CN111446303A - Diamond Schottky barrier diode device with table-board terminal and preparation method thereof - Google Patents

Abstract

The invention discloses a diamond Schottky barrier diode device with a table-board terminal and a preparation method thereof. Aiming at the problem that the withstand voltage of the existing diamond Schottky barrier diode device is reduced due to the fact that the Schottky contact electrode has a high fringe electric field, the Schottky contact electrode is used as a mask to etch the drift layer, self-alignment of the Schottky contact electrode and the etched drift layer is achieved, and the preparation technology of the diamond Schottky barrier diode device with the table-board terminal is developed.

Description

Diamond Schottky barrier diode device with mesa termination and method of making the same

technical field

The invention relates to a diamond Schottky barrier diode device with a mesa terminal and a preparation method thereof, belonging to the technical field of semiconductor device preparation.

Background technique

Diamond semiconductor material has excellent properties such as ultra-wide band gap, high critical breakdown field strength and high thermal conductivity, and is an ideal material for the development of next-generation high-performance power devices. The Schottky barrier diode developed with diamond has the advantages of low on-resistance, high breakdown voltage, good high temperature stability and strong radiation resistance. However, the fringe electric field effect occurs at the edge of the Schottky electrode, which causes the electric field to break down in advance due to the accumulation of the electric field, thereby greatly reducing the reverse breakdown voltage of the device. Using various termination techniques is an effective way to reduce the peak electric field at the edge of Schottky barrier diode devices. Among them, the mesa termination technology is widely used in various pn diode devices, and enables the device to obtain a near-ideal breakdown voltage. However, due to the inability to achieve complete registration of the Schottky electrode and the drift layer after etching, the mesa termination technology has not been successfully applied to diamond Schottky barrier diode devices.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a diamond Schottky barrier diode device with a mesa terminal and a preparation method thereof, which solves the problem that the fringe electric field aggregation of the existing diamond Schottky barrier diode device leads to the decrease of the voltage withstand capability of the device , has the characteristics of strong fringe electric field suppression ability, low on-resistance, good high temperature stability and strong radiation resistance.

The present invention adopts the following technical solutions for solving the above-mentioned technical problems:

A diamond Schottky barrier diode device with a mesa terminal, including an ohmic contact metal layer, a highly doped diamond substrate, a lightly doped drift layer, a Schottky electrode, and a highly doped diamond substrate arranged in order from bottom to top The lower surface of the ohmic contact metal layer has the same size as the upper surface of the ohmic contact metal layer. The cross-section of the highly doped diamond substrate is a convex shape, and the lightly doped drift layer is arranged on the surface of the convex part of the convex shape. The lower surface of the Schottky electrode The size of the upper surface of the lightly doped drift layer is the same as that of the upper surface of the Schottky electrode, the two ends of the upper surface of the Schottky electrode, the side of the Schottky electrode, the side of the lightly doped drift layer, and the upper surface of the highly doped diamond substrate except for the protruding part The surfaces are covered with passivation medium.

As a preferred solution of the diode device of the present invention, the doping types of the highly doped diamond substrate and the lightly doped drift layer are the same, and both are n-type doping or p-type doping.

As a preferred solution of the diode device of the present invention, the ohmic contact metal layer is a multi-layer metal structure based on titanium, and the thickness of the titanium is greater than 10 nm and less than 50 nm.

As a preferred solution of the diode device of the present invention, the Schottky electrode is one of titanium, aluminum, nickel, gold, platinum, tungsten, and copper, or a combination of at least two metals, and the Schottky electrode is The thickness is 100 nm to 1000 nm.

The preparation method of a diamond Schottky barrier diode device with a mesa terminal comprises the following steps:

Step 1, use organic reagents to clean the diamond material sample by ultrasonic. The structure of the diamond material sample includes a highly doped diamond substrate, a lightly doped drift layer arranged in sequence from bottom to top, and the highly doped diamond substrate and The doping type of the lightly doped drift layer is the same;

Step 2, prepare an ohmic contact metal layer on the lower surface of the highly doped diamond substrate by electron beam evaporation or sputtering, and perform alloying treatment under vacuum conditions;

Step 3, using photoresist to define a Schottky contact area on the upper surface of the lightly doped drift layer, and then using a metal evaporation and lift-off process to prepare a Schottky electrode;

Step 4, using the Schottky electrode as a mask, the lightly doped drift layer is completely etched, and part of the highly doped diamond substrate is etched at the same time, and the total etching thickness is greater than the thickness of the lightly doped drift layer and less than The sum of the thickness of the lightly doped drift layer and the highly doped diamond substrate;

Step 5, performing damage repair on the sample obtained in step 4;

Step 6, for the sample obtained in Step 5, deposit a passivation medium on other surfaces except the side surface of the highly doped diamond substrate, the side surface of the ohmic contact metal layer, and the lower surface of the ohmic contact metal layer;

In step 7, a photoresist is used to define a dielectric hole region on the passivation medium, the medium in the dielectric hole is etched to expose the Schottky electrode, and an organic cleaning agent is used to remove the photoresist.

As a preferred solution of the preparation method of the present invention, the etching gas used in the etching in step 4 is oxygen, or at least one gas of argon, carbon tetrafluoride and sulfur hexafluoride is added on the basis of oxygen ; The etching method used for etching is reactive ion etching or inductively coupled plasma etching.

As a preferred solution of the preparation method of the present invention, the damage repair method in step 5 is plasma treatment or treatment with a non-strong oxidizing acid solution or treatment with a weak alkaline solution.

As a preferred solution of the preparation method of the present invention, the passivation medium in step 6 is one of aluminum oxide, silicon dioxide, silicon nitride, and diamond, or a combination of at least two of them.

As a preferred solution of the preparation method of the present invention, the deposition method in step 6 is plasma-enhanced chemical vapor deposition method or microwave plasma chemical vapor deposition method or atomic layer deposition method or pulsed laser deposition method or magnetron sputtering.

As a preferred solution of the preparation method of the present invention, in step 7, the medium in the medium hole is etched by wet method or reactive ion etching method or inductively coupled plasma etching method.

Compared with the prior art, the present invention adopts the above technical scheme, and has the following technical effects:

1. The invention is based on the technology of using the Schottky electrode as a mask to etch the drift layer to realize the self-alignment of the Schottky electrode and the drift layer after etching, and develops a diamond Schottky barrier diode device with a mesa terminal and a According to the preparation method, a diamond Schottky barrier diode device with low on-resistance, high breakdown voltage, good high temperature stability and strong radiation resistance can be realized through the technology.

2. The invention has the advantages of strong Schottky metal fringe electric field suppression capability, low on-resistance, good high temperature stability, and strong radiation resistance.

Description of drawings

FIG. 1 is a schematic structural diagram of a diamond Schottky barrier diode device with a mesa termination according to the present invention.

Fig. 2(a)-Fig. 2(g) are flow charts of the method for preparing a diamond Schottky barrier diode device with a mesa termination according to the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, but not to be construed as a limitation of the present invention.

As shown in FIG. 1 , the diamond Schottky barrier diode device with mesa terminal includes an ohmic contact metal layer 3 , a highly doped diamond substrate 1 , a lightly doped drift layer 2 , a Schottky contact layer 3 arranged in order from bottom to top Base electrode 4, the lower surface of the highly doped diamond substrate 1 has the same size as the upper surface of the ohmic contact metal layer 3, the cross section of the highly doped diamond substrate 1 is a convex shape, and the lightly doped drift layer 2 is arranged in a convex shape On the surface of the protruding part, the lower surface of the Schottky electrode 4 has the same size as the upper surface of the lightly doped drift layer 2, the two ends of the upper surface of the Schottky electrode 4, the side surface of the Schottky electrode 4, and the lightly doped drift layer 2. The side surfaces of the drift layer 2 and the upper surface of the highly doped diamond substrate 1 except for the protruding portion are covered with a passivation medium 5 .

The invention relates to a method for preparing a diamond Schottky barrier diode device with a mesa terminal, which includes preparing an ohmic contact metal layer on the back of a sample; preparing a front Schottky electrode; etching and repairing the etching damage of the front drift layer; Front-side passivation dielectric deposition and dielectric hole etching. Its steps include:

(1) Use organic reagents such as acetone and ethanol to clean the sample by ultrasonic, and the structure of the sample includes a highly doped substrate 1 and a lightly doped drift layer 2;

The highly doped diamond substrate 1 and the lightly doped drift layer 2 have the same doping type, and are both n-type doped or p-type doped.

(2) making the ohmic contact metal layer 3 on the back of the sample, and performing alloying treatment under vacuum conditions;

The ohmic contact metal is Ti/Al, Ti/Au and other multi-layer metal structures with Ti as the base. The thickness of titanium (Ti) is greater than 10nm and less than 50nm, the vacuum of the alloy is lower than 3E-4Pa, and the alloy temperature is higher than 600 ℃.

(3) through conventional photolithography and development processes, using photoresist to define the Schottky contact area, and then using metal evaporation and stripping processes to prepare the Schottky electrode 4;

The Schottky contact metal is one or more combinations of titanium (Ti), aluminum (Al), nickel (Ni), gold (Au), platinum (Pt), tungsten (W), copper (Cu), etc. The total thickness The thickness is 100-1000 nm, and the thickness can be sufficient to block the etching of the etching gas in step (4).

(4) using the Schottky electrode as a mask to etch the drift layer 2, completely etch away the drift layer 2, and partially etch to the highly doped substrate 1;

The etching gas is O ₂ , and one or more of argon (Ar), carbon tetrafluoride (CF4), sulfur hexafluoride (SF6) and other gases can be selectively added, and the etching method is RIE (Reactive ion etching , reactive ion etching) or ICP (Inductively Coupled Plasma, inductively coupled plasma etching).

(5) Repair damage to the etched sample;

The etching damage repair method is plasma treatment or treatment with a non-strong oxidizing acid solution such as hydrochloric acid, hydrofluoric acid, phosphoric acid, or a weak alkaline solution such as ammonia water.

(6) depositing passivation medium 5 to protect the sidewall;

The passivation medium is one or more combinations of aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), silicon tetranitride (Si ₃ N ₄ ), diamond, etc., and the deposition method is PECVD (Plasma Enhanced Chemical Vapor Deposition, plasma enhanced chemical vapor deposition method), MPCVD (Microwave Plasma Chemical Vapor Deposition, microwave plasma chemical vapor deposition), ALD (Atomic layer deposition, atomic layer deposition), PLD (Pulsed Laser Deposition, pulsed laser deposition), magnetron sputtering, etc.

(7) Through the conventional photolithography and development process, the photoresist 6 is used to define the dielectric hole area, the medium in the dielectric hole is etched, the Schottky electrode is exposed, and the photoresist 6 is removed by organic cleaning reagents such as acetone ethanol.

Dielectric hole etching methods are wet method, ICP, RIE, etc.

A specific embodiment will be described below. As shown in Figure 2(a)-Figure 2(g), it is a preparation method of a diamond Schottky barrier diode device with a mesa terminal according to the present invention, and the specific process is as follows:

(1) Use organic reagents such as acetone and ethanol to clean the diamond material sample by ultrasonic. The structure of the sample includes a p-type boron-doped diamond substrate 1 with a thickness of 300 μm, a doping concentration of 5E19cm ^-3 , and a p-type boron-doped diamond substrate 1 . The hetero-diamond drift layer 2 has a thickness of 200 nm and a doping concentration of 1E16cm ^-3 , as shown in Figure 2(a);

(2) Prepare Ti(20nm)/Au(300nm) ohmic contact metal layer 3 by electron beam evaporation on the back of the sample, and treat at 700℃ for 3min under vacuum pressure 1E-4Pa, as shown in Figure 2(b);

(3) Through the conventional photolithography and development process, use photoresist to define the Schottky contact area, then use electron beam evaporation equipment to evaporate 400nm metal nickel, and ultrasonically peel off in acetone solution to form Schottky electrode 4, as shown in the figure 2(c);

(4) Using the Schottky electrode as a mask, the drift layer 2 and the high-doped substrate 1 are partially etched with O ₂ in the ICP equipment, and the total etching depth is 300 nm, as shown in Figure 2(d);

(5) Treat the surface of the sample with 20% dilute hydrochloric acid;

(6) ALD equipment was used to deposit Al ₂ O ₃ passivation medium 5 at 300°C with a thickness of 300 nm, as shown in Figure 2(e);

(7) Through the conventional photolithography and development process, the photoresist 6 is used to define the area of the medium hole, as shown in Figure 2(f), the Al ₂ O ₃ in the medium hole is etched with Cl ₂ in the ICP equipment, The Schottky electrode is exposed, as shown in FIG. 2( g ), and the photoresist 6 is removed by using an organic cleaning agent such as acetone ethanol to obtain a diode device.

The above embodiments are only to illustrate the technical idea of the present invention, and cannot limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the present invention. Inside.

Claims (10)

1. The diamond Schottky barrier diode device with the table-board terminal is characterized by comprising an ohmic contact metal layer (3), a highly doped diamond substrate (1), a lightly doped drift layer (2) and a Schottky electrode (4) which are sequentially arranged from bottom to top, wherein the size of the lower surface of the highly doped diamond substrate (1) is the same as that of the upper surface of the ohmic contact metal layer (3), the cross section of the highly doped diamond substrate (1) is in a convex shape, the lightly doped drift layer (2) is arranged on the surface of the convex part in the convex shape, the size of the lower surface of the Schottky electrode (4) is the same as that of the upper surface of the lightly doped drift layer (2), the two ends of the upper surface of the Schottky electrode (4), the side surface of the lightly doped drift layer (2) and the surface of the upper surface of the highly doped diamond substrate (1) except the convex part are all covered with passivation media (5).

2. The diamond schottky barrier diode device with mesa terminal as claimed in claim 1, wherein the highly doped diamond substrate (1) and the lightly doped drift layer (2) are doped with the same type, either n-type or p-type.

3. The mesa-terminated diamond schottky barrier diode device according to claim 1, wherein the ohmic contact metal layer (3) is a titanium-based multilayer metal structure, and a thickness of titanium is greater than 10nm and less than 50 nm.

4. The diamond schottky barrier diode device with mesa terminal as claimed in claim 1, wherein the schottky electrode (4) is one of titanium, aluminum, nickel, gold, platinum, tungsten, copper, or a combination of at least two metals, and the thickness of the schottky electrode (4) is 100nm to 1000 nm.

5. The preparation method of the diamond Schottky barrier diode device with the table-board terminal is characterized by comprising the following steps:

step 1, cleaning a diamond material sample by adopting an organic reagent in an ultrasonic mode, wherein the structure of the diamond material sample comprises a highly-doped diamond substrate and a lightly-doped drift layer which are sequentially arranged from bottom to top, and the doping types of the highly-doped diamond substrate and the lightly-doped drift layer are the same;

step 2, preparing an ohmic contact metal layer on the lower surface of the highly-doped diamond substrate by an electron beam evaporation or sputtering method, and carrying out alloy treatment under a vacuum condition;

step 3, defining a Schottky contact area on the upper surface of the lightly doped drift layer by using photoresist, and then preparing a Schottky electrode by using metal evaporation and stripping processes;

step 4, completely etching off the lightly doped drift layer by taking the Schottky electrode as a mask, and simultaneously etching part of the highly doped diamond substrate, wherein the total etching thickness is greater than the thickness of the lightly doped drift layer and less than the sum of the thicknesses of the lightly doped drift layer and the highly doped diamond substrate;

step 5, repairing damage of the sample obtained in the step 4;

step 6, depositing a passivation medium on the other surfaces of the sample obtained in the step 5 except the side surface of the high-doped diamond substrate, the side surface of the ohmic contact metal layer and the lower surface of the ohmic contact metal layer;

and 7, defining a dielectric hole area on the passivation medium by using photoresist, etching the medium in the dielectric hole to expose the Schottky electrode, and removing the photoresist by using an organic cleaning reagent.

6. The method of claim 5, wherein the etching gas used in the etching in step 4 is oxygen, or at least one of argon, carbon tetrafluoride and sulfur hexafluoride is added based on oxygen; the etching method used for etching is a reactive ion etching method or an inductive coupling plasma etching method.

7. The method of claim 5, wherein the step 5 of repairing the damage is performed by plasma treatment or treatment with a non-strongly oxidizing acid solution or treatment with a weakly alkaline solution.

8. The method of claim 5, wherein the passivation dielectric of step 6 is one of alumina, silicon dioxide, silicon nitride, diamond, or a combination of at least two of the foregoing.

9. The method for manufacturing a diamond schottky barrier diode device with a mesa terminal as claimed in claim 5, wherein the deposition in step 6 is a plasma-enhanced chemical vapor deposition method, a microwave plasma chemical vapor deposition method, an atomic layer deposition method, a pulsed laser deposition method, or a magnetron sputtering method.

10. The method of claim 5, wherein the etching of the dielectric in the dielectric hole in step 7 is performed by wet etching, reactive ion etching, or inductively coupled plasma etching.

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