JP3111416B2 - Semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory using a ferroelectric, and more particularly to a structure of an electrically rewritable nonvolatile memory.

[Summary of the Invention]

The present invention relates to a structure of a memory using a ferroelectric film, in which a capacitor is integrated on a semiconductor substrate, between the active element such as a transistor formed on the semiconductor substrate and the capacitor made of a ferroelectric. By forming an insulating film made of SiN, a memory having excellent transistor characteristics and excellent characteristics such as the relative dielectric constant of a ferroelectric capacitor is obtained.

[Conventional technology]

As a conventional semiconductor non-volatile memory, an MIS transistor is generally used, which uses a phenomenon in which a surface potential of a silicon substrate is modulated by injecting charges from a silicon substrate into a trap or a floating gate in an insulated gate. EPROM (ultraviolet erasing nonvolatile memory) and EEPROM (electrically rewritable nonvolatile memory)
It has been put to practical use.

[Problems to be solved by the invention]

However, these non-volatile memories have drawbacks such as a high information rewriting voltage of about 20 V or an extremely long rewriting time (for example, several tens of msec for EEPROM). Further, the number of times of rewriting of information is about 10 ⁵ times, very small, is problematic when used repeatedly.

For a nonvolatile memory using a ferroelectric material whose polarization can be electrically inverted, the write time and the read time are almost the same in principle, and the polarization is maintained even when the power is turned off. There is a possibility that it will be an effective nonvolatile memory. For a nonvolatile memory using such a ferroelectric, for example, as in US Pat. No. 4,149,302, a structure in which a ferroelectric capacitor is integrated on a silicon substrate, or as in US Pat. Proposals have been made for a nonvolatile memory in which a ferroelectric film is disposed in a portion. Recently, MOs as shown in Fig. 3
Non-volatile memory stacked on S-type semiconductor device is IED
M'87 pp. 850-851. In FIG.
301 is a P-type Si substrate, 302 is a LOCOS oxide film for element isolation, 303 is an N-type diffusion layer serving as a source, and 304 is an N-type diffusion layer serving as a drain. 305 is a gate electrode, 3
06 is an interlayer insulating film. 308 is a gate insulating film. 309
Is a ferroelectric film, which is sandwiched between the electrodes 310 and 311 to constitute a capacitor. 307 is a second interlayer insulating film;
Reference numeral 12 denotes Al serving as a wiring electrode. Now, in the ferroelectric memory having such a structure, it is necessary to anneal in an atmosphere containing oxygen in order to improve the characteristics of the ferroelectric.
When such oxygen annealing is performed, characteristics such as threshold voltage of a transistor fluctuate. Therefore, the present invention solves such a problem, and an object thereof is a ferroelectric memory in which the characteristics of a transistor and the like do not change even when oxygen annealing is performed to improve the characteristics of a ferroelectric. In particular, it is to provide a nonvolatile memory.

[Means for solving the problem]

The semiconductor device of the present invention is a semiconductor device in which a capacitor having a ferroelectric film is formed on a semiconductor substrate on which an active element is formed, wherein an insulating film whose main component is SiN is lower than the capacitor. In addition, the insulating film is formed on the entire surface of the active element forming region in a layer above the active element, and the insulating film is in a non-contact state with the semiconductor substrate between the insulating film and the semiconductor substrate. And an interlayer insulating film for separating the insulating film from the semiconductor substrate.

 Further, the SiN contains oxygen.

〔Example〕

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

101 is a P-type Si substrate, for example, using a wafer having a specific resistance of 200 hm · cm. Reference numeral 102 denotes an insulating film for element isolation. For example, an oxide film of 6000 A is formed by a conventional LOCOS method. An N-type diffusion layer 103 serving as a source is formed by, for example, implanting phosphorus at 80 KeV5E15 cm-2. Reference numeral 104 denotes an N-type diffusion layer serving as a drain, which is formed by ion implantation at the same time as 103. Reference numeral 105 denotes a gate electrode, which uses, for example, poly-Si doped with phosphorus. 108 is a gate electrode, for example, by a thermal oxidation method, an SiO ₂ film 25
0A is formed. 109 is a ferroelectric film of PbTiO ₃ , PZT (PbZrO
₃ , PbTiO ₃ , PLZT (La, PbZrO ₃ , PbTiO ₃ ), which is formed by, for example, a sputtering method. 111 is one of the electrodes of the ferroelectric film (hereinafter referred to as the lower electrode),
For example, Pt, Al, MoSi, WSi or the like is formed by, for example, a sputtering method. Reference numeral 110 denotes another electrode (hereinafter, referred to as an upper electrode) of the ferroelectric film electrodes.
l, MoSi, WSi, etc., formed by, for example, a sputtering method.
106 and 107 are interlayer insulating films.
A 3000 A film is formed on each of the SiO ₂ films. Reference numeral 113 denotes an insulating film mainly containing SiN according to the present invention. In the case of FIG. 1, the insulating film is formed between the lower electrode 111 and the interlayer insulating film 106 by a vapor phase growth method. Reference numeral 112 denotes a wiring electrode connecting the source diffusion layer 103 and the upper electrode 110, and is formed of, for example, Al. The 112 wiring electrodes are other wirings, for example, M
It may be used for connection between OS transistors.

The operation of the present invention is as follows. By adopting the structure as shown in FIG. 1, even if the ferroelectric capacitor is formed and then annealed in an atmosphere containing oxygen, oxygen remains at 113 SiN.
And the MOS transistor below the SiN was not affected. For example, the threshold voltage of the MOS transistor obtained a value that did not change from that before annealing.

FIG. 2 is a main sectional view of another embodiment of the semiconductor device of the present invention.

The feature of the embodiment shown in FIG. 2 in comparison with the embodiment shown in FIG. 1 is that an insulating film 201 mainly composed of SiO ₂ is further provided between the interlayer insulating film 107 and the SiN film 113. It is in the point which formed.

In FIG. 1, since the lower electrode of 111 was in direct contact with the SiN of 113, a problem such as peeling occurred due to the stress of SiN depending on the annealing conditions. By sandwiching SiO ₂ between the lower electrode and SiN as shown in FIG. ₂ , the effect of the present invention, that is, even if annealing is performed in an atmosphere containing oxygen, MO
The problems such as the characteristics of the S-transistor not changing and the peeling were solved.

〔The invention's effect〕

As in the present invention, a capacitor made of a ferroelectric film is
In an integrated semiconductor device, by forming an insulating film composed mainly of SiN between an active element such as a transistor and a capacitor composed of a ferroelectric, to improve the characteristics of the ferroelectric film. There is an effect that a semiconductor device such as a transistor whose characteristics do not change even if oxygen annealing is performed can be obtained.

[Brief description of the drawings]

FIG. 1 is a main cross-sectional view of one embodiment of the semiconductor device of the present invention, and FIG. 2 is a main cross-sectional view of another embodiment of the semiconductor device of the present invention. FIG. 3 is a main sectional view of a conventional semiconductor device. 101,301 ... Si substrate 102,302 ... Element isolation insulating film 103,303 ... Source diffusion layer 104,304 ... Drain diffusion layer 105,305 ... Gate electrode 106,107,306,307 ... Interlayer insulation film 108,308 ... Gate electrode 109,309 ... Ferroelectric film 110,310 ... Upper electrode 111,311… Lower electrode 112,312… Wiring electrode 113… SiN film 201… SiO ₂ film

Claims (2)

(57) [Claims] A capacitor having a ferroelectric film is a semiconductor device formed on a semiconductor substrate on which an active element is formed, wherein a main component is formed below the capacitor and above the active element. Comprises an insulating film made of SiN, the insulating film is formed on the entire surface of the active element forming region except for an electrical junction between the semiconductor substrate on which the active element is formed and the layer above the insulating film; Between the film and the semiconductor substrate, an interlayer insulating film that separates the insulating film and the semiconductor substrate so that the insulating film is in a non-contact state with the semiconductor substrate; It is configured such that oxygen is prevented from reaching the active element by oxidation annealing for the purpose of improving the characteristics of the capacitor, so that the characteristic of the active element does not change due to this. That the semiconductor device. 2. The semiconductor device according to claim 1, wherein said insulating film contains oxygen.