JP3270020B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

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

[0003]

2. Description of the Related Art Conventional semiconductor nonvolatile memories include:
2. Description of the Related Art A MIS transistor using a phenomenon in which the surface potential of a silicon substrate is modulated by injecting electric charge from a silicon substrate into a trap or a floating gate in an insulated gate is generally used. Memory) and EEPROM (electrically rewritable nonvolatile memory).

[0004]

However, in these nonvolatile memories, the information rewriting voltage is usually as high as about 20 V, and the rewriting time is very long (for example, EEP).
It has disadvantages such as tens of mSEC in the case of ROM. In addition, the number of times of rewriting of information is about 10 ⁵ times, which is very small, and there are many problems when repeatedly used.

In a nonvolatile memory using a ferroelectric substance whose polarization can be electrically inverted, the writing time and the reading time are almost the same in principle, and the polarization is maintained even when the power is turned off. Has the potential to become an ideal non-volatile memory. For a nonvolatile memory using such a ferroelectric, for example, a structure in which a capacitor made of a ferroelectric is integrated on a silicon substrate as in U.S. Pat.
Non-volatile memories in which a ferroelectric film is disposed at the gate of an S-type transistor have been proposed. Further, recently, in FIG. 3, a non-volatile memory having a structure stacked on a MOS type semiconductor device is shown in FIG.
851. In FIG. 3, 301 is P
302 is a LOCOS oxide film for element isolation; 303 is an N-type diffusion layer serving as a source;
Is an N-type diffusion layer serving as a drain. 305 is a gate electrode, and 306 is an interlayer insulating film. 308 is a gate insulating film. 309 is a ferroelectric film, and the electrode 310
And 311 constitute a capacitor. 3
Reference numeral 07 denotes a second interlayer insulating film, and reference numeral 312 denotes Al serving as a wiring electrode. Now, in the ferroelectric memory having such a structure, it is necessary to perform annealing in an atmosphere containing oxygen in order to improve the characteristics of the ferroelectric. When such oxygen annealing is performed, characteristics such as a threshold voltage of a transistor fluctuate. Therefore, the present invention solves such a problem, and an object of the present invention is to provide a ferroelectric memory in which characteristics of a transistor and the like do not change even when oxygen annealing is performed to improve the characteristics of the ferroelectric. In particular, to provide a non-volatile memory.

[0006]

According to a first aspect of the present invention, there is provided a semiconductor device in which a capacitor having a ferroelectric film sandwiched between a pair of an upper electrode and a lower electrode has the same structure as an active element. In a semiconductor device integrated on a semiconductor substrate, a first insulating film formed above the active element and mainly composed of SiN, and a first insulating film formed on the first insulating film and mainly composed of SiO ₂ Two insulating films, and the second insulating film
And having the lower electrode formed thereon. Further, in the semiconductor device according to claim 2 of the present invention, the lower electrode is made of any one of Pt, Al, MoSi, and WSi. Further, the semiconductor device according to claim 3 of the present invention is characterized in that the first insulating film mainly composed of SiN contains oxygen. The semiconductor device according to claim 4 of the present invention is characterized in that the active element and the capacitor form a laminated structure in a thickness direction.

[0007]

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

Reference numeral 101 denotes a P-type Si substrate, for example, 20
A wafer having a specific resistance of 0 hm · cm is used. Reference numeral 102 denotes an insulating film for element isolation.
An oxide film of 6000 A is formed by the OS method. Reference numeral 103 denotes an N-type diffusion layer serving as a source.
It is formed by implanting 5E15 cm-2 ions.
Reference numeral 104 denotes an N-type diffusion layer serving as a drain, which is formed at the same time as 103 by ion implantation. Reference numeral 105 denotes a gate electrode, which uses, for example, poly-Si doped with phosphorus. 1
Reference numeral 08 denotes a gate electrode, which is formed, for example, by thermal oxidation.
An O ₂ film is formed at 250A. Pb 109 is ferroelectric
TiO _{3 ,} PZT (PbZrO ₃ , PbTiO ₃ , PLZT
(La, PbZrO ₃ , PbTiO ₃ ) and is formed by, for example, a sputtering method. Reference numeral 111 denotes one of the electrodes of the ferroelectric film (hereinafter, referred to as a lower electrode), for example, Pt, Al, MoSi, WSi, or the like;
It is formed by a sputtering method. Reference numeral 110 denotes another electrode (hereinafter, referred to as an upper electrode) of the ferroelectric film electrodes, which is, for example, Pt, Al, MoSi, WSi, or the like, and is formed by, for example, a sputtering method. 106 and 107 is an interlayer insulating film, for example, a SiO ₂ film, respectively 3 by vapor deposition
000A. 113 is SiN according to the gist of the present invention.
In the case of FIG. 1, it is formed between the lower electrode 111 and the interlayer insulating film 106 by a vapor deposition method. A wiring electrode 112 connects the source diffusion layer 103 and the upper electrode 110, and is formed of, for example, Al. The wiring electrode 112 may be used for other wiring, for example, connection between MOS transistors.

By the effect of the present invention, the pressure is made into a structure as shown in FIG. 1, so that even if the ferroelectric capacitor is formed and then annealed in an atmosphere containing oxygen, the oxygen is 113 SiN. The MOS transistor under the SiN was not affected, and the threshold voltage of the MOS transistor, for example, had a value which was not changed from that before annealing.

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

The embodiment shown in FIG. 2 is characterized in that the embodiment shown in FIG. 1 is compared with the interlayer insulating film 107 and the insulating film (first insulating film) mainly composed of the SiN film 113. 2 more
The point is that an insulating film (second insulating film) containing SiO ₂ as a main component is formed.

In FIG. 1, the lower electrode of 111 is 113
Directly contacted with the insulating film (first insulating film) containing SiN as a main component, a problem such as peeling occurred due to stress of SiN depending on annealing conditions. By interposing an insulating film (second insulating film) containing SiO ₂ as a main component between the lower electrode and the SIN as shown in FIG. 2, the effect of the present invention, that is, the MOS even when annealed in an atmosphere containing oxygen, can be obtained. Problems such as the transistor characteristics not changing and peeling were solved.

[0013]

According to the present invention, in a semiconductor device in which a ferroelectric film capacitor is integrated, a main component of SiN is placed between an active element such as a transistor and a ferroelectric capacitor. By forming such an insulating film, there is an effect that a semiconductor device with no change in characteristics such as a transistor can be obtained even if oxygen annealing is performed to improve the characteristics of the ferroelectric film.

[Brief description of the drawings]

FIG. 1 is a main cross-sectional view of one embodiment of a semiconductor device of the present invention.

FIG. 2 is a main sectional view in an embodiment for a semiconductor device of the present invention.

FIG. 3 is a main cross-sectional view of a conventional semiconductor device.

[Explanation of symbols]

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 insulating 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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 29/788 29/792

Claims (4)

(57) [Claims] 1. A semiconductor device in which a capacitor having a ferroelectric film sandwiched between a pair of electrodes of an upper electrode and a lower electrode is integrated on the same semiconductor substrate on which an active element is formed. A first insulating film mainly made of SiN, a second insulating film formed on the first insulating film and mainly made of SiO _2, and a second insulating film formed on the second insulating film A semiconductor device having a lower electrode . 2. The method according to claim 1, wherein the lower electrode is made of Pt, Al, MoSi,
2. The semiconductor device according to claim 1, comprising one of WSi. 3. The semiconductor device according to claim 1, wherein the first insulating film whose main component is SiN contains oxygen. 4. The device according to claim 1, wherein the active element and the capacitor form a laminated structure in a thickness direction.
4. The semiconductor device according to any one of claims 1 to 3.