Patent Application
20160209326
The subject matter of this disclosure is generally related to fabrication of an integrated computational element (ICE) used in optical analysis tools for analyzing a substance of interest, for example, crude petroleum, gas, water, or other wellbore fluids. For instance, the disclosed ICE fabrication uses spatially-resolved measurement techniques for in-situ monitoring of the ICE fabrication.
Information about a substance can be derived through the interaction of light with that substance. The interaction changes characteristics of the light, for instance the frequency (and corresponding wavelength), intensity, polarization, and/or direction (e.g., through scattering, absorption, reflection or refraction). Chemical, thermal, physical, mechanical, optical or various other characteristics of the substance can be determined based on the changes in the characteristics of the light interacting with the substance. As such, in certain applications, one or more characteristics of crude petroleum, gas, water, or other wellbore fluids can be derived in-situ, e.g., downhole at well sites, as a result of the interaction between these substances and light.
Integrated computational elements (ICEs) enable the measurement of various chemical or physical characteristics through the use of regression techniques. An ICE selectively weights, when operated as part of optical analysis tools, light modified by a sample in at least a portion of a wavelength range such that the weightings are related to one or more characteristics of the sample. An ICE can be an optical substrate with multiple stacked dielectric layers (e.g., from about 2 to about 50 layers), each having a different complex refractive index from its adjacent layers. The specific number of layers, N, the optical properties (e.g. real and imaginary components of complex indices of refraction) of the layers, the optical properties of the substrate, and the physical thickness of each of the layers that compose the ICE are selected so that the light processed by the ICE is related to one or more characteristics of the sample. Because ICEs extract information from the light modified by a sample passively, they can be incorporated in low cost and rugged optical analysis tools. Hence, ICE-based downhole optical analysis tools can provide a relatively low cost, rugged and accurate system for monitoring quality of wellbore fluids, for instance.
Errors in fabrication of some constituent layers of an ICE design can degrade the ICE's target performance. In most cases, deviations of <0.1%, and even 0.01% or 0.0001%, from point by point design values of the optical characteristics (e.g., complex refractive indices), and/or physical characteristics (e.g., thicknesses) of the formed layers of the ICE can reduce the ICE's performance, in some cases to such an extent, that the ICE becomes operationally useless. For example, non-uniformities in the spatial-profile of a deposition plume provided by a deposition source lead to corresponding non-uniformities of complex refractive indices and thicknesses of the formed layers of ICEs that are spatially distributed relative the deposition source within a fabrication batch. To prevent degradation of ICE performance due to the noted non-uniformities, the ICEs being fabricated are often moved (sometimes periodically) relative to the deposition source along a direction of motion along which the spatial-profile of the deposition plume is non-uniform. Conventionally, complex refractive indices and thicknesses of layers of a fabricated ICE are determined by performing in-situ measurements during fabrication of the ICEs at a single location located either along the direction of motion or at a particular lateral distance from the direction of motion. Those familiar or currently practicing in the art will readily appreciate that the ultra-high accuracies required by ICE designs challenge the state of the art in spatially-resolved measurement techniques used for monitoring thin film fabrication.
Like reference symbols in the various drawings indicate like elements.
Technologies are described for forming layers of ICEs by moving the ICEs along a direction of motion and in-situ monitoring the forming of the ICE layers at various locations along a direction orthogonal to the direction of motion. Such spatially-resolved (or location-dependent) monitoring enables accurate determinations of complex refractive indices and thicknesses of the formed layers of the ICEs within a fabrication batch. In some implementations, completion of each of the ICE layers is triggered, on an ICE-by-ICE manner, when the determined thickness of an ICE layer for an ICE located at a given lateral distance from the direction of motion along the orthogonal direction matches an associated target thickness. In other implementations, when the completion of each of the ICE layers is triggered based on statistics of the determined complex refractive indices and thicknesses over the entire batch, fabricated ICEs can be sorted and binned based on their locations along the direction orthogonal to the direction of motion.
The complex refractive indices and thicknesses of the formed layers determined from results of the disclosed spatially-resolved monitoring are potentially more accurate than if they were conventionally determined from results of conventional in-situ monitoring performed at a fixed location relative to the direction of motion. As values of the determined complex refractive indices and thicknesses of the formed layers are used to adjust forming of layers of the ICEs remaining to be formed, the more accurate in-situ monitoring of the disclosed ICE fabrication translates into improved batch yield and yield consistency batch-to-batch relative to conventional ICE fabrication.
Prior to describing example implementations of the disclosed technologies for ICE fabrication, the following technologies are described below: in Section (1)—optical analysis tools based on ICE along with examples of their use in oil/gas exploration, and in Section (2)—techniques for designing an ICE.
Each of the configurations 100, 100′, 100″ of the well logging system illustrated in
In each of the above configurations 100, 100′ and 100″ of the well logging system, the values of the one or more characteristics measured by the well logging tool 110 are provided (e.g., as a detector signal 165) to the telemetry transmitter 30. The latter communicates the measured values to a telemetry receiver 40 located above the ground surface 102. The telemetry transmitter 30 and the telemetry receiver 40 can communicate through a wired or wireless telemetry channel. In some implementations of the system configurations 100, 100′ illustrated in
The measured values of the one or more characteristics of the wellbore fluids 130 received by the telemetry receiver 40 can be logged and analyzed by a computer system 50 associated with the rig 14. In this manner, the measurement values provided by the well logging tool 110 can be used to generate physical and chemical information about the wellbore fluids 130 in the wellbore 38.
Referring again to
The light source 120 outputs light with a source spectrum over a particular wavelength range, from a minimum wavelength λmin to a maximum wavelength λmax. In some implementations, the source spectrum can have non-zero intensity over the entire or most of the wavelength range λmax-λmin. In some implementations, the source spectrum extends through UV-vis (0.2-0.8 μm) and near-IR (0.8-2.5 μm) spectral ranges. Alternatively, or additionally, the source spectrum extends through near-IR and mid-IR (2.5-25 μm) spectral ranges. In some implementations, the source spectrum extends through near-IR, mid-IR and far-IR (25-100 μm) spectral ranges. In some implementations, the light source 120 is tunable and is configured in combination with time resolved signal detection and processing.
The light source 120 is arranged to direct a probe beam 125 of the source light towards the optical interface 116 where it illuminates the sample 130 at a location 127. The source light in the probe beam 125 interacts with the sample 130 and reflects off it as light modified by the sample 130. The light modified by the sample has a modified spectrum I(λ) 135′ over the particular wavelength range. In the reflective configuration of the well logging tool 110 illustrated in
In general, the modified spectrum I(λ) 135′ encodes information about multiple characteristics associated with the sample 130, and more specifically the encoded information relates to current values of the multiple characteristics. In the example illustrated in
With continued reference to
The optical spectrum w(λ) 150 is determined offline by applying conventional processes to a set of calibration spectra I(λ) of the sample which correspond to respective known values of the characteristic to be measured. As illustrated by optical spectrum w(λ) 150, optical spectrums generally may include multiple local maxima (peaks) and minima (valleys) between λmin and λmax. The peaks and valleys may have the same or different amplitudes. For instance, an optical spectrum w(λ) can be determined through regression analysis of Nc calibration spectra Ij(λ) of a sample, where j=1, . . . , Nc, such that each of the calibration spectra Ij(λ) corresponds to an associated known value of a given characteristic for the sample. A typical number Nc of calibration spectra Ij(λ) used to determine the optical spectrum w(λ) 150 through such regression analysis can be Nc=10, 40 or 100, for instance. The regression analysis outputs, within the Nc calibration spectra Ij(λ), a spectral pattern that is unique to the given characteristic. The spectral pattern output by the regression analysis corresponds to the optical spectrum w(λ) 150. In this manner, when a value of the given characteristic for the sample is unknown, a modified spectrum Iu(λ) of the sample is acquired by interacting the probe beam 125 with the sample 130, then the modified spectrum Iu(L) is weighted with the ICE 140 to determine a magnitude of the spectral pattern corresponding to the optical spectrum w(λ) 150 within the modified spectrum Iu(λ). The determined magnitude is proportional to the unknown value of the given characteristic for the sample.
For example, the sample can be a mixture (e.g., the wellbore fluid 130) containing substances X, Y and Z, and the characteristic to be measured for the mixture is concentration cx of substance X in the mixture. In this case, Nc calibration spectra Ij(λ) were acquired for Nc samples of the mixture having respectively known concentration values for each of the substances contained in the Nc samples. By applying regression analysis to the Nc calibration spectra Ij(λ), a first spectral pattern that is unique to the concentration cx of the X substance can be detected (recognized), such that the first spectral pattern corresponds to a first optical spectrum wcX(λ) associated with a first ICE, for example. Similarly, second and third spectral patterns that are respectively unique to concentrations cY and cZ of the Y and Z substances can also be detected, such that the second and third spectral patterns respectively correspond to second and third optical spectra wcY(λ) and wcZ(λ) respectively associated with second and third ICEs. In this manner, when a new sample of the mixture (e.g., the wellbore fluid 130) has an unknown concentration cX of the X substance, for instance, a modified spectrum Iu(λ) of the new sample can be acquired by interacting the probe beam with the mixture, then the modified spectrum Iu(λ) is weighted with the first ICE to determine a magnitude of the first spectral pattern within the modified spectrum Iu(λ). The determined magnitude is proportional to the unknown value of the concentration cX of the X substance for the new sample.
Referring again to
Throughout this specification, a complex index of refraction (or complex refractive index) n* of a material has a complex value, Re(n*)+iIm(n*). Re(n*) represents a real component of the complex index of refraction responsible for refractive properties of the material, and Im(n*) represents an imaginary component of the complex index of refraction (also known as extinction coefficient κ) responsible for absorptive properties of the material. In this specification, when it is said that a material has a high complex index of refraction n*H and another material has a low complex index of refraction n*L, the real component Re(n*H) of the high complex index of refraction n*H is larger than the real component Re(n*L) of the low complex index of refraction n*L, Re(n*H)>Re(n*L). Materials of adjacent layers of the ICE are selected to have a high complex index of refraction n*H (e.g., Si), and a low complex index of refraction n*L (e.g., SiO2). Here, Re(n*Si)≈2.4>Re(n*SiO2)≈1.5. For other material pairings, however, the difference between the high complex refractive index n*H and low complex refractive index n*L may be much smaller, e.g., Re(n*H)≈1.6>Re(n*L)≈1.5. The use of two materials for fabricating the N layers is chosen for illustrative purposes only. For example, a plurality of materials having different complex indices of refraction, respectively, can be used. Here, the materials used to construct the ICE are chosen to achieve a desired optical spectrum w(λ) 150.
A set of design parameters 145—which includes the total number of stacked layers N, the complex refractive indices n*H, n*L of adjacent stacked layers, and the thicknesses of the N stacked layers t(1), t(2), t(N−1), t(N)—of the ICE 140 can be chosen (as described below in connection with
In view of the above, the beam 155 of processed light output by the ICE 140 has a processed spectrum P(λ)=*w(λ){circle around (×)}I(λ)155′ over the wavelength range λmax-λmin, such that the processed spectrum 155′ represents the modified spectrum I(λ) 135′ weighted by the optical spectrum w(λ) 150 associated with the characteristic to be measured.
The beam 155 of processed light is directed from the ICE 140 to the optical transducer 160, which detects the processed light and outputs an optical transducer signal 165. A value (e.g., a voltage) of the optical transducer signal 165 is a result of an integration of the processed spectrum 155′ over the particular wavelength range and is proportional to the unknown value “c” 165′ of the characteristic to be measured for the sample 130.
In some implementations, the well logging tool 110 can include a second ICE (not shown in
In some implementations, the determined value 165′ of the characteristic to be measured can be logged along with a measurement time, geo-location, and other metadata, for instance. In some implementations, the detector signal 165, which is proportional to a characteristic to be measured by the well logging tool 110, can be used as a feedback signal to adjust the characteristic of the sample, to modify the sample or environmental conditions associated with the sample, as desired.
Characteristics of the wellbore fluids 130 that can be related to the modified spectrum 135′ through the optical spectra associated with the ICE 140 and other ICEs (not shown in
Aspects of a process for designing an ICE associated with a characteristic to be measured (e.g., one of the characteristics enumerated above) are described below. Here, an input of the ICE design process is a theoretical optical spectrum wth(λ) associated with the characteristic. An output of the ICE design process is an ICE design that includes specification of (1) a substrate and a number N of layers to be formed on the substrate, each layer having a different complex refractive index from its adjacent layers; and (2) complex refractive indices and thicknesses of the substrate and layers that correspond to a target optical spectrum wt(λ). The target optical spectrum wt(λ) is different from the theoretical optical spectrum wth(λ) associated with the characteristic, such that the difference between the target and theoretical optical spectra cause degradation of a target performance relative to a theoretical performance of the ICE within a target error tolerance. The target performance represents a finite accuracy with which an ICE having the target optical spectrum wt(λ) is expected to predict known values of the characteristic corresponding to a set of validation spectra of a sample with a finite (non-zero) error. Here, the predicted values of the characteristic are obtained through integration of the validation spectra of the sample respectively weighted by the ICE with the target optical spectrum wt(λ). The theoretical performance represents the maximum accuracy with which the ICE—if it had the theoretical optical spectrum wth(λ)—would predict the known values of the characteristic corresponding to the set of validation spectra of the sample. Here, the theoretically predicted values of the characteristic would be obtained through integration of the validation spectra of the sample respectively weighted by the ICE, should the ICE have the theoretical optical spectrum wth(λ).
At 210 during the jth iteration of the design process 200, thicknesses {ts(j), t(1;j), t(2;j), t(N−1;j), t(N;j)} of the substrate and a number N of layers of the ICE are iterated.
At 220, a jth optical spectrum w(λ;j) of the ICE is determined corresponding to complex refractive indices and previously iterated thicknesses {ts(j), t(1;j), t(2;j), t(N−1;j), t(N;j)} of the substrate and the N layers, each having a different complex refractive index from its adjacent layers. The iterated thicknesses of the substrate and the N layers are used to determine the corresponding jth optical spectrum w(λ;j) of the ICE in accordance with conventional techniques for determining spectra of thin film interference filters.
At 230, performance of the ICE, which has the jth optical spectrum w(λ;j) determined at 220, is obtained. To do so, a set of validation spectra of a sample is accessed, e.g., in a data repository. Respective values of a characteristic of the sample are known for the validation spectra. For instance, each of Nv validation spectra I(λ;m) corresponds to a value v(m) of the characteristic of the sample, where m=1, . . . , Nv. In the example illustrated in
Graph 235 shows (in open circles) values c(m;j) of the characteristic of the sample predicted by integration of the validation spectra I(λ;m) weighted with the ICE, which has the jth optical spectrum w(λ;j), plotted against the known values v(m) of the characteristic of the sample corresponding to the validation spectra I(λ;m). The predicted values c(m;1) of the characteristic are found by substituting, in formula 165′ of
In this specification, the SEC is chosen as a metric for evaluating ICE performance for the sake of simplicity. Note that there are other figures of merit that may be used to evaluate performance of ICE, as is known in the art. For example, sensitivity—which is defined as the slope of characteristic change as a function of signal strength—can also be used to evaluate ICE performance. As another example, standard error of prediction (SEP)—which is defined in a similar manner to the SEC except it uses a different set of validation spectra—can be used to evaluate ICE performance. Any of the figure(s) of merit known in the art is/are evaluated in the same general way by comparing theoretical performance with that actually achieved. Which figure(s) of merit or combinations are used to evaluate ICE performance is determined by the specific ICE design.
The iterative design process 200 continues by iterating, at 210, the thicknesses of the substrate and the N layers. The iterating is performed such that a (j+1)th optical spectrum w(λ;j+1)—determined at 220 from the newly iterated thicknesses—causes, at 230, improvement in performance of the ICE, to obtain SEC(j+1)<SEC(j). In some implementations, the iterative design process 200 is stopped when the ICE's performance reaches a local maximum, or equivalently, the SEC of the ICE reaches a local minimum. For example, the iterative process 200 can be stopped at the (j+1)th iteration when the current SEC(j+1) is larger than the last SEC(j), SEC(j+1)>SEC(j). In some implementations, the iterative design process 200 is stopped when, for a given number of iterations, the ICE's performance exceeds a specified threshold performance for a given number of iterations. For example, the iterative design process 200 can be stopped at the jth iteration when three consecutive SEC values decrease monotonously and are less than a specified threshold value:
SEC0>SEC(j−2)>SEC(j−1)>SEC(j).
In either of these cases, an output of the iterative process 200 represents a target ICE design 245 to be used for fabricating an ICE 140, like the one described in
In this manner, the thicknesses of the substrate and the N layers associated with the ICE design 245 are denoted {ts, t(1), t(2), t(N−1), t(N)} and are referred to as the target thicknesses. The optical spectrum associated with the ICE design 245 and corresponding to the target thicknesses is referred to as the target optical spectrum wt(λ) 150. The SEC associated with the ICE design 245—obtained in accordance with the target optical spectrum wt(λ) 150 corresponding to the target thicknesses—is referred to as the target SECt. In the example illustrated in
As described above in connection with
Thickness and complex refractive index uniformity of deposited layers can be controlled across a batch of ICEs being fabricated by moving a support—that supports these ICEs during fabrication—along a direction of motion with respect to a deposition source. Typically, the direction of motion is chosen to match a direction along which a spatial profile of a deposition plume of the deposition source is non-uniform. However, actual values of complex refractive indices and/or thicknesses of deposited layers can be different from their target values due to deposition rate drifts (i) during fabrication of one or more layers of the ICEs fabricated within a batch, or (ii) from batch-to-batch. For example, deposition rate changes may be caused by contamination of materials used for deposition (Si, SiO2), or by modifications of deposition chamber conditions (e.g., pressure or temperature). The deposition rate changes can lead to changes in thicknesses and/or complex refractive indices of the deposited layers compared to their respective targets, which in turn result in degradation of the fabricated ICEs' performance with respect to a target performance. Effects of changes in the fabrication process on the performance of fabricated ICEs are minimized by monitoring the ICE fabrication. For instance, the foregoing process changes can be detected and corrected or prevented altogether by in-situ monitoring the ICE fabrication.
Conventionally, in-situ ellipsometry, optical monitoring or spectroscopy for monitoring the ICE fabrication is performed on one or more witness samples—which are moving with the ICEs along the direction of motion and are located at a single lateral distance relative the direction of motion along a direction orthogonal to the direction of motion—to measure characteristics of probe-light that interacted with the witness sample(s). The witness sample(s) can include one or more of the ICEs being fabricated. The measured characteristics are used next to determine characteristics of deposited layers of the ICEs, e.g., their respective complex refractive indices and thicknesses. Throughout this specification, determining a complex refractive index n* of a layer means that both the real component Re(n*) and the imaginary component Im(n*) of the complex refractive index are being determined Differences between the determined and target complex refractive indices and thicknesses of the formed layers are used to obtain new target complex refractive indices and/or thicknesses for the layers that remain to be deposited. The foregoing steps of such conventional in-situ measurements and optimizations are repeated after deposition of each of the layers of the ICEs being fabricated.
In accordance with technologies disclosed herein, the in-situ monitoring is performed on one or more witness samples—which are moving with the ICEs along the direction of motion and are located at respective lateral distances relative the direction of motion along the orthogonal direction—to measure characteristics of probe-light that interacted with the witness samples. Note that probe-light represents any type of electromagnetic radiation having one or more probe wavelengths from an appropriate region of the electromagnetic spectrum. Results of this spatially-resolved monitoring are used to determine complex refractive indices and thicknesses of layers of the witness samples as a function of the witness samples' lateral distances relative to the direction of motion. As such, actual non-uniformities of the complex refractive indices and thicknesses caused by non-uniformity in the spatial profile of the deposition plume along the orthogonal direction are determined. The complex refractive indices and thicknesses of the formed layers—which can be accurately determined as a function of the witness samples' lateral distances relative to the direction of motion—are used during ICE fabrication to provide feedback for adjusting the ICE fabrication in real-time or near real-time. In this manner, the systems and techniques described herein can provide consistent batch-to-batch yields, and/or improvement of batch yield for the ICE fabrication.
Details of one or more of the foregoing embodiments are described below.
A target ICE design can be provided to an ICE fabrication system in which one or more ICEs are fabricated based on the target ICE design. Technologies for in-situ adjusting ICE fabrication based on results of spatially-resolved measurements are disclosed below. A fabrication system for implementing these technologies is described first.
The deposition chamber 301 includes one or more deposition sources 303 to provide materials with low complex index of refraction n*L and high complex index of refraction n*H used to form layers of the ICEs 306. Here, the deposition sources(s) 303 is(are) at rest relative to the deposition chamber 301. Substrates on which layers of the ICEs 306 will be deposited are placed on a substrate support 302, such that the ICEs 306 are within the field of view of the deposition source(s) 303. The substrates have a thickness ts and a complex refraction index n*S specified by a target ICE design 307 (e.g., 145 or 245 described above in connection with
In accordance with PVD techniques, the layers of the ICE(s) are formed by condensation of a vaporized form of material(s) of the source(s) 305, while maintaining vacuum in the deposition chamber 301. One such example of PVD technique is electron beam (E-beam) deposition, in which a beam of high energy electrons is electromagnetically focused onto material(s) of the deposition source(s) 303, e.g., either Si, or SiO2, to evaporate atomic species. In some cases, E-beam deposition is assisted by ions, provided by ion-sources (not shown in
Power provided to the deposition source 303 and its arrangement relative to the current instances of ICEs 306, etc., can be controlled to obtain a specified deposition rate R. For instance, if an ICE design 307 specifies that a jth layer L(j) of the N layers of an ICE is a Si layer with a target thickness t(j), a stack including the previously formed ICE layers L(1), L(2), . . . , L(j−1) is exposed to a Si source—from among the deposition sources 303—for a duration ΔT(j)=t(j)/RSi, where RSi is a deposition rate of the Si source. In the examples illustrated in
Referring again to
The formed layers of any one or more of the current instances of the ICEs 306 can be used as a witness sample by the measurement system 304 to monitor ICE layer deposition in the deposition chamber 301. Note that for in-situ reflectivity measurements configured in accordance with
In some implementations, the measurement system 304 is an ellipsometer implemented based on configuration 304-A illustrated in
In other implementations, the measurement system 304 is an optical monitor that can be implemented in a reflectance configuration 304-A illustrated in
In some other implementations, the measurement system 304 is a spectrometer that can be implemented in a transmittance configuration 304-B illustrated in
As a spatial distribution of a deposition plume provided by the PVD source(s) 303 is non-uniform (e.g., the plume can have a 1/r2 spherical distribution or a “cosine emission” Lambertian distribution), a relative orientation, separation and motion between the deposition source(s) 303 and the substrate support 302 are configured to provide desired deposition rate(s) and spatial uniformity across the ICEs 306 distributed on the substrate support 302. For instance, the substrate support 302 is periodically moved with respect to the deposition source(s) 303 along a direction of motion (e.g., rotated about the substrate support 302's center axis that is spaced apart relative to deposition source axis 321) to obtain reproducibly uniform layer deposition of those ICEs being fabricated which are distributed along the direction of motion at a fixed lateral distance relative to the deposition source(s) 303 along a direction orthogonal to the direction of motion (e.g., at r=constant along the radial direction “r” of the substrate support 302 that is rotating along the angular direction “θ”.) However, as the spatial distribution of the deposition plume is non-uniform along the orthogonal direction (e.g., the radial direction “r”), ICEs distributed along the direction of motion (e.g., the angular direction “θ”) at a first lateral distance (e.g., r1) relative to the deposition source(s) 303 have layers deposited to a first set of thicknesses, other ICEs distributed along the direction of motion at a second lateral distance (e.g., r2) relative to the deposition source(s) 303 that is larger than the first lateral distance (r2>r1) have layers deposited to a second set of thicknesses smaller than the thicknesses of the first set, and so on. To determine, in real-time or near real-time, the different sets of thicknesses corresponding to the different lateral distances (r1, r2, . . . ) relative to the deposition source(s) 303, the computer system 305 uses results of in-situ measurements of characteristics of probe-light that interacted with witness samples 309 distributed along the direction (e.g., “r”) perpendicular to the direction of motion (e.g., “θ”) of the ICEs 306 being fabricated in the deposition chamber 301.
Here, “k” witness samples 309 (k≧1) are used for each desired non-zero lateral distance (e.g., r1, r2, . . . ) relative to the deposition source(s) 303 where measurements will be taken. As such, the “k” witness samples 309 are placed along the orthogonal direction (e.g., “r”) at each of the desired lateral distances (e.g., rj) relative to the deposition source(s) 303. For example if k=1, a single witness sample is placed at a desired lateral distance rj along the “12 o'clock radius” of a circular platen. In the examples illustrated in
In the limiting case when k→∞, a single “platen-size witness sample” is used. Such a platen-size witness sample covers the entire substrate support 302 and rotates about an azimuthal axis passing through its center. In this case, the measurement system 304 is translated continuously along the translation stage(s) 515, starting from above the center of the platen-size witness sample, continuing over the deposition source(s) 303 and ending at the edge of the platen-size witness sample, while the detector OD continuously collects the light interacted with the platen-size witness sample along a spiral path that is continuously illuminated by the source OS. Here, a continuous thickness profile 425 along the AA′ diameter of the platen-size witness sample is determined based on results of the continuous measurements acquired in-situ along the spiral path. As it was in the case of the (2k+1) discrete witness samples described above, the thickness profile 425 along the AA′ diameter of the platen-size witness sample also is non-uniform, in conformance with the non-uniformity of the spatial distribution 420 of the deposition plume provided by the deposition source(s) 303 and its position relative to the center of the platen-size witness sample.
In some of the implementations shown in
In other implementations shown in
One complication with measurements of near-infrared (NIR) or mid-infrared (MIR) transmission spectra (as shown in the transmittance configuration of the measurement system 304-B in
The computer system 305 includes one or more hardware processors and memory. The memory encodes instructions that, when executed by the one or more hardware processors, cause the fabrication system 300 to perform processes for fabricating the ICEs 306. Examples of such processes are described below in connection with
The retrieved ICE design 307 includes specification of a substrate and a total number N of layers to be formed in the deposition chamber 301 on the substrate; specification of a complex refractive index n*S of a material of the substrate, a high complex refractive index n*H and a low complex refractive index n*L of materials (e.g., Si and SiO2) to form the N layers with adjacent layers having different complex refractive indices; and specification of target thicknesses {ts, t(k), k=1−N} of the substrate and the N layers. Implicitly or explicitly, the ICE design 307 also can include specification of a target optical spectrum wt(λ) associated with the given characteristic; and specification of a target SECt representing expected performance of an ICE associated with the retrieved ICE design 307. The foregoing items of the retrieved ICE design 307 were determined, prior to fabricating the ICEs 306, in accordance with the ICE design process 200 described above in connection with
The complex refractive indices and target thicknesses {t(k), k=1−N} of the N layers, as specified by the retrieved ICE design 307, are used by the computer system 305, in conjunction with aspects of deposition capability of the ICE fabrication system 300, to control deposition rate(s) of the deposition source(s) 303 and respective deposition times for forming the ICE layers. While forming the ICE layers, the computer system 305 instructs the measurement system 304 associated with the ICE fabrication system 300 to measure characteristics of probe-light that interacted with formed layers of ICEs being fabricated by performing spatially-resolved in-situ measurements. The measured characteristics of the probe-light that interacted with the formed layers of the ICEs are used by the computer system 305 to determine complex refractive indices and thicknesses of the formed layers as a function of the ICEs' locations relative to the deposition source(s) 303. Then, the computer system 305 can instruct the ICE fabrication system 300 to complete the forming of the current layer—in some cases on an ICE-by-ICE basis—upon determining that its thickness target has been reached. If necessary, the computer system 305 also instructs the ICE fabrication system 300 to adjust the forming of layers remaining to be formed based on the determined complex refractive indices and thicknesses of the formed layers of the ICEs.
At 610, an ICE design is received. The received ICE design includes specification of a substrate and N layers L(1), L(2), . . . , L(N), each having a different complex refractive index from its adjacent layers, and specification of target complex refractive indices and thicknesses ts, t(1), t(2), . . . , t(N). In this manner, an ICE fabricated in accordance with the received ICE design selectively weights, when operated, light in at least a portion of a wavelength range by differing amounts. The differing amounts weighted over the wavelength range correspond to a target optical spectrum wt(λ) of the ICE and are related to a characteristic of a sample. For example, a design process for determining the specified (1) substrate and number N of layers of the ICE, each having a different complex refractive index from its adjacent layers, and (2) complex refractive indices and thicknesses of the substrate and the N layers that correspond to the target optical spectrum wt(λ) of the ICE is described above in connection with
Loop 615 is used to fabricate one or more ICEs based on the received ICE design. Each iteration “i” of the loop 615 is used to form a layer L(i) of a total number N of layers. Here, the total number N of layers can be either specified in the received ICE design or updated during the ICE fabrication. Updates to the received ICE design are performed when necessary for preventing performance of the fabricated ICE to degrade under a threshold value.
At 620, an ith layer L(i) of the total number N of layers is formed to a target thickness t(i) while moving a plurality of ICEs being fabricated along a direction of motion. The target thickness t(i) of the layer L(i) can be specified by the received ICE design or updated based on optimization(s) carried out after forming previous one or more of the layers of the ICEs. Characteristics of the motion—e.g., distance and orientation of the direction of motion relative to the deposition source(s) 303, whether the motion is periodic, and if so its period—are configured to mitigate deposition non-uniformities among the plurality of ICEs within a fabrication batch, the non-uniformities being caused by a non-uniform spatial profile of a deposition plume provided by the deposition source(s) 303. In the examples shown in
For some of the layers of the ICE, a deposition source having a deposition rate R is used for a total time duration ΔT(i)=t(i)/R to deposit the layer L(i) to its target thickness as part of a single deposition step. Other layers are deposited to the target thickness t(i) using multiple deposition steps by discretely or continuously forming respective sub-layers of the layer L(i). Here, the deposition rate used for depositing each of the sub-layers can be the same or different from each other. In the case when the deposition rates for forming the sub-layers are different, the last few sub-layers of the layer L(i) can be formed using slower rates than the ones used for forming the first few sub-layers of the layer L(i).
At 630, while the layer L(i) is being formed, spatially-resolved, in-situ optical measurements are performed to determine changes in characteristics of a probe-light due to its interaction with the layer currently being formed and the previously formed layers. The measured characteristics are spatially-resolved along a first direction (e.g., r) orthogonal to the direction of motion (e.g., θ) of the ICEs being fabricated. In the examples illustrated in
For some of the layers of the received ICE design, the spatially-resolved optical measurements can be skipped altogether. In this case, either no optical measurements are taken, or optical measurements are taken at a single location relative to the deposition source(s) 303 (in a non-spatially-resolved manner.) For some other layers, the spatially-resolved optical measurements are carried out continuously during the deposition of a layer L(i), in some implementations. In other implementations, the spatially-resolved optical measurements are taken a finite number of times during the deposition of the layer L(i). In the latter case, the finite number of times can represent times when at least some of the sub-layers of the layer L(i) are completed.
At 640, complex refractive indices n*′H(r) and n*′L(r) and thicknesses t′(1;r), t′(2;r), . . . , t′(i−1;r), t′(i;r) of the layers L(1), L(2), . . . , L(i−1) formed in previous iterations of the loop 615 and the layer L(i) that is currently being formed are determined in real-time (or near real-time) as a function of the lateral distance (e.g., “r”) to the deposition source along the direction orthogonal to the direction of motion (e.g., “0”) of the ICEs. In this manner, thickness profiles, e.g., 425 in
For instance, the measurement system 304 is translated on the translation stage 315 at r±1, “above” one or more of the ICEs located on the substrate support 302 nearest to the deposition source axis 321, such that probe-light provided by the source OS illuminates the nearest ICE(s). At r±1, the measurement system 304 measures characteristics of the probe-light that interacted with the nearest ICE(s), and the computer system 305 uses the measured characteristics to determine in real-time a thickness t′(i;r±1) of the current layer L(i) for the nearest ICE(s). When the determined thickness t′(i;r±1) of the current layer L(i) of the nearest ICE(s) meets the target thickness t(i), the nearest ICE(s) is(are) covered for the remainder of the deposition of the current layer L(i) of all the remaining ICEs in the batch. Further, the measurement system 304 is translated along the translation stage 315 to a radius r±2, above one or more ICEs that are next-to-nearest to the deposition source axis 321, such that probe-light provided by the source OS illuminates the next-to-nearest ICE(s). At r±2, the measurement system 304 measures characteristics of the probe-light that interacted with the next-to-nearest ICE(s), and the computer system 305 uses the measured characteristics to determine in real-time a thickness t′(i;r±2) of the current layer L(i) for the next-to-nearest ICE(s). When the determined thickness t′(i;r±2) of the current layer L(i) of the next-to-nearest ICE(s) meets the target thickness t(i), the next-to-nearest ICE(s) is(are) covered for the remainder of the deposition of the current layer L(i) of all the remaining ICEs in the batch.
In general, at 622, the measurement system 304 is translated along the translation stage 315 to a radius r±k, above one or more ICEs that are kth-to-nearest to the deposition source axis 321, such that probe-light provided by the source OS illuminates the kth-to-nearest ICE(s). At r±k, the measurement system 304 measures characteristics of the probe-light that interacted with the kth-to-nearest ICE(s), and the computer system 305 uses the measured characteristics to determine in real-time a thickness t′(i;r±k) of the current layer L(i) for the k′-to-nearest ICE(s). When the determined thickness t′(i;r±k) of the current layer L(i) of the kth-to-nearest ICE(s) meets the target thickness t(i), the kth-to-nearest ICE(s) is(are) covered for the remainder of the deposition of the current layer L(i) of all the remaining ICEs in the batch. And so on until deposition of the current layer L(i) is completed for all the ICEs in the batch.
At 628, the covered ICEs are uncovered upon completing deposition of the current layer L(i) for all ICEs and prior to starting deposition of next layer L(i+1).
Referring again to
One or more of the obtained statistics can be used to control completion of the deposition of the layer L(i) currently being formed. As such, in some implementations, deposition (at 620) of current layer L(i) is completed when a statistic of the thickness <t′(i;r)>r of the current layer L(i)—taken over the determined thicknesses {t′(i;r±1), t′(i;r±2), . . . } of the layer L(i) for the ICEs supported on the substrate support 302 at the lateral distances r±1, r±2, . . . —meets a target thickness t(i). Additionally, the obtained statistics can be used to modify deposition of the current layer L(i) and of the subsequent layers L(i+1), L(i+2), . . . as described below.
At 650, deposition of current and subsequent layers L(i), L(i+1), . . . of the ICE(s) being fabricated in the deposition chamber 301 is adjusted, if necessary, based on the obtained statistics of the complex refractive indices <n*′H(r)>r, <n*′L(r)>r and thicknesses {<t′(1;r)>r, <t′(2;r)>r, <t′(i−1;r)>r, <t′(i;r)>r} of deposited layers L(1), L(2), . . . , L(i−1) and layer L(i) currently being deposited. The foregoing statistics are referred to as the statistical complex refractive indices and the statistical thicknesses. For example, a deposition rate used to form the layer L(i) currently being formed and other layers L(i+1), L(i+2), . . . remaining to be formed can be adjusted based on a comparison between the statistical complex refractive indices and thicknesses of the layers of the current instance of the ICEs and their respective target values. Alternatively or additionally, complex refractive indices corresponding to the layer L(i) being current formed and other layers L(i+1), L(i+2), . . . remaining to be formed can be adjusted based on a comparison between the statistical complex refractive indices and thicknesses of the layers of the current instance of the ICEs and their respective target values.
Further, in order to determine whether target thicknesses of the layer L(i) being current formed and other layers L(i+1), L(i+2), . . . , L(N) remaining to be formed should be updated, the following verification is performed. An SEC(i) of the ICE is predicted to represent an ICE's performance if the ICE were completed to have the formed layers L(1), L(2), . . . , L(i−1) with the statistical thicknesses <t′(1;r)>r, <t′(2;r)>r, . . . , <t′(i−1;r)>r, and the layer L(i) currently being formed and other layers L(i+1), L(i+2), . . . , L(N) remaining to be formed with target thicknesses t(i), t(i), . . . , t(N). Here, the predicted SEC(i) is caused by deviations of the statistical complex refractive indices and thicknesses of the formed layers from their respective complex refractive indices and target thicknesses specified by the current ICE design. If the predicted SEC(i) does not exceed the maximum allowed SECmax, SEC(i)≦SECmax, then the forming of the current layer L(i) is completed in accordance to its target thickness t(i) and a next iteration of the loop 415 will be triggered to form the next layer L(i+1) to its target thickness t(+1).
If, however, the predicted SEC(i;N) exceeds the maximum allowed SECmax, SEC(i;N)>SECmax, then target thicknesses of the layer L(i) currently being formed and other layers L(i+1), L(i+2), . . . , L(N) remaining to be formed are modified based on the statistical complex refractive indices and thicknesses of the formed layers L(1), L(2), . . . , L(i). This optimization may change the total number of layers of the ICE from the specified total number N of layers to a new total number N′ of layers, but constrains the thicknesses of the layers L(1), L(2), . . . , L(i) (of the current instance of the ICE) to the statistical thicknesses <t′(1;r)>r, <t′(2;r)>r, . . . , <t′(i−1;r)>r. In this manner, the optimization obtains, in analogy with the process 200 described above in connection with
Once the previous instance of the ICE design is updated with specification of the new total number of layers N′ and the new target thicknesses t″(i), t″(i+1), . . . , t″(N′)—which are used to form the current layer L(i) and the remaining layers L(i+1), . . . , L(N′) and correspond to the new target SEC′t(i;N′)—the forming of the current layer L(i) is completed in accordance with its new target thickness t″(i) and a next iteration of the loop 615 will be triggered to form the next layer L(i+1) from the new total number of layers N′ to its new target thickness t″(i+1). In this manner, the remaining layers of the ICE will be formed based on the updated ICE design, at least until another update is performed.
Other modifications and/or extensions of the process 600 can be implemented based on the thickness profiles obtained at 640.
At 660, once fabrication of ICEs of the current batch is completed, the fabricated ICEs are sorted and binned based on their spatially-resolved thicknesses determined at 640. For instance, the N layers of a first set of ICEs located at a lateral distance r±1 from the deposition source axis 321 were fabricated with thicknesses {t′(1;r±1), t′(2;r±1), . . . , t′(N;r±1)}. As such, the ICEs of the first set have a corresponding optical spectrum w(λ;r±1) different from the target optical spectrum wt(λ) and a predicted SEC(r±1) from the target performance corresponding to differences between the optical spectrum w(λ;r±1) and the target optical spectrum wt(λ). Further, the N layers of a second set of ICEs located at a lateral distance r±2 from the deposition source axis 321 were fabricated with thicknesses {t′(1;r±2), t′(2;r±2), . . . , t′(N;r±2)}. As such, the ICEs of the second set have a corresponding optical spectrum w(λ;r±2) different from the target optical spectrum wt(λ) and a predicted SEC(r±2) from the target performance corresponding to differences between the optical spectrum w(λ;r±2) and the target optical spectrum wt(λ). In general, the N layers of a kth set of ICEs located at a lateral distance r±k from the deposition source axis 321 were fabricated with thicknesses {t′(1;r±k), t′(2;r±k), t′(N;r±k)}. As such, the ICEs of the kth set have a corresponding optical spectrum w(λ;r±k) different from the target optical spectrum wt(λ) and a predicted SEC(r±k) from the target performance corresponding to differences between the optical spectrum w(λ;r±k) and the target optical spectrum wt(λ).
In this manner, the foregoing sets of ICEs can be ranked based on the predicted SEC, such that the pth set of ICEs with the smallest degradation from the target performance SEC(r±p) is considered to be the most performing set, and the qth set of ICEs with the largest degradation from the target performance SEC(r±q) is considered to be the least performing set. Moreover, the sets of ICEs for which corresponding degradation from the target performance (expressed in terms of SEC(r)) exceeds the maximum allowed SECmax can be discarded.
Some embodiments have been described in detail above, and various modifications are possible. While this specification contains many specifics, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments.
Other embodiments fall within the scope of the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/077688 | 12/24/2013 | WO | 00 |
