Coverage management method, coverage management system and computing system
阅读说明:本技术 覆盖管理方法、覆盖管理系统及计算系统 (Coverage management method, coverage management system and computing system ) 是由 林资程 汪青蓉 左克伟 王咏生 彭旸尹 于 2019-06-27 设计创作,主要内容包括:本发明提供一种覆盖管理方法、覆盖管理系统及计算系统,阐述用于使用机器学习来管理半导体制造中的垂直对齐或覆盖的技术。通过所公开的技术来评估及管理扇出型晶片级封装工艺中内连特征的对齐。使用大数据及神经网络系统来使覆盖误差源因子与覆盖计量类别相关。所述覆盖误差源因子包括工具相关覆盖源因子、晶片或管芯相关覆盖源因子、以及处理上下文相关覆盖误差源因子。(Techniques for managing vertical alignment or overlay in semiconductor manufacturing using machine learning are described. The disclosed techniques evaluate and manage the alignment of interconnect features in a fan-out wafer level packaging process. A big data and neural network system is used to correlate overlay error source factors to overlay metrology categories. The overlay error source factors include tool-dependent overlay source factors, wafer or die-dependent overlay source factors, and process context-dependent overlay error source factors.)
1. A method of coverage management, comprising:
determining a tool position relative to a wafer processing tool that forms a first feature on a first wafer;
determining an item location of a first portion of the first wafer corresponding to the first feature;
determining a coverage metric relative to the first feature;
generating a data set including the tool location, the project location, and the coverage metric; and
generating a function by machine learning based on the dataset, the function relating one or more of the tool positions or the item positions on a first side of the function to the coverage metric on a second side of the function.
2. The method of claim 1, wherein the tool position comprises one or more of a wafer stage position, a stepper position, a photomask key position, or an exposure position.
3. The method of claim 1, wherein the item position comprises one or more of a wafer offset or a wafer rotation of the first wafer positioned on a wafer stage.
4. The method of claim 1, further comprising:
determining a context in which to form the first feature on the first wafer; and
generating the data set including the context.
5. The method of claim 1, further comprising generating an estimated alignment metric for a second wafer based on the function.
6. The method of claim 5, further comprising evaluating the function by comparing the estimated alignment metric of the second wafer to a measured alignment metric of the second wafer.
7. The method of claim 5, further comprising generating alignment correction data relative to the second wafer based on the function, the alignment correction data specifying an adjustment to at least one of the tool position or the item position.
8. An overlay management system comprising:
a wafer processing tool configured to form features on a wafer;
a metrology tool configured to measure overlay alignment of the features on the wafer;
an overlay modeling tool configured to generate an estimated overlay alignment metric for the feature based on one or more of an alignment parameter of the wafer processing tool or an alignment parameter of the wafer; and
a process control tool configured to adjust one or more of the alignment parameters of the wafer processing tool or the alignment parameters of the wafer based on the estimated overlay alignment metrology.
9. The overlay management system of claim 8, wherein the overlay modeling tool generates a function that relates one or more of the alignment parameters of the wafer processing tool or the alignment parameters of the wafer to an overlay metrology of the feature.
10. A computing system, comprising:
a processor; and
a storage unit having stored thereon executable instructions that, when executed by the processor, configure the processor to perform acts comprising:
receiving data relative to a tool position of a wafer processing tool that forms a first feature on a first wafer;
receiving data of an item location relative to a location of the first wafer on a wafer-holding tool that formed the first feature on the first wafer;
receiving data relative to a context in which the first feature was formed on the first wafer; and
generating data for adjusting one or more of the tool location or the project location based on applying at least one of the data for the tool location, the data for the project location, and the data for the context into a regression model function that correlates at least one of the data for the tool location, the data for the project location, and the data for the context to an overlay metrology of the first feature on the first wafer.
Technical Field
Embodiments of the present invention relate to semiconductor technology, and more particularly, to an overlay management method, an overlay management system and a computing system.
Background
As semiconductor technology evolves, semiconductor dies are becoming smaller and smaller, while more and more functionality is being integrated into a single die. Accordingly, there is a need to include an increasing number of input/output (I/O) pads in integrated circuit ("IC") packages along with smaller area die surfaces. Fan-out wafer level packaging ("WLP") is a packaging technology that holds promise for such challenging scenarios. In fan-out WLP, the die are cut from the original front-end wafer, after which the die are positioned on a carrier wafer to be packaged with connection wiring and I/O pads. In a fan-out WLP process, it is an advantage that the I/O pads associated with the die can be rerouted to a larger area than the surface of the die itself. Thus, the number of I/O pads that are populated with a die may be increased.
Fan-out WLP packages may be used to fill one die, multiple dies side-by-side, or multiple dies in a package-on-package ("POP") vertical configuration. The POP configuration in fan-out WLP is achieved by vertically connecting the interconnect features (e.g., vias) of multiple dies.
Overlay metrology processes are used in various semiconductor manufacturing processes to monitor and control vertical alignment. Overlay metrology generally indicates how accurately the alignment of a first patterned layer or features thereon is with respect to a second patterned layer disposed at a different vertical level, e.g., vertical alignment, than the first patterned layer. Overlay error refers to a misalignment between a first portion on a first patterned layer and a second portion on a second patterned layer. An overlay error metric (e.g., a measurement) may be measured based on an offset between the first portion and the second portion or between an actual position of the first portion and a target position of the first portion. The target location may be determined during wafer processing based on advanced process control ("APC").
In fan-out WLP, the die that are tested as good are positioned onto a carrier wafer. Multi-layer interconnect features are formed that connect the die to associated I/O pads and within each layer of interconnect features itself. The interconnects are formed by a wafer level process in which photoresist and photolithography processes are used similarly to in the front-end wafer fabrication process. Therefore, it is desirable to manage vertical alignment between or among the interconnect elements in successive layers.
Disclosure of Invention
The embodiment of the invention provides a coverage management method, which comprises the following steps: determining a tool position relative to a wafer processing tool that forms a first feature on a first wafer; determining an item location of a first portion of the first wafer corresponding to the first feature; determining a coverage metric relative to the first feature; generating a data set including the tool location, the project location, and the coverage metric; and generating a function by machine learning based on the dataset, the function relating one or more of the tool position or the item position on a first side of the function to the coverage metric on a second side of the function.
An embodiment of the present invention provides a coverage management system, including: a wafer processing tool configured to form features on a wafer; a metrology tool configured to measure overlay alignment of the features on the wafer; an overlay modeling tool configured to generate an estimated overlay alignment metric for the feature based on one or more of an alignment parameter of the wafer processing tool or an alignment parameter of the wafer; and a process control tool configured to adjust one or more of the alignment parameters of the wafer processing tool or the alignment parameters of the wafer based on the estimated overlay alignment metrology.
An embodiment of the present invention provides a computing system, including: a processor; and a storage unit having stored thereon executable instructions that, when executed by the processor, configure the processor to perform acts comprising: receiving data relative to a tool position of a wafer processing tool that forms a first feature on a first wafer; receiving data of an item location relative to a location of the first wafer on a wafer-holding tool that formed the first feature on the first wafer; receiving data relative to a context in which the first feature was formed on the first wafer; and generating data for adjusting one or more of the tool location or the project location based on applying at least one of the data for the tool location, the data for the project location, and the data for the context into a regression model function that correlates at least one of the data for the tool location, the data for the project location, and the data for the context to an overlay metrology of the first feature on the first wafer.
Drawings
The various aspects of the invention are best understood from the following detailed description when read with the accompanying drawing figures. In the drawings, the same reference numbers identify similar elements or acts unless context dictates otherwise. The dimensions and relative positioning of elements in the figures are not necessarily drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
FIG. 1 is an exemplary system for managing overlay alignment;
fig. 2 is an exemplary error source data set;
FIG. 3 is an exemplary overlay error data set;
FIG. 4 is an exemplary neural network system;
FIG. 5 is an exemplary operation of a neural network system;
FIG. 6 is an exemplary process of overlay alignment management;
FIG. 7 is an exemplary carrier wafer with die positioned thereon in a fan-out wafer level packaging process;
FIG. 8 is an exemplary overlay metrology on the wafer shown in FIG. 7;
the reference numbers illustrate:
100: an overlay management system/system;
110: a wafer in-situ fabrication system;
112: wafer processing tool set/lithography tool set/toolset;
114: a process log;
116: a metrology tool set;
120: inputting a data set;
122: overlay error data;
124: error source data/overlay source data;
126: other data;
130: a big data unit;
140: a neural network unit/machine learning unit;
142: an alignment control unit;
144: a verification unit/verification module;
150: output data set/alignment control output data;
152: error prediction data;
154: corrective adjustment data;
210: a subset of tool alignment error source factors/tool alignment subset;
212: previous tool alignment data;
214: wafer stage position data/wafer stage position/tool alignment factor;
216: step position data/step position/tool alignment factor;
218: photomask key position data/photomask key positions/tool alignment factors;
220: exposure position data/exposure position/tool alignment factor;
250: a subset of wafer/die alignment error source factors/wafer/die alignment subset;
252: wafer offset data;
254: wafer rotation data;
256: die offset data;
258: die rotation data;
280: a subset of context error source factors/a subset of context error sources;
282: focal depth data;
284: exposure duration data;
286: step speed data;
288: irradiating the setting data;
290: illumination source/illumination source data;
292: enhance global alignment position/EGA position data;
294: field position data;
296: metering position data/metering position;
310: overlay metrology location data;
320: x-axis overlay error data;
330: y-axis overlay error data;
340: overlay rotation (angle) data;
410: a processing unit;
420: a storage unit;
430: a neural network application;
432: a training set generation module;
434: a machine learning module;
436: a verification module;
438: a prediction module;
440: a communication unit;
450: an interface unit;
460: other components;
500: an operating structure;
510: operating;
520: machine learning operations/machine learning processes;
530: performing a prediction operation;
600: an operation process;
610. 620, 630, 640, 650, 660, 670: operating;
700: carrier wafer/carrier wafer;
702: a target wafer position;
710. 710A: a die;
712. 712A: a target location;
720: a portion of a wafer;
722. 724: an alignment mark;
730: a wafer stage;
810: metrology data of the interconnect features;
x, Y, Z: a shaft.
Detailed Description
Techniques for managing vertical alignment or overlay in semiconductor manufacturing using machine learning are set forth. For example, the alignment of interconnect features in a fan-out WLP process is evaluated and managed by the disclosed techniques.
In an embodiment, a big data and neural network system is used to correlate overlay error source factors to overlay metrology classes. The overlay error source factors include tool-dependent overlay source factors, wafer or die-dependent overlay source factors, and process context-dependent overlay error source factors. The tool-related overlay source factor includes, but is not limited to, a light source position, a photomask position, a lens position, a scan direction, a stepper position at exposure, or a wafer stage position. The wafer or die related overlay error source factors include, but are not limited to, a positional shift or rotation of the wafer, a positional shift or rotation of the die on the wafer, a shape characteristic of the wafer (e.g., a size deviation or a thickness deviation), a shape characteristic of the die (e.g., a shape deviation or a thickness deviation). The process context overlay error source factors include, but are not limited to, global alignment regions (e.g., regions on the wafer processed under global alignment control), global alignment positions (i.e., measurement positions on the wafer used to determine global alignment adjustments in enhanced global alignment ("EGA") control), field alignment positions (e.g., positions on the wafer processed under site-by-site or field-by-field alignment control), tool characteristics (such as wafer stage shape), exposure field positions (e.g., vertical position of the photomask, which translates to exposure size, depth of focus, exposure duration), stepper tool stepping speed, illumination source (white, green, ivory, or yellow light), other illumination settings, or metrology positions used to measure layer overlay. Coverage metering information is also obtained. For example, the categories of overlay errors include the size of the overlay error (e.g., on the x-axis and y-axis), the rotational offset between features, or the location of the overlay error (e.g., relative to the wafer or relative to the die). Those coverage metering data are collected and fed into machine learning.
A neural network type machine learning technique is used to correlate overlay error source factors with overlay error metrics. A regression model function is obtained as a result of the machine learning. The data is continuously updated and enhanced to continuously train the machine learning process and thus the regression model function. The regression model function may be used to predict or estimate overlay metrology values on interconnect layers formed in a fan-out WLP packaging process. Corrective adjustments to the tool alignment settings and/or wafer alignment settings may be obtained based on the regression model function.
The regression model function may be verified in various ways. For example, the estimated overlay metrology value of the reference wafer may be compared to the actual metrology value. The reference wafer may be a newly processed wafer or a previously processed wafer. Overlay error source data and actual metrology data for a reference wafer are determined or retrieved from a database. The overlay error source data for the reference wafer is applied to a regression model function to estimate the overlay metrology value. The estimated overlay metrology value is compared to the actual metrology data to determine if the estimate is sufficiently accurate. A threshold is used for the comparison. The threshold may be determined based on overlay tolerance requirements of features or layers of a wafer processing program. For example, in a fan-out WLP, a threshold of about 0.1 μm may be selected to determine whether the estimated overlay metrology values satisfy the actual metrology data for the interconnect features over the die packaged in the fan-out WLP.
The regression model function may also be verified with respect to the estimated corrective adjustment. For example, estimated corrective adjustments to tool alignment or wafer/die alignment may be made through a newly processed reference wafer. Overlay metrology is performed on the reference wafer to determine if overlay error is reduced or eliminated as estimated by the regression model function. The threshold value may be used again.
Using the disclosed techniques, the effective capacity of a metrology tool is increased due to Artificial Intelligence (AI) based coverage metrology. In an embodiment, the effective capacity of the physical metrology tool is increased by a factor of about 40. For example, using the disclosed virtual overlay metering techniques, the processing capacity of the overlay metering team has increased from 292 WLP/day to about 11400 WLP/day. Overlay metrology measurement accuracy improves to a level of less than 0.1 μm. The processing cycle covering the associated quality control is substantially reduced from about 4 hours to substantially real time. Thus, the overall process cycle time for fan-out WLP has also improved, for example, a cycle time of 0.1 days.
Since the estimated coverage values are also compared to the actual coverage values in cross-validation of artificial intelligence functions, the disclosed techniques may avoid the problem of model overfitting.
In the disclosure herein, the disclosed techniques are illustrated using a stepper-machine related coverage metrology process as an illustrative example, which is not intended to limit the scope of the present invention. The disclosed techniques may also be used to predict overlay metrology with respect to other bumping alignment tools, such as die-to-die shift metrology or ball mount template alignment metrology. Furthermore, the disclosed virtual overlay metrology techniques may also be applied with respect to front-end semiconductor process alignment tools or processes.
The following disclosure provides many different embodiments, or examples, for implementing different features of the described subject matter. Specific examples of components and configurations are set forth below to simplify the present description. Of course, these are merely examples and are not intended to be limiting. For example, forming a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Furthermore, for ease of description, spatially relative terms such as "under.," (below), "(lower)," (above), "(upper)," or the like, may be used herein to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may have other orientations (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly as well.
In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures associated with electronic components and fabrication techniques have not been described in detail in order to avoid unnecessarily obscuring the description of the embodiments of the invention.
Unless the context requires otherwise, throughout the description and the following claims, the word "comprise" and variations such as "comprises" and "comprising" should be interpreted in an open, inclusive sense, i.e., "including but not limited to".
The use of ordinal terms such as first, second and third, does not necessarily imply a ranked order of significance, but may merely distinguish between multiple instances of an action or structure.
Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the content clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.
Fig. 1 is an exemplary
In operation,
The process logs 114 are configured to monitor, measure, determine, and record wafer processing parameters associated with the
After
The
The
The
The neural network unit 140 (or the machine learning unit 140) is an artificial intelligence machine learning unit configured to perform a supervised learning process using the data provided by the
In performing "supervised learning," the
Where one or more regression model functions are inferred through a supervised machine learning process, the regression model functions are used by the
The
In an embodiment, the
The verification module 144 of the
Fig. 2 illustrates exemplary
The previous
Wafer
The
The photomask
The
It should be noted that for each of the
These three types of tool alignment data (e.g., measured position, pre-EGA position, post-EGA position) may be correlated with one another. For example, the post-EGA position is obtained based on the pre-EGA position. However, additional or different factors may be introduced in obtaining each of the three types, which may contribute to possible bias. For example, EGA may be affected by the EGA measurement points (referred to as "EGA locations") selected on the wafer to determine the EGA adjustment. Thus, by including one or more of the three types of location data in the
Other ways to determine tool alignment may also exist and are encompassed by the present invention.
In the wafer/die
The
Die offset
Similar to the
The measured position, pre-EGA position, post-EGA position are provided as examples of data types for the alignment position data category. These examples are not intended to limit the scope of the present invention. For the category of alignment position data, there may also be other data types, all of which are included in the present invention. For example, there may also be field alignment of the wafer or die, and tool/wafer/die locations before and after the field alignment operation may be used in
The depth of
The
The
The
It should be understood that the exemplary error source data categories listed in fig. 2 are merely examples and do not limit the scope of the invention. Other factors that contribute to the occurrence and/or magnitude of overlay error may also be used and included in
Fig. 3 illustrates exemplary
Various methods may be used to define overlay error. In an embodiment, the overlay error is determined based on an actual metric and a target metric of the feature. In another embodiment, the overlay error is determined based on the alignment between the upper and lower features. Other methods to determine overlay alignment accuracy or overlay error may also exist and are included in the present invention.
Fig. 4 illustrates an exemplary
The
One or more of the components of the
Furthermore, the components of the
Fig. 5 illustrates an
In an embodiment, in
In a
As shown in fig. 5, the prediction of overlay error may be made for the entire wafer. Within the wafer, the overlay errors may follow a consistent pattern, or may vary between/among different fields on the wafer. Wafer processing settings may be adjusted to specifically correct overlay errors on individual fields on a wafer using stepper devices used in wafer processing. However, there are the following cases: overlay errors on two or more fields on a wafer cannot be individually corrected and correlated to each other under wafer processing operations. A decision-making operation can be performed to determine an overall corrective adjustment of the wafer processing operation to balance between/among the two or more fields for overlay alignment.
The results of the
The
Fig. 6 is a flow chart of an exemplary
In an
Fig. 7 shows a
In addition, the item positions may also include an x-axis tube offset and/or a y-axis tube offset. As shown as an illustrative example in fig. 7, the dies 710 positioned on the lower portion of the
The wafer alignment position and the die alignment position may be determined together by the
In an
In an
In
In an
In an
The techniques are described with a fan-out WLP process as an example. It should be appreciated that the techniques are similarly applicable to front end wafer processing operations and other back end wafer processing operations.
The invention may be further understood by reference to the following examples:
in a method embodiment, a tool position of a wafer processing tool is determined. The wafer processing tool is used to form a first feature on a first wafer. An item location for a first portion of the first wafer is determined. The first portion corresponds to the first feature. An overlay gauge relative to the first feature is determined. Generating a data set including the tool location, the project location, and the coverage metric. Generating a function that relates one or more of the tool position or the project position on a first side of the function to the overlay metrology on a second side of the function. The function is generated by machine learning using the data set.
In a related embodiment, the tool position includes one or more of a wafer stage position, a stepper position, a photomask key position, or an exposure position.
In a related embodiment, the item position includes one or more of a wafer offset or a wafer rotation of the first wafer positioned on a wafer stage.
In a related embodiment, the item location further includes one or more of a die offset or a die rotation of a die positioned on the first portion of the first wafer.
In a related embodiment, the tool position includes one or more of a measured position, a pre-alignment position, and a post-alignment position.
In a related embodiment, the item position includes one or more of a measured position, a pre-alignment position, and a post-alignment position.
In a related embodiment, the method further comprises: determining a context in which to form the first feature on the first wafer; and generating the data set including the context.
In related embodiments, the context includes one or more of: a measurement location on the first wafer that enhances a global alignment operation, an exposure field relative to which the first feature is formed, and a metrology location on the first wafer at which the overlay metrology is measured.
In a related embodiment, the method further comprises: determining a previous tool position relative to the wafer processing tool that formed the first feature on the previous first wafer; and generating the data set including the previous tool positions.
In a related embodiment, the machine learning is performed by a neural network system.
In a related embodiment, the method further includes generating an estimated alignment metric for the second wafer based on the function.
In a related embodiment, the method further includes evaluating the function by comparing the estimated alignment gauge of the second wafer to a measured alignment gauge of the second wafer.
In a related embodiment, the method further includes generating alignment correction data relative to the second wafer based on the function, the alignment correction data specifying an adjustment to at least one of the tool position or the project position.
In another embodiment, a system comprises: a wafer processing tool configured to form features on a wafer; a metrology tool configured to measure overlay alignment of the features on the wafer; an overlay modeling tool configured to generate an estimated overlay alignment metric for the feature based on one or more of an alignment parameter of the wafer processing tool or an alignment parameter of the wafer; and a process control tool configured to adjust one or more of the alignment parameters of the wafer processing tool or the alignment parameters of the wafer based on the estimated overlay alignment metrology.
In a related embodiment, the overlay modeling tool generates a function that relates one or more of the alignment parameters of the wafer processing tool or the alignment parameters of the wafer to an overlay metrology of the feature.
In a related embodiment, the system further comprises a big data unit configured to combine the alignment parameters of the wafer processing tool, the alignment parameters of the wafer, and overlay metrology measurements of the features on the wafer into a data set.
A computing system includes a processor and a memory unit having executable instructions stored thereon. When executed by the processor, the executable instructions configure the processor to perform various acts including: receiving data relative to a tool position of a wafer processing tool that forms a first feature on a first wafer; receiving data of an item location relative to a location of the first wafer on a wafer-holding tool that formed the first feature on the first wafer; receiving data relative to a context in which the first feature was formed on the first wafer; and generating data for adjusting one or more of the tool location or the project location based on applying at least one of the data for the tool location, the data for the project location, and the data for the context into a regression model function that correlates at least one of the data for the tool location, the data for the project location, and the data for the context to an overlay metrology of the first feature on the first wafer.
In a related embodiment, the data for tool position includes one or more of an x-axis tool offset, a y-axis tool offset, and a tool rotation.
In a related embodiment, the data for the item location includes one or more of an x-axis wafer offset, a y-axis wafer offset, a wafer rotation, an x-axis die offset, a y-axis die offset, or a die rotation.
In a related embodiment, one or more of the data for the tool position or the data for the project position includes measured data, pre-alignment data, and post-alignment data.
The various embodiments described above can be combined to provide further embodiments. All U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the application data sheet, are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary, to employ concepts of the various patents, applications and publications to provide yet other embodiments.
These and other changes can be made to the embodiments in light of the above detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.
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