JPS60121605A - Composite dielectric film and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a composite dielectric film and a method for manufacturing the same, and this composite dielectric film is used as a dielectric film used in semiconductor devices, solid-state display devices, etc. It is something that can be done.

Conventional Structures and Their Problems In dielectric films used in semiconductor devices and the like, the electric field strength applied thereto often has a high value of 105v/6n or more. Therefore, in such applications, the dielectric film must have a sufficiently high breakdown voltage. The dielectric film is
Vapor deposition, sputtering.

The film is manufactured by a method such as CVD, but in either case, defects may occur due to dust adhering to the substrate before film formation or pinholes generated during film formation, causing dielectric breakdown. When dielectric breakdown occurs in a dielectric film, there are two cases: a so-called self-healing dielectric breakdown, in which the dielectric film becomes short-circuited after the breakdown, and a so-called self-healing dielectric breakdown, in which the dielectric film becomes open after the breakdown. Among the self-healing non-breakdown dielectric films that cause dielectric breakdown leading to short-circuit conditions, some have a dielectric constant of 100 or more and a dielectric breakdown electric field of about IMV/cm. However, unless this dielectric breakdown property is self-healing, it cannot be applied as a dielectric film for various electronic devices.

Even in the case of an insulating film that does not self-heal, this mode of dielectric breakdown can be made less likely to occur if the upper electrode is made extremely thin. For example, when a thin Au electrode of about 20 nm is used, self-healing dielectric breakdown can be achieved. However, if it is made too thin, the resistance becomes high and it is not suitable as an electrode, so the minimum thickness is about several tens of nanometers. In addition to Au, Zn,
Self-recovery dielectric breakdown can also be achieved by using Al. However, the upper electrode is made of thin Au with a thickness of several tens of nanometers.
There are dielectric films that do not undergo self-healing dielectric breakdown even when using Zn or AI electrodes. Although the cause is not clear, it is assumed that dielectric breakdown in this state is caused by the inherent properties of the material. On the other hand, it has been discovered that there are electric films that have a dielectric constant of 20 or less but a dielectric breakdown electric field of 3 MV/an or more, and that there are some that undergo self-healing dielectric breakdown in which the dielectric breakdown state becomes open. However, since the dielectric constant is low, unless the film thickness is thinned, the same capacitance as a film with a high dielectric constant cannot be obtained, so it has the advantage of having a large dielectric breakdown electric field and self-recovery as the circuit opens after dielectric breakdown. In some cases, the advantage of doing so could not be utilized. In particular, among the dielectric films mentioned above that have a high dielectric constant but become short-circuited after dielectric breakdown, there are many materials with very excellent properties; However, the dielectric breakdown spread over a wide area, making it difficult to use in electronic devices.

Purpose of the Invention The present invention has been made in view of the above-mentioned points. The purpose is to use it in electronic components.

Structure of the Invention The structure of the present invention has a relative dielectric constant ε1. On a dielectric film (thickness d,) that does not undergo self-healing dielectric breakdown in the dielectric breakdown electric field F1,
Specific dielectric constant ε2 smaller than ε1. A self-healing dielectric film (thickness d
2) respectively applied voltage V1. vl for v2
＜dlFl〈V2〈d2F2 By laminating a film with a thickness that satisfies the conditions and forming an upper electrode on top of it, the dielectric breakdown that occurs at the defective part in the film can be self-healed, making it possible to create a dielectric material with high capacitance. This allows the membrane to be used in electronic devices.

Description of examples Hereinafter, details of the present invention will be explained together with examples.

FIG. 1 is a diagram showing the structure of an embodiment of the composite dielectric film of the present invention. In the figure, 11 is a substrate, on which a lower electrode 12 is formed. 13 has a dielectric constant of 81. 014, which is the first dielectric film that is in a dielectric breakdown state that does not self-recover with a dielectric breakdown electric field F1, has a dielectric constant ε2 of the first
The upper electrode 15 is formed on the second dielectric film, which is smaller than the dielectric film 13 of FIG. Usually, films having various functions are often formed between the lower electrode 12 and the dielectric film 13 or between the dielectric films 13 and 14. With this configuration, even if a hole 16 is formed in the dielectric film due to dielectric breakdown that occurs below the driving voltage due to a defect in the film, the properties of the upper dielectric film will be exhibited, and the upper electrode 16 will remain intact. It scatters around the hole 16, creating an electrically open circuit, and the dielectric breakdown can be self-recovered.

The features of the composite dielectric film according to the present invention are shown in the equivalent circuit of FIG. The permittivity, applied voltage, applied electric field, and film thickness electric capacitance of the first dielectric film 13 and the second dielectric film 14 are determined by ε.
1. ε2. ``1.■2' ``1. E2. dl, d2C1
, C2. The capacitance C of this composite membrane is C-(C1+02)...(1) =S(d1/61+d2/62>-1...() where S is the electrode area.
It can be expressed as 2). Therefore, the dielectric constant ε of the entire composite film is ε−d(d1/ε1+d2/ε2)−1・・・・・・(
3) is given by On the other hand, if the voltage applied to the entire composite film is V, the voltage ■1°F2 applied to each layer is "1"(cl-"102-')-1, (+)
1 F2-- (c,-1+c2')' ・・・・・・-
(5) 2, and the electric field strength E1 of each dielectric film 13.14. E2 is E1=~(C1"-"+02") -1・-
・(6)1d1 E2== −(C1-1+02-1)−” =(7)2
It can be expressed as d2.

Here, the dielectric constant ratio ε1/ε2 of each dielectric film. Voltage ratio V1
/V2. Electric field strength ratio E1/E2 and film thickness ratio d1/d2
There is the following relationship between them.

ε1/ε2−ε2/ε1... (8) ■1/■2=
(ε2d1)/(ε1d2) (9) Generally, the dielectric breakdown of a composite dielectric film is determined by the dielectric strength voltage of each layer. In this case, the dielectric film 13 is d, Fl, and the dielectric film 14 is d
It is 2F2. Here, Fl and F2 are dielectric breakdown electric fields of each dielectric. Therefore, when a dielectric film that does not undergo self-healing dielectric breakdown and a dielectric film that exhibits self-healing dielectric breakdown are combined as a composite dielectric, the conditions for the dielectric breakdown to be self-healing are as follows: (1) Self-healing dielectric breakdown (2) The voltage applied to the dielectric film that causes self-healing dielectric breakdown is higher than the withstand voltage of the dielectric film that does not cause self-healing dielectric breakdown (F2>dlFl) At 02 points One thing has become clear from the experimental facts. This (1)
, (2) in other words, the voltage v1 applied to the dielectric film on the lower electrode side is smaller than the voltage v2 on the dielectric film on the upper electrode side, which can be expressed by the following equation.

vl<dlFl<F2<d2F2 (1o) The following two types of dielectric breakdown mechanisms can be considered under this condition. (1) The lower dielectric layer 13 becomes short-circuited due to a defect in the film, and the entire voltage ■(=■1+■
2) is applied and the withstand voltage d2F2 is exceeded, (2) the entire voltage is applied to the lower dielectric layer due to the defect in the upper dielectric layer 14, the withstand voltage d1F1 is exceeded, a short circuit occurs, and furthermore, in the local area of the upper dielectric layer This is a case where the applied voltage exceeds the breakdown voltage d2F2. In both cases, it can be seen that dielectric breakdown of the composite film occurs only when the upper dielectric layer undergoes dielectric breakdown. That is, dielectric breakdown is dominated by the dielectric material that undergoes self-healing dielectric breakdown on the upper electrode side.

Furthermore, in general, dielectric films with a high dielectric constant tend to have a low dielectric breakdown electric field, and since high dielectric constant films are less likely to undergo self-healing dielectric breakdown, the above conditions ε1>ε2. Fl<F2 - (11) increases the degree of freedom in selecting the cumulative month and is convenient in terms of design. Furthermore, since the overall permittivity ε of the composite dielectric is given by equation (3), ε
It is better for both 1/d1 and ε2/d2 to be large, and conversely, the lower of the two will control the overall dielectric constant. In order to obtain high capacitance, it is possible to reduce the film thickness, but
Since the dielectric strength voltage decreases, it is ideal to use a dielectric material with a high dielectric constant and a high withstand voltage, and whose dielectric breakdown is self-healing. However, according to the present invention, by knowing in advance the dielectric constant and dielectric breakdown electric field of the dielectric film that does not cause self-healing dielectric breakdown, we can create a structure in which dielectric films that exhibit self-healing dielectric breakdown are laminated. The excellent properties of a high dielectric material can be utilized. In fact, in order to manufacture a composite dielectric according to the present invention based on this design, it is initially considered to utilize a dielectric film consisting of two different compositions, on the one hand, strontium titanate and When a dielectric film is formed by sputtering using a composite oxide sintered body such as a solid solution of barium titanate as a target, if the film is formed at a substrate temperature of 200°C or less, the dielectric constant is less than 20, which is still When a film is formed at a substrate temperature of 400'C or higher, the dielectric constant becomes 100 or higher, and films with different dielectric properties can be obtained even if the same rare gas and oxygen gas are flowed and the gas pressure is constant.

A further noteworthy point is that some of the films with low dielectric constants (20 or less) obtained when the substrate temperature is kept below 200'C.
There is a film that undergoes self-healing dielectric breakdown, and on the other hand, when the substrate temperature is
When the temperature is 00'C or higher, there are films that have a high dielectric constant but do not undergo self-healing dielectric breakdown, and the composite dielectric structure of the present invention can also be applied to this case.

[Example 1] A transparent conductive film of indium tin oxide was deposited on a glass substrate to a thickness of 300 nm by electron beam evaporation, and this was used as a lower electrode. On top of this S r Z ro, 2T 1o
, 8os film was deposited to a thickness of 760 nm by magnetron RF sputtering method. Target yt-(!
: A sintered body of 5rZr0.2TI0.803 was used. The sputtering gas contains oxygen and argon in a ratio of 1:4.
using a mixture of gases.

Gas pressure is 0.6 Pa. The substrate temperature was 400°C. The thus obtained elements were designated as four-part elements 1 to 4.

A 45 nm thick BaTa 206 film was further deposited on element 2 by magnetron RF sputtering. Similarly to element 2, element 3 has B a T a 2
06 film was deposited to a thickness of 280 nm, and a 700 nm film was deposited on element 4.
n and m were attached. As a target, BaTa2O
A sintered body of No. 6 was used. 02 and A for sputtering gas
Using a 1:4 mixed gas of r, the gas pressure. , 1Pa
And so. The substrate temperature is 100'C.

In addition, the lower dielectric film S r Z ro, 2T
1o, 5o3) The film thickness was 380 nm, and elements 2,
As in 3.4, B a T a 2 is used as the upper dielectric film.
06 at 45 nm, 270 nm.

Element sputtered with a thickness of 700 nm 6°6.
7 was produced. Next, an AI film with a thickness of 100 nm was deposited on the elements 1 to 7 by resistance heating vapor deposition, and this was used as an upper electrode. Table 1 shows the characteristics of the thin film capacitor thus formed.

Note: Table 1 in the margin below *Measurement frequency I KHz **SZT is S r Z ro, 2T 1 o,
Abbreviation for so3 ***BT is an abbreviation for B a Ta a206 △ "Au electrode (20 nm) is used for the two-part electrode.However,
When measuring the dielectric breakdown electric field, for elements 1 and 2°6,
Since a short circuit occurred when a voltage was applied and measurement was no longer possible, the dielectric breakdown electric field was measured using a 20 nm thick vapor deposited gold film as the upper electrode instead of the AI film.

From this result, S r Z ro, 2T 1 o,
The dielectric constant of the SOS dielectric film (hereinafter abbreviated as SZT film) is 107, the dielectric breakdown electric field is 1.1 MV/cm, and B
aT a 206 Dielectric film (hereinafter abbreviated as BT film)
It is calculated from equations (3), (4), and (12) that the dielectric constant of is 21 and the dielectric breakdown electric field is 3.6 MV/cn. Here, regarding the structure of the SZT film and the BT film, the inequality (10) necessary for designing the composite dielectric film mentioned above is used.
The side results for are shown. Dielectric constant ε of the first dielectric film
1 is 107, and the dielectric breakdown electric field F1 is 1, 1 hi
V/crn, film thickness d1 is 760 nm, 380 n
m, the dielectric constant ε2 of the second dielectric film is 21, the dielectric breakdown electric field F2 is 3.5 MV, 4 seas, and the film thickness d2 is Onm.
, 45 nm, 270 nm, 280 nm.

700 nm, the characteristics of the composite dielectric film corresponding to elements 1 to 7 are expressed by formulas (1), (2), (4), (5
), the voltage v1゜v2 and electric capacity C (C-ε
08TS/d) and further dlFl and d2
F2 was calculated and summarized in Table 2.

From this table, it can be seen that elements 3, 4, and 6.7 satisfy inequality (10), while elements 1 and 2.6 do not.
2, 5id, a short-circuit state occurs, but the elements 3□4, 6.7 are in an open state from the initial stage, which corresponds to whether inequality (1o) holds true.

Lower margin [Example 2] A transparent conductive film of indium tin oxide was deposited to a thickness of 300 nm on a glass substrate by electron beam evaporation, and this was used as a lower electrode. On top of this, S ro, eB ao, 4
A T tos film was deposited to a thickness of 70 nm (=1) by magnetron RF sputtering.S
Sintered bodies of r o, eB ao, and 4T103 were used. The sputtering gas contains oxygen and argon, 1=4.
The gas pressure was set to 0.8 Pa. The substrate temperature was 380'C. The device thus obtained was divided into two parts, forming devices 1 and 2. Device 2 was further processed by magnetron RF sputtering using the same target at a substrate temperature of 200'C. A 700 nm thick S ro, eB ao, 4T IQ3 film was deposited. Also, in the same manner as above, a S ro, eB ao, 4T IQ3 film with a substrate temperature of 200° C. was deposited on a substrate on which a transparent conductive film was deposited on a glass substrate.
Element 3 was fabricated to which an eBao, 4T 103 film was attached. Next, an Al film with a thickness of 1100 nm (=j) was deposited on the soil of elements 1 to 3 by resistance heating vapor deposition, and this was used as an upper electrode.Table 3 shows the characteristics of the thin film capacitor thus formed. Element 1 was in a short-circuit state at the time of dielectric breakdown, and the dielectric breakdown propagated, but elements 2 and 3 were in an open state. This result is similar to the result of Example 1. Therefore, the same composition It has become clear that even when using a sintered body of as a target, films with different dielectric properties and dielectric breakdown states can be formed by sputtering simply by changing the substrate temperature, and the composite dielectric thin film according to the present invention can be formed. Ta.

This difference in film quality is presumed to be due to the difference in crystallinity within the film, which is related to dielectric properties.

Some of these included ferroelectric materials and exhibited piezoelectric and pyroelectric electro-optic effects with polarized films.

As described in detail below, the present invention uses a gold electrode (thickness: 20 nm) as the third surface water upper electrode.According to the present invention, the present invention has various excellent physical properties, but has no self-healing dielectric breakdown, that is, no electric resistance. By laminating a dielectric film that undergoes self-healing dielectric breakdown, that is, becomes electrically open, on top of a dielectric film that becomes short-circuited when the film thickness is determined by considering the dielectric breakdown electric field and dielectric constant of each film. , the dielectric breakdown that occurs at the defective portion is self-healing, and the excellent physical properties of the dielectric film, which does not have self-healing dielectric breakdown when used alone, can be fully utilized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of a composite dielectric material according to an embodiment of the present invention, and FIG. 2 is a diagram showing an equivalent circuit of the composite dielectric material shown in FIG. 1. 11... Substrate, 12... Lower electrode, 13...
Pa... Self-healing dielectric film that does not break down, 14...
...Dielectric film with self-healing dielectric breakdown, 16...
Upper electrode, 16...Dielectric breakdown hole. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure (phantom (b)) Figure 2

Claims (2)

[Claims] (1) Relative dielectric constant ε, film thickness d1. On the self-healing type non-breakdown first dielectric film of the dielectric breakdown electric field F1, a dielectric constant ε2 (where ε2<ε1), a film thickness d2. Breakdown electric field F
A second dielectric film that undergoes self-healing dielectric breakdown which becomes an open circuit after dielectric breakdown of F2>Fl is laminated, and these first dielectric films are laminated. The voltage applied to each of the second dielectric films is 1.
■ When 2, the film thickness d1 of the first degree second dielectric film
．． A composite dielectric film characterized in that it satisfies the condition of d2 power <dlFl<F2<d2F2. (2) Using a sintered body of the same composition as a target and changing the substrate temperature, a self-healing dielectric film that does not cause dielectric breakdown and a dielectric film that causes self-healing dielectric breakdown are formed by sputtering. A method for manufacturing a composite dielectric film.