CN203733810U - HEMT gate leakage current separating structure based on capacitance structure - Google Patents
HEMT gate leakage current separating structure based on capacitance structure Download PDFInfo
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- CN203733810U CN203733810U CN201320766525.7U CN201320766525U CN203733810U CN 203733810 U CN203733810 U CN 203733810U CN 201320766525 U CN201320766525 U CN 201320766525U CN 203733810 U CN203733810 U CN 203733810U
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Abstract
The utility model discloses an HEMT gate leakage current separating structure based on a capacitance structure. The HEMT gate leakage current separating structure includes two annular Schottky gate capacitors with different areas, namely, a first Schottky capacitor and a second Schottky capacitor; each capacitor is of a two-end structure and includes a gate electrode and an ohmic electrode; the shape of the Schottky gate of the second Schottky capacitor is a ring deposited with no gate metal on the middle part, the outer ring radius of the gate is equal to the radius of the first Schottky capacitor, and the inner ring radius is 0.707 times as large as the radius of the first Schottky capacitor; the distances between the gate electrodes and the ohmic electrodes of the two Schottky capacitors are equal. The HEMT gate leakage current separating structure disclosed by the utility model has the characteristics of simple structure and reliable result, and can be extensively applied to such works as material growth and device process optimization of HEMT devices and subsequent reliability evaluation, and the like.
Description
Technical field:
The utility model belongs to a kind of HEMT grid leakage current isolating construction based on capacitance structure.
Background technology:
GaN material has good electrology characteristic, as wide energy gap, high breakdown electric field, higher thermal conductivity, corrosion-resistant, radioresistance etc., be described as third generation semi-conducting material, there is the two-dimensional electron gas of high concentration, high mobility in the heterostructure transistors (HEMT) that especially material such as itself and AlGaN forms, has huge advantage and application prospect at aspects such as making high frequency, high temperature, high pressure, high power electronic device and microwave device at heterojunction boundary place.In recent years, researcher has carried out research extensively and profoundly to HEMT device both at home and abroad, and has obtained considerable progress.
Although GaN HEMT is having advantageous advantage aspect high temperature, high frequency and High-Power Microwave device, but integrity problem is to affect it to realize the significant obstacle that large-scale commercial is applied, wherein grid leakage current is a key factor that causes integrity problem.Conventionally, HEMT device selects metal as grid material, and the Schottky gate that this metal/semiconductor forms tends to form obvious grid leakage current, and then affects electric property and the long-term reliability of HEMT device.Such as, increase noise and quiescent dissipation, inducing current avalanche phenomenon under low frequency of HEMT device, reduce device efficiency and reduce the puncture voltage of HEMT device and then reduce power output etc.Therefore, extremely important for the research of HEMT device grid leakage current.
Due to the design feature of HEMT device, its grid leakage current often comprises three parts: body leakage current I
bulk, surface leakage current I
surf(as shown in Figure 1) and mesa edge leakage current, wherein mesa edge leakage current can be realized control by special process at present, thereby first two leakage current is occupied an leading position in grid leakage current.The formation mechanism of body leakage current and surface leakage current is each different, therefore in order to carry out targetedly correlative study, certainly will will carry out Quantitative Separation to this two parts electric current.But up to the present, conventional test structure often can not be realized Quantitative Separation to them, can only carry out general test.In recent years, there is researcher to propose the HEMT device Schottky gate current separation structure based on double grid.This structure is isolated surface leakage current by increase an electrode between grid and drain electrode ohmic contact.But this structure makes the structurally difference to some extent of it and conventional H EMT device, is not easy to for studying electric property and the degenerate case of HEMT device under actual working state.
Generally speaking, up to the present, especially effectively do not carry out the method for Quantitative Separation for HEMT device Schottky gate leakage current.This also gives relevant Material growth and the device technology optimization of HEMT device, and the research of component failure mechanism and Performance Evaluation etc. are further studied and brought certain difficulty.
Summary of the invention:
The utility model object is to provide a kind of HEMT grid leakage current isolating construction based on capacitance structure, is HEMT device material growth and device technology optimization, and defect sign, reliability assessment etc. are offered help.
In order to solve the existing problem of background technology, the utility model by the following technical solutions:
A HEMT grid leakage current isolating construction based on capacitance structure, comprises two annular Schottky gate electric capacity with different area: first Schottky electric capacity and second Schottky electric capacity;
Each electric capacity is two-end structure, comprises a gate electrode and an Ohmic electrode;
Second Schottky electric capacity, its Schottky gate is the annular that mid portion does not have deposit grid metal, the outer shroud radius of grid equates with the radius of first Schottky electric capacity, 0.707 times of the radius that interior ring radius is first Schottky electric capacity;
Distance between the grid-Ohmic electrode of two Schottky electric capacity is identical.
When this structure separates for HEMT grid leakage current, step comprises:
(1) when keeping Ohmic electrode ground connection, apply negative voltage at the grid of above-mentioned two devices respectively, seal in an ammeter at grid, measure the size of the grid current of each electric capacity under same voltage simultaneously.
(2), according to the test result of grid current, in conjunction with the difference of two device grid physical dimensions, by the method such as numerical computations when, realize the Quantitative Separation of body leakage current and surface leakage current in HEMT device Schottky gate leakage current.
Further, in step (2), for first Schottky electric capacity, suppose at certain grid voltage V
gunder biasing, body leakage current and surface leakage current are designated as respectively I
bulkand I
surf, their sums are the result I measuring
g, 1, its relation is as the following formula shown in (1); And for second Schottky electric capacity, same grid voltage V
gunder biasing, body leakage current size should be 0.5I
bulk, surface leakage current size is still I
surf, their sums are the Schottky gate leakage current I that actual measurement obtains
g, 2, its relation is as the following formula shown in (2);
I
g, 1=I
bulk+ I
surfformula (1)
I
g, 2=0.5I
bulk+ I
surfformula (2)
The above-mentioned formula of simultaneous (1) (2), can calculate:
I
bulk=2(I
g,1-I
g,2)
I
surf=2I
g,2-I
g,1。
The utility model contrast prior art has following beneficial effect: the current separation that the utility model proposes is simple in structure, be easy to realize, and is applicable to any conventional HEMT device; Use conventional semiconductor parametric test equipment, only by the electrical measurement on two Schottky gate electric capacity, in conjunction with simple numerical computations, can obtain the size of body leakage current and surface leakage current in HEMT device Schottky gate leakage current.Therefore, have that structure and method are simple, the feature of reliable results, can be widely used in the work such as the Material growth of HEMT device and device technology optimization and follow-up reliability assessment.
Brief description of the drawings:
Fig. 1 is grid leakage current component schematic diagram in loop configuration HEMT;
Fig. 2 is conventional HEMT device grid leakage current testing structural circuit schematic diagram;
The circular Schottky gate capacitance structure schematic diagram that Fig. 3 adopts for the utility model;
Fig. 4 is the test result schematic diagram based on the utility model test structure;
Fig. 5 is the leakage current separating resulting schematic diagram of realizing based on test structure of the present utility model;
Fig. 6 is the affect schematic diagrames of different gate electrode-Ohmic electrodes apart from effects on surface leakage current.
Embodiment:
Below in conjunction with the drawings and specific embodiments, the utility model is further described:
Fig. 1 is grid leakage current component schematic diagram in loop configuration HEMT, (a) profile, (b) top view.Typical loop configuration HEMT comprises two electrodes: schottky gate electrode (Schottky Gate) and Ohmic electrode (Ohmic).The grid leakage current of HEMT device is the key factor that affects device property.As shown in figure (a), HEMT device grid leakage current mainly comprises two parts: the lateral surfaces leakage current (I between Schottky gate and ohmic contact
surf) with the body leakage current (I that forms by barrier layer perpendicular to Schottky gate surface
bulk); Figure (b) is the top view of annular HEMT structure, surface leakage current I
surfmainly produced by the high electric field between Schottky gate and Ohmic electrode.The utility model is based on conventional H EMT material structure, adopt circular Schottky gate electric capacity, periphery is annular Ohmic electrode, therefore in the Schottky gate leakage current of this structure, does not have the etching table top leakage current in conventional H EMT device, and grid leakage current is mainly by body leakage current I
bulkwith surface leakage current I
surftwo parts composition.
Fig. 2 is conventional HEMT device grid leakage current testing structural circuit schematic diagram.In measurement, conventionally keep Ohmic electrode ground connection, seal in an ammeter at grid, and apply negative voltage V
g, record corresponding electric current, be grid leakage current I
g, its occlusion body leakage current (I
bulk) and surface leakage current (I
surf) two parts.
Fig. 3 is the annular Schottky capacitance structure schematic diagram that the utility model adopts.Its structure mainly comprises two independently annular Schottky electric capacity.Each electric capacity comprises a gate electrode, an Ohmic electrode.For first Schottky electric capacity (electric capacity-1), its Schottky gate is circular, and radius is R
1, therefore its area is π R
1 2, girth is 2 π R
1.Second Schottky electric capacity (electric capacity-2), its Schottky gate is annular (mid portion does not have deposit grid metal), the outer shroud radius of grid is R
1, interior ring radius is 0.707R
1, therefore the real area of Schottky gate is 0.5 π R
1 2, the girth of Schottky gate is still 2 π R
1.In order to make surface leakage current there is comparativity, must guarantee that the electric field between gate electrode and Ohmic electrode is identical, therefore the distance between the grid-Ohmic electrode of above-mentioned two devices is identical, is (R
2-R
1).Above-mentioned two electric capacity have formed one group of isolating construction for body leakage current and surface leakage current in HEMT Schottky gate leakage current.
Fig. 4 is the test result schematic diagram based on the utility model test structure.Based on two kinds of loop configuration Schottky electric capacity in Fig. 3, adopt Fig. 2 method of measurement and the grid leakage current that obtains and the relation curve of voltage bias.Ordinate is absolute value (the occlusion body leakage current I of the grid leakage current that measures
bulkand surface leakage current I
surftwo parts), abscissa is the voltage bias between annular capacitor grid and Ohmic electrode, numerical value is for negative.The wherein measurement result of electric capacity-1 in heavy line presentation graphs 3, and the measurement result of electric capacity-2 in dotted line presentation graphs 3.P, 2 of Q represent respectively under same bias voltage, and the grid leakage current measuring on electric capacity-1, electric capacity-2 is I
g, 1, I
g, 2.
Fig. 5 is the leakage current separating resulting schematic diagram of realizing based on the utility model test structure.
According to the method for Fig. 2, on the grid of above-mentioned two Schottky electric capacity, apply respectively continuous negative sense scanning voltage, can obtain grid leakage current I
gwith gate bias voltage V
gcorresponding relation curve I
g～V
g, as shown in Figure 4.For fear of the impact of the effects such as contrary piezoelectricity, gate bias voltage V
gselection should be moderate.
According to the mechanism of production of HEMT device grid leakage current, body leakage current I
bulkresult from the golden half hitch that metal gate/semi-conducting material forms, therefore, under same grid-Ohmic electrode electric field, its size is directly proportional to the area of metal/semiconductor knot, and surface leakage current I
surfresult from the surface field between schottky gate electrode and Ohmic electrode, therefore in circular Schottky gate, in the situation that between gate electrode and Ohmic electrode, surface field is certain, I
surfbe directly proportional to the girth of Schottky gate.
Taking the structure in this experiment as example, for first Schottky electric capacity (electric capacity-1 of Fig. 3), suppose at certain grid voltage V
gunder biasing, body leakage current and surface leakage current are designated as respectively I
bulkand I
surf, their sums are the result I measuring
g, 1(some P), its relation is as the following formula shown in (1); And for second Schottky electric capacity (electric capacity-2 of Fig. 3), same grid voltage V
gunder biasing, because the area of Schottky gate reduces half, the relation being directly proportional to Schottky gate area according to body leakage current, its body leakage current size should be 0.5I
bulk, and its Schottky gate girth is constant, therefore surface leakage current size is still I
surf, their sums are the Schottky gate leakage current I that actual measurement obtains
g, 2(some Q), its relation is as the following formula shown in (2).
I
g,1=I
bulk+I
surf（1）
I
g,2=0.5I
bulk+I
surf（2）
The above-mentioned formula of simultaneous (1) (2), can calculate:
I
bulk=2(I
g,1-I
g,2)
I
surf=2I
g,2-I
g,1
Also be R for gate electrode radius
1, grid and Ohmic electrode spacing are (R
2-R
1) annular Schottky electric capacity, the grid leakage current I that it is total
g,
1in the body leakage current I that comprises
bulkand surface leakage current I
surfbe respectively 2 (I
g, 1-I
g, 2), 2I
g, 2-I
g, 1.Based on the method, in conjunction with the measurement result of Fig. 4, can calculate electric capacity-1 at any gate bias voltage V
gunder body leakage current and surface leakage current, as shown in Figure 5, and then realized the separation of different component leakage current in circular Schottky electric capacity grid leakage current.
The i.e. measurement result based on obtaining in Fig. 4, in conjunction with equation (1) and (2), can obtain two kinds of grid leakage current I of electric capacity-1 in Fig. 3
surfwith I
bulk.
Above-mentioned grid leakage current isolating construction and method can also be used for the correlative study of HEMT device.Fig. 6 is the affect schematic diagrames of different gate electrode-Ohmic electrodes apart from effects on surface leakage current.Along with the development of HEMT device, device size is more and more less, and the distance of schottky gate electrode and Ohmic electrode is more and more less, and the impact of its effects on surface grid leakage current is increasing, therefore more and more important to its quantitatively characterizing.Based on the loop configuration in Fig. 3, the distance that changes schottky gate electrode and Ohmic electrode (is also (R
2-R
1) size), the separation method that utilizes the present invention to propose, can obtain the affect relation of the lower different gate electrode-Ohmic electrodes of fixed voltage biasing apart from effects on surface leakage current, for the design of small size HEMT device provides guidance.
The utility model adopts two area differences, but the on all four annular Schottky gate electric capacity such as girth, device architecture and preparation technology, the mechanism of production different from surface leakage current according to body leakage current, can obtain the relation between them.In conjunction with the grid leakage current of actual measurement on two Schottky gate electric capacity under identical gate bias voltage, can quantitatively calculate the size of different component in grid leakage current.Current separation that this structure proposes is simple in structure, be easy to realize, and is suitable for any conventional HEMT device; Only need to use conventional semiconductor parametric test equipment, by simple electrical measurement, in conjunction with correlation computations, can obtain reliable result.Therefore, there is feature simple in structure, reliable results, in the work such as the Material growth, defect that can be widely used in HEMT device characterizes, device technology optimization and follow-up reliability assessment.
The foregoing is only preferred embodiment of the present utility model; not in order to limit the utility model; obviously for those skilled in the art; understanding after content of the present invention and principle; any amendment of doing within spirit of the present utility model and principle, be equal to and replace and improvement etc., within all should being included in protection range of the present utility model.
Claims (1)
1. the HEMT grid leakage current isolating construction based on capacitance structure, is characterized in that, comprises two annular Schottky gate electric capacity with different area: first Schottky electric capacity and second Schottky electric capacity;
Each electric capacity is two-end structure, comprises one and draws together gate electrode and an Ohmic electrode;
Second Schottky electric capacity, its Schottky gate is the annular that mid portion does not have deposit grid metal, the outer shroud radius of grid equates with the radius of first Schottky electric capacity, 0.707 times of the radius that interior ring radius is first Schottky electric capacity;
Distance between the grid-Ohmic electrode of two Schottky electric capacity is identical.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103646968A (en) * | 2013-11-27 | 2014-03-19 | 西安电子科技大学 | A HEMT gate leakage current separating structure and method based on capacitor structure |
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|---|---|---|---|---|
| CN103646968A (en) * | 2013-11-27 | 2014-03-19 | 西安电子科技大学 | A HEMT gate leakage current separating structure and method based on capacitor structure |
| CN103646968B (en) * | 2013-11-27 | 2017-01-11 | 西安电子科技大学 | A HEMT gate leakage current separating structure and method based on capacitor structure |
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| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20140723 Termination date: 20141127 |
|
| EXPY | Termination of patent right or utility model |