JPS62228446A - Aluminum alloy for semiconductor wiring material - Google Patents

Abstract

PURPOSE:To obtain an aluminum alloy effective in preventing hillock formation as well as electromigration and extremely excellent as semiconductor wiring material, by adding specific amounts of Ti and B to Al. CONSTITUTION:The aluminum alloy for semiconductor wiring material has a composition consisting of, by weight, 0.002-0.5% Ti, 0.002-0.5% B, and the balance Al with inevitable impurities or further containing 0.5-1.5% Si. An aluminum casting with the above composition is machined in the above state to be formed into semiconductor wiring material such as vapor deposition material, target plate for sputtering, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an aluminum alloy for semiconductor wiring material used for connection wiring of each electrode of an MO3 type semiconductor.

[Prior Art] Semiconductor integrated circuits have developed rapidly in recent years, and as their functions have expanded, thin film metal interconnections that electrically interconnect constituent elements are becoming increasingly finer and denser.

Book film gold 1. Currently, an Al deposited film is often used as wiring. This is because Al (a) can easily make ohmic contact with silicon.

(b) A film with good conductivity can be obtained by vacuum evaporation.

(c) Good adhesion to silicon oxide film (S i O,).

(d) Chemically stable and does not react with Sio2.

(e) Processing with photoresist is easy.

(f) Good lead bonding properties.

This is because it is considered to be advantageous overall. As the Al alloy for vapor deposition, an Al-1wt%Si alloy is usually used.

[Problems to be Solved by the Invention] On the other hand, the disadvantages of the Al wiring film are as follows: (a) Electromigration occurs and the wire breaks when the current density becomes 10'A/cm2 or more. It is difficult to form a film with a uniform thickness during sputtering or vacuum deposition, especially where there are steps.

As shown in FIG. 1, when a thin portion 3 is formed in a portion, the current density in that portion becomes high, so that the above-mentioned electromigration occurs, and the wire may be disconnected from that portion.

(b) Protrusions called hillocks occur between adjacent wires (
In the case of multi-layer wiring, short circuits occur between the layers.

and so on.

[Means to solve the problem] Electromigration is the process by which AI is produced under high current density.
As atoms gain kinetic energy by colliding with electrons and move in the direction of electron movement, atomic vacancies (voids) are generated in the traces where the x atoms of Al have moved, resulting in a decrease in the cross-sectional area of the wiring. However, the current density increases further, causing a rise in temperature due to Joule heat, etc., which accelerates the growth of voids, eventually leading to wire breakage. This Al
) The movement of M molecules is normally caused by grain boundary diffusion that propagates through the grain boundaries of Al, and if the grain boundaries are blocked with some kind of precipitate, grain boundary diffusion becomes difficult to occur and electromigration can be prevented.

Next, hillocks are caused by Al atoms diffusing along grain boundaries and protrusions on the surface due to stress during heat treatment, by grains rising due to grain boundaries and forming surface protrusions, and by electromigration mentioned above. In some cases, the transferred Al atoms protrude toward the surface. In order to prevent these, it is effective to block the grain boundaries with some kind of precipitate to make it difficult for grain boundary diffusion to occur, similar to electromigration.

As described above, in order to prevent electromigration and hillocks, it is considered effective to precipitate some element at grain boundaries to suppress grain boundary diffusion. There are some alloying elements that cause precipitation at grain boundaries, but elements with high solubility in the matrix cannot be used because they increase the electrical resistance of the Al alloy. Therefore, as a result of extensive research into alloying elements, the present inventors found that both Ti and B have a small solid solubility limit in Al, and that TiB2 particles, which are an intermetallic compound of Ti and B, have an effect of inhibiting grain boundary diffusion. The present invention was based on this finding.

[Configuration of the invention] That is, the present invention provides the following: (1) Ti 0.002-0.5wt%, BO,0
Aluminum alloy for semiconductor wiring material consisting of 02 to 0.5 wt%, balance Δ1 and unavoidable impurities
and (2) T i O, OO2~
0,5 wt%, BO,002-0,5 wt%
, Si 0.5~l.

Provided is an Aluminum 11 alloy for semiconductor wiring material comprising 5 wt%, the remainder Al and unavoidable impurities.

[Effect of the invention] AI-Ti-B alloy and Al-S i-T of the present invention
i-B alloy prevents electromigration,
It is effective in preventing the formation of hillocks and is an extremely excellent material for semiconductor wiring.

[Detailed Description of the Invention] Here, if the amount of Ti and B added is 0.002wt%, it will be completely dissolved in Al or At-8i alloy and will not precipitate, and if it exceeds 0.5wt%. The amount of Ti O,00 added is undesirable as it increases the electrical resistance of the wiring.
2-0.5wt%.

BO, 002 to 0.5 wt%. More preferably, Si can be added to the Al-Ti-B alloy of the present invention to suppress mutual diffusion of the semiconductor S1 and Al. Si
If the amount added is less than 0.5%, the effect of preventing mutual diffusion of Si and Al in the Al-8i contact part is small;
If it exceeds 1.5 wt%, the electrical resistance of the wiring increases, which is undesirable, so the amount of Si added is set to 0.5 to 1.5 wt%.

Moreover, the Al-Ti-B alloy and Al-3i-Ti of the present invention
In addition to the -B alloy, Cu and Ni are said to be effective in preventing electromigration.

Co and Cr can also be added.

The second aluminum alloy for semiconductor wiring materials is usually high purity (99,999wt%) Al or high purity (99,999wt%) Al.
High purity (99,99wt%) purified by electron beam melting etc.
9wt%) Ti and high purity (99.95wt%) crystal B
can be melted and cast in the atmosphere, and then this cast material can be machined as it is to make a vacuum evaporation material or a target plate for sputtering. In the target plate thus produced, during the above-mentioned casting, a portion of Ti and B becomes TiB, and this TiB2 causes a nuclear effect.

Ti that remains in the cast material while refining the cast structure,
Due to the large amount of B, the uniformity of the thin film produced by sputtering or vacuum evaporation is very good.Furthermore, in this thin film, the above-mentioned Ti and B become TiB2 and precipitate at the grain boundaries, preventing electromigration and hillock formation. It acts extremely effectively. In addition, instead of a cast material, it is also possible to process the material into a predetermined shape after casting and further heat-treat it to make a sputtering or vacuum evaporation material. In this case, when recrystallized by heat treatment, TiB precipitates and the crystals become finer due to the nucleation effect, improving the uniformity of the structure of the sputtering or vacuum evaporation material.

This can also improve the uniformity of the thin film.

Next, an example will be described.

[Example] High purity (99,999wt-%) Al or high purity Al-
8i alloy, high purity (99,999wt%) Ti purified by electron beam melting and high purity (99,9!
After adjusting the composition of Crystal B (5 wt%) to the composition shown in Tables 1 and 2, it was charged into a high-purity aluminum crucible and melted in a resistance heating furnace by increasing the molten metal humidity to approximately 1100°C in the air. . After melting, the temperature was lowered slightly to bring the temperature of the molten metal to about 700°C, and then cast into a predetermined mold. The cast material was machined as it was, cut and polished into a predetermined shape and used as a target plate for sputtering.

A sputtering fish film having a width of 6 microns and a length of 380 microns was formed on a silicon substrate using the above target plate. In order to investigate the characteristics of this thin film, a current was continuously applied at a temperature of 175° C. and a current density of 1×10'A/cm''.

Table 1 shows the average time to failure (average time to failure) at that time.

Table 1 also shows test results for pure Al, Al-Cu alloy, and A1-Cu-Si alloy as comparative examples.As is clear from Tables 1 and 2, conventional pure Al
, Al-Cu alloy and Al-Cu-31 alloy, the present invention's Δ], -T i -B alloy and Δl-3i
- The mean failure time of vapor-deposited wiring films made of Ti-B alloy under high temperature and continuous current flow has been significantly improved, and the Al-Cu-3
This is more than twice that of i-alloy. In this way, A of the present invention
l-Ti-B alloy and A l -S i -T i -
It can be seen that the B alloy is effective in preventing electromicration and hillock formation, and is an extremely excellent material as a semiconductor wiring material.

Margin below Table 1 Table 2

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a portion where an Al wiring film is deposited on a silicon substrate. 1: Silicon substrate 2: Al wiring film

Claims (1)

Scope of Claims: (1) An aluminum alloy for semiconductor wiring material comprising 0.002 to 0.5 wt% of Ti, 0.002 to 0.5 wt% of B, and the remainder Al and inevitable impurities. (2) Ti0.002-0.5wt%, B 0.002-0.5wt%, Si0.5-1.5wt%
, the balance being Al and unavoidable impurities, an aluminum alloy for semiconductor wiring material.