Author Affiliations
1Optoelectronic Technology R&D Department, Beijing Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China2Beijing RSLaser Opto-Electronics Technology Co., Ltd, Beijing 100176, Chinashow less
Fig. 1. Schematic diagram of potential energy for ArF excimer laser
[1] Fig. 2. Position of lithography system in integrated circuit technology and schematic diagram of lithography system. (a) Position; (b) schematic diagram
Fig. 3. Trend of exposure wavelength reduction and theoretical resolution limit for laser source of lithography system
[1] Fig. 4. Diagram of E95 and FWHM
Fig. 5. Schematic of single-chamber excimer laser system
Fig. 6. Cross section of discharge chamber
[10] Fig. 7. Schematic of dual-chamber excimer laser system
Fig. 8. Light path of MOPA dual-chamber
Fig. 9. Ring light path of MOPRA dual-chamber
Fig. 10. Light path of injection lock structure
Fig. 11. Schematic of clearance in discharge region
[1] Fig. 12. Basic schematic of gas lifetime controller system
[40] Fig. 13. Diagram of light propagation
Fig. 14. Intensity distributions of Gaussian mode and excimer mode and their curves of knife edge. (a) Beam of Gaussian fundamental mode
[48]; (b) beam of excimer laser
[48]; (c) relationship between knife edge ratio
∈ and
Dc/
σx for several Gaussian modes
[49] Fig. 15. Recent excimer laser source is improved in many aspects, including production ratio, durability and optical performance
Fig. 16. Concept schematic of Gigaphoton hTGM Neon recycling system
[54] Fig. 17. Concept schematic of Cymer XLGR Neon recycling system
［56］ Fig. 18. Relationship between change of E95 and change of critical dimension is basically linear correlation
Fig. 19. Excimer laser inspection system ExciStar S-Industrial designed by Coherent Inc
[64] Fig. 20. Cross section of fiber structure used in laser inspection system
[65] | Halogen | Excimer laser gasmixture |
|---|
| Excimer | | ArF | KrCl | KrF | XeBr | XeCL | XeF（B-X） | | Wavelength /nm | 157 | 193 | 222 | 248 | 262 | 308 | 351 |
|
Table 1. Wavelengths of different excimer lasers
| Year | Research institution | Landmark of progression |
|---|
| 1970 | Lebedev Physical Institute in Moscow | The first excimer lasing was invented | | 1974 | University of Cambridge，Cambridge，UK；Kansas State University，Kansas，USA；Avco Everett Research Laboratory，Everett，Massachusetts，USA | The fluorescence spectra of rare-gas halides were investigated | | 1975 | Naval Research Laboratory，Washington，USA；Northrop Research and Technology Center，Hawthorne，USA；Avco Everett Research Laboratory，Everett，Massachusetts，USA；Sandia Laboratories，Albuquerque，USA | The first laser of exciplexes was demonstrated | | 1979 | Lambda Physik | The first commercial excimer laser system was developed | | 1980 | IBM | Jain proposed the concept of excimer laser on lithography | | 1980 | IBM | The lithographic exposure experiment by excimer lasers in contact mode was carried out | | 1982 | IBM | With the modified Micralign system，the projection lithography by excimer laser was experimentally demonstrated |
|
Table 2. Development history of excimer lasers
| Company | Model | Exposure type | Resolution /nm | Laser source | NA | Output rate（Wafer /h） |
|---|
| ASML | NXT1980Di | Double immersion step-and-scan exposure | 38 | 193 nm ArF | 1.35 | 275 | | NXT1950i | 175 | | XT1450H | Double dry step-and-scan exposure | 65 | 0.93 | 162 | | XT1000K | 80 | 248 nm KrF | 180 | | XT860K | 110 | 0.80 | 210 | | XT400K | 350 | 365 nm high pressure mercury lamp | 0.65 | 220 | | PAS5500/1150C | Single step-and-scan exposure | 90 | 193 nm ArF | 0.75 | 135 | | PAS5500/850D | NA | 110 | 248 nm KrF | 0.80 | 145 | | PAS5500/450F | NA | 220 | 365 nm high pressure mercury lamp | 0.65 | 150 | | Nikon | NSR-S631E | immersion step-and-scan exposure | 38 | 193 nm ArF | 1.35 | 270 | | NSR-S621D | 200 | | NSR-S322F | step-and-scan exposure | 65 | 248 nm KrF | 0.92 | 230 | | NSR-S210D | 110 | 0.86 | 176 | | Canon | FPA-6300ES6a | step-and-scan exposure | 90 | 248 nm KrF | 0.86 | 200 |
|
Table 3. Some models of lithography systems for ASML, Nikon and Canon, and laser sources of these systems
| Critical dimension |
|---|
| Lithography | Lens aberrations | Focus | Dose control | Optical proximity effect | Illumination | | Lasers | Linewidth | Wavelength stability | Energy stability | Bandwidth stability | Beam stability | | Spectral shape | | Beam stability | Beam stability | Degree of polarization |
|
Table 4. Influence of laser source parameters on critical dimension of lithography system
| Process node /nm | Type | Linewidth（FWHM）/pm | Center wavelength stability /pm |
|---|
| 180‒110 | KrF single-chamber | ≤0.35‒0.60 | ≤0.050 | | 90‒65 | ArF dual-chamber，dry | ≤0.25 | ≤0.030 | | 45‒28 | ArF dual-chamber，immersion | ≤0.25 | ≤0.030 | | 14 | ArF dual-chamber，immersion，multiple exposure | ≤0.25 | ≤0.018 | | 7 | ArF dual-chamber，immersion，multiple exposure | ≤0.25 | ≤0.012 |
|
Table 5. Relationship of process node with linewidth and center wavelength stability
| Year | Cymer | Gigaphoton |
|---|
| 2015 | With GLX system and Neon reduction system，75% of Neon usage is saved for XLR700ix | Helium is replaced by Nitrogen for GT64A，and it saves 80 kL Nitrogen per year；For GT63A，with help of eTGM Neon reduction system，usage of Neon is reduced from 200 kL per year to 100 kL per year | | 2016 | | 2017 | | 2018 | On basis of Neon reduction system，90% Neon is saved by XLGR Neon recycling system for XLR800ix | On basis of eTGM，92% Neon is recycled by hTGM Neon recycling system for GT65A | | 2019 |
|
Table 6. Comparison of gas reduction and recycling between Cymer and Gigaphoton in recent years
| Year | Cymer | Gigaphoton |
|---|
| 2015 | Maximum lifetime of XLR700ix is 90 billion pulses | Maximum chamber lifetime of GT64A is 40 billion pulses | | 2016 | | 2017 | | 2018 | Maximum chamber lifetime of XLR800ix is 120 billion pulses | Maximum chamber lifetime of GT64A is 60 billion pulses | | 2019 | | 2020 | Expected maximum chamber lifetime of XLR900ix is 180 billion pulses | Maximum chamber lifetime of GT66A-1 is 100 billion pulses | | Future | NA | Maximum chamber lifetime of GT66A-1 is 120 billion pulses and maximum line narrowing module lifetime is 180 billion pulses |
|
Table 7. Comparison of laser lifetime between Cymer and Gigaphoton in recent years
![Schematic diagram of potential energy for ArF excimer laser[1]](/richHtml/lop/2022/59/9/0922020/img_01.jpg)
![Trend of exposure wavelength reduction and theoretical resolution limit for laser source of lithography system[1]](/Images/icon/loading.gif){kind=icon}
