This application claims the priority of Korean Patent Application No. 2006-105229 filed on Oct. 27, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a capacitor embedded laminated structure, and more particularly, to a capacitor embedded printed circuit board adapted to improve a binding strength between an electrode and an insulation resin layer and also prevent defects caused by process tolerance in a laser-drilling process, and a manufacturing method thereof.
2. Description of the Related Art
Recently, with an ongoing trend toward miniaturization, high functionality, and high frequency performance of electronic products, there has been introduced an embedded passive device technology where passive devices are not simply mounted on a printed circuit board (PCB) but are embedded into the PCB. This technology is adapted to embed passive devices (generally, half of them are capacitors), which occupy an area of 50% or more of the total surface area, into the PCB or the like, thus contributing to the miniaturization of products and the increase in design flexibility. In addition, this technology improves work reliability by virtue of the decrease in solder connectors, and further it is possible to decrease a parasitic inductance through reduction in noise and connection path.
In particular, a decoupling capacitor is disposed in the vicinity of an integrated circuit (IC) for supplying power and removing noise by a switching operation. Meanwhile, the decoupling capacitor with higher capacitance and lower equivalent series inductance (ELS) is increasingly demanded due to the high-speed performance of an IC chip.
However, a typical embedded decoupling capacitor uses a prepreg type insulation resin layer, of which both sides are attached with copper films, as a dielectric layer. Therefore, there is a limitation in that the embedded decoupling capacitor is hardly used for a desired purpose due to its low capacitance density. Another technology is being developed so as to improve the capacitance density by dispersing ferroelectric fillers into the insulation resin layer and reducing the thickness. This technology does not sufficiently secure the capacitance density per an occupation area yet, and thus the capacitor prepared by this technology is not adapted for the decoupling capacitor.
To overcome such a limitation, researches for developing an embedded thin film capacitor adopting a high dielectric constant thin film have been actively conducted. The embedded thin film capacitor can realize high capacitance and low ESL characteristics because of its small thickness.
The conventional embedded thin film capacitor is prepared by a method including: forming a dielectric layer on a copper film having a thickness of several tens of micrometers or on a bottom electrode deposited on an additional insulation resin of a laminated plate; and forming a top electrode on the dielectric layer. The conventional process of forming the top electrode may be performed using a thin film deposition process such as a sputtering process taking into account of capacitor characteristics.
However, the thin film deposition process requires a long process time and a high fabrication cost in forming a layer to a thickness of about 1 μm. In the case where the top and bottom electrodes are thin, it is difficult to obtain a high Q value due to the increase in loss caused by the electrode and also difficult to apply the thin film deposition process to a fabrication process of PCBs adopting a thick film forming process.
Particularly, to increase the physical binding force between an insulation resin and a conductor such as the copper film and the electrode, a roughening treatment is required upon a surface of a conductor. However, when the electrode has a small thickness, it is impossible to perform the roughening treatment, thus leading to delamination as illustrated in
Because the dielectric layer and the electrode layer are formed very thinly, they are very weak physically and chemically due to their own characteristics. Therefore, when the thin dielectric layer and the electrode are used for the PCB, they may be susceptible to be damaged because they may be exposed owing to acid or basic solution during a coating process. For these reasons, it is difficult to directly form the top electrode on the dielectric thin film using a coating process or the like.
Furthermore, in order to prevent the damage (see an arrow of
An aspect of the present invention provides a method of manufacturing a capacitor embedded printed circuit board (PCB) with improved electrode formation process in order to solve the damage and/or the delamination of a dielectric layer caused by a thick film forming process while securing electrical properties of a thin film capacitor.
An aspect of the present invention also provides a capacitor embedded PCB with an improved electrode structure, which can be advantageously used in a thick film forming process while securing superior electrical properties of a thin film capacitor.
According to an aspect of the present invention, there is provided a method of manufacturing a capacitor embedded printed circuit board (PCB), including: preparing a laminated body including a laminated plate having first and second copper films on both sides thereof, at least one bottom electrode being provided on at least one side; forming a dielectric layer on the at least one bottom electrode; forming a metal layer on a region of a top surface of the dielectric layer where a capacitor is to be formed; forming a conductive paste layer on at least one region of a top surface of the metal layer, the conductive paste layer and the metal layer being provided as a top electrode; forming insulation resin layers on both sides of the laminated plate, respectively; and forming a conductive via in the insulation resin layer so as to be connected to the conductive paste layer of the top electrode.
The forming of the conductive paste layer may include forming the conductive paste layer on a substantially entire region of the top surface of the metal layer. In this case, a binding force between the conductive paste and the resin can be sufficiently secured, which makes it possible to improve the biding force several tens of times or greater than that of the conventional art without any additional roughening treatment.
Taking into account of capacitor characteristics and process time, the metal layer of the top electrode may have a thickness ranging from about 50 nm to about 300 nm. The metal layer of the top electrode may include a metal selected from the group consisting of gold (Au), silver (Ag), platinum (Pt) and copper (Cu). The forming of the metal layer of the top electrode may be performed by a physical deposition process or a chemical deposition process.
The conductive paste layer of the top electrode may have a thickness of at least about 2 μm. The conductive paste layer of the top electrode may include Ag or Cu.
Before forming the dielectric layer, the method may further include forming a first metal barrier layer on a top surface of the bottom electrode. In addition, before the forming of the metal layer of the top electrode, the method may further include forming a second metal barrier layer on a top surface of the dielectric layer.
The first and second metal barrier layers may include a metal selected from the group consisting of tantalum (Ta), titanium (Ti), chromium (Cr) and nickel (Ni). The first and second metal barrier layers may have a thickness ranging from about 5 nm to about 100 nm.
The forming of the conductive via in the insulation resin layer may include: forming a via hole in the insulation resin layer using a laser-drilling process, the via hole partially exposing the conductive paste layer; and applying a conductive material to the via hole so as to form an interlayer circuit. This makes it possible to prevent a damage of the dielectric layer caused by a direct contact of the top electrode having the conductive paste layer with laser, a desmear necessarily accompanied by the contact with the laser, and a damage caused by chemical corrosion in a coating process.
An embedded region of the thin film capacitor may be set to an appropriate interlayer region of the PCB. In one implementation, the bottom electrode may be at least one of the first and second copper films of the laminated plate. In alternative implementation, the laminated body may include an additional insulation resin layer provided on one side of the laminated plate, and the bottom electrode may be provided in the embedded region of the thin film capacitor. The method may adopt a combination of these two implementations, if necessary.
According to another aspect of the present invention, there is provided a capacitor embedded PCB manufactured by the above method.
The capacitor embedded PCB includes: a laminated body including a laminated plate having first and second copper films on both sides thereof, at least one bottom electrode being provided on at least one side; a dielectric layer on a top surface of the at least one bottom electrode; a top electrode including a metal layer provided on a region of a top surface of the dielectric layer where a capacitor is to be formed using a thin film deposition process, and a conductive paste layer on at least one region of a top surface of the metal layer; and an insulation resin layer on the laminated body, the insulation resin layer having a conductive via that is connected to the conductive paste layer of the top electrode.
The present invention is not limited to a PCB, but it can be advantageously applied to a manufacturing technology of a thin film capacitor that is embedded in a variety of laminated structures.
According to still another aspect of the present invention, there is provided a method of manufacturing an embedded capacitor, including: preparing a laminated body having a first electrode layer on at least one side thereof; forming a dielectric layer on the first electrode layer; forming a metal layer on the dielectric layer using a thin film deposition process; and forming a conductive paste layer on the metal layer, the conductive paste layer and the metal layer being provided as a second electrode.
In this case, the method may further include forming an insulation layer on at least one side of the laminated body; and forming a conductive via in the insulation layer such that the conductive via is connected to the second electrode layer.
The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
Referring to
Referring to
The thickness td of the dielectric layer 13 may be differently designed depending on a required capacitance. Typically, the dielectric layer 13 may have a thickness td ranging from several tens of nanometers to several hundreds of nanometers, and may be formed by a well-known thin film deposition process such as an atomic layer deposition (ALD), a physical deposition process and a chemical deposition process.
Referring to
The metal layer 14a adopted in this embodiment may include a metal selected from the group consisting of gold (Au), silver (Ag), platinum (Pt) and copper (Cu). Desirably, the metal layer 14a may be formed of Cu. The forming of the metal layer 14a may be performed using a well-known thin film deposition process such as a physical deposition process, e.g., a sputtering process, and a chemical deposition process.
Similar to the process of
Referring to
In consideration of such an aspect, the conductive paste layer 14b may be formed to a thickness te of at least about 2 μm. Alternatively, the conductive paste layer 14b may have a thickness te of about 100 μm or greater according to circumstances, if an interlayer space allows. More desirably, the conductive paste layer 14b may be in the range of about 5 μm to about 30 μm. The conductive paste layer 14b may include a conductive paste containing Ag or Cu. The conductive paste layer 14b adopted in the present invention may be implemented by a thick film forming process such as a screen printing process.
The conductive paste layer 14b provides such an advantageous merit that its surface has a strong binding force with an insulation resin layer, which will be provided thereon in a subsequent process, in virtue of a resin bond without an additional roughening treatment. For example, in case of pull-off test, while there is an immeasurably weak binding strength between the top electrode and the insulation resin layer according to the conventional deposition, the conductive paste layer 14b adopted in the present invention can exhibit a high binding strength, e.g., 20 kgf/cm2 or greater, with the insulation resin layer.
Referring to
Although the embodiment exemplarily illustrates the laminated plate having the copper films on both sides thereof in which two regions of the first copper film 12a are provided as the top electrode, the present invention is not limited to this so that the inventive method of
For instance, the method of manufacturing the thin film capacitor can be applied to another laminated structure where the second copper film 12b is provided as the bottom electrode or an additional insulation resin layer is provided on one side of the laminated plate. Alternatively, it is possible to realize a PCB by a combination of plurality of laminated structures.
Furthermore, although
However, since it is difficult to apply the roughening treatment to the metal layer 14a itself, it is desirable that the conductive paste layer 14b is provided in a substantially entire region of the metal layer 14a as illustrated in
Hereinafter, advantageous effects of the capacitor of the present invention will be more fully illustrated through specific embodiments.
To confirm the improvement effect of thin film capacitor according to the present invention, platinum (Pt) for a bottom electrode was deposited to a thickness of about 150 nm on a silicon wafer using a sputtering process, and nickel (Ni) for a metal barrier layer was deposited to a thickness of about 100 nm on the bottom electrode.
A dielectric thin film of Al2O3 was deposited to a thickness ranging from about 70 nm to about 100 nm on the metal barrier layer using an ALD process. Through a sputtering technique using a photoresist process, a Pt metal layer was deposited to a thickness of about 300 nm in a desirable region (e.g., about 25 mm3) where a capacitor was to be formed. Thereafter, a conductive paste containing 80% by weight of Ag was applied on a portion of the metal layer having about an area of 2 mm3 in consideration of an area where the conductive vias were to be formed. Afterwards, the conductive paste was cured for about an hour at about 180° C. to form a conductive paste layer having a thickness of about 15 μm, thus obtaining a thin film capacitor (referred to as sample A).
A thin film capacitor (referred to as sample B) of the second embodiment was prepared according to the same process and conditions as those of the foregoing embodiment except that the conductive paste was applied on an entire region of the Pt metal layer and then cured to form the conductive paste layer.
A thin film capacitor (referred to as sample C) of the comparative example 1 was prepared by the same process and conditions as those of the foregoing embodiments except that the top electrode was prepared by forming only the Pt metal layer without the conductive paste layer like the conventional art.
A thin film capacitor (referred to as sample D) of the comparative example 1 was prepared by the same process and conditions as those of the foregoing embodiments except that the top electrode was prepared by forming only the conductive paste layer on the dielectric layer without the Pt metal layer.
To compare characteristics of the thin film capacitors prepared by the embodiments 1 and 2 and the comparative examples 1 and 2, capacitances and loss factors are measured at 10 MHz, which will be shown in
Referring to
Although it is exemplarily illustrated that the present invention is applied to the PCB and the manufacturing method thereof, it can be appreciated by a person of ordinary skill in the art that the present invention can be usefully applied to other structures having an embedded thin film capacitor.
According to the present invention, a top electrode of an embedded thin film capacitor is provided with a metal layer densely deposited on an underlying dielectric layer, and a conductive paste layer thickly provided on the metal layer, thus reliably maintaining electrical properties of the capacitor. Furthermore, it is possible to effectively solve the damage of the dielectric layer and/or delamination which may be caused in a thick film forming process of a PCB.
While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.
Number | Date | Country | Kind |
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10-2006-0105229 | Oct 2006 | KR | national |