JPS6342146A - Manufacture of semiconductor - Google Patents

Abstract

PURPOSE:To obtain the structure of excellent multilyer interconnections without step cutting and the like, by smoothing the edge part of a conductor layer comprising polycrystalline silicon. CONSTITUTION:A polycrystalline silicon film 3 is entirely etched until the thin part beneath an oxide film 6 is eliminated. With the remaining polycrystalline silicon film 3 as a mask, a gate oxide film 2 is removed. Then, a second gate oxide film 8 and an insulating oxide film 9 are formed on the exposed surface of a silicon substrate 1 and the polycrystalline silicon film 3 by hydrogen burning oxidation. The gate oxide film 8 is removed by wet etching. A second gate oxide film 8a is formed again by dry oxidation this time. At this time, the insulating oxide film 9 is also etched once. An oxide film 9a is obtained by dry oxidation. A polycrystalline silicon film 10 is deposited on the gate oxide film 8a and the oxide film 9a to form the upper conductor layer. Thus the conductor layer, which comprises a polycrystalline silicon layer and has a smooth edge, is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a semiconductor device including a method of forming a multilayer electrode.

[Conventional technology]

Generally, dynamic MOS memory or CCD
The device employs a two-layer polycrystalline silicon structure, and a conventional manufacturing method will be described below.

FIGS. 3(a) to 3(c) are cross-sectional views of a semiconductor chip shown in order of steps for explaining a conventional method of manufacturing a semiconductor device.

First, as shown in FIG. 3 (a), a first gate insulating film 2 is formed on a silicon substrate 1 by thermal oxidation, a polycrystalline silicon film 3' is grown, and an N-type impurity, for example, phosphorus is added. Spread.

Next, as shown in FIG. 3(b), the polycrystalline silicon 3' and the gate insulating film 2 are etched using a well-known photolithography technique. At this time, since the etching rate of polycrystalline silicon into which impurities have been diffused is generally fast, there is almost no oxide etching and the edges of the polycrystalline silicon 3' are very steep.

Next, as shown in FIG. 3(C), the polycrystalline silicon 3' is oxidized to form an oxide film 9' for the glabellar insulating film, and at the same time, a second gate insulating film 8' is also formed on the silicon substrate 1. do. Thereafter, after growing the second polycrystalline silicon 10', phosphorus is diffused as an N-type impurity similarly to the polycrystalline silicon film 3'.

[Problem that the invention seeks to solve]

In the conventional semiconductor device manufacturing method described above, the edge of the polycrystalline silicon conductor layer is steep, so as the interlayer insulating film and the upper layer of the polycrystalline silicon conductor layer are deposited on top of the edge, the step portion is formed. There is a drawback that the irregularities become more severe and take on the shape of a corner 7' as shown in FIG. 3(C), making it impossible to cover uniformly and making it easy to cause breakage and the like.

[Means for solving problems]

Insulating film and polycrystalline silicon film on the surface of the semiconductor substrate.

a step of sequentially forming a first oxide film and an oxidation-resistant film; selectively and sequentially removing at least the oxidation-resistant film and the first oxide film to expose the polycrystalline silicon film to a predetermined thickness; a step of forming a second oxide film by oxidizing the exposed portion using the oxidation-resistant film as a mask; and a step of removing the oxidation-resistant film, the first and second oxide films. A conductive layer with smooth edges made of the polycrystalline silicon film is formed.

[Actual city example]

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(f) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining the embodiment of FIG. 1 of the present invention.

First, as shown in FIG.
A polycrystalline silicon film 3 of 5,000 layers is further deposited by the CVD method, and then phosphorus is diffused using P OCe 3 as a diffusion source. Next, a CV with a thickness of 1000 people
An oxide film 4 having a thickness of D and a nitride film 5 having a thickness of 500 mm are sequentially formed.

Next, as shown in FIG. 1(b), the nitride film 5. The oxide film 4 and the polycrystalline silicon film 3 are sequentially etched to form an exposed portion of the polycrystalline silicon film 3 with a thickness of approximately 3,000 mm.

Next, as shown in FIG. 1(c), an oxide film 6 is formed on the exposed portion of the polycrystalline silicon film 3 by hydrogen burning oxidation at 1000'C using the nitride film 5 as a mask, and The silicon film 3 should have a capacity of about 1,000 people. At this time, the oxidized portion t15!6 below the edge of the nitride film 5 takes the shape of a bird's beak 7. Note that when forming the oxide film 6, the polycrystalline silicon film 6 is formed under the oxide film 6 to prevent phosphorus contained in the polycrystalline silicon film 3 from pile-up and reaching the silicon substrate 1- through the gate oxide film 2. It is necessary to leave about 500 to 2,000 people in the silicon film 3.

Next, as shown in FIG. 1(d), nitride film 5° oxide film 4
After removing the oxide film 6 and 6, the entire surface of the polycrystalline silicon film 3 is etched by reactive ion etching until the thin portion under the oxide film 6 is removed. Furthermore, gate oxide film 2 is removed using remaining polycrystalline silicon film 3 as a mask.

Next, as shown in FIG. 1<e), a second gate oxide film 8 and an insulating film are formed on the exposed surfaces of the silicon substrate 1 and the polycrystalline silicon film 3 with a thickness of 350 mm by hydrogen burning oxidation at 850°C. An oxide film 9 having a thickness of 1000''A is formed.

However, the dielectric strength voltage of the oxide film formed by hydrogen burning oxidation is as low as -i, so the gate oxide film 8 is removed by wet etching at 950° C. as shown in FIG. 1(f). A second gate oxide film 8a having a thickness of 350 wafers is again formed by dry oxidation. At this time, the insulating oxide film 9 is also etched, resulting in 650 people.
By dry oxidation, an oxide film 9a having a thickness of approximately 1000 wafers is formed. Furthermore, a polycrystalline silicon film 10 is deposited on gate oxide film 8a and oxide film 9a to form an upper conductor layer.

FIG. 2 is a sectional view of a semiconductor chip for explaining a second embodiment of the present invention.

In this embodiment, a phosphosilicate glass (hereinafter referred to as PSG) film 11 is formed after the conductor layer of the polycrystalline silicon film 3 is formed. Furthermore, using photolithography technology, PSG
After a contact window is opened on the polycrystalline silicon film 3 of the film 11, A2 is deposited by electron beam evaporation and shaped into a predetermined pattern to form an Ae electrode 12 connected to the polycrystalline silicon film 3.

〔Effect of the invention〕

As explained above, in the present invention, the edges of the conductor layer made of polycrystalline silicon are smoothed, so that the insulating film laminated thereon and the upper conductor layer are uniformly formed even on the edges, and the edges of the conductor layer made of polycrystalline silicon are smoothed. This has the effect of providing a good multilayer wiring structure with no breaks or the like.

[Brief explanation of drawings]

1(a) to 1(f) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining the first embodiment of the present invention;
The figure is a cross-sectional view of a semiconductor chip for explaining the second embodiment of the present invention, and FIGS. FIG. 1... Silicon substrate, 2... Gate oxide film, 3, 3
'... Polycrystalline silicon film, 4... Oxide film, 5...
Nitride film, 6... Oxide film, 7... Bird's beak, 7'
...Angle, 8°8', 8a...Gate oxide film, 9.
9', 9a...Oxide film, 10.10'...Polycrystalline silicon film, 11...PSG film, 12...Aff
electrode. 0 magazine) (d) (b)
(e) (C)
(f Tsugi / Concave (C) (b)

Claims (1)

[Claims] a step of sequentially forming an insulating film, a polycrystalline silicon film, a first oxide film, and an oxidation-resistant film on the surface of a semiconductor substrate, selectively and sequentially removing at least the oxidation-resistant film and the first oxide film; a step of forming an exposed portion of a predetermined thickness in the polycrystalline silicon film; a step of oxidizing the exposed portion using the oxidation-resistant film as a mask to form a second oxide film; A method for manufacturing a semiconductor device, comprising the step of removing the first and second oxide films to form a conductor layer made of the polycrystalline silicon film with smooth edges.