Method for evaluating the bending stiffness of high aspect ratio nanosized structures

A method for evaluating a process uniformity of a first process that is applicable on a semiconductor substrate, the method comprising:

• producing a plurality of test patterns by a lithography and etch sequence in a respective plurality of different areas of the semiconductor substrate, wherein each test pattern comprises a regular array of high aspect ratio nanosized structures, wherein the regular arrays are produced using a same design pattern, wherein the test patterns are produced by applying a same etch recipe, and wherein the lithography and etch sequence exhibits a degree of non-uniformity so that one or more parameters which define the regular arrays exhibit a variation between different test patterns as produced in respective different areas of the semiconductor substrate;
• applying a second process for evaluating a bending stiffness of the high aspect ratio nanosized structures to the regular arrays to obtain a plurality of collapse rate measurements for the regular arrays, wherein the second process comprises:
• scanning the regular arrays in the plurality of test patterns by an electron beam produced according to a same set of beam conditions for each array;
• from the scanning of the regular arrays, deriving images of the regular arrays in the respective test patterns by electron beam microscopy;
• and
• determining from each of the images an e-beam induced collapse rate, wherein the e-beam induced collapse rate comprises a value between 0 and 1 representative of a percentage of structures in each array that have collapsed under an influence of the electron beam scanning, wherein the e-beam induced collapse rate is indicative of a bending stiffness of the structures, wherein one or more parameters define the array, wherein the one or more parameters exhibit a variation between different test patterns as produced in respective different areas of the semiconductor substrate, and wherein the beam conditions are configured so that the variation leads to a corresponding variation in the collapse rate;
• performing the first process on:
• the substrate, wherein the test patterns further comprise at least one duplicate of the array in the respective plurality of different areas;
• or
• on another substrate of a same size as the substrate and comprising duplicates of the array in the same plurality of different areas;
• determining the collapse rate induced by the first process on images of the respective duplicates of the array;
• and
• using the e-beam induced collapse rates in order to eliminate an effect of the non-uniformity of the lithography and etch sequence from the process-induced collapse rates.

A method comprising:

• determining a first bending stiffness of first high aspect ratio nanosized structures arranged in a first test pattern produced by lithography and etching in a first area of a semiconductor substrate, wherein the first test pattern comprises a first regular array of the first high aspect ratio nanosized structures:
• scanning the first regular array in the first test pattern by a first electron beam;
• from the scanning of the first regular array, deriving a first image of the first regular array in the first test pattern by electron beam microscopy;
• and
• determining from the first image a first e-beam induced collapse rate, wherein the first e-beam induced collapse rate comprises a first value between 0 and 1 representative of a percentage of structures in the first array that have collapsed under an influence of the first electron beam scanning, and wherein the first e-beam induced collapse rate is indicative of a bending stiffness of the first structures;
• determining a second bending stiffness of second high aspect ratio nanosized structures arranged in a second test pattern produced by lithography and etching in a second area of a semiconductor substrate, wherein the second test pattern comprises a second regular array of the second high aspect ratio nanosized structures:
• scanning the second regular array in the second test pattern by a second electron beam, wherein the second electron beam is produced according to a same set of beam conditions as the first electron beam;
• from the scanning of the second regular array, deriving a second image of the second regular array in the second test pattern by electron beam microscopy;
• and
• determining from the second image a second e-beam induced collapse rate, wherein the second e-beam induced collapse rate comprises a second value between 0 and 1 representative of a percentage of structures in the second array that have collapsed under an influence of the second electron beam scanning, and wherein the second e-beam induced collapse rate is indicative of a bending stiffness of the second structures;
• and
• comparing:
• the second bending stiffness to the first bending stiffness;
• or
• the second e-beam induced collapse rate to the first e-beam induced collapse rate.