Method for growing large-area single crystal diamond by adsorption splicing
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of material growth, and particularly relates to a method for growing large-area monocrystalline diamond by adsorption splicing.
[ background of the invention ]
At present, the microwave plasma chemical vapor deposition method is mainly used for growing the single crystal diamond, and the method uses a 2.45GHz microwave source to carry out epitaxy under the conditions of 50-200Torr, 700-3000W and 1000 ℃. The method has the advantages that the size of the plasma can be regulated and controlled through the cavity pressure, so that the epitaxy of diamonds with different sizes is met, and conditions are provided for the epitaxy of large-area single crystal diamonds. The method has the advantages that the single crystal diamond obtained by epitaxy has less impurities and high purity, and is suitable for the field of semiconductor electronic devices.
In order to obtain large-sized single crystal diamond, heteroepitaxy and homosplicing epitaxy methods are often used. Heteroepitaxy generally uses a microwave plasma chemical vapor deposition method to epitaxially grow large-area single-crystal diamond on an iridium substrate, but the method causes the grown single-crystal diamond to have more impurities and poor quality because of epitaxy on the iridium substrate, and cannot meet the requirements of preparing electronic devices. The homogeneous splicing epitaxy method is that two single crystal diamonds are spliced together and put into a microwave plasma chemical deposition system, splicing cracks are bonded together by using newly grown single crystal diamonds through epitaxial growth, and then epitaxial growth is continued to obtain the complete large-area single crystal diamond. However, in the splicing process, due to the existence of stress or mechanical vibration, the positions of the samples are easy to slide relatively, even one of the samples is tilted and suspended in the air, which will result in the increase of the thermal resistance of the samples, so that the whole environment of epitaxial growth is completely changed, and finally the splicing seam is polycrystalline, even the spliced sample is cracked, and the splicing fails.
[ summary of the invention ]
The invention aims to provide a method for growing large-area single crystal diamond by adsorption splicing, which aims to solve the problems that the relative position of a sample in the growing process is easy to change and even the sample warps in the existing splicing process due to the existence of stress or mechanical vibration.
The invention adopts the following technical scheme: a method for growing large-area single crystal diamond by adsorption splicing,
based on a sample holder, at least two groups of adsorption channels are vertically arranged on the sample holder in a penetrating way, each group of adsorption channels comprises one or more through holes, and the through holes are used for sucking air in the through holes from the lower part of the through holes to form a low vacuum state;
the method comprises the following steps:
1) preparing at least two cleaned diamonds;
2) each diamond is closely placed on the upper surface of the sample support in parallel, and the bottom of each diamond is covered with a group of adsorption channels;
3) vacuumizing the adsorption channel to enable each diamond to be firmly adsorbed on the sample holder;
4) and simultaneously growing complete diamonds on the upper surfaces of the diamonds by using a plasma chemical deposition technology.
Further, the diamond is a single crystal diamond, and the upper and lower surfaces thereof are precisely polished with a roughness between 1nm and 100 μm.
Further, the cross-sectional area of the through-hole is smaller than the area of the lower surface of the diamond in contact therewith.
Further, the sample holder is a flat or concave platform.
Furthermore, the sample holder is made of molybdenum metal, and the roughness of the upper surface of the sample holder is between 1nm and 1 mm.
The invention has the beneficial effects that: after the two single crystal diamonds are spliced together, the two samples are firmly adsorbed on the sample support by using the through holes, and then homoepitaxy is carried out to grow the complete large-area single crystal diamond. The sample holder has the advantages that the structure is very simple, the air suction device is arranged below the sample holder, the sample holder is punched, and a sample can be directly fixed on the sample holder, so that the structure is very simple; in addition, impurities cannot be introduced in the whole process of fixing the sample, the surface of the diamond is polluted, and the epitaxial growth of the diamond is facilitated.
[ description of the drawings ]
FIG. 1 is a schematic view of a sample holder of the present invention with two single crystal diamonds placed thereon;
FIG. 2 is a schematic view of another sample holder of the present invention with two single crystal diamonds placed thereon;
FIG. 3 is a schematic illustration of the effect of growing a large area single crystal diamond using the sample of FIG. 1;
figure 4 is a graph illustrating the effect of growing a large area single crystal diamond using the sample of figure 2.
Wherein, 1, single crystal diamond I, 2, single crystal diamond II, 3, sample holder, 4, through hole, 5, large area single crystal diamond.
[ detailed description ] embodiments
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention comprises two or more single crystal diamonds, a sample holder and an adsorption channel; placing a plurality of single crystal diamonds on a sample holder in parallel; the lower surfaces of the single crystal diamonds are covered with the through holes; the through hole penetrates through the sample holder; the complete large-area single crystal diamond is extended on the upper surfaces of the plurality of single crystal diamonds; the invention reduces the problems that the relative position of the sample changes and the sample tilts up at one side in the growth process due to factors such as mechanical vibration, internal stress and the like, and provides a new method for splicing and growing large-area single crystal diamond.
The invention is based on a sample holder (3), at least two groups of adsorption channels are vertically arranged on the sample holder in a penetrating way, each group of adsorption channels comprises one or more through holes (4), and the through holes (4) are used for sucking air in the holes from the lower part of the through holes to form a low vacuum state. The adsorption channel is used for providing negative pressure so that the diamond is firmly adsorbed on the sample holder.
The method of the invention comprises the following steps:
1) preparing at least two cleaned diamonds;
2) each diamond is closely placed on the upper surface of the sample support 3 in parallel, and the bottom of each diamond is covered with a group of adsorption channels;
3) each diamond is firmly adsorbed on the sample holder 3 by vacuumizing the adsorption channel;
4) the entire diamond 5 is simultaneously grown on the upper surface of each diamond using a plasma chemical deposition technique.
The method of the present invention will be described below by taking single crystal diamond I1 and single crystal diamond II2 as examples.
To splice and grow the single crystal diamond I1 and the single crystal diamond II2, two adsorption channels are arranged on the sample holder 3, each adsorption channel can comprise one or more through holes, and the single crystal diamond I1 and the single crystal diamond II2 are closely and parallelly arranged on the two through holes of the sample holder 3; vacuumizing the through hole 4 to ensure that the single crystal diamond I1 and the single crystal diamond II2 are firmly adsorbed on the sample holder 3, and the single crystal diamond I1 and the single crystal diamond II2 are still closely arranged; plasma chemical deposition techniques were then used to extend the entire large area single crystal diamond 5 beyond the upper surface of single crystal diamond I1 and single crystal diamond II 2.
Wherein the single crystal diamond I1 and the single crystal diamond II2 are single crystal diamonds and the upper and lower surfaces are precisely polished to a roughness of between 1nm and 100 μm; the sample holder 3 is made of molybdenum metal, the upper surface of the sample holder is accurately polished, and the roughness is between 1nm and 1 mm; the through hole 4 penetrates through the sample holder 3, and the aperture range does not exceed the lower surfaces of the single crystal diamond I1 and the single crystal diamond II 2; air in the through hole can be sucked away under the through hole 4, a low vacuum state is formed, and the single crystal diamond I1 and the single crystal diamond II2 are firmly adsorbed on the upper surface of the sample holder 3.
Examples
1) Preparing a cylindrical molybdenum, wherein the diameter of the cylinder is 50 mm, and the height of the cylinder is 30 mm;
2) a space with the diameter of 20 mm and the depth of 15 mm is dug downwards on the upper surface of the cylindrical molybdenum. The center of the upper surface of the cylindrical molybdenum is circularly superposed with the upper surface of the hollow cylinder;
3) two through holes are vertically drilled downwards from the lower surface of the hollow cylinder, the diameter of each through hole is 2 mm, and the distance between each through hole and the center of the lower surface of the hollow cylinder is 0.5mm at two sides of the center of the lower surface of the hollow cylinder, as shown in figure 2;
4) two 3X 0.5mm3The diamond of (2) was placed over the two through holes and the two samples were held close together as shown in fig. 2;
5) the through holes are evacuated, and then the two samples can be fixed on the sample holders, as shown in fig. 2.
The prior art is to weld the sample to the sample holder using metal welding, such as gold foil, and weld the sample and the sample holder together at high temperature. The prior art has the following defects: (1) because the welding material exists between the sample and the sample holder, the melting point and the evaporation temperature of the welding material limit the temperature in the diamond growth process, namely the diamond growth temperature cannot be higher than the melting point and the evaporation temperature of the welding material, otherwise, the welding material is melted and evaporated, so that the sample is moved and polluted, and the defect limits the adjustment range of the diamond growth process and is very unfavorable for the diamond growth; in addition, the solder has thermal resistance, so that the thermal resistance from the sample to the cavity cooling table is changed, and the optimal growth condition is changed. (2) The surface of a sample is easily polluted in the welding process, so that the subsequent diamond epitaxy is very unfavorable, polycrystalline diamond is easily grown in the polluted position, or pollutants are wrapped in the epitaxial diamond, so that the quality of the diamond epitaxy is reduced; (3) the welding technology is needed, and the process is complex.
The method for growing the large-area monocrystal diamond by the adsorption splicing method adopts the following technology: punch on the sample holds in the palm, in addition equipment itself can adsorb the sample and hold in the palm, this just makes the inside air of through-hole can automatic evacuation to hold in the palm with sample can all be firm absorption in whole growth process on the sample. The method of the present invention completely overcomes the disadvantages of the prior art. From the current literature and data, all sample holders have no through-hole structure, because people are used to fix the samples by using a metal welding process; in addition, it is customary to consider that the sample holder should be complete and flat so that the sample is uniformly thermally conductive, and therefore it is not conceivable to provide through holes beneath the sample to hold the sample. The method of the invention leads the sample to conduct heat uniformly by adjusting the position, size, number and the like of the through holes.
According to the invention, after two single crystal diamonds are spliced together, two samples are firmly adsorbed on the sample holder by using the through holes, and then homoepitaxy is carried out to grow the complete large-area single crystal diamond. The invention firmly adsorbs the two single crystal diamonds on the sample holder, reduces the problems that the relative position of the sample changes and the sample tilts up at one side caused by factors such as mechanical vibration, internal stress and the like in the growth process, and provides a new method for splicing and growing large-area single crystal diamonds.