Adjustable shadow mask for improving uniformity of film deposition using multiple monitoring points along radius of substrate

• US 20020139666A1
• Filed: 03/29/2001
• Published: 10/03/2002
• Est. Priority Date: 03/29/2001
• Status: Active Grant

• Current Assignee: Super Talent Electronics, Inc.
• Original Assignee: Super Light Wave Corporation
• Inventors: Ma, Michael, Schiesser, Hans, Hsueh, Paul, Ma, Abraham C., Hsu, Jack, Chang, Shyang
• Granted Patent: US 6,547,939 B2
• Time in Patent Office: Days
• US Class Current: 204/298.03
• CPC Class Codes: C23C 14/044 using masks to redistribute rather than totally prevent coating, e.g. producing thickness gradient
• CPC Class Codes: C23C 14/46 by ion beam produced by an external ion source
• CPC Class Codes: C23C 14/547 using optical methods

Abstract

A vacuum chamber deposits thin films on a substrate by sputtering a target. The beam of atoms or ions from the target is partially blocked by a shadow or adjustable uniformity mask, reducing the deposition rate onto the substrate. The adjustable uniformity mask has several adjustable fingers. The fingers extend or retract to enlarge or reduce the size of the mask. Each finger covers a different annular region or radius of the substrate. The deposition rate at different substrate radii is thus adjustable by the fingers. Several optical beams monitor the film transmittance at different substrate radii. A transmittance profile is continually generated during deposition. As deposition proceeds, radii with a thicker film have their fingers extended to reduce their deposition rate, producing a more uniform film thickness across all radii. Motors extend or retract the individual fingers.

Claims

1. An adjustable uniformity-mask deposition system comprising:

a low-pressure chamber for depositing a film on a substrate;

a target containing material to be deposited as the film on the substrate;

a target beam for transporting material from the target to the substrate for deposition on the substrate in the film;

a shadow mask located to intercept a portion of the target beam, reducing a rate of deposition of the material onto the substrate;

a monitor measuring a transmittance of the film at different radial locations on the substrate; and

adjustable fingers, on the shadow mask, for intercepting different radial portions of the target beam, each of the adjustable fingers being extendable to reduce a deposition rate at a radius of the adjustable finger and retractable to increase the deposition rate at the radius of the adjustable finger, whereby film deposition rates at different radii of the substrate are adjustable by the adjustable fingers of the shadow mask.

2. The adjustable uniformity-mask deposition system of claim 1 further comprising:

a computer, receiving measurements of film transmittance from the monitor, for calculating adjustments to the adjustable fingers;

wherein the adjustments extend an adjustable finger at a radial region with a higher-than-average film thickness indicated by the monitor to reduce the deposition rate at the radius for the higher-than-average film thickness.

3. The adjustable uniformity-mask deposition system of claim 2 further comprising:

a motor, coupled to the substrate by a rotating shaft, for rotating the substrate during deposition.

4. The adjustable uniformity-mask deposition system of claim 3 wherein the shadow mask comprises at least three adjustable fingers, each adjustable finger being independently adjustable.

5. The adjustable uniformity-mask deposition system of claim 4 wherein the shadow mask further comprises:

a plurality of motors, activated by signals from the computer, for extending or retracting the adjustable fingers, whereby motors adjust the adjustable fingers.

6. The adjustable uniformity mask deposition system of claim 5 wherein the adjustable fingers overlap each other with spaces in between.

7. The adjustable uniformity mask deposition system of claim 5 wherein the adjustable fingers have a U-shape cross-section.

8. The adjustable uniformity mask deposition system of claim 5 wherein the adjustable fingers are on multiple sides of an opening in a disk of the shadow mask.

9. The adjustable uniformity mask deposition system of claim 5 wherein the adjustable fingers are on two sides of an opening in the shadow mask;

wherein an adjustable finger has a range of travel sufficient to meet an opposing adjustable finger to close the opening for a radius of the adjustable finger.

10. The adjustable uniformity-mask deposition system of claim 5 wherein the plurality of motors move the adjustable fingers by an amount signaled by the computer, the adjustable fingers being adjustable over a range of extensions and retractions.

11. The adjustable uniformity-mask deposition system of claim 5 wherein the shadow mask further comprises:

a shaft having a plurality of concentric tubes for transferring movement by a motor to one of the adjustable fingers.

12. The adjustable uniformity-mask deposition system of claim 11 wherein the shadow mask further comprises:

a motor cam on a first end of each concentric tube, the motor cam coupled to a motor, the motor rotating the concentric tube by moving the motor cam; and

a finger cam on a second end of each concentric tube, the finger cam linked to an adjustable finger, whereby movement of the motor cam by the motor rotates the concentric tube and the finger cam, extending or retracting the adjustable finger linked to the motor by the motor cam, concentric tube, and finger cam.

13. The adjustable uniformity-mask deposition system of claim 3 wherein measurements and adjustments are repeatedly made before an endpoint is reached and deposition of the film is ended, whereby in-situ measurements and deposition-rate adjustments are made to deposit the film with a more uniform thickness at different radii.

14. The adjustable uniformity-mask deposition system of claim 13 further comprising:

an ion-beam generator for generating an ion beam aimed at the target to sputter material from the target into the target beam.

15. The adjustable uniformity-mask deposition system of claim 14 wherein the monitor is an optical monitor that comprises:

a plurality of light sources generating a plurality of light beams that fall upon the film at different radial locations;

a plurality of optical detectors that measure intensity of the plurality of light beams after attenuation by the film on the substrate, whereby optical monitoring uses several light beams.

16. The adjustable uniformity-mask deposition system of claim 15 wherein the different radial locations measured by the light beams is opposite a target region of the substrate that receives the target beam, whereby measurement areas of the substrate are separated from deposition areas.

17. The adjustable uniformity-mask deposition system of claim 16 wherein a computer program determines when the monitor detects an endpoint when a measured transmittance of the film reaches a desired thickness, the ion-beam generator being disabled when the endpoint is reacted to end deposition of the film.

18. The adjustable uniformity-mask deposition system of claim 13 wherein several layers of films are deposited, the several layers including layers of alternating film properties.

20. The deposition system of claim 19 further comprising:

motors, activated by the computer, for moving the finger plates.

21. The deposition system of claim 20 wherein each of the motors connects to one of the finger plates through a rotating shaft coupled to the motor by a motor cam and coupled to the finger plate by a finger cam, whereby one motor is used to control each of the finger plates.

22. The deposition system of claim 21 wherein the motors are inside a vacuum chamber that contains the substrate, target, and shadow mask.

24. The film depositor of claim 23 wherein the modulate means comprises:

mask means for blocking a portion of the target beam, the mask means comprising a plurality of radial-mask means for partially blocking a portion of the target beam for one of the different radial bands.

25. The film depositor of claim 23 wherein the feedback modulate means includes programmable means to deposit films of varying thickness at different radial bands, whereby different film thicknesses are deposited at different radial bands of a same substrate.

26. The film depositor of claim 23 wherein the measure means comprises a scan means for scanning a light source to different radial positions of the substrate to measure transmittance of the film in the different radial bands of the substrate, whereby a single light source is scanned to different radial positions.

19. A deposition system for adjusting radial deposition rates of a film to produce a radially-uniform film thickness comprising:

an ion beam generator for generating an ion beam;

a target that receives the ion beam and generates a target beam;

a substrate being rotated through the target beam, the substrate being only partially covered by the target beam;

an optical-beam generator for generating optical beams that are altered by a film being deposited on a surface of the substrate;

an optical detector for measuring the optical beams to determine transmittance of the film a several different radial locations on the substrate;

a shadow mask with finger plates that partially block the target beam, the finger plates being adjustable during deposition to decrease or increase deposition rates at several annular regions with different radii of the substrate;

and a computer, coupled to the optical detector and coupled to control the finger plates, for adjusting positions of the finger plates during deposition of the film to produce a more radially-uniform thickness of the film on the substrate, whereby radial deposition rates are adjusted to produce a more radially-uniform thickness of the film.

23. A film depositor comprising:

substrate rotation means for holding a substrate and for rotating the substrate during deposition of a film on a surface of the substrate;

sputter means for sputtering a target to generate a target beam of material to be deposited in the film on the substrate;

modulate means, situated to partially block the target beam before reaching the substrate, for modulating film deposition rates of different radial bands of the substrate;

measure means for measuring a transmittance of the film in the different radial bands of the substrate; and

feedback modulation means, coupled to the measure means and to the modulate means, for modulating film deposition rates of the different radial bands in response to transmittance measurements of the different radial bands of the substrate, whereby film deposition rates at different radial bands of the substrate are modulated in response to transmittance measurements of the film in the different radial bands.