Introduction to FIRST-Lab DWL66+ Laserwriter (ver.1.1)

This document describes the introductory process for getting access to the DWL66+ direct laser writer system at ETHZ/FIRST-Lab, and should be read thoroughly by prospective users for preparation before participation in the introductory course.

Overview of DWL66+ System

The DWL66+ system is located in the "nanolitho" room of FIRST-Lab and consists of the main unit (in cleanroom environment) housing the stage, climatisation and lasers, the electronics rack in the adjacent service area, and an operator station with monitors, mouse and keyboard. It is manufactured by Heidelberg Instruments Mikrotechnik (HIMT).

The main unit is enclosed in a housing with a pneumatic door, providing additional stabilisation of temperature as well as shielding against particles and light.

FIRST-Lab has two write-heads available, the so-called "10 mm" and the "HiRes" head. The former allows for exposing features with sizes down to about 1 micron, the latter down to less than 0.5 micron. Sample sizes can be basically anything between 10 and 200 mm diameter and 0.2 to 5 mm thickness; however, not all features are available for all sizes.

Exposure wavelength is 375 nm from a solid state (diode) laser, allowing processing of common positive and negative photoresists. Automatic focus correction is possible with pneumatic or optical control.

Generation of Designs (Patterns for Writing)

Designs can be provided in Gerber, GDSII, CIF, bitmap, STL and DXF formats; preferred (and supported by FIRST staff) are GDSII and CIF. Users may use AutoCAD or similar software to generate DXF files, however this is not recommended.

FIRST-Lab suggests using of free tools like Klayout or XIC (on Windows computers) or KIC (on Linux or BSD based Unix systems) or the proprietary L-Edit from Tanner Tools (with a limited number of licenses available for use on ETH-internal computers — please contact FIRST staff for installation instructions if use is desired). These programs allow for direct generation of CIF or GDSII files with correct syntax.

Preliminary Requirements

People applying for an introduction to the DWL66+ system:

• must have experience with standard photolithography processes (resists, spinning, pre- and post-exposure baking, developing) at least for standard positive resists (AZ and S1500 series or similar) and have passed the lithography intro in FIRST-Lab; experience with e-beam lithography (resists, spinning, baking, developing) is sufficient, maskaligner work is not required;
• must understand the basics of pattern design as used for generation of photomasks (polarity and closed polygons, CD);
• must apply for an introduction with the DWL66+ responsible(s), who will then provide access to the fldwl66 file share;
• must plan for two separate exposure runs during the two weeks following the introduction, to get some initial experience (do not apply for an introduction if you do not have an immediate need and desire to use the system afterwards); and
• should provide a suitable design (features 1 micron or larger, designed by themselves or well understood) in one of the preferred formats (GDSII, CIF) and of reasonable size (up to some square mm, to keep exposure time acceptable) before introductory training starts.

If the last point is missing, the introduction will be given with test design data from FIRST-Lab.

Topics of Introduction

The intro will take about half a day, and cover explanation of the system (hardware and basics of control software) and a demonstration of data transfer, design conversion and exposure of a simple (one layer) design. If desired, alignment procedures for exposing onto samples with existing markers can be demonstrated as well.

The exposures will be done on chromium covered glass plates (mask blanks) or Silicon wafers covered with standard positive photoresist, depending on availability. Other substrates may be used in agreement with the equipment responsibles.

The procedures will be based on those described in the short manual for the system, which will be provided to users when introductions are scheduled. In general, only use of the "10 mm" write-head will be shown; the introduction may be done with the "HiRes" write-head, provided the user can supply suitable design data and will regularly require HiRes-work.

2019-2-7 // Y.Bonetti