Browse Prior Art Database

New Injector Design for CVD Process Chambers

IP.com Disclosure Number: IPCOM000008273D
Original Publication Date: 2002-May-31
Included in the Prior Art Database: 2002-May-31
Document File: 3 page(s) / 1M

Publishing Venue

Motorola

Related People

Larry E. Frisa: AUTHOR

Abstract

When fabricating semiconductor devices, within-wafer uniformity is an important parameter to control. This is especially true for 300mm wafers, since uniformity is harder to produce over an area 2.25 times larger than 200mm wafers. This improvement is targeted for high-density plasma (HDP) chemical vapor deposition (CVD) reactors that deposit thin oxide films.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

New Injector Design for CVD Process Chambers

Larry E. Frisa          

Introduction

When fabricating semiconductor devices, within-wafer uniformity is an important parameter to control.  This is especially true for 300mm wafers, since uniformity is harder to produce over an area 2.25 times larger than 200mm wafers.  This improvement is targeted for high-density plasma (HDP) chemical vapor deposition (CVD) reactors that deposit thin oxide films. 

The CVD chamber contains injector tubes for the CVD reactant gases positioned symmetrically around the chamber.  The thickness map shown in Figure 1 corresponds to a tool configuration with 24 short injectors and 6 long injectors, although other combinations are sometimes used.  The chamber is designed for reactant gases to mix in the upper part of the dome before they reach the wafer below.  The effects of inhomogeneous mixing in 300mm chambers can be seen on the deposited wafers.  Non-uniformity measured on processed wafers corresponds to the locations of the injection tubes above the wafer.  Figure 1 shows a typical thickness map of HDP oxide deposited in a typical CVD chamber.  An increase in film thickness was measured in the locations directly below the long injectors as indicated by the arrows.  This non-uniformity is caused from inhomogeneous mixing of reactive gases that are introduced from these injection tubes.  If modifications could be made to the injector tubes to allow the reactants to mix more completely before coming in contact with the wafer, a more uniform film would result.

 

Prior Art

To improve the film uniformity on the wafer, various designs have been used on CVD chambers to improve gas mixing.  One method places inserts with different sized orifices into each injector tube to regulate the flow of gases.  Typically, multi-step process recipes are used.  Additionally, changes in the angle, lengths, and number of   tubes can be made.

By increasing the number of injectors, the gases are more homogeneously mixed.  When the number of long injectors was increased, the uniformity improved (as seen in Figure 1).  However, since there is a practical and physical limit to the number of injector tubes that can fit in a chamber, this solution does not adequately solve the problem. 

Positioning longer injector tubes at higher angles allowed a longer time/path for the gases to mix and moved the thicker deposition that forms under the long injectors to a position off the edge of the wafer.

Figure 2 shows the standard designs of the injector tips.  The standard tip is a ceramic tube where the end is cut off at a right angle to the sh...