JPH1154505A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce hydrogen content of silicon nitride film, by forming a silicon nitride film to be used as a passivation film covering a semiconductor substrate surface and/or an interlayer insulating film by using a plasma CVD method, and heat-treating the silicon nitride film in a vacuum atmosphere. SOLUTION: A gate 6 is laminated on a gate oxide film 4. A source electrode 7 is in contact with a source region 2. A drain electrode 8 is in contact with a drain region 3. The gate 6, the source electrode 7 and the drain electrode 8 are composed of Al material. As to the gate 6, poly-Si also is much used for a gate electrode. Surfaces of Al wiring layers 6-8 and a field oxide film 5 are covered with a silicon nitride film 9 for passivation, which is a P-SiN film formed by a plasma CVD method. The composition is SiNy Hz . By heat- treating the P-SiN film 9 in a vacuum atmosphere, the hydrogen content of the film is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device for reducing the hydrogen content of a silicon nitride film formed by a plasma CVD method.

[0002]

2. Description of the Related Art Since a silicon nitride film (Si ₃ N ₄ ) is excellent in a function of preventing diffusion of moisture and sodium (Na) and a function of blocking radiation, a silicon (Si) substrate has a semiconductor integrated circuit (IC / LSI). Used as a passivation film or an interlayer insulating film. This silicon nitride film is also used as a mask during selective oxidation of the silicon substrate.

A silicon nitride film is formed by thermal CVD, optical CVD,
It is formed by various methods such as plasma CVD. A silicon nitride film formed by a plasma CVD method (hereinafter, referred to as P-SiN to be distinguished from a silicon nitride film formed by another method) contains a relatively large amount of hydrogen (H ₂ ) in the film. The hydrogen content depends on the growth conditions. The composition of the silicon nitride film formed by plasma CVD (P-SiN) is strictly not the Si ₃ N ₄ is SixNy Hz form in which a hydrogen is bound to Si and N in the form of Si-H and N-H Take.

In plasma CVD, for example, a processing temperature (250 ° C.) lower than the processing temperature (700-800 ° C.) of low pressure CVD
Although there is an advantage that a silicon nitride film can be grown at −350 ° C.), the hydrogen content (20-25 atomic%) is large, and reaches several times the hydrogen content (4-8 atomic%) of low-pressure CVD. .

In a MOS type semiconductor device using a silicon nitride film, when hydrogen liberated from the nitride film enters the gate oxide film, an electron trap is formed, which causes unstable device characteristics. In a bipolar semiconductor device using a silicon nitride film, when hydrogen in the nitride film enters the Si substrate, it causes a change in the current amplification factor hFE.

In order to reduce the hydrogen content in a silicon nitride film formed by plasma CVD, (1) oxygen (O ₂ ) is added to a gas during growth to mix SiO ₂ and Si ₃ N _4. (2) A method of lowering the power supply frequency of plasma generation is known.

[0007]

The above-mentioned method (1) for adding oxygen or the method (2) for lowering the power supply frequency imposes additional conditions on the plasma CVD process, and therefore controls the growth of the silicon nitride film. There is a problem that the setting of the original conditions of the plasma CVD is limited. This is a problem to be solved by the present invention.

It is an object of the present invention to provide a method of manufacturing a semiconductor device capable of reducing the hydrogen content of a formed silicon nitride film without restricting the formation of the silicon nitride film by a plasma CVD method. And

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to form a silicon nitride film used as a passivation film and / or an interlayer insulating film covering a semiconductor substrate surface by a plasma CVD method. Heat-treating in a vacuum atmosphere to reduce the hydrogen content.

[0010] Plasma CVD for forming a silicon nitride film
If a step for reducing the hydrogen content of the silicon nitride film is provided after the step, the plasma CVD step is performed by plasma CVD with only the conditions relating to the silicon nitride film such as the thickness and composition of the silicon nitride film to be grown in mind. Can be executed. Heat treatment as a post-process is performed in a vacuum atmosphere,
Hydrogen contained in the silicon nitride film is efficiently desorbed. As a result, the reaction between hydrogen and hot carriers is reduced, and deterioration of device characteristics is prevented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings. FIG. 1 shows the first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a MOS semiconductor device according to the first embodiment.
In the figure, 1 is a p-type silicon (Si) semiconductor substrate, 2 and 3 are n ⁺ -type source and drain regions diffusedly formed on the surface of the substrate 1, and 4 is a layer for oxidizing an upper layer of a channel region on the substrate 1 Gate oxide film (SiO ₂ )
5 is a thick field oxide film (S
iO ₂ ), 6 are gates stacked on the gate oxide film 4,
Reference numeral 7 denotes a source electrode that contacts the source region 2, and 8 denotes a drain electrode that contacts the drain region 3.

Gate 6, source electrode 7, drain electrode 8
Are all aluminum (Al) materials. Of these gates, the gate electrode is often poly-si. The surfaces of these Al wiring layers 6, 7, 8 and field oxide film 5 are covered with a silicon nitride film 9 for passivation.
Covered with. This silicon nitride film 9 is P-SiN formed by plasma CVD, and has a composition of SixNyHz. In the present invention, the P-SiN film 9 is heat-treated in a vacuum atmosphere to reduce the hydrogen content in the film.

FIG. 2 is a sectional view of a bipolar semiconductor device according to a second embodiment of the present invention. In the figure, 11 is an n-type Si semiconductor substrate, 12 is a p-type base region formed by deep diffusion on the surface of the substrate 11, and 13 is this base region 1.
An n ⁺ -type emitter region which is thinly diffused on the surface of
Reference numeral 14 denotes an n ⁺ -type collector extraction region which is thinly diffused and formed on the surface of the n-type substrate 11 (the collector region is the n-type substrate 11
15) is a field oxide film (SiO ₂ ) obtained by oxidizing the surface of the substrate 11, 16, 17, and 18 are base, emitter and collector electrodes of Al material, and 19 is a silicon nitride film for passivation which covers the entire surface. It is.

This silicon nitride film 19 is formed by plasma CVD.
Is a P-SiN formed at a composition of SixNyHz
is there. In the present invention, the P-SiN film 19 is heat-treated in a vacuum atmosphere to reduce the hydrogen content in the film.

FIG. 3 is a cross-sectional view of a bipolar semiconductor device of a two-layer wiring type showing a third embodiment of the present invention. In the figure, 11 is an n-type Si semiconductor substrate, 12 is a p-type base region deeply formed on the surface of the substrate 11, and 13 is an n ⁺ -type emitter region thinly formed on the surface of the base region 12. Reference numeral 14 denotes an n ⁺ -type collector extraction region which is thinly diffused and formed on the surface of the n-type substrate 11 (the collector region is the n-type substrate 11 itself, 15 is a field oxide film (SiO ₂ ) obtained by oxidizing the surface of the substrate 11, 16, 17, 1
8 is a base, emitter and collector electrode of Al material,
Reference numeral 19 denotes a first layer silicon nitride film for interlayer insulation.

A second layer of Al wiring layers 20, 21, and 22 are formed on the first layer of silicon nitride film 19, and the entire surface thereof is formed of a second layer of silicon nitride film 2 for passivation.
Covered with 3. Each of the silicon nitride films 19 and 23 is P-SiN formed by plasma CVD, and has a composition of Si.
xNyHz. In the present invention, the P and P of the first and second layers are
Heat treating the SiN films 19 and 23 in a vacuum atmosphere to reduce the hydrogen content in the films;

[Embodiment 1] The P-SiN films 9, 19 and 23 of the semiconductor device shown in FIGS.
° C) and a processing time (230 sec) by plasma CVD to a film thickness (6500 °).
^-5 Torr), processing temperature (350 ° C.), processing time (30
Vacuum heat treatment was performed under the conditions of sec).

[0018]

As described above, according to the present invention, it is possible to reduce the hydrogen content of a formed silicon nitride film without limiting the formation of the silicon nitride film by the plasma CVD method. Can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a MOS semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a bipolar semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a two-layer wiring type bipolar semiconductor device according to a third embodiment of the present invention.

[Explanation of symbols]

 1,11 Si semiconductor substrate 2 source region 3 drain region 4 gate oxide film 5,15 field oxide film 6 gate 7 source electrode 8 drain electrode 9,19,23 silicon nitride film (P-SiN) 12 base region 13 emitter region 14 Collector extraction region 16 Base electrode 17 Emitter electrode 18 Collector electrode 20, 21, 22 Second Al wiring layer

Claims (1)

[Claims] A step of forming a silicon nitride film used as a passivation film and / or an interlayer insulating film covering a surface of a semiconductor substrate by a plasma CVD method, and a heat treatment of the silicon nitride film in a vacuum atmosphere to reduce a hydrogen content. A method of manufacturing a semiconductor device, comprising: