JPH08227889A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE: To prevent impurities from being deposited without providing a deposit preventing film by a method wherein an interlayer insulating film of silicon oxide which contains B and P is formed on a circuit pattern, and the surface layer of the interlayer insulating film is formed of densified layer which contains a lot of oxygen. CONSTITUTION: A gate oxide film 2 and a circuit pattern 3 of polycrystalline silicon film and the like are formed on a semiconductor substrate 1 of Si or the like. A silicon oxide film 4 as an interlayer insulating film which contains B and P is grown as thick as required on the circuit pattern 3. Oxygen is introduced into the surface of the silicon oxide film 4 twice as high in dose as usual to densify only the surface of the silicon oxide film 4, the semiconductor substrate 1 is thermally treated to make the silicon oxide film 4 fluid and flat. By this setup, impurities are capable of being prevented from being deposited without providing a deposit preventing film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a structure of an interlayer insulating film constituting the semiconductor device and a forming method thereof.

[0002]

2. Description of the Related Art As the degree of integration of semiconductor integrated circuits has improved, the three-dimensional structure of the circuit has become more and more complicated, but the necessity of lithography technology has led to the formation of an interlayer insulating film on a circuit pattern having irregularities. The demand for high flatness has become more severe in recent years. The most commonly used planarization method in the past is to form an interlayer insulating film with phosphorus (P) or boron (B).
It is formed by using a silicon oxide film (borophosphosilicate glass, hereinafter referred to as BPSG) to which impurities such as are added, and is subjected to heat treatment at a temperature equal to or higher than the melting point to planarize by flow due to surface tension (hereinafter referred to as reflow). , The easiest to do.

Conventional planarization is performed by reflowing a BPSG single layer, but after the BPSG film is formed, a silicon oxide film or a polycrystalline silicon film is formed on the BPSG upper layer for the purpose of preventing the precipitation of impurities from the surface. A method of performing reflow after formation is also proposed (Japanese Patent Laid-Open No. 61-237448).
(Japanese Patent Laid-Open No. 3-237744). The conventional flattening process of the interlayer insulating film will be described below with reference to FIG.

First, as shown in FIG. 4A, a circuit pattern 3 composed of a gate oxide film 2 and a polycrystalline silicon film or the like is formed on a semiconductor substrate 1, and then a chemical vapor deposition method (hereinafter referred to as C
VD method) is used to grow a BPSG film 4 having a P concentration of 3 to 6 mol% and a B concentration of 8 to 18 mol% added to a desired thickness, and then an appropriate CVD method is used to prevent P and B precipitation. A silicon oxide film 6 is grown as a film to a thickness of about 10 nm.

Next, as shown in FIG. 4 (b), heat treatment is performed for 5 to 30 minutes in a nitrogen atmosphere at about 900 ° C.
The SG film 4 is flattened. When a polycrystalline silicon film is selected as the deposition preventing film, reflow is performed in an oxygen atmosphere at 900 ° C. to flow the BPSG film 4 and simultaneously oxidize the polycrystalline silicon film. The thickness of the polycrystalline silicon film at this time is 5 to 20 nm.

[0006]

In this conventional method for flattening an interlayer insulating film, a silicon oxide film or a polycrystalline silicon film is formed on a BPSG film as a precipitation preventing film, but the following problems occur. There is.

First of all, this precipitation prevention film hinders the flattening of the BPSG film. That is, since the diffusion of B and P into the precipitation preventing film is insufficient, the reflow becomes incomplete as compared with the case without the precipitation preventing film. Secondly, if the film thickness of the precipitation preventing film is not constant in the plane of the wafer or between the planes, the shape of the BPSG film after flattening will be remarkably different.

Thirdly, in the present state-of-the-art devices, the reflow process is shortened in time because of the necessity of preventing the expansion of the shallow diffusion layer, and 900 ° C. is usually about 5 to 10 minutes. Due to insufficient thermal reflow with such heat history, sufficient flatness cannot be obtained, and in addition, it will be possible to cope with the low temperature of the heat treatment of 800 to 850 ° C required by next-generation devices. I can't. Fourthly, since the step of forming the precipitation preventing film is required, the process is complicated and the productivity is reduced. In addition, in the current fine semiconductor device manufacturing process, if heat treatment is performed in an oxygen atmosphere,
Oxidizing species reach the substrate through the silicon oxide film formed by the CVD method as an interlayer insulating film, increasing the gate oxide film thickness and degrading the device characteristics. Therefore, heat treatment in a nitrogen atmosphere is common.

An object of the present invention is to provide a semiconductor device having an interlayer insulating film which can prevent precipitation of impurities without forming a precipitation preventing film and which is excellent in reflowability, and a manufacturing method thereof.

[0010]

A semiconductor device according to a first aspect of the present invention is an interlayer insulating film formed of a circuit pattern formed on a semiconductor substrate and a silicon oxide film containing B and P formed on the circuit pattern. And a surface layer of the interlayer insulating film is formed of a densified layer containing a large amount of oxygen.

The semiconductor device manufacturing method of the second invention is a method of manufacturing a semiconductor device, wherein a silicon oxide film containing B and P is formed as an interlayer insulating film by a CVD method on a semiconductor substrate having a circuit pattern formed thereon. Only the surface layer of the oxide film is a densified layer containing a large amount of oxygen.

In the case of a BPSG film having a high growth rate, which is generally formed by the CVD method, the bond between B and P and Si is incomplete and contains a large amount of OH groups. However, when the active oxygen is increased and the growth rate is slowed down, the oxidation reaction is sufficient, so that the OH groups are few, the bond between B and P and Si is almost complete, and the BPSG film becomes dense. Therefore, the precipitation of impurities in the BPSG film is almost eliminated by the heat treatment during the reflow.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to the drawings.
1 (a) and 1 (b) are sectional views of a semiconductor chip in order of process for explaining the first embodiment of the present invention, and FIG. 2 is an enlarged sectional view of an arrow A portion in FIG. 1 (a). Is. FIG. 3 is a schematic diagram of a TEOS (tetraethyl orthosilicate) -O ₃ system CVD apparatus for carrying out the present invention. The first to nth (final) n chambers are provided on the wafer 10. and it is configured such that the BPSG film of the n-layer is formed by 51 to 5 _n.

First, as shown in FIG. 1A, a circuit pattern 3 composed of a gate oxide film 2 and a polycrystalline silicon film or the like is formed on a semiconductor substrate 1 of Si or the like, and then TEOS-O ₃ is formed.
The atmospheric pressure CVD method is used to grow a BPSG film 4 having a phosphorus concentration of 3 to 6 mol% and a boron concentration of 8 to 13 mol% to a desired film thickness (0.5 to 1.0 μm). At this time, C
Strictly speaking, the BPSG film formed by the VD device having a plurality of chamber configurations as shown in FIG. 3 is a multilayer (n) film as shown in FIG. Normal TE here
In the OS-O ₃ system atmospheric pressure CVD method, usually 90 to 120 g /
Film formation is carried out at an O ₃ concentration of 1 (4 to 5 times the amount of the reaction gas), but only in the final chamber 5 _n , 180 to 250 g / l, which is twice the normal amount of O, compared to an independent gas supply system. ₃ is added to densify only the surface layer 4 _n of the BPSG film 4 as shown in FIG. Reason for increasing the final chamber 5 _n only O ₃ concentration, if increased markedly O ₃ concentration as in the embodiment, the deposition rate is extremely reduced, because impairing productivity.

Next, as shown in FIG. 1B, heat treatment is performed in a nitrogen atmosphere at about 900 ° C. for 5 to 30 minutes so that the BPSG film 4 is fluidized and the planarization is completed. According to the present example, the outermost surface layer densified by increasing the O ₃ concentration functions as a precipitation preventing film, and the heat treatment is performed during the heat treatment as compared with the case where the film is formed at a normal O ₃ concentration. BP
Since the outward diffusion of P and B from the SG film surface is suppressed,
The flattened shape is superior to when the film is formed at the same concentration.

According to the first embodiment, in addition to the reduction of defects due to the precipitation of impurities, the improvement of the flatness reduces the short defects due to the residue at the step portion of the interlayer film of the metal wiring, and in the lithography process. The yield of the semiconductor device can be improved by about 20% as compared with the conventional one due to the effect of reducing the focus defect. The preferable thickness of the surface layer 4 _n is 10 nm or more.

In the first embodiment, the reflow is performed by using the heat treatment in the nitrogen atmosphere at 900 ° C., but in the second embodiment, the case of performing the low temperature reflow at about 800 to 950 ° C. will be described. . For low temperature reflow, the total impurity concentration of phosphorus and boron is required to be 25 to 30 mol% or more, while the deposition limit concentration of the BPSG film is about 18 mol%. I can't. Therefore, it becomes necessary to further densify the surface layer 4 _n of the BPSG film as compared with the first embodiment.

First, as in the case of FIG. 1A, TEOS-O ₃
Using a systematic atmospheric pressure CVD method, a BPSG film added with a phosphorus concentration of 5 to 10 mol% and a boron concentration of 20 to 25 mol% is grown to a desired film thickness. At this time, as in the case of the first embodiment, 300 to 350 g / l or more of O is only provided in the final chamber 5 _n.
Add ₃ to densify the outermost layer of the film. Then 800
Perform heat treatment for 5 to 30 minutes in a nitrogen atmosphere at ~ 850 ° C,
Flow the BPSG to complete the planarization.

In the second embodiment, due to the effect of increasing the concentration of B and P, even if the heat treatment at 800 to 850 ° C. is used,
It is possible to obtain a flattened shape equivalent to that of the embodiment. Further, since the second embodiment can cope with the low temperature of the reflow, the heat history can be shortened and the effect of preventing the expansion of the shallow diffusion layer can be exerted.

In the above embodiment, a TEOS-O ₃ type atmospheric pressure CVD apparatus was used as the BPSG film forming apparatus, but this apparatus has the highest productivity, and therefore an interlayer insulating film (BPSG) forming apparatus will be used in the future. This is due to the fact that it is a mainstream, and that the apparatus can have a plurality of chambers, and the process can be controlled relatively easily when densifying only the film surface layer as in the present invention. Other apparatus may be used as long as it is possible to densify the film surface layer which is the object of the present invention, and a silane-based gas and activated oxygen by plasma decomposition may be used as the reaction gas.

[0021]

As described above, according to the present invention, a low melting point silicon oxide film containing B and P is formed as an interlayer insulating film, and its surface layer is made dense by increasing the amount of active oxygen in the reaction gas. The use of the converted silicon oxide film has an effect that a semiconductor device having an interlayer insulating film with excellent reflowability and a method for manufacturing the semiconductor device can be obtained without precipitation of impurities even when heat treatment for planarization is performed. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor chip for explaining a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an arrow A portion in FIG.

FIG. 3 is a schematic diagram of a CVD apparatus used in Examples.

FIG. 4 is a sectional view of a semiconductor chip for explaining a conventional example.

[Explanation of symbols]

1 Semiconductor Substrate 2 Gate Oxide Film 3 Circuit Pattern 4, 4 ₁ to 4 _n BPSG Film 5 _{1 to} 5 _n 1st to nth Chamber 6 Silicon Oxide Film 10 Wafer

Claims (4)

[Claims] 1. A semiconductor device having a circuit pattern formed on a semiconductor substrate and an interlayer insulating film made of a silicon oxide film containing B and P formed on the circuit pattern, the surface of the interlayer insulating film. A semiconductor device, wherein the layer is composed of a densified layer containing a large amount of oxygen. 2. A method for manufacturing a semiconductor device, wherein a silicon oxide film containing B and P is formed as an interlayer insulating film by CVD on a semiconductor substrate having a circuit pattern formed thereon, wherein only the surface layer of the oxide film contains oxygen. A method of manufacturing a semiconductor device, comprising forming a densified layer containing a large amount. 3. The method for manufacturing a semiconductor device according to claim 2, wherein the densified layer is formed by increasing the amount of active oxygen in the reaction gas immediately before the completion of forming the silicon oxide film by the CVD method. 4. The method of manufacturing a semiconductor device according to claim 3, wherein a TEOS-O ₃ based reaction gas is used.