JP2002359151A - Thin film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film capacitor which effectively suppresses the leakage between first and second adjacent bump terminals. SOLUTION: The thin film capacitor is constituted so as to avoid deteriorating a thin film dielectric layer exposed from separate portions between an upper electrode layer and an upper base conductor layer on a substrate. A capacitor element is formed by laminating a thin film lower electrode layer 2, a thin film dielectric layer 3 and a thin film upper electrode layer 4 on a support substrate 1, and the element is covered with an insulation protective layer 7 with bump terminals 5, 6 exposed. The terminals 5, 6 are electrically connected to the thin film lower electrode layer 2 and the thin film upper electrode layer 4. The protective film 7 has irregularities 72 on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film such as a decoupling capacitor and an inductance component which are used together with an inductance component to prevent a malfunction due to a voltage fluctuation of an IC power supply as a clock frequency becomes higher. It relates to a capacitor.

[0002]

2. Description of the Related Art For example, in recent years, as for decoupling capacitors, a thin film capacitor for low inductance, small size and low profile has been demanded in response to computer technology which is becoming smaller and faster. As such a thin film capacitor, a thin film lower electrode layer, a thin film dielectric layer, and a thin film upper electrode layer are sequentially formed on a supporting substrate to form a capacitor element, and the thin film lower electrode layer, the thin film upper electrode layer are formed. There is known a thin film capacitor in which the capacitor element is covered with an insulating protective layer so that a bump terminal electrically connected to the capacitor terminal is exposed.

Specifically, as shown in FIG. 6, a thin film lower electrode layer 2, a thin film dielectric layer 3, a thin film upper electrode layer 4a, and a pair of bump terminals 5, 6 are formed on a support substrate 1. The terminal region conductor layers 4b and 4c defining the regions are sequentially laminated with the upper conductor layer 4 to form the pair of terminal region conductor layers 4b and 4c.
4c, the bump terminals 5 and 6 are formed.
That is, a predetermined capacitance component is generated in a region sandwiched between the thin film lower electrode layer 2 sandwiching the thin film electrode layer 3 and the thin film upper electrode layer 4a. In such a thin film capacitor, since the thin film lower electrode layer 2, the thin film dielectric layer 3, and the upper conductor layer 4 can be processed by using a photolithography etching step, the bump terminals 5, 6 are provided at the center of the support substrate 1. Can be arranged, a structure in which the interval between the bump terminals 5 and 6 is narrowed becomes possible, and low inductance can be realized.

In the thin film capacitor having such a structure, an insulating protective layer 70 is formed on the entire surface from BCB (benzocyclobutene) or the like so as to expose the bump terminals 5 and 6.

[0005]

As described above, to reduce the inductance, it is effective to shorten the bump terminals 5 and 6. In addition, the distance between the bump terminals 5 and 6 tends to be short, and the insulating protection layer 70
Is a resin material, and the surface shape is flattened. For this reason, when a thin film capacitor is mounted on a printed wiring board, the moisture of the air adsorbs on the surface of the insulating protective layer 70, and as a result, a leak occurs between the two bump terminals 5 and 6. was there.

The present invention has been devised in view of the above-mentioned problems, and an object of the present invention is to provide a thin-film capacitor capable of effectively suppressing leakage between two adjacent bump terminal electrodes. It is in.

[0007]

According to the present invention, a capacitor element is formed by sequentially forming a thin film lower electrode layer having bump terminals, a thin film dielectric layer, and a thin film upper electrode layer having bump terminals on a support substrate. In addition, the present invention is a thin film capacitor in which each of the bump terminals is exposed so that the capacitor element is covered with an insulating protective layer. The insulating protective layer is a thin-film capacitor having a surface having irregularities. Here, the thin film lower electrode layer having a bump terminal and the thin film upper electrode layer having a bump terminal are defined as a bump terminal and a thin film lower electrode layer, and a bump terminal and a thin film upper electrode layer being directly or indirectly connected. It refers to what is electrically connected.

The insulating protective layer may be provided with irregularities on the entire surface of the protective layer, or a convex portion may be formed around bump terminals, and the surface of the insulating protective layer may be uneven. . Further, the above-mentioned uneven portion may be formed of the insulating protective layer itself, and particularly, the uneven portion is used as a surface layer.
It may be made of a material different from the insulating protective layer, for example, a fluorine-based resin material that is too water-repellent or an inorganic material made of a metal oxide that absorbs less moisture.

Further, only the projections forming the above-mentioned irregularities are
The above materials may be used.

According to the present invention, since the surface of the protective layer between the adjacent bump terminals is uneven, the unevenness of the protective layer is larger than the distance between the center points of the two bump terminals formed on the flat protective layer. Between the bump terminals (the surface distance of the protective layer) increases.

Therefore, even if moisture is adsorbed on the protective layer and two adjacent bump terminals have different polarities, the distance through which a leak current flows between them is increased, and as a result, the occurrence of leak is effectively suppressed. be able to.

Further, the insulating protective layer has a multilayer structure,
By forming the surface layer from an inorganic material made of a fluororesin-based resin material having excellent water repellency or a metal oxide having no moisture adsorption, in addition to the above-described increase in the physical distance, the material properties of the surface layer are also reduced. In combination, the occurrence of leak can be further effectively prevented.

Further, in the insulating protective layer, only the convex portions forming the surface irregularities may be made of an inorganic material made of a fluororesin-based resin material or a metal oxide. Further, focusing on the leak between the bump terminals, the convex portion of the insulating protective layer may be patterned so as to surround the bump terminals.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thin film capacitor according to the present invention will be described below with reference to the drawings. FIG. 1 is an external perspective view of a thin film capacitor of the present invention, and FIG. 2 is a sectional structural view thereof.

In the figure, 1 is a support substrate, 2 is a lower electrode layer, 3 is a thin film dielectric layer, 4 is an upper conductor layer, 5 and 6 are bump terminals, and 7 is an insulating protective layer.

The lower electrode layer 2 is formed on the capacitor element (capacitance generating region), and particularly extends slightly outside the capacitance generating region to be electrically connected to the first bump terminal 5.

The upper conductor layer 4 becomes the thin film upper electrode layer 4a in the capacitance generation region, and the region where the first bump terminal 5 is formed on the upper portion becomes the first terminal region conductor layer 4b in the region other than the capacitance generation region. The region where the second bump terminal 6 is formed becomes the second terminal region conductor layer 4c. The second terminal region conductor layer 4c is continuous with the thin film upper electrode layer 4a,
The first terminal region conductor layer 4b is formed separately from the thin film upper electrode layer 4a, and is connected to the extended portion of the lower electrode layer 2 described above.

The first terminal region conductor layer 4
A first bump terminal 5 is formed on b, and a second bump terminal 6 is formed on the second terminal region conductor layer 4c.

The support substrate 1 is made of a heat-resistant and insulating material and has a very flat surface, such as alumina, sapphire, aluminum nitride, MgO single crystal, SrTiO ₃ single crystal,
A substrate made of silicon oxide, glass, quartz, or the like.

The thin film lower electrode layer 2 is an electrode layer mainly made of Au, and has a thickness of 0.3 to 0.5 μm in consideration of impedance in a high frequency region and coatability of the film. Incidentally, in order to enhance the adhesion of the thin film lower electrode layer 2, Ti and Pt may be formed as an adhesion layer, and Au may be formed as an intermediate layer. The thin film lower electrode layer 2 is formed by forming these conductor layers and using a photolithography technique.

The thin-film dielectric layer 3 may be made of a dielectric material composed of a perovskite-type oxide crystal having a high relative dielectric constant in a high-frequency region, for example, Pb (Mg, Nb) O.
₃ system, Pb (Mg, Nb) O ₃ -PbTiO ₃ system, Pb
(Zr, Ti) O ₃ , Pb (Mg, Nb) O ₃ -Pb
(Zr, Ti) O ₃ system, (Pb, La) ZrTiO ₃ system,
It may be a BaTiO ₃ system, a (Sr, Ba) TiO ₃ system, or a compound obtained by adding or substituting other additives thereto, and is not particularly limited. Further, the thickness of the thin film dielectric layer 3 is desirably 0.3 to 1.0 μm in order to ensure high capacity characteristics and insulation. This is because when the thickness is less than 0.3 μm, the coverage is not good, and the insulating property may decrease. When the thickness is more than 1.0 μm, the capacitance component tends to decrease. The thickness of the thin film dielectric layer 3 is preferably 0.4 to 0.8 μm.

The thin film dielectric layer 3 is formed by photolithography after forming a dielectric layer on the entire surface of the support substrate 1.

The thin film upper electrode layer 4a, which is the upper conductor layer 4,
The first and second terminal region conductor layers 4b and 4c are electrode layers mainly made of Au, and have a thickness of 0.3 to 0.5 μm in consideration of impedance in a high frequency region and film coverage.
m. In order to enhance the adhesion of the upper conductor layer 4, Ti, Cr, or Pt may be formed as an adhesion layer or an intermediate layer.

The upper conductor layer 4 is formed by forming these conductor layers on the entire surface of the support substrate 1 and by photolithography. The thin film upper electrode layer 4a and the second terminal region conductor layer 4c are formed in series, and a separation region is formed between the thin film upper electrode layer 4a and the first terminal region conductor layer 4b.

In the upper conductor layer 4, bump terminals 5, 6 made of solder bumps are arranged on the first and second terminal region conductor layers 4b, 4c. In this solder pump,
At least one metal of Ag, In, Cu, Bi, Sb and Zn is added. For this, materials having different melting points and eutectic temperatures may be selected according to the use of the thin film capacitor. The bump terminals 5 and 6 are formed by using a known technique such as screen printing or a ball mounter.

The first and second terminal area conductor layers 4b, 4b
In order to prevent the diffusion of the solder, which is the material of the bump terminals 5 and 6, during soldering, the solder diffusion preventing metal layer (Ti, C
r, Ni, Cu, Pd, Pt, or an alloy of two or more selected from these metals, and may be formed by sputtering, vapor deposition, plating, or the like.

The first and second bump terminals 5, 6
The insulating protection layer 7 is formed of, for example, BCB (benzocyclobutene) resin or the like so as to expose the plurality of capacitance generating regions continuously.

In such a thin film capacitor, the first terminal region conductor layer 4b and the second terminal region conductor layer 4b are exposed by covering the capacitance generation region. That is, the first bump terminal 5 is formed on the first terminal region conductor layer 4 b and connected to the thin film lower electrode layer 2. Also, the second
The terminal region conductor layer 4c has the second bump terminal 6 formed thereon and is connected to the thin film upper electrode layer 4a via the second terminal region conductor layer 4b.

Therefore, the capacitance component of the capacitance generating region is obtained between the first and second bump terminals 5 and 6 which are arranged at the center of the support substrate 1 and are close to each other.

The effective use of the support substrate 1 and the first and second
The proximity of the pump terminals 5 and 6 and the reduction in the height of the bump terminals 5 and 6 are possible, and the size of the package B is getting smaller.
A low inductance characteristic corresponding to GA can be realized, and the thin film capacitor is particularly suitable for a decoupling capacitor in a high frequency circuit.

Here, the present invention resides in that irregularities are formed on the surface of the insulating protective layer 7 described above. For example, (1) By forming the convex portion 71 on the surface of the insulating protective layer 7, the insulating protective layer 7 has an uneven shape as a whole. As a result, the distance between the adjacent first bump terminals 5 and second bump terminals 6 (each having a different polarity during mounting), that is, the distance on the surface of the insulating protective layer 7 is reduced as in the prior art. The distance increases as compared with the case where the surface of the protective layer 7 is flat.

For example, if the surface material of the insulating protective layer 7 is BCB
In the case of a resin such as (benzocyclobutene) or the like, the first bump terminals 5 adjacent to each other can be easily absorbed by the moisture of the atmosphere.
The surface distance of the insulating protection layer 7 between the first bump terminal 5 and the second bump terminal 6 is increased.
Can be reduced. The uneven shape of the insulating protective layer 7 may be, for example, a difference between the convex portion and the concave portion of 2 μm or more, and the height of the convex portion 71 may be set to the first and second bump terminals 5.
Set lower than 6.

In FIG. 2 and FIG. 3, on the insulating protective layer 7, around the bump terminals 5, 6, a convex portion 71 forming an uneven shape is provided around. Here, the protrusion 71 is positioned as a surface layer of the insulating protective layer 7 and may be formed of the same material as the insulating protective layer 7, for example, BCB (benzocyclobutene). Further, as shown in FIG. 4, irregularities may be formed on the entire surface of the insulating protective layer 7 itself. Further, as shown in FIG. 5, a surface layer 72 having an uneven surface may be formed on the insulating protective layer 7. In addition, this surface layer 72
The insulating protective layer 7 may be formed of a different material.

Here, the convex portion 71 or the surface layer 72 is made of S
It is preferable to use an inorganic material such as a metal oxide such as iO ₂ or Si ₃ N ₄ or a metal nitride. This is because these inorganic materials have lower hygroscopicity than general resins and can effectively suppress the occurrence of leaks. As another material, a fluorine resin may be used. In the case of such a fluorine-based resin, since the water-repellency is superior to that of a general resin, the occurrence of leak can be effectively suppressed. Further, the insulating protection layer 7 itself is
It may be made of an inorganic material such as a metal oxide such as SiO ₂ or Si ₃ N ₄ or a metal nitride. In this case, the same material can be used for the insulating protection layer 7 and the projections 71 and the surface layer 72 that form the irregularities. Thus, the protrusion 71 and the surface layer 72 can be regarded as integral with the insulating protective layer 7.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS On an alumina substrate 1 having a thickness of 0.25 μm (φ3 inch), Ti, which serves as an adhesion layer, Pt, which serves as an intermediate layer, and Au, which serves as an electrode layer, are used in an order of 0.1 and 0.1. Three,
The thin film lower electrode layer 2 is formed with a thickness of 0.5 μm. In principle, an Au electrode alone may be used, but from the viewpoint of adhesion to the substrate 1 and prevention of solder erosion, the layer structure is the above three layers. The thickness was 1 μm or less in total, and the size of one element pattern was 3 mm square. Specifically, the above-described three-layered conductive thin film can be deposited by sputtering using a mask having a predetermined shape.

Next, a predetermined volume of PZT (lead / zirconia / titanium) is added to the metal alkoxide of the thin film dielectric layer 3 to prepare a dielectric sol solution. This dielectric sol solution is applied by a spin coater and dried at about 300 degrees,
Next, the dielectric is fired at 700 to 1000 degrees,
Is formed. The patterning is performed by wet etching of the dielectric using photolithography.

At this time, it is necessary to perform selective etching which can etch only the dielectric without eroding the Au electrode of the thin film lower electrode layer 2. Specifically, etching was performed using a mixed acid using hydrofluoric acid, utilizing the acid resistance of Au.

Upper conductor layer 4 including thin film upper electrode layer 4a
Includes the adhesion layer as well as the lower electrode layer by sputtering,
A plurality of layers are formed and patterned by photolithographic etching using a photosensitive resist similarly to the dielectric layer.

In order to protect the capacity generating area formed in these steps from moisture and impact, an insulating protective layer 7 of photosensitive BCB (benzocyclobutene) is applied by a spin coater.
Processing using an exposure process to make the shape uneven, exposure,
Surface treatment was performed by partial development. At this time, the height of the projection was set to 2 μm or more.

Next, the first and second bump terminals 5, 6 are
It is baked at about 250 ° C. using a solder paste having a small particle size.

As a final step, a dicing machine is used, and the CU is used.
Perform T.

When the thin film capacitor produced by these processes is measured using an impedance analyzer,
In the frequency range of the measurement frequency 1 MHz to 1 GHz, the capacitance C =
A value of about 50 nF and an inductance L = about 30 pH could be measured. Then, the first bump terminal 5 and the second bump terminal 6
It was confirmed that leakage did not occur even if a current of 10 V was applied between these steps. The shortest distance between the first bump terminal 5 and the second bump terminal 6 on a straight line is 150 μm, and the shortest distance in consideration of the surface of the insulating protection layer 7 is 168 μm.

In the above-described embodiment, the arrangement of the capacitance generating region and the arrangement of the thin film lower electrode layer, the thin film upper electrode layer, the first bump terminal, and the second bump terminal may be variously changed.

[0043]

As described above, since the surface of the insulating protective layer is made uneven, the distance between the adjacent first pump terminal and second bump terminal (the surface distance of the protective layer) increases. Leaks generated between the bump terminals can be effectively suppressed.

In particular, since at least the portion of the protective layer where the irregularities are formed is made of an inorganic material or a fluororesin, moisture is not adsorbed on the surface of the protective layer, and the occurrence of leak is effectively suppressed. be able to.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a thin film capacitor of the present invention.

FIG. 2 is a sectional view of the thin film capacitor of the present invention.

FIG. 3 is a partially enlarged view of the thin film capacitor of the present invention.

FIG. 4 is another partially enlarged view of the thin film capacitor of the present invention.

FIG. 5 is another partially enlarged view of the thin film capacitor of the present invention.

FIG. 6 is a sectional view of a conventional thin film capacitor.

[Explanation of symbols]

 1. Support substrate 2. Thin film lower electrode layer 3. Thin film dielectric layer 4. Upper conductor layer 4a Thin film upper electrode layer 4b First terminal region conductor layer 4c Second terminal region conductor layer 5, 6 Bump terminal 7 Insulation protection layer 71 Projection 72 Surface layer

Claims (4)

[Claims] 1. A capacitor element is formed by sequentially forming a thin film lower electrode layer having a pump terminal, a thin film dielectric layer, and a thin film upper electrode layer having a bump terminal on a support substrate, and exposing each of the bump terminals. A thin film capacitor in which the capacitor element is covered with an insulating protective layer in such a manner that the insulating protective layer has irregularities formed on a surface thereof. 2. The thin film capacitor according to claim 1, wherein the insulating protective layer is provided so that a convex portion formed on the surface surrounds the bump terminal. 3. The thin film capacitor according to claim 1, wherein the surface of the insulating protection layer is made of an inorganic material made of a fluororesin-based resin material or a metal oxide. 4. The thin film capacitor according to claim 2, wherein the projections formed on the surface of the insulating protective layer are made of an inorganic material made of a fluororesin-based resin material or a metal oxide. .