1 / 21

Plasma Etching

Plasma Etching. Josh Gentle Matthew Grund ELEC 6570. Overview. What is etching? Two types of etching Application of Plasma in etching Process Mechanisms Reactive Ion Etching (RIE) System Problems. Questions.

piera
Download Presentation

Plasma Etching

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Plasma Etching Josh Gentle Matthew Grund ELEC 6570

  2. Overview • What is etching? • Two types of etching • Application of Plasma in etching • Process • Mechanisms • Reactive Ion Etching (RIE) System • Problems

  3. Questions • What are the three types of grass like cones and ways to stop the forming of cones? • What are two benefits of the laser inferometer has compared to the optical emission spectrometer?

  4. Introduction • What is etching? • the removal of material from the surface by physical and or chemical process • Two classes of etching processes • Wet etching is where the material is dissolved when immersed in a chemical solution • Dry etching is where the material is sputtered or dissolved using reactive ions or a vapor phase etchant

  5. Types of Etching • Anisotropic Etching • means different etch rates in different directions in the material. • Isotropic (wet) Etching • means uniform etch rates in all directions in the material. Figure 1: Difference between anisotropic and isotropic wet etching. http://www.memsnet.org/mems/beginner/etch.html

  6. Comparison • Review of wet etching characteristics • Wet etching is limited to pattern sizes of 3 microns or less. • Wet etching is isotropic (equally in all directions), can result in sloped walls. • Wet etching requires rinse and dry steps. • Wet etching has an intrinsic contamination potential. • Wet etching can undercut if the resist-wafer bond fails. • Review of dry etching characteristics • Dry etching has lower cost of chemicals • Dry etching has lower impact on the environment • Dry etching has higher cost of equipment • Dry etching has variable selectivity http://planet.tvi.cc/fabian/newpage7.htm

  7. Application of Plasma in Etching • Four step process • Formation of active gas species • Transport of the active species to the surface • Reaction at the surface • Pump out the reaction products http://www.gs68.de/tutorials/plasma/node12.html

  8. Mechanisms of Plasma Etching Sputter Etching • Ions created by the plasma and propelled by the sheath potentials to knock loose particles • Pressure has to be low http://web.ask.com/redir?bpg=http%3a%2f%2fweb.ask.com%2fweb%3fq%3dplasma%2betching%26o%3d0%26page%3d1&q=plasma+etching&u=http%3a%2f%2ftm.wc.ask.com%2fr%3ft%3dan%26s%3da%26uid%3d244ddcdb544ddcdb5%26sid%3d344ddcdb544ddcdb5%26qid%3d12D092709F75EE45A75DE585C39D7B48%26io%3d0%26sv%3dza5cb0ddf%26o%3d0%26ask%3dplasma%2betching%26uip%3d44ddcdb5%26en%3dte%26eo%3d-100%26pt%3dPlasma%2bEatching%2b-%

  9. Mechanisms of Plasma Etching Chemical Etching • Plasma generates neutral species • Neutral species spontaneously react with substrate material http://web.ask.com/redir?bpg=http%3a%2f%2fweb.ask.com%2fweb%3fq%3dplasma%2betching%26o%3d0%26page%3d1&q=plasma+etching&u=http%3a%2f%2ftm.wc.ask.com%2fr%3ft%3dan%26s%3da%26uid%3d244ddcdb544ddcdb5%26sid%3d344ddcdb544ddcdb5%26qid%3d12D092709F75EE45A75DE585C39D7B48%26io%3d0%26sv%3dza5cb0ddf%26o%3d0%26ask%3dplasma%2betching%26uip%3d44ddcdb5%26en%3dte%26eo%3d-100%26pt%3dPlasma%2bEatching%2b-%

  10. Mechanisms of Plasma Etching Accelerated Ion-assisted Etching • Ion are created by the plasma and accelerated by the sheath potentials which “damage” the surface • Neutral etchant are now able to react more easily with surface http://web.ask.com/redir?bpg=http%3a%2f%2fweb.ask.com%2fweb%3fq%3dplasma%2betching%26o%3d0%26page%3d1&q=plasma+etching&u=http%3a%2f%2ftm.wc.ask.com%2fr%3ft%3dan%26s%3da%26uid%3d244ddcdb544ddcdb5%26sid%3d344ddcdb544ddcdb5%26qid%3d12D092709F75EE45A75DE585C39D7B48%26io%3d0%26sv%3dza5cb0ddf%26o%3d0%26ask%3dplasma%2betching%26uip%3d44ddcdb5%26en%3dte%26eo%3d-100%26pt%3dPlasma%2bEatching%2b-%

  11. Application of Plasma in Etching • Reactive Ion Etching (RIE) Typical parallel-plate reactive ion etching system http://www.memsnet.org/mems/beginner/etch.html

  12. Aluminium and Tungsten Metal Etching • Most popular materials used for interconnnection • Chlorine is used for etching and bromine is being investigated • Tungsten has excellent deposition conformability http://web.ask.com/redir?bpg=http%3a%2f%2fweb.ask.com%2fweb%3fq%3dplasma%2betching%26o%3d0%26page%3d1&q=plasma+etching&u=http%3a%2f%2ftm.wc.ask.com%2fr%3ft%3dan%26s%3da%26uid%3d244ddcdb544ddcdb5%26sid%3d344ddcdb544ddcdb5%26qid%3d12D092709F75EE45A75DE585C39D7B48%26io%3d0%26sv%3dza5cb0ddf%26o%3d0%26ask%3dplasma%2betching%26uip%3d44ddcdb5%26en%3dte%26eo%3d-100%26pt%3dPlasma%2bEatching%2b-%

  13. Polymer Etching • Cheaper Fabrication • Lower Processing Temperatures • Good vertical profile mask selectivity is important • Hydrogen generally used for etching • UHF-ECR etchers http://www.oxinst.com/pdf/PolymerEtchArticle.pdf Katasuya Watanabe, Kenetsu Yokogawa, Yutaka Omoto, Hiroyuki Makino, “UHF-ECR Plasma Etching System for Dielectric Films of Next-generation Semiconductor Devices,” Hitachi Review 166-170, Vol.52 (2003).

  14. Ashing • Requirements • Ash rate 1-2um/min • Remove resist without contamination • High Temperature Oxygen Process • Uses pure • C • Infinite Selectivity to Silicon • Low Temperature Process with Fluorine • Carried out at room temperature • Inorganic materials can be removed • Low k material ashing http://www.gs68.de/tutorials/plasma/node19.html

  15. Selectivity • Is the ability to etch one material and refrain from etching another • Crucial for avoiding line width loss • depends on both chemistry and charged particle bombardment • most demanding in etching gates for MOSFETs Commission on Physical Sciences, Mathematics, and Applications, ”Plasma Processing of Materials: Scientific Opportunities and Technological Challenges,” 13-36, (1991)

  16. End Point Detection • Laser interferometer • In-situ etch rate monitoring • Endpoint does not require etch stop layer • Endpoint can be chosen anywhere within the layer (onnce etch rate has been established) • Optical Emission • Monitoring of reactive species or etch by-products provides endpoint signal. • Endpoint relies on etch stop layer. • Scanned monochromator allows full spectrum analysis. http://www.oxfordplasma.de/technols/rie.htm

  17. Uniformity • Uniformity is the preservation of both the profile and critical dimension (CD) of the etch across the entire wafer • Reaction by-products are a cause of Irregularities in the etch • To achieve uniformity • Uniform plasma and etching gas distribution in the etching chamber • uniform distribution of etching by-products on the wafer. • Little or no charge damage must occur Shinji Kawamura, Naoshi Itabashi, Akitaka Makino, Masamichi Sakaguchi., “UHF-ECR Plasma Etching System for Gate Electrode Processing,” Hitachi Review Vol. 51 (2002), No. 4

  18. Deposits (a) Trapezoidally shaped deposits (b) Horns (c) Bowed Walls (d) Rounded Bottoms http://users.ece.gatech.edu/~alan/Lecture11-Etching%20especially%20Plasma%20Etching.pdf

  19. Grass • Formation of Cones • Several Types • Aluminum • Sputtered • Polymer • Solutions • Gold Coating • Eliminating O2 • Reducing Gas Pressure Aluminum Grass Sputtered Grass Polymer Grass http://www.triontech.com/techPapers/RIEGrass.html

  20. Trenching • Etch attack at the edge of the gate • Usually observed at low gas pressure • Solved by increasing etch selectivity http://web.ask.com/redir?bpg=http%3a%2f%2fweb.ask.com%2fweb%3fq%3dplasma%2betching%26o%3d0%26page%3d1&q=plasma+etching&u=http%3a%2f%2ftm.wc.ask.com%2fr%3ft%3dan%26s%3da%26uid%3d244ddcdb544ddcdb5%26sid%3d344ddcdb544ddcdb5%26qid%3d12D092709F75EE45A75DE585C39D7B48%26io%3d0%26sv%3dza5cb0ddf%26o%3d0%26ask%3dplasma%2betching%26uip%3d44ddcdb5%26en%3dte%26eo%3d-100%26pt%3dPlasma%2bEatching%2b-%

  21. Answers to Questions • Three types of grass and solutions. • Aluminum- eliminating O2 • Sputtered- gold coating • Polymer- Reducing gas pressure • Two benefits Laser interferometer has compared to the Optical emission spectrometer. • Does not require etch stop layer • Endpoint can be chosen anywhere within the layer

More Related