Browse Prior Art Database

Improving Brightness and Current of Photoelectron Lithography

IP.com Disclosure Number: IPCOM000036745D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 64K

Publishing Venue

IBM

Related People

Chiu, G: AUTHOR [+4]

Abstract

A technique is described whereby a photoelectron lithography implementation improves throughput of electron-beam lithography. Described is a method of achieving high brightness as well as high current by adjusting the spot size of the laser beam.

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Improving Brightness and Current of Photoelectron Lithography

A technique is described whereby a photoelectron lithography implementation improves throughput of electron-beam lithography. Described is a method of achieving high brightness as well as high current by adjusting the spot size of the laser beam.

In prior art, considerable advantages were obtained using a photocathode instead of a thermionic or field emission cathode [1]. The concept described herein concentrates on improving the brightness and spot size as follows: First, the brightness of a photocathode is higher than that of the thermionic case (LaB6, W), and may approach that of the field emission case [2]. Although the high brightness was predicted qualitatively [1], a quantitative statement can be made only when a particular light source (beam energy and photon wavelength) and cathode (material and surface treatment) are specified. The brightness is important for the high spatial resolution (delineating fine features) required in lithography. Second, the laser beam spot size is adjustable, and, therefore, the emission spot size of the cathode is also adjustable. Since the current density of the photoelectrons Jph is proportional to the power density P of the incident laser beam, by keeping P constant, it is possible to generate a larger amount of photocurrent Iph with a larger spot of laser illumination: Iph = Jph x fr2 where r is the radius of the spot size.

Since large current is needed for exposing a large area, the throughput of the lithography tool can be significantly enhanced as a result of the adjustable amount of beam current available.

The figure is an illustration of common photocathodes. Shown are typical reponse curves of photocathode/glass envelope combinations. A few watts of CW lase...