JP2006324616A - Thin-film capacitor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film capacitor capable of eliminating the necessity of a film forming substrate and suppressing a manufacturing cost, and a manufacturing method thereof. <P>SOLUTION: The thin-film capacitor is composed of a dielectric layer 10 and conductor layers 21, 22 formed on both surfaces of the dielectric layer 10. The dielectric layer 10 is formed by baking a ceramic green sheet containing dielectric ceramic powder and a binder, and the conductor layers 21, 22 are formed by baking a conductor green sheet containing conductive powder and a binder. At least either of the conductor layers 21, 22 is patterned, and D<SB>90</SB>of a diameter of a crystallite in its surface direction is not larger than 1/10 of the minimum dimension of a pattern or not larger than 10 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a thin film capacitor used for decoupling of an integrated circuit.

  Conventionally, a thin film capacitor used for decoupling of an integrated circuit has been formed by forming a lower conductor, a dielectric thin film, and an upper conductor on a Si substrate. When a thin film capacitor is manufactured by this method, it is impossible to make the thickness of the entire thin film capacitor equal to or less than the thickness of the Si substrate that does not contribute to the capacitance. Therefore, in order to advance miniaturization, it is necessary to realize a structure and manufacturing method that do not require a substrate.

  In the invention described in Patent Document 1, a thin film capacitor is formed by forming a dielectric thin film on a metal foil body by RF magnetron sputtering and forming a metal body on the dielectric thin film by RF magnetron sputtering. is doing.

On the other hand, since electronic parts are generally required to be small and inexpensive, reduction of manufacturing cost is also an issue for thin film capacitors.
JP-A-8-78283

  In the invention described in Patent Document 1, since a dielectric thin film is formed on a metal foil body, it is not necessary to provide a film formation substrate such as a Si substrate, and the thin film capacitor can be miniaturized.

  However, Patent Document 1 describes that the formation of the dielectric thin film is preferably performed by a vacuum process such as vapor deposition or sputtering. However, these vacuum processes are high in process cost and cause an increase in manufacturing cost. In addition, the material cost of the metal foil is high, which also leads to an increase in manufacturing cost.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a thin-film capacitor that does not require a film-forming substrate such as Si and can be manufactured at low cost, and a method for manufacturing the same. And

In order to solve the above problems, a thin film capacitor according to the present invention is a thin film capacitor comprising a dielectric layer and conductor layers formed on both principal surfaces of the dielectric layer, wherein the dielectric layer A ceramic green sheet containing a dielectric ceramic powder and a binder is fired, and the conductor layer is fired a conductor green sheet containing a conductive powder and a binder, and at least one of the conductor layers is patterned. The D ₉₀ of the crystallite size distribution in the plane direction is 1/10 or less of the minimum dimension of the pattern.

The thin film capacitor according to the present invention is a thin film capacitor comprising a dielectric layer and conductor layers formed on both principal surfaces of the dielectric layer, wherein the dielectric layer comprises a dielectric ceramic powder. A ceramic green sheet containing a binder and a binder, and the conductor layer is a conductor green sheet containing a conductive powder and a binder, and at least one of the conductor layers is patterned and has a planar direction. The D ₉₀ of the crystallite size distribution is 10 μm or less.

The method for manufacturing a thin film capacitor according to the present invention is a method for manufacturing a thin film capacitor comprising a dielectric layer and conductor layers formed on both principal surfaces of the dielectric layer. And a step of preparing a ceramic green sheet including a binder and a conductive green sheet including a conductive powder and a binder, and forming a laminate in which the conductive green sheets are disposed on both main surfaces of the ceramic green sheet. A step of forming a sintered body by firing the laminate, and a step of patterning at least one of the conductor layers exposed on the end face in the stacking direction of the sintered body by etching. D ₉₀ of the crystallite diameter distribution of the conductor layer formed is 1/10 or less of the minimum dimension of the pattern.

The method for manufacturing a thin film capacitor according to the present invention is a method for manufacturing a thin film capacitor comprising a dielectric layer and conductor layers formed on both principal surfaces of the dielectric layer. And a step of preparing a ceramic green sheet including a binder and a conductive green sheet including a conductive powder and a binder, and forming a laminate in which the conductive green sheets are disposed on both main surfaces of the ceramic green sheet. A step of forming a sintered body by firing the laminate, and a step of patterning at least one of the conductor layers exposed on the end face in the stacking direction of the sintered body by etching. D ₉₀ of the crystallite diameter distribution of the conductor layer formed is 10 μm or less.

  According to the thin film capacitor and the manufacturing method thereof according to the present invention, the ceramic green sheet is fired to form the dielectric layer, and the conductor green sheet is fired to form the conductor layer. Is not necessary, and the manufacturing cost is low.

Further, since the crystallite diameter D ₉₀ of the patterned conductor layer is set to 1/10 or less of the minimum dimension of the pattern or 10 μm or less, high patterning accuracy can be obtained.

This is based on the following findings obtained by the inventors of the present invention. That is, when patterning of the conductor layer is performed by etching such as wet etching, the conductor layer is etched in such a way that particles are dropped off, so that the accuracy of the pattern formed by etching may be greatly influenced by the crystallite diameter of the conductor layer. all right. Therefore, sufficient patterning accuracy can be obtained by controlling D ₉₀ of the crystallite size distribution of the conductor layer to 1/10 or less of the minimum pattern size or 10 μm or less. More preferably, D ₉₀ of the crystallite size distribution of the conductor layer is controlled so as not to exceed the smaller one of 1/10 or 10 μm of the minimum dimension of the pattern.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a sectional view showing a thin film capacitor according to the present invention. The thin film capacitor according to the present invention includes a dielectric layer 10 made of dielectric ceramics, a first conductor layer 21 formed on both main surfaces of the dielectric layer 10 and opposed to each other with the dielectric layer 10 therebetween. This is a so-called MIM capacitor having two conductor layers 22 and comprising one dielectric layer and two conductor layers.

The dielectric layer 10 is made of a dielectric ceramic such as BaTiO ₃ , SrTiO ₃ , (Ba, Sr) TiO _{3, and the} like, and is formed by firing a ceramic green sheet containing a dielectric ceramic powder and a binder. It is a thing.

The first and second conductor layers 21 and 22 are made of a conductive green sheet mainly composed of a metal such as Ni, Ag, or Cu, or a conductive metal oxide, and includes a conductive powder and a binder. It is formed by firing. The first and second conductor layers are patterned by etching, and D ₉₀ (cumulative 90% crystallite diameter) of the crystallite diameter distribution of the first and second conductor layers is 1 / minimum of the minimum pattern dimension. 10 or less, or 10 μm or less.

  Here, the minimum pattern dimension refers to the minimum length in the plane direction of the pattern formed by patterning (line width of wiring, diameter of land, spacing between conductors, etc.). From FIG. 1, the minimum pattern dimension of this thin film capacitor is 100 μm. However, the dimension of each part shown in FIG. 1 is an example to the last.

  Next, a method for manufacturing a thin film capacitor according to the present invention will be described.

(1) Step of preparing ceramic green sheet and conductive green sheet Dielectric ceramic powder made of dielectric ceramics such as BaTiO ₃ series, SrTiO ₃ series, (Ba, Sr) TiO ₃ series, a binder and a solvent are mixed. To obtain a ceramic slurry. You may add a plasticizer, a dispersing agent, an antifoamer, etc. to a ceramic slurry as needed. The particle size of the dielectric ceramic powder is preferably about 0.05 to 0.30 μm. As the binder, polyvinyl butyral, vinyl acetate, methacrylic acid ester, polyvinyl alcohol, polyvinyl acetate and the like can be used, and two or more of these may be used in combination. Next, the ceramic slurry is formed into a sheet shape by a known method such as a doctor blade method to obtain a ceramic green sheet.

  Moreover, conductive powder made of a conductive material such as a metal such as Ni, Ag, or Cu, an alloy thereof, or a conductive metal oxide, a binder, and a solvent are mixed to obtain a conductor slurry. You may add a plasticizer, a dispersing agent, an antifoamer, etc. to a conductor slurry as needed. The particle size of the conductive powder is preferably about 0.2 to 1.0 μm. As the binder, polyvinyl butyral, vinyl acetate, methacrylic acid ester, polyvinyl alcohol, polyvinyl acetate and the like can be used, and two or more of these may be used in combination. Next, a conductive green sheet is obtained by forming the conductive slurry into a sheet by a known sheet forming method such as a doctor blade method, a roll coater method, or a dipping and pulling method.

  At this time, it is preferable that the thickness of the conductor green sheet is thicker than that of the ceramic green sheet and becomes 2 μm or more after firing. The reason will be described later.

(2) Step of Forming Laminated Body As shown in FIG. 2A, the laminated body is laminated so that the conductor green sheets 32 are arranged on both sides of the ceramic green sheet 31, and press-bonded under predetermined conditions. obtain.

(3) Step of obtaining sintered body Next, this laminate is sandwiched from above and below by a setter 40 made of high-purity alumina (Al ₂ O ₃ ) as shown in FIG. And fire.

At this time, in order to prevent the laminate from sticking to the setter 40 during firing, a powder of a hardly sinterable material that does not sinter at the firing temperature of the laminate is applied to the contact surface between the laminate and the setter 40. It may be left. For example, alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), a composite oxide of aluminum and zirconium, boron nitride (BN), or the like can be used as the hardly sinterable powder. It is preferable to consist of the same material. The firing conditions are appropriately set so that the dielectric is sufficiently sintered and sufficiently densified.

  By firing, a sintered body composed of the dielectric layer 10 and the first and second conductor layers 21 and 22 is obtained. At this time, the thickness of the conductor green sheet 32 is thicker than that of the ceramic green sheet 31, and is 2 μm or more, more preferably 5 μm or more after firing (in the state of the first and second conductor layers 21 and 22). As a result, the dielectric layer 10 can be densified.

  The mechanism will be described. Since the conductor green sheet 32 generally has a larger shrinkage than the ceramic green sheet 31 during firing, the conductor green sheet 32 exerts a compressive force in the in-plane direction on the ceramic green sheet 31. By setting the conductor green sheet 32 to the above thickness, this stress effectively acts on the ceramic green sheet 31, and the dense dielectric layer 10 can be obtained.

  Also, by setting the conductor green sheet 32 to the above thickness, the sintered body can be handled without using a support or the like. In order to provide the sintered body with mechanical strength that can withstand handling, the thickness of the dielectric layer 10 or the first and / or second conductor layers 21 and 22 may be increased. When the thickness is increased, the capacity is reduced. Therefore, it is preferable to ensure the mechanical strength of the sintered body mainly by the thickness of the first and / or second conductor layers 21 and 22.

(4) Patterning Step Next, a resist 41 is formed on the first and second conductor layers 21 and 22 as shown in FIG. 2 (c), and the resist 41 is exposed and developed to obtain FIG. 2 (d). As shown, a part of the resist 41 is removed. Then, the first and second conductor layers 21 and 22 are patterned by immersing the sintered body in an etching solution. Thereby, the thin film capacitor shown in FIG. 2E is completed. As the etching solution, an appropriate well-known etching solution may be selected according to the material of the first and second conductor layers 21 and 22, but it is necessary to select an etching solution that does not substantially dissolve the dielectric layer 10. . Although both the first and second conductor layers 21 and 22 are patterned here, only one of them may be patterned.

  The method for controlling the crystallite diameter of the first and second conductor layers 21 and 22 will be described. The main conditions affecting the crystallite diameter are (a) firing temperature, (b) firing atmosphere, and (c). There is a thickness of the conductor green sheet.

(A) Firing temperature Since the growth of metal crystal grains is promoted as the firing temperature is higher, it is preferable that the firing temperature is not set too high. However, if the firing temperature is too low, sintering and densification of the dielectric layer become insufficient and a high dielectric constant cannot be obtained. Therefore, the firing temperature should be set to such an extent that does not hinder sintering and densification of the dielectric layer. It is preferable to keep it low.

(A) Firing atmosphere Since the crystal growth of the metal is promoted as the oxygen partial pressure during firing is lower, it is preferable not to make the oxygen partial pressure too low.

(C) Thickness of the conductor green sheet Since the growth of metal crystal grains is promoted and the crystallite diameter increases as the thickness of the conductor green sheet increases, it is preferable that the thickness of the conductor green sheet is not excessively increased. However, as described above, it is preferable that the thickness of the conductor green sheet is larger than the thickness of the dielectric layer and the thickness after firing is 2 μm or more, so that it does not become as thick as possible while satisfying this condition. Is preferred.

  In the following, more specific examples of the present invention will be described.

(1) Step of preparing a ceramic green sheet and a conductor green sheet (Ba, Ca) Dielectric ceramic powder having an average particle diameter of 0.2 μm made of dielectric ceramics containing TiO ₃ as a main component, and polyvinyl butyral as a main component The binder to be mixed was mixed at a volume ratio of 1: 1, and further a solvent and a dispersant in which toluene and ethanol were mixed at a ratio of 1: 1 were added and mixed and dispersed to obtain a ceramic slurry. At this time, the volume ratio of solid content in the slurry (dielectric ceramic powder and binder ratio in the slurry) was adjusted to 15%. Next, this ceramic slurry was formed into a sheet by a doctor blade method to obtain a ceramic green sheet having a thickness of 2 μm.

  Also, conductive powder made of Ni having an average particle size of 0.5 μm and a binder mainly composed of polyvinyl butyral were mixed at a volume ratio of 1: 1, and toluene and ethanol were further mixed at a ratio of 1: 1. A solvent and a dispersant were added and mixed and dispersed to obtain a conductor slurry. At this time, the solid content volume ratio in the slurry (the ratio of the conductive powder and the binder in the slurry) was adjusted to 15%. Next, this conductor slurry was formed into a sheet by a doctor blade method to obtain a conductor green sheet having a thickness of 6 μm.

(2) Step of Forming Laminated Body Referring again to FIG. 2, as shown in FIG. 2 (a), lamination is performed so that the conductor green sheets 32 are arranged on both sides of the ceramic green sheet 31, and the temperature is set to 50 ° C. While being heated, pressure bonding was performed at 200 mPa for 30 seconds to form a laminate composed of one ceramic green sheet 31 and two conductor green sheets 32.

(3) Step of obtaining a sintered body Next, a load of 0.03 MPa is applied in a state where this laminate is sandwiched from above and below by a setter 40 made of high purity alumina (Al ₂ O ₃ ) as shown in FIG. Baking is performed for 2 hours at 1100 ° C. in a reducing atmosphere. Thus, a sintered body composed of the dielectric layer 10 and the first and second conductor layers 21 and 22 is obtained.

(4) Patterning Step Next, as shown in FIG. 2 (c), a resist 41 is formed on the first and second conductor layers 21 and 22, and exposed and developed, as shown in FIG. 2 (d). Then, a part of the resist 41 is removed. Subsequently, the sintered body is immersed in an FeCl ₃ solution, and the first and second conductor layers 21 and 22 are patterned. Further, the resist 41 is removed to complete the thin film capacitor shown in FIG.

(5) Measurement of crystallite diameter and confirmation of etching end face The obtained thin film capacitor is cut substantially perpendicular to the main surface, and a SIM (scanning ion microscope) image of the cut surface is subjected to image analysis to obtain a crystal in the plane direction. By measuring the core diameter (maximum diameter), the D ₉₀ of the crystallite diameter in the plane direction was determined, and D ₉₀ = 8 μm.

  Moreover, the etching end surface which appeared on the main surface of the thin film capacitor was observed by SEM (scanning electron microscope) (FIG. 3). In FIG. 3, the light line appearing in the left-right direction near the center in the vertical direction in the figure is the etching end face, the portion above the etching end face is the exposed portion of the dielectric layer, and the bottom is the first or second conductor layer Is the part where is formed. As is clear from FIG. 3, the etching end face is formed on a substantially straight line without significant disturbance, and sufficient etching accuracy (patterning accuracy) is obtained.

(6) Confirmation of Denseness of Dielectric Layer The thin film capacitor was cut substantially perpendicular to the main surface, and a SEM image of a cross section of the dielectric layer that appeared on the cut surface was taken (FIG. 4). It was confirmed that the dielectric layer has sufficient density.

[Comparative Example 1]
A thin film capacitor was fabricated under the same conditions as in the above example except that the thickness of the conductor green sheet was 15 μm and the firing temperature was 1320 ° C. When D ₉₀ of the crystallite size distribution in the plane direction was determined by the same method as described above, D ₉₀ = 15 μm. This is considered to be because the crystal growth of the metal was promoted in the conductor green sheet because the firing temperature was higher than in the examples.

Moreover, the etching end surface was observed by SEM by the same method as above (FIG. 5). In FIG. 5, a light-colored line appearing in the left-right direction near the center in the vertical direction in the figure is the etching end face, the portion above the etching end face is the exposed portion of the dielectric layer, and the bottom is the first or second conductor layer. Is the part where is formed. As is clear from comparison between FIG. 3 and FIG. 5, in Comparative Example 1, the etching end face is greatly formed in the vertical direction in the figure, and sufficient etching accuracy (patterning accuracy) is not obtained. This is presumably because D ₉₀ of the crystallite size distribution was as large as 15 μm.

[Comparative Example 2]
Using a 20 μm thick metal foil made of Ni instead of the conductor green sheet, a laminate was formed by pressure bonding under the same conditions as in the example, and this was fired under the same conditions as in the example to produce a sintered body.

  When the dielectric layer that appeared on the cut surface of the sintered body was observed by SEM (FIG. 6), it was found that the dielectric layer was inferior to the dielectric layer of the example shown in FIG. 3. This is because the ceramic green sheet tends to shrink in the in-plane direction during firing, whereas the metal foil hardly shrinks in the in-plane direction, so the metal foil laminated on both main surfaces of the ceramic green sheet This is because the shrinkage of the ceramic green sheet is suppressed. As a result, the denseness of the dielectric thin film is lowered, which may cause an increase in leakage current and a decrease in voltage resistance.

[Modification]
A modification of the present invention will be described. In the above embodiment, the laminate is fired by sandwiching it between plate-like setters, but the setters may have a lattice shape, a net shape, a honeycomb shape or the like. An example of a grid-like setter is shown in FIG.

  The setter 42 is made of alumina. The width of the grid bars is about 0.5 mm, and one side of the through hole is about 3.0 mm. By using such a grid-like setter 42, (1) the contact area between the laminated body and the setter is reduced, so that sticking during firing is less likely to occur, and (2) the laminated body during firing is in the furnace atmosphere. Since the number of parts that directly touch the surface increases, the difference in the firing conditions between the edge and the center of the laminate is reduced, and the in-plane variation in characteristics is reduced. (3) The volume of the setter is reduced and the heat capacity is reduced. Therefore, there are advantages such as improved temperature followability of the firing furnace, and (4) the setter is lighter, so that a large number of laminates can be accommodated in the furnace at a time, and the manufacturing cost can be reduced.

In particular, the above (2) and (3) are important in controlling D ₉₀ of the crystallite size distribution of the conductor layer within the range of the present invention.

It is sectional drawing which shows the thin film capacitor of this invention. It is sectional drawing which shows the manufacturing process of the thin film capacitor of this invention. It is the SEM image which imaged the surface near the etching end face of the thin film capacitor of the example of the present invention. It is the SEM image which image | photographed the cross section of the dielectric material layer of the thin film capacitor of the Example of this invention. 4 is a SEM image obtained by photographing the surface of the thin film capacitor of Comparative Example 1 in the vicinity of an etching end surface. 4 is a SEM image obtained by photographing a cross section of a dielectric layer of a thin film capacitor of Comparative Example 2. It is a perspective view which shows the setter of the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dielectric layer 21 1st conductor layer 22 2nd conductor layer 31 Ceramic green sheet 32 Conductor green sheet 40,42 Setter 41 Resist

Claims (4)

A thin film capacitor comprising a dielectric layer and a conductor layer formed on both main surfaces of the dielectric layer,
The dielectric layer is formed by firing a ceramic green sheet containing a dielectric ceramic powder and a binder,
The conductor layer is formed by firing a conductor green sheet containing conductive powder and a binder,
A thin film capacitor, wherein at least one of the conductor layers is patterned, and a D ₉₀ of a crystallite diameter distribution in a plane direction is 1/10 or less of a minimum dimension of the pattern. A thin film capacitor comprising a dielectric layer and a conductor layer formed on both main surfaces of the dielectric layer,
The dielectric layer is formed by firing a ceramic green sheet containing a dielectric ceramic powder and a binder,
The conductor layer is formed by firing a conductor green sheet containing conductive powder and a binder,
A thin film capacitor, wherein at least one of the conductor layers is patterned, and a D ₉₀ of a crystallite diameter distribution in a plane direction is 10 μm or less. A method of manufacturing a thin film capacitor comprising a dielectric layer and a conductor layer formed on both main surfaces of the dielectric layer,
Preparing a ceramic green sheet containing a dielectric ceramic powder and a binder, and a conductor green sheet containing a conductive powder and a binder;
Forming a laminate in which the conductor green sheets are arranged on both main surfaces of the ceramic green sheet;
Firing the laminate to form a sintered body;
Patterning at least one of the conductor layers exposed on the end face in the stacking direction of the sintered body by etching, and
A method for producing a thin film capacitor, wherein D ₉₀ of the crystallite diameter distribution of the patterned conductor layer is 1/10 or less of the minimum dimension of the pattern. A method of manufacturing a thin film capacitor comprising a dielectric layer and a conductor layer formed on both main surfaces of the dielectric layer,
Preparing a ceramic green sheet containing a dielectric ceramic powder and a binder, and a conductor green sheet containing a conductive powder and a binder;
Forming a laminate in which the conductor green sheets are arranged on both main surfaces of the ceramic green sheet;
Firing the laminate to form a sintered body;
Patterning at least one of the conductor layers exposed on the end face in the stacking direction of the sintered body by etching, and
A method for producing a thin film capacitor, wherein D ₉₀ of the crystallite diameter distribution of the patterned conductor layer is 10 μm or less.