Focus masking structures, focus patterns and measurements thereof

Abstract

Methods and device structures used to determine the focus quality of a photolithographic pattern or a photolithographic system are disclosed. One aspect of the invention relates to focus masking structures configured to form focus patterns that contain focus information relating to the focus quality. The focus masking structures generally include a plurality of parallel source lines that are separated by alternating phase shift zones. Another aspect of the invention relates to focus patterns that change with changes in focus. The focus patterns generally include a plurality of periodic structures that form measurable shifts therebetween corresponding to the sign and magnitude of defocus. Another aspect of the invention relates to a method of determining the focus quality of a photolithographic pattern or a photolithographic system. The method generally includes: providing a focus masking structure, forming a focus pattern on a work piece with the focus masking structure, and obtaining focus information from the focus pattern. The focus information may be obtained using a variety of techniques, as for example, scatterometry techniques, scanning techniques, imaging techniques, phase based techniques, and the like.

1 . A focus masking structure used to determine the focus quality of a photolithographic pattern or a photolithographic system, said focus masking structure being disposed on a substrate, said focus masking structure comprising: 
 a plurality of source lines; and    a plurality of phase shift zones configured to separate said plurality of source lines, said plurality of phase shift zones alternating between a first phase shift zone and a second phase shift zone thereby creating alternating first and second phase transitions, said first and second phase shift zones having phases that are not equal to the phase of the substrate, and a phase difference therebetween that is not equal to 0 or 180 degrees or integer multiples of 180 degrees.    
   
   
       2 . The focus masking structure as recited in  claim 1  wherein said plurality of source lines and said phase shift zones cooperate to produce a focus pattern that includes elements that shift relative to one another with changes in focus, said shift being based on the sign and magnitude of defocus and the sign and magnitude of the phase difference.  
   
   
       3 . The focus masking structure as recited in  claim 2  wherein the focus pattern includes at least two periodic structures that shift relative to one another with changes in focus.  
   
   
       4 . The focus masking structure as recited in  claim 1  wherein the line widths of said first and second phase shift zones are not equal to one another.  
   
   
       5 . The focus masking structure as recited in  claim 1  wherein the lines widths of said source lines are equal to one another.  
   
   
       6 . The focus masking structure as recited in  claim 1  wherein the lines widths of said phase shift zones are larger than the lines widths of said source lines.  
   
   
       7 . The focus masking structure as recited in  claim 1  wherein the pitches of said source lines and said phase shift zones are equal to one another.  
   
   
       8 . The focus masking structure as recited in  claim 1  further comprising an attenuating phase shifter disposed between the source lines and the substrate.  
   
   
       9 . A focus masking structure used to determine the focus quality of a photolithographic pattern or a photolithographic system, said focus masking structure being disposed on a substrate, said focus masking structure comprising: 
 a plurality of source lines; and    a plurality of phase shift zones configured to separate said plurality of source lines, said plurality of phase shift zones alternating between a first phase shift zone and a second phase shift zone thereby creating alternating first and second phase transitions, a phase difference between the first and second phase shift zones not being equal to 0 or 180 degrees or integer multiples of 180 degrees,    wherein said plurality of source lines and said phase shift zones cooperate to produce a focus pattern that includes at least two periodic structures that shift relative to one another with changes in focus, said shift being based on the sign and magnitude of defocus and the sign and magnitude of the phase difference.    
   
   
       10 . The focus masking structure as recited in  claim 9  wherein the periodic structures have the same number of lines  
   
   
       11 . The focus masking structure as recited in  claim 9  wherein the periodic structure have different number of lines  
   
   
       12 . The focus masking structure as recited in  claim 9  wherein the size and pitch of the lines of the periodic structures are arranged to coincide with the size and pitch of a circuit pattern.  
   
   
       13 . The focus masking structure as recited in  claim 9  wherein each periodic structure includes a plurality of coarsely segmented parallel lines, and wherein the coarsely segmented lines of at least one of the periodic structures include finely segmented elements.  
   
   
       14 . The focus masking structure as recited in  claim 12  wherein the finely segmented elements are about the same size as the structures of an integrated circuit formed therewith.  
   
   
       15 . The focus masking structure as recited in  claim 12  wherein the coarsely segmented lines of a first periodic structure are formed with first finely segmented elements, and the coarsely segmented lines of a second periodic structure are formed with second finely segmented elements that are different than the first finely segmented elements.  
   
   
       16 . The focus masking structure as recited in  claim 9  wherein the at least two periodic structures are oriented in one of the X or Y directions.  
   
   
       17 . The focus masking structure as recited in  claim 9  wherein the at least two periodic structures are oriented in an angled direction relative to the X or Y directions.  
   
   
       18 . The focus masking structure as recited in  claim 9  wherein the at least two periodic structures are oriented in both the X and Y direction.  
   
   
       19 . A method of determining best fit focus masking structure, comprising: 
 selecting a process for creating focus patterns with focus masking structures;    selecting a technique for measuring position shift of focus patterns; and    selecting or optimizing characteristics of focus masking structure based on process parameters associated with the process or the measurement technique.    
   
   
       20 . The method as recited in  claim 19  wherein selecting or optimizing characteristics of focus masking structure are based on process parameters associated with process.  
   
   
       21 . The method as recited in  claim 20  wherein the focus masking structure is selected or optimized based on the device features being generated with the focus pattern.  
   
   
       22 . The method as recited in  claim 19  wherein selecting or optimizing characteristics of focus masking structure are based on measurement technique.  
   
   
       23 . The method as recited in  claim 22  wherein the focus masking structure is selected or optimized based on the measurement technique's sensitivity to focus.  
   
   
       24 . The method as recited in  claim 22  wherein the measurement technique is a scatterometry measurement technique.  
   
   
       25 . The method as recited in  claim 24  wherein the measurement technique is selected from reflectometry, spectroscopic ellipsometry, multiwavelength reflectometry or angled resolved scatterometry.  
   
   
       26 . The method as recited in  claim 19  wherein selecting or optimizing characteristics of focus masking structure are based on process parameters associated with process and the measurement technique.  
   
   
       27 . The method as recited in  claim 19  wherein said focus masking structure comprises a plurality of source lines, and a plurality of phase shift zones configured to separate said plurality of source lines, said plurality of phase shift zones alternating between a first phase shift zone and a second phase shift zone thereby creating alternating first and second phase transitions, a phase difference between the first and second phase shift zones not being equal to 0 or 180 degrees or integer multiples of 180 degrees.  
   
   
       28 . The method as recited in  claim 27  wherein said plurality of source lines and said phase shift zones cooperate to produce a focus pattern that includes at least two periodic structures that shift relative to one another with changes in focus, said shift being based on the sign and magnitude of defocus and the sign and magnitude of the phase difference.  
   
   
       29 . The method as recited in  claim 27  wherein said first and second phase shift zones have phases that are not equal to the phase of a substrate.