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Submicron Interdigital Electrode Fabrication

IP.com Disclosure Number: IPCOM000034807D
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 4 page(s) / 92K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+2]

Abstract

A technique is described whereby optical lithography is used to fabricate submicron gratings and interdigital electrodes. Two methods are described: ion beam etching and wet chemical etching. Both utilize single level optical lithography evaporation. Certain device applications, such as optoelectronic switches, require interdigital electrode arrays. Typically, fabrication of equal fingers and spaces with small dimensions (submicron) require the use of (Image Omitted) electron beam, holography, or X-ray lithography. Optical lithography sets a limit on the order of one micron line width using normal exposure techniques. Utilizing III-V compounds [1] for optoelectronic switches for near infrared (IR) and far IR [2] requires small gaps and interdigital electrode structures.

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Submicron Interdigital Electrode Fabrication

A technique is described whereby optical lithography is used to fabricate submicron gratings and interdigital electrodes. Two methods are described: ion beam etching and wet chemical etching. Both utilize single level optical lithography evaporation. Certain device applications, such as optoelectronic switches, require interdigital electrode arrays. Typically, fabrication of equal fingers and spaces with small dimensions (submicron) require the use of

(Image Omitted)

electron beam, holography, or

X-ray lithography. Optical lithography sets a limit on the order of one micron line width using normal exposure techniques. Utilizing III-V compounds [1] for optoelectronic switches for near infrared (IR) and far IR [2] requires small gaps and interdigital electrode structures. This requirement of small gaps, or finger spacing, leads to a lower on-state resistance. This is because the value of the on-state resistance is proportional to the length (L) squared, along with other material properties. L is defined as the finger and space length. The concept described herein fabricates the sub-micron interdigital electrode arrays using simple optical lithographic techniques. The two techniques described use optical lithography, evaporation ion beam etching and chemical etching. The initial photoresist pattern, for example, an interdigital finger pattern, is transferred to the substrate with a Period (P), which is then reduced by a factor of two. The two techniques are as follows:

(Image Omitted)

1) A comb-shaped photoresist pattern is produced on the wafer,

as shown in Fig. 1. A metal layer is then deposited on the

sidewalls of the photoresist layer by means of evaporation,

as shown in Fig. 2. The thin metal layer produced on the

top of the resist pattern and the surface of the substrate is

removed by either wet or dry etching, as shown in Fig. 3,

and the resist layer is removed. The electrode material is

then deposited, as shown in Fig. 4, and the fine line

structure previously produced is removed by wet etching. The

final product, as shown in Figs. 5 and 6, results in a period

that is one half of the original structure.

2) The...