JP2003301262A - Ferroelectric thin film and sputtering target material for producing ferroelectric thin film - Google Patents

Abstract

(57) [Summary] PROBLEM TO BE SOLVED: To provide a uniform and uniform crystal grain size at 100 nm or less.
PZT thin film with low leakage current and strength for obtaining it
Provision of sputtering target for dielectric thin film production
The title. SOLUTION: Lead, zircon, titanium, lanthanum, and
Composed of oxygen, (Pb _1-XLa_x) (Zr_yTi_z) O_ThreeAnd x is 0
Above, 0.10 or less, and a compound in which (y + z) is represented by 0.95 to 1.0
A mixture of PbO and metal silicate, (Pb_1-XLa_x) (Z
r_yTi_z) O_ThreeIs 1 mol, PbO is 0.02-0.30 moles
Target with a metal silicate content of 0.05 to 0.20 mol
Using materials, lead, zircon, titanium, lanthanum, and
Composed of oxygen, (Pb_1-xLa_x) (Zr_yTi_z) O_ThreeAnd x is 0
Above, 0.10 or less, and a compound in which (y + z) is represented by 0.95 to 1.0
Formed as a mixture of metal silicates,
The chemical formula is La_TwoSiO_FiveAnd a dielectric thin film containing this
The composition of ((Pb_1-xLa_x) (Zr_yTi_z) O_Three)_1-a(La_TwoSiO_Five)
_aTo obtain a dielectric thin film in which a is 0.05 to 0.20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric film used for a ferroelectric memory, a piezoelectric actuator, etc., and a sputtering target material for obtaining the same.

[0002]

2. Description of the Related Art Lead zirconate titanate (hereinafter referred to as "PZ
"T". ) Or SrBi2Ta2O9 (hereinafter abbreviated as SBT) ferroelectric film of Y1 compound such as non-volatile memory, dynamic random access memory capacitor, piezoelectric element,
Its application to optical devices has been studied, and its use as a ferroelectric memory has already been realized. Although such a ferroelectric film is formed by a sputtering method, a sol-gel method, a CVD method or the like, it is recommended to form it by the sputtering method because of its simplicity.

[0003]

By the way, the ferroelectric memory using the PZT thin film has a problem that it cannot always be operated at a low voltage. This is due to the characteristic of PZT, which has a large ferroelectricity but a large coercive electric field. Therefore, it can be estimated that the ferroelectric memory can be operated at a low voltage by reducing the thickness of the PZT thin film and increasing the effective electric field strength.

However, it is known that the following problems occur when a PZT thin film of 100 nm or less is formed by a sputtering method. 1. The obtained PZT thin film becomes a polycrystalline film, but the grain sizes of the crystals that make up the polycrystalline film become uneven, and the ferroelectricity deteriorates. When the film pressure is about 2.100 nm, the obtained film thickness is likely to be non-uniform and the leak current tends to be large.

An object of the present invention is to provide a ferroelectric thin film which does not cause such a defect and a sputtering target material for preparing a ferroelectric thin film for obtaining the thin film.

[0006]

The first invention for solving the above-mentioned problems is composed of lead, zircon, titanium, lanthanum, and oxygen, and (Pb _1-x La _x ) (Zr _y Ti _z ) O _{In 3} , x is 0 or more, 0.10 or less, (y + z) is formed as a mixture of a compound represented by 0.95 to 1.0 and a metal silicate, and the thickness thereof is 100 n.
It is a ferroelectric thin film characterized by having a thickness of m or less. And, preferably, the metal silicate is represented by the chemical formula La ₂ SiO ₅ , and the composition of the dielectric thin film containing this is ((Pb _1-x La _x ).
(Zr _y Ti _z ) O ₃ ) _1-a (La ₂ SiO ₅ ) _a , where a is 0.05 to 0.20
It is characterized by being.

The second invention for solving the above problems is a target for obtaining the thin film of the first invention,
It is composed of lead, zircon, titanium, lanthanum, and oxygen. In (Pb _1-X La _x ) (Zr _y Ti _z ) O ₃ , x is 0 or more and 0.10 or less, and (y + z) is 0.95 to 1.0. It is a mixture of the represented compound, PbO, and a metal silicate, and when (Pb _1-X La _x ) (Zr _y Ti _z ) O ₃ is 1 mol, PbO is 0.02 to 0.30 mol and the metal silicate is 0.05 to It is a target material for forming a ferroelectric thin film, which has a content of 0.20 mol.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors should achieve the above object.
Various studies were conducted. As a result, lead, zircon, chita
It is composed of oxygen, lanthanum, and oxygen._1-xLa_x)
(Zr_yTi_z) O₃X is 0 or more, 0.10 or less, (y + z) is 0.95 ~
Mixing the compound represented by 1.0 with a mixture of metal silicates
The ferroelectric film formed as a compound is especially
La as a ₂SiO_FiveIs effective for thinning.
The present invention has been accomplished by finding out that.

That is, the dielectric thin film of the first invention is
Consists of lead, zircon, titanium, lanthanum, and oxygen
, (Pb_1-xLa_x) (Zr_yTi_z) O₃X is 0 or more, 0.10 or less
Below, the compounds and metal silicates with (y + z) of 0.95 to 1.0
Ferroelectric thin film characterized by being formed as a mixture of
It is a film. And, preferably the metal silicate is chemically
Expression La₂SiO_FiveAnd the composition of the dielectric thin film containing this is
((Pb_1-xLa_x) (Zr_yTi_z) O ₃)_1-a(La₂SiO_Five)_aAnd
And a is 0.05 to 0.20.
It In the present invention, adding La reduces the coercive electric field.
However, x exceeds 0.10 in the above composition formula.
Then, the ferroelectricity deteriorates. In the present invention, x is 0
Including. The composition ratio of Zr and Ti is different depending on the application of the thin film.
It is possible to choose. Zr: T for ferroelectric memory
i is preferably about 4: 6 to 7: 3. (Pb_1-xLa_x) (Zr_yTi_z) O
₃In, y + z is 0.95 to 1.0. When y + z is less than 0.95
There is too much Pb, lead does not volatilize sufficiently during sintering, and lead in the thin film
As a residual current, which may increase the leakage current.
Alternatively, volatilized lead adheres to the inner wall surface of the sintering furnace and the equipment management is complicated.
It becomes coarse, and if it exceeds 1.0, the ferroelectricity will deteriorate.
is there.

The ratio of (Pb _1-x La _x ) (Zr _y Ti _z ) to the metal silicate is (Pb _1-x La _x ) (Zr _y Ti _z ) _1-a (La ₂ SiO ₅ ).
_{In a} , if a is smaller than 0.05, there is no thinning effect, and 0.
If it is larger than 20, the ferroelectric property is deteriorated. Next, the second invention will be described. The second invention of the present invention is a target for obtaining the film of the first invention. As for this target, the Pb of the film obtained by sputtering is lower than that of the target composition.
It is necessary to add bO in excess. Therefore, it is composed of lead, zircon, titanium, lanthanum, and oxygen,
(Pb _1-X La _x ) (Zr _y Ti _z ) O ₃ where x is 0 or more and 0.10 or less, (y
+ z) is a compound represented by 0.95 to 1.0, a mixture of PbO and a metal silicate. That is, (Pb _1-X La _x ) (Zr _y Ti _z ).
When O ₃ is 1 mol and the metal silicate is 0.05 to 0.20 mol, PbO is 0.02 to 0.30 mol. The composition difference between the obtained thin film and the target changes depending on the sputtering conditions, but if PbO is less than 0.02 mol, the Pb in the film is small and perovskite is difficult to form, and if it exceeds 0.30 mol, the Pb in the film is too much. A desired thin film composition cannot be obtained. The study of the present invention was conducted as follows. First, lanthanum oxide and SiO ₂ are mixed, melted and cooled.
A polycrystal of La ₂ SiO ₅ was prepared and crushed to prepare a powder. Since La ₂ SiO ₅ was formed at a high temperature, it was not a single phase but a mixture of multiple oxides. PbZrO ₃ and PbTiO ₃ and La ₂ O
₃ was mixed in an appropriate amount and calcined at 700 ℃ ~ 1000 ℃ to prepare calcined powder of PZT and PLZT. This PZT or PLZT calcined powder and La ₂ Si
O ₅ and lead oxide were taken in appropriate amounts, mixed in a ball mill, pressure-pressed, and the resulting compact was sintered at 900 ° C. to 1200 ° C. to produce a sintered body (sputtering target material). Next, the outer surface of the obtained sputtering target material is (molded ) ground , attached to a backing plate as a target, and using this target, a ferroelectric thin film is created by the sputtering method according to the procedure shown below. The characteristics of each film obtained by using a tester were obtained. 1) A 500 nm SiO ₂ layer was formed on a Si wafer by a thermal oxidation method, Ti, TiO _x or TiN was formed thereon as an adhesion layer, and a Pt layer was formed thereon as an electrode film. The adhesion layer and the electrode film were formed by the sputtering method.
If the adhesion layer is thinner than 2 nm, the adhesion between SiO ₂ and Pt will not be improved, and if it is thicker than 5 nm, the unevenness of the Pt surface will become large, so that
m and Pt is 50 because of the durability of the electrode film and the resistance value.
It was set to ~ 200 nm. 2) Next, a ferroelectric film having a film thickness of 50 nm was formed on the electrode having such a structure by an Rf magnetron sputtering method using pure Ar gas. 3) The thin film obtained by the sputtering method is 600 ° C for 30 minutes in a tubular furnace.
It was annealed and crystallized under atmospheric conditions. 4) After crystallization of the film, Pt was sputtered as the upper electrode to 100 nm.
The Pt film was obtained, and thereafter, in order to recover the damage of the ferroelectric film caused by Pt sputtering, annealing was performed in air at 400 ℃ or more for 10 to 30 minutes. Annealing temperature is 40
If the temperature is lower than 0 ° C, the damage recovery is slow, and the upper limit of the annealing temperature is the same as that of the crystallization annealing. However, considering the handling of the sample, it is preferable to perform the annealing at 600 ° C or lower. The optimum annealing time depends on the annealing temperature, but damage does not recover in 10 minutes or less, and 30 minutes at an annealing temperature of 550 ° C.
It was found that the damage recovery was saturated after about a minute of processing. 5) Characterize.

[0011]

EXAMPLES The present invention will be specifically described with reference to Examples and Comparative Examples of the present invention. (Example 1-6) target for creating the study example and in the same manner as _{(Pb 1-X La x)} (Zr y Ti z) O 3
x = 0.02, y + Z = 0.98, y: z = 52: 48, and (Pb
_1-x La _x ) (Zr _y Ti _z ) 1 mol, PbO becomes 0.15 mol excess, and (La ₂ SiO ₅ ) is 0.05 mol (Examples 1 to 3),
0.07 mol (Examples 4 to 6), 0.15 mol (Example 7 to
9) and 0.20 mol (Examples 10 to 12) of ceramic targets were prepared.・ Ferroelectric film formation 50n film thickness by sputter deposition method using the above target
Ferroelectric films with m, 80 nm and 100 nm were prepared.

The substrate used was a 500 nm SiO ₂ layer formed on a Si wafer by a thermal oxidation method, and a Ti 2 layer as an adhesion layer was formed on the SiO ₂ layer.
Of 15 nm and Pt of 200 nm formed as an electrode film thereon.

RF sputtering is used as the sputtering method, and the condition is a target-sample distance of 60.
mm and Ar gas pressure was 3.0 Pa. RF power is 200
W.

The obtained film was subjected to crystallization annealing at 600 ° C. for 30 minutes in an oxygen flow using a tubular furnace. afterwards,
P as a circular upper electrode with a diameter of 0.5 mm using a metal mask
A film having a thickness of 100 nm was formed by sputtering. In order to recover the damage to the dielectric film caused by the upper electrode sputtering, the second annealing was performed at 600 ° C for 30 minutes in an oxygen flow.

Measurement and evaluation of the ferroelectric properties of the film The ferroelectric properties of the film are the ferroelectric measurement device TF200 manufactured by aixACCT.
The hysteresis loop of polarization with respect to the electric field was measured using 0FE. The applied voltage was 5 V at maximum and 100 Hz. The polarization value at the electric field 0 of the hysteresis curve is called remanent polarization (Pr), and it is used as an amount that indicates the magnitude of ferroelectricity.
Two remanent polarization differences 2Pr are used. Further, the electric field strength at which the polarization value becomes 0 is called a coercive electric field, and is a quantity indicating the likelihood of polarization reversal. Since the coercive electric field does not have a symmetrical shape of hysteresis, the sum of positive and negative coercive electric fields was calculated as 2Ec. 2P
Table 1 shows the measurement results of r, the coercive electric field, and the residual polarization value when 0.8 V was applied.

(Comparative Examples 1 to 6) Preparation of Target In the same manner as in the above-mentioned study example, (Pb _1-X La _x ) (Zr _y Ti _z ) O ₃ was used.
x = 0.02, y + Z = 0.98, y: z = 52: 48, and (Pb
_1-x La _x ) (Zr _y Ti _z ) 1 mol, PbO becomes 0.15 mol excess, (La ₂ SiO ₅ ) 0.02 mol (Comparative Examples 1 to 3), 0.4
A ceramic target having 0 mol (Comparative Examples 4 to 6) was produced.・ Ferroelectric film formation 50n film thickness by sputter deposition method using the above target
Example 1 except that ferroelectric films of m, 80 nm and 100 nm were prepared
A ferroelectric film was obtained in the same manner as in. -Measurement and Evaluation of Ferroelectric Property of Film The measurement and evaluation of ferroelectric property of the film were performed in the same manner as in the example. The obtained results are also shown in Table 1.

(Comparative Examples 7 to 12) Preparation of Target In the same manner as in the above-mentioned examination example, (Pb _1-X La _x ) (Zr _y Ti _z ) O ₃ was used.
x = 0.02, y + Z = 0.98, y: z = 52: 48, and (Pb
0.15 mol excess of PbO per 1 mol of _1-x La _x ) (Zr _y Ti _z ), 0.02 mol (Comparative Example 7), 0.05 mol (Comparative Example 8), 0.07 mol (La ₂ SiO ₅ ) Comparative Example 9), 0.15 mol (Comparative Example 10), 0.20 mol (Comparative Example 11), 0.40 mol (Comparative Example 1)
A ceramic target for 2) was prepared.・ Preparation of ferroelectric film 150n thick by sputtering film formation method using the above target
A ferroelectric film was obtained in the same manner as in Example 1 except that a ferroelectric film of m was prepared. Obtained ((Pb _1-x La _x ) (Zr _y Ti _z ).
The O ₃ ) _1-a (La ₂ SiO ₅ ) _a film composition was determined. The x, y, z, and a of each film are also shown in Table 1. -Measurement and Evaluation of Ferroelectric Property of Film The measurement and evaluation of ferroelectric property of the film were performed in the same manner as in the example. The obtained results are also shown in Table 1.

Table 1 (La ₂ SiO ₅ ) Membrane pressure 5 V applied 0.8 V membrane composition Remarks 2 Pr 2 Ec residual x yz a Dipole polarization value (2Pr) mol nm μC / cm ² kV / cm μC / cm ² 0.02 50 ----- --0.02 0.50 0.50 0.02 Comparative Example 1 0.02 80 45 300 0.02 0.51 0.49 0.02 Comparative Example 2 0.02 100 51 231 11 0.02 0.50 0.50 0.02 Comparative Example 3 0.02 150 60 197 12 0.02 0.50 0.50 0.02 Comparative Example 7 0.05 50 40 251 27 0.02 0.51 0.49 0.06 Example 1 0.05 80 47 242 24 0.02 0.51 0.49 0.06 Example 2 0.05 100 51 237 22 0.02 0.51 0.49 0.06 Example 3 0.05 150 55 233 10 0.02 0.51 0.49 0.06 Comparison Example 8 0.07 50 39 251 28 0.02 0.51 0.49 0.07 Example 4 0.07 80 43 239 26 0.02 0.50 0.50 0.07 Example 5 0.07 100 48 234 23 0.02 0.50 0.50 0.07 Example 6 0.07 150 55 233 10 0.02 0.50 0.50 0.07 Comparative Example 9 0.15 50 35 242 32 0.02 0.50 0.50 0.14 Example 7 0.15 80 42 237 24 0.02 0.51 0.49 0.14 Example 8 0.15 100 48 233 22 0.02 0.51 0.49 0.14 Example 9 0.15 150 51 231 8 0.02 0.50 0.50 0.14 Comparative Example 10 0.20 50 36 244 28 0.02 0.51 0.49 0.19 Example 10 0.20 80 40 242 23 0.02 0.51 0.49 0.18 Example 11 0.20 100 44 240 19 0.02 0.51 0.49 0.19 Example 12 0.20 150 48 235 7 0.02 0.50 0.50 0.19 Comparative Example 11 0.40 50 25 303 8 0.02 0.51 0.49 0.38 Comparative Example 4 0.40 80 27 281 12 0.02 0.51 0.49 0.39 Comparative Example 5 0.40 100 15 274 10 0.02 0.51 0.49 0.39 Comparative Example 6 0.40 150 15 274 10 0.02 0.51 0.49 0.39 Comparative Example 12 From Table 1, the ferroelectric thin film of the present invention to which La2SiO5 is added is
When the applied voltage is 1 V or less, the remanent polarization value (2Pr) shows a value of ²⁰ μC / cm ² or more, which shows that the device can operate at a low voltage.

Applied voltage 1 for use as a ferroelectric memory
The larger 2Pr below V is, the better, but 18 μC / cm ² is practically desirable. Even with the film composition of the present invention, the film thickness is 100 n
If m is exceeded, good ferroelectric characteristics cannot be obtained at an applied voltage of 1 V or less.

Comparative Example 13 A target and a ferroelectric film were prepared in the same manner as in Example 1 except that excess PbO was not added, and the ferroelectricity was evaluated. None of the samples showed ferroelectricity.

Comparative Example 14 A target and a ferroelectric film were prepared in the same manner as in Example 1 except that the excess PbO was 0.4, and the ferroelectricity was evaluated. All samples had a large leak current and the ferroelectricity could not be measured.

(Examples 13 to 14) ・ Create target (Pb_1-XLa_x) (Zr_yTi_z) O₃so
x = 0, y + Z = 0.98, y: z = 52: 48, and (Pb_1-xL
a_x) (Zr_yTi_z) 0.15 mol excess of PbO per mol
, (La₂SiO_Five) Is 0.07 mol (Example 13), 0.15 mol
(Example 14) A ceramic target to be the
It was ・ Creation of ferroelectric film A film thickness of 80 nm is formed by the sputtering film formation method using the above target.
A ferroelectric film was prepared in the same manner as in Example 1 except that the ferroelectric film of
A dielectric film was obtained. Obtained ((Pb_1-xLa_x) (Zr _yTi_z)
O₃)_1-a(La₂SiO_Five)_aThe film composition was determined. Of each membrane
Table 2 shows x, y, z, and a. ・ Measurement and evaluation of ferroelectric properties of film The measurement and evaluation of the ferroelectric properties of the film were performed in the same manner as in the example.
It was The obtained results are shown in Table 2.

Table 2 (La ₂ SiO ₅ ) Film pressure 5 V applied 0.8 V film composition Remarks 2Pr 2Ec residual x yz a Dielectric polarization value (2Pr) mol nm μC / cm ² kV / cm μC / cm ² 0.07 80 44 245 23 0.0 0.51 0.49 0.07 Example 13 0.15 80 43 248 21 0.0 0.51 0.49 0.14 Example 14

(Examples 15 to 16) -Preparation of target By using (Pb _1-X La _x ) (Zr _y Ti _z ) O ₃ in the same manner as in the above-mentioned study example.
x = 0.06, y + Z = 0.98, y: z = 52: 48, and (Pb
_1-x La _x ) (Zr _y Ti _z ) 1 mol of PbO is 0.15 mol excess, and (La ₂ SiO ₅ ) is 0.07 mol (Example 15) and 0.15 mol (Example 16). Was produced.・ Preparation of ferroelectric film 80nm thickness by sputter deposition method using the above target
A ferroelectric film was obtained in the same manner as in Example 1 except that the above ferroelectric film was prepared. Obtained ((Pb _1-x La _x ) (Zr _y Ti _z ).
The O ₃ ) _1-a (La ₂ SiO ₅ ) _a film composition was determined. Table 3 shows x, y, z, and a of each film. -Measurement and Evaluation of Ferroelectric Property of Film The measurement and evaluation of ferroelectric property of the film were performed in the same manner as in the example. The results obtained are shown in Table 3.

Table 3 (La ₂ SiO ₅ ) Membrane pressure 5 V 0.8 V membrane composition Remarks 2Pr 2 Ec residual x yz a Dielectric polarization value (2Pr) mol nm μC / cm ² kV / cm μC / cm ² 0.07 80 41 219 25 0.06 0.51 0.49 0.07 Example 15 0.15 80 40 223 23 0.06 0.51 0.49 0.14 Example 16

(Examples 17 to 18) ・ Create target (Pb_1-XLa_x) (Zr_yTi_z) O₃so
x = 0.10, y + Z = 0.98, y: z = 52: 48, and (Pb
_1-xLa_x) (Zr_yTi_z) 0.15 mol excess of PbO per mol
Next to (La₂SiO_Five) Is 0.07 mol (Example 15), 0.15 mol
A ceramic target to be a (Example 16)
It was ・ Creation of ferroelectric film A film thickness of 80 nm is formed by the sputtering film formation method using the above target.
A ferroelectric film was prepared in the same manner as in Example 1 except that the ferroelectric film of
A dielectric film was obtained. Obtained ((Pb_1-xLa_x) (Zr _yTi_z)
O₃)_1-a(La₂SiO_Five)_aThe film composition was determined. Of each membrane
Table 4 shows x, y, z, and a. ・ Measurement and evaluation of ferroelectric properties of film The measurement and evaluation of the ferroelectric properties of the film were performed in the same manner as in the example.
It was The obtained results are shown in Table 4.

Table 4 Composition of (La ₂ SiO ₅ ) membrane pressure of 5V 0.8V membrane composition Remarks 2Pr 2Ec residual xyz a Dipole polarization value (2Pr) mol nm μC / cm ² kV / cm μC / cm ² 0.07 80 37 197 24 0.10 0.50 0.50 0.07 Example 17 0.15 80 34 201 22 0.10 0.50 0.50 0.15 Example 18

(Comparative Examples 15 to 16) ・ Create target (Pb_1-XLa_x) (Zr_yTi_z) O₃so
x = 0.12, y + Z = 0.98, y: z = 52: 48, and (Pb
_1-xLa_x) (Zr_yTi_z) 0.15 mol excess of PbO per mol
Next to (La₂SiO_Five) Is 0.07 mol (Example 15), 0.15 mol
A ceramic target to be a (Example 16)
It was ・ Creation of ferroelectric film A film thickness of 80 nm is formed by the sputtering film formation method using the above target.
A ferroelectric film was prepared in the same manner as in Example 1 except that the ferroelectric film of
A dielectric film was obtained. Obtained ((Pb_1-xLa_x) (Zr _yTi_z)
O₃)_1-a(La₂SiO_Five)_aThe film composition was determined. Of each membrane
Table 5 shows x, y, z, and a. ・ Measurement and evaluation of ferroelectric properties of film The measurement and evaluation of the ferroelectric properties of the film were performed in the same manner as in the example.
It was The results obtained are shown in Table 5.

Table 5 (La ₂ SiO ₅ ) Film pressure 5 V applied 0.8 V film composition Remarks 2Pr 2 Ec residual x yz a Dielectric polarization value (2Pr) mol nm μC / cm ² kV / cm μC / cm ² 0.07 80 29 189 15 0.12 0.51 0.49 0.07 Comparative example 15 0.15 80 27 195 12 0.12 0.51 0.49 0.14 Comparative example 16

(Comparative Examples 17-18) ・ Create target (Pb_1-XLa_x) (Zr_yTi_z) O₃so
x = 0.02, y + Z = 1.2, y: z = 52: 48, and (Pb_1-x
La_x) (Zr_yTi_z) 0.15 mol excess of PbO per mol
, (La₂SiO_Five) Is 0.07 mol (Example 17), 0.15 mol
(Example 18) A ceramic target to be the
It was ・ Creation of ferroelectric film A film thickness of 80 nm is formed by the sputtering film formation method using the above target.
A ferroelectric film was prepared in the same manner as in Example 1 except that the ferroelectric film of
A dielectric film was obtained. Obtained ((Pb_1-xLa_x) (Zr _yTi_z)
O₃)_1-a(La₂SiO_Five)_aThe film composition was determined. Of each membrane
Table 6 shows x, y, z, and a. ・ Measurement and evaluation of ferroelectric properties of film The measurement and evaluation of the ferroelectric properties of the film were performed in the same manner as in the example.
It was The obtained results are shown in Table 6.

Table 6 (La ₂ SiO ₅ ) Membrane pressure 5 V applied 0.8 V applied film composition Remarks 2Pr 2Ec remaining residue x yz a Dipole polarization value (2Pr) mol nm μC / cm ² kV / cm μC / cm ² 0.07 80 20 331 2 0.02 0.61 0.59 0.07 Comparative Example 17 0.15 80 15 351 2 0.12 0.61 0.58 0.15 Comparative Example 18

(Comparative Examples 19 to 20) -Preparation of Target By using (Pb _1-X La _x ) (Zr _y Ti _z ) O ₃ in the same manner as in the above-described study example.
x = 0.02, y + Z = 0.90, y: z = 52: 48, and (Pb
_1-x La _x ) (Zr _y Ti _z ) 1 mol of PbO is 0.15 mol excess, and (La ₂ SiO ₅ ) is 0.07 mol (Example 17) and 0.15 mol (Example 18). Was produced.・ Preparation of ferroelectric film 80nm thickness by sputter deposition method using the above target
A ferroelectric film was obtained in the same manner as in Example 1 except that the above ferroelectric film was prepared. -Measurement and Evaluation of Ferroelectric Property of Film The measurement and evaluation of ferroelectric property of the film were performed in the same manner as in the example. All samples had a large leak current and the ferroelectricity could not be measured.

[0033]

As described above, it is composed of lead, zircon, titanium, lanthanum, and oxygen, and (Pb _1-x La _x )
In (Zr _y Ti _z ) O ₃ , x is 0 or more and 0.10 or less, and (y + z) is 0.95 to
If the ferroelectric thin film of the present invention formed as a mixture of the compound represented by 1.0 and a metal silicate is used, a thin film that can operate even at a low voltage of 1 V or less can be obtained. It is composed of lead, zircon, titanium, lanthanum, and oxygen, and (Pb _1-X La _x ) (Zr _y Ti _z ) O ₃ where x is 0 or more and 0.10 or less, (y + z) is 0.95 to Compound represented by 1.0 and Pb
A mixture of O and a metal silicate, (Pb _1-X La _x ) (Zr _y
Ti _z ) O ₃ is 1 mol, PbO is 0.02 to 0.30 mol,
When a thin film is obtained with a target prepared by using the target material for preparing a ferroelectric thin film of the present invention having a metal silicate content of 0.05 to 0.20 mol, the ferroelectric thin film of the present invention is obtained.

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Claims (3)

[Claims] 1. It is composed of lead, zircon, titanium, lanthanum, and oxygen, and (Pb _1-x La _x ) (Zr _y Ti _z ) O ₃ where x is 0 or more and 0.10 or less, (y + z) Is formed as a mixture of a compound expressed by 0.95 to 1.0 and a metal silicate, and its thickness is 100n.
A ferroelectric thin film having a thickness of m or less. 2. The metal silicate is represented by the chemical formula La ₂ SiO ₅ , and the composition of the dielectric thin film containing this is ((Pb _{1 -x} La _x ).
(Zr _y Ti _z ) O ₃ ) _1-a (La ₂ SiO ₅ ) _a , where a is 0.05 to 0.20
The ferroelectric thin film according to claim 1, wherein 3. It is composed of lead, zircon, titanium, lanthanum and oxygen, and (Pb _1-X La _x ) (Zr _y Ti _z ) O ₃ where x is 0 or more and 0.10 or less, (y + z) Is expressed as 0.95 to 1.0 and Pb
A mixture of O and a metal silicate, (Pb _1-X La _x ) (Zr _y
Ti _z ) O ₃ is 1 mol, PbO is 0.02 to 0.30 mol,
A sputtering target material for preparing a ferroelectric thin film, characterized in that the metal silicate content is 0.05 to 0.20 mol.