KR20180132947A - Measurement of semiconductor structure using capillary condensation - Google Patents

Abstract

Methods and systems for performing optical measurements of geometric structures filled by a capillary condensation process are disclosed. A measurement is performed while the structures under measurement are being processed using a flow of purge gas comprising a controlled amount of filler. A portion of the filler is condensed on the structures under measurement and charges openings of structural features, spaces between structural features, and small volumes such as notches, trenches, slits, contact holes, and the like. The degree of saturation of the vaporized material of the gas stream is adjusted based on the maximum feature size to be filled. In some examples, measurement data such as spectroscopic data or image data is collected when the structure is not filled and when the structure is filled by capillary condensation. The collected data is combined to improve measurement performance.

Description

Measurement of semiconductor structure using capillary condensation

Cross reference of related application

This patent application is a continuation-in-part of US Provisional Patent Application No. 62 / 330,751 entitled " Porosity and Critical Dimension Measurement Using Capillary Condensation ", filed on May 2, 2016, U.S. Provisional Patent Application No. 62 / 441,887 entitled " Measurement of Critical Dimensions Using Fluid Filling ", and U.S. Patent Application entitled " Measurement of Critical Dimensions Using Capillary Condensation " filed July 7, No. 15,204,938, each of which is incorporated herein by reference in its entirety.

Technical field

The described embodiments relate to metrology systems and methods, and more particularly to methods and apparatus for improved measurement of structures fabricated in the semiconductor industry.

Semiconductor devices such as logic and memory devices are typically fabricated in the order of the processing steps applied to the specimen. Several features of semiconductor devices and multiple structure levels are formed by these processing steps. For example, in particular, lithography is one semiconductor fabrication process that involves producing a pattern on a semiconductor wafer. Additional examples of semiconductor fabrication processes include, but are not limited to, chemical mechanical polishing, etching, deposition, and ion implantation. A plurality of semiconductor elements can be fabricated on a single semiconductor wafer and separated into discrete semiconductor elements.

The metrology processes are used in several steps during the semiconductor fabrication process to detect defects on the wafers to create higher yields. Model-based metrology techniques offer the potential for high throughput without the risk of sample breakage. Many model-based metrology-based techniques, including analytical algorithms related to scatterometry, ellipsometry, and reflectometry implementations, have been used to measure the critical dimensions, film thickness, composition, and is used to characterize overlay and other parameters.

Modern semiconductor processes are employed to create complex structures. A complex measurement model using multiple parameters is needed to represent these structures and to account for process and dimensional changes. A number of complicated parameter models include modeling errors induced by parameter correlation and low measurement sensitivity to some parameters. Also, the regression of a large number of complex parameter models with relatively large floating parameter values may not be computationally manageable.

In order to reduce the effects of these error sources and reduce computational effort, a number of parameters are typically fixed in model-based measurements. Fixing the values of a plurality of parameters may also improve errors in the estimates of the parameter values, while improving the computation speed and reducing the influence of the parameter correlations.

At present, a solution to complex multiple parameter measurement models often requires unsatisfactory compromise. Current model shrinking techniques are sometimes computationally manageable and can not reach sufficiently accurate measurement models. In addition, complex multiple parameter models make it difficult or impossible to optimize system parameter selection (e.g., wavelength, angle of incidence, etc.) for each of the parameters of interest.

Future metrology applications address the challenges of increasingly smaller resolution requirements, multi-parameter correlation, increasingly complex geometric structures, and increased use of opaque materials. Thus, there is a need for a method and system for improved measurement.

Methods and systems for performing optical measurements of filled geometries with a capillary condensation process are presented in this document. The measurement is performed while the local environment around the structures under measurement is being processed using a flow of purge gas including a controlled amount of filler. A portion of the filler (i.e., condensate) condenses on the structures under measurement and fills small volumes such as opening of structural features, spacing between structural features, notches, trenches, slits, contact holes, and the like.

In one aspect, the degree of saturation of the vaporized material in the gas stream fed to the structures under measurement is adjusted based on the maximum feature size to be filled by capillary condensation.

In yet another aspect, measurements are performed using a data set comprising measurement signals collected from structures having geometric features filled with condensate. The presence of the condensate changes the optical properties of the structure under measurement compared to the measurement scenario where there is no filler in the purge gas.

In some instances, multiple measurements of the structure are performed for different condensation states, respectively. Each measurement corresponds to a different amount of condensate that is condensed onto the structures under measurement. By collecting measurement signal information associated with structures having geometric features each filled with a different amount of condensate, the parameter correlation between the floating measurement parameters is reduced and the measurement accuracy is improved.

In some instances, measurement data is collected when the structure is filled with capillary condensation, and measurement data is collected from the same structure when the structure is not charged (i. E., Is not affected by capillary condensation).

In some embodiments, the amount of vaporized filler in the gas flow fed to the structures under measurement is controlled by controlling the partial pressure of the filler in the gas flow. In some embodiments, the flow of unsaturated purge gas is mixed with the flow of saturated purge gas. The proportion of these flows is adjusted to regulate the partial pressure of the fill of the mixed flow.

In some embodiments, the purge gas is bubbled through the liquid water bath of the filler to create a flow of purge gas that is completely saturated with the filler. The partial pressure of the vaporized filler in the purge gas stream is equal to the equilibrium pressure of the filler for the liquid bath of the filler.

In some embodiments, the liquid bath of the filler is maintained at the same temperature as the sample being measured. In some other embodiments, the liquid bath of the filler is maintained at a lower temperature than the sample under measurement.

In some embodiments, the degree of saturation of the vaporized filler in the wafer is controlled by adding a nonvolatile solute to the liquid bath of the filler that suppresses the equilibrium vapor pressure of the filler. In these embodiments, the degree of saturation of the vaporized filler is controlled by controlling the concentration of the solute in the solution.

In some embodiments, the filler exhibits fluorescence emission in response to illumination light being supplied to structures under measurement to enhance measurement contrast, particularly in image-based measurement applications.

The foregoing is a summary, and as such, simplifies, generalizes, and omits details as needed; As a result, one of ordinary skill in the art will appreciate that the summary is by way of example only and is not limiting in any way. Other aspects, inventive features, and advantages of the devices and / or processes described in this document will become apparent in the non-limiting detailed description set forth herein.

1 is a diagram illustrating a system 100 for measuring structures of a semiconductor wafer subject to capillary condensation.
FIG. 2 is a diagram illustrating a vapor injection system 120 of system 100 in one embodiment.
FIG. 3 is a diagram illustrating a vapor injection system 120 of system 100 in yet another embodiment.
Figure 4 shows a table (127) containing the enthalpy of evaporation of water, toluene and ethanol, [Delta] H. Table 127 also shows the difference between the temperature of the wafer and the temperature of the liquid filler bath to achieve a relative saturation of 0.9 filler in the wafer.
Figure 5 shows a plot 128 of partial pressure of water as a function of the concentration of hydrochloric acid in the bath.
Figure 6 shows a plot 135 of the dispersion characteristics of the demineralized water as a function of wavelength.
Figure 7 shows a table 129 depicting the molar volume and surface tension associated with water, toluene, and ethanol.
Figure 8 shows a plot 172 showing the maximum diameter of a cylindrical hole that can be filled by capillary condensation at different partial pressures according to the Kelvin equation for water, ethanol, and toluene as fillers.
Figure 9 shows a plot 160 showing the maximum diameter of a trench-like feature that can be filled by capillary condensation at different partial pressures, respectively, according to the Kelvin equation for water, ethanol, and toluene as fillers.
Figure 10 shows a non-filled line-space metrology target on which a periodic, two-dimensional resist lattice structure is fabricated on a substrate.
Figure 11 shows the line space measurement target shown in Figure 10 filled with filler.
12A shows a non-filled metrology target having a plurality of layers including a top layer with a cylindrical contact hole.
12B shows the measurement target shown in Fig. 12A including a cylindrical contact hole filled with filler.
FIG. 13 is a graph showing the relationship between the measurement results obtained with the multi-target model using the data collected with and without the shape filling, and the measurements obtained without the shape filling, with respect to the plurality of parameters relating to the measurement target shown in FIG. And the results are compared.
Figure 14 illustrates a method 200 for performing measurements of structures subject to capillary condensation in one example.
FIG. 15 shows a chart 210 for relative humidity RH for each different combination of flows F ₁ and F ₂ defined with respect to equation (1).
FIG. 16 shows a plot 220 for the spectroscopic polarization analysis parameter a for measurements of the same structure in both unfilled and filled states.
FIG. 17 shows a plot 230 regarding the spectral difference between the spectroscopic polarization analysis measurements shown in FIG.
FIG. 18 shows a plot 240 for the spectroscopic polarization analysis parameter? For measurements of the same structure in both unfilled and filled states.
FIG. 19 shows a plot 250 for the spectral difference between the spectroscopic polarization analysis measurements shown in FIG.

Reference to background art examples and examples of the present invention will be described in detail below, and examples of the present invention are shown in the accompanying drawings.

A method and system for performing optical measurements of a geometry filled with a condensate by a capillary condensation process is presented in this document. Model-based measurements are performed using a rich set of data including measurement signals collected from metrology targets having geometric features filled with condensate. This reduces the parameter correlation between the floating measurement parameters and improves the measurement accuracy. Thus, sufficiently accurate model-based measurement results can be obtained and often include reduced computational effort.

Measurements are performed while the local environment around the measurement target being measured is being processed using a flow of purge gas including a controlled amount of filler. A portion of the filler (i.e., condensate) condenses on the structures under measurement and fills openings of structural features, openings between structural features, and the like. The presence of the condensate changes the optical properties of the structure under measurement compared to the measurement scenario where there is no filler in the purge gas.

In some instances, multiple measurements on the metrology target are performed for different condensation states, respectively. That is, each measurement corresponds to a different amount of condensate that is condensed onto the structures under measurement. Model-based measurements are performed using a rich set of measurement data by collecting measurement signal information associated with metrology targets having geometric features each filled with a different amount of condensate.

In one example, measurement data is collected when the structure is not filled, and additional measurement data is collected when the same structure is filled by capillary condensation. The collected data is combined in a multi-target model based measurement to estimate the value of one or more parameters of interest with reduced parameter correlation and improved measurement performance.

Figure 1 shows a system 100 for measuring characteristics of a semiconductor wafer. The system 100 can be used to perform spectroscopic polarization analysis measurements of one or more structures 114 of a semiconductor wafer 112 disposed on a wafer positioning system 110, have. In this regard, the system 100 may include a spectroscopic polarimetry analyzer 101 having an illuminator 102 and a spectrometer 104. The illuminator 102 of the system 100 is configured to direct illumination of the structure 114 disposed on the surface of the semiconductor wafer 112 to produce illumination of a selected wavelength range (e.g., 100-2500 nm). Ultimately, the spectrometer 104 is configured to receive light from the surface of the semiconductor wafer 112. In addition, light from the illuminator 102 uses the polarization state generator 107 to produce a polarized and polarized illumination beam 106. The radiation reflected by the structure 114 disposed on the wafer 112 passes through the polarization state analyzer 109 and is transmitted to the spectrometer 104. The radiation received by the spectrometer 104 at the collection beam 108 is analyzed with respect to the polarization state, taking into account the spectral analysis of the radiation passed by the analyzer. The detected spectra 111 are transmitted to the computing system 130 for analysis of the structure 114.

The computing system 130 is configured to receive measurement data 111 associated with measurements (e.g., critical dimensions, film thickness, composition, process, etc.) of the structure 114 of the filled sample 112 due to capillary condensation. In one example, the measurement data 111 includes an indication of the measured spectral response of the sample by the measurement system 100 based on one or more sampling processes from the spectrometer 104. In some embodiments, the computing system 130 is also configured to determine sample parameter values of the structure 114 from the measurement data 111. In one example, the computing system 130 may be configured to access real-time model parameters by employing Real Time Critical Dimensioning (RTCD), or may be configured to access at least one target parameter associated with the target structure 114 The library of pre-computed models can be accessed to determine the value. In some embodiments, the estimated values of one or more parameters of interest are stored in a memory (e.g., memory 132). In the embodiment shown in Figure 1, the estimated values 115 of one or more parameters of interest are passed to an external system (not shown).

In general, polarization analysis is an indirect method of measuring the physical properties of a sample being examined. In most cases, the raw measurement signals (e.g., alpha _meas and beta _meas ) can not be used to directly determine the physical properties of the sample. The nominal measurement process consists of parameterization of the structure (e.g., film thickness, critical dimensions, material properties, etc.) and parameterization of the machine (e.g., wavelength, angle of incidence, polarization angle, etc.). A measurement model is created that attempts to predict the measured values (e.g., alpha _meas and beta _meas ). As shown in equations (1) and (2), the model includes machine related parameters (P _machine ) and sample related parameters (P _specimen ).

The machine parameters are the parameters used to characterize the metrology tool (e.g., the polarization analyzer 101). Exemplary machine parameters include an incident angle (AOI), an analyzer angle (A ₀ ), a polariser angle (P ₀ ), an illumination wavelength, a numerical aperture (NA), a compensator or a wavelength plate (if present) The sample parameters are parameters used to characterize the sample (e.g., sample 112 including structure 114). For a thin film sample, exemplary sample parameters include refractive index, dielectric tensor, nominal layer thickness of all layers, layer sequence, and the like. For a CD sample, exemplary sample parameters include geometric parameter values associated with different layers, refractive indices associated with different layers, and the like. For measurement purposes, the machine parameters are treated as known fixed parameters and one or more of the sample parameters are treated as unknown floating parameters.

In some instances, the floating parameters are solved by an iterative process (e.g., regression) that produces a best fit between the theoretical prediction and the experimental data. Unknown sample parameters P _specimens may vary and may vary as long as they cause a close match between model output values (e.g., alpha _model and beta _model ) and empirically measured values (e.g., alpha _meas and beta _meas ) The model output values are calculated until the sample parameter values of the set are determined. In a model-based measurement application, such as a spectroscopic polarimetry for a CD sample, a regression process (e. G., ≪ / RTI > to identify sample parameter values that minimizes the difference between the model output values and the experimentally measured values for a fixed set of machine parameter values For example, a general least squares regression method) is adopted.

In some instances, floating parameters are resolved by searching through a library of pre-computed solutions to find the closest match. In a model-based measurement application, such as a spectroscopic polarimetry for a CD sample, a library is used to identify sample parameter values that minimize the difference between pre-computed output values and experimentally measured values for a fixed set of machine parameter values A search process is adopted.

In some other examples, a model-based library regression or signal response metric model is employed to estimate the values of the parameters of interest.

In model-based measurement applications, simplifying assumptions often requires maintaining sufficient throughput. In some instances, the order of truncation of Rigorous Coupled Wave Analysis (RCWA) must be reduced to minimize computation time. In another example, the number or complexity of library functions is reduced to minimize search time. In another example, the number of floating parameters is reduced by fixing certain parameter values. In some instances, simplifying these assumptions results in unacceptable errors in the estimation of the values of one or more parameters of interest (e.g., critical dimension parameters, overlay parameters, etc.). By performing measurements of structures subject to capillary condensation as described in this document, model-based measurement models can be resolved with reduced parameter correlations and increased measurement accuracy.

As shown in FIG. 1, the metrology system 100 includes a vapor injection system 120 configured to supply a gas stream 126 to the structure 114 during measurement. In an aspect, the gas stream 126 comprises a purge gas and a filler vaporized into the purge gas. As the gas flow contacts the structure 114, condensation occurs and a portion of the filler (i.e., condensate) condenses on the structure 114 under measurement. The condensate fills at least a portion of one or more structural features of the structure (114). The presence of the condensate changes the optical properties of the measured structure.

In some embodiments, a single measurement is performed when the purge gas flow does not include a filler (e.g., pure nitrogen gas or clean dry air), and the purge gas Another measurement is performed when the flow contains filler. The measurement data collected from these two measurements is passed to the computing system 130 and an estimate of one or more structural parameters of interest is made based on the two sets of measurement data.

In some embodiments, a series of measurements are performed under different condensation conditions such that the amount of condensation onto the structural features being measured is different for each measurement. The measurement data collected from the series of measurements is passed to the computing system 130 and an estimate of one or more structural parameters of interest is made based on the collected measurement data.

As shown in FIG. 1, a significant amount of filler 123 is transported from filler source 121 to vapor injection system 120. Also, the flow of purge gas 124 is carried from the purge gas source 122 to the vapor injection system. The vapor injection system 120 causes the filler to be vaporized into a flow of purge gas to produce a gas stream 126 that is fed to the structure 114 under measurement. In the embodiment shown in FIG. 1, the flow of purge gas and the amount of filler vaporized by the flow of purge gas is controlled by command signals 125 that are transferred from the computing system 130 to the vapor injection system 120. Thus, the command signals 125 control the desired composition of the gas flow 126. 1, the gas flow 126 passes through a nozzle 105 which directs the gas flow 126 to a desired location on the wafer 110 using suitable flow characteristics. In some embodiments, the nozzles 105 are positioned in close proximity to the measurement area to move the filler into areas surrounding the structures under measurement. After the measurement, the condensed filler is vaporized with a general wafer-level purge gas stream and transported off the wafer. In some instances, the gas flow 126 is supplied to the wafer 112 at a flow rate of between 1000 standard cubic centimeters per minute (SCCM) and 2000 SCCM. However, in general, any suitable flow rate can be considered within the scope of this patent document.

Figure 1 shows the gas flow 126 being supplied locally to the metrology target being measured. However, in general, gas flow 126 may be supplied throughout the entire wafer, through any portion of the beam path from the illumination source to the detector, or any combination thereof. Various examples of supplying purge gas flow across the wafer and through the beam path between the illumination source and the detector are described in U.S. Patent No. 7,755,764 to Kwak, Hee-Dong et al., Filed on July 13, 2010, Are all merged into this document by reference.

As shown in FIG. 1, the vapor injection system 120 causes the filler 123 to vaporize into a flow 124 of purge gas to produce a gas stream 126 that is fed to the structure 114 under measurement. Generally, however, the vapor injection system 120 can control the vaporization of two or more different fillers into the purge gas flow to produce a gas flow to be supplied to the structure 114 under measurement. In this manner, the vapor injection system 120 supplies a gas flow 126 to the wafer 112 containing a controlled amount of different fillers.

Embodiments of the system 100 shown in Figure 1 may also be configured as described in this document. In addition, the system 100 may be configured to perform any other block (s) of any of the method embodiments (s) described herein.

2 is a diagram illustrating a vapor injection system 120 in one embodiment. In this embodiment, the amount of filler vaporized in the gas stream 126 fed to the wafer 112 under measurement (i.e., the partial pressure of the condensate) is adjusted. By adjusting the partial pressure of the filler, the structural dimensions to be filled by the capillary condensation are controlled.

In the embodiment shown in Figure 2, the partial pressure of the filler (e.g. nitrogen gas, clean dry air, etc.) vaporized in the purge gas flow is equal to the equilibrium pressure of the filler for the liquid bath of the filler through which the purge gas bubbles Do. In one example, a bubbler type of steam injection system is a model 1.2 liter capacity stainless steel bubbler model Z553360 available from Sigma-Aldrich of St. Louis, Missouri, USA.

2, a portion 146 of the purge gas flow 124 passes through a mass flow controller 148A and another portion 145 of the purge gas flow 124 passes through a mass flow controller (not shown) 148B. The flow rates of the gas flows 146 and 145 are controlled by the state of the mass flow controllers 148A and 148B, respectively. In this manner, the amount of purge gas flow 124 in which the filler is vaporized is controlled by the mass flow controller 148B and the amount of purge gas flow 124 that is not susceptible to vaporization is directed to the mass flow controller 148B . 2, the command signal 125 transmitted from the computing system 130 to the vapor injection system 120 includes a plurality of signals 149A-C. Signal 149A includes an indication of the desired state of mass flow controller 148A. Correspondingly, the mass flow controller 148A adjusts the desired state of the purge gas flow to the desired state, and hence the filler, that is not vaporized. Signal 149B includes an indication of the desired state of mass flow controller 148B. Correspondingly, the mass flow controller 148B adjusts to the desired state and thus the desired rate of purge gas flow in which the filler is vaporized. The portion 145 of the purge gas flow 124 passes through the check valve 142 and the flow control valve 143 and flows into the bubbler 140. In bubbler 140, a significant amount of filler is vaporized into a portion 145 of purge gas flow 124 to produce purge gas and filler gas flow 147. Gas stream 147 combines with a portion 146 of purge gas that does not flow through bubbler 140 to produce gas stream 126.

In some embodiments, the mass flow controllers 148A and 148B are controlled so that the entire purge gas flows through the bubbler 140 or bypasses the bubbler 140 completely. In this manner, the gas stream 126 may be a dry purge gas stream 124 with a partial pressure of the filler of zero (0) or the entire purge gas stream 124 may be affected by the filler vaporization.

As filler is vaporized in bubbler 140 and carried to gas stream 147, additional filler 123 flows out of filler source 121 to maintain a constant fill level in bubbler 140. In some embodiments, the charge level is automatically controlled based on the level sensor and flow control scheme. In some other embodiments, the charge level is maintained periodically by a passive charge operation.

In one embodiment, the degree of saturation of the vaporized filler of gas stream 126 at ambient temperature T _a is proportional to the portion of purge gas stream 146 that is not affected by vaporization, and the purge gas stream 145, By controlling the ratio of In a preferred embodiment, the temperature of the filler in the bubbler 140 is maintained at the same temperature (e.g., ambient temperature T _a ) as the wafer under measurement. Under these conditions, the relative saturation p ₀ / p of the filler of the gas stream 126 is shown in equation 1, where F ₁ is the flow rate of the fully saturated gas stream 147 and F ₂ is the flow rate of the unsaturated gas stream (146).

As shown in FIG. 2, gas flows 146 and 147 are combined to create a gas flow 126 that is fed to the wafer under measurement. Thus, the total flow supplied to the wafer under measurement is controlled by delivering command signals 149A and 149B to adjust the sum of F ₁ and F ₂ . The relative saturation of the flow supplied to the wafer under measurement is controlled by delivering command signals 149A and 149B to adjust the ratio of F ₁ and F ₂ .

FIG. 15 shows a chart 210 for relative humidity RH for different combinations of flows F ₁ and F ₂ defined with respect to Equation (1).

In another embodiment, the degree of saturation of the vaporized filler at ambient temperature T _a is controlled by maintaining the liquid bath at a temperature T below the ambient temperature. The relationship between the equilibrium vapor pressure p ₀ of the pure substance and the temperature T is given by the Clausius-Clapeyron equation shown in equation (2), where H is the enthalpy of vaporization of the pure substance and R is the ideal gas constant 8.31 J / mole · K.

Based on Equation (2), the saturation degree p / p ₀ relative to the filler that saturates at a temperature T lower than the ambient temperature T _a is represented by Equation (3).

Figure 4 shows a table (127) containing the enthalpy of vaporization of water, toluene, and ethanol, [Delta] H. Each of these materials may be suitable as fillers as described in this document. In addition, table 127 indicates the difference between the ambient temperature (i.e., die temperature) and the bath temperature when the ambient temperature is 25 degrees and the relative saturation p / p ₀ of the desired filler 0.9 days Celsius. As shown in Table 127, a partial pressure of 0.9 is maintained for each listed filler by keeping the bath temperature as low as the ambient temperature. It is relatively simple to maintain a temperature difference of about 2 degrees Celsius between the wafer and the liquid bath of the bubbler 140, so it may be advantageous to use any of these materials as a filler. In this embodiment it is possible to control the degree of saturation of the vaporized filler of the gas stream 126 at ambient temperature T _a without combining the flow of dry purge gas 146 with the flow of saturated purge gas 147 . That is, the flow 146 may be set to zero, and the saturation of the vaporized filler of the gas stream 126 at ambient temperature T _a is controlled by the temperature difference between the bubbler temperature and the wafer temperature. The flow 146 of dry purge gas is combined with the flow 147 of saturated purge gas and the degree of saturation of the vaporized filler of gas flow 126 at ambient temperature T _a is determined by the bubbler temperature Temperature and the ratio of the flow rates of the gas flow 146 and the gas flow 147. [

In some embodiments, the bath temperature and wafer temperature are measured and communicated to computing system 130. The computing system determines the difference between the wafer temperature and the bath temperature and calculates the desired wafer temperature, bath temperature, or both. In some embodiments, the computing system 130 generates a command signal 149C indicative of the desired bath temperature in the vapor injection system 120. Correspondingly, the vapor injection system 120 regulates the bath temperature to a desired value using a local heating or cooling unit (not shown). In some embodiments, the computing system 130 generates a command signal (not shown) indicating a desired wafer temperature in a wafer conditioning subsystem (not shown). Correspondingly, the wafer conditioning system adjusts the wafer temperature to a desired value using a wafer heating or cooling unit (not shown). In some embodiments, the computing system 130 generates a command signal 113 (shown in FIG. 1) that indicates the desired wafer temperature to the local wafer heating element 103. Correspondingly, the heating unit 103 regulates the wafer temperature locally (i.e., immediately adjacent to the measurement location) to a desired value using a radioactive heating element.

In some embodiments, the temperature difference control between the wafer and the water bath is controlled by a computing system associated with the vapor injection system 120. In this regard, the control of the temperature difference between the wafer and the water bath by the computing system 130 is provided through a non-limiting example. Any suitable control architecture and temperature regulation scheme may be considered within the scope of this patent document.

3 is a diagram illustrating a vapor injection system 120 in yet another embodiment. Equally numbered elements are similar to those described in connection with FIG.

As shown in FIG. 3, the purge gas flow 124 passes through a three-way valve 141. In some embodiments, the three-way valve 141 passes through the bubbler 140 and a portion 145 of the purge gas flow 124 that flows through the bubbler 140 based on the position of the three- Adjust the non-flowing portion 146 to an appropriate ratio. In this way, the amount of purge gas flow 124 in which the filler is vaporized is controlled by the three-way valve 141. 3, the command signal 125 transmitted from the computing system 130 to the vapor injection system 120 includes a plurality of signals 149C-D. In the embodiment shown in Fig. 3, the signal 149D includes an indication as to the desired position of the three-way valve 141. Fig. Correspondingly, the three-way valve 141 is adjusted to the desired position, so that the purge gas flow in which the filler is vaporized is adjusted to a desired ratio. A portion 145 of the purge gas flow 124 flows through the check valve 142 and the flow control valve 143 into the bubble path 140. At bubbler 140, a significant amount of filler is vaporized into a portion 145 of purge gas flow 124 to produce purge gas and filler gas flow 147. The gas stream 147 combines with the portion 146 of the purge gas that does not flow through the bubbler 140 to produce a gas stream 126.

In some embodiments, the three-way valve 141 is controlled such that the entire purge gas flow 124 flows through the bubbler 140 or completely bypasses the bubbler 140 based on the position of the three-way valve . In this manner, the gas flow 126 is either a dry purge gas flow 124 with a partial pressure of the filler of zero, or the entire purge gas flow 124, depending on the state of the three-way valve, being influenced by the filler vaporization.

3, the amount of filler to be supplied to the wafer under measurement is proportional to the portion 146 of the purge gas flow 124 that is not affected by the filler vaporization, 124). ≪ / RTI > The degree of saturation of the vaporized filler at the wafer temperature is also controlled by adjusting the difference between the wafer temperature and the bath temperature.

In yet another embodiment, the degree of saturation of the vaporized filler at ambient temperature is determined by adding a nonvolatile solute to the liquid bath of the solvent (i. E., Filler) so as to suppress the equilibrium vapor pressure of the solvent relative to the equilibrium vapor pressure in the case of solvent alone Respectively. In one example, a solution formed from water as a solvent and a nonvolatile solute (e.g., sodium chloride, hydrochloric acid, etc.) shows the vapor pressure of water less than the equilibrium vapor pressure of pure water. Figure 5 shows a plot 128 as to the partial pressure of water as a function of the concentration of hydrochloric acid in the water bath. Similar results exist for the sodium chloride solution dissolved in water. For example, a solution of 6 percent sodium chloride in water exhibits a relative humidity p / p ₀ of 90%.

In these embodiments, the degree of saturation of the vaporized filler (i.e., solvent) is controlled by controlling the solute concentration of the solution. In some embodiments, the amount of solvent in the bath is controlled to maintain the desired concentration and thus maintain the desired partial pressure of the vaporized solvent. In these embodiments, precise temperature control is not necessary as long as the bath temperature is nominally maintained at ambient temperature (i. E., Wafer temperature).

In general, any suitable purge gas and filler may be selected for use in performing the measurements as described herein. Exemplary purge gases include inert gases, nitrogen, and clean dry air. The selection of a suitable purge gas is mainly driven by the availability of semiconductor manufacturing facilities. Exemplary fillers include water, ethanol, isopropyl alcohol, methanol, benzene, toluene, and the like. The selection of suitable fillers is induced by the ability to control the vapor pressure, void filling characteristics, optical properties, and any chemical interactions between the filler and the sample being measured.

For example, both the refractive index of the filler and the absorption coefficient of the filler are regarded as liquid fillers which, in the basic measurement model, not only refract incident light but also absorb incident light. Both of these properties can be used to determine the difference between measurements performed using the charge, especially with relatively short illumination wavelengths (e.g., vacuum ultraviolet wavelengths ranging from 120 nanometers to 190 nanometers) Lt; / RTI > Thus, the choice of a liquid filler that is significantly different from air in both refractive index and absorption coefficient provides an opportunity for reduced parameter correlations in multi-target measurement analysis.

In addition, the choice of liquid filler to vary both in refractive index and in absorption coefficient as a function of illumination wavelength provides an opportunity for reduced parameter correlations in spectral measurement analysis. Figure 6 shows a plot 135 for the dispersion of demineralized water as a function of wavelength. Plot line 136 shows the extinction coefficient and plot line 137 shows the index of refraction. As shown in FIG. 6, the demineralized water exhibits strong dispersion changes in the ultraviolet, vacuum ultraviolet, and ultraviolet regions as well as in the infrared regions. Spectroscopic instruments operating in these wavelength ranges use dispersion changes when water is used as condensate in a periodic structure.

In some embodiments, measurements using demineralized water as a filler can be performed using a variety of spectral metrology techniques that capture a wide wavelength range between 100 nanometers and 2,500 nanometers. Exemplary metrology techniques include spectroscopic polarimetry, Muller matrix polarization analysis, spectroscopic reflectometry, angle-resolved reflectometry, and the like.

In yet another aspect, the selection of a liquid filler that exhibits fluorescence at the illumination wavelength provides an opportunity for reduced parameter correlations in image-based measurement assays. In some embodiments, the fluorescence of the filler improves image contrast and improves the measurement performance of image-based measurement techniques such as image-based overlay, image-based inspection (e.g., darkfield and bright field inspection)

In yet another aspect, the spacing between the geometric structural features of the metrology target itself (e.g., critical dimension (CD) structures, lattice structures, overlay structures, etc.) during measurement of the metrology target by capillary condensation Capillary condensation is employed to charge. Generally, the desired degree of saturation of the material vaporized in the gas stream 126 is determined based on the maximum feature size to be filled by capillary condensation. Capillary condensation is employed to fill the filler with small features (e.g., small volumes such as notches, trenches, slits, contact holes, etc.). The Kelvin equation provides an approximation of the maximum feature size that can be charged for a particular filler, the partial pressure of the filler, and the ambient temperature (e.g., wafer temperature). Equation 3 represents the Kelvin equation for a condensed meniscus with two different radii r ₁ and r ₂ , where R is the ideal gas constant, T _a is the ambient temperature, V is is the molar volume of the filler, γ is the surface tension constant associated with the filler, p / p ₀ is a partial pressure of the filling material.

Figure 7 shows a table 129 depicting the molar volume and surface tension associated with water, toluene, and ethanol.

For cylindrical hole features, r ₁ is equal to r ₂ . Figure 8 shows a plot 172 showing the maximum diameter of a cylindrical hole that can be filled by capillary condensation according to equation (3). Plot 172 is generated by water (plot line 175), ethanol (plot line 174), and toluene (plot line 173) for various partial pressures of each filler at an ambient temperature of 25 degrees Celsius. Shows the maximum diameter of a cylindrical hole that can be filled. As shown in FIG. 8, cylindrical holes with diameters up to 40 nanometers can be filled when the gas stream 126 is fed to the metrology target at a partial pressure of water or ethanol of at least 95%. Also, as shown in FIG. 8, cylindrical holes with diameters up to 90 nanometers can be filled when the gas stream 126 is fed to the metrology target with a partial pressure of toluene greater than 95%.

For lines and spaces, r ₂ is zero. FIG. 9 shows a plot 160 showing the maximum diameter of a long trench-like feature that can be filled by capillary condensation according to equation (3). Plot 160 is shown by water (plot line 164), ethanol (plot line 163), and toluene (plot line 162) for various partial pressures of each filler at an ambient temperature of 25 degrees Celsius. Shows the maximum diameter of the trench that can be charged. As shown, the maximum diameter across the long trench-like feature is half the maximum diameter of the cylindrical hole feature. As shown in Figures 8 and 9, the plot lines of water and ethanol appear to overlap because the performance of ethanol as a filler is very similar to that of water.

In an aspect, the degree of saturation of the vaporized filler at ambient temperature T _a is adjusted to fill all features smaller than the desired maximum feature size. In some embodiments, this is accomplished by controlling the ratio of the flow of purge gas under the influence of vaporization and the flow of purge gas under the influence of vaporization, as described above. In some embodiments, this is accomplished by controlling the temperature difference between the wafer and the liquid bath of the filler. In some other embodiments, this is accomplished by controlling the concentration of the nonvolatile solute dissolved in the liquid bath of the filler.

In yet another aspect, measurements are performed with each different degree of saturation of the vaporized filler at ambient temperature such that all features smaller than the range of maximum feature sizes are filled. The measurements are combined in a multi-target model based measurement to estimate the value of one or more parameters of interest with reduced parameter correlation and improved measurement capabilities.

FIG. 10 shows an unfilled line-space metrology target 150 having a repetitive two-dimensional resist grating structure 152 fabricated on a substrate 151. The grating structure 152 has a nominal top critical dimension (TCD) of 7 nanometers and a height H of 50 nanometers.

FIG. 11 illustrates a filled line-space metrology target 155. The spacing between the resist lattice structures 152 is filled with the filler material 153 while the line-space metrology target 155 comprises the same repetitive two-dimensional resist lattice structure 152 fabricated on the substrate 151. This can be accomplished, in one example, by supplying a gas stream 126 to a metrology target 155 comprising toluene at a partial pressure of at least about 70%. In another example, filling the lattice structure 152 can be accomplished by supplying a gas stream 126 to a metrology target 155 that contains water or ethanol at a partial pressure of at least about 85%.

12A shows an unfilled metrology target 156 comprising a plurality of layers including a top layer with a cylindrical contact hole. 12A, the metrology target 156 includes a first layer 166, a second layer 167, a third layer 168, and a fourth layer 169 having a nominal height of 135 nanometers, . The fourth layer includes a cylindrical hole feature 170 passing through a fourth layer having a nominal diameter of 10 nanometers. The structure of the metrology target 165 has a nominal width of 40 nanometers and a nominal length of 40 nanometers.

Figure 12B shows a filled metrology target 157 including the same metrology target 156 except that the cylindrical hole 170 is filled with a significant amount of filler 171. [ This can be accomplished, in one example, by supplying a gas stream 126 to a metrology target 156 comprising toluene at a partial pressure of at least about 85%. In another example, filling of the cylindrical hole 170 can be accomplished by supplying a gas stream 126 to a metrology target 155 that contains water or ethanol at a partial pressure of at least about 95%.

The measurement targets shown in Figures 10 to 12B are provided through non-limiting examples. Generally, a site includes one or more metrology targets that are measured by a metrology system (e.g., metrology system 100 shown in FIG. 1). In general, the measurement data collection may be performed over the entire wafer or a subset of the wafer regions. Also, in some embodiments, metrology targets are designed for printability and sensitivity to process parameters, structural parameters of interest, or both. In some instances, the metrology targets are specialized targets. In some embodiments, the metrology targets are based on conventional line / space targets. As a non-limiting example, a CD target, a SCOL target, or an AiM ^TM target by KLA-Tencor Corporation of Milpitas, CA may be employed. In some other embodiments, the metrology targets are device-like structures. In some other examples, the metrology targets are part of device structures or device structures. Regardless of the type of metrology target employed, a set of metrology targets that exhibit sensitivity to both process changes, structural changes, or both being analyzed can be shaped fill by capillary condensation as described in this document .

In another aspect, the measurement data indicates that when the structures are charged (i.e., when subjected to capillary condensation as described in this document) and not charged (i.e., when capillary condensation is not affected) (E.g., CD structures, overlay structures, etc.). The collected data are combined in multi-target model-based measurements to improve measurement performance. In one example, measurement data is collected when the metrology target 156 is not charged, as shown in Figure 12A. In this scenario, the gas flow 126 is supplied to the metrology target 156 without the filler being vaporized into the flow. Also, as shown in FIG. 12B, measurement data is collected when the measurement target 156 is charged. In this scenario, the gas flow 126 is supplied to the metrology target 156 with a filler of sufficient saturation to fill the cylindrical hole 170, as described with respect to Fig. 12B. The collected data is received by the computing system 130. The computing system 130 performs model-based measurement analysis using both measurement data sets, including multi-target models, to estimate values of the parameters of interest. In some examples, the multi-target model described in this document, for example, is implemented in off-line by the computing system implementing the AcuShape ^® by KLA-Tencor Corporation of Milpitas, California. The resulting multi-target model is integrated into one component of the AcuShape ^® library accessible by a metrology system that performs measurements using multi-target models.

13 is a graph showing the relationship between the measurement results obtained using the multi-target model using the collected data with and without the shape fill, Lt; / RTI > shows the comparison of the measurement results obtained. The parameter L1_HT refers to the height of the first layer 166 of the metrology target 156 shown in FIG. 12A. L2_HT refers to the height of the second layer 167. L3_HT refers to the height of the third layer 168. G4_TCD refers to the highest critical dimension of the cylindrical hole 170. G4_BCD refers to the lowest critical dimension of the cylindrical hole 170. G4_EL refers to the ellipticity of the cylindrical hole 170. As shown in FIG. 13, the measurement accuracy improvement of each of L1_HT, L2_HT, L3_HT, G4_TCD, G4_BCD, and G4_EL is improved by a significant percentage as indicated by each of the measurement bars 177A-F. Similarly, the measurement correlation of each of L1_HT, L2_HT, L3_HT, G4_TCD, G4_BCD, and G4_EL is improved (ie, reduced) by a significant percentage as indicated by each of measurement bars 178A-F.

FIG. 16 shows a plot 220 for the spectroscopic polarization analysis parameter a for measurements of the same structure in both uncharged and charged states. Plot line 221 shows the spectral results for the measurement scenario when the structures are not charged. Plot line 222 shows the spectral results for the measurement scenario when the structures were charged.

FIG. 17 shows a plot 230 regarding the spectral difference between the spectroscopic polarization analysis measurements shown in FIG. Plot line 231 shows the difference between the measurement results for parameter a. As shown in Figure 17, the spectral differences are quite dramatic. These data sets are effectively employed in multi-target analysis to break correlations and improve measurement performance.

FIG. 18 shows a plot 240 for the spectroscopic polarization analysis parameter β for measurements of the same structure in both the uncharged and charged states. Plot line 241 shows the spectral results for the measurement scenario when the structures were not charged. Plot line 242 shows the spectral results for the measurement scenario when the structures were charged.

FIG. 19 shows a plot 250 for the spectral difference between the spectroscopic polarization analysis measurements shown in FIG. Plot line 251 shows the difference between the measurement results for parameter β. As shown in Figure 19, the spectral differences are quite dramatic. In addition, these data sets are effectively employed in multi-target analysis to break correlations and improve measurement performance.

In another aspect, a series of measurements are performed such that each set of measurement data is collected from the metrology target structures when the metrology target structures are each filled with a different filler or combination of different fillers. The collected data is combined in a multi-target model-based measurement to reduce parameter correlations and improve measurement performance.

In another aspect, measurement data is collected from a metrology target that is subject to condensation when the condensation process reaches a steady state. That is, the amount of charge supplied by the condensation process reaches a steady state.

In another aspect, measurement data is collected from a measurement target that is subject to condensation before the condensation process reaches a steady state. That is, the amount of charge supplied by the condensation process changes during the measurement time.

Figure 14 shows a method 200 for performing measurements of structures subject to capillary condensation. The method 200 is suitable for implementation by a metrology system such as the metrology system 100 shown in Figure 1 of the present invention. It will be appreciated that, in an aspect, the data processing blocks of the method 200 may be performed through a pre-programmed algorithm executed by the computing system 130 or any other general purpose computing system. It is noted in this document that certain spectral aspects of the metrology system 100 do not represent limitations and should be interpreted as illustrative only.

At block 201, a first amount of illumination light is provided to one or more structural elements disposed on the sample.

At block 202, a first gas flow comprising a first filler in the vapor phase is supplied to one or more structural elements during illumination of one or more structural elements. A portion of the first filler is condensed on the at least one structural element in liquid phase. A portion of the first filler fills at least a portion of the space between the one or more geometric features of the one or more structural elements.

At block 203, a first amount of collected light is detected from one or more structural elements in response to the first amount of illuminating light.

At block 204, a first set of measurement signals representing a first amount of collected light is generated.

In the embodiment shown in FIG. 1, spectroscopic polarimeter measurements are performed on measurement targets that are affected by a gas flow having a varying amount of liquid filler. However, in general, any suitable metering technique may be employed to perform measurements on metrology targets that are subject to a gas flow with varying amounts of liquid filler in accordance with the methods and systems described herein.

Suitable metrology techniques include, but are not limited to, spectroscopic polarimetry and spectroscopic reflectometry, including single wavelength, multiple wavelength, and angular resolution implementations, spectroscopic scatterometry including angular and polarization resolution implementations, scatterometry Overlay, beam profile reflectometry, and beam profile polarization analysis, and the imaging overlay, darkfield and bright field pattern wafer inspection can be considered individually or in any combination.

In one example, images of charged structures and images of the same structures in an uncharged state are used in image-based measurements such as overlay, patterned wafer defects, and the like. In another example, only images of filled structures are used in image-based measurements such as overlay, patterned wafer defects, and the like. In the imaging overlay example, AIM targets or box-in-box targets are charged and measured and analyzed to estimate overlay errors. In these examples, image-based analysis is employed to estimate the values of the parameters of interest.

In general, the measurement techniques described above can be applied to the measurement of process parameters, structural parameters, layout parameters, dispersion parameters, or any combination thereof. (E.g., critical dimension, height, sidewall angle), process parameters (e.g., lithography focus and lithography dose), dispersion parameters, layout parameters (e.g., pitch Pitch walk, edge placement errors), film thickness, composition parameters, or any combination of parameters may be measured using the techniques described above.

By way of non-limiting example, the structures measured using shape filling include line-space lattice structures, FinFet structures, SRAM device structures, flash memory structures, and DRAM memory structures.

In yet another additional aspect, the metrology targets located on the wafer are design rule targets. That is, the metrology targets adhere to the design rules applicable to the basic semiconductor manufacturing process. In some instances, the metrology targets are preferably located within the active die area. In some instances, the metrology targets have dimensions of 15 micrometers by 15 micrometers or less. In some other examples, the metrology targets are located on scribe lines, otherwise outside the active die area.

In some instances, model-based measurements are performed using form fill to estimate a single parameter of interest. Thus, the measurement models associated with the parameters of interest are independently optimized. By separately measuring each of the parameters of interest, the computational burden is reduced and the basic measurement capability can be maximized by selecting each different wavelength, measurement subsystem, and measurement method optimized for each individual parameter. In addition, for each of the parameters of interest, different model-based measurement solvers may be selected or configured differently.

However, in some other examples, model-based measurements are performed using form fill to simultaneously estimate a plurality of parameters of interest. Thus, a measurement model is developed to obtain a number of parameters of interest.

In some instances, although data may be collected from multiple sites on a wafer, the measurement of the parameters of interest performed at a particular measurement site depends solely on the data collected from that particular measurement site. In some other examples, measurement data collected from a plurality of sites across a wafer or a subset of wafers is used for measurement analysis. This may be desirable for capturing parameter variations across the wafer.

In some instances, measurements of the parameters of interest may be based on charged measurement targets using a number of different measurement techniques including single target techniques, multiple target techniques, and spectral feed forward techniques . The accuracy of the measured parameters can be enhanced by any combination of feed-side-way analysis, feed-forward analysis, and parallel analysis. The feed-side-way analysis refers to taking multiple sets of data on different regions of the same sample and transferring common parameters determined from the first set of data onto a second set of data for analysis. Feedforward analysis refers to taking data sets on different samples and forwarding common parameters to subsequent analyzes using a stepwise accurate parametric copy feed forward approach. Parallel analysis refers to the parallel or concurrent application of a nonlinear fitting methodology to a plurality of data sets to which at least one common parameter is combined during fitting.

A number of tool and structure analyzes refer to feedforward, feed-side way, or parallel analysis based on regression, look-up tables (i.e., "library" matching), or another fitting procedure of multiple data sets. Exemplary methods and systems for analyzing multiple tools and structures are described in U.S. Patent No. 7,478,019, filed on January 13, 2009, by KLA-Tencor Corporation, which is incorporated herein by reference in its entirety do.

In another aspect, the measurement results obtained as described herein can be used to provide active feedback to process tools (e.g., lithography tools, etch tools, deposition tools, etc.). For example, the values of the critical dimensions determined using the method and system described herein may be communicated to the lithography tool to adjust the lithography system to achieve the desired output. In a similar manner, etch parameters (e.g., etch time, diffusivity, etc.) or deposition parameters (e.g., time, concentration, etc.) may be included in the measurement model to provide active feedback to etch tools or deposition tools, respectively. In some examples, corrections to process parameters determined based on measured device parameter values may be communicated to a lithography tool, an etch tool, or a deposition tool.

It will be appreciated that the various steps described throughout the present invention may be performed by a single computer system 130, a plurality of computer systems 130, or a number of different computer systems 130. Also, each of the subsystems of the system 100, such as the spectroscopic polarimeter 101, may comprise a computer system suitable for performing at least a portion of the steps described in this document. Accordingly, the foregoing description is by way of example only and is not to be construed as a limitation on the invention. In addition, the computing system 130 may be configured to perform any other step (s) of any of the method embodiments described in this document.

Computing system 130 may include, but is not limited to, a personal computer system, a mainframe computer system, a workstation, an image computer, a parallel processor, or any other device known in the art. In general, the term " computer system " may be broadly defined to encompass any device or combination of devices, including one or more processors that execute instructions from a memory medium. In general, the computing system 130 may be integrated with a measurement system, such as the measurement system 100, or alternatively, in whole or in part, from any measurement system. In this regard, the computing system 130 may be remotely located to receive measurement data from any measurement source and transmit command signals to any element of the measurement system 100.

Program instructions 134 that implement methods such as those described herein may be transmitted via a transmission medium such as a wire, cave, or wireless transmission link. The memory 132 that stores the program instructions 134 may include a read only memory, a random access memory, a magnetic or optical disk, or a computer readable medium such as a magnetic tape.

The computing system 130 may also be communicatively coupled to the illuminator subsystem 102 of the spectrometer 104 or the polarization analyzer 101 in any manner known in the art.

Computing system 130 may receive data or data from subsystems (e.g., spectrometer 104, illuminator 102, vapor injection system 120, etc.) of the system via a transmission medium that may include wired and / And may be configured to receive and / or obtain information. In this manner, the transmission medium may serve as a data link between the computer system 130 and other subsystems of the system 100. In addition, the computing system 130 may be configured to receive measurement data via a storage medium (i.e., memory). For example, the spectral results obtained using the spectrometer of the polarization analyzer 101 may be stored in a permanent or semi-permanent memory device (not shown). In this regard, the spectral results can be retrieved from an external system. In addition, the computer system 130 may receive data from external systems via a transmission medium.

The computing system 130 may receive data or data from subsystems (e.g., spectrometer 104, illuminator 102, vapor injection system 120, etc.) of the system via a transmission medium, which may include wired and / May be configured to transmit information. In this manner, the transmission medium may serve as a data link between the computer system 130 and other subsystems of the system 100. In addition, the computing system 130 may be configured to transmit command signals and measurement results via a storage medium (i.e., memory). For example, measurement results 115 obtained through analysis of spectral data may be stored in a permanent or semi-permanent memory device (not shown). In this regard, the spectral results can be exported to an external system. In addition, the computer system 130 may transmit data to external systems via a transmission medium. Also, the determined values of the parameter of interest are stored in memory. For example, the values may be stored on-board to the measurement system 100, e.g., in the memory 132, or may be delivered to an external memory device (e.g., via the output signal 115).

The term " capillary condensation ", as described in this document, includes any process in which a vaporized filler is deposited onto structures being measured in liquid form. This includes absorption and any other related physical mechanisms. Whereby the filler may alternatively be referred to as a condensate material or an absorbent material.

The term " critical dimension ", as described herein, refers to any critical dimension of the structure (e.g., bottom critical dimension, medium critical dimension, top critical dimension, sidewall angle, (E.g., the distance between two structures), and a displacement between two or more structures (e.g., overlay displacements between overlapping lattice structures, etc.). The structures may include three-dimensional structures, patterned structures, overlay structures, and the like.

The term " critical dimension application " or " critical dimension measurement application ", as described herein, includes any critical dimension measurement.

The term " metrology system ", as described herein, is adapted to at least partially characterize a sample in any aspect, including measurement applications such as critical dimension measurements, overlay metrology, focus / ≪ / RTI > However, such technical field terms do not limit the scope of the term " metrology system " described in this document. In addition, the metrology system 100 may be configured for measurement of patterned wafers and / or non-patterned wafers. The metrology system can be used to optimize system parameters based on critical dimension data based on LED inspection tools, edge inspection tools, back inspection tools, macro inspection tools, or multi-mode inspection tools (including data from one or more platforms at the same time) Such as any other metrology or inspection tool that obtains a desired measurement value. For purposes of this patent document, the terms "metrology" and "inspection" systems are synonyms.

Various embodiments of a semiconductor processing system (e.g., inspection system or lithography system) that may be used to process a sample are described in this document. The term " sample " is used in this document to refer to a wafer, a reticle, or any other sample that can be processed (e.g., printed or checked for defects) by means known in the art.

As used herein, the term " wafer " refers generally to substrates formed of semiconductor or non-semiconductor materials. Examples include, but are not limited to, single crystal silicon, gallium arsenide, and indium phosphide. Such substrates can often be found and / or processed in semiconductor manufacturing facilities. In some cases, the wafer may contain only a substrate (i.e., a bare wafer). Alternatively, the wafer may comprise one or more layers of different materials formed on the substrate. One or more layers formed on the wafer may be " patterned " or " unpatterned ". For example, the wafer may comprise a plurality of dies with repeating pattern features.

A " reticle " may be a reticle at any stage of the reticle manufacturing process, or it may be a complete reticle that may or may not be released for use in a semiconductor manufacturing facility. A reticle or " mask " is generally defined as a generally transparent substrate having opaque regions formed thereon and composed of a pattern. The substrate, for example, may include a glass material such as amorphous SiO _2. The reticle may be placed on a wafer over which the resist is covered during the exposure step of the lithographic process so that the pattern on the reticle can be transferred to the resist.

One or more layers formed on the wafer may be patterned or not patterned. For example, the wafer may comprise a plurality of dice each having repeating pattern features. The formation and processing of such material layers may ultimately lead to complete devices. A variety of different types of devices can be formed on a wafer, and the term wafer used in this document encompasses wafers on which any type of device known in the art is fabricated.

In one or more exemplary embodiments, the described functions may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on or transmitted via one or more instructions or code on a computer readable medium. Computer-readable media includes both computer storage media and communication media including any medium that enables movement of a computer program from one location to another. The storage medium may be any available media that can be accessed by a general purpose computer or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise a computer-readable medium such as RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, Or any other medium that can be used to store, transmit, or store information and which can be accessed by a general purpose or special purpose computer, or a general purpose or special purpose processor. Also, any connection may be suitably referred to as a computer-readable medium. For example, using wireless technologies such as coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or infrared, radio, or microwave, software may be transmitted from a website, server, Wireless technologies such as coaxial cable, fiber optic cable, twisted pair, DSL, or infrared, radio, or microwave are included within the definition of the medium. Discs and discs used in this document may be in the form of a compact disc (CD), a laser disc, an optical disc, a digital versatile disc (DVD), a floppy disc disk, and a Blu-ray disc, where the disc usually reproduces data magnetically, while discs reproduce data optically using a laser. Combinations of the above should also be included within the scope of computer readable media.

Although certain specific embodiments have been described for purposes of illustration, the contents of this patent document are of general applicability and are not limited to the specific embodiments described above. Accordingly, various modifications, adaptations, and combinations of the various features of the described embodiments may be made without departing from the scope of the invention as set forth in the claims.

Claims (28)

In a measurement system,
An illumination source configured to supply a first amount of illumination light to one or more structural elements disposed on a specimen;
A vapor injection system configured to supply a first gas flow comprising a first filler in a vapor phase to the at least one structural element during illumination of the at least one structural element, Wherein at least a portion of the first filler fills at least a portion of the space between the at least one geometric feature of the at least one structural element. And
And a detector configured to receive a first amount of collection light from the one or more structural elements in response to the first amount of illumination light and to generate a first set of measurement signals representative of the first amount of collection light, system. The method according to claim 1,
Wherein the vapor injection system is further configured to supply a second gas flow in a vapor phase to the at least one structural element during illumination of the at least one structural element, wherein a portion of the second filler is in liquid phase, Wherein a portion of the second filler fills at least a portion of the space between the at least one geometric feature of the at least one structural element. The method according to claim 1,
Receive the first set of measurement signals associated with a first measurement of the one or more structural elements; And
To estimate a value of a parameter of interest of the one or more structural elements based at least in part on the first set of measurement signals
Wherein the system further comprises a configured computing system. The method according to claim 1,
Wherein the illumination source is further configured to supply a second amount of illumination light to the one or more structural elements disposed on the sample, wherein the vapor injection system is configured to dispense the first filler at a partial pressure different than the first gas flow Wherein the detector is configured to receive a second amount of collected light from the one or more structural elements in response to the second amount of illuminated light and to receive the second amount of collected light in response to the second amount of illuminated light, And to generate a second set of measurement signals. 5. The method of claim 4,
Receive the first set of measurement signals associated with a first measurement of the one or more structural elements;
Receive the second set of measurement signals associated with a second measurement of the one or more structural elements; And
Target values of the one or more structural elements based at least in part on the first set and the second set of measurement signals and the multi-target measurement model
Wherein the system further comprises a configured computing system. 5. The method of claim 4,
Wherein the partial pressure of the first filler of the second gas flow is approximately zero. The method according to claim 1,
The measurement system may be configured as either a spectroscopic ellipsometer, a spectroscopic reflectometer, an angle resolved reflectometer, a dark field inspection system, a bright field inspection system, and an imaging overlay measurement system. . The method according to claim 1,
Wherein the first amount of illumination light is broadband light comprising an illumination wavelength of 100 nanometers to 2,500 nanometers. The method according to claim 1,
Wherein the temperature of the sample is approximately the same as the temperature of the first filler vaporized in the first gas flow. The method according to claim 1,
Wherein the vapor injection system mixes an unsaturated purge gas of a first flow with a purge gas of a second flow saturated with a first filler in a vapor phase to provide a first gas flow. 11. The method of claim 10,
Wherein the vapor injection system adjusts the partial pressure of the first filler of the first gas flow by changing the ratio of the unsaturated purge gas flow and the purge gas flow saturated with the first filler in the vapor phase. 11. The system of claim 10,
A bubbler comprising a first filler in liquid phase, wherein a portion of the liquid filler is vaporized with a purge gas of the second flow to saturate the purge gas of the second flow with the first filler in a gaseous phase And the bubbler. The method according to claim 1,
Wherein the filler is water, ethanol, toluene, isopropyl alcohol, methanol, and benzene. The method according to claim 1,
Wherein the first filler exhibits fluorescence emission in response to the first amount of illumination light. The method of claim 3,
Wherein estimating the value of the parameter of interest comprises any of model-based regression, model-based library search, model-based library regression, image-based analysis, and signal response metrology model. There is a measuring system,
An illumination source configured to supply an amount of illumination light to one or more structural elements disposed on a sample;
As a steam injection system,
A first mass flow controller for regulating the flow rate of the purge gas in the first flow,
A second mass flow controller for regulating the flow rate of the purge gas in the second flow, and
Wherein the purge gas of the second flow passes through the bubbler and a portion of the liquid filler is vaporized by the purge gas of the second flow to vaporize the purge gas of the second flow into the first filler Wherein the purge gas of the first flow and the purge gas of the second flow saturated with the first filler are combined so as to saturate the purge gas of the second flow, Said bubbler comprising a bubbler, said bubbler forming a gas flow to be supplied to said at least one structural element; And
And a detector configured to receive a first amount of collected light from the one or more structural elements in response to a first amount of illumination light and generate a first set of measured signals indicative of the first amount of collected light , Measurement system. 17. The method of claim 16,
To deliver a first command signal to the first mass flow controller to cause the first mass flow controller to regulate the flow rate of the purge gas of the first flow; And
Such that the ratio of the flow rate of the purge gas of the first flow to the flow rate of the purge gas of the second flow is adjusted to achieve a desired partial pressure of the first filler of the gas flow, To deliver a second command signal to the second mass flow controller to adjust the flow rate of the purge gas in the second flow
Wherein the system further comprises a configured computing system. In the method,
Providing a first amount of illumination light to one or more structural elements disposed on a sample;
Providing a first gas flow comprising a first filler in a vapor phase to the at least one structural element during illumination of the at least one structural element, wherein a portion of the first filler is condensed on the at least one structural element in liquid phase The portion of the first filler filling at least a portion of the space between the at least one geometric feature of the at least one structural element;
Detecting a first amount of collected light from the one or more structural elements in response to the first amount of illuminating light; And
Generating a first set of measurement signals representative of the first amount of collected light. 19. The method of claim 18,
Providing a second gas flow comprising a second filler in a vapor phase to the at least one structural element during illumination of the at least one structural element, wherein a portion of the second filler is condensed on the at least one structural element in liquid phase And wherein the portion of the second filler fills at least a portion of the space between the at least one geometric feature of the at least one structural element. 19. The method of claim 18,
Supplying a second quantity of illumination light to the one or more structural elements disposed on the sample;
Providing a second gas flow comprising the first filler at a partial pressure different from the first gas flow;
Detecting a second amount of collected light from the one or more structural elements in response to the second amount of illumination light; And
And generating a second set of measurement signals representative of the second amount of collected light. 21. The method of claim 20,
Further comprising estimating a value of a parameter of interest of the one or more structural elements based at least in part on the first set and the second set of measurement signals. 22. The method of claim 21,
Wherein estimating the value of the parameter of interest comprises any of model-based regression, model-based library search, model-based library regression, image-based analysis, and signal response metrology model. 19. The method of claim 18,
Wherein the temperature of the sample is approximately the same as the temperature of the first filler vaporized in the first gas flow. 19. The method of claim 18,
Wherein supplying the first gas stream comprises mixing an unsaturated purge gas of the first stream with a purge gas of the second stream saturated with the first filler in a vapor phase. 25. The method of claim 24,
Further comprising adjusting the partial pressure of the first filler of the first gas flow by changing the ratio of the unsaturated purge gas flow and the purge gas flow saturated with the first filler to the vapor phase. 19. The method of claim 18,
Wherein the filler is water, ethanol, toluene, isopropyl alcohol, methanol, and benzene. 19. The method of claim 18,
Wherein the first filler exhibits fluorescence emission in response to the first amount of illumination light. 19. The method of claim 18,
Further comprising adjusting the degree of saturation of the first filler in the first gas flow such that any space between one or more geometric features below the desired maximum feature size is filled.

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