System for in-situ film stack measurement during etching and etch control method

• US 9,059,038 B2
• Filed: 07/18/2013
• Issued: 06/16/2015
• Est. Priority Date: 07/18/2012
• Status: Active Grant

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Li, Shifang, Bao, Junwei, Chu, Hanyou, Jin, Wen, Meng, Ching-Ling, Xu, Weiwen, Wang, Ping, Tuitje, Holger, Mihaylov, Mihail, Tian, Xinkang
• Primary Examiner(s): OLSEN, ALLAN W
• Application Number:
  US13/945,759
• Publication Number:
  US 20140024143A1
• Time in Patent Office: 698 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H01J 37/32972 Spectral analysis
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32

Abstract

Disclosed is an in-situ optical monitor (ISOM) system and associated method for controlling plasma etching processes during the forming of stepped structures in semiconductor manufacturing. The in-situ optical monitor (ISOM) can be optionally configured for coupling to a surface-wave plasma source (SWP), for example a radial line slotted antenna (RLSA) plasma source. A method is described to correlate the lateral recess of the steps and the etched thickness of a photoresist layer for use with the in-situ optical monitor (ISOM) during control of plasma etching processes in the forming of stepped structures.

Claims

1. A method for monitoring and controlling plasma etching, the method comprising:

a) loading a substrate into a plasma processing chamber, the substrate comprising a structure which comprises a first layer formed thereupon and a radiation-sensitive material layer formed on top of the first layer;

b) initiating a first plasma etch process in the plasma processing chamber, the first plasma etch process recipe being selected to selectively reduce the thickness of the radiation-sensitive material layer and laterally trim the radiation-sensitive material layer;

c) illuminating the structure on the substrate with an incident light beam, the reflection of the incident light beam from the structure forming a reflected light beam;

d) measuring a first intensity of the reflected light beam;

e) determining the etched thickness of the radiation-sensitive material layer from the measured first intensity of the reflected light beam during the first plasma etch process;

f) determining the amount of lateral recess of the first layer from a previously-established correlation of the amount of lateral recess of the first layer to the etched thickness of the radiation-sensitive material layer;

g) comparing the amount of lateral recess of the first layer to a desired lateral recess of the first layer, and stopping the first plasma etch process if the amount of lateral recess of the first layer is equal to or greater than the desired lateral recess of the first layer, otherwise repeating steps c) through g), thereby forming a trimmed radiation-sensitive material pattern;

h) initiating a second plasma etch process, the second plasma etch process recipe being selected to selectively etch the first layer so as to transfer the trimmed radiation-sensitive material pattern into the first layer;

i) illuminating the structure on the substrate with the incident light beam, the reflection of the incident light beam from the structure forming the reflected light beam;

j) measuring a second intensity of the reflected light beam;

k) determining an etched thickness of the first layer in a region not covered by the radiation-sensitive material layer, from the measured second intensity of the reflected light beam; and

l) comparing the etched thickness of the first layer to a desired etched thickness of the first layer, and stopping the second plasma etch process if the etched thickness of the first layer is greater than or equal to the desired etched thickness of the first layer, otherwise repeating steps j) through l), thereby forming a step in the first layer.

2. The method of claim 1, further comprising:

m) repeating steps b) through l) until a stepped structure is formed in the first layer on the substrate, wherein successive steps formed in the first layer have a progressively smaller lateral dimension as a distance of a step from the substrate increases.

3. The method of claim 2, further comprising:

removing any residual radiation-sensitive material from the stepped structure.

4. The method of claim 1, wherein establishing the correlation of the amount of lateral recess of the first layer to the etched thickness of the radiation-sensitive material layer comprises measuring the amount of lateral recess of the first layer with a scanning electron microscope (SEM).

5. The method of claim 4, wherein establishing the correlation of the amount of lateral recess of the first layer to the etched thickness of the radiation-sensitive material layer is performed prior to step a), using test substrates.

6. The method of claim 1, wherein the first layer comprises a plurality of sublayers.

7. The method of claim 6, wherein the plurality of sublayers comprise alternating materials across the thickness of the first layer.

8. The method of claim 1, wherein the steps of measuring the first and second intensities of the reflected light beam are performed using a reflectometer, comprising:

a light source for providing an incident light beam for substrate illumination, the incident light beam being reflected from the substrate to form a reflected light beam;

a photodetector for measuring an intensity of the reflected light beam,

an optical window mounted on a wall of the plasma processing chamber opposite the substrate, the optical window being configured to transmit the incident light beam and the reflected light beam, the optical window comprising an upper window, a lower window, and a window mesh.

9. A method for monitoring and controlling plasma etching, the method comprising:

a) loading a substrate into a plasma processing chamber, the substrate comprising a structure which comprises a first layer formed thereupon and a radiation-sensitive material layer formed on top of the first layer;

b) initiating a first plasma etch process in the plasma processing chamber, the first plasma etch process recipe being selected to selectively reduce the thickness of the radiation-sensitive material layer and laterally trim the radiation-sensitive material layer;

c) illuminating the structure on the substrate with an incident light beam, the reflection of the incident light beam from the structure forming a reflected light beam;

d) measuring a first intensity of the reflected light beam;

e) determining the etched thickness of the radiation-sensitive material layer from the measured first intensity of the reflected light beam during the first plasma etch process;

f) determining the amount of lateral recess of the first layer from a previously-established correlation of the amount of lateral recess of the first layer to the etched thickness of the radiation-sensitive material layer;

g) comparing the amount of lateral recess of the first layer to a desired lateral recess of the first layer, and stopping the first plasma etch process if the amount of lateral recess of the first layer is equal to or greater than the desired lateral recess of the first layer, otherwise repeating steps c) through g), thereby forming a trimmed radiation-sensitive material pattern;

h) initiating a second plasma etch process, the second plasma etch process recipe being selected to selectively etch the first layer so as to transfer the trimmed radiation-sensitive material pattern into the first layer;

i) stopping the second plasma etch process after a predetermined time or after an etch endpoint signal is received from an optical emission spectroscopy (OES) device attached to the plasma processing chamber, thereby forming a step in the first layer.

10. The method of claim 9, further comprising:

j) repeating steps b) through i) until a stepped structure is formed in the first layer on the substrate, wherein successive steps formed in the first layer have a progressively smaller lateral dimension as a distance of a step from the substrate increases.