JP2975930B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor device provided with BPSG, which viscously flows by heat treatment, as an insulating film and a method of manufacturing the same.

[0002]

2. Description of the Related Art Wiring between elements of a semiconductor integrated circuit device has been designed to have a multi-layered structure with higher integration. In the case of performing such multi-layer wiring, a step on the surface due to the lower layer wiring affects the wiring in the upper layer. In particular, when the pattern is miniaturized, the disconnection of the wiring is likely to occur, and therefore, it is important to calm the steps, that is, to flatten the surface. Such flattening techniques include PSG and BPS.
Glass flow using the thermal fluidity of G is widely used. In the glass flow using PSG or BPSG, PSG or BPSG is stacked as an interlayer insulating film after a lower wiring is formed, and heated to viscous flow to reduce a step. Generally, BPSG rather than PSG
Since BPSG has a lower melting point and causes viscous flow at a lower temperature, BPSG is more often used.

FIG. 3 is a sectional view of a conventional semiconductor device in the order of steps showing a method of manufacturing the same.

First, as shown in FIG. 3A, a silicon substrate (1) on which various elements are formed is placed on a silicon substrate (1) via a SiO ₂ film (2).
The poly-Si wiring (3) of the layer is formed, and this poly-Si wiring is formed.
A BPSG film (4) is formed so as to cover (3). This BPS
G film (4) is, C of _{SiH 4, B 2 H 6,} PH 3 and O ₂ gas system
It is formed by the VD method. Next, as shown in FIG.
Heating to about 900 ° C. softens the BPSG film (4) and flattens the surface by viscous flow. This glass flow cannot be used in the process after forming the Al wiring because the processing temperature is 900 ° C. or higher.

After using a glass flow, as shown in FIG. 3C, a photoresist (5) is applied on the PBSG film (4), and a gap (6) is formed in a region where an upper wiring is to be connected. Subsequently, as shown in FIG.
Etching the BPSG film (4) using (5) as a mask,
A contact hole (7) reaching the substrate (1) is formed. The contact hole (7) is formed by first performing isotropic wet etching to obtain a tapered shape.
A contact hole (7) is formed halfway through the G film (4), and then the remaining BPSG film (4) is etched by anisotropic etching such as reactive ion etching to form a Si substrate (1).
A contact hole (7) that reaches the contact hole is formed. Therefore,
The contact hole (7) has a tapered shape extending toward the surface of the BPSG film (4).

In this case, the contact hole (7) is provided after the glass flow. However, there is a case where the glass flow is performed after the contact hole (7) is provided to reduce the step. In this case, B around the contact hole (7)
Since the PSG film (4) also causes viscous flow, the step at the contact hole (7) is also reduced. However, when the Si substrate (1) exposed at the bottom of the contact hole (7) is thermally oxidized, or when the BPSG film (4) is exposed to the contact hole (7).
Since the bottom of the contact hole may be covered, it is necessary to newly etch the inside of the contact hole (7) after the glass flow.

[0007] Then, as shown in FIG.
(4) A second-layer Al wiring (8) is formed on the substrate and connected to the Si substrate (1) through the contact hole (7). Here, the contact hole (7) is not limited to the one that reaches the Si substrate (1), and one that reaches the Poly-Si wiring (3) is also formed if necessary. The wiring (8) is connected.

[0008]

However, the BPSG film used as the first and second interlayer insulating films (4)
Has poor adhesion to the photoresist (5),
At the time of wet etching, an etching solution penetrates between the BPSG film (4) and the photoresist (5), and the BPSG film (4)
May be etched more than necessary. As a result, the shape of the contact hole (7) collapses, and the BPSG film (4)
This causes a problem that the reliability of the semiconductor device is reduced due to breakage of the semiconductor device or leakage of current from the Al wiring (8) or the Poly-Si wiring (3).

Accordingly, the present invention improves the adhesion between the interlayer insulating film between the first and second layers and the photoresist applied on the interlayer insulating film without impairing the thermal fluidity of BPSG. It is another object of the present invention to prevent unnecessary etching when forming a contact hole.

[0010]

According to the present invention, there is provided a semiconductor device comprising:
A first wiring formed on a semiconductor substrate is covered with an insulating film mainly composed of low-melting glass containing boron, a second wiring is formed on the insulating film, and the second wiring is formed on the insulating film. In a semiconductor device connected to each region of the semiconductor substrate via a contact hole formed in the insulating film, the boron concentration of the insulating film is reduced near the surface from the semiconductor substrate side. Features.

The method of manufacturing a semiconductor device according to the present invention comprises the steps of: forming a first wiring on one main surface of a semiconductor substrate;
Stopping or reducing the supply of boron in the middle, laminating a low-melting glass containing boron on the semiconductor substrate, and forming an insulating film in which the concentration of boron decreases near the surface; Forming a photoresist film having a predetermined gap, etching the first and second insulating films using the photoresist film as a mask, and forming a contact hole reaching the semiconductor substrate or the first wiring; A second wiring connected to each region of the semiconductor substrate or the first wiring through the contact hole.
The step of forming the wiring described above.

According to the present invention, the adhesion of the interlayer insulating film to the photoresist is reduced by reducing the boron concentration of the interlayer insulating film between the first wiring and the second wiring on the second wiring side. Is improved. Thus, when a photoresist is used as an etching mask when forming a contact hole in the interlayer insulating film, an etchant does not easily enter between the interlayer insulating film and the photoresist.

[0013]

FIG. 1 is a sectional view showing an embodiment of a semiconductor device according to the present invention, and FIG. 2 is a profile diagram of the boron concentration in the thickness direction (on the line XX in FIG. 1) in an interlayer insulating film. It is.

In the semiconductor device of the present invention, a first layer of Pol is formed on an Si substrate (1) on which various elements are formed via an SiO ₂ film (2).
A y-Si wiring (3) is formed, and an interlayer insulating film is formed so as to cover the poly-Si wiring (3). And BP
An Al wiring (8) connected to a specific region of the Si substrate (1) is formed through a tapered contact hole 7 provided in the SG film (4 ').

In this embodiment, the Si substrate (1)
The O ₂ film (2), the Poly-Si wiring (3) and the Al wiring (8) are the same as those in FIG. A feature of the present invention is that, as shown in FIG.
The reason is that the boron concentration in (4 ′) is reduced on the surface side. When the distance from the SiO ₂ film (2) is 0, BP
SG film (4 ') the boron concentration in the indicates a predetermined value B _0, the value B ₀ is BPSG film (4' are kept to near the middle of). Then, the distance decreases toward the surface of the BPSG film (4 ′), and the distance to the SiO ₂ film (2) is reduced to the film thickness T of the BPSG film (4 ′).
_When it becomes ₀ , that is, on the surface of the BPSG film (4 ′), it is set to be almost 0.

It has been confirmed that the adhesiveness of the photoresist to the BPSG film is greatly affected by the boron concentration in the BPSG film. When the boron concentration is reduced, good adhesiveness with the photoresist can be obtained. I know. Therefore, by making the boron concentration of the BPSG film (4 ′) have a distribution as shown in FIG. 2 in the film thickness direction, good adhesion to the photoresist is obtained, and the characteristic of BPSG at a low temperature is obtained. Enables glass flow. Such a BPSG film (4 ') has a high boron concentration in a deep portion of the film, and enables glass flow at a low temperature. At the same time, the surface has a low boron concentration, and good adhesion to the photoresist is obtained. Therefore, during the wet etching, unnecessary intrusion of the etchant can be prevented, and the contact hole (7) can be formed in a desired shape.

Next, the manufacturing method will be described.

The manufacturing method of the present invention is the same as the steps shown in FIGS. 3A to 3E except for the step of forming the BPSG film (4 '). The feature of the present invention lies in the step of laminating the BPSG film (4 ').

The BPSG film (4 ') is made of BPSG by CVD.
When laminating SG, it is formed such that the boron concentration is reduced during lamination. That is, the BPSG film (4 ′) is made of Si
Since it is formed by the CVD method using H ₄ , B ₂ H ₆ , PH ₃ and O ₂ -based gas, the flow rate of B ₂ H ₆ , which is a supply source of boron, is reduced or stopped in the middle of the lamination, The boron concentration in the reaction tube decreases, and the boron concentration of the BPSG to be laminated decreases. As a result, a BPSG film (4 ′) having a boron concentration distribution as shown in FIG. 2 can be obtained.

The formation of the contact hole (7) may be performed before the BPSG film (4 ') is flattened by a glass flow.

[0021]

According to the present invention, it is possible to prevent the etchant from entering between the BPSG film and the photoresist, so that a contact hole having a predetermined shape according to the pattern of the photoresist can be obtained. Prevention of wiring breakage can improve reliability.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a semiconductor device of the present invention.

FIG. 2 is a profile diagram of a boron concentration of an interlayer insulating film of the semiconductor device of the present invention.

FIG. 3 is a process sectional view showing a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

1 Si substrate 2 SiO ₂ film 3 Poly-Si wiring 4, 4 'BPSG film 5 photoresist 6 gap 7 contact hole 8 Al wiring

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 21/31 H01L 21/312-21/3205 H01L 21/3213 H01L 21/768

Claims (3)

(57) [Claims] 1. A first wiring formed on a semiconductor substrate is covered with an insulating film mainly containing low-melting glass containing boron, and a second wiring is formed on the insulating film. In a semiconductor device in which the second wiring is connected to each region of the semiconductor substrate through a contact hole formed in the insulating film, the boron concentration of the insulating film is
The semiconductor is at least substantially at the center in the thickness direction of the insulating film.
A semiconductor device characterized by being constant on the body substrate side and substantially zero near the surface of the insulating film . 2. A process of forming a first wiring on one main surface of the semiconductor substrate, a predetermined concentration by supplying a gas including boron boro
At least half of the specified thickness
And the rest of stopped or reduced in the course of the supply of boron
By forming the insulating film, the boron concentration becomes
Constant on the semiconductor substrate side from the substantial center of the insulating film thickness
And near the surface of the insulating film, the semiconductor substrate
Forming an insulating film lower than the plate side ; forming a photoresist film having a predetermined gap on the first insulating film; using the photoresist film as a mask to form the first and second insulating films; Forming a contact hole reaching the semiconductor substrate or the first wiring by etching an insulating film, and a second wiring connected to each region of the semiconductor substrate or the first wiring through the contact hole Forming a semiconductor device. 3. The method according to claim 2, further comprising the step of heating the insulating film made of a low-melting glass containing boron to cause a viscous flow of the insulating film so as to reduce a step on the surface due to the first wiring. A method for manufacturing a semiconductor device.