JPS6324638A - Microscopic hole filling method - Google Patents

Abstract

PURPOSE:To completely fill microscopic holes by a method wherein a microscopic hole is partially filled with a conductive film in such a manner that the thickness of the deposited conductive film on the bottom part of the hole is formed uniformly, and the surface of the filled part is almost flattened by forming a conductive film on the non-filled part. CONSTITUTION:After an Si oxide film 2 has been deposited on the Si substrate 1 having the flat surface using a CVU method, a contact hole 3 is formed by performing the commonly used photoresist process and a dry etching process. Then, an Al film 4 is deposited on the whole surface of the substrate 1 by performing an arc discharge type ion-plating method. Under the above-mentioned condition, the Al film 4 is deposited on the whole surface of the substrate 1, a film of uniform thickness is deposited on the stepped part of the contact hole 3 in such a manner that an inclined surface of the prescribed range of angle is formed on the shoulder part of said stepped part. Then, an Al film 4 is deposited by performing a bias sputtering method. As a result, the thickness of the Al film deposited on the bottom part of the contact hole 3 is formed thicker than the film 2, and the Al film on the film 2 is almost flattened.

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 is provided in a semiconductor device, contact holes are formed in an insulating film that protects the surface, and a conductive film is deposited thereon. Recent advances in exposure technology and dry etching technology have enabled the formation of contact holes in LSIs, etc., to approximately 1 μm in thickness in an insulating film.
It is now possible to have a size on the order of μm square. When depositing a conductor film onto such a fine contact hole, two important things are: one is to densely fill the fine contact hole with the conductor film, 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.

(The problem that the invention is trying to solve) However, LSI
Since the contact hole has steep sides and a large step, when a conductive film is deposited using the conventional parallel plate sputtering method or vapor deposition method, as shown in Figure 2, a large amount of material is deposited on the shoulder of the step of the contact hole. Due to the shadow effect of the conductor film itself, step coverage deteriorates, wiring is easily cut or thinned, and the manufacturing yield and reliability of LSIs are significantly reduced. 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. This is not a preferable improvement method because it will hinder the high integration of LSI. Therefore, a method has been proposed in which a conductive film is deposited with good step coverage on steep, high aspect ratio grooves or contact holes.
One of them is a sputtering method using a planetary type substrate holder. It has been experimentally verified that the planetary sputtering method provides better step coverage than the parallel plate sputtering method. However, recently, A, R. Neureuther et al. conducted a comparison between simulation and experiment on the step coverage of fine and deep grooves using planetary sputtering method. (IEEE Trans, ED, 27
．． 1449 (1980)). According to the report, the radius is 211m, and the aspect ratio (depth 7 width) is 0.5.
It has been stated that when a film is deposited on the groove by planetary sputtering, the step coverage is extremely deteriorated due to the shadow effect. More recently, chemical vapor deposition (CV
D) Ito et al. reported in the Proceedings of the Symposium on Brnis Eye Technology that aluminum formed by the method has improved film deposition on the side walls of contact holes compared to the sputtering method described above. (1982 Symp, onVLSI Techno
logy(Sept, 1-3.1982, 0iso, J
apan) Digest of Technical
Papers, p, 20. )It is described in. However, it has been reported that the formed A1 film has the drawbacks of high resistivity and large variations, and there are many problems in using it as an integrated circuit wiring.

Furthermore, it has recently been known that by depositing a conductor film in the contact hole using bias sputtering, it is possible to fill the inside of the contact hole more densely with the conductor film and to flatten the surface of the deposited conductor film. There is. However, when using the bias sputtering method, there is a limit to the aspect ratio (depth l diameter) of the contact hole when filling the contact hole, and if the aspect ratio of the contact hole is 1 or more, the contact hole will be It is also known that voids remain in the conductor film within the conductor film, resulting in incomplete filling.

The purpose of the present invention is to solve the conventional microscopic problem (a means for solving the problem) as described above. A first step of filling a part of the depth of the fine hole with a conductive film using a vapor deposition method so that the conductor film deposited at the bottom of the fine hole has a uniform thickness, and a bias sputtering method to fill the deposited conductor film at the bottom of the fine hole with a conductive film having a uniform thickness. and a second step of burying the unfilled portions with a conductive film.

(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 aspect ratio of the hole. By further depositing a conductive film on the hole with a reduced aspect ratio using a bias sputtering method, we can completely fill the fine hole with a high aspect ratio, which could only be incompletely filled with the bias sputtering method. It can be embedded and the surface can be flattened at the same time.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1(a) to 1(c) are schematic sectional views sequentially showing steps of an embodiment of the present invention.

In FIG. 1(a), a silicon oxide film 2 with a thickness of about 111 m is deposited on a silicon substrate 1 with a flat surface by the CVD method, and then a contact hole 3 with a diameter of 1 pm is formed by a normal photoresist process and dry etching process. This shows the state in which it has been formed.

Next, as shown in FIG. 1(b), an aluminum film 4 is applied to the entire surface of the substrate 1 by an arc discharge ion blating method using an aluminum source under conditions of an arc discharge ionization current of 2 OA and a substrate bias voltage of -3 kV. , about 0.51 J, m thick is deposited. The aluminum film deposited under these conditions has a uniform thickness at the bottom of the contact hole, and is deposited so as 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 FIG. 1(C), the aluminum target power 1. An aluminum film 4 of about 0.5 μm is further deposited by bias sputtering under conditions of OKW, substrate bias voltage of −600 V, and argon pressure of 3 mTorr. 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 and silicide can also be used.

Furthermore, in the above embodiment, a contact electrode was formed to connect the substrate and the wiring immediately above it (layer wiring). 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 arc discharge type ion blating method and bias sputtering method when embedding a conductive 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 bias sputtering alone.

[Brief explanation of drawings]

FIGS. 1(a) to (c) are schematic cross-sectional views sequentially showing one embodiment of the present invention step by step, and FIG. 2 shows a conductor film having a steep side surface formed by a conventional sputtering method or vapor deposition method. There is a schematic cross-section of a contact hole portion when deposited on a substrate with a contact hole formed therein. The numbers in the figure indicate the following. 1...Silicon substrate 2...Silicon oxide layer 3...Contact hole 4...Aluminum film Fig. 1

Claims (1)

[Claims] Using an ionization vapor deposition method for a substrate in which fine holes are formed in an insulating film deposited on the surface, a conductor film deposited at the bottom of the fine hole is formed with a uniform thickness to cover part of the depth of the fine hole. A method for filling a fine hole, the method comprising: a first step of filling with a conductive film; and a second step of filling an unfilled portion of the fine hole with a conductive film using a bias sputtering method.