Integrated circuit device having strip line structure therein.

0001The 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 including a stacked layer unit having a triplate strip line structure therein.

0002Semiconductor 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-arsenic (GaAs), etc., and which, for example, are operable at high-speed, e.g., one giga bits per second, data processing or optical data processing, are known. Such semiconductor IC chips must be naturally hermetically sealed by a package in the same way as for normal semiconductor IC chips.

0003In high speed IC devices, connection (lead) wires of resistive material between circuit elements in the device must be regarded as not only resistance components but also as inductance 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 difference 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 insulation 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.

0004The above requirement for the impedance matching should be applied to external connection wires connecting between the high speed IC device and other high speed IC devices or other high speed operation circuits. Accordingly, triplate strip lines or microstrip lines are used for such external connection wires. However, in the prior art, the triplate strip lines or microstrip lines suffer from the disadvantage of a poor impedance matching, etc., which will be described later with reference to a specific example. In particular, the above poor impedance matching is not admissible for high speed IC devices, e.g., approximately more than one giga bits per second.

0005It is accordingly desirable to provide an integrated circuit device having a good impedance matched strip line structure therein for an external connection wire.

0006It is further desirable to provide an high speed integrated circuit device having improved high speed signal propagation characteristics.

0007According to an embodiment of the present invention, there is provided an integrated circuit device including: at least one semiconductor chip having a plurality of circuit elements; a package enclosing the semiconductor chip with a hermetic seal; and a strip line unit for connecting the circuit elements in the semiconductor chip to circuits outside of the package, having a microstrip line structure and a triplate strip line structure serial-connected to the microstrip line structure and connecting the outside circuits. The triplate strip line structure has a characteristic impedance equal to that of the microstrip line structure, so that the strip line unit has a satisfactory impedance matching.

0008The strip line unit may be formed in a stacked layer unit including at least three stacked layers, each having an insulation layer and at least one conductive layer formed on a surface of the insulation layer, and a cavity defined by the package. A microstrip line of the microstrip line structure is connected to a center conductive layer strip line of the triplate strip line structure in series. The center conductive layer strip line has a predetermined impedance so that the triplate strip line structure has a same characteristic impedance as the microstrip line structure.

0009The microstrip line structure may be formed by the microstrip line having predetermined thickness and width and facing the cavity, an insulation layer of the stacked layer unit having a predetermined dielectric constant and the microstrip line being mounted thereon at a plane, and a conductive layer of the stacked layer unit mounted on the insulation layer at another plane opposite to the plane of the microstrip line. The triplate strip line structure also may be formed by the center conductive layer strip line directly connected to the microstrip line, the insulation layer, the center conductive layer strip line mounted thereon at one plane, the conductive layer mounted on the insulation layer at another plane, another insulation layer having a predetermined dielectric constant and a predetermined length, formed on the center conductive layer strip line and the insulation layer and forming a part of the package, and another conductive layer formed on another insulation layer.

0010Preferably, the microstrip line and the center conductive layer strip line have the same thickness, and the center conductive layer strip line has a smaller width than that of the microstrip line along the length of the another insulation layer.

0011In addition, the triplate strip line structure may be further formed by the center conductive layer strip line, a second insulation layer of the stacked layer unit having a predetermined dielectric constant, the conductive layer strip line contacting thereon at one plane, a second conductive layer formed on the second insulation layer at another plane, a third insulation layer of the stacked layer unit having a predetermined dielectric constant, the conductive layer strip line mounted thereon at one plane, and a third conductive layer formed on the third insulation layer at another plane. The microstrip line may be formed on a different insulation layer on which the center conductive layer strip line is formed. The microstrip line is connected to the center conductive layer strip line through a conductive member embedded in the second and third insulation layers in a direction perpendicular to a plane of the second and third insulation layers.

0012The first conductive layer of the microstrip line structure and the second conductive layer of the triplate strip line structure may be unified and positioned on a same level in the stacked layer unit.

0013Preferably, the microstrip line and the center conductive layer strip line have same thickness, and the center conductive layer strip line has a smaller width than that of the microstrip line.

0014The stacked layer unit may be formed as a part of the package. The semiconductor chip is mounted on a top insulation layer of the stacked layer unit. The semiconductor chip and the strip line unit are enclosed by the package and the stacked layer unit with a hermetic seal.

0015Reference will now be made, by way of example, to the accompanying drawings, in which: <ul id="ul0001" list-style="none"><li>Fig. la shows a sectional view of a part of an integrated circuit (IC) device of the prior art taken along the line X-X' in Fig. lb;</li><li>Fig. lb shows a plan view of the IC device taken along the line H-H' in Fig. la;</li><li>_Fig. 2 shows a sectional view of an IC device embodying the present invention;</li><li>Fig. 3 shows aplan view of a part of the IC device shown in Fig. 2, indicated by a reference A₁ and taken along the line H-H' in Fig. 2;</li><li>_Fig. 3b shows a sectional view of the IC device taken along the line Y-Y' in Fig. 3a;</li><li>Fig. 4 shows a perspective view of a part of the IC device shown in Fig. 2 and indicated by reference B.</li></ul>

0016Referring to Figs. la and lb, an IC device includes a semiconductor IC chip 3 having a semiconductor substrate of Si or GaAs and a plurality of transistors and other circuit elements formed on the substrate and mounted on an insulation layer 32 of ceramic or the like. The IC device also includes a stacked layer structure consisting of a conductive wire strip 31 formed on the insulation layer 32, a metal film 34 placed beneath the insulation layer 32 and mounted on another insulation layer 36. The IC device further includes a package including an insulator 33 and a metal cap 35. A cavity. 20' wherein the IC chip 3 is located is defined and hermetically sealed by the package and the stacked layer structure. The conductive wire strip 31 is connected to a terminal of the IC chip 3 by soldering 31. The conductive wire strip 31 extends outside of the IC device through a hermetic seal portion and is soldered to a connection wire 39 on a substrate 38 positioned outside and adjacent to the IC device. Accordingly, the conductive wire strip 31 functions as an external connection wire. Another conductive wire strip 31-1 (Fig. lb) also can be provided.

0017In Fig. la, a structure of the conductive wire strip 31 indicated by reference Ai may be a microstrip line structure, because the metal film 34 is provided beneath the conductive wire strip 31 through the insulation layer 32, and the cavity 20' is provided above the conductive wire strip 31. In addition, another structure of the conductive wire strip 31 indicated by reference A₂' may be a balanced-type strip line structure, i.e. a triplate strip line structure, because the conductive wire strip 31 is provided between the metal cap 35 and the metal film 34 through the insulator 33 and the insulation layer 32, both having the same thickness and same dielectric constant.

0018Note, the thickness t₀ and width W₀ of the conductive wire strip 31 are identical at portions indicated by references Ai and A2. For example, when the dielectric constant ε of the insulator 33 and the insulation layer 32 is ten, i.e., ε = 10, the thickness d₀ of the insulator 33 and the insulation layer 32 is 330 µm, i.e. d₀ = 330 µm, the thickness t₀ of the conductive wire strip 31 is 15 µm, i.e. t₀ = 15 µm, and the width W₀ of the conductive wire strip 31 is 300 µm, i.e.. W₀ = 300 µm. Also a characteristic impedance Z₀ at the portion indicated by reference Ai is 50 Ω, which is a desired characteristic impedance in the example. However, another characteristic impedance Z₀' at the portion indicated by reference A₂' will be reduced due to the effect of the dielectric constant of the insulator 33 and is approximately 33 Ω. As a result, a mismatching between the characteristic impedance brings about a reflection loss.

0019The preferred embodiments of the present invention will now be described.

0020Referring to Fig. 2, an IC device 1 embodying 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 a plurality of circuit elements formed on a semiconductor substrate of Si or GaAs, 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. Generally speaking, the above insulation material is a dielectric material.

0021The 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.

0022The 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 a dielectric layer as shown by the layer 11-lb for the upper layer 11-1, and at least one conductive layer strip as shown by the strip 11-la. The insulation layers 11-lb, etc., are formed of a sintered ceramic and have a thickness of approximately 330 µm and a dielectric constant of 10.

0023Two conductive wire strips 15-1 and 15-2 are also provided on the insulation layer 11-lb adjacent to the IC chip 3.

0024The conductive layer strips of the second layer 11-2 are used for ground lines or power supply lines. 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. The conductive layer strips of the fifth layer 11-5 are used for low speed signal lines. Connection wires connecting between the circuit elements in the IC chip 3 are formed by the conductive layer strips and connection members embedded in the insulation layers in a direction perpendicular to the plane of the insulation layers and connecting between the circuit elements and the conductive layer strips. However, these internal connection wires are omitted in Fig. 2, because they do not directly pertain to the present invention.

0025Figure 3a is a plan view of a part of the IC device in Fig. 2, indicated by references A₁ and A₂ in Fig. 2 and taken along the line H-H' in Fig. 2. Figure 3b is a sectional view of the IC device, taken along the line Y-Y' in Fig. 3a. Figures 3a and 3b correspond to Figs. la and lb discussed above.

0026In Figs. 2, 3a, and 3b, the conductive wire strip 15-2 includes a wide width portion 15-2a, a narrow width portion 15-2b, and a wide width portion 15-2c. The width W a of the wide width portions 15-2a and 15-2c is 300 µm and the width W_b of the narrow width portion 15-2b is 100 µm. The thickness t of the conductive wire strip 15-2b is 15 µm, throughout the portions 15-2a to 15-2c. The length of the narrow width portion 15-2b is identical to that of the seal layer 23. The conductive wire strip 15-2 functions as an external connection wire. One end of the conductive wire strip 15-2 is connected to a terminal of the IC chip 3 at the wide width portion 15-2a inside of the IC device through a wire 18-2 and another end of the conductive wire strip 15-2 may be connected to other circuits in other IC devices by the wide width portion 15-2c outside of the IC device and extending on the side wall 24. The wide width portion 15-2C may be formed as a coplaner.

0027The structure of the wide width portion 15-2a of the conductive wire strip 15-2 indicated by reference A in Fig. 2 is similar to that shown in Fig. la and thus is formed as a microstrip line structure, because the conductive layer 11-2a formed on the insulation layer 11-2b of the second layer 11-2 is provided beneath the wide width portion 15-2a and the cavity 20 is provided above the wide width portion 15-2a. The insulation layer 11-2b between the wide width portion 15-2a of the conductive wire strip 15-2 and the conductive layer 11-2a is also formed of a sintered ceramic and has a thickness of approximately 330 um and a dielectric constant of 10. As a result, a characteristic impedance of the microstrip line structure is 50 n.

0028In addition, another structure of the conductive wire strip 15-2 indicated by reference A₂ includes the seal layer 23 consisting of an insulation layer 23b formed of a sintered ceramic and having a thickness t₂₃ of approximately 330 µm, identical to the thickness t_11-1 of the insulation layer 11-lb, and a dielectric constant of 10, and a conductive layer 23a formed on the insulation layer 23b, a narrow width portion 15-2b having the width Wb of 100 µm which is narrower than that of the wide width portion 15-2a, and the conductive layer 11-2a. Capacitors are formed in the insulation layer 23b and the insulation layer 11-lb. Accordingly, another structure is formed as a triplate strip line structure. By providing the above capacitors above and below of the portion 15-2b, the width W_bof the narrow width portion 15-2b may be reduced. In this triplate strip line structure, the width W_b of the narrow width portion 15-2b, i.e., W_b = 100 µm, is designed so that any adverse affect due to the dielectric constant of the insulation layer 23b may be cancelled. As a result, a characteristic impedance of the triplate strip line structure is 50 Ω, identical to that of the microstrip line structure set forth above.

0029Apparently, the impedance matching is achieved throughout the conductive wire strip 15-2 as the external connection wire, with the result that losses such as reflection loss do not occurs

0030In the above embodiment, the essence is to make the characteristic impedance of the triplate strip line structure, which is affected by the insulation layer 23b, equal to that of the microstrip line structure. More specifically, a capacitance of the narrow width portion 15-2b is designed to have a predetermined impedance so that an impedance matching is achieved there between.

0031The characteristic impedance can be arbitrary, such as 75 Ω.

0032Figure 4 is a perspective view of the IC device at the portion indicated by reference B in Fig. 2. In Figs. 2 and 4, the conductive wire strip 15-1 formed on the insulation layer 11-lb is connected to the conductive strip 11-3a formed on the insulation layer 11-3b, through a viahole 14-1 which formed by charging an electrical conductive material in a throughhole 12-1 formed in a direction perpendicular to the plane of the stacked layer unit 11 and in the insulation layers 11-lb and 11-2b, and accordingly, becomes electrically conductive.

0033A structure formation stack by the conductive layer 11-2a, the insulation layer 11-lb, the conductive wire strip 15-1, and the cavity 20 above the conductive wire strip 15-1 is formed as a microstrip line structure in the same way as set forth with reference to Figs. 3a and 3b. The thickness t_l of the conductive wire strip 15-1 is 15 µm and the width W₁ 300 µm, these being equal to those of the conductive wire strip 15-2. The thickness and material of the insulation layer 11-lb are as mentioned above. Accordingly, a characteristic impedance of the structure of the conductive wire strip 15-1 is 50 Ω.

0034Another structure formed as a stack by the conductive layer 11-4a formed on the insulation layer 11-4b, the insulation layer ll-3b, the conductive strip 11-3a, the insulation layer 11-2b, and the conductive layer 11-2a is formed as a triplate strip line structure in the same way as set forth with reference to Figs. 3a and 3b. Capacitors CS₁ and CS₂ are formed in the insulation layers 11-2b and 11-3b. The thickness t₂ of the conductive strip 11-3a is identical to that of t₁ of the conductive wire strip 15-2, and the width W₂ of 100 µm is identical to that of W_b in Fig. 3a. By providing the capacitors CS₁ and CS₂ above and below the conductive strip ll-3a, the width W₂ may be reduced as described previously. The thickness and material of the insulation layer 11-3b are identical to those of the insulation layer 11-2b. The width W₂ is smaller than the width W₁ , and accordingly, the triplate strip line structure has a characteristic impedance of 50 Ω identical to that of the microstrip line structure of the conductive wire strip 15-1, even if the affect of the dielectric constant of the insulation layer 11-2b is felt, as described above with reference to Figs. 3a and 3b.

0035In this embodiment, the impedance matching between the microstrip line structure and the triplate strip line structure is achieved throughout a connection line of the conductive wire strip 15-1, the viahole 14-1, and the conductive layer 11-3a, as an external connection wire, with the result that losses such as reflection loss do not occur.

0036An end of the external connection wire is connected to a terminal of the IC chip 3 inside of the IC device, and another end outside of the IC device is connected to a coplaner 25 mounted on the surface of the side wall 24 as shown in Fig. 2.

0037Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in this specification, except as defined in the appended claims.