阅读说明：本技术 一种碳化硅肖特基二极管的势垒调节方法 (Potential barrier adjusting method of silicon carbide Schottky diode ) 是由 王颖 时定坤 曹菲 于成浩 包梦恬 于 2019-10-09 设计创作，主要内容包括：本发明公开了一种碳化硅肖特基二极管的势垒调节方法,在Ti/4H-SiC的肖特基二极管中插入一层Al<Sub>2</Sub>O<Sub>3</Sub>薄膜,从而改善界面不均匀性以及调节势垒高度。本发明通过在溅射金属Ti之前,原子层沉积生长一层不同厚度的Al<Sub>2</Sub>O<Sub>3</Sub>薄膜层,通过后续Al<Sub>2</Sub>O<Sub>3</Sub>与碳化硅发生反应形成偶极子层,引起界面两侧的电势差,从而降低肖特基势垒高度,减小器件功耗,Al<Sub>2</Sub>O<Sub>3</Sub>薄膜也与碳化硅会产生正势垒,从而也可以减小肖特基二极管的反向泄露电流；通过调整不同的Al<Sub>2</Sub>O<Sub>3</Sub>薄膜层厚度,产生不同的势垒高度,从而实现势垒高度的可调性。(The invention discloses a potential barrier adjusting method of a silicon carbide Schottky diode, wherein a layer of Al is inserted into a Ti/4H-SiC Schottky diode 2 O 3 Thin film, thereby improving interface non-uniformity and adjusting barrier height. The invention grows a layer of Al with different thicknesses by atomic layer deposition before sputtering metal Ti 2 O 3 Thin film layer, by subsequent Al 2 O 3 Reacts with silicon carbide to form dipole layers to cause potential difference at two sides of an interface, thereby reducing the height of a Schottky barrier and the power consumption of a device, and Al 2 O 3 The film and the silicon carbide can generate a positive potential barrier, so that the reverse leakage current of the Schottky diode can be reduced; by adjusting different Al 2 O 3 Thickness of thin film layer to generate different barrier heightsThe adjustability of the barrier height.)

1. A potential barrier adjusting method of a silicon carbide Schottky diode is characterized in that: sputtering and depositing a Schottky metal layer (5) with low barrier and low forward voltage drop on the silicon carbide, and inserting Al between the Schottky metal layer (5) and the silicon carbide₂O₃A thin film (3), finally an Al layer (6) is sputtered on the Schottky metal layer (5), and Al is passed through₂O₃The thin film (3) reacts with the silicon carbide to form a dipole layer and a positive barrier.

2. The method of adjusting a barrier of a silicon carbide schottky diode according to claim 1, wherein: the Al is₂O₃The thickness of the film (3) is 0.8nm or 1.2nm or 2 nm.

3. The method of adjusting a barrier of a silicon carbide schottky diode according to claim 1, wherein: depositing the Al by atomic layer deposition₂O₃A film (3).

4. The method of adjusting a barrier of a silicon carbide schottky diode according to claim 3, wherein: the reactor chamber was maintained at 200 ℃ during film deposition using 97% trimethylaluminum as precursor and deionized water as oxidant and using thermal growth method, the precursors and water were introduced into the reactor chamber by Ar flow at a deposition rate of 0.1 nm/cycle, and phosphoric acid was used to etch away Al other than the schottky metal layer (5)₂O₃Film (3) leaving Al on the Schottky metal window₂O₃A film (3).

Technical Field

The invention belongs to the technical field of microelectronic devices, and relates to a method for adjusting potential barrier of a Schottky diode made of a third generation wide band gap semiconductor material 4H-SiC.

Background

Compared with a common P-N junction diode, the Schottky diode (SBD) has the advantages of reduced forward conduction voltage, short reverse recovery time, strong surge current resistance and the like, and is used in a high-speed and high-efficiency rectifying circuit, a microwave circuit and a high-speed integrated circuit. The Schottky diode is a metal semiconductor device which is made by using metal as a positive electrode, wherein the metal is selected from Au, Ag, A1, Pt, Mo, Ni and Ti, an N-type semiconductor as a negative electrode, and a semiconductor as SiC, and a barrier with rectification characteristic is formed on the contact surface of the metal and the semiconductor.

Nowadays, semiconductor devices are continuously advancing towards high energy and low price, and the process steps are especially worthy of attention of researchers as important factors for limiting the production cost of the devices. The simple and easy operation of the process steps and the convenient and easily-obtained process consumables are all important methods for optimizing the device process. SiC-based SBDs have many advantages such as high breakdown voltage (> 600V) and low switching loss to avoid unnecessary power consumption due to parasitic resistance, and thus semiconductor devices require low Schottky Barrier Height (SBH) and low contact resistivity at metal/semiconductor contacts.

Ti has low Schottky Barrier Height (SBH) and low forward voltage drop, but Ti/SiC SBDs often have some undesirable I-V characteristics due to the influence of incomplete SBH caused by interface state, pollution caused by residual processing and non-uniformity, and the conventional rescue work generally adopts heat treatment for improving the non-uniformity of the interface and obtaining lower Schottky barrier height, but the heat treatment method cannot avoid silicification and thermal budget, so that the power consumption and the operation cost of the device are high.

Disclosure of Invention

The invention aims to provide a potential barrier adjusting method of a silicon carbide Schottky diode, so that interface nonuniformity is improved, and the height of the potential barrier is adjusted.

In order to achieve the purpose, the invention provides the following scheme: the invention provides a carbonA method for regulating potential barrier of silicon carbide Schottky diode includes sputtering and depositing Schottky metal layer with low potential barrier and low forward voltage drop on silicon carbide, and inserting Al between Schottky metal layer and silicon carbide₂O₃A film, finally sputtering an Al layer on the Schottky metal layer, passing through Al₂O₃The film reacts with the silicon carbide to form a dipole layer, a positive barrier.

Preferably, the Al₂O₃The film thickness is 0.8nm or 1.2nm or 2 nm.

Preferably, the Al is deposited by atomic layer deposition₂O₃A film.

Preferably, the reactor chamber is maintained at 200 ℃ during film deposition using 97% trimethylaluminum as a precursor, deionized water as an oxidant, and the precursors and water are introduced into the reactor chamber through an Ar flow in the following order using a thermal growth method, with a deposition rate of 0.1 nm/cycle, and phosphoric acid is used to etch away Al other than the schottky metal layer₂O₃Film, leaving Al on the Schottky metal window₂O₃A film.

The invention discloses the following technical effects: the invention provides an adjusting method for changing Schottky barrier height, namely, Al is inserted on the basis of Ti-SBD₂O₃And the film is used for adjusting the height of the potential barrier, so that the forward voltage drop and the device power consumption are reduced, and the Schottky reverse leakage current is reduced. By adjusting different Al₂O₃The thickness of the thin film layer generates different barrier heights, so that the adjustability of the barrier heights is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic view of a Schottky diode structure according to the present invention;

FIG. 2 shows no Al insertion₂O₃Film and insertion of Al of different thicknesses₂O₃A film forward voltage I-V diagram;

FIG. 3 shows no Al insertion₂O₃Film and insertion of Al of different thicknesses₂O₃The change graph of the barrier height of the film along with the test temperature;

wherein the ohmic contact layer 1, the epitaxial layer 2, Al₂O₃ Film 3, SiO₂Passivation layer 4, schottky metal layer 5, Al layer 6.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

Referring to fig. 1-3, a method of making a silicon carbide schottky contact includes the steps of:

step 1, standard RCA cleaning is carried out on the 4H-SiC substrate and the epitaxial layer 2: firstly, ultrasonically treating acetone and Isopropanol (IPA) twice for 5min respectively; the second step using NH₄OH:H₂O₂:H₂Heating in 70-80 deg.c water bath for 10 min; the third step uses HCl H₂O₂:H₂Heating in 70-80 deg.c water bath for 10min to eliminate metal oxide, hydroxide, active metal and other impurities from the surface of 4H-SiC substrate; the fourth step uses HF: H₂Soaking for 30 seconds in a ratio of 1:50 to remove natural oxides on the surface of the substrate; and finally, washing the product by using deionized water, and finally drying the product by using nitrogen.

Step 2, SiO₂Growing an oxide layer, namely putting the cleaned SiC substrate into a heating furnace immediately and placing the SiC substrate in 115 degrees centigradeDry oxygen oxidation growth of 50nm SiO on the epitaxial layer 2 at 0 deg.C in an oxygen atmosphere₂The oxide layer was then annealed at 1100 ℃ for 1 hour in a nitrogen atmosphere. Then growing the film to a thickness of 250nmSiO by a PECVD method₂Passivation layer 4, eventually SiO thereof₂The thickness of the passivation layer 4 is 300nm, and after the passivation layer is grown, the passivation layer is densified in an oxidation furnace for 1 hour.

In which SiO is grown₂The process conditions of the passivation layer 4 are as follows: the growth temperature is 300 ℃, and the growth time is 300 seconds; the reaction gas in the growth process is SiH₄And C₃H₈In which is SiH₄And C₃H₈The ratio of (A) to (B) is 5: 1; the protective gas is hydrogen; the pressure in the reaction chamber was 500 mT.

Step 3, preparing ohmic contact on the back and annealing: the back oxide was cleaned with BOE solution, Ni metal was sputtered to a thickness of 150nm on the back of the cleaned SiC substrate by sputtering, and the device was then subjected to rapid thermal annealing (RTP) in an annealing furnace in a nitrogen atmosphere at 1000 ℃ for 2 minutes to form the ohmic contact layer 1.

Step 4, photoetching the middle passivation layer and etching the front SiO₂Layer (b): firstly, coating photoresist with the thickness of 0.2um on the surface of a passivation layer, developing, then flushing in ultrapure water for 2 minutes, and flushing in a nitrogen atmosphere; secondly, the photoresist is used as a barrier layer, and SiO in the middle is etched by a reactive ion etching method₂And a passivation layer 4 is not over-etched, about 10nm is left, and then the sample is soaked in BOE solution to etch off the residual SiO about 10nm in the Schottky contact region₂Thereby forming a schottky window. And finally, after etching, using stripping liquid to carry out organic cleaning on the device, and removing the residual photoresist.

The process conditions of Reactive Ion Etching (RIE) are as follows: the reaction gas being CF₄And O₂(ii) a The pressure in the reaction chamber is 5 mT; the power of the reaction cavity is 50W;

step 5, Al₂O₃Atomic layer deposition and etching: deposition of Al by Atomic Layer Deposition (ALD)₂O₃A film 3. Use 97% of threeMethylaluminium (TMA) was used as precursor and deionized water was used as oxidant. The reactor chamber was maintained at 200 ℃ during film deposition and a thermal growth method was used. The precursor and water were introduced into the reactor chamber by Ar flow in the following order: 150ms pulse (TMA), 500ms (purge), 150ms pulse (H2O) and 750ms (purge). The deposition rate was estimated to be within 0.1 nm/cycle. Al thus grown₂O₃The thicknesses were 0.8, 1.2 and 2nm, respectively. Etching off SiO at two sides outside the window of the Schottky metal by using phosphoric acid₂Al on the layer₂O₃Film 3, leaving Al on the Schottky Metal Window₂O₃A film 3.

Step 6, preparing a Schottky contact and field plate terminal: in SiO₂Passivation layer 4 and schottky window (Al)₂O₃Coating photoresist on the surface of the film 3) and developing, forming a pattern region of a field plate terminal on the surface of a passivation layer, and forming a pattern region of Schottky contact on the surface of a Schottky window; after the pattern area is formed, the device is placed in ultrapure water to be flushed for 2 minutes and flushed to be dry in a nitrogen atmosphere; and depositing Ti metal in the formed pattern area by using magnetron sputtering, wherein the thickness of the Ti metal is 100nm, and forming a Schottky metal layer 5 on the Schottky window. Continuously depositing an Al layer 6 on the Ti metal layer, wherein the thickness of the Al layer 6 is 300nm and the Al layer is used as a protective electrode; after the field plate terminal is formed to contact with the Schottky, the device is subjected to organic cleaning by using a stripping solution to remove the residual photoresist, and the residual stripping solution is cleaned by using ethanol and acetone.

Step 7, annealing the Schottky metal: annealing in a rapid annealing furnace at 300 deg.C under argon atmosphere for 5 min.

To this end, the formation of Al₂O₃The structure of the interlayer Ti metal schottky barrier diode is shown in fig. 1.

The invention grows a layer of very thin Al by atomic layer deposition before sputtering metal Ti₂O₃Thin film layer, by subsequent Al₂O₃Reacts with silicon carbide to form dipole layers to cause potential difference at two sides of an interface, thereby reducing the height of a Schottky barrier and the power consumption of a device, and Al₂O₃The film also creates a positive barrier with the silicon carbide, which also reduces the diode's reverse leakage current. Al (Al)₂O₃The film thickness is 0.8nm or 1.2nm or 2nm, and different Al is adjusted₂O₃The thickness of the thin film layer generates different barrier heights, so that the adjustability of the barrier heights is realized. Finally, an Al layer is sputtered on the Ti metal and used for protecting the electrode.

In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, are merely for convenience of description of the present invention, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.