JPH04333226A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a stabilized metallic wiring by evenly filling up contact holes in high aspect ratio with a metal. CONSTITUTION:An interlayer insulating film 5 is formed on a silicon substrate 12 and after making contact holes 6 by etching away said insulating film 5, these holes 6 are filled up with tungsten 7 by selective CVD-tungsten step using WF6 and SiH4. Next, after the formation of bonded layers 8 comprising Ti, TiW, etc., by sputtering step, another tungsten 9 is grown on the whole surface to completely fill up the contact holes 6.

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. More specifically, the present invention relates to a method of forming an electrically conductive portion.

0002

[Background Art] In recent years, with the miniaturization of semiconductor devices, the diameter of contact holes has also become smaller, and the ratio of the depth to diameter of contact holes (
As the aspect ratio (aspect ratio) is getting larger and larger, it is becoming difficult to coat the inside of the contact hole with the wiring material using the normal thin film forming method using sputtering. To solve this problem, chemical vapor deposition (hereinafter referred to as "CVD method") of high-melting point metals such as tungsten has conventionally been used.
). The CVD method includes a selective growth method and an all-over growth method. In the selective growth CVD method, by appropriately selecting conditions, tungsten does not grow on the insulating film, but grows only on Si, silicide, and metal, and by growing tungsten inside the contact hole, Contact holes are filled in to reduce the aspect ratio. In the full-surface growth method, the contact hole can be filled by covering the entire surface with an adhesion layer such as Ti or TiW by sputtering and then growing tungsten over the entire surface.

0003

[Problem to be solved by the invention] Sputtering of Ti and TiW required when growing tungsten by the full surface growth method
An adhesion layer such as tungsten is essential not only for adhering tungsten and an insulating film but also as a barrier metal to suppress Si erosion during tungsten growth, but it increases the aspect ratio of the contact hole. As a result, it has become difficult to coat the inside of the contact hole with the required amount of adhesive layer using the conventional thin film forming method using sputtering. It is said that the limit of the aspect ratio of a contact to which the full surface growth method can be applied is about 2.5.

On the other hand, when filling a contact hole with tungsten using the selective growth method, the growth rate slows down as the aspect ratio of the contact hole increases, and the longer the aspect ratio of the contact hole to fill, the longer it takes. Therefore, the selectivity deteriorates and tungsten nuclei are easily formed on the insulating film. Furthermore, in actual devices, contacts of various depths coexist, making it difficult to obtain the optimal film thickness for all contacts.

[0005] In recent years, as LSIs have become increasingly finer and the aspect ratio of contact holes has become larger, the above problems can no longer be ignored. The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for manufacturing a semiconductor device that can uniformly fill a contact hole with a high aspect ratio.

[0006]

According to the present invention, an insulating layer is formed on a silicon substrate, a contact hole is opened by etching the insulating layer, and a contact hole is formed halfway into the contact hole.
Using WF6 and SiH4, tungsten is embedded by selective CVD-tungsten method, and then Ti and TiW are implanted.
A method of manufacturing a semiconductor device is provided, which is characterized in that after forming an adhesive layer such as by sputtering, tungsten is grown on the entire surface to completely fill a contact hole.

[0007] The tungsten wiring in the present invention is for inputting or outputting signals to an element consisting of layers of N+Si, P+Si, and WSix, and WF6 and SiH4 are inserted into contact holes leading to these layers. Tungsten can be deposited and formed by a combination of the selective CVD-tungsten method and the full-surface CVD-tungsten method used. In this invention, the impurity diffusion layer is formed by ion-implanting a dopant as an impurity before forming the insulating film. The CVD-tungsten method in this invention may be carried out under conditions known in the art. Selective tungsten heats the substrate placed in the CVD equipment at 250°C to 350°C.
For example, WF6 and SiH4 are heated to 30/24 to 3
The flow rate ratio is 0/16, and the pressure is, for example, 0.01 to 0.1.
At 2 Torr, the contact hole is usually 0.5 to 0.
Deposit a thickness of 7 μm. Next, by sputtering, Ti
500 to 1000 Å of tungsten is deposited on this adhesion layer, and the substrate placed in a CVD apparatus is heated to 410°C to 450°C, and WF6 and H2 are deposited, for example, at 450/65 to 520/400°C. The flow rate is 80 sccm and the pressure is, for example, 70 to 90 Torr, usually 0.
A thickness of 4-0.7 μm is deposited to completely fill the contact hole. Next, the tungsten on the insulating film is etched back to form a contact hole filling plug, and wiring and the like are formed thereon to manufacture a semiconductor device.

[0008]

[Operation] Tungsten is buried halfway into the contact hole by selective CVD-tungsten using WF6 and SiH4. Next, an adhesion layer of Ti or TiW is formed by sputtering, and then tungsten is grown on the entire surface. Since the contact hole is filled, the aspect ratio can be reduced by selective CVD, and even if tungsten nuclei are generated during selective CVD, tungsten is subsequently grown over the entire surface, so the nuclei can be removed during etchback. Since the entire surface growth method is used, it is possible to completely fill contact holes of various depths. In other words, by combining selective growth and full-surface growth, the shortcomings of both are mutually compensated for, making it possible to uniformly fill contact holes with a high aspect ratio.

[0009]

EXAMPLES Examples of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following examples. Selective CVD for filling SRAM contact holes
A semiconductor device fabrication method using the tungsten method combined with full-surface CVD will be described. As shown in FIG. 1(a), on a silicon substrate 12, an element isolation region 1, a WSi
After forming an element consisting of a gate electrode 2 having a stacked structure of an x layer 2B and a poly-Si layer 2A, an N+Si layer 3 and a P+Si layer 4, an interlayer insulating film 5 is deposited by the CVD method.
This interlayer insulating film is etched by photolithography to open contact holes 6 on the N+Si layer 3 and P+Si layer 4 and on the WSix layer 2B of the gate electrode 2. The contact holes are all 0.3 μm in diameter, N+, P+S.
The depth above the i layer is 1.0 μm and the depth above the WSix layer is 0.
．． It is 8 μm. After immersing the silicon substrate in 1% buffered hydrofluoric acid for 45 seconds to remove the natural oxide film on the device, the film formation temperature was 270°C and the pressure was 0.5°C, as shown in (b).
02 Torr, the flow rates of WF6 and SiH4 were each 10
sccm and 8 sccm, contact hole is 0.5
The selective CVD tungsten layer 7 was grown for 240 seconds until it was buried by μm. Next, as shown in FIG. 1(c), TiW8 was sputtered to a thickness of 500 Å, and as shown in FIG. 1(d), the substrate temperature was 430°C, the pressure was 80 Torr, and the flow rates of WF6 and H2 were 500 sccm and 75 sccm, respectively.
As a result, a 0.4 μm thick tungsten layer 9 is grown over the entire surface in 60 seconds. Subsequently, as shown in (e), etchback is performed to remove the tungsten and TiW on the interlayer insulating film, and the contact hole filling plug is completed.

FIG. 2 shows a case where tungsten is buried only by selective tungsten CVD. If tungsten nuclei 10 are generated on the interlayer insulating film 5 and buried in a shallow contact hole, subsequent disconnection of the Al wiring is likely to occur in the deep contact hole. In addition, in Figure 3, the entire tungsten C
This shows the case where only the VD is embedded. When the adhesion layer 8 is deposited by sputtering, a sufficient film thickness as a barrier metal cannot be obtained at the bottom of a contact hole with a high aspect ratio, and when tungsten is grown on the entire surface, erosion 11 of the underlying Si etc. occurs, which deteriorates the contact characteristics. deteriorates.

[0011]

As described above in detail, according to the present invention, contact holes with a high aspect ratio can be filled uniformly, and stable metal wiring can be formed.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the manufacturing process of a semiconductor device showing the configuration of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor device manufactured by a conventional technique.

FIG. 3 is a cross-sectional view of a semiconductor device manufactured by a conventional technique.

[Explanation of symbols]

1 Element isolation region 2 Gate electrode 2A Poly-Si layer 2B WSix layer 3 N+Si layer 4 P+Si layer 5 Interlayer insulation film 6 Contact hole 7 Selected CVD tungsten 8 TiW 9 Fully CVD tungsten 10 Tungsten core 11 Silicon substrate erosion 12 Silicon substrate

Claims (1)

[Claims] 1. An insulating layer is formed on a silicon substrate, the insulating layer is etched to open a contact hole, and WF6 and SiH4 are used in the contact hole to form a selective CVD-
1. A method of manufacturing a semiconductor device, which comprises embedding tungsten using a tungsten method to reduce an aspect ratio, and then growing tungsten on the entire surface using a blanket CVD-tungsten method.