Silicon carbide-based high resistance resistor and method of manufacturing the same

Abstract

The application discloses a silicon carbide-based high-resistance resistor, which comprises a semi-insulating 4H-SiC type silicon carbide substrate, symmetric aluminum oxide insulation layers with an atomic thickness are arranged on a silicon surface and a carbon surface of the silicon carbide substrate, the thickness of the aluminum oxide insulation layer is 0.2nm-2nm, and conductive metal electrodes are evaporated on two sides of the aluminum oxide insulation layer, and the thickness of the metal electrode is 100nm-500nm. The silicon carbide-based high-resistance resistor with the above structure is used to make an ohmic contact electrode on the semi-insulating silicon carbide substrate, so that a resistor with a resistance value of 100TΩ or more is obtained, and the needs of the precision measurement industry are met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor resistance elements, and particularly relates to a silicon carbide-based high-resistance resistor and a preparation method thereof. BACKGROUND

[0002] A resistor is a device made by using the hindering effect of current flowing through a substance, which can limit the current passing through in a circuit. The resistor is a two-terminal electronic element, which is the most important type of element in an electronic circuit and can be used as a shunt and a voltage divider in a circuit, and can also be used as a circuit matching load. At present, there are various types of resistors on the market, which can be divided into fixed resistors, adjustable resistors, and sensitive resistors according to the resistance value characteristics. The resistance value span of the resistor is very large, which can be as low as 1 mΩ or even lower, and can be as high as 100 TΩ or even higher.

[0003] High-resistance resistors are widely used, especially in micro-current detection and generation. The process of human exploration of the micro-current world has entered the era of single electron from pA to fA to aA. High-resistance resistors are essential elements for successful micro-current detection, and the insulation leakage resistance of the micro-current detection circuit must be several orders of magnitude higher than the measured circuit's Davenny equivalent resistance. In addition, the generation of precise weak current also cannot do without high-resistance resistors. When the tested current is more precise, or when a weaker current is to be generated, a resistor with a higher resistance value must be used. Obviously, the test precision and generation precision of the current directly depend on the resistance value of the resistor. For example, the measurement of 1 pA current requires the use of a resistor with a resistance value of 100 GΩ, and accordingly, the measurement of 1 fA current requires the use of a resistor with a resistance value of 100 TΩ, and the measurement of aA and lower current requires the use of a resistor with a resistance value of 1 PΩ or above.

[0004] High-resistance resistors are usually made of materials with relatively high resistivity, such as metal oxide films and organic materials. Among them, Teflon, an organic material, is the most common resistor material for measuring currents above 10 fA. Its main disadvantage is that when deformed, internal charges will appear, causing false voltage and current. The bulk resistivity of polystyrene and polyethylene, which are organic materials, is close to that of Teflon, but the resistance value of polystyrene will decrease under high humidity, and polyethylene will melt at high temperatures. Sapphire is the best insulating material and is often used in the application of 10 -18 A to 10 -15 A range current, the main limiting factors of which are high price and complex manufacturing process.

[0005] Silicon carbide is a wide band gap semiconductor material, which has good stability in extreme environments such as high temperature, high pressure, high frequency and strong radiation. Silicon carbide substrate has two types, one is conductive type, and the other is semi-insulating type. Among them, the semi-insulating silicon carbide has extremely low intrinsic carrier concentration, and based on this, a high resistance resistor can be developed. As a realization scheme of high resistance element, the silicon carbide based high resistance resistor is compatible with the manufacturing process of silicon carbide transistor, and is expected to realize silicon carbide integrated circuit suitable for extreme environment, and promote the significant innovation of precision measurement technology in extreme environment. If a metal electrode is directly made on the silicon carbide substrate, a Schottky contact, rather than an ohmic contact, will be obtained. The silicon carbide two-terminal element with Schottky contact on the top and bottom cannot be used as a high resistance resistor. Therefore, it is the key to make a metal electrode with ohmic contact characteristics on the semi-insulating silicon carbide substrate to obtain a high resistance resistor. SUMMARY

[0006] The purpose of the present application is to provide a silicon carbide based high resistance resistor and a preparation method thereof, which makes an ohmic contact electrode on a semi-insulating silicon carbide substrate to obtain a resistor with a resistance of 100TΩ or more, meeting the needs of the precision measurement industry.

[0007] To achieve the above-mentioned purpose, the present application provides a silicon carbide based high resistance resistor, comprising a semi-insulating 4H-SiC type silicon carbide substrate, symmetric aluminum oxide insulating layers with an atomic thickness are arranged on the silicon surface and the carbon surface of the silicon carbide substrate, the thickness of the aluminum oxide insulating layer is 0.2nm-2nm, and conductive metal electrodes are deposited on both sides of the aluminum oxide insulating layer, the thickness of the metal electrode is 100nm-500nm. Preferably, the metal electrode is selected from one or more of gold, silver, copper or aluminum.

[0008] A preparation method of a silicon carbide based high resistance resistor, comprising the following steps:

[0009] Step one: select a semi-insulating 4H-SiC type silicon carbide substrate with a certain thickness and resistivity, and calibrate the carbon surface and the silicon surface of the substrate by atomic force microscope;

[0010] Step two: clean and dry the silicon carbide substrate, repeatedly rub the carbon surface and the silicon surface of the silicon carbide substrate with disposable gloves until a uniform water film is formed on the carbon surface and the silicon surface after washing with deionized water; then place the silicon carbide substrate in an ultrasonic cleaner, and ultrasonically clean it with deionized water, acetone and isopropyl alcohol for 15 minutes respectively, and then reserve the cleaned silicon carbide substrate;

[0011] Step three: use atomic layer deposition technology or magnetron sputtering technology to deposit an aluminum oxide insulating layer with a thickness of 0.2nm-2nm on the carbon surface and the silicon surface of the silicon carbide substrate respectively;

[0012] Step four: paste the electrode mask on both sides of the deposited alumina insulating layer, and determine the covering area of the electrode mask according to the resistance value of the resistor to be made;

[0013] Step five: put the silicon carbide with the pasted mask into the cavity of the magnetron sputtering instrument, and use the magnetron sputtering method to sputter a layer of 100-500 nm thick metal electrode on the carbon surface and the silicon surface of the deposited silicon carbide, and the material of the metal electrode is one or more of gold, silver, copper and aluminum;

[0014] Step six: take out the sample from the plating chamber, remove the mask, obtain a silicon carbide-based high-resistance resistor, and test the volt-ampere characteristics of the prepared resistor using a semiconductor analyzer.

[0015] Compared with the prior art, the present application has the following beneficial effects:

[0016] Silicon carbide is a highly stable semiconductor material. Compared with traditional high-resistance materials such as metal oxide film and organic material, silicon carbide material can withstand high temperature, high pressure, high frequency and strong radiation in extreme environments. The silicon carbide-based high-resistance resistor is suitable for precise testing in extreme environments.

[0017] Before making a metal electrode on the silicon carbide substrate, a layer of atomic-level thick alumina interface modification layer is introduced, which is beneficial to obtain a volt-ampere characteristic curve with ohmic contact characteristics. By adjusting the effective area of the electrode, the resistance value is directly adjusted. The high-resistance resistor obtained by this method is conducive to direct monolithic integration with silicon carbide transistors, and promotes the development of silicon carbide integrated circuit technology.

[0018] The technical solutions of the present application will be further described in detail below through the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a structure diagram of an embodiment of a silicon carbide-based high-resistance resistor of the present application;

[0020] Figure 2 is a current-voltage curve of a silicon carbide device before depositing alumina in the present application;

[0021] Figure 3 is a volt-ampere characteristic curve of a silicon carbide-based high-resistance resistor with an electrode area of 500x500μm 2 after depositing alumina in the present application, and the resistance value is about 400TΩ. DETAILED DESCRIPTION

[0022] The technical solutions of the present application will be further described in detail below through the drawings and examples.

[0023] EMBODIMENT

[0024] As shown in the figure, a silicon carbide-based high resistance resistor includes a semi-insulating 4H-SiC silicon carbide substrate, symmetric aluminum oxide insulation layers with an atomic thickness are arranged on the silicon surface and the carbon surface of the silicon carbide substrate, the thickness of the aluminum oxide insulation layer is 0.2nm-2nm, and the aluminum oxide insulation modification layer is used to adjust the contact characteristics of the metal electrode and the silicon carbide substrate, so that the metal electrode and the silicon carbide form a good ohmic contact.

[0025] Conductive metal electrodes are evaporated on both sides of the aluminum oxide insulation layer, and the thickness of the metal electrode is 100nm-500nm. The metal electrode is selected from one or more of gold, silver, copper or aluminum.

[0026] A preparation method of a silicon carbide-based high resistance resistor, the steps are as follows:

[0027] Step one: select a substrate of 500μm thick semi-insulating 4H-SiC silicon carbide substrate, the bulk resistivity is above 10 12 Ω·cm, and the carbon surface and the silicon surface of the substrate are calibrated by atomic force microscope;

[0028] Step two: clean and dry the silicon carbide substrate, repeatedly rub the carbon surface and the silicon surface of the silicon carbide substrate with disposable gloves until a uniform water film is formed on the carbon surface and the silicon surface after washing with deionized water; place the silicon carbide substrate in an ultrasonic cleaner, and ultrasonically clean it with deionized water, acetone and isopropanol for 15min, and then reserve the cleaned silicon carbide substrate;

[0029] Step three: use atomic layer deposition technology or magnetron sputtering technology to deposit 0.2nm-2nm aluminum oxide insulation layer on the carbon surface and the silicon surface of the silicon carbide substrate, and when using atomic layer deposition technology, the thickness of the aluminum oxide insulation layer is controlled by controlling the number of cycles;

[0030] Step four: paste electrode mask on both sides of the deposited aluminum oxide insulation layer, and determine the covering area of the electrode mask according to the resistance value of the resistor to be made, and the effective area of the electrode determines the cross-sectional area of the resistor, the larger the area, the smaller the resistance value of the resistor to be made, and the cross-sectional area is from μm 2 to mm 2 ;

[0031] Step five: place the silicon carbide with the pasted mask into the cavity of the magnetron sputtering instrument, and use the magnetron sputtering method to sputter a layer of 100nm-500nm thick metal electrode on the carbon surface and the silicon surface of the deposited aluminum carbide, and the material of the metal electrode is one or more of gold, silver, copper and aluminum;

[0032] Step six: taking out the sample from the coating chamber, removing the mask, obtaining a silicon carbide-based high resistance resistor, and using the B1500 semiconductor analyzer of Keysight to test the prepared resistor for volt-ampere characteristics. Figure 3 As can be seen, the volt-ampere characteristic curve of the high resistance ohmic contact characteristics is obtained.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] Silicon carbide is a highly stable semiconductor material. Compared with traditional high resistance materials such as metal oxide films and organic materials, silicon carbide material can withstand extreme environments such as high temperature, high pressure, high frequency and strong radiation. The silicon carbide-based high resistance resistor is suitable for precise testing in extreme environments.

[0035] Before making a metal electrode on the silicon carbide substrate, a layer of atomic-level thick aluminum oxide interface modification layer is introduced, which is beneficial to obtain a volt-ampere characteristic curve with ohmic contact characteristics. By adjusting the effective area of the electrode, the resistance value is directly adjusted. The high resistance resistor obtained by this method is conducive to direct monolithic integration with silicon carbide transistors, and promotes the development of silicon carbide integrated circuit technology.

[0036] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A silicon carbide-based high-resistance resistor, characterized in that: The substrate includes a semi-insulating 4H-SiC type silicon carbide substrate, wherein a symmetrical alumina insulating layer with atomic-level thickness is disposed on the silicon and carbon surfaces of the silicon carbide substrate, the thickness of the alumina insulating layer being 0.2nm-2nm, and conductive metal electrodes are vapor-deposited on both sides of the alumina insulating layer, the thickness of the metal electrodes being 100nm-500nm. The metal electrode is selected from one or more of gold, silver, copper or aluminum.

2. The method for preparing a silicon carbide-based high-resistance resistor according to claim 1, characterized in that: The steps are as follows: Step 1: Select a semi-insulating 4H-SiC type silicon carbide substrate with a certain thickness and resistivity, and calibrate the carbon and silicon surfaces of the substrate using an atomic force microscope. Step 2: Clean and dry the silicon carbide substrate. Wearing disposable gloves, repeatedly and gently rub the front and back sides of the silicon carbide substrate until a uniform water film is formed when rinsing the front and back sides with deionized water. Then, place the cleaned silicon carbide substrate in an ultrasonic cleaner and ultrasonically clean it for 15 minutes each with deionized water, acetone, and isopropanol. Set the cleaned silicon carbide substrate aside for later use. Step 3: Deposit 0.2nm-2nm aluminum oxide insulating layers on the carbon and silicon surfaces of the silicon carbide substrate using atomic layer deposition or magnetron sputtering techniques, respectively; Step 4: Attach electrode masks to both sides of the deposited alumina insulating layer. The coverage area of ​​the electrode masks is determined according to the resistance value of the resistor to be manufactured. Step 5: Place the silicon carbide with the mask attached into the magnetron sputtering instrument cavity, and use magnetron sputtering to sputter a 100nm-500nm thick metal electrode on the silicon and carbon surfaces of the silicon carbide after alumina deposition. The metal electrode material is one or more of gold, silver, copper, and aluminum. Step 6: Remove the sample from the coating chamber, remove the mask, and obtain a silicon carbide-based high-resistance resistor. Then, use a semiconductor analyzer to test the current-voltage characteristics of the prepared resistor.

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