Bibliographic record
Abstract
In 1979, Electronics magazine reported that stepper lithography would be a passing fancy superseded by direct-write electron beam lithography by the year 1985. It was admitted in a follow-up article, written for that same magazine in 1985, that the demise of optical lithography had been predicted prematurely and that it would take until 1994 for shipments of optical wafer steppers to be of lower volume than those of x-ray step-and-repeat systems. It was expected that optical lithography, once it reached its resolution limit of 0.5 μm, would need to be replaced. Both pronouncements were based upon accepted expert opinion. This book has been written in the year 2005, and optical lithography is still going strong, but there are a number of programs dedicated to developing alternative lithography techniques. It is worth reviewing earlier arguments as to why optical lithography was nearing its end of life, and what arguments are being presented today to justify billions of dollars of investment in new lithography techniques. 10.1 The diffraction limit The argument that optical lithography has limited resolution is based upon Rayleigh's scaling laws of resolution and depth-of-focus. From Chapter 2, resolution is given by Resolution=k 1 λ NA , where the prefactors of Eqs. (2.4) and (2.7) are replaced by a general factor k 1 . Similarly, the expression for depth-of-focus can be written as Depth-of-focus=±k 2 λ NA 2 . It has long been recognized that Rayleigh's and equivalent expressions are inexact predictors of resolution, but do correctly capture the trends associated with wavelengths and numerical apertures. Other factors, such as the resist process, are captured by the coefficients k 1 and k 2 . In 1979, the state-of-the-art lens had a resolution of 1.25 μm, a ± 0.75-μm depth-of-focus, a numerical aperture of 0.28, and imaged at the mercury g-line. This produced values of 0.80 and 0.13 for k 1 and k 2 , respectively. With these values for the coefficients in Eqs. (10.1) and (10.2), the numerical aperture of a g-line lens capable of producing 0.8-μm features would be 0.44, with a ± 0.3-μm depth-of-focus.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.004 | 0.008 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.002 | 0.008 |
| Scholarly communication | 0.006 | 0.009 |
| Open science | 0.002 | 0.004 |
| Research integrity | 0.003 | 0.007 |
| Insufficient payload (model declined to judge) | 0.010 | 0.005 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".