Patent Application
20130030760
Equipment Engineering System (EES) systems have long been employed to record tool-related data (e.g., pressure, temperature, RF power, process step ID, etc.) in a typical semiconductor processing equipment. To facilitate discussion,
Yield Management System (YMS) systems have also long been employed to record material-related data (e.g., post-process critical dimension measurements, etch depth measurements, electrical parameter measurements, etc.) on post-processing wafers.
Since YMS 152 focuses on yield-related data, e.g., measurement data from the wafers, YMS 152 is capable of ascertaining, from the wafers analyzed, which tool may cause a yield problem. For example, YMS 152 may be able to ascertain from the metrology data and the electrical parameter measurements that tool #2 has been producing wafers with poor yield. However, since YMS 152 does not focus on or collect significant and detailed tool-related data, it is not possible for YMS system 152 to ascertain the conditions and/or settings (e.g., the specific chamber pressure during a given etch step) on the tool that may cause the yield-related problem. Further, as an example, lacking access to the data regarding the tool conditions/settings, it is not possible for YMS 152 to perform analysis to ascertain the common tool conditions/settings (e.g., chamber pressure or bias power setting) that exist when the poor yield processing occurs on one or more batches of wafers. Conversely, since EES 102 focuses on tool-related data, EES 102 may know about the chamber conditions and settings that exist at any given time but may not be able to ascertain the yield-related results from such conditions or settings.
In the prior art, a process engineer, upon seeing the poor process results generated by YMS 152, typically needs to access other tools (such as EES 102) to obtain tool-related data. By painstakingly correlating YMS data pertaining to low wafer yield to data obtained from tools (e.g., EES data), the engineer may, with sufficient experience and skills, be able to ascertain the parameter(s) and/or sub-step of the process(es) that cause the low wafer yield.
However, this approach requires highly skilled experts performing painstaking, time-consuming data correlating between the YMS data from the YMS system and the EES data from the EES system and painstaking, time-consuming analysis (e.g., weeks or months in some cases) and even if such experts can successfully correlate manually the two (or more) independent systems and detect the root cause of the yield-related problem, the prior art process is still time consuming and incapable of being leveraged for timely automatic analysis of cause/effect data to facilitate problem detection and/or alarm generation, and/or tool control and/or prediction with a high degree of data granularity.
The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
The present invention will now be described in detail with reference to a few embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention.
Various embodiments are described herein below, including methods and techniques. It should be kept in mind that the invention might also cover articles of manufacture that includes a computer readable medium on which computer-readable instructions for carrying out embodiments of the inventive technique are stored. The computer readable medium may include, for example, semiconductor, magnetic, opto-magnetic, optical, or other forms of computer readable medium for storing computer readable code. Further, the invention may also cover apparatuses for practicing embodiments of the invention. Such apparatus may include circuits, dedicated and/or programmable, to carry out tasks pertaining to embodiments of the invention. Examples of such apparatus include a general-purpose computer and/or a dedicated computing device when appropriately programmed and may include a combination of a computer/computing device and dedicated/programmable circuits adapted for the various tasks pertaining to embodiments of the invention.
Embodiments of the invention relate to systems for integrating both cause data (tool-related or process-related data) and effect data (material-related or material-related data) on a single platform. In one or more embodiments, an integrated yield/equipment data processing system for collecting and analyzing integrated tool-related data and material-related data pertaining to at least one wafer processing tool and at least one wafer is disclosed. By integrating cause-and-effect data in a single platform, the data necessary for automated problem detection (e.g., automated root cause analysis) and prediction is readily available and correlated, which shortens the cycle time to detection and facilitates efficient and timely automated tool management and control.
As the term is employed herein, the synonymous term “automatic”, “automatically” or “automated” (e.g., “automated root cause analysis, automated problem detection, automated model building, etc.) denotes, in one or more embodiments, that the action (e.g., analysis, detection, optimization, model building, etc.) occur automatically without human intervention as tool-related and material-related data are received, correlated, and analyzed by logic (software and/or hardware). In one or more embodiments, prior human input (in the form of domain knowledge, expert knowledge, rules, etc.) may be pre-stored and employed in the automated action, but the action that results (e.g., analysis, detection, optimization, model building, etc.) does not need to wait for human intervention to occur after the relevant tool-related and material-related data are received. In one or more embodiments, minor human intervention (such as issuing the start command) may be involved and is also considered part of the automated action but on the whole, all the tool-related and material-related data as well as models, rules, algorithms, logic, etc. to execute the action (e.g., analysis, detection, optimization, model building, etc.) are available and the action does not require substantive input by the human operator to occur.
As the term is employed herein, a knowledge base is a storage area designed specifically for storing, classifying, indexing, updating, and searching domain knowledge and case study results (or historical results). It may contain tool and process profiles, models for prediction, analysis, control and optimization. The content in the knowledge base can be input and updated manually or automatically using the YiEES system. It is used as prior knowledge by YiEES system for model building, analysis, tool and process control and optimization.
For example, one or more embodiments of the invention integrate both cause and effect data on a single platform to facilitate automatic analysis using computer-implemented algorithms that automatically detect material-related problems and pin-point the tool-related data (such as a specific pressure reading on a specific tool) that causes such material-related problems and/or build prediction models for better process control, identify optimal process condition, provide prediction for timely machine maintenance, etc. Once the root cause is determined/or an model is built and traced to a specific tool and/or step in the process, automated tool control may be initiated to correct the problem or set the process to its optimal condition, for example.
In this manner, the time-consuming aspect of manual data correlation and analysis of the prior art is substantially eliminated. Further, by removing the need for human data correlation and analysis, human-related errors can be substantially reduced. Root cause analysis may now be substantially automated, which reduces error and improves speed.
The features and advantages of embodiments of the invention may be better understood with reference to the figures and discussions that follow.
The material-related data from tools 214-220 may be collected using an appropriate I/O module or I/O modules and may include, for example, wafer ID or material ID, wafer history data or material history data, which contains the date/time information, the process step ID, the tool ID, the processing recipe ID, and any material-related quality measurements such as any physical measurements, for example film thickness, film resistivity, critical dimension, defect data, and any electrical measurements, for example transistor threshold voltage, transistor saturation current (IDSAT), or any equivalent material-related quality measurements. The tool-related data from tools 204-210 may be collected using an appropriate I/O module or I/O modules and may include, for example, the date/time information, the tool ID, the processing recipe ID, subsystems and tool component historical data, and any other process-related measurements, for example pressure, temperature, gas flows
In one or more embodiments, the date/time, tool ID and optionally recipe ID, may be employed as common attributes or correlation keys to align or correlate, using appropriate logic (which may be implemented via dedicated logic or as software executed in a programmable logic/processor for example) the tool-related data with the material-related data (for example, tool-related parameter values with metrology measurement values on specific materials (i.e., wafers), thereby permitting a computer-implemented algorithm to correctly correlate and perform the automated analysis on the combined material-related data and tool-related data.
Online control/analysis layer 306 represents the layer that contains the plug-and-play modules for performing automated control, optimization, analysis, and/or prediction based on the integrated tool-related and material-related data collected from data layer 304. To facilitate plug-and-play modules for online control/analysis, a data/connectivity platform 330 serves to interface with bus 328 to obtain tool-related and material-related data from data layer 304 as well as to present a standard interface to communicate with the plug-and-play modules. For example, data/connectivity platform 330 may implement APIs (application programming interfaces) with pre-defined connectivity and communication options for the plug-and-play modules.
Plug-and-play modules 340, 342, 344, 346 represent 4 plug-and-play modules to, for example, perform the automated control (SPC, MPC, APC), tool profiling, process profiling, tool optimization, processing optimization, modeling building, dynamic model update and modification, analysis, and/or prediction using the integrated tool-related and material-related data collected from data layer 304. The plug-and-play modules may be implemented via dedicated logic or as software executed in a programmable logic/processor, for example. Each of plug-and-play modules 340, 342, 344, 346 may be configured as needed depending on the specifics of a process, the needs of a particular customer, etc. Sharing the same platform allow each module to feed and receive useful information from others.
For example, if the YiEES system, for example the offline analysis part (to be discussed later herein), found a strong correlation between a specific tool-related parameter (such as etch time) with a material-related parameter of interest (e.g., leakage current of transistors), this knowledge is saved in the knowledge base 368 as part of the tool profile and/or used to create or update existing models related to this tool/or process in process control, prediction, and/or process optimization. A plug-and-play module 340 that is coupled with data/connectivity layer 330 may monitor etch time values (e.g., with high/low limit) and use the result of that monitoring to control the tool and/or optimize the tool and/or process in order to ensure the process is controlled/optimized to satisfy a particular leakage current specification. The new knowledge can also be used by existing module for new model creation or existing model updates. This is an example of a plug-and-play tool that can be configured and updated quickly by the tool user and plugged into data/connectivity platform 330 to receive integrated tool-related and material-related data (e.g., both cause and effect data) and to provide additional control/optimization capability to satisfy a customer-specific material-related parameter of interest.
As another example, if the YiEES system, for example the off-line analysis part (to be discussed later herein), found a strong correlation between a group of specific tool-related parameters (such as etch time and chamber pressure and RF power to the electrodes) with a material-related parameter of interest (e.g., critical dimension of a via), this knowledge is saved in the knowledge base as part of the tool profile and/or used to create or update existing models related to this tool/or process in process control, prediction, and/or process optimization. A plug-and-play module 342 that is coupled with data/connectivity layer 330 may monitor values associated with this group of specific tool-related parameters (which may be conceptualized as a virtual parameter that is a composite of individual tool-related parameters) and use the result of that monitoring to control the tool and/or optimize the tool and/or process in order to ensure the process is controlled/optimized to satisfy a particular via CD (critical dimension) specification. The new knowledge can also be used by existing module for new model creation or existing model optimization. This is an example of another plug-and-play tool that can be configured and updated quickly by the tool user and plugged into data/connectivity platform 330 to receive integrated tool-related and material-related data (e.g., both cause and effect data) and to provide additional control/optimization capability to satisfy a customer-specific material-related parameter of interest or a group of material-related parameters of interest.
As another example, if the YiEES system, for example the off-line analysis part (to be discussed later herein), found a strong correlation between specific tool-related (e.g., temperature) parameter and/or material-related (e.g., leakage current) parameter with yield, this knowledge is saved in the knowledge base as part of the tool profile and/or used to create or update existing models related to this tool/or process in process control, prediction, and/or process optimization. Plug-and-play module 344 or plug-and-play module 346 that is coupled with data/connectivity layer 330 in order to monitor these specific tool-related parameter (e.g., temperature) and material-related parameter (e.g., leakage current) may predict the yield with high data granularity. The new knowledge can also be used by existing module for new model creation or existing model optimization. Each of modules 344 or 346 is an example of a plug-and-play tool that can be configured and updated quickly by the tool user and plugged into data/connectivity platform 330 to receive integrated tool-related and material-related data (e.g., both cause and effect data) and to provide analysis and/or prediction capability to satisfy a customer-specific yield requirement.
Online integrated tool-related and material-related database 348 represents a data store that stores at least sufficient data to facilitate the online control/analysis needs of modules 340-346. Since database 348 conceptually represents the data store serving the online control/analysis needs, archive tool-related and material-related data from past processes may be optionally stored in database 348 (but not required in database 348 in one or more embodiments).
Offline analysis layer 308 represents the layer that facilitates off-line data extraction, analysis, viewing and/or configuration by the user. In contrast to online control/analysis layer 306, offline analysis layer 308 relies more heavily on archival data as well as analysis result data from online control/analysis layer 306 (instead of or in addition to the data currently collected from tools 310-316 and wafers 320-324) and/or knowledge base and facilitates interactive user analysis/viewing/configuration.
A data/connectivity platform 360 serves to interface with online control/analysis layer 306 to obtain the data currently collected from tools 310-316 and wafers 320-324, from the analysis result data from the plug-and-play modules of online control/analysis layer 306, from the data stored in database 348, from a knowledge base from the archival database 362 (which stores tool-related and material-related data), and/or from the legacy databases 364 and 366 (which may represent, for example, third-party or customer databases that may have tool-related or material-related or analysis results that may be of interest to the off-line analysis).
Data/connectivity platform 360 also presents a standard interface to communicate with the plug-and-play offline modules. For example, data/connectivity platform 360 may implement APIs (application programming interfaces) with pre-defined connectivity and communication options for the offline plug-and-play extraction module or offline plug-and-play configuration module or offline plug-and-play analysis module or offline plug-and-play viewing module. The off-line plug-and-play modules may be implemented via dedicated logic or as software executed in a programmable logic/processor, for example. These offline extraction, analysis, configuration and/or viewing modules may be quickly configured as needed by the customer and plugged into data/connectivity platform 360 to receive current and/or archival integrated tool-related and material-related data (e.g., both cause and effect data) as well as current and/or archival online analysis results and/or data from third party databases in order to service a specific extraction, analysis, configuration and/or viewing need.
Interaction facility 370 conceptually implements the aforementioned offline plug-and-play modules and may be accessed by any number of user-interface devices, including for example smart phones, tablets, dedicated control devices, laptop computers, desktop computers, etc. In terms of viewing, different industries may have different preferences for different viewing methodologies (e.g., pie chart versus timeline versus spreadsheets). A web server 372 and a client 374 are shown to conceptually illustrate that offline extraction, analysis, configuration and/or viewing activities may be performed via the internet, if desired.
Control/optimization module 408, which represents a plug-and-play module, may automatically analyze the tool-related data and the material-related data and determine that there is a correlation between chamber pressure during the polysilicon etch step (a tool-related data parameter) and the leakage current of a gate (a material-related data parameter). This analysis result may be employed to modify a recipe setting, which is sent to process recipe management block 420 to create a modified recipe to perform tool control or to optimize tool control for tool 404. Note that the presence of highly granular tool-related data and material-related data permit root cause analysis that narrows down to one or more specific parameters in a specific tool, which facilitates highly-accurate recipe modification. Accordingly, the availability of both tool-related data and material-related data and the ease of configuring/implementing a plug-and-play module to perform the analysis on the integrated tool-related data and material-related data greatly simplify the automated analysis and control task. In addition, based on the above analysis, a prediction model can be built or optimized and its results can be passed to other plug and play modules (for example 406) as inputs. This is also an example of feed-forward and feed-backward capability of the plug and play module in the system.
Automated analysis of effect (e.g., yield result based on integrated tool-related and material-related data) and/or prediction (e.g., predicted yield result based on integrated tool-related and material-related data) may be improved using a knowledge base. In one or more embodiments, human experts may input root-cause analysis or prediction knowledge into a knowledge base to facilitate analysis and/or prediction. The human expert may, for example, indicate a relationship between saturation current measurements for a transistor gate and polysilicon critical dimension (C/D).
Previously obtained root-cause analysis (which pinpoints tool-related parameters correlating to yield-related problems) and previously obtained prediction models from the YiEES system (such as from one or more of plug-and-play modules 340-346 of online control/analysis layer 306 of
The root-cause analysis and/or prediction knowledge from the human expert and/or from prior analysis/prediction module outputs may then be applied against the integrated tool-related data and material-related data to perform root cause analysis or to build new prediction models. The combination of a knowledge base, tool-related data, and material-related data in a single platform renders the automated analysis more accurate and less time-consuming.
In one or more embodiments, multiple potential root causes or prediction models may be automatically provided by the knowledge base, along with a ranking of probability, in order to give the tool operator multiple options to investigate. Furthermore, the root-cause analysis and/or prediction models obtained using the assistance of the knowledge base may be stored back into the knowledge base to improve future root-cause analysis and/or prediction. To ensure the accuracy of the generated root-cause analysis or prediction models, cross validation using independent data may be performed periodically if desired.
Expert or domain knowledge may also be employed to automatically filter the analysis result candidates or influence the ranking (via changing the weight assigned to the individual results, for example) of the analysis result candidates. For example, the set of candidate analysis results (obtained with statistical method alone or with or without know ledge base assistance) may be automatically filtered by expert or domain knowledge to de-emphasize certain analysis result, or emphasize certain analysis result, or eliminate certain analysis result, in order to influence the ranking of the analysis result candidates.
As an example, the expert may input, as a rule into the analysis engine, that yield loss around the edge is likely associated with etch problems and more specifically with high bias power during the main etch step. Accordingly, the set of analysis result candidates that may have been obtained using a purely statistical approach or a combination of a statistical approach and other knowledge base rules may be influenced such that those candidates associated with etch problems and more specifically those analysis results associated with high bias power during main etch step would be emphasized (and other candidates de-emphasized). Note that this type of root cause analysis granularity is possible only with the provision of integrated tool-related data and material-related data in a single platform, in accordance with one or more embodiments of the invention.
Analysis may, alternatively or additionally, be made more efficient/accurate by first performing automated clustering/classification of wafers, and then applying different automated analyses to different groups of wafers. With the availability of material-related data, it is possible to cluster or classify the processed wafers into smaller subsets for more efficient/accurate analysis.
For example, the processed wafers may be grouped according the processed patterns (e.g., over-etching along the top half, over-etching along the bottom half, etc.) or any tool-related parameter (e.g., chamber pressure) or any material-related parameter (e.g., a particular critical dimension range of values) or any combination thereof. Note that this type of classification/clustering is possible because both highly granular tool-related and material-related data are available and aligned on a single platform. Generically speaking, clustering/classification aims to group subsets of the materials into “single cause” groups or “single dominant cause” groups to improve accuracy in, for example, root-cause analysis. For example, when a subset of the materials (e.g., wafers) are grouped into a group that reflects a similar process result or a set of similar process results, it is likely to be easier to pinpoint the root cause for the similar process result(s) for that subset than if the wafers are arbitrarily grouped into arbitrary subsets/groups without regard for process result similarities or not grouped at all.
Classification refers to applying predefined criteria or predefined libraries to the current data set to sort the wafer set into predefined “buckets”. Clustering refers to applying statistical analysis to look for common attributes and creating sub-sets of wafers based on these common attributes/parameters.
In accordance with one or more embodiments, different types of analysis may then be applied to each sub-set of wafers after classification/clustering. By way of example, if a sub-set of wafers has been automatically grouped based on a specific range of critical dimension and it is known that critical dimension is not influenced by process gas flow volume, for example, considerable time/effort can be saved by not having to analyze that subset of wafers for correlation with process gas flow.
However, that subset of wafers may be analyzed in a more focused and/or detailed manner using a particular analysis methodology tailored toward detecting problems with critical dimensions. Examples of different analysis methodologies include equipment analysis, chamber analysis, recipe analysis, material analysis, etc.
In accordance with one or more embodiments, different statistical methods may be applied to different subsets of wafers after clustering/classification (depending on, for example, how/why these wafers are classified/clustered and/or which analysis methodology is employed). For example, a specific statistical method may be employed to automatically analyze wafers grouped for equipment analysis while another specific statistical method may be employed to analyzed wafers grouped for recipe analysis. This is unlike the prior art wherein a single statistical method tends to be employed for all root-cause analyses for the whole batch of wafers. Since both tool-related and material-related data are available, automated analysis may pinpoint the root-cause to a specific tool parameter or a specific combination of tool parameters. This type of data granularity is not possible with prior art systems that only have tool-related data or material-related data.
As can be appreciated from the foregoing, the integration and data alignment of both cause and effect data (e.g., tool-related data and material-related data) in the same platform simplify the task of automatically correlating data from traditional EES system and YMS system, as well as facilitate time-efficient automated analysis. The use of automated data alignment and automated analysis also substantially eliminates human-related errors in the data correlation and automated data analysis tasks. Since high granularity tool-related data and process-related data are available on a single platform, both automated root cause analysis and automated prediction may be more specific and timely, and it becomes possible to quickly pinpoint a yield-related problem to a specific tool-related parameter (such as chamber pressure in tool #4) or a group of tool-related parameters (such as chamber pressure and bias power in tool #2). Furthermore, the use of knowledge base and/or cross-validation and/or wafer clustering/classification also improves the automated analysis results.
While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents, which fall within the scope of this invention. For example, although the examples herein refer to wafers as examples of materials to be processed, it should be understood that one or more embodiments of the invention apply to any material processing tool and/or any material. In fact, one or more embodiments of the invention apply to the manufacture of any article of manufacture in which tool information as well as material information is collected and analyzed by the single platform. If the term “set” is employed herein, such term is intended to have its commonly understood mathematical meaning to cover zero, one, or more than one member. The invention should be understood to also encompass these alterations, permutations, and equivalents. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. Although various examples are provided herein, it is intended that these examples be illustrative and not limiting with respect to the invention.
