JP2002151353A - Dielectric thin film, manufacturing method therefor, and temperature-compensating capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature-compensating capacitor, in which the capacity temperature coefficient has negative sign and an absolute value of the order of 100 ppm/K. SOLUTION: A temperature-compensating capacitor 1 of the present invention includes a silicon hydride oxidation film composed of a silicon atom, an oxidation atom, and a hydrogen atom between a lower electrode layer 3 and an upper electrode layer 5, and a dielectric thin film 4, having a negative capacity temperature coefficient, is interposed therebetween. The silicon oxidation hydride film has an Si-OH bond, and the ratio of hydrogen atoms contained in the film is set at 0.5 to 7 atomic percent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric thin film, a method for manufacturing the same, and a capacitor for temperature compensation, and more particularly to a dielectric thin film suitable for use as a capacitor for temperature compensation in an electric circuit such as a resonance circuit. .

[0002]

2. Description of the Related Art A thin film capacitor generally has a structure in which a thin film-like lower electrode layer, a dielectric layer, and an upper electrode layer are sequentially laminated on a substrate. In some cases, a thin film capacitor is formed on a semiconductor substrate having a function as a lower electrode layer. In some cases, a structure in which a dielectric layer and an upper electrode layer are laminated is adopted. In this type of thin film capacitor, the dielectric layer is designed to have a large relative dielectric constant and to have any positive or negative temperature coefficient centered on zero. The thin film capacitor itself is small in size, and the application to various electronic devices is increasing from the viewpoint that the size of a circuit board on which the thin film capacitor is mounted can be reduced.

[0003] Such a thin film capacitor can be used as a temperature compensating capacitor for an electric circuit. An example of its use is shown in FIG. The electric circuit shown in FIG. 5 is an example of a resonance circuit in which a capacitor C ₀ and a varactor diode D _c are connected in parallel to a coil L, and a thin film capacitor C ₁ for temperature compensation is connected in parallel to the varactor diode D _c. connects the respective output terminals 50 and 51 to the upper and lower electrodes of the thin film capacitor C _1, it incorporates a resistor R between one of the electrodes of the input and output terminals 50 and 51 and the thin-film capacitor C _1.

In this resonance circuit, the capacitance of the varactor diode D _c changes according to the voltage, and the temperature coefficient of the varactor diode D _c is usually
Takes a positive value. Therefore, this varactor diode D _c
Temperature coefficient of, by the temperature coefficient to offset a thin film capacitor C ₁ having a negative value, it is possible to achieve excellent resonant circuit temperature stability.

[0005]

[SUMMARY OF THE INVENTION Incidentally, in the resonant circuit shown in FIG. 5, the temperature coefficient of the varactor diode D _c usually takes a value of about + 200~ + 500ppm / K. Therefore, in order to offset this, the temperature coefficient of the thin film capacitor for temperature compensation is -200 to -500 ppm /
It is required to take a value of about K. A very common dielectric film used for a thin film capacitor is a silicon oxide film (SiO ₂ ). In the case of a silicon oxide film,
As described in various papers and patent publications, the temperature coefficient of capacitance generally indicates a positive value at about 0 ± 50 ppm / K. Therefore, it is impossible to obtain a temperature coefficient of capacitance of a general silicon oxide film having a negative sign and an absolute value of the order of 100 ppm / K, and it is necessary to select a special film such as a perovskite-type composite oxide. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is based on the premise that a silicon oxide film-based dielectric film is used.
It is an object of the present invention to provide a dielectric thin film having a capacitance / temperature coefficient of the order of / K, a method of manufacturing the same, and a capacitor for temperature compensation using the same.

[0007]

In order to achieve the above object, a dielectric thin film for a temperature compensating capacitor according to the present invention comprises:
It is made of hydrogenated silicon oxide composed of silicon atoms, oxygen atoms, and hydrogen atoms, and has a negative temperature coefficient of capacitance. In particular, it is preferable that the hydrogenated silicon oxide has a Si-OH bond, and the proportion of hydrogen atoms contained in the film is in the range of 0.5 to 7 atomic percent.

The present inventors have found that, in the case of a general silicon oxide film, the capacitance temperature coefficient is 0 ± 50 ppm /
While it shows a positive value at about K, Si (silicon) atom and 0
In the case of a hydrogenated silicon oxide film containing an H (hydrogen) atom in addition to an (oxygen) atom, especially when the silicon oxide film has a Si—OH bond,
It has been found that the capacitance temperature coefficient shows a negative value due to the dipole polarization of the i-OH bond. When the ratio of hydrogen atoms contained in the film is less than 0.5 atomic percent, the characteristics are almost the same as those of a general silicon oxide film, and the temperature coefficient of capacitance shows a positive value. Since the Q value becomes too small (dielectric loss becomes too large), the ratio of hydrogen atoms contained in the film is preferably in the range of 0.5 to 7 atomic percent.

The method for producing a dielectric thin film for a temperature compensating capacitor according to the present invention is a method for producing a dielectric thin film according to the present invention using a dual frequency excitation plasma CVD method using a mixed gas of monosilane gas, dinitrogen monoxide gas and an inert gas as a source gas. A dielectric thin film for a temperature compensating capacitor is formed.

According to this method, the silicon hydride oxide film of the present invention having a negative temperature coefficient of capacitance can be formed by a simple method, and various conditions at the time of film formation can be appropriately adjusted. Accordingly, the value of the capacitance temperature coefficient and the Q value can be set to desired values.

The temperature compensating capacitor of the present invention is characterized in that the above-mentioned dielectric thin film for a temperature compensating capacitor of the present invention is sandwiched between a pair of electrodes. By using this capacitor for temperature compensation in an electronic circuit such as a resonance circuit, a resonance circuit having excellent temperature stability can be realized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a plan view showing a temperature compensating capacitor according to the present embodiment, and FIG.
It is sectional drawing which follows a line.

The temperature compensating capacitor 1 of the present embodiment
As shown in FIGS. 1 and 2, a lower electrode layer 3, a dielectric thin film 4, and an upper electrode layer 5, each having a rectangular shape in plan view, are sequentially laminated on the upper surface of a substrate 2 having a rectangular shape in plan view. . Substrate 2
Is not particularly limited in its material and the like, but has a thickness sufficient to impart appropriate rigidity to the entire capacitor, and has a thin-film lower electrode layer 3, a dielectric thin film 4, When forming the electrode layer 5 on the substrate 2 by a film forming method, any material can be used as long as it can withstand the film forming processing temperature. Examples of substrate materials satisfying the above conditions include ceramics such as glass, silicon, and alumina.

The lower electrode layer 3 and the upper electrode layer 5 are made of copper,
It may have a single-layer structure made of a metal such as silver, gold, or platinum, or may have a laminated structure made of a combination of these metals. The thickness is desirably about 1000 to 3000 nm, for example, 1500 nm. FIG.
Of the upper electrode layer 5 is, for example, 50 to 100.
It is about 0 μm × 50 to 1000 μm, which is a substantial area of the capacitor.

The dielectric thin film 4 is made of a hydrogenated silicon oxide film, has a Si--OH bond, and preferably contains hydrogen atoms in the film in the range of 0.5 to 7 atomic percent. Capacity temperature coefficient. The film thickness is 50 ~
It is desirable that the thickness be about 1000 nm, for example, 300
nm.

Such a hydrogenated silicon oxide film having a negative temperature coefficient of capacitance can be formed by using a two-frequency excitation plasma CVD apparatus shown in FIG. In the two-frequency excitation plasma CVD apparatus 10, a matching circuit for obtaining impedance matching between the first high-frequency power supply 11 and the plasma excitation electrode 12 is interposed. Is supplied to the plasma excitation electrode 12 by the power supply plate 13 through the matching circuit. The matching circuit and the power supply plate 13 are housed in a matching box 15 formed by a housing 14 made of a conductor.

A shower plate 17 having a large number of holes 16 is provided below the plasma excitation electrode 12, and a space 18 defined by the plasma excitation electrode 12 and the shower plate 17 is formed. Is provided with a gas introduction pipe 19. The gas introduced from the gas introduction pipe 19 is supplied into the chamber 21 formed by the chamber wall 20 through the hole 16 of the shower plate 17. Reference numeral 22 denotes an insulator that insulates the chamber wall 20 from the plasma excitation electrode 12. The illustration of the exhaust system is omitted in FIG.

On the other hand, a wafer susceptor 23 (susceptor electrode) on which the substrate 2 is placed and which serves as the other plasma excitation electrode is provided in the chamber 21, and a susceptor shield 24 is provided around the wafer susceptor 23. I have. The wafer susceptor 23 and the susceptor shield 24 can be moved up and down by a bellows 25.
The distance between the wafer 2 and the wafer susceptor 23 can be adjusted. A second high frequency power supply 27 is connected to the wafer susceptor 23 via a matching circuit accommodated in a matching box 26. Also, reference numeral 28
a, 28b, 29a and 29b are resonance circuits, which function as band eliminators or filters.

In the case of this embodiment, the first high-frequency power supply 1
1, the plasma excitation electrode 12 from the second high frequency power supply 27,
Different high-frequency powers are applied to the wafer susceptor 23, and SiH ₄ gas (monosilane gas), N ₂ O gas (dinitrogen monoxide gas), and He
Gas, introducing a mixed gas of an inert gas such as Ar gas,
If the dielectric thin film 4 is formed by using a so-called two-frequency excitation plasma CVD method, a silicon hydride oxide film having a negative temperature coefficient of capacitance can be formed.

[0020]

EXAMPLES The present inventors actually manufactured a capacitor having a dielectric thin film using the film forming method of the above embodiment,
Characteristics such as temperature coefficient of capacitance and Q value were evaluated. The results are reported below.

As shown in Table 1 below, SiH ₄ gas flow rate, N ₂ O gas flow rate, He gas (or Ar gas) flow rate [sccm], chamber pressure [Pa], plasma excitation electrode (f: 40 MHz) RF power (R in Table 1)
F power 1), wafer susceptor (f: 1.6 MH)
Four types of samples (samples A to D) were prepared in which the film forming conditions such as the RF power applied to z) (RF power 2 in Table 1) and the distance between the upper and lower electrodes were varied. The film thickness is 300n
m.

[Table 1]

For the four types of samples prepared above,
Measurements were made on evaluation items such as the hydrogen content in the film, the temperature coefficient of capacitance (Tcc), the withstand voltage strength (Ebd), and the Q value [f: 1 GHz]. The hydrogen content in the film was measured using SIMS (secondary ion mass spectrometry). Note that the presence of the Si—OH bond can be confirmed using FT-IR (Fourier transform infrared spectroscopy). Regarding the withstand voltage strength, a value equivalent to 10 MV / cm was obtained over all the samples. FIG. 4 summarizes the results of other items. FIG. 4 is a graph showing the hydrogen content dependency of the capacity temperature coefficient and the Q value, and the horizontal axis represents the hydrogen content in the film [atom.
%], The vertical axis on the left side is the capacitance temperature coefficient [ppm / K], and the vertical axis on the right side is the Q value [-]. In FIG. 4, the capacity temperature coefficient is indicated by “□”, and the Q value is indicated by “●”. At this time, the structure of each sample is the same as that shown in FIG. 1, the area of the upper electrode layer 1 is 1 mm ² , and the sheet capacity is 120 to 1
It was 30 pF / mm ² .

As is apparent from FIG. 4, when the hydrogen content in the film is in the range of 0.5 to 7 atom%, the sign of the temperature coefficient of capacitance is in the negative region, and the absolute value increases with the increase in the hydrogen content in the film. -300pp when the hydrogen content in the film is 7 atom%
It was confirmed that a capacity temperature coefficient of m / K or less (absolute value of 300 ppm / K or more) was obtained. On the other hand, when looking at the Q value, it was confirmed that the Q value decreased with an increase in the hydrogen content in the film, and the hydrogen content in the film was reduced to about 30 at 7 atom%. Based on this result, from the viewpoint that the sign of the capacity temperature coefficient is negative and an absolute value of the order of 100 ppm / K is obtained, and the Q value can be secured to a certain value, the hydrogen content in the film is set to 0.5 to 7 atom%. It has been demonstrated that it is better to control the range.

According to the present invention, by forming a capacitor using the above-mentioned silicon hydride oxide film as a dielectric thin film, a temperature compensation having a negative sign and an absolute value having a capacitance temperature coefficient of the order of 100 ppm / K is achieved. By using the temperature compensation capacitor in an electronic circuit such as a resonance circuit, a resonance circuit having excellent temperature stability can be realized.

The technical scope of the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention. For example, specific descriptions of materials, film thicknesses, plane dimensions, film forming conditions, etc. of each film constituting the capacitor are merely examples,
It can be changed as appropriate.

[0026]

As described above in detail, according to the present invention, it is possible to realize a temperature compensating capacitor having a negative sign and an absolute value having a temperature coefficient of capacitance of the order of 100 ppm / K. By using the compensation capacitor in an electronic circuit such as a resonance circuit, a resonance circuit having excellent temperature stability can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view showing a temperature compensation capacitor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a cross-sectional view showing a schematic configuration of a two-frequency excitation plasma CVD apparatus used for forming a dielectric thin film forming a capacitor.

FIG. 4 is a graph showing evaluation results of a sample which is an example of the present invention, and is a graph showing a hydrogen content dependency of a capacity temperature coefficient and a Q value.

FIG. 5 is an equivalent circuit diagram of a resonance circuit using a temperature compensation capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Temperature compensation capacitor 2 Substrate 3 Lower electrode layer 4 Dielectric thin film 5 Upper electrode layer

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) H01G 13/00 391 H01G 4/06 102 (72) Inventor Hitoshi Kitagawa 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps F term (reference) in Electric Co., Ltd. 4K030 AA01 AA06 BA44 FA03 LA11 5E082 AB03 BC15 FG03 FG27 FG42 KK01 PP03 5G303 AA01 AB06 AB11 BA03 CA01 CB30 DA01

Claims (4)

[Claims] 1. A dielectric thin film for a temperature compensating capacitor, comprising a hydrogenated silicon oxide composed of silicon atoms, oxygen atoms, and hydrogen atoms, having a negative temperature coefficient of capacitance. 2. The hydrogenated silicon oxide has a Si—OH bond, and the ratio of hydrogen atoms contained in the film is 0.5 to 7
2. The method according to claim 1, wherein the ratio is in the range of atomic percent.
A dielectric thin film for a capacitor for temperature compensation according to the above. 3. The temperature-compensating capacitor dielectric thin film according to claim 1, which is formed by a two-frequency excitation plasma CVD method using a mixed gas of monosilane gas, nitrous oxide and an inert gas as a source gas. A method for producing a dielectric thin film for a temperature compensating capacitor, comprising: 4. A temperature compensating capacitor characterized in that the dielectric thin film for a temperature compensating capacitor according to claim 1 is sandwiched between a pair of electrodes.