Even though its resolution limit is far from the modern step-and-scan tools used in IC industry today, its higher depth of focus makes it a suitable tool for MEMS, where lithography over severe topography is often mandatory. The process parameters used to form the printed structures are generally configured to keep the shape parameters within desired specifications. The wafer may be a product wafer that has the potential to produce working devices. The Bossung Plot illustrates curves of the focus exposure dependence of height for a line space grating designed for nm line width and nm pitch. Each profile is defined by shape parameters and thus the shape parameters are known once the profile is found. For example, the shape parameters as a function of process parameters may be inverted to produce process parameters as a function of shape parameters. The method as recited in claim 24 wherein the scatterometry sites differ in shape, pitch, mask construction, position or orientation.
Alternatively, the Bossung Plot may be inverted such that it plots exposure vs. It should be noted, however, that the shape information may also be contained in wavelengths larger than 65 percent of the feature in interest. The optimum focus exposure conditions can be used to control the lithographic process. As should be appreciated, stopping the production run reduces the throughput of the lithography system thereby increasing cycle time and cost. You may download, display and print this publication for Your own personal use. The optimal values are typically determined in block That is, the production run must be stopped so that a focus exposure matrix test wafer can be inserted into the system.
Inspection apparatus, inspection method, lithographic apparatus and manufacturing bossunt. The processing generally includes printing a plurality of scatterometry measurement sites in a layer of photoresist with a lithography system e.
For example, the printed structures may take the form of a grating structure, as for example a line space grating or a grid space grating. When using multiple test wafers, the same or different test reticles may be used.
Stepper lithography optimization
In another embodiment, the dependencies include one or more process parameters as a function of one or more shape parameters.
For example, the estimated or predicted values of the process parameters determined in block 16 may be used to control subsequent processing to keep the process within desired limits. As should be appreciated, determining a plurality of shape parameters in block 14 provides more than one input and may allow for a solution for more than one process parameter, i. For reasons of clarity, FIG. In one embodiment, the dependencies produced in block  12 are used to determine the best process parameter settings for driving the process.
In most cases, the scatterometry measurement sites have an identical pattern so that the different combinations may be properly characterized. The method generally begins at block where a resist process model is obtained.
The method as recited in claim 1 wherein multiple shape parameters are correlated with multiple process parameters. Scatterometry techniques will be described in greater detail below. For the optimization of our Stepper tool, photoresist profiles obtained with different exposure parameters and test masks were analysed with Scanning Electron Microscope SEM and optical microscope delegated to measurement of Critical Dimensions CD.
The scatterometry technique used to measure the grating structure e. Workload performance projection for future information handling systems using microarchitecture dependent data.
In one particular implementation, the dependencies include more than one shape parameter as a function of both focus and exposure. The wafer may be a simple test wafer used for testing the lithography system. The method as recited in claim 1 wherein a single shape parameter of the second set of one or more shape parameters is used to solve for a single process parameter of the second wibdow of one or more process parameters. The first process flow, steps -may be performed incrementally as needed to ensure that the dependencies are accurate.
Determining one or more profile parameters of a structure using optical metrology and a correlation between profile models and key profile shape variables. The method includes correlating the values of a first set of one or more shape parameters with the values of a first set of bossung or more process parameters to produce dependencies.
After block  16post estimating steps may be performed. Although the method described herein with regards bosxung using scatterometry does not directly compare spectra proxess. By way of example, the shape parameters may correspond to linewidths CDline height, wall angle, and the like, and the process parameters may correspond to focus, exposure and the like.
The test data may be produced using a variety of techniques. The method as recited in claim 30 wherein the determined optical aberrations are used to determine the mask design including feature orientation or mask feature parameters so as to minimize the negative effects of the optical aberrations.
USA1 – Method for determining lithographic focus and exposure – Google Patents
For example, the unique solutions may be demonstrated by the intersections of curves of constant line width and curves of constant line height at only one point of focus and exposure as shown in FIGS. In accordance with another embodiment, the shape information from multiple measurement sites in a stepper exposure field can also be analyzed to determine the imperfections or optical aberrations of the stepper lens system.
These dependencies may be produced by deriving one or more shape parameters as a function of one or more process parameters as discussed aboveand then converting these functions to form one or more process parameters as a function of one or more shape parameters.
The lithographic measurement methods, on the other hand, generally produce calibration data by printing a plurality of structures on one or more test wafers using various process parameters, determining the shape parameters associated with each of the structures, and correlating the shape parameters with the various process parameters so as to form dependencies.
In the simplest terms, the determined values of the shape parameters in block 14 are compared with the calibrated values of the shape parameters in block 12 so as to determine the values of the process parameters for the determined values. The method as recited in claim 40 wherein the determined optical aberrations are used to determine the mask design including feature orientation or mask feature parameters so as to minimize the negative effects of the optical aberrations.
The difference is that the measurement sites are on a production wafer or a test wafer not a focus exposure matrix wafer. The objective is to find a profile whose calibrated spectra matches the measured spectra.
The method as recited in claim 14 wherein the scatterometry measurement sites are formed using a different combination of focus and exposure. In another embodiment, multiple sites are measured per field. The pitch P should be as large as is practical for the scatterometry measurement system. After block the process flow proceeds to block where focus exposure dependencies of shape parameters are determined. System and method for characterizing macro-grating test patterns in advanced lithography and etch processes.
The correction may be used to help control the lithographic process by adjusting the process parameters.
Focus Effects and Process Window
For example, the decision may be to not make a correction because its too small. This is generally accomplished by by matching the different focus-exposure combinations used to form the measurement sites with the appropriate profiles of the measured spectra.
The invention relates, in another embodiment, to a method of focus exposure monitoring of a lithographic system. For example, referring to FIG. The overlapped bossung plot is configured to demonstrate a unique solution for focus and exposure determined from middle CD measurements on a first line grating type and side wall angle SWA and resist loss RL measurement on a different line grating with a different pitch.
These curves describe all the possible solutions for focus and exposure for a given set of shape parameters. A method of focus exposure monitoring of a lithographic system, comprising: The method as recited in claim 12 wherein the values of the second set of shape parameters are determined via scatterometry measurements.
In production, the printed structures are typically printed in the scribeline between device structures e.
US20030048458A1 – Method for determining lithographic focus and exposure – Google Patents
The focus-exposure matrix may be visualized using a Bossung Plot. The term printed structures generally refers to structures that are printed on a wafer e. The structure may be in the form of a wijdow that is typically periodic. The method also includes determining the values of a second set of one or more shape parameters associated with one or more structures.
An example of solving for focus and exposure using MCD data from one line grating target and sidewall angle and resist loss measured for a line grating target with different pitch is given in FIG. Furthermore, in contrast to the present invention, CD-SEM and line end shortening methods cannot be performed with scatterometry, nor can they obtain good quality shape information outside of the XY plane.