Patent Application
20130203188
Embodiments of the subject matter described herein generally relate to semiconductor device structures and related fabrication methods and metrologies, and more particularly, embodiments of the subject matter relate to determining hybrid measurements of physical features, dimensions, or other attributes of a semiconductor device structure using measurements obtained from different metrology tools.
Semiconductor devices, such as transistors, are the core building block of the vast majority of electronic devices. In practice, it is desirable to accurately and precisely fabricate transistors and other semiconductor devices with physical features having specific physical dimensions, to thereby achieve semiconductor devices having their intended performance characteristics and improve yield. However, the hardware tools used to fabricate the devices may exhibit performance variations. As a result, devices may be fabricated with features that deviate from their specified physical dimensions, which, in turn, could lead to failures at wafer test and/or reduce yield. Thus, it is desirable to measure physical features, critical dimensions and/or other properties of devices during fabrication to correct any deviations from the intended physical dimensions and thereby reduce the likelihood of failures at wafer test and/or improve yield. However, obtaining highly accurate measurements typically takes an undesirably long amount of time or involves destructive metrologies which reduce yield. At the same time, non-destructive measurement tools may be limited in their ability to accurately measure all of the physical features, critical dimensions, and profile information of a device, which, in turn, limits the ability of the foundry (or fab) to maximize yield.
In one embodiment, an exemplary measurement system is provided. The measurement system includes a first metrology tool and a second metrology tool. The first metrology tool provides a first measurement of a semiconductor device structure and the second metrology tool obtains the first measurement and determines a hybrid measurement of the semiconductor device structure based at least in part on the first measurement.
In another embodiment, a method for fabricating a semiconductor device structure is provided. The method involves obtaining a first measurement for the semiconductor device structure from a first metrology tool, obtaining a second measurement of a first attribute of the semiconductor device structure from a second metrology tool, and determining a hybrid measurement for the first attribute based at least in part on the first measurement and the second measurement.
In yet another embodiment, a method for fabricating a semiconductor device structure involves determining a weighting factor for a first measurement of the semiconductor device structure from a first metrology tool, obtaining a second measurement of the semiconductor device structure from a second metrology tool, determining a hybrid measurement of the semiconductor device structure based at least in part on the first measurement, the second measurement, and the weighting factor, adjusting the weighting factor to reduce a difference between the hybrid measurement and a reference measurement of the semiconductor device structure, and determining a second hybrid measurement of the semiconductor device structure based at least in part on the adjusted weighting factor.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
A more complete understanding of the subject matter may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures.
The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Any implementation described herein as exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
Embodiments of the subject matter described herein relate to determining hybrid (or composite) measurements of attributes of semiconductor device structures fabricated on a semiconductor substrate using measurements obtained from different metrology tools. Depending on the embodiment, the attribute being measured may be a physical feature, structure or dimension, an absence of a physical feature or structure (e.g., a recess, void or the like), or an intrinsic property (e.g., ion concentration, index of refraction, bulk modulus, electron mobility, or other compositional and/or optical properties). Thus, although the subject matter may be described herein in the context of measuring physical features and/or dimensions of semiconductor device structures, it should be understood that the subject matter is not limited to physical features and/or dimensions and may be utilized to obtain hybrid measurements of intrinsic properties of a semiconductor device structure. As described in greater detail below, a hybrid measurement is calculated using measurements obtained from more than one metrology tool to provide a composite measurement of a particular attribute. For example, in accordance with one or more embodiments, each metrology tool determines measurements of one or more physical features and/or dimensions of a semiconductor device structure based on measurement data measured or otherwise obtained using measurement hardware associated with that metrology tool. The measurements obtained from the different metrology tools are weighted based on their relative accuracy and/or reliability or other characteristics of their respective metrology tool to provide a composite measurement with an accuracy and/or reliability that is greater than the accuracy and/or reliability of the individual measurements obtained by the individual metrology tools.
Turning now to
In an exemplary embodiment, after fabrication of one or more physical features of the semiconductor device(s) on the wafer 110, the metrology tools 102, 104 are utilized to measure or otherwise quantify the fabricated dimensions of various physical features on the wafer 110 using a measurement technique, such as, for example, scatterometry, scanning electron microscopy, atomic force microscopy, interferometry, reflectometry, ellipsometry, and the like. In this regard, each metrology tool 102, 104 may use a different measurement technique than the other metrology tools 102, 104 in the measurement system 100. In exemplary embodiments, each metrology tool 102, 104 utilizes a non-destructive measurement technique (or technology) so that the wafer 110 is still suitable for its intended operation after being measured. In accordance with one or more embodiments, the host computing device 106 communicates with the metrology tools 102, 104 to signal, command, or otherwise indicate, to a respective metrology tool 102, 104, which features on the wafer 110 are to be measured by that respective metrology tool 102, 104 along with additional information pertaining to how that respective metrology tool 102, 104 should perform the measurement. After a respective metrology tool 102, 104 finishes measuring the physical feature(s) on the wafer 110, the metrology tool 102, 104 may provide the feature measurements to the host computing device 106 and/or another metrology tool 102, 104. In an exemplary embodiment, one metrology tool 102 receives or otherwise obtains the feature measurements from one or more of the other metrology tools 104 for use in determining hybrid measurements for one or more physical feature(s) on the wafer 110, as described in greater detail below. For purposes of explanation, the metrology tool 102 which obtains the feature measurements from the other metrology tools 104 and determines final hybrid measurements is alternatively referred to herein as the primary metrology tool, while the remaining metrology tool(s) 104 in the measurement system 100 are alternatively referred to herein as the secondary metrology tool(s) 104. As described in greater detail below, a secondary metrology tool 104 may also obtain a hybrid measurement determined by the primary metrology tool 102 and potentially other feature measurements from other secondary metrology tool(s) 104 to adjust the feature measurements obtained by the secondary metrology tool 104. Thus, the secondary metrology tool(s) 104 may also determine hybrid (or composite) measurements.
Still referring to
In the illustrated embodiment, the communications arrangement 202 generally represents the hardware, software, firmware and/or combination thereof which are coupled to the processing module 206 and cooperatively configured to support communications to/from the metrology tool 200 via a network (e.g., network 108) in a conventional manner. The measurement arrangement 204 generally represents the combination of radiation sources, illumination devices, electron guns, sensors, optics, and/or other hardware components of the metrology tool 200 which are utilized to measure physical features, dimensions and/or other attributes of semiconductor devices on a wafer. In accordance with one or more embodiments, the measurement arrangement 204 is capable of transmitting, emitting, or otherwise directing a reference signal towards a wafer and sensing, receiving, or otherwise measuring a response signal from the wafer. In this regard, the physical features, dimensions and/or other attributes of the wafer modulate or otherwise influence characteristics of the reference signal resulting in the response signal that is sensed or otherwise received by the measurement arrangement 204. Thus, the response signal corresponds to raw feature measurement data that is indicative of the dimensions of the various physical features, dimensions and/or other attributes on the wafer 110, which can be determined based on characteristics of the response signal (e.g., the spectral characteristics, waveforms, or the like) or the relationship between the response signal and the reference signal.
The processing module 206 generally represents the hardware, firmware, processing logic, and/or other components of the metrology tool 200 configured to control or otherwise operate the measurement arrangement 204 to measure physical features and/or dimensions on a wafer, communicate feature measurements to/from the metrology tool 200, store feature measurements in the memory 208, and execute various functions and/or processing tasks as described in greater detail below. Depending on the embodiment, the processing module 206 may be implemented or realized with a general purpose processor, a microprocessor, a controller, a microcontroller, a state machine, a content addressable memory, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. Furthermore, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in firmware, in a software module executed by the processing module 206, or in any practical combination thereof. The memory 208 represents any non-transitory short or long term storage media capable of storing programming instructions for execution by the processing module 206, which, when read and executed by the processing module 206, cause the processing module 206 to perform certain tasks, operations, functions, and processes described in more detail herein. In accordance with one or more embodiments, the memory 208 also stores feature measurements obtained using the measurement arrangement 204 and/or feature measurements obtained from other metrology tools, as described in greater detail below.
Referring to
In an exemplary embodiment, the hybrid measurement process 300 also obtains measurements for one or more physical features, dimensions and/or other attributes on a wafer from the primary metrology tool (task 304). In a similar manner as described above, the wafer 110 is placed in a chamber proximate to or otherwise associated with a primary metrology tool 102 such that the wafer 110 is aligned with the measurement arrangement 204 of the primary metrology tool 102, and the host computing device 106 provides commands and/or instructions to the primary metrology tool 102 regarding which physical features and/or dimensions on the wafer 110 should be measured. In response to receiving commands and/or instructions from the host computing device 106, the processing module 206 of the primary metrology tool 102 signals or otherwise operates the measurement arrangement 204 to measure the physical features and/or dimensions on the wafer 110 in the manner indicated by the host computing device 106. The processing module 206 of the primary metrology tool 102 receives or otherwise obtains the raw feature measurement data from the measurement arrangement 204, calculates or otherwise determines measurements for the physical features and/or critical dimensions on the wafer 110 utilizing the raw feature measurement data, and stores or otherwise maintains the feature measurements in its memory 208.
In an exemplary embodiment, the hybrid measurement process 300 continues by calculating or otherwise determining hybrid measurements for one or more physical features, dimensions and/or other attributes of the wafer based on the feature measurements obtained using the secondary metrology tool(s) and the feature measurements obtained using the primary metrology tool (task 306). In an exemplary embodiment, the hybrid feature measurements for a particular feature and/or dimension are calculated as a function of the measurement for that feature and/or dimension obtained using the primary metrology tool 102 and one or more feature measurements from one or more secondary metrology tool(s) 104. The secondary metrology tool feature measurement(s) used in determining a hybrid measurement for a feature may be for that feature or a different feature on the wafer 110. In an exemplary embodiment, the primary metrology tool 102 and/or the host computing device 106 determines the hybrid measurement for a particular feature and/or dimension by weighting the primary metrology tool feature measurement and the secondary metrology tool feature measurement(s) in accordance with their relative accuracy and/or reliability. For example, as described in greater detail below in the context of
In accordance with one embodiment, the metrology tool 102 and/or the host computing device 106 calculates the hybrid measurement for a particular feature on the wafer 110 as a weighted sum of the feature measurements from the secondary tool(s) 104 and the metrology tool 102 using the quality weighting factors. For example, for a particular critical dimension measured by the primary metrology tool 102 and a secondary metrology tool 104, the metrology tool 102 may calculate a hybrid measurement of a critical dimension (CD) using the equation CDH=γS1CDS+γP1CDP, where CDS is the measurement for the critical dimension that was determined or otherwise measured by the secondary tool 104, CDP is the measurement for the critical dimension that was determined or otherwise measured by the primary metrology tool 102, γS1 is the quality weighting factor associated with the secondary metrology tool 104 determined by the primary metrology tool 102, and γP1 is the quality weighting factor associated with the primary metrology tool 102. In one embodiment, the sum of the quality weighting factors is equal to one, where γP1=1−γS1, such that the quality weighting factor associated with the primary metrology tool corresponds to and compensates for the relative difference between the secondary tool feature measurement (e.g., CDS) and the weighted secondary tool feature measurement (e.g., γS1CDS). As described above, in some embodiments, the secondary tool feature measurement may be for a different physical feature and/or dimension than the primary tool feature measurement. For example, the secondary metrology tool 104 may be realized as an atomic force microscopy (AFM) tool that measures a sidewall angle of a gate structure fabricated on the wafer 110 and the primary metrology tool 102 may be realized as a optical critical dimension (OCD) tool that measures a gate dielectric undercut and determines a hybrid measurement for the gate dielectric undercut based on its own measurement of the gate dielectric undercut and the measurement of the gate sidewall angle obtained from the AFM metrology tool.
Still referring to
After a secondary metrology tool determines an adjusted feature measurement, the hybrid measurement process 300 repeats the step of determining a hybrid measurement for that physical feature and/or dimension based on the adjusted feature measurements determined by the secondary metrology tool(s) 104 (task 306). In this regard, the primary metrology tool 102 obtains an adjusted feature measurement from a secondary metrology tool 104 and calculates an adjusted hybrid feature measurement as a function of the adjusted feature measurement and the previous feature measurement determined by the metrology tool 102. In one or more embodiments, the metrology tool 102 calculates the adjusted hybrid measurement as a weighted sum of the previous feature measurement determined by the primary metrology tool 102 and the adjusted feature measurement determined by the secondary metrology tool 104. For example, the metrology tool 102 may calculate an adjusted hybrid measurement of a critical dimension (CD) using the equation CDH
In an exemplary embodiment, the hybrid measurement process 300 repeats the steps of iteratively adjusting the secondary metrology tool measurements and determining updated hybrid feature measurements until a desired number of iterations have been performed (tasks 306, 308, 310). In this regard, the desired number of iterations to be performed is chosen to achieve final hybrid feature measurements having a desired level of accuracy and/or reliability. For example, in one or more embodiments, the metrology tool 102 provides the hybrid feature measurements determined at the end of each iteration to the host computing device 106. In accordance with one exemplary embodiment, the host computing device 106 determines that the desired number iterations have been performed when the difference between successive hybrid feature measurements provided by the primary metrology tool 102 is less than a threshold amount. For example, when a hybrid feature measurement determined by the metrology tool 102 differs from the previous hybrid feature measurement provided by the metrology tool 102 by less than a threshold amount (e.g., a percentage of the previous hybrid feature measurement or a fixed amount), the host computing device 106 commands, signals, or otherwise indicates to the metrology tools 102, 104 that the desired number of iterations have been performed. In other embodiments, the host computing device 106 counts or otherwise monitors the number of iterations performed by the metrology tool 102 and commands, signals, or otherwise indicates to the metrology tools 102, 104 that the desired number of iterations have been performed when the counted number of iterations exceeds a threshold number chosen to result in hybrid measurements with a desired accuracy and/or reliability. After the desired number of iterations have been performed, the hybrid measurement process 300 stores or otherwise maintains the final hybrid measurements for the physical features and/or dimensions of the semiconductor devices on the wafer 110 in memory and displays or otherwise presents the final hybrid measurements to the user (tasks 312, 314). In this regard, the processing module 116 stores the final hybrid measurements obtained from the metrology tool 102 in memory 118, and when a user subsequently accesses the host computing device 106 to view measurements for the physical features and/or dimensions on the wafer 110, the processing module 116 presents or otherwise displays the final hybrid measurements (or a graphical representation thereof) on the display device 114.
In an exemplary embodiment, the weighting factor determination process 400 begins by determining or otherwise identifying the number of different feature measurements from different metrology tools to be utilized by a particular tool in determining a hybrid measurement (task 402). For example, the primary metrology tool 102 may identify the total number of secondary metrology tools 104 in the system as the number of different feature measurements to be utilized by the metrology tool 102 when determining hybrid measurements. After identifying the number of different feature measurements to be utilized, the weighting factor determination process 400 continues by determining initial quality weighting factors for each respective feature measurement based on correlation metrics for the respective feature measurement and/or characteristics of the metrology tool associated with the respective feature measurement (task 404). In accordance with one embodiment, the metrology tool 102 determines a numerical range for the quality weighting factors, and then determines, for each respective feature measurement, an initial quality weighting factor value based on one or more correlation metrics (e.g., TMU, RMSU, R2 values or other correlation coefficients, and the like) associated with that feature measurement and/or one or more characteristics of the secondary metrology tool 104 (e.g., FMP or other tool matching metrics, the precision of the tool, the throughput of the tool, the configuration and/or type of tool, the age of the tool, performance characteristics of the measurement arrangement, and the like) providing that feature measurement that are likely to impact the reliability of that feature measurement. In other words, each quality weighting factor is determined as a function of one or more correlation metrics and/or one or more characteristics of the respective metrology tool providing that feature measurement to reduce or otherwise eliminate measurement noise and thereby improve the metrology performance of the hybrid measurement using that feature measurement. The initial quality weighting factor associated with a feature measurement provided by a first secondary metrology tool 104 may be greater than the initial quality weighting factor associated with a feature measurement provided by a second secondary metrology tool 104 when the correlation metric(s) and/or tool characteristic(s) of the first secondary metrology tool 104 are indicative of the measurements from the first secondary metrology tool 104 being more accurate than measurements from the second secondary metrology tool 104, and vice versa.
Still referring to
After iteratively adjusting the quality weighting factors to optimize the hybrid measurement calculation, the weighting factor determination process 400 continues by maintaining the final quality weighting factors for use in subsequent hybrid measurement determinations (task 410). In an exemplary embodiment, the metrology tool 102 stores the final quality weighting factors (or the final quality weighting factor equations and/or functions) resulting from the iterative adjustments in its memory 208 for use in calculating subsequent hybrid measurements, as described above in the context of the hybrid measurement process 300. In other embodiments, the metrology tool 102 may provide the final quality weighting factors to the host computing device 106, which maintains the quality weighting factors in memory 118. In an exemplary embodiment, the weighting factor determination process 400 is performed for each different hybrid measurement determined by a metrology tool 102, 104 and/or the host computing device 106, including the adjusted measurements determined by the secondary metrology tools 104 and/or the host computing device 106, as described above.
To briefly summarize, one advantage of the hybrid measurement process 300 and the weighting factor determination process 400 is that accurate and/or reliable hybrid measurements for physical features and/or dimensions on a wafer are determined using measurements from different metrology tools, which might otherwise provide less accurate and/or less reliable measurements. To put it another way, composite measurements determined as a function of measurements from different non-destructive metrology tools may achieve a level of accuracy and/or reliability on par with highly accurate metrology tools which require longer amounts of measurement time and/or rely on destructive metrology techniques. Thus, highly accurate measurements can be obtained in a reduced amount of time and in a non-destructive manner by combining independent measurements from different metrology tools, as described above, thereby allowing a foundry or other fabrication entity to achieve a higher yield. For example, a foundry may fabricate a particular physical feature and/or dimension of interest for a semiconductor device or integrated circuit on a wafer of semiconductor material using conventional semiconductor fabrication techniques and utilize multiple metrology tools to measure that physical feature and/or dimensions and determine a hybrid measurement of that physical feature and/or dimension which is accurate and/or reliable without utilizing a destructive metrology technique (e.g., TEM or the like), thereby allowing the semiconductor device structure to function in the desired manner after being measured.
For the sake of brevity, conventional techniques related to correlation and/or uncertainty analysis, semiconductor metrology tools and/or methods, semiconductor fabrication, and other functional aspects of the systems (and the individual operating components of the systems) are not described in detail herein. While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.
