JPH0569294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of filling minute holes such as contact holes with a conductive film.

(Prior art) When wiring a semiconductor device, contact holes are made in an insulating film that protects the surface.
This is done by depositing a conductive film thereon.
Recent advancements in exposure technology and dry etching technology have made it possible to form contact holes in LSIs, etc., of about 1 μm square in an insulating film with a thickness of about 1 μm. In depositing a conductor film onto such a fine contact hole, two important things are: one is to densely bury the conductor film in the fine contact hole, and the other is to ensure that the conductor film is not deposited in the fine contact hole. After that, the surface should be flat.

(Problem to be solved by the invention) However, since contact holes in LSIs have steep sides and large steps, it is recommended to deposit a conductor film using the conventional parallel plate sputtering method or vapor deposition method, as shown in Figure 2. As shown in the figure, the shearing effect of the many conductive films on the shoulders of the contact hole steps deteriorates the step coverage, making it easy for the wiring to break or become thin, which significantly reduces the manufacturing yield and reliability of LSIs. Ta. In order to prevent these drawbacks, the side surfaces of minute contact holes are tapered and sloped to ensure that the conductor film is uniform. What to have
This is not a preferable improvement method because it hinders the high integration of LSI. Therefore, methods have been proposed for depositing a conductive film with good step coverage on steep, high aspect ratio grooves or contact holes. One of these methods is the sputtering method using a planetary type substrate holder. There is. It has been experimentally verified that the planetary sputtering method provides better step coverage than the parallel plate sputtering method. However, recently, ARNeuther et al. conducted a simulation and experimental comparison of the step coverage of fine, deep grooves using the planetary sputtering method using the iTripleE Transaction of Electron Device (IEEETrans.ED). .27, 1449
(1980)). According to the report, width
It has been stated that when a film is deposited by a planetary sputtering method on a groove with a diameter of 2 μm and an aspect ratio (depth/width) of 0.5, the step coverage is extremely deteriorated due to the shadow effect. Furthermore, T. Ito et al. recently found that aluminum formed by chemical vapor deposition (CVD) improves film deposition on the sidewalls of contact holes compared to the sputtering method described above. Proceedings of the Symposium on BLSI Technology (1982Symp.
onVLSI Technology (Sept.1~3, 1982, Oiso,
Japan) Digest of Technical Papers.p.20.). However, it has been reported that the formed Al film has the drawbacks of high resistivity and large variations, and there are many problems in using it as integrated circuit wiring.

Furthermore, it has recently become known that by depositing a conductive film in the contact hole using a bias sputtering method, it is possible to fill the inside of the contact hole densely with the conductive film and to flatten the surface of the deposited conductive film. ing. However, when using the bias sputtering method, there is a limit to the aspect ratio (depth/diameter) of the contact hole when filling the contact hole. It is also known that voids remain in the conductor film within the hole, resulting in incomplete filling.

The object of the present invention is to solve the problems of the conventional method of filling fine holes as described above, and to provide a method for forming a flat surface of the deposited conductor film without leaving any voids in the deposited conductor film, especially in the part of the fine hole. It is about providing.

(Means for Solving the Problems) The method of the present invention uses an ionization vapor deposition method on a substrate in which a fine hole is formed in an insulating film deposited on the surface, and deposits the film at the bottom of the fine hole. A first step of filling a part of the depth of the fine hole with a conductive film with a uniform thickness, and using a bias sputtering method, a portion of the fine hole that is not yet filled is filled with the conductive film. and a second step of embedding.

(Function) In the present invention, in a fine hole with an aspect ratio of 1 or more, a conductive film is deposited in advance in the hole using an ionization vapor deposition method, and at the same time, a conductor film is deposited on the shoulder of the step in the hole portion using a specific method specific to the ionization vapor deposition method. form an inclined surface. This reduces the apparent aspect ratio of the hole. By further depositing a conductor film on the hole with a reduced aspect ratio using the bias sputtering method, it is possible to fill the fine holes with a high aspect ratio, which could only be incompletely filled using the bias sputtering method, with the conductor film. It can be completely embedded and the surface can be flattened at the same time.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIGS. 1a to 1c are schematic cross-sectional views showing one embodiment of the present invention step by step.

In Figure 1a, a silicon oxide film 2 with a thickness of approximately 1 μm is deposited by CVD on a silicon substrate 1 with a flat surface, and then a contact hole 3 with a diameter of 1 μm is formed using a normal photoresist process and dry etching process. Indicates the state in which

Next, as shown in FIG. 1b, an aluminum film 4 is deposited over the entire surface of the substrate 1 by arc discharge ionization deposition using an aluminum source under conditions of an arc discharge ionization current of 20 A and a substrate bias voltage of -3 kV. Deposits approximately 0.5 μm. The aluminum film deposited under these conditions is deposited to a uniform thickness at the bottom of the contact hole, and is deposited to form an inclined surface with an inclination angle of 40° to 60° at the shoulder of the contact hole step.

Next, as shown in Figure 1c, the aluminum target power was 1.0kW, the substrate bias voltage was -600V,
The aluminum film 4 is further coated by bias sputtering under an argon pressure of 3 mTorr.
Deposit 0.5μm. Under these conditions, the thickness of the aluminum film deposited at the bottom of the contact hole is twice the thickness of the aluminum film deposited on the silicon oxide film 2, and the aluminum film on the silicon oxide film with the contact hole is almost flat. become.

In the embodiment described above, an aluminum film is deposited, but there is no need to be limited to this; other metals such as molybdenum, and alloys such as polycrystalline silicon doped with impurities, silicide, etc. can be used.

Further, in the above embodiment, a contact electrode was formed to connect the substrate and the wiring immediately above it (first layer wiring), but the contact electrode is not limited to this. This method can be applied to cases where a conductive film is well embedded in a fine through-hole that connects.

(Effects of the Invention) As explained above, the present invention uses a combination of an arc discharge ionization vapor deposition method and a bias sputtering method when filling a conductor film into a fine hole with an aspect ratio of 1 or more. It is possible to fill minute holes with an aspect ratio of 1 or more, which was impossible with only the bias sputtering method.

[Brief explanation of the drawing]

Figures 1a to 1c are schematic sectional views showing one embodiment of the present invention step by step, and Figure 2 is a contact hole with a steep side surface formed by forming a conductive film using a conventional sputtering method or vapor deposition method. FIG. 3 is a schematic cross-sectional view of a contact hole portion when deposited on a formed substrate. The numbers in the figure indicate the following. 1...Silicon substrate, 2...Silicon oxide film, 3...Contact hole, 4...Aluminum film.

Claims (1)

[Claims] 1 Using an ionization vapor deposition method, a substrate with fine holes formed in an insulating film deposited on the surface
A first step in which the conductive film deposited at the bottom of the fine hole is filled with a conductive film with a uniform film thickness and a part of the depth of the fine hole is filled with the conductive film, and a bias sputtering method is used to bury the conductive film in a part of the depth of the fine hole. and a second step of burying the missing portion with a conductive film.