JP2000031151A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance residual polarization characteristics by forming a dielectric film on a semiconductor substrate directly or through other layer and then performing annealing while applying a field to the dielectric film. SOLUTION: Platinum is deposited by DC sputtering onto a first interlayer insulation film, i.e., a silicon oxide film 202, formed on a semiconductor substrate 201 and then a lower electrode 203 is formed by etching followed by formation of a dielectric film 204 by sputtering. Subsequently, the semiconductor substrate 201 is placed in a heating furnace and subjected to annealing while applying a DC voltage of 100 V between parallel plate electrodes. Thereafter, an upper electrode 205 is formed on the dielectric film 204 followed by sequential formation of a second interlayer insulating film 206 of silicon oxide film, a contact hole, an aluminum wiring layer 207 and a protective film 208 thus forming a semiconductor device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device,
More specifically, the present invention relates to a method for manufacturing a semiconductor device in which a dielectric element is integrated on the same semiconductor substrate on which an active element is formed.

[0002]

2. Description of the Related Art A method of manufacturing a semiconductor device includes a step of forming a ferroelectric film directly or via another layer on a semiconductor substrate, and a step of annealing the dielectric film.
It is known that it is effective to align the direction of spontaneous polarization in the ferroelectric, that is, to make the orientation axis of the crystal constant in order to improve the remanent polarization. However, conventionally, only a heat treatment was performed without applying an electric field to the ferroelectric during crystallization of the ferroelectric, and after the crystallization, a polarization treatment was performed by applying an electric field to the ferroelectric again. Therefore, the direction of spontaneous polarization during crystallization is not aligned in each domain, and polarization processing is performed later, but due to the strain at that time, the ferroelectric characteristics of the ferroelectric are considerably larger than those of the bulk crystal. Was inferior. Its characteristics are, for example,
Of Applied Physics (Journal o
f Applied Physics), 1991,
According to Vol. 70, No. 1, paragraphs 382 to 388, when PZT (Pb (Zr _0.5 Ti _0.5 ) O ₃ ) is used as the ferroelectric, the remanent polarization is obtained at a ferroelectric film thickness of 0.5 μm. Pr was about 15 μC / cm ² .

[0003]

However, since the area of the ferroelectric element is necessarily limited by microfabrication such as integration of the ferroelectric on a semiconductor substrate, the value of this remanent polarization is not practical. It was not enough.

The present invention solves such a problem, and an object of the present invention is to improve remanent polarization characteristics.

[0005]

According to the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of forming a dielectric film on a semiconductor substrate directly or through another layer, and applying an electric field to the dielectric film. And annealing step. The electric field may be applied only when the temperature is lowered in the annealing step, and the applied electric field may be an AC electric field. Further, when the dielectric has a structure sandwiched between two electrodes, the electric field can be directly applied to the electrodes. Further, PZT is used as the dielectric material.
A ferroelectric material such as (Pb (ZrTi) O ₃ ) may be used.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an explanatory view of a first embodiment of a method of manufacturing a semiconductor device according to the present invention. First, as shown in FIG. 2A, 0.2 μm of platinum (Pt) is formed on a silicon oxide film 202 as a first interlayer insulating film on a semiconductor substrate 201 by a DC sputtering method, and a photo process is performed. The lower electrode 203 is formed by etching by ion beam etching using argon ions. After that, P
ZT (Pb (ZrTi) O ₃ ) is formed to a thickness of 0.3 μm to form a dielectric film 204 (FIG. 2B).

Next, the semiconductor substrate 103 on which the dielectric film 204 is formed by the above procedure is placed on the inside of a quartz tube heater 102 with a mesh-type parallel plate electrode 101 having a distance of 10 cm between electrodes as shown in FIG. In a heating furnace, heat treatment is performed at 600 ° C. for 1 hour in an oxygen atmosphere with a DC voltage of 100 V applied between the parallel plate electrodes.

Thereafter, the dielectric film 2 is formed on the semiconductor substrate.
Pt 0.2 μm is formed as an upper electrode 205 on
After photo-etching (FIG. 2C), a second interlayer insulating film 206 made of a silicon oxide film is formed by a vapor phase epitaxy (CVD) method, a contact hole is opened, an Al wiring layer 207 is formed, After forming a silicon nitride film as the protective film 208 by the CVD method, a semiconductor device having a sectional shape as shown in FIG. When the remanent polarization Pr of the ferroelectric capacitor in the semiconductor device of the present embodiment was measured, it was found to be about 30 μC / cm ² at a voltage of 5 V at a dielectric film thickness of 0.3 μm.

FIG. 3 is an explanatory view of a second embodiment of the method of manufacturing a semiconductor device according to the present invention. First on the semiconductor substrate 301
Platinum (Pt) is formed by a DC sputtering method on a silicon oxide film 302 as an interlayer insulating film to a thickness of 0.2 μm, and is etched by ion beam etching using argon ions through a photo process to form a lower electrode 303. (FIG. 3 (a)). Then, PZT (P
b (ZrTi) O ₃ ) is formed to a thickness of 0.3 μm, and a dielectric film 304 is formed by a photo process and an etching process (FIG. 3B). Thereafter, Pt 0.2 μm is formed as the upper electrode 305 on the dielectric film on the semiconductor substrate by a DC sputtering method.
After the etching step, a structure as shown in FIG. 3C was obtained.

Next, the semiconductor substrate 105 on which the upper electrode 305 is formed by the above procedure is placed on the first interlayer insulating film 302 on the semiconductor substrate in a heating furnace as shown in FIG.
Annealing is performed at 600 ° C. for 1 hour with an AC voltage 104 of 1 V and 50 Hz applied between the two electrodes.

Thereafter, a silicon oxide film is formed as a second interlayer insulating film 306 by a vapor phase growth (CVD) method, a contact hole is opened by dry etching, an Al wiring layer 307 is formed by sputtering, and CVD is performed. Through the formation of a silicon nitride film as a protective film 308 by a method,
A semiconductor device having a sectional shape as shown in FIG.

When the remanent polarization Pr of the ferroelectric capacitor in the semiconductor device manufactured in the present embodiment was measured, it was found to be about 32 μC / cm ² at an applied voltage of 5 V at a dielectric film thickness of 0.3 μm. did. Also, a value of about 25 fF / μm ² was obtained for the capacitance density.

In this embodiment, the voltage is applied over the entire annealing time. However, the voltage may be applied only when the temperature of the annealing falls, and the frequency of the alternating current is high (13.56 M).
Hz), and is not particularly limited. further,
When the dielectric film is a ferroelectric, it is good for controlling the spontaneous polarization and improving the remanent polarization, but BaTiO3, (SrB
a) In the case of a paraelectric film having a perovskite crystal structure such as TiO3 or a paraelectric film of a capacitance storage capacitor such as TaO5, SiO2 or SiNx, the film quality can be improved and the capacitance density can be improved. Further, Zr composition ratio x of the In the present embodiment PZT (Pb (ZrxTi1 over x) O ₃₎
Was set to 0.5, but another composition may be used.

[0015]

As described above, in the method of manufacturing a semiconductor device according to the present invention, when an electric field is applied to a dielectric film during annealing, when the dielectric film is a ferroelectric, the inside of the crystal is reduced. In order to perform polarization processing with minimum distortion,
A larger remanent polarization characteristic than before was obtained. Further, even when the dielectric film is a paraelectric material, the film quality is improved and the capacitance density is larger than before. As a result, sufficient remanent polarization or capacitance density can be realized even when the capacitor area is reduced with miniaturization of the semiconductor device.

[Brief description of the drawings]

FIG. 1 is a schematic view of a heating furnace used in first and second embodiments of the present invention.

FIG. 2 is an explanatory view of a process according to a first embodiment of the present invention.

FIG. 3 is an explanatory view of a process according to a second embodiment of the present invention.

[Explanation of symbols]

 Semiconductor substrate 201, 301 First interlayer insulating film 202, 302 Lower electrode 203, 303 Dielectric film 204, 304 Upper electrode 205, 305 Second interlayer insulating film 206, 306 Al wiring layer 207, 307 Protective film 208, 308 Mesh type parallel plate electrode 101 Quartz tube heater 102 Semiconductor substrate including lower electrode and dielectric film 103 AC power supply 104 Semiconductor substrate including upper and lower electrodes and dielectric film 105

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[Procedure amendment]

[Submission date] August 4, 1999 (1999.8.4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Semiconductor device

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

According to the present invention, there is provided a semiconductor device comprising:
A semiconductor device having a dielectric capacitor having a dielectric film sandwiched between first and second electrodes, the semiconductor device having a first extending portion extending in a first direction beyond the dielectric film. It has a first electrode and the second electrode having a second extension extending beyond the dielectric film in a direction different from the first direction. In addition, in addition to the above, the first
And the second extension portion is arranged on the same layer.

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Claims (5)

[Claims] 1. A semiconductor device comprising: a step of forming a dielectric film directly on a semiconductor substrate or via another layer; and a step of annealing the dielectric film in a state where an electric field is applied. Manufacturing method. 2. A method for manufacturing a semiconductor device, comprising: a step of forming a dielectric film directly on a semiconductor substrate or through another layer; and a step of annealing the dielectric film. A method for manufacturing a semiconductor device, wherein an electric field is applied to the dielectric film. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the applied electric field is an AC electric field. 4. The method for manufacturing a semiconductor device according to claim 1, wherein said dielectric has a structure sandwiched between two electrodes, and said electric field is applied between said two electrodes. A method for manufacturing a semiconductor device, comprising: 5. The method for manufacturing a semiconductor device according to claim 1, wherein said dielectric is a ferroelectric having a perovskite crystal structure.