JP3629360B2 - Manufacturing method of light receiving element with built-in circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a light receiving element, in particular an optical pickup, a method of manufacturing a circuit-integrated light-receiving element with a built-in signal processing circuit used like in the optical remote controller.
[0002]
[Prior art]
FIG. 8 is a schematic sectional view showing a conventional light receiving element with a built-in circuit. The light receiving element with a built-in circuit includes a photodiode part 21 that is a light receiving part in which the light receiving element is formed, and a signal processing circuit part 22 in which a signal processing circuit is formed. An N-type epitaxial layer 5 is formed on the P-type semiconductor substrate 1, and a photodiode portion 21 and a signal processing circuit portion 22 are configured on the P-type semiconductor substrate 1 and the epitaxial layer 5. Several diffusion layers are formed for this purpose. 2 is an N-type buried diffusion layer, 3 is a P-type buried isolation diffusion layer, 4 is a P-type separation diffusion layer, P-type buried isolation diffusion layer 3, and P-type separation diffusion layer 4 is formed so as to overlap. 6 is a P-type diffusion layer, and 8 is an N-type diffusion layer.
[0003]
A SiO ₂ film 7 of silicon oxide film is formed on this and patterned. Reference numeral 9 denotes a first metal layer, which forms the wiring of the signal processing circuit unit 22. A second metal layer 13 is formed on the first interlayer insulating film 11 made of silicon nitride or silicon oxide formed by CVD. The first metal layer and the second metal layer form a multilayer wiring of the signal processing circuit unit 22. The second metal layer 13 also has a function as a light shielding member of the signal processing circuit unit 22, and has a function of reflecting intrusion light on the surface of the signal processing circuit unit 22 to prevent malfunction of the signal processing circuit unit 22. A second insulating film 12 is formed on the second metal layer 13 to protect the second metal layer 13.
[0004]
[Problems to be solved by the invention]
However, in the circuit-incorporated light receiving element having the above-described structure, the signal processing circuit is formed by two-layer wiring. From the gap between the first metal layer 9 and the second metal layer 13 forming the wiring pattern, for example, The disturbance light as shown by the arrow A in FIG. 8 may enter and cause the signal processing circuit to malfunction.
[0005]
For example, in the case of a writable CD device, the intensity of disturbance light is higher when writing data than when reading data. In the case of an optical pickup system using a hologram pattern, the sub beam of light diffracted by the hologram pattern is also applied to the signal processing circuit unit other than the photodiode. However, the intensity of light irradiation increases during data writing, and the sub beam The strength also increases, and the possibility that the signal processing circuit malfunctions increases. That is, when the intensity of disturbance light input to the light receiving element is strong, malfunction of the signal processing circuit unit cannot be prevented due to disturbance light incident on the signal processing circuit unit.
[0006]
In addition, in the conventional light receiving element with a built-in circuit, when a light shielding metal layer is further formed thereon, the surface of the wiring metal is formed in order to make an ohmic contact between the wiring metal layer and the light shielding metal layer. It is necessary to perform etching by reverse sputtering for the purpose of cleaning. At this time, the antireflection film on the light receiving element is etched, the film thickness is reduced, and the function of the reflection type antireflection film is deteriorated. When this silicon nitride film is etched, the reflectance of the photodiode surface increases, and further, the surface of the photodiode is damaged by reverse sputtering, and the leakage current of the photodiode increases.
[0007]
The present invention has been made in view of the above problems, purpose of the present invention, to prevent a reduction in film thickness of the antireflection film by the subsequent steps of the anti-reflection film formed on the light receiving element upper surface It is an object of the present invention to provide a method of manufacturing a light receiving element with a built-in circuit capable of performing the above.
[0008]
[Means for Solving the Problems]
The present invention has a light receiving portion in which a light receiving element is formed and a signal processing circuit portion in which a signal processing circuit is formed on the same semiconductor substrate, and the signal processing circuit portion has a first wiring metal layer, A second wiring metal layer is provided on the first wiring metal layer in the signal processing circuit section with an interlayer insulating film interposed therebetween, and the signal processing circuit section is entirely over the signal processing circuit section. A light shielding metal layer is formed to cover the signal processing circuit so as to shield the disturbance light. The light receiving element has an antireflection film, and the antireflection film in the periphery of the light receiving element is formed on the antireflection film. A method of manufacturing a light-receiving element with a built-in circuit , wherein the light-shielding metal layer is formed of a corrosion-resistant metal , the metal layer including a part of the wiring metal layer ; The first wiring metal layer and the second wiring metal formed on And a second interlayer insulating film made of one composition that completely covers the surface of the antireflection film and the second wiring metal layer completely covering the surface of the antireflection film and the second wiring metal layer. And forming a second interlayer insulating film covering the antireflection film as a protective film, and forming the light shielding metal layer over the signal processing circuit portion, and then forming the protective film as the protective film. The second interlayer insulating film on the antireflection film is removed.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic sectional view showing a configuration of a light receiving element with a built-in circuit according to an embodiment of the present invention. The light receiving element with a built-in circuit according to the present invention includes a light receiving part 21 in which a light receiving element is formed and a signal processing circuit part 22 in which a signal processing circuit is formed. An N-type epitaxial layer 5 is formed on the P-type semiconductor substrate 1. The P-type semiconductor substrate 1 and the epitaxial layer 5 are provided with a light receiving unit 21 and a signal processing circuit unit 22. Several diffusion layers are formed. 2 is an N ⁺ type buried diffusion layer, 3 is a P ⁺ type buried isolation diffusion layer, 4 is a P ⁺ type separation diffusion layer, and P ⁺ type buried isolation diffusion layer 3 and P ⁺ type The separation diffusion layer 4 is formed so as to overlap. Reference ^numeral 6 denotes a P ⁺ type diffusion layer, and reference numeral 8 denotes an N ⁺ type diffusion layer.
[0010]
The PN junction by N-type P-type epitaxial layer 5 of the substrate 1 is composed, which is a main component light-receiving element of the light receiving portion 21, the N ⁺ -type diffusion layer 8 formed in the epitaxial layer 5, one electrode Removal (metal layer 9) is performed. In the signal processing circuit unit 22, the collector of the N type epitaxial layer 5 (the N ⁺ diffusion layer 8 for terminal extraction) on the N ⁺ type buried diffusion layer 2, the base of the P ⁺ type diffusion layer 6, A vertical NPN transistor is constituted by the emitter of the N ⁺ -type diffusion layer 8.
[0011]
A SiO ₂ film 7 is formed and patterned on the epitaxial layer 5 on which several diffusion layers necessary for constituting a circuit element are formed. A first metal layer 9 is formed on the SiO ₂ film 7 to form wirings (including extraction terminals) for the light receiving unit 21 and the signal processing circuit unit 22. Further, a first interlayer insulating film 11 made of silicon nitride or silicon oxide formed by CVD or the like is formed on the first metal layer 9, and a second metal layer 13 is formed thereon. ing. The interlayer insulating film 11 is provided with a patterned hole, and a part of the metal layer 13 is electrically connected to the metal layer 9 through the hole, and a signal processing circuit is formed by a two-layer multilayer wiring. Is formed. A second interlayer insulating film 12 is formed on the metal layer 13. A gold layer (metal layer) 14 that is a corrosion-resistant metal layer is formed on the second interlayer insulating film 12.
[0012]
The gold layer 14 on the signal processing circuit unit 22 formed for light shielding does not have a wiring function, and covers the signal processing circuit unit 22 all over, and the gold layer 14 is a light receiving unit. The entire surface of the signal processing circuit unit 22 excluding 21 is covered. For this reason, the signal processing circuit unit 22 can be reliably shielded from light as compared with the case where a part of the multilayer wiring is formed as a light shielding layer. Even if it is irradiated, generation of parasitic current due to disturbance light is suppressed, and malfunction of the signal processing circuit section circuit can be completely prevented.
[0013]
In addition, since the signal processing circuit unit 22 is configured by the multilayer multilayer wiring including the metal layers 9 and 13, the chip size can be reduced. Further, by connecting the gold layer 14 to a constant potential such as a ground potential, the noise resistance of the light receiving element with a built-in circuit can be improved.
[0014]
In the light receiving unit 21, an N-type epitaxial layer 5 is stacked on a P-type semiconductor substrate, and an antireflection film 10 formed of silicon nitride or the like is covered thereon. On the antireflection film corresponding to the frame portion (peripheral portion) of the incident light window of the light receiving element of the light receiving portion 21, there is a region 9a formed with the metal layer 9, and there is a metal layer 13a. Light is prevented from being transmitted from the end face of the first interlayer insulating film 11 to the signal processing circuit unit. The metal layer 9a and the metal layer 13a are laminated. Further, since the gold layer 14 covers the circuit-incorporated light-receiving element 22 including the terminal part of the light-receiving unit 21 adjacent to the circuit-incorporated light-receiving element 22, the signal processing circuit unit 22 can be more reliably shielded from light. .
[0015]
The metal 14 covering the signal processing circuit section 22 may be a metal having high corrosion resistance. For example, a metal layer such as a gold alloy, platinum, TiW, or TiN may be used instead of the gold layer 14. Is possible. By using a corrosion-resistant metal, it is not necessary to form a new protective film on the surface of the corrosion-resistant metal, and the gold layer 14 is formed in the same process as the bonding pad portion on the surface of the light receiving element with a built-in circuit. Can be formed.
[0016]
2 to 3 are diagrams showing a manufacturing process of a light receiving element with a built-in circuit according to an embodiment of the present invention. In FIG. 2, P-type or N-type impurity diffusion is performed on a semiconductor substrate having a P-type semiconductor substrate 1 and an N-type epitaxial layer 5, and a SiO ₂ film 7 is formed thereon and patterned. An antireflection film 10 made of a material such as silicon nitride is formed on a portion that becomes a light receiving portion. Subsequently, a first metal layer 9 made of aluminum is formed.
[0017]
Subsequently, a first interlayer insulating film 11 made of Si ₂ N ₄ or the like is formed. Subsequently, a second metal layer 13 is formed. The first metal layer and the second metal layer form a two-layer multilayer wiring structure. Furthermore, it is also possible to form a multilayer wiring structure by laminating an interlayer insulating film and a metal layer. Next, a metal layer 9 and a metal layer 13 are laminated on the incident light window of the light receiving element of the light receiving unit 21, and the incident light window of the light receiving element of the light receiving unit 21 is formed by metal etching in this region. A metal layer 9a and a metal layer 13a are formed on the antireflection film corresponding to the frame portion (peripheral portion). Subsequently, a second interlayer insulating film 12 made of PSG (phosphosilicate glass), NSG (non-doped silicate glass), polyimide film or the like is formed.
[0018]
Thereafter, as shown in FIG. 3, a gold layer 14 which is a highly corrosion-resistant metal layer is formed on the interlayer insulating film 11 by sputtering. At this time, a bonding pad (not shown) is formed before the gold layer 14 is formed. In order to clean the surface of the portion that needs to be in ohmic contact with the metal layer, dry etching by reverse sputtering is performed. However, since the surface of the light receiving portion 21 is protected by the second interlayer insulating film, the antireflection film 10 is not etched. Therefore, the problem that the thickness of the antireflection film on the light receiving element does not change and the function of the antireflection film is deteriorated can be prevented. In addition, there is no fear of leakage current due to ion damage during reverse sputtering. The second interlayer insulating film 12 functions as a protective film for the antireflection film 10.
[0019]
After the above-described cleaning process by reverse sputtering, the gold layer 14 is subsequently formed. Further, patterning is performed to remove the gold layer 14 on the antireflection film 10, and then the second interlayer insulating film 12 on the antireflection film 10 is removed, whereby the light reception with built-in circuit shown in FIG. An element is formed. Further, a region 9 a formed with the metal layer 9 is formed on the antireflection film 10 corresponding to the frame portion (peripheral portion) of the incident light window of the light receiving element of the light receiving portion 21. Through the above-described steps, a highly reliable light receiving element with built-in circuit can be obtained without damaging the antireflection film on the surface of the light receiving element when the metal layer on the surface is formed.
[0020]
FIG. 4 is a schematic cross-sectional view showing a configuration of a light receiving element with a built-in circuit as a reference example, and FIGS. 5 to 7 are views showing a method for manufacturing the light receiving element with a built-in circuit. First, FIGS. 5 to 7 will be described.
[0021]
In FIG. 5, an N type epitaxial layer 5 is formed on a P type semiconductor substrate 1, and a light receiving unit 21 and a signal processing circuit unit 22 are provided on the P type semiconductor substrate 1 and the epitaxial layer 5. Several diffusion layers for construction are formed. 2 is an N ⁺ type buried diffusion layer, 3 is a P ⁺ type buried isolation diffusion layer, 4 is a P ⁺ type separation diffusion layer, and P ⁺ type buried isolation diffusion layer 3 and P ⁺ type The separation diffusion layer 4 is formed so as to overlap. Reference ^numeral 6 denotes a P ⁺ type diffusion layer, and reference numeral 8 denotes an N ⁺ type diffusion layer.
[0022]
The main part of the light receiving part 21 is constituted by the PN junction of the P type of the substrate 1 and the N type of the epitaxial layer 5, and one electrode is taken out by the N ⁺ type diffusion layer 8 formed in the epitaxial layer 5. ing. In the signal processing circuit unit 22, the collector of the N type epitaxial layer 5 (the N ⁺ diffusion layer 8 for terminal extraction) on the N ⁺ type buried diffusion layer 2, the base of the P ⁺ type diffusion layer 6, A vertical NPN transistor is constituted by the emitter of the N ⁺ -type diffusion layer 8.
[0023]
An SiO ₂ film 7 is formed and patterned on the epitaxial layer 5 on which several diffusion layers are formed. An antireflection film 10 made of silicon nitride or the like is formed on a portion that becomes a light receiving portion. Subsequently, a first metal layer 9 made of aluminum is formed. The metal layer 9 is formed on the upper surface of the semiconductor substrate and is patterned by etching. At this time, the metal layer 9 corresponding to the light receiving portion 21 is left.
[0024]
Subsequently, a first interlayer insulating film 11 made of Si ₂ N ₄ or the like is formed. Subsequently, a second metal layer 13 is formed. The metal layer 13 is formed on the upper surface of the semiconductor substrate and is patterned by etching. At this time, the metal layer 13 corresponding to the light receiving portion 21 is left. The first metal layer 9 and the second metal layer 13 form a two-layer multilayer wiring structure.
[0025]
Furthermore, it is also possible to form a multilayer wiring structure by laminating an interlayer insulating film and a metal layer. Subsequently, as shown in FIG. 6, a second interlayer insulating film 12 made of PSG, NSG, polyimide film or the like is formed.
[0026]
Next, as shown in FIG. 7, a gold layer 14 which is a metal layer having corrosion resistance is formed on the interlayer insulating film 12 by sputtering. At this time, before the gold layer 14 is formed, dry etching by reverse sputtering is performed to clean the surface of a portion that needs to be in ohmic contact with a metal layer such as a bonding pad (not shown). Since the surface is protected by the metal layer 9 and the metal layer 13, the thickness of the antireflection film 10 does not change, and there is no fear of leakage current due to ion damage. That is, the metal layer 9 and the metal layer 13 function as a protective film for the antireflection film 10. After the gold layer 14 is formed, the gold layer 14 is patterned by wet etching, and then the metal layer 9 and the metal layer 13 in the light receiving portion 21 are removed. At this time, the region metal layer 9a formed with the metal layer 9 and the metal layer 13a on the antireflection film 10 corresponding to the frame portion (peripheral portion) of the incident light window of the light receiving element of the light receiving portion 21 and the metal layer 13a. To leave. As a result, the gold layer (metal layer) 14a, the metal layer 9a, and the metal layer 13a are continuously connected. As a result, the side wall surface of the light receiving portion 21 (the frame portion of the incident light window of the light receiving element) is covered with the metal film. In this manner, the circuit built-in light receiving element shown in FIG. 4 is formed.
[0027]
In FIG. 4, the gold layer 14 covers the upper part of the signal processing circuit unit 22 and shields it from light. Moreover, the film thickness of the antireflection film 10 of the light receiving portion 21 is formed without changing. Further, the side surface of the light receiving portion 21 (the frame portion of the incident light window of the light receiving element) is entirely covered with the metal layer 9a, the metal layer 13a, and the gold layer 14a, which are metal layers. It is possible to reliably prevent light from leaking from the side wall surface and from being transmitted to the signal processing circuit unit 22 from the end surfaces of the first interlayer insulating film 11 or the second interlayer insulating film 12. Further, since the gold layer 14 covers the circuit built-in light receiving element 22 including the terminal part of the light receiving unit 21 adjacent to the circuit built-in light receiving element 22, the signal processing circuit unit 22 can be completely shielded from light.
[0028]
【The invention's effect】
According to the method for manufacturing a light receiving element with a built-in circuit according to the first aspect of the present invention, the light receiving part in which the light receiving element is formed and the signal processing circuit part in which the signal processing circuit is formed are provided on the same semiconductor substrate. The processing circuit unit includes a first wiring metal layer, and the signal processing circuit unit includes a second wiring metal layer on the first wiring metal layer. The signal processing circuit unit includes: A light shielding metal layer is formed to cover all over the signal processing circuit portion and shield disturbance light to the signal processing circuit, the light receiving element has an antireflection film, and the periphery of the light receiving element A light receiving element with a built-in circuit in which a metal region comprising a part of the metal layer for wiring is formed on the antireflection film of the portion, and the light shielding metal layer is formed of a corrosion-resistant metal. The first wiring mem- ber formed on the antireflection film. One composition that completely covers the antireflection film surface and the second wiring metal layer surface on the antireflection film surface and the second wiring metal layer surface after removing the copper layer and the second wiring metal layer Forming a second interlayer insulating film comprising: and forming the light shielding metal layer over the signal processing circuit portion, and then removing the second interlayer insulating film on the antireflection film. It is a feature. Therefore, by removing the second interlayer insulating film on the antireflection film after forming the light shielding metal layer, the film thickness of the antireflection film is not changed, and the light receiving element is not subjected to ion damage. A highly reliable light receiving element with a built-in circuit can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a light receiving element with a built-in circuit according to an embodiment of the present invention.
FIG. 2 is a diagram showing a manufacturing process of a circuit built-in light receiving element according to an embodiment of the present invention.
FIG. 3 is a diagram showing a manufacturing process of the light-receiving element with a built-in circuit according to the embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view showing a light receiving element with a built-in circuit according to another embodiment of the present invention.
FIG. 5 is a diagram showing a manufacturing method of a light receiving element with a built-in circuit according to another embodiment of the present invention.
FIG. 6 is a diagram showing a manufacturing method of a light receiving element with a built-in circuit according to another embodiment of the present invention.
FIG. 7 is a diagram showing a method of manufacturing a circuit built-in light receiving element according to another embodiment of the present invention.
FIG. 8 is a schematic cross-sectional view showing a conventional light receiving element with a built-in circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 5 Epitaxial layer 9 Metal layer 9a The area | region 10 in which the metal layer 9 is formed on the antireflection film 10 Antireflection film 11 Interlayer insulation film 12 Interlayer insulation film 13 Metal layer 13a Metal layer 14 on the side wall surface of the light receiving element Metal layer (gold layer)
14a Metal layer (gold layer) on side wall surface of light receiving element
21 light receiving unit 22 signal processing circuit unit

Claims (1)

While having the light receiving part in which the light receiving element is formed and the signal processing circuit part in which the signal processing circuit is formed on the same semiconductor substrate,
The signal processing circuit unit has a first wiring metal layer,
On the first wiring metal layer in the signal processing circuit section, there is a second wiring metal layer via an interlayer insulating film,
The signal processing circuit unit is formed with a light shielding metal layer for covering all over the signal processing circuit unit and blocking disturbance light to the signal processing circuit,
The light receiving element has an antireflection film, and has a metal region formed of a part of the wiring metal layer on the antireflection film in the periphery of the light receiving element.
The light shielding metal layer is a method of manufacturing a light receiving element with a built-in circuit formed of a corrosion-resistant metal,
After removing the first wiring metal layer and the second wiring metal layer formed on the antireflection film, the antireflection film is formed on the antireflection film surface and the second wiring metal layer surface. Forming a second interlayer insulating film having one composition that completely covers the film and the second wiring metal layer, and forming the second interlayer insulating film covering the antireflection film as a protective film;
A light receiving element with a built-in circuit, wherein the second interlayer insulating film on the antireflection film as the protective film is removed after the light shielding metal layer is formed so as to cover all over the signal processing circuit portion. Manufacturing method.

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