阅读说明：本技术 具有第iva族离子注入的mosfet的结构与制造方法 (MOSFET structure with group IVA ion implantation and manufacturing method thereof ) 是由 黄智方 江政毅 王胜弘 洪嘉庆 于 2019-07-25 设计创作，主要内容包括：本发明揭露一种具有第IVA族离子注入的MOSFET的结构与制造方法,第IVA族离子注入层设置于基极之中,且第IVA族离子注入层接近于该栅极氧化层与该基极的交界面；其中,第IVA族离子注入层用来改变结构的一通道的性质。本发明提出的第IVA族离子注入的金属氧化物半导体场效应晶体管的结构与制造方法可用来改善栅极氧化层品质,提升场效电子迁移率。(The invention discloses a MOSFET structure with IVA ion implantation and a manufacturing method thereof.A group IVA ion implantation layer is arranged in a base electrode and is close to the interface of a grid oxide layer and the base electrode; wherein the group IVA ion implanted layer is used to modify a property of a channel of the structure. The structure and the manufacturing method of the metal oxide semiconductor field effect transistor implanted by the IVA group ions can be used for improving the quality of a grid oxide layer and enhancing the mobility of field effect electrons.)

1. A MOSFET structure having group IVA ion implantation, comprising:

a base electrode;

a gate electrode having a gate oxide layer between the gate electrode and the base electrode; and

a group IVA ion implantation layer disposed in the base electrode and close to the interface between the gate oxide layer and the base electrode;

wherein the group IVA ion implanted layer is configured to modify a property of a channel of the structure.

2. The structure of claim 1, wherein the channel properties include a channel electron mobility and a threshold voltage.

3. The structure of claim 2, wherein said group IVA ion implanted layer is configured to increase bonding of said base.

4. The structure of claim 3, wherein the group IVA ion implanted layer is a silicon ion implanted layer.

5. The structure of claim 4, wherein said silicon ion implanted layer is not disposed on said gate oxide layer.

6. The structure of claim 5, further comprising:

a source electrode layer arranged on the upper surface of the base electrode;

a source electrode disposed on the upper surface of the source layer and contacting a sidewall of the gate oxide layer, wherein the source electrode covers a portion of the source layer;

a drain layer arranged on the upper surface of the base electrode; and

a drain electrode arranged on the upper surface of the drain layer and contacting the other side wall of the gate oxide layer, wherein the drain electrode covers part of the drain layer;

wherein the gate oxide layer covers a portion of the source layer, a portion of the drain layer and a portion of the base; the source layer and the drain layer are made of a first type semiconductor material; and the base is a semiconductor material of a second type; and the silicon ion injection layer is arranged in the source electrode layer and the drain electrode layer and is close to the interface of the source electrode layer and the source electrode, the interface of the source electrode layer and the grid oxide layer, the interface of the drain electrode layer and the drain electrode and the interface of the drain electrode layer and the grid oxide layer.

7. The structure of claim 5, further comprising:

a source electrode layer arranged on the upper surface of the base electrode, and part of the source electrode layer is covered by the base electrode;

a source electrode disposed on the upper surface of the source layer and contacting a sidewall of the gate oxide layer, wherein the source electrode covers a portion of the source layer;

a drift layer arranged and contacted with the lower surface of the grid oxide layer and coating the base electrode;

a substrate contacting and disposed under the drift layer; and

a drain electrode disposed under the substrate;

wherein the gate oxide layer covers a portion of the source layer, a portion of the base and a portion of the drift layer; the source layer, the drift layer and the substrate are made of a first type semiconductor material; the base is a second type semiconductor material; and the silicon ion injection layer is arranged in the source layer and the drift layer and is close to the interface of the source layer and the source electrode, the interface of the source layer and the gate oxide layer and the interface of the drift layer and the gate oxide layer.

8. The structure of claim 5, further comprising:

a metal layer respectively arranged on an upper surface and a bottom surface of the structure to respectively form a source electrode and a drain electrode;

a substrate disposed on the drain electrode;

a drift layer disposed on the substrate;

a base electrode arranged on the drift layer;

a source layer disposed above the base;

a trench extending through the base and source layers, the bottom of the trench terminating in the drift layer, and the gate oxide layer disposed in the trench, the gate electrode being encapsulated by the gate oxide layer;

wherein the gate oxide layer covers a portion of the source layer, a portion of the base and a portion of the drift layer; the source layer, the drift layer and the substrate are made of a first type semiconductor material; the base is a second type semiconductor material; and the silicon ion injection layer is arranged in the source layer and the drift layer and is close to the interface of the source layer and the source electrode, the interface of the source layer and the gate oxide layer and the interface of the drift layer and the gate oxide layer.

9. A method of fabricating a MOSFET structure having group IVA ion implantation, comprising:

a base implantation process: implanting an aluminum ion into a base electrode;

ion implantation of a source layer or a drain layer: defining the area of the source layer or the drain layer by a photoetching process, and injecting phosphorus ions into the source layer or the drain layer; and

a process for group IVA ion implantation: implanting group IVA ions to a predetermined depth from the surface of the source layer, the drain layer or the base to form a group IVA ion implanted layer near the surface of the source layer, the drain layer or the base.

10. The method of claim 9, wherein the group IVA ion is a silicon ion and the predetermined depth is within 100 nm.

11. The method of claim 9, wherein the group IVA ion implantation is performed prior to oxidation of a gate oxide layer.

Technical Field

The invention relates to a structure and a manufacturing method of a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) with group IVA ion implantation, in particular to a structure and a manufacturing method for improving 4H-SiC oxidation by utilizing group IVA ion implantation (implantation) before oxidizing a grid Oxide layer.

Background

In the prior art, the field effect electron mobility of the SiC MOSFET is too low (5-10 cm) ²V-s) has been the biggest drawback of silicon carbide devices, and it has been developed in recent years that thermal annealing using oxidized nitric oxide can effectively increase electron mobility to about 30cm ²/V·s。

Hui-feng Li, university of Greefield, Australia, proposed in 1997 that after an oxidation process in a 6H-SiC Metal Oxide Semiconductor Capacitor (MOSC), Nitric Oxide (NO) and nitrous oxide (N) ₂O) rapid heating process (RTP), and the Interface trap density (D) measured by MOSC of NO RTP process _it) Lower than the results measured by the general process.

In 2001, Olympic university G.Y.Chung.et.al used this technology in 4H-SiC horizontal MOSFET, after oxidation, thermal annealing at 1175 deg.C, 1atm,2hr, NO, successfully changed the Channel electron mobility from 5cm ²The V.s is increased to 37cm ²V.s. The reason is that nitrogen atoms can enter SiC/SiO ₂The interface and Si form bonding, Si and C bonding are removed, and bonding between C and C is reduced.

In 2010, Dai Okamoto, university of Nara's institute of advanced science and technology, published a new thermal annealing technique, which was modified by phosphorus oxychloride (POCl) ₃) Nitrogen (N) ₂) With oxygen (O) ₂) The mixed gas lasts for 10min under the environment of 1000 ℃, and the research is successful in improving the channel electron mobility to 89cm ²V.s, but also associated with the side effect of the threshold voltage (V) _TH) And sharply becomes smaller.

Disclosure of Invention

The invention provides a structure and a manufacturing method of a metal oxide semiconductor field effect transistor implanted by IVA group ions to improve the quality of a grid oxide layer and improve the mobility of field effect electrons.

Unlike the prior art, the present invention improves electron mobility by implanting group IVA ions on the surface of the base (Body) before the Gate Electrode (Gate Electrode) is oxidized, and the Gate oxidation is affected by changing the surface structure of the base, thereby reducing defect density and increasing channel electron mobility.

The invention provides a structure and a manufacturing method of a metal oxide semiconductor field effect transistor implanted by IVA group ions, which are used for changing Threshold Voltage (V) _TH)。

One embodiment of the present invention discloses a mosfet structure with group IVA ion implantation, comprising: a base (Body); a gate electrode having a gate oxide layer between the gate electrode and the base electrode; and a group IVA ion implantation layer disposed in the base electrode, wherein the group IVA ion implantation layer is close to the interface between the gate oxide layer and the base electrode; wherein the group IVA ion implanted layer is used to modify a Channel property of the structure.

A method of fabricating a structure of a mosfet with group IVA ion implantation, comprising: a base implantation process: implanting an aluminum ion into a base electrode; ion implantation of a source layer or a drain layer: defining the area of the source layer or the drain layer by a photoetching process, and injecting phosphorus ions into the source layer or the drain layer; implanting group IVA ions to a predetermined depth from the surface of the source layer, the drain layer or the base to form a group IVA ion implanted layer near the surface of the source layer, the drain layer or the base.

Drawings

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, in accordance with industry standard practice, the various features are not drawn to scale and are merely illustrative. In fact, the dimensions of the devices may be arbitrarily increased or reduced to clearly illustrate the features of the present invention.

FIGS. 1-3 show schematic views of an embodiment of the present invention.

Fig. 4 is a graph of Si ion implantation concentration versus depth.

FIGS. 5a to 5d are experimental flow charts.

FIGS. 6a and 6b are CV diagrams obtained by measuring a capacitance having a diameter of 200 μm.

FIGS. 6c and 6d are Hi-Lo CV measurement charts.

FIG. 6e shows Hi-Lo converted D _itAnd (5) position distribution map.

FIG. 6f shows current density-electric field (J) _g-ε _OX) Figure (a).

FIG. 6g is the result of SEM measurement to observe the actual oxide layer thickness of the standard process.

Fig. 6h shows the result of SEM measurement of the actual oxide layer thickness of the silicon ion implantation process.

FIGS. 7a to 7d are I of the device _dV _gAnd I _dV _dAnd (6) measuring the result.

FIG. 8a and FIG. 8b are temperature variation I _dV _g。

Reference numerals:

structures 100, 200, 300

Base 101, 201, 301

Gate electrodes 102, 202, 302

Group IVA ion implanted layers 103, 203, 303

Gate oxide layers 104, 204, 304

Source layers 105, 205, 305

Source electrodes 106, 206, 306

Drain layer 107

Drain electrodes 108, 207, 307

Drift layers 208, 308

Substrates 209, 309

Detailed Description

Referring to fig. 1, fig. 1 shows a schematic diagram of a structure of a mosfet with group IVA ion implantation according to an embodiment of the present invention, where the structure 100 includes: a base 101; a gate electrode 102; a group IVA ion-implanted layer 103; a gate oxide layer 104; a source layer 105; a source electrode 106; a drain layer 107; and a drain electrode 108.

A gate oxide layer 104 is arranged between the gate electrode 102 and the base 101, and a group IVA ion implantation layer 103 is disposed in the base 101, the group IVA ion implantation layer 103 being close to an interface between the gate oxide layer 104 and the base 101, as shown by a dotted line; the group IVA ion implantation layer 103 is used to increase the electron mobility of the channel of the structure 100, and the group IVA ion implantation layer 103 is not disposed in the gate oxide layer 104.

In one embodiment, the group IVA ions may be realized by ions of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), titanium (Fl).

The source layer 105 is disposed on the upper surface of the base 101; the source electrode 106 is disposed on the upper surface of the source layer 105 and contacts a sidewall of the gate oxide layer 104, and the source electrode 106 covers a portion of the source layer 105. The drain layer 107 is disposed on the upper surface of the base 101; the drain electrode 108 is disposed on the upper surface of the drain layer 107 and contacts the other sidewall of the gate oxide layer 104, and the drain electrode 108 covers a portion of the drain layer 107.

The gate oxide layer 104 covers a portion of the source layer 105, a portion of the drain layer 107, and a portion of the base 101; the source layer 105 and the drain layer 107 are of a first type semiconductor material, and the base 101 is of a second type semiconductor material.

Note that when the structure 100 is an NMOS transistor, the first type semiconductor material is an N-type semiconductor material and the second type semiconductor material is a P-type semiconductor material; when the structure 100 is a PMOS transistor, the first type semiconductor material is a P-type semiconductor material and the second type semiconductor material is an N-type semiconductor material.

In one embodiment, the group IVA ion implantation layer 103 is disposed between the source layer 105 and the drain layer 107, and the group IVA ion implantation layer 103 is close to the interface between the source layer 105 and the source electrode 106, the interface between the source layer 105 and the gate oxide layer 104, the interface between the drain layer 107 and the drain electrode 108, and the interface between the drain layer 107 and the gate oxide layer 104.

The structure 100 affects the oxidation phenomenon by changing the surface structure of the base 101, and when the gate oxide layer 104 is oxidized, the implanted group IVA ions are used as a reactant, and nitrogen monoxide (NO) is not present, so that the damage of silicon carbide (SiC) bonding to the base 101 is reduced, and the defect density is reduced and the channel electron mobility is increased. In the present embodiment, the group IVA ions are realized by silicon ions.

Referring to fig. 2, fig. 2 shows a schematic diagram of a structure of a mosfet with group IVA ion implantation according to an embodiment of the present invention, and the structure 200 is a Vertical double-diffused mosfet (Vertical DMOS).

The structure 200 includes: a base 201, a gate electrode 202, a group IVA ion implantation layer 203, a gate oxide layer 204, a source layer 205, a source electrode 206, a drain electrode 207, a Drift layer (Drift layer)208, and a Substrate (Substrate) 209.

It is noted that a gate oxide layer 204 is disposed between the gate electrode 202 and the base 201, and a group IVA ion implantation layer 203 is disposed in the base 201, the group IVA ion implantation layer 203 being close to the interface between the gate oxide layer 204 and the base 201, as shown by the dashed line.

The source layer 205 is disposed on the upper surface of the base 201, and a portion of the source layer 205 is covered by the base 201; a source electrode 206 disposed on the upper surface of the source layer 205 and contacting a sidewall of the gate oxide layer 204, wherein the source electrode 206 covers a portion of the upper surface of the source layer 205; the gate oxide layer 204 covers a portion of the upper surface of the base 201 and the upper surface of the source layer 205.

The drift layer 208 is disposed on and in contact with the lower surface of the gate oxide layer 204 and covers the base 201; the substrate 209 contacts and is disposed under the drift layer 208; and a drain electrode 207 is disposed under the substrate 209.

Wherein, the gate oxide layer 204 also covers part of the source layer 205, part of the base 201 and part of the drift layer 208; the source layer 205, the drift layer 208 and the substrate 209 are of a first type semiconductor material; the base 201 is a second type semiconductor material; in the present embodiment, the first type semiconductor material is an N-type semiconductor material, and the second type semiconductor material is a P-type semiconductor material.

The group IVA ion implantation layer 203 is disposed in the source layer 205 and the drift layer 208, and the group IVA ion implantation layer 203 is close to an interface between the source layer 205 and the source electrode 206, an interface between the source layer 205 and the gate oxide layer 204, and an interface between the drift layer 208 and the gate oxide layer 204.

In one embodiment, the group IVA ions may be realized by ions of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), titanium (Fl).

Referring to fig. 3, fig. 3 is a schematic diagram of a structure of a mosfet with group IVA ion implantation according to an embodiment of the present invention, and the structure 300 is a Vertical trench mosfet (Vertical UMOS).

The structure 300 includes: a base 301, a gate electrode 302, a group IVA ion implantation layer 303, a gate oxide layer 304, a source layer 305, a drift layer 308, and a substrate 309; further, the structure 300 has metal layers respectively disposed on an upper surface and a bottom surface of the structure 300 to form the source electrode 306 and the drain electrode 307, respectively.

The substrate 309 is disposed on the drain electrode 307; the drift layer 308 is disposed on the substrate 309; the base 301 is disposed on the drift layer 308; the source layer 305 is disposed over the base 301; the trench T extends through the base 301 and the source layer 305, and the bottom of the trench terminates in the drift layer 308, and the gate oxide layer 304 is disposed in the trench, and the gate electrode 302 is wrapped by the gate oxide layer 304.

Wherein the gate oxide layer 304 covers a portion of the source layer 305, a portion of the base 301, and a portion of the drift layer 308; the source layer 305, the drift layer 308, and the substrate 309 are of a first type semiconductor material; the base 301 is a semiconductor material of a second type; and the group IVA ion implantation layer 303 is disposed between the source layer 305 and the drift layer 308, and the group IVA ion implantation layer 303 is close to an interface between the source layer 305 and the source electrode 306, an interface between the source layer 305 and the gate oxide layer 304, and an interface between the drift layer 308 and the gate oxide layer 304.

Next, a method for manufacturing a structure according to the present invention will be described (Si ion implantation is used as an example in the following description), and a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) device according to the present invention uses a 4H-SiC silicon carbide substrate having a concentration of 1X 10 ²⁰cm ^-3And a P-type epitaxial layer (epi layer) is grown thereon with a concentration and a thickness of 6 × 10 ¹⁵cm ^-3And 5 μm, as in FIG. 5 a. Because the SiC material is not diffused, the source electrode, the drain electrode and the base electrode of the invention need to use the ion implantation technology, grow the grid oxide layer by the thermal oxidation technology, and finally plate the electrode by the thermal evaporation way to finish the device.

The invention aims to change the surface structure of SiC so as to observe whether SiC oxidation difference is caused, because the annealing treatment after implantation is not carried out any more, the low-energy implantation is adopted for Si ion implantation, and the influence on the device characteristics caused by surface roughness (surface roughness) is avoided. And the implanted Si ions are only left on the surface layer. Through Silvaco simulation, the parameters are determined as shown in Table 1, the simulation depth is about 60nm, and FIG. 4 is a graph of Si ion implantation concentration versus depth.

TABLE 1 Si ion implantation parameters

The invention adopts an N-type 4H-SiC substrate, and a P-type epitaxial layer is grown on the N-type 4H-SiC substrate, wherein the concentration and the thickness are respectively 6 multiplied by 10 ¹⁵cm ^-3And 5 μm. Table 2 shows the mask sequence used in the present experiment, and fig. 5a to 5d show the experimental flow chart.

TABLE 2 Experimental mask numbering

Mask film	Process for the preparation of a coating
		Mask#1.	Photoetching key
Mask#
	2.	Base ion implantation
Mask#
	3.	Source drain ion implantation
Mask#
	4.	Device isolation region
Mask#
	5.	Source drain ohmic contact
Mask#
	6.	Base ohmic contact
Mask#
	7.	Grid metal and pad metal

The process is carried out by basic cleaning for cleaning metal ions and organic matter on the surface. The first step of cleaning is generally carried out by soaking in sulfuric acid (H) ₂SO ₄)100ml of hydrogen peroxide (H) ₂O ₂)100ml of catalytic solution for 10 minutes, the process can clean the surface of metal particles and organic matters. And secondly, soaking the Oxide layer etching solution (BOE) for 10 minutes, wherein the native Oxide layer (Natvive Oxide) can be removed by the process. After each process, the wafer was rinsed with deionized water (DI water) for 3 to 5 minutes to avoid residue, and then blown dry with a nitrogen gun, as shown in FIG. 5 a.

And (4) defining a photoetching key and a photoetching process (Alignment key & lithograph). And step one of the photoetching process, spin-coating the photoresist, namely firstly using an LOR photoresist, rotating for 45 seconds at a rotation parameter of 3000, soft-baking at 170 ℃ for 5 minutes, then using an S1813 photoresist, rotating for 30 seconds at a rotation parameter of 5000, and soft-baking at 90 ℃ for 3 minutes to finish the spin-coating of the photoresist.

And step two, carrying out photoetching by using an exposure machine, putting the test piece on the exposure machine for photoetching, carrying out exposure development after the photoetching is finished, wherein the parameters are respectively exposure for 19 seconds and development for 24 seconds, and carrying out hard baking at 120 ℃ for 5 minutes after the pattern is confirmed to be error-free by using a microscope to finish the photoetching process.

And performing a photoetching process by using Mask #1, reserving residual photoresist on the photoresist, etching the SiC defined on the surface by using Reactive Ion Etching (RIE) to complete photoetching bonds, protecting other places from being damaged by RIE etching by the photoresist, and cleaning the photoresist after the etching is finished.

The photoresist is cleaned by soaking in Acetone (ACE) for 10min, Isopropanol (IPA) for 10min, heating PG remover solution to 90 deg.C over water, and soaking the test piece for 10 min.

Base region ion Implantation (Body Implantation): firstly, carrying out plasma chemical vapor deposition (PECVD) on a test piece to deposit a layer of silicon dioxide with the thickness of about 1 μm, wherein the silicon dioxide can be used as an ion implantation barrier layer of a non-defined region, carrying out a photoetching process by using Mask #2 to define a base region, etching the silicon dioxide on the base region by RIE, removing surface photoresist after etching is finished, and carrying out ion implantation after the processing is finished. The implantation was carried out by high temperature (650 ℃) aluminum (Al) ion implantation, and the energy and concentration were as shown in Table 3. After the injection, the silicon dioxide on the test piece is removed by BOE solution.

TABLE 3 Al ion implantation parameters

Source and Drain region ion Implantation (Source Drain Implantation): performing Plasma Enhanced Chemical Vapor Deposition (PECVD) on the test piece for one time to deposit a layer of silicon dioxide with the thickness of about 1 μm, using Mask #3 to perform a photoetching process to define a source electrode and a drain electrode region, etching the silicon dioxide on the drain electrode region by RIE, etching to remove the photoresist on the surface, and performing ion implantation after the treatment is finished. The implantation method was high temperature (650 ℃) phosphorus (P) ion implantation, and the energy concentration was as shown in Table 4. After the injection, the silicon dioxide on the test piece is removed by BOE solution, and the cross section of the ion injection of the base, the source and the drain is shown in FIG. 5 b.

TABLE 4P ion implantation parameters

The electric activation is carried out for 30 minutes under the condition of argon atmosphere with ultrahigh temperature (1650 ℃), but the SiC surface forms a molten state under the high-temperature environment to cause volatilization, so a carbon film (Graphite Cap) needs to be covered on the test piece before the electric activation is carried out to avoid volatilization. The test piece is spin-coated with photoresist S1813, and is directly hard-baked at 120 deg.C for 5 min after spin-coating, and placed in a furnace tube at 800 deg.C under argon atmosphere for 30 min to form a carbon film. After the activation is finished, the surface carbon film is subjected to oxidation reaction to generate CO or CO in an oxygen environment of 900 ℃ in a furnace tube for 30 minutes ₂Thereby removing the surface carbon film.

The whole surface high temperature (650 ℃) silicon ion implantation is adopted, the experimental design relationship needs to control the implantation depth to be near the surface, so that the simulation is firstly carried out by Silvaco, the finally determined energy concentration is shown in the table 1, the simulation result is shown in the figure 2, and the ion implantation depth is about 60nm, as shown in the figure 5 c.

In order to avoid electric leakage between devices after injection, a device isolation region with the width of 5 mu m is designed and manufactured in an etching mode. The isolation region is defined by using Mask #4 to perform a photolithography process, the SiC depth is etched by RIE to about 148nm, and the photoresist is removed after the etching is finished.

Gate Oxidation (Gate Oxidation): before oxidation, the test piece is firstly subjected to RCA cleaning method (RCA clean), and the process can remove all impurities, organic matters and metal ions on the surface of the test piece, so that the test piece is oxidized under the purest state. The RCA clean procedure is as follows:

soaking in sulfuric acid (H) ₂SO ₄) With hydrogen peroxide (H) ₂O ₂) Mixed solution of (2) for 10 minutes.

The BOE solution was soaked for 5 minutes.

Soaking ammonia (NH) ₄OH) solution for 10 minutes, the process requires heating over water until the solution temperature reaches 90 ℃.

The BOE solution was soaked for 1 minute.

The solution of hydrochloric acid (HCl) is soaked for 10 minutes, and the process needs to be heated over water until the temperature of the solution reaches 90 ℃.

The BOE solution was soaked for 1 minute.

The oxidation parameters were 1150 ℃ for 6 hours in dry oxygen, as shown in FIG. 5d

Source and Drain ohmic contacts (Source, Drain Contact): mask #5 is used for photoetching to define source and drain regions, the RIE etches the oxide layer on the source and drain regions, and the RIE etching is selected to have the advantage that the RIE is anisotropic etching, so that the influence of side etching on the channel length can be avoided. The ohmic contact metals titanium (Ti) and nickel (Ni) are evaporated in a thermal evaporation mode, the titanium metal can provide an ohmic contact point for increasing the metal adhesion, and the nickel metal can also prevent the metal from reacting with oxygen in the air during high-temperature thermal annealing later. The thickness of the metal is respectively

Then the other metals are removed by Lift-off (Lift-off).

Base ohmic Contact (Body Contact): mask #6 is used to define the base contact area and RIE is used to etch the top oxide layer. The P-type semiconductor has high ohmic contact difficulty, and the metals are titanium, aluminum and nickel, wherein the aluminum can increase ohmic contact points, and the metals are respectively titanium, aluminum and nickel

Then removing other metals by lifting.

Rapid Thermal Annealing (RTA): the metal has better ohmic contact characteristic only after high-temperature thermal annealing, the rapid thermal annealing parameter is 1000 ℃ for 3 minutes, and the rapid thermal annealing parameter needs to be carried out in a vacuum environment, so that the ohmic characteristic is prevented from being influenced by the reaction of the metal and air.

The gate Metal and Pad Metal (Pad Metal) are patterned by using Mask #7 to define a region, and then thermally evaporatedEvaporating the metal titanium and aluminum in a hairdo way, wherein the thicknesses of the metal titanium and the metal aluminum are respectively

The thickness is increased to avoid the probe from piercing through the metal during measurement and affecting the measurement result. And finally, a cross section of the finished horizontal MOSFET device.

Vertical capacitance measurement: in the Voltage-Capacitance measurement (CV) in MOSC, the Capacitance (C) from the accumulation layer can be measured by using a high frequency (1M Hz) _OX) In the conversion of (A) to (B) _OT) The conversion formula is shown in formula 1.

Wherein epsilon _OXIs the silicon dioxide dielectric constant and A is the area. FIGS. 6a and 6b are CV diagrams obtained by measuring capacitance with a diameter of 200 μm and calculating equivalent oxide thicknesses of 53nm and 50nm, respectively, wherein FIG. 6a is a standard process of the prior art and FIG. 6b is a silicon ion implantation process of the present invention; the two processes do not have much difference in oxide layer thickness because the implantation energy is very small and the surface lattice is intact, which does not help much in increasing the oxidation rate.

Hi-Lo CV measurement is shown in FIGS. 6c and 6D, wherein FIG. 6c is a standard process of the prior art, FIG. 6D is a silicon ion implantation process of the present invention, the high frequency measurement frequency is 1MHz, the Quasi-static CV measurement step voltage is 0.1V/s, and D is calculated _itThe pattern of band position is shown in FIG. 6e, which shows that D of the test piece subjected to the silicon ion implantation process is less than 0.3eV from the conduction band _itObviously lower than the standard process test piece, and proves that the interface defect density can be reduced by the silicon ion implantation process. The oxide layer voltage withstand measurement, which is based on CV measurement to obtain an equivalent oxide layer thickness of about 50nm or less, is performed by setting the limiting current at 1 μ A, and FIG. 6f shows the current density-electric field (J) of the two processes _g-ε _OX) As a result, the electric field at the maximum of 6MV/cm or more starts to leak into FN, and it was confirmed that the strength of the oxide layer after Si ion implantation was not deteriorated. Finally, SEM measurement is utilized to observe actual oxidationThe results of layer thickness are shown in fig. 6g and fig. 6h, wherein fig. 6g is a standard process of the prior art, and fig. 6h is a silicon ion implantation process of the present invention, and the actual thickness is 56nm and 46nm, respectively.

Forward current measurement: this example measurement uses a device with a channel length of 5 μm, including drain current versus gate voltage measurement (I) _dV _g) And drain current to drain voltage measurement (I) _dV _d)。

When measuring the drain current versus the gate voltage, a very small voltage is applied at the drain terminal (V) _d0.1V) so that the formula of the drain current can be simplified as in formula 2, additionally from I _dV _gIn the figure I _dTo V _gThe transduction gain (g) is obtained after differentiation _m) Equation 3, and using the maximum value (g) _mMAX) and the Field-effect mobility (μ) is obtained by the equation 4 _FE)。

I _d＝μ _FE×C _OX×W/L×V _d(formula 2)

Table 5 summarizes the measurements, and the mean field effect electron mobility of the standard process test piece is 6.38cm ²The average field effect electron mobility of the test piece subjected to Si ion implantation before oxidation is improved to 7.59cm ²The voltage/V.s is increased by about 15% and the threshold voltage does not vary much. The reason is that Si exists on the SiC surface in an impurity mode without high-temperature activation after ion implantation, the surface lattice integrity is not damaged by low-energy implantation, the Si atoms required by the oxidation reaction are partially provided by the implanted impurities to reduce the damage of original SiC bonds, thereby reducing the broken bonds generated in the oxidation reaction and lowering the D _itAnd the threshold voltage is not changed too much by doping Si in a neutral way. Drawing (A)7 a-7 d are I representative devices under two process conditions _dV _gAnd I _dV _dThe results of the measurements are shown in FIGS. 7a and 7c, which are standard processes of the prior art, and in FIGS. 7b and 7d, which are silicon ion implantation processes of the present invention.

TABLE 5 average electron mobility and threshold voltage for different processes

Measuring temperature-changing electricity: FIG. 8a and FIG. 8b are temperature variation I _dV _gWhere fig. 8a is a standard process of the prior art and fig. 8b is a process of implanting silicon ions according to the present invention, the current increases, the electron mobility increases and the threshold voltage decreases as the temperature increases. Because the SiC has high-density interface defects to capture electrons, the captured electrons can be effectively released by temperature rise, so that the channel electron concentration is improved, the channel inversion is easier to achieve, the threshold voltage is reduced, the electron mobility is increased, and the threshold voltage is reduced by a lower amplitude than that of a standard process test piece, so that the device is easier to avoid entering a normally open mode in advance. Table 6 and table 7 are collated with detailed temperature change data.

TABLE 6 Standard Process temperature Change measurement

TABLE 7 measurement of Si-implant temperature variation

According to the invention, Si ions are implanted to change the surface characteristics before the oxidation process, so that the oxidation environment is improved, and the electron mobility of the SiC horizontal metal oxide semiconductor field effect transistor is improved.

The field effect electron mobility is changed from the original 6.38cm by Si ion implantation before oxidation ²The lift of/V.s is 7.59cm ²The increase of the/V.s is about 15 percent, and the average interface defect density is also from 4.079 multiplied by 10 ¹²eV ^-1cm ^-2Down to 3.764 × 10 ¹²eV ^-1cm ^-2Although there is NO such large electron mobility increase due to the thermal annealing of NO, the side effect of threshold voltage shift is avoided and other electrical properties such as ohmic contact are not affected.