JPH07249633A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To smooth the shape of an edge part of a contact hole by introducing phosphor and as its result to smooth step coverage of a conductive film in a contact hole. CONSTITUTION:After forming an interlayer insulating film 2 on a semiconductor substrate 1 consisting of silicon, the interlayer insulating film 2 is melted by using a diffusion furnace so as to flatten its surface. Later, phosphor 6 is ion- implanted to heighten phosphor concentration near the surface of the interlayer insulation film 2. Next, a photoresist pattern 5 is formed to form a contact hole by wet etching and dry etching having this as a mask. After removing the photoresist pattern 3a conductive film 4 is formed on the interlayer insulating film 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, which improves step coverage of a conductive film when forming a contact hole for contacting the conductive film and a semiconductor substrate.

[0002]

2. Description of the Related Art A conventional method of manufacturing a semiconductor device will be described below.

3A to 3C are sectional views in order of the steps, showing a conventional method for manufacturing a semiconductor device. In FIG. 3, 1 is a semiconductor substrate made of silicon, 2 is an interlayer insulating film formed on the semiconductor substrate 1, 3 is a photoresist pattern formed on the interlayer insulating film 2, 4 is a contact hole in the interlayer insulating film. It is a conductive film formed after the formation. Reference numeral 5 is an edge portion of the contact hole.

First, as shown in FIG. 3A, an interlayer insulating film 2 is formed on a semiconductor substrate 1. The interlayer insulating film 2 is mainly composed of a fusible insulating film such as boron phosphorus glass (BPS).
G) is used. After forming the interlayer insulating film 2, the interlayer insulating film is melted and flattened in a nitrogen atmosphere using a diffusion furnace. Then, a photoresist is applied on the interlayer insulating film 2, and the photoresist is patterned to form a photoresist pattern 3 (FIG. 3B).

After that, the interlayer insulating film 2 is etched to a half of its film thickness using buffered hydrofluoric acid (FIG. 3C). Furthermore, a contact hole of 1 μm square is formed in the interlayer insulating film 2 by dry etching (FIG. 3D). Next, after removing the photoresist pattern 3, the conductive film 4 is formed by the sputtering method (FIG. 3).
(E)).

[0006]

However, in the above-mentioned structure, when the interlayer insulating film 2 is etched using buffered hydrofluoric acid, the phosphorus concentration in the interlayer insulating film 2 is almost constant in any part of the film. Since they are the same, the interlayer insulating film 2 is isotropically etched. For this reason, the edge portion of the contact hole has a substantially vertical angular shape. Therefore, when the conductive film is formed by the sputtering method after forming the contact hole, the growth speed of the conductive film at the edge portion of the contact hole is high, and the growth speed inside the contact hole is low. As a result, the step coverage of the conductive film in the contact hole is deteriorated, and the film thickness of the thinnest part of the conductive film in the contact hole is only about 20% of the film thickness of the flat part. .

The present invention solves the above conventional problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device capable of improving step coverage of a conductive film in a contact hole.

[0008]

To achieve this object, a method of manufacturing a semiconductor device according to the present invention comprises a step of forming an interlayer insulating film on a semiconductor substrate, a step of planarizing the interlayer insulating film, A step of injecting phosphorus into the interlayer insulating film under the condition that a range exists near the surface of the interlayer insulating film, a step of forming a photoresist pattern on the interlayer insulating film, and a buffered hydrofluoric acid using the photoresist pattern as a mask. A step of etching the interlayer insulating film up to about half of its film thickness by using, a dry etching step of forming a contact hole by using the photoresist pattern as a mask, and a conductive film on the interlayer insulating film after removing the photoresist pattern. And a step of forming.

Further, a step of forming an interlayer insulating film on a semiconductor substrate, a step of planarizing the interlayer insulating film, a step of melting the interlayer insulating film in a POCl ₃ gas atmosphere, and an interlayer insulating film. A step of forming a photoresist pattern on the top, a step of etching the interlayer insulating film to about half its thickness using buffered hydrofluoric acid with the photoresist pattern as a mask, and a contact hole using the photoresist pattern as a mask And a step of forming a conductive film on the interlayer insulating film after removing the photoresist pattern.

[0010]

According to the present invention, when the interlayer insulating film is etched using buffered hydrofluoric acid, the etching rate near the surface of the interlayer insulating film is increased and the interlayer insulating film at the edge of the contact hole is formed. The shape is gentle.

Therefore, when the conductive film is formed by the sputtering method, the growth rate of the conductive film inside the contact hole is increased, and as a result, the step coverage of the conductive film in the contact hole can be improved. It is also possible to reduce the contact resistance and improve the electromigration resistance.

[0012]

Embodiments of the method of manufacturing a semiconductor device according to the present invention will be described below with reference to the drawings.

FIGS. 1A to 1C are sectional views in order of steps of one embodiment of the present invention. In FIG. 1, 1 is a semiconductor substrate, 2 is an interlayer insulating film formed on the semiconductor substrate 1 made of silicon, and 6 is phosphorus implanted in the interlayer insulating film 2. 3 is a photoresist pattern formed on the interlayer insulating film 2, and 4 is a conductive film formed after forming a contact hole in the interlayer insulating film 2. Reference numeral 5 is an edge portion of the contact hole.

First, as shown in FIG. 1A, an interlayer insulating film 2 having a thickness of 500 to 800 nm is formed on a semiconductor substrate 1. In this embodiment, the interlayer insulating film 2 is made of boron phosphorus glass (BPSG) which is a fusible insulating film. Phosphor glass (PSG), which is another fusible insulating film, may be used, but BPSG is preferable from the viewpoint of film stability and meltability. After forming the interlayer insulating film 2, the interlayer insulating film 2 is melted and flattened in a nitrogen atmosphere at 900 ° C. using a diffusion furnace. After that, phosphorus 6 is implanted on the interlayer insulating film 2 by using an ion implantation device under the conditions of an acceleration energy of 20 keV and a dose amount of 1 × 10 ¹⁵ cm ⁻² . Under this condition, the range of phosphorus is about 25 nm, so phosphorus 6 is distributed near the surface of the interlayer insulating film 2. After that, as shown in FIG. 1B, a photoresist is applied and the photoresist is patterned to form a photoresist pattern 3. Using the photoresist pattern 3 as a mask, as shown in FIG. 1C, the interlayer insulating film 2 is etched by about half (250 to 400 nm) its thickness using buffered hydrofluoric acid. Further, as shown in FIG. 1D, a 1 μm square contact hole is formed in the interlayer insulating film 2 by dry etching.

Next, after the photoresist pattern 3 is removed, as shown in FIG. 1 (e), aluminum (Al) / silicon (Si), Al / is formed by a sputtering method.
The conductive film 4 for wiring is formed of Si / copper (Cu), tungsten (W), Cu, or the like.

The dose of phosphorus used in this embodiment is
It is determined by the type of the interlayer insulating film 2, and the dose amount changes depending on the type of the interlayer insulating film 2.

In the present embodiment, when the interlayer insulating film 2 is wet-etched using buffered hydrofluoric acid, the etching rate increases as the phosphorus concentration in the interlayer insulating film 2 increases. Therefore, by implanting phosphorus 6 at an acceleration energy of 20 keV after forming the interlayer insulating film 2, the etch rate near the surface of the interlayer insulating film 2 can be increased. Since the concentration of the injected phosphorus 6 has a continuous distribution with a peak near the surface, the shape of the edge portion 5 of the contact hole formed by wet etching using buffered hydrofluoric acid becomes gentle. As a result, when the conductive film is formed by the sputtering method, the growth rate of the conductive film inside the contact hole is increased, and the step coverage of the conductive film 4 in the contact hole can be improved.

As described above, according to this embodiment, the step coverage of the conductive film 4 in the contact hole can be improved. In addition, the contact resistance between the semiconductor substrate 1 and the conductive film 4 can be reduced and the electromigration resistance can be improved.

Next, another embodiment of the method for manufacturing a semiconductor device of the present invention will be described. 2A to 2D are cross-sectional views in order of the processes of this embodiment. In FIG. 2, 1 is a semiconductor substrate, 2 is an interlayer insulating film formed on the semiconductor substrate 1, and 7 is a POCl ₃ gas used for diffusing phosphorus into the interlayer insulating film 2. 3 is a photoresist pattern formed on the interlayer insulating film 2,
Reference numeral 4 is a conductive film formed after forming a contact hole in the interlayer insulating film 2. Reference numeral 5 is an edge portion of the contact hole.

This embodiment is different from the above-mentioned embodiment in that
This is a method for increasing the phosphorus concentration near the surface of the interlayer insulating film 2.

First, as shown in FIG. 2A, an interlayer insulating film 2 having a thickness of 500 to 800 nm is formed on a semiconductor substrate 1. In this embodiment, the interlayer insulating film 2 is made of boron phosphorous glass (BPSG) which is a fusible insulating film. After forming the interlayer insulating film 2, the interlayer insulating film 2 is melted and flattened in a nitrogen atmosphere at a temperature of 900 ° C. using a diffusion furnace. Then, while maintaining the temperature of 900 ° C., POCl ₃ gas 7 is introduced into the furnace in addition to nitrogen gas, and phosphorus is diffused in the interlayer insulating film 2. Since phosphorus is diffused only in the vicinity of the surface of the interlayer insulating film 2, it is appropriate to introduce the POCl ₃ gas 7 for 5 minutes. After that, as shown in FIG. 2B, a photoresist is applied, and the photoresist is patterned to form a photoresist pattern 3. Using this photoresist pattern 3 as a mask,
As shown in (c), the interlayer insulating film 2 is etched with buffered hydrofluoric acid by about half the film thickness (250 to 400 nm). Furthermore, by dry etching, FIG.
As shown in (d), a 1 μm square contact hole is formed in the interlayer insulating film 2.

Next, after the photoresist pattern 3 is removed, as shown in FIG. 2E, the conductive film 4 for wiring is made of Al / Si, Al / Si / Cu, W or Cu by the sputtering method. To form.

The diffusion time of phosphorus used in this embodiment is
It is determined by the type of the interlayer insulating film 2, and the diffusion time changes depending on the type of the interlayer insulating film 2.

When the interlayer insulating film 2 is wet-etched using buffered hydrofluoric acid, the etching rate increases as the phosphorus concentration in the interlayer insulating film 2 increases. Therefore, by performing phosphorus diffusion near the surface of the interlayer insulating film 2 after forming the interlayer insulating film 2, the etch rate near the surface of the interlayer insulating film 2 can be increased. Since the diffused phosphorus concentration has a continuous distribution with a peak on the surface, the shape of the edge portion 5 of the contact hole formed by wet etching using buffered hydrofluoric acid becomes gentle. As a result, when the conductive film 4 is formed by the sputtering method, the growth rate of the conductive film 4 inside the contact hole is increased, and the step coverage of the conductive film 4 in the contact hole can be improved.

[0025]

According to the present invention, by increasing the phosphorus concentration near the surface of the interlayer insulating film, the shape of the interlayer insulating film at the edge portion of the contact hole is made smooth, and the step coverage of the conductive film in the contact hole is improved. Can be made.

[Brief description of drawings]

1A to 1E are cross-sectional views in order of the steps of an embodiment of a method for manufacturing a semiconductor device of the present invention.

2A to 2E are cross-sectional views in order of the steps of another embodiment of the method for manufacturing a semiconductor device of the present invention.

3A to 3E are cross-sectional views in order of steps of a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

1 semiconductor substrate 2 interlayer insulating film 3 photoresist 4 conductive film 5 edge part 6 phosphorus 7 POCl ₃

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/306 H01L 21/306 SF

Claims (2)

[Claims] 1. A step of forming an interlayer insulating film on a semiconductor substrate, a step of planarizing the interlayer insulating film, and a step of forming phosphorus on the interlayer insulating film under the condition that a range exists near the surface of the interlayer insulating film. And a step of forming a photoresist pattern on the interlayer insulating film, and using the photoresist pattern as a mask, the interlayer insulating film is etched to about half its thickness using buffered hydrofluoric acid. A method of manufacturing a semiconductor device comprising: a step of forming a contact hole using the photoresist pattern as a mask; and a step of forming a conductive film on the interlayer insulating film after removing the photoresist pattern. . 2. A step of forming an interlayer insulating film on a semiconductor substrate, a step of planarizing the interlayer insulating film, and a step of melting the interlayer insulating film in a POCl ₃ gas atmosphere. Forming a photoresist pattern on the interlayer insulating film; etching the interlayer insulating film to about half its thickness using buffered hydrofluoric acid using the photoresist pattern as a mask; and the photoresist pattern A method of manufacturing a semiconductor device, comprising: a dry etching step of forming a contact hole using the mask as a mask; and a step of forming a conductive film on the interlayer insulating film after removing the photoresist pattern.