Measuring in-situ UV intensity in UV cure tool

• US 7,935,940 B1
• Filed: 01/08/2008
• Issued: 05/03/2011
• Est. Priority Date: 01/08/2008
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Original Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Inventors: Smargiassi, Eugene
• Primary Examiner(s): Johnston; Phillip A
• Application Number:
  US12/008,149
• Time in Patent Office: 1,211 Days
• Field of Search: 250/492.1
• US Class Current: 250/492.1
• CPC Class Codes: G01N 21/33 using ultraviolet light G01N21/39 takes precedence
• CPC Class Codes: H01L 21/67115 mainly by radiation
• CPC Class Codes: H01L 21/67248 Temperature monitoring

Abstract

Consistent ultraviolet (UV) intensity for a semiconductor UV cure chamber is measured in-situ with a hot pedestal in vacuum by measuring reflected UV light from a calibration substrate at a UV detector mounted in the lamp assembly. The measurement apparatus includes a UV detector, a cover that protects the detector from UV light while not in use, and a mirror disposed between the chamber window and the UV detector. Measured UV intensity from the substrate reflection and from the mirror reflection help determine a course of maintenance action to maintain wafer-to-wafer uniformity.

Claims

1. An ultraviolet (UV) apparatus for semiconductor processing, the apparatus comprising:

(a) a process chamber comprising a substrate holder and a window; and

,

(b) a UV radiation assembly external to the process chamber, the assembly comprising

i) at least two UV lamps,

ii) one or more reflectors operable to direct a portion of the UV radiation from the at least two UV lamps through the window towards the substrate holder,

iii) an in situ UV intensity detector disposed between the at least two UV lamps, and

iv) a shutter or iris configured to isolate the UV intensity detector from the UV radiation between measurements; and

,

(c) a controller configured to execute a set of instructions, the set of instructions comprising;

opening the shutter or iris to expose a UV detector to the UV radiation;

measuring a UV intensity at a UV radiation power with the UV detector;

after measuring, closing a shutter or iris to isolate the UV detector from the UV radiation;

calculating a deviation based on the measurement and a baseline intensity; and

,

adjusting the UV radiation power or exposure duration to compensate for the deviation.

2. An ultraviolet (UV) apparatus for semiconductor processing, the apparatus comprising:

(a) a process chamber comprising a substrate holder and a window; and

,

(b) a UV radiation assembly external to the process chamber, the assembly comprising

i) at least two UV lamps,

ii) one or more reflectors operable to direct a portion of the UV radiation from the at least two UV lamps through the window towards the substrate holder,

iii) an UV intensity detector positioned between the at least two UV lamps to receive UV radiation from the at least two UV lamps reflected through the window,

iv) a cover configured to isolate the UV detector from radiation from the at least two UV lamps.

3. The apparatus of claim 2, wherein the detector is oriented towards the window.

4. The apparatus of claim 2, wherein the UV intensity detector comprises a silicon carbide photodiode.

5. The apparatus of claim 2, wherein the UV intensity detector includes a diffuser.

6. The apparatus of claim 2, wherein the UV radiation assembly further comprises a mirror disposed in between the UV intensity detector and the window.

7. The apparatus of claim 6, wherein the mirror is oriented towards the detector.

8. The apparatus of claim 4, wherein the mirror is detachable from the UV radiation assembly.

9. The apparatus of claim 4, wherein the mirror is coated with a high temperature UV coating or an aluminum coating.

10. A method of calibrating an ultraviolet (UV) apparatus, the method comrising:

(a) receiving a calibration indication or determining that a calibration is required;

(b) setting a UV radiation power from at least two UV lamps to a first power; and

,

(c) measuring an output over a duration of an in situ UV intensity detector disposed between the at least two UV lamps;

wherein a chamber vacuum is maintained during the calibration and wherein the method further comprises opening a shutter to expose a UV detector to the UV radiation prior to (c); and

closing a shutter to isolate the UV detector from the UV radiation after (c).

11. The method of claim 10, further comprising:

positioning a calibration substrate on a substrate holder; and

,

removing the calibration substrate.

12. The method of claim 10, further comprising:

(a) maintaining a substrate holder temperature.

13. The method of claim 10, further comprising:

(a) calculating a UV intensity based on the UV detector output measured;

(b) calculating a deviation based on the calculated UV intensity and a baseline intensity; and

,

(c) adjusting the UV radiation power or exposure time to compensate for the deviation.

14. The method of claim 10, further comprising:

(a) determining a remedial activity.

15. The method of claim 10, wherein the first power is 100% power.

16. The method of claim 10, wherein the calibration substrate is a polished silicon wafer.

17. The method of claim 10, wherein the calibration substrate is coated with a high temperature UV coating.

18. The method of claim 10, wherein the calibration substrate is an aluminum-coated silicon wafer.

19. The method of claim 10, further comprising:

(a) positioning a mirror between a process chamber and a UV detector;

(b) measuring the reflected UV radiation; and

,

(c) determining whether a window between the mirror and the substrate requires a cleaning.