INTEGRATED CIRCUIT DEVICE HAVING STACKED CONDUCTIVE LAYERS CONNECTING CIRCUIT ELEMENTS THERETHROUGH

Abstract: An integrated circuit (IC) device including a stacked layer unit (11) having a plurality of stacked layers (11-1 to 11-6) each having an insulation layer (11-1b to 11-6b) and at least one conductive layer strip (11-1a to 11-6a) formed on a surface of the insulation layer, and at least one ship (3) mounted on the top of the insulation layer and having a plurality of circuit elements. The IC device also includes at least one first conductive member (13) formed in the stacked layer unit, having a low inductance for first signals applied thereto and operatively connecting the first signals to be trans­ ferred between the circuit elements; at least one second conductive member (14) formed in the stacked layer unit, having a higher inductance for the first signals than that of the first conductive member and operatively con­ necting second signals to be transferred between the cir­ cuit elements ; and, a package (21 to 24) enclosing the stacked layer unit, the chip, and the first and second conductive members, with a hermetic seal.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated circuit device. More particularly, it relates to an integrated circuit device suitably applicable to a high speed operation circuit and having stacked conductive layers connecting circuit elements in the device with inductive elements embedded therein. 2. Description of the Related Art Semiconductor integrated circuit (IC) chips in which a plurality of circuit elements, such as transistors and resistors, are formed in a semiconductor chip of silicon (Si), gallium-arsenide (GaAs), etc., and which, for example, are operable for high-speed, e.g., one gigabit per second, data processing or optical data processing, are known. Such semiconductor IC chips must naturally be hermetically sealed by a package in the same way as for normal semiconductor IC chips. In high speed IC devices, connection (lead) wires of resistive material between circuit elements in the device, must be regarded not only as resistive components but also as inductive components, due to the application of a high frequency, and wires having a low resistance and low inductance are required for high speed signal transfer lines. On the other hand, wires having a high inductance are required for power supply lines and low speed signal transfer lines, to improve isolation between different power sources and between the circuit elements in the device. In high speed IC devices, an impedance matching of the connection wires is also required, thus a normal wire connection technology as used in well known normal semiconductor IC devices cannot be used. Accordingly, the high speed IC devices are provided with multi-stacked layers, each consisting of an dielectric layer and a plurality of conductive layer strips, and connection members embedded in the multi-stacked layers in a direction perpendicular to the planes of the stacked layers. The IC chip in which the circuit elements are formed is mounted on the top of the stacked layers and hermetically sealed by the package. The connection of the circuit elements in the IC device is achieved by the connection members and the conductive layer strips of the multi-stacked layers. In the prior art high speed IC devices, however, to facilitate manufacturing, cross-sectional areas of viaholes, which are charged with an electrical conductive material therein, for the connection members in the stacked layers are identical, with the result that the cross-sectional areas of the connection members are identical for high speed signal transfer and power supply. This discrepancy to the above requirement, that is, low inductance for high speed signal transfer and not necessarily low inductance for power supply and low speed signal transfer, may be acceptable for low speed IC devices, e.g., approximately lower than one gigabit per second. However, the above discrepancy is not admissible for high speed IC devices, e.g., approximately more than several gigabits per second, because, even if each circuit element has a high speed characteristic, a high speed operation of the high speed IC devices cannot be obtained. SUMMARY OF THE INVENTION An object of the present invention is to provide an integrated circuit device operable for high speed signals. Another object of the present invention is to provide an integrated circuit device having an improved noise resistance and isolation between circuits under the application of high speed signals. According to the present invention, there is provided an integrated circuit (IC) device including: a stacked layer unit including a plurality of stacked layers each having an insulation layer and at least one conductive layer strip formed on a surface of the insulation layer; at least one chip mounted on the top of the insulation layer of the stacked layer in the stacked layer unit and including a plurality of circuit elements; at least one first conductive member formed in the stacked layer unit, having a low inductance for first signals applied thereto and operatively connecting the first signals to be transferred between the circuit elements in the chip; at least one second conductive member formed in the stacked layer unit, having higher inductance for the first signals than that of the first conductive members and operatively connecting second signals to be transferred between the circuit elements in the chip; and a package enclosing the stacked layer unit, the chip and the first and second conductive members with a hermetic seal. Each of the first and second conductive members includes a viahole formed in the insulation layer(s) of the stacked layer unit and operatively connected to one of the conductive layer strips at any stacked layer, or to two conductive layer strips placed on different insulation layers at end(s) thereof. According to an aspect of the present invention, preferably, the first members have a large cross-sectional area and the second conductive members have a small cross-sectional area, when the first and second conductive members are formed of the same conductive material. The cross-sectional area of each first conductive member may be defined in such a way that a predetermined low inductance for a predetermined frequency is obtained for the first signal. Also, the cross-sectional area of each second conductive member may be defined in such a way that a predetermined high inductance is obtained for the first signal. According to another aspect of the present invention, preferably, each of the first conductive members have a short length along an axial line of the viahole and each of the second conductive members have a long length along the same axial line, when the first and second conductive members are formed of the same conductive material. The short length of each of the first conductive members may be defined in such a way that a predetermined low inductance is obtained for the first signal. Also, the long length of each of the second conductive members may be defined in such a way that a predetermined high inductance is obtained for the first signal. According to still another aspect of the present invention, more preferably, the first conductive members have a large cross-sectional area and a short length along an axial line of the viahole, and the second conductive members have a small cross-sectional area and long length along the same axial line, when the first and second conductive members are formed of the same conductive material. The short length and large cross-sectional area of each of the first conductive members may be defined in such a way that a predetermined low inductance is obtained for the first signal. Also, the long length and small cross-sectional area of each of the second conductive members may be defined in such a way that a predetermined high inductance is obtained for the first signal. According to yet another aspect of the present invention, the second conductive members may include coil(s) inserted into a throughhole(s), and having a high inductance. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and features of the present invention will be described below in detail with reference to the accompanying drawings, in which: Fig. 1 is a sectional view of an integrated circuit (IC) device of an embodiment in accordance with the present invention, taken along the line X-X' in Fig. 2; Fig. 2 is a plan view of the IC device in Fig. 1, taken along the line H-H' in Fig. 1; Fig. 3 is a circuit diagram of the IC device shown in Fig. 1; Fig. 4 is a sectional view of a part of an IC device of another embodiment in accordance with the present invention; and Fig. 5 is a sectional view of a part of an IC device of still another embodiment in accordance with the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 1, an IC device 1 of an embodiment in accordance with the present invention includes a package 2 consisting of a cap 21 formed of an insulation material, an upper shield wall 22 formed of an insulation material, a seal layer 23 and a side wall 24 formed of an insulation material, an IC chip 3 including circuit elements as shown in Fig. 3, and a stacked layer unit 11. The IC chip 3 is mounted on the top of the stacked layer unit 11 and is located in a hermetically sealed cavity 20 defined by the package 2 and the stacked layer unit 11. The above insulation material is, more generally speaking, a dielectric material. The IC device 1 is mounted on a printed circuit board 52 through conductive leads 51 and secured to a plate 53 through a stud 54 having one end fixed to a bottom surface 11-6C of the stacked layer unit 11, the shaft of the stud 54 passing through a hole 56 in the printed circuit board 52 and the plate 53, and the other end of the stud 54 being fastened thereto by a nut 55. The stacked layer unit 11 includes six stacked layers 11-1 to 11-6. Each of the stacked layers 11-1 to 11-6 includes an insulation layer (or dielectric layer) as shown by the layer 11-1b for the upper layer 11-1, and at least one conductive layer strip as shown by the strip 11-1a. The insulation layers 11-1b, etc., are formed of a sintered ceramic and have a thickness of, for example, 250 µm. An exemplary plan view of the upper layer 11-1 (hereinafter called chip mount layer) is shown in Fig. 2. A plurality of conductive layer strips 11-1a are provided on the insulation layer 11-1b as microstrip lines around the IC chip 3. A plurality of microstrip lines 15-1 and 15-2 are also provided on the insulation layer 11-1b adjacent to the IC chip 3. The conductive layer strips of the second layer 11-2 are used for ground lines or power supply lines, and thus the second layer 11-2 hereinafter is called a ground layer. The conductive layer strips of the fourth and sixth layers 11-4 and 11-6 are also used for ground lines or power supply lines. Conductive layer strips of the third layer 11-3 are used for high speed signal lines, and thus the layer 11-3 is hereinafter called a high speed signal layer. The conductive layer strips of the fifth layer 11-5 are used for low speed signal lines, and thus the layer 11-5 is hereinafter called a low speed signal layer. In Fig. 1, the conductive layer strip of the high speed signal layer 11-3 is provided between the conductive layer strips of the ground layers 11-2 and 11-4, forming a triplate strip line structure of these three layers 11-2 to 11-4 suitable for an impedance matching of, for example, 50Ω or 75Ω. The conductive layer strip of the high speed signal layer 11-3 is led to the outside by a coplaner 25, having a constant characteristic impedance independent of distance, provided on an outer wall of the side wall 24. Conductive members 13-1, 14-1 and 14-2 consist of viaholes 12-1 to 12-3 formed vertically to the plane of the chip mount layer 11-1 in the stacked layer unit 11. The first conductive member 13-1 has a large cross-sectional area, but the second conductive members 14-1 and 14-2 have a small cross-sectional area which is the same for both the conductive members 14-1 and 14-2. The first conductive member 13-1 is shorter than the second conductive members 14-1 and 14-2. The conductive member 14-1 is longer than the conductive member 14-2. When these conductive members 13-1, 14-1, and 14-2 are made of the same conductive material, such as tungsten (W) or molybdenum (Mo), the first conductive member 13-1 has the lowest resistance and the conductive member 14-1 has the highest resistance. Taking into account an inductance which may appear due to the application of a high frequency, the first conductive member 13-1 may have a small inductance, but the conductive member 14-1 may have a large inductance. In the same way, the ground layer 11-4, the low speed signal layer 11-5, and the ground layer 11-6 are also constructed as a triplate strip line structure. In addition, the seal layer 23 has an insulation layer 23b and a conductive layer 23a as for the ground layer which is connected to the ground layer 11-2, and accordingly, the seal layer 23 functions not only as the hermetic sealing but also as ground layer. The seal layer 23a, the chip mount layer 11-1, and the ground layer 11-2 are formed as a partial-triplate strip line. These triplate strip line structures are also suitable for impedance matching. The above stacked layer unit 11 and the conductive members 13-1, 14-1 and 14-2 are formed by the following steps; (1) preparing thin ceramic films having a thickness of 250 µm, i.e., so-called green sheets, forming insulation layers 11-1b to 11-6b; (2) making viaholes (12-1 to 12-3) by punching holes and filling conductive material, for example, tungsten (W) or molybdenum (Mo), in the holes; (3) patterning and forming the conductive layer strips 11-1a to 11-6a of, for example, tungsten (W) or molybdenum (Mo), and having a thickness of, for example, 15 µm, and a width of, for example, 100 µm or more, on the insulation layers 11-1b to 11-6b; (4) stacking the insulating layers 11-1b to 11-6b having the conductive layer strips 11-1a to 11-6a formed thereon and the viaholes 12-1 to 12-3; (5) sintering the same stacked layers at a temperature high enough, for example, 1500°C, to sinter the ceramic films. Referring to Fig. 3, the IC chip 3 in Fig. 1 includes a field effect transistor (FET) 31 with resistors 32 to 34, and capacitors 35 and 36 at the outside of the IC chip 3, forming a first stage circuit. An FET 41, resistors 42 to 44, and capacitors 45 and 46, forming a second stage circuit, and a cut-off capacitor 40 between the first and second stage circuits are also mounted in the package by other chips not shown in Figs. 1 and 2. In Fig. 3, lead wires between the above circuit elements are indicated by bold lines, for example, 13a, 13b, 13c, 13d, are high-speed signal transfer lines. Other wires between other circuit elements and indicated by thin lines, e.g., 14a, are low-speed signal transfer lines. Power is supplied through a terminal V or by grounding. As described above, in order to ensure a high speed signal propagation, the lead wires for high speed signal transfer must have a low inductance, to avoid signal propagation delay and wave distortion. Accordingly, as shown in Fig. l, the high speed signal transfer lead wires 13a to 13d, etc., are formed by a bold wire 18 having a large cross-sectional area and a short length, a microstrip line 15-1 having a low impedance and used for impedance matching, a conductive member 13-1, and a conductive layer strip of the high speed signal layer 11-3. These elements have an essentially low resistance for a low frequency signal, but inductance components are added by applying a high frequency signal of, for example, several gigabits per second. The inductance values appearing in these connection members 18, 15-1, 13-1, and 11-3 may be kept at a low level due to the above structure, nature, and features. The diameter of the conductive member 13-1 of tungsten (W) or molybdenum (Mo) is, for example, 1 mm, and the length is 1 mm. Consequently, signals passing through a path including, for example, an input terminal T IN , a gate of the FET 31, a drain of the FET 31, the capacitor 40, a gate of the FET 41, a drain of the FET 41, and an output terminal T OUT , may be propagated at a high speed defined by the response characteristic of the FETs 31 and 41, etc. The lead wire 13a in Fig. 3 may be formed by the conductive layer strip of the high speed signal layer 11-3, the conductive member 13-1, the microstrip line 15-1, and the wire 18. In this path, the impedance matching is carried out at the triplate strip line of the high speed signal layer 11-3 and the microstrip line 15-1. On the other hand, in order to ensure isolation between different power supplies and between the circuits, the lead wires for low speed signal transfer, power supply, etc., preferably have a higher inductance than that of the high speed signal transfer lead wires. Accordingly, the power supply lead wires are formed by a lead wire 19, the conductive member 14-1, and the ground layer 11-6, or the conductive member 14-2 and the ground layer 11-4. These connection members have a small cross-sectional area and a long length, and have a high resistance, with the result that a high inductance appears due to the application of a high frequency signal. As a result, the high speed signals on the power supply lead wires are attenuated, improving the isolation between different power sources, and thus improving the resistance to noise. Figure 4 shows another stacked layer unit 11' including layers 11-1' to 11-4'. Conductive members 13-5, 13-6 and 14-5 to 14-7 consist of viaholes 12-5 to 12-9, respectively. The conductive members 13-5 and 13-6 have a large cross-sectional area, and thus a low inductance and low inductance for a high frequency signal, and accordingly, may be used as the high speed signal transfer lead wires. The ends of the conductive member 13-5 are placed in contact with the adjacent conductive layer strips 11-1a' and 11-2a', respectively, and thus the length of the conductive member 13-5 is short. One end of the conductive member 13-6 is placed in contact with a bottom conductive layer strip 11-4a', and the other end is connected to a circuit element on the IC chip through a lead (not shown), thus the length of the conductive member 13-6 is longer than that of the conductive member 13-5. In order to obtain a low inductance for a high frequency signal, in the same way as for the conductive member 13-5, the cross-sectional area of the conductive member 13-6 is made larger than that of the conductive member 13-5. These lengths and cross-sectional areas may be designed to have a suitable low impedance by taking into account the material to be used therefor. The conductive members 14-5 to 14-7 have a small cross-sectional area, and thus may be used for low speed signal transfer lead wires, including power supply lines. The cross-sectional areas of the conductive members 14-5 to 14-7 are the same in this embodiment. The conductive member 14-5 is both placed in contact with the adjacent conductive layer strips 11-1a" and 11-2", and electrically isolated from the conductive layer strips 11-1a' and 11-2a', respectively. The conductive member 14-6 is also both placed in contact with the conductive layer strips 11-2a" and 11-4a", and electrically isolated from the conductive layer strip 11-4a'. The conductive member 14-7 is placed in contact with the conductive layer strips 11-1a" and 11-4a". The conductive members for the low speed signal transfer and power supply are preferably formed with a small uniform cross-sectional area, to facilitate design and patterning of the viaholes and the conductive members. Figure 5 is a partial sectional view of layers 11-1"' and 11-2"' and a coil 16 inserted in a throughhole 12-9 formed in the layers 11-1"' and 11-2"'. One end of the coil 16 is connected to a conductive layer strip 11-1a"' and the other end of the coil is connected to a conductive layer strip 11-2a"', by sintered conductive paint pads 17-1 to 17-4. The coil 16 has a large inductance, as described later, and thus may be used for the power supply lines. The above construction may be formed by the following steps; (1) preparing thin ceramic films having a thickness of, for example, 250 µm, to form insulaion layers 11-1b"' 20 and 11-2b"'; (2) patterning and forming conductive layer strips 11-1a"' and 11-2a"' having a thickness of, for example, 15 µm, on the insulation layers 11-1b"' and 11-2b"'; (3) forming a throughhole 12-9 in a position where 25 the conductive layer strips do not exist in the insulation layers 11-1b" and 11-2b"; (4) inserting the coil 16 in the throughhole 12-9; (5) coating the conductive paint pads 17-1 to 17-4 on the ends of the coil 16; (6) stacking the insulation layers 11-1b" and 11-2b"; and (7) sintering the stack at a high temperature of approximately 1500 °C. The material of the coil 16 may be tungsten (W), molybdenum (Mo) or the like, which have a high resistance to a high sintering temperature. The inductance L of the coil 16 can be represented by the equation (1): where, R .... radius of the coil [m] N .... number of turns in the coil ℓ .... length of the coil [m] µ r ... specific magnetic permeability K .... Nagaoka's coefficient. For example, when ℓ=2500 µm, R=1000 µm, N=10, and the inductance L is 120 nH. At a frequency of 1.8 GHz, the inductance L may be regarded as an impedance of 1.35 kΩ. Accordingly, when the coil 16 is inserted in the power feeding line, the coil 16 functions as a noise eliminating element, improving the noise elimination effect. Other modifications of the formation of the high inductance element provided in the power supply line may be made in addition to that shown in Fig. 5. In Fig. 4, a high inductance component may be obtained by series-connecting the conductive members 14-5 to 14-7 through the conductive layer strips 11-2a" and 11-4a", however, the conductive layer strip 11-1a" between the conductive members 14-5 and 14-7 must be cut to make a series-connected conductive element having a high inductance. A high inductive element also may be obtained by inserting a folded wire into a throughhole, for example, throughhole 12-9 in Fig. 5. In Figs. 1 and 4, the viaholes and throughholes are normally formed with a circular cross section, however, this cross section may be formed in another shape, such as a square. In addition, the insulation layers of the stacked layer unit 11 do not necessarily have the same thickness. Furthermore, the chip mounted on the package may be a single GaAs FET chip, not an IC.

Claims: An integrated circuit device comprising : a plurality of stacked insulation layers (11-1b to 11-6b); a plurality of conductive layer strips (11-1a to 11-6a), one of which is formed on a surface of each of said insulation layers; a chip (3), mounted on the uppermost of said insulation layers, and including a plurality of circuit elements; first conductive means (13), formed in said stacked insulation layers and coupled to said chip and having a first inductance, for supplying a first signal, which is a high frequency signal, applied to or received from said circuit elements in said chip; second conductive means (14), formed in said stacked layers and coupled to said chip and having a second inductance higher than said first inductance, for supplying a second signal, which is a low frequency signal having a lower frequency than that of the high frequency signal, applied to or received from said circuit elements in said chip; and package means (21 to 24) for enclosing and hermetically sealing said stacked insulation layers, said chip, and said first and said second conductive means, wherein said first (13) and said second (14) conductive means each comprise: a viahole (12-1 to 12-3) formed in said stacked insulation layers, and a conductive material (13-1, 14-1, 14-2) having first and second ends, formed in said via hole, which is connected to one of said conductive layer strips at said first end and connected to another of said conductive layer strips at said second end. An integrated circuit device according to claim 1, wherein each of said first conductive means (13) has a large crosssectional area and each of said second conductive means (14) has a small cross-sectional area. An integrated circuit device according to claim 2, wherein said first (13) and second (14) conductive means are formed of the same conductive material. An integrated circuit device according to claim 3, wherein said cross-sectional area of said each first conductive means (13) is defined in such a way that a predetermined low inductance is obtained for said first signal. An integrated circuit device according to claim 4, wherein said cross-sectional area of said each second conductive means (14) is defined in such a way that a predetermined high inductance is obtained for said first signal. An integrated circuit device according to claim 1, wherein each of said first conductive means (13) has a short length along an axial line of said viahole (12-1 to 12-3) and each of said second conductive means (14) has a long length along said axial line. An integrated circuit device according to claim 6, wherein said first (13) and second (14) conductive means are formed of the same conductive material. An integrated circuit device according to claim 7, wherein said short length of each of said first conductive means (13) is defined in such a way that a predetermined low inductance is obtained for said first signal. An integrated circuit device according to claim 8, wherein said long length of each of said second conductive means (14) is defined in such a way that a predetermined high inductance is obtained for said first signal. An integrated circuit device according to claim 1, wherein each of said first conductive means (13) has a large crosssectional area and a short length along an axial line of said viahole (12-1 to 12-3), and each of said second conductive means (14) has a small cross-sectional area and a long length along said axial line. An integrated circuit device according to claim 10, wherein said first (13) and second (14) conductive means are formed of the same conductive material. An integrated circuit device according to claim 11, wherein said short length and large cross-sectional area of each of said first conductive means (13) are defined in such a way that a predetermined low inductance is obtained for said first signal. An integrated circuit device according to claim 12, wherein said long length and small cross-sectional area of each of said second conductive means (14) are defined in such a way that a predetermined high inductance is obtained for said first signal. An integrated circuit device according to claim 1, wherein said second conductive means (14) comprise coil/s inserted in a/several throughhole/s (12-1 to 12-3) and having a high inductance.

Inventors: EMORI, SHINJI, KITASAGAMI, HIROO, MIYAUCHI, AKIRA, NISHIMOTO, HIROSHI C/O SUZUKI, OKIYAMA, TADASHI, SUGIMOTO, MASAHIRO, TAMADA, HARUO
Applicants: FUJITSU LIMITED
Application year: 1986
Main classification: H01L23
IPC codes: H01P5, H01L23, H05K3, H05K1, H01P3, H01P1, H01L21