CN100424839C - Method for producing heavy blended gallium nitride field effect transistor - Google Patents
Method for producing heavy blended gallium nitride field effect transistor Download PDFInfo
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- CN100424839C CN100424839C CNB2006100860592A CN200610086059A CN100424839C CN 100424839 C CN100424839 C CN 100424839C CN B2006100860592 A CNB2006100860592 A CN B2006100860592A CN 200610086059 A CN200610086059 A CN 200610086059A CN 100424839 C CN100424839 C CN 100424839C
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Abstract
This invention provides a method for manufacturing heavy doped GaN field effect transistors including: growing a nucleation layer, a buffer layer and a channel layer on a substrate, then growing an AlN isolation layer and a heavy doped AlGaN potential barrier layer and finally making mesa-isolation and ohm contact to photo-etch a grating electrode window after growing a non-doped cap layer then to be processed by CF4 fluorin plasma process to control the emission power and process time to adjust the pinch off voltage to a designed sphere, then self-aligning the deposited grating metal on the barrier layer of the window to manufacture the Schottky barrier and annealing in the N2 atmosphere to eliminate defect generated in the plasma process to get the heavy doped field effect transistor.
Description
Technical field
The present invention relates to a kind of manufacture method of semiconductor device, especially a kind of manufacture method of heavy doping variant barrier gallium nitride FET, specifically a kind of method of making heavy blended gallium nitride field effect transistor.
Background technology
GaAs HFET mixes in barrier layer, and the electron transfer that the impurity ionization produces forms two-dimensional electron gas in raceway groove, reached good radio-frequency performance.This modulation doping method is transplanted among the GaN HFET, and the device of early stage research all mixes in barrier layer.Yet nitride is a kind of polar semiconductor, has very strong polarization charge and very big can be with rank on the AlGaN/GaN heterogeneous interface.Barrier layer undopes and just can produce 10
13/ cm
2The high electron gas density of magnitude.Whether also needing mixes in barrier layer more further improves electron gas density just becomes the focus that everybody discusses.
Electron gas density among the GaN HFET is than the high magnitude of GaAs HFET.High electron gas density has improved leakage current and power output.But thing followed major issue is how to control high like this electron gas density.In field effect transistor, the channel electrons air tightness is subjected to gate electrode control.Barrier layer thickness is thin more, and gate electrode is near more from electron gas, and is just big more to the control dynamics of electron gas.In order to improve the operating efficiency of device, must reduce the quiescent current of device as far as possible.Therefore, all in dark AB class work, the quiescent current of device has only 3～5% of maximum leakage current to high power device.In the radio frequency negative half period, raceway groove is all by pinch off.Therefore, the pinch off behavior of device usually is the key factor that influences device performance.Along with electron gas density increases, pinch-off voltage reduces.Under strong minus gate voltage, very strong electric field peak appears in the raceway groove.Electronics is quickened the back by highfield and just transits to surface state easily, produces current collapse.Therefore the pinch-off voltage of high-power H FET all is not less than-5V.In order to reach this pinch-off voltage, must be when improving electron gas density, the attenuate barrier layer thickness increases the control dynamics of grid to electron gas, and the nW product becomes a constant.But when barrier layer was too thin, the probability that channel electrons is tunneling to surface state increased greatly, produced the heavy current avalanche.Thereby the concentration of electron gas can not be too big, has a nW product upper limit.Many researchers find that the material that electron gas density is too high can not produce high-power device.At present, among the high-performance GaN HFET of development, the nW product all remains on 2.5～3 * 10 both at home and abroad
7In/cm the scope.Constitute the upper limit of electron gas density.
The electron gas upper density limit directly has influence on the modulation doping problem among the GaN HFET.Many authors have compared the performance of the doping and the potential barrier device that undopes from experiment.Find that the doping device has higher leakage current, mutual conductance and power output, and current collapse a little less than.But, being subjected to the constraint of electron gas upper density limit, the doping in the barrier layer all is not more than 5*10
12/ cm
2, mixing only makes the channel electrons air tightness improve 2～2.5 * 10
12/ cm
2, the electron gas density in the raceway groove.From present foreign study result, this limited doping does not demonstrate in GaAs HFET effect big the modulation doping.The barrier layer doping has increased the electric field strength under the grid metal, has increased the tunnelling current of gate electrode.Also reduced the mobility and the increase 1/f noise of two-dimensional electron gas in the raceway groove simultaneously.Particularly on the doping potential barrier layer, can not make Schottky barrier, just can not grooving.Its limitation is all arranged in many aspects.Present most of high-power component all is to make of undoping potential barrier.How to bring into play the modulation doping advantage and further improve device performance, become the new problem that everybody is concerned about.
Solve the above-mentioned predicament of modulation doping, at first must further investigate the control of gate electrode raceway groove.The structure that Fig. 1 has drawn HFET.1,2 and 3 represent source, grid and leakage respectively.5 and 6 refer to AlGaN and GaN layer respectively.On the AlGaN barrier layer surface 4 between grid and the drain electrode, can accumulate certain negative electrical charge during device work, the electron gas density in the following raceway groove of these charge energies influences.Thereby form grid that do not have metal, usually it is called empty grid.The voltage of gate electrode and empty grid is different, and the electron gas density in the raceway groove 7 and 8 below them also is different.For discussing conveniently, the raceway groove under the gate electrode 7 is called interior raceway groove, and the raceway groove under the empty grid 8 is called outer raceway groove.During the device radio frequency operation, control interior raceway groove with gate electrode, outer raceway groove wishes that then it opens always, reduces series resistance as far as possible.In high-frequency element, grid are long very short, and raceway groove is longer in the outer fissure channel ratio, form complicated electric field and electron gas density distribution in whole raceway groove.Theoretical and experimental studies have found that interior raceway groove quantum well is depended in the pinch off behavior of device, and the leakage current of raceway groove when opening mainly is limited by outer raceway groove quantum well.If we are heavy doping in barrier layer, outer raceway groove potential barrier is very low, and electron gas density is very high, can reach very high leakage current.And the potential barrier of raceway groove in suitably improving, still can be controlled at pinch-off voltage-3～-5V, do not cause the heavy current avalanche.Break through the restriction of nW product, solved the contradiction between interior raceway groove pinch off and electron gas concentration.
But, also have very strong interaction between inside and outside raceway groove.Add minus gate voltage make in during the raceway groove pinch off, in the outer raceway groove near the grid edge a very strong electric field peak appears.The high energy hot electron transits to surface state, gives empty grid charging, makes outer raceway groove part pinch off.When raceway groove was opened in grid voltage rises, the negative electrical charge on the empty grid had limited opening of outer raceway groove, just produces current collapse.Expect easily that if heavy doping in barrier layer make electron gas density in the outer raceway groove much larger than the existing nW product upper limit, so outer raceway groove just can not be by pinch off, current collapse will alleviate greatly.
In sum, manufacture and design different inside and outside raceway groove potential barriers and just become the electron gas upper density limit of breaking through in the above-mentioned modulation doping, the key that increases device creepage and inhibition current collapse.
Summary of the invention
The objective of the invention is to cause its performance can not improved problem owing to doping can't improve at existing gallium nitride FET, invent and a kind ofly can carry out heavy doping gallium nitride FET, again can be because of heavy doping does not cause common current collapse phenomenon, thus can enlarge markedly the method for the manufacturing heavy blended gallium nitride field effect transistor of power output.
Technical scheme of the present invention is:
A kind of method of making heavy blended gallium nitride field effect transistor is characterized in that it may further comprise the steps:
At first on substrate 9, grow into stratum nucleare 10, resilient coating 11 and channel layer 12; Growing AIN separator 13 and heavy doping AlGaN barrier layer 14 then, the thickness of controlled doping layer 14 and doping content make it to reach 10
13/ cm
2The highly doped amount of magnitude to increase the electron gas density in the outer raceway groove, improves leakage current, make outer raceway groove radio frequency operation in the cycle not by pinch off, utilize the outer raceway groove electron gas of high density to stabilize electric field peak in the raceway groove simultaneously, stop the high energy hot electron to be tunneling to empty grid surface, suppress current collapse; Undope cap layer 15 after mesa-isolated, ohmic contact are made back photoetching gate electrode window in growth at last, and use CF
1(carbon tetrafluoride) carries out fluoro plasma and handles, control plasma emission power is between 100-150W, processing time is between 120-180s, to realize pinch-off voltage is adjusted to the purpose of setting range, autoregistration deposit grid metal on the barrier layer of institute's windowing is again made Schottky barrier and at N
2Anneal in the atmosphere and promptly get heavy doping field-effect transistor of the present invention with the defective of eliminating the plasma treatment generation.
The present invention has the following advantages:
(1) make Schottky barrier after fluoro plasma is handled, the barrier height in effectively controlling on the raceway groove is under the different barrier heights inside and outside raceway groove, has different electron gas density in the inside and outside raceway groove.The pinch off behavior of raceway groove no longer is limited by original nW product limit.Can enough strong doping significantly improve electron gas density, increase leakage current, improve power output.
(2) the heavy doping barrier layer has improved the electron gas density of outer raceway groove, and its nW product has improved nearly one times.Raceway groove can not be by pinch off outside under the radio-frequency voltage swing.In addition, high electron gas density helps stabilizing the electric field peak in the outer raceway groove, and reduction hot electron tunnelling reduces current collapse.Therefore, this novel HFET can effectively suppress current collapse.
(3) after fluoro plasma is handled, make Schottky gate, improved barrier height, reduced grid current.
(4) this device does not need special grooving and field plate technology.Both simplify technology, reduced parasitic parameter again, improved gain, helped developing the millimeter wave high-frequency element.
(5) the high electron gas density in the outer raceway groove has reduced series resistance, helps improving mutual conductance, the f of device
TAnd f
Max
Description of drawings
Fig. 1 is an AlGaN/GaN HFET structure chart of the present invention.
1 is the source among Fig. 1, the 2nd, and grid, the 3rd, leak, the 4th, empty grid, the 5th, AlGaN potential barrier, the 6th, GaN, the 7th, interior raceway groove, the 8th, outer raceway groove
Fig. 2 is the material structure figure of variant barrier modulation doping GaN HFET of the present invention.
9 is substrates among Fig. 2, the 10th, and nucleating layer, the 11st, resilient coating, the 12nd, channel layer, the 13rd, the AlN separator, the 14th, doped with Al GaN barrier layer, the 15th, AlGaN cap layer undopes
Embodiment
The present invention is further illustrated for following structure drawings and Examples.
As shown in Figure 2.
A kind of method of making heavy blended gallium nitride field effect transistor is at first to grow into stratum nucleare 10, resilient coating 11 and channel layer 12 on substrate 9, growing AIN separator 13 and heavy doping AlGaN barrier layer 14 then, the cap layer 15 that undopes of growth at last.The thickness of controlled doping layer 14 and doping content reach 10
13/ cm
2The high-concentration dopant of magnitude.Enlarge markedly the electron gas density in the outer raceway groove, both improved leakage current, make again outer raceway groove radio frequency operation in the cycle not by pinch off.Simultaneously stabilize electric field peak in the raceway groove, stop the high energy hot electron to be tunneling to empty grid surface, suppress current collapse by the outer raceway groove electron gas of high density.The pinch-off behavior of interior raceway groove can be used unit are channel capacitance C
eDescribe.At pinch-off voltage V
TDown, electron gas density reduces to zero by n, therefore
ε and ε in the formula
0Be respectively relative dielectric constant and permittivity of vacuum.Obtain easily thus
The nW product substitution that characterizes the existing doping upper limit is calculated, obtain pinch-off voltage to be about～-5V.The raceway groove potential barrier is than the high 5V of outer raceway groove potential barrier in supposing, the electron gas density of so outer raceway groove just can double than the existing doping upper limit.Enlarge markedly leakage current density.
Photoetching gate electrode window after mesa-isolated, ohmic contact are made is used CF
4(carbon tetrafluoride) carries out fluoro plasma and handles, control plasma emission power is between 100-150W, processing time is at 120-180 between second, to realize pinch-off voltage is adjusted to the purpose of setting range, autoregistration deposit grid metal on the barrier layer of institute's windowing is again made Schottky barrier and at N
2Anneal in the atmosphere and promptly get heavy doping field-effect transistor of the present invention with the defective of eliminating the plasma treatment generation.Then at N
2Anneal in the atmosphere, eliminate the defective that plasma treatment produces.Use this fluoro plasma treatment process to improve barrier height on the gate electrode, make variant barrier HFET.
Below be the concrete Production Example of utilizing said method:
Concrete Production Example 1: get cap layer thickness d
7=2nm, doping bed thickness d
6=20nm, doping content is 10
19Cm
-3, isolate bed thickness d
5=1nm, the Al component ratio of barrier layer is 0.3.Find the solution Schrodinger equation and the Poisson's equation electron gas density when drawing barrier layer and mixing and undope and be respectively 2.27*10 from being in harmony
13/ cm
2And 1.24*10
13/ cm
2With formula (2) calculate pinch-off voltage be respectively-10.1V and-5.5V.Pinch-off voltage just in time meets said n W rule when undoping, and raceway groove can normal pinch off.For doping potential barrier, use fluoro plasma handle (control plasma emission power between 100-150W, processing time at 120-180 between second) make in the raceway groove potential barrier improve 5V, then the pinch-off voltage of interior raceway groove is-5.1V.Satisfy the nW rule equally, can normal pinch off.And the pinch-off voltage of outer raceway groove is-10.1V.During the device radio frequency operation, the voltage swing on the empty grid is always less than the voltage swing of gate electrode.Therefore, whole rf period China and foreign countries' raceway groove can not produced significant current collapse by pinch off.Modulation doping makes outer raceway groove electron gas density from 1.24*10
13/ cm
2Bring up to 2.27*10
13/ cm
2, leakage current will improve nearly one times.
Concrete Production Example 2:, usually make the lower structure of Al component in order to reduce the strain in the heterojunction.Suppose that Al component ratio is 0.25.Other structure is identical with example 1.Electron gas density when then barrier layer mixes and undopes is respectively 2.03*10
13/ cm
2And 1.01*10
13/ cm
2With formula (2) calculate pinch-off voltage be respectively-9.04V and-4.5V.Plain pinch-off voltage is-4.5V to meet said n W rule, the normal pinch off of raceway groove energy.For doping potential barrier, use fluoro plasma handle (control plasma emission power between 100-150W, processing time at 120-180 between second) make in the raceway groove potential barrier improve 5V, then the pinch-off voltage of interior raceway groove is-4.04V.Satisfy the nW rule equally, can normal pinch off.And the pinch-off voltage of outer raceway groove is-9.04V.Whole rf period China and foreign countries' raceway groove can not produced significant current collapse by pinch off.Modulation doping makes outer raceway groove electron gas density from 1.01*10
13/ cm
2Bring up to 2.03*10
13/ cm
2, leakage current will improve nearly one times.
Concrete Production Example 3: when Al component ratio was lower, electron gas density reduced, and can suitably increase barrier layer thickness W and improve electron gas density.Getting Al component ratio is 0.2, doping bed thickness d
6=25nm, doping content is 8*10
18Cm
-3Electron gas density when at this moment, barrier layer mixes and undopes is respectively 1.81*10
13/ cm
2And 7.88*10
12/ cm
2With formula (2) calculate pinch-off voltage be respectively-9.82V and-4.27V.Plain pinch-off voltage-4.27V also meets said n W rule, and raceway groove can normal pinch off.After barrier layer mixes, use fluoro plasma handle (control plasma emission power between 100-150W, processing time at 120-180 between second) make in the raceway groove potential barrier improve 5V, then the pinch-off voltage of interior raceway groove is-4.82V.Also in the nW scope that requires, energy is pinch off normally.And the pinch-off voltage of outer raceway groove is-9.82V.Whole rf period China and foreign countries' raceway groove can not produced significant current collapse by pinch off.Modulation doping makes outer raceway groove electron gas density from 7.88*10
12/ cm
2Bring up to 1.81*10
13/ cm
2, leakage current will improve nearly one times.
Claims (1)
1. method of making heavy blended gallium nitride field effect transistor is characterized in that it may further comprise the steps:
At first on substrate (9), grow into stratum nucleare (10), resilient coating (11) and channel layer (12); Growing AIN separator (13) and heavy doping AlGaN barrier layer (14) then, the thickness and the doping content of controlled doping layer (14) make it to reach 10
13/ cm
2The highly doped amount of magnitude to increase the electron gas density in the outer raceway groove, improves leakage current, make outer raceway groove radio frequency operation in the cycle not by pinch off, utilize the outer raceway groove electron gas of high density to stabilize electric field peak in the raceway groove simultaneously, stop the high energy hot electron to be tunneling to empty grid surface, suppress current collapse; Undope cap layer (15) after mesa-isolated, ohmic contact are made back photoetching gate electrode window in growth at last, and use CF
1Carrying out fluoro plasma handles, control plasma emission power is between 100-150W, and the processing time is between 120-180s, to realize pinch-off voltage is adjusted to the purpose of setting range, autoregistration deposit grid metal on the barrier layer of institute's windowing is again made Schottky barrier and at N
2Anneal in the atmosphere and promptly get the heavy doping field-effect transistor with the defective of eliminating the plasma treatment generation.
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| CN101459080B (en) * | 2007-12-12 | 2010-04-14 | 中国科学院微电子研究所 | Method for manufacturing gallium nitride-based field effect transistor |
| CN102064108B (en) * | 2010-11-12 | 2014-11-26 | 中国电子科技集团公司第五十五研究所 | Method for manufacturing medium/nitride composite structure enhanced field effect transistor |
| CN108807526B (en) | 2012-04-20 | 2021-12-21 | 苏州晶湛半导体有限公司 | Enhanced switching device and method of making same |
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|---|---|---|---|---|
| CN1753196A (en) * | 2004-09-23 | 2006-03-29 | 璨圆光电股份有限公司 | N type contact layer structure of gallium nitride multiple quantum trap luminous diode |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1753196A (en) * | 2004-09-23 | 2006-03-29 | 璨圆光电股份有限公司 | N type contact layer structure of gallium nitride multiple quantum trap luminous diode |
Non-Patent Citations (6)
| Title |
|---|
| AlGaN/GaN异质结构欧姆接触的研制. 焦刚，曹春海，薛舫时，杨立杰等.固体电子学研究与进展，第24卷第1期. 2004 |
| AlGaN/GaN异质结构欧姆接触的研制. 焦刚，曹春海，薛舫时，杨立杰等.固体电子学研究与进展，第24卷第1期. 2004 * |
| GaN HFET研究的最新进展. 薛舫时.微纳电子技术，第9期. 2004 |
| GaN HFET研究的最新进展. 薛舫时.微纳电子技术，第9期. 2004 * |
| III族氮化物HFET中的电流崩塌和二维电子气. 薛舫时.微纳电子技术，第1期. 2004 |
| III族氮化物HFET中的电流崩塌和二维电子气. 薛舫时.微纳电子技术，第1期. 2004 * |
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