JPH04147964A - Production of thin film of ferroelectric substance - Google Patents

Abstract

PURPOSE:To reduce the vapor pressure of PbO and to obtain films having a uniform compsn. with high reproducibility by using two or more kinds of alloys selected among PbTiO3, PbZrO3 and PbO as targets and inhibiting the evaporation of PbO at the time of sputtering. CONSTITUTION:Targets 2a, 2b of two or more kinds of alloys selected among PbTiO3, PbZrO3 and PbO are arranged on the circumference of a circle in a vacuum chamber. A rotating substrate holder 1 holding substrates S is placed opposite to the targets 2a, 2b, rotated and heated and the targets 2a, 2b are sputtered to emit particles. These particles are successively collided against the surfaces of the moving substrates S and thin films of a ferroelectric substance are formed on the surfaces of the substrates S.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of forming a ferroelectric thin film on a substrate surface. In particular, the present invention relates to a method for forming a PZT thin film and a PLZT thin film.

<Prior Art> PZT thin films and PLZT thin films have been applied to various electronic devices due to their respective functionality. For example, there are memory elements, piezoelectric elements, pyroelectric elements, etc. that use DE hysteresis.

Conventionally, PZT thin films, PL
When forming a ZT thin film, P is used as an alloy target.
bZrxT1+-xos was used. In this case, lead evaporates and is likely to react with oxygen used as a reaction gas, so a large amount of PbO is generated. Therefore, as the vapor pressure of PbO increases, a compositional shift occurs in the stacked films. In order to eliminate this compositional deviation, it has been common practice to use a Pb-rich target in advance, or to perform sputtering in a PbO atmosphere.

<Problem to be solved by the invention> By the way, in the conventional technology, a single target is used, and although sputtering has been performed in a Pb-rich or PbO atmosphere, a composition mismatch with the target occurs, resulting in unstable sputtering. However, it was not possible to form a film that

In view of the above problems, it is an object of the present invention to form a stable ferroelectric thin film without causing compositional deviation from the target.

Means for Solving the Problems> The thin film manufacturing method of the present invention rotates a rotating substrate holder disposed in a vacuum chamber facing a plurality of targets arranged along the same circumference. By sequentially moving the substrate to a position above the target, the substrate is heated at the same time, and the particles released by sputtering the target are sequentially bombarded with the surface of the moving substrate, thereby forming a thin film on the surface of the substrate. In the method for producing P b T i Os, PbZrO3 and PbO
The present invention is characterized in that at least two of these alloys are used as the target and sputtered simultaneously.

<Action> PbTiO2, PbZr0. Since the target contains an alloy of at least two of PbO and PbO, there is very little evaporation of PbO during sputtering. Therefore, the vapor pressure of PbO can be kept low.

In addition, since sputtering is performed while heating the substrate, and the composition ratio of Ti/Zr, etc. is changed by applying a discharge voltage that controls the deposition rate of each target component and discharging at the same time, the thickness of the layer of each component can be adjusted. The film has a stoichiometric composition as a whole, and a thin film having the desired perovskite structure can be formed.

<Example> FIG. 1 is an explanatory diagram of the main parts of a manufacturing apparatus used in an example of the present invention.

A substrate S is held by a rotating substrate holder 1 in a vacuum chamber (not shown). This substrate S is in a heated state by a substrate heater (not shown).

Further, the targets 2a and 2b are arranged on the same circumference. A substrate S is placed opposite these targets 2a and 2b. In the embodiment of the present invention, targets 2a, 2
b are respectively PbTi0. , P b Z r Os.

Further, the rotating substrate holder 1 is rotated by a drive mechanism (not shown) disposed outside the vacuum chamber, and by this rotation, the substrate S is configured to sequentially rotate and move over each target 2a, 2b. There is.

Next, a method for manufacturing a ferroelectric thin film with the above configuration will be described.

After the vacuum chamber is evacuated, a mixed gas of argon and oxygen is introduced into the chamber.

After that, when a voltage is applied to each target 2a, 2b with the baked substrate S grounded, plasma is generated between each target 2a, 2b and the rotating substrate holder 1, and argon ions in the plasma are transferred to each target. 2
a, 2b, and each atom emitted by the impact is sequentially deposited on the substrate S when the substrate S is positioned above each target 2a, 2b, forming a desired ferroelectric thin film. .

Now, the feature of the embodiment of the present invention is that PbT is used as the target.
The reason is that iO3 and PbZrO2 were used. That is,
These compounds have a higher P level during sputtering than PZT.
Since there is very little evaporation of bO, it is possible to prevent the evaporated PbO, which is the cause of composition deviation, from reaching a high vapor pressure.

In addition, by simultaneously discharging each target while controlling the discharge voltage, the deposition speed of each target can be controlled, and since sputtering is performed on the heated substrate S, the thickness of the layer of each component can be adjusted by the stoichiometric amount as a whole. A PZT film having a theoretical composition and a desired perovskite structure can be formed.

FIG. 2 is a schematic cross-sectional view of a PZT thin film formed by the above method.

The PZT thin film formed on the substrate S is PbZr0.3b
One molecular layer of each of PbT 1Os3a and PbT 1Os3a are alternately stacked.

In the embodiment of the present invention, two types of targets are used, but any two types of targets among PbTiO3, PbZrOs, and PbO may be combined, or three types may be used. There may be three types if necessary.

<Effects of the Invention> As explained above, according to the present invention, evaporation of PbO can be prevented and the deposition rate of each component can be controlled in film formation based on multi-component sputtering, so compositional deviations can be avoided. A high-quality ferroelectric thin film with a uniform composition can be obtained with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a main part of a manufacturing apparatus used in an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a PZT thin film formed according to an embodiment of the present invention. 1...Rotating substrate holder 2a, 2b...Targeter 3a-PbTiO* 3b・PbZr0°S...Substrate

Claims (1)

[Claims] By rotating a rotating substrate holder placed in a vacuum chamber facing a plurality of targets arranged along the same circumference, the substrates are sequentially moved to positions above the targets and simultaneously heated. , a method of manufacturing a thin film on the surface of the moving substrate by sequentially colliding particles released by sputtering the target with the surface of the moving substrate, in which PbTiO_3, Pb
A method for producing a ferroelectric thin film, characterized in that sputtering is performed simultaneously using an alloy of at least two of ZrO_3 and PbO as the target.