JPH10145017A - High-frequency integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a high-frequency integrated circuit with improved highfrequency performance. SOLUTION: The thickness of a semiconductor substrate 13 at a device part for constituting an impedance matching circuit other than a semiconductor device 2 is thinned, for example, by etching, an insulation resin 12 is provided on the semiconductor substrate 13 of the thin-layer part, the thickness of a part where the insulation layer is provided is made equal to that of the part of the semiconductor device 2, and an impedance matching circuit element such as a micro strip line 10 and a spiral inductance 8 is provided on it, thus greatly reducing the loss of a circuit element for constituting the impedance matching circuit and improving the performance of, for example, an amplifier and an oscillator at a high-frequency region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit in a high-frequency region, more specifically, a microstrip line, a spiral inductance, a resistor, a semiconductor element such as a transistor or a diode on the same substrate.
The present invention relates to a circuit configuration of a high-frequency integrated circuit provided with an impedance matching circuit element such as a capacitor.

[0002]

2. Description of the Related Art In the case where an impedance matching circuit such as a microstrip line or a spiral inductance is provided on a conductive semiconductor substrate such as a silicon substrate in a high frequency region, generally, SiO2 is first provided on the semiconductor substrate.
An example in which a dielectric layer is formed by a method such as the above, and a line is formed by a metal conductor layer on the dielectric layer (Transactions of the Institute of Electronics, Information and Communication Engineers' 7
0/10 Vol. 53-B No. 1) etc. Hereinafter, a conventional technique will be described using a Si-MOSFET generally used as a semiconductor element in a high-frequency region as an example. FIG. 6 shows a cross-sectional structure of the Si-MOSFET. In the figure, 21 is a gate electrode, 22
Is a source electrode, and 23 is a drain electrode. Reference numeral 24 denotes an interlayer insulating film, which is generally made of SiO or PSG. Reference numeral 25 denotes a high resistance layer for forming an element.
Ω · cm or more is used, and 26 is a low-resistance layer for reducing source resistance, and is generally 0.1 Ω · cm or less. 27 is an earth conductor made of a metal layer provided on the back surface of the substrate. Below the source electrode 22, there is provided a hole of a low resistance layer for reducing the resistance when the source is dropped to the ground. FIG. 7 shows the Si-MOSFET.
2 shows a cross-sectional structure when a microstrip line is connected to the gate electrode and the drain electrode. The interlayer insulating film is used as a dielectric layer, and the metal layers of the gate electrode and the drain electrode are used as they are as conductors of the line. FIG. 8 shows an equivalent circuit of a basic configuration of a high-frequency amplifier circuit using a MOSFET as a semiconductor element. The high-frequency signal is input from the signal input terminal 1, amplified by the semiconductor element 2, and output to the signal output terminal 3. A gate bias is applied from a gate bias terminal 4 through a resistor 6 and a drain bias is applied from a drain bias terminal 5 through an inductance 8-3. Capacitors 7-3, 7-4
Is for short-circuiting a high frequency, and the capacitors 7-1, 7-2, 7-5, 7-6 and the inductances 8-1, 8-2 are circuit elements for impedance matching.
FIG. 9 shows a configuration of a high-frequency integrated circuit that embodies the equivalent circuit shown in FIG. In the figure, 9 is a ground terminal connected to a ground conductor on the back surface, 10 is a microstrip line, and 11 is SiO2 on a silicon substrate.

[0003]

In a high-frequency integrated circuit having a conventional structure as shown in FIG. 7, a microstrip line has 21 and 23 as line conductors, 24 insulating films as dielectric layers, and 25 A silicon substrate, which is a conductive semiconductor substrate, functions as both a dielectric layer and a lower conductor (earth conductor). In general, the electrical resistance of a silicon substrate is about several Ω · cm in a high resistance layer and 0.02 Ω · cm in a low resistance layer.
There is a degree. For this reason, when the silicon substrate is regarded as the lower conductor, the electric resistance is much larger than that of a conductor formed of a metal layer, for example, 1.7 × 10 Ω · cm of copper. In addition, when the silicon substrate is regarded as a dielectric, the dielectric loss is extremely large, and in any case, the loss of the line is greatly increased. As a result, in the line having this structure, the amplifier using the spiral inductance, and the like, the gain and the output power are greatly reduced.

An object of the present invention is to reduce a loss such as a microstrip line and a spiral inductance in a high-frequency integrated circuit in which a semiconductor element and its matching circuit are formed on the same substrate using a conductive semiconductor substrate such as silicon. This aims to improve the high-frequency performance of amplifiers, oscillators, and the like.

[0005]

According to the present invention, in order to achieve the above object, for elements constituting an impedance matching circuit other than a semiconductor element, for example, for a microstrip line or a spiral inductance, the substrate thickness at this portion is etched or the like. Thinner, an insulating resin is provided on the thinned portion of the semiconductor substrate, and the thickness of the portion provided with the insulating layer is the same as the thickness of the semiconductor element,
On top of that, an impedance matching circuit element such as a microstrip line or a spiral inductance is provided.

The loss of a microstrip line is generally expressed by the following equation (Equation 1) (IEEE Vol. MTT).
-16, NO. 6 JUNE 1968).

[0007]

(Equation 1)

Here, Po is the output end power of the line, Pi is the input end power of the line, α is the attenuation constant, and l is the line length.

The attenuation constant α is an attenuation constant α determined by a loss generated by a dielectric loss (tan δ) of a dielectric constituting the line.
d and the sum of the attenuation constant αc determined by the loss generated by the electric resistance components of the line conductor and the ground conductor. The attenuation constant αc determined by the conductor loss is proportional to the electrical resistance between the line conductor and the earth conductor as in the following equation (Equation 2).

[0010]

(Equation 2)

Here, ρ is the specific resistance of the line conductor, and ρ is
The specific resistance of the conductor, Zo is the characteristic impedance of the line, k
1 and k2 are constants determined by the frequency and the like.

That is, when a conductive semiconductor substrate such as silicon is used as a dielectric material constituting a microstrip line, it is equivalent to an increase in both the dielectric loss and the conductor loss, and the line loss increases. According to the present invention, the semiconductor substrate in the portion constituting the matching circuit element is made thinner, an insulating resin is provided in this portion, and this resin operates as a dielectric substrate, thereby greatly reducing line loss.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail.

FIG. 1 is a top view showing a structure of an embodiment of the present invention, in which an equivalent circuit of the high-frequency amplifier shown in FIG. 8 is embodied. In the figure, a high-frequency signal is input from a signal input terminal 1, amplified by a semiconductor element 2, and output to a signal output terminal 3. A gate bias is applied from a gate bias terminal 4 through a resistor 6 and a drain bias is applied from a drain bias terminal 5 through an inductance 8-3. Capacitors 7-3 and 7-4 are for short-circuiting the high frequency to the ground. Capacitors 7-1 and 7-2 and an inductance 8-1 are a circuit element for impedance matching on the input side, and capacitors 7-5 and 7-5. 7-6 and inductance 8-2 are circuit elements for impedance matching on the output side, 9 is a ground terminal connected to the ground conductor on the back surface, 10 is a microstrip line, and 11 is a portion between the silicon substrate and the conductor line. SiO2, 12-1 to 3-3 forming the insulating layer is an insulating resin embedded in a thinned portion of the semiconductor substrate below a portion constituting the spiral inductor.

FIG. 2 is a view showing a cross section of a part of FIG. 1, and shows a semiconductor element and a spiral inductance. In the figure, 12 is an insulating resin provided below the spiral inductance, 13 is a semiconductor substrate, and 14 is a ground conductor on the back surface. In this embodiment,
Among the circuit elements constituting the matching circuit, the resin is provided only below the spiral inductance, which most affects the reduction in the gain of the amplifier when the loss of the substrate is large.

FIG. 3 shows another embodiment according to the present invention, in which a semiconductor substrate under a spiral inductor or a conductor line portion other than a semiconductor element, a capacitor and a resistor is thinned, and resin is embedded in this portion. FIG. 11 is a top view showing the configuration in the case where the above is the case. FIG. 4 is a view showing a cross section of a part of FIG. 3, in which an insulating resin 12 is embedded in the entire spiral inductance 8 except for the semiconductor element 2 and the lower part of the strip line 10. In this embodiment, the insulating resin 1 is used.
2 is a case where the lower part of a circuit element such as a capacitor or a resistor, which would complicate the process when formed on a resin, is removed.

FIG. 5 shows another embodiment according to the present invention, in which the entire semiconductor substrate except for the lower portion of the semiconductor element is thinned and the insulating resin 12 is embedded in the entire portion. The configuration is shown.

[0018]

According to the present invention, in an integrated circuit in which a semiconductor element and its matching circuit are formed on the same substrate using a conductive semiconductor substrate such as silicon, the loss of the circuit element forming the matching circuit is reduced. Can be greatly reduced, and the performance of an amplifier, an oscillator, and the like in a high frequency region can be improved. Furthermore, in a high-output amplifier, it is important to reduce the loss of the microstrip line and the spiral inductance as a matching circuit from the viewpoint of high output and high efficiency. For this reason, resistors and capacitors with complicated process steps are formed on a semiconductor substrate that can be formed relatively easily even if the loss increases somewhat, and microstrip lines and spiral inductances have insulating properties that are advantageous for reducing loss. It is possible to sufficiently improve the performance simply by forming it on a resin.

[Brief description of the drawings]

FIG. 1 is a top view showing the structure of a high-frequency integrated circuit according to the present invention.

FIG. 2 is a sectional view showing the structure of a high-frequency integrated circuit according to the present invention.

FIG. 3 is a top view showing the structure of the high-frequency integrated circuit according to the present invention.

FIG. 4 is a cross-sectional view showing the structure of the high-frequency integrated circuit according to the present invention.

FIG. 5 is a top view showing the structure of the high-frequency integrated circuit according to the present invention.

FIG. 6 shows a conventional high-frequency semiconductor device (Si-MOSFE).
Sectional drawing which shows the structure of T).

FIG. 7 is a cross-sectional view showing a structure of a high-frequency integrated circuit using a conventional conductive semiconductor substrate.

FIG. 8 is a diagram showing an example of a high-frequency amplifier circuit using a semiconductor element as an equivalent circuit.

FIG. 9 is a top view showing a structure of a high-frequency integrated circuit using a conventional conductive semiconductor substrate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Signal input terminal, 2 ... Semiconductor element, 3 ... Signal output terminal, 4 ... Gate bias terminal, 5 ... Drain bias terminal, 6 ... Resistance, 7-1, 7-2, 7-3, 7-4, 7 -5, 7-6: capacitor, 8-1, 8-2, 8-3: inductance, 9: ground terminal, 10: microstrip line, 11: SiO2, 12-1, 12-2, 12
-3: resin, 21: gate electrode, 22: source electrode, 2
3 ... Drain electrode, 24 ... Interlayer insulating film, 25 ... High resistance layer, 26 ... Low resistance layer, 27 ... Ground conductor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Suzuki 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd.

Claims (13)

[Claims] 1. A high-frequency integrated circuit comprising a semiconductor substrate, a ground conductor formed on the back side of the semiconductor substrate, and a semiconductor element and an impedance matching circuit formed on the front side of the semiconductor substrate. The semiconductor substrate below at least one of the plurality of circuit elements constituting the circuit is thinned, and an insulating resin is provided between the at least one circuit element and the semiconductor substrate. A high-frequency integrated circuit device characterized by the above-mentioned. 2. A high-frequency integrated circuit comprising: a semiconductor substrate; a ground conductor formed on a back surface of the semiconductor substrate; and a semiconductor element and an impedance matching circuit formed on a front surface of the semiconductor substrate. A high-frequency integrated circuit device, wherein the semiconductor substrate below the inductance constituting the circuit is thinned, and an insulating resin is provided between the inductance and the semiconductor substrate. 3. A high-frequency integrated circuit comprising a semiconductor substrate, a ground conductor formed on the back side of the semiconductor substrate, and a semiconductor element and an impedance matching circuit formed on the front side of the semiconductor substrate. A high-frequency integrated circuit device, wherein the semiconductor substrate in a lower part of a circuit is thinned, and an insulating resin is provided between the impedance matching circuit and the semiconductor substrate. 4. A high-frequency integrated circuit comprising a semiconductor substrate, a ground conductor formed on the back side of the semiconductor substrate, and a semiconductor element and an impedance matching circuit formed on the front side of the semiconductor substrate. A thickness of the semiconductor substrate below at least one of the plurality of circuit elements constituting the circuit is smaller than a thickness of the semiconductor substrate below the semiconductor element;
An RF integrated circuit device, wherein an insulating resin is provided between the at least one circuit element and the semiconductor substrate. 5. A high-frequency integrated circuit having a semiconductor substrate, a ground conductor formed on the back side of the semiconductor substrate, and a semiconductor element and an impedance matching circuit formed on the front side of the semiconductor substrate. The thickness of the semiconductor substrate below the inductance constituting the circuit is smaller than the thickness of the semiconductor substrate below the semiconductor element, and an insulating resin is provided between the inductance and the semiconductor substrate. High frequency integrated circuit device. 6. A high-frequency integrated circuit comprising a semiconductor substrate, a ground conductor formed on the back side of the semiconductor substrate, and a semiconductor element and an impedance matching circuit formed on the front side of the semiconductor substrate. The thickness of the semiconductor substrate below the circuit is smaller than the thickness of the semiconductor substrate below the semiconductor element, and an insulating resin is provided between the impedance matching circuit and the semiconductor substrate. High frequency integrated circuit device. 7. A high-frequency integrated circuit having a semiconductor substrate, a ground conductor formed on the back side of the semiconductor substrate, and a semiconductor element and an impedance matching circuit formed on the front side of the semiconductor substrate. A high-frequency integrated circuit device, wherein an insulating resin is provided between at least one of the plurality of circuit elements constituting the circuit and the semiconductor substrate. 8. A high-frequency integrated circuit having a semiconductor substrate, a ground conductor formed on the back side of the semiconductor substrate, and a semiconductor element and an impedance matching circuit formed on the front side of the semiconductor substrate. A high-frequency integrated circuit device, wherein an insulating resin is provided between an inductance forming a circuit and the semiconductor substrate. 9. A high-frequency integrated circuit comprising a semiconductor substrate, a ground conductor formed on the back side of the semiconductor substrate, and a semiconductor element and an impedance matching circuit formed on the front side of the semiconductor substrate. A high-frequency integrated circuit device, wherein an insulating resin is provided between a circuit and the semiconductor substrate. 10. An insulating layer is provided on the same substrate as a semiconductor substrate on which a semiconductor element such as an FET or a bipolar transistor is formed. In an integrated circuit in which an impedance matching circuit is formed, the substrate thickness of at least one circuit portion of a portion constituting a matching circuit other than a semiconductor element is thinned by etching or the like. A high-frequency integrated circuit comprising: an insulating resin provided on a semiconductor substrate; and the impedance matching circuit formed thereon. 11. The high-frequency integrated circuit according to claim 1, wherein the thickness of the semiconductor substrate below the spiral inductance part constituting the impedance matching circuit is reduced by etching or the like, and the semiconductor substrate is made thinner in the previous period. A high-frequency integrated circuit comprising: an insulating resin provided thereon; and the impedance matching circuit formed thereon. 12. The high-frequency integrated circuit according to claim 1, wherein the thickness of the semiconductor substrate under a portion made of only a conductor such as a spiral inductance portion or a line is reduced by etching or the like. A high-frequency integrated circuit, wherein an insulating resin is provided on a semiconductor substrate formed as described above, and a portion made of only a conductor such as the spiral inductance portion or a line is formed thereon. 13. A wireless device using the high-frequency integrated circuit according to claim 1.