JPH05343642A - Manufacture of dielectric substance element - Google Patents

Abstract

PURPOSE:To improve ferroelectric or paraellectric characteristics like residual polarization or permittivity, and obtain a large capacity DRAM or nonvolatile storage device excellent in reliability, by improving the orientation of a specified crystal face of dielectric crystal, reducing grain diameter, and making a film dense. CONSTITUTION:The title method contains a process wherein an amorphous dielectric substance film 105 is formed on a silicon substrate 101, and a process wherein the amorphous dielectric substance film is irradiated with ultraviolet rays like excimer laser, and the amorphous dielectric substance film is crystallized 107 by absorbing energy of the ultraviolet rays.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a ferroelectric capacitor mainly used in a dynamic random access memory (DRAM) or a non-volatile memory, and more particularly to a method of crystallizing a dielectric capacitor. .

[0002]

2. Description of the Related Art Conventionally, for example, Applied Physics Letters (Applied Physics Letters) is used.
ters), 1991, Vol. 58, No. 11, Item 1161-1163, used for large-capacity dynamic random access memory (DRAM) and non-volatile memory using ferroelectrics. Lead zirconate titanate (PZT) is used for the so-called ferroelectric capacitor, and high-speed heat treatment using a lamp is performed as its crystallization annealing.

Lamp heating conditions are, for example, 650 ° C. and 1
It was 0 second and 100 ° C./sec.

[0004]

However, the remanent polarization density when the conventional lamp heating is used is 10 μm / cm ²
Therefore, when this ferroelectric capacitor is used as a large-capacity non-volatile memory, it cannot be said to be a sufficient value in consideration of the retention characteristic of remanent polarization and film fatigue due to repeated polarization reversal.

The retention characteristic and film fatigue due to repeated polarization reversal will be briefly described below.

Writing of information in a non-volatile memory device using a ferroelectric substance is performed depending on the polarization direction of the ferroelectric film.

That is, the ferroelectric film has a capacitor structure sandwiched between two upper and lower electrodes, and for example, the coercive electric field of the ferroelectric film or more is set so that the upper electrode has a positive potential with respect to the lower electrode. When biased, the polarization direction is downward, and when biased in the opposite direction, it is upward.

The direction of this polarization corresponds to information 0 and 1.

Therefore, the value of the remanent polarization density is 0 μm / cm.
If it becomes ² , 0 or 1 of the information cannot be discriminated and memory destruction occurs.

The memory retention characteristic is whether or not the information held at the time of reading can be read out by holding the polarization direction downward, for example.

In general, the value of remanent polarization decays with temperature and time, so that the retained information disappears.

On the other hand, when rewriting information, the direction of the bias applied to the capacitor is changed, and it is known that the remanent polarization value is attenuated even if this is repeated, and this is called film fatigue due to repeated polarization reversal. .

Therefore, the present invention is intended to solve such a conventional problem, and its purpose is to:
Even when a ferroelectric capacitor is used as a large-capacity non-volatile memory, the remanent polarization density is improved so that there is no practical problem even if the retention characteristic of remanent polarization and film fatigue due to repeated polarization reversal are taken into consideration. To provide a method of manufacturing a dielectric element.

[0014]

The method of manufacturing a dielectric element according to the present invention comprises: (1) a step of forming an amorphous dielectric film on a semiconductor substrate directly or through another layer; The method may further include the step of crystallizing the amorphous dielectric film by irradiating the amorphous dielectric film with ultraviolet rays.

(2) The ultraviolet ray of (1) above is an excimer laser.

(3) The crystalline structure of the crystalline dielectric film of (1) and (2) above is a perovskite structure.

(4) The above (1), (2) and (3)
Is characterized in that an active element is formed on the semiconductor substrate.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the method of manufacturing a dielectric element according to the present invention will be described with reference to the manufacturing process sectional views of FIGS.

As shown in FIG. 1A, a silicon substrate 10
On top of which a silicon dioxide film (SiO ₂ ) 1 is formed as an interlayer insulating film.
After forming 02, Pt104 of the lower electrode is formed through the titanium (Ti) film 103 of the adhesion layer, and Pb, Pb,
Amorphous dielectric film 105 containing Zr, Ti, and O as main components
Of, for example, Pb _1.1 (Zr _0.5
It is formed by a high frequency magnetron sputtering method using Ti _0.5 ) O _3.1 as a target.

This amorphous dielectric film is made of polycrystalline lead zirconate titanate Pb (Zr _0.5 Ti _0.5 ) O ₃ , which exhibits ferroelectric characteristics by crystallization annealing described later, which is a group which becomes PZT for short. is there.

The SiO ₂ 102 was formed by the plasma chemical vapor deposition method of tetra ethyl ortho silicate (TEOS), and its film thickness was 5000 Å.

The Ti film 103 and the Pt 104 are formed by the DC sputtering method, and the film thicknesses thereof are 200 Å and 5 respectively.
It was 000Å.

The thickness of the amorphous dielectric film 105 is set to 5000
Å

Next, as shown in FIG. 1B, for example, the dielectric film 105 is irradiated with a XeCl excimer laser 106 perpendicularly to the silicon substrate.

Since the XeCl excimer laser is ultraviolet light and its wavelength is 308 nm, the dielectric film 10
In the absorption band of No. 5, the dielectric film 105 absorbs the excimer laser and heats rapidly, and due to the temperature thereof, crystallizes itself.

The excimer laser irradiation conditions were 500 mJ, 20 Hz and 10 W in an oxygen atmosphere, and irradiation was performed for 0.5 seconds.

As a result, a polycrystalline PZT107 having a perovskite crystal structure is formed as shown in FIG. 1 (c).

At this time, the degree of crystal orientation of the polycrystalline PZT107 shows a strong (111) orientation, and the grain size of PZT is 20.
It was about 0Å, and a very dense film was obtained.

The residual polarization density was 20 μC / cm ² .

A second embodiment of the method for manufacturing a dielectric element according to the present invention will be described with reference to the manufacturing process sectional view of FIG.

The difference from the first embodiment is that a silicon dioxide film (SiO ₂ ) 108 is formed as a cap layer on the amorphous dielectric film 105.

The film thickness of SiO ₂ 108 is 500 Å,
Part of the ultraviolet light is absorbed by SiO ₂ 108, but part of it is transmitted.

As described above, by providing the cap layer on the amorphous dielectric film 105, it is possible to prevent the evaporation of oxygen from the dielectric film 105. Therefore, it is not necessary to use an oxygen atmosphere, and it is not necessary to use oxygen in a vacuum. Crystallization can also be performed with.

In the above two embodiments, X is used as the ultraviolet ray source.
As described above using the eCl excimer laser, ArCl,
ArF, KrCl, KrF, XeBr, XeCl, Xe
Even if an excimer laser such as F is used, the absorption band of the dielectric film is reached, which is of course preferable.

Further, ultraviolet rays such as hydrogen discharge tubes, low-pressure and high-pressure mercury lamps, and Xe lamps may be used.

Further, as the method for forming the amorphous dielectric film, the high frequency magnetron sputtering has been described.
Of course, the sol-gel method may be used.

Although the angle of impact of the excimer laser 106 on the silicon substrate 101 has been described as vertical, the angle of incidence may be any number as long as it is greater than 0 degrees and less than 90 degrees.

Although PZT was used as the ferroelectric film, PbTiO ₃ , KNbO ₃ and Pb (MnNb) were used.
Oxide ferroelectrics having other perovskite crystal structure such as O ₃ may be used, and lanthanum (La), calcium (Ca), niobium (Nb), neodymium (N) may be used.
Impurities such as d), bismuth (Bi), antimony (Sb), and tantalum (Ta) may be doped.

Further, in the above embodiment, the capacitor is formed on the silicon substrate, but an active element such as a transistor may be formed on the silicon substrate.

In this case, by suppressing the penetration depth of ultraviolet rays to the extent of an amorphous dielectric film, it is possible to prevent the underlying active element from being adversely affected.

[0041]

As described above, the method of manufacturing a dielectric element according to the present invention irradiates the amorphous dielectric material with ultraviolet rays which can be absorbed by the dielectric material, and crystallizes the amorphous dielectric material very rapidly. It can be crystallized, the degree of orientation of specific crystal planes can be increased, the grain size can be reduced, and the film can be made dense, so that the remanent polarization of the ferroelectric substance can be increased and the characteristics of each crystal grain can be made uniform. It is possible to reduce the coercive electric field and the saturation electric field, and even in the case of a paraelectric material, it is possible to increase the dielectric constant. Furthermore, it is possible to form an active element such as a transistor. When integrated on a semiconductor substrate, the dielectric element can be integrated without adversely affecting the active element, and crystallization can be performed at a higher speed than in the past, so it can be manufactured in a short time. Have the effect.

[Brief description of drawings]

FIG. 1 is a manufacturing step sectional view illustrating a first embodiment of a method for manufacturing a dielectric element according to the present invention.

FIG. 2 is a cross sectional view of a manufacturing process illustrating a second embodiment of the method for manufacturing a dielectric element according to the present invention.

[Explanation of symbols]

101 Silicon Substrate 102 SiO ₂ 103 Ti Film 104 Pt Lower Electrode 105 Amorphous Dielectric Film 106 Excimer Laser 107 Polycrystalline PZT 108 SiO ₂

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical indication location H01L 27/04 C 8427-4M 27/105 29/788 29/792 H01L 29/78 371

Claims (4)

[Claims] 1. A step of forming an amorphous dielectric film on a semiconductor substrate directly or through another layer, and irradiating the amorphous dielectric film with ultraviolet rays to form the dielectric film. A method of manufacturing a dielectric element, which comprises the step of crystallizing. 2. A method for manufacturing a dielectric element, wherein the ultraviolet ray according to claim 1 is an excimer laser. 3. A method of manufacturing a dielectric element, wherein the crystalline structure of the crystalline dielectric film according to claim 1 is a perovskite structure. 4. A method of manufacturing a dielectric element, wherein an active element is formed on the semiconductor substrate according to any one of claims 1, 2 and 3.