System and method for controlling critical dimension in a semiconductor manufacturing process
AssigneeYield Dynamics, Inc.
InventorsStacy K. Firth, W. Jarrett Campbell
Life of this patent
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Abstract
A system and method for controlling critical dimension in a semiconductor manufacturing process. The system 10 controls critical dimension by altering focus and exposure settings, based on a single measured attribute (i.e., critical dimension) and on a process model equation. The system 10 further systematically varies focus and exposure settings (e.g., by introducing variable deviation values), in order to provide unique and stable solutions for parameters within the process model equation.
Claims22
A control system for a semiconductor photolithography process, said control system being adapted to control critical dimension by adjusting focus and exposure settings within said photolithography process based upon a single measured attribute, critical dimension, and by use of the following process model equation:
- CD k = a k E k + b k F k 2 + c k F k + d k
- where CDk is critical dimension at run k, Ek is the exposure setting at run k, Fk is the focus setting at run k, and ak, bk, ck, and dk are adjustable parameters, and where the control system updates one or more of the adjustable parameters by use of a least squares estimation procedure.
An apparatus for controlling an output attribute in a semiconductor fabrication process, said apparatus comprising:
- means for measuring said output attribute;
- a first control portion which is adapted to control said output attribute by simultaneously adjusting a plurality of inputs to said semiconductor fabrication process, based upon said measured output attribute and a process model equation including a plurality of parameters;
- and
- a second control portion which is adapted to/estimate updates for said plurality of parameters;
- wherein said first control portion systematically varies said plurality of inputs in a manner that ensures stable estimates for said plurality of parameters.
A run-to-run control system for controlling critical dimension in a photolithography process, said control system comprising:
- a photolithography tool for performing said photolithography process;
- a control law portion that is communicatively coupled to said photolithography tool, said control law portion being adapted to determine focus and exposure settings based upon a process model equation, and being further adapted to communicate said focus and exposure settings to said photolithography tool for controlling said photolithography process;
- and
- an observer portion that is communicatively coupled to said control law portion, said observer portion being adapted to estimate a plurality of parameter values for said process model equation based upon at least one prior measured critical dimension value, and to communicate said plurality of parameter values to said control law portion.
A method for controlling an output attribute in a semiconductor fabrication process, said method comprising the steps of:
- measuring said output attribute;
- controlling said output attribute by simultaneously adjusting a plurality of inputs to said semiconductor fabrication process, based upon said measured output attribute and a process model equation including a plurality of parameters;
- estimating updates for said plurality of parameters;
- and
- systematically varying said plurality of inputs in a manner that ensures stable estimates for said plurality of parameters.
A method of controlling critical dimension in a photolithography process, said method comprising the steps of:
- monitoring a single measured attribute;
- and
- controlling critical dimension by selectively adjusting focus and exposure in said photolithography process based upon said single measured attribute, critical dimension, and by use of the following process model equation:
- CD k = a k E k + b k F k 2 + c k F k + d k
- where CDk is critical dimension at run k, Ek is the exposure setting at run k, Fk is the focus setting at run k, and ak, bk, ck, and dk are adjustable parameters.
A method for controlling critical dimension in a semiconductor photolithography process, comprising the steps of:
- determining a focus setting by use of a best focus value and a variable deviation value;
- determining an exposure setting by use of a control law equation;
- running said photolithography process using said focus and exposure settings;
- obtaining a resulting critical dimension measurement;
- and
- utilizing said critical dimension measurement to update a plurality of parameters used within said control law equation;
- wherein said focus setting is determined by use of the following equation:
- Fk=Fo,k+dFk
- where Fk is the focus setting at run k, Fo,k is the best focus value, and dFk is the deviation value, which is varied in a pseudorandom manner.
A method for controlling critical dimension in a semiconductor photolithography process, comprising the steps of:
- determining a focus setting by use of a best focus value and a variable deviation value;
- determining an exposure setting by use of a control law equation;
- running said photolithography process using said focus and exposure settings;
- obtaining a resulting critical dimension measurement;
- and
- utilizing said critical dimension measurement to update a plurality of parameters used within said control law equation;
- wherein said exposure setting is determined by use of the following control law equation:
- E k = a k ( T + dCD k ) - b k F k 2 - c k F k - d k
- where Ek is the exposure setting at run k, T is a critical dimension target value, Fk is the focus setting at run k, ak, bk, ck, and dk are parameters used within said control law and dCDk is a deviation value, which is varied in a pseudorandom manner.
Dependencies are inferred from the claim text.