Browse Prior Art Database

Alignment Technique for Ion Beam Writing

IP.com Disclosure Number: IPCOM000050400D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

McKenna, CM: AUTHOR [+3]

Abstract

A marker is formed by implanting neon or argon. When an ion beam hits the implanted marker, X-rays are liberated which have different energy than X-rays liberated from other elements, such as silicon, aluminum, etc. The marker X-rays are selectively detected by filtering liberated X-rays through a multilayer structure which absorbs the other X-rays.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Alignment Technique for Ion Beam Writing

A marker is formed by implanting neon or argon. When an ion beam hits the implanted marker, X-rays are liberated which have different energy than X-rays liberated from other elements, such as silicon, aluminum, etc. The marker X-rays are selectively detected by filtering liberated X-rays through a multilayer structure which absorbs the other X-rays.

It has been proposed that sub-micron integrated circuits can be formed by using an ion beam with dimensions of less than a micron to implant dopants without a mask and to write patterns in photoresist. If ion beam writing is used, it is necessary to align the beam with previously formed circuit structures. Although conventional techniques (such as using a Scanning Electron Microscope (SEM)) are possible, a problem arises in maintaining the alignment of the micro-ion beam with the aligning SEM beam, and tool operation becomes more complex and unreliable. It would be more practical to use the ion beam itself for alignment.

We propose to ion implant neon (or possibly argon) at the center of the fiduciary mark which is used for alignment in other (not ion beam) fabrication steps, such as metallurgy etching.

To align the ion beam, the ion beam would be raster-scanned over the area of the fiduciary mark. When it hits the neon (or argon) marker, neon (or argon) X-rays will be generated. A detector is placed nearby to sense these X-rays. For the neon case, the entrance window would ideally be a triple-layered filter structure: (1) 20 Mum beryllium (absorbs X-rays below 800 KeV)

(2) 4 Mum magnesium (absorbs A1 X-rays)

(3) 15 Mum aluminum (absorbs X-rays above 1500 eV,

particularly Si).

The purpose of all these filters is to create a detector which will only be sensitive to neon X-rays, and which will be protected from X-rays from aluminum, silicon, and heavier elements. We have demonstrated that the above filter will attenuate s...