KR19990006168A - Photodiode and its manufacturing method - Google Patents

Abstract

The present invention provides a photodiode and a method of manufacturing the same, which can obtain a maximum antireflection film effect and a minimum pad capacity by simultaneously forming an antireflection film and a protective film as a double dielectric material film of a SiN film and a SiO ₂ film.

The photodiode according to the present invention comprises a first conductive buffer type, an absorbing layer, a window layer, a second conductive diffusion layer formed on a predetermined portion of the window layer, and a diffusion layer sequentially stacked on the first conductive compound semiconductor substrate. An ohmic contact layer patterned in a predetermined shape on both sides, a protective film formed of a first double dielectric material film on the window layers on both sides of the diffusion layer, and a second double dielectric material film formed on the diffusion layer between the ohmic contact layer. And an antireflection film and a pad formed on the protective film while being in contact with the ohmic contact layer. In addition, according to the method of manufacturing a photodiode according to the present invention, a protective film and an antireflection film are simultaneously formed of a double dielectric material film in which a SiN film and a SiO ₂ film are laminated.

Description

Photodiode and its manufacturing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light-receiving element and a method for manufacturing the same, and more particularly, to a photodiode having a protective film and an antireflective film made of a double dielectric material film, and a method for manufacturing the same.

A light receiving element is an element that receives an optical signal containing information and converts it into an electrical signal. InGaAs / InP photodiodes are particularly used for receiving light having a wavelength of 1.0 to 1.6 mu m, are essentially used at the receiver of the optical communication system, and are also used as the laser diode output monitor of the transmitter. It is also used as a detector for measuring instruments in the wavelength range of 1.0 to 1.6 mu m.

1 is a cross-sectional view showing a conventional photodiode. As shown in FIG. 1, an n ⁺ -InP buffer layer 2, an n-InGaAs (P) absorbing layer 3, and a u-InP window layer 4 are sequentially formed on an n ⁺ -InP substrate 1. do. A p ⁺ -InP diffusion layer 6 is formed on the u-InP window layer 4, and a u -InGaAs ohmic contact layer 5 is formed on both sides of the p ⁺ -InP diffusion layer 6. An antireflection film 7 made of a single dielectric material such as SiN or SiO ₂ is formed on the p ⁺ -InP diffusion layer 6 between the u-InGaAs ohmic contact layer 5, and the p ⁺ -InP diffusion layer 6 A protective film 8 made of a single dielectric material such as SiN or SiO ₂ is formed on both upper and u-InP window layers 4. In addition, a pad 9 in contact with the u-InGaAs ohmic contact layer 5 is formed on the protective film 8.

However, although the photodiode can obtain a sufficient antireflection film effect due to the antireflection film 7, the pad capacity is relatively large due to the formation of the pad 9 on the protective film 8, thereby degrading the characteristics of the photodiode. .

In contrast, conventionally, pads were formed only on the p ⁺ -InP diffusion layer to reduce pad capacity. 2 is a cross-sectional view of a conventional photodiode in which pads are formed only on top of a diffusion layer. As shown in FIG. 2, the n ⁺ -InP buffer layer 12, the n-InGaAs (P) absorbing light 13, and the u-InP window layer 14 are sequentially disposed on the n ⁺ -InP substrate 11. Is formed. A p ⁺ -InP diffusion layer 16 is formed on the u-InP window layer 14, and a u-InGaAs ohmic contact layer 15 is formed on an upper end of the p ⁺ -InP diffusion layer 16. On the exposed p ⁺ -InP diffusion layer 16 and the u-InP window layer 14, an antireflection film 17 and a protective film 18 made of a single dielectric material such as SiN or SiO ₂ are formed, respectively, and u-InGaAs The pad 19 which contacts the ohmic contact layer 15 is formed.

That is, in the conventional photodiode, a single dielectric material of an SiN film or a SiO ₂ film is used as an anti-reflective coating film and a protective film. Meanwhile, in the photodiode shown in FIG. 2, as the pad 19 is formed on the p ⁺ -InP diffusion layer 16, the capacity of the pad is reduced as compared with the case where the pad 19 is formed on the protective film as shown in FIG. There is only a dose increase. However, in this case, since the doping concentration of the n-InGaAs (P) absorbing layer 13 must be lowered, the pn junction during the wire bonding due to the low doping concentration of the n-InGaAs (P) absorbing layer 13 is affected by the impact of the bonding machine. It is easy to be damaged by

Accordingly, the present invention has been made in view of the above-mentioned problems, and a photodiode capable of simultaneously forming an antireflection film and a protective film using a double dielectric material film of a SiN film and a SiO ₂ film to obtain a maximum antireflection film effect and a minimum pad capacity; Its purpose is to provide a method for its manufacture.

1 and 2 are cross-sectional views showing a conventional photodiode.

3 is a cross-sectional view showing a photodiode according to an embodiment of the present invention.

4 is a graph showing the thickness of the SiO ₂ film having a minimum reflectance according to the thickness of the SiN film when the light receiving wavelength is 1.55 μm.

5 is a graph showing the change in reflectance according to the thickness of the SiN film in the thickness combination of the SiN / SiO ₂ film having the smallest reflectance when the light receiving wavelength is 1.55 μm.

FIG. 6 is a graph showing the change of pad capacitance different in the thickness of the SiN film in the thickness combination of the SiN / SiO ₂ film having the minimum reflectance when the light receiving wavelength is 1.55 μm. FIG.

7 is a graph showing the thickness of the SiO ₂ film having a minimum reflectance according to the thickness of the SiN film when the light receiving wavelength is 1.3 μm.

8 is a graph showing the change in reflectance according to the thickness of the SiN film in the thickness combination of the SiN / SiO ₂ film having the smallest reflectance when the light receiving wavelength is 1.3 μm.

9 is a graph showing a change in pad capacity according to the thickness of the SiN film in the thickness combination of the SiN / SiO ₂ film having the smallest reflectance when the light receiving wavelength is 1.3 μm.

Explanation of symbols for the main parts of the drawings

21: n ⁺ -InP substrate 22: n ⁺ -InP buffer layer

23: n-InGaAs (P) absorption layer 24: u-InP window layer

25: u-InGaAs ohmic contact layer 26: p ⁺ -InP diffusion layer

27a / 27b, 28a / 28b: SiN / SiO ₂

27: shield 28: anti-reflective

The photodiode according to the present invention for achieving the above object is a first conductive buffer layer, an absorbing layer, a window layer and a second conductive type formed on a predetermined portion of the window layer sequentially stacked on the first conductive compound semiconductor substrate A diffusion layer, an ohmic contact layer patterned in a predetermined shape on both sides of the diffusion layer, a protective film formed of a first double dielectric material film on the window layers on both sides of the diffusion layer, and a second double layer on the diffusion layer between the ohmic contact layer. An antireflection film formed of a dielectric material film and a pad formed on the passivation layer while contacting the ohmic contact layer are included.

In addition, the method of manufacturing a photodiode according to the present invention for achieving the above object is a first conductive buffer layer, an absorbing layer, a window layer are sequentially stacked on top, the second conductive diffusion layer formed on a predetermined portion of the window layer Providing a first conductive compound semiconductor substrate having an ohmic contact layer formed on the both sides of the diffusion layer and patterned in a predetermined shape; Simultaneously forming a protective film and an antireflection film made of a double dielectric material film on the diffusion layer between the window layer and the ohmic contact layer on both sides of the diffusion layer; And forming a pad in contact with the ohmic contact layer on the passivation layer.

In addition, the double dielectric material film is formed of a film in which a SiN film and a SiO ₂ film are sequentially stacked. When the optimal thickness of the SiN film and the SiO ₂ film is 1.55 µm, the thickness of the SiN film is 1,500 to 1,700 ,, and the SiO _{2, the} thickness of the film is 6,200 to 6,400 Å, the light receiving wavelength is 1.3 占 퐉, the thickness of the SiN film is 1,200 to 1,400 ,, and the thickness of the SiO ₂ film is 5,300 to 5,600 Å.

According to the present invention described above, in a photodiode having a predetermined light receiving wavelength, a double dielectric material film of SiN / SiO ₂ is optimally set according to the light receiving wavelength and is simultaneously formed as an antireflective film and a protective film, thereby having a minimum reflectance. In addition, it has a minimum pad capacity.

EXAMPLE

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention.

3 is a cross-sectional view for describing a method of manufacturing a photodiode according to an exemplary embodiment of the present invention.

As shown in FIG. 3, the n ⁺ -InP buffer layer 22, the n-InGaAs (P) absorbing light 23, and the u-InP window layer 24 are sequentially formed on the n ⁺ -InP substrate 21. Is formed. u-InP p ⁺ -InP diffusion layer 26 to the window layer 24 is formed, p ⁺ the upper side amounts to a u-InGaAs ohmic contact layer 25 is patterned into a predetermined form of -InP diffusion layer 26 is Is formed. A SiN / SiO ₂ double thin film in which a thin film of SiN 27a and SiO 2 27b is laminated, and a protective film 27 is formed on the u-InP window layer 4 on both sides of the p ⁺ -InP diffusion layer 26. At the same time, an antireflective film 28 is formed on the P ⁺ -InP diffusion layer 6 between the u-InGaAs ohmic contact layer 25. In addition, a pad 9 in contact with the u-InGaAs ohmic contact layer 25 is formed on the passivation layer 27.

In the present invention described above, the protective film 27 and the anti-reflective film 28 are formed of a SiN / SiO ₂ double thin film material, wherein the protective film 27 and the anti-reflective film 28 have optimal protective film properties and optimal anti-reflective film properties. In order to have, the proper thickness setting of the SiN film and the SiO ₂ film is important according to the light receiving wavelength. On the other hand, in order to calculate the optimum reflectance using the following equation for the multilayer thin film reflectance.

Reflectance (R) = | E ₃ ^- / E ₃ ⁺ | ² …. … … … … … … Formula (1-1)

Transmittance (T) = | E ₀ ⁺ / E ₃ ⁺ | ² x n ₀ / n ₃ . … … Formula (1-2)

In this case, it is assumed that the incidence angle is perpendicular to the light-receiving surface, and in Equation (1-1) and Equation (1-2), E ₃ ⁺ is the incident energy of SiN / SiO _{2 into} the thin film material and InP layer from air. , E ₃ ⁻ is the reflected energy, and E ₀ ⁺ is energy passing through the double thin film material of SiN / SiO ₂ from the air, and its value is set according to the refractive index of the double thin film material of SiN / SiO ₂ . The refractive index (n ₀ ) of the InP layer is 3.2, the refractive index (n ₁ ) of the lower SiN film is 1.9, the refractive index (n ₂ ) of the upper SiO ₂ film is 1.46, the refractive index (n ₃ ) of the air is 1, and the light receiving wavelength is 1.55 mu m. In addition, the thick dielectric film by so could degrade the quality of the film here is set to a predetermined thickness range, the SiN film thickness is from 0 to 3,000Å, SiO ₂ film thickness is in the range of 1,000 to 8,000Å, for a given thickness of the SiN film The thickness change of the SiO ₂ film is calculated. On the other hand, when the light receiving wavelength is 1.3 mu m, the thickness of the SiN film is set in the range of 0 to 3,000 Pa and the SiO ₂ film is in the range of 1,000 to 7,000 Pa.

First, the thickness setting of the SiN film and the SiO ₂ film for obtaining optimal protective film characteristics and anti-reflective film characteristics when the light receiving wavelength is 1.55 μm will be described with reference to FIGS. 4 to 6. In this case, the double dielectric material film of SiN / SiO ₂ is set to nine thicknesses as follows. ① a SiN film is 1,200 ± 100Å and the SiO ₂ film is 6,900 ± 200Å thick thickness, ② a SiN film is 1,400 ± 100Å thick, and the SiO ₂ film thickness of 6,600 ± 200Å, ③ it is 1,600 ± 100Å SiN film thickness and SiO ₂ The thickness of the film is 6,300 ± 200Å, the thickness of the SiN film is 1,800 ± 100 SiO, the thickness of the SiO ₂ film is 5,900 ± 200Å, the thickness of the SiN film is 2,000 ± 100Å, the thickness of the SiO ₂ film is 5,400 ± 200Å, and the thickness of the ⑥ SiN film is 2,200 ± 100Å, SiO ₂ film thickness is 4,900 ± 200Å, ⑦ SiN film thickness is 2,400 ± 100Å, SiO ₂ film is 4,400 ± 200Å, ⑧ SiN film thickness is 2,600 ± 100Å, SiO ₂ film is 4,100 ± The thickness of the 200 kPa, 9 SiN film is 2,800 ± 100 kPa, and the thickness of the SiO ₂ film is 3,800 ± 200 kPa.

4 is a graph showing the thickness of the SiO ₂ film having a minimum reflectance according to the thickness of the SiN film. As shown in FIG. 4, it can be seen that as the thickness of the SiN film increases, the thickness of the SiO ₂ film decreases. FIG. 5 is a graph showing the change in reflectance according to the thickness of the SiN film in the thickness combination of the SiN / SiO ₂ film having the smallest reflectance, and the reflectance in the thickness combination of the SiN / SiO ₂ film in the thickness range of 1,200 to 2,800 Pa. Is 0.5% or less and has a very low reflectance of 0.1% or less at about 1,600 Hz and 2,600 Hz thickness. In this case, the pad capacity is calculated from the thickness combination of the SiN / SiO ₂ film having the smallest reflectance. The total capacity of the SiN / SiO ₂ film corresponds to the capacitor capacity connected in series, and is calculated using the following equation.

1 / C _toc = 1 / C _SiN + 1 / C _SiO2 ... … … … … … … Formula (2)

Where C _SiN = (ε _SiN ε ₀ A) / W

C _{SiO 2} = (ε _{SiO 2} ε ₀ A) / W.

The dielectric constant ε _SiN of SiN and SiO ₂ is 6, ε _{SiO 2} is 4, ε ₀ is 8.854 × 10 ^-14 F / cm, and W is the thickness of each dielectric material film. FIG. 6 is a graph showing a change in pad capacity different from the thickness of the SiN film in the thickness combination of the SiN / SiO ₂ film having the minimum reflectance when the pad diameter is 60 μm. As shown in FIG. 6, as the thickness of the SiN film increases in the thickness combination of the SiN / SiO ₂ film, the pad capacitance C is almost constant in the range of 0 to 1,500 kPa, about 0.13 pF, and is in the range of 2,500 to 3,000 kPa. It is constant at about 0.17pF, and increases from 0.13pF to 0.17pF in the range of 1,500 to 2,000Å.

Therefore, it is the case of the light wavelength 1.55㎛, SiN / SiO ₂ film thickness combined with optimal condition of the reflection film and the protective film is a SiN film, a lower layer of a thickness of 1,500 to 1,700Å, an upper layer of SiO ₂ film thickness of 6,200 to 6,400Å to be. Preferably, when the thickness combination of the SiN / SiO ₂ film is 1,600 / 6,300 Pa, the reflectance is 0.01% and the pad capacity is 0.136 pF, which has the minimum reflectance and the minimum pad capacity.

In addition, the thickness setting of the SiN film and the SiO ₂ film for obtaining the optimum protective film and anti-reflective film properties when the light receiving wavelength is 1.3 μm by the above method will be described with reference to FIGS. 7 to 9. In this case, the double dielectric material film of SiN / SiO ₂ is set to eight thicknesses as follows. The thickness of the SiN film is 1,000 ± 100 SiO, the thickness of the SiO ₂ film is 5,800 ± 200Å, the thickness of the SiN film is 1,200 ± 100Å, the thickness of the SiO ₂ film is 5,600 ± 200Å, the thickness of the SiN film is 1,400 ± 100Å, and the SiO ₂ having a thickness of 5,300 ± 200Å, ④ SiN film thickness of the film is 1,600 ± 100Å, SiO ₂ film is 4,800 ± 200Å, the thickness and ⑤ a thickness of SiN film is 1,800 ± 100Å, SiO ₂ film having a thickness of 4,300 ± 200Å, ⑥ SiN film thickness Is 2,000 ± 100Å, the thickness of the SiO ₂ film is 3,800 ± 200Å, the thickness of the SiN film is 2,200 ± 100Å, the thickness of the SiO ₂ film is 3,500 ± 200Å, the thickness of the SiN film is 2,400 ± 100Å, and the thickness of the SiO ₂ film is 3,200 ± 100 ±. ± 200 Hz.

7 is a graph showing the thickness of the SiO ₂ film having a minimum reflectance according to the thickness of the SiN film. As the thickness of the SiN film increases, the thickness of the SiO ₂ film decreases. 8 is a graph showing the change in reflectance according to the thickness of the SiN film in the thickness combination of the SiN / SiO ₂ film having the smallest reflectance, wherein the thickness combination of the SiN / SiO ₂ film in the thickness range of 1,000 to 2,400 kPa. Has a reflectance of 0.5% or less and has a very low reflectance of 0.1% or less at thicknesses of about 1,400 Hz and 2,200 Hz. At this time, the pad capacity is calculated from the thickness combination of the SiN / SiO ₂ film having the minimum reflectance, and the total capacity of the SiN / SiO ₂ film corresponds to the capacitor capacity connected in series, and is calculated using Equation (2).

In addition, FIG. 9 is a graph showing a change in pad capacitance different from the thickness of the SiN film in the thickness combination of the SiN / SiO ₂ film having the minimum reflectance when the pad diameter is 60 µm. As shown in FIG. 6, as the thickness of the SiN film is increased in the thickness combination of the SiN / SiO ₂ film, the pad capacitance C is almost constant in the range of 0 to 1,500 kPa, about 0.15 pF, and is in the range of 2500 to 3,000 kPa. Constant at about 0.21 pF, increasing from 0.15 pF to 0.2 pF in the 1,500 to 2,000 Hz range.

Therefore, when the light receiving wavelength is 1.3 mu m, the thickness combination of the SiN / SiO ₂ film having the optimum reflecting film and the protective film conditions is 1,200-1,400 kPa of the lower SiN film, and 5,300-5,600 kPa of the upper SiO ₂ film. to be. Preferably, when the thickness combination of the SiN / SiO ₂ film is 1,400 두께 / 5,300Å, the reflectance is 0.01%, the pad capacity is 0.136pF, the 2,200, / 3,500Å, the reflectance is 0.031%, and the pad capacity is 0.208pF. It has minimal reflectance and minimum pad capacity.

According to the above embodiment, in a photodiode having a predetermined light receiving wavelength, a double dielectric material film of SiN / SiO ₂ is optimally set according to the light receiving wavelength and is simultaneously formed as an antireflective film and a protective film, thereby having a minimum reflectance and In addition, it has a minimum pad capacity. As the antireflective film and the protective film are simultaneously formed of the above-mentioned double dielectric material, the effect of the process shortening can be obtained, and as the pad is formed on the protective film, the photodiode is not directly influenced at the time of wire bonding afterwards. The reliability and yield are improved.

In addition, this invention is not limited to the said Example, It can variously deform and implement within the range which does not deviate from the technical summary of this invention.

Claims (24)

A first conductive buffer type, an absorption layer, and a window layer sequentially stacked on the first conductive compound semiconductor substrate; A second conductive diffusion layer formed on a predetermined portion of the window layer; An ohmic contact layer patterned in a predetermined shape on both sides of the diffusion layer; A protective film formed of a first double dielectric material film on the window layers on both sides of the diffusion layer; An antireflection film formed of a second double dielectric material film on the diffusion layer between the ohmic contact layers, And a pad formed on the passivation layer while contacting the ohmic contact layer. The photodiode of claim 1, wherein the first double dielectric material layer of the passivation layer is a film in which a SiN film and a SiO ₂ film are sequentially stacked. The photodiode according to claim 2, wherein when the light receiving wavelength is 1.55 占 퐉, the thickness of the SiN film is 900 to 2,900 ,, and the thickness of the SiO ₂ film is 3,600 Å to 7,100 Å. 4. The photodiode according to claim 3, wherein when the light receiving wavelength is 1.55 mu m, the thickness of the SiN film is 1,500 to 1,700 kHz, and the thickness of the SiO ₂ film is 6,200 to 6,400 kHz. The photodiode according to claim 2, wherein when the light receiving wavelength is 1.3 mu m, the thickness of the SiN film is 900 to 2,500 mW, and the thickness of the SiO ₂ film is 3,400 to 6,000 mW. 6. The photodiode according to claim 5, wherein when the light receiving wavelength is 1.3 mu m, the thickness of the SiN film is 1,200 to 1,400 mW, and the thickness of the SiO ₂ film is 5,300 to 5,600 mW. The photodiode of claim 1, wherein the second double dielectric material film of the antireflective film is a film in which a SiN film and a SiO ₂ film are sequentially stacked. 8. The photodiode according to claim 7, wherein when the light receiving wavelength is 1.55 mu m, the thickness of the SiN film is 900 to 2,900 mW, and the thickness of the SiO ₂ film is 3,600 mW to 7,100 mW. 9. The photodiode according to claim 8, wherein when the light receiving wavelength is 1.55 mu m, the thickness of the SiN film is 1,500 to 1,700 mu s and the thickness of the SiO ₂ film is 6,200 to 6,400 mu s. 8. The photodiode of claim 7, wherein when the light receiving wavelength is 1.3 [mu] m, the thickness of the SiN film is 900 to 2,500 mW, and the SiO ₂ film is 3,400 to 6,000 mW. The photodiode according to claim 10, wherein when the light receiving wavelength is 1.3 mu m, the thickness of the SiN film is 1,200 to 1,400 mW, and the thickness of the SiO ₂ film is 5,300 to 5,600 mW. The photodiode of claim 1, wherein the first and second double dielectric material layers of the passivation layer and the antireflective layer are the same layer, and the SiN layer and the SiO ₂ layer are sequentially stacked. 13. The photodiode of claim 12, wherein when the light receiving wavelength is 1.55 mu m, the SiN film has a thickness of 900 to 2,900 mW, and the SiO ₂ film has a thickness of 3,600 mW to 7,100 mW. The photodiode according to claim 13, wherein when the light receiving wavelength is 1.55 mu m, the thickness of the SiN film is 1,500 to 1,700 mW, and the thickness of the SiO ₂ film is 6,200 to 6,400 mW. 13. The photodiode according to claim 12, wherein when the light receiving wavelength is 1.3 mu m, the thickness of the SiN film is 900 to 2,500 mW, and the thickness of the SiO ₂ film is 3,400 to 6,000 mW. 16. The photodiode of claim 15, wherein when the light receiving wavelength is 1.3 mu m, the thickness of the SiN film is 1,200 to 1,400 mW, and the thickness of the SiO ₂ film is 5,300 to 5,600 mW. The method of claim 1, wherein the substrate is n ⁺ -InP, the buffer layer is n ⁺ -InP, the absorption layer is n-InGaAs (P), the window layer is u-InP, and the ohmic contact layer is u A photodiode characterized by InGaAs. A first conductive buffer layer, an absorbing layer, and a window layer are sequentially stacked on the upper portion, and a second conductive diffusion layer formed on a predetermined portion of the window layer is formed, and patterned in a predetermined shape on both sides of the diffusion layer. Providing a first conductive compound semiconductor substrate having an ohmic contact layer formed thereon; Simultaneously forming a protective film and an antireflective film made of a double dielectric material film on the diffusion layer between the window layers on both sides of the diffusion layer and the ohmic contact layer; And, And forming a pad in contact with the ohmic contact layer on the passivation layer. The method of claim 18, wherein the double dielectric material layer is formed of a film in which a SiN film and a SiO ₂ film are sequentially stacked. 20. The method of manufacturing a photodiode according to claim 19, wherein when the light receiving wavelength is 1.55 mu m, the SiN film has a thickness of 900 to 2,900 mW, and the SiO ₂ film has a thickness of 3,600 mW to 7,100 mW. 21. The method of manufacturing a photodiode according to claim 20, wherein when the light receiving wavelength is 1.55 mu m, the thickness of the SiN film is 1,500 to 1,700 Å, and the thickness of the SiO ₂ film is 6,200 to 6,400 Å. 20. The method of manufacturing a photodiode according to claim 19, wherein when the light receiving wavelength is 1.3 [mu] m, the SiN film has a thickness of 900 to 2,500 mW and the SiO ₂ film has a thickness of 3,400 to 6,000 mW. 23. The method of manufacturing a photodiode according to claim 22, wherein when the light receiving wavelength is 1.3 mu m, the thickness of the SiN film is 1,200 to 1,400 mW, and the thickness of the SiO ₂ film is 5,300 to 5,600 mW. The method of claim 1, wherein the substrate is n ⁺ -InP, the buffer layer is n ⁺ -InP, the absorption layer is n-InGaAs (P), the window layer is u-InP, and the ohmic contact layer is u -InGaAs manufacturing method of a photodiode characterized in that.