KR101388141B1 - Microphones integrated with CMOS circuits and fabrication method thereof - Google Patents

Abstract

A microphone integrated with a miniaturized CMOS circuit and a manufacturing method thereof are proposed in a simple process. The proposed microphone is a microphone integrated with a CMOS circuit, in which an acoustic sensor including a silicon nanowire and a CMOS signal processing circuit are integrally located on a silicon substrate.

Description

Microphones integrated with CMOS circuits and method for manufacturing the same

The present invention relates to a microphone integrated with a CMOS circuit and a method of manufacturing the same, and more particularly, to a microphone integrated with a CMOS circuit miniaturized by a simple process and a method of manufacturing the same.

Nano-sized small diameter materials have recently become very important because of their unique electrical, optical and mechanical properties. Therefore, researches on such nano-sized materials have been carried out in various fields. Recent researches on nanostructures have shown quantum effect as a possibility of being a new photonic device in the future. In particular, nanostructures can be used not only as single electron transistor devices, but also as various chemical sensors and biosensors, and are attracting attention as new optical device materials.

In particular, silicon nanowires have a very large piezoresistive effect because of their very small cross-sectional area. Therefore, by using the piezoresistive effect of the silicon nanowires, since the resistance change due to mechanical stress caused by the vibration of the microphone can be sensitive, a highly sensitive microphone can be manufactured.

The microphone is manufactured separately from the ASIC chip for analog signal processing of the acoustic sensor and the acoustic sensor, and then connects the two devices by wire bonding. When the microphone is manufactured in this way, it is difficult to miniaturize the device, the packaging cost according to the process such as wire bonding is increased, and the mass production is not good.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a microphone integrated with a miniaturized CMOS circuit in a simple process and a method of manufacturing the same.

A microphone according to an aspect of the present invention for achieving the above object is a microphone in which a CMOS circuit is integrated, and an acoustic sensor and a CMOS signal processing circuit including silicon nanowires are integrally located on a silicon substrate.

The silicon nanowires may be electrically insulated from the CMOS signal processing circuit by trenches formed in the silicon substrate.

The silicon nanowires may be electrically insulated from the CMOS signal processing circuit by doping impurities into the silicon substrates on both ends of the silicon nanowires.

According to another aspect of the invention, the step of forming silicon nanowires by anisotropic silicon etching and wet oxide film formation on the silicon substrate; Forming a silicon nitride film on a silicon substrate on which silicon nanowires are formed, and then removing a portion of the silicon nitride film and forming a p-MOSFET and an n-MOSFET to form a CMOS signal processing circuit; And removing the silicon substrate to expose the silicon nanowires to the outside, and electrically insulating the silicon nanowires from the CMOS signal processing circuit to form an acoustic sensor.

The silicon nanowires may be electrically insulated from the CMOS signal processing circuit by forming trenches by etching silicon substrates on both ends of the silicon nanowires.

The silicon nanowires may be electrically insulated from the CMOS signal processing circuit by doping impurities into the silicon substrates across the silicon nanowires.

In addition, the method of manufacturing a microphone integrated with the CMOS circuit may further include forming support means in a silicon nitride film region corresponding to a region in which silicon nanowires are formed. In this case, the support means may be a polyimide structure formed in a region corresponding to both ends of the silicon nanowires of the silicon nitride film.

The microphone integrated with the CMOS circuit according to the present invention is integrally formed on a silicon substrate, so that the connection process is unnecessary, such as when a separate acoustic sensor and a signal processing circuit are manufactured. There is an effect that the reliability is improved.

In addition, since the microphone integrated with the CMOS circuit according to the present invention uses the piezoresistive effect of silicon nanowires, the microphone is used as an acoustic sensor, thereby making it possible to manufacture a miniaturized high-sensitivity microphone at low cost.

1A is a plan view of a microphone integrated with a CMOS circuit according to an exemplary embodiment of the present invention, and FIG. 1B is a rear view of the microphone integrated with the CMOS circuit of FIG. 1A.
2 to 14 are views provided to explain a method of manufacturing the silicon nanowires according to an embodiment of the present invention.
15 to 45 are views provided to explain a method of manufacturing a CMOS signal processing circuit according to an embodiment of the present invention.
46 to 48 are views provided to explain a method of manufacturing an acoustic sensor according to an embodiment of the present invention.
49A and 49B are views provided to explain a method of manufacturing an acoustic sensor according to another exemplary embodiment of the present invention.
50A and 50B are a cross-sectional view and a perspective view of a microphone integrated with a CMOS circuit according to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. In the accompanying drawings, there may be a component having a specific pattern or having a predetermined thickness, but this is for convenience of description or distinction. It is not limited only.

1A is a plan view of a microphone integrated with a CMOS circuit according to an exemplary embodiment of the present invention, and FIG. 1B is a rear view of the microphone integrated with the CMOS circuit of FIG. 1A.

The microphone according to the present invention is a microphone 100 in which a CMOS circuit is integrated, and an acoustic sensor including a silicon nanowire 111 and a CMOS signal processing circuit 120 are integrally positioned on a silicon substrate as shown in FIG. 1A. . That is, the silicon nanowires 111 and the CMOS circuit 120 are integrally formed on the silicon substrate 130 at the same time.

In FIG. 1A, the microphone 100 includes a diaphragm in which silicon nanowires 111 are formed on a thin silicon nitride film 112 that is positioned in a process. Diaphragm means an acoustic sensor that can respond to sound. When the diaphragm bends the silicon nitride film 112 in the diaphragm by sound pressure, the silicon nanowire 111 is subjected to tensile stress, and the resistance is changed by the piezoresistive effect. When such a change in resistance is converted into an electric signal, it is possible to convert it into an acoustic electric signal.

FIG. 1B is a rear view of a microphone in which a CMOS circuit is integrated, and the silicon nanowires 111 of the microphone 100 may include silicon blocks connected to both sides of the silicon nanowires due to a deep trench formation process during the diaphragm formation process. Hereinafter, a silicon nanowire supporting block 113 may be formed in an island structure to be electrically isolated from other components. As can be seen in Figures 1a and 1b, the silicon nitride film 112 not only serves as a membrane in response to negative pressure, but also serves as an auxiliary support means for maintaining the silicon nanowire support block 113. .

In contrast, a method of electrically separating the silicon nanowires from other components includes a method of doping impurities into silicon substrates on both ends of the silicon nanowires, which will be further described with reference to FIGS. 49A and 49B.

Hereinafter, a method of manufacturing a microphone integrated with a CMOS circuit according to the present invention will be described. A method of manufacturing a microphone integrated with a CMOS circuit is largely provided by forming silicon nanowires on a silicon substrate, forming a CMOS signal processing circuit, and electrically separating the formed silicon nanowires from the CMOS signal processing circuit. Divided into steps to form. Hereinafter, a description will be given with reference to FIGS. 2 to 48.

2 to 14 are views provided to explain a method of manufacturing the silicon nanowires according to an embodiment of the present invention. In order to manufacture the silicon nanowires, first, a silicon substrate having a top surface having a crystal direction of <100> is prepared (FIG. 2), a silicon oxide film is formed through a wet oxide film formation process (FIG. 3), and a silicon oxide film is formed on the silicon oxide film. Forming a silicon nitride film (FIG. 4), applying a photoresist and then patterning it (FIG. 5), and sequentially etching the exposed silicon nitride film and the silicon oxide film after photoresist patterning (FIG. 6). In FIG. 6, the silicon nitride film and the silicon oxide film are etched and removed to etch the exposed silicon substrate to a predetermined depth (FIG. 7), and to remove the photoresist (FIG. 8), using a KOH solution or a TMAH solution. To form a triangular structure such as an hourglass shape through anisotropic silicon etching (FIG. 9), and form a silicon nanowire through a wet oxide film forming process. The step (Fig. 10), and removing the silicon nitride film remaining (FIG. 11) that it is carried out sequentially. FIG. 12 is a cross-sectional view taken along line AA ′ of FIG. 11.

When the silicon nanowires are formed, the electrical resistance of the nanowires is controlled by injecting impurities of a certain concentration into the silicon nanowires through an ion implantation process as shown in FIG. 13. In FIG. 13, a photoresist is first applied and patterned, followed by implanting impurities into the silicon nanowires through an ion implantation process. When the heat treatment is performed as shown in FIG. 14, the implanted impurities are activated to complete the doping of the silicon nanowires. In addition to the silicon nanowires, impurities are also injected into portions of the silicon substrates connected to the silicon nanowires.

15 to 45 are views provided to explain a method of manufacturing a CMOS signal processing circuit according to an embodiment of the present invention. When the silicon nanowires are formed according to FIGS. 2 to 14, an analog signal processing circuit is formed by a CMOS process on the same silicon substrate. In particular, the CMOS signal processing circuit is formed through a CMOS process using an empty space in which silicon nanowires are not formed on a silicon substrate on which silicon nanowires are formed. Analog signal processing circuits generally consist of devices such as p-MOSFETs, n-MOSFETs, capacitors, and resistors. In the present invention, a method of simultaneously forming a p-MOSFET and an n-MOSFET on a substrate on which silicon nanowires are formed is illustrated, and illustrations of devices such as capacitors and resistors are omitted.

A method of forming a CMOS signal processing circuit is as follows. First depositing a silicon nitride film on a substrate on which silicon nanowires are formed (FIG. 15), performing silicon nitride patterning and n-well implantation (FIG. 16), performing indentation oxidation (FIG. 17), and silicon nitride film patterning. And performing a p-well implantation (FIG. 18), forming an N-well and a P-well through a well drive-in process through heat treatment (FIG. 19), and removing an oxide film on the substrate surface (FIG. 19). 20), Buffer oxidation and silicon nitride deposition step (FIG. 21), silicon nitride patterning step (FIG. 22), field oxidation step (FIG. 23), silicon nitride strip and sacrificial oxidation step (FIG. 24), photoresist patterning and channel threshold adjust ion implantation step (FIG. 25), photoresist removal and low-stress silicon nitride deposition step (FIG. 26), silicon nitride patterning step (FIG. 27), gate oxidation, polysilicon deposition, POCl ₃ doping and TEOS (TetraEthyl O) rthoSilicate) deposition step (FIG. 28), polysilicon and TEOS patterning step (FIG. 29), N-LDD photolithography and ion implantation step (FIG. 30), P-LDD photolithography and ion implantation step (FIG. 31), TEOS deposition / Etch, and recovery oxidation step (FIG. 32), N + S / D photoetch and ion implantation step (FIG. 33), P + S / D photoetch and silicon nanowire contact photoetch and ion implantation steps (FIG. 34), Activating the implanted ions through the heat treatment process (FIG. 35), depositing TEOS as the insulating film (FIG. 36), opening the contact through contact photolithography and TEOS etching (FIG. 37), and Depositing a metal (FIG. 38), patterning a first metal (FIG. 39), depositing an oxide film as an insulating film (FIG. 40), opening a contact through contact photolithography and oxide etching Step (FIG. 41), depositing the second metal (FIG. 42), patterning the second metal 43, a process of manufacturing an analog signal processing circuit is completed through depositing an oxide film as an insulating film (FIG. 44) and etching an oxide film covering the silicon nanowires through oxide etching (FIG. 45). . Referring to FIG. 45, a state in which p-MOSFET 121, n-MOSFET 122, and Si nanowire piezoresistor 111 are simultaneously formed on one silicon substrate is illustrated.

After the silicon nanowire manufacturing process (FIGS. 2 to 14) and the analog signal processing circuit manufacturing process (FIGS. 15 to 45) through the CMOS process are completed, a process of forming the silicon nanowires into diaphragms capable of reacting to sound Do this. 46 to 48 are diagrams illustrating a diaphragm fabrication step, including applying and patterning a photoresist on a silicon substrate back surface (FIG. 46), etching a silicon substrate to expose silicon nanowires (FIG. 47), and a photo The step of removing the resist (FIG. 48) is shown. FIG. 48 shows that the silicon nanowires are exposed on the back surface of the silicon substrate, and the silicon nitride film is exposed on the top surface to form a diaphragm, and they are connected to the contact electrode to form an acoustic sensor unit.

48 is a cross-sectional view of the microphone in which the acoustic sensor and the signal processing circuit according to the present invention are integrally formed. In FIG. 48, the silicon nanowires are electrically separated from the signal processing circuit by forming silicon support blocks connected to both sides through a deep trench formation process during diaphragm formation. The silicon nitride film of FIG. 48 not only serves as a film responding to the negative pressure but also serves as a support means for making the silicon nanowire support block adhere well.

49A and 49B are views provided to explain a method of manufacturing an acoustic sensor according to another exemplary embodiment of the present invention. The silicon nanowire piezoresistor shown in FIG. 49A is doped with impurities in the electrode contact regions on both sides of the silicon nanowires instead of structural separation through deep trench formation for electrical separation of the silicon nanowire piezoresistor as shown in FIG. 48. Thus, electrical isolation (isolation) was formed using junction isolation. After the dopants are doped in the electrode contact regions across the silicon nanowires, the silicon substrate is etched to expose the silicon nanowires to form a diaphragm as shown in FIG. 49B. Since the electrical separation using the junction isolation through the doping is possible, the silicon nanowire support block is unnecessary.

50A and 50B are a cross-sectional view and a perspective view of a microphone integrated with a CMOS circuit according to another embodiment of the present invention. As shown in FIG. 48, when the silicon nanowire device is electrically separated from the signal processing circuit by deep trench formation, support may be insufficient only by the silicon nanowire support block. Therefore, it is preferable to further support means on the upper surface of the silicon substrate as shown in Figure 50a and 50b. At this time, the support means may be further formed using a polyimide which is easy to process.

The support means is preferably formed as a thicker structure than the silicon nitride film that surrounds a part of the silicon nitride film and a part of the electrode structure formed on the upper surface of the silicon substrate as shown in Figure 50a to more effectively support the silicon nanowires.

The invention is not to be limited by the foregoing embodiments and the accompanying drawings, but should be construed by the appended claims. In addition, it will be apparent to those skilled in the art that various forms of substitution, modification, and alteration are possible within the scope of the present invention without departing from the technical spirit of the present invention.

100 microphone
111 silicon nanowires
112 silicon nitride film
113 Silicon Nanowire Support Block
120 CMOS Signal Processing Circuit
121 p-MOSFET
122 n-MOSFET
130 silicon substrate

Claims (8)

delete delete delete Forming silicon nanowires by anisotropic silicon etching and wet oxide film formation on the silicon substrate;
Forming a silicon nitride film on the silicon substrate on which the silicon nanowires are formed, and then removing a portion of the silicon nitride film and forming a p-MOSFET and an n-MOSFET to form a CMOS signal processing circuit;
Removing the silicon substrate to expose the silicon nanowires to the outside and electrically insulate the silicon nanowires from the CMOS signal processing circuit to form an acoustic sensor for sensing a piezoelectric resistance change; And
And forming support means in a silicon nitride film region on a region where the silicon nanowires are formed.
The support means is a polyimide structure formed in the silicon nitride film region laminated on both ends of the silicon nanowires,
And a CMOS circuit in which a CMOS signal processing circuit for processing the acoustic sensor and the sensed piezoresistive change signal is integrally formed. The method of claim 4,
Forming a trench by etching silicon substrates on both ends of the silicon nanowires to electrically insulate the silicon nanowires from the CMOS signal processing circuit. The method of claim 4,
And insulating the silicon substrate from both ends of the silicon nanowire to electrically insulate the silicon nanowire from the CMOS signal processing circuit. delete delete

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