JPS61248471A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a multi-layer wiring with an extremely high wiring density and a high reliability by a method wherein a conductive substance composed of a column shape single crystal is employed as a layer connector which is so provided as to penetrate through a layer insulation film. CONSTITUTION:An N-type impurity doped layer 12 and a surface protection film 13 are formed on a silicon wafer 11. Gold is implanted by a converged ion-beam method into the part of the impurity doped layer 12 where the layer connection is necessary. The wafer is transferred into a cylindrical reaction furnace and placed inside the reaction furnace where the temperature is kept at 375 deg.C and a mixture gas of SiCl4/H2 system is introduced and reaction is induced by a photoexcitation and supersaturated silicon is deposited from liquid alloy drop and a column shape silicon single crystal 14 with a diameter of about 1mum is made to grow by VLS. Then a layer insulation film 15 is formed for the thickness of 2mum and the whole surface of the layer insulation film 15 is etched to expose the top of the column shape single crystal 14 and aluminum or aluminum alloy is evaporated to form an upper wiring layer 16. With this constitution, as the wiring layer is evaporated on the insulation film surface without difference in level, a film with excellent uniformity can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a semiconductor device, and more particularly, to a semiconductor device having fine multilayer wiring having high reliability.

[Background of the invention]

Generally, in a semiconductor device, an impurity-doped layer, a conductive layer such as polycrystalline silicon, metal silicide, or an aluminum alloy is arranged on the surface of a semiconductor substrate together with an insulating film in a multilayer structure. In order to electrically connect these conductive layers to each other, a hole is formed in a part of the insulating film located between the conductive layers (such an opening in the insulating film is called a contact hole). This contact hole is filled with a conductive material to establish electrical connection between the upper and lower conductive layers. By the way, the insulating film usually has a thickness of about 160 to 2.5 μm, so when a contact hole is formed from the upper part of the insulating film to the lower conductive layer, the thickness is about 1.0 to 2.5 μm.
A step difference of up to 2.5 μm occurs. For this reason, if, for example, an aluminum wiring layer is formed on the insulating film after contact holes are opened, the wiring layer becomes extremely thin at the stepped portions, and depending on the shape of the contact hole, the wiring may be completely disconnected. There is also. As a result, not only the yield is significantly lowered, but also the life of the wiring is shortened in the portion where the wiring layer is thinner, and the reliability is also significantly lowered.

In order to solve this problem, a method has been proposed in which a part or all of the contact hole is filled with polycrystalline silicon or the like, as described in, for example, Japanese Patent Laid-Open No. 59-103355. However, when polycrystalline silicon having grain boundaries is used as the interlayer connector, a problem arises in that the conductivity of the connector becomes extremely low.

Furthermore, as the contact holes in multilayer wiring become further miniaturized, it may become extremely difficult to make glabella connections using such fine contact holes after forming the contact holes using conventional techniques. is expected.

Furthermore, a method of forming a columnar interlayer connection body made of polycrystalline aluminum alloy or the like by a lift-off method or the like has been proposed, for example, as described in Japanese Patent Application Laid-Open No. 58-225650. However, even if this method is used, as the interlayer connections become finer, disconnections will occur due to the grain boundaries that exist across the polycrystalline connections, making it difficult to create highly reliable fine connection pillars. was difficult to form.

[Purpose of the invention]

The purpose of the present invention is to solve the problems of the above-mentioned prior art,
An object of the present invention is to provide a semiconductor device having extremely high density and highly reliable multilayer wiring.

[Summary of the invention]

In order to achieve the above object, the present invention uses a conductor made of columnar single crystal as an interlayer connector provided through an interlayer insulating film. That is, before forming the glabellar insulating film, for example, VLS (Vapor-Liquid
-5olid) A columnar single crystal is formed on a semiconductor substrate or a wiring substrate by a growth method. This VLS growth is described in the Journal of Electrochemical
Society (J, Electrocham, Soc,
) 113.1300 (1966), “Controlled Vapor-Liquid-Solid Growth of Silicon Crystals” (Con
Trolled Vapor-Liquid-3oli
d Growth of Silicon Crysta
It is described in a paper entitled ls). According to this method, a single interlayer insulating film is formed after growing a columnar single crystal of a conductive material having a desired height. After that, etching is performed using, for example, a bias sputtering method to expose the tops of the columnar single crystals, and a second wiring layer is formed thereon, thereby forming an interlayer insulator made of the columnar single crystals of a conductive material. , multilayer wiring is formed.

At this time, if a film made of a material with flatness is used as the insulating film, and if the top of the columnar single crystal is exposed by bias sputtering or the like, the flatness and the upper wiring layer can be improved. The electrical connections are all very good.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to 6 Examples. Embodiment 1 FIGS. 1(a) to 1(d) are process diagrams showing one embodiment of the present invention.

As shown in FIG. 1(a), an N-type impurity doped layer 12 and a surface protection film 13 were formed on a silicon wafer 11 (plane orientation (111), P type) by a diffusion method or an ion implantation method. Gold was implanted into the impurity-doped layer 12 at positions where interlayer connections were required by a focused ion beam method.

By adjusting the diameter or intensity of this ion beam, the size of the gold-silicon alloy region can be adjusted from 0.5 to 1
It is possible to control within a range of 0 μm.

When the wafer is transferred to a cylinder-type reactor and heated to the eutectic temperature of 370°C or higher for gold-silicon alloy (31at%Si), droplets of gold-silicon eutectic alloy are formed at the positions where gold is injected. Ru. The reactor was placed in a reactor maintained at 375°C, a mixed gas of S x CQ 4 / Hx was introduced, and a reaction was carried out using a photoexcitation method to precipitate supersaturated silicon from the alloy droplets, forming a columnar shape with a diameter of approximately 1 μm. A silicon single crystal 14 was grown by vLS (FIG. 1(b)).

In this embodiment, the columnar single crystal body 14 has a height of 1.5 μm.
grew up to. The growth direction of the columnar single crystal 4 is <111>, and the columnar faces are 6 (211) faces,
It was confirmed by X-ray diffraction that (110) was composed of 6 planes, a total of 12 planes. This columnar single crystal body 14
The direct diameter of the gold-silicon alloy region can be controlled within a range of 0.5 to 10 μm by adjusting the size of the gold-silicon alloy region. The columnar single crystal body 14 was doped with phosphorus or boron to make it a conductor. As a result, the conductivity of the interlayer connector could be improved approximately three times as compared to the conventional method using polycrystalline silicon as the interlayer connector of the contact hole.

Next, as shown in FIG. 1(c), an interlayer insulating film 15 having a flattening effect was formed to a thickness of 2 μm.

In this embodiment, as the glabellar insulating film 15, a thread using a SiO2 film formed by bias sputtering, a 5in2 film formed by ordinary chemical vapor deposition, Si, N4 film, etc., which is planarized by sputter etching, are also used. be able to. The entire surface of the interlayer insulating film 15 was etched to expose the tops of the columnar single crystals 14. Subsequently, aluminum or an aluminum alloy was deposited as the upper wiring layer 16. In this way, since the vapor is deposited on the surface of the insulating film with no steps, it is possible to form a film with good uniformity.

Embodiment 2 FIG. 2 is a cross-sectional view showing a connection between the eyebrows of wiring as another embodiment of the present invention. The wiring layer 23 on which the layer 23 is formed is made of aluminum, aluminum alloy, etc. with a thickness of about 0.5 to 1.2 μm, but it is preferable to form it into a single crystal in advance.In this example, the plane orientation ( 111) was used.This wiring layer 23
After wiring patterning was performed by photoetching, the entire surface was covered with a surface protective film 24. After locally removing the oxide film covering the positions requiring interlayer connections on the wiring layer 23, germanium was implanted by the focused ion beam method in the same manner as in Example 1. When the above substrate is heated in a cylindrical reactor to the eutectic temperature of aluminum-germanium alloy (30,3 at% Ge) of 424°C or higher, aluminum-germanium eutectic alloy droplets are formed at the positions where germanium is injected. . Therefore, triisobutylaluminum gas was introduced into the reactor maintained at 430° C., supersaturated aluminum was precipitated from the alloy droplets, and columnar aluminum single crystals 25 with a diameter of about 1 μm were grown by VLS. The diameter of the columnar single crystal body 25 can be controlled within the range of 0.5 to 10 μm.

Next, in the same manner as in Example 1, an interlayer insulating film 26 having a flattening effect was formed, and then the entire surface of the acid film was etched to expose the tops of the columnar single crystal bodies 25. Subsequently, aluminum or an aluminum alloy was deposited as the upper wiring layer 27 to form a two-layer wiring.

In this example, since aluminum single crystal was used as the interlayer connector, both conductivity and reliability were significantly improved compared to conventional wiring.

Furthermore, since the connecting body is made of a single crystal, it is possible to completely prevent disconnection at grain boundaries, which is often a problem in conventional polycrystalline connecting bodies. This effect is
In particular, when the direct diameter of the connecting body is reduced to about 1 μm, the g
3 to 3 compared to using conventional polycrystalline connectors.
It was found that the lifespan was S times longer.

In the above embodiment, gold and germanium were used as the metals to be doped to create the eutectic in the VLS method, but other materials may also be used. Also,
The method for producing columnar single crystals is not VLS@'11, but selective growth in contact hole areas may be used, or after forming a single crystal film on the entire surface, unnecessary parts are selectively removed by dry etching. Good too. In the above example, Au and Go are used as the implanted metals to make the eutectic.
Although an example using Sn was shown, there are also other examples using Sn.

Even if Si, Be, etc. are used, a low melting point eutectic is formed and can be used in the present invention.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to effectively eliminate various obstacles that occur due to the step difference in the contact hole portion of the conventional device. Furthermore, since the interlayer connector is made of single crystal, the conductivity can be improved by about three times compared to the case of polycrystalline silicon.

Furthermore, when a conductive material such as aluminum single crystal is used as an interlayer connector, the conductivity of the interlayer connector can be further improved, and at the same time, it is possible to further improve the conductivity of the interlayer connector. Disconnection at grain boundaries is also prevented. On the other hand, according to the present invention, since there is no need to specifically form contact holes, it is possible to miniaturize the semiconductor device by reducing the dimensions of the columnar single crystal as the interlayer connector, thereby improving the degree of integration and reliability. can be significantly improved.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are a process diagram and a sectional view showing different embodiments of the present invention, respectively. 11.21... Semiconductor substrate, 12... N-type diffusion layer (
first conductive layer), 13.24... surface protective film, 14.
...Columnar silicon single crystal (interlayer connection), 15°26
...Interlayer insulating film, 16.27... Upper wiring layer (second
conductive layer), 22... oxide film, 23... lower wiring layer (first conductive layer), 25... columnar aluminum single crystal ■
1 figure

Claims (1)

[Claims] 1. At least a first conductive layer having a desired shape and a second conductive layer formed on the first conductive layer via an insulating film, the first and second conductive layers having a columnar shape. A semiconductor device characterized in that the semiconductor devices are electrically connected to each other by a single crystal conductor.