JPH10308325A - Production of thin-film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin-film capacitor which is compact and large in capacitance, and is highly reliable and can match easily a production process for an MMIC(monolithic microwave integrated circuit), etc. SOLUTION: This production method is used to form a thin-film capacitor which is formed of a substrate, a lower electrode formed thereon, a dielectric thin film formed thereon, an upper electrode formed thereon, and the dielectric thin-film contains at least Sr, Ti and O and is formed at 350 deg.C or lower through a plasma CVD. In addition, it is preferably made of SrTiO3 -based perovskite type compound in consideration of permittivity, etc. Further, it is formed through diode parallel plate plasma CVD, and the high-frequency output at that time is preferably 2 W/cm<2> or more and 8 W/cm<2> or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film capacitor, and more particularly to, for example, an MMIC (Monolithic Microwave Integrate).
d circuit).

[0002]

2. Description of the Related Art Conventionally, thin film capacitors used in highly integrated circuits represented by MMIC have been formed by a plasma CVD method using a gas source such as SiH ₄ . In this case, the dielectric thin film material is Si
Materials such as O ₂ and SiN _X have been used. However, since these dielectric thin film materials have a small relative dielectric constant of 10 or less, in order to obtain a predetermined capacitance, the capacitor area must be increased, and the chip size cannot be reduced. Was. In order to solve this problem, for example, Japanese Patent Application Laid-Open No. Sho 56-144523 discloses A
There has been proposed a method of manufacturing a multilayer ceramic capacitor in which a thin film such as l ₂ O ₃ and TiO ₂ and an electrode are respectively formed by a sputtering method.

[0003]

However, in such a conventional method, Al ₂ O ₃ , S
Since the relative dielectric constant of materials such as TiO ₂ and TiO ₂ is low, it is necessary to make the film very thin in order to increase the capacitance of the capacitor.
There has been an inconvenience that the reliability as an electronic component is reduced. In addition, MMICs generally have an FE under a dielectric thin film.
Since it has a T, a diode, an epi-resistance part, an electrode part, a wiring part, etc., it is necessary to form a film on a three-dimensional structure. However, the sputtering method has a lower step coverage than the CVD method. Therefore, when manufacturing the MMIC by the sputtering method, the thickness of the dielectric thin film must be increased. As a result, there is a disadvantage that the capacity of the capacitor cannot be increased. Further, in the MMIC, since the substrate temperature cannot be raised too much, it is desired that the substrate temperature at the time of manufacturing the thin film capacitor be 350 ° C. or lower. This is an MMIC using GaAs.
At 500 ° C. or higher, As is likely to evaporate, and in the MMIC using Si, the reaction between Si and the electrode occurs. In this case, the ohmic electrode layer exists under the dielectric thin film, but if the substrate temperature is raised, the ohmic property may be lost.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a small, large-capacity, high-reliability, and MMI
An object of the present invention is to provide a method of manufacturing a thin film capacitor that is easily compatible with a manufacturing process such as C.

[0005]

A method of manufacturing a thin film capacitor according to the present invention comprises a substrate, a lower electrode formed on the substrate, a dielectric thin film formed on the lower electrode, and a dielectric thin film formed on the dielectric thin film. A method of manufacturing a thin film capacitor including the formed upper electrode, wherein the dielectric thin film has at least Sr, T
This is a method of manufacturing a thin film capacitor containing i and O and formed at 350 ° C. or lower by a plasma CVD method. According to the method of manufacturing a thin film capacitor according to the present invention, Sr
A thin film capacitor having a TiO-based dielectric thin film is obtained. When the dielectric thin film of the thin film capacitor is made of SrTiO, the capacitance is dramatically improved. In addition, in the manufacturing method according to the present invention, since the plasma CVD method is used, the step coating property is good. Therefore, in a highly integrated circuit such as an MMIC, the film thickness can be reduced as long as the reliability as an electronic component is not reduced, and the capacity of the thin film capacitor can be increased. Further, according to the manufacturing method of the present invention, since the plasma CVD method is used, the film can be formed while the substrate temperature is kept at 350 ° C. or lower.
It is easy to adapt to manufacturing conditions such as MIC.

In the method of manufacturing a thin film capacitor according to the present invention, it is preferable that the dielectric thin film is made of a SrTiO ₃ -based perovskite compound from the viewpoint of a high dielectric constant. In the present invention, the SrTiO ₃ -based perovskite compound includes SrTiO ₃ and SrTiO _3.
Is substituted by an alkaline earth metal such as Ba.

Further, in the method of manufacturing a thin film capacitor according to the present invention, the dielectric thin film is formed by a parallel plate type plasma CVD method, and the high frequency output at that time is 2 W /
It is preferably at least 8 cm ^{2 and no} more than 8 W / cm ² . By controlling the high-frequency output below 2W / cm ² or more 8W / cm ² in forming a dielectric thin film, without lowering the deposition rate, dielectric constant and high dielectric strength, short ratio small thin film capacitor Can be obtained.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments of the present invention with reference to the drawings.

[0009]

FIG. 1 is a plan view showing an example of a thin film capacitor manufactured by the manufacturing method according to the present invention (however, only an electrode made of a Pt layer is shown), and FIG. It is sectional drawing in II. FIG.
FIG. 3 is an illustrative view showing a manufacturing step of the thin-film capacitor shown in FIGS. 1 and 2; The thin film capacitors shown in FIGS. 1 and 2 are for evaluation of the manufacturing method according to the present invention. In order to manufacture the thin film capacitor 10 for evaluation, first, a substrate material (2 inches in diameter (10
0) A Si substrate 12 made of a Si single crystal is prepared. Next, a 100 nm-thickness
SiO ₂ layer 14 is formed by thermal oxidation of. SiO ₂
The layer 14 is for preventing Pt or the like from diffusing into the surface of the Si substrate 12. Further, the SiO ₂ layer 1
4 and the pattern shown in FIG. 2 and FIG.
The layer 16 is formed by a sputtering method. The Ti layer 16
This is for increasing the bonding strength of the first Pt layer 18 to be described later to the SiO ₂ layer 14. And the Ti layer 1
6 and a first Pt layer 18 is formed by a sputtering method in a pattern shown in FIGS. The first Pt layer 18 is to be one electrode of the thin film capacitor 10.

On the first Pt layer 18, for example, an Sr—Ti—O-based dielectric thin film 20 is formed in a pattern shown in FIGS. 2 and 3C. The dielectric thin film 20 is formed using, for example, a plasma CVD apparatus shown in FIG. The plasma CVD apparatus 100 shown in FIG. 4 supplies a source gas into a vacuum deposition chamber 134 and generates a plasma by applying a high-frequency voltage between the electrodes 150, and a desired dielectric thin film is formed on the Si substrate 12. This is a so-called parallel plate type plasma CVD apparatus.

Here, the plasma CVD apparatus shown in FIG. 4 will be described. Plasma CVD apparatus 100 shown in FIG.
Includes a first source gas path 102. The first source gas path 102 is a path for passing a first source gas described later. A carrier gas delivery device (not shown) is connected upstream of the first path 102 via a mass flow controller (hereinafter abbreviated as MFC) 104 for controlling the flow rate of the carrier gas. A filter 106 for removing impurities and the like is connected downstream of the MFC 104, and a pressure gauge 108 is connected downstream of the filter 106. A first raw material tank 112 is connected downstream of the pressure gauge 108 via a valve 110. The first raw material tank 112 is provided with a heater as a heating device for heating and vaporizing the raw material. The heater and the first raw material tank 112 form a first vaporizer. In the first raw material tank 112, for example, S
Sr (DPM) ₂ (phen) ₂ as the r raw material is retained. Here, DPM is dipivaloylmethane C ₁₁ H ₁₉ O ₂ (2,2,6,6-tetramethyl-3,5
-Heptanedione), and phen is an abbreviation for phenanthroline. A variable valve 114 for adjusting the flow rate of the first raw material gas is connected downstream of the first raw material tank 112.

A plasma CVD apparatus 10 shown in FIG.
0 includes the second source gas path 118. The second source gas path 118 in this example is a path for flowing a second source gas described later. An MF for controlling the flow rate of the carrier gas is provided upstream of the second path 118.
The carrier gas delivery device common to the first path 102 is connected via C120. As the carrier gas for the raw material flowing through the first path 102 and the second path 118, for example, an inert gas such as Ar is used. A filter 122 for removing impurities and the like is connected downstream of the MFC 120. A pressure gauge 124 is connected downstream of the filter 122. Downstream of the pressure gauge 124, a second raw material tank 128 is connected via a valve 126.
Is connected. The second raw material tank 128 is also provided with a heater as a heating device for heating and vaporizing the raw material. This heater and the second raw material tank 128
Form a second vaporizer. Second raw material tank 12
8 contains, for example, Ti (i.OP) as a Ti raw material.
r) ₄ is retained. Here, i.O-Pr is an abbreviation for isopropoxide. Second raw material tank 1
Downstream of 28, a variable valve 130 for adjusting the flow rate of the second source gas is connected.

A source gas conduit 116 is connected downstream of the variable valve 114 in the first path 102 and the variable valve 130 in the second path 118. Source gas conduit 11
In 6, the first source gas and the second source gas are mixed. The source gas conduit 116 is connected to the mixed gas conduit 144 via the valve 132, and the downstream end of the mixed gas conduit 144 is introduced into the film forming chamber 134. The first source gas path 10 through which the source gas flows is used.
2. Second source gas path 118 and source gas conduit 1
In order to keep the raw material gas in a vaporized state, at least a portion surrounded by a broken line in FIG.

Further, a plasma CVD apparatus 1 shown in FIG.
00 includes an oxidizing gas path 136. The oxidizing gas path 136 is a path for flowing an oxidizing gas for oxidizing the above-described source gas. Oxidizing gas path 136
Upstream of the MFC1 for controlling the flow rate of the oxidizing gas
An oxidizing gas delivery device (not shown) is connected via 38. As the oxidizing gas, for example, O ₂ gas is used, but it is not limited to this, and for example, ozone gas, nitrous oxide gas, or the like may be used. A filter 140 for removing impurities and the like is connected downstream of the MFC 138. The downstream end of the filter 140
Is connected to the mixed gas conduit 144. Therefore, the first source gas, the second source gas, and the oxidizing gas are mixed inside the mixed gas conduit 144, and the mixed gas is supplied into the film formation chamber 134.

Further, the plasma CVD apparatus 100 includes:
Includes a high frequency power supply 146. The high-frequency power supply 146 is connected to an electrode 150 that is disposed facing the inside of the film forming chamber 134 via a matching box 148. Then, on one electrode 150, Si single crystal substrate 12 on which up to first Pt layer 18 is formed in advance is placed.

Outside the film forming chamber 134, a first rotary pump 152 and a second rotary pump 154 for sucking and depressurizing the passages and conduits 102, 116, 118, 136 and the inside of the film forming chamber 134 are provided. And a turbo molecular pump 156. The first rotary pump 152 is connected to the source gas conduit 1 via a valve 158.
16 and via a valve 160 to a deposition chamber 134. First rotary pump 152
Is used during film formation. During the film formation, the film formation chamber 134 is sucked by the first rotary pump 152 with the valve 158 closed and the valves 132 and 160 opened. The second rotary pump 154 and the turbo molecular pump 156
Are connected to the film forming chamber 134 and the valve 160 via the. The second rotary pump 154 and the turbo molecular pump 156 are used to make the inside of the film forming chamber 134 to a high vacuum state before the film formation. In addition,
In the plasma CVD apparatus 100, it is natural that the connections between the respective paths, the conduits, the respective pumps and the respective valves are made by pipes or tubes.

The crystallinity of the dielectric thin film 20 formed by the above-described plasma CVD apparatus 100 was evaluated using a thin film X-ray diffractometer. Further, a second pattern is formed on the dielectric thin film 20 in the pattern shown in FIGS. 2 and 3D.
Pt layer 22 is formed by a sputtering method. 2nd P
The t layer 22 is to be the other electrode of the thin film capacitor 10. Thus, the thin film capacitor 10 for evaluation is completed. In this thin film capacitor 10, a capacitance is formed in the laminated portion 24 shown in FIGS. 1, 2 and 3 (D).

Next, referring to Tables 1 to 3, the dielectric thin film 20 in the thin film capacitor 10 having the above-described structure will be described.
Will be described.

[0019]

[Table 1]

[0020]

[Table 2]

In order to examine the change in the characteristics of the dielectric thin film 20 due to the film forming conditions, Examples 1, 2, 3 and Comparative Examples 1 and 2 were prepared under the conditions shown in Tables 1 and 2, respectively. did. The thin film capacitors 10 of each of the examples and comparative examples have the above-described structures, and are common in that the dielectric thin film 20 is formed under the conditions shown in Table 1. Although the temperature is 350 ° C., the plasma CVD apparatus 100 for forming the dielectric thin film 20 is used.
Is changed as shown in Table 2. In Table 2, RF POWER indicates high-frequency output. In each of the examples and comparative examples, the film forming time of the dielectric thin film 20 was measured by a preliminary experiment, and the film forming time was set so that the obtained film thickness was about 200 nm. Table 3 shows the film forming speed and the film forming time.

[0022]

[Table 3]

Next, the capacitance, the breakdown voltage of the thin film, the short-circuiting ratio between the electrodes, and the powder X-ray diffraction (XRD) of the thin film were measured for 100 samples of the thin film capacitor 10 obtained in each of the examples and comparative examples. The measurement was performed, and the results are shown in Table 3. The capacitance is 1 GHz, 100 mV
It measured on condition of.

As is evident from Table 3, in the case of Examples 1 to 3, that is, in the case of high-frequency output of ^{2 to} 8 W / cm ² , generation of SrTiO ₃ was confirmed by powder X-ray diffraction. In this case, the capacitance was as large as 18 pF or more, and the breakdown voltage was as large as 17 V or more. On the other hand, the short-circuit rate was as low as 7% or less. In the case of Comparative Example 1, that is, in the case of 1 W / cm ^2, no SrTiO ₃ peak was confirmed by powder X-ray diffraction. Further, both the capacitance and the breakdown voltage were low, and 3/4 or more electrodes were short-circuited. In the case of Comparative Example 2, ie, 10
In the case of W / cm ² , SrTiO
₃ peaks were confirmed. Further, the capacitance was large. However, the breakdown voltage was low and a quarter of the electrodes were short-circuited. Also, as the output increases, the deposition rate decreases,
In the case of 10 W / cm ² , it took 18 hours or more to form a film having a thickness of 200 nm.

In this embodiment, Sr, Ti, and O 3
The preparation of thin films of components has been described.
The raw material is easily obtained, and for the element whose film formation is generally performed, it is possible to replace a part of the perovskite structure with the component and change the temperature characteristics and the like as in the case of the firing method. is there. In the present embodiment,
Although a parallel plate type plasma CVD apparatus is used, the present invention is not limited to this, and another type of plasma CVD apparatus may be used.

[0026]

According to the method for manufacturing a thin film capacitor according to the present invention, a small-sized, large-capacity, and highly reliable thin-film capacitor can be obtained. In addition, the method of manufacturing a thin film capacitor according to the present invention is easily compatible with a manufacturing process of an MMIC or the like.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a thin film capacitor manufactured by a manufacturing method according to the present invention.

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

FIG. 3 is an illustrative view showing a manufacturing step of the thin-film capacitor for evaluation shown in FIGS. 1 and 2;

FIG. 4 is an illustrative view showing one example of a CVD apparatus used for a method of manufacturing a thin film capacitor according to the present invention.

DESCRIPTION OF REFERENCE NUMERALS 10 thin film capacitor 12 Si substrate 14 SiO ₂ layer 16 Ti layer 18 first Pt layer 20 dielectric thin film 22 second Pt layer

Claims (3)

[Claims] 1. A method of manufacturing a thin film capacitor including a substrate, a lower electrode formed on the substrate, a dielectric thin film formed on the lower electrode, and an upper electrode formed on the dielectric thin film. The method, wherein the dielectric thin film contains at least Sr, Ti, O,
A method of manufacturing a thin film capacitor formed at 350 ° C. or lower by a plasma CVD method. 2. The method according to claim 1, wherein the dielectric thin film is made of a SrTiO ₃ -based perovskite compound. 3. The dielectric thin film is formed by a parallel plate type plasma CVD method, and the high frequency output at that time is 2 W /
cm ² or more and 8 W / cm ² or less,
A method for manufacturing a thin film capacitor according to claim 1.