JPH118234A - Semiconductor device - Google Patents

Abstract

(57) [Problem] To provide a highly reliable semiconductor device in which characteristics are not deteriorated by reducing the amount of hydrogen in an interface with a semiconductor substrate and in an insulating film. SOLUTION: A semiconductor substrate 1 on which a circuit element is formed,
A semiconductor device comprising: an insulating film provided on the semiconductor substrate; a metal wiring 9 provided on the insulating film; and a protective insulating film provided on the metal wiring, provided on the semiconductor substrate. The insulating film has at least three insulating films, the first insulating film 6 near the semiconductor substrate is made of silicon oxide having a hydrogen concentration of 1 at% or less, and the second insulating film 7 is made of silicon. The third insulating film 8 is made of an excessive silicon oxide film, a silicon nitride film or a silicon oxide nitride film, and the silicon nitride film having a silicon concentration of less than 50 at%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor device on which an integrated circuit is formed. More specifically, the present invention relates to a semiconductor device which prevents generation of trap levels in a silicon interface or an insulating film and does not cause deterioration of element characteristics even when a high electric field is applied.

[0002]

2. Description of the Related Art In a conventional semiconductor device on which an integrated circuit is formed, a thermal oxide film 2 for element isolation is formed on a surface of, for example, a p-type semiconductor substrate 1 as shown in FIG. Are formed, a thin gate oxide film 3 and a gate electrode 4 made of polysilicon are formed on the surface of the semiconductor substrate 1 therebetween, and n ^{+ type} diffusion regions 5a of source and drain are formed on the semiconductor substrate 1 on both sides of the gate electrode 4. By forming 5b, a MOSFET is formed, an interlayer insulating film 11 made of silicon oxide (hereinafter, referred to as SiO) is provided on semiconductor substrate 1 and gate electrode 4, and metal wiring 9 is provided thereon. And is connected to the gate electrode 4 and the like via a contact hole (not shown). Further, a silicon nitride (hereinafter referred to as SiN)
) Is provided.

An insulating film such as an interlayer insulating film or a protective insulating film is provided by a CVD method such as a plasma CVD method.
Typically, the interlayer film on polysilicon is made of SiO (SiO
Phosphosilicate glass (PS) doped with phosphorus
G) or boron phosphosilicate glass (BPSG) in which boron and phosphorus are doped into SiO), and when metal wiring is provided in a plurality of layers, SiO or SiN is used as an interlayer insulating film between them. Have been.

[0004]

The insulating film formed by the above-mentioned CVD method contains hydrogen (H).
As shown by the dashed line in FIG. 4, this H advances to the semiconductor substrate 1 side and interacts with hot carriers generated by a high electric field, and trap levels appear at the silicon (Si) interface and in each insulating film (FIG. 4). A) and trap charges (see FIG. 4B). In particular, a SiN film formed by a plasma CVD method usually has a hydrogen concentration of about 20 at%,
It is about one digit larger than SiO by the VD method, and is the largest hydrogen supply source. However, in the manufacture of the above-described semiconductor device, Al or the like of metal wiring may be weak to heat.
An SiN film formed by a plasma CVD method is used as an interlayer insulating film. Therefore, trap levels and trap charges are likely to be generated in a portion closer to the semiconductor substrate 1 where the element is formed and high voltage is applied. There is a problem that the element characteristics are deteriorated with time due to these levels and charges.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to reduce the amount of hydrogen in an interface with a semiconductor substrate and in an insulating film so that a highly reliable semiconductor device which does not cause deterioration in characteristics can be obtained. The purpose is to provide.

[0006]

A semiconductor device according to the present invention comprises a semiconductor substrate on which circuit elements are formed, an insulating film provided on the semiconductor substrate, a metal wiring provided on the insulating film, and a metal wiring. A semiconductor device having a protective insulating film provided thereon, wherein the insulating film provided on the semiconductor substrate has at least three layers of insulating films, and an insulating layer of a first layer close to the semiconductor substrate is provided. The film has a hydrogen concentration of 1 at
% Of silicon oxide, the second-layer insulating film is made of silicon-excess silicon oxide film or silicon nitride film or silicon oxide nitride film, and the third-layer insulating film has a silicon concentration of 50 at (atoms). % Of the silicon nitride film.

Here, the silicon oxide film, silicon nitride film or silicon oxide nitride film refers to a compound of silicon and oxygen and / or nitrogen, or a material obtained by doping phosphorus, boron or the like, hydrogen, or the like. It is meant to include those in which other elements are mixed.

An insulating film of the same type as the first or second insulating film is further provided between the first and second insulating films and / or between the second and third insulating films. May be provided. Even when an insulating film is further provided with a large number of metal wiring layers, entry of hydrogen into the semiconductor substrate can be prevented by providing such an insulating film in the insulating film.

[0009]

Next, a semiconductor device according to the present invention will be described with reference to the drawings. In addition, each drawing is shown as an explanatory diagram, and the insulating film portion is illustrated as being enlarged and thicker than the semiconductor substrate portion.

A semiconductor device according to the present invention has, for example, a p-type S type as shown in FIG.
A circuit element such as a transistor is formed on a semiconductor substrate 1 made of i, and at least three insulating films are formed thereon.
Out of the three layers, the first insulating film 6 closest to the semiconductor substrate is made of silicon oxide (SiO) having a hydrogen concentration of 1 at% or less. The second insulating film 7 is made of silicon-excess silicon oxide (SiO) or silicon nitride (SiN) or silicon oxide nitride (Si) in which the amount of Si is greater than the stoichiometric composition ratio.
ON). For example, in the case of a SiN film, Si
The concentration is 50 at% or more. And the third on the most front side
The insulating film 8 is a SiN film having a Si concentration of less than 50%. Although not shown, the surface of the third insulating film 8 is further provided with a junction coat resin (JC
R) or a protective film such as polyimide may be provided.

In FIG. 1, a semiconductor substrate 1 is provided with a thermal oxide film 2 for element isolation on the surface thereof, and a gate electrode 4 made of polysilicon or the like with a gate insulating film 3 interposed therebetween. For example, source and drain regions 5a and 5b formed of n ⁺ -type regions are formed on the semiconductor substrate 1 on both sides of the gate electrode 4, so that the MOS
An FET is formed.

On the gate electrode 4 made of polysilicon,
The above-mentioned first insulating film 6 is provided with a thickness of about 0.5 to 2 μm. The first insulating film 6 is made of SiO formed so that the hydrogen concentration becomes 1 at% or less. That is, since SiN tends to have a high hydrogen concentration, it is made of SiO.
Also, even in BPSG doped with boron and phosphorus, the base is SiO, and the hydrogen concentration can be reduced.
In this case, when a film is formed by plasma CVD using monosilane (SiH ₄ ) as a source gas as a base, it is difficult to reduce the hydrogen concentration to 1 at% or less. When SiH ₄ is used, normal pressure CVD (thermal CVD) is used. ), Or when the film is formed by a plasma CVD method, TEOS (tetraethyl orthosilicate) is preferably used as a base of the source gas.

A contact hole (not shown) is formed in the first insulating film 6, and a metal such as Al is formed and patterned to connect to the lower gate electrode 4 and a wiring (not shown). The wiring 9 is formed. Then, a second-layer insulating film 7 is provided thereon.

The second insulating film 7 is made of a Si-excess SiO, SiN or SiON in which the Si content is larger than the stoichiometric composition ratio.
And is formed to a thickness of about 0.2 to 1 μm. For example, in the case of SiN, it is preferable to set the Si concentration to 50 at% or more from the viewpoint of gettering efficiency and conductivity. To form such an Si-excessive insulating film 7,
When the film is formed by the CVD method or the like, the film is easily formed by increasing the flow rate of SiH ₄ or the like as the Si source gas and forming the film by the plasma CVD method or the thermal CVD method.

The third insulating film 8 has an Si concentration of 50 at.
% Of SiN, and is formed to a thickness of about 0.2 to 1 μm. This is a SiN film formed by an ordinary method, and is formed by a plasma CVD method or the like.
This SiN film contains a certain amount of hydrogen at the time of film formation, but is a dense film and prevents intrusion of impurities such as hydrogen based on moisture and the like from outside air.

According to the present invention, the insulating film formed on the semiconductor substrate comprises at least three layers of insulating films, and the three layers prevent accumulation of hydrogen on the semiconductor substrate side. Therefore, even when a high electric field is generated, a trap level does not occur and electric characteristics are not deteriorated.

That is, since the insulating film of the first layer on the side close to the substrate is made of SiO having a low hydrogen concentration, the penetration of hydrogen during film formation is small, and the interface with the semiconductor substrate and the semiconductor substrate at the initial stage are not formed. The hydrogen concentration in a close insulating film can be reduced. Therefore, formation of trap levels and generation of trap charges can be prevented even when a high electric field is generated. Further, the insulating film of the second layer is made of Si excess Si.
Since it is made of O, SiN, or SiON, it has many dangling bonds (non-bonding orbitals exposed on the surface) and at the same time becomes semiconductive. Therefore, it is chemically very active, has a large reaction on the surface, and has excellent gettering action. As a result, it is possible to capture hydrogen diffused from an upper layer such as the third insulating film and to prevent entry into the first insulating film. Further, it functions to escape trapped charges generated by a high electric field at the Si interface, the first layer insulating film, and the like, and to electrically cancel the trapped charges. The third layer insulating film is formed of a dense insulating film of SiN, and prevents entry of hydrogen or the like due to moisture or the like from the outside. On the other hand, SiN tends to contain hydrogen at the time of film formation, but the hydrogen does not enter the first layer side because the hydrogen is gettered by the insulating film of the second layer. As a result, the possibility that hydrogen is present on the semiconductor substrate side close to the circuit element is greatly reduced, and no trap level is generated even when a high electric field is applied. Therefore, a highly reliable semiconductor device in which electric characteristics are not deteriorated can be obtained.

An NMOS semiconductor device having an insulating film of this structure is manufactured, and a reverse bias of several tens of volts to several hundred volts is applied, and the temperature is increased to 150 ° C. and the relative humidity is increased to 85% under the stress of an atmosphere. When the accelerated test of high temperature, high humidity, and reverse bias is performed for a long time, the result is compared with the result of the accelerated test under the same conditions of the semiconductor device with the same circuit element formed with the conventional insulating film. FIG. As is clear from FIG. 2, the case C using the conventional insulating film is 2
Almost 100% of the products were rejected under the stress of about 00 hours, but the product D of the structure of the present invention had a rejection rate of almost 0 even after 200 hours or more.

FIGS. 3A to 3C show a modification of the structure of FIG. 1, in which metal wirings 9a and 9b are provided in two layers. In the example shown in FIG. 3A, the first metal wiring 9a is provided on the insulating film 6 of the first layer,
Is provided on the second-layer insulating film 7, and a third-layer insulating film 8 is provided thereon. The structures of the first to third insulating films 6 to 8 are the same as those in the example shown in FIG. 1. Even when the metal wiring has two layers, intrusion of hydrogen can be similarly prevented.

The example shown in FIG. 3B is an example in which the number of insulating films is increased in accordance with the increase in the number of metal wirings, and between the insulating film 6 of the first layer and the insulating film 7 of the second layer. A fourth insulating film 10 is provided, and a first metal wiring 9 a is formed on the first insulating film 6.
Is provided, and a second metal wiring 9 b is provided on the fourth insulating film 10. The fourth insulating film 10 needs to prevent the intrusion of hydrogen in the same manner as described above. Like the first insulating film 6, the fourth insulating film 10 may be formed of a SiO film having a hydrogen concentration as low as 1 at% or less, or Excess Si as well as layer
By forming an O, SiN, or SiON film, entry of hydrogen can be prevented.

In the example shown in FIG. 3C, the increase in the thickness of the insulating film due to the increase in the number of metal wirings is caused by the fourth insulating film 8 between the second insulating film 7 and the third insulating film 8. It is provided as a film 10. Also in this example, as in the example of FIG. 3B, the fourth insulating film 10 is formed by using an insulating film of the same material as the first insulating film or the second insulating film, so that hydrogen is used. Can be sufficiently prevented from entering the substrate side.

[0022]

According to the structure of the present invention, the amount of hydrogen on the semiconductor substrate side is very small, and hydrogen does not diffuse to the substrate side thereafter. No aging degradation occurs. As a result, stable electric characteristics can be maintained, and a highly reliable semiconductor device can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of an insulating film portion of an embodiment of a semiconductor device of the present invention.

FIG. 2 is a diagram showing a defect rate when an accelerated test is performed by applying stress to the semiconductor device having the structure of FIG. 1 in comparison with a defect rate of a conventional structure.

FIG. 3 is a diagram showing a structure of an insulating film portion of another embodiment of the semiconductor device of the present invention.

FIG. 4 is a diagram showing a structure of an insulating film portion of a conventional semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 6 first-layer insulating film 7 second-layer insulating film 8 third-layer insulating film 9 metal wiring 10 fourth insulating film

Claims (3)

[Claims] 1. A semiconductor substrate on which a circuit element is formed, an insulating film provided on the semiconductor substrate, a metal wiring provided on the insulating film, and a protective insulating film provided on the metal wiring. Wherein the insulating film provided on the semiconductor substrate has at least three insulating films, and the first insulating film on the side closer to the semiconductor substrate has a hydrogen concentration of 1 at% or less. The second layer insulating film is made of a silicon oxide film or a silicon nitride film having a silicon concentration of excess silicon, and the third layer insulating film is made of a silicon chip having a silicon concentration of less than 50 at%. Semiconductor device consisting of an oxide film. 2. The semiconductor device according to claim 1, further comprising an insulating film of the same type as the first or second insulating film, between the first and second insulating films. 3. The semiconductor device according to claim 1, wherein an insulating film of the same kind as the first or second layer is further provided between the second and third insulating films.