JPH0236559A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To inhibit the reaction of a capacitor film to an electrode, which is caused by a heat treatment in a post-process subsequent to the formation of the electrode, to prevent an increase in a leakage current in the capacitor film and the deterioration of the dielectric strength of the capacitor film and to make possible the formation of a superior capacitor having a large capacitance by a method wherein a nitrogen- containing metal oxide film is held between a metal oxide film and the electrode consisting of polysilicon, a silicide or the like. CONSTITUTION:The structure of a capacitor part consists of a poly Si electrode 31 which is a first electrode, a Ta2O5 film 51 which is a capacitor insulating film and a dielectric layer, a nitrogen-containing tantalum oxide film 52 and a poly Si electrode 61 which is a second electrode. By putting the film 52 in between the film 51 and the electrode 61, the reaction of the film 51 to the electrode 61, which is caused by a heat treatment in a post-process subsequent to the formation of the electrode 61 (the second electrode), is prevented, the generation of a pinhole and a weak spot, which are generated in the capacitor film, is inhibited and an increase in a leakage current in the capacitor film, the deterioration of the dielectric strength of the capacitor film and a reduction in the reliability of the capacitor film can be inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to a structure of a capacitive part using a metal oxide film and a method of manufacturing the same.

[Conventional technology]

Conventionally, a capacitor part that uses a metal oxide film with a high dielectric constant as a capacitor insulating film has a lower electrode (first electrode) made of a silicon substrate or polysilicon, and a capacitor part that uses a metal oxide film such as Taxes or Hf 02. There are those with a structure consisting of an insulating film and an upper electrode (second electrode) such as polysilicon or silicide, and those with a structure where a camellia film is provided between the metal oxide film and the upper electrode.

As this barrier film, metal nitride such as titanium nitride or S
An insulating film such as Si3N4 is used.

[Problem to be solved by the invention]

In the conventional capacitive structure described above, when the upper electrode is provided directly on the metal oxide film, a reaction occurs between the metal oxide film and the upper electrode in the post-heat treatment process, resulting in a significant increase in leakage current from the capacitor insulating film. Kaa1 noru. Next, when providing a barrier film, 5if2 or Si3
When an insulating film such as N4 is used, it becomes a two-layer insulating film consisting of a metal oxide film and a barrier film, so there is a problem in that the capacitance value decreases when a barrier film is used. Furthermore, when a metal nitride such as titanium nitride is used as a barrier film, there is no problem of such a decrease in capacitance because the metal nitride is a conductor. However, since the metal nitride is formed by reactive sputtering, the groove capacitance On an uneven pattern such as a stack capacitor, the metal nitride has poor step coverage, and there are problems in that leakage current is likely to flow and defects such as pinholes are likely to occur.

[Means to solve the problem]

The capacitor structure of the present invention includes a first electrode, a dielectric layer including a metal oxide film, a metal oxide film containing nitrogen formed on the metal oxide film, and a second electrode. Manufacturing such a capacitor structure includes at least the steps of forming a first electrode, a step of forming a metal oxide film, a step of forming a metal oxide film containing nitrogen, and a step of forming a second electrode. Formed by a manufacturing method. Furthermore, in the step of forming a metal oxide film containing nitrogen, the metal oxide film is heat-treated by lamp annealing in an NH3 atmosphere, a N2 atmosphere, or a mixed atmosphere of NHz and N2.
It can effectively prevent leakage current while preventing pinholes in the insulating film.

〔Example〕

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

FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention. The structure of the capacitive part in this embodiment is that the polysilicon electrode 31 of the first electrode
, a Ta2es film 51 as a capacitive insulating film, a tantalum oxide 52 containing nitrogen, and a polysilicon electrode 61 as a second electrode.

A T a 20 s film 51 is made of tantalum oxide 52 containing nitrogen.
By placing it between the polysilicon electrode 61 and the polysilicon electrode 61, it is possible to prevent the reaction between the TEL 20s film 51 and the polysilicon electrode 61 due to post-process heat treatment after forming the polysilicon electrode 61 (second electrode), and to prevent deterioration of electrical characteristics. can be prevented. The concentration of nitrogen contained in tantalum oxide 52 is 1 in terms of the number of atoms.
It may be about 0 to 70%.

Regarding the capacitance structure of the Ta2es/polysilicon electrode (second electrode), after forming the second electrode, the capacitance structure was
Figure 2 shows the leakage current characteristics when heat treatment was performed for 1 hour at °C. When heat treatment is performed after forming the second electrode, the leakage current characteristics of this embodiment and the conventional example are almost the same, as shown by the broken line in FIG. 2. In the case of this embodiment, the leakage current does not increase due to the heat treatment, but in the conventional example, the leakage current increases significantly when the heat treatment is performed.

This occurs when the tantalum oxide 52 containing nitrogen 8 is between the polysilicon electrode 61 and the Ta20s51.

13S i+2Tazos-e4Tas iz+5s
This is because reactions such as those caused by Ioz are effectively prevented.

Thereby, it is possible to suppress the occurrence of pinholes and weak spots in the capacitive film, and to suppress an increase in leakage current of the capacitive film, deterioration in dielectric strength, and reduction in reliability.

Next, regarding the manufacturing method of the capacitor structure of the first embodiment, the third
This will be explained with reference to FIGS. (a) to (h).

First, polysilicon is formed on 5iO22 formed on a silicon substrate 1 by a 1000-10000 phase growth method (abbreviated as CVD) or the like (FIG. 3(a)). Next, the first electrode is patterned using a photoresist 41 (FIG. 3(b)).

(C)). Then, CVD is performed on the polysilicon electrode 3.

Alternatively, 50 to 500 Ta 20 s films 51 are formed by reactive sputtering or the like (FIG. 3(d)). Furthermore, Ta
The 205 film 51 is heat-treated in the range of 900 to 1150° C. in an N Hz atmosphere using Lambanie-V for several seconds to several hundreds of seconds to form tantalum oxide 52 containing nitrogen in about 30 to 100 layers from the surface. Figure 3(e)). Then, 2000 ml of polysilicon was applied on the tantalum oxide 52 containing nitrogen.
Form ~4000 people and use photoresist 42,
Buttering is performed to form a polysilicon electrode as a second electrode (FIG. 3(f) to (h)).

FIG. 4 is a schematic cross-sectional view of another embodiment of the present invention. The capacitance of this example is that the polysilicon electrode 31 of the first electrode,
Si, N4 film 53 and HfO2 film 54 of the capacitive insulating film,
It is composed of titanium oxide 56 containing nitrogen and a polysilicon electrode 61 as a second electrode.

In this example, the capacitive insulating film is made of Si3N4/HfO2.
By forming a layered film, the capacitance value becomes smaller than that of a single layer of HfO2 film, but a capacitance with less leakage current can be obtained. Further, as in the embodiments shown in FIGS. 1 to 3, by inserting nitrogen-containing titanium oxide 56 between the HfO2 film 54 and the polysilicon electrode 61 of the second electrode, post-processing after forming the second electrode is possible. It is possible to prevent deterioration of the electrical characteristics of the capacitive film due to

Note that the nitrogen concentration contained in the titanium oxide 56 is preferably about 10 to 70% in terms of the number of atoms, similar to the first embodiment.

Next, the method for manufacturing the capacitor structure of this example will be explained in the fifth section.
This will be explained with reference to FIGS. (a) to (j).

First, polysilicon 3 is formed on SiO□2 formed on silicon substrate 1 by CVD or the like for 1,000 to 10,000 times (FIG. 5(a)). Next, photo resist 41
The first electrode is patterned using
), (c)). Then, 20 to 10% of 5isN453 is applied on the polysilicon electrode 31 by CVD, direct thermal nitridation, etc.
Then, 50 to 500 people form the HfO2 film 54 by CVD, reactive sputtering, etc. (FIG. 5(d)). (Figure 5(e)).

Next, 3 layers of TiO2 film 55 are formed by CVD, reactive sputtering, etc.
0 to 100 people (Fig. 5 (r)), heat-treated at 900 to 1150°C in a lamp annealing in an NH3 atmosphere.
The TiO2 film 55 is converted into a titanium oxide 56 containing nitrogen by carrying out the process for several seconds to several hundred seconds (FIG. 5(g)). next,
2,000 to 4,000 polysilicon layers are formed on the nitrogen-containing titanium oxide 56 by CvD or the like, and a second electrode is patterned using a photoresist 42 to form a polysilicon electrode 61 (see FIG. 5). h) ~ (j))
.

In each embodiment of the present invention, TazOs and TiO2 have been described as metal oxide films, but Y203. Nb
The present invention can also be applied to other metal oxide films such as 20S, and films containing other metals in the metal oxide film. In addition, although tantalum oxide containing nitrogen and titanium oxide containing nitrogen have been described as metal oxide films containing nitrogen, other metal oxide films containing nitrogen may also be used, and combinations of metal oxide films and metal oxides containing nitrogen may also be used. is free.

Furthermore, although the embodiment shown in FIGS. 4 and 5 has a two-layer film structure in which HfO2 is formed on Si3N4, the present invention can also be applied to a case where a metal oxide film is formed on another insulating film such as Sigh.

Further, in the embodiment, the case where the first electrode is made of polysilicon has been explained, but the present invention is also applicable to the case where the first electrode is made of a silicon substrate, silicide, high melting point metal, etc., and the second electrode is made of silicide, polycide, etc. However, the effect remains the same.

Further, heat treatment can be freely performed after forming the metal oxide film. Furthermore, the method for forming the metal oxide film containing nitrogen is arbitrary, such as forming the metal by sputtering in a nitrogen atmosphere containing oxygen, or thermally nitriding the metal oxide film using a diffusion furnace.

〔Effect of the invention〕

As explained above, in the present invention, by sandwiching a metal oxide film containing nitrogen between a metal oxide film and an electrode made of polysilicon, silicide, etc., a capacitive film and an electrode can be formed by heat treatment in a post-process after electrode formation. This has the effect of suppressing the reaction with the capacitor film, preventing an increase in leakage current of the capacitor film and deteriorating the dielectric breakdown voltage, and making it possible to obtain an excellent capacitance with a large capacitance value.

Further, by forming the metal oxide film containing nitrogen by lamp annealing, the semiconductor device of the present invention can be manufactured with good mass productivity.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention, and FIG. 2 is a graph showing leakage current characteristics of an embodiment of the present invention and a prior art example, where the vertical axis is the current density of the leakage current, and the horizontal axis is the current density of the leakage current. is the electric field strength applied to the capacitive membrane. Figure 3 (a) to (h)
) is a sectional view illustrating a manufacturing method according to an embodiment of the present invention in the order of steps. FIG. 4 is a schematic cross-sectional view of another embodiment of the present invention, and FIGS. 5(a) to (j) are cross-sectional views illustrating a manufacturing method of another embodiment of the present invention in the order of steps. 1... Silicon substrate, 2... SiO
z, 3... Polysilicon, 31... Polysilicon electrode for the second electrode, 41.42...
Photoresist, 51...Ta205.52.
...Tantalum oxide containing nitrogen, 53...
Si3N4.54...HfO2,55...
...TiO□, 56...Titanium oxide containing nitrogen, 6...Polysilicon, 61...2nd
Polysilicon electrode for electrode. Agent Patent Attorney Uchihara Shinden Shog Degree ζM Gansha 2) $ 2 Chika (C) CD) Leather 3 Chika (Z'J (d + $5 Fucha)

Claims (1)

[Claims] 1. A first electrode of a semiconductor substrate or a conductive film, a dielectric layer containing a metal oxide, a metal oxide film containing nitrogen covering the metal oxide film, and a metal oxide film containing nitrogen. 1. A semiconductor device comprising: a capacitor portion including a second electrode formed thereon by a conductive layer of silicide, polycide, or polycrystalline silicon. 2. A semiconductor device that forms a capacitive part by at least the steps of forming a first electrode, forming a metal oxide film, forming a metal oxide film containing nitrogen, and forming a second electrode. In the manufacturing method, the step of forming the metal oxide film containing nitrogen includes a step of heat-treating the metal oxide film by lamp annealing in an NH_3 atmosphere, an N_2 atmosphere, or a mixed atmosphere of NH_3 and N_2. A method for manufacturing a semiconductor device, characterized in that: