Abstract

We develop a modified thin film model with adjustable ratio of the illuminated surface areas for accurate reflectivity calculation of deep via structures. We also propose a method combining a half oblate spheroid model and a reflectance modulation algorithm for extraction of via bottom profile from the measured reflectance spectrum. We demonstrate the use and enhancement of an existing wafer metrology tool, spectral reflectometer by implementing novel theoretical model and measurement algorithm for through-silicon via (TSV) inspection. Our non-destructive solution can measure TSV profile diameters as small as 5 μm and aspect ratios greater than 13:1. The measurement precision is in the range of 0.02 μm. Metrology results from actual 3D interconnect processing wafers are presented.

© 2010 OSA

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References

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  1. ITRS Assembly & Packaging 2008.
  2. P. de Groot and X. C. de Lega, “Valve cone measurement using white light interference microscopy in a spherical measurement geometry,” Opt. Eng. 42(5), 1232 (2003).
    [CrossRef]
  3. J. H. Belk, and D. E. Hulsey, “ Non-contact hole depth gage”, US patent 2003/0107728 A1.
  4. D. Marx, D. Grant, R. Dudley, A. Rudack, and W. H. Teh, “Wafer Thickness Sensor (WTS) for Etched Depth Measurement of TSV,” IWLPC-International Wafer-level packaging conference proceeding (2009).
  5. Z. Liu, X. Zhang, J. Hu, and D. J. Roy, “Measurement of deep silicon trench profile using normal incidence optical CD metrology,” Proc. SPIE 5752, 1152–1160 (2005).
    [CrossRef]
  6. C. A. Duran, A. A. Maznev, G. T. Merklin, A. Mazurenko, and M. Gostein, “Infrared Reflectometry for Metrology of Trenches in Power Devices,” IEEE/SEMI Advanced Semiconductor Manufacturing Conference, p. 175, (2007).
  7. C. J. Raymond, M. Littau, R. Markle, and M. Purdy, “Scatterometry for shallow trench isolation (STI) process metrology,” Proc. SPIE 4344, 716–725 (2001).
    [CrossRef]
  8. M. Horie, S. Shiota, S. Yamaguchi, and ., “UV-reflectometry for fast trench-depth measurement,” Proc. SPIE 6922, 69223D (2008).
    [CrossRef]
  9. S. Yamaguchi, and M. Horie, “Measuring Method and Apparatus for Measuring Depth of Trench Pattern,” US patent 2008/0049222 A1.
  10. B. Chao, Z. Chun, H. Low, H. L. Lee, S. Y. Loong, and G. Guo, “Via electromigration improvement by changing the via bottom geometric profile,” US patent 7045455B2.
  11. K. K. Kirby, “Methods for forming interconnects in microelectronic workpieces and microelectronic workpieces formed using such method,” US patent 7271482.
  12. A. Kadyshevitch, C. Talbot, D. Shur, and A. G. Hegedus, “Contact Opening Metrology,” US patent 2007/0257191 A1.

2008 (1)

M. Horie, S. Shiota, S. Yamaguchi, and ., “UV-reflectometry for fast trench-depth measurement,” Proc. SPIE 6922, 69223D (2008).
[CrossRef]

2005 (1)

Z. Liu, X. Zhang, J. Hu, and D. J. Roy, “Measurement of deep silicon trench profile using normal incidence optical CD metrology,” Proc. SPIE 5752, 1152–1160 (2005).
[CrossRef]

2003 (1)

P. de Groot and X. C. de Lega, “Valve cone measurement using white light interference microscopy in a spherical measurement geometry,” Opt. Eng. 42(5), 1232 (2003).
[CrossRef]

2001 (1)

C. J. Raymond, M. Littau, R. Markle, and M. Purdy, “Scatterometry for shallow trench isolation (STI) process metrology,” Proc. SPIE 4344, 716–725 (2001).
[CrossRef]

de Groot, P.

P. de Groot and X. C. de Lega, “Valve cone measurement using white light interference microscopy in a spherical measurement geometry,” Opt. Eng. 42(5), 1232 (2003).
[CrossRef]

de Lega, X. C.

P. de Groot and X. C. de Lega, “Valve cone measurement using white light interference microscopy in a spherical measurement geometry,” Opt. Eng. 42(5), 1232 (2003).
[CrossRef]

Horie, M.

M. Horie, S. Shiota, S. Yamaguchi, and ., “UV-reflectometry for fast trench-depth measurement,” Proc. SPIE 6922, 69223D (2008).
[CrossRef]

Hu, J.

Z. Liu, X. Zhang, J. Hu, and D. J. Roy, “Measurement of deep silicon trench profile using normal incidence optical CD metrology,” Proc. SPIE 5752, 1152–1160 (2005).
[CrossRef]

Littau, M.

C. J. Raymond, M. Littau, R. Markle, and M. Purdy, “Scatterometry for shallow trench isolation (STI) process metrology,” Proc. SPIE 4344, 716–725 (2001).
[CrossRef]

Liu, Z.

Z. Liu, X. Zhang, J. Hu, and D. J. Roy, “Measurement of deep silicon trench profile using normal incidence optical CD metrology,” Proc. SPIE 5752, 1152–1160 (2005).
[CrossRef]

Markle, R.

C. J. Raymond, M. Littau, R. Markle, and M. Purdy, “Scatterometry for shallow trench isolation (STI) process metrology,” Proc. SPIE 4344, 716–725 (2001).
[CrossRef]

Purdy, M.

C. J. Raymond, M. Littau, R. Markle, and M. Purdy, “Scatterometry for shallow trench isolation (STI) process metrology,” Proc. SPIE 4344, 716–725 (2001).
[CrossRef]

Raymond, C. J.

C. J. Raymond, M. Littau, R. Markle, and M. Purdy, “Scatterometry for shallow trench isolation (STI) process metrology,” Proc. SPIE 4344, 716–725 (2001).
[CrossRef]

Roy, D. J.

Z. Liu, X. Zhang, J. Hu, and D. J. Roy, “Measurement of deep silicon trench profile using normal incidence optical CD metrology,” Proc. SPIE 5752, 1152–1160 (2005).
[CrossRef]

Shiota, S.

M. Horie, S. Shiota, S. Yamaguchi, and ., “UV-reflectometry for fast trench-depth measurement,” Proc. SPIE 6922, 69223D (2008).
[CrossRef]

Yamaguchi, S.

M. Horie, S. Shiota, S. Yamaguchi, and ., “UV-reflectometry for fast trench-depth measurement,” Proc. SPIE 6922, 69223D (2008).
[CrossRef]

Zhang, X.

Z. Liu, X. Zhang, J. Hu, and D. J. Roy, “Measurement of deep silicon trench profile using normal incidence optical CD metrology,” Proc. SPIE 5752, 1152–1160 (2005).
[CrossRef]

Opt. Eng. (1)

P. de Groot and X. C. de Lega, “Valve cone measurement using white light interference microscopy in a spherical measurement geometry,” Opt. Eng. 42(5), 1232 (2003).
[CrossRef]

Proc. SPIE (3)

Z. Liu, X. Zhang, J. Hu, and D. J. Roy, “Measurement of deep silicon trench profile using normal incidence optical CD metrology,” Proc. SPIE 5752, 1152–1160 (2005).
[CrossRef]

C. J. Raymond, M. Littau, R. Markle, and M. Purdy, “Scatterometry for shallow trench isolation (STI) process metrology,” Proc. SPIE 4344, 716–725 (2001).
[CrossRef]

M. Horie, S. Shiota, S. Yamaguchi, and ., “UV-reflectometry for fast trench-depth measurement,” Proc. SPIE 6922, 69223D (2008).
[CrossRef]

Other (8)

S. Yamaguchi, and M. Horie, “Measuring Method and Apparatus for Measuring Depth of Trench Pattern,” US patent 2008/0049222 A1.

B. Chao, Z. Chun, H. Low, H. L. Lee, S. Y. Loong, and G. Guo, “Via electromigration improvement by changing the via bottom geometric profile,” US patent 7045455B2.

K. K. Kirby, “Methods for forming interconnects in microelectronic workpieces and microelectronic workpieces formed using such method,” US patent 7271482.

A. Kadyshevitch, C. Talbot, D. Shur, and A. G. Hegedus, “Contact Opening Metrology,” US patent 2007/0257191 A1.

C. A. Duran, A. A. Maznev, G. T. Merklin, A. Mazurenko, and M. Gostein, “Infrared Reflectometry for Metrology of Trenches in Power Devices,” IEEE/SEMI Advanced Semiconductor Manufacturing Conference, p. 175, (2007).

J. H. Belk, and D. E. Hulsey, “ Non-contact hole depth gage”, US patent 2003/0107728 A1.

D. Marx, D. Grant, R. Dudley, A. Rudack, and W. H. Teh, “Wafer Thickness Sensor (WTS) for Etched Depth Measurement of TSV,” IWLPC-International Wafer-level packaging conference proceeding (2009).

ITRS Assembly & Packaging 2008.

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Figures (13)

Fig. 1
Fig. 1

Theoretical modeling of reflectance spectrum for via depth 30.00 and 30.25 μm. The spectrum for via depth 30.00 μm is well separated with the one for 30.25 μm

Fig. 2
Fig. 2

Theoretical modeling of reflectance spectrum for via depth 30.00 with 1 μm oxide hard mask on top of it. The ratio of the illuminated surface areas of the silicon surface and the via bottom surface is 81% to 19% in this simulation case.

Fig. 3
Fig. 3

(a) Cross-sectional view of 5 μm via hole; the bottom is composed of a slow ascent portion in the center area and a steep ascent portion connects to the sidewall corner. (b). Oblate spheroid model for the HDTSV via bottom profile

Fig. 4
Fig. 4

Schematic of via cross section view (left) and top view (right). The bottom effective area with a diameter e which depth variations inside this area are beyond the depth resolution limit Δdvia

Fig. 5
Fig. 5

Simulated spectrum from HDTSV with varying minor axis length b from 0 to 0.5a (a: major axis length). Via depth is 30.00 μm with 1 μm oxide hard mask on top of it

Fig. 6
Fig. 6

(a) Model fitting for a nominal 80um depth TSV structure. (b) Schematic of illumination beam spot which is two third inside the via hole and one third on top of the Si surface, the ratio of spot in hole to spot on Si surface is around 55% .

Fig. 7
Fig. 7

(a) Experimental reflectance spectra with depth of 80.54 um.(b) Fourier transform of the reflectance spectra with peak value at 81.48 um.

Fig. 8
Fig. 8

Model fitting to the reflectance spectrum of high aspect ratio HDTSV array structure. The via CD is around 5 μm, via pitch is around10 um, via depth is 65.08 μm.

Fig. 9
Fig. 9

The measurement precision is better than 0.20 μm from multiple times measurement results. The uniformity of TSV depth is better than 3.16 μm from multiple sites measurement results.

Fig. 10
Fig. 10

(a) Experimental reflectance spectra from a HDTSV array structure with thin oxide hard mask on top of it. The via CD is around 5um (b) Theoretical model fitting to the low frequency features with oxide hard mask thickness of 596 nm. (c) Theoretical model fitting to the high frequency features with via depth of 37.16 nm.

Fig. 11
Fig. 11

Left: cross section SEM result of top oxide layer. Middle: cross section SEM result of deep via structure. Right: top view of HDTSV sample with nominal CD 5 um, pitch 10 um, illumination spot around 30 um.

Fig. 12
Fig. 12

(a) HDTSV experimental spectrum fitting with the modeling reflectance spectrum structure with minor axis length b = 0.52a. The via depth of 37.16 um and top oxide layer of 0.596 um. (b) The coordinate of effective circular area as shown in Fig. 10(b) can be expressed as (600, -b + 40) nm.

Fig. 13
Fig. 13

cross section SEM result of via bottom profile.

Tables (1)

Tables Icon

Table 1 effective area radius and the corresponding amplitude attenuation

Equations (9)

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I ¯ = C o n s t | E 1 2 + E 2 2 + 2 E 1 E 2 cos ( 2 π ( 2 d / λ ) ) |
I ¯ = C o n s t | ( α E 1 ) 2 + [ ( 1 α ) E 2 ] 2 + 2 ( α E 1 ) [ ( 1 α ) E 2 ] cos ( 2 π ( 2 d / λ ) ) |
I ¯ = C o n s t | ( r S i + α E 1 ) 2 + [ r S i + ( 1 α ) E 2 ] 2 + 2 ( r S i + α E 1 ) [ r S i + ( 1 α ) E 2 ] cos ( 2 π ( 2 d / λ ) ) |
Δ r o p d = 2 n o x i d e ( λ ) d o x i d e
Δ r o p d = 2 n o x i d e ( λ ) d o x i d e = m λ , m = 1 , 2 , 3....
x 2 a 2 + y 2 b 2 = 1
Δ d v i a = m Δ λ 2 = d v i a Δ λ λ
e 2 a 2 + ( b + Δ d v i a ) 2 b 2 = 1
600 2 a 2 + ( b + 40 ) 2 b 2 = 1

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