JPH0774244A - Fabrication of semiconductor device - Google Patents

Abstract

PURPOSE:To enhance step coverage at each contact hole while realizing fine patterning and high integration by forming a round shape corresponding to the depth of a contact hole above each contact hole without effecting round etching. CONSTITUTION:A first insulation film 5 applicable to reflow is formed thick on an underlying layer having level difference and a second insulation film applicable to reflow is formed relatively thin thereon. The second insulation film 6 is then etched back and contact holes 9A, 9B are made through an interlayer insulation film comprising the first and second insulation films 5, 6. Subsequently, the second insulation film 6 is reflow-processed through heat treatment thus forming a round shape corresponding to the depth of contact hole at the opening of contact hole.

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 semiconductor device in which a contact hole is formed in an interlayer insulating film formed on a base having a step.

[0002]

2. Description of the Related Art Conventionally, as semiconductor devices have been miniaturized and highly integrated, planarization of semiconductor devices has become more and more important. Therefore, as one of methods for achieving flattening of a semiconductor device, flattening of an interlayer insulating film formed on a base having a step is performed.

As a method for flattening the interlayer insulating film, for example, an inorganic fluid such as a silica film or an organic fluid such as a polyimide resin is used as an insulating film having a reflow property on a base having a step. Is applied to form a flat interlayer insulating film, CVD (Chemical Vapor Depos
ition) method, various flattening methods have been introduced, such as a method of depositing an insulating film having a reflow property and then etching it back to form a flat interlayer insulating film.

However, when the interlayer insulating film is flattened by the above method, the interlayer insulating film is formed in a state of having a different film thickness depending on the step of the underlying layer. Therefore,
When a contact hole is formed in the interlayer insulating film, a portion where the film thickness of the interlayer insulating film is large (that is, a valley portion of the underlying step,
Hereinafter, the depth of the contact hole formed in the "step valley" becomes deeper (higher aspect ratio), and the portion where the film thickness of the interlayer insulating film is thin (that is, the peak portion of the underlying step, hereinafter, Since the depth of the contact holes formed in "the stepped mountain portion") becomes shallow, contact holes having different depths coexisted on the same substrate. The deep contact holes have poor step coverage, and the thickness of the reflowable insulating film is large. Therefore, during heat treatment performed in a subsequent step, the insulating film flows and the contact holes The overhang shape was formed at the opening, further deteriorating the step coverage characteristic.

Therefore, in order to solve the problem, conventionally, round etching (selective isotropic etching) is performed on the upper portions of all the contact holes in accordance with the deep contact holes to make the contact holes. The upper part has a round shape to improve the step coverage of the contact hole.

[0006]

However, according to the conventional example in which the upper portions of all the contact holes are rounded in accordance with the deep contact holes, the contact holes are formed when the interlayer insulating film is formed on the base or when the contact is formed. When forming the holes,
The line and space must be designed in consideration of the width of the insulating film that is lost when forming the round shape, and in the case of a contact hole with a shallow depth, the contact hole expands more than necessary, and miniaturization and There was a problem that it hindered high integration.

SUMMARY OF THE INVENTION The present invention has an object to solve such a conventional problem, and it is possible to adjust the depth of each contact hole above each contact hole without performing round etching. It is an object of the present invention to provide a method for manufacturing a semiconductor device in which the step coverage of a contact hole is improved by forming a round shape and miniaturization and high integration are achieved.

[0008]

In order to achieve this object, the present invention provides a method of manufacturing a semiconductor device in which a contact hole is formed in an interlayer insulating film formed on a base having a step, the step having the step. A first step of thickly forming a first insulating film having no reflow property on the lower ground and a second insulating film having reflow property on the first insulating film with respect to the first insulating film. The second step of forming a relatively thin film, and the second step of forming the second insulating film so that at least a part of the second insulating film remains.
Of the first insulating film and the second insulating film are etched back.
A third step of forming an interlayer insulating film made of the insulating film, a fourth step of opening a contact hole in the interlayer insulating film after the etching back, and a heat treatment after opening the contact hole. A fifth step of reflowing the insulating film,
The present invention provides a method for manufacturing a semiconductor device including:

The first insulating film is made of non-doped silicate glass, and the second insulating film is made of borosilicate glass, which provides a method for manufacturing a semiconductor device. . In the second insulating film after the contact hole is opened, the relationship between the width in the horizontal direction in the region having the largest film thickness and the film thickness is: film thickness / width in the horizontal direction = 0.6.
The present invention provides a method for manufacturing a semiconductor device, which is formed as follows.

[0010]

According to the present invention, the first insulating film having no reflow property is formed thick on the base having a step, and the second insulating film having reflow property is formed relatively thin on the first insulating film. After that, the second insulating film is etched back so that at least a part of the second insulating film remains, and an interlayer insulating film including the first insulating film and the second insulating film is formed. A second insulating film is thickly formed on the valley portion of the step. Therefore, the second insulating film is thinly formed or removed at the mountain portion of the step. Then, after a contact hole is opened in the interlayer insulating film, a heat treatment is performed to reflow the second insulating film, so that an end portion (near the opening of the contact hole) of the second insulating film is removed. The corners are rounded. Therefore, a round shape is formed above the contact hole without performing round etching. At this time, since the diameter of the round shape of the second insulating film can be increased as the film thickness of the second insulating film is increased, the diameter of the contact hole having a deeper depth (round shape) is increased. The shallower the depth (round shape) of the contact hole, the smaller the depth. In this way, a round shape with the optimum size according to the depth of each contact hole is easily formed on the top of each contact hole, so consider the line and space design by round etching of the contact hole. You don't have to.

The first insulating film may be, for example, a film made of non-doped silicate glass, and the second insulating film may be, for example, a film made of borosilicate glass. In the second insulating film after the opening of the contact hole, the relationship between the width in the horizontal direction in the region having the largest film thickness and the film thickness in this region is film thickness / width in the horizontal direction =
By forming it so as to be 0.6 or less, the above action can be further improved.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 5 are partial enlarged cross-sectional views showing a part of the manufacturing process of the semiconductor device according to the embodiment of the invention. In the step shown in FIG. 1, after a gate oxide film 3 is formed on a semiconductor substrate 1 which is element-isolated by a field oxide film 2, a gate electrode forming material is formed on the gate oxide film 3 and the field oxide film 2. Then, a polycrystalline silicon film is deposited and patterned to form a gate electrode 4. Thus, a base having a step was formed. Next, on the surface of the gate electrode 4, the gate oxide film 3, the field oxide film 2 and the wiring 11, as an insulating film having no reflow property, non-doped silicate glass (NSG;
A doped Silica Glass) film is deposited with a film thickness of about 7,000 Å to form the first insulating film 5. Then, a borosilicate glass (BPSG) film as a reflowable insulating film is deposited on the first insulating film 5 to a thickness of about 6000 Å, and the second insulating film 6 is formed. To form.

Next, in the step shown in FIG. 2, a sacrificial film 7 to be used in the later etch back step is formed on the second insulating film 6 obtained in the step shown in FIG. Next, in the step shown in FIG. 3, the sacrificial film 7 obtained in the step shown in FIG. 2 is etched back, and a part of the exposed second insulating film 6 is further etched back to form the second insulating film 6. Flatten. At this time,
In the region of the second insulating film 6 having the thickest film thickness b, the second insulating film 6 has a horizontal width a after opening a contact hole formed in a later step, which is b / a = 0. Etching back was performed to 6 or less, and the second insulating film 6 was formed thick at the valley portion of the underlying step and thinned at the peak portion of the underlying step. In this way, the interlayer insulating film 10 including the first insulating film 5 and the second insulating film 6 was formed.

Next, in the step shown in FIG. 4, a photoresist film is applied on the second insulating film 6 formed in the step shown in FIG. 3 and is patterned to form a resist pattern 8 for opening a contact hole. To form. Then, the interlayer insulating film 10 and the gate oxide film 3 are anisotropically etched by using the resist pattern 8 as a mask to form contact holes 9A.
And 9B are opened.

Next, in the step shown in FIG. 5, the wafer obtained in the step shown in FIG. 4 is heat-treated at a temperature of 800 ° C. or higher to reflow the second insulating film 6 and to cover the upper portion of the contact hole 9. Open in a round shape. At this time, since the second insulating film 6 is formed thick on the upper side wall of the contact hole 9A having a large depth, a round shape having a large opening diameter is opened. On the other hand, since the second insulating film 6 is thinly formed on the upper side wall of the contact hole 9B having a shallow depth, a round shape having a small opening diameter is opened. Therefore, it is possible to obtain an opening having an optimum size capable of improving the step coverage characteristic according to the depth of the contact hole.

Thereafter, desired steps such as forming wiring are performed to complete the semiconductor device. In addition, in the present embodiment, a non-doped silicate glass (NSG) film is used as the first insulating film 5, but the present invention is not limited to this, as long as the film has an insulating property and does not have a reflow property. Alternatively, another insulating film may be formed. Further, in this embodiment, a borosilicate glass (BPSG) film is used as the second insulating film 6, but the second insulating film 6 is not limited to this.
Another insulating film may be formed as long as it has an insulating property and a reflow property.

[0017]

As described above, in the method of manufacturing a semiconductor device according to the present invention, the second insulating film having the reflow property is formed thick in the valley portion of the underlying step, and the second insulating film having the reflow property is formed in the mountain portion of the underlying step. After forming the interlayer insulating film in a state where the second insulating film is thinly formed or removed, a contact hole is opened in the interlayer insulating film, and then heat treatment is performed to reflow the second insulating film. The corner of the edge of the film (in the vicinity of the upper portion of the opening of the contact hole) can be rounded. Therefore, the round shape can be formed on the upper portion of the contact hole without performing the round etching. At this time, the round-shaped diameter of the second insulating film is
The thicker the insulating film, the larger the thickness of the insulating film.
The larger the contact hole is, the smaller the contact hole has a shallower depth (round shape). Therefore, it is possible to easily form the round shape having the optimum size according to the depth of each contact hole on the top of each contact hole. As a result, the step coverage of the contact hole can be improved, and since the line and space design by round etching of the contact hole is not taken into consideration, miniaturization and high integration can be significantly improved.

In the second insulating film, the relation between the horizontal width in the region having the largest film thickness and the film thickness in this region is film thickness / horizontal width = 0.6 or less. By forming such a structure, the above-mentioned action can be further improved.

[Brief description of drawings]

FIG. 1 is a partial enlarged cross-sectional view showing a part of a manufacturing process of a semiconductor device according to an embodiment of the invention.

FIG. 2 is a partial enlarged cross-sectional view showing a part of the manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 3 is a partial enlarged cross-sectional view showing a part of the manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 4 is a partial enlarged cross-sectional view showing a part of the manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 5 is a partial enlarged cross-sectional view showing a part of the manufacturing process of the semiconductor device according to the embodiment of the invention.

[Explanation of symbols]

 1 semiconductor substrate 2 field oxide film 3 gate oxide film 4 gate electrode 5 first insulating film 6 second insulating film 7 sacrificial film 8 resist pattern 9A contact hole 9B contact hole 10 interlayer insulating film 11 wiring

Claims (3)

[Claims] 1. A method of manufacturing a semiconductor device, comprising forming a contact hole in an interlayer insulating film formed on a stepped base, wherein a first insulating film having no reflow property is thickened on the stepped base. A first step of forming, a second step of forming a reflowable second insulating film on the first insulating film relatively thinly with respect to the first insulating film, and a second insulating step A third step of etching back the second insulating film so that at least a part of the film remains, and forming an interlayer insulating film composed of the first insulating film and the second insulating film, and ending the etch back. After that, a fourth step of opening a contact hole in the interlayer insulating film, and a fifth step of performing a heat treatment and reflowing the second insulating film after opening the contact hole are performed. Production method. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the first insulating film is made of non-doped silicate glass, and the second insulating film is made of borosilicate glass. 3. The second insulating film after the opening of the contact hole has a relationship between the width in the horizontal direction and the film thickness in a region having the largest film thickness: film thickness / horizontal width = 0.6. The method of manufacturing a semiconductor device according to claim 1, wherein the method is formed as follows.