Sandwich passivation layer structure with side wall and preparation method thereof

Abstract

The invention discloses a sandwich passivation layer structure with a side wall and a preparation method of the sandwich passivation layer structure. The sandwich passivation layer structure comprises a semiconductor epitaxial layer, an interlayer dielectric layer, an interlayer barrier layer and a metal aluminum layer, wherein the edge ends of the interlayer barrier layer and the metal aluminum layer are jointly etched to the surface of the interlayer dielectric layer; the surface of the metal aluminum layer, the side walls of the etched sides of the metal aluminum layer and the interlayer barrier layer and the surface of the interlayer dielectric layer are coated with first passivation layers; a second passivation layer side wall is arranged on one side, close to the metal aluminum layer side wall, of the first passivation layer; and the surface of the first passivation layer and the surface of the side wall of the second passivation layer are coated with a third passivation layer. The sandwich passivation layer structure with the side wall is adopted at the metal edge, so that the step difference of the metal edge is reduced, the coverage of the passivation layer is improved, the cracking of the passivation layer is inhibited, and the moisture resistance and reliability of the power semiconductor device are improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor electronic information technology, and more particularly to a sandwich passivation layer structure with side walls and a preparation method thereof. Background Art

[0002] Since the surface of power semiconductor devices is very susceptible to the influence of the external environment, such as impurity contamination and moisture erosion, which will directly affect the electrical performance of the device and seriously reduce the stability and reliability of the device, it is necessary to adopt a surface passivation technology that can effectively shield the influence of the external environment on the device and improve the device's moisture resistance, reliability and stability. Among them, the most common passivation layer material is silicon nitride, which has a dense structure, high hardness, high dielectric strength, and good chemical stability. Except for a slight reaction with hydrofluoric acid and hot phosphoric acid, it hardly reacts with any acid. In addition, silicon nitride has a good masking effect on sodium ions because the solid solubility of sodium ions in silicon nitride is greater than its solid solubility in silicon oxide;

[0003] However, the stress of silicon nitride film layer is large, thicker silicon nitride is very easy to crack and its step coverage ability is weak. When the step height is greater than 2um, it is difficult to form a complete seamless continuous film, which leads to cracks easily appearing at the metal step when the device is under stress, such as Figure 1 As shown. However, in the process of switching and controlling high voltage and high current, power semiconductor devices will inevitably produce large losses. These losses are converted into heat energy and dissipated into the surrounding environment, causing the device to continuously withstand high temperature stress during high-frequency switching. In addition, due to the mismatch between the thermal expansion coefficient of the metal and the semiconductor epitaxy and passivation layer, the metal film will ratchet toward the center of the chip during the power cycle, and huge stress will be generated in the passivation film, leading to very serious cracking of the passivation layer. Usually, cracks in the passivation layer will also propagate downward to the semiconductor epitaxial layer, causing an electrical short circuit, and in a high-humidity environment, moisture will penetrate into the device from the external environment, causing metal corrosion or other moisture-related defects, seriously affecting the stability and reliability of power semiconductor devices. Summary of the invention

[0004] In view of this, the present invention provides a sandwich passivation layer structure with side walls and a preparation method thereof. The sandwich passivation layer structure with side walls is used at the metal edge to reduce the step difference of the metal edge, improve the coverage of the passivation layer, inhibit the cracking of the passivation layer, and enhance the moisture resistance and reliability of the power semiconductor device.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A sandwich passivation layer structure with sidewalls, comprising: a semiconductor epitaxial layer and an interlayer dielectric layer, an interlayer barrier layer and a metal aluminum layer sequentially located thereon;

[0007] Wherein, the interlayer barrier layer and the edge of the metal aluminum layer are etched together to the surface of the interlayer dielectric layer;

[0008] The surface of the metal aluminum layer, the sidewalls of the metal aluminum layer and the interlayer barrier layer on the etching side, and the surface of the interlayer dielectric layer are all coated with a first passivation layer;

[0009] A second passivation layer sidewall is disposed on one side of the first passivation layer close to the sidewall of the metal aluminum layer;

[0010] The surface of the first passivation layer and the surface of the sidewall of the second passivation layer are covered with a third passivation layer.

[0011] Preferably, the interlayer barrier layer includes a titanium nitride barrier layer and a titanium adhesion layer, and the titanium nitride barrier layer and the titanium adhesion layer are arranged one above the other.

[0012] Preferably, the material of the sidewalls of the first passivation layer and the second passivation layer is a silicon nitride or silicon oxide passivation material, and the sidewalls of the first passivation layer and the second passivation layer are made of different materials.

[0013] Preferably, the material of the third passivation layer is silicon nitride.

[0014] Another object of the present invention is to provide a method for preparing the sandwich passivation layer structure with sidewalls. After the front metal aluminum layer process of the power semiconductor device is completed, the first passivation layer film is deposited, and then the second passivation layer film is deposited, and the second passivation layer sidewall structure is etched out by plasma etching and sidewall protection process, and finally the third silicon nitride passivation layer structure is covered. The first passivation layer and the second passivation layer are made of different materials. For example, when the first passivation layer is made of silicon nitride, the second passivation layer material is silicon oxide, thereby providing an etching selectivity ratio when the second layer material is plasma etched.

[0015] The specific steps include:

[0016] (1) depositing an interlayer dielectric layer and an interlayer barrier layer on the semiconductor epitaxial layer;

[0017] (2) depositing metal aluminum on the interlayer barrier layer and performing photolithography, etching and annealing on the interlayer barrier layer, and the interlayer barrier layer will be etched simultaneously with the metal aluminum layer during this process;

[0018] (3) depositing a first passivation layer on the surface of the metal aluminum layer, the sidewalls of the metal aluminum layer and the interlayer barrier layer on the etched side, and the surface of the interlayer dielectric layer;

[0019] (4) depositing a second passivation layer made of a material different from that of the first passivation layer on the first passivation layer;

[0020] (5) plasma etching the second passivation layer, and using the organic polymer generated by the photoresist sputtering during the plasma etching and the introduction of nitrogen or methane gas to achieve side wall protection, the second passivation layer film at the side wall of the metal aluminum layer is retained without being etched, thereby leaving the second passivation layer side wall structure;

[0021] (6) Depositing a third passivation layer structure on the surface of the first passivation layer and on the surface of the sidewalls of the second passivation layer to complete a sandwich passivation layer structure with sidewalls.

[0022] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. Etch the second passivation layer on the first passivation layer at the metal edge using plasma etching and sidewall protection technology and leave the sidewall structure of the second passivation layer;

[0024] 2. Use the sidewall structure of the second passivation layer to reduce the metal edge step difference;

[0025] 3. Use a sandwich passivation layer structure with sidewalls to resist the stress caused by the mismatch of thermal expansion coefficients between the metal and the passivation layer during temperature cycling;

[0026] 4. Use a sandwich passivation layer structure with side walls to improve the cracking problem of the passivation layer;

[0027] 5. The device's moisture resistance is enhanced by using a sandwich passivation layer structure with sidewalls and a third silicon nitride passivation layer;

[0028] 6. Use a sandwich passivation layer structure with sidewalls to improve the moisture resistance and reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 Schematic diagram of the traditional passivation layer structure;

[0031] Figure 2 It is a schematic structural diagram of a sandwich passivation layer structure with side walls of the present invention;

[0032] Figure 3 It is a schematic diagram of the preparation process of the present invention.

[0033] Among them, in the figure: 1-semiconductor epitaxial layer; 2-interlayer dielectric layer; 3-titanium adhesion layer; 4-titanium nitride barrier layer; 5-metal aluminum layer; 6-first passivation layer; 7-second passivation layer side wall; 8-third passivation layer. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment provides a sandwich passivation layer structure with sidewalls, comprising: a semiconductor epitaxial layer 1 and an interlayer dielectric layer 2, an interlayer barrier layer and a metal aluminum layer 5 sequentially located thereon;

[0037] The interlayer barrier layer and the edge of the metal aluminum layer 5 are etched together to the inner side of the interlayer dielectric layer 2;

[0038] The surface of the metal aluminum layer 5, the surface of the metal aluminum layer 5 and the surface of the interlayer barrier layer are all coated with a first passivation layer 6;

[0039] A second passivation layer sidewall 7 is disposed on one side of the first passivation layer 6 close to the sidewall of the metal aluminum layer 5;

[0040] The surface of the first passivation layer 6 and the surface of the second passivation layer sidewall 7 are coated with a third passivation layer 8 .

[0041] In this embodiment, the interlayer barrier layer includes a titanium nitride barrier layer 4 and a titanium adhesion layer 3, and the titanium nitride barrier layer 4 and the titanium adhesion layer 3 are arranged one above the other.

[0042] In this embodiment, the materials of the first passivation layer 6 and the second passivation layer sidewall 7 are silicon nitride or silicon oxide passivation materials, and the first passivation layer 6 and the second passivation layer sidewall 7 are made of different materials.

[0043] In this embodiment, the material of the third passivation layer 8 is silicon nitride.

[0044] Example 2

[0045] This embodiment provides a method for preparing a sandwich passivation layer structure with sidewalls, comprising the following steps:

[0046] (1) depositing an interlayer dielectric layer and an interlayer barrier layer on the semiconductor epitaxial layer;

[0047] (2) depositing metal aluminum on the interlayer barrier layer and performing photolithography, etching and annealing on the interlayer barrier layer, and the interlayer barrier layer will be etched simultaneously with the metal aluminum layer during this process;

[0048] (3) depositing a first passivation layer on the surface of the metal aluminum layer, the sidewalls of the metal aluminum layer and the interlayer barrier layer on the etched side, and the surface of the interlayer dielectric layer;

[0049] (4) depositing a second passivation layer made of a material different from that of the first passivation layer on the first passivation layer;

[0050] (5) plasma etching the second passivation layer, and using the organic polymer generated by the photoresist sputtering during the plasma etching and the introduction of nitrogen or methane gas to achieve side wall protection, the second passivation layer film at the side wall of the metal aluminum layer is retained without being etched, thereby leaving the second passivation layer side wall structure;

[0051] (6) Depositing a third passivation layer structure on the surface of the first passivation layer and on the surface of the sidewalls of the second passivation layer to complete a sandwich passivation layer structure with sidewalls.

[0052] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0053] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sandwich passivation layer structure with sidewalls, characterized in that: include: A semiconductor epitaxial layer and an interlayer dielectric layer, an interlayer barrier layer and a metal aluminum layer sequentially disposed thereon; Wherein, the interlayer barrier layer and the edge of the metal aluminum layer are etched together to the surface of the interlayer dielectric layer; The surface of the metal aluminum layer, the sidewalls of the metal aluminum layer and the interlayer barrier layer on the etching side, and the surface of the interlayer dielectric layer are all coated with a first passivation layer; A second passivation layer sidewall is disposed on one side of the first passivation layer close to the sidewall of the metal aluminum layer; The surface of the first passivation layer and the surface of the sidewall of the second passivation layer are covered with a third passivation layer.

2. The sandwich passivation layer structure with sidewalls according to claim 1, characterized in that: The interlayer barrier layer includes a titanium nitride barrier layer and a titanium adhesion layer, and the titanium nitride barrier layer and the titanium adhesion layer are arranged one above the other.

3. The sandwich passivation layer structure with sidewalls according to claim 1, characterized in that: The materials of the sidewalls of the first passivation layer and the second passivation layer are silicon nitride or silicon oxide passivation materials, and the sidewalls of the first passivation layer and the second passivation layer are made of different materials.

4. The sandwich passivation layer structure with sidewalls according to claim 1, characterized in that: The material of the third passivation layer is silicon nitride.

5. The method for preparing a sandwich passivation layer structure with side walls according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) depositing an interlayer dielectric layer and an interlayer barrier layer on the semiconductor epitaxial layer; (2) depositing metal aluminum on the interlayer barrier layer and performing photolithography, etching and annealing on the interlayer barrier layer, and the interlayer barrier layer will be etched simultaneously with the metal aluminum layer during this process; (3) depositing a first passivation layer on the surface of the metal aluminum layer, the sidewalls of the metal aluminum layer and the interlayer barrier layer on the etched side, and the surface of the interlayer dielectric layer; (4) depositing a second passivation layer made of a material different from that of the first passivation layer on the first passivation layer; (5) plasma etching the second passivation layer, and using the organic polymer generated by the photoresist sputtering during the plasma etching and the introduction of nitrogen or methane gas to achieve side wall protection, the second passivation layer film at the side wall of the metal aluminum layer is retained without being etched, thereby leaving the second passivation layer side wall structure; (6) Depositing a third passivation layer structure on the surface of the first passivation layer and on the surface of the sidewalls of the second passivation layer to complete a sandwich passivation layer structure with sidewalls.

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