High power microwave plasma reaction unit for chemistry for gas phase depositing diamond film
Technical field
The invention belongs to chemistry for gas phase depositing diamond film technical field, a kind of high power microwave plasma reaction unit for chemistry for gas phase depositing diamond film.
Background technology
Chemical vapor deposition (CVD) diamond film has that hardness is high, heat conductivity is good, thermal coefficient of expansion is little, optically and electrically excellent performance, the many merits such as acoustic propagation velocity is fast, dielectric properties are good, makes it have a wide range of applications in fields such as radiator, high-performance anti-radiation detector and the sensors of such as infrared optical window, high-capacity LED, high power and altofrequency electronics and opto-electronic device and system.At present, the method preparing diamond film that people are the most frequently used has hot filament CVD (HFCVD), Dc arc plasma jet CVD chemical gaseous phase deposition (DC arc plasma jet CVD) method and microwave plasma CVD (MPCVD) method three kinds.In these three method, MPCVD
The feature of method is that the controlling of diamond film deposition process is good, the pollution of discharge off electrode, is in the world for preparing the prefered method of high quality diamond film.But, MPCVD
The major defect of method is that when preparing high quality diamond film, sedimentation rate is low, causes diamond film cost high, expensive, limits its promotion and application in multiple fields.
In the preparation process of MPCVD diamond film, in plasma, the concentration of hydrogen atom plays conclusive effect to quality and the sedimentation rate of diamond film, can improve the concentration of hydrogen atom in plasma by increasing power density.But, simple dependence improves deposition pressure, and the method for plasma compression volume improves power density, can reduce the area of prepared diamond film.Therefore, sedimentation rate to be taken into account and area are accomplished by, while raising deposition pressure, increasing input power, and this is accomplished by research and development can accommodate the MPCVD device of high microwave power.
Quartz tube type MPCVD device in early days, microwave focusing power is poor, and the quartz tube because using is less simultaneously, and the etching problem of quartz ampoule causes its power allowed to be only about 800W.In the MPCVD device of the several types often used current people, cylinder resonator formula MPCVD device [P.Bachmann, Chemical &
Engineering News 67 (1989) 24] higher power can be accommodated, but secondary plasma can be produced near flat quartz glass medium window when its major defect is high power, cause the etching of quartz glass and the dispersion of energy;Crystal clock bell-type MPCVD device [P.Bachmann, D.Leers, H.Lydtin, Diamond Relat.Mater.
1 (1991) 1] and ellipsoid resonant cavity type MPCVD device [M.Funer, C.Wild, P.Koidl, Appl.Phys.Lett. 72 (1998) 1149] all employ quartz bell cover as medium window, plasma is constrained in quartz bell cover, also cannot avoid the plasma etching to bell jar under higher power condition.Additionally, the use of quartz bell cover makes being necessarily placed on deposition base station into and out of hole of the reacting gas of device, the uniformity causing gas to be distributed is poor.
Non-cylindrical chamber circumference Antenna Type MPCVD device (SekiTechnotron Corp., http://www.sikitech.biz/.) use quartz ring as medium window, circumference antenna is simultaneously as chip bench, quartz ring is arranged on the lower section of chip bench, can thoroughly avoid the plasma etching to this window.But, this device still suffers from following shortcoming: first, device is provided with four air inlets at upper cover, for enabling reacting gas to be uniformly distributed at substrate surface, employ an other quartz ring in practice and be enclosed within chip bench (circumference antenna) outside, owing to quartz ring is higher than chip bench, quartz ring still can be caused etching to pollute by plasma, and this becomes one of factor limiting device raising microwave input power.Second, the position of the height of cavity and chip bench (circumference antenna) is all fixing, all cannot be carried out regulation, lacks microwave electric field in resonator cavity and the real-time monitoring means of the corresponding plasma produced, and when using the substrate deposition of differing heights, the uniformity of diamond film it is difficult to ensure that.3rd, owing to the structure of cavity is more complicated, being only capable of the regional area of cavity above chip bench (circumference antenna) and plasma and arrange water-cooling structure, the cavity temperature too high when carrying out diamond film deposition also becomes another key factor limiting its high microwave power of receiving.4th, quartz ring window is placed in below deposition table, is unfavorable for the holding of vacuum in reaction chamber, is i.e. unfavorable for the raising of diamond film quality.
Patent JP 2000-54142A, US20090120366 have employed the annular medium window similar with non-cylindrical chamber circumference Antenna Type MPCVD device and circumference antenna structure, for strengthening focusing power, circumference antenna surface is designed to groove to the part of vacuum cavity, and base station can move up and down the real-time adjustment realizing plasma by governor motion.The shortcoming of both devices is: is only adjusted by lifting base station plasma, limits used substrate height;Device reaction gas be arranged at cavity bottom into and out of hole, cause the gas skewness of substrate surface, affect the uniformity of diamond film;The riding position of the 4th shortcoming, i.e. quartz ring that device there is also non-cylindrical chamber circumference Antenna Type MPCVD device is unfavorable for the holding of vacuum in reaction chamber.
Patent CN101864560B have employed the structure identical with non-cylindrical chamber circumference Antenna Type MPCVD device, i.e. uses circumference antenna simultaneously as chip bench and the medium window of annular.This device adds liftable reflector on cavity top, it is possible to realize microwave electric field and the real-time monitoring of the corresponding plasma produced;Its cavity is cylindrical structural, simple shape, and the parts contacted with plasma all achieve water-cooled.But, find time actually used that this device exists three shortcomings: one is, compared with other devices, poor to the focusing power of microwave electric field, under the same terms, the sedimentation rate of diamond film is relatively low;Two are, the outlet of reacting gas is arranged on the side of vacuum cavity, there is the problem that the diamond film uniformity caused due to reacting gas skewness is poor;Three are, when using under the conditions of higher-wattage, portion of energy can be scattered on the small cylinder in the middle of reflector, and its surface there will be the deposition of amorphous carbon material, is unfavorable for the preparation of high quality diamond film.It addition, the 4th shortcoming of this device the most unresolved non-cylindrical chamber circumference Antenna Type MPCVD device.
Circumference antenna is designed to semi-ellipsoidal shape by patent CN103305816 A, improves the device focusing power to microwave electric field;Patent 103695865A is provided with movably cylinder upper cavity in circular cylindrical cavity and, to improve focusing power, realizes the real-time regulation to microwave electric field and plasma by the position of regulation reflector in upper cavity.Both devices are all provided with full water cooling structure, but all there is second and the 4th shortcoming of non-cylindrical chamber circumference Antenna Type MPCVD device, the most all there is second shortcoming of patent CN101864560B.
Circumference antenna is designed to the cheese focusing with enhancing microwave energy by patent CN 103668127 A, stops that microwave is propagated to reflector top by sheet metal reflector simultaneously, makes microwave be gathered in more above substrate.The scalable annular edge deposition table of device, cavity and the lifting of scalable center deposition platform, it is possible to achieve the real-time regulation to microwave electric field and plasma, quartz ring is arranged on the lower section of circumference antenna and improves the vacuum performance of device.The shortcoming of this structure is: first, and sheet metal reflector directly contacts plasma, and plate is relatively thin cannot be passed through cooling water, when causing it to use under high power conditions, the deposition of amorphous carbon material that is too high due to temperature and that cause often occurs;Secondly, although quartz ring has been arranged between the slit that resonance cavity wall is formed, but still directly facing plasma, the situation polluting diamond film under high power conditions because quartz ring is etched yet suffers from;Finally, device does not design special venthole, after reacting gas air inlet from loop aerial enters reaction chamber, can only be discharged by the gap of scalable annular edge deposition table with cavity and scalable center deposition platform.Due in device work process, annular edge deposition table and center deposition platform are required to be adjusted, it is difficult to ensure that this gap equivalently-sized, so the flowing of gas and the uniformity of matrix surface gas distribution cannot ensure in whole reaction cavity at twice actually used.
In sum, by the end of at present, various types of microwave plasma reaction units for chemistry for gas phase depositing diamond film that people use and propose, all there is the different factors being unfavorable under high power conditions preparing high quality diamond film, therefore in the urgent need to designing the high power reaction unit of a kind of structure and perfect performance, to meet the quick preparation of high quality diamond film.
Summary of the invention
The present invention is to solve above-mentioned problems of the prior art, and provides a kind of high power microwave plasma reaction unit for chemistry for gas phase depositing diamond film.What this device can overcome that current existing all kinds of reaction units exist to varying degrees lack governor motion, medium opening etch, focusing power are poor, critical component is difficult to water-cooled, power dissipation, substrate surface gas shortcoming pockety, therefore, it is possible to be applied to the uniform fast deposition of high quality diamond film under high power conditions.
The present invention is achieved through the following technical solutions:
A kind of high power microwave plasma reaction unit for chemistry for gas phase depositing diamond film, including Cylindrical resonant cavity, Cylindrical resonant cavity is divided into upper cavity, middle cavity and lower chamber, and the diameter of middle cavity is less than upper cavity and the diameter of lower chamber;The top, chamber of upper cavity is cone, bottom in upper cavity is close to cavity wall and is provided with circular quartz microwave window, the upper port of circular quartz microwave window is provided with a circle mounting groove, discoid coupled antenna is installed in mounting groove, being provided with down convex cylinder boss at the bottom centre of discoid coupled antenna, reaches the standard grade and offers air inlet along its axis in discoid coupling sky;The bottom of lower chamber is provided with total venthole, lower chamber inner close fitting cavity wall is provided with the first cylindrical reflector, the bottom surface of the first cylindrical reflector is rounding mesa-shaped plane, that end face is downward depression, the first cylindrical shape installing hole is offered along its axis on first cylindrical reflector, and offer some ventholes in the position of next-door neighbour's the first cylindrical shape installing hole, it is fitted with the second cylindrical reflector in first cylindrical shape installing hole, offer the second cylindrical shape installing hole along its axis on second cylindrical reflector, in the second cylindrical shape installing hole, be fitted with cylindrical base station;First cylindrical reflector, the second cylindrical reflector and cylindrical base station can realize lifting action respectively by the elevating mechanism each arranged;
Upper cavity, middle cavity, lower chamber, circular quartz microwave window, discoid coupled antenna, the first cylindrical reflector, the second cylindrical reflector, cylindrical base station are for being coaxially set;Between circular quartz microwave window and upper cavity, between circular quartz microwave window and discoid coupled antenna, between the first cylindrical reflector and lower chamber, between the first cylindrical reflector and the second cylindrical reflector, between the second cylindrical reflector and cylindrical base station, it is designed with sealing ring.
Upper cavity, middle cavity and lower chamber together constitute the resonant cavity of apparatus of the present invention, and the conical cavity top design of upper cavity, this structure can effectively strengthen the coupling of microwave power, reduces reflection power.Lumen body is positioned between circular quartz microwave window and cylindrical base station (can form plasma on cylindrical base station), and the diameter of middle cavity is less than upper cavity and the diameter (diameter of middle cavity is again smaller than the diameter of circular quartz microwave window) of lower chamber, therefore lumen body can be formed on circular quartz microwave window and cylindrical base station plasma isolation, it is to avoid the plasma etching to circular quartz microwave window.
By the sealing ring arranged between disk and the circular quartz microwave window of discoid coupled antenna, this more than first cylindrical reflector segment space is made in below discoid coupled antenna, lower chamber to form vacuum response chamber, the gravity of discoid coupled antenna and the common effect of atmospheric pressure can make the vacuum that the holding of vacuum response chamber is good, the beneficially deposition of high quality diamond film.Convex cylinder boss and the end face rounding mesa-shaped structure with the first cylindrical reflector under discoid coupled antenna bottom centre, it is possible to be greatly enhanced the focusing power of microwave electromagnetic field.First cylindrical reflector, the second cylindrical reflector and cylindrical base station are both provided with elevating mechanism, three can each change the height in lower chamber, so it is not only able to realize microwave electric field in lower chamber and the real-time monitoring of corresponding plasma, and when the substrate using differing heights carries out diamond film deposition, can the state of optimizing regulation plasma, make plasma be evenly distributed in substrate surface all the time, thus ensure the uniformity of diamond film deposition.The air inlet of apparatus of the present invention is arranged on the axis of discoid coupled antenna, also some ventholes are offered on first cylindrical reflector, between first cylindrical reflector and lower chamber, between first cylindrical reflector and the second cylindrical reflector, it is designed with sealing ring between second cylindrical reflector and cylindrical base station, after reacting gas is entered reaction chamber by air inlet, can only be by some ventholes of the first cylindrical reflector, total venthole through lower chamber is discharged to outside device again, this turnover gas mode ensure that reacting gas is uniformly distributed at substrate surface, thus ensure the uniformity of prepared diamond film.
Further, the hypotenuse on the conical cavity top of upper cavity and horizontal angle are 5-20 °, and conical cavity top is designed to such angular range, and the coupling that strengthens microwave power, the effect reducing reflection power are the most excellent.Hypotenuse on first cylindrical reflector and horizontal angle are 10-25 °, are designed to the round table-like of this angular range, and the focusing power for microwave electromagnetic field improves maximum.
Upper cavity, middle cavity, lower chamber, discoid coupled antenna, the first cylindrical reflector and elevating mechanism thereof, the second cylindrical reflector and elevating mechanism thereof, cylindrical base station and elevating mechanism thereof are all directly cooled down by recirculated cooling water.Specifically upper cavity, middle cavity, lower chamber, discoid coupled antenna, the first cylindrical reflector, the second cylindrical reflector, cylindrical base station is designed with hollow sandwich, and it is provided with the entery and delivery port communicated with hollow sandwich, cooling water is entered by water inlet and flows out from outlet, reaches the purpose of cooling with this.The design of above-mentioned recirculating cooling water system makes apparatus of the present invention can accommodate higher microwave power.
Fig. 2 is the microwave electric field analog result figure of apparatus of the present invention, and as can be seen from the figure device only has the electric field region of an amplitude maximum in being positioned at above substrate, therefore has the ability of the strongest focusing electric field;Highfield is separated by middle cavity with quartz microwave window, and does not has obvious electric field near quartz microwave window, therefore can avoid the excited plasma etching to this window;Other region electric field magnitude are not enough to excite plasma, this avoid secondary plasma and occur.
Apparatus of the present invention compared with prior art, have the advantages that
1) the conical cavity top of the device that the present invention proposes, it is possible to effectively strengthen the coupling of microwave power, reduces reflection power.Cylindrical boss on discoid coupled antenna and the end face rounding mesa-shaped structure of the first cylindrical reflector, it is possible to be greatly enhanced the focusing power of microwave electromagnetic field;
2) mounting groove of the circular quartz microwave window upper port of the device that the present invention proposes, it is possible to facilitate the installation of discoid coupled antenna and be accurately positioned;
3) present invention proposes the first cylindrical reflector of device, the second cylindrical reflector and cylindrical base station possess independent elevating mechanism, the therefore respective position of scalable respectively.By the cooperation of three position, the state of plasma under optimizing regulation substrates of different diameter and substrates of different thickness condition, it is ensured that the uniformity of substrate surface plasma under the conditions of high power density;
4) device that the present invention proposes is provided with some ventholes on the first cylindrical reflector, after reacting gas is entered reaction chamber by the air inlet being arranged on discoid coupled antenna central authorities, can only be discharged to outside device by venthole, again total venthole through lower chamber, it is ensured that the uniformity of substrate surface gas distribution;
5) in the device that the present invention proposes, entirety makes to be cooled with circulating water, including upper cavity, middle cavity, lower chamber, discoid coupled antenna, the first cylindrical reflector and elevating mechanism thereof, the second cylindrical reflector and elevating mechanism thereof, cylindrical base station and elevating mechanism thereof, it is possible to ensure device long-play of safety and stability under the conditions of high power density;
6) device that the present invention proposes is capable of large area, the high rate deposition of high uniformity diamond film material.
Accompanying drawing explanation
Fig. 1 is the structural representation of apparatus of the present invention.
Fig. 2 is the microwave electric field analog result figure of apparatus of the present invention.
Fig. 3 is the surface microscopic topographic figure of the diamond film using apparatus of the present invention to prepare.
Fig. 4 is the Raman line of the diamond film using apparatus of the present invention to prepare.
In figure: cavity, 3-lower chamber, the circular quartz microwave window of 4-, the discoid coupled antenna of 5-, 6-cylinder boss, 7-air inlet, 8-the first cylindrical reflector, 9-the second cylindrical reflector, 10-cylinder base station, 11-venthole, 12-elevating mechanism, the total venthole of 13-, 14-sealing ring, 15-substrate, 16-plasma in 1-upper cavity, 2-.
Detailed description of the invention
Below in conjunction with accompanying drawing, the present invention is further described:
As shown in Figure 1, a kind of high power microwave plasma reaction unit for chemistry for gas phase depositing diamond film, including Cylindrical resonant cavity, described Cylindrical resonant cavity is divided into upper cavity 1, middle cavity 2 and lower chamber 3, and the diameter of middle cavity 2 is less than upper cavity 1 and the diameter of lower chamber 3;The top, chamber of upper cavity 1 is cone, bottom in upper cavity 1 is close to cavity wall and is provided with circular quartz microwave window 4, the upper port of circular quartz microwave window 4 is provided with a circle mounting groove, discoid coupled antenna 5 is installed in mounting groove, convex cylinder boss 6 it is provided with down at the bottom centre of discoid coupled antenna 5, offering air inlet 7 along its axis on discoid coupled antenna 5, the diameter of air inlet 7 may select 3-8mm;The bottom of lower chamber 3 is provided with total venthole 13, lower chamber 3 inner close fitting cavity wall is provided with the first cylindrical reflector 8, the bottom surface of the first cylindrical reflector 8 is plane, end face is the rounding mesa-shaped of downward depression, the first cylindrical shape installing hole is offered along its axis on first cylindrical reflector 8, and offer venthole 11 in the position of next-door neighbour's the first cylindrical shape installing hole, the diameter of venthole 11 may select 4-6mm, quantity is 8-24, the second cylindrical reflector 9 it is fitted with in first cylindrical shape installing hole, the second cylindrical shape installing hole is offered along its axis on second cylindrical reflector 9, cylindrical base station 10 it is fitted with in second cylindrical shape installing hole;First cylindrical reflector the 8, second cylindrical reflector 9 and cylindrical base station 10 can realize lifting action respectively by the elevating mechanism 12 each arranged;
Upper cavity 1, middle cavity 2, lower chamber 3, circular quartz microwave window 4, discoid coupled antenna the 5, first cylindrical reflector the 8, second cylindrical reflector 9, cylindrical base station 10 are for being coaxially set;Between circular quartz microwave window 4 and upper cavity 1, between circular quartz microwave window 4 and discoid coupled antenna 5, between the first cylindrical reflector 8 and lower chamber 3, between the first cylindrical reflector 8 and the second cylindrical reflector 9, between the second cylindrical reflector 9 and cylindrical base station 10, it is designed with sealing ring 14.
When being embodied as, the hypotenuse on the conical cavity top of upper cavity 1 and horizontal angle are 5-20 °;Hypotenuse on first cylindrical reflector 8 and horizontal angle are 10-25 °.
Upper cavity 1, middle cavity 2, lower chamber 3, discoid coupled antenna the 5, first cylindrical reflector 8 and elevating mechanism the 12, second cylindrical reflector 9 thereof and elevating mechanism 12, cylindrical base station 10 and elevating mechanism 12 thereof are all directly cooled down by recirculated cooling water.
Below in conjunction with a concrete use embodiment, then apparatus of the present invention are further described:
Embodiment 1
1, a diameter of 65mm is used, thickness is that the monocrystalline silicon piece of 3mm is as substrate 15 material, first the bortz powder that deposition surface particle diameter is 5 μm of circular substrate 15 is uniformly ground, use deionized water and acetone by clean for substrate 15 surface ultrasonic cleaning the most respectively, and with hot blast drying, be placed on the end face of cylindrical base station 10;
2, close vacuum response chamber, and use vacuum pump that the pressure in reaction chamber is extracted into below 1Pa;
3, ON cycle water cooling system, is passed through cooling water to device each several part;
4, in device reaction chamber, the hydrogen that flow is 600sccm it is passed through, the pressure in regulation reaction chamber to 2kPa;
5, it is to open after 2kW by the power setting that frequency is 2.45GHz microwave source, reaction chamber produces plasma 16;
6, adjusting first cylindrical reflector the 8, second cylindrical reflector 9 and the position of cylindrical base station 10, make plasma 16 be positioned at the top of substrate 15, and make reflection power minimum, the intensity of plasma 16 reaches the highest;
7, the microwave input power in device and pressure are gradually stepped up, and finally make power reach 11kW, pressure reaches 25kPa, each elevating mechanism 12 is utilized to adjust first cylindrical reflector the 8, second cylindrical reflector 9 and the position of cylindrical base station 10 in this course, remain that reflection power is minimum, the intensity of plasma 16 reaches the highest, and make the temperature on substrate 15 surface reach 900 DEG C, by the height of the cylindrical base station 10 of fine setting, the temperature deviation of substrate 15 surface diverse location is made to control at ± 3 DEG C;
8, in reaction chamber, it is passed through the methane gas that flow is 12sccm, after 1h, completes the forming core of diamond film on substrate 15 surface;Methane flow being adjusted to 6sccm, starts the growth of diamond film, the thickness of diamond film depends on the persistent period of deposition;
9, after deposition 60h, the pressure being gradually lowered in reaction chamber and microwave input power, it is down to 5kPa at pressure, microwave power is when being down to 3kW, closes microwave source, hydrogen, methane and vacuum pump successively, terminate the deposition of diamond film;
10, opening charge valve to being filled with air in device to after an atmospheric pressure, opening device takes out sample;
11, the nitric acid using volume ratio to be 2:1 and Fluohydric acid. mixed solution, by monocrystalline silicon substrate 15 erosion removal, obtain the high quality diamond film that thickness is about 0.42mm, and calculating its sedimentation rate is 7 μm/h, unevenness < 5%.Fig. 3 is the surface microscopic topographic figure of the diamond film using apparatus of the present invention to prepare, and as can be seen from the figure prepared diamond film is continuous, fine and close, does not has obvious gap, the most there is not the defects such as obvious second nucleation granule between diamond crystal boundary.Fig. 4 is the Raman line of the diamond film using apparatus of the present invention to prepare, as can be seen from the figure only 1332 cm in the Raman spectrum of diamond film-1A neighbouring diamond characteristic peak, and do not have the characteristic peak of obvious graphite and other impurity to occur, the halfwidth of diamond raman characteristic peak is 2.4 cm-1, this shows that prepared diamond film has fine qualities.