Residual layer thickness measurement and correction
View Patent ↗In nano-imprint lithography it is important to detect thickness non-uniformity of a residual layer formed on a substrate. Such non-uniformity is compensated such that a uniform residual layer may be formed. Compensation is performed by calculating a corrected fluid drop pattern.
1. In an imprint lithography system, a method comprising:
depositing a plurality of drops of polymerizable imprint fluid on a substrate, the plurality of drops having a drop pattern in which each of the plurality of drops has an assigned size and position on the substrate;
performing a first imprint of the plurality of drops of polymerizable imprint fluid by varying the distance between a mold and the substrate to define a desired volume therebetween filled by the imprint fluid and then solidifying the imprint fluid resulting in a first patterned imprinted layer having a residual layer;
measuring a variation of thicknesses of sub-portions of the residual layer at a plurality of points;
calculating a new drop pattern that compensates for nonuniformities in the thickness of the residual layer by adjusting the assigned size and position of certain ones of the plurality of drops; and
performing a second imprint of a plurality of drops using the new drop pattern resulting in a second imprinted layer having a uniform residual layer thickness.
2. The method of claim 1 , further comprising measuring a thickness of a residual layer of the second imprinted layer.
3. The method of claim 2 , wherein the second imprinted layer has a residual layer with desired uniformity of the thickness.
4. The method of claim 1 , wherein the measuring the variation of thicknesses of subportions at a plurality of points of the residual layer further includes:
employing a film thickness measurement tool; and
employing a processor operated on a computer readable program to analyze and construct a map of the thickness of the sub-portions.
5. The method of claim 4 , wherein the film thickness measurement tool provides an image of the first imprinted layer.
6. The method of claim 5 , wherein the processor uses an algorithm to convert the image into an imprint area.
7. The method of claim 6 , wherein the processor converts differences in color and shade grades of the image into a Z-height profile of the first imprinted layer.
8. The method of claim 4 , wherein the map of the thickness of the sub-portions is obtained using a polynomial two-dimensional function with assigned specific thickness to each point.
9. The method of claim 8 , wherein average thickness of the points and deviation from the average is determined.
10. The method of claim 9 , wherein deviation is used to provide local unit fluid volume, number of drops, position of drops and drop volume.
11. The method of claim 1 , wherein adjusting the assigned size and position of certain ones of the plurality of drops includes adding droplets.
12. The method of claim 1 , wherein adjusting the assigned size and position of certain ones of the plurality of drops includes subtracting droplets.
13. In an imprint lithography system, a method comprising:
imprinting a first field on a substrate using a first drop pattern of polymerizable fluid, the first drop pattern having a plurality of drops with each drop assigned a size and a position on the substrate, the first field formed by solidifying the polymerizable fluid between a mold and the substrate, the formed first field having a first residual layer;
measuring thickness of the first residual layer across a dense array of points in the imprinted first field using a film thickness measurement tool;
altering the first drop pattern based on the thickness measurements of the first residual layer to provide a second drop pattern, the second drop pattern configured to provide a substantially uniform residual layer; and
imprinting a second field using the second drop pattern.
14. The method of claim 13 , wherein the second drop pattern compensates for evaporation of the plurality of drops.
15. The method of claim 13 , further comprising calibrating the imprint lithography system to determine how much fluid to dispense on the substrate to make the first field with a desired thickness.
16. The method of claim 13 , wherein the first drop pattern is a uniform distribution of the fluid on the substrate.
17. The method of claim 13 , wherein altering includes adding droplets.
18. The method of claim 13 , wherein altering includes subtracting droplets.
19. An imprint lithography method comprising:
depositing a plurality of drops of polymerizable imprint fluid on a substrate, the plurality of drops having a drop pattern in which each of the plurality of drops has an assigned size and position on the substrate;
varying the distance between an imprint lithography template having a patterning surface thereon and the substrate to define a desired volume therebetween filled by the imprint fluid;
solidifying the imprint fluid to form a first patterned layer conforming to the patterning surface, the patterned layer having a residual layer;
separating the imprint lithography template from the formed first patterned layer;
measuring the thickness of the residual layer at a plurality of points;
mapping the thickness of the residual layer as a two dimensional function, f(x,y) with an assigned thickness for each measured point;
calculating the average thickness, g(x,y), of the residual layer;
calculating the deviation from the average as w(x,y)=g(x,y)−f(x,y); and
altering the first drop pattern by calculating offsets in the x and y direction based on g(x,y) and adjusting local unit fluid volume, number of drps, position of drops and drop volume based on deviation w(x,y) to provide a second drop pattern that provides for a substantially uniform residual layer.
20. The method of claim 19 further comprising forming a second patterned layer on a substrate using the second drop pattern.