JP3147341B2 - Photodetector and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photodetector for infrared and visible light regions and a method for manufacturing the same, and more particularly to improvement in operation stability and device size.

[0002]

2. Description of the Related Art Conventionally, as a photodetector in the infrared region,
Quantum-type semiconductor sensors and thermal-type pyroelectric elements are used, but they have different sensitivities depending on the wavelength region, and must be used properly depending on the application.Cooling is required to suppress the influence of noise due to heat. And had In addition, there is a problem that the response speed is slow, and a minute device that can be mounted on a micromachine has not yet been obtained.

On the other hand, as a photodetector having a high response speed, an MIM (Metal Insulator Met) is used.
al) Point contact diodes with junctions are known.
Hereinafter, a conventional point contact diode and a method of manufacturing the same will be described with reference to the drawings. FIG. 4 is a configuration diagram of a conventional point contact diode. In FIG. 4, the point contact diode is configured such that the tip 11 of the tungsten antenna 10 lightly contacts the contact surface 51 of the nickel metal post 50.

An extremely thin nickel oxide film 40 of about 10 angstroms is formed on the contact surface 51,
1 is polished to several hundred angstroms, and the oxide film 40 on the contact surface 51 of the metal post 50 and the tip 1 are polished.
1 form an MIM junction. In this case, the contact surface 5
The contact area between the tip 1 and the tip 11 is determined by the radius of curvature of the tip 11 and is about 10 ^-11 cm ² .

Next, the operation of light detection using the point contact diode shown in FIG. 4 will be described. FIGS. 5 and 6 are diagrams illustrating the operation of light detection using the point contact diode shown in FIG. In FIG. 5, a voltage source 12 and an ammeter 13 are connected in series between a metal post 50 and an antenna 10.

When a voltage is applied between the metal post 50 and the antenna 10, the point contact diode exhibits a current-voltage characteristic of a tunnel diode having nonlinearity as shown in FIG. This non-linearity is believed to be due to a difference in work function between the metal post 50 and the antenna 10.

Here, when the antenna 10 is irradiated with light while the bias voltage V _B is applied between the metal post 50 and the antenna 10 by the voltage source 12, the antenna 1
The electrons in 0 are excited by the energy of light. The excited electrons do not cross the potential difference barrier between the antenna 10 and the metal post 50, and the oxide film 4 formed on the contact surface 51.
Tunneling through zero, the point contact diode operates as a tunnel diode.

In this case, as shown in FIG. 6, the point contact diode is used to
Is detected at the bias voltage V _B by the nonlinearity of the point contact diode, and a detection current 15 having an amplitude _{hp 2} corresponding to the amplitude _{hp 1} of the photoelectric field 14 is measured by the ammeter 13.

In such a point contact diode,
The smaller the contact area between the contact surface 51 and the tip 11, the higher the detection sensitivity and the faster the response speed. Therefore, it is desirable that the contact area is small. Also, by changing the shape of the antenna 10, the wavelength band in which the point contact diode has the detection sensitivity can be changed.

Next, a method of manufacturing the point contact diode shown in FIG. 4 will be described. First, the contact surface 51 of the nickel metal post 50 is mirror-polished, and then the mirror-polished contact surface 51 is naturally oxidized or thermally oxidized in the air to form an oxide film 40 of about 10 angstroms.

Next, the diameter of the tip 11 of the tungsten antenna 10 is sharpened to several hundred angstroms by electrolytic polishing. Then, the tip 11 is lightly brought into contact with the contact surface 51 of the metal post 50. In this case, the contact area is determined by the radius of curvature of the tip 11, and is about 10 ^-11 cm ² .

However, such a conventional technique has the following problems. (A) The characteristics of the point contact diode change due to the contact pressure of the tip 11 on the contact surface 51, but it is difficult to keep this contact pressure constant during the measurement, and the characteristics change during the measurement. . (B) Since the tip 11 is exposed to the atmosphere, it is deteriorated under the influence of the atmosphere such as being oxidized, and its life as a point contact diode is shortened (about several days). (C) The characteristics of the point contact diode fluctuate depending on the conditions for polishing the tip 11 (concentration of electrolyte, degree of contamination, polishing time, etc.) and the state of the contact surface 51 (dirt, polishing state, etc.). Since it is difficult to control the state, it is difficult to manufacture a point contact diode having stable characteristics. (D) The point contact diode is too large to be used in a micromachine. SUMMARY OF THE INVENTION The present invention has been made in view of the conventional problems, and an object of the present invention is to provide a photodetector having a small size, high stability of characteristics, a long life, and a method of manufacturing the same. That is.

[0012]

To achieve the above object, according to the present invention, a first conductor formed on one surface of a dielectric film and another of the dielectric film are provided. A conductor hole that penetrates through the dielectric film from the surface and reaches the first conductor, a tunnel barrier insulating film formed on the bottom surface of the conductor hole, and the conductor hole through the tunnel barrier insulating film. And a second conductor to be embedded, comprising: receiving light to be detected on at least one of the first conductor and the second conductor; by a current flowing between the first conductor and the second conductor. A photodetector element for detecting the light to be measured, wherein a step of forming a first conductor on one surface of a dielectric film and the other surface of the dielectric film according to claim 2. Irradiating a focused ion beam to the first conductor through the dielectric film Forming a conductive hole to be formed, forming a tunnel barrier insulating film on the bottom surface of the conductive hole, and forming a second conductive material embedded in the conductive hole via the tunnel barrier insulating film. And a step of processing at least one of the first conductor and the second conductor into a desired shape.

[0013]

According to the present invention, in the first aspect,
The first conductor and the second conductor receive the light to be measured and excite free electrons, and the dielectric film blocks the contact between the second conductor embedded in the conductor hole and the tunnel barrier insulating film from the atmosphere. Then, the free electrons pass through the tunnel barrier insulating film. In claim 2, the focused ion beam applied to the other surface of the dielectric film having the first conductor formed on one surface has the diameter of the focused ion beam and passes through the dielectric film. Forming a conductor hole reaching one conductor, the first conductor and a tunnel barrier insulating film formed on the lower surface of the conductor hole and the second conductor formed by embedding metal in the conductor hole , Forming a tunnel junction.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a photodetector according to an embodiment of the present invention. FIG. 2 is a top view showing an example of the shape of the first conductor of the photodetector shown in FIG. In FIG. 1, the photodetector passes through the dielectric film 2, the first conductor 1 formed on one surface of the dielectric film 2, and the other surface of the dielectric film 2. A conductor hole 3 reaching the first conductor 1, a tunnel barrier insulating film 4 formed on the bottom surface of the conductor hole 3, and a metal buried in the conductor hole 3 via the tunnel barrier insulating film 4. And the second conductor 5 to be formed.

The first conductor 1 is made of, for example, nickel,
At least one of the first conductor 1 and the second conductor 5 functions as an antenna for receiving the light to be measured, and has an appropriate shape and size so as to have a detection sensitivity in a desired wavelength band, for example, as shown in FIG. It is patterned in such a spiral shape.
The dielectric film 2 is, for example, a film of silicon dioxide or silicon nitride, and has a thickness of about 500 to 1000 angstroms. The diameter of the conductor hole 3 is several hundred angstroms, and the thickness of the tunnel barrier insulating film 4 is several tens angstroms.

Since the conductor hole 3 is formed by irradiating the dielectric film 2 with a focused ion beam of gallium in a vacuum, the radius of curvature of the conductor hole 3 is determined by the diameter of the focused ion beam. An MIM junction is formed between the first conductor 1, the tunnel barrier insulating film 4, and the second conductor 5, and the contact area between the tunnel barrier insulating film 4 and the second conductor 5 is determined by the diameter of the conductor hole 3. , About 10 ^-11 cm ²
It is about the same as the point contact diode described above. Therefore, the detection sensitivity of the photodetector according to the present embodiment can be increased, and the response speed can be increased.

Since such a photodetector has an MIM junction like the above-mentioned point contact diode, it exhibits the current-voltage characteristics of a tunnel diode having non-linearity. Therefore, the light detecting element is provided with a bias voltage applied between the first conductor 1 and the second conductor 5.
It is possible to detect a photoelectric field due to light to be measured incident on at least one of the first conductor 1 and the second conductor 5 and output a detection current corresponding to the amplitude of the photoelectric field. If the same light to be measured is received by both the first conductor 1 and the second conductor 5 having the same shape, the detection sensitivity can be doubled by the principle of the antenna.

Since the second conductor 5 is always in contact with the tunnel barrier insulating film 4 in a constant state, the characteristics of the photodetecting element do not change during the measurement and always exhibit stable characteristics. . Further, since the joint 8 of the second conductor 5 is covered with the dielectric film 2 and is shielded from the atmosphere, the joint 8 of the second conductor 5 is not oxidized or deteriorated. The life as a photodetector can be greatly extended.

In this embodiment, the first conductor 1 is made of nickel. However, the first conductor 1 is made of polysilicon or silicon doped with a high concentration of conductive impurities, and the junction is MOS ( Metal Oxide Sili
con) or MIS (Metal Insulato)
(r Silicon) structure.

FIG. 3 is a schematic view showing a manufacturing process of a photodetector according to an embodiment of the present invention, which is a sectional view of the photodetector shown in FIG. I have. In FIG. 3A, for example, silicon dioxide or silicon nitride thin films having a thickness of about 500 to 1000 Å are formed as dielectric films 2 and 20 on both surfaces of a silicon substrate 6 whose plane orientation is (100). Further, a window is opened in the dielectric film 20 on one surface of the silicon substrate 6, and patterning is performed.

Next, referring to FIG. 3B, the silicon substrate 6 is anisotropically etched using the patterned dielectric film 20 as a mask to form one of the dielectric films 2 on the other surface of the silicon substrate 6. Expose the surface. Then, a nickel film 7 is laminated on the other surface of the dielectric film 2.

Next, referring to FIG.
Is patterned in a spiral shape as shown in FIG. 2 to form the first conductor 1. Then, one surface of the exposed dielectric film 2 is irradiated with a focused ion beam 8 of, for example, gallium in a vacuum to form a conductor hole 3 penetrating through the dielectric film 2 and reaching the first conductor 1. . In this case, the radius of curvature of the conductor hole 3 is determined by the diameter of the focused ion beam 8, and the radius is about several hundred angstroms.

Next, in FIG. 3D, the surface of the first conductor 1 exposed by forming the conductor hole 3 and serving as the bottom surface of the conductor hole 3 is thermally oxidized or naturally Oxidation is performed to form a tunnel barrier insulating film 4. When the tunnel barrier insulating film 4 is formed by oxidizing the first conductor 1 made of nickel, the film thickness is stably controlled to 10 to 20 angstroms. The tunnel barrier insulating film 4 can also be formed by depositing an insulator by, for example, molecular beam epitaxy.

Next, in FIG. 3E, a metal is buried in the conductor hole 3 by vapor deposition or the like to form a second conductor 5. Thus, the MIM junction is formed by the first conductor 1, the tunnel barrier insulating film 4, and the second conductor 5, and the junction area is determined by the radius of curvature of the conductor hole 3, that is, the diameter of the focused ion beam. The bonding area is about 10 ⁻¹¹ cm ² .

According to such a method of manufacturing the photodetector, the second conductor 5 is always in contact with the tunnel barrier insulating film 4 in a constant state, so that the characteristics of the photodetector change during measurement. And stable characteristics are always exhibited. Further, since the bonding portion 8 of the second conductor 5 is covered with the dielectric film 2 and is shielded from the atmosphere, the bonding portion 8 does not deteriorate due to oxidation or the like, and the life as the photodetector is not affected. Can be greatly lengthened.

Further, since there is no difficult step of polishing the tip of the antenna of the point contact diode in the step of forming the junction, a point contact diode having stable characteristics can be manufactured. Therefore, it is possible to realize a small element size that can be used for a micromachine.

In this embodiment, the first conductor 1 is formed by laminating and processing a nickel film. However, the first conductor 1 is made of polysilicon or silicon doped with conductive impurities, and this junction is formed by MOS. (Metal Oxide Si
silicone) or MIS (Metal Insula)
(tor silicon) structure.

[0028]

As described above, according to the first aspect of the present invention, the second conductor 5 is always in contact with the tunnel barrier insulating film 4 in a constant state, and the junction of the second conductor 5 is formed. 8 is configured to be covered with the dielectric film 2 so as to be shielded from the atmosphere, so that it is possible to provide a photodetector having high stability of characteristics and a long service life. Is a first conductor 1 using a semiconductor manufacturing technique.
Is formed on one surface of the dielectric film 2 and the other surface of the dielectric film 2 is irradiated with a focused ion beam to form a conductor hole 3, and a tunnel barrier insulating film 4 is formed on the conductor hole 3. Since the second conductor 5 is formed by embedding a metal through the interposition, it is possible to provide a method for manufacturing a photodetector having a small size, high stability of characteristics, and a long life.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a photodetector according to an embodiment of the present invention.

FIG. 2 is a top view showing an example of the shape of an electrode of the photodetector shown in FIG.

FIG. 3 is a schematic view of a manufacturing process of a photodetector showing an embodiment of the invention described in claim 2;

FIG. 4 is a configuration diagram of a conventional point contact diode.

5 is a diagram illustrating an operation of light detection using the point contact diode shown in FIG.

FIG. 6 is a diagram illustrating an operation of light detection using the point contact diode shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 First conductor 2 Dielectric film 3 Conductor hole 4 Tunnel barrier insulating film 5 Second conductor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-166774 (JP, A) JP-A-62-222678 (JP, A) JP-A-54-62787 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) H01L 31/00-31/119 G01J 1/00-1/60 H01L 49/00-49/02 H01L 29/88

Claims (2)

(57) [Claims] A first conductor formed on one surface of the dielectric film, a conductor hole penetrating from the other surface of the dielectric film through the dielectric film and reaching the first conductor; A tunnel barrier insulating film formed on the bottom surface of the conductor hole; and a second conductor embedded in the conductor hole via the tunnel barrier insulating film. The first conductor and the second conductor A photodetector, wherein the light to be detected is received by at least one of a body and the light to be measured is detected by a current flowing between the first conductor and the second conductor. 2. A step of forming a first conductor on one surface of the dielectric film, and irradiating the other surface of the dielectric film with a focused ion beam to penetrate the dielectric film and form the first conductor. Forming a conductor hole reaching the body, forming a tunnel barrier insulating film on the bottom surface of the conductor hole, and embedding a second conductor in the conductor hole via the tunnel barrier insulating film. And a step of processing at least one of the first conductor and the second conductor into a desired shape.