Abstract

Measurement and control is an important step for production-worthy through silicon vias etch. We demonstrate the use and enhancement of an existing wafer metrology tool, spectral reflectometer by implementing novel theoretical model and measurement algorithm for high density through-silicon via (HDTSV) inspection. It is capable of measuring depth and depth variations of array vias by Discrete Fourier Transform (DFT) analysis in one shot measurement. Surface roughness of via bottom can also be extracted by scattering model fitting. 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.

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References

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  1. ITRS Assembly & Packaging2009.
  2. H. Singh, C. Rusu, and V. Vahedi, “Etch challenges for 3-D integration,” 3rd Workshop on Plasma Etch and Strip in Microelectronics 2010, Grenoble, France.
  3. M. Puech, J. M. Thevenoud, J. M. Gruffat, N. Launay, N. Arnal, and P. Godinat, “Fabrication of 3D packaging TSV using DRIE,” Symposium on Design, Test, Integrate ion and Packaging of MEMS/MOEMS, 2008.
  4. W. H. Teh, R. Caramto, J. Qureshi, S. Arkalgud, M. O’Brien, T. Gilday, K. Maekawa, T. Saito, K. Maruyama, T. Chidambaram, W. Wang, D. Marx, D. Grant, and R. Dudley, “A route towards production-worthy 5 μm x 25 μm and 1 μm x 20 μm non-Bosch through-silicon-via (TSV) etch, TSV metrology, and TSV integration,” IEEE 3DIC Conference, 2009.
  5. F. Liu, R. R. Yu, A. M. Young, J. P. Doyle, X. Wang, L. Shi, K.-N. Chen, X. Li, D. A. Dipaola, D. Brown, C. T. Ryan, J. A. Hagan, K. H. Wong, M. Lu, X. Gu, N. R. Klymko, E. D. Perfecto, A. G. Merryman, K. A. Kelly, S. Purushothaman, S. J. Koester, R. Wisnieff, and W. Haensch, “A 300-mm wafer-level three-dimensional integration scheme using tungsten through-silicon via and hybrid Cu-adhesive bonding,” Proc. International Electron Devices Meeting (IEDM) (2008) p. 599.
  6. M. Puech, J. M. Thevenoud, and J. M. Gruffat, “DRIE for MEMS devices,” Advanced Packaging, 2008.
  7. D. Marx, D. Grant, R. Dudley, A. Rudack, and W. H. Teh, “Wafer thickness sensor (WTS) for etch depth measurement of TSV,” IEEE International Conference on 3D System Integration, 2009.
  8. M. Knowles, “Optical metrology for TSV process control,” 3D Interconnect Metrology at SEMATECH Workshop during SEMICON West 2009.
  9. P. K. Schenck, D. L. Kaiser, and A. V. Davydov, “High throughput characterization of the optical properties of compositionally graded combinatorial films,” Appl. Surf. Sci. 223(1-3), 200–205 (2004).
    [CrossRef]
  10. Y. Feng, X. Zhang, B. Cheung, Z. Liu, M. Isao, and M. Hayashi, “OCD study of critical dimension and line-shape control of shallow-trench-isolation structures,” Proc. SPIE 5375, 1173–1182 (2004).
    [CrossRef]
  11. H. T. Huang and F. L. Terry., “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455–456, 828–836 (2004).
    [CrossRef]
  12. Y. S. Ku and F. S. Yang, “Reflectometer-based metrology for high-aspect ratio via measurement,” Opt. Express 18(7), 7269–7280 (2010).
    [CrossRef] [PubMed]
  13. H. E. Bennett and J. O. Porteus, “Relation between surface roughness and specular reflectance at normal incidence,” J. Opt. Soc. Am. 51(2), 123–129 (1961).
    [CrossRef]
  14. V. C. Venugopal and A. J. Perry, “Method for in-situ monitoring of patterned substrate processing using reflectometry,” US patent 7019844.
  15. M. Bass, Handbook of Optics, 3rd ed. (McGraw-Hill, 2009) Vol. 4.
  16. K. C. Huang, “The study of high aspect ratio TSV metrology,” master thesis, National Tsing Hua University, 2010.
  17. ITRS Metrology 2007 ed.2007.
  18. R. A. Leitgeb, W. Drexler, A. Unterhuber, B. Hermann, T. Bajraszewski, T. Le, A. Stingl, and A. Fercher, “Ultrahigh resolution Fourier domain optical coherence tomography,” Opt. Express 12(10), 2156–2165 (2004).
    [CrossRef] [PubMed]

2010 (1)

2004 (4)

P. K. Schenck, D. L. Kaiser, and A. V. Davydov, “High throughput characterization of the optical properties of compositionally graded combinatorial films,” Appl. Surf. Sci. 223(1-3), 200–205 (2004).
[CrossRef]

Y. Feng, X. Zhang, B. Cheung, Z. Liu, M. Isao, and M. Hayashi, “OCD study of critical dimension and line-shape control of shallow-trench-isolation structures,” Proc. SPIE 5375, 1173–1182 (2004).
[CrossRef]

H. T. Huang and F. L. Terry., “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455–456, 828–836 (2004).
[CrossRef]

R. A. Leitgeb, W. Drexler, A. Unterhuber, B. Hermann, T. Bajraszewski, T. Le, A. Stingl, and A. Fercher, “Ultrahigh resolution Fourier domain optical coherence tomography,” Opt. Express 12(10), 2156–2165 (2004).
[CrossRef] [PubMed]

1961 (1)

Bajraszewski, T.

Bennett, H. E.

Cheung, B.

Y. Feng, X. Zhang, B. Cheung, Z. Liu, M. Isao, and M. Hayashi, “OCD study of critical dimension and line-shape control of shallow-trench-isolation structures,” Proc. SPIE 5375, 1173–1182 (2004).
[CrossRef]

Davydov, A. V.

P. K. Schenck, D. L. Kaiser, and A. V. Davydov, “High throughput characterization of the optical properties of compositionally graded combinatorial films,” Appl. Surf. Sci. 223(1-3), 200–205 (2004).
[CrossRef]

Drexler, W.

Feng, Y.

Y. Feng, X. Zhang, B. Cheung, Z. Liu, M. Isao, and M. Hayashi, “OCD study of critical dimension and line-shape control of shallow-trench-isolation structures,” Proc. SPIE 5375, 1173–1182 (2004).
[CrossRef]

Fercher, A.

Hayashi, M.

Y. Feng, X. Zhang, B. Cheung, Z. Liu, M. Isao, and M. Hayashi, “OCD study of critical dimension and line-shape control of shallow-trench-isolation structures,” Proc. SPIE 5375, 1173–1182 (2004).
[CrossRef]

Hermann, B.

Huang, H. T.

H. T. Huang and F. L. Terry., “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455–456, 828–836 (2004).
[CrossRef]

Isao, M.

Y. Feng, X. Zhang, B. Cheung, Z. Liu, M. Isao, and M. Hayashi, “OCD study of critical dimension and line-shape control of shallow-trench-isolation structures,” Proc. SPIE 5375, 1173–1182 (2004).
[CrossRef]

Kaiser, D. L.

P. K. Schenck, D. L. Kaiser, and A. V. Davydov, “High throughput characterization of the optical properties of compositionally graded combinatorial films,” Appl. Surf. Sci. 223(1-3), 200–205 (2004).
[CrossRef]

Ku, Y. S.

Le, T.

Leitgeb, R. A.

Liu, Z.

Y. Feng, X. Zhang, B. Cheung, Z. Liu, M. Isao, and M. Hayashi, “OCD study of critical dimension and line-shape control of shallow-trench-isolation structures,” Proc. SPIE 5375, 1173–1182 (2004).
[CrossRef]

Porteus, J. O.

Schenck, P. K.

P. K. Schenck, D. L. Kaiser, and A. V. Davydov, “High throughput characterization of the optical properties of compositionally graded combinatorial films,” Appl. Surf. Sci. 223(1-3), 200–205 (2004).
[CrossRef]

Stingl, A.

Terry, F. L.

H. T. Huang and F. L. Terry., “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455–456, 828–836 (2004).
[CrossRef]

Unterhuber, A.

Yang, F. S.

Zhang, X.

Y. Feng, X. Zhang, B. Cheung, Z. Liu, M. Isao, and M. Hayashi, “OCD study of critical dimension and line-shape control of shallow-trench-isolation structures,” Proc. SPIE 5375, 1173–1182 (2004).
[CrossRef]

Appl. Surf. Sci. (1)

P. K. Schenck, D. L. Kaiser, and A. V. Davydov, “High throughput characterization of the optical properties of compositionally graded combinatorial films,” Appl. Surf. Sci. 223(1-3), 200–205 (2004).
[CrossRef]

J. Opt. Soc. Am. (1)

Opt. Express (2)

Proc. SPIE (1)

Y. Feng, X. Zhang, B. Cheung, Z. Liu, M. Isao, and M. Hayashi, “OCD study of critical dimension and line-shape control of shallow-trench-isolation structures,” Proc. SPIE 5375, 1173–1182 (2004).
[CrossRef]

Thin Solid Films (1)

H. T. Huang and F. L. Terry., “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455–456, 828–836 (2004).
[CrossRef]

Other (12)

V. C. Venugopal and A. J. Perry, “Method for in-situ monitoring of patterned substrate processing using reflectometry,” US patent 7019844.

M. Bass, Handbook of Optics, 3rd ed. (McGraw-Hill, 2009) Vol. 4.

K. C. Huang, “The study of high aspect ratio TSV metrology,” master thesis, National Tsing Hua University, 2010.

ITRS Metrology 2007 ed.2007.

ITRS Assembly & Packaging2009.

H. Singh, C. Rusu, and V. Vahedi, “Etch challenges for 3-D integration,” 3rd Workshop on Plasma Etch and Strip in Microelectronics 2010, Grenoble, France.

M. Puech, J. M. Thevenoud, J. M. Gruffat, N. Launay, N. Arnal, and P. Godinat, “Fabrication of 3D packaging TSV using DRIE,” Symposium on Design, Test, Integrate ion and Packaging of MEMS/MOEMS, 2008.

W. H. Teh, R. Caramto, J. Qureshi, S. Arkalgud, M. O’Brien, T. Gilday, K. Maekawa, T. Saito, K. Maruyama, T. Chidambaram, W. Wang, D. Marx, D. Grant, and R. Dudley, “A route towards production-worthy 5 μm x 25 μm and 1 μm x 20 μm non-Bosch through-silicon-via (TSV) etch, TSV metrology, and TSV integration,” IEEE 3DIC Conference, 2009.

F. Liu, R. R. Yu, A. M. Young, J. P. Doyle, X. Wang, L. Shi, K.-N. Chen, X. Li, D. A. Dipaola, D. Brown, C. T. Ryan, J. A. Hagan, K. H. Wong, M. Lu, X. Gu, N. R. Klymko, E. D. Perfecto, A. G. Merryman, K. A. Kelly, S. Purushothaman, S. J. Koester, R. Wisnieff, and W. Haensch, “A 300-mm wafer-level three-dimensional integration scheme using tungsten through-silicon via and hybrid Cu-adhesive bonding,” Proc. International Electron Devices Meeting (IEDM) (2008) p. 599.

M. Puech, J. M. Thevenoud, and J. M. Gruffat, “DRIE for MEMS devices,” Advanced Packaging, 2008.

D. Marx, D. Grant, R. Dudley, A. Rudack, and W. H. Teh, “Wafer thickness sensor (WTS) for etch depth measurement of TSV,” IEEE International Conference on 3D System Integration, 2009.

M. Knowles, “Optical metrology for TSV process control,” 3D Interconnect Metrology at SEMATECH Workshop during SEMICON West 2009.

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Figures (12)

Fig. 1
Fig. 1

(a) Schematic of light normal incidence into TSV sample surface (b) Schematic of measurable slope of 2.0° (c) Modeled reflectance spectrum for via depth 50.0 um with measurable slope of 2.0° compared to the one with normal incidence.

Fig. 2
Fig. 2

Simulation of via bottom roughness effect. The root mean square roughness is modeled from 0 to 100 nm.

Fig. 3
Fig. 3

Theoretical modeling of reflectance spectrum for via depth 50.0 and 51.0 μm. The combined spectrum shows interference between two oscillations, perceived as periodic variations in amplitude.

Fig. 4
Fig. 4

Theoretical modeling of reflectance spectrum for via depth 50.0 with 0.6 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. 5
Fig. 5

Theoretical modeling of combined reflectance spectrum of via depth 50.0 and 51.0 μm. The DFT spectrum of via depth 50.0 μm is well separated with the one of 51.0 μm.

Fig. 6
Fig. 6

Theoretical modeling of high freq. term of reflectance spectrum of via depth 50.0 with 0.6 μm oxide on top of it. The DFT spectrum shows three optical depth of 48.2 μm, 49.1 μm and 50.0 μm which corresponding to d-2*doxide , d-doxide and d.

Fig. 7
Fig. 7

(a) Top view of HDTSV sample shows current spot size just about covers five to nine vias in one shot. (b) The cross section SEM done for one site cut measurement.

Fig. 8
Fig. 8

(a) Model fitting to the reflectance spectrum of high aspect ratio HDTSV array structure with via CD 5 μm/pitch 10 μm. The fitting results reveal the bottom roughness is around 110 nm and via depth is around 65.08 μm. (b) Cross section SEM result of via bottom surface roughness in a range of tens to hundred nm.

Fig. 9
Fig. 9

(a). The extracted high frequency data from Fig. 8(a). (b) The DFT result shows the corresponding via depths of 64.04, 65.08, 65.70, 66.13 and 66.56 μm respectively. The via depth uniformity is 4.5% (3σ) within the illumination area.

Fig. 10
Fig. 10

The major five depths of each site are consistent in continuous three times measurement although there are some amplitudes difference and peak broadening situations. The via depth variations are 4.5% (3σ), 4.4% (3σ) and 3.4% (3σ) respectively of site a, b and c.

Fig. 11
Fig. 11

Upper left: Cross sections SEM result of top oxide layer. Bottom left: cross section SEM result of deep via array structure. Bottom right: top view of HDTSV sample with nominal CD 5 μm, pitch 10 μm, illumination spot is around 30 μm.

Fig. 12
Fig. 12

(a): Experimental spectrum from an HDTSV array structure with a thin oxide hard mask on top of it. The low and high frequency oscillations were extracted using a spectrum processing algorithmy. (b) The low frequency oscillations show an excellent theoretical model fit to the reflectance spectra and its associated hard mask thicknesses at 596 nm. (c) The high frequency oscillation features were analyzed by DFT algorithm to extract multiple via depths within one shot measurement. (d) The DFT result shows six discrete via depths d of 36.27, 36.70, 38.00, 38.55, 39.86 and 41.28 μm respectively. Some via depths signal of d-2doxide and d-doxide are also obtained. The optical thickness of oxide film doxide is 0.87 μm ( = 1.46*0.596 μm).

Tables (1)

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Table 1 Effective Illumination Area Radius and the Corresponding Aspect Ratio/Depth of 5 um CD via

Equations (11)

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I ¯ = C o n s t | α E 0 2 + ( 1 α ) E 0 2 + 2 α ( 1 α ) E 0 2 cos ( 2 π ( 2 d / λ ) ) |
I ¯ = C o n s t | α ( r S i + E 0 ) 2 + ( 1 α ) ( r S i + E 0 ) 2 + 2 α ( 1 α ) ( r S i + E 0 ) 2 cos ( 2 π ( 2 d / λ ) ) |
f = B o t t o m I l l u . a r e a T o p C D . a r e a = ( 2 R T o p   C D ) 2 = ( M a x   m e a s u r a b l e   d e p t h v i a   d e p t h M a x   m e a s u r a b l e   d e p t h ) 2
I ¯ = C o n s t | α ( r S i + E 0 ) 2 + f ( 1 α ) ( r S i + E 0 ) 2 + 2 α f ( 1 α ) ( r S i + E 0 ) 2 cos ( 2 π ( 2 d / λ ) ) |
R s = R 0 exp [ ( 4 σ π ) 2 / λ 2 ]
I ¯ = C o n s t | α ( r S i + E 0 ) 2 + f ( 1 α ) e x p [   ( 4 σ π ) 2 / λ 2 ] ( r S i + E 0 ) 2 + 2 α f ( 1 α ) e x p [   ( 4 σ π ) 2 / λ 2 ] ( r S i + E 0 ) 2 cos ( 2 π ( 2 d / λ ) ) |
E f i l m = α E 0 r f i l m = α E 0 ( r 12 + t 12 r 23 t 21 e i 2 ( 2 π d o x i d e λ ) 1 r 21 r 23 e i 2 ( 2 π d o x i d e λ ) )
E v i a = f ( 1 α ) e x p [   ( 4 σ π ) 2 / λ 2 ] E 0 r s i + e i 2 π ( 2 d λ )
T M U = ( Presion ) 2 + ( D e t e c t o r r e s o l u t i o n ) 2 + ( D F T r e s o l u t i o n ) 2
Δ d = m Δ λ 2 = d Δ λ λ
Δ D = 1 2 N * Δ ( 1 λ )

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