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Direct Write Electron Beam Lithography System

 

Overview

 

Funded by a Hong Kong University Grants Committee (UGC) Special Equipment Grant, a new Elionix ELS7800 80kV direct write electron beam lithography (EBL) system has been installed at the Chinese University of Hong Kong (CUHK). The EBL system is located in the CUHK Faculty of Engineering’s clean-room annex (built in 2005), which also has a available ICP dry etching and other semiconductor processing equipment to complement the new electron beam lithography capability. The new EBL system is now available for R&D users in Hong Kong at highly-affordable initial introductory rates.

http://cleanroom.erg.cuhk.edu.hk/Image/EBL_s.JPG

 

 

 

 

 

 

 

Fig 1 Elionix ELS 7800 EBL system installed in the class-100 area of the cleanroom at CUHK.

EBL System Highlights

  • Direct write of wafers up to 6” in diameter;
  • Ultrafine isolated lines down to 8nm in width;
  • write-fields sizes of 75, 150, 300, 600, 1200μm (80kV beam voltages).
  • Stitching error under 30nm
  • Pattern overlay with 35nm accuracy;
  • Gratings with periods down to 40nm;
  • Direct write lithography of chirped gratings, photonic crystals and other nano-structures;
  • compatible with GDSII and DXF CAD files;
  • Availability of proximity effect correction software to correct for electron forward and back scattering to define complex patterns.

 

 

Fig 2 - 80kV electron beam column scans the focussed 2nm diameter electron beam within a small write-field area on a wafer. The wafer is mounted on a laser controlled X-Y -Z motion stage that can position the beam to any location within the 6” wafer.

 

Fig 3 - Scanning electron microscope (SEM) photographs of 8nm wide lines (left) and 50nm grating period (right) patterned on 200nm thick PMMA resist.

 

 

Conditions of use and cost-recovery charges

 

The system is offered for use on a ”best-efforts” basis and there is no guarantee on the results attainable. Users are required to contribute towards the direct costs of operating the EBL system. The following introductory* cost-recovery charging scheme is implemented with effect from 1 September 2009:

 

*we reserve the right to revise the charges after initial 6 months

 

EBL System Charges

 

Type of User

Hourly Charge (HKD)

UGC funded institutions

400

Non-UGC funded organizations

500

 

The following additional charges may also be applicable for use of the EBL system:

 

Item

Hourly Charge (HKD)

Operator labor 1

380

CUHK clean room access 2

450 for 4 hour session

 

1. Operator charges are only applicable if the end user requests help because he is not qualified to operate the EBL system. This charge is not applicable if technical support is not needed to operate the EBL machine (eg. Wafer preparation, data preparation, sample loading, and EBL machine adjustments etc). Frequent users are encouraged to undergo training to operate the equipment themselves.

 

2. Clean room access charges is set by the clean room management committee and is applicable to users from outside CUHK Faculty of Engineering: it covers the costs associated with using the clean room facility (e.g. use of clean room garments, use of wet benches for resist processing, chemical waste disposal, optical microscopes for inspection, disposable face masks and gloves etc).

 

As a condition of use of this equipment, any publications which describe work involving use of the EBL system should carry the following acknowledgment: ”The work described in this paper was substantially/partially supported by Special Equipment Grant SEG_CUHK01 from the University Grants Committee of Hong Kong S.A.R, China.”

 

Further information and contact

 

Please contact Mr M.T. Yeung (mtyeung@ee.cuhk.edu.hk) to arrange use of the equipment or for further information on access to the clean room facility at the Chinese University of Hong Kong. For information on possible nanotechnology research collaboration please contact Prof. H.K. Tsang (hktsang@ee.cuhk.edu.hk).

 

 

 

 

 

(a)

 

(b)

 

(c)

 

 

Fig 4 - SEM photograph of structures written on 200nm thick PMMA by ELS7800 system: (a) 100nm wide array of perpendicular lines written without proximity effect correction (PEC) (b) Array of 200nm octagonal holes (c) optical arrayed waveguide grating structure written without PEC.