Electron beam metrology of 193-nm resists at ultralow voltage

Abstract

Resist slimming under electron beam exposure introduces significant measurement uncertainty in the metrology of 193 nm resists. Total critical dimension (CD) uncertainty of up to 10 nm can arise from line slimming through a combination of the line slimming during the initial measurement pass and the variation of line slimming across the wafer. For a 100 nm process, the entire CD error budget, can be consumed by line slimming. This research examines the uncertainty that results from the use of offset techniques to account for resist slimming in the process control of 193 nm resist CDs. The uncertainty associated with such offset techniques can be as great as 10 nm, depending upon the 193 nm resist and landing energy evaluated. Data are presented to demonstrate that 193 nm resist CD features experience line slimming greater than 5 nm at 500 eV landing energy during the initial measurement pass. Further, subsequent measurements demonstrate greatly reduced slimming and as a result are not indicative of the true magnitude of line slimming. Experiments conducted using CD-AFM pre-and post-analysis, demonstrate that ultra low landing energies significantly decrease the line slimming, reducing it to 1 nm or less.

CD-SEM-based critical shape metrology of integrated circuits

“…Etched polysilicon CSM CD and sidewall angle results are a significant improvement over maximum slope algorithm, closing CD offset gap and adding shape information to the reported data. The AFM precision on the photoresist was not as good as on the etched polysilicon; a result that is consistent with earlier data 14 . Several factors could possibly contribute to it: surface contamination of the resist, molecular transfer of microscopic resist particles to the AFM tip causing AFM tip growth, catastrophic changes in tip shape caused by tip contamination, and excessive edge roughness of the resist sidewall.…”

“…Of particular concern was the difference in CD between dynamic runs of the same wafer, which can be in part attributed to deficiencies of dynamic tip characterization. Possible 193nm resist charging and shrinkage could affect CD-SEM images and thus CSM measurement algorithm precision and accuracy on ArF resist 14 . To avoid significant resist shrinkage, low number of frames and ultra-low voltage (200V) were employed for top-down CD-SEM measurements of 193nm resist.…”

Scanning electron microscope dimensional metrology using a model‐based library

“…The magnitude of the difference is consistent with previously observed shrinkage rates. 15,16 The methods had a random difference with standard deviation of 5 nm, 3 nm of which is expected from the observed linewidth roughness.…”

Ultraviolet Nanoimprint Lithography in the Mixture of Condensable Gases with Different Vapor Pressures

“…The reason for experimental control of linewidth is as follows. The line width can be adjusted by the exposure dose and developing time of the photoresist in conventional photolithography using an ArF scanner [32,33], which helps the device manufacturer to enhance flexibility in the lithography process. However, in UV-NIL features, it is difficult to adjust the linewidth in the process because the patterns are faithfully transferred by the mold structures.…”