CN100511706C - GaN device based on component-gradient GaN MISFET and preparing method thereof - Google Patents

GaN device based on component-gradient GaN MISFET and preparing method thereof Download PDF

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CN100511706C
CN100511706C CNB2007100187728A CN200710018772A CN100511706C CN 100511706 C CN100511706 C CN 100511706C CN B2007100187728 A CNB2007100187728 A CN B2007100187728A CN 200710018772 A CN200710018772 A CN 200710018772A CN 100511706 C CN100511706 C CN 100511706C
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layer
aln
component
gan
algan
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CNB2007100187728A
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CN101132022A (en
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郝跃
陈军峰
张进城
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西安电子科技大学
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Abstract

The present invention discloses a GaN device based on component-gradual-changed GaN MISFET and its processing method. The device includes substrate (1), buffer layer (2), intrinsic GaN layer (3), AlN isolating layer (4) and source (7), drain (8), gate (9), in which component-gradual-changed AlGaN layer (5) and AlN cap layer (6) are orderly set on the AlN isolating layer. The process of the device includes: the GaN or AlN buffer layer are orderly extended on sapphire or silicon carbide substrate; the intrinsic GaN layer is deposited; the AlN isolating layer is deposited; the component-gradual-changed AlGaN is deposited; the AlN cap layer is deposited; two sides of the AlN cap layer on top and parts of two sides of component-gradual-changed AlGaN layer are separately etched to form a step structure which is high in central and low in two sides; ohmic contacts of the source and the drain and metal contact of the gate are separately made on different steps of the structure. The present invention has low drain current and high gate voltage, and can be used to process high power microwave devices.

Description

GaN device and preparation method based on component-gradient GaN MISFET

Technical field

The invention belongs to microelectronics technology, relate to and partly lead device architecture and manufacture method, a kind of specifically GaN device and preparation method based on component-gradient GaN MISFET can be used for the making of high-power GaN device.

Background technology

In recent years with SiC, GaN be the third generation semiconductor material with wide forbidden band of representative owing to have good characteristics such as big energy gap, high critical field strength, high heat conductance, high carrier saturation rate, heterojunction boundary two-dimensional electron gas height, make it be subjected to people and pay close attention to widely.In theory, utilize the devices such as high electron mobility transistor (HEMT), heterojunction bipolar transistor HBT, LED, laser diode LD of these material will have the incomparable excellent properties of existing device, therefore both at home and abroad it has been carried out extensive and deep research and has obtained the achievement that attracts people's attention in succession in recent years.

Existing GaN power device uses Si more 3N 4And SiO 2Two kinds of materials are as the cap layer of device, constitute MISFET or two kinds of structures of MOSFET, but because these two kinds of materials can't carry out a secondary growth with the GaN material, and must be independent carry out diauxic growth, cause this structure still to have higher surface state and defective, make that the leakage current of device is higher; Simultaneously, these two kinds of materials mostly are polycrystalline structure and cause the voltage endurance of device relatively poor, can't give play to the high characteristics of GaN material breakdown voltage, are difficult to further improve the power density of device; In addition, existing planar structure GaN MISFET is because the AlGaN layer is generally high Al component doping, make the Al component raising and make between the ohmic contact and produce contradiction, promptly in order to obtain the higher two-dimensional electron gas that gets, require to improve the Al component, and in order to make ohmic contact preferably, the Al component again can not be too high.Research with people such as Arulkumaran is example, sees Journal of Vacuum Science ﹠amp; Technology B:Microelectronics and NanometerStructures, March 2003, and Volume 21, Issue 2, pp.888-894, and the Al component of its AlGaN layer is up to 43%, this moment, the ohmic contact of device was made comparatively difficulty, had seriously restricted the raising of device performance.

The content of invention

The objective of the invention is to overcome above-mentioned the deficiencies in the prior art, a kind of GaN device and preparation method based on component-gradient GaN MISFET is provided, to reduce the GaN device creepage, to solve the contradiction between Al component and the ohmic contact.

The technical scheme that realizes the object of the invention is to have adopted the cap layer of AlN material as device, and has adopted the AlGaN material layer and the ledge structure of component-gradient simultaneously, forms a kind of new GaNMISFET structure.

Device architecture of the present invention comprises substrate layer, resilient coating, GaN intrinsic material layer, AlN separator and source, leakage, gate electrode, wherein on the AlN separator, be provided with AlGaN component-gradient layer and AlN cap layer successively, this AlGaN graded bedding and AlN cap layer constitute ledge structure after by etching, and from each step surface extraction electrode.

The manufacture method of device of the present invention comprises:

With sapphire as substrate, its process is as follows:

Extension one deck GaN resilient coating on Sapphire Substrate;

Deposit one deck GaN intrinsic material layer is as the service area of device on this resilient coating;

Deposit one deck AlN material is as separator on described GaN intrinsic layer;

Deposit AlGaN component-gradient layer on the AlN separator;

Deposit AlN cap layer on AlGaN component-gradient layer;

On AlGaN component-gradient layer and AlN cap layer, make mask, etch the step that is used for the contact of deposit gate metal, drain electrode and source electrode ohmic contact, at the diverse location depositing metal of step, make source electrode and the ohmic contact of drain electrode and the Metal Contact of grid respectively.

With carborundum as substrate, its process is as follows:

Extension one deck AlN resilient coating on the SiC material substrate;

Deposit one deck intrinsic GaN material layer is as the service area of device on this resilient coating;

Deposit one deck AlN material is as separator on described GaN intrinsic layer;

Deposit AlGaN component-gradient layer on the AlN separator;

Deposit AlN cap layer on AlGaN component-gradient layer;

On AlGaN component-gradient layer and AlN cap layer, make mask, etch the step that is used for the contact of deposit gate metal, drain electrode and source electrode ohmic contact, at the diverse location depositing metal of step, make source electrode and the ohmic contact of drain electrode and the Metal Contact of grid respectively.

The present invention is owing to adopted single crystal AlN material cap layer, component-gradient barrier layer and ledge structure, and relatively have the following advantages with existing high-power GaN device: at first, single crystal AlN material cap layer has been avoided traditional employing SiO 2And Si 3N 4The problem of the necessary diauxic growth of cap layer has effectively reduced the density of states of device surface, thereby has significantly reduced the leakage current of device; The second, the single crystal characteristics of AlN and high K characteristic have significantly improved the grid voltage of device and the power density of device; The 3rd, use component-gradient AlGaN to substitute traditional fixedly Al component AlGaN layer, use ledge structure to replace the planar structure of traditional GaN HEMT device, these two features combine and have solved the contradiction of the heavily stressed and high Al component ohmic contact of making between single crystal AlN cap layer and the AlGaN layer effectively.Because the AlGaN layer is higher than the Al component of close AlN separator one side at the Al component near AlN cap layer one side, thereby make AlN cap layer growth on the AlGaN of high Al component, can reduce heavily stressed that lattice mismatch causes, and after etching ledge structure, the ohmic contact of source electrode and drain electrode is produced on the lower table top of AlGaN layer Al component, can reduce the difficulty of making ohmic contact.

Further specify technology contents of the present invention below in conjunction with drawings and Examples.

Description of drawings

Fig. 1 is the structure chart of device of the present invention;

Fig. 2 is the making flow chart of device of the present invention;

Fig. 3 is silicon carbide substrates device architecture figure of the present invention;

Fig. 3 is Sapphire Substrate device architecture figure of the present invention.

Embodiment

With reference to Fig. 1, device architecture of the present invention is from bottom to top: substrate 1, resilient coating 2, GaN intrinsic layer 3, AlN separator 4, AlGaN component-gradient layer 5, AlN cap layer 6.AlGaN graded bedding and AlN cap layer constitute the step of device behind over etching, and the AlGaN layer is higher than Al component near AlN separator one side at the Al component near AlN cap layer one side, with reduce that lattice mismatch causes heavily stressed with make the difficulty of ohmic contact.On the table top of AlN cap layer 6, make gate metal contact 8, on the table top at AlGaN component-gradient layer 5 two ends, make drain electrode ohmic contact 7 and source electrode ohmic contact 9 respectively.This AlN separator 4, it is interrupted further to improve conduction band, increases the concentration of the two-dimensional electron gas in the GaN intrinsic layer 3; Can isolate simultaneously that ionized impurity improves the mobility of electronics in the conducting channel to the scattering process of two-dimensional electron gas in the AlGaN graded bedding 5.

With reference to Fig. 2, manufacturing process of the present invention is as follows:

Select sapphire or SiC material backing material, and use MOCVD method extension one deck GaN or AlN resilient coating thereon as device as device;

Using MOCVD method epitaxial thickness on resilient coating is 1~3 micron, and plain GaN intrinsic material layer is as the service area of device;

On the GaN intrinsic layer, use MOCVD method extension one deck AlN material separator.This AlN material can the enhance device conduction band discontinuity, improve the concentration of two-dimensional electron gas in the GaN material work area;

On the AlN separator, use the AlGaN graded bedding of an Al component-gradient of MOCVD method extension.The Al component of this layer changes in 10% to 70% scope continuously;

On the AlGaN graded bedding, use MOCVD method extension one deck AlN cap layer;

The AlN cap layer both sides at top are etched away, and the part of AlGaN graded bedding both sides is also etched away, middle AlN cap layer does not carry out etching, and the position is the highest, high, the low ledge structure in both sides in the middle of forming;

On the table top of AlN cap layer, make the gate metal contact, on the table top at AlGaN component-gradient layer two ends, make drain electrode ohmic contact and source electrode ohmic contact respectively.

Embodiment 1

Make the high-power GaN MISFET device process of silicon carbide substrates of the inventive method.

The first step adopts the MOCVD method on the SiC backing material, be 1050 degree with temperature, and pressure is that condition deposit one layer thickness of 20Torr is the AlN material of 50 nanometers, as the resilient coating of subsequent growth GaN material.

Second step, on resilient coating, adopt the MOCVD technology, be 1000 degree in temperature, pressure is under the condition of 20Torr, deposit one layer thickness is 2 microns a GaN intrinsic layer.

The 3rd step, on the GaN intrinsic layer, adopt the MOCVD technology, be 1000 degree in temperature, pressure is that deposit one layer thickness is the AlN material layer of 1 nanometer under the condition of 20Torr.

The 4th step, on the AlN material layer, adopt the MOCVD technology, be 1000 degree in temperature, pressure is that deposition thickness is 10 nanometers under the condition of 20Torr, the Al component is for being gradient to 60% AlGaN component-gradient material layer from 10%.Along with the increase of Al component, temperature is increased to 1020 degree from 1000 degree gradually.

The 5th step, on AlGaN component-gradient material layer, adopt the MOCVD technology, be 1020 degree in temperature, pressure is that deposition thickness is the AlN material of 3 nanometers under the 20Torr condition, this AlN material is as the cap layer of device.

The 6th step, on AlN cap layer, make mask, etch the step that is used for deposit drain electrode and source electrode ohmic contact as shown in Figure 3.

The 7th step, use electron beam evaporation technique respectively depositing metal Ni/Au on the step on both sides as source electrode and leak the ohmic contact of level and the step in the centre on depositing metal Ni/Au as the Metal Contact of grid.

Embodiment 2

Make the high-power GaN MISFET device process of Sapphire Substrate of the inventive method.

The first step adopts the MOCVD technology on saphire substrate material, be 550 degree in temperature, and pressure is that deposit one layer thickness is the GaN material of 100 nanometers under the condition of 40Torr, as the resilient coating of subsequent growth GaN material.

Second step, on resilient coating, adopt the MOCVD technology, be 900 degree in temperature, pressure is under the condition of 40Torr, deposit one layer thickness is 3 microns a GaN intrinsic layer.

The 3rd step, on the GaN intrinsic layer, adopt the MOCVD technology, be 1000 degree in temperature, pressure is that deposit one layer thickness is the AlN separator of 2 nanometers under the condition of 20Torr.

The 4th step, on the AlN separator, adopt the MOCVD technology, be 1000 degree in temperature, pressure is that deposition thickness is 15 nanometers under the condition of 20Torr, the Al component is for being gradient to 50% AlGaN graded bedding from 10%, and along with the increase of Al component, temperature is increased to 1020 degree gradually from 1000 degree.

The 5th step, adopt the MOCVD technology on the AlGaN graded bedding, be 1020 degree in temperature, pressure is that deposition thickness is the AlN material of 3 nanometers under the condition of 20Torr.This AlN material is as the cap layer of device.

In the 6th step, on AlN cap layer, make mask, the step that is used for deposit drain electrode and source electrode ohmic contact shown in the etching discrepancy accompanying drawing 4.

The 7th step, use electron beam evaporation technique respectively depositing metal Ni/Au on the step on both sides as source electrode and leak the ohmic contact of level and the step in the centre on depositing metal Ni/Au as the Metal Contact of grid.

With reference to Fig. 3, the high-power GaN MISFET device architecture of silicon carbide substrates of the present invention is followed successively by from bottom to top: silicon carbide substrates, AlN resilient coating, GaN intrinsic layer, AlN separator, AlGaN graded bedding, AlN cap layer.High both sides low ledge structure in the middle of wherein being etched with on AlGaN and AlN cap layer is being made the contact of Ni/Au gate metal, making the Ni/Au ohmic contact on the minimum AlGaN graded bedding table top in both sides on the highest cap layer table top of centre.

With reference to Fig. 4, the high-power GaN MISFET device architecture of Sapphire Substrate of the present invention is followed successively by from bottom to top: Sapphire Substrate, GaN resilient coating, GaN intrinsic layer, AlN separator, AlGaN graded bedding, AlN cap layer.High both sides low ledge structure in the middle of wherein being etched with on AlGaN and AlN cap layer is being made the contact of Ni/Au gate metal, making the Ni/Au ohmic contact on the minimum AlGaN graded bedding table top in both sides on the highest cap layer table top of centre.

For those skilled in the art; after having understood content of the present invention and principle; can be under the situation that does not deviate from the principle and scope of the present invention; the method according to this invention is carried out various corrections and the change on form and the details, but these are based on correction of the present invention with change still within claim protection range of the present invention.

Claims (9)

1. GaN device based on component-gradient GaN MISFET, comprise bottom (1), resilient coating (2), intrinsic GaN material layer (3), AlN separator (4) and source, leakage, gate electrode, it is characterized in that on the AlN separator, being provided with successively AlGaN component-gradient layer (5) and AlN cap layer (6), the ledge structure that this AlGaN graded bedding and AlN cap layer constitute after by etching, and on each step surface, make ohmic contact and Metal Contact.
2. GaN device according to claim 1 is characterized in that making gate metal contact 8 on the table top of AlN cap layer (6), makes drain electrode ohmic contact (7) and source electrode ohmic contact (9) on the table top at AlGaN component-gradient layer (5) two ends respectively.
3. GaN device according to claim 1 is characterized in that the AlGaN layer at the Al component that is higher than near the Al component of AlN cap layer one side near AlN separator one side, with reduce that lattice mismatch causes heavily stressed with make the difficulty of ohmic contact.
4, the described GaN device of a kind of making claim 1 method comprises following process:
Extension one deck GaN resilient coating on Sapphire Substrate;
Deposit one deck GaN intrinsic material layer is as the service area of device on this resilient coating;
Deposit one deck AlN material is as separator on described GaN intrinsic layer;
Deposit AlGaN component-gradient layer on the AlN separator;
Deposit AlN cap layer on AlGaN component-gradient layer;
On AlGaN component-gradient layer and AlN cap layer, make mask, etch the step that is used for the contact of deposit gate metal, drain electrode and source electrode ohmic contact, at the diverse location depositing metal of step, make source electrode and the ohmic contact of drain electrode and the Metal Contact of grid respectively.
5. method according to claim 4, the pressure that it is characterized in that deposit AlGaN component-gradient layer on the AlN separator is 20Torr, and temperature is 1000 degree~1020 degree, and the Al component is for to be gradient to 50% from 10%, along with the increase of Al component, temperature is increased to 1020 degree gradually from 1000 degree.
6. want 4 described methods according to right, the temperature that it is characterized in that deposit AlN cap layer on AlGaN component-gradient layer is 1000 degree~1020 degree, and pressure is 20Torr.
7. make the described GaN device of claim 1 method for one kind, comprise following process:
Extension one deck AlN resilient coating on the SiC material substrate;
Deposit one deck GaN intrinsic material layer is as the service area of device on this resilient coating;
Deposit one deck AlN material is as separator on described GaN intrinsic layer;
Deposit AlGaN component-gradient layer on the AlN separator;
Deposit AlN cap layer on AlGaN component-gradient layer;
On AlGaN component-gradient layer and AlN cap layer, make mask, etch the step that is used for the contact of deposit gate metal, drain electrode and source electrode ohmic contact, at the diverse location depositing metal of step, make source electrode and the ohmic contact of drain electrode and the Metal Contact of grid respectively.
8. method according to claim 7, the temperature that it is characterized in that deposit AlN cap layer on AlGaN component-gradient layer are 1000 degree~1020 degree, and pressure is 20Torr.
9. method according to claim 7, the temperature that it is characterized in that deposit AlGaN component-gradient layer on the AlN separator is 1000 degree~1020 degree, and pressure is 20Torr, and the Al component is for to be gradient to 60% from 10%, along with the increase of Al component, temperature is increased to 1020 degree gradually from 1000 degree.
CNB2007100187728A 2007-09-29 2007-09-29 GaN device based on component-gradient GaN MISFET and preparing method thereof CN100511706C (en)

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