some embodiments) the total weight of the collimator assembly. Such spring compression can advantageously stabilize the first support relative to the second support and prevent the collimator assembly from wobbling during operation of the end point detection device. Operation of one or more adjustment screws 603 can achieve the desired tilt of the optical axis of the collimator, similar to the operation described in connection with FIG. 4 above.

[0037] To accommodate movement of the first housing support 602-1 relative to the second housing support 602-2, a tiltable gap 616 can be implemented. The tiltable gap 616 can extend symmetrically around the circumference of the housing 602 (when the housing has a cylindrical shape) or can be designed to be asymmetric. One or more tilt adjustment screws are operated (e.g., by a human operator), and as a result the housing 602 tilts, allowing the body of the housing to freely contact the second housing support 602-2 until further adjustment of the tilt is blocked. The amount of the 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 a tilt of up to 1° from a reference (e.g., vertical) direction (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 property evaluation of a target within a processing chamber, according to some embodiments of the present disclosure. In some embodiments, the broadband collimator assembly is spatially adjustable. Method 700 can be implemented 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 implemented in response to instructions from a processing device 136. The processing device 136 can be coupled to one or more memory devices 138. In some embodiments, method 700 can be implemented while a substrate is being processed in the processing chamber 102. In some embodiments, method 700 can be implemented while a calibration device or a reference substrate is within the processing chamber 102.

[0039] Method 700 can include outputting an optical signal by 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 can have a broad spectral distribution (or can be a collection of multiple narrow band distributions). The optical signal can have a range of many wavelengths (e.g., λj - Δλj / 2, λj + Δλj / 2, where j = 1, 2, 3...). Each range can be characterized by a central wavelength and a width Δλj. Each range can include a plurality of spectral components. Since the spectral components can represent a continuum (which can be characterized by a Fourier integral), the number of components within each range can be very large or infinite.

[0040] In operation 720, method 700 can 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 and irradiating a first region on the target surface. Similarly, in operation 730, method 700 can 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 and irradiating a first region on the target surface. The first plurality of spectral components and the second plurality of spectral components can be sent to a broadband collimator via one or more first optical fibers. The collimator can have an achromatic lens. After passing through the broadband collimator, a first beam (which can be a collimated beam, a focused beam, or a divergent beam) including the first plurality of spectral components can have a cross-section substantially the same as that of a second beam including the second plurality of spectral components. As a result, a first region on the surface of the target (e.g., a substrate to be processed by etching or other methods) irradiated by the first beam can be made substantially the same as a second region on the target surface irradiated 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 and continuously.

[0041] Each beam directed at the target surface is backpropagated through a collimator, received by a (one or more) second optical fiber, and sent to a photodetector. More specifically, in operation 740, a first reflected beam (including 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 (including 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 can continue with receiving, by a photodetector, via a second optical fiber, a first plurality of reflected spectral components of light and a second plurality of reflected spectral components of light. In operation 770, the photodetector (in some embodiments, in cooperation with a processing device and / or memory) can determine a reflectance at the target surface based on the first plurality of reflected spectral components of the received light and the second plurality of reflected spectral components of the received light. In some embodiments, the reflectance can be determined for an entire first range of wavelengths and an entire second range of wavelengths. In some embodiments, additional (e.g., third, fourth, etc.) wavelength ranges can be further used in a manner similar to the method 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 100 - 400 nm interval, and the third (second) range is within the 700 - 900 nm of wavelengths.

[0043] FIG. 8 is a flowchart of one possible embodiment of a method 800 for adjusting the tilt of a collimator assembly adjustable for accurately evaluating the optical characteristics of a target within 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 can be performed in response to instructions from a processing device 136.

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

[0045] In operation 820, method 800 can then output an incident light beam to a target via an (adjustable) collimator assembly. For example, one or more light sources can generate a light beam. The light beam is sent to the collimator assembly (e.g., via one or more input optical fibers), passes through the optics of the collimator assembly, and is then directed at the target. The target may be a calibration device, a standard substrate with known optical properties, or a normal substrate scheduled to receive a process (e.g., etching) provided that its optical properties are known.

[0046] The target can generate a reflected beam by the incident beam. The reflected beam can pass through the optical components of the collimator (in the reverse direction) and can 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 communicating with the photodetector and the memory device can retrieve calibration data of the target from the memory device. In some embodiments, the calibration data can include the reflectivity of the target as a function of the incident angle of the incident beam. In operation 850, method 800 can continue with the processing device performing a comparison between the intensity data obtained from the photodetector and 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 changes in the processing chamber setup performed). For example, the reflectivity may decrease (or increase) with the degree of misalignment.

[0047] In operation 860, method 800 can output a tilt adjustment value applied to the 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 considering the output value.

[0048] FIG. 9 shows 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 can be connected to other processing devices within a LAN, intranet, 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, a 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. Further, although only a single exemplary processing device is shown, the term "processing device" is to be construed 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 methods described herein.

[0049] The exemplary processing device 900 can 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)), 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 can 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 that executes other instruction sets, or a processor that implements a combination of instruction sets. Also, processor 902 may be one or more dedicated processing devices (e.g., application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), digital signal processor (DSP), network processor, etc.). According to one or more aspects of the present disclosure, processor 902 may be configured to execute instructions for implementing method 700 of deploying a broadband collimator assembly for accurate optical property evaluation of a target within a processing chamber and / or method 800 of adjusting the tilt of an adjustable collimator assembly.

[0051] Furthermore, exemplary processing device 900 may include a network interface device 908 that can be communicatively coupled to network 920. Additionally, exemplary processing device 900 may include a video display 910 (e.g., liquid crystal display (LCD), touch screen, or cathode ray tube (CRT)), an alphanumeric input device 912 (e.g., keyboard), an input control device 914 (e.g., cursor control device, touch screen control device, mouse), and a signal generation device 916 (e.g., acoustic 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, in which one or more sets of executable instructions 922 are stored. In one or more aspects of the present disclosure, the executable instructions 922 can include executable instructions for performing a method 700 of deploying a broadband collimator assembly for accurate optical property evaluation of a target within a processing chamber and / or a method 800 of adjusting the tilt of an adjustable collimator assembly.

[0053] Also, the executable instructions 922 can be present, in whole or at least in part, within the main memory 904 and / or within the processor 902 during execution by an exemplary processing device 900, main memory 904, and processor 902 that constitute a computer-readable storage medium. Further, the executable instructions 922 can be transmitted or received over a network via a network interface device 908.

[0054] Although the computer-readable storage medium 928 is shown as a single medium in FIG. 9, the term "computer-readable storage medium" should be interpreted to include a single medium or multiple media (e.g., a centralized or distributed database and / or associated caches and servers) that store one or more sets of operating instructions. Also, the term "computer-readable storage medium" should be interpreted to include any medium that can store or encode a set of instructions for execution by a machine to perform any one or more of the methods described herein. Thus, the term "computer-readable storage medium" should be interpreted to include, but not be 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 be apparent to those of ordinary skill in the art upon reading and understanding the above description. Although the present disclosure describes specific examples, the systems and methods of the present disclosure are not limited to the examples described herein and can be implemented with modifications within the scope of the appended claims. Accordingly, the specification and drawings are to be interpreted in an illustrative rather than a limiting sense. Therefore, the scope of the present disclosure should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

[0056] The above-described method, hardware, software, firmware, or code embodiments can be executed via instructions or code stored in a machine-accessible, machine-readable, computer-accessible, or computer-readable medium executable by a processing element. "Memory" includes any mechanism that provides information (i.e., stores and / or transmits) in a form readable by a machine (e.g., a computer or an electronic system, etc.). For example, "memory" includes random access memory (RAM) such as static RAM (SRAM) and 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 to "one embodiment" or "an embodiment" throughout this specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases "one embodiment" or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0058] In the foregoing specification, detailed descriptions have been made with reference to specific exemplary embodiments. However, it is obvious that various modifications and changes can be made without departing from the broader spirit and scope of the present disclosure as set forth in the appended claims. Therefore, the specification and drawings should be construed in an illustrative sense rather than a limiting sense. Further, even if the terms "embodiment" and / or "other example" have been used, they do not necessarily mean the same embodiment or the same example, but may potentially mean different embodiments from the same embodiment.

[0059] The terms "example" or "exemplary" are used in this specification to mean by way of example, instance, or illustration. 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, the use of the terms "example" or "exemplary" is intended to present concepts in a concrete manner. The term "or" used in this application 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, "X includes A or B" is satisfied by any of the following examples: when X includes A, when X includes B, and when X includes both A and B. Further, the articles "a" and "one" used in this application and the appended claims should generally be construed to mean "one or more" unless otherwise specified or it is clear from the context that the singular form is being referred to. Further, the use of the term "embodiment" or "an embodiment" is not intended to mean the same embodiment or embodiments unless so described. Also, the terms "first", "second", "third", "fourth", etc. used in this specification are labels for distinguishing different elements and may not necessarily have an ordinal meaning according to their numerical designations.

Claims

1. A collimator assembly, comprising a collimator housing, an interface configured to optically couple to a processing chamber having a target surface, a port for receiving a first optical fiber, the first optical fiber sending 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 into an enclosure formed by the collimator housing, the first range being within the 400 - 700 nm wavelength interval and the second range being outside the 400 - 700 nm wavelength interval, and a collimator housing having such a port, an achromatic lens at least partially disposed within the enclosure formed by the collimator housing, directing a first plurality of spectral components of light onto the target surface to irradiate a first region on the target surface, directing a second plurality of spectral components of light onto the target surface to irradiate a second region on the target surface, the overlap between the second region and the first region being at least 85% of each of the first region and the second region, and an achromatic lens; A collimator assembly comprising a conduit providing access to the first optical fiber and a second optical fiber to the enclosure formed by the collimator housing.

2. The collimator assembly according to claim 1, wherein the overlap between the second region and the first region is at least 90% of each of the first region and the second region.

3. The collimator assembly according to claim 1, wherein the overlap between the second region and the first region is at least 95% of each of the first region and the second region.

4. The port of the collimator housing is for receiving a second optical fiber, the second optical fiber Collect the first plurality of spectral components of the light reflected from the target surface, which are generated by the first plurality of spectral components of the light directed at the target surface. Collect the second plurality of spectral components of the light reflected from the target surface, which are generated by the second plurality of spectral components of the light directed at the target surface. The collimator assembly according to claim 1, which sends the first plurality of spectral components of the reflected light and the second plurality of reflected spectral components of the reflected light to a photodetector.

5. The collimator assembly according to claim 1, wherein the achromatic lens is held by frictional force in an enclosure formed by the collimator housing.

6. The collimator assembly according to claim 1, wherein the achromatic lens is a triplet lens.

7. The first plurality of spectral components of the light directed onto the target surface by the achromatic lens form a collimated beam. The collimator assembly according to claim 1.

8. The collimator assembly according to claim 1, having an optically transparent filler that fills at least a portion of the enclosure formed by the collimator housing.

9. For each of the first range of wavelengths and the second range of wavelengths, it is at least 100 nm wide, and the center of the first range is at least 200 nm away from the center of the second range. The collimator assembly according to claim 1.

10. The first optical fiber is for sending a third plurality of spectral components of light belonging to a third range of wavelengths into an enclosure formed by a collimator housing, and the achromatic lens directs the third plurality of spectral components of light onto a target surface, irradiating a third region of the target surface, and the overlap between the third region and the first region is at least 85% of each of the first region and the third region, and the third range of wavelengths is outside the 400-700 nm interval of wavelengths and is different from the second range, the collimator assembly according to claim 1.

11. The collimator housing comprises a tilt adjustment mechanism for changing the alignment of the axis of the collimator housing with respect to the processing chamber, the collimator assembly according to claim 1.

12. The corrected alignment of the axis of the collimator housing moves the first region and the second region relative to the target surface, the collimator assembly according to claim 11.

13. The tilt adjustment mechanism comprises a plurality of adjustment screws, and the adjustment of each of the plurality of adjustment screws changes the alignment of the axis of the collimator housing, the collimator assembly according to claim 11.

14. A first support rigidly coupled to the collimator housing, a second support rigidly coupled to the processing chamber, and a gap between the first support and the second support, the gap being for accommodating the movement of the first support caused by the corrected alignment of the axis of the collimator housing, the collimator assembly according to claim 13.

15. Comprising one or more tension springs for stabilizing the first support relative to the second support, the collimator assembly according to claim 14.

16. The target surface is one of a processing chamber calibration device or a surface of a substrate being processed in the processing chamber, the collimator assembly according to claim 1.

17. An end point detection system, a light source that 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, a collimator housing, an interface configured to be optically coupled to a processing chamber having a target surface, a port that receives a first optical fiber, the first optical fiber sending 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 into an enclosure formed by the collimator housing, the first range being within the 400 - 700 nm wavelength interval, and the second range being outside the 400 - 700 nm wavelength interval, and a collimator housing having the port, an achromatic lens at least partially disposed within an enclosure formed by the collimator housing, directing a first plurality of spectral components of light onto the target surface and irradiating a first region on the target surface, directing a second plurality of spectral components of light onto the target surface and irradiating a second region on the target surface, the overlap between the second region and the first region being at least 85% of each of the first region and the second region, and an achromatic lens, a second optical fiber, collecting 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, a second optical fiber that 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, a photodetector that receives a first plurality of spectral components of the reflected light and a second plurality of spectral components of the reflected light via the second optical fiber, An endpoint detection system including a processing device communicatively coupled to a photodetector, the processing device determining a reflectance of a target surface based on a first plurality of spectral components of received reflected light and a second plurality of spectral components of the received reflected light.

18. The endpoint detection system according to claim 17, comprising a tilt adjustment mechanism for changing the alignment of the axis of the collimator housing with respect to the processing chamber.

19. A step of outputting, by a light source, 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, wherein 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; Directing, via an achromatic lens, a first plurality of spectral components of light onto the target surface to irradiate a first region on the target surface; Directing, via an achromatic lens, a second plurality of spectral components of light onto the target surface to irradiate a second region on the target surface, wherein the overlap between the second region and the first region is at least 85% of each of the first region and the second region; Collecting, by a second optical fiber, a first plurality of spectral components of light reflected from the target surface generated by the first plurality of spectral components of light directed onto the target surface; Collecting, by a second optical fiber, a second plurality of spectral components of light reflected from the target surface generated by the second plurality of spectral components of light directed onto the target surface; Receiving, by a photodetector via the second optical fiber, a first plurality of spectral components of the reflected light and a second plurality of reflected spectral components of the reflected light; A method including the step of determining a reflectance of a target surface based on a first plurality of reflected spectral components of received reflected light and a second plurality of reflected spectral components of received reflected light by a processing device communicatively coupled to a photodetector.

Images