JP3410185B2 - Semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a decoupling ceramic capacitor integrally connected to a silicon semiconductor element. 2. Description of the Related Art In recent years, the scale and speed of semiconductor integrated circuits using semiconductor elements made of silicon single crystal have been rapidly increasing, and digital circuits using such semiconductor integrated circuits have become increasingly common. It's getting more complicated. And with that,
In a digital circuit, several switching operations are performed simultaneously, and the voltage in the circuit fluctuates due to the current generated at that time, causing malfunction of the circuit or limiting the performance of the circuit system. A problem such as getting lost has come to occur. The magnitude of such a voltage fluctuation, that is, the noise depends on the magnitude of the current in the circuit and its rise time, and the inductance of the semiconductor element. As a countermeasure against the above problem, a capacitor (decoupling capacitor) which is a supply source of a current required for switching and which decouples an inductance of a package containing a semiconductor element is used for a current circuit used for switching. The method is generally adopted. In this case, the decoupling capacitor is required not only to have a small internal inductance but also to have a small inductance (loop inductance) between the decoupling capacitor and the semiconductor element. Therefore, as a method of using the above decoupling capacitor, a low-inductance capacitor, for example, a porcelain capacitor is built in a package containing a semiconductor element, or electrically and mechanically through a gold ball to a silicon single crystal semiconductor element. It has been proposed to fix and directly join together. [0004] As described above, a porcelain capacitor is used for the decoupling capacitor which is integrally coupled to the semiconductor element made of silicon single crystal because of its low inductance. However, BaTiO ₃ , which is a main material of a conventional ceramic capacitor, has a larger linear thermal expansion coefficient than a silicon single crystal, and the difference is too large, so that the temperature range of a semiconductor device using a silicon single crystal semiconductor element is large. There is a drawback in that the capacitor porcelain cannot withstand a temperature cycle load at a certain temperature of -55 to + 150 ° C. and is broken from a joint with a semiconductor element due to thermal stress caused by a difference in linear thermal expansion coefficient. Therefore, as a material for the decoupling capacitor, a dielectric material of a high dielectric constant type having a small difference in linear thermal expansion coefficient from a silicon single crystal has been demanded. An object of the present invention is to provide a decoupling capacitor which is electrically and mechanically integrated with a semiconductor element made of silicon single crystal and has a small linear thermal expansion coefficient.
A decoupling porcelain capacitor having a small difference from a linear thermal expansion coefficient of a silicon single crystal at 55 ° C. to + 150 ° C., and thus having a small thermal stress applied when integrally bonded to the silicon single crystal and having a large relative dielectric constant; Accordingly, it is an object of the present invention to provide a semiconductor device including a decoupling capacitor that is electrically and mechanically integrated with a semiconductor element made of silicon single crystal. [0007] A semiconductor device according to the present invention comprises:
A semiconductor device comprising: an insulating substrate; a semiconductor element made of silicon single crystal mounted on the insulating substrate; and a decoupling capacitor electrically and mechanically integrated on an upper surface of the semiconductor element. The capacitor includes a perovskite-type composite oxide dielectric ceramic containing Pb, Mg, Zn, and Nb, a plurality of internal electrodes laminated inside the dielectric ceramic, and a capacitor connected to the internal electrodes. And a difference in linear thermal expansion coefficient between the semiconductor element and the semiconductor element in a temperature range of −55 ° C. to + 150 ° C. is 3.0 × 10 ⁻⁶ / ° C. or less. And The P which forms the decoupling capacitor of the present invention
As a perovskite-type composite oxide dielectric porcelain containing b, Mg, Zn and Nb (hereinafter abbreviated as the present dielectric porcelain), Pb (Mg _1/3 Nb _2/3 ) O ₃ porcelain and Pb (Zn
_1/3 Nb _2/3 ) O ₃ dissolved in solid solution to shift the Curie temperature to around room temperature, and Pb (Mg _1/3 N)
b _2/3 ) O ₃ porcelain in which Pb (Sm _1/2 Nb _1/2 ) O ₃ is dissolved in solid solution to adjust the temperature characteristics. The present inventor has found that such a dielectric porcelain has a linear thermal expansion coefficient (hereinafter, referred to as a linear expansion coefficient) very close to that of a silicon single crystal as compared with a conventional dielectric material, BaTiO ₃ porcelain. It has been found that the dielectric constant is high, the temperature characteristics are good, and the ceramics for a capacitor have excellent characteristics. That is, a silicon single crystal of -55 to +150
The coefficient of linear expansion at ℃ is about 1.8 to 3.1 × 10 ^-6 / ° C.
About 5.8 to 10.5 × 10 for BaTiO _3.
^It is as large as ^-6 / ° C. On the other hand, the present dielectric porcelain, for example, P
b (Mg _1/3 Nb _2/3 ) O ₃ with Pb (Zn _1/3 N
b _2/3 ) The porcelain in which O ₃ is dissolved is 1.3 to 5.3 × 1.
0 ⁻⁶ / ° C., and the difference in linear expansion coefficient from the silicon single crystal is small. Further, the present inventors joined a dielectric ceramic porcelain plate having various linear expansion coefficients of 12 mm square and 0.6 mm thickness to a silicon single crystal plate so that the distance between joints became 10 mm. When the difference in linear expansion coefficient, which is fixed mechanically and does not break due to a temperature cycle load in a temperature range of -55 to + 150 ° C, is examined, it is necessary that the difference be 3.0 × 10 ^-6 / ° C or less. And more preferably 2.2 × 10 ⁻⁶ /
It has been found that the temperature is desirably not more than ° C. The inventor considers the reason as follows. The thermal stress generated in the dielectric porcelain mechanically joined to the silicon single crystal by the temperature cycle load is obtained by multiplying the product of the difference Δα of the coefficient of linear expansion at each temperature and the Young's modulus E of the dielectric porcelain by −55 to −55. It is determined as an integral over the temperature range of + 150 ° C. Young's modulus E is
It is approximately 1.1 to 1.8 × 10 ⁻⁶ kgf / cm ² , and if the difference in linear expansion coefficient between the dielectric ceramic and the silicon single crystal is within the above range, almost no tensile stress remains in the dielectric ceramic. It is considered that the thermal stress generated in the dielectric porcelain does not exceed the flexural strength of the porcelain when it is ideally joined so as not to be bonded. Therefore, by using the present dielectric porcelain as a decoupling capacitor that is electrically and mechanically integrated with the silicon single crystal semiconductor element, it is stable against a temperature cycle load and does not break down due to thermal stress. A semiconductor device can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present dielectric ceramic, a decoupling capacitor using the same, and a semiconductor device will be described in detail based on specific examples. As a starting material for this dielectric porcelain,
PbO, MgO, were prepared powders of _{Nb 2 O 5, ZnO, Sm} 2 O 3 and BaTiO _3. Further, BaTiO ₃ , BaZnO _3, and N
Each powder of d ₂ O ₃ was prepared. The purity of each powder is Sm ₂
O ₃ and Nd ₂ O ₃ are at least 99.9%, and others are at least 99.5%. A sample of the present dielectric porcelain was prepared as follows. First, the powders of the above-mentioned starting materials were converted into the following A and B
Were weighed so as to have the composition shown in Table 1 and mixed by a ball mill. These were placed in a magnesia porcelain container, calcined at 800 ° C., coarsely ground, and further finely ground with a ball mill using zirconia balls as media. Next, a dispersant, water and an organic binder were added to the obtained powder to form a slurry, and a green sheet having a thickness of 50 μm was formed by a doctor blade method. This green sheet was provided with a through hole for connecting the internal electrode and the external electrode of the multilayer capacitor. On the other hand, an ethyl cellulose resin and a naphtha-based solvent were added to Ag powder and kneaded to prepare an internal electrode paste. Then, the internal electrode paste was printed on the green sheet, and further printed on the through holes to fill the internal electrode paste. After laminating the green sheets and hot pressing, the green sheets were cut into individual green chips of 15 mm × 15 mm square. This chip is degreased at 300 ° C., placed in a magnesia porcelain container, and baked at 900 to 930 ° C. for 2 hours, and is about 12 mm × 12 mm square and about 0.1 mm thick.
Samples A and B of 6 mm square chip were obtained. [Sample A] Pb (Mg _1/3 Nb _2/3 )
O ₃ : 62.50 mol% Pb (Zn _1/3 Nb _2/3 ) O ₃ : 37.50 mol% [Sample B] Pb (Mg _1/3 Nb _2/3 ) O ₃ : 48.97
_{Mol% Pb (Zn 1/3 Nb 2/3)} O 3: 44.13 _{mol% Pb (Sm 1/2 Nb 1/2)} O 3: 2.00 mol% BaTiO _3: 4.90 mole%. In the preparation of a conventional dielectric ceramic sample, each of the starting material powders was weighed so as to have the composition shown in C below, and the Pd powder was used as the internal electrode paste and the firing temperature was determined. A sample C was obtained in the same manner as described above except that the temperature was set to 1280 ° C. [Sample C] BaTiO ₃ : 91.00 mol% BaZrO ₃ : 8.40 mol% Nd ₂ O ₃ : 0.60 mol% And square plates of the obtained samples A, B and C On one principal plane where the through-hole end of the chip is exposed,
About 0.6mm x 0.6mm as external electrode (terminal electrode)
Ag-Pd electrode film was formed. FIG. 2 is a cross-sectional view showing the configuration of the decoupling capacitor manufactured in this manner. In the figure, reference numeral 1 denotes a dielectric porcelain forming a body of a capacitor, in which an internal electrode 2 which is printed and laminated is provided.
It is connected as one electrode group, is guided to one main plane of the dielectric ceramic 1, and is connected to the external electrode 4. The capacity of each of the samples A, B and C thus produced was 3
03 nF, 128 nF, and 225 nF. Next, the linear expansion coefficients of the samples A, B and C and the silicon single crystal plate in the temperature range of -55 ° C. to + 150 ° C. were measured using a Rigaku TS-200 type TMA device (thermomechanical analyzer). The measurement was performed using liquid nitrogen as a refrigerant. The result is shown in FIG. In the figure, the horizontal axis represents temperature, and the vertical axis represents the value of the linear expansion coefficient. The symbols △, Δ, ×, and ● in the figure indicate the results of measurement of the linear expansion coefficients of the samples A, B, C, and silicon single crystal, respectively. The diagram connecting the symbols indicates the linear expansion of each sample. The temperature change of the coefficient is shown. From the results shown in FIG. 3, the linear expansion coefficients of the samples A and B are smaller than those of the sample C (conventional example) and are close to the linear expansion coefficient of the silicon single crystal.
It can be seen that the difference in linear expansion coefficient between the present composition and the silicon single crystal in the temperature range of 0 ° C. is 3.0 × 10 ⁻⁶ / ° C. or less. Next, the configuration of the semiconductor device according to the present invention will be described.
FIG. 1 is a sectional view. In the figure, reference numeral 5 denotes an insulating substrate made of alumina porcelain or the like, which is a substrate of this semiconductor device.
A silicon single crystal semiconductor element 6 such as a semiconductor integrated circuit element is mounted on the insulating substrate 5, and further on the semiconductor element 6 via a bonding portion 7 made of a gold ball or the like.
The decoupling capacitor 8 composed of the above-mentioned ceramic capacitor is electrically and mechanically integrated. Further, on the insulating substrate 5 around the semiconductor element 6, a porcelain layer 9, 1 formed by sintering simultaneously with the substrate 5 with porcelain of the same quality as the substrate 5.
0 and 11 are sequentially formed, and the porcelain layers 9 and 10 have wiring thereon made of tungsten or the like, and portions of the wiring exposed in the space where the semiconductor element 6 is mounted are: Gold plated. The gold-plated portion of the wiring is connected to the wiring of the semiconductor element 6 by the gold wire 12. The porcelain layer 11 is formed of the semiconductor element 6.
When sealing the space on which is to be mounted, it serves as a platform for receiving the sealing member. With respect to the decoupling capacitor integrally coupled to the silicon single crystal semiconductor device in such a configuration, the durability of the integrally coupled decoupling capacitor to a temperature cycle load was evaluated by performing the following test. First, the decoupling capacitors of Samples A, B, and C were integrally connected to a semiconductor element made of silicon single crystal as follows. That is, 15
An Ag-Pd film is formed by metallizing on a silicon single crystal plate having a size of about 15 mm square and a thickness of about 1.2 mm, and a spherical solder made of a Sn-Pb eutectic alloy is formed on this film,
Temperature cycle load evaluation samples a and b in which the four points at the four corners of the decoupling capacitor sample are joined so that the distance between the joining points is 10 mm, and the decoupling capacitor and the silicon single crystal plate are mechanically integrated. And c were produced. Samples a, b and c thus prepared
Were alternately placed in a constant temperature bath at −55 ° C. and a constant temperature bath at + 150 ° C. for 30 minutes, and a temperature cycle load was applied for 40 cycles. After this test, the solder at the junction between the decoupling capacitor of each sample and the silicon single crystal plate was melted, the decoupling capacitors were removed, and each was observed under a stereoscopic microscope of 20 times magnification. As a result, no change was observed in Samples a and b as compared to before the test, whereas in Sample c, cracks occurred in the capacitor porcelain starting from the junction and were broken by the temperature cycle load. Was done. As described above, while cracks occur in the capacitor porcelain only due to the temperature cycle load on the sample c,
Since cracks did not occur in samples a and b, the difference in the coefficient of linear expansion between the capacitor porcelain and the silicon single crystal was 3.
0 × 10 ⁻⁶ / ° C. or less is −55 ° C. to + 150 ° C.
It is understood that it is necessary to withstand a temperature cycling load in the temperature range of ° C. Thus, it has been confirmed that the ceramic capacitor made of the dielectric ceramic according to the present invention has excellent characteristics as a decoupling capacitor integrated with a silicon single crystal semiconductor element, and is stable against a temperature cycle load. Thus, a semiconductor device which is not broken by thermal stress was obtained. As described in detail above, according to the present invention,
A dielectric ceramic suitable for a decoupling ceramic capacitor, having a small linear expansion coefficient, a small difference from the linear expansion coefficient of a silicon single crystal, and a large relative permittivity, could be provided. According to the present invention, a decoupling capacitor having a small thermal stress with a silicon single crystal and capable of reducing destruction due to a temperature cycle load when electrically and mechanically integrated with a semiconductor element made of a silicon single crystal. And thereby a semiconductor device that is stable against a temperature cycle load and does not break down due to thermal stress can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a configuration of an embodiment of a semiconductor device of the present invention. FIG. 2 is a sectional view showing a configuration of a decoupling capacitor according to an embodiment of the present invention. FIG. 3 is a diagram showing a temperature change of a linear expansion coefficient of a dielectric ceramic and a silicon single crystal plate according to the present invention. [Description of Signs] 1... Dielectric ceramic 2... Internal electrode 4... External electrode 5. 6 ... Semiconductor element 7 ... Junction 8 ... Decoupling capacitors 9, 10, 11 ... Ceramic layer 12 ...・ Gold wire

Claims (1)

Claims: 1. An insulating substrate, a semiconductor element made of silicon single crystal mounted on the insulating substrate, and a decoupling electrically and mechanically integrated integrally with an upper surface of the semiconductor element. A decoupling capacitor comprising: Pb, Mg, Zn,
A perovskite-type composite oxide dielectric porcelain containing Nb ;
A plurality of internal electrodes laminated inside the dielectric porcelain;
Connected to the internal electrode and formed on the main surface of the dielectric porcelain
Together with external electrodes was, -55 ° C. to + 150 ℃
A semiconductor device having a linear thermal expansion coefficient difference of 3.0 × 10 ⁻⁶ / ° C. or less in the above temperature range.