Browse Prior Art Database

ION IMPLANT TILT - TWIST CALCULATOR AND VISUALIZATION TOOL

IP.com Disclosure Number: IPCOM000009875D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-25
Document File: 4 page(s) / 212K

Publishing Venue

Motorola

Related People

David C. Sing: AUTHOR

Abstract

The specification of the alignment of the silicon crystal structure with respect to the ion beam direction is an important ion implant parameter. The ion beam orientation is commonly specified by the'tilt' and 'twist' angles. The tilt angle specifies the angle between the ion beam direction and the normal vector to the wafer surface. The twist angle specifies the angle between the wafer notch or flat and the vector formed by the projection of the ion beam direction vector on to the wafer.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 30% of the total text.

MOTOROLA

Technical Developments

ION IMPLANT TILT - TWIST CALCULATOR AND VISUALIZATION TOOL

by David C. Sing

PROBLEM DEFINITION

The specification of the alignment of the silicon crystal structure with respect to the ion beam direction is an important ion implant parameter. The ion beam orientation is commonly specified by the'tilt' and 'twist' angles. The tilt angle specifies the angle between the ion beam direction and the normal vector to the wafer surface. The twist angle specifies the angle between the wafer notch or flat and the vector formed by the projection of the ion beam direction vector on to the wafer.

Failure to correctly specify the tilt and twist correctly can lead to incorrect depth of implant due to the presence or absence of ion channeling, and also incorrect shadowing of the ion beam by vertical structures such as photoresist, gates and trenches.

Changes in transistor electrical parameters and yield loss can result from these errors.

Complicating the situation is that the major ion implant tool manufacturers do not have a common convention for specifying the tilt and twist angles.

Therefore. an implant process developed on a particular tool platform may not transfer to another tool platform correctly unless the tilt and twist angles specified by the original tool platform have been correctly translated to the new tool platform.

The Eaton Corporation GSDTM series of ion implanters utilize a two axis wafer orientation which differs considerably from conventional tilt-twist ori~ entation systems. This publication describes a mechanical device which automatically calculates the matching parameters between the GSD series and conventional ion implant tools. Also, the device provides a three dimensional representation of the ion beam incident upon the wafer surface which aids in the understanding of the two axis wafer orientation system.

Motorola, Inc. 2000

SPECIFICATION OF BEAM ORIENTATION BY TILT AND TWIST ANGLES

Ion implant tools which utilize the conventional tilt-twist orientation system use a mechanism to determine the wafer notch (or flat) position, then rotate the wafer notch by a twist angle which is specified by the ion implant recipe. The wafer is then loaded to a platen in the case of serial implant tools or a wheel or disk in the case of batch implant tools. The tilt is then accomplished by tilting the platen, wheel, or disk along a single axis before the ion beam is scanned across the wafer surface.

However, there are no standards for specifying the tilt and twist angles. Depending on the manufacturer, the recipe twist angle can result in either clockwise or counterclockwise rotation of the wafer.

The tilt angle is similarly complicated by differences in which side of the wafer is tilted into the beam when a non-zero tilt angle is specified.

For example, the Varian E220/B500TM serial implanter loads the a wafer with zero twist angle with the notch facing the down. Non zero twist is specified by a counter clockwise rot...