United Microelectronics Corp.

Ya-Lun Cheng

Chin-Cheng Chien

Neng-Hui Yang

Yu-Kun Chen

Yu-Ren Wang

Yi-Chia Lee

A cleaning method and cleaning recipes are disclosed. The present invention relates to a method for cleaning a semiconductor substrate and cleaning recipes. The present invention utilizes a first cleaning solution including diluted hydrofluoric acid and a second cleaning solution including hydrogen chloride and hydrogen peroxide (HO) to clean a semiconductor substrate without using an alkaline solution including ammonium hydroxide. Accordingly, a clean surface of a semiconductor substrate is provided in selective epitaxial growth (SEG) process to grow an epitaxial layer with smooth surface.

Method of cleaning a semiconductor substrate

A method of forming a transistor involves firstly forming at least one gate structure on a semiconductor substrate. Then, a surface cleaning process is performed. In the surface cleaning process, a chemical oxidation method is utilized for forming a first oxide layer on a surface of the semiconductor substrate not covered with the gate structure and the first oxide layer is removed subsequently. Finally, a selective epitaxial growth method is utilized for forming a first epitaxial layer on the surface of the semiconductor substrate.

Method of forming a transistor using selective epitaxial growth

A method for preventing to form a spacer undercut in SEG preclean process is provided. This present invention utilizes HFEG solution to etch the first spacer and the second spacer simultaneously, which can prevent from producing a spacer undercut, meanwhile; a native oxide layer upon a surface of a semiconductor substrate is removed. Hence, the clean surface on the semiconductor substrate is obtained. This method includes the steps as follows: Firstly, the native oxide layer upon the surface of the semiconductor substrate is removed by DHF (HF in deionized water) solution. Then, etching the first spacer and the second spacer at the same time by HFEG (HF diluted by ethylene glycol) solution. Also, the native oxide upon the semiconductor substrate is removed. Therefore, it obtains the clean semiconductor surface without a serious spacer undercut.

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Taipei, Taiwan

Ya-Lun Cheng