JPS60111451A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To increase capacity to improve voltage-withstanding and leak characteristics of a device by a method wherein a metal silicide layer is formed on a semiconductor substrate, the layer is subjected to oxidation, and electrodes are built in the layer of oxide. CONSTITUTION:A metal silicide layer, such as a TaSix layer 12, is formed on an Si substrate 11 with its surface crystal orientation of (100) by means of sputtering. The composition of the TaSix layer 12 is adjustable during the sputtering process. The TaSix layer 12 is then subjected to oxidation at 1,000 deg.C. A change indicated by 2TaSix+yO2=Ta2O5+zSiO2 takes place and an SiO2 layer 13 and a Ta2O5 layer 14 are formed on the substrate 11. A process follows wherein a polycrystalline Si layer is vapor-deposited, doped with Al or a P type impurity, on the Ta2O5 layer 14. A patterning is performed and an electrode 15 is built. In a device constructed as such, the quality is improved of the film along the interface of the substrate 11 and the device is provided with better leak and voltage-withstanding characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor device with an improved dielectric for a canopy and a method for manufacturing the same.

[Technical background of the invention and its problems]

As is well known, semiconductor devices such as dynamic RAM
The integration of dRAM (dRAM) has progressed to the point where 256 bits have now been realized, and this higher integration necessarily reduces the area of the capacitor.

Incidentally, the capacitor capacitance C8 is determined by the following formula, when the capacitance with the semiconductor substrate serving as the base layer is ignored.

In Equation (1), ε represents a dielectric constant, S represents a capacitance/mother area, and d represents a dielectric film thickness.

In the same equation, in order to increase the capacitance of the capacitor, the first
As a means of achieving this, it is possible to reduce the dielectric film thickness d. Regarding this, improvements in film formation have made it possible to make the film considerably thinner. For example, in a 256 RAM, the film thickness is S i O, and t = 200 to 250A. However, in the case of 5102, the dielectric constant is as low as 3.9, and in terms of film thickness, ~100 A is considered to be the limit from the viewpoint of breakdown voltage. Moreover, as a second means, Si3N4. It is conceivable to use a dielectric material with a high dielectric constant such as Ta, O, or the like. However, these dielectrics have not yet reached the level of practical use in terms of process and reliability. Recently, Ta has been formed by sputtering and 'ra
There have been several reports on the use of 2o as a dielectric material, but
It has insufficient characteristics in terms of withstand voltage and leakage characteristics. Furthermore, as a third means, it may be possible to increase the area of the canopy, but this is not suitable for high integration of elements.

[Purpose of the invention]

The present invention has been made in view of the above circumstances.
It is an object of the present invention to provide a semiconductor device which has improved breakdown voltage and leakage characteristics by increasing the capacitance of the capacitor, and a method for manufacturing the same.

[Summary of the invention]

The first invention of the present application has a structure in which an oxide layer obtained by oxidizing a metal silicide layer is formed on a semiconductor substrate, and an electrode is further formed on this oxide layer, thereby improving breakdown voltage and leakage characteristics. The main points of this plan are to:

The second invention of the present application is to form a metal silicide layer on a semiconductor substrate, oxidize the metal silicide layer to form an oxide layer, and then form an electrode on the oxide layer. , the same effect as the first invention of the present application can be obtained.

[Embodiments of the invention]

Hereinafter, the present invention will be explained with reference to the drawings.

First, a metal silicide layer, for example TaSix, can be prepared on a silicon substrate 11 with a surface crystal orientation (1oo). Subsequently, oxidation was performed at a high temperature of 1000°C. As a result, the Ta5iX layer 12 is 2TaSix + y0
2=Ta205+zSiQ□, and S on the substrate 11
An iO2 layer 13 and a Ta20a layer 14 were formed (
(Illustrated in FIG. 1(b)). Next, A is applied on the Ta, O, layer 14.
After depositing a polycrystalline silicon layer doped with I- or P-type impurities, the electrodes 15 were formed by turning the elbows (first
Figure (e) shown).

As shown in FIG. 1(e), the semiconductor device according to the present invention has the following features:
SiO2 layer 13, Ta2O, layer 1 on silicon substrate 11
4 are sequentially formed, and the layer stack 4 is formed on these 'ra, o, and layers 14.

According to the present invention, after forming the Ta5iX layer 12 on the substrate 11, the substrate 11 is oxidized at high temperature.
8102 layer 13,'ra,o on top.

Form each layer 14 and then 'ra2o. By forming the electrode 15 on the layer 14, a structure as shown in FIG. 1(e) is obtained. Therefore, the film quality at the interface of the substrate 11 becomes good, and leakage characteristics and breakdown voltage can be improved. This will be explained in detail below. 1 to (c), 'ra, o, layers 14, sio forming the dielectric
x layer 13 husband kF) film thickness jl+tl! , and assuming that the respective capacitances are C1 and C2, the total dielectric constant C becomes 3. In equation (2), the ratio of tIpt2 can be determined by the density, molecular weight, and reaction formula of each dielectric. be. Here, Ta shown in Table 1, 0. .

Based on the density to dielectric constant values of the 5io2 layer, the composition ratio of Ta5iz and the total dielectric constant of the two layers are as shown in FIG.

According to Table 1 and the same figure, when X=0, that is, when only Ta is deposited, the dielectric constant is 28, which coincides with 'ratoa, and fc x
= slope, the dielectric constant of SiO2 is equal to 3.9, and it can be confirmed that any value can be obtained between them. That is, by setting the dielectric constant to an arbitrary value, the capacitor capacity can be increased, and since the interface between the substrate 1 and the substrate 1 becomes the 5io2 layer 13, the withstand voltage and leakage characteristics can be improved.

In addition, in the above example, the oxidation treatment was performed at a high temperature (1000°C).
Although we have described the case where the
Oxidation may be carried out at low temperatures of 0 to 900°C. In this case, as shown in FIG. 3, a mixture layer 16 of 5in2 and TjLlo is formed on the silicon substrate 1. Note that the idea of the above embodiment can be applied to the capacity calculation. Also,
In the above embodiment, after the Ta5iX layer 12 is deposited on the substrate 11, oxidation treatment is performed to form 5102 layers on the substrate 11.
RA2O, layer 14 is formed in the double layer type 4, but the present invention is not limited to this. By performing oxidation treatment for a long time in the above temperature range, as shown in FIG.
A mixture layer 18 of 'ra,o' and 'ra,o' may be formed.

In such a case, the relationship shown in FIG. 2 can be maintained. In addition, FIG. S shows a characteristic diagram of Auger analysis when Ta5iX is subjected to oxidation treatment at 900° C. for 15 minutes. From the same figure, it can be confirmed that Ta is precipitated at the initial stage of oxidation, but 15
What oxidation treatment is used to completely oxidize the precipitated Ta and reduce Ta to 20. As a result, a mixed insulator of Ta, O, and SiO2 could be formed.

Further, in the above embodiment, Ta5i is used as the metal silicide layer.
Although the z layer is used, the present invention is not limited to this, and for example, TtSi may be used.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a semiconductor device and a method for manufacturing the same that can improve breakdown voltage and leakage characteristics.

[Brief explanation of drawings]

FIGS. 1(a) to (cl) are cross-sectional views showing the manufacturing method of a semiconductor device according to an embodiment of the present invention in order of process, and FIG. 2 shows the relationship between the composition ratio and dielectric constant of 'paSi according to the present invention. The characteristic diagram shown in Figure 3 is a cross-sectional view of the silicon substrate after low-temperature oxidation.
FIG. 4 is a cross-sectional view of a silicon substrate after oxidation at low temperature for a long time, and FIG. 5 is a characteristic diagram showing Auger analysis when T a S 1 z is oxidized. 11...Silicon substrate, 12...'l'as i
x layer (metal silicide layer), 13.17...SiO, layer, 14...Ta0 layer, 15...electrode, 16, 1
8-810. and 'l'a205 mixture layer. Applicant's agent Patent attorney Suzue TakehikotllllllJ Figure 2, 13'. 1J5WA 7゜shi=qT, rough An2

Claims (4)

[Claims] (1) A semiconductor device comprising a semiconductor substrate, an oxide layer formed on the substrate and obtained by oxidizing a metal silicide layer, and an electrode formed on the oxide layer. (2) The semiconductor device b according to claim 1, characterized in that a 'l'ag Sis layer is used as the metal silicide layer. (3) comprising the steps of forming a metal silicide layer on a semiconductor substrate, oxidizing this metal silicide layer to form an oxide layer, and forming an electrode on this oxide layer. A method for manufacturing a semiconductor device, characterized in that: (4) The method of manufacturing a semiconductor device according to claim 3, wherein the metal silicide layer is formed after forming a thin oxide film on the semiconductor substrate.