3D NAND STAIRCASE CD CONTROL BY USING INTERFEROMETRIC ENDPOINT DETECTION

• US 20150011027A1
• Filed: 07/08/2014
• Published: 01/08/2015
• Est. Priority Date: 07/08/2013
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: LIAN, Lei
• Granted Patent: US 9,240,359 B2
• Time in Patent Office: Days
• US Class Current: 438/16
• CPC Class Codes: G03F 7/40 Treatment after imagewise removal, e.g. baking
• CPC Class Codes: H01L 21/0273 characterised by the treatment of photoresist layers
• CPC Class Codes: H01L 21/31133 by chemical means
• CPC Class Codes: H01L 21/8221 Three dimensional integrated circuits stacked in different levels
• 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
• CPC Class Codes: H10B 41/27 the channels comprising vertical portions, e.g. U-shaped channels
• CPC Class Codes: H10B 43/27 the channels comprising vertical portions, e.g. U-shaped channels

Abstract

Embodiments of the present disclosure provide methods for forming stair-like structures with accurate profiles control in manufacturing three dimensional (3D) stacking of semiconductor chips using precise photoresist trimming process endpoint control. In one example, a method of determining a photoresist trimming endpoint for forming stair-like structures on a substrate includes performing a trimming process on a substrate to trim a patterned photoresist layer disposed on a film stack from a first width to a second width in a processing chamber, wherein the patterned photoresist layer exposes a portion of the film stack uncovered by the patterned photoresist layer during the trimming process, directing an optical signal to a surface of the patterned photoresist layer while trimming the patterned photoresist layer, collecting a return reflected optical signal reflected from the photoresist layer, and determining a trimming endpoint by analyzing the return optical signal reflected from the photoresist layer.

Claims

1. A method of determining a photoresist trimming endpoint for forming stair-like structures on a substrate, comprising:

performing a trimming process on a substrate to trim a patterned photoresist layer disposed on a film stack from a first width to a second width in a processing chamber, wherein the patterned photoresist layer exposes a portion of the film stack uncovered by the patterned photoresist layer during the trimming process;

directing an optical signal to a surface of the patterned photoresist layer while trimming the patterned photoresist layer;

collecting a return reflected optical signal reflected from the photoresist layer; and

determining a trimming endpoint by analyzing the return optical signal reflected from the photoresist layer.

2. The method of claim 1, wherein collecting the return reflected optical signal further comprises:

analyzing a waveform indicating reflected intensity change over different wavelengths obtained during the photoresist trimming process.

3. The method of claim 2, wherein analyzing the waveform further comprises:

comparing the reflected intensify with an intensify obtained from a referenced waveform obtained from a reference substrate.

4. The method of claim 3, wherein the reference substrate is a bare-silicon substrate.

5. The method of claim 3, further comprising:

computing a ratio of the reflected intensity obtained during the photoresist trimming process with an reflected intensity obtained from the referenced waveform from a reference substrate.

6. The method of claim 5, further comprising:

obtaining a nominal reflectivity by the computation of the ratio.

7. The method of claim 6, further comprising:

extracted a minimal pattern from the nominal reflectivity to determine photoresist thickness loss.

8. The method of claim 7, wherein the minimal pattern is fringes shown in the waveform.

9. The method of claim 1, wherein the photoresist layer has a substantially similar lateral and vertical trimming rates.

10. The method of claim 7, wherein the trimming process endpoint is obtained when a determined photoresist thickness loss is obtained.

11. The method of claim 1, wherein performing a trimming process on a substrate further comprises:

performing an etching process to etch a portion of the film stack exposed by the patterned photoresist layer.

12. The method of claim 1, wherein the film stack includes a multi-material layer made from repeated pairs of layers.

13. The method of claim 12, wherein each repeated pair includes first layer that is a dielectric layer and a second layer that is a dielectric layer or a conductive layer.

14. The method of claim 1, directing the optical signal further comprises:

generating a plasma within the processing chamber.

15. The method of claim 13, wherein the first layer is a silicon oxide layer and the second layer is a silicon nitride layer.

16. The method of claim 11, wherein the photoresist trimming process and the etching process may be repeated performed to gradually trim dimension of the photoresist layer in each trimming process cycle to form stair-like structures in the film stack.

17. A method of determining a photoresist trimming process endpoint comprises:

performing a trimming process on a substrate to trim a patterned photoresist layer disposed on a film stack from a first width to a second width in a processing chamber, wherein the patterned photoresist layer exposes a portion of the film stack uncovered by the patterned photoresist layer during the trimming process;

performing an etching process to etch a portion of the film stack exposed by the trimmed patterned photoresist layer;

directing an optical signal to a surface of the trimmed patterned photoresist layer continuously during the trimming and the etching process;

collecting a return reflected optical signal reflected from the trimmed patterned photoresist layer;

determining a change of reflected intensify of the return reflected optical signal as collected; and

calculating a photoresist thickness loss based on the change of the reflected intensity.

18. The method of claim 17, the change of reflected intensity is obtained by computing a ratio of the reflected intensity or the derivative of the reflected intensity with respect to time obtained during the photoresist trimming process with a reflected intensity obtained from the referenced waveform from a referenced substrate.

19. The method of claim 18, wherein referenced substrate is a bare-silicon wafer.

20. A method of determining a photoresist trimming process endpoint comprises:

performing a trimming process on a substrate to trim a patterned photoresist layer disposed on a film stack from a first width to a second width in a processing chamber, wherein the patterned photoresist layer exposes a portion of the film stack uncovered by the patterned photoresist layer during the trimming process;

performing an etching process to etch a portion of the film stack exposed by the trimmed patterned photoresist layer;

repeatedly performing the trimming process and the etching process;

directing an optical signal to a surface of the trimmed patterned photoresist layer continuously during the repeated trimming and the etching process;

collecting a return reflected optical signal reflected from the trimmed patterned photoresist layer; and

analyzing the return reflected optical signal to calculate a photoresist thickness loss.