Stationary aperture plate for reactive sputter deposition

• US 5,415,753 A
• Filed: 07/22/1993
• Issued: 05/16/1995
• Est. Priority Date: 07/22/1993
• Status: Expired due to Term

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Materials Research Corporation (Linde Plc)
• Inventors: Wagner, Israel, Hurwitt, Steven D.
• Primary Examiner(s): NGUYEN, NAM X
• Application Number:
  US08/095,950
• Time in Patent Office: 663 Days
• Field of Search: 204/192.12, 204/298.11, 204/298.19, 204/298.07
• US Class Current: 204/192.12
• CPC Class Codes: C23C 14/0068 characterised by means for confinement of gases or sputtered material, e.g. screens, baffles
• CPC Class Codes: C23C 14/044 using masks to redistribute rather than totally prevent coating, e.g. producing thickness gradient
• CPC Class Codes: H01J 37/34 operating with cathodic sputtering H01J37/36 takes precedence ; methods of cathodic sputtering C23C14/34
• CPC Class Codes: H01J 37/3447 Collimators, shutters, apertures
• CPC Class Codes: H01J 37/347 Thickness uniformity of coated layers or desired profile of target erosion

Abstract

The aperture plate of the present invention is positioned between a sputter target and a substrate to be coated with a film of target material. The substantially non-collimating plate contains a plurality of apertures which intercept a percentage of the sputter particles while allowing other sputter particles to be deposited upon the substrate to form the film. The rate of deposition achieved by the aperture plate is less than the rate of sputtering so that the target may be sputtered at a sufficiently higher rate to reduce the formation of a reactant film on the sputter target while the deposition rate is sufficiently low to allow adequate reaction between a reactive gas and sputter particles to form the desired reactant film on the substrate. In accordance with another aspect of the invention, the apertures of the plate have different aspect ratios or different densities in various different regions of the plate to achieve various different deposition rates in different areas of the substrate. The aspect ratios of the apertures may be selectively varied to achieve a more uniform film thickness or a film of selectively varied thicknesses. The various aspect ratios are achieved by selectively varying a cross-sectional area and/or depth of the apertures in the plate.

Claims

1. A reactive sputter deposition apparatus for reactively depositing a uniform film and reducing the formation of a reactive film layer on the surface of the sputter target including an evacuatable chamber, the apparatus further comprising:

a mount for holding a sputter target within the evacuatable chamber;

an electrical system for electrically biasing the sputter target;

a gas introduction system for introducing an ionizable gas into the chamber proximate to the sputter target;

an ionizing system for ionizing the gas into a plasma containing ionized particles having an electrical charge opposite in polarity to the biased sputter target so that the ionized particles are attracted away from the plasma to bombard the target and sputter particles from the target at a first rate;

a substrate mount for holding a substrate generally opposite the sputter target so that sputtered particles deposit upon a surface of the substrate to form a film;

a reactive gas introduction system for introducing a reactive gas proximate to the substrate surface to chemically react with the sputter particles which deposit upon the substrate surface and thereby form a reaction product film on the substrate surface;

an aperture plate situated between the target and the substrate, the plate having a plurality of apertures with low aspect ratios in the range of 0.05 to 0.5 formed therein so as to be substantially non-collimating, the apertures having associated cross-sectional areas and depth dimensions and configured to intercept a percentage of the sputter particles and to allow other particles to pass through the plate and deposit on the substrate at a second rate which is lower than the first rate by an amount sufficient to allow the reactive deposition reaction to occur at the substrate but not lower by more than approximately 75%, the plate being spaced from said substrate to virtually eliminate any sharp delineation of the aperture pattern onto the substrate surface, the first and second rates being maintained by the plate such that the target is sputtered away at a rate sufficiently high to reduce the formation of a reactive layer on the target, but the deposited particles are deposited upon the substrate at a rate sufficiently low to achieve a desired reaction between the sputter particles and the reactive gas at the substrate surface; and

the plate having various regions, and the apertures in one region having aspect ratios different than aspect ratios of apertures in another region to vary the deposition rates between the regions relative to a non-uniform sputtering rate and produce a more uniformly deposited film on the substrate;

whereby a desired uniform film is formed on the substrate while the formation of an undesired reactant film on the target is reduced.

2. The sputter deposition apparatus of claim 1 wherein the plate has a center region and a peripheral region, the apertures in the center region being dimensioned to have greater aspect ratios than the apertures in the peripheral region so as to selectively decrease the deposition rate in a center area of the substrate relative a peripheral area of the substrate.

3. The sputter deposition apparatus of claim 1 wherein the apertures have approximately the same depth dimensions throughout the aperture plate and center region apertures have smaller cross-sectional areas than peripheral region apertures.

4. The sputter deposition apparatus of claim 1 wherein the apertures have approximately the same cross-sectional area throughout the aperture plate and the center region apertures have greater depth dimensions than the peripheral region apertures.

5. The sputter deposition apparatus of claim 1 wherein the plate is spaced from the substrate a distance of at least approximately 0.5 inches.

6. A method for reactively depositing a uniform film on a substrate and reducing the formation of an undesired reactive film of sputter coating material on the surface of an electrically biased sputter target inside a sputter deposition chamber while depositing the film, the method comprising the steps of:

a.) introducing an ionizable gas into a chamber containing an electrically biased target;

b.) ionizing the gas to create a plasma containing ionized particles having an electrical charge opposite in polarity to the biased target so that the ionized particles are attracted away from the plasma to bombard the target surface and sputter particles of the sputter coating material away from the target;

c.) positioning a substrate generally opposite the sputter target so that sputtered target particles deposit upon a surface of the substrate;

d.) introducing a reactive gas proximate to the substrate surface to chemically react with the sputter particles of sputter coating material which deposit upon the substrate surface and thereby form a reactive film on the substrate surface;

e.) sputtering the target at a first rate that is generally higher than a reaction rate of the reactive gas with the sputter coating material at the target surface to reduce the formation of a reactive film on the target surface;

f.) intercepting a percentage of the sputter particles sputtered at the first rate with an aperture plate situated between the target and substrate, the plate including a plurality of apertures with aspect ratios in the range of 0.05 to 0.5 such that the plate is generally non-collimating and affects the first rate such that the sputter particles are deposited on the surface of the substrate at a second rate which is lower than the first rate by an amount sufficient to allow the deposition reaction to occur at the substrate but which is not lower than the first rate by more than approximately 75%, the apertures of one region of the plate having aspect ratios different than aspect ratios of apertures in another region of the plate to vary the deposition rates between the regions relative to a non-uniform sputtering rate and produce a uniform deposited reactive film on the substrate, whereby the target is sputtered away at a first rate sufficiently high to reduce the formation of a film on the target while the deposited particles are deposited upon the substrate at a second rate sufficiently low to achieve the desired reaction between the sputter particles and the reactive gas at the substrate surface and the deposited particles are uniformly distributed for a uniform film.

7. The method of claim 6 wherein the plate has a center region and a peripheral region, the apertures in the center region being dimensioned to have greater aspect ratios than the apertures in the peripheral region so as to selectively decrease the deposition rate in a center area of the substrate relative a peripheral area of the substrate surface.

8. The method of claim 6 further comprising the step of:

(a) positioning the plate to be spaced from the substrate a sufficient distance to virtually eliminate any sharp delineation of the aperture pattern onto the substrate surface.

9. The method of claim 6 further comprising the step of:

(a) positioning the plate spaced from the substrate a distance of at least approximately 0.5 inches.

10. The method of claim 6 wherein the apertures in the one region of the plate have different cross-sectional areas than the apertures in the other region of the plate.

11. The method of claim 6 wherein the apertures in one region of the plate have different depth dimensions than the apertures in the other region of the plate.