Diamond film etching method, graphical diamond film and application thereof
阅读说明：本技术 金刚石膜刻蚀方法、图形化金刚石膜及其应用 (Diamond film etching method, graphical diamond film and application thereof ) 是由 杨国永 江南 马洪兵 王博 褚伍波 于 2020-05-06 设计创作，主要内容包括：本申请公开了一种金刚石膜刻蚀方法、图形化金刚石膜及其应用,所述方法包括：将基片置于腔体内,所述基片包括硅片和金刚石膜,所述硅片的一面设有由沟槽形成的图形,所述金刚石膜覆盖在所述硅片的沟槽所在的表面上且填充满所述沟槽；在所述腔体内形成等离子体对所述基片进行刻蚀,得到图形化金刚石膜,其中,所述刻蚀的具体条件包括：H-(2)和O-(2)作为气源,且O-(2)的流量为H-(2)流量的1～6％；微波作为能量源,且微波功率为3～8KW；刻蚀温度为600～700℃。该方法无需设置掩体,刻蚀完成后直接形成图形化金刚石膜,无需再去除掩体,操作简单、效率高。(The application discloses a diamond film etching method, a graphical diamond film and application thereof, wherein the method comprises the following steps: placing a substrate in a cavity, wherein the substrate comprises a silicon wafer and a diamond film, one surface of the silicon wafer is provided with a pattern formed by a groove, and the diamond film covers the surface of the silicon wafer where the groove is located and is filled with the groove; and forming plasma in the cavity to etch the substrate to obtain a patterned diamond film, wherein the specific etching conditions comprise: h 2 And O 2 As a gas source, and O 2 Has a flow rate of H 2 1-6% of the flow; microwave is used as an energy source, and the microwave power is 3-8 KW; the etching temperature is 600-700 ℃. The method does not need to arrange a mask, directly forms the graphical diamond film after the etching is finished, and does not need to remove the diamond filmThe shelter is simple to operate and high in efficiency.)
1. A diamond film etching method is characterized by at least comprising the following steps:
(1) placing a substrate in a cavity, wherein the substrate comprises a silicon wafer and a diamond film, one surface of the silicon wafer is provided with a pattern formed by a groove, and the diamond film covers the surface of the silicon wafer where the groove is located and is filled with the groove;
(2) and forming plasma in the cavity to etch the substrate to obtain a patterned diamond film, wherein the specific etching conditions comprise:
H2and O2As a gas source, and O2Has a flow rate of H21-6% of the flow;
microwave is used as an energy source, and the microwave power is 3-8 KW;
the etching temperature is 600-700 ℃.
2. The method for etching a diamond film according to claim 1, wherein in the step (1), the width of the opening of the trench is 14 to 20 μm, and the depth of the trench is 14 to 20 μm.
3. The method according to claim 1, wherein the diamond film in step (1) is prepared by a hot wire chemical vapor deposition process;
the thickness of the diamond film is 8-12 mu m.
4. The method for etching a diamond film according to claim 1, wherein the specific conditions for the etching in the step (2) further include:
the pressure in the cavity is 10-12 Kpa.
5. The diamond film etching method according to claim 1, wherein the H is2And O2Total flow rate of 500-550 sccm, the ratio of O2Has a flow rate of H23-6% of the flow.
6. The method for etching a diamond film according to claim 1, wherein the microwave power is 3 to 5KW, the etching temperature is 600 to 690 ℃, and the etching time is 3 to 5 hours.
7. The diamond film etching method according to claim 1, wherein the H is2And O2As the gas source, the method comprises the following steps:
firstly, H is introduced into the cavity2After plasma formation, O is introduced2。
8. The method of claim 1, wherein the etching is performed in a microwave plasma chemical vapor deposition apparatus.
9. A patterned diamond film etched by the diamond film etching method according to any one of claims 1 to 8.
10. The application of the patterned diamond film obtained by etching the diamond film according to any one of claims 1 to 8 in the fields of micromachines, microelectronics, microsensors and micro-opto-electromechanical systems.
Technical Field
The application relates to a diamond film etching method, a graphical diamond film and application, and belongs to the field of diamond materials.
Background
In recent years, microelectronic technology is in the fields of aviation, aerospace, industry, agriculture, national defense and the like, and the huge 'magic' of small silicon wafers is not imaginable at all by our predecessors, and certain research is carried out in the field of diamond along with the wide application. For example, diamond film is plated on a silicon wafer and then patterned by etching, so that the silicon wafer can be used as devices such as microelectronics, microsensors and the like.
The diamond has the characteristics of high hardness, wear resistance, corrosion resistance, excellent heat conductivity, insulativity and the like, and has certain difficulty in etching the surface of the diamond due to the serial influences of surface orientation, grain size, thickness, roughness and the like. Arranging a groove on the silicon wafer according to the pattern, growing a diamond layer in the groove, etching off the diamond film outside the groove and only keeping the diamond film at the groove, thus forming a patterned diamond film on the silicon wafer; however, in the current etching method, the patterned diamond film can be obtained only by protecting the trench.
Disclosure of Invention
According to the first aspect of the application, the method for etching the diamond film is provided, the step of setting a mask is omitted, the patterned diamond film is directly formed after the etching is finished, the mask does not need to be removed, and the method is simple to operate and high in efficiency.
The diamond film etching method at least comprises the following steps:
(1) placing a substrate in a cavity, wherein the substrate comprises a silicon wafer and a diamond film, one surface of the silicon wafer is provided with a pattern formed by a groove, and the diamond film covers the surface of the silicon wafer where the groove is located and is filled with the groove;
(2) and forming plasma in the cavity to etch the substrate to obtain a patterned diamond film, wherein the specific etching conditions comprise:
H2and O2As a gas source, and O2Has a flow rate of H21-6% of the flow, preferably O2Has a flow rate of H23-6% of the flow;
microwave is used as an energy source, and the microwave power is 3-8 KW;
the etching temperature is 600-700 ℃.
The etching temperature in this application refers to the substrate temperature.
In one embodiment, in the step (1), the width of the opening of the trench is 14 to 20 μm, and the depth of the trench is 14 to 20 μm.
In a specific embodiment, the diamond film in step (1) is prepared by a hot wire Chemical Vapor Deposition (CVD) process;
optionally, the specific conditions of the hot wire chemical vapor deposition process include:
with H2And CH4As a carbon source, wherein H2And CH4The total flow rate is 200-350 sccm, CH4Has a flow rate of H22-6% of flow, 5-7 tantalum wires in total, 800-900W of monofilament power, 1-3 KPa of working pressure, 850-950 ℃ of silicon wafer temperature and 10-20 h of growth time;
the thickness of the diamond film is 8-12 mu m.
In the application, the diamond film can be prepared by adopting a conventional hot wire CVD process, and the specific process parameters can be adjusted according to the thickness of the diamond film and the like. The diamond film thickness refers to the thickness of the diamond film formed on the plane where the groove opening is located.
Optionally, the specific conditions of the etching in step (2) further include:
the pressure in the cavity is 10-12 Kpa, preferably 10 Kpa.
Alternatively, the H2And O2The total flow rate is 500 to 550sccm, preferably 520 to 530sccm, and the O2Has a flow rate of H23-6% of the flow.
Optionally, the microwave power is 3-5 KW, and 4KW is preferable.
Optionally, the etching temperature is 600-690 ℃, and preferably 680 ℃.
Optionally, the etching time is 3-5 h, preferably 4 h.
Said H2And O2As the gas source, the method comprises the following steps:
after the machine is started, H is firstly introduced into the cavity2After plasma is formed, the power, air pressure and the like reach preset parameter values, and O is added into the cavity2A gas.
The etching is performed in a microwave plasma CVD apparatus.
In one embodiment, a method for etching a diamond film includes the steps of:
1. the interior of the cavity is cleaned by using dust-free cloth and absolute ethyl alcohol, a molybdenum sheet with the thickness of three millimeters is filled as a substrate, and the substrate is vacuumized until the pressure is lower than 0.01 Pa.
2. H of 400-600 sccm is adopted2The gas is used as etching gas (gas source), and the power of 3-8 KW is increased along with the same proportion of the gas pressure and is controlled to be 8-12 Kpa of a specific pressure parameter set value.
3. Firstly introducing H2Matching with the same air pressure and power, and introducing O after the plasma is stabilized2Gas of which O2Flow rate at H2The gas flow is 1-6%, and enough energy sources can perform ionization bombardment on the surface of the diamond for 3-5 h.
The diamond coating (diamond film) has reached the continuous film formation in the ditch groove of silicon chip and silicon chip surface course in the course of growing, the surface of silicon chip passes the existing graphical process, the integrated circuit deep groove of photoengraving figure, reuse the microwave plasma to etch its superficial diamond coating to bombard and ionize, the temperature will be lower in the ditch groove in the course of coating relatively speaking, form the graphite phase more easily than the surface course, the quality of the membrane will be lower than the surface course.
By means of H2/O2As etching gas, plasma formed by combining the etching gas is subjected to energy diffusion, the plasma etches the graphite phase while etching the diamond, but the etching speed of the graphite phase is far higher than that of the diamond (about 50 times), and the graphite phase is easier to etch due to the fact that the internal growth density is lower than that of the surface layer. The inventor is in the realization of the inventionIt was not intended to discover during the inventive process that H was controlled by the etching gas2/O2The proportion, the microwave power and the etching temperature can reduce the adsorption ratio of the interior of the groove to etching gas, so that the aim of removing the diamond coating on the surface layer of the silicon wafer and retaining the coating in the groove is fulfilled.
Meanwhile, the microwave plasma etching process provided by the invention can improve the etching rate and ensure that the etching process has higher uniformity, higher anisotropy and lower irradiation damage, and the microwave plasma generated by microwave discharge realizes low-temperature, high-efficiency and pollution-free surface treatment due to the characteristics of high density, high ionization degree, low working gas pressure, anisotropy and the like.
Preferably, in the step of etching the diamond coating, the plasma density and the sample temperature value are adjusted by adjusting the microwave power and the chamber pressure.
Preferably, the value range of the power and the pressure of the chamber is 3-8 KW/8-12 KPa; preferably 3-6 KW/10-12 KPa.
Preferably, the substrate temperature is 600 ℃ to 700 ℃. Preferably, in the step of etching the diamond coating, the power value range of the microwave plasma CVD equipment is 3-8 KW.
According to the diamond coating etching method provided by the invention, the etching requirement of the diamond coating is finished at one time in a single-step etching mode, the diamond coating is etched by using a microwave plasma CVD device under high power and high air pressure, the microwave power and the high air pressure are combined with hydroxide ions to bombard the surface of the diamond, meanwhile, uneven stubborn film layers or particles are remained, the particle ionization rate reaches a threshold value along with the increase of the air pressure, more neutral particles become the obstruction of effective particle collision, and the ionization rate is reduced. The sample temperature is high, so that certain influence is generated on etching, and the bombardment strength of the diamond film layer is reduced along with the high temperature.
The gas flow reflects the rate of renewal of various components within the chamber, and therefore has a significant impact on the etch rate. Researches show that the etching rate is rapidly increased along with the increase of the flow, but the etching rate is reduced at higher flow; the analysis shows that under the condition of low flow, the etching rate is limited by insufficient supply of active reaction particles, the gas flow is increased, more active reaction particles of gas can be provided, and meanwhile, products can be taken away more quickly, and the etching is accelerated; under the condition of high flow, the active particles are not ready to fully react with the etched material and are pumped away, and the gas is not fully utilized.
H adopted in the present application2And O2The ratio of the flow rates is 100: the power and the chamber pressure are within the range of 3-100: 6, the power and the chamber pressure are within the range of 3-6 KW/10-12 KPa, the substrate temperature is 600-700 ℃, the experiment time is 2-5 hours, the optimal bombardment energy is ensured, the diamond coating on the surface layer of the silicon wafer can be removed, and the coating in the groove can be kept.
According to a second aspect of the present application, there is provided a patterned diamond film etched by the diamond film etching method described in any one of the above.
Optionally, the thickness of the patterned diamond film is 10-14 μm.
According to a third aspect of the present application, there is provided an application of the patterned diamond film etched by the diamond film etching method described in any one of the above in the fields of micromachines, microelectronics, microsensors, and micro-opto-electromechanical systems.
The beneficial effects that this application can produce include:
the method can avoid the situation that the etching force does not act on the diamond film enough, can also avoid the situation that the etching speed is too high to cause the etching of the inner part of the groove, does not need to arrange a mask, directly forms the graphical diamond film after the etching is finished, does not need to remove the mask, and is simple to operate and high in efficiency.
Drawings
Fig. 1 is an electron microscope photograph of a silicon wafer with a diamond film grown on the surface thereof according to embodiment 1 of the present invention, where a is an overhead electron microscope photograph before etching a trench portion, b is a front cross-sectional electron microscope photograph before etching a trench, and c is a cross-sectional electron microscope photograph of a bonding portion between the surface of the silicon wafer and the diamond film;
FIG. 2 is an SEM (Electron microscope) photograph of a silicon wafer after etching in example 2 of the present invention, wherein a is an SEM photograph of a top view of a surface layer and a trench, b is an enlarged SEM photograph of a local top view with a trench, and c is an SEM photograph of a cross section of the trench;
FIG. 3 is an electron micrograph of the silicon wafer after etching in comparative example 2, wherein a is a local overlook electron micrograph, and b is a cross-sectional electron micrograph of the trench portion;
FIG. 4 is an SEM image of the etched silicon wafer of comparative example 4, wherein a is a local overlook SEM image and b is a sectional SEM image of the trench portion.
Detailed Description
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
The raw materials in the examples of the present application were all purchased commercially, unless otherwise specified.
The hot wire chemical vapor deposition equipment used in the method is HF-650 model provided by Beijing Taikono company;
the microwave plasma CVD deposition apparatus used in this application is a HMPS-2150 model available from Chengman and Richardson;
the application obtains an electron microscope scanning image through an EVO18 model large cavity scanning electron microscope (SEM4) device provided by ZEISS company in Germany.
EXAMPLE 1 growth of Diamond film on silicon wafer surface
Carrying out nucleation growth on the silicon wafer by adopting hot filament chemical vapor deposition equipment, wherein the specific process conditions comprise:
with H2And CH4As a gas source, H2And CH4The total flow rate is 200sccm, where CH4Has a flow rate of H2The total power of 5 tantalum wires and monofilaments is 850W, the working pressure is 1-3 KPa, the temperature of the silicon wafer is 900 ℃, and the growth time is 15h, wherein the flow rate is 5 percent;
the upper surface of the silicon chip is patterned in a groove etching mode, the section of the groove is rectangular, the opening width is 18 microns, and the groove depth is 16 microns;
finally, a substrate, namely a silicon wafer with a diamond film on the surface is obtained, as shown in figure 1, the obtained diamond film layer fills the groove and is combined with the upper surface of the silicon wafer, and the thickness of the obtained diamond film is about 10 mu m.
EXAMPLE 2 etching of Diamond film
The method comprises the steps of cleaning the interior of a microwave cavity of microwave plasma chemical vapor deposition equipment by using dust-free cloth and absolute ethyl alcohol, padding a molybdenum sheet with the thickness of two millimeters as a substrate, placing the substrate prepared in the embodiment 1 on the substrate, and vacuumizing to be lower than 0.01 Pa.
Adjusting the microwave power to 4KW, and introducing H into the microwave cavity at a flow rate of 500sccm2
As etching gas, the pressure in the microwave cavity is 10KPa, and the temperature of the substrate is 680 ℃.
After the plasma has stabilized, i.e. H2Power, air pressure, and O of 20-30 sccm is introduced about 5 minutes after the parameters are fixed to the experimental parameters2In cooperation with H2And performing ionization bombardment on the surface of the diamond film for 4 hours as mixed etching gas to obtain the silicon wafer with the graphical diamond film.
Comparative example 1
The etching method is the same as that provided in embodiment 2, except that:
H2flow rate 600sccm, O2The flow is 6-30 sccm, the microwave power is 8KW, the pressure in the microwave cavity is 12Kpa, and the substrate temperature is 870 ℃.
Comparative example 2
The etching method is the same as that provided in embodiment 2, except that:
H2flow rate 600sccm, O2The flow is 12-30 sccm, the microwave power is 7KW, the pressure in the microwave cavity is 11Kpa, and the substrate temperature is 840 ℃.
Comparative example 3
The etching method is the same as that provided in embodiment 2, except that:
H2flow rate 500sccm, O2The flow is 15-30 sccm, the microwave power is 6KW, the pressure in the microwave cavity is 10Kpa, and the substrate temperature is 780 ℃.
Comparative example 4 the same etching method as provided in example 2, except that:
H2flow rate 500sccm, O2Flow rate of 10-30 sccm, microwaveThe power is 6KW, the pressure in the microwave cavity is 12Kpa, and the substrate temperature is 810 ℃.
Comparative example 5
The etching method is the same as that provided in embodiment 2, except that:
H2flow rate 500sccm, O2The flow rate is 20-30 sccm, the microwave power is 4KW, the pressure in the microwave cavity is 11Kpa, and the substrate temperature is 710 ℃.
The products provided in example 2 and each proportion are characterized, wherein, referring to fig. 2, the plasma in example 2 is effectively bombarded, so that the surface layer (the diamond film on the surface of the silicon wafer) is basically etched clean, and the diamond in the groove is well preserved;
referring to fig. 3, a typical representative of comparative examples 1 and 2 is comparative example 2, as shown in fig. 3, under which etching is performed, the surface layer is only partially etched by plasma, but diamond inside the groove is substantially etched;
referring to fig. 4, a representative of comparative examples 3, 4 and 5 is comparative example 4, in which the etching is performed under the condition that the surface layer is substantially etched, but most of the diamond inside the groove is also etched, as shown in fig. 4.
The process parameters and diamond film etching conditions of the comparative examples and example 2 are shown in table 1:
TABLE 1 Process parameters and results
In the application, the surface uniformity is not good when the time does not reach 4 h; part of the area is not etched cleanly, and the proper air pressure and H are combined when the temperature is about 680 DEG C2And a high oxygen flow value, so that the etching rate is stably improved; thereby achieving the best etching effect.
Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.