JPH10256467A - Silicon high frequency integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inductor, a capacitor, etc., high in Q of a circuit element using a silicon substrate, by electrically connecting a first silicon substrate high in specific resistance and a second silicon substrate low in specific resistance. SOLUTION: A transistor TR1 and resistors R1, R2, and R3 not requiring high Q are made by conventional silicon high frequency integrated circuit process, and inductors L1 and L2 and capacitors C1 and C2 requiring high Q are made in a separate high-resistance silicon substrate. Then, both silicon substrates are connected with each other, using a mounting technique such as a chip-on- chip technique, a multichip module technique, or the like, and they are accommodated in the same package, whereby a silicon high-frequency integrated circuit is constituted. Accordingly, the area of the silicon chip made of high-resistance silicon can be small by minimizing the size of the portion, where high Q is required, of the high-resistance silicon substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-frequency integrated circuit using a silicon substrate.

[0002]

2. Description of the Related Art With the demand for smaller and lighter wireless devices and the like, it has become essential to integrate high-frequency circuits into integrated circuits. Conventional high-frequency integrated circuits include gallium arsenide MMICs (microwave monolithic integrated circuits). However, since the gallium arsenide substrate is more expensive than the silicon substrate, there is a problem that the price of the integrated circuit increases. Therefore, realization of a high-frequency integrated circuit on a silicon substrate is desired.

FIG. 4 illustrates an RF amplifier using a conventional silicon high-frequency integrated circuit. As shown in FIG. 4, the transistors that can be integrated are transistors,
A silicon high-frequency integrated circuit 22 comprising a bias circuit, wherein the input matching circuit 21 and the output matching circuit 23 are formed as discrete circuits by discrete components due to problems such as low Q (quality factor) of circuit elements on silicon. ing.

[0004]

In a silicon high-frequency integrated circuit, since the silicon substrate has conductivity, the Q of an element such as an inductor having a spiral structure is reduced, and the capacitance of a capacitor to a substrate is generated. There is a problem.

Therefore, the conventional silicon high-frequency integrated circuit is composed of the transistor, the resistor, and the capacitor as described above, and the input matching circuit and the output matching circuit using the inductor are not built in.

In recent years, there has been reported a silicon high-frequency integrated circuit in which a silicon substrate having a high specific resistance is used to increase the resistance of the substrate and improve the quality factor of an element such as an inductor.

However, in this case, there is a problem that a new integrated circuit process needs to be developed by increasing the specific resistance of the silicon substrate.

Further, even if a new integrated circuit process is developed, a transistor element having good high-frequency characteristics must be formed at the same time, so that there is a problem that the specific resistance of the substrate cannot be increased to a certain degree or more.

SUMMARY OF THE INVENTION It is an object of the present invention to realize an inductor or a capacitor having a high Q of a circuit element by a process using a silicon substrate, and to provide a silicon high-frequency integrated circuit using the element.

[0010]

According to the present invention, there is provided a silicon high-frequency integrated circuit comprising a first silicon substrate having a high specific resistance on which a circuit element requiring a high Q is formed, and a circuit element not requiring a high Q. And a second silicon substrate having a low specific resistance, wherein the first silicon substrate and the second silicon substrate are electrically connected to each other.

In the silicon high frequency integrated circuit according to the present invention, a circuit element such as a transistor and a resistor which does not require high Q is formed by a conventional silicon high frequency integrated circuit process, and an inductor, a capacitor, etc. are formed by using another high resistance silicon substrate. Circuit elements that require a high Q of
Because the two silicon processes can be optimized independently,
Higher-performance electrical characteristics can be obtained than a silicon high-frequency integrated circuit in which all elements are formed on the same substrate.

In the silicon high frequency integrated circuit according to the present invention, a matching circuit may be formed on the first silicon substrate. A high Q is required for the inductor and the capacitor constituting the matching circuit, which can cope with this.

In the silicon high-frequency integrated circuit according to the present invention, the first and second silicon substrates may be chip-on-chip and electrically connected to form a single package. The substrates may be electrically connected as a multi-chip module to form a single package. By doing so, the appearance is the same as the conventional silicon high frequency integrated circuit, and the handling becomes easy.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A silicon high-frequency integrated circuit according to the present invention will be described with reference to an embodiment.

FIG. 1 is a block diagram showing a configuration of a silicon high-frequency integrated circuit according to an embodiment of the present invention, and is an example of an RF amplifier (amplifier) that is a high-frequency circuit of a wireless communication device.

FIG. 1 shows the configuration of an RF amplifier using a silicon high-frequency integrated circuit according to an embodiment of the present invention.
FIGS. 2A, 2B and 3 show an example in which a silicon chip formed of a silicon substrate having a high specific resistance and a silicon chip formed of a silicon substrate having a low specific resistance are electrically connected.

The RF amplifier 1 using the silicon high-frequency integrated circuit according to the embodiment of the present invention shown in FIG. 1 includes a bipolar transistor TR1, a bias circuit 2 for supplying a bias voltage and a bias current to the transistor TR1, and an input. It comprises a matching circuit 3 and an output matching circuit 4. In order to amplify a high frequency band signal, the transistor TR
1, impedance matching is required on the input terminal side and the output terminal side.

In the RF amplifier 1 using a silicon high-frequency integrated circuit, a signal output from a signal source comprising a transistor TR1, an inductor L1 connected in an L-type, and a capacitor C1 is supplied to the transistor TR1, and the output impedance of the signal source is changed. An input matching circuit 3 for impedance matching between the transistor TR1 and the input impedance of the transistor TR1, and resistors R1, R2, R3 and a decoupling capacitor C3 for high-frequency signals.
A bias circuit 2 for applying a predetermined bias voltage to 1;
It comprises an L-connected inductor L2 and a capacitor C2, to which a collector output voltage of the transistor TR1 is supplied, and an output matching circuit 4 for impedance matching between the output impedance of the transistor TR1 and the load impedance.

Here, the input matching circuit 3 and the output matching circuit 4 are formed on a silicon chip 11 made of a silicon substrate having a high specific resistance, and the bias circuit 2 and the transistor TR1 are formed on a silicon chip 12 made of a silicon substrate having a low specific resistance. The two silicon chips 11 and 12 are electrically connected in one package to form a silicon high-frequency integrated circuit.

Although the transistor TR1 is a bipolar transistor, it may be a unipolar transistor.

FIGS. 2A and 2B show an example in which a silicon chip 11 made of a silicon substrate having a high specific resistance and a silicon chip 12 made of a silicon substrate having a low specific resistance are electrically connected. FIG. 2A is a schematic plan view, and FIG.
(B) shows a schematic sectional view.

In this example, the silicon chip 11 and the silicon chip 12 are electrically connected by the bumps 14a to 14d, and are connected by the chip-on-chip mounting technique of connecting the silicon chip 11 to the lead terminals by the bonding wires 13a to 13d. An example is shown. If the RF amplifier 1 thus configured is mounted on the lead frame 10 and housed in a package, the appearance is the same as that of the conventional silicon high-frequency integrated circuit, and the handling becomes easy.

In this case, one of the silicon chip 11 and the silicon chip 12 may be a mother chip or a daughter chip.

Next, another example of electrically connecting the silicon chip 11 and the silicon chip 12 is shown in FIG.

As shown in FIG. 3, the silicon chips 11 and 12 are connected to bonding wires 15a to 15a.
5d, the silicon chips 11, 1
2, the connection may be made electrically by a multi-chip module mounting technique of connecting to lead terminals by bonding wires 13a to 13d. Further, as shown in FIG.
If this is mounted on a lead frame and stored in a package, the appearance will be exactly the same as before and handling will be easier.

In the silicon high-frequency integrated circuit according to the embodiment of the present invention described above, the case of the RF amplifier 1 including the matching circuit has been exemplified, but it is needless to say that the present invention can be applied to other high-frequency circuits.

Next, the conventional case and the silicon high-frequency integrated circuit according to the embodiment of the present invention will be described in comparison.

The specific resistance of the silicon substrate used in the conventional silicon high frequency integrated circuit process is several tens Ω · cm.
It is about. When a spiral-structured inductor or the like is formed on the silicon substrate, the Q of the element is reduced.

On the other hand, when an inductor or the like having a spiral structure is formed using a high-resistance silicon substrate having a large specific resistance and on the order of several kΩ · cm, a circuit element and an inductor having the same degree of Q as those formed by a gallium arsenide substrate are used. Etc. can be realized.

Therefore, in the silicon high-frequency integrated circuit according to one embodiment of the present invention, the transistor TR1 and the resistors R1, R2, and R3, which do not need to have a high Q, are formed by a conventional silicon high-frequency integrated circuit process. Inductors L1 and L2 and capacitor C required to have high
1. C2 is formed on another high resistance silicon substrate. Then, both silicon substrates are connected by using a mounting technology such as a chip-on-chip or a multi-chip module, and are housed in the same package to constitute a silicon high-frequency integrated circuit.

Most of the current silicon substrates are C-MOS
The specific resistance of a silicon substrate manufactured by a process and used in a C-MOS process is generally 1 to 20 Ω · cm. Therefore, a high-resistance silicon substrate is expensive. However, as in the silicon high-frequency integrated circuit according to the embodiment of the present invention, the size of the high-resistance silicon substrate is minimized to a portion where a high Q is required, so that the silicon chip 11 made of the high-resistance silicon substrate is reduced. The area is small, and when the silicon chip 12 made of a low-resistance silicon substrate and the silicon chip 11 made of a high-resistance silicon substrate are electrically connected, the whole is made of the silicon chip 11 made of a high-resistance silicon substrate. This has the effect of being cheaper than that.

Even if the frequency of the input signal changes, it can be handled by changing only the silicon chip 11 of the matching circuits 3 and 4 by using the configuration of the silicon high-frequency integrated circuit according to the embodiment of the present invention. be able to. As a result, the effect that the versatility of the silicon high-frequency integrated circuit is improved can be obtained.

In the case where the silicon chip is formed integrally, the diffusion conditions on the high-resistance silicon substrate are different from those in the conventional case. This necessitates the development of a new silicon integrated circuit process, but the silicon high-frequency integrated circuit according to one embodiment of the present invention has the effect that the conventional process can be used as it is.

Furthermore, in the conventional silicon integrated circuit process, a P-type isolation is formed on the substrate to separate the N-type buried layer from the device in order to reduce the collector resistance. Also,
Re-diffusion from the substrate to the epitaxial layer also occurs. The conventional silicon integrated circuit process is completed by optimizing these diffusion conditions. However, if the specific resistance of the substrate is increased, these conditions must be optimized. Even if a new condition is obtained, the diffusion increases as the specific resistance increases, which is not an advantageous direction for miniaturization of the transistor.

On the other hand, in order to increase the Q of the inductors L1 and L2, the capacitors C1 and C2, it is conceivable to increase the thickness of the wiring and reduce the series resistance. However, if the thickness of the wiring is increased in the conventional silicon integrated circuit process, there are constraints such as a problem of flatness.

However, according to the silicon high-frequency integrated circuit according to the embodiment of the present invention, the inductors L1 and L
2. By integrating elements requiring high Q, such as the capacitors C1 and C2, into chips of another silicon substrate, silicon integration for manufacturing a silicon chip 11 having a high specific resistance and a silicon chip 12 having a low specific resistance is performed. The circuit process can be independently optimized, eliminating the above-mentioned restrictions of the silicon integrated circuit process that occur when a conventional silicon chip is formed as an integrated type, and increasing the wiring thickness and the wiring process. Or the like can be changed.

Further, when a capacitor is formed by a conventional silicon integrated circuit process, a series parasitic element of a parasitic resistance and a parasitic capacitor connected to the electrode of the capacitor occurs. This parasitic resistance is due to the substrate. However, as in the silicon high-frequency integrated circuit according to the embodiment of the present invention, by increasing the specific resistance of the silicon substrate on which the capacitor is formed, the resistance value of the parasitic resistance increases, and the influence of the parasitic element on the capacitor is reduced. The effect of reduction is also obtained.

Further, since the specific resistance of the silicon substrate on which the transistor is formed is not increased as in the silicon high-frequency integrated circuit according to the embodiment of the present invention, this occurs when the specific resistance of the silicon substrate is increased. The effect that the miniaturization of the transistor is not hindered is also obtained.

[0039]

As described above, according to the silicon high-frequency integrated circuit of the present invention, an inductor, a capacitor, etc., which require a high Q, are formed on a silicon substrate having a high specific resistance, and a transistor, etc., having good high-frequency characteristics are formed. A specific resistance is generated on a conventional silicon substrate, and two silicon chips composed of silicon substrates having different specific resistances are connected using a mounting technology such as a chip-on-chip or a multi-chip module and stored in one package. As a result, a silicon high frequency integrated circuit having a built-in matching circuit or the like having a high Q of the circuit element can be obtained, and it can be used similarly to a conventional integrated circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a silicon high-frequency integrated circuit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram when a silicon chip having a high specific resistance and a silicon chip having a low specific resistance constituting the silicon high-frequency integrated circuit according to one embodiment of the present invention are electrically connected;

FIG. 3 is another explanatory diagram when a silicon chip having a high specific resistance and a silicon chip having a low specific resistance that constitute the silicon high-frequency integrated circuit according to the embodiment of the present invention are electrically connected.

FIG. 4 is a block diagram showing a configuration of a conventional silicon high-frequency integrated circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 RF amplifier 2 Bias circuit 3 Input matching circuit 4 Output matching circuit 11, 12 Silicon chip 13a-13d, 15a-15d Bonding wire 14a-14d Bump C1, C2 Capacitor C3 Decoupling capacitor L1, L2 Inductor R1, R2, R3 Resistance TR1 transistor

Claims (4)

[Claims] A first silicon substrate having a high specific resistance on which a circuit element requiring a high Q is formed, and a second silicon substrate having a low specific resistance on which a circuit element not requiring a high Q is formed; 1. A silicon high-frequency integrated circuit, wherein a first silicon substrate and a second silicon substrate are electrically connected to each other. 2. The silicon high-frequency integrated circuit according to claim 1, wherein a matching circuit is formed on the first silicon substrate. 3. The silicon high-frequency integrated circuit according to claim 1, wherein the first and second silicon substrates are chip-on-chip and electrically connected to form a single package. . 4. The silicon high-frequency integrated circuit according to claim 1, wherein the first and second silicon substrates are electrically connected as a multi-chip module to form a single package. .