JPH061772B2 - Wiring layer formation method - Google Patents

Description

DETAILED DESCRIPTION [Outline] Al-S containing 1 to 3% of normal Si for forming an Al wiring layer
When the i alloy is used, the p-type solid phase epitaxial layer grows in contact with the n-type substrate, which deteriorates the contact characteristics. The present invention has a two-layer wiring layer structure of an Al-Si alloy containing 40% or more of Si and pure Al, and the growth temperature is controlled to improve the contact characteristics.

[Industrial application field]

The present invention relates to formation of an Al wiring layer having good contact characteristics.

In integrated circuits, Al is widely used as a material for wiring layers. However, if pure Al is used, there is a problem that the reliability of spikes, electromigration, hillocks, etc. in the wiring layer or the contact surface deteriorates.
An alloy containing i, Cu, refractory metal or the like is often used.

Among them, an Al-Si alloy in which Si is mixed with a few percent of Si is often used, but this method has a problem of solid phase epitaxial growth of p-type Si in a contact hole, and improvement thereof is desired.

[Conventional technology]

As a material for the wiring layer as a measure for preventing spikes and electromigration on the electrode contact surface, Al is 1 to 3% Si, Cu is 4% or less, or refraction metal such as Ti, Mo, W is 1%. An Al alloy to be mixed in as described below is used.

Among these, the Al-Si alloy, which has good contact characteristics, is most widely used.

Further, as a method of laminating the wiring layers, there are a vacuum vapor deposition method and a sputtering method, but recently, a magnetron sputtering method suitable for mass production is mainly applied.

The magnetron sputtering method is
Although the rate is large and the adhesive force is large, the substrate is usually heated to 200 to 300 ° C. during the deposition in order to improve the step coverage in the contact hole.

[Problems to be solved by the invention]

Using the Al-Si alloy target in which 1 to 3% Si is mixed as described above, the wiring layers are stacked by the magnetron sputtering method while heating the substrate at 200 ° C., for example. The problem of solid phase epitaxial layer growth arises.

Al exhibits p-type impurity characteristics with respect to Si, and Al-S
Even though the contact resistance is low immediately after the step of stacking i, the solid phase epitaxial layer growth of p-type Si proceeds in the contact hole due to the subsequent wafer process or heating during operation as an integrated circuit.

Therefore, the contact resistance of the contact surface with the n-type region of the Si substrate increases, and the characteristics of the transistor deteriorate.

[Means for solving problems]

The above-mentioned problem is that after forming a thin film of an Al-Si alloy film containing Si in an amount of 40% or more on a substrate under non-heating conditions, a thick film of substantially pure Al is laminated on the thin film, and Si on the substrate side. This is solved by a method of forming a wiring layer, which is characterized in that a high concentration region is formed.

[Action]

The growth of the p-type solid phase epitaxial layer is significantly affected by the conditions of Al—Si content and growth temperature.

In the present invention, the formation of the wiring layer has a two-layer structure, the Al-Si layer is only a thin film growth to prevent the generation of spikes on the contact surface, and the growth of the solid phase epitaxial layer of p-type Si is suppressed as much as possible. The best condition was experimentally obtained by using pure Al for the layer.

〔Example〕

An embodiment according to the present invention will be described in detail. In this example, two magnetron sputtering apparatuses were used, and targets of the magnetron sputter gun were Al—Si alloy (Si content rate 45%) and pure Al targets, respectively.

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

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

A magnetron sputter gun made of an Al-Si alloy is used to grow Al-Si (45%) having a film thickness of about 400Å. Then, the substrate is transferred to a preliminary vacuum chamber and preheated to 200 ° C.

Then, the substrate is transferred to the second sputtering device and pure A
l is sputtered to a film thickness of about 9500Å, and the substrate is taken out from the preliminary vacuum chamber. This completes the stacking of wiring layers.

Although the substrate is heated in the preliminary vacuum chamber in the above description, the same applies when the substrate is heated from the back surface in the sputtering apparatus.

In this embodiment, the Si content ratio is set to 45%, but if it is 40% or more, almost satisfactory results can be obtained. If the Si content exceeds 50%, it will be difficult to manufacture the target itself, and if the ratio of Si having a high melting point is higher than that of Al, the sputtering characteristics will deteriorate and the quality of the grown film will also deteriorate. .

In the drawing, when Al-Si (1%) is grown at a temperature of 200 ° C. and grown at one time by the conventional method (characteristic curve I), the method of this embodiment (characteristic curve II), Al-Si (45%) is used. And growth of pure Al are both heated at 200 ° C. (characteristic curve III), and when the Si content is 40% by the same method as in this embodiment (characteristic curve)
IV).

The data was measured by forming 10 wiring layers each having contacts at two positions on both ends on an n-type Si substrate and connecting them in series to measure the resistance at both ends.

The vertical axis represents the relative value of contact resistance, and the horizontal axis represents the time for forcibly heating the sample to 500 ° C.

Al-Si (45%) explained in this example is not heated and pure A
The most desirable result is obtained by the characteristic curve III in which 1 is grown in two stages under heating conditions.

As described above, in one embodiment of the present invention, aluminum containing no impurities at all has been described as an example. However, the aluminum may contain impurities or a mixture to some extent. Even such an aluminum wiring layer exerts the same action / effect to the same problem,
Of course, it can be a solution to problems.

〔The invention's effect〕

As described above, it becomes possible to form a wiring layer having good contact characteristics by using the method for forming a wiring layer of the present invention.

[Brief description of drawings]

The drawings show diagrams for comparatively explaining contact resistance characteristics of wiring layers formed by the method of the present invention.

Claims (1)

[Claims] 1. A thin film of an Al--Si alloy film containing 40% or more of Si is formed on a substrate under non-heating conditions, and then a thick film of substantially pure Al is laminated on the thin film. A method of forming a wiring layer, characterized in that a high concentration region is formed.