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Simulation of the Si-CCD irradiated by millisecond pulse laser
Optik 131 (2017) 67–71
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.de/ijleo
Original research article
Simulation of the Si-CCD irradiated by millisecond pulse laser Mingxin Li, Guangyong Jin ∗ , Yong Tan School of Science, Changchun University of Science and Technology, Jilin Key Laboratory of Solid-State Laser Technology and Application, Changchun, 130022, China
a r t i c l e
i n f o
Article history: Received 26 May 2016 Received in revised form 1 July 2016 Accepted 7 November 2016 PACS: 42.62.-b 44.10.+I 85.60.Gz Keywords: Millisecond pulse laser Thermal-stress coupling model Thermal damage Stress damage
a b s t r a c t Based on the Fourier heat conduction equation and the thermoelastic equation, the thermalstress coupling model of the Si-CCD irradiated by millisecond pulse laser was established, the time-space distribution of the temperature field and the stress field on the Si-CCD was calculated. The results show that: the damage firstly occurred in the color filter layer; increased the laser energy density, part of the microlens and the color filters were missing; then continued to increase the laser energy density, the photosensitive area in the N-Si layer was melting; when the channels in the N-Si layer were damaged, the Si-CCD was under functional loss. In this paper, the simulation results were consistent with the experiment results. © 2016 Elsevier GmbH. All rights reserved.
1. Introduction Since 1990s, native and foreign experts and scholars have carried out a lot of research on the performance degradation and the permanent failure of the Si-CCD. The experimental results are rich and varied, but the theoretical results are not enough. The existing models are shown as follows: the thermal-stress coupling model of the Si-CCD irradiated by nanosecond pulse laser [1], the thermal model of the MOS array irradiated by short pulse laser [2], the thermal-stress coupling model of the MOS pixel irradiated by millisecond pulse laser [3,4], the thermal-stress coupling model of the shielding aluminum film irradiated by mixed frequency laser [5–7], the thermal model of the silicon substrate irradiated by nanosecond pulse laser [8,9], and the thermal-stress coupling model of the silicon substrate irradiated by continuous laser [10,11]. The millisecond pulse laser had the advantages of the high peak power and the difficulty in producing a plasma-shielding phenomenon. In this paper, the simulation of the Si-CCD irradiated by millisecond pulse laser was studied, and the time-space distribution of the temperature field and the stress field on the Si-CCD under different laser energy densities were calculated, providing the theoretical support for laser damage and laser protection. 2. Simulation method Since the laser has focused on the photosensitive area by the microlens layer, the vertical CCD was shading theoretically. Even if the laser irradiated the vertical CCD, the shading structure protected the vertical CCD from the laser. Therefore,
∗ Corresponding author. E-mail address: [email protected] (G. Jin). http://dx.doi.org/10.1016/j.ijleo.2016.11.045 0030-4026/© 2016 Elsevier GmbH. All rights reserved.
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M. Li et al. / Optik 131 (2017) 67–71
Fig. 1. The sectional structure diagram of the Si-CCD.
the geometric model of the Si-CCD is simplified as follows: the length and width of the Si-CCD are 4.8 mm and 3.6 mm respectively; the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer’s thickness are 2 m, 5.5 m, 3 m and 570 m respectively. The sectional structure diagram of the Si-CCD is shown in Fig. 1. The thermal-stress coupling model of the Si-CCD irradiated by millisecond pulse laser is established and the following assumptions are made: the initial temperature is 300 K; the interface of any two layers meets the continuous conditions of heat flow and temperature; the adiabatic condition and the free boundary condition are applied to all boundaries; the Si-CCD is an absolute elastic body(the stress-strain relation of the material is applied to Hooke’s law). When the Si-CCD is irradiated by millisecond pulse laser, the expression of the Fourier transient heat conduction equation is as follows: j cj
∂Tj (x, y, z, t) ∂ ∂Tj (x, y, z, t) ∂fsj − ) = j cj Lj + Qj (kj ∂t ∂i ∂t ∂i
(i = x, y, z)
(1)
i
In the formula, Tj (x, y, z, t) represents the time-space distribution of the temperature in the j layer, j , cj , kj , Lj , fsj and Qj represent the density, the specific heat capacity, the thermal conductivity, the latent heat, the solid fraction and the heat source in the j layer respectively.The expression of the heat source can be described as: Qj = 0.678 ∗ I0 ∗ Aj ∗ ˛j ∗ e
−
(x2 +y2 ) 2∗r 2
∗ e−˛j z
(2)
In the formula, 0.678 is the transmission of the K9 optical window under 1064 nm laser, I0 is the central power density of the laser, Aj and ˛j represent the absorption rate and the absorption coefficient in the j layer respectively, r is the spot radius of the laser. The thermoelastic equations, coupled with the heat conduction equation, are as follows: 2 uxj +
∂εj ∂Tj (x, y, z, t) 2(1 + j ) 1 ˇj − = 0 1 − 2j ∂x 1 − j ∂x
(3)
2 uyj +
∂εj ∂Tj (x, y, z, t) 2(1 + j ) 1 ˇj − = 0 1 − 2j ∂y 1 − j ∂y
(4)
2 uzj +
∂εj ∂Tj (x, y, z, t) 2(1 + j ) 1 ˇj − = 0 1 − 2j ∂z 1 − j ∂z
(5)
In the formula, uxj , uyj and uzj represent the displacements on the x, y and z directions in the j layer respectively, εj , j and ˇj represent the volume strain, the Poisson’s ratio and the thermal expansion coefficient in the j layer respectively. The physical parameters of each layer on the Si-CCD are as follows: the melting point of the microlens layer is 513 K, the melting and boiling points of the color filter layer are 429 K and 693 K respectively, the melting point of the silicon nitride layer is 2173 K, the melting and boiling points of the N-Si layer are 1687 K and 2628 K respectively. In addition, the material parameters of each layer have nonlinear properties, including the thermal conductivity, the density, the specific heat capacity, the absorption rate, the absorption coefficient, the Poisson’s ratio, the thermal expansion coefficient and the Young’s modulus. 3. Results and analysis 3.1. Analysis of the temperature field The relationship between the temperature of the central point on the Si-CCD and the depth direction under different energy densities was as shown in Fig. 2, and Fig. 2(b) was the partial enlarged detail of Fig. 2(a). The microlens layer, the color filter layer and the silicon nitride layer’s maximum temperature rise appeared in the upper surface, the maximum
M. Li et al. / Optik 131 (2017) 67–71
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Fig. 2. The relationship between the temperature of the central point on the Si-CCD and the depth direction under different energy densities.
Fig. 3. The relationship between the temperature of the central point on the N-Si layer and the time under different energy densities.
temperature rise of the N-Si layer appeared in the lower surface. With the energy density of 3.98 J/cm2 , the maximum temperature rise of the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer were 309.7 K, 511.7 K, 511.8 K and 511.8 K respectively. The microlens was relatively intact; the color filters melted and solidified, leading to the damage on the color filter layer. With the energy density of 15.92 J/cm2 , the maximum temperature rise of the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer were 359.4 K, 1167.5 K, 1167.8 K and 1167.8 K respectively. The color filters reached the boiling point, due to the recoil pressure caused by the splash phenomenon, part of the microlens and the color filters were missing. With the energy density of 27.86 J/cm2 , the maximum temperature rise of the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer were 409 K, 1823.2 K, 1823.8 K and 1823.8 K respectively. Part of the microlens and the color filters were missing, the photosensitive area in the N-Si layer was melting, and the Si-CCD was unable to convert all the optical signals into the electrical signals. With the energy density of 39.8 J/cm2 , the maximum temperature rise of the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer were 458.7 K, 2479 K, 2479.8 K and 2479.8 K respectively. The central part of the Si-CCD appeared deep damage due to the thermal effect and the stress effect, thus, part of the microlens, the color filters and the silicon nitride were missing. The damage depth of the N-Si layer was up to 100 m, the channels in the N-Si layer were damaged, and the Si-CCD was under functional loss condition [12]. Fig. 3 showed the relationship between the temperature of the central point on the N-Si layer and the time under different energy densities. The laser energy densities were 3.98 J/cm2 , 15.92 J/cm2 , 27.86 J/cm2 and 39.8 J/cm2 respectively, the maximum temperature rises were 511.8 K, 1167.8 K, 1823.8 K and 2479.8 K respectively. With the increase of the laser energy density, the maximum temperature rise of the N-Si layer was also increased. With the maximum temperature rise exceeded the melting point, the N-Si layer appeared morphology damage.
3.2. Analysis of the stress field With the energy density of 15.92 J/cm2 , the local stress distribution of the Si-CCD was as shown in Fig. 4. From this figure, we could see that the maximum stress value appeared in the interface between the color filter layer and the silicon nitride layer. The relationship between the radial stress of the central point on the Si-CCD and the depth direction under different energy densities was as shown in Fig. 5, and Fig. 5(b) was the partial enlarged detail of Fig. 5(a). The tensile stress and the compressive stress alternated with each other of the two layers, the adhesive strength of the two layers decreased due to the drastic changes on the radial stress. The Si-CCD occurred layer crack, part of the microlens and the color filters were
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M. Li et al. / Optik 131 (2017) 67–71
Fig. 4. With the energy density of 15.92 J/cm2 , the local stress distribution of the Si-CCD.
Fig. 5. The relationship between the radial stress of the central point on the Si-CCD and the depth direction under different energy densities.
Fig. 6. The experimental system of millisecond pulse laser irradiating the CCD detector.
missing. With the increase of the laser energy density, the maximum compressive stress of the Si-CCD increased, the area of the layer crack increased.
3.3. Error analysis between experiment and simulation Fig. 6 showed the experimental system of millisecond pulse laser irradiating the CCD detector, the CCD detector was an ICX405AK-type CCD detector. The laser source was a 1064 nm Q-switched Nd:YAG laser operating at a repetition rate of 10 Hz, the laser went through the energy attenuator and the beam splitter. The reflecting part was detected by the energy meter, and the transmitting part was focused by the converging lens. The position of the CCD detector was adjusted by one-dimensional translation table, and the laser beam was irradiated to the surface of the CCD detector. In addition, laser and point-thermometer triggered at the same time by DG645 synchronous trigger element [12]. We used different laser conditions to irradiate the CCD detector, the experimental and simulation results of the maximum temperature rise on the CCD detector were listed in Table 1. When the laser went through the K9 optical window, the reflection and refraction phenomena occurred. The K9 optical window had an influence on the accuracy of the point thermometer, the actual position and the laser spot had some deflection, so the range of error was from tens of K to several hundred K.
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71
Table 1 The experimental and simulation results of the maximum temperature rise on the CCD detector. No.
Energy
Pulse width
Spot radius
Experimental temperature
Simulation temperature
Error
1 2 3 4 5 6
4.07 J 4.47 J 6.35 J 6.8 J 8.33 J 7.07 J
1 ms 1 ms 1.5 ms 1.5 ms 2 ms 2.5 ms
2 mm 2 mm 2.5 mm 2.5 mm 2 mm 2 mm
1766 K 2012 K 1825 K 2015 K 3766 K 2813 K
1926 K 2090 K 1728 K 1967 K 3218 K 2570 K
160 K 78 K 97 K 48 K 548 K 243 K
4. Conclusion In summary, the damage on the Si-CCD under a millisecond long pulse laser included two aspects: the thermal damage and the stress damage. The damage firstly occurred in the color filter layer; increased the laser energy density, the color filters reached the boiling point and splashing, part of the microlens and the color filters were missing by the recoil pressure; then continued to increase the laser energy density, part of the microlens and the color filters were missing, the photosensitive area in the N-Si layer was melting, and the Si-CCD was unable to convert all the optical signals into the electrical signals; when the channels in the N-Si layer were damaged, the Si-CCD was under functional loss. The maximum stress value appeared in the interface between the color filter layer and the silicon nitride layer, the adhesive strength of the two layers decreased due to the drastic changes on the radial stress. The Si-CCD occurred layer crack, part of the microlens and the color filters were missing. With the increase of the laser energy density, the maximum compressive stress of the Si-CCD increased, the area of the layer crack increased. In this paper, the simulation results were consistent with the experimental results. Funding Natural Science Foundation of Jilin Province (Grant No. 61405017). Acknowledgment We thank the Jilin key laboratory of solid-state laser technology and application for the use of their equipment. References [1] N. Jiang, C. Zhang, Y.X. Niu, X.J. Shen, H.L. Yang, Y. Chen, L. Wang, B. Zhang, Numerical simulation of pulsed laser induced damage on CCD arrays, Laser Infrared 38 (2008) 1004–1007. [2] M. Wu, X.Y. Li, C.H. Niu, Y. Lv, Thermal effect simulation of CCD detector under single-laser-pulse irradiation, Laser J. 35 (2014) 78–81. [3] B. Peng, Study on the Thermal Stress of Millisecond Pulsed Laser Irradiation CCD Image Detectors, Changchun University of Science and Technology, Chang Chun, 2014 (M. A. Dissertation). [4] J. Bi, X.H. Zhang, X.W. Ni, Mechanism for long pulse laser-induced hard damage to the MOS pixel of CCD image sensor, Acta Phys. Sin. 60 (2011) 114–210. [5] Q. Zhang, Y.F. Wang, Y.D. Han, M.J. Huang, W. Dong, X.T. Duan, W.W. Jia, Z.Y. Yin, Damage effect of mixture frequency laser to CCD detectors, Electro Opt. Technol. Appl. 25 (2010) 4–8. [6] Q. Zhang, Y.F. Wang, Y.D. Han, M.J. Huang, W. Dong, X.T. Duan, W.W. Jia, Z.Y. Yin, Simulation of mixture frequency laser irradiation on CCD detectors, Semicond. Optoelectron. 31 (2010) 787–792. [7] G. Li, H.B. Shen, L. Li, C. Zhang, S.J. Mao, Y.B. Wang, Laser-induced damages to charge coupled device detector using a high-repetition-rate and high-peak-power laser, Opt. Laser Technol. 47 (2013) 221–227. [8] J. Xu, S.H. Zhao, R. Hou, S.B. Zhan, Y.X. Li, J.L. Wu, Researches on high power laser jamming effect on typical laser guiding photoelectric detectors, Opt. Tech. 34 (2008) 80–82. [9] J. Xu, S.H. Zhao, R. Hou, X.L. Li, J.L. Wu, Y.X. Li, W. Meng, Y.H. Ni, L.H. Ma, Laser-jamming analysis of combined fiber lasers to imaging CCD, Opt. Lasers Eng. 47 (2009) 800–806. [10] J. Li, Z.H. Chen, Study of thermal and mechanical damage in Si-CCD induced by laser, Electron. Sci. Technol. 24 (2011) 122–124. [11] J.S. Nie, X. Wang, H. Li, J.T. Bian, X.N. Hao, Thermal and mechanical damage in CCD detector induced by 1.06 m laser, Infrared Laser Eng. 42 (2013) 380–386. [12] M.X. Li, G.Y. Jin, Y. Tan, Study on the mechanism of a charge-coupled device detector irradiated by millisecond pulse laser under functional loss, Appl. Opt. 55 (2016) 1257–1261.
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.de/ijleo
Original research article
Simulation of the Si-CCD irradiated by millisecond pulse laser Mingxin Li, Guangyong Jin ∗ , Yong Tan School of Science, Changchun University of Science and Technology, Jilin Key Laboratory of Solid-State Laser Technology and Application, Changchun, 130022, China
a r t i c l e
i n f o
Article history: Received 26 May 2016 Received in revised form 1 July 2016 Accepted 7 November 2016 PACS: 42.62.-b 44.10.+I 85.60.Gz Keywords: Millisecond pulse laser Thermal-stress coupling model Thermal damage Stress damage
a b s t r a c t Based on the Fourier heat conduction equation and the thermoelastic equation, the thermalstress coupling model of the Si-CCD irradiated by millisecond pulse laser was established, the time-space distribution of the temperature field and the stress field on the Si-CCD was calculated. The results show that: the damage firstly occurred in the color filter layer; increased the laser energy density, part of the microlens and the color filters were missing; then continued to increase the laser energy density, the photosensitive area in the N-Si layer was melting; when the channels in the N-Si layer were damaged, the Si-CCD was under functional loss. In this paper, the simulation results were consistent with the experiment results. © 2016 Elsevier GmbH. All rights reserved.
1. Introduction Since 1990s, native and foreign experts and scholars have carried out a lot of research on the performance degradation and the permanent failure of the Si-CCD. The experimental results are rich and varied, but the theoretical results are not enough. The existing models are shown as follows: the thermal-stress coupling model of the Si-CCD irradiated by nanosecond pulse laser [1], the thermal model of the MOS array irradiated by short pulse laser [2], the thermal-stress coupling model of the MOS pixel irradiated by millisecond pulse laser [3,4], the thermal-stress coupling model of the shielding aluminum film irradiated by mixed frequency laser [5–7], the thermal model of the silicon substrate irradiated by nanosecond pulse laser [8,9], and the thermal-stress coupling model of the silicon substrate irradiated by continuous laser [10,11]. The millisecond pulse laser had the advantages of the high peak power and the difficulty in producing a plasma-shielding phenomenon. In this paper, the simulation of the Si-CCD irradiated by millisecond pulse laser was studied, and the time-space distribution of the temperature field and the stress field on the Si-CCD under different laser energy densities were calculated, providing the theoretical support for laser damage and laser protection. 2. Simulation method Since the laser has focused on the photosensitive area by the microlens layer, the vertical CCD was shading theoretically. Even if the laser irradiated the vertical CCD, the shading structure protected the vertical CCD from the laser. Therefore,
∗ Corresponding author. E-mail address: [email protected] (G. Jin). http://dx.doi.org/10.1016/j.ijleo.2016.11.045 0030-4026/© 2016 Elsevier GmbH. All rights reserved.
68
M. Li et al. / Optik 131 (2017) 67–71
Fig. 1. The sectional structure diagram of the Si-CCD.
the geometric model of the Si-CCD is simplified as follows: the length and width of the Si-CCD are 4.8 mm and 3.6 mm respectively; the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer’s thickness are 2 m, 5.5 m, 3 m and 570 m respectively. The sectional structure diagram of the Si-CCD is shown in Fig. 1. The thermal-stress coupling model of the Si-CCD irradiated by millisecond pulse laser is established and the following assumptions are made: the initial temperature is 300 K; the interface of any two layers meets the continuous conditions of heat flow and temperature; the adiabatic condition and the free boundary condition are applied to all boundaries; the Si-CCD is an absolute elastic body(the stress-strain relation of the material is applied to Hooke’s law). When the Si-CCD is irradiated by millisecond pulse laser, the expression of the Fourier transient heat conduction equation is as follows: j cj
∂Tj (x, y, z, t) ∂ ∂Tj (x, y, z, t) ∂fsj − ) = j cj Lj + Qj (kj ∂t ∂i ∂t ∂i
(i = x, y, z)
(1)
i
In the formula, Tj (x, y, z, t) represents the time-space distribution of the temperature in the j layer, j , cj , kj , Lj , fsj and Qj represent the density, the specific heat capacity, the thermal conductivity, the latent heat, the solid fraction and the heat source in the j layer respectively.The expression of the heat source can be described as: Qj = 0.678 ∗ I0 ∗ Aj ∗ ˛j ∗ e
−
(x2 +y2 ) 2∗r 2
∗ e−˛j z
(2)
In the formula, 0.678 is the transmission of the K9 optical window under 1064 nm laser, I0 is the central power density of the laser, Aj and ˛j represent the absorption rate and the absorption coefficient in the j layer respectively, r is the spot radius of the laser. The thermoelastic equations, coupled with the heat conduction equation, are as follows: 2 uxj +
∂εj ∂Tj (x, y, z, t) 2(1 + j ) 1 ˇj − = 0 1 − 2j ∂x 1 − j ∂x
(3)
2 uyj +
∂εj ∂Tj (x, y, z, t) 2(1 + j ) 1 ˇj − = 0 1 − 2j ∂y 1 − j ∂y
(4)
2 uzj +
∂εj ∂Tj (x, y, z, t) 2(1 + j ) 1 ˇj − = 0 1 − 2j ∂z 1 − j ∂z
(5)
In the formula, uxj , uyj and uzj represent the displacements on the x, y and z directions in the j layer respectively, εj , j and ˇj represent the volume strain, the Poisson’s ratio and the thermal expansion coefficient in the j layer respectively. The physical parameters of each layer on the Si-CCD are as follows: the melting point of the microlens layer is 513 K, the melting and boiling points of the color filter layer are 429 K and 693 K respectively, the melting point of the silicon nitride layer is 2173 K, the melting and boiling points of the N-Si layer are 1687 K and 2628 K respectively. In addition, the material parameters of each layer have nonlinear properties, including the thermal conductivity, the density, the specific heat capacity, the absorption rate, the absorption coefficient, the Poisson’s ratio, the thermal expansion coefficient and the Young’s modulus. 3. Results and analysis 3.1. Analysis of the temperature field The relationship between the temperature of the central point on the Si-CCD and the depth direction under different energy densities was as shown in Fig. 2, and Fig. 2(b) was the partial enlarged detail of Fig. 2(a). The microlens layer, the color filter layer and the silicon nitride layer’s maximum temperature rise appeared in the upper surface, the maximum
M. Li et al. / Optik 131 (2017) 67–71
69
Fig. 2. The relationship between the temperature of the central point on the Si-CCD and the depth direction under different energy densities.
Fig. 3. The relationship between the temperature of the central point on the N-Si layer and the time under different energy densities.
temperature rise of the N-Si layer appeared in the lower surface. With the energy density of 3.98 J/cm2 , the maximum temperature rise of the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer were 309.7 K, 511.7 K, 511.8 K and 511.8 K respectively. The microlens was relatively intact; the color filters melted and solidified, leading to the damage on the color filter layer. With the energy density of 15.92 J/cm2 , the maximum temperature rise of the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer were 359.4 K, 1167.5 K, 1167.8 K and 1167.8 K respectively. The color filters reached the boiling point, due to the recoil pressure caused by the splash phenomenon, part of the microlens and the color filters were missing. With the energy density of 27.86 J/cm2 , the maximum temperature rise of the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer were 409 K, 1823.2 K, 1823.8 K and 1823.8 K respectively. Part of the microlens and the color filters were missing, the photosensitive area in the N-Si layer was melting, and the Si-CCD was unable to convert all the optical signals into the electrical signals. With the energy density of 39.8 J/cm2 , the maximum temperature rise of the microlens layer, the color filter layer, the silicon nitride layer and the N-Si layer were 458.7 K, 2479 K, 2479.8 K and 2479.8 K respectively. The central part of the Si-CCD appeared deep damage due to the thermal effect and the stress effect, thus, part of the microlens, the color filters and the silicon nitride were missing. The damage depth of the N-Si layer was up to 100 m, the channels in the N-Si layer were damaged, and the Si-CCD was under functional loss condition [12]. Fig. 3 showed the relationship between the temperature of the central point on the N-Si layer and the time under different energy densities. The laser energy densities were 3.98 J/cm2 , 15.92 J/cm2 , 27.86 J/cm2 and 39.8 J/cm2 respectively, the maximum temperature rises were 511.8 K, 1167.8 K, 1823.8 K and 2479.8 K respectively. With the increase of the laser energy density, the maximum temperature rise of the N-Si layer was also increased. With the maximum temperature rise exceeded the melting point, the N-Si layer appeared morphology damage.
3.2. Analysis of the stress field With the energy density of 15.92 J/cm2 , the local stress distribution of the Si-CCD was as shown in Fig. 4. From this figure, we could see that the maximum stress value appeared in the interface between the color filter layer and the silicon nitride layer. The relationship between the radial stress of the central point on the Si-CCD and the depth direction under different energy densities was as shown in Fig. 5, and Fig. 5(b) was the partial enlarged detail of Fig. 5(a). The tensile stress and the compressive stress alternated with each other of the two layers, the adhesive strength of the two layers decreased due to the drastic changes on the radial stress. The Si-CCD occurred layer crack, part of the microlens and the color filters were
70
M. Li et al. / Optik 131 (2017) 67–71
Fig. 4. With the energy density of 15.92 J/cm2 , the local stress distribution of the Si-CCD.
Fig. 5. The relationship between the radial stress of the central point on the Si-CCD and the depth direction under different energy densities.
Fig. 6. The experimental system of millisecond pulse laser irradiating the CCD detector.
missing. With the increase of the laser energy density, the maximum compressive stress of the Si-CCD increased, the area of the layer crack increased.
3.3. Error analysis between experiment and simulation Fig. 6 showed the experimental system of millisecond pulse laser irradiating the CCD detector, the CCD detector was an ICX405AK-type CCD detector. The laser source was a 1064 nm Q-switched Nd:YAG laser operating at a repetition rate of 10 Hz, the laser went through the energy attenuator and the beam splitter. The reflecting part was detected by the energy meter, and the transmitting part was focused by the converging lens. The position of the CCD detector was adjusted by one-dimensional translation table, and the laser beam was irradiated to the surface of the CCD detector. In addition, laser and point-thermometer triggered at the same time by DG645 synchronous trigger element [12]. We used different laser conditions to irradiate the CCD detector, the experimental and simulation results of the maximum temperature rise on the CCD detector were listed in Table 1. When the laser went through the K9 optical window, the reflection and refraction phenomena occurred. The K9 optical window had an influence on the accuracy of the point thermometer, the actual position and the laser spot had some deflection, so the range of error was from tens of K to several hundred K.
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Table 1 The experimental and simulation results of the maximum temperature rise on the CCD detector. No.
Energy
Pulse width
Spot radius
Experimental temperature
Simulation temperature
Error
1 2 3 4 5 6
4.07 J 4.47 J 6.35 J 6.8 J 8.33 J 7.07 J
1 ms 1 ms 1.5 ms 1.5 ms 2 ms 2.5 ms
2 mm 2 mm 2.5 mm 2.5 mm 2 mm 2 mm
1766 K 2012 K 1825 K 2015 K 3766 K 2813 K
1926 K 2090 K 1728 K 1967 K 3218 K 2570 K
160 K 78 K 97 K 48 K 548 K 243 K
4. Conclusion In summary, the damage on the Si-CCD under a millisecond long pulse laser included two aspects: the thermal damage and the stress damage. The damage firstly occurred in the color filter layer; increased the laser energy density, the color filters reached the boiling point and splashing, part of the microlens and the color filters were missing by the recoil pressure; then continued to increase the laser energy density, part of the microlens and the color filters were missing, the photosensitive area in the N-Si layer was melting, and the Si-CCD was unable to convert all the optical signals into the electrical signals; when the channels in the N-Si layer were damaged, the Si-CCD was under functional loss. The maximum stress value appeared in the interface between the color filter layer and the silicon nitride layer, the adhesive strength of the two layers decreased due to the drastic changes on the radial stress. The Si-CCD occurred layer crack, part of the microlens and the color filters were missing. With the increase of the laser energy density, the maximum compressive stress of the Si-CCD increased, the area of the layer crack increased. In this paper, the simulation results were consistent with the experimental results. Funding Natural Science Foundation of Jilin Province (Grant No. 61405017). Acknowledgment We thank the Jilin key laboratory of solid-state laser technology and application for the use of their equipment. References [1] N. Jiang, C. Zhang, Y.X. Niu, X.J. Shen, H.L. Yang, Y. Chen, L. Wang, B. Zhang, Numerical simulation of pulsed laser induced damage on CCD arrays, Laser Infrared 38 (2008) 1004–1007. [2] M. Wu, X.Y. Li, C.H. Niu, Y. Lv, Thermal effect simulation of CCD detector under single-laser-pulse irradiation, Laser J. 35 (2014) 78–81. [3] B. Peng, Study on the Thermal Stress of Millisecond Pulsed Laser Irradiation CCD Image Detectors, Changchun University of Science and Technology, Chang Chun, 2014 (M. A. Dissertation). [4] J. Bi, X.H. Zhang, X.W. Ni, Mechanism for long pulse laser-induced hard damage to the MOS pixel of CCD image sensor, Acta Phys. Sin. 60 (2011) 114–210. [5] Q. Zhang, Y.F. Wang, Y.D. Han, M.J. Huang, W. Dong, X.T. Duan, W.W. Jia, Z.Y. Yin, Damage effect of mixture frequency laser to CCD detectors, Electro Opt. Technol. Appl. 25 (2010) 4–8. [6] Q. Zhang, Y.F. Wang, Y.D. Han, M.J. Huang, W. Dong, X.T. Duan, W.W. Jia, Z.Y. Yin, Simulation of mixture frequency laser irradiation on CCD detectors, Semicond. Optoelectron. 31 (2010) 787–792. [7] G. Li, H.B. Shen, L. Li, C. Zhang, S.J. Mao, Y.B. Wang, Laser-induced damages to charge coupled device detector using a high-repetition-rate and high-peak-power laser, Opt. Laser Technol. 47 (2013) 221–227. [8] J. Xu, S.H. Zhao, R. Hou, S.B. Zhan, Y.X. Li, J.L. Wu, Researches on high power laser jamming effect on typical laser guiding photoelectric detectors, Opt. Tech. 34 (2008) 80–82. [9] J. Xu, S.H. Zhao, R. Hou, X.L. Li, J.L. Wu, Y.X. Li, W. Meng, Y.H. Ni, L.H. Ma, Laser-jamming analysis of combined fiber lasers to imaging CCD, Opt. Lasers Eng. 47 (2009) 800–806. [10] J. Li, Z.H. Chen, Study of thermal and mechanical damage in Si-CCD induced by laser, Electron. Sci. Technol. 24 (2011) 122–124. [11] J.S. Nie, X. Wang, H. Li, J.T. Bian, X.N. Hao, Thermal and mechanical damage in CCD detector induced by 1.06 m laser, Infrared Laser Eng. 42 (2013) 380–386. [12] M.X. Li, G.Y. Jin, Y. Tan, Study on the mechanism of a charge-coupled device detector irradiated by millisecond pulse laser under functional loss, Appl. Opt. 55 (2016) 1257–1261.