JPH0334580A - Electronic parts - Google Patents

Abstract

PURPOSE:To prevent the crack generation of the ferroelectric substance film sandwiched by electrodes by forming a first ferroelectric film through an insulating layer on a silicon substrate, and providing at least one or more layers of second ferroelectric films, in the condition of being sandwiched by the electrodes, on the ferroelectric substance film. CONSTITUTION:This is made in such structure that a first ferroelectric substance film 3 is formed through an insulating layer 2 or a silicon substrate 1, and that at least one or more layers of second ferroelectric film 6 are provided, in the conditions of being caught by electrodes 5 and 7, on the ferroelectric substance film. Hereby, the difference of thermal expansion coefficient of the insulating layer 2 and the second ferroelectric substance film 6 by thermal effect can be approximated by suppressing it with the first ferroelectric film 2 formed on the insulating layer, so electric parts high in reliability can be obtained, in which the crack generation of the second ferroelectric substance film sandwiched by electrodes is prevented. Moreover, by providing an oxide layer, which has at least one kind among Mg and Zr for its main ingredient, as a ground layer for the first ferroelectric substance film, the composition changes of the first and second ferroelectric substance films are suppressed.

Description

[Detailed description of the invention] C Purpose of the invention] (Industrial application field) The present invention relates to an electronic component including a ferroelectric thin film.

(Prior art) Ferroelectric thin films have recently been used in pyroelectric infrared sensor optical switches, display devices, FETs, ferroelectric memories, etc. as electronic components become more sophisticated, smaller in size, and more highly integrated. It is used. The ferroelectric thin film usually uses perovskite oxide in many cases.
T (solid solution of PbT10. and PbZr0i) PLZT
(PZTI, added with La) is typically used, but other materials such as LI Ta O, Li
Nb Oq KTa Os, KNbOi or B14
Bismuth titanate series such as Tl 2012, BaTi0
i series, 5rTi03 series, etc. are also used. PbTl
There are examples where Oi is used for pyroelectric sensors and PLZT is used as optical switches.

Incidentally, as electronic components (for example, ferroelectric memories) equipped with ferroelectric thin films, electronic components having the following structure are conventionally known. That is, Sl s N4 and Sj 0 are deposited on a silicon substrate on which semiconductor elements, wiring, etc. have already been formed.
2. A first insulating layer made of Si02 glass, PSG (phosphosilicate glass), etc. is coated, and a lower electrode formed by vapor deposition and buttering of an electrode material layer such as Pt is provided on this insulating layer, and A ferroelectric thin film is formed on this lower electrode, and an upper electrode is further formed on this ferroelectric thin film by vapor deposition and patterning of an electrode material layer such as Pt. A ferroelectric thin film in a ferroelectric memory having such a structure is formed by a CVD method, a sputtering method, or a vacuum evaporation method. At this time, in order to crystallize the ferroelectric thin film, the substrate is heated to a high temperature of 500 to 800[deg.] C. during the film formation process, and annealing is performed at the same temperature after film formation.

However, in electronic components with the above structure, PbT
Since the coefficient of thermal expansion is different between the ferroelectric thin film made of iO3, PZT and the insulating layer made of 5in2 or the like on which the thin film is formed, cracks occur in the thin film portion during the formation of the ferroelectric thin film. As a result, leakage occurs between the lower electrode and the upper electrode 7 that sandwich the ferroelectric thin film above and below, resulting in a problem of significantly lowering the reliability of the electronic component.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and provides a highly reliable electronic component that prevents the occurrence of cracks in the ferroelectric thin film sandwiched between electrodes. This is what I am trying to do.

[Structure of the Invention] (Means for Solving the Problems) The electronic component of the present invention includes a first ferroelectric thin film formed on a silicon substrate via an insulating layer, and a second ferroelectric thin film formed on the ferroelectric thin film.
The device is characterized in that at least one layer of ferroelectric thin film is provided between electrodes.

The ferroelectric materials constituting the first and second thin films may be the same or different, but from the viewpoint of approximating the coefficient of thermal expansion and productivity, the first and second thin films may be made of the same ferroelectric material. It is desirable to form a Examples of such ferroelectric materials include Pb 2 O, a solid solution of PbT10i and PbZrO3 (PZT), and a perovskite oxide mainly composed of PZT, such as PLZT, which is PZT with La added. The thickness of the first ferroelectric thin film is preferably in the range of 1,000 to 1,000 mm.

The insulating layer is made of, for example, Sl 3 N4, Si 02,
It is made of SiO2 glass, PSG, etc.

The electrodes are made of, for example, PL.

Another electronic component of the present invention has a structure in which an oxide layer containing at least one of Mg and Zr as a main component is provided as a base layer of the first ferroelectric layer.

Examples of the above-mentioned oxide containing Mg as a main component include Mg
Examples of oxides containing Zr as a main component include ZrO. The thickness of such an oxide insulating layer is preferably 500 Å or more. The reason for this is that when the thickness is less than 500 Å, a barrier is formed to prevent PB, which is a component of the ferroelectric, from diffusing toward the substrate during high-temperature heating of the substrate to crystallize the ferroelectric thin film. This is because it becomes difficult to make it act as a layer.

(Function) According to the present invention, the first
By forming a ferroelectric thin film and providing at least one layer of a second ferroelectric thin film on the ferroelectric thin film with electrodes sandwiching the second ferroelectric thin film, the second ferroelectric thin film is
The difference in thermal expansion coefficient of the ferroelectric thin film with respect to the insulating layer can be suppressed and approximated by the first ferroelectric thin film formed on the insulating layer. It is possible to obtain a highly reliable electronic component that prevents the occurrence of clubbing and scratching of the body thin film.

Furthermore, Mg and Zr are used as the base layer of the first ferroelectric thin film.
An oxide WA containing at least one of the following as a main component (for example, M
g 01ZrO A suitable orientation (orientation in the axial direction of polarization) is possible.

In other words, for electronic components having a structure in which a ferroelectric thin film is sandwiched between electrodes and this is provided on an insulating film of a silicon substrate, the substrate is heated to a high temperature and annealed to crystallize the ferroelectric thin film. Components such as PB constituting the dielectric diffuse into the insulating film made of 5H02 glass, PSG, etc., through the lower electrode made of PT. As a result, not only the resistivity of the insulating film decreases, but also the composition of the ferroelectric thin film changes and the lattice matching at the interface with the electrode is disturbed, causing a problem of deterioration of the characteristics of the ferroelectric thin film. For this reason, by providing an oxide layer such as MgO or ZrO2 on the base layer of the first ferroelectric thin film, that is, an insulating film such as SIO□, the second ferroelectric thin film provided on the electrode In high-temperature heat treatment for crystallizing the ferroelectric thin film, diffusion of Pb, etc., which is a constituent of the first ferroelectric, into the insulating film can be prevented by the barrier action of the oxide layer. In history,
Since the composition of the first ferroelectric thin film does not change, it is also possible to prevent PB, etc., which are the constituent components of the second ferroelectric thin film, from diffusing through the electrode below. As a result, 5IO
The resistivity of the second insulating film can be lowered, and composition fluctuations of the second ferroelectric thin film sandwiched between the electrodes can be suppressed to maintain the ferroelectric properties of the thin film in a good state.

Further, in order to improve the ferroelectric properties of the ferroelectric thin film, it is desirable that the axis of polarization be oriented.

Orientation of a ferroelectric thin film is greatly influenced by its underlying layer. The orientation of the base layer is greatly influenced by the layer below it. The electrode made of Pt, which is the base of the second ferroelectric thin film, is easily oriented in <111> by sputtering or the like, but the insulating film, which is the base of the first ferroelectric thin film, is Since it is made of Sl 02 or the like, the first ferroelectric thin film cannot be oriented in the <100> direction, and it is difficult to orient the PT lower electrode in the <100> direction. As a result, it becomes difficult to orient the ferroelectric thin film with the Pt lower electrode as the base layer in the <100> direction, and it becomes difficult to orient the ferroelectric thin film in the optimal direction such as <100> depending on its composition etc. The problem was that I couldn't do it. On the other hand, the MgO or ZrO2 oxide layer can be oriented in <100>, <100>, etc. directions by changing the sputtering conditions for depositing it, so that The first ferroelectric thin film and electrode formed on the substrate can also be oriented in the same direction. As a result, the second ferroelectric thin film, which is based on the electrode, can also be oriented in these directions, making it possible to achieve an orientation suitable for the composition of the thin film (orientation in the polarization axis direction), resulting in excellent ferroelectric properties. It is possible to obtain electronic components having characteristics.

(Example) Hereinafter, an example of the present invention will be described in detail together with a manufacturing method shown in the drawings.

Example 1 First, an insulating film 2 made of Sl 02 glass is deposited on a silicon wafer 1 on which semiconductor elements and wiring have already been formed, and then an oxide film 2 made of MgO with a thickness of 5000λ is deposited on the entire surface by RF magnetron sputtering under the following conditions. A material layer 3 was formed (as shown in FIG. 1(a)). M thus formed
The oxide layer 3 made of gO is crystallized and has a thickness of <10
0> direction.

(MgO film formation conditions) Target: 5-inch φ MgO ceramic wafer bonded to a water-cooled Cu plate Temperature: 500°C Gas: Ar10□ Gas pressure: 0.5Pa Distance M between wafer and target: 1oOa+11 Power/target: 200 W Next, a first Pb Tl 03 thin film 4 for the base layer with a thickness of 2000 was deposited on the entire surface of the oxide layer 3 by RF magnetron sputtering under the following conditions (see Fig. 1(b)).
). The thin film 4 thus formed had a single phase and exhibited strong <001> orientation.

(Film formation conditions for PbTlOi) Target: 5 inch φ Pb Tl 03 ceramic wafer bonded to a water-cooled Cu plate Temperature: 600°C Gas: Ar/02 Gas pressure: 0.8 Pa Distance between wafer and target: 100 μm power/target; 200 W Next, the entire surface of the PbT10i thin film 4 was subjected to R under the following conditions.
A Pt film with a thickness of 2000 μm was formed by F magnetron sputtering. In this case, the temperature of wafer l is set to 60
By raising the temperature to 0℃, the PT film becomes the same as the base < 100
> direction. lower wafer temperature,
For example, if the temperature is kept at about room temperature, it will not be affected by the underlying material and will be oriented in the <111> direction. Thereafter, the Pt film was patterned by ion milling to form the first electrode 5 (as shown in FIG. 1(c)).

(Pt film formation conditions) Target: 5 inch φ PT plate bonded to water-cooled Cu plate Wafer Temperature: 600°C Gas: A Gas pressure: 0.5 Pa Distance between wafer and target: 110G5 power/target ; 500W Next, the Pb Tl 03 thin film 4 including the first electrode 5 was heated.
A second Pb T10.0 film with a thickness of 5000 Å was deposited on top of the thin film by RF magnetron sputtering under the same conditions as the thin film. A thin film was formed. The PbTlO3 thin film thus formed had a single phase, similar to the first thin film 4, and exhibited strong orientation in the <001> direction. Next, the pb'rto
After forming a resist pattern (not shown) on the thin film by photolithography, the thin film is selectively etched using an IF etching solution using the resist pattern as a mask to form a PbT10s thin film pattern 6 on the electrode 5. Formed. After this, the resist pattern was removed.

Subsequently, a resist pattern (not shown) was formed by photolithography, and then a Pt film with a thickness of 2000 Å was formed on the entire surface including the resist pattern under the same conditions as described above (however, the wafer temperature was room temperature). Then, a second electrode 7 was formed on the PbTiO3 thin film pattern 6 by patterning by a lift-off method in which the resist pattern and the Pt film thereon were removed (the first
Figure (d) (illustrated).

When the remanent polarization of the ferroelectric thin film element of Example 1 was measured as a ferroelectric property, a large remanent polarization was obtained because the Pb Ti O thin film pattern 8 had a strong orientation in the <001> direction. It was confirmed that it has excellent ferroelectric properties. Furthermore, before forming the second electrode 7, P
When the bT10g thin film pattern 6 was observed with an electron microscope, it was confirmed that it had a good film structure with no cracks.

Example 2 The second a electrode 7 was made of PbT1 by the same method as in Example 1.
It was formed on the 0i thin film pattern B. Subsequently, RF magnetron sputtering was performed under the same conditions as in Example 1 to give a thickness of 5 mm.
000 Å thick PbT103 thin film is formed and selectively etched to form a second PbT10. After forming a thin film pattern 8, a third electrode 9 made of PT was further formed on the thin film pattern 8 to produce a ferroelectric thin film element (as shown in FIG. 2).

Regarding the ferroelectric thin film element of Example 2, when residual polarization was measured as a ferroelectric property, it was found that Pb TI O and thin film pattern 6.8 each had a strong orientation in the <001> direction, so a large residual polarization was observed. It was confirmed that the material had excellent ferroelectric properties. Also, a PbTjOi thin film pattern 6 sandwiched between the first and second electrodes 5.7, and a second PbT1 sandwiched between the second and third electrodes 7.9.
The Oi thin film patterns 8 can be used as independent ferroelectric layers.

Example 3 First, an insulating film made of SiO2 glass was deposited on a silicon wafer on which semiconductor elements and wiring had already been formed, and then an oxide layer made of Zr02 with a thickness of 5000λ was deposited on the entire surface by RF magnetron sputtering under the following conditions. A film was formed. The oxide layer made of Zr 2 O 2 thus formed was crystallized and oriented in <100>.

(ZrO film formation conditions) Target: 5 inch φ ZrO2 ceramic wafer bonded to water-cooled Cu plate Temperature: 500°C Gas: Ar10□ Gas pressure: 0.5 Pa Distance between wafer and target: 100+A power /
Target: 200W Next, the first PbTl0 was heated in the same manner as in Example 1.
i thin film, first electrode made of pt, Pb TI O*F
A ferroelectric thin film element having the same structure as that shown in FIG. 1(d) described above was manufactured by forming an IF film pattern and a second electrode made of Pt.

Regarding the ferroelectric thin film element of Example 3, PbT10
Since the i thin film pattern has a strong orientation in the <001> direction, it was confirmed that a large residual polarization was obtained and that it had excellent ferroelectric properties. Furthermore, when the PbTiOi thin film pattern was observed using an electron microscope, it was confirmed that it had a good film structure without cracks.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to prevent the occurrence of cracks in the ferroelectric thin film sandwiched between electrodes, and it is also possible to prevent cracks from occurring in the ferroelectric thin film sandwiched between the electrodes, and to prevent the occurrence of cracks during high-temperature heating of the substrate for crystallizing the ferroelectric thin film. It is possible to prevent the diffusion of ferroelectric components into insulating films, etc., and it is also possible to orient the ferroelectric thin film in a direction depending on its composition. Electronic components such as dielectric thin film elements and pyroelectric sensors can be provided.

[Brief explanation of drawings]

1(a) to (d) are cross-sectional views showing the manufacturing process of a ferroelectric thin film element according to Example 1 of the present invention, and FIG. 2 is a ferroelectric thin film element obtained according to Example 2 of the present invention. FIG. l...Silicon wafer, 2...Insulation M, 3...M
g An oxide layer consisting of O, 4...PbTiOi thin film,
5.7.9... Electrode, 6.8... Pb Tl 03
Thin film pattern.

Claims (2)

[Claims] (1) A first ferroelectric thin film is formed on a silicon substrate via an insulating layer, and at least one layer of a second ferroelectric thin film is provided on the ferroelectric thin film with electrodes sandwiched therebetween. An electronic component characterized by: (2) Mg and Zr as the base layer of the first ferroelectric thin film
2. The electronic component according to claim 1, further comprising an oxide layer containing at least one of the following as a main component.