Effects of silicon and germanium groove interface etched by plasma Cleaning machine equipment on the shape of Sigma groove and the growth of silicon and germanium epitaxy

• Categories:Technical Support
• Author:plasma cleaning machine-surface treatment equipment-CRF plasma machine-Sing Fung Intelligent Manufacturing
• Origin:
• Time of issue:2020-12-10
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(Summary description)It is well known that a large number of polymer by-products are produced during the dry etching of silicon in plasma cleaning machine equipment. The total amount of reaction in the intensive area of the pattern is large, so the by-products are easy to aggregate. In the graphics silicon wafer experiment, the thick etching by-products in the dense area of the graphics lead to the shallow depth compared with the sparse area of the graphics. Such depth differences become more pronounced when the TMAH is embedded, and even prevent the formation of normal-shaped Sigma silicon grooves. This is because the plasma cleaning machine equipment etching post-treatment process requires a clean silicon interface to do the wet etching to form the Sigma silicon groove. This difference in depth can be induced by the Presence of Cl2 in the etching gas. Compared with other gases (such as HBr), the by-products formed by chlorine and silicon have better gasification, which can effectively reduce the deposition of etching by-products and improve the etching load. Experimental results show that the addition of Cl2 is very effective for improving the depth difference. By introducing Cl, the depth difference caused by this pattern can be improved by 60%. On the other hand, prior to the introduction of Cl2, subsequent processing processes often fail to form normal Sigmoid silicon grooving, which can be solved after the introduction of Cl2.   On the other hand, wet cleaning after dry etching of plasma cleaning machine also plays an important role in the formation of sigma silicon groove. The silicon oxide growing on the silicon groove surface will hinder the subsequent ammonium tetramethyl hydroxide treatment, leading to the failure of the formation of sigma silicon groove. In IC manufacturing, dilute hydrofluoric acid is usually used to remove the silicon oxide, ensuring that there is no silicon oxide or other contamination on the silicon surface. By adjusting the process time of hydrofluoric acid, the depth difference of sigma silicon groove with different graphics is greatly improved. All experiments were based on the same dry etching and ashing processes. When the amount of diluted hydrofluoric acid exceeds a certain amount, the depth difference of the Sigma groove can be controlled at a lower level. However, excessive hydrofluoric acid cleaning will remove too much shallow trench isolation silica, resulting in device isolation performance degradation. Therefore, both the cleaning effect of silicon trench and the loss of silicon oxide in shallow trench should be taken into account in the use of hydrofluoric acid.   The epitaxial growth of germanium silicon is very sensitive to the surface properties of silicon groove, and it is easy to form various epitaxial defects. So it is very important to choose the ashing process after dry etching of silicon trench plasma cleaning machine. In the ashing process, not only the residual photoresist is removed, but also the pure silicon surface is obtained to facilitate the epitaxial growth of germanium silicon. The podcasting process consists of oxidized podcasting, low-hydrogen hybrid gas (nitrogen hydrogen gas containing 4% hydrogen) podcasting, and high-hydrogen hybrid gas (hydrogen content greater than 20%) podcasting. The low hydrogen gas mixture ashing process can effectively reduce the photoresist and the residue of etching by-products, but the epitaxial growth defects are not significantly improved, because the photoresist and etching by-products are not the main causes of epitaxial defects. It has been reported in the literature that the Si-C bond is the main cause of the epitaxial defect. Carbon atoms come from photoresist and etching gases and are injected into the silicon during etching. In the process of plasma etching in the plasma cleaning machine, the carbon reacts with the volume silicon or the silicon chloride on the side wall to form the SI-C bond. Therefore, it is necessary to find a way to remove si-C bond effectively to improve the epitaxial defects of germanium silicon. Compared with the low hydroashing process, the high hydroashing process can remove the Si-C bond on the silicon groove surface more effectively, so as to improve the silicon and germanium epitaxial defects. The oxidizing ashing process of plasma cleaning machine can also improve the epitaxial defects on the basis of increasing the amount of oxidation. However, such a process will form a thicker silicon oxide layer on the surface of the trench. As mentioned above, the process of removing the silica layer produced by the ashing will also cause the damage of the shallow trench isolation silica layer, which will affect the device performance. Therefore, the oxidized ashing process is not applicable to the germanium silicon process.