JP3154133B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device,
In particular, the present invention relates to a semiconductor device having a capacitor.

[0002]

2. Description of the Related Art Conventionally, as a method of setting a capacitance of a capacitor to a desired value in a semiconductor device using a capacitor (capacitor) in terms of circuit configuration, a polycrystalline silicon (Si) film or a metal thin film forming an electrode of the capacitor is used. There is a so-called laser trimming method in which a laser beam is selectively irradiated and evaporated.

FIG. 6 shows an example of a method for setting the capacitance of a capacitor by such a laser trimming method. That is, as shown in FIG. 6, a capacitor C 'is formed by forming a polycrystalline Si film 103 of a predetermined shape used as an electrode on an insulating film 102 formed on a semiconductor substrate 101, and further forming a polycrystalline Si film. After forming the wiring 104 at one end of the film 103, a desired region of the polycrystalline Si film 103 is selectively irradiated with a strong laser beam L ′ to evaporate the polycrystalline Si film 103 in the irradiated portion. As a result, the area of the polycrystalline Si film 103 used as an electrode of the capacitor C ', that is, the area of the capacitor C' becomes a desired size, and the capacitance of the capacitor C 'is set to a desired value.

[0004]

However, in the above-described method for setting the capacitance of the capacitor C 'by the conventional laser trimming method, the substance evaporated by the irradiation of the laser beam L' is indicated by an arrow in FIG. There is a problem in reliability and quality of the semiconductor device because it re-adheres to the vicinity of the irradiated portion to cause a malfunction of the circuit or damage to the insulating film 102 used as a dielectric of the capacitor C ′.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a semiconductor device having a capacitor in which the capacitance of the capacitor can be set to a desired value without lowering the reliability and quality of the semiconductor device. It is in. Another object of the present invention is to provide a semiconductor device having a capacitor, in which the capacitance of the capacitor can be freely set to a desired value according to its use without lowering the reliability and quality of the semiconductor device. It is to provide a device.

[0006]

According to a first aspect of the present invention, there is provided a capacitor (C) having at least one electrode formed of a polycrystalline semiconductor film (3) containing a group IV element as a main component. ), The polycrystalline semiconductor film (3) is selectively irradiated with light (L) to be amorphous.
The capacitance of the capacitor (C) is set to a desired value by causing the phase transition described above.

[0007] The second invention is to provide a semiconductor device having a capacitor (C) which is formed by a polycrystalline semiconductor film in which at least one of the electrodes mainly composed of group IV element (3), a polycrystalline semiconductor film ( The capacity of the capacitor (C) can be adjusted by selectively irradiating 3) with light (L) to cause a phase transition to amorphous . Also,
In a third aspect, at least one electrode mainly includes a group IV element.
Component formed by the polycrystalline semiconductor film (3)
In a semiconductor device having a capacitor (C), a polycrystalline semiconductor
The body film (3) is selectively irradiated with light (L) to form an amorphous phase.
By causing the transition, the impedance of the capacitor (C) is
In this case, the dance characteristics are set to desired characteristics. Ma
Further, in the fourth invention, at least one electrode has a group IV element.
Formed by a polycrystalline semiconductor film (3) mainly composed of
In a semiconductor device having a capacitor (C),
The semiconductor film (3) is selectively irradiated with light (L) to be amorphous
Of the capacitor (C) by causing the phase transition of
The impedance characteristic can be adjusted. First ,
Second, as the polycrystalline semiconductor film mainly composed of group IV element in the third and fourth aspects of the present invention (3), in addition to Si film or germanium (Ge) film, a polycrystalline comprising a compound of Si and Ge A semiconductor film can be given.

[0008]

According to the semiconductor device of the first aspect of the present invention, the semiconductor film (3) is selectively irradiated with light (L) to cause a crystal-amorphous phase transition. Since the capacity of the capacitor (C) is set to a desired value, the substance evaporated by the irradiation of the laser beam adheres to the vicinity of the irradiated portion as in the case of using the laser trimming method, and the malfunction of the circuit may occur. The problem that causes it does not occur. Further, since the intensity of the irradiated light (L) is sufficiently smaller than the case where the capacitance is set by the laser trimming method, the insulating film used as the dielectric of the capacitor (C) is not damaged. . Therefore, the reliability and quality of the semiconductor device do not deteriorate.

According to the semiconductor device of the second aspect of the present invention, the semiconductor film (3) is selectively irradiated with light (L) to cause a crystal-amorphous phase transition. Since the capacity of the capacitor (C) is adjustable, the capacity of the capacitor (L) is reversibly changed without lowering the reliability and quality of the semiconductor device, and the capacity is changed to a desired value according to the application. Can be set freely.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding portions are denoted by the same reference numerals. FIG. 1 is a plan view showing a semiconductor device according to an embodiment of the present invention, and particularly shows a capacitor portion thereof. FIG. 2 is a sectional view taken along line 2-2 of FIG.

As shown in FIGS. 1 and 2, in a semiconductor device according to this embodiment, an insulating film 2 such as an SiO ₂ film is formed on a semiconductor substrate 1 such as a Si substrate. In addition, a Si film 3 having, for example, a rectangular shape used as an electrode is formed. In this case, the Si film 3 is heavily doped with a p-type impurity such as boron (B) or an n-type impurity such as phosphorus (P). These semiconductor substrate 1, insulating film 2 and Si film 3
Form a capacitor C. Reference numeral 4 denotes a wiring made of a metal such as aluminum (Al) connected to one end of the Si film 3.

In this case, one side of the Si film 3 on the side of the wiring 4 is a polycrystalline Si portion 3a, and the remaining portion is an amorphous S
This is the i part 3b. Although the polycrystalline Si portion 3a has a low resistance, the amorphous Si portion 3b does not work as an electrode because it has an extremely high resistance. Therefore, only the polycrystalline Si portion 3a actually works as an electrode. That is, the effective area of capacitor C is equal to the area of polycrystalline Si portion 3a.

Such a capacitor C is formed by the following method. That is, as shown in FIG. 3, first, a polycrystalline S
After the i-film 3 is formed and the polycrystalline Si film 3 is doped with impurities to reduce the resistance, the polycrystalline Si film 3 is patterned into a rectangular shape by etching. Thereby, the capacitor C is formed. Next, for example, after forming an Al film on the entire surface, the Al film is patterned by etching to form the wiring 4.

Next, a portion of the polycrystalline Si film 3 to be amorphized is selectively irradiated with a laser beam L having a wavelength and intensity suitable for the amorphization, whereby the laser beam L The irradiated portion of the polycrystalline Si film 3 is made amorphous. here,
Generally, the intensity of the laser light L required for the amorphization can be considerably smaller than the intensity of the laser light when the laser trimming method is used. As the laser light L, specifically, for example, a pulsed laser light (wavelength 308 nm) by a XeCl excimer laser can be used. 1 and 2 by the irradiation of the laser beam L.
As shown in (1), an amorphous Si portion 3b is formed in a portion irradiated with the laser beam L. Si film 3 in the portion other than the amorphous Si portion 3b is polycrystalline Si portion 3 a. As described above, FIG.
And a capacitor C having a desired capacitance as shown in FIG.
Is formed.

As described above, according to this embodiment, the polycrystal-amorphous phase transformation is caused by selectively irradiating the polycrystalline Si film 3 used as an electrode with the laser beam L. Since the amorphous Si portion 3b is formed in the irradiating portion and the capacitance of the capacitor C is set to a desired value by this, a laser is used as in the case of using the above-described capacitance setting method by the conventional laser trimming method. There is no problem that the substance evaporated by the light irradiation re-adheres to the vicinity and causes a malfunction of the circuit. In addition, since the intensity of the laser light L can be sufficiently smaller than that of the laser trimming method, the irradiation of the laser light L does not cause damage to the insulating film 2 used as the dielectric of the capacitor C. . Thus, it is possible to prevent a decrease in reliability and quality of the semiconductor device. Moreover, the laser light L
Because there is no contact and no electromagnetic interference due to the use of
By irradiating the laser light L while measuring the characteristics of the semiconductor device, the capacitance of the capacitor C can be accurately set to a desired value.

In the above-described embodiment, as shown in FIG. 3, the polycrystalline Si film 3 is exposed to the laser beam L in a state where the polycrystalline Si film 3 is exposed. Alternatively, even after the interlayer insulating film 5 is formed, the laser light L is irradiated to the polycrystalline Si film 3 through the interlayer insulating film 5 to perform amorphization. Obtainable. In this case, since the laser light L is irradiated while the capacitor C is protected by the interlayer insulating film 5, it is preferable in terms of the reliability of the semiconductor device. The interlayer insulating film 5 is, for example, an SiO ₂ film, and its thickness is, for example, 5000 °.

Next, a case where a video signal processing IC is considered as an example of a semiconductor device having a capacitor, and a case where the capacitance of the capacitor of the video signal processing IC is set by using the method according to the above-described embodiment will be described. FIG. 5 shows an example of a signal processing circuit of such a video signal processing IC.

In FIG. 5, the collector of the transistor T is connected to a power supply V _CC via a resistor R _L and a coil I. This emitter of the transistor T is connected to the resistor R _E, which is further connected to a bypass capacitor C _B in parallel with the resistor R _E. Base bias voltage V _BB of the transistor T is obtained by dividing the V _CC by the resistors R _A and R _B. On the other hand, the collector of the transistor T is connected to the output terminal via a capacitor C _C for dc component cutting. A capacitor C is connected between the emitter and the collector of the transistor T.
In this circuit, an input signal V _IN is input between the emitter and the base of the transistor T, and an output signal V _OUT is extracted between the emitter and the collector.

Here, it is assumed that the capacitance of the capacitor C connected between the emitter and the collector of the transistor T is set to a desired value. Now, assuming that an SiO ₂ film having a thickness of 100 ° is used as an insulating film used as a dielectric of the capacitor C, the capacitance of the capacitor C is approximately 36 pF per 100 μm × 100 μm = 10 ⁴ μm ² . The resistivity of a p-type or n-type polycrystalline Si film doped with a high concentration of impurities is 10 ⁻³ Ωc.
m, for example, when the film thickness is 500 °,
The sheet resistance of this polycrystalline Si film is R _sp = 200Ω / □.

When the polycrystalline Si film is made amorphous by irradiation with laser light, the resistivity of the amorphous Si film formed thereby becomes about 10 Ωcm, which is about four orders of magnitude larger than that of the polycrystalline Si film. . In this case, the sheet resistance of this amorphous Si film is R _sa = 2 MΩ / □. Now, assuming that the area of the capacitor C is 10 ⁴ μm ² as described above, the cut-off frequencies f _cp and f _ca determined by the capacitance of this capacitor (about 36 pF) and the above-mentioned sheet resistance R _sp or R _sa are respectively f _cp ≒ 1 / (2π × 36 × 10 ⁻¹² × 200) = 25 MHz f _ca ≒ 1 / (2π × 36 × 10 ⁻¹² × 2 × 10 ⁶ ) = 2.5 kHz.

Therefore, if a video signal in a frequency band of several hundred kHz to several MHz is handled, for example, the capacitor C
Of the polycrystalline Si portion 3 of the Si film 3 used as the electrode
a functions as an electrode because its cutoff frequency _fcp is higher than the signal frequency, but the amorphous Si portion 3b of the Si film 3 behaves as an insulator because its cutoff frequency _fca is lower than the signal frequency. . In this case, the area of the capacitor C is equal to the area of the polycrystalline Si portion 3a of the Si film 3. The above-mentioned cutoff frequencies _fcp and _fca can be changed depending on the area of the capacitor C, the material and thickness of the insulating film 2, the thickness of the Si film 3, and the like. Can be designed.

Now, assuming that the center frequency f _{0 of the} video signal to be handled is 4 MHz, the inductance L _I of the coil I in the circuit shown in FIG. 5 is L _I = 1 / (2πf ₀ ) ² C = 1 / ( 2π × 4 × 10 ⁶ ) ² (36 × 10 ⁻¹² ) ≒ 40 μH. In this case, R _L , R _E ,
The values of C _B , C _C , R _A and R _B are, for example, R _L is 10
0 .OMEGA, R _E is 1 k [Omega, C _B is 500 pF, the C _C 500
pF, the R _A 33kΩ, R _B is 17Keiomega. Also,
In this case, the Q of the resonance circuit including the coil I and the resistance R _L
Is about 10. Note that, for example, V _CC = 5V.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and various modifications based on the technical concept of the present invention are possible. For example, as the laser light L, not only laser light from various excimer lasers other than the XeCl excimer laser, but also laser light from a laser other than the excimer laser can be used. It is also possible to use light.

Further, in the above-described embodiment, the case where the present invention is applied to a video signal processing IC has been described.
D) The present invention can be applied to the case where the capacitance of a capacitor is set in various semiconductor devices such as a converter, an analog IC, and a gate array. Further, in the above-described embodiment, the polycrystalline Si film 3 is irradiated with the laser light L to make it amorphous, but conversely, the amorphous Si film is irradiated with the laser light L. It is also possible to make the irradiated part polycrystalline.

Further, the capacitor C in the above embodiment is used.
Uses the semiconductor substrate 1 as a lower electrode, but the present invention can also be applied to the case where the capacitance of a capacitor C using an Si film for both the upper electrode and the lower electrode is set. Furthermore, for example, in a semiconductor device in which a capacitor using an Si film as an upper electrode and a lower electrode is formed on a glass substrate, a transparent laser beam L is applied to the glass substrate from the back side of the glass substrate. It is possible to set the capacitance of the capacitor by irradiating the lower electrode of the capacitor through the substrate.

Further, according to the present invention, it is possible to realize a variable capacitor used as a tuning capacitor in a receiver or a transmitter. That is, for example, the polycrystalline Si film 3 used as the electrode of the capacitor C in the above-described embodiment is selectively irradiated with the laser beam L to cause the crystal-amorphous phase transition to occur reversibly. Since the capacity of the capacitor C can be reversibly changed, the capacitor C can be used as a variable capacitor. Therefore,
By tuning the desired frequency by reversibly changing the capacity of the capacitor C by irradiating the laser light L, it is possible to perform tuning using light. As a light source of the laser light L used for such channel selection by light, a semiconductor laser which is small and can be incorporated in a receiver or a transmitter is preferable. In order to cause the above-described crystal-amorphous phase transition, for example, laser light L having a short wavelength in the ultraviolet region is preferably used. It is possible to use, as the laser light L, a laser light that is oscillated and whose wavelength is shortened to a half wavelength by a second harmonic generator (SHG). The light source of the laser light L does not necessarily need to be built in a receiver or a transmitter.

[0027]

As described above, according to the present invention,
By selectively irradiating the polycrystalline semiconductor film with light to cause a phase transition to an amorphous state, the capacitance of the capacitor is set to a desired value without lowering the reliability and quality of the semiconductor device. Or the capacitor impedance
The dance characteristics can be set to desired characteristics. In addition, by selectively irradiating the polycrystalline semiconductor film with light to cause a phase transition to an amorphous state, the capacitance or the capacity of the capacitor is increased.
Since the impedance characteristic can be adjusted, the capacitance or impedance characteristic of the capacitor can be freely set to a desired value or characteristic according to the application without lowering the reliability and quality of the semiconductor device.

[Brief description of the drawings]

FIG. 1 is a plan view showing a semiconductor device according to one embodiment of the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a cross-sectional view for explaining a method of setting the capacitance of a capacitor in a semiconductor device according to one embodiment of the present invention.

FIG. 4 is a sectional view showing a semiconductor device according to another embodiment of the present invention.

FIG. 5 is a circuit diagram illustrating an example of a signal processing circuit of a video signal processing IC.

FIG. 6 is a cross-sectional view illustrating a conventional method for setting the capacitance of a capacitor in a semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 insulating film 3 Si film 3a polycrystalline Si portion 3b amorphous Si portion C capacitor L laser beam

Continuation of the front page (72) Inventor Yasuhiko Tobita 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-A-4-206959 (JP, A) JP-A-4-206968 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 27/04 H01L 21/268 H01L 21/822

Claims (4)

(57) [Claims] [Claim 1] At least one electrode in a semiconductor device having a capacitor formed by a polycrystalline semiconductor film mainly composed of group IV element, amorphous selectively irradiating light to the polycrystalline semiconductor film the semiconductor device is characterized in that the capacitance of the capacitor is set to a desired value by causing <br/> phase transition to. Wherein at least one electrode in a semiconductor device having a capacitor formed by a polycrystalline semiconductor film mainly composed of group IV element, amorphous selectively irradiating light to the polycrystalline semiconductor film wherein a capacitance of the capacitor is adjustable by causing <br/> phase transition to. 3. At least one electrode mainly contains a group IV element.
Capacitor formed by polycrystalline semiconductor film as component
In a semiconductor device having By selectively irradiating the polycrystalline semiconductor film with light,
By causing a phase transition, the impedance of the capacitor
-Dance characteristics set to desired characteristics Characterized by
Semiconductor device. 4. At least one electrode mainly contains a group IV element.
Capacitor formed by polycrystalline semiconductor film as component
In a semiconductor device having By selectively irradiating the polycrystalline semiconductor film with light,
By causing a phase transition, the impedance of the capacitor
-Dance characteristics can be adjusted Semiconductor characterized by the following:
apparatus.