JPS6159747A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To flatten a field oxide film surface by coating the entire surface of a semiconductor substrate on which a field oxide film is formed by a selective oxide film forming method with a silica film and executing ion etching with inactive gas ion. CONSTITUTION:A semiconductor element and a field oxide film 6 which protects a semiconductor element are formed on a semiconductor substrate 1 by the selective oxide film forming method. Next, entire surface of substrate is coated with a silica film 9. Thereby, the film 9 is formed thin at the recessed part corresponding to the bird's head 8. The ion etching (sputter etching) 10 is carried out using inactive gas such as Ar, etc. and the remaining film 9 is removed. Thereby, since the etching rate is almost equal in the case of film 9 and oxide film 6, the extruded part of bird's head 8 is etched and the element surface is flattened. Accordingly, disconnection at the stepped part of metal wirings is not easily generated.

Description

Detailed Description of the Invention (Field of Application on M Beams) The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device including a step of planarizing a field oxide film formed by a selective oxide film forming method. .

(Prior art) Conventionally, element isolation technology using selective oxide film formation was applied to LSI
It has been widely applied as the definitive solution to higher miniaturization and higher integration. FIG. 4 is a cross-sectional view of an example of a bipolar transistor to which the conventional selective oxide film formation method is applied. As shown in FIG. 4, a collector N-N is placed on the Pfi substrate 1.
An element region consisting of an epi region 2, a base P region 3, and an emitter N region 4 is formed, and finally a metal wiring 5 is formed. As is clear from FIG. 4, the semiconductor device formed in this manner suffers from problems such as the bird's beak phenomenon that occurs at the end of the field oxide film 6 and the bird's head phenomenon that occurs on the surface of the field oxide film. (bi
rd's head) B phenomenon Kaal.

Bird's peaks impede device miniaturization, while bird's heads cause unevenness in the field oxide film, resulting in loss of device surface flatness. Therefore, if metal wiring is formed on a field oxide film in which such bird's heads exist, disconnection will occur. Particularly in multilayer wiring, the frequency of such failures tended to be high. As a result, there were disadvantages in that the chip yield decreased and the cost increased.

(Objective of the Invention) The object of the present invention is to eliminate the above-mentioned drawbacks, eliminate the depressions and protrusions on the field oxidation layer, and prevent disconnection of metal wiring by improving the flatness of the device surface. Another object of the present invention is to provide a method for manufacturing a semiconductor device that can improve reliability and reduce costs.

(Structure of the Invention) A method for manufacturing a semiconductor device according to the present invention includes a step of forming a field oxide film on one main surface of a semiconductor substrate by a selective intensification film forming method, and a step of forming a circuit element in one circuit element formation region. , a step of applying a silica film to the entire surface of the substrate on which a field oxide film is formed, and a step of flattening the surface of the field oxide film by performing ion etching from the upper surface of the silica film using inert gas ions. be done.

(Function) According to the present invention, a silica film is first applied to the surface of the field oxide film formed by selective oxidation, which has large irregularities due to perspective peaks and bird's heads. Therefore, the silica film is guided at the convex portions and thickened at the concave portions, so the surface of the silica film is #1 at the concave and convex portions.
It becomes flat.

Next, an inert gas such as Ar is ionized from the upper surface of the silica film to perform ion etching. Unlike reactive ion etching, this etching has approximately the same etching rate for the silica film and the oxide film, so the device surface can be uniformly etched and a flat oxide film surface can be formed.

Therefore, if wiring is formed on this flattened surface, a highly reliable and low-cost semiconductor device without disconnection accidents can be obtained.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 (6) is a sectional view showing the steps in order to explain an embodiment of the present invention.

First, as shown in FIG. 1(a) Jc, a P-type semiconductor substrate 1 is
Collector N” Nepi area 2, base,
A P region 3, an emitter region, an N+ region 4, and a field oxide film 6 for isolating each element and protecting the element surface are formed. In the 1st ff1(a), 7#i is Bird's Peak and 8 is Bird's Head. The steps up to this point can be applied to the conventional method of forming a selective acid film.

Next, as shown in FIG. 1(b), a silica film 9 is formed on the entire surface of each region 2, 3.4 and the field oxide film 6. As shown in the figure, the convex portion corresponding to the bird's head 8 is thin.

The silica film 90 is coated thickly in the concave portions, and the surface of the silica film 90 becomes substantially flat in the concave and convex portions.

Next, as shown in FIG. 1C, an inert gas such as Ar is ionized from the upper surface of the silica film 9, and ion etching (also referred to as sputter etching) is performed.

Unlike reactive ion etching, the etching rates of the silica film and the oxide film are approximately equal, so they are etched uniformly.

Next, as shown in FIG. 1(d), ion etching is performed for an appropriate time to remove the convex portion of the bird's head together with the silica film. Thereafter, the remaining silica 7 is removed, the protrusions of the parsing head 8 are relaxed, and a flattened surface is obtained.

Next, as shown in FIG. 1(e), a metal wiring 5 is formed to obtain the semiconductor device formed in this embodiment in which the metal wiring is formed on a flat surface as shown in the figure.

In the semiconductor device i formed with an edge in this example, the level difference in the metal wiring on the 8th surface of the bird's head is greatly reduced. After planarizing the oxide film and removing the silica film, oxidation is performed again to thicken the field oxide film, and a polycrystalline silicon contact 11 or a contact 12 made of TiW material is provided to improve the reliability of the metal wiring. be. By increasing the thickness of the field oxide, relaxation and planarization of the perspective head are not compromised, but rather are improved along with reliability.

(Effects of the Invention JJ7:) As explained above, according to the present invention, the bird's head formed by the selective oxide film formation method is relaxed or eliminated by ion etching, and there is no wiring step breakage.
Semiconductor devices can be manufactured with high yield.

[Brief explanation of the drawing]

1@(a) to (e) are sectional views shown in the order of steps to explain one embodiment of the present invention, FIG. 2 is a sectional view to explain another embodiment of the present invention, and 3. Figure 6 is a cross-sectional view of a bipolar transistor manufactured using a conventional selective oxide film formation method. 1... P-type semiconductor substrate, 2... Collector/Nepi region, 3... Base P region, 4
...Emitter N+ region, 5...Metal wiring, 6...Field oxide film, 7...
Bird's Peak, 8...Bird's Head, 9.
..... Silica film, 10 ....-Inert gas ion, 11 ..... Polycrystalline silicon contact, 12 ..... Ti W contact. 1st area

Claims (1)

[Claims] A step of forming a field oxide film on one principal surface of a semiconductor substrate by a selective oxide film formation method, a step of forming a circuit element in a circuit element formation area, and a step of forming a silica film on the entire surface of the substrate on which the field oxide film has been formed. 1. A method of manufacturing a semiconductor device, comprising the steps of coating and forming the field oxide film, and planarizing the surface of the field oxide film by performing ion etching from the upper surface of the silica film using inert gas ions.