CN103094360A - Variable capacitor and manufacturing method thereof - Google Patents
Variable capacitor and manufacturing method thereof Download PDFInfo
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- CN103094360A CN103094360A CN2012102569997A CN201210256999A CN103094360A CN 103094360 A CN103094360 A CN 103094360A CN 2012102569997 A CN2012102569997 A CN 2012102569997A CN 201210256999 A CN201210256999 A CN 201210256999A CN 103094360 A CN103094360 A CN 103094360A
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Abstract
The invention provides a variable capacitor and a manufacturing method thereof. The variable capacitor comprises a high-resistance gallium nitride (GaN) layer, a high-mobility GaN layer, an aluminum(Al) GaN barrier layer and a metal layer, wherein the high-resistance GaN layer, the high mobility GaN layer, the AlGaN barrier layer and the metal layer are sequentially arranged. The manufacturing method comprises the steps that: a buffering layer is grown on a substrate; the high-resistance GaN layer and the high-mobility GaN layer are sequentially grown on the buffering layer; the AlGaN barrier layer is grown on the high-mobility GaN layer; an isolation land is corroded on the AlGaN barrier layer in an inductively coupled plasma (ICP)- reactive ion etching (RIE) method; photoresist is coated, photoetching, exposure and developing are conducted, and a schottky electrode pattern is formed; and then the metal layer is evaporated through electron beams, and the variable capacitor can be formed after the photoresist is peeled off. By means of the variable capacitor and the manufacturing method thereof, the variable capacitor which is compatible with a high electron mobility transistor (HEMT) process can be achieved on the GaN substrate, and important meaning is brought to achievement of circuits of low-noise amplifiers (LNAs), voltage controlled oscillators (VCOs), mixers and the like.
Description
Technical field
The invention belongs to microelectronics technology, relate to semiconductor device and integrated circuit fabrication process technology, be specifically related to a kind of variable capacitance and preparation method thereof.
Background technology
Along with the development of wireless communication field in recent years, and the progress of military technological applications (such as radar system etc.), require progressively to improve for the indices of Microwave Power Tubes.Because the GaN breakdown strength of material is large and the electronics saturation drift velocity is high, more have superiority than the device based on conventional semiconductor material in high-frequency high-power is used based on the device of GaN base.As GaN based hemts (High Electron Mobility Transistor) device, its high-output power density makes and can reach identical power output with the smaller szie device.And high impedance loss when the input-output adapt ation of amplifier that small size device causes is less.And because the device breakdown electric field is larger, can bear higher puncture voltage, not only not need voltage transitions when making its work, also might obtain higher efficient, another important indicator when this is also amplifier work.In addition, the broad stopband can make the GaN base device be operated under hot conditions, and this is significant for military fields such as space flight, aviations.The HEMT device is than MESFET(Metal-Semiconductor FET in addition, metal-semiconductor field effect transistor) noise of device is less.
Development along with Modern Communication System and electronic technology, the application that passive component such as inductance capacitance etc. and active device are integrated on chip piece is more and more extensive, because can reduce on a large scale chip area like this, save cost, sort circuit also is known as monolithic integrated circuit (MMIC).Low noise amplifier (LNA) that the GaN monolithic integrated circuit makes, voltage controlled oscillator (VCO), power amplifier (PA) etc. have been reported at present abroad.In GaN MMIC, need a large amount of planar spiral inductor, electric capacity of using.These performance of devices directly affect the overall performance of monolithic integrated circuit.Therefore, design with HEMT process compatible and well behaved passive device and become very important.
Because the AlGaN/GaN chemical property is different from silicon, have different places at making variable capacitance on GaN from make electric capacity on silicon, the wide variable capacitance of making and transistor technology compatibility and adjustable extent seems particularly important.
Summary of the invention
The object of the invention is for the problems referred to above, a kind of variable capacitance and preparation method thereof is provided, can with standard A lGaN/GaN HEMT process compatible, the metal-semiconductor-metal of made (MSM) variable capacitance has wide adjustable extent, and there are high quality factor at the place at minimum and maximum capacitance.
For achieving the above object, the present invention adopts following technical scheme:
A kind of variable capacitance comprises the high resistant GaN layer, high mobility GaN layer, AlGaN barrier layer and the metal level that are arranged in order.
Further, the thickness of described resistive formation is 2.0 ~ 2.5 μ m, and the thickness of described high mobility layer is 150 ~ 200nm, and the thickness of described AlGaN barrier layer is 20 ~ 30nm.
Further, described metal level comprises Ni layer and Au layer, shown in the Ni layer as the adhesive layer of described AlGaN barrier layer and described Au layer; Wherein the Ni layer thickness is 20 ~ 50nm, and the Au layer thickness is 150 ~ 250nm.
A kind of method of making above-mentioned variable capacitance, its step comprises:
1) at the Grown resilient coating;
2) growing high resistant GaN layer and high mobility GaN layer successively on described resilient coating;
3) growth AlGaN barrier layer on described high mobility GaN layer;
4) adopt ICP-RIE(ICP:Inductive Coupled Plasma, RIE:Reactive Ion Etching on described AlGaN barrier layer) method etching isolated island;
5) at the surperficial resist coating that generates described isolated island, carry out photoetching, exposure and development, form the Schottky electrode figure;
6) pass through electron beam evaporation one metal level on the surface that covers photoresist, then with photoresist lift off, form variable capacitance.
Further, described substrate is Sapphire Substrate or SiC substrate; Described resilient coating is GaN or AlN.
Further, the thickness of described high resistant GaN layer is 2.0 ~ 2.5 μ m, and the thickness of described high mobility GaN layer is 150 ~ 200nm; The thickness of described AlGaN barrier layer is 20 ~ 30nm; The degree of depth of described etching is 150 ~ 200nm.
Further, described step 6) is first made the Ni layer, as adhesive layer; Then make the Au layer on described Ni layer; Wherein the Ni layer thickness is 20 ~ 50nm, and the Au layer thickness is 150 ~ 250nm.
Further, step 5) is toasted described photoresist, then exposes and develops, and the temperature of described baking is 90 ~ 100 ℃, and the time is 90 ~ 100 seconds; Step 6) adopts organic solvent to peel off described photoresist, and described organic solvent comprises: acetone, ethanol.
Further, growth one AlN insert layer between described high mobility GaN layer and described AlGaN barrier layer.
Further, the method for described growth comprises: metal organic chemical vapor deposition, molecular beam epitaxy, hydride gas-phase epitaxy.
The method of making variable capacitance of the present invention, can with standard A lGaN/GaN HEMT process compatible; The variable capacitance of made has wide adjustable extent; There are high quality factor at the place at minimum and maximum capacitance, and for realizing LNAs, the circuit such as VCOs and frequency mixer are significant.
Description of drawings
Fig. 1 is the flow chart of steps of method of the making variable capacitance of the embodiment of the present invention.
Fig. 2 is the process flow diagram of the making variable capacitance of the embodiment of the present invention.
Fig. 3 is the microphoto of the variable capacitance of employing the inventive method making.
Fig. 4 is the capacitance of the variable transfiguration adopting the inventive method and the make schematic diagram with bias variations.
Embodiment
Below by specific embodiment and coordinate accompanying drawing, the present invention is described in detail.
Fig. 1 is the flow chart of method of the making variable capacitance of the present embodiment, and as shown in the drawing, the method comprises the following steps:
Step 101: at the Grown resilient coating.Substrate can be selected Sapphire Substrate or SiC substrate, and the present embodiment is selected sapphire (0001) substrate.Resilient coating can also adopt AlN except adopting GaN, also can direct growth go out quality high resistant GaN preferably on it; The present embodiment is selected the GaN resilient coating.
Step 102: growing high resistant GaN layer and high mobility GaN layer on the GaN resilient coating.
The thickness of high resistant GaN layer is preferably 2.0 ~ 2.5 μ m, and the thickness of high mobility GaN layer is preferably 200nm.The high resistant GaN layer can directly have influence on the minimum value of variable capacitance.Because the minimum value of variable capacitance appears in the situation that in raceway groove, two-dimensional electron gas exhausts, if this resistive formation poor quality can make to exhaust slowly, perhaps can't exhaust fully, thereby can not get satisfactory position of minimum capacitance.Due to the two-dimensional electron gas that need to use when realizing the function of this variable capacitance between AlGaN and GaN, thus need to be on high resistant GaN long one deck high mobility GaN again, to guarantee the mobility of two-dimensional electron gas in raceway groove.
Step 103: growth AlGaN barrier layer on high mobility GaN layer.The thickness of AlGaN barrier layer is preferably 20 ~ 30nm.
Step 104: carry out ICP-RIE etching isolated island on the AlGaN barrier layer.The degree of depth of etching is preferably 150 ~ 200nm.
Step 105: resist coating, photoetching, exposure, development photoresist layer.
Photoetching is in order to form the electrode of Schottky contacts.There is no zone covered by photoresist after development is the zone that needs to form Schottky electrode.Namely carry out subsequently electron beam evaporation, the metal of part surface covered by photoresist can remove along with peeling off glue-line, does not have the metal of part covered by photoresist will be retained the formation Schottky electrode.
Step 106: electron beam evaporation layer of metal on the surface that covers photoresist forms variable capacitance after stripping photoresist.
In above-mentioned steps, resilient coating, high resistant GaN layer, high mobility GaN layer and AlGaN barrier layer can all adopt MOCVD(Metal-organic Chemical Vapor Deposition, metal organic chemical vapor deposition) method grows.In addition, also can pass through MBE(Molecular Beam Epitaxy, molecular beam epitaxy) and HVPE(Hydride Vapor Phase Epitaxy, hydride gas-phase epitaxy) two kinds of methods realize Material growth.Three kinds of methods are compared, and MBE method Material growth speed is the slowest, and the quality of materials that obtains is best, and price is also the most expensive; HVPE method Material growth is fastest, and the quality of materials that obtains is the poorest; MOCVD is between MBE and HVPE.
In above-mentioned steps, one deck AlN insert layer can also be arranged between high mobility GaN layer and AlGaN, in order to improve the mobility of two-dimensional electron gas.At one deck GaN block layer of can also growing on the AlGaN barrier layer, under metal level, this GaN block layer can suppress current collapse when making HEMT (High Electron Mobility Transistor) device; During as the electric capacity of individualism, owing to there not being the current collapse effect, can there is no GaN block layer.
Fig. 2 is the schematic diagram that the present invention makes the variable capacitance process, below in conjunction with the method that the Figure further illustrates above-mentioned making variable capacitance:
1) growing low temperature 20nmGaN resilient coating 2 on sapphire (0001) substrate 1 is as shown in Fig. 2 (a).Because there are lattice mismatch issue in GaN and Sapphire Substrate, this resilient coating of growing can reduce lattice mismatch.
2) growth 2.3 μ m high resistant GaN layers and 200nm high mobility GaN layer 3 on the GaN resilient coating are as shown in Fig. 2 (b).
3) the AlGaN barrier layer 4 of growth 25nm on high mobility GaN layer is as shown in Fig. 2 (c).
4) carry out the isolated island 5 that the ICP-RIE etching depth is 160nm on the AlGaN barrier layer, as shown in Fig. 2 (d).
5) generating the thick AZ5214 photoresist 6 of surface coating 2 μ m of described isolated island, then baking 90 seconds at 95 ℃ of temperature is as shown in Fig. 2 (e).
The substrate that 6) will be coated with photoresist exposes under the contact exposure machine, the substrate after exposure is placed in developer solution develops, as shown in Fig. 2 (f).
7) electron beam evaporation 50nmNi and 250nmAu metal level 7 on substrate are as shown in Fig. 2 (g).This step is first evaporated the Ni metal level, then evaporates the Au metal level; Because the adhesiveness on Au and AlGaN barrier layer surface is bad, thus before evaporation Au the evaporation layer of Ni as adhesive layer.
8) peel off with organic solvent-acetone or ethanol, remaining photoresist is removed, namely form variable capacitance, as shown in Fig. 2 (h).
Fig. 3 (a) is the microphotograph that utilizes the variable capacitance of variable capacitance manufacture method realization provided by the invention, Fig. 3 (b) is the schematic diagram of this capacitance structure, can be regarded as the vertical view of Fig. 2 (h), wherein W represents that interpolation is wide, S represents the distance between interpolation, and L represents the length of interpolation.
The operation principle of above-mentioned variable capacitance is: be added in voltage on electrode by change, thereby change the concentration of the two-dimensional electron gas between AlGaN and GaN, electric weight Q changes along with the variation of voltage V like this, shows as variable capacitance.Maximum capacitor appears at two-dimensional electron gas when maximum, and position of minimum capacitance appears at two-dimensional electron gas when depleted.The computing formula of the quality factor of this variable capacitance is:
Wherein C is the equivalent capacitance value in this variable capacitance equivalence first order modeling, and R is the equivalent resistance in variable capacitance equivalence first order modeling for this reason.The C of maximum capacitor place depends primarily on the barrier capacitance of AlGaN layer, and this moment is because there is high two-dimensional electron gas, so R is less.The minimum capacity place, two-dimensional electron gas exhausts basically, and C depends primarily on sidewall capacitance, and this moment, the RF signal was mainly to propagate by sidewall capacitance, and the loss of generation is less, and namely equivalent resistance is less.The Q value that to sum up goes out at maximum capacitor and minimum capacity is all higher.
Fig. 4 utilizes the capacitance of the variable transfiguration that variable capacitance manufacture method provided by the invention realizes with the schematic diagram of bias variations.Shown in figure, variable capacitance is of a size of: finger beam 2um, interpolation spacing 5um refers to long 50um.Test frequency is 100MHz.As shown in the drawing: capacitance maximum is 5.7pF, and the electric capacity minimum value is 251fF, and maximum can be 22.7 times of minimum value, and wider adjustable extent is arranged.
Above embodiment is only in order to technical scheme of the present invention to be described but not be limited; those of ordinary skill in the art can modify or be equal to replacement technical scheme of the present invention; and not breaking away from the spirit and scope of the present invention, protection scope of the present invention should be as the criterion so that claim is described.
Claims (10)
1. a variable capacitance, is characterized in that, comprises the high resistant GaN layer, high mobility GaN layer, AlGaN barrier layer and the metal level that are arranged in order.
2. variable capacitance according to claim 1, it is characterized in that: the thickness of described resistive formation is 2.0 ~ 2.5 μ m, and the thickness of described high mobility layer is 150 ~ 200nm, and the thickness of described AlGaN barrier layer is 20 ~ 30nm.
3. variable capacitance according to claim 1, it is characterized in that: described metal level comprises Ni layer and Au layer, described Ni layer is as the adhesive layer of described AlGaN barrier layer and described Au layer; Wherein the Ni layer thickness is 20 ~ 50nm, and the Au layer thickness is 150 ~ 250nm.
4. a method of making variable capacitance, is characterized in that, comprises the steps:
1) at the Grown resilient coating;
2) growing high resistant GaN layer and high mobility GaN layer successively on described resilient coating;
3) growth AlGaN barrier layer on described high mobility GaN layer;
4) adopt ICP-RIE method etching isolated island on described AlGaN barrier layer;
5) at the surperficial resist coating that generates described isolated island, carry out photoetching, exposure and development, form the Schottky electrode figure;
6) pass through electron beam evaporation one metal level on the surface that covers photoresist, then with photoresist lift off, form variable capacitance.
5. the method for making variable capacitance according to claim 4, it is characterized in that: described substrate is Sapphire Substrate or SiC substrate; Described resilient coating is GaN or AlN.
6. the method for making variable capacitance according to claim 4, it is characterized in that: the thickness of described high resistant GaN layer is 2.0 ~ 2.5 μ m, and the thickness of described high mobility GaN layer is 150 ~ 200nm; The thickness of described AlGaN barrier layer is 20 ~ 30nm; The degree of depth of described etching is 150 ~ 200nm.
7. the method for according to claim 4 or 6 described making variable capacitances, it is characterized in that: described step 6) is first made the Ni layer, as adhesive layer; Then make the Au layer on described Ni layer; Wherein the Ni layer thickness is 20 ~ 50nm, and the Au layer thickness is 150 ~ 250nm.
8. the method for making variable capacitance according to claim 4, it is characterized in that: step 5) is toasted described photoresist, then exposes and develops, and the temperature of described baking is 90 ~ 100 ℃, and the time is 90 ~ 100 seconds; Step 6) adopts organic solvent to peel off described photoresist, and described organic solvent comprises: acetone, ethanol.
9. the method for making variable capacitance according to claim 4, is characterized in that, growth one AlN insert layer between described high mobility GaN layer and described AlGaN barrier layer.
10. the method for according to claim 4 or 9 described making variable capacitances, is characterized in that, the method for described growth comprises:
Metal organic chemical vapor deposition, molecular beam epitaxy, hydride gas-phase epitaxy.
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Cited By (2)
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| CN106206259A (en) * | 2016-08-30 | 2016-12-07 | 上海华力微电子有限公司 | A kind of method reducing variodenser minimum capacity |
| CN108365019A (en) * | 2018-02-11 | 2018-08-03 | 中国工程物理研究院电子工程研究所 | A kind of heterojunction semiconductor varactor arrangement of transversary |
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| US20090243039A1 (en) * | 2005-12-28 | 2009-10-01 | Bong Jun Kim | MIM Capacitor And Method For Manufacturing the Same |
| CN101562182A (en) * | 2008-04-02 | 2009-10-21 | 香港科技大学 | Integrated hemt and a combination, method as well as a system of a horizontal field effect rectifier |
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| US20090243039A1 (en) * | 2005-12-28 | 2009-10-01 | Bong Jun Kim | MIM Capacitor And Method For Manufacturing the Same |
| CN101562182A (en) * | 2008-04-02 | 2009-10-21 | 香港科技大学 | Integrated hemt and a combination, method as well as a system of a horizontal field effect rectifier |
| US20100207166A1 (en) * | 2009-02-18 | 2010-08-19 | Alpha & Omega Semiconductor, Inc. | Gallium Nitride Heterojunction Schottky Diode |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106206259A (en) * | 2016-08-30 | 2016-12-07 | 上海华力微电子有限公司 | A kind of method reducing variodenser minimum capacity |
| CN106206259B (en) * | 2016-08-30 | 2019-05-31 | 上海华力微电子有限公司 | A method of reducing variodenser minimum capacity |
| CN108365019A (en) * | 2018-02-11 | 2018-08-03 | 中国工程物理研究院电子工程研究所 | A kind of heterojunction semiconductor varactor arrangement of transversary |
| CN108365019B (en) * | 2018-02-11 | 2021-02-26 | 中国工程物理研究院电子工程研究所 | Semiconductor heterojunction varactor device with transverse structure |
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Application publication date: 20130508 |