Abstract:
System(s) and method(s) are provided for adjustment and analysis of performance of a tool through integration of tool operational data and spectroscopic data related to the tool. Such integration results in consolidated data that enable, in part, learning at least one relationship amongst selected portions of the consolidated data. Learning is performed autonomously without human intervention. Adjustment of performance of the tool relies at least in part on a learned relationship and includes generation of process recipe parameter(s) that can adjust a manufacturing process in order to produce a satisfactory tool performance in response to implementation of the manufacturing process. A process recipe parameter can be generated by solving an inverse problem based on the learned relationship. Analysis of performance of the tool can include assessment of synthetic performance scenarios, identification of spectroscopic condition(s) that affect performance, and extraction of endpoints based at least on time dependence spectroscopic data.

Description:
TECHNICAL FIELD 
     The subject disclosure relates to merging disparate information related to a semiconductor manufacturing process and autonomously learning tool performance improvements with the merged information. 
     BACKGROUND 
     On-going technological evolution of electronics and computing devices drives advances in semiconductor technology. In addition, growing consumer demand for smaller, higher performing, and more efficient computer devices and electronics has lead to a down scaling of semiconductor devices. In addition, to meet device demand while restraining costs, silicon wafers upon which semiconductor devices are formed have increased in size. 
     Fabrication plants working with large wafer sizes utilize automation to implement and control wafer processing. Such plants can be capital intensive and, accordingly, it is desirable to maintain highly efficient operation of fabrication equipment to minimize downtime and maximize yields. To facilitate these goals, measurement equipment can be employed to monitor fabrication equipment during wafer processing and acquire measurement information on both the equipment and the processed wafer. The measurement information can be analyzed to optimize fabrication equipment. 
     According to an example, the measurement information can include tool level information which indicates a state or condition of fabrication equipment or a portion thereof, wafer metrology information specifying physical and/or geometric conditions of wafers being processed, electrical text information, and the like. In addition, spectroscopic data, e.g., spectral line intensity information, can be gathered to facilitate identification of etch endpoints by process engineers. However, in conventional fabrication environments, various measurement data is handled independently of one another, for different purposes. Accordingly, inter-relationships among various measurement data are not leverage for advanced optimization of fabrication processes. 
     The above-described deficiencies of today&#39;s semiconductor fabrication measurement and optimization systems are merely intended to provide an overview of some of the problems of conventional systems, and are not intended to be exhaustive. Other problems with conventional systems and corresponding benefits of the various non-limiting embodiments described herein may become further apparent upon review of the following description. 
     SUMMARY 
     A simplified summary is provided herein to help enable a basic or general understanding of various aspects of exemplary, non-limiting embodiments that follow in the more detailed description and the accompanying drawings. This summary is not intended, however, as an extensive or exhaustive overview. Instead, the sole purpose of this summary is to present some concepts related to some exemplary non-limiting embodiments in a simplified form as a prelude to the more detailed description of the various embodiments that follow. 
     In one embodiment, spectroscopic data (e.g., spectral line intensities), sensor data, and material measurement data related to a semiconductor production tool can be acquired and consolidated into a data structure (e.g., a matrix). According to an example, sensor data can include performance counter measurements such as, but not limited to, elapsed time since wet-clean, age of one or more parts (e.g., age of focus ring, age of CEL, etc.), and the like. The data structure can be utilized as training data for a learning engine configured to generate expressions for a field of interest in terms of other fields of the data structure. For instance, an etch bias at a given location on a wafer can be expressed in terms of a chamber pressure, an intensity of a given wavelength (e.g., spectral line), a critical dimension measurement, or the like. 
     In another embodiment, the expressions can be leveraged to tune or optimize performance of the semiconductor production tool. For instance, based upon the expressions, operating ranges of configurable parameters of the tool, and target values for outputs, values for the configurable parameters can be identified to achieve the target outputs. The semiconductor production tool can be tuned in accordance with the values. 
     In yet another embodiment, the learning engine can be leveraged to identify influential characteristics of a first semiconductor production tool with high performance (e.g., high yields), where the influential characteristics operate to distinguish the first semiconductor production tool from other semiconductor production tools or underperforming chambers of the first semiconductor tool. A status field can be incorporated into the data structure and the learning engine can generate an expression for values of the status field based upon other fields in the data structure. From the expression, influential characteristics, e.g., variables in the expression, can be identified. 
     In a further embodiment, endpoint detection in etching steps can utilize mechanisms described herein. For instance, wavelengths, e.g., spectral lines, which are good predictors of endpoint conditions, can be identified. A status field is introduced which indicates a processed wafer is a good wafer, e.g., acceptable, or a bad wafer, e.g., unacceptable. The learning engine can generate an expression for status based upon the wavelengths identified as good predictors. A semiconductor production tool, e.g., an etching tool, can pass real-time information to the expression during wafer processing and halt etching when the expression predicts the status indicates a good wafer. 
     These and other embodiments are described in more detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various non-limiting embodiments are further described with reference to the accompanying drawings in which: 
         FIG. 1  is a flow diagram illustrating an exemplary, non-limiting embodiment for learning relationships among disparate information related to a semiconductor production tool; 
         FIG. 2  is an exemplary, non-limiting illustration of a data structure formed from an integration of spectral intensity information, tool operation information, and wafer measurement information according to one or more aspects; [Is it necessary to change FI-CD(1), FI-CD(2) . . . to CD(1), CD(2), etc. The rational being that FI-CD is typical of measurements after processing and we wish to ensure that we can take data about the wafer before entry into the process (e.g., DI-CD(1), DI-CD(2) . . . , and after exit from the process FI-CD(1), FI-CD(2), . . . . ] 
         FIG. 3  is a flow diagram illustrating an exemplary, non-limiting embodiment for normalizing spectroscopic data prior to consolidation into a training matrix; 
         FIG. 4  is a block diagram illustrating an exemplary, non-limiting system for aggregating disparate information related to a semiconductor production tool and determining relationships therein; 
         FIG. 5  is a flow diagram illustrating an exemplary, non-limiting embodiment for generating a recipe including optimized parameters identified based upon learned expressions from aggregate information; 
         FIG. 6  is a block diagram illustrating an exemplary, non-limiting system for selecting values of configurable parameters which achieve target output values; 
         FIG. 7  is a flow diagram illustrating an exemplary, non-limiting embodiment for identifying influential conditions of high yield production equipment; 
         FIG. 8  is an exemplary, non-limiting illustration of data structures employed as training matrices according to one or more aspects; 
         FIG. 9  is an exemplary, non-limiting illustration of a graph of intensity values over time for a plurality of chambers of a tool in accordance with one or more aspects; 
         FIG. 10  is a block diagram of an exemplary, non-limiting system for determining influential variables which affect yield performance; 
         FIG. 11  is a flow diagram illustrating an exemplary, non-limiting embodiment for identifying one or more sets of wavelengths suitable for endpoint detection during an etching process; 
         FIG. 12  is an exemplary, non-limiting illustration of graphs, for a plurality of chambers of a tool, of a pair of wavelengths whose corresponding intensities are plotted versus time. 
         FIG. 13  is a flow diagram illustrating an exemplary, non-limiting embodiment for autonomous, learning-based endpoint detection and process control; 
         FIG. 14  is an exemplary, non-limiting illustration of a data structure employed as a training matrix according to one or more aspects; 
         FIG. 15  is a block diagram illustrating an exemplary, non-limiting system for endpoint detection during a wafer etch process; 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     As discussed in the background, a variety of information can be gathered from semiconductor production tools, also referred to herein as fabrication equipment, fabrication machines, semiconductor process equipment, semiconductor production equipment, tools, or other similar terminology derived from the foregoing. Such information can include tool operational data, e.g., data from sensors monitoring and/or integrated with tools; device measurement data, e.g., physical and geometric characteristics of a wafer; and spectroscopic data, e.g., intensities of wavelengths or spectral lines due to concentrations of various gas compounds within the tool. Conventionally, the individual types of information are independently analyzed and utilized for disparate purposes. Accordingly, interesting relationships between disparate types of information remain unnoticed. 
     Through integration or consolidation of the various types of information, such relationships can be leveraged to achieve optimal tool performance, improved tool control, and greater understanding of conditions of good yielding tools or tool components. Consolidation and analysis of disparate information enables hard to measure or infrequently measured features to be accurately predicted or inferred from more easily acquired metrics. For instance, wafer measurements such as, but not limited to, develop inspection critical dimension (DI-CD), final inspection critical dimension (FI-CD), layer thickness, etch bias, or the like, are typically taken prior to processing or subsequent to processing. As such, in-situ values of wafer measurements are typically unavailable during processing. However, integration of information and relationship learned through integration enable such wafer measurements to be expressed by quantities readily obtainable, in-situ, during wafer processing. For instance, such wafer measurements can be expressed in terms of spectral intensity information and/or tool operational data, which can be monitored in real-time. 
     In various, non-limiting embodiments, semiconductor production equipment can leverage a learning engine, which aggregates disparate types of information, e.g., operational information, measurement information, spectroscopic information, etc., and generates at least one expression for a given field, column, or variable of the aggregate information that describes a value for the given field in terms of other fields of the aggregate information. For instance, an expression for etch bias can be generated in terms of a gas pressure within a chamber of a tool; intensities of one or more spectral lines; a elapsed time in wafer processing; various wafer measurements, pre- or post-processing; etc. The generated one or more expressions can facilitate modeling of wafer processing to predict possible outcomes given modifications to configurable parameters such as gas flow, chamber pressure, upper radio frequency (RF) power, etc. 
     According to further embodiments, the generated one or more expressions can be employed to select values for configurable parameters to achieve output targets. For instance, parameter values can be selected to achieve an etch bias within acceptable limits. In another embodiment, expressions can be generated which predict whether a given tool or chamber within a tool offers high yield performance. Such expressions can facilitate identification of conditions of the tool or chamber that are good indicators of yield performance. Further, expression can be generated which identify when a good wafer is produced or a good etch on a wafer is achieved. Such expressions can be utilized in connection with real-time data to control an etching process, for example. 
     Herein, an overview of some of the embodiments for improving performance of semiconductor production equipment through linkage of disparate information has been presented above. As a roadmap for what follows next, various exemplary, non-limiting embodiments and features for autonomous learning of relationships and improving tool performance with the relationships are described in more detail. Then, some non-limiting implementations and examples are given for additional illustration, followed by representative network and computing environments in which such embodiments and/or features can be implemented. 
     Understanding Semiconductor Production Equipment Performance Through Integration of Spectroscopic Information, Sensor Information, and Measurement Information 
     As mentioned above, in various embodiments, a semiconductor production tool can utilize a learning engine to consolidate disparate types of information into a single matrix of training data. The learning engine, based upon the matrix of training data, can autonomously generate at least one relationship that expresses a parameter of the matrix in terms of other parameters included in the matrix. The at least one relationship can be leveraged for “what-if?” analysis, equipment tuning or configuration, identification of conditions influencing yield performance, etch endpoint detection, and the like. 
     In a specific, non-limiting example, the semiconductor production tool can be a etch system configured to generate and control high-energy ions from a plasma to remove material from a wafer. An etching tool can include a plurality of plasma chambers independently processing different wafers. Within a chamber, highly reactive plasma gasses react with the wafer to remove a film, e.g., a layer of material, where a photoresist pattern leaves the film exposed. In the etch system, spectroscopy or other similar techniques (e.g., optical emission spectroscopy (OES), Fourier transform infrared spectroscopy (FTIR), laser induced fluorescence (LIF), etc.) can be utilized to detect gas compounds in a chamber as well as determine relative concentrations of disparate compounds. Typically, spectroscopy involves detecting light emitted from electron transitions occurring within atoms or molecules of the gas compounds with the chamber. Generally, different compounds emit light at different sets of wavelengths or spectral lines. Accordingly, a particular set of spectral lines detected can operate as a fingerprint to identify a particular compound. In addition, an intensity associated with the spectral lines can indicate a relative concentration of the compound. 
     With conventional fabrication processes, spectroscopic data, as described above, can be studied by a process engineer to identify and define endpoint conditions of an etch. Careful control of etching leads to better formed features on the wafer and, accordingly, to higher yields per wafer. For an etch intended to form a cavity in a material, the depth of the cavity can be controlled via etching time and a known etch rate. Some etches undercut a masking layer and form cavities with sloping sidewalls in the underlying material. The distance of undercutting is referred to etch bias or simply, bias. With conventional fabrication processes, the process engineer studies spectroscopic data to identify a good endpoint for an etch with the goal of etching a feature with a desirable critical dimension is formed while reducing bias as much as possible. 
     In accordance with an embodiment, spectroscopic data can be linked with disparate types of data such as sensor data (e.g., chamber pressures, gas flows, upper RF power, elapsed time, etc.) and wafer measurements (e.g., DI-CD, FI-CD, bias, thickness, etc.). Once linked, spectral intensities within a chamber can facilitate identification and prediction of favorable conditions which can improve tool performance. While aspects herein are described relative to etch systems, it is to be appreciated that etch systems are an exemplary environment to aide in explanation and description of various embodiments. Moreover, it will be appreciated that techniques described herein can be employed with other types of semiconductor production equipment beyond etch systems. For instance, equipment such as, but not limited to thermal processing equipment, coaters/developers, surface preparation systems, deposition systems, wafer probe systems, material modification or doping system, etc., can be improved with one or more embodiments herein. 
     With respect to one or more non-limiting ways to aggregate disparate information into a data structure and utilize the data structure to increase tool efficient and performance as described above,  FIG. 1  shows a flow diagram illustrating an exemplary, non-limiting embodiment for learning relationships among disparate information related to a semiconductor production tool. At  100 , disparate information regarding operation and performance of the semiconductor production tool is consolidated into a data structure. The data structure can be a matrix that incorporates spectral intensity information, tool operational information, and wafer measurement information. Spectral intensity information can include intensities of light at particular wavelengths or spectral lines as detected by a spectroscope or other similar measurement device. Tool operation information can include gas flows, chamber pressures, upper RF power, elapsed time, RF-Hours, age of tool parts (e.g., focus ring, CEL, MFC&#39;s) etc., as measured by sensor coupled with the semiconductor production tool. Further, wafer measurement information can include DI-CD, FI-CD, bias, thickness, etc. acquired by wafer metrology devices before and/or after a wafer processing step. 
     Turning briefly to  FIG. 2 , illustrated is an exemplary, non-limiting data structure  200  that incorporates spectral intensity information, tool operation information, and wafer measurement information. As shown in  FIG. 2 , data structure  200  can include a field  210  that specifies identification (ID) tags for a unit of processing. In the example of  FIG. 2 , the unit or processing is a wafer. Accordingly, field  210  includes Wafer IDs. In an embodiment data structure  200  can include information corresponding to K wafers, where K is an integer greater than or equal to one. Fields  220  of data structure  200  include tool operation information such as time which reports a number of seconds elapsed in a process. In an embodiment, the process can be partitioned into distinct steps, such that tool operation information can include an additional field, e.g., step ID (not shown), that indicates a step of the process from which other fields relate. In addition to process time and/or process steps associated with a process the semiconductor production tool implements, fields  220  can include sensor measurements such as chamber pressure, gas flows, upper RF power, etc. As shown in  FIG. 2 , the pressure field of fields  220  can include distinct pressure measurements (e.g., P 1 , P 2 , P 3 , . . . ) corresponding to particular time increments of a process on a particular wafer denoted by Wafer ID field. 
     Fields  230  of data structure  200  include spectral intensity information. The spectral intensity information includes intensity values for N wavelengths of light, where N is an integer greater than or equal to one. Similar to sensor measurements described above, for a given wavelength, such as wavelength 1 (λ 1 ), fields  230  can include intensity measurements a (I 11 , I 21 , I 31 , . . . ) corresponding to particular time increments of a process on a particular wafer denoted by Wafer ID. 
     To account for typical measurement error of intensity of spectral lines in different tools, chambers of tools, etc., measured intensities can be normalized. Turning briefly to  FIG. 3 , a flow diagram of an exemplary, non-limiting embodiment for normalizing spectroscopic data prior to consolidation into a training matrix is illustrated. At  300 , measured spectral intensity information is obtained. At  302 , a total intensity is determined based upon a reference. For instance, the total intensity can be computed for some arbitrarily chosen reference tool or chamber. The total intensity, according to an embodiment, is determined by evaluating an integral of a spectrum over a wavelength range. For example, given a spectrum ranging in wavelength from 200 nanometers (nm) to 800 nm with a 0.5 nm resolution, the integral is evaluated as a sum of spectral intensity values multiplied by 0.5. At  304 , the measured spectral intensity information is normalized with the total intensity. For instance, a normalized intensity value can correspond to a measured intensity value divided by the total intensity. It is to be appreciated that other normalizing techniques can be employed as well. For instance, normalizing spectral intensity can be accomplished by dividing a given set of intensity measurements at a wavelength by the peak measured magnitude of that intensity for each chamber. 
     As further depicted in  FIG. 2 , data structure  200  includes wafer measurement information in fields  240 . While only FI-CD measurements are shown in fields  240 , it is to be appreciated that fields  240  can include other wafer measurements such as bias measurements, DI-CD measurements, thickness measurements, and the like. Wafer measurements, such as FI-CD, can be acquired at multiple locations on the wafer. Accordingly, the numeral included in parentheses indicates a region of the wafer. As shown in  FIG. 2 , measurements can be taken at M regions of a wafer, where M is an integer greater than or equal to one. Wafer measurements are acquired before wafer processing or after wafer processing. Accordingly, for a given process step, wafer measurements are identical. For instance, assuming t 1 , t 2 , and t 3  correspond to time instants within the same process step on wafer ID 1, a FI-CD measurement at region 1 for time instants t 1 , t 2 , and t 3  is the same. 
     As shown in  FIG. 2 , total operation information, spectral intensity information, and wafer measurement information can be consolidated or aggregated in terms of wafer IDs, process time and/or process steps. For instance, the disparate information can be aligned in time or step and by wafer. Thus, a linkage is formed which enables various relationships to be derived as discussed below. 
     Turning back to  FIG. 1 , at  102 , at least one field from the data structure (e.g., data structure  200 ) is selected as a distinguished output. For instance, the at least one field can be bias fields corresponding to a particular region, a subset of regions, or all regions. At  104 , at least one relationship is autonomously generated, wherein the relationship corresponds to the at least one field and expresses the at least one field in terms of other fields of the data structure. In an embodiment, the at least one field (e.g., the distinguished output) can be selected by an agent (e.g., a software tool) in addition to being selected by a user (e.g., a tool operator, process engineer, etc.). 
     The data structure can be utilized as a training data matrix. The at least one relationship, for the selected field, can be learned via a genetic algorithm. However, it is to be appreciated that other types of learning can be implemented. For instance, the at least one relationship can be determined with linear approximation, multi-linear approximation, polynomial curve fitting, neural networks, or the like. 
     In a specific, non-limiting example, the at least one relationship can include an expression for etch bias at region 1 on a wafer. The expression can be denoted by the following:
 
bias 1 =ƒ(pressure, . . . , I (λ 1 ), . . . , DI - CD (1), . . . )
 
Where pressure is a chamber pressure of the tool, I(λ 1 ) is a spectral intensity corresponding to a wavelength of λ 1 , and DI-CD(1) is a DI-CD measurement at region 1. While the foregoing expression depicts only one sensor variable, one intensity variable, and one measurement variable, it is to be appreciated that the learned expression for bias 1  can include any number of sensor variables, intensity variables, and measurement variables illustrated in the expression by the ellipses.
 
     Learning of relationships, such as the expression described above, can occur autonomously, without human intervention, such that expressions of the relationships are learned at substantially every measurement point in terms of related sensor variable, related spectral intensity variables, and related measurement variables. According to another, non-limiting example, spectral line intensity is typically a result of distinct gases in a tool chamber in distinct proportions. Accordingly, a particular spectral intensity at a wavelength can be a result of one gas in a chamber or many distinct gases in the chamber. Thus, the at least one relationship generated can be mapping between a spectral intensity at a wavelength and various gas flows, wherein the mapping can take the form of the following:
 
 I (λ 1 )= g (gas(1),gas(2), . . . gas( n ))
 
Where λ 1  represents a wavelength at which a spectral intensity, I, is expressed and gas(n) is a gas flow, in standard cubic centimeters per minute (sccm), for example, for gas n, where n is an integer greater than or equal to one.
 
     Relationships learned for wafer attributes, e.g., wafer measurements, and wavelength intensities enable key insights into the behavior of a semiconductor production tool or a chamber of the semiconductor production tool. In addition, the relationships can be employed to perform “what-if?” style analysis. For instance, various questions can be readily answered; questions such as, “what happens to I(λ 1 ) when a flow of gas 1 (e.g., gas(1)) is increased by one percent?”, “what happens to bias(1), bias(2), . . . , bias(M) when gas(1) is increased by one percent?”, “what happens to FI-CD(1) when pressure is increased by two percent?”, “what happens to I(λ 1 ) when upper RF power is increased by 50 watts?”, etc. 
       FIG. 4  shows a block diagram illustrating an exemplary, non-limiting system  400  of aggregating disparate information related to a semiconductor production tool and determining relationships therein. As shown in  FIG. 4 , a tool  410  (also referred to as a fabrication machine, semiconductor production tool, semiconductor production equipment, etc.) can receive input wafers  402  and output processed wafers  404 . In an exemplary, non-limiting embodiment, tool  410  can be a etch tool that removes unmasked material from input wafers  402  via an etching process (e.g., wet etch, dry etch, plasma etching, . . . ) to generate processed wafers  404  having cavities and features formed thereon. 
     A variety of measurement devices, such as spectroscope  420 , tool sensors  430 , and device measurement equipment  440 , can monitor the process performed by tool  410  to acquire disparate information relating to various aspects, conditions, or results of the process. As an example, spectroscope  420  can acquire spectral intensity information  422  which includes a set of intensities for respective wavelengths or spectral lines observable by spectroscope  420 . Spectral intensity information  422  can be time-series data such that spectroscope  420  measures intensities for respective wavelengths at regular intervals (e.g., every second, every 2 seconds, every 100 milliseconds, etc.). Spectroscope  420  can also correlate spectral intensity information  422  with wafer IDs associated with specific wafers processed by tool  410 . Accordingly, spectroscope  420  can acquire spectral intensity information  422 , individually, for each wafer in a set of wafers processed by tool  410 . 
     Tool sensors  430  can monitor and measure tool operation characteristics while tool  410  processes wafers  402  and generate corresponding sensor information  432 . Sensor information  432 , similar to spectral intensity information  422 , can be time-series data correlated on a per-wafer basis. Sensor information  432  can include measurements from a variety of sensors. Such measurements include pressures within one or more chambers of tool  410 , gas flows for one or more distinct gases, temperature, upper RF power, elapsed time since last wet-clean, age of tool parts, and the like. 
     Device measurement equipment  440  can measure physical and geometric properties of wafers and/or features fabricated on wafers. For instance, device measurement equipment  440  can measure DI-CD, FI-CD, etch bias, thickness, and so forth, at predetermined locations or regions of wafers. The measured properties can be aggregated, on a per-location, per-wafer basis, as device measurement information  442 . Properties of wafers are typically measured before processing or after processing. Accordingly, device measurement information  442  is time-series data acquired at a different interval as compared with spectral intensity information  422  and sensor information  432 . 
     As shown in  FIG. 4 , spectral intensity information  422 , sensor information  432 , and device measurement information  442  can be input to a learning engine  450  configured to consolidate the disparate information into a unified matrix, such as data structure  200  described above with respect to  FIG. 2 . Also input to learning engine  450  is parameter selection  452 , which specifies a variable, parameter, or field of the unified matrix. As the unified matrix is an integration of spectral intensity information  422 , sensor information  432 , and device measurement information  442 , parameter selection  452  also acts to select a field, variable, or parameter from one of spectral intensity information  422 , sensor information  432 , or device measurement information  442 . Learning engine  450  is further configured to learn a relationship between the field, variable, or parameter specified by parameter selection  452  and other fields in the unified matrix at every measurement point. In an embodiment, learning engine  450  generates at least one least one expression  454 , which conveys the learned relationship. According to a non-limiting example, learning engine  450  implements a genetic algorithm to derive the relationship and, accordingly, expression  454 . However, it is to be appreciated that learning engine  450  can employ other learning techniques. 
     Moreover, learning engine  450  can accept multiple parameter selections  452  as input and output multiple expressions, respectively. For example, parameter selection  452  can indicate a selection of all bias fields for all locations of a wafer. Parameter selections  452  can originate from an agent (e.g., a software utility or application) or a user (e.g., a tool operator, a process engineer, etc.). In response to input of parameters selections  452 , learning engine  450  outputs respective expressions  454  representing bias at every location in terms of other fields of the unified matrix. 
     Further, while  FIG. 4  depicts spectroscope  420 , tool sensors  430 , device measurement equipment  440 , and learning engine  450  as distinct and separate components from tool  410 , it is to be appreciated that such configuration is provided for purposes of explanation and is not intended to be limiting. For instance, another suitable configuration for system  400  integrates the various components within tool  410  to provide an all-in-one semiconductor production tool capable of self-monitoring, self-learning, and self-tuning. 
     Optimizing Semiconductor Production Equipment Performance with Learned Relationships Among Disparate Process Information 
     As described above, spectroscopic information, sensor information, and measurement information related to semiconductor production equipment can be consolidated into a unified data structure to facilitate generated of learned expressions describing relationships among disparate data. In addition, to enabling an understanding of behaviors and performance of the semiconductor production equipment, the learned expressions can enable autonomous optimization, configuration, or tuning of the equipment. To this end,  FIG. 5  illustrates a flow diagram of an exemplary, non-limiting embodiment for generating a recipe including optimized parameters identified based upon learned expressions from aggregate information. At  500 , a variety of information is obtained. The information can include a set of expressions describing wafer output characteristics in terms of disparate information, a set of spectral intensity expressions characterizing intensity of spectral lines at particular wavelengths in terms of gas flows, a set of controllable parameter expressions which provide ranges and resolutions of configurable parameters of a semiconductor production tool, and a set of target values. 
     By way of a non-limiting example, the set of expressions describing wafer output characteristics can include a plurality of etch bias expressions, which are functions of other sensor data, wafer characteristics, and intensity information. For instance, the following expressions can be included in the set:
 
bias 1 =ƒ 1 (pressure, . . . , I (λ 1 ), . . . , DI - CD , . . . )
 
bias 2 =ƒ 2 (pressure, . . . , I (λ 1 ), . . . , DI - CD , . . . )
 
. . .
 
bias n =ƒ n (pressure, . . . , I (λ 1 ), . . . , DI - CD , . . . )
 
Where bias n  represents an etch bias at region n of a wafer, with n being an integer greater than or equal to 1, and f n  represents a function that expresses a bias at region n in terms of other sensor information (e.g., pressure, gas flows, etc.), other spectral intensity information (e.g., I(λ 1 ), I(λ 2 ), etc.), and other measurement inputs (e.g., DI-CD at various regions, FI-CD at various regions, thickness at various regions, etc.).
 
     The set of spectral intensity expressions can include one or more expressions of spectral intensity in terms of respective gas flows of a plurality of distinct gases in a chamber of the semiconductor production tool. Such expressions can take the form of the following, for example:
 
 I (λ 1 )= g   1 (gas(1),gas(2), . . . ,gas( p ))
 
 I (λ 2 )= g   2 (gas(1),gas(2), . . . ,gas( p ))
 
. . .
 
 I (λ m )= g   m (gas(1),gas(2), . . . ,gas( p ))
 
Where I(λ m ) is an intensity value of a spectral line of wavelength m, where m is an index of wavelengths from a minimum up to a maximum at a predetermined resolution (e.g., wavelength 1 is 200 nanometers, wavelength m is 800 nanometers, and the resolution is 0.5 nanometers) and g m  is an expression of intensity in terms of gas flows of p gases, where p is an integer greater than or equal to one.
 
     The set controllable parameter expressions provide minimums, maximums, and resolutions of configurable parameters. For example, the set can include the following: 
     Pressure: Minimum: 80; maximum: 90; resolution: 1 milliTorr (mTorr) 
     Gas(1): Minimum: 10; maximum: 12; resolution 0.1 sccm 
     . . . 
     Upper RF Power: Minimum: 1400; maximum: 1600; resolution: 1 Watt 
     Where minimum specifies a smallest configurable value for a parameter, maximum specifies a largest configurable value for a parameter, and resolution indicates a minimum variation in a parameter which is supported by the semiconductor production tool. 
     The set of target values specify values for the output characteristics specified in the set of expressions. For example, for the bias expressions described above, the set of target values can include the following:
 
bias 1 =40
 
bias 2 =40
 
. . .
 
bias n =40
 
While the above target values, in this example, are the same, it is to be appreciated that different values for each target can be specified. For instance, differences in target values, enables variation induced by prior processing tool can be compensated by the semiconductor production tool. As an example, where the semiconductor production tool is an etch tool, the target values can be different as DI-CD lines at edges of a wafer can be thicker, thus demanding a smaller etch bias as the edges.
 
     At  502 , values for the controllable parameters are identified, wherein the identified values achieve the target values. In an embodiment, the expression and target values described above can be input to an inverse problem solver, which utilizes a simulated annealing algorithm to identify values for the controllable parameters that allow the target values to be met. It is to be appreciated that other inverse problem solving techniques, such as simplex, gradient search, genetic algorithms, etc., can be employed in addition to or in place of the simulated annealing algorithm. At  504 , a recipe is generated for the semiconductor production tool, wherein the recipe includes recipe parameters established in accordance with the identified values of the controllable parameters. The recipe can be executed by the semiconductor production tool to produce optimal wafer output. 
       FIG. 6  shows a block diagram illustrating an exemplary, non-limiting system  600  of selecting values of configurable parameters which achieve target output values. As shown in  FIG. 6 , a tool  610  (also referred to as a fabrication machine, semiconductor production tool, semiconductor production equipment, etc.) can receive input wafers  602  and output processed wafers  604 . In an exemplary, non-limiting embodiment, tool  610  can be a etch tool that removes unmasked material from input wafers  602  via an etching process (e.g., wet etch, dry etch, plasma etching, . . . ) to generate processed wafers  604  having cavities and features formed thereon. 
     In accordance with an embodiment, system  600  can include a tuning engine  620 , which accepts learned expressions  622  as input. The learned expressions can be learned relationships generated by a learning engine, such as learning engine  450  described with respect to  FIG. 4 . Tuning engine  620  also obtains controllable parameters  624  and target values  626  as input. In an example, tuning engine  620  implements inverse problem solving techniques to identify suitable values of controllable parameters  624 , which achieve target values  626 , based upon the learned expressions  622 . The identified values can be collected and output as a recipe  628 , storable in recipe store  630  and employable by tool  610  to configure itself for optimal performance. 
     Identification of Important Conditions Influencing Good Yielding Chambers of a Semiconductor Production Tool 
     As described above, learned expressions generated from integrated spectral information, sensor information, and measurement information facilitate identification of optimal configurations for a semiconductor production tool. However, in some circumstances an inverse situation can arise. For instance, for a set of semiconductor productions tools or a given semiconductor production tool with multiple processing chambers, it can be observed that one or more tools or chambers consistently outperforms other tools or chambers. Identification of conditions which influence a particular chambers ability to outperform other chambers can enable under-achieving chambers to be reconfigured and optimized. 
     To this end,  FIG. 7  shows a flow diagram illustrating an exemplary, non-limiting embodiment for identifying influential conditions of high yield producing equipment. At  700 , disparate information regarding operation and performance of a set of tools (or a set of chambers of a tool) is consolidated. For instance, the disparate information can include spectral intensity information, tool operational information, and wafer measurement information, which is integrated into a data structure or unified matrix as described above. In addition, to the foregoing information, a performance status field can be incorporated into the data structure. The performance status field, in an embodiment, is set to a value of 1 for a best performing tool or chamber and is set to a value of 0 for all other tools or chambers included in the data structure. It is also to be appreciated that the performance status field can also be defined to be a real number indicative of the relative performance of a chamber instead of a Boolean status. 
     At  702 , at least one expression is autonomously generated, wherein the at least one expression predicts the status of a chamber in terms of other parameters included in the data structure. According to one embodiment, the other parameters are spectral intensities only. In accordance with another embodiment a mixed-mode expression is generated such that the other parameters include spectral intensities and sensor information variables. When spectral intensities only are employed, training matrix  800  depicted in  FIG. 8  is employed by a learning engine to drive the at least one expression that predicts the Status field shown in training matrix  800 . In a mixed-mode, the learning engine can utilize training matrix  850 , also shown in  FIG. 8 . As seen in  FIG. 8 , training matrices  800  and  850  include status fields, wafer ID fields, equipment ID fields (identifying a particular tool or chamber), and spectroscopic data. In the mixed-mode, sensor data is employed as well, so training matrix  850  further includes sensor data fields, such as pressure. To facilitate explanation, the following discussion describes examples where spectral intensities only are utilized to derive the at least one expression. However, it will be readily appreciated how the following techniques are extended to the mixed-mode which includes sensor data. 
     In a non-limiting example, the at least one expression can be a Boolean valued function, F, such as the following:
 
Status= F ( I (λ 1 ), I (λ 2 ), . . . , I (λ m ))
 
Pursuant to this example, Status is predicted based upon spectral intensity values for a set of m wavelengths or spectral lines, where m is an integer greater than or equal to one. The learning engine can be configured such that the number of intensity values included in the Boolean valued function, F, can be restricted to smaller number if only the largest contributors to status are desired.
 
     At  704 , a variable from the at least one expression is selected. At  706 , a plot of the selected variable is generated for each tool or chamber.  FIG. 9  illustrates such a plot of an intensity of a spectral line for four chambers of a tool (CH1 through CH4). At  708 , an order is identified, based on the plots. The order is an order of the tools or chambers with respect to the selected variables. For example, in  FIG. 9 , the order can be (1) CH4, (2) CH3, (3) CH1, and (4) CH2. At  710 , the identified order is compared with an order of yields corresponding to the tools or chambers. At  712 , the variable is output as an influential factor in yield performance when the identified order matches the order of yields. 
       FIG. 10  shows a block diagram of an exemplary, non-limiting system  1000  for determining influential variables which affect yield performance. As shown in  FIG. 10 , a tool  1010  can include one or more chambers  1012 . Chambers  1012  can individually and independently process input wafers and produce output wafers. For example, chambers  1012  can be distinct plasma chambers of an etch tool. 
     In accordance with an embodiment, system  1000  includes a learning engine  1020  which obtains operational and performance information  1014  from tool  1010  (or measurement devices associated with tool  1010 ) and status information  1022  per chamber. The learning engine  1020  can generate a training matrix from operational and performance information  1014 . Learning engine  1020  can further incorporate status information  1022  into the training matrix. In an embodiment, status information  1022  indicates a status of 1 for a good performing chamber among chambers  1012  and indicates a status of 0 for the remaining chambers. 
     Learning engine  1020  outputs a learned expression for a status in terms of fields or variables included in the training matrix. The learned expression  1024  is input to a condition evaluation component  1030  which identifies influential variables  1032 , included in the learned expression  1024 , which are instrumental in determining yield performance of a chamber among chambers  1012 . 
     Autonomous Endpoint Detection 
     As discussed above, in conventional fabrication processes, spectroscopic data (e.g., spectral intensity information) can be studied by a process engineer to identify and define endpoint conditions of an etch. Careful control of etching leads to better formed features on the wafer and, accordingly, to higher yields per wafer. For an etch intended to form a cavity in a material, the depth of the cavity can be controlled via etching time and a known etch rate. Some etches undercut a masking layer and form cavities with sloping sidewalls in the underlying material. The distance of undercutting is referred to etch bias or simply, bias. With conventional fabrication processes, the process engineer studies spectroscopic data to identify a good endpoint for an etch with the goal of etching a feature with a desirable critical dimension is formed while reducing bias as much as possible. However, even through careful study, it is not always possible to identify wavelengths that can be used for endpoint detection. 
     In an embodiment, wavelengths or spectral lines, whose intensities are good indicators of endpoint conditions are autonomous identified. Such spectral lines can be employed in connection with learned expressions to facilitate automatic endpoint detection and etching control. With respect to one or more non-limiting ways to identify endpoint spectral lines and to detect endpoint conditions,  FIG. 11  illustrates a flow diagram of an exemplary, non-limiting embodiment for identifying one or more sets of wavelengths suitable for endpoint detection during an etching process. At  1100 , spectral intensity information of a wafer fabrication process is received and a subset of the information, corresponding to a process step of interest, is identified. For example, spectral intensity information can be associated with an entire wafer fabrication process, whereas the process step of interest corresponds to an etch step. Accordingly, a portion of the spectral intensity information corresponding to the etch step is identified. 
     At  1102 , within the subset of the spectral intensity information, a first set of wavelengths is identified. The first set of wavelengths or spectral lines include those wavelengths with intensities that increase at a start of the process step of interest (e.g., an increase in intensity at a beginning portion of the subset of information). At  1104 , during a period of the process step of interest where wavelengths in the first set exhibit a decrease in intensity, a second set of wavelengths is identified which show an increase in intensity in the period. According to an example, the second set of wavelengths correspond to emissions from by-product compounds in an etching chamber. At  1106 , an instant (e.g., time instant) is identified where intensity values for wavelengths in the first set and intensity values for wavelengths in the second set stabilize (or cross-over) after initial decrease and increase, respectively. The stabilization (or cross-over) is illustrated in graphs  1200  through  1206  of  FIG. 12 , which show intensities of two wavelengths or spectral lines for each of four chambers. Such an instant of stabilization, if identified, indicates the first and second sets of wavelengths are suitable for endpoint detection as the endpoint of etching corresponds to when intensities stabilize or cross-over. At  1108 , the first and second sets of wavelengths are utilized for endpoint detection. 
       FIG. 13  illustrates a flow diagram of an exemplary, non-limiting embodiment for autonomous, learning-based endpoint detection and process control. At  1300 , spectral intensity information from a wafer fabrication process, identified sets of wavelengths suitable for endpoint detection, and performance information are received. According to an example, the spectral intensity information can be time-series data of intensities for a plurality of spectral lines observed during a semiconductor production step, such as an etching step. The set of wavelengths suitable for endpoint detection can be identified in accordance with the embodiment described above with respect to  FIG. 11 . Further, performance information can be acquired by an operator or process engineer. Performance information indicates wafers where fabrication performance was good. Such performance information can be integrated with the spectral intensity information to form training matrix  1400  illustrated in  FIG. 14 . The status column, shown in  FIG. 14 , can be integrated as follows. For a good wafer (e.g., a wafer with well-formed features and good yields, such as wafer ID 1  of training matrix  1400 ), the value of the status field is initially zero and, subsequently, is one when wavelengths in the identified sets stabilize or cross-over. Thus, for good wafers, the status column is initially zero and become one after the endpoint reached. For a wafer exhibiting poor results, the status column has a value of zero for all time instants 
     At  1302 , at least one expression is autonomously generated. The at least one expression predicts wafer performance in terms of intensity information corresponding to wavelengths in the identified sets of wavelengths. The at least one expression can be generated by a learning engine (e.g., employing a genetic algorithm or other suitable learning technique) based upon training matrix  1400 . At  1304 , real-time spectral information from an ongoing wafer fabrication process step is acquired. At  1306 , a status is determined based on the real-time spectral information and the at least one expression. At  1308 , a determination is made as to whether the status is good. If yes, at  1310 , the process step is stopped as the endpoint is reached. If no, at  1312 , a determination is made as to whether a maximum time limit has elapsed. If yes, the process step is stopped at  1310 . If no, the process step is continued at  1314 , and a new status is determined at  1306 . Accordingly, the fabrication process step is monitored in this manner until either a good status is determined or a maximum time elapses. 
       FIG. 15  illustrates a block diagram of an exemplary, non-limiting system  1500  for endpoint detection during a wafer etch process. As shown in  FIG. 10 , a tool  1510  (e.g., a semiconductor production tool such as an etch tool) can provide operational information  1512  to a wavelength identification component  1520 . The operational information includes spectral intensity information corresponding to process steps performed on one or more wafers. The wavelength identification component  1520  outputs endpoint wavelengths  1522  based upon the operational information  1512 . 
     System  1500  includes a learning engine  1530  which obtains operational information  1512  from tool  1510  (or measurement devices associated with tool  1510 ), endpoint wavelengths  1522 , and status information  1532 . The learning engine  1530  can generate a training matrix from operational information  1512 . Learning engine  1530  can further incorporate status information  1532  into the training matrix as depicted in  FIG. 14 . Learning engine  1530  outputs a learned expression  1534  for a status in terms of intensities of endpoint wavelengths  1522 . The learned expression  1534  is input to an endpoint detection component  1540  which also accepts real-time information  1514  from tool  1510 . Based upon the learned expression  1534  and the real-time information  1514 , endpoint detection component  1540  can be configured to send a stop signal  1542  to tool  1510  when a endpoint is detected or when a maximum time expires as described above with respect to  FIG. 13 . 
     The word “exemplary” is used herein to mean serving as an example, instance, or illustration. For the avoidance of doubt, the subject matter disclosed herein is not limited by such examples. In addition, any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs, nor is it meant to preclude equivalent exemplary structures and techniques known to those of ordinary skill in the art. Furthermore, to the extent that the terms “includes,” “has,” “contains,” and other similar words are used, for the avoidance of doubt, such terms are intended to be inclusive in a manner similar to the term “comprising” as an open transition word without precluding any additional or other elements when employed in a claim. 
     As mentioned, the various techniques described herein may be implemented in connection with hardware or software or, where appropriate, with a combination of both. As used herein, the terms “component,” “engine,” “system” and the like are likewise intended to refer to a computer-related entity, either hardware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on computer and the computer can be a component. One or more components may reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. 
     As it employed in the subject specification, the term “processor” can refer to substantially any computing processing unit or device comprising, but not limited to comprising, single-core processors; single-processors with software multithread execution capability; multi-core processors; multi-core processors with software multithread execution capability; multi-core processors with hardware multithread technology; parallel platforms; and parallel platforms with distributed shared memory. Additionally, a processor can refer to an integrated circuit, an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), a programmable logic controller (PLC), a complex programmable logic device (CPLD), a discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. Processors can exploit nano-scale architectures such as, but not limited to, molecular and quantum-dot based transistors, switches and gates, in order to optimize space usage or enhance performance of user equipment. A processor may also be implemented as a combination of computing processing units. 
     In the subject specification, terms such as “store,” “storage,” “data store,” data storage,” “database,” “repository,” and substantially any other information storage component relevant to operation and functionality of a component, refer to “memory components,” or entities embodied in a “memory” or components comprising the memory. It will be appreciated that the memory components described herein can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. 
     By way of illustration, and not limitation, nonvolatile memory can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM), which acts as external cache memory. By way of illustration and not limitation, RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM). Additionally, the disclosed memory components of systems or methods herein are intended to comprise, without being limited to comprising, these and any other suitable types of memory. 
     Various aspects or features described herein may be implemented as a method, apparatus as either hardware or a combination of hardware and software or hardware and firmware, or article of manufacture using standard programming and/or engineering techniques. Implementation(s) as a method, or as a combination of hardware and software, for example, can be effected at least in part through a processor or processing unit (e.g., processing platform  385 ) that executes computer-accessible code instructions retained in a memory. In one or more aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the various functionality described herein can be stored or transmitted as one or more instructions or code on a computer-readable storage medium or memory. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage medium may be any available media that can be accessed by a computer. The term “article of manufacture” as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer readable media can include but are not limited to magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips . . . ), optical disks [e.g., compact disc, digital versatile disc (DVD) . . . ], smart cards, and flash memory devices (e.g., card, stick, key drive . . . ). 
     Various aspects of the subject disclosure can be implemented by processor(s) or computing devices including the processor(s). The computing device typically include a variety of media, which can include computer-readable storage media and/or communications media, which two terms are used herein differently from one another as follows. Computer-readable storage media can be any available storage media that can be accessed by the computer and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer-readable storage media can be implemented in connection with any method or technology for storage of information such as computer-readable instructions, program modules, structured data, or unstructured data. Computer-readable storage media can include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or other tangible and/or non-transitory media which can be used to store desired information. Computer-readable storage media can be accessed by one or more local or remote computing devices, e.g., via access requests, queries or other data retrieval protocols, for a variety of operations with respect to the information stored by the medium. 
     Communications media typically embody computer-readable instructions, data structures, program modules or other structured or unstructured data in a data signal such as a modulated data signal, e.g., a carrier wave or other transport mechanism, and includes any information delivery or transport media. The term “modulated data signal” or signals refers to a signal that has one or more of its characteristics set or changed in such a manner as to encode information in one or more signals. By way of example, and not limitation, communication media include wired media, such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. 
     What has been described above includes examples of the claimed subject matter. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the claimed subject matter, but one of ordinary skill in the art may recognize that many further combinations and permutations of the claimed subject matter are possible. Accordingly, the claimed subject matter is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the terms “includes” or “including” are used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the terms “comprises” or “comprising” as “comprises” or “comprising” is interpreted when employed as a transitional word in a claim. 
     The aforementioned systems have been described with respect to interaction between several components. It can be appreciated that such systems and components can include those components or specified sub-components, some of the specified components or sub-components, and/or additional components, and according to various permutations and combinations of the foregoing. Sub-components can also be implemented as components communicatively coupled to other components rather than included within parent components (hierarchical). Additionally, it can be noted that one or more components may be combined into a single component providing aggregate functionality or divided into several separate sub-components, and that any one or more middle layers, such as a management layer, may be provided to communicatively couple to such sub-components in order to provide integrated functionality. Any components described herein may also interact with one or more other components not specifically described herein but generally known by those of skill in the art. 
     In view of the exemplary systems described supra, methodologies that may be implemented in accordance with the described subject matter can also be appreciated with reference to the flowcharts of the various figures. While for purposes of simplicity of explanation, the methodologies are shown and described as a series of blocks, it is to be understood and appreciated that the various embodiments are not limited by the order of the blocks, as some blocks may occur in different orders and/or concurrently with other blocks from what is depicted and described herein. Where non-sequential, or branched, flow is illustrated via flowchart, it can be appreciated that various other branches, flow paths, and orders of the blocks, may be implemented which achieve the same or a similar result. Moreover, some illustrated blocks are optional in implementing the methodologies described hereinafter. 
     In addition to the various embodiments described herein, it is to be understood that other similar embodiments can be used or modifications and additions can be made to the described embodiment(s) for performing the same or equivalent function of the corresponding embodiment(s) without deviating therefrom. Still further, multiple processing chips or multiple devices can share the performance of one or more functions described herein, and similarly, storage can be effected across a plurality of devices. Accordingly, the invention is not to be limited to any single embodiment, but rather is to be construed in breadth, spirit and scope in accordance with the appended claims.