JP3967964B2 - Thin film electronic components - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin film electronic component, for example, a high frequency thin film electronic component suitably used for a thin film capacitor, a thin film filter and the like.
[0002]
[Prior art]
In recent years, with the downsizing and high functionality of electronic devices, there has been an increasing demand for downsizing, thinning, and high frequency compatibility for electronic components installed in electronic devices.
[0003]
For example, in a computer that processes a large amount of information at high speed, the clock frequency for driving the CPU chip exceeds 1 GHz, and the clock frequency of the inter-chip bus is further pursued from 133 MHz.
[0004]
In addition, as the degree of integration of LSI increases, power supply voltage tends to be lowered to reduce power consumption in order to suppress heat generation from the chip. As these integrated circuits increase in speed, density, and voltage, passive components such as capacitors are required to have excellent characteristics with respect to high-frequency or high-speed pulses in conjunction with downsizing and large capacity. .
[0005]
As the operating frequency increases, the resistance and inductance of the element cause an instantaneous drop in the power supply voltage on the logic circuit side and new voltage noise, which causes an error in the logic circuit. In addition, recent LSIs reduce the increase in power consumption due to the increase in the total number of elements, and the power supply voltage is lowered to suppress heat generation, so the allowable fluctuation range of the power supply voltage is also reduced. In the future, in order to further increase the number of elements and increase the operating frequency, it is necessary to take measures to reduce the influence of the resistance and inductance components of the mounting portion.
[0006]
Moreover, not only the electrical characteristics of the passive element itself as described above, such as improvement in mounting accuracy with the increase in the number of elements and improvement in reflow resistance with component mounting, but also characteristics related to mounting (mounting accuracy, mounting reliability) There is a growing demand for high reliability such as moisture resistance reliability.
[0007]
In response to such requirements, USP 4,439,813 sequentially provides a lower electrode, a dielectric layer, an upper electrode, and a protective layer on a support substrate, and a lower electrode made of Ti / W, Ta, Al, or Cu. In order to obtain an electrical signal from the shortest distance, a through hole is provided in the dielectric layer, the upper electrode and the protective layer, and a BLM layer made of Cr / Cu / Au is formed on the inner wall of the through hole. A thin film decoupling capacitor formed by forming solder bumps is disclosed.
[0008]
This thin film decoupling capacitor is mounted by aligning the solder bumps of the thin film decoupling capacitor with a predetermined wiring formed on the surface of the mounting substrate and performing a reflow (heating) treatment.
[0009]
Further, this thin film decoupling capacitor has a low inductance structure, and it is intended to solve the problem associated with the high frequency operation of the LSI chip by making it possible to arrange the thin film decoupling capacitor in the vicinity of the LSI chip and reducing the overall inductance.
[0010]
[Problems to be solved by the invention]
However, in the above-described conventional thin film capacitor, solder bumps are formed in the through-holes provided in the protective layer. Therefore, the solder bumps shrink due to the application of heat when the solder bumps are formed or mounted on the mounting board. Thus, a load is applied to the protective layer having a through hole in which the solder bump is formed. Therefore, there has been a problem that the interface (upper electrode layer) between the protective layer and the layer of the thin film capacitor in contact with the protective layer is peeled off, or the protective layer itself is cracked to deteriorate the moisture resistance.
The present invention has been devised in view of the above-described problems, and an object thereof is to provide a thin-film electronic component that can sufficiently exhibit the moisture resistance of a protective film.
[0011]
[Means for Solving the Problems]
Thin-film electronic components of the present invention comprises a support substrate, a lower electrode layer, a thin film element sequentially laminated dielectric layers, and an upper electrode layer, and a terminal electrode electrically connected with the electrode layer, the thin film element A first protective layer that has a through hole that covers and exposes the terminal electrode; and a second protective layer that covers the first protective layer so as to cover an inner wall of the through hole in a state where the terminal electrode is exposed. a thin film electronic component consisting, in which the thermal expansion coefficient of the second protective layer is set to be larger than the thermal expansion coefficient of the first protective layer. In particular, the thermal expansion coefficient of the first protective layer is 1.0 × 10 ⁻⁷ ° C.− ¹ or more and less than 1.0 × 10 ⁻⁵ ° C.− ¹ , and the thermal expansion coefficient of the second protective layer is 1.0 × 10 6. It is set to ⁻⁵ ° C. ⁻¹ or more and less than 1.0 × 10 ⁻³ ° C. ⁻¹ .
[0012]
By adopting such a configuration, heat is applied to the terminal electrode via the external terminal when an external terminal such as a solder bump is formed on the terminal electrode or when a thin film electronic component is mounted on a mounting board. In this case, even if thermal contraction occurs in the external terminal electrode, the thermal expansion coefficient of the second protective layer is larger than that of the first protective layer. The first protective layer is hardly affected by the thermal contraction of the external terminal, the interface between the first protective layer and the thin film element in contact with the first protective layer is peeled off, or the first protective layer is cracked. In addition, the first protective layer can fulfill its original function, that is, the function of improving the moisture resistance, thereby improving the moisture resistance of the thin film electronic component.
[0013]
Further, a first protective layer is formed around the terminal electrode with a gap of 10 μm or more. The second protective layer is formed around the inner wall of the through hole with a width of 10 μm or more in the radial direction of the through hole. Thereby, the influence on the first protective layer due to the thermal shrinkage of the external terminal can be reduced, and the original function of the first protective layer can be achieved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The thin film electronic component of the present invention will be described in detail below with reference to the drawings.
[0015]
FIG. 1 is a cross-sectional view of a thin film capacitor which is an example of a thin film electronic component. The thin film capacitor shown in FIG. 1 includes a lower electrode layer 5 comprising a lower electrode layer 5a and its extension 5b on a support substrate 1, a dielectric layer 3 formed on the lower electrode layer 5a, and the dielectric An upper electrode layer 7a formed on the body layer 3 and an upper electrode layer 7 composed of an extension portion 7b are sequentially deposited. The lower electrode layer 5a, the dielectric layer 3, and the upper electrode layer 7a constitute a thin film element A that generates a predetermined capacity. Further, a plurality of thin film elements A may be provided on the support substrate 1 as necessary.
[0016]
The lower electrode layer 5 is annularly etched in accordance with the region where the extended portion 7b of the upper electrode layer 7a is formed. The lower electrode layer 5 is divided into a lower electrode layer 5a that forms a capacitor and an extended portion 5b (region where a terminal electrode is formed) that does not form a capacitor.
[0017]
The upper electrode layer 7 is etched so as to expose the lower electrode layer 5a, and is divided into an upper electrode layer 7a that forms a capacitor and an extension portion 7b that does not form a capacitor.
[0018]
Further, a solder diffusion prevention layer 17 is formed at least on the extension part 7b of the upper electrode layer 7a and the extension part 5b of the lower electrode layer 5a, and on this solder diffusion prevention layer 17, a solder serving as a terminal electrode is formed. An adhesion layer 18 is formed. External terminals 11 a and 11 b such as solder balls are provided via the solder adhesion layer 18.
[0019]
The support substrate 1 is not particularly limited as it is selected from alumina, sapphire, aluminum nitride, magnesium oxide single crystal, strontium titanate single crystal, surface silicon oxide, glass, quartz and the like.
The material of the electrode layers 5 and 7 is limited depending on the use of the thin film electronic component and the purpose of use of each part. For example, when used in a high-speed signal circuit, a material having a low electric resistance is preferable. Etc. can be exemplified.
[0020]
As the material of the dielectric layer 3, beryllium titanate, strontium titanate, strontium beryllium titanate, or the like is used. However, the relative permittivity is high to some extent, and a large amount of charge can be accumulated. Consists of the above materials.
[0021]
The solder diffusion preventing layer 17 is made of any one of Ti, Cr, Ni, Cu, Pd, Pt, or an alloy composed of two or more selected from these metals, and can be formed by sputtering, vapor deposition, plating, or the like. It ’s fine. The thickness of the solder diffusion preventing layer 17 may be 0.3 μm or more in order to exhibit a function as a solder barrier.
[0022]
The solder adhesion layer 18 is desirably a material having good solder wettability, and examples of the material include Ni—Cr and Au, and Au is particularly desirable. Further, in order to improve the adhesion between the solder diffusion preventing layer 17 and the electrode layers 5 and 7 made of, for example, Ti or Cr which are known adhesion materials may be interposed therebetween.
[0023]
In the thin film capacitor of the present invention, at least the thin film element A is covered with the first protective layer 13, and the first protective layer 13 in the dielectric layer non-formation region B is formed with through holes 23a and 23b. , 23b, the solder adhesion layer 18 is exposed. Moreover, the 2nd protective layer 14 is formed so that the inner wall of the 1st protective layer 13 and the through-holes 23a and 23b may be covered. That is, through holes 25a and 25b smaller than the through holes 23a and 23b formed in the first protective layer 13 are formed in the second protective layer 14 in the dielectric layer non-forming region B, and are formed on the bottom surfaces of the through holes 25a and 25b. The solder adhesion layer 18 is exposed and becomes a terminal electrode. That is, the second protective layer 14 is formed wider than the formation region of the first protective layer 13.
[0024]
FIG. 2 is a plan view showing the relationship between the formation region of the first protective layer 13 and the formation region of the second protective layer 14. A solid line indicates a region where the first protective layer 13 is formed, and a dotted line indicates a region where the second protective layer 14 is formed. In the through holes 23 and 25, the through holes 25 a and 25 b of the second protective layer 14 are made smaller than the through holes 23 a and 23 b of the first protective layer 13, so that 2 The area where the protective layer 14 is formed is widened. More specifically, a non-formation region (gap d) of the first protective layer of 10 μm or more is formed around the through holes 25 a and 25 b, and the gap d is covered with the second protective layer 14. As shown in FIG. 2, the second protective layer 14 may be formed wider than the first protective layer 13 in the outer peripheral portion.
[0025]
The first protective layer 13 is preferably made of a material having high moisture resistance, and for example, an inorganic material such as silicon nitride or silica is particularly desirable. Further, a laminated structure using two or more of these materials may be used. The first protective layer 13 made of these inorganic materials has a thermal expansion coefficient of 1.0 × 10 ⁻⁷ ° C. ^{− 1} or more and less than 1.0 × 10 ⁻⁵ ° C. ^{− 1} .
[0026]
The material of the second protective layer 14 is not particularly limited, and may be an inorganic material as described above, or an organic material such as polyimide or benzocyclobutene (BCB). . Further, a laminated structure using two or more of these materials may be used. Is less than ^{1 -} These materials are the thermal expansion coefficient greater than the thermal expansion coefficient of the first protective layer, for example, 1.0 × 10 ^-5 ° C. ^{- 1} or 1.0 × 10 ^-3 ℃.
[0027]
Accordingly, when viewed as a whole of the protective layer, the thermal expansion coefficients of the second and first protective layers 14 and 13 from the outside of the protective layer are set so as to decrease gradually toward the thin film element.
[0028]
External terminals 11 a and 11 b are formed in the through holes 25 a and 25 b of the second protective layer 14.
[0029]
The external terminals 11a and 11b have a ball shape, a bump shape, a foil shape, a plate shape, a line shape, a paste shape, and the like, and are not particularly limited, and a plurality of shapes may be combined. Moreover, there are Pb, Sn, Au, Pt, Pd, Al, Ni, Ag, In, Cu, Bi, Sb, Zn, and the like as long as they are conductive, and a plurality of materials may be combined. .
[0030]
As shown in FIG. 3, the thin film capacitor 43 as described above is joined to the predetermined wirings 41a and 41b formed on the surface of the mounting substrate 40 by positioning the external terminals 11a and 11b and then performing a reflow process. Implemented.
[0031]
In the case of the thin-film electronic component shown in FIG. 1, for example, when the external terminals 11a and 11b are constituted by solder balls, the external terminals 11a are formed on the solder adhesion layer 18 by using screen printing or ball mounter, which are known techniques. , 11b are provided, and then reflow processing is performed to join and mount to the predetermined wirings 41a and 41b of the mounting substrate 40.
[0032]
In the thin film capacitor configured as described above, since the formation region of the second protection layer 14 is larger than the formation region of the first protection layer 13, external terminals are provided in the through holes 25a and 25b of the second protection layer 14. The effects of thermal contraction of the external terminals 11a and 11b when the thin film capacitors are mounted on the mounting substrate 40, specifically, the solder adhesion layer 18 directly or indirectly from the external terminals 11a and 11b. Even if the terminal electrode is affected by thermal stress, since the thermal expansion coefficient of the second protective layer 14 is larger than the thermal expansion coefficient of the first protective layer 13, the stress is applied to the second protective layer 14. Easy to absorb. As a result, the interface between the first protective layer 13 and the layer in contact with the first protective layer 13 and the interface between the first protective layer 13 and the upper electrode layer 7a are not peeled off, and the first protective layer 13 is not cracked. The primary function of the first protective layer 13 can be achieved. Therefore, the moisture resistance of the thin film capacitor can be improved.
[0033]
Although the thin film capacitor has been described as an example of the thin film electronic component of the present invention, the present invention is not limited to the above example. For example, the present invention is applied to a thin film composite component such as a thin film LC filter or a thin film RC component. Of course, it may be applied.
[0034]
【Example】
The lower electrode layer 5, the upper electrode layer 7, the solder diffusion prevention layer 17 and the solder adhesion layer 18 were formed by DC sputtering, and the dielectric layer 3 (dielectric thin film) was prepared by RF sputtering.
[0035]
First, a 30 nm adhesion layer made of TiO ₂ was formed on the support substrate 1 made of sapphire, and a 30 nm Au layer was formed on the upper surface of this adhesion layer to form the lower electrode layer 5.
[0036]
The lower electrode layer 5 was patterned using a photolithographic technique. A dielectric layer 3 made of Ba (Sr _1/3 Ti _2/3 ) O _{3 having a} film thickness of 0.5 μm was formed on the processed lower electrode layer 5 by RF sputtering. Thereafter, the dielectric layer 3 was patterned using a photolithography technique.
[0037]
Next, on the dielectric layer 3 and the lower electrode layer 5 exposed from the dielectric layer 3, an upper electrode layer made of Au with a thickness of 30 nm, and a solder diffusion prevention layer 17 made of Ni with a thickness of 1.0 μm, Then, a solder adhesion layer 18 made of Au having a thickness of 0.1 μm was sequentially formed. Thereafter, using the photolithography technique, first, the solder adhesion layer 18 was processed into a shape having a diameter of 100 μm, the solder diffusion preventing layer 17 was processed into a shape having a diameter of 200 μm, and then the upper electrode 7 was patterned.
[0038]
Thereafter, SiO ₂ having a thickness of 5.0 μm is formed by CVD, and through holes 23a and 23b having a diameter of 120 μm and a depth of 5.0 μm are provided so that the solder adhesion layer 18 made of Au is exposed. A first protective layer was formed. In this case, forming regions of the first protective layer of SiO ₂ is a vertical 2.0mm lateral 1.8 mm, the thermal expansion coefficient of 1.0 × 10 ^-6 ℃ ^{- 1.}
[0039]
Thereafter, a photosensitive BCB is applied, exposed and developed, and a second protective layer 14 having through holes 25a and 25b with a diameter of 80 μm and a depth of 1 μm is exposed so that the solder adhesion layer 18 made of Au is exposed. Formed. At this time, the formation region of the second protective layer 14 made of BCB was 2.04 mm long and 2.02 mm wide. At this time, the resin component was adjusted to 1.0 × 10 ⁻⁴ ° C. ^{- 1} so that the thermal expansion coefficient of the second protective layer 14 was lower than 1.0 × 10 ⁻⁶ ° C. ^{− 1} .
[0040]
The difference between the through hole of the first protective layer and the through hole of the second protective layer, that is, the gap (hereinafter referred to as the through hole difference D) was 20 μm.
[0041]
Finally, eutectic solder paste composed of 63% by weight of Pb and 37% by weight of Sn is transferred onto the solder adhesion layer 18 in the through-holes 25a and 25b by screen printing, reflowed, and solder bumps. And a thin film capacitor as shown in FIG. 1 was obtained.
[0042]
The effective electrode area of the obtained thin film capacitor is 1.8 mm ² , and the capacitance at a frequency of 1 MHz is about 30 nF. Even when mounted on the mounting substrate 40, the first protective layer 13 is peeled off and the first There were no cracks in the protective layer 13.
[0043]
Moreover, only the difference D of the above-mentioned through-hole was changed by changing only the formation area of the 1st protective layer 13, and others obtained several types of thin film capacitors produced similarly to the above. And these thin film capacitors were subjected to a bath temperature of 85 ° C. and a bath relative humidity of 85% R.D. H. In the test tank, the time change of the insulation resistance value when the applied voltage of 2.0 V was continuously loaded was observed. FIG. 4 shows the result. Referring to FIG. 4, when the through-hole difference D is 10 μm or more, the insulation resistance value does not change from the initial value even after 500 hours or more have elapsed. On the other hand, when the difference D of the through holes is less than 10 μm, it can be seen that the insulation resistance value is deteriorated with respect to the initial value as time passes, and the deterioration is faster as the difference D is smaller.
[0044]
Incidentally, the present inventor has a material of the first protective layer 13 with various changes and sets the coefficient of thermal expansion less than 1.0 × 10 ^-7 ℃ ^-1 or 1.0 × 10 ^-5 ℃ ^-1 The material of the second protective layer is changed variously, and its thermal expansion coefficient is 1.0 × 10 ⁻⁵ ° C. ⁻¹ or more and 1.0 × 10 ⁻³ ° C. ⁻ so as to be lower than the first thermal expansion coefficient. The same effect was confirmed even when the range was set to less than ¹ . Conversely, when the thermal expansion coefficient is reversed between the first protective layer and the second protective layer, the stress due to the heat treatment concentrates on the interface between the first protective layer and the second protective layer, and isolation at the interface and the first protective layer Cracks are generated in the second protective layer, so that the original function of the protective layer cannot be exhibited, and the moisture resistance of the thin film capacitor is greatly deteriorated.
[0045]
【The invention's effect】
As described in detail above, according to the present invention, the effect of thermal contraction and stress of the external terminals generated when the thin film electronic component is mounted or the external terminal of the thin film electronic component is formed on the second protective layer. Since the first protective layer itself does not crack or the interface between the first protective layer and the thin film electronic component layer in contact with the first protective layer does not peel off, the original function of the first protective layer can be obtained. This can be achieved sufficiently and the moisture resistance of the thin film electronic component is improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a thin film capacitor which is an example of a thin film electronic component of the present invention.
FIG. 2 is a plan view showing a relationship between formation regions of a first protective layer and a second protective layer.
FIG. 3 is a cross-sectional view showing a mounted state of a thin film capacitor as an example of the thin film electronic component of the present invention.
4 is a test bath temperature of 85 ° C. and a relative humidity of 85% in the bath. H. It is the characteristic view which showed the time change of the insulation resistance value with respect to an initial value when 2.0V continuous load is carried out in this test environment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Support substrate 3 ... Insulator layer 5 ... Lower electrode layer 5a ... Lower electrode layer 7 ... Upper electrode layer 7a ... Upper electrode layer 11a, 11b ... External terminal 18 ... Solder adhesion layer (terminal electrode)
13 ... 1st protective layer 14 ... 2nd protective layer 23a, 23b ... Through-hole 25a, 25b formed in 1st protective layer ... Through-hole A formed in 2nd protective layer ... Thin film element

Claims (2)

Exposed on a supporting substrate, a lower electrode layer, a thin film element sequentially laminated dielectric layers, and an upper electrode layer, and the terminal electrodes to be connected to the electrode layer electrically, the terminal electrodes while covering the thin film element A thin-film electronic component comprising: a first protective layer having a through-hole, and a second protective layer covering the first protective layer so as to cover an inner wall of the through-hole with the terminal electrode exposed. ,
Thin film electronic component thermal expansion coefficient of the second protective layer is equal to or larger than the thermal expansion coefficient of the first protective layer. 2. The thin film electronic component according to claim 1, wherein the second protective layer is formed around the inner wall of the through hole with a width of 10 μm or more in a radial direction of the through hole .

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