Plasma etching cleaning machine indium phosphide etching

Plasma etching cleaning machine indium phosphide etching:

Indium phosphide can not only be used as the substrate material of the epitaxial layer, but also can be used as the channel material or electrode material itself, so relative to other 35 groups of materials, the plasma etching of indium phosphide material cleaning machine plasma etching research is also more. Using CH4 and H2 to etch phosphated steel is a kind of method that appeared earlier. This method can be applied to large area and large size indium phosphide etching. Etching rate is significant, but in the graphics complex and concentration areas domain due to produce by-products is difficult to volatilize, and plasma etching of cleaning machine plasma etching gas polymer is very heavy, it is easy to etch termination occurs at the bottom of the etched pattern, or graphic morphology change poor phenomenon, therefore, CH4 and H2 gas combinations need to be further improved to become the industrial applications of indium phosphide etching method.

Literature shows that the low temperature etching of indium phosphide with chlorine as the main etching gas has the problems of low etching rate and difficult removal of by-products at low temperature. Chlorine is very sensitive to temperature, and the higher the temperature, the faster the etching rate. However, when the temperature is low, due to the large number of by-products and difficulty in volatilization, the enrichment effect of by-products will cause the etching termination when the total amount of etching is too large (InClx is difficult to volatilize). However, the low temperature etching mainly with CH4 and H2 is faced with the phenomenon of low etching rate causing the etching stop. Therefore, how to realize the etching of InP materials at low temperature has become a common research hotspot. The more common method is to mix other gases with conventional indium phosphide etching gas, and the earlier research in this area was reported by Carlotta in New Zealand. Using Cl2/Ar/H2 mixed gas, good indium phosphide graphics can be obtained at 150℃, and smooth and continuous graphic morphology can be obtained at high temperature, but 150℃ is not low temperature after all.

In 2007, Tsinghua University reported a method to further optimize the gas ratio and improve other conditions to overcome these problems. This etching method can overcome the problem of difficult-to-volatilize by-products at room temperature. Because the appropriate ratio of CH4 and chlorine gas will form In(CH)x by-products, which are easier to volatilize and remove than InClx. The surface roughness of indium phosphide is low and there is no residue of by-products. The etching conditions are as follows :Cl2:CH4:Ar=12∶12:3; 4 mt; TCP is 1000 w; Bias voltage 300 v. The calculated etching rate is 8600 A /min, and the selective ratio of SiN is 10∶1, which can meet the requirements of the current process.

However, the disadvantages of this method are also obvious: the by-product is completely volatile, the side wall of the graph is not protected enough, resulting in the overall shape will be concave. However, such morphology can hardly meet the requirements of device performance no matter as gate, epitaxial layer or mask. Therefore, another gas mixture Cl2/N2/Ar has been developed by the authors, which uses different etching mechanism and adds N2 to better remove indium phosphide by physical bombardment. This kind of method can realize the vertical graph of phosphated steel.

The study on etching rate and selection ratio of different flow ratio is summarized in Table 8.2. It can be seen that in the absence of N2, the selection ratio is high, but the surface roughness is poor. With the increase of N2, the roughness is continuously improved, but a lot of selection ratio will be sacrificed. Based on the existing etching machine, we should be able to make better use of different etching steps, using different etching gas ratios and other conditions, and synchronously improve these contradictions to obtain the desired graphics.

The above methods are implemented in the ICP machine, and earlier in the RIE machine has also been studied to explore the impact of pressure on the etching of indium phosphate. With the increase of pressure, the by-products continue to accumulate so that the selection ratio continues to decrease, and the etching is terminated. Under the condition of 5 pa, is there a silicon nitride environment of hard mask etching pattern is almost the same, but under the 10 pa, the absence of silicon nitride hard mask, in the graphics area density is bigger, the by-product or polymers is more, etching rate fell sharply, and got there is a big difference between different graphics environment etching depth; When the pressure is 20Pa, the etching will stop regardless of the density surrounding the pattern. This is because the amount of polymer is so large that it covers all the pattern and the etching cannot be carried out.

A more detailed study of the control of the shape came from a report in 2012. From the simulation results, the morphology of deep groove or deep hole is related to the plasma adsorption rate and adsorption law of plasma etching cleaning machine, and whether there are two or more adsorption will directly affect the top of the graph morphology. Different plasma adsorption has a great influence on the morphology near the opening of deep hole or deep groove, and the actual results of surface simulation and experiment are also in good agreement, which shows that the simulation results are very reliable. The root cause is that the etching is divided into two different stages due to the different adsorption positions of different plasmas in the deep hole. Near the exit, there are more InCl2 and InCl by-products with more chlorine, so the top is dominated by chemical etching. And the bottom of the chlorine-containing plasma etching cleaning machine plasma and byproducts are less, mainly to physical etching. So you have a different shape.

Because the existing plasma etching cleaning machine has the function of controlling the dissociation rate and filtering the plasma that is not needed, we can accurately define the graphics we need through the advanced etching machine configuration. To achieve the precise control of the purpose of patterning. With the continuous upgrading of the etching machine, it is believed that the function of controlling more ideal graphics will be developed continuously, the control ability of single or continuous graphic morphology changes will be strengthened continuously, and the conversion between graphic forms will be more continuous and natural.