JP7040858B2 - Semiconductor devices and methods for manufacturing semiconductor devices - Google Patents

Description

The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.

The following techniques are known as techniques related to photodiodes formed on semiconductor substrates. For example, Patent Document 1 describes a step of forming an antireflection film on a light receiving element region on a substrate, a film reduction on the antireflection film due to overetching that occurs in a later step, and antireflection from process damage. A method for manufacturing a semiconductor device with a built-in light receiving element, which includes a step of forming a protective film that protects the film, is described. Specifically, a polycrystalline silicon film as a protective film is formed on the antireflection film, the wiring interlayer film is removed by dry etching, and then the polycrystalline silicon film as a protective film is removed by wet etching.

Japanese Patent Application Laid-Open No. 2003-264310

The method for manufacturing a semiconductor device provided with a photodiode is, for example, a step of forming an antireflection film covering a light receiving region on the surface of a semiconductor substrate on which a photodiode is formed, and forming a wiring electrically connected to the photodiode. A step of forming an external connection terminal electrically connected to the wiring, and a step of cleaning the external connection terminal may be included.

Heavy metals such as Au are used as the material for the external connection terminals. Therefore, in order to avoid fluctuations in the characteristics of semiconductor devices due to heavy metal contamination, each process up to the formation of the external connection terminal is performed in the wafer manufacturing process (pre-process), and each process after the formation of the external connection terminal is performed. Performed in the assembly process (post-process).

Here, the present inventor has discovered that the antireflection film is etched in the cleaning process of the external connection terminal, and the film thickness of the antireflection film changes from the film thickness at the time of film formation. Since the reflectance of the antireflection film depends on the film thickness of the antireflection film, it is important to control the film thickness of the antireflection film. When the antireflection film is etched in the cleaning step of the external connection terminal, the reflectance of the antireflection film fluctuates, resulting in a variation in the light receiving sensitivity of the photodiode.

To solve this problem, the technique described in Patent Document 1 is applied, a polycrystalline silicon film as a protective film is formed on the antireflection film, the wiring interlayer film is removed by dry etching, and then the polycrystal as a protective film is formed. A method of removing the silicon film by wet etching can be considered. However, in this case, since it is necessary to etch the polysilicon film in the assembly process (post-process), a high-priced device dedicated to etching the polysilicon film is required, which results in an increase in manufacturing cost.

The present invention has been made in view of the above points, and an object of the present invention is to suppress a change in the film thickness of the antireflection film at low cost.

The method for manufacturing a semiconductor device according to the present invention includes a step of preparing a semiconductor substrate on which a photodiode is formed, and a refraction that covers the light receiving region of the photodiode on the surface of the semiconductor substrate and is smaller than the refractive index of the semiconductor substrate. A step of forming an insulator layer having a ratio, a wiring including a first conductive film and a second conductive film electrically connected to the photodiode, and a portion of the insulator layer corresponding to the light receiving region. The step of forming the first conductive film and the mask containing the second conductive film, the first opening for exposing at least a part of the upper surface of the wiring, and the upper surface and the side surface of the mask. A step of forming a protective film having a second opening to be exposed and covering the side surface of the wiring on the insulator layer, and a terminal electrically connected to the wiring in the first opening. It includes a step of forming the terminal and a step of removing the mask with an etching solution that dissolves the first conductive film after the formation of the terminal.

The semiconductor device according to the present invention is provided with a semiconductor substrate on which a photodiode is formed, an insulator layer covering the light receiving region of the photodiode on the surface of the semiconductor substrate, and the light receiving region provided on the insulator layer. The insulating layer includes a protective film having an opening in a region to be included and a terminal provided on the protective film and electrically connected to the photodiode, and the insulator layer is the opening of the protective film. It has a recess along the end.

According to the present invention, it is possible to suppress fluctuations in the film thickness of the insulator layer that functions as an antireflection film at low cost.

It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows an example of the manufacturing method of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows the structure of the semiconductor device which concerns on embodiment of this invention. It is a top view which shows the structure of the semiconductor device which concerns on embodiment of this invention. It is sectional drawing which shows the structure of the semiconductor device which concerns on a comparative example. It is sectional drawing which shows the structure of the semiconductor device which concerns on other embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, substantially the same or equivalent components or parts are designated by the same reference numerals.

1A to 1S are cross-sectional views showing an example of a method for manufacturing a semiconductor device according to an embodiment of the present invention. First, a semiconductor substrate 10 including an n-type substrate layer 10a and an n-type epitaxial layer 10b composed of a silicon single crystal is prepared. Next, the thermal oxide film 11 is formed on the surface of the epitaxial layer 10b by using a known thermal oxidation method. Next, using a known photolithography technique, a resist mask 100 having an opening 100A at a position where an N-type region is to be formed is formed on the semiconductor substrate 10.

Next, the N-type region 21 that functions as a cathode in the surface layer portion of the epitaxial layer 10b by injecting an N-type impurity into the epitaxial layer 10b through the opening 100A of the resist mask 100 using a known ion implantation technique. To form. After that, the resist mask 100 is removed (FIG. 1B).

Next, the heat diffusion treatment of the N-type region 21 is performed. That is, the heat treatment diffuses the N-type impurities in the N-type region 21 deep into the epitaxial layer 10b. The N-type region 21 reaches the vicinity of the interface between the epitaxial layer 10b and the substrate layer 10a (FIG. 1C).

Next, using a known photolithography technique, a resist mask 101 having an opening 101A at a position where a P-shaped region is to be formed is formed on the semiconductor substrate 10 (FIG. 1D).

Next, a P-type region 22 that functions as an anode in the surface layer portion of the epitaxial layer 10b by injecting a P-type impurity into the epitaxial layer 10b through the opening 101A of the resist mask 101 using a known ion implantation technique. To form. After that, the resist mask 101 is removed (FIG. 1E).

Next, using a known photolithography technique, a resist mask 102 having an opening 102A at a position where an N ⁺ region contained in the N-type region 21 is to be formed is formed on the semiconductor substrate 10 (FIG. 1F).

Next, by injecting a high concentration of N-type impurities into the N-type region 21 through the opening 102A of the resist mask 102 using a known ion implantation technique, the surface layer portion of the N-type region 21 is used as a contact region. Form a functioning N ⁺ region 23. After that, the resist mask 102 is removed (FIG. 1G). Through the above steps, the photodiode 200 is formed on the semiconductor substrate 10.

Next, an insulator layer 30 that functions as an antireflection film is formed on the surface of the semiconductor substrate 10. Specifically, a first insulator layer 31 is formed on the surface of the semiconductor substrate 10 by using a known CVD method (chemical vapor deposition), and a second insulator is formed on the surface of the first insulator layer 31. The layer 32 is formed (FIG. 1H). That is, the insulator layer 30 is composed of a laminated film in which a first insulator layer 31 and a second insulator layer 32 are laminated. By forming the first insulator layer 31 and the second insulator layer 32 with a material having a refractive index smaller than that of the semiconductor substrate 10, the insulator layer 30 functions as an antireflection film. .. NSG (Non doped Silicate Glasses) can be used as the first insulator layer 31, and PSG (Phospho Silicate Glasses) can be used as the second insulator layer 32. By controlling the ratio of the film thickness of the first insulator layer 31 to the film thickness of the second insulator layer 32, a desired reflectance can be obtained in the insulator layer 30 functioning as an antireflection film. .. Therefore, by suppressing the variation in the film thickness of the first insulator layer 31 and the second insulator layer 32, it is possible to suppress the variation in the light receiving sensitivity of the photodiode 200.

Next, using known photolithography techniques and etching techniques, a contact hole reaching the P-shaped region 22 and a contact hole reaching the N ⁺ region 23 are formed in the insulator layer 30. Then, by sequentially embedding the barrier metal 41 and the refractory metal 42 in each of the above contact holes using a known CVD method, the plugs 40A connected to the P-shaped region 22 and the plugs connected to the N ⁺ region 23 are connected. Form 40B. As the barrier metal 41, for example, TiN (titanium nitride) can be used, and as the refractory metal 42, for example, W (tungsten) can be used. The barrier metal 41 and the refractory metal 42 deposited on the surface of the insulator layer 30 are removed by etchback or CMP (Chemical Mechanical Polishing) (FIG. 1I).

Next, using a known sputtering method, the first conductive film 51 is formed on the surface of the insulator layer 30, and the second conductive film 52 is formed on the first conductive film 51. As the material of the first conductive film 51, for example, Mo (molybdenum) can be used. As the material of the second conductive film 52, for example, AlSiCu can be used. Next, using a known photolithography technique, a resist mask 103 for patterning the first conductive film 51 and the second conductive film 52 is formed on the second conductive film 52 (FIG. 1J).

Next, by using a known etching technique to etch the portions of the first conductive film 51 and the second conductive film 52 exposed from the resist mask 103, the first conductive film 51 and the second conductive film 52 are conductive. The film 52 is patterned. As a result, the wiring 53 electrically connected to the P-type region 22 via the plug 40A and the wiring 54 electrically connected to the N-type region 21 via the plug 40B are formed on the insulator layer 30. Will be done. Further, a metal mask 55 is formed on the insulator layer 30 at a position corresponding to the light receiving region. Most of the region corresponding to the light receiving region of the insulator layer 30 is covered with the metal mask 55. After that, the resist mask 103 is removed (FIG. 1K).

Next, using a known CVD method, a protective film (passivation film) 60 covering the upper surfaces and side surfaces of the wirings 53 and 54 and the metal mask 55 is formed on the surface of the insulator layer 30 (FIG. 1L). As the material of the protective film 60, for example, an insulator such as SiN (silicon nitride) can be used.

Next, a resist mask 104 for patterning the protective film 60 is formed on the protective film 60 using a known photolithography technique (FIG. 1M).

Next, the protective film 60 is patterned by etching the portion of the protective film 60 exposed from the resist mask 104 using a known etching technique. As a result, openings 60A and 60B that expose the upper surfaces of the wirings 53 and 54 are formed in the protective film 60. Further, an opening 60C that exposes the upper surface and the side surface of the metal mask 55 is formed in the protective film 60. A part of the upper surface and the side surface of the wirings 53 and 54 and a part of the surface of the insulator layer 30 are covered with the protective film 60 (FIG. 1N). Each of the above processes is carried out in the wafer manufacturing process (preliminary process). Subsequently, an assembly process (post-process) for packaging the semiconductor device is carried out.

Next, a known sputtering method is used to form the barrier metal 71 that covers the entire surface of the semiconductor substrate 10. The surface of the protective film 60, the upper surface of the wirings 53 and 54, the portion exposed from the protective film 60, and the upper surface and the side surface of the metal mask 55 are covered with the barrier metal 71. As the material of the barrier metal 71, for example, TiN (titanium nitride) can be used. After that, a resist mask 105 having openings 105A and 105B at the forming positions of the wirings 53 and 54 is formed on the semiconductor substrate 10. That is, the upper surfaces of the wirings 53 and 54 covered with the barrier metal 71 are exposed at the openings 105A and 105B of the resist mask 105, respectively, and the other portions are covered with the resist mask 105 (FIG. 1O).

Next, by a known electrolytic plating method, external connection terminals 81 and 82 electrically connected to the wires 53 and 54 exposed in the openings 105A and 105B of the resist mask 105 are formed (FIG. 1P). Heavy metals such as Au can be used as the material for the external connection terminals 81 and 82. After that, the resist mask 105 is removed (FIG. 1Q).

Next, the barrier metal 71 is removed by etching using the external connection terminals 81 and 82 as masks. After that, the external connection terminals 81 and 82 are washed. In the cleaning step of the external connection terminals 81 and 82, the portion of the insulator layer 30 corresponding to the light receiving region is not etched because it is covered with the metal mask 55, and the protective film 60 or the metal mask of the insulator layer 30 is not etched. The portion not covered by 55 is etched. Therefore, the insulator layer 30 is formed with a recess (groove) 33 along the end of the opening 60C of the protective film 60. In other words, a recess (groove) 33 along the outer edge of the light receiving region of the photodiode is formed in the insulator layer 30 (FIG. 1R).

Next, the metal mask 55 is removed by the lift-off method. Specifically, nitric acid is used as the etching solution to etch the first conductive film 51 of the metal mask 55 containing Mo (molybdenum). As a result, the metal mask 55 is peeled off from the insulator layer 30 (FIG. 1S).

FIG. 2 is a cross-sectional view of the semiconductor device 1 according to the embodiment of the present invention manufactured through each of the above steps, and FIG. 3 is a plan view of the semiconductor device 1. The semiconductor device 1 covers the semiconductor substrate 10 on which the photodiode 200 is formed and the light receiving region 300 of the photodiode 200 on the surface of at least the semiconductor substrate 10, and has an antireflection film having a refractive index smaller than the refractive index of the semiconductor substrate 10. An opening 60C is provided in an insulator layer 30 that functions as a semiconductor, wirings 53 and 54 electrically connected to the photodiode 200, and an opening 60C provided on the insulator layer 30 and includes a light receiving region 300 of the photodiode 200. It includes a protective film (passion film) 60 that has and covers the side surfaces of the wirings 53 and 54, and external connection terminals 81 and 82 that are provided on the protective film 60 and are electrically connected to the wirings 53 and 54, respectively. .. The insulator layer 30 that functions as an antireflection film has a recess (groove) 33 along the end portion (or the outer edge of the light receiving region) of the opening 60C of the protective film 60.

FIG. 4 is a cross-sectional view of the semiconductor device 1X according to a comparative example with respect to the present invention. The semiconductor device 1X according to the comparative example is different from the semiconductor device 1 according to the embodiment of the present invention in that the external connection terminals 81 and 82 are cleaned with the surface of the insulator layer 30 exposed. Case When the external connection terminals 81 and 82 are washed with the surface of the insulator layer 30 exposed, the exposed portion of the insulator layer 30 is etched. The reflectance of the insulator layer 30 that functions as an antireflection film depends on its film thickness. When the film thickness of the insulator layer 30 is changed by etching the insulator layer 30 in the cleaning process of the external connection terminals 81 and 82, the reflectance of the insulator layer 30 fluctuates and the light receiving sensitivity of the photodiode varies. The result is.

On the other hand, according to the manufacturing method of the semiconductor device 1 according to the present embodiment, the portion of the insulator layer 30 that functions as the antireflection film corresponding to the light receiving region is covered with the metal mask 55, so that the external connection terminal is used. In the cleaning steps of 81 and 82, fluctuations in the film thickness of the insulator layer 30 can be suppressed. As a result, fluctuations in the reflectance of the insulator layer 30 can be suppressed, and variations in the light receiving sensitivity of the photodiode between devices can be suppressed.

Further, according to the manufacturing method of the semiconductor device 1 according to the present embodiment, the formation of the metal mask 55 and the patterning of the protective film 60 are completed before the external connection terminals 81 and 82 are formed, so that the cost is low. The metal mask 55 can be removed using a wet etching apparatus. That is, according to the manufacturing method of the semiconductor device 1 according to the present embodiment, it is possible to suppress fluctuations in the film thickness of the insulator layer 30 that functions as an antireflection film at low cost.

Further, the metal mask 55 for avoiding etching of the insulator layer 30 is made of the same material as the wirings 53 and 54, and the metal mask 55 forming step is performed in parallel with the wiring 53 and 54 forming steps. .. Therefore, no dedicated equipment or process for forming the metal mask 55 is required. That is, according to the manufacturing method of the semiconductor device 1 according to the present embodiment, it is possible to suppress fluctuations in the thickness of the insulator layer 30 that functions as an antireflection film without adding equipment or increasing the number of steps. It will be possible.

FIG. 5 is a diagram showing the configuration of the semiconductor device 1A according to the second embodiment of the present invention. In the semiconductor device 1 according to the first embodiment described above, the wirings 53 and 54 are composed of a first conductive film 51 containing Mo (molybdenum) and a second conductive film 52 containing AlSiCu, respectively. On the other hand, in the semiconductor device 1A according to the second embodiment, the wirings 53 and 54 are tied between the first conductive film 51 containing Mo (molybdenum) and the second conductive film 52 containing AlSiCu. A film 57 and a TiN film 57 are provided. By providing the Ti film 56 and the TiN film 57 between the Mo film and the AlSiCu film in this way, the wiring property of AlSiCu is improved, thereby suppressing electromigration, and the reliability of the semiconductor device can be suppressed. It can enhance the sex. In the cleaning step of the external connection terminals 81 and 82, the etching of the insulator layer 30 is suppressed by the metal mask having the same laminated structure (Mo / Ti / TiN / AlSiCu) as the wirings 53 and 54.

1, 1A Semiconductor device 10 Semiconductor substrate 30 Insulator layer 31 First insulator layer 32 Second insulator layer 33 Recess (groove)
51 First conductive film 52 Second conductive film 53, 54 Wiring 55 Metal mask 60 Protective film 60C Opening 81, 82 External connection terminal 200 Photodiode 300 Light receiving area

Claims (11)

The process of preparing a semiconductor substrate on which a photodiode is formed, and
A step of forming an insulator layer that covers the light receiving region of the photodiode on the surface of the semiconductor substrate and has a refractive index smaller than that of the semiconductor substrate.
The first conductive film and the second conductive film covering the wiring including the first conductive film and the second conductive film electrically connected to the photodiode and the portion of the insulator layer corresponding to the light receiving region. And the process of forming the mask containing the conductive film of
A protective film having a first opening for exposing at least a part of the upper surface of the wiring and a second opening for exposing the upper surface and the side surface of the mask and covering the side surface of the wiring is provided on the insulator layer. And the process of forming
The step of forming a terminal electrically connected to the wiring in the first opening, and
A step of removing the mask with an etching solution that dissolves the first conductive film after the formation of the terminal.
A method for manufacturing a semiconductor device including. The step of forming the wiring and the step of forming the mask are
The step of laminating the first conductive film and the second conductive film on the insulator layer, and
The step of patterning the first conductive film and the second conductive film,
The manufacturing method according to claim 1. The step of forming the insulator layer is from a material different from the step of forming the first insulator layer on the semiconductor substrate and the material of the first insulator layer on the first insulator layer. The manufacturing method according to claim 1 or 2, comprising the step of forming the second insulator layer. The manufacturing method according to any one of claims 1 to 3, further comprising a step of cleaning the terminals before removing the mask. The production method according to any one of claims 1 to 4, wherein the first conductive film contains Mo and the second conductive film contains AlSiCu. The production method according to any one of claims 1 to 4, wherein the first conductive film contains Mo and the second conductive film contains Ti, TiN and AlSiCu. A semiconductor substrate on which a photodiode is formed and
An insulator layer covering the light receiving region of the photodiode on the surface of the semiconductor substrate, and
A protective film provided on the insulator layer and having an opening in a region including the light receiving region,
A terminal provided on the protective film and electrically connected to the photodiode.
Including
The insulator layer is a semiconductor device having a recess on the surface along the end of the opening of the protective film. The semiconductor device according to claim 7, wherein the insulator layer has a refractive index smaller than that of the semiconductor substrate. Further, on the insulator layer, wiring electrically connected to the photodiode is provided.
The semiconductor device according to claim 7 or 8, wherein the protective film covers the side surface of the wiring. The semiconductor device according to any one of claims 7 to 9, wherein the terminal is exposed to the outside. The semiconductor device according to any one of claims 7 to 10, wherein the terminal is made of a heavy metal.

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