METHOD OF DETECTING END POINT OF PLASMA ETCHING PROCESS

• US 20080186473A1
• Filed: 02/02/2007
• Published: 08/07/2008
• Est. Priority Date: 07/25/2007
• Status: Active Grant

• Current Assignee: Macronix International Co., Ltd.
• Original Assignee: Macronix International Co., Ltd.
• Inventors: Lee, Hong-Ji
• Granted Patent: US 7,427,519 B2
• Time in Patent Office: Days
• US Class Current: 356/72
• CPC Class Codes: G01J 3/443 Emission spectrometry
• CPC Class Codes: G01N 21/73 using plasma burners or torches
• 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

A method of detecting an end point of a plasma etching process for etching a first layer on a second layer is described, the first layer producing a first etching product and the second layer a second etching product. Time-dependent intensity [I_{j=1 to m}(t)] of a number “m” (m≧1) of spectral line(s) of the first etching product in emission spectrum of the plasma and that [I_{i=1 to n}(t)] of a number “n” (n≧1) of spectral line(s) of the second etching product in the emission spectrum are collected, wherein “m+n≧3” is satisfied. One index of

$\mathrm{Lm}\left(t\right)\left[=\prod _{i=1,j=1}^{n,m}\frac{I_i\left(t\right)}{I_j\left(t\right)}\right],\mathrm{Ls}\left(t\right)\left[=\prod _{i=1,j=1}^{n,m}\frac{I_i\left(t\right)}{I_j\left(t\right)}\right],{\mathrm{Lm}}^{\prime }\left(t\right)\left\{=\left[\mathrm{Lm}\left(t\right)\right]/t\right\}\mathrm{and}{\mathrm{Ls}}^{\prime }\left(t\right)\left\{=\left[\mathrm{Ls}\left(t\right)\right]/t\right\}$

is calculated in real time and plotted with the time. An etching end-point is identified from the plot of the one index with the time.

Claims

1. A method of detecting an end point of a plasma etching process for etching a first layer on a second layer that comprises a material different from that of the first layer, wherein the first layer produces a first etching product and the second layer produces a second etching product, the method comprising:

collecting time-dependent intensity [I_{j=1 to m}(t)] of a number “

m”

(m≧

1) of spectral line(s) of the first etching product in an emission spectrum of the plasma and time-dependent intensity [I_{i=1 to n}(t)] of a number “

n”

(n≧

1) of spectral line(s) of the second etching product in the emission spectrum, wherein “

m+n≧

3”

is satisfied;

calculating, in real time, one index of

$\mathrm{Lm}<br><br>\left(t\right)\left[=\underset{i=1,j=1}{\overset{n,m}{\prod <br><br>}}<br><br>\frac{I_i<br><br>\left(t\right)}{I_j<br><br>\left(t\right)}\right],<br><br>\mathrm{Ls}<br><br>\left(t\right)\left[=\underset{i=1,j=1}{\overset{n,m}{\prod <br><br>}}<br><br>\frac{I_i<br><br>\left(t\right)}{I_j<br><br>\left(t\right)}\right],$

Lm′

(t) {=d[Lm(t)]/dt} and Ls′

(t) {=d[Ls(t)]/dt} and plot the same with the time; and

identifying at least one etching end-point from the plot of the one index with the time.

2. The method of claim 1, wherein the one index is Lm(t) or Lm′

(t).

3. The method of claim 1, wherein the plasma etching process is for forming multiple holes having different etching end-points.

4. The method of claim 3, wherein the holes have different widths and thus have the different etching end-points.

5. The method of claim 1, wherein the second layer is an etching stop layer.

6. The method of claim 5, wherein the first and the second layers both are dielectric layers.

7. The method of claim 6, wherein the plasma etching process is for forming contact holes in the first layer.

8. The method of claim 7, wherein the contact holes have the same width or include at least two groups of holes wherein each group of holes has a different width.

9. The method of claim 5, wherein the first layer comprises silicon oxide and the second layer comprises silicon nitride.

10. The method of claim 9, wherein the first etching product is CO and the second etching product is CN.

11. The method of claim 1, wherein the first layer is a dielectric layer, and the second layer is a silicon substrate.

12. The method of claim 11, wherein the plasma etching process is for forming self-aligned contact (SAC) holes in the first layer.

13. The method of claim 11, wherein the second etching product is SiF.

14. A method of detecting an end point of a plasma etching process for etching a first layer on a second layer comprising a material different from that of the first layer, wherein the first layer produces a first etching product and the second layer produces a second etching product, the method comprising:

collecting respective time-dependent intensities of spectral lines of N (≧

2) groups caused by the first and the second etching products in an emission spectrum of the plasma, wherein the k-th group among the N groups includes a number “

m(k)”

[m(k)≧

1] of spectral line(s) of the first etching product having intensity “

I_{k,j=1 to m(k)}(t)” and

a number “

n(k)”

[n(k)≧

1] of spectral line(s) of the second etching product having intensity “

I_{k,i=1 to n(k)}(t)”

, and “

m(k)+n(k)≧

3”

is satisfied;

calculating, in real time, one index of Lm(t)

$\left[{\mathrm{Lm}}_k<br><br>\left(t\right)=\underset{i=1,j=1}{\overset{n<br><br>\left(k\right),m<br><br>\left(k\right)}{\prod <br><br>}}<br><br>\frac{I_{k,i}<br><br>\left(t\right)}{I_{k,j}<br><br>\left(t\right)}\right],<br><br>\mathrm{Ls}<br><br>\left(t\right)<br><br>\left[{\mathrm{Ls}}_k<br><br>\left(t\right)=\underset{i=1,j=1}{\overset{n<br><br>\left(k\right),m<br><br>\left(k\right)}{\prod <br><br>}}<br><br>\frac{I_{k,i}<br><br>\left(t\right)}{I_{k,j}<br><br>\left(t\right)}\right],$

Lm′

(t) {Lm_k′

(t)=d[Lm_k(t)]/dt} and Ls′

(t) {Ls_k′

(t)=d[Ls_k(t)]/dt} for each group among the N groups and plot the same with the time; and

identifying at least one etching end point from the plots of the one index with the time respectively for the N groups.

15. The method of claim 14, wherein the one index Lm(t) or Lm′

(t).

16. The method of claim 14, wherein the plasma etching process is for forming multiple holes having different etching end-points.

17. The method of claim 16, wherein the holes have different widths and thus have the different etching end-points.

18. The method of claim 17, wherein the first and second layers both are dielectric layers, the second layer is an etching stop layer, and the two holes are contact holes.

19. The method of claim 18, wherein the first layer comprises silicon oxide and the second layer comprises silicon nitride.

20. The method of claim 19, wherein the first etching product is CO and the second etching product is CN.