JP3157203B2 - High voltage semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high breakdown voltage semiconductor device, and more particularly to a structure of a peripheral portion of a chip of a high breakdown voltage semiconductor device such as a power MOSFET, an IGBT, or a power bipolar transistor.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view of a peripheral portion of a chip of a conventional high breakdown voltage semiconductor device. Generally, the structure of a peripheral portion of a chip such as a power MOSFET having a high withstand voltage of several hundred volts or a bipolar transistor has a structure as shown in FIG. Here, reference numeral 1 denotes a semiconductor substrate such as silicon, reference numeral 2 denotes a guard ring diffusion layer, and reference numeral 3 denotes an annular diffusion layer. In the N-type semiconductor substrate 1, the P-type guard ring diffusion layer 2 has a function of widening the depletion layer to the outside, thereby alleviating the electric field concentration at the edge of the base diffusion region in the power transistor, thereby increasing the breakdown voltage. Have. The N ⁺ -type annular diffusion layer 3 has a function of preventing the spread of the inversion layer at the oxide film interface together with the shield aluminum 14 which is the shield metal provided on the N ⁺ -type annular diffusion layer 3. In the peripheral portion of such a chip, a first layer insulating film 5 is provided on the surface of the semiconductor substrate 1, and the first layer insulating film 13 is usually
A thermal oxide film is used. Then, a field nitride film 6 is deposited thereon, and a protective film such as a phosphorus glass film which is the second layer insulating film 7 is further formed thereon. Here, the field nitride film 6 and the second layer insulating film 7 are for preventing invasion of mobile ions to the interface between the first layer insulating film 5 and the semiconductor substrate 1 and for ensuring the reliability of the semiconductor device. is there. Further, the phosphorus glass film, which is the second insulating film 7, is cleaned by the getter function of phosphorus, and the nitride film is made of the second insulating film 7 and the field nitride film 6 because of the property of preventing the passage of contaminants. By shutting out exogenous contaminants, the silicon interface was stabilized.

[0003]

In such a conventional high breakdown voltage semiconductor device, however, the second layer insulating film on the field nitride film is made of a phosphorus glass film to purify the film quality. However, since the field nitride film is provided, there is a problem that the gettering effect of the underlying first-layer insulating film, that is, the cleaning of the quality of the first-layer insulating film cannot be achieved.

[0004]

In order to solve the problems of the prior art, a first layer insulating film formed on a semiconductor substrate, a field nitride film formed on the first layer insulating film, In a high-breakdown-voltage semiconductor device having a second-layer insulating film formed on the field nitride film, the first-layer insulating film is configured to perform a gettering process before the formation of the field nitride film.

[0005]

According to this structure, since the first layer insulating film is subjected to the gettering process, the film quality is cleaned, and the field insulating film and the second layer insulating film subjected to the phosphorus treatment are used together with the semiconductor substrate such as silicon. Interface cleaning is achieved,
A highly reliable high breakdown voltage semiconductor device is provided.

[0006]

FIG. 1 is a sectional view of a peripheral portion of a chip of a high breakdown voltage semiconductor device according to an embodiment of the present invention. Reference numeral 1 denotes an N-type silicon semiconductor substrate, and a P-type guard ring diffusion layer 2.
And an N ⁺ type annular diffusion layer 3. An aluminum shield 14 is formed on the annular diffusion layer 3 as a shield metal. The backing 12 constitutes a lower electrode of the semiconductor substrate 1. This portion is a peripheral portion of the chip, and is formed in a central portion of the chip (not shown) connected to the base diffusion layer 11 and the aluminum film 9.
Alternatively, it is located around the element region of the bipolar transistor.

On the surface of the semiconductor substrate 1 is provided a first layer insulating film 5 which has been subjected to a phosphorus treatment, and a field nitride film 6 is deposited thereon, and a second layer insulating film 7 is further formed thereon. A protective film such as a certain phosphorus glass film is formed. Since the first-layer insulating film has been subjected to the phosphorus treatment, the first-layer insulating film that is directly in contact with the silicon semiconductor substrate interface is cleaned by the gettering action of phosphorus. Further, the field nitride film 6 and the second-layer insulating film 7 are such that the phosphorus glass film is cleaned by a gettering action of phosphorus, and the nitride film is a second-layer insulating film because of the property of not allowing contaminants to pass through. The extrinsic contaminants are shut out by the field nitride film 7 and the field nitride film 6 to stabilize the silicon interface.

Hereinafter, one embodiment of a method of manufacturing the high breakdown voltage semiconductor device will be described. The first layer insulating film 5 is a thermal oxide film, and is first formed on the semiconductor substrate 1 when manufacturing a MOSFET or a bipolar transistor. A photoresist is applied and an oxide film is opened by photoetching to form a base diffusion layer 11 and a guard ring diffusion layer 2 or a P-type deep diffusion region serving as a diffusion layer for separating cells of transistors. . Boron, which is a P-type impurity, is deposited or ion-implanted, and a diffusion layer is formed by heat treatment.

Before the field nitride film 6 is formed, a gettering process using phosphorus is performed. This phosphorous treatment is performed by, for example, turning the surface of the thermal oxide film that is the first layer insulating film 5 into phosphor glass using POCl ₃ . Thereafter, a nitride film to be the field nitride film 6 is grown by chemical vapor deposition (CVD). Then, a pattern of the field nitride film 6 is formed by photoetching. Next, a second layer insulating film 7 is formed by CVD. And
The second layer insulating film 7 and the first layer insulating film 5 are opened by photoetching according to the annular pattern. Then, an N ⁺ -type deep diffusion layer serving as the annular diffusion layer 3 at the end of the chip is formed by depositing phosphorus and driving in.

Thereafter, a MOS region is formed in the cell region at the center of the chip.
For example, an emitter diffusion region or the like constituting an FET or a bipolar transistor is formed, and an oxide film is formed.
Next, the CVD oxide film as the second layer insulating film 7 is subjected to a phosphorus treatment. The phosphorus treatment is performed in the same manner as in the first insulating film, for example, by POC
Use l _3, is carried out by phosphorylating vitrifying CVD oxide film which is the second layer insulation film 7. Finally, a contact opening is provided by photoetching, an aluminum film 9 is applied, and an electrode pattern is formed, thereby completing a high breakdown voltage semiconductor device.

[0011]

According to the present invention, in a high breakdown voltage semiconductor device having a first layer insulating film, a field nitride film, and a second layer insulating film, the first layer insulating film is subjected to a phosphorus treatment before the field nitride film is formed. Therefore, the interface between the semiconductor substrate and the first-layer insulating film is cleaned by the gettering action of phosphorus,
The reliability of the high breakdown voltage semiconductor device is improved by reducing the leakage current and preventing the breakdown voltage from deteriorating.

[Brief description of the drawings]

FIG. 1 is a sectional view of a peripheral portion of a chip of a high breakdown voltage semiconductor device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a peripheral portion of a chip of a conventional high breakdown voltage semiconductor device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 29/78 H01L 21/318 H01L 21/322 H01L 21/336 H01L 29/06 H01L 29/73-29 / 739

Claims (2)

(57) [Claims] A first layer insulating film formed on a semiconductor substrate by thermal oxidation, a field nitride film formed on the first layer insulating film, and a first layer insulating film formed on the field nitride film. A high-breakdown-voltage semiconductor device having a second-layer insulation film, wherein the first-layer insulation film is gettered before the field nitride film is formed. 2. The high breakdown voltage semiconductor device according to claim 1, wherein the first and second insulating films are both subjected to a gettering process.