Switching device based on planar back-to-back nickel-silicon-germanium Schottky junction and preparation method thereof

Abstract

The invention discloses a switching device based on a planar back-to-back nickel-silicon-germanium Schottky junction and a preparation method thereof. The switching device is provided with an SOI substrate comprising a bottom layer silicon, a buried oxide layer and a top layer silicon, after the top layer silicon on the buried oxide layer is thinned and etched, two separated NiSi (1-x) Gex alloys are formed in the top layer silicon through annealing, the two NiSi (1-x) Gex alloys and the thinned top layer silicon form a planar back-to-back Schottky junction, and metal contact electrodes are arranged above the NiSi (1-x) Gex alloys. When voltage is applied to the metal contact electrode, barriers at the interface of the two back-to-back Schottky junctions are affected by interface states, energy bands change differently, at the moment, current is controlled by unsaturated current of reverse bias junctions, the heights of the asymmetrical barriers on the two sides are affected by silicon-germanium components, no composite charge exists in the barrier, contact resistance is small, and the barrier is not damaged. And the reaction speed is high, and the exchange phenomenon of current carriers and defects at an interface is faster, so that a high-frequency change switching device is obtained.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device structure and integrated circuit, and in particular to a switch device based on a planar back-to-back nickel-silicon-germanium Schottky junction and a preparation method thereof. Background Art

[0002] With the rapid development of information technology, modern electronic devices have increasing requirements in terms of processing speed, energy efficiency and reliability. Especially in the fields of smart phones, the Internet of Things, switching power supplies and RF power amplifiers, the demand for the response speed and energy efficiency of switching devices is becoming increasingly urgent. Traditional pn junction diodes still face many challenges in high-frequency applications, such as switching delays caused by carrier storage effects and increased forward voltage drop. Therefore, the development of new materials and device structures to improve performance has become an important research direction. Schottky diodes are widely used in electronic circuits for their low forward voltage drop and fast switching characteristics. However, traditional Schottky materials (such as metal-silicon contacts) are affected by contact resistance and poor interface work function when operating at high frequencies, resulting in reduced switching speed and increased energy loss. To address this problem, researchers have begun to explore new materials, especially those with good conductivity and adjustable band gap. Summary of the invention

[0003] The purpose of the present invention is to provide a switch device based on a planar back-to-back nickel-silicon-germanium Schottky junction and a preparation method thereof, in view of the shortcomings of existing high-frequency and high-speed devices, by adjusting the silicon-germanium composition to control the NiSi 1-x Ge x Interface energy band changes, combined with Si 1-x Ge x The advantages of low contact resistance and strong stability and high withstand voltage of planar back-to-back double Schottky junctions make it possible to use the switch device under high-frequency, high-speed and high-temperature conditions, which is a feasible solution to break through the performance of traditional RF application devices. By applying a DC bias, different barrier heights give it stronger rectification characteristics and can control its fast switching; by applying an AC signal, the defects at the interface have a high-frequency capture / release response phenomenon to carriers, which can be used as a high-frequency changing signal source to achieve a fast changing signal source.

[0004] According to the first aspect of the present specification, a switch device based on a planar back-to-back nickel-silicon-germanium Schottky junction is provided. The switch device has an SOI substrate including a bottom silicon layer, a buried oxide layer and a top silicon layer. The top silicon layer on the buried oxide layer is thinned and etched, and then annealed to form two separate NiSi layers. 1-x Ge x Alloy, two pieces of NiSi 1-x Ge xThe alloy forms a planar back-to-back Schottky junction with the thinned top silicon. 1-x Ge x A metal contact electrode is provided on the alloy.

[0005] Furthermore, the thickness of the thinned top silicon layer is 5 nanometers to 10 nanometers.

[0006] Furthermore, the NiSi 1-x Ge x The alloy is formed by etching a silicon island on the thinned top silicon surface, photolithography two independent windows on the silicon island and evaporating germanium respectively, and annealing to form Si 1-x Ge x layer, and then deposit nickel and anneal to form NiSi 1-x Ge x alloy.

[0007] Further, the Si 1-x Ge x In the layer, the range of x is 0.1-0.9.

[0008] Furthermore, the NiSi 1-x Ge x In the alloy, Ni and Si 1-x Ge x The mass ratio is 1:1.

[0009] Furthermore, a test voltage V is applied to a metal contact electrode. 1 , V 1 The range enables the switch device to work normally; a test voltage V is applied to the other metal contact electrode 2 , V 2 Set to V 1 The middle value of the range; by adjusting the silicon germanium composition, controlling the NiSi 1-x Ge x Alloy interface energy band changes;

[0010] For the positive bias condition V 1 >V 2 ,After applying a forward DC bias voltage, the Schottky barrier height decreases, the carrier concentration increases, the switching device is turned on, and the signal is transmitted;

[0011] For the reverse bias condition V 1 <V 2 , after applying the reverse DC bias voltage, the Schottky barrier height increases, the carriers are difficult to flow in the forward direction, the switching device is turned off, and the signal is interrupted.

[0012] Furthermore, for the reverse bias condition V 1 <V 2When an AC signal is applied, the carrier injection phenomenon of the Schottky junction is reduced, and the defects at the interface have a high-frequency capture / release response phenomenon to carriers, which can serve as a high-frequency changing signal source.

[0013] According to a second aspect of the present specification, a method for preparing a switching device based on a planar back-to-back nickel-silicon-germanium Schottky junction is provided, the method comprising:

[0014] (1) Preparing an SOI substrate including a bottom silicon layer, a buried oxide layer and a top silicon layer;

[0015] (2) Using thermal oxidation to consume the top silicon to form a silicon dioxide layer;

[0016] (3) Etch the silicon dioxide layer formed by oxidation cleanly, leaving behind a thinned top layer of silicon;

[0017] (4) Photolithography is performed on the thinned top silicon layer to form a silicon island;

[0018] (5) Photolithography of two independent windows on the silicon island and evaporation of germanium on each window;

[0019] (6) After evaporation, the sample is annealed to ensure that the silicon and germanium are evenly mixed to form two Si 1-x Ge x Layer, where x ranges from 0.1-0.9;

[0020] (7) Perform secondary overlay and 1-x Ge x Ni is deposited within the range of the layer, and the Ni and Si 1-x Ge x The mass ratio is 1:1;

[0021] (8) Anneal the sample to form two separate NiSi 1-x Ge x alloy;

[0022] (9) In two NiSi 1-x Ge x Metals are deposited on the alloys to prepare metal contact electrodes.

[0023] Furthermore, in step (4), the silicon island is circular in shape with a diameter of 1 μm to 2 μm; in step (5), the two windows photoetched on the silicon island are circular windows of the same size, with a diameter of 400 nm to 800 nm, and a distance between the two circular windows of 200 nm to 400 nm.

[0024] Furthermore, in step (5), the method of growing germanium is thermal evaporation, the thickness of the germanium film is 10 nanometers to 50 nanometers, the evaporation vacuum is 5×10-4Pa, the evaporation current is 600A, and the evaporation speed is 1Å / s.

[0025] The beneficial effects of the present invention are as follows: the present invention adopts a planar back-to-back nickel-silicon-germanium Schottky junction for high-speed switching. When voltage is applied to the metal contact electrode, the barrier heights on both sides are different, and the germanium component causes the contact resistance to decrease. At this time, the carrier tunneling and emission process continuously passes through the interface to the other side, and there is no charge storage effect of minority carriers, which is suitable for high-frequency and high-speed fields. In addition, if an AC signal is applied to the device, the defects at the interface will respond to signal fluctuations of different frequencies, and high-frequency changing signals can be generated, which can be used as a high-frequency signal source. The switching device provided by the present invention has the advantages of fast speed, small forward voltage drop, low contact resistance, strong thermal stability, high integration density, and suitability for high-frequency and high-speed, low-voltage and low-power circuits. It can be widely used in various current semiconductor processes and has broad application prospects in the fields of radio frequency, switching power supplies, and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram of the structure of an SOI substrate provided in an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of a device structure after thermal oxidation provided by an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of a thinned device structure provided by an embodiment of the present invention;

[0030] Figure 4 A schematic diagram of a structure in which a silicon island is etched out of the top layer of silicon according to an embodiment of the present invention;

[0031] Figure 5 A schematic diagram of the structure of evaporating germanium onto a silicon island provided in an embodiment of the present invention;

[0032] Figure 6 The uniform Si formed after thermal annealing provided by the embodiment of the present invention 1-x Ge x Structural diagram;

[0033] Figure 7A schematic diagram of the structure after sputtering nickel provided in an embodiment of the present invention;

[0034] Figure 8 The NiSi formed after thermal annealing provided in the embodiment of the present invention 1-x Ge x Structural diagram;

[0035] Fig. 9 A schematic diagram of the structure after the sputtering metal contact electrode provided in an embodiment of the present invention;

[0036] Fig.10 A top view of a switch device provided by an embodiment of the present invention;

[0037] Fig.11 A schematic diagram of device power-up and carrier movement provided by an embodiment of the present invention;

[0038] Fig.12 A schematic diagram showing the variation of the thin layer specific contact resistivity with Ge content provided by an embodiment of the present invention;

[0039] Fig.13 A schematic diagram of a Schottky junction energy band provided by an embodiment of the present invention;

[0040] In the figure, bottom silicon 12, buried oxide layer 11, top silicon 10, silicon dioxide layer 20, thinned top silicon 30, silicon island 40, first germanium film 50, second germanium film 51, first Si 1-x Ge x Layer 60, second Si 1-x Ge x layer 61, first metal nickel 70, second metal nickel 71, first NiSi 1-x Ge x Alloy 80, Second NiSi 1-x Ge x Alloy 81 , first metal contact electrode 90 , and second metal contact electrode 91 . DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0042] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0043] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0044] The present invention provides a switch device based on a planar back-to-back nickel-silicon-germanium Schottky junction. The switch device has a SOI (Silicon-On-Insulator) substrate including a bottom silicon layer, a buried oxide layer and a top silicon layer. The top silicon layer on the buried oxide layer is thinned and etched, and the inside is annealed to form two separated NiSi 1-x Ge x Alloy, two pieces of NiSi 1-x Ge x The alloy forms a planar back-to-back Schottky junction with the thinned top silicon, NiSi 1-x Ge x A metal contact electrode is provided on the alloy.

[0045] It should be noted that the preparation method of the SOI substrate includes but is not limited to oxygen injection treatment, hot compression bonding and smart-cut technology, the etching method includes but is not limited to plasma dry etching and wet etching, the annealing method includes but is not limited to rapid thermal annealing, tube furnace annealing, microwave annealing, laser annealing, the metal contact electrode material includes but is not limited to nickel, tungsten, copper, and the buried oxide layer material includes but is not limited to silicon dioxide.

[0046] In the present invention, a thinned SOI structure is used. Since the top silicon thickness is very thin, the NiSi 1-x Ge x The interface between the alloy and the top silicon will form a fully depleted Schottky junction. There is no charge storage effect inside the Schottky junction, which has a faster reaction speed. 1-x Ge x As the Ge content of the alloy increases, NiSi 1-x Ge x The interface contact resistivity between the alloy and the top silicon will gradually decrease, and the carrier movement at the interface will be faster, further improving the speed of the switching device and obtaining a high-speed switching device. In addition, the barrier height of the Schottky junction is affected by the interface state, NiSi 1-x Ge x The energy band will change differently due to factors such as alloy work function. At this time, the carrier tunneling and emission in the two back-to-back Schottky junctions are controlled by the unsaturated current of the reverse biased junction. The asymmetric barrier height on both sides is affected by the silicon germanium component. The increase in germanium concentration will cause the work function of the alloy side to decrease. The present invention adopts a planar back-to-back NiSi 1-x Ge xThe Schottky junction has the advantages of fast switching speed, low reverse leakage, low power consumption, high efficiency, strong thermal stability, and is suitable for high-frequency and high-speed circuits.

[0047] In the following embodiments, a method for preparing a switch device based on a planar back-to-back nickel-silicon-germanium Schottky junction is described in detail:

[0048] (1) If Figure 1 As shown, an SOI substrate including a bottom silicon 12, a buried oxide layer 11 and a top silicon 10 is prepared, the buried oxide layer 11 is made of silicon dioxide, and the doping type of the bottom silicon 12 is n-type; specifically, the preparation method of the SOI substrate includes but is not limited to oxygen injection treatment, hot pressing bonding and smart-cut technology, the original thickness of the top silicon 10 is 50 nanometers to 150 nanometers, and the thickness of the buried oxide layer 11 is 500 nanometers to 1 micrometer;

[0049] (2) If Figure 2 As shown, the top silicon 10 is consumed by thermal oxidation to form a silicon dioxide layer 20; specifically, the oxidation method includes but is not limited to tubular furnace thermal oxidation, and the thermal oxidation rate at 1000° C. is 2.8 nm / 1 min;

[0050] (3) If Figure 3 As shown, the silicon dioxide layer 20 formed by oxidation is etched cleanly, leaving a thinned top silicon layer 30; specifically, the thickness of the thinned top silicon layer 30 is 5 nanometers to 10 nanometers, and the etching method includes but is not limited to BOE wet etching or plasma dry etching;

[0051] (4) If Figure 4 As shown, a window is opened by photolithography on the thinned top silicon 30, and unnecessary silicon is etched away to form an independent silicon island 40; specifically, in order to make the spin coating and photolithography more uniform, the silicon island 40 is circular in shape with a diameter between 1 micron and 2 microns, and the photolithography method includes but is not limited to ultraviolet lithography, laser direct writing and electron beam lithography, and the etching method includes but is not limited to TMAH wet etching or plasma etching; when preparing the switching device array, the distance between the silicon islands is between 300 nanometers and 500 nanometers;

[0052] (5) If Figure 5 As shown, two circular windows of the same size are photolithographically formed on the silicon island 40, and a first germanium film 50 and a second germanium film 51 are evaporated respectively; specifically, the diameter of the circular window is between 400 nanometers and 800 nanometers, the distance between the two circles is between 200 nanometers and 400 nanometers, the photolithography method includes but is not limited to ultraviolet lithography, laser direct writing and electron beam lithography, the method of growing germanium includes but is not limited to thermal evaporation, the thickness of the germanium film is 10 nanometers to 50 nanometers, the evaporation vacuum is 5×10-4Pa, the evaporation current is 600A, and the evaporation speed is 1Å / s;

[0053] (6) If Figure 6 As shown, after the evaporation is completed, the sample is placed in an acetone solution for a lift-off process and blown dry with nitrogen. The sample is then placed in a 700°C annealing nitrogen atmosphere for 10 minutes to ensure that the silicon and germanium are evenly mixed to form the first Si 1-x Ge x Layer 60 and the second Si 1-x Ge x Layer 61; specifically, the annealing method includes but is not limited to rapid thermal annealing, tube furnace annealing, microwave annealing, laser annealing, and the range of x is 0.1-0.9;

[0054] (7) Figure 7 As shown, a secondary overlay is performed, and a first metal nickel 70 and a second metal nickel 71 are deposited respectively. The thickness of the metal nickel is in the range of tens to hundreds of nanometers, and the mass ratio of the two is controlled to be Ni:Si. 1-x Ge x =1:1; Specifically, the photolithography method includes but is not limited to ultraviolet lithography, laser direct writing and electron beam lithography, and the method for depositing metal nickel includes but is not limited to thermal evaporation or magnetron sputtering;

[0055] (8) Figure 8 As shown, the sample was placed in a nitrogen atmosphere at 450°C for 10 minutes to metallize the surface and form a uniform first NiSi 1-x Ge x Alloy 80 and Second NiSi 1-x Ge x Alloy 81, using HCl aqueous solution to etch away the unreacted metal nickel on the surface; specifically, the annealing method includes but is not limited to rapid thermal annealing, tube furnace annealing, microwave annealing, and laser annealing;

[0056] (9) Fig. 9 As shown in the first NiSi 1-x Ge x Alloy 80 and Second NiSi 1-x Ge x Depositing metals on the alloy 81 respectively to prepare a first metal contact electrode 90 and a second metal contact electrode 91, and forming a switch device based on a planar back-to-back nickel-silicon-germanium Schottky junction; specifically, the method of depositing the metal includes but is not limited to thermal evaporation or magnetron sputtering, and the metal contact electrode material includes but is not limited to nickel, tungsten, and copper;

[0057] (10) The top view structure of the prepared switch device is as follows: Fig.10 As shown, there are only two symmetrical NiSi 1-x Ge xSchottky junction, by controlling the value of the Ge content x (x is between 0.1 and 0.9) evaporated in the left and right junctions, affects the curvature of the barrier height, forming two asymmetric back-to-back nickel-silicon-germanium Schottky junctions. Fig.12 As shown in Figure 2, with the increase of Ge content, the contact resistivity of the interface thin layer gradually decreases, which is beneficial to the response speed of the switching device. In addition, NiSi 1-x Ge x The energy band diagram formed by the contact between the alloy and the top silicon is shown in Fig.13 As shown, after increasing the Ge content, the work function on the alloy side decreases. When the work function of the semiconductor remains unchanged, its band bending can be affected by controlling the work function on the alloy side. Fig.13 In, E F is the Fermi level on the alloy side, E c is the conduction band bottom of the top silicon side, E v is the top of the valence band on the top silicon side.

[0058] In the following embodiments, the method for using a switch device based on a planar back-to-back nickel-silicon-germanium Schottky junction is described in detail:

[0059] like Fig.11 As shown, a test voltage V is applied to the first metal contact electrode 90. 1 , test voltage V 1 The range enables the switch device to work normally. In this embodiment, V 1 The range is -1.8V~1.8V; a test voltage V is applied to the second metal contact electrode 91 2 , for the convenience of testing, set V 2 is a fixed value, and its value is V 1 mid-range value, thus V 1 In this embodiment, V 2 Take 0V; by adjusting the silicon germanium composition, control NiSi 1-x Ge x The alloy interface energy band changes, such as Fig.13 As shown in the figure, due to the difference in the barrier heights of the left and right Schottky junctions, the energy required for carriers to cross the barrier is different. Different barrier heights give the switch device stronger rectification characteristics. Forward bias condition: Apply a forward DC bias voltage (i.e. V 1 >V 2 ), the Schottky barrier height decreases, the carriers at the Schottky junction interface move toward the positive voltage direction, the carrier concentration increases, the switch device is turned on, and the signal is transmitted. Reverse bias condition: Apply a reverse DC bias voltage (i.e. V 1 <V 2), the Schottky barrier height increases, the depletion layer width at the Schottky junction interface becomes larger, carriers are difficult to flow forward, the switch device is turned off, and the signal is interrupted. Carriers respond quickly in this planar structure, there is no charge storage effect, and nickel silicon germanium provides good temperature stability. The low interface contact resistance helps the high-speed response of the switch device and can achieve a higher switching frequency.

[0060] In addition, if an AC signal is applied under reverse bias conditions, the carrier injection phenomenon of the Schottky junction is reduced, e.g. Fig.13 As shown, the defects at the interface have a high-frequency capture / release response phenomenon to carriers, which can be used as a high-frequency changing signal source to realize the occurrence of a rapidly changing signal source.

[0061] The above description is merely a preferred embodiment of one or more embodiments of the present specification and is not intended to limit one or more embodiments of the present specification. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present specification shall be included in the scope of protection of one or more embodiments of the present specification.

Claims

1. A switching device based on a planar back-to-back nickel-silicon-germanium Schottky junction, characterized in that: The switch device has an SOI substrate including a bottom silicon layer, a buried oxide layer and a top silicon layer. The top silicon layer on the buried oxide layer is thinned and etched, and then annealed to form two separate NiSi 1-x Ge x Alloy, two pieces of NiSi 1-x Ge x The alloy forms a planar back-to-back Schottky junction with the thinned top silicon. 1-x Ge x A metal contact electrode is provided on top of the alloy.

2. The switch device based on planar back-to-back nickel-silicon-germanium Schottky junction according to claim 1, characterized in that: The thickness of the thinned top silicon layer is 5 to 10 nanometers.

3. The switch device based on planar back-to-back nickel-silicon-germanium Schottky junction according to claim 1, characterized in that: The NiSi 1-x Ge x The alloy is formed by etching a silicon island on the thinned top silicon surface, photolithography two independent windows on the silicon island and evaporating germanium respectively, and annealing to form Si 1-x Ge x layer, and then deposit nickel and anneal to form NiSi 1-x Ge x alloy.

4. The switch device based on planar back-to-back nickel-silicon-germanium Schottky junction according to claim 3, characterized in that: The Si 1-x Ge x In the layer, the range of x is 0.1-0.

9.

5. The switch device based on planar back-to-back nickel-silicon-germanium Schottky junction according to claim 3, characterized in that: The NiSi 1-x Ge x In the alloy, Ni and Si 1-x Ge x The mass ratio is 1:

1.

6. The switch device based on planar back-to-back nickel-silicon-germanium Schottky junction according to claim 1, characterized in that: A test voltage V1 is applied to a metal contact electrode, and the range of V1 enables the switch device to work normally; a test voltage V2 is applied to another metal contact electrode, and V2 is set to the middle value of the V1 range; by adjusting the silicon germanium composition, the NiSi 1- x Ge x Alloy interface energy band changes; For the forward bias condition V1>V2, after applying the forward DC bias voltage, the Schottky barrier height decreases, the carrier concentration increases, the switching device turns on, and the signal is transmitted; For the reverse bias condition V1<V2, after applying the reverse DC bias voltage, the Schottky barrier height increases, the carriers are difficult to flow in the forward direction, the switching device is turned off, and the signal is interrupted.

7. The switch device based on planar back-to-back nickel-silicon-germanium Schottky junction according to claim 6, characterized in that: For the reverse bias condition V1<V2, when an AC signal is applied, the carrier injection phenomenon of the Schottky junction is reduced, and the defects at the interface have a high-frequency capture / release response phenomenon to the carriers, which can serve as a high-frequency changing signal source.

8. A method for preparing a switch device based on a planar back-to-back nickel-silicon-germanium Schottky junction, characterized in that: include: (1) Preparing an SOI substrate including a bottom silicon layer, a buried oxide layer and a top silicon layer; (2) Using thermal oxidation to consume the top silicon to form a silicon dioxide layer; (3) Etch the silicon dioxide layer formed by oxidation cleanly, leaving behind a thinned top layer of silicon; (4) Photolithography is performed on the thinned top silicon layer to form a silicon island; (5) Photolithography of two independent windows on the silicon island and evaporation of germanium on each window; (6) After evaporation, the sample is annealed to ensure that the silicon and germanium are evenly mixed to form two Si 1-x Ge x Layer, where x ranges from 0.1 to 0.9; (7) Perform secondary overlay and 1-x Ge x Ni is deposited within the range of the layer, and the Ni and Si 1-x Ge x The mass ratio is 1:1; (8) Anneal the sample to form two separate NiSi 1-x Ge x alloy; (9) In two NiSi 1-x Ge x Metals are deposited on the alloys to prepare metal contact electrodes.

9. The preparation method according to claim 8, characterized in that: In step (4), the silicon island is circular in shape and has a diameter of 1 μm to 2 μm. In step (5), the two windows photoetched on the silicon island are circular windows of the same size, with a diameter of 400 nm to 800 nm, and a distance between the two circular windows of 200 nm to 400 nm.

10. The preparation method according to claim 8, characterized in that: In step (5), the method for growing germanium is thermal evaporation, the thickness of the germanium film is 10 nanometers to 50 nanometers, the evaporation vacuum is 5×10-4Pa, the evaporation current is 600A, and the evaporation speed is 1Å / s.

Images