Monitoring of minimum features on a substrate

A method of measuring lithographic process bias of a minimum feature formed in a lithographic process, using a measurement tool, comprising the steps of:

• creating at least a pair of array of elements on a substrate, each element having a nominal length and a nominal width, and each adjacent element having a nominal space therebetween wherein the nominal width and the nominal space correspond to said minimum feature, said arrays of elements having an average nominal separation and an average nominal length;
• measuring average length of said created elements in said arrays and average separation between said pair of created arrays resulting from said lithographic process;
• calculating change in average length of elements and average separation from said average nominal length and average nominal separation respectively;
• and,
• means for calculating lithographic process bias of said minimum feature (width, space) from said change in average length of said elements and average separation between said pair of arrays.

A method of selecting a lithographic process from a plurality of lithographic processes for minimizing bias of a minimum feature created by use of said lithographic process, comprising the steps of:

• creating an array of elements on a substrate, each element having a nominal length and a nominal width, and each adjacent element having a nominal space therebetween, wherein the nominal width of each element and the nominal space between adjacent elements correspond to said minimum feature, using a plurality of lithographic processes;
• measuring length of said created elements in the array corresponding to said plurality of lithographic processes;
• calculating change in length of said created elements from nominal length;
• means for calculating bias of the minimum feature (width, space) from said change in length of said elements corresponding to said plurality of lithographic processes;
• and,
• selecting a lithographic process from said plurality of lithographic processes, corresponding to smallest calculated bias of said minimum feature.

A method of selecting a lithographic process from a plurality of lithography processes for minimizing bias of a minimum feature created by the use of said lithographic process, comprising the steps of:

• creating at least a pair of array of elements on a substrate, each element having a nominal length and a nominal width, and each adjacent element having a nominal space therebetween wherein the nominal width and the nominal space correspond to said minimum feature, said arrays of elements having an average nominal length and average nominal separation, using a of different lithographic process conditions;
• measuring average length of said created elements in the array and average separation between said pair of created arrays, corresponding to said plurality of lithographic processes;
• calculating change in average length of elements and average separation between said pair of arrays from said average nominal length and average nominal separation respectively;
• means for calculating bias of the minimum feature from said change in average length and average separation corresponding to said plurality of lithographic processes;
• and,
• selecting the lithographic process from said plurality of lithographic processes, corresponding to smallest calculated bias of said minimum feature.

A method of selecting hardware and software changes to an exposure tool, to achieve a preselected bias corresponding to a minimum feature size, comprising the steps of:

• modifying the exposure tool using a plurality of hardware and software changes;
• creating an array of elements on a substrate, each element having a nominal length and a nominal width, and adjacent elements having a nominal space therebetween, wherein the nominal width of each element and the space between adjacent elements corresponding to said minimum feature size, using said plurality of hardware and software changes;
• measuring length of said elements in the array resulting from said plurality of hardware and software changes;
• calculating change in length of said created elements from nominal length;
• means for calculating bias of the minimum feature (width, space) corresponding to said plurality of hardware and software changes;
• and,
• selecting the hardware and software changes corresponding to said calculated bias of said minimum feature that is less than said preselected bias.

A method of measuring an etch process bias in forming a minimum feature, said etch process using a resist image from a lithographic process, said etch process bias determined by the difference between a combined bias of said minimum feature measured subsequent to said etch process, and a lithographic process bias measured prior to said etch process, comprising the steps of:

• creating an array of elements on a substrate each element having a nominal length and a nominal width and adjacent elements having a nominal space therebetween, wherein the nominal width of each element and the nominal space between adjacent elements correspond to said minimum feature, using said lithographic process;
• measuring length of said created elements in the array resulting from said lithographic process;
• calculating change in length of said created elements from the nominal length;
• means for calculating said lithographic process bias of the minimum feature (width, space) from said change in length of said elements in the array;
• subjecting said substrate to an etch process;
• remeasuring length of said etched elements in the array;
• calculating the change in length of said etched elements from the nominal length;
• means for calculating said combined process bias from said change in length of said elements in the array;
• and,
• determining said etch process bias from said combined process bias and said lithographic process bias.

A method of measuring an etch process bias in forming a minimum feature, said etch process using a resist image from a lithographic process, said etch process bias determined by the difference between a combined bias of said minimum feature measured subsequent to said etch process, and a lithographic process bias measured prior to said etch process, comprising the steps of:

• creating at least a pair of array of elements on a substrate, using the lithographic process each element having a nominal length and nominal width, and adjacent elements having a nominal space therebetween wherein the nominal width and the nominal space correspond to said minimum feature, said arrays of elements having an average nominal length and average nominal separation;
• measuring average length of said created elements in the array and average separation between said pair of created arrays, corresponding to said lithographic process;
• calculating change in the average length of said elements and average separation between said pair of arrays from said average nominal length and average nominal separation respectively;
• means for calculating said lithographic process bias of the minimum feature (width, space) from said change in average length and said change in average separation;
• subjecting said substrate to an etch process;
• remeasuring the average length of said etched elements in the array and average separation between said pair of created arrays;
• calculating change in the average length of said elements in the array and average separation between said pair of arrays;
• means for calculating the combined process bias from said change in average length of said elements in the array and change in average separation between said pair of arrays;
• and,
• determining said etch process bias from said combined process bias and said lithographic process bias.

A method of processing a substrate in a production environment, by use of a preselected bias of a minimum feature, comprising the steps of:

• creating a test pattern on the substrate, said test pattern comprising at least two arrays, each array having a plurality of array elements, each element having a nominal width and a nominal space corresponding to the minimum feature, and each array having an average nominal length, and adjacent arrays having an average nominal separation therebetween;
• measuring average length of said created array elements;
• measuring average separation between said created adjacent arrays;
• calculating change in average length and average separation from said average nominal length and average nominal separation;
• means for calculating bias of said minimum feature (width, space) using said change in average length of said array elements and said change in separation between adjacent arrays;
• comparing said calculated bias to said preselected bias;
• and,
• accepting said substrate for further processing if said calculated bias is less than said preselected bias.

A method of simultaneously determining lithographic process bias for a plurality of preselected feature sizes, comprising the steps of:

• creating a test pattern with a plurality of arrays on a substrate, each of said arrays having a plurality of array elements having an unique nominal width and nominal spacing, corresponding to one of said preselected feature sizes, and a nominal length;
• measuring length of said created elements in each of said arrays;
• calculating change in length of array elements from the nominal length for each of said arrays;
• and,
• means for calculating bias for said preselected feature size (width,space) from the calculated change in length of elements from corresponding arrays .