JPS594014A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To avoid the increase of contact resistance by removing a natural oxide film formed onto a diffusion layer of the semiconductor device, attaching pure Al wiring to the natural oxide film and coating the upper section of the Al wiring with a wiring metallic layer, which contains Si and consists of Al, when metallic wiring is attached onto the diffusion layer. CONSTITUTION:An n<+> type region 24 is diffused and formed to a p type Si substrate 21, the region 24 is coated with a PSG film 22 with an opening corresponding to the region 24, and the region 24 exposed in the opening is coated with an amorphous Si layer 25. The pure Al layer 23 is sputtered to the whole surface at a temperature of 300-400 deg.C, and spikes 26 are grown in the region 24 through a reaction with the amorphous layer 25. The spikes 26 penetrate the Si layer 25 and intrude into the region 24 at that time, but they need not intrude into the substrate 21. The whole surface is coated with the Al layer 27 containing 1-2% Si, and the metallic wiring in which contact resistance does not increase is obtained.

Description

Detailed Description of the Invention (1) Technical Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for preventing an increase in contact resistance at a contact portion between a diffusion layer and a wiring metal. .

(2) Background of the Technology In forming a contact between a diffusion layer formed on a semiconductor substrate, such as a silicon substrate, and a metal wiring (for example, aluminum) (1), it is important to keep the contact resistance low. The diffusion layer is formed by implanting impurities into a standard silicon substrate and then performing heat treatment diffusion.
A natural oxide film (natural oxide) with a maximum thickness of about 200 nm is generally formed on the surface of this diffusion layer, and since this oxide film becomes a high resistance layer when making electrode contact, it is conventionally removed by etching. There is.

However, radio frequency (RF) etching using argon (Ar) plasma is used, which is a simple process, but as a result of this process, the surface of the diffusion layer becomes amorphous (non-crystalline) and a high resistance layer is formed. It is confirmed that it is being tolerated.

(3) Prior art and problems Although this amorphous layer has a lower resistance than the above-mentioned natural oxide film, it has been confirmed that its influence on the operating characteristics of semiconductor devices cannot be ignored, and some countermeasures are desired. There is.

Figure 1 is a cross-sectional view of the main part of a semiconductor device (2) for explaining a method of forming a contact between a diffusion layer and a wiring metal in the prior art. After forming a phosphorus silicate glass (PSG) film 2 on a P-type silicon semiconductor substrate 1, a window is opened in the contact area, and then R is applied using argon plasma.
Contact pretreatment is performed using F etching to remove the natural oxide film (not shown) on the surface of the diffusion layer (FIG. 4(a)).

At this time, it was confirmed that the crystallinity of the surface of the diffusion layer 3 was disturbed and it became amorphous. Although this amorphous part (shown as sandy area 4 in the figure (BL)) has the disadvantage of increasing the contact resistance, it has a lower resistance compared to the natural oxide film, and by removing this amorphous part, the contact resistance increases. Since the technology to measure resistance has not yet been developed, the same figure (C1
As shown in the figure, a method is used in which contact is made by directly attaching an aluminum wiring 5 containing 1 to 2% silicon (Si).The i wiring 5 is made to have a thickness of 1 μm by spattering or vapor deposition. The silicon attached to and contained in the aluminum wiring 5 is caused by the suction of silicon atoms from the substrate 1 into the aluminum wiring 5 (3).It has the purpose of preventing the bonding of the diffusion layer from being destroyed due to the alloying reaction during filtration. .

As mentioned above, in the prior art, as a result of pre-treatment during contact formation, the expansion is 18! The problem of high contact resistance due to the formation of amorphous portions on the layer surface remains unsolved.

(4) Purpose of the Invention In view of the above-mentioned conventional problems, an object of the present invention is to provide a method for forming a contact between a metal wiring and a diffusion layer, which can prevent an increase in contact resistance.

(5) Structure of the invention and this object is that according to the method of the invention, after the pretreatment, a pure aluminum layer of a suitably selected thickness is applied to the wiring area under a suitably selected pretreatment temperature. The reaction between the aluminum and the silicon substrate causes the growth of aluminum needle-like projections (called spikes) in the diffusion layer that penetrate the amorphous layer but do not break through the diffusion layer. To provide a method for manufacturing a semiconductor device, characterized in that a silicon-containing i-wiring metal is formed on a pure i-layer, and these spikes (4) are used to prevent an increase in contact resistance between a diffusion layer and a wiring metal. The pretreatment temperature and pure single layer thickness achieved by ζ are such that the Al spikes described above extend through the amorphous layer and into the diffusion layer, but only when they penetrate through the diffusion layer and reach the bulk of the substrate. Make sure that there are no problems.

(6) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a cross-sectional view of the main part of a semiconductor device for explaining the present invention in detail. Referring to the figure, first, as in the prior art, pretreatment by RF etching is performed to form an amorphous layer on the surface of the diffusion layer. (Fig. 1 ta+, (b)
)I do.

Next, as shown in FIG. 2(a), pure aluminum J
When -23 is formed to a thickness of less than 1,000 by spackling at a temperature of 300° C. to 400° C., spikes 26 grow in the diffusion layer 24 due to reaction with the amorphous layer 25. In the figure, 21 is, for example, a 1) type silicon substrate, 22 is a PSG film, and 25 is an amorphous (
5) Indicates the layer.

Incidentally, the spikes 26 penetrate through the amorphous layer 25 from the surface of the substrate 21 as shown in the figure, but the spikes 26 pass through the amorphous layer 25 from the surface of the substrate 21.
It is formed so that it does not pass through and reach the bulk of the substrate 21. The formation of such spikes can be controlled by the thickness of the pure aluminum layer 23 and the processing temperature. The specific numbers mentioned above are just one example. However, the principle of the invention is not limited to this value; it can be selected experimentally in each case.

Note that the depth of the diffusion layer is 3000 to 600 in the above example.
Formed to a depth of 0 people.

Next, an aluminum layer 27 containing 1 to 2% silicon is deposited to a thickness of 1 μm to form a contact between the wiring metal and the diffusion layer (Figure (b)). After this, PS is applied in the usual manner.
G cover film, electrode pan F, etc. are formed to complete the semiconductor device.

(7) Effects of the Invention As explained in detail above, according to the method of the present invention, the spikes formed by the reaction between the amorphous layer and pure aluminum (6) improve the contact between the metal wiring and the diffusion layer. Therefore, it is possible to prevent an increase in contact resistance, which has been a problem in the past, and is highly effective in improving semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part of a semiconductor device for explaining a conventional method for forming a contact between a wiring metal and a diffusion layer, and FIG. It is a diagram. 1.21-・Semiconductor substrate, 2.22-・PSG film, 3
．． 24-Diffusion layer, 4.2-Amorphous layer, 5.27
- Silicon-containing aluminum wiring layer, 26- Spikes (7) Fig. 1 □ (b) □ □ (C) Fig. 2 □ -

Claims (1)

[Claims] A method for forming a contact portion between a metal wiring and a diffusion layer in a semiconductor device includes a step of attaching pure aluminum to the wiring region after performing a pretreatment step of removing the natural oxide film on the surface of the diffusion layer, and then a step of attaching pure aluminum to the wiring region. 1. A method of manufacturing a semiconductor device, comprising the step of depositing and forming a wiring metal layer.