JPH053190A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent voids from being formed inside a passivation film when a passivation film is made to grow on a semiconductor device. CONSTITUTION:A BPSG 13 is made to grow on a semiconductor substrate where a metal wiring of Al-Si-Cu or the like is formed, and then the substrate is thermally treated (reflow) to eliminate voids 14 generated in the BPSG 13. Boric acid contained in BPSG is so set in concentration not to induce stress migration in a metal wiring at reflow, whereby voids generated in a passivation film can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a protective film on a semiconductor substrate.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional semiconductor device protective film (hereinafter referred to as passivation) has a metal wiring 3
1 has a silicon nitride layer (hereinafter referred to as S
iN) 32 or a phosphorous glass layer (hereinafter referred to as PSG) 42 is grown on a semiconductor substrate on which metal wiring 41 is formed as shown in FIG.
Was growing 3.

[0003]

In recent years, as the degree of integration of semiconductor devices has increased, the metal wiring width and the distance between metal wirings have rapidly narrowed with respect to the passivation film thickness. When the passivation is grown on the metal wiring under such circumstances, it is extremely difficult to grow the passivation having a uniform thickness on the side surface of the metal wiring and on the substrate between the metal wirings. That is, as in the conventional passivation shown in FIGS. 3 and 4, the cusping phenomenon in which the passivation grows thickly on the upper side surface of the metal wiring and thinly grows on the lower side surface is remarkable. When the passivation film becomes relatively thick, the portion surrounded by the cuspings 35a, b or 46a, b becomes a cavity (hereinafter referred to as a void) and remains during the passivation, which causes moisture intrusion, adsorption of impurity gas, etc. Has become.

[0004]

A semiconductor device according to the present invention comprises (1) a step of forming metal wiring on a semiconductor substrate, and (2) a step of growing BPSG on a semiconductor substrate having the metal wiring formed thereon (3). ) Heat treatment of BPSG and (4)
Generation of voids during passivation is prevented by using a manufacturing method including a step of growing SiN on the heat-treated BPSG.

[0005]

Function: Immediately after growing BPSG on a semiconductor substrate having metal wiring formed thereon, the BPSG film thickness is non-uniform and cusping is observed. However, when heat treatment (hereinafter referred to as reflow) is performed, BPSG is melted and the cusping generated on the side surface of the metal wiring is relaxed.

[0006]

Embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A to 1D are views for explaining the first embodiment of the present invention in the order of manufacturing steps. First, as shown in FIG. 1A, a metal wiring layer is grown on a semiconductor substrate 12 and a metal wiring 11 is formed by a photolithography process. Here, the material of the metal wiring layer is Al-Si (1%)-Cu (0.
1%) is assumed.

Next, as shown in FIG. 1B, BPSG1
3 is grown to the same thickness as the metal wiring. In this state, the portion surrounded by the cuspings 15a and 15b remains as the void 14, and no difference from the conventional passivation can be seen. Here, the boric acid concentration of the BPSG 13 may be determined in consideration of the reflow temperature described below.

Next, as shown in FIG. 1C, the semiconductor substrate is heated and reflowed. The heating temperature is a temperature within a range where stress migration does not occur in the metal wiring. By the reflow, the BPSG 13 shown in FIG. 1B is melted and the cusping 15 is relaxed. As a result, BPSG13
The void 14 remaining inside is filled with the BPSG 16 and disappears.

Next, as shown in FIG. 1D, BPSG1
SiN 17 is grown on 6. Although SiN has a property of easily causing cusping, a relatively uniform film thickness can be obtained by growing SiN 17 on the BPSG 16 that has been subjected to the above-mentioned reflow, and unevenness on the surface of SiN can be relaxed.

FIGS. 2A to 2F are views for explaining the second embodiment of the present invention in the order of manufacturing steps. In this embodiment, the case where there is a step such as a polysilicon wiring before the metal wiring is formed is described.

First, as shown in FIG. 2A, polysilicon is grown on a semiconductor substrate 201 and a polysilicon wiring 202 is formed by a photolithography process.

Next, as shown in FIG. 2B, the interlayer insulating film 2 is formed.
Grow 03. Here, the material of the interlayer insulating film 203 is assumed to be a silicon oxide film formed by a vapor phase epitaxy method.

Next, as shown in FIG. 2C, a metal wiring layer is grown and a metal wiring 204 is formed on the polysilicon wiring by a photolithography process.

Next, as shown in FIG. 2D, BPSG2
05 is grown to the same thickness as the metal wiring. In this embodiment, since the metal wiring 204 is formed on the polysilicon wiring 202, the step between the upper portion of the metal wiring and the portion where the metal wiring is not formed is steep. Therefore, in this state, the void 206 surrounded by the cuspings 208a and 208b is formed.
In addition, voids 207 are generated due to the recesses in the interlayer insulating film.

Next, as shown in FIG. 2E, the semiconductor substrate is heated and reflow is performed. Figure 2 (d) by reflow
The void 206 on the side surface of the metal wiring disappears and the void 207 on the concave portion of the interlayer insulating film also disappears.

Next, as shown in FIG. 2 (f), BPSG2
SiN 210 is grown on 09. In the case of this embodiment, B
The surface of PSG is not so flat, but the recess of BPSG is shallower than that of the conventional manufacturing method.
It is possible to prevent the occurrence of voids inside.

[0018]

As described above, in manufacturing a semiconductor device, as described above, (1) a step of forming metal wiring on a semiconductor substrate, and (2) growing a borate phosphorus glass layer on the semiconductor substrate on which the metal wiring is formed. By using the manufacturing method including the steps of (3) heat treating the phosphoric acid borate glass layer and (4) growing the silicon nitride layer on the heat treated phosphoric acid borate glass layer, the passivation between the metal wirings is performed. It is possible to prevent the occurrence of voids.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention in the order of manufacturing steps using sectional views of a semiconductor device.

FIG. 2 is a diagram showing a second embodiment of the present invention in the order of manufacturing steps using sectional views of a semiconductor device.

FIG. 3 is a view showing a manufacturing process according to a conventional technique by using a sectional view of a semiconductor device.

FIG. 4 is a view showing a manufacturing process according to a conventional technique using a cross-sectional view of a semiconductor device.

[Explanation of symbols]

 11 --- Metal wiring 12 --- Semiconductor substrate 13 --- BPSG 14 --- Void 15a, b --- Casping 16 --- ... BPSG 17 after reflow ... SiN 201 ... semiconductor substrate 202 ... polysilicon wiring 203 ... interlayer insulating film 204 ...・ ・ ・ Metal wiring 205 ・ ・ ・ ・ BPSG 206 ・ ・ ・ ・ ・ Void 207 ・ ・ ・ ・ ・ Void 208a, b ・ ・ ・ Casping 209 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ BPSG after reflow 210 ・ ・ ・・ ・ ・ ・ SiN 31 ・ ・ ・ ・ Semiconductor substrate 32 ・ ・ ・ ・ ・ Metal wiring 33 ・ ・ ・ ・ SiN 34 ・ ・ ・ ・ Voids 35a, b ・ ・ ・ ・Casping 41 ..... Semiconductor substrate 42 .. Genus wiring 43 ······· PSG 44 ······· SiN 45 ······· voids 46a, b · · · · Kasupingu

Claims (1)

Claims: (1) A step of forming metal wiring on a semiconductor substrate; (2) A step of growing a phosphoric acid borate glass layer on a semiconductor substrate on which the metal wiring is formed; and (3) A method of manufacturing a semiconductor device comprising a step of heat-treating a phosphorous borate glass layer and (4) a step of growing a silicon nitride layer on the heat-treated phosphorous borate glass layer.