Reservation  -     

Center of MicroNanoTechnology CMi

Resists for Lift Off

Table of content

  1. Vistec EBPG5000 overview
  2. What is an electron beam (ebeam) lithography system?
  3. Electrons, resists and substrates
  4. Process Flow for Ebeam Lithography
  5. Data conversion
  6. Running the ebeam

III.2.a. HSQ basics

This is a negative resist and the highest resolution ebeam resist available. Our machine has regularly demonstrated < 10nm resolution with this resist. Chemically, once exposed to the ebeam, it is similar to SiO2 which makes it a very interesting etch mask for Si etching. It also has very low line edge roughness (LER) which is one of the most important problems to resolve in future < 20nm CD devices. Ultimate resolution is unknown. Isolated features < 8nm are achievable. 22nm period gratings have been demonstrated (11nm lines 11nm spaces).

HSQ is the chemical abbreviation which actually stands for hydrogen silsesquioxane. Commercially this is made by Dow Corning and is called XR-1541-002, XR-1541-006 and FOX16.

HSQ can be very difficult to use. It needs to be stored in a refridgerator at 4 degrees C. It is very sensitive to the surface condition of your sample and so correct surface preparation can make the difference between your features sticking to the surface well, or just washing away in developer. We have found that performing an oxygen plasma clean or rinsing samples in TMAH developer solution (eg CD26) can both be useful in helping to prepare a good surface.

III.2.b. HSQ data

Polarity

Negative

Doses

Dose can be quite high. Large and dense features typically have doses around 700µC/cm2 for very high resolution features 7000µC/cm2 or higher.

Resolution

few nanometers.

Chemical capabilities

For Si HSQ has very good dry etch selectivity. This resist can be striped with SiO2 wet etchant in a BHF bath (contaminated BHF bath on the plade oxide in zone 2).