KR19990006160A - Avalanche Photodiode and Manufacturing Method Thereof - Google Patents

Abstract

The present invention provides an avalanche photodiode and a method of manufacturing the same that can precisely control the diffusion interface when Zn or Cd wool is diffused to form a p-InP diffusion layer.

The avalanche photodiode according to the present invention includes a first conductive buffer layer, a first conductive absorbing layer, a grading layer, a first conductive type difference sheet layer, and a charge sheet layer formed sequentially on a first conductive compound semiconductor substrate. A diffusion barrier layer formed on the diffusion barrier layer to prevent diffusion of impurities into the charge sheet layer, a growth layer formed on the diffusion barrier layer, and a second conductive diffusion layer formed in the growth layer and in contact with the upper boundary of the diffusion barrier layer. do.

Description

Avalanche Photodiode and Manufacturing Method Thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light-receiving element and a method of manufacturing the same, and more particularly, to an avalanche photodiode and a method of manufacturing the same, which can precisely control a diffusion interface when forming a diffusion layer.

The light receiving element is essential for an optical communication system, and detects an optical signal transmitted through an optical fiber and converts the optical signal into an electrical signal. As such a light receiving element, there is a photodiode in a semiconductor diode, and p-i-n photodiode and an avalanche photodiode (APD) are included in a III-V compound semiconductor diode.

In general, APD causes carriers generated by incident light to collide by collisional ionization to produce further carriers. 1 is a cross-sectional view showing a conventional APD, as shown in Figure 1, a conventional APD is a n-InP buffer layer (2), n-InGaAs absorbing layer (3), InGaAsP on the n ⁺ -InP substrate (1) A grading layer 4, an n-InP charge sheet layer 5, and a u-InP growth layer 6 are sequentially stacked. A p-InP diffusion layer 8 in which Zn or Cd is diffused is formed in the u-InP propagation layer 6, and an InGaAs ohmic contact layer 7 is formed on predetermined portions on both sides of the p-InP diffusion layer 8. The protective film 10 made of a SiN / SiO ₂ film or an ARC (Anti-Reflective Caoting) film is formed on the entire surface of the substrate except for the InGaAs ohmic contact layer 7. In addition, a metal pattern 10 in contact with the InGaAs ohmic contact layer 7 is formed, and a gold plated layer 11 is formed on the metal pattern 10. The n-type electrode 12 is formed on the back surface of the substrate 1.

In the conventional avalanche photodiode as described above, the doping thickness of the n-InP charge sheet layer 5 is important in order to obtain desired gain and frequency characteristics. However, in order to form the p-InP diffusion layer 8 in the u-InP propagation layer 6, the doping of Zn or Cd has a very gentle slope when diffusing Zn or Cd, so it is difficult to remove the diffusion interface. it's difficult. Thus, for example, when the diffusion interface is too close to the n-InP charge sheet layer 5, the doping thickness of the u-InP charge sheet layer 5 is changed, and the characteristics of the avalanche photodiode are degraded. On the other hand, if the diffusion interface of Zn or Cd is too far from the n-InP charge sheet 5, not only the noise of the avalanche photodiode increases but also the gain decreases, resulting in deterioration of the characteristics of the avalanche photodiode. .

Accordingly, the present invention has been made in view of the above-described problems, and provides an avalanche photodiode and a method of manufacturing the same which can accurately control a diffusion interface when Zn or Cd wool is diffused to form a p-InP diffusion layer. There is a purpose.

1 is a cross-sectional view showing a conventional avalanche photodiode.

2 is a cross-sectional view illustrating a method of manufacturing an avalanche photo diode according to an embodiment of the present invention.

3 is a cross-sectional view illustrating a method of manufacturing an avalanche photodiode according to another embodiment of the present invention.

Explanation of symbols for the main parts of the drawings

11, 31: n ⁺ -InP substrate 12, 32: n-InP buffer layer

13, 33: n-InGaAs absorption layer 14, 34: InGaAsP grading layer

15, 35: n-InP charge sheet layer 16, 36: diffusion barrier layer

17, 37: u-InP growth layer 18, 38: InGaAs ohmic contact layer

19, 39: p-InP diffusion layer 40: guard ring

20, 41: protective film 21, 42: metal pattern

22, 43: gold-plated layer 23, 44: n-type electrode

The avalanche photodiode according to the present invention for achieving the above object is a first conductive buffer layer, a first conductive type absorbing layer, a grading layer, a first conductive type difference sheet layer and sequentially formed on the first conductive compound semiconductor substrate And a diffusion barrier layer formed on the charge sheet layer to prevent diffusion of impurities into the charge sheet layer, a growth layer formed on the diffusion barrier layer, and a material formed in the growth layer and in contact with the upper boundary of the diffusion barrier layer. And a two-conductive diffusion layer.

In addition, the method of manufacturing an avalanche photodiode according to the present invention for achieving the above object is the first conductive buffer layer, the first conductive absorption layer, the grading layer, the first conductive charge on the first conductive compound semiconductor substrate Sequentially forming the sheet layers; Forming a predetermined diffusion barrier layer on the charge sheet layer to prevent diffusion of impurities into the charge sheet layer; Sequentially forming a growth layer and an ohmic contact layer on the diffusion barrier layer; Patterning the ohmic contact layer such that the proliferation layer is partially exposed; Diffusing the metal into the exposed growth layer to form a second conductive diffusion layer in contact with the upper interface of the diffusion barrier layer.

According to the present invention described above, as the diffusion barrier layer is formed on the charge sheet layer, the diffusion interface can be accurately controlled when the diffusion layer is formed, so that the thickness variation of the charge sheet layer does not occur.

EXAMPLE

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

2 is a cross-sectional view illustrating a method of manufacturing an avalanche photodiode according to an embodiment of the present invention.

As shown in FIG. 2, a concentration of 2 × 10 ¹⁸ ions / cm 3 and a 0.5 μm-thick n-InP buffer layer 12 and a concentration of 2 × 10 ¹⁵ ions / cm 3 on the n ⁺ -InP substrate 11. And 2.3 μm thick n-InGaAs absorbing layer 13, 2 × 10 ¹⁵ ions / cm 3 and 0.15 μm thick InGaAsP grading layer 14, 1 × 10 ¹⁷ ions / cm 3 and 0.2 μm An n-InP charge sheet layer 15 of thickness is formed sequentially. Then, a diffusion barrier for preventing impurity diffusion into the n-InP charge sheet layer 35 at a concentration of 5x10 ¹⁶ ions / cm 3 and a thickness of 0.01 μm on the n-InP charge sheet layer 15. Layer 16 is formed. In this case, the diffusion barrier layer 16 is formed by doping silicon into the n-InP charge sheet layer 15. Subsequently, on the diffusion barrier layer 16, a concentration of 2 × 10 ¹⁵ ions / cm 3 and a 2.5 μm thick u-InP propagation layer 17, and a concentration of 2 × 10 ¹⁵ ions / cm 3 and a 0.2 μm thick InGaAs ohmic The contact layer 18 is formed sequentially.

The InGaAs ohmic contact layer 18 is then etched to expose a portion of the u-InP propagation layer 17 and Zn or Cd is diffused into the exposed u-InP propagation layer 17. Diffusion to the interface of the p-InP diffusion layer 19 is formed to contact the upper interface of the u-InP growth layer 17. Thereafter, after the InGaAs ohmic contact layer 18 is patterned in a predetermined form, a protective film 20 made of SiN / SiO ₂ is formed on the entire surface of the substrate. In this case, an anti-reflective coating (ARC) film may be formed instead of the protective film 20 to prevent loss of incident light. The protective film 20 is selectively etched to expose the InGaAs ohmic contact layer 18, and a metal pattern 21 is formed to contact the exposed InGaAs ohmic contact layer 18, and then a gold plating layer is formed on the metal pattern 21. (22) is formed. Then, an n-type electrode 23 is formed on the back surface of the substrate 11.

That is, according to the embodiment, as the diffusion barrier layer 16 is formed on the n-InP charge sheet layer 15, the diffusion interface is exactly at the time of diffusion of Zn or Cd for the formation of the p-InP diffusion layer. It can be controlled so that the thickness variation of the n-InP charge sheet layer 15 does not occur.

In addition, the diffusion barrier layer 16 may be applied to an APD having a guard ring structure. That is, FIG. 3 is a cross-sectional view of an APD having a guard ring structure according to another embodiment of the present invention, and another embodiment of the present invention will be described with reference to FIG. 3.

As shown in FIG. 3, the n-InP buffer layer 32, the n-InGaAs absorbing layer 33, the InGaAsP grading layer 34, and the n-InP charge sheet layer 35 on the n ⁺ -InP substrate 31. These are sequentially formed, and a diffusion barrier layer 36 for preventing impurity diffusion into the n-InP charge sheet layer 35 is formed on the n-InP charge sheet layer 35. In this case, the diffusion barrier layer 36 is formed by doping silicon into the n-InP charge sheet layer 35. Subsequently, the u-InP growth layer 37 and the InGaAs ohmic contact layer 38 are sequentially formed on the diffusion barrier layer 36. The InGaAs ohmic contact layer 38 is then etched to expose a portion of the u-InP propagation layer 37 and Zn or Cd is diffused into the exposed u-InP propagation layer 37. It diffuses to the interface of the p-InP diffusion layer 19 is formed in contact with the upper interface of the u-InP growth layer 37. Subsequently, a mask pattern (not shown) is formed on the substrate to expose a predetermined portion of both edge portions of the p-InP diffusion layer 39, and a diffusion process using the mask pattern is used to form the p-InP diffusion layer 39. The guard ring 40 is formed at an edge portion at a predetermined depth shallower than that of the p-InP diffusion layer 39. By the guard ring 40, edge breakdown is prevented.

Thereafter, the mask pattern is removed by a known method, and the InGaAs ohmic contact layer 38 is patterned in a predetermined form, and then a protective film 41 made of SiN / SiO ₂ is formed on the entire surface of the substrate. In this case, an ARC film may be formed instead of the protective film 41 to prevent loss of incident light. The protective film 41 is selectively etched to expose the InGaAs ohmic contact layer 38, and a metal pattern 42 is formed on the metal pattern 42 to contact the exposed InGaAs ohmic contact layer 38. 43 is formed. The n-type electrode 44 is formed on the rear surface of the substrate 31.

According to the above embodiment, as the diffusion barrier layer is formed on the n-InP charge sheet layer, the diffusion interface can be accurately controlled when Zn or Cd is diffused to form the p-InP diffusion layer. The thickness variation of the charge sheet layer does not occur. Thus, the characteristics of the avalanche photodiode 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 (7)

A first conductive buffer layer, a first conductive absorption layer, a grading layer, and a first conductive type difference sheet layer sequentially formed on the first conductive compound semiconductor substrate; A diffusion barrier layer formed on the charge sheet layer and preventing diffusion of impurities into the charge sheet layer; A growth layer formed on the diffusion barrier layer; And a second conductive diffusion layer formed in the propagation layer and in contact with an upper boundary of the diffusion barrier layer. The method of claim 1, wherein the substrate is n ⁺ -InP, the buffer layer is n-InP, the absorption layer is n-InGaAs, the grading layer is InGaAsP, the charge sheet layer is n-InP, An avalanche photodiode, wherein the growth layer is u-InP and the diffusion layer is p-InP. The avalanche photodiode of claim 2, wherein the diffusion barrier layer is a layer formed by doping silicon on the n-InP charge sheet layer. Sequentially forming a first conductive buffer layer, a first conductive absorption layer, a grading layer, and a first conductive charge sheet layer on the first conductive compound semiconductor substrate; Forming a predetermined diffusion barrier layer on the charge sheet layer to prevent diffusion of impurities into the charge sheet layer; Sequentially forming a growth layer and an ohmic contact layer on the diffusion barrier layer; Patterning the ohmic contact layer such that the growth layer is partially exposed; And diffusing a second conductive impurity into the exposed growth layer to form a second conductive diffusion layer in contact with an upper boundary surface of the diffusion barrier layer. The method of claim 4, wherein the substrate is n ⁺ -InP, the buffer layer is n-InP, the absorption layer n-InGaAs, the grading layer is InGaAsP, the charge sheet layer is n-InP, and the growth The layer is u-InP, the ohmic contact layer is InGaAs, the diffusion layer is p-InP manufacturing method of the avalanche photodiode. The method of claim 5, wherein the diffusion barrier layer is formed by doping silicon on the n-InP charge sheet layer. The method of claim 5, wherein in the forming of the second conductive diffusion layer, the second conductive impurity is Zn or Cd.