KR100861472B1 - High voltage semiconductor device and manufacturing method thereof - Google Patents

Abstract

The present invention is to provide a semiconductor device and a method of manufacturing the semiconductor device capable of mass production by using the electric field structure to obtain a breakdown voltage characteristics of high voltage, the silicon oxide Schottky diode according to the present invention comprises: a cathode electrode (250); A substrate 240 having a high doping concentration for excellent ohmic characteristics; A low concentration base layer 230 to have high breakdown voltage characteristics; A thermal oxide film 220 having a low surface charge concentration and a high electric field strength; A benzocyclobutyne (BCB) layer 210 capable of achieving a sufficient thickness while having a high electric field strength in a relatively easy manner; The thermal oxide film 220 and the benzocyclobutene layer 210 penetrate the contact with the base layer, and the edge may include a Schottky junction and termination structure 220 formed on a suitable size on the benzocyclobutyne layer.

The high-voltage silicon carbide Schottky diode has a simple structure but has a termination structure showing high breakdown voltage characteristics and does not include a separate device protection layer, thereby reducing the number of masks and reducing manufacturing costs.

Description

High voltage semiconductor device and manufacturing method thereof

1 is a structural diagram of a conventional semiconductor device using silicon carbide,

       2 is an electric field distribution chart when breakdown occurs in the device of FIG.

       3 is a cross-sectional view showing a semiconductor device implemented according to the present invention;

4 is a cross-sectional view illustrating a fabrication procedure of a semiconductor device implemented according to the present invention.

5 is a view showing an embodiment of a silicon carbide Schottky diode manufactured through the process of FIG.

      6 is a view showing the breakdown voltage characteristics with respect to the configuration and thickness change of the insulating film in the conventional structure and the structure according to the present invention.

      7 is a diagram showing the application of the electric field structure of the present invention to PiN, MOSFET, IGBT, JFET

      8 is a view showing a structure composed of a multi-layered insulating layer which is another embodiment of the electric field structure of the present invention.

  <Description of Main Sign of the Present Invention>

200 anode electrode 210 benzocyclobutene (BCB) layer (insulating layer)

220: oxide film 230: silicon carbide base layer

240: silicon carbide substrate 250: cathode electrode

The present invention relates to a high voltage semiconductor device and a method of manufacturing the same.

In general, the breakdown voltage of a diode is determined by the breakdown caused by impact ionization and the impact ionization is influenced by the magnitude of the maximum electric field.

Figure 1 and the formula shows the breakdown voltage formula for the structure and design parameters of the Schottky diode, respectively.

(Equation)

V _B = qN _D W ² / 2ε _S

Where V _B is the breakdown voltage, q is the charge of electrons, N _D is the doping concentration of the base region, W is the thickness of the base region, and finally ε _S is the dielectric constant of the base region semiconductor. When designing a high voltage Schottky diode, the breakdown voltage is primarily determined by the thickness of the base region and the doping concentration.

The formula is simple for designing high voltage devices in a structure in which the state of the wafer is clean (that is, there is no lattice defect or the like in the wafer at all) and the anode and the cathode are infinitely extended in the direction perpendicular to the direction of crystal growth. This is an equation that can be applied.

However, in the actual device structure, the anode and cathode electrodes are finite and have an asymmetric structure, so the maximum electric field occurs at the edge of the anode electrode where electrostatic concentration of the electric field occurs.

Therefore, if the proper termination technique for dispersing the concentrated electric field in the corner region is not used, breakdown voltage is lower than the theoretical value.

FIG. 2 shows a bias voltage of about -600V applied to the anode without using a termination structure in the Schottky diode, which was mass-produced to have a breakdown voltage of 600V (designed to have over-specification in consideration of process and wafer defects). When the electric field distribution is shown. In this case, the edge of the anode is larger than the maximum electric field value of 2.16 MV / cm and breakdown occurs when the voltage of the anode is -607V.

Generally, a field plate structure (FP), a field limiting ring (FLR), a junction termination extension (JTE), and a high resistance layer are inserted to obtain a high breakdown voltage. The structure which mixes these is used.

In the case of the field-limiting band structure and the junction termination extension structure, a process of injecting P-type ions is required to disperse the electric field concentrated at the edge of the anode, and in the case of silicon carbide, the implanted ions are larger than 1600 ^o C to be electrically activated. High temperature processes are also required.

In addition, these P-type regions require a gentle extension of the potential to prevent electric field concentration, which requires a sufficient space.

Compared with these structures, the structure of the plate structure is simple and does not require a complicated process and occupies a small area. However, in order to apply the structure of the plate structure, a high quality thick oxide film is required. There was this.

In particular, in the case of silicon oxide, it is more difficult to cultivate a high quality thick oxide film because the oxide film must be grown at a higher temperature than silicon, and carbon remains at the junction with the semiconductor to serve as a trap.

There is no case of applying the structure of the structure of the plate to the power semiconductor using silicon carbide in Korea, and US patent US7180103B2 uses Al ₂ O ₃ as the insulating film for the structure of the plate to improve the breakdown voltage of the power MESFET. However, a structure that can withstand high voltages has not been proposed.

In addition, the US patent US6949797 uses a structure in which a high resistance layer insertion and an electric field panel structure are mixed in order to improve the breakdown voltage characteristic of the power MOSFET, but since there is no mention of an insulating film for obtaining a high voltage. There was no mass production of semiconductor devices that could be used for practical use.

The present invention is to solve the above problems,

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device capable of mass production and a method of manufacturing the same by using a field board structure to obtain a breakdown voltage characteristic of high voltage.

Another object is to realize the structure of the structure of the board structure using a high quality oxide film and a thick insulating layer in the Schottky diode using silicon carbide to reduce the process step and reduce the manufacturing cost of expensive power devices.

Another object is to provide a low-cost semiconductor device having a simple structure and high breakdown voltage characteristics by using benzocyclobutyne (BCB) and a thin thermal oxide film as an insulating layer, and a semiconductor that does not need a separate protective layer to protect the device. It is to provide a method of manufacturing a device.

In order to achieve the above object, the present invention provides a substrate having a high doping concentration for excellent ohmic characteristics, a low concentration base layer having high breakdown voltage characteristics, a thermal oxide film having a low surface charge concentration, and a high electric field strength; The benzocyclobutene (BCB) layer, which has a high electric field strength and can realize a sufficient thickness in a relatively easy manner, contacts the base layer through the thermal oxide film and the benzocyclobutyne (BCB) layer, and the corners of the benzocyclo moiety. And a Schottky junction and termination structure formed in a suitable size on the tin layer.

A semiconductor device composed of such high voltage silicon carbide has a simple structure and a termination structure showing high breakdown voltage characteristics, and does not include a separate device protection layer, thereby reducing the number of masks and reducing manufacturing costs.

In addition, the method of manufacturing a semiconductor device includes the steps of forming a high quality thermal oxide layer, depositing and heat treating an ohmic metal on a substrate to form a cathode electrode, and having a high electric field strength in a relatively easy manner and having sufficient thickness. Applying a benzocyclobutene layer capable of implementing the step, and forming a termination structure for forming a schottky junction through the benzocyclobutene layer and an oxide layer after applying and curing the benzocyclobutyne layer, and the schottky junction And depositing an anode electrode metal to form an electric field structure.

In order to achieve the above purpose, a simple termination structure is used, and a high voltage field termination structure has a high electric field strength and a thick insulating material is required. When thermal oxide film is used, the electric field strength is high at 10 MV / cm but is higher than 600 V. It is difficult to obtain the thickness necessary to obtain high voltage in silicon monoxide.

That is, in order to obtain a high quality oxide film from silicon carbide, it is necessary to grow a thermal oxide film in a high temperature dry oxygen atmosphere. The growth rate of the thermal oxide film is about 12.7 nm / h in 1150 ^o C, O ₂ (5LPM) atmosphere.

Therefore, in order to obtain a breakdown voltage of 600V, the thickness of the oxide film is required to be at least 200 nm. To this end, the thermal oxidation process should be performed for 15.8 hours.

This is because, as the oxide film becomes thicker, the quality of the thermal oxide film generally decreases. In the case of oxide and nitride films using other chemical vapor deposition techniques, the quality of the film is poor compared to the thermal oxide film and causes breakdown at low voltage due to the surface charge between the semiconductor and the insulating thin film.

Therefore, in the present invention, high breakdown voltage characteristics are obtained by forming a high quality thin thermal oxide film and coating a benzocyclobutyne (BCB) layer having a relatively high electric field strength thereon to prevent degradation of film quality and premature yielding due to surface charge. I made it.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view showing a semiconductor device implemented according to the present invention.

In order to implement an electric field structure (FP) in a semiconductor device (specifically, a Schottky device for silicon using silicon carbide) using the silicon carbide of the present invention, a thick insulating layer, a benzocycle butene (BCB) layer and a high quality thermal oxide film This is implemented.

Such a shoddy diode has a plurality of layers between the lower cathode electrode 250 and the upper anode electrode 200 and has a high doping concentration for excellent ohmic characteristics on the upper cathode electrode 250. The silicon carbide substrate 240 is coated, and a low concentration base layer 230 is coated thereon to have high breakdown voltage characteristics.

The benzocyclobutyne (BCB) layer 210 may be formed on the base layer 230 to form a thermal oxide film 220 having a low surface charge concentration and a high electric field strength, and have sufficient electric field strength thereon while having a sufficient electric field strength. Is implemented in the usual way.

In addition, the anode layer 200 is coated by using a termination structure that penetrates the thermal oxide film 220 and the benzocyclobutene layer 210 and contacts the base layer 230.

The termination structure is in contact with the benzocyclobutene layer 210 on the lower surface of the anode layer 200 in the horizontal direction, and the thermal oxide film 220 and the benzocyclobutene layer 210 on the longitudinal side. It is in contact.

The Schottky barrier diode configured as described above has a structure of a metal combined with a semiconductor instead of the structure of a diode of a general PN junction, and thus may have advantages of high speed and high current.

A method of manufacturing a high voltage silicon carbide Schottky diode having the above characteristics is shown in FIG. 4.

4 shows the procedure of the manufacturing method for manufacturing the silicon carbide Schottky diode according to the present invention.

(a) forming an oxide layer (FIG. 4A)

First, as in the conventional manufacturing process of the shock key diode (see FIG. 1), the low concentration base layer 230 is formed on the silicon carbide substrate 240 having a high doping concentration.

As such, in the state where the base layer 230 is formed on the silicon carbide substrate 240, a high quality oxide layer 220 is formed thereon.

(b) forming a cathode electrode (FIG. 4b)

In order to form a cathode electrode on the bottom of the silicon carbide substrate 240, the ohmic metal 250 is deposited on the substrate, and then heat treatment is performed.

(c) insulation layer application step (FIG. 4C)

Using a general semiconductor manufacturing process, an insulating layer having a high electric field strength and having a sufficient thickness can be coated on the oxide layer. The insulating layer uses a polymer-based polymer having good insulating properties, and preferably a benzocyclobutyne layer. It is applied to the oxide layer 220 using the (210).

After applying the polymer-based benzocyclobutyne layer 210, the curing process is carried out according to the specifications provided by the manufacturer supplying benzocyclobutene.

The insulating layer may have the same insulating properties by using a ferroelectric such as Al ₂ O ₃ , SiN, Ta ₂ O ₅ , in addition to the polymer-based insulating layer. In general, since they have a large dielectric constant compared to polymer series, they have the advantage that the thickness required to obtain the same breakdown voltage can be thickened, so that they can be used in spite of low insulation strength.

As the polymer series used in the insulating layer coating step, benzocyclobutyne, polyethylene terephthalate, polypropylene, polyphenylene sulfite (PPS), or the like may be used.

(d) termination structure forming step (FIG. 4D)

The termination structure 260 is formed for the Schottky junction through which the benzocyclobutene layer 210 and the oxide layer 220 which are the insulating layers are connected, and are connected to the base layer 230.

In this case, the termination structure is formed using a mask process, a photoresist process, and an etching process used in a general semiconductor manufacturing process.

(e) Anode Formation Step (FIG. 4E)

The anode electrode metal 270 is deposited on the termination structure 260 to form a schottky junction and an electric plate structure plate structure.

As a result, the anode layer 200 is in contact with the benzocyclobutene layer 210 in the transverse lower surface, and in contact with the thermal oxide film 220 and the benzocyclobutin layer 210 in the longitudinal side. It becomes a state.

The high-voltage semiconductor device produced using the electric field structure termination structure implemented by forming a metal layer on the oxide layer and the polymer insulating layer as described above may include Schottky diode, MOSFET, IGBT, PiN, JFET and the like.

As a specific example, a technique used for mass production of a Schottky diode will be described with reference to FIG. 5.

That is, FIG. 5 illustrates an embodiment of a high voltage silicon carbide Schottky diode manufactured through the process of FIG. 4.

Here, the high-quality oxide layer 220 is grown in a 1150 ^o C oxygen or N ₂ O atmosphere in order to fabricate a 600V class device to have a thickness of about 10 ~ 60nm.

At this time, the electric field strength of SiO ₂ should be more than 8MV / cm. The insulating layer benzocyclobutene layer 210 below must have a thickness such that the dislocation distribution has a gentle curvature at the end of the anode so that the metal superimposed on the benzocyclobutene and the semiconductor located below it maintain a capacitive bond. do.

In addition, considering that the electric field strength of the benzocyclobutene layer 210 is 5.7 MV / cm, the benzocyclobutene layer should not be made too thin. In the case of mass production of a 600 V device, the thickness (t _BCB ) of the _{benzocyclobutene} layer should be It should be at least 1.2um and be configured not to exceed 3.5um for capacitive coupling.

In addition, the length L _FP of the anode electrode 200 superimposed on the benzocyclobutene layer 210 is completed by making a size similar to the thickness of the base layer 230 region.

7 (a) to 7 (d) show an embodiment of PiN, MOSFET, IGBT, and JFET according to the present invention. Detailed description of each device structure is already well known and thus the description is omitted. However, in order for these devices to have a high breakdown voltage, they must have a termination structure capable of distributing an electric field. The structure according to the present invention includes an anode electrode 370 of a PiN diode, a gate electrode 420 of a MOSFET, an IGBT, and a JFET. 520 and 620 can be equally applicable.

In addition, FIG. 8 according to another embodiment of the present invention shows an example in which different materials are stacked on the insulating layer and the thermal oxide layer stacked structure of FIG.

In particular, in FIG. 8, the multilayer insulating layer 710 is shown. Since the electric field structure is a structure in which an electric field is dispersed by the degree of inductive coupling between an anode electrode disposed on the insulating layer and a semiconductor below, the multilayer insulating layer is theoretically possible. The same breakdown voltage can be obtained when the capacitance 720 by the layer and the capacitance 740 by the insulating layer 730 of FIG. 8 are the same. This multi-layered structure can insert an insulating layer having a small dielectric constant but high insulation strength, and thus can complement an insulating layer having a large dielectric constant but low insulation strength, which is another embodiment of FIG. 3.

As described above, the breakdown voltage characteristics of a semiconductor device having a termination structure using a silicon carbide substrate have excellent characteristics when the electric field structure structure is implemented by using a thin oxide layer and a benzocyclobutyne layer, which is a film layer, as shown in FIG. 6. It was confirmed to have.

In other words, when the termination structure was not used (described as "underminated" in the drawing), the wafer was grown using an epitaxial wafer exceeding the specification, and the yield occurred at around 600V. When used, the breakdown voltage was obtained at around 750V.

However, a high temperature oxidation process must be performed for 5 hours in order to grow a 60 nm oxide film on an over spec wafer exceeding the specification, and an oxidation process must be performed for a longer time to obtain a higher voltage.

On the other hand, in the case of the semiconductor device using the termination structure according to the present invention (the structure of the electric field structure plate of benzocyclobutyne, which is an insulating film having a thin oxide film of 10 nm and a thickness of 2 μm), the breakdown voltage is 920V, compared with the oxide film having a thickness of 60 nm. As can be seen from the diagram, the breakdown voltage improved by 21%.

As described above, in the present invention, a high yield yielding a simple structure termination technique using a thin thermal oxide film characterized by high electric field strength and excellent thin film quality and benzocyclobutyne which can form a thick film with relatively high electric field strength is achieved. A semiconductor device having voltage characteristics can be provided,

In addition, when the silicon carbide Schottky diode is constituted according to the present invention, it has a high breakdown voltage characteristic due to the advantages of physical properties and at the same time, a simple manufacturing step can reduce the number of masks and a separate device protection layer (passivation) for protecting the device. There is an advantage of not needing a layer), which can greatly reduce the manufacturing cost.

Claims (7)

In the semiconductor device formed of a plurality of layers between the lower cathode electrode 250 and the upper anode electrode 200, A silicon carbide substrate 240 formed on the cathode electrode 250 and having a high doping concentration; A base layer 230 formed on the silicon carbide substrate 240 and coated at a low concentration to have high breakdown voltage characteristics; A thermal oxide layer 220 coated on the base layer 230 and having a low surface charge concentration and a high electric field strength; The benzocyclobutyne layer 210 of the polymer system is applied on the thermal oxide layer 220 and has a sufficient thickness while having a high electric field strength, An anode electrode having a vertical structure in which the thermal oxide layer 220 and the benzocyclobutyne layer 210 are in contact with the base layer 230 in a horizontal direction, and are in longitudinal contact with the thermal oxide layer and the benzocyclobutyne layer. A semiconductor device, characterized in that the metal layer 270 is deposited. The method of claim 1, The device produced as a terminal structure of the electric field structure plate formed by forming a metal layer on the thermal oxidizing film and the benzocyclobutyne layer 210 of the polymer system is a high-voltage schottky diode, MOSFET, IGBT, PiN, JFET. Semiconductor element. (a) an oxide film forming step of forming a low concentration base layer 230 on a silicon carbide substrate 240 having a high doping concentration, and then forming a high quality oxide layer 220 thereon; (b) a cathode electrode forming step of depositing an ohmic metal 250 on the substrate and then performing a heat treatment to form a cathode on the bottom of the silicon carbide substrate 240; (c) an insulating layer coating step of applying an insulating layer on the oxide layer 220 to the oxide layer having a high electric field strength and a sufficient thickness using a general semiconductor manufacturing process; (d) forming a termination structure through the insulating layer 210 and the oxide layer 220 so as to be connected to the base layer 230 in a horizontal direction; (e) an anode electrode forming step of depositing an anode electrode metal 270 on the termination structure 260 to form a Schottky junction and field structure plate structure after the termination structure forming step; Method for manufacturing a semiconductor device, characterized in that consisting of. The method of claim 3, wherein The insulating layer used in the insulating layer coating step is formed of any one of a polymer-based benzocyclobutin, polyethylene terephthalate, polypropylene, polyphenylene sulfite (PPS) A method of manufacturing a semiconductor device. The method of claim 3, wherein The anode layer 200 formed in the termination structure forming step is in contact with the base layer 230 with the lower surface in the horizontal direction, and in contact with the thermal oxide film 220 and the insulating layer 210 in the longitudinal side. And a Schottky junction and an electric field structure plate structure in a state. The method of claim 3, wherein The insulating layer is a method of manufacturing a semiconductor device, characterized in that the ferroelectric of any one of Al ₂ O ₃ , SiN, Ta ₂ O ₅ in addition to the polymer series. delete

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