KR100700914B1 - Bipolar Phototransistor and Fabrication Process Method Thereof - Google Patents

Abstract

A bipolar photo-transistor and its manufacturing method are provided to improve a photo conversion efficiency and to enhance a current gain by performing selectively an ion implantation using a lattice type base. An epitaxial layer(311) is formed on a silicon substrate(310). A lattice type base(330) is formed on the epitaxial layer. The lattice type base is selectively implanted with predetermined ions. An emitter(350) is formed on the base. An ARC(Anti-Reflective coating)(360) is deposited on the resultant structure. An emitter electrode(380) for contacting the emitter is formed on the ARC. A collector electrode is formed by depositing a metallic material onto a lower surface of the substrate.

Description

Bipolar phototransistor and its manufacturing method {Bipolar Phototransistor and Fabrication Process Method Thereof}

1A is a plan view of a bipolar phototransistor according to the prior art.

FIG. 1B is a cross-sectional view of the bipolar phototransistor taken along line II ′ of FIG. 1A.

2A to 2F are process flowcharts illustrating step-by-step manufacturing processes of the bipolar phototransistors of FIGS. 1A and 1B.

3A is a plan view of a bipolar phototransistor according to the present invention.

3B is a cross-sectional view of the bipolar phototransistor taken along line II-II ′ of FIG. 3A.

4 is a block diagram illustrating a manufacturing process of the phototransistor of FIG. 3B step by step.

5A through 5F are step by step process diagrams of FIG. 4.

Detailed description of the main parts of the drawings

100, 300: phototransistor 110, 310: substrate

111, 311: epi layer 130, 330: base

331: injection region (clear) 332: non-infusion region (dark)

150, 350 emitter 355: barrier layer

160, 360: anti-reflective film 180, 380: emitter (metal) electrode

The present invention relates to a bipolar phototransistor and a method for manufacturing the same, and more particularly, to a bipolar phototransistor and a method for manufacturing the same that can improve the characteristics of the device, such as to improve the current gain and reduce the leakage of current.

In general, the phototransistor can obtain the output current with the characteristic that the light input from the outside is converted into current (photovoltaic effect) and amplified. The phototransistor has a slower response speed than photodiode (two-pole device), which is one of the devices that generate current when light is input, but because it is a three-pole device, the input light is converted into current and amplified and displayed as an output. It can be used as a light sensor. In addition, the characteristics of the phototransistor device include amplification factor (current gain), leakage current, response speed, breakdown voltage, and the like, and various materials and processing methods exist to be appropriately used in an application field in consideration of each characteristic.

Hereinafter, an optical transistor according to the prior art will be described with reference to the accompanying drawings.

FIG. 1A is a plan view of a bipolar phototransistor according to the prior art, and FIG. 1B is a cross-sectional view of the bipolar phototransistor taken along line II ′ of FIG. 1A.

1A and 1B, a conventional bipolar phototransistor 100 includes a substrate 110, a base 130 formed on the substrate 110, an emitter 150, and a collector formed under the substrate 110. And 170. In addition, the phototransistor 100 further includes an epitaxial layer 111, a semireflective film 160, and a metal electrode 180.

2A to 2F are process flowcharts illustrating step-by-step manufacturing processes of the bipolar phototransistor of FIG. 1.

Referring to FIG. 2A, to manufacture the bipolar phototransistor 100 of FIG. 1, first, a substrate 110 is prepared, and an epitaxial layer 111 is formed on the substrate 110. At this time. The substrate 110 uses a high concentration silicon substrate, and the epi layer 111 uses a relatively low concentration.

Referring to FIG. 2B, an epitaxial layer 111 is formed on the substrate 110, and then an oxide film 112 is grown on the epitaxial layer 111. After the oxide film 112 is grown, a base shape is defined on a photoresist film (not shown) by using a photographic transfer operation. When the base shape is defined, the base shape is reproduced in the oxide film 112 through an etching process, and then base impurities are implanted into the base shape. When the base impurity is injected into the base shape, the photoresist layer is removed, and then the base 130 is formed by performing a heat treatment process. At this time, the oxide film 113 is formed when the heat treatment process is performed.

Referring to FIG. 2C, after the base 130 is formed, an emitter shape is defined on a photoresist film (not shown) by using a photographic transfer operation. When the emitter shape is defined, the emitter impurities are ion implanted after reproducing the emitter shape on the oxide film 113 through an etching process. When the emitter impurities are injected into the emitter shape, the photoresist film is removed and then a heat treatment process is performed to form the emitter 150. At this time, an oxide film 114 is formed on the substrate 110 during the heat treatment process.

Referring to FIG. 2D, a semireflective film 160 is formed on the epitaxial layer 111 and the oxide films 112 and 114 formed on the base 130 and the emitter 150.

Referring to FIG. 2E, the emitter contact window is defined using a photo transfer operation on a photoresist film (not shown) formed on the antireflection film 160. When the emitter contact window 165 is defined, the semi-reflective film 160 and the oxide film 114 are etched to form the emitter contact window 165. Next, after depositing a metal film (not shown), the metal electrode shape is defined on the photoresist film (not shown) by photo transfer, and the metal film is etched according to the metal electrode shape to form the emitter metal electrode 180. do.

Referring to FIG. 2F, the phototransistor 100 is completed by depositing a metal on the lower surface of the substrate 110 and then performing a heat treatment process to form the collector 170.

However, in the conventional bipolar phototransistor fabricated using the above-described process, the efficiency of converting light into current is affected by the depletion layer region formed on the base, and a leakage current is generated due to the depletion layer formed on the wafer cutting surface during device operation. Can be. In addition, since the concentration of the base surface is lowered by frequent heat treatment after the emitter is formed, there is a disadvantage that can cause leakage of current.

Accordingly, the present invention has been devised to solve the above problems, and an object of the present invention is to improve the efficiency of converting light into a current to improve a current gain, thereby improving bipolar phototransistors and their fabrication. To provide a way.

According to an aspect of the present invention, to achieve the above object, a method of manufacturing a bipolar phototransistor of the present invention comprises the steps of forming an epitaxial layer having a concentration lower than the concentration of the silicon substrate on a silicon substrate; Forming a base having a lattice shape in which impurities are implanted on the epitaxial layer; Forming an emitter on the base; Depositing a semi-reflective film on the silicon substrate on which the emitter is formed; Forming an emitter electrode on said antireflective film to contact said emitter; And forming a collector electrode by depositing a metal on a lower surface of the silicon substrate.

Preferably, the forming of the base may include defining a base shape having a lattice shape on the photoresist film to form the base, ion implanting the impurity into a portion of the defined lattice shape, and After the injection, the photoresist film is removed, and the photoresist film is removed and then thermally treated. The lattice-shaped base includes an injection region into which impurities are injected and an uninjection region into which impurities are not injected.

Before forming the semi-reflective film, further comprising forming a blocking layer along the edge of the epi layer formed on the substrate. The blocking layer can be formed simultaneously with the formation of the emitter.
Forming the emitter includes ion implanting emitter impurities and heat treating the ion implanted emitter. The emitter impurities injected into the emitter are injected into the blocking layer.

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The forming of the emitter electrode may include forming a barrier metal layer on the emitter, forming a wiring metal layer on the barrier metal layer, and etching the wiring metal layer and the barrier metal layer. In the etching step, a plasma etching process of etching the wiring metal layer and a wet etching process of etching the barrier metal layer are used.

The method may further include ion implanting impurities on the entire surface of the silicon substrate before forming the anti-reflective film or after the blocking layer is formed.

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 According to another aspect of the present invention for achieving the above object, an epitaxial layer formed on a silicon substrate; A lattice-shaped base formed on the epi layer; An emitter formed on the base; A blocking layer formed on the epi layer along a circumferential direction of the edge of the epi layer; An antireflection film formed on the epi layer, the blocking layer, and the base; A metal electrode formed on the emitter to be in contact with the emitter; And a collector formed on the bottom surface of the silicon substrate.

Preferably, the lattice-shaped base includes an injection region into which impurities are injected and an uninjection region into which impurities are not injected.

Hereinafter, a silicon bipolar phototransistor according to the present invention will be described in more detail with reference to the accompanying drawings.

3A is a plan view of a bipolar phototransistor according to the present invention, and FIG. 3B is a cross-sectional view of the bipolar phototransistor along line II-II 'of FIG. 3A.

3A and 3B, the bipolar phototransistor 300 according to the present invention includes a substrate 310, an epi layer 311, a base 330, an emitter 350, and a collector 370. In addition, the phototransistor 300 further includes a semi-reflective film 360 and a metal electrode 380.

The base 330 of the bipolar phototransistor 300 according to the present invention has a lattice structure. Referring to an enlarged view of region A in FIG. 3A, the structure of the base 330 according to the present invention is divided into an injection region 331 into which base impurities are injected and a non-injection region 332 not injected. In addition, the phototransistor 300 of the present invention further includes a blocking layer 355 formed to surround the outer region of the base 330.

4 is a block diagram illustrating a manufacturing process of the phototransistor of FIG. 3B step by step, and FIGS. 5A to 5F are process steps of FIG. 4. Hereinafter, a manufacturing process of an optical transistor according to the present invention will be described in detail with reference to the drawings.

First, referring to FIGS. 5A and 4, in order to manufacture the phototransistor 300 according to the present invention, first, a substrate 310 is prepared (S401). When the substrate 310 is prepared, the epi layer 311 is formed on the substrate 310 (S402). When preparing the substrate 310, it is preferable to prepare by considering the wavelength and the use of light to be applied to the phototransistor 300, in particular, the concentration and thickness adjustment of the epitaxial layer 311 is made of the phototransistor 300 It is an important factor in In the present embodiment, description will be made based on the use of an optical wavelength of about 470 nm. Therefore, in the present embodiment, a low concentration (n−; 10 to 20 Ohm / cm) epitaxial layer 311 on a high concentration (n +; <1 Ohm / cm) silicon substrate 310 generally known for fabricating a high performance device. ) Is formed to a thickness of 10 ~ 20㎛.

Next, referring to FIG. 5B, an oxide film 312 is formed on the epitaxial layer 311 (S403). The oxide layer 312 is grown in a range of 180 to 220 nm, and in this embodiment, is grown to a thickness of about 200 nm. After the oxide film 312 is grown, a photosensitive film (not shown) is formed on the oxide film 312 to perform a photo transfer operation defining a base shape (S404). In step S404, the base shape is defined as a lattice shape, and the lattice shape is an injection region (clear width, see FIG. 3A) 331 into which impurities are injected and a non-implantation region (dark width, see FIG. 3A) into which impurities are not injected. ), And the current gain varies depending on the lattice shape. In the present embodiment, the clear width is defined as 10 μm, and the dark width is defined as 2 μm. Once the base shape is defined, a base shape is formed in the oxide film 312 through an etching process (S405), an ion is implanted into the formed base shape, then the photoresist film is removed, and then a desired heat treatment is performed by performing a heat treatment. ) To complete (S406). An oxide film 313 is formed in the heat treatment process of step S406.

Referring to FIG. 5C, after the base 330 is formed, a photosensitive film is formed on the oxide film 312 to perform a photo transfer operation of defining an emitter shape and a blocking layer shape (S407). Next, after forming the emitter and the blocking layer through an etching process (S408), after implanting impurities, the photoresist is removed and heat treatment is performed to complete the emitter 350 and the blocking layer 355 ( S409). When the heat treatment is performed (S409), an oxide film 314 is formed. In this embodiment, since the blocking layer 355 is formed at the edge of the epi layer 311 along the circumferential direction of the device, it is possible to minimize the area where the depletion layer is formed on the wafer cut surface during the device operation. Meanwhile, in the present embodiment, the emitter 350 and the blocking layer 355 are simultaneously formed, but the emitter 350 and the blocking layer 355 may be formed separately.

Referring to FIG. 5D, after the base 330 and the emitter 350 are formed, the base impurity ↓ injected in the step S406 is injected into the entire surface of the substrate 310 (S410). By performing the step (S410), it is possible to increase the impurity concentration of the surface of the base 330 that can be lowered by the heat treatment process performed in the previous step.

Referring to FIG. 5E, a semireflective film 360 is formed on the substrate 310 on which the base 330 and the emitter 355 are formed (S411). The thickness of the semi-reflective film 360 is determined in consideration of the refractive index of the semi-reflective film in order to minimize the reflection of incident light. In the present embodiment, the semi-reflective film 360 is formed of a nitride film. When the wavelength of the incident light is 470 nm, the thickness of the semireflective film 360 formed of the nitride film is approximately 50 to 70 nm. Next, the emitter contact window 351 is formed by defining the emitter contact window 351 on the photoresist film on the semi-reflective film 360 through phototransfer operation, and etching the semi-reflective film 360 and the oxide film 314. do. Next, after depositing a metal film, that is, a barrier metal layer 380a (for example, TiW 200 nm) and a wiring metal layer (380b, for example, Al 900 nm), the shape of the metal electrode is defined and then etched through photo transfer. (S412). In the etching process, the wiring metal layers 380a and Al are etched by performing a plasma metal etching process. In this case, the barrier metal layers 380b and TiW are used as etch stop layers to prevent the antireflective film 360 from being damaged. Next, the barrier metal layer Tiw is etched using a wet etching process in a H ₂ O ₂ solution heated to about 40 ° C., and then the emitter (metal) electrode 380 is formed by heat treatment.

Next, referring to FIG. 5F, a lower region of the substrate 310 is cut to a predetermined thickness, and then a collector (electrode) 370 is formed by depositing a metal (eg, Au) on the lower surface of the substrate 310. Through the above-described steps (S401 to S413), it is possible to manufacture a bipolar transistor proposed in the present invention.

Although the technical spirit of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will appreciate that various embodiments are possible within the scope of the technical idea of the present invention.

As described above, according to the above, in the present invention, by manufacturing the base in the form of a lattice, injecting impurities only into a region defined selectively, the depletion region is enlarged during the operation of the device to improve the light conversion efficiency, thereby improving the current gain.

In addition, by forming a blocking layer on the edge of the device and injecting impurities, the leakage current can be reduced by minimizing the region where the depletion layer is formed on the wafer cutting surface during the device operation.

Claims (12)

In the manufacturing method of a bipolar phototransistor, Forming an epitaxial layer having a concentration lower than that of the silicon substrate on the silicon substrate; Forming a base having a lattice shape in which impurities are implanted on the epitaxial layer; Forming an emitter on the base; Depositing a semi-reflective film on the silicon substrate on which the emitter is formed; Forming an emitter electrode on said antireflective film to contact said emitter; And Depositing a metal on the bottom surface of the silicon substrate to form a collector electrode Method of manufacturing a bipolar phototransistor comprising a. The method of claim 1, Forming the base Defining a grating-shaped base shape on the photosensitive film to form the base, Ion implanting the impurity into a portion of the defined lattice shape; Removing the photoresist after the impurity is implanted; Heat treatment after the photoresist film is removed Method of manufacturing a bipolar phototransistor comprising a. The method of claim 2, The lattice-shaped base includes a bipolar phototransistor manufacturing method including an injection region into which impurities are injected and an uninjection region into which impurities are not injected. The method of claim 3, And forming a blocking layer along an edge of the epi layer formed on the substrate before forming the semi-reflective film. The method of claim 4, wherein The blocking layer may be formed simultaneously with the formation of the emitter bipolar phototransistor manufacturing method. The method according to claim 1 or 4, Forming the emitter A method of manufacturing a bipolar phototransistor comprising ion implantation of emitter impurities, and heat treatment of the ion implanted emitter. The method of claim 6, And a method of manufacturing a bipolar phototransistor in which the emitter impurities injected into the emitter are injected into the blocking layer. The method of claim 1, Forming the emitter electrode Forming a barrier metal layer on the emitter; Forming a wiring metal layer on the barrier metal layer; Etching the wiring metal layer and the barrier metal layer Method of manufacturing a bipolar phototransistor comprising a. The method of claim 8, In the etching step, a plasma etching process for etching the wiring metal layer and a wet etching process for etching the barrier metal layer. The method according to claim 1 or 4, And ion implanting the same impurity as the impurity implanted into the base onto the silicon substrate before the antireflection film is formed or after the blocking layer is formed. An epitaxial layer formed on the silicon substrate; A lattice-shaped base formed on the epi layer; An emitter formed on the base; A blocking layer formed on the epi layer along a circumferential direction of the edge of the epi layer; An antireflection film formed on the epi layer, the blocking layer, and the base; A metal electrode formed on the emitter to be in contact with the emitter; And Collector formed on the lower surface of the silicon substrate Bipolar phototransistor comprising a. The method of claim 11, The lattice-shaped base includes a bipolar phototransistor including an injection region into which impurities are injected and an uninjection region into which impurities are not injected.

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