JPH046866A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a DRAM having a capacitor of a large capacity and sufficient insulation breakdown strength by forming a ferroelectric film on a high concentration diffused layer, and forming a silicon oxide or nitride film at least part between the ferroelectric film and the diffused layer. CONSTITUTION:An oxide film 102 of an element isolating insulating film is formed on a P-type Si substrate 101, an N-type diffused layer 103 is formed by ion implanting, an N-type diffused layer 104 to become a drain is simultaneously formed, and a gate electrode 105 is formed. Then, a ferroelectric film 106 is formed on the diffused layer. In this case, a uniform Si oxide film 110 is formed by lamp annealing in an atmosphere containing oxygen before the film 106 is formed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a structure of a memory using a ferroelectric material, and in particular, a dynamic RAM that stores signals by storing charge in a capacitor. .

C. Summary of the Invention] The present invention provides a memory structure using a ferroelectric film, in which the ferroelectric film is formed on a high concentration diffusion layer, and at least one layer between the ferroelectric film and the high concentration diffusion layer. Partly, Si oxide
Alternatively, by forming a Si nitride film, a memory in which a capacitor having a high dielectric constant and a high dielectric strength voltage is integrated can be obtained.

[Conventional technology]

In a conventional semiconductor memory DRAM, 5i02 was used as a capacitor insulating film on a heavily doped diffusion layer.

[Problem to be solved by the invention]

However, in recent years, miniaturization has progressed and efforts have been made to reduce the element area. As miniaturization progresses, the area on which a capacitor is formed also becomes smaller, making it difficult to secure the capacity necessary to store charge. Therefore, for example, in order to increase the area of the capacitor, trench-type capacitors,
Attempts are being made to increase the area of the capacitor by changing its structure, such as stacked capacitors in which the capacitor is integrated up to the top of the transistor, and by using materials with high dielectric constants such as SiN and TaO2. Attempts have been made to increase the capacity of

However, none of these methods has reached the point where sufficient capacity can be obtained. The present invention is intended to solve these problems, and its purpose is to create a capacitor with a large capacitance and sufficient dielectric strength by using a ferroelectric film with an order of magnitude higher relative dielectric constant. It is located in a place that provides semiconductor memory such as RAM.

[Means to solve the problem]

In the semiconductor device of the present invention, a ferroelectric film is formed on a high concentration diffusion layer, and a Si oxide or Si nitride film is formed at least in a portion between the ferroelectric film and the high concentration diffusion layer. It is characterized by

〔Example〕

FIG. 1 is a main sectional view of an embodiment of the semiconductor device of the present invention. The semiconductor device of the present invention will be described below with reference to FIG. For convenience of explanation, a Si substrate is used here.
An example using an N-channel transistor will be explained.

(101) is a P-type Si substrate, for example, 200hm,
A wafer with a resistivity of cm is used. (102) is an insulating film for element isolation, for example, the conventional technology LOCO5
An oxide film with a thickness of 600 OA is formed by the method. (103) is an N-type diffusion layer that becomes a source, and for example, phosphorus is heated to 80KeV.
It is formed by implanting 5E15 cm-2 ions.

(104) is an N-type diffusion layer that becomes a drain, and (10
3) Form at the same time. (105) is a gate electrode, for example, poly-Si doped with phosphorus is used. (10
6) is a Pb which is a ferroelectric film which is a component of the present invention.
TiO3, PZT (PbZr03, PbTiO3, P
It is LZT (La, PbZrO3, PbTi03), and is formed with a thickness of 100 OA by, for example, a sputtering method. (
Reference numeral 107) is made of poly-Si, for example, which becomes the electrode of the ferroelectric film, and is formed to a thickness of 1500 Å by the CVD method. (1
08) is an insulating film that separates the electrode (107) from (109), which is the wiring electrode to the drain.
A 5i02 film of 4000A is formed using the D method. and(
110) or Si oxide which is another component of the present invention
For example, a uniform Si oxide film of 15 A is formed by lamp annealing in an atmosphere containing oxygen before forming the ferroelectric film (106).

Now, if we consider the capacitance of a capacitor with the structure shown in Figure 1, the relative dielectric constant of the ferroelectric film is approximately 1000 if PZT is used as the ferroelectric film, so it is 1/C. = 1/C (S i 02) + 1/C (PZT), and when calculated using the film thickness mentioned above, it is 14 in terms of 5i02.
Capacitor A can be formed. This equivalent film thickness is (11
The thickness is almost the same as that of the Si oxide film in (0), but the thickness is (11
0), when only a 15A thick Si oxide film was directly used as the insulating film of the capacitor, the dielectric strength was only a few volts, and the device could not be constructed. On the other hand, by laminating a Si oxide film and a ferroelectric film as shown in Figure 1, a dielectric strength voltage of 20V can be obtained, which is sufficient as a dielectric strength voltage and has a very high capacity. The capacitance value per unit area or the large capacitor was obtained.

In the above explanation, the case where an oxidized S1 film is used as the insulating film on which the ferroelectric film is laminated has been explained, but it is also possible to use a Si nitride film or a laminated film of a Si oxide film and a Si nitride film. Needless to say.

〔Effect of the invention〕

As in the present invention, the Si oxide or Si nitride film is formed on the ferroelectric film or the high concentration diffusion layer, and at least in a portion between the ferroelectric film and the high concentration diffusion layer. This has the effect that a capacitor having a high dielectric strength voltage and a very large capacitance per unit area can be integrated.

[Brief explanation of drawings]

FIG. 1 is a main sectional view of the present invention. ・81 board ・Element isolation insulating film ・Source diffusion layer ・Drain diffusion layer ・Gate electrode ・Ferroelectric film ·electrode ・Interlayer insulation film ・Wiring electrode ・Capacitor insulation film Applicant: Seiko Epson Corporation

Claims (1)

[Claims] (1) In a semiconductor device in which a ferroelectric film is integrated on the same semiconductor substrate on which active elements are formed, the ferroelectric film is formed on a high concentration diffusion layer, and the ferroelectric film 1. A semiconductor device characterized in that an insulating film of either Si oxide or Si nitride film is formed at least in a portion between the layer and the high concentration diffusion layer.