JPS62211936A - Formation of interconnection layer - Google Patents

Abstract

PURPOSE:To obtain an interconnection layer having desirable contact char acteristics, by depositing a thin film of Al-Si alloy containing 40% or more of Si on a substrate under non-heating conditions and then depositing a thick film of pure aluminium on the thin film with the substrate being heated. CONSTITUTION:In the first step, a thin film of Al-Si alloy containing 40% or more of Si is grown on a substrate without heating the substrate. In the second step, pure aluminium is deposited to form a thick interconnection layer on the substrate while the substrate is being heated. Since growth of a P-type solid-phase epitaxial layer is affected considerably by proportions of components in Al-Si alloys and growing temperatures, the interconnection layer is composed of two layers consisting of the Al-Si layer and the main interconnection layer of pure aluminium. While the Al-Si layer is grown only to form a thin film for avoiding spikes on the contact surface and for suppressing the growth of a P-type solid-phase epitaxial layer, the main interconnection layer is formed of pure aluminium so as to obtain optimum growing conditions experimentally.

Description

[Detailed Description of the Invention] [Summary] For the formation of the Aβ wiring layer, ordinary Af containing 1 to 3% Si is used.
When a fi-Si alloy is used, a p-type in-phase epitaxial layer grows in contact with an n-type substrate, deteriorating the contact characteristics. The present invention includes 5i40% or more of A7! −
A two-layer wiring structure of Si alloy and pure AN was adopted, and the growth temperature was controlled to improve the contact characteristic +z[.

[Industrial field of use]

The present invention relates to the formation of an An wiring layer with good contact characteristics.Aff is widely used as a material for wiring layers in integrated circuits. However, pure A7! If A1 is used, there are problems such as spikes, electronic migration, and hillocks on the wiring layer or contact surface, reducing reliability. Often used.

Among these, an Aff-Si alloy in which several percent of Si is mixed into Al2 is often used, but this method has the problem of in-phase epitaxial growth of p-type Si in the :z contact hole, and an improvement is desired.

[Conventional technology]

To prevent spikes, electromigration, etc. on the electrode contact surface, the material for the wiring layer should be A/ with 1 to 3% St, 4% or less Cu, or T.
An A1 alloy is used in which a flux metal such as i, Mo, or W is mixed in an amount of 1% or less.

Among these, the Ae-3i alloy, which has good properties of contact 1 and above, is most widely used.

Further, methods for laminating wiring layers include vacuum evaporation and sputtering, but recently magnetron sputtering, which is suitable for IX production, has been mainly applied.

The magnetron sputtering method is a sputtering method.
Although it is characterized by a high rate and strong adhesion, the substrate is usually heated to 200 to 300° C. during vapor deposition to improve step coverage in contact holes.

[Problem that the invention seeks to solve]

When a wiring layer is laminated by magnetron sputtering while heating the substrate to, for example, 200°C using the Al4-3i alloy target mixed with 1 to 3% Si as described above, p-type Si is formed in the contact hole. This gives rise to the problem of solid phase epitaxial layer growth.

A7! shows the characteristics of p-type impurity compared to St, and Al
Although the contact resistance immediately after the lamination process of 1-3i is low, the subsequent wafer process, or number.
P is generated in the contact hole due to heating etc. during operation as an integrated circuit.
In-phase epitaxial layer growth of Si type progresses.

For this reason, contact resistance increases at the contact surface with the n-type region of the Si substrate, accompanied by deterioration of transistor characteristics.

[Means for solving problems]

In order to solve the above problems, in the first step, a thin film of Al-3i alloy with a Si content of 40% or more was grown on the substrate without heating, and then in the second step, the substrate was heated. This problem is solved by the method of the present invention, which comprises forming a wiring layer by laminating a thick layer of pure Al on the substrate.

[Effect]

The growth of a p-type in-phase epitaxial layer is significantly affected by the Al-3i content ratio and growth temperature conditions! receive.

In the present invention, the wiring layer is formed in a two-layer structure, and the Al-3i layer is grown only as a thin film to prevent the occurrence of spikes on the contact surface, and the growth of the p-type Si solid-phase epitaxial layer is suppressed as much as possible. The best conditions were experimentally determined using pure Aff as the layer.

〔Example〕

An embodiment according to the present invention will be described in detail. In this embodiment, two magnetron sputtering devices are used, and the targets of each magnetron sputter gun are Aj! -3i alloy (Si content: 45%) and pure Aff targets were used.

Each magnetron sputtering device is equipped with a preliminary vacuum chamber, which allows the substrate to be attached to and removed from the substrate support mechanism of the device without breaking the vacuum atmosphere. Heating can also be performed.

In the method of the invention, in the first step, the substrate is introduced into the first magnetron sputtering device without being heated in a preliminary vacuum chamber.

An AIf-3i (45%) film with a thickness of approximately 400 mm is grown using a magnetron sputter gun made of an Al-3i alloy. Next, the substrate is transferred to a pre-vacuum chamber and pre-heated at 200°C.

The substrate is then transferred to a second sputtering device and pure A
After performing sputtering in step 1 to a film thickness of about 9,500 mm, the substrate was taken out from the preliminary vacuum chamber. This completes the stacking of wiring layers.

In the above explanation, the substrate was heated in the preliminary vacuum chamber, but the same effect can be achieved by heating the substrate from the back side in the sputtering apparatus.

In this example, the content ratio of St was 45%, but 40%
With the above conditions, almost satisfactory results can be obtained.

If the content ratio of Si exceeds 50%, it becomes difficult to manufacture the target itself, and if the ratio of St, which has a high melting point compared to /l, is large, the sputtering characteristics will deteriorate and the quality of the grown film will be poor. Become.

In the drawing, Al-3i (1%) was heated at 200°C using the conventional method.
When the growth can be performed at one time by heating with (characteristic curve I), the JJ method of this example (characteristic curve II)
5%) and pure/l growth at 200°C (special +?1 curve III).
The case where the content is 40% (characteristic curve IV) is shown.

The data was measured by forming 10 (IIil) wiring layers each having contacts at two ends on an n-type Si substrate-L, connecting them in series, and measuring the resistance at both ends.

The vertical axis shows the relative value of contact resistance, and the horizontal axis shows the test t'-
1 is forcibly heated to 500°C.

The most desirable result was obtained with the characteristic curve (2), which is described in this example, in which Aff-3i (45%) is grown in two stages under non-heating conditions and pure AI is grown under heating conditions.

〔Effect of the invention〕

As explained above, by using the wiring layer forming method of the present invention, it has become possible to form a wiring layer with good contact characteristics.

[Brief explanation of drawings]

The drawings are diagrams for comparing and explaining contact resistance characteristics of wiring layers formed by the method of the present invention.

Claims (1)

[Claims] A wiring layer characterized in that a thin film of an Al-Si alloy film containing 40% or more of Si is laminated on a substrate under non-heating conditions, and then a thick film of pure Al is laminated on the thin film by heating the substrate. Formation method.