Analysis of Core Wet Cleaning Process

I． RCA Standard Wash

The RCA cleaning method is a classic wet cleaning sequence that consists of two main steps:

SC1 cleaning solution

Composition: Ammonia, hydrogen peroxide and deionized water are mixed in the ratio of NH₄OH:H₂O₂:H₂O=1:2:10

Process conditions: The temperature is usually controlled at 50±3°C. Function: The solution is mainly used to remove particulate pollution on the surface of silicon wafers, and can remove slight organic matter and some light metal contaminants. The mechanism is that ammonia evenly etches the silicon surface in a small amount, and at the same time, hydrogen peroxide oxidizes the surface and makes the particles fall off under the action of electrostatic repulsion by adjusting the surface potential

SC2 cleaning fluid

Composition: hydrochloric acid, hydrogen peroxide and deionized water

HCl:H₂O₂: H₂O=1:2:5 ratio mixing process conditions: the temperature is also 50±3°C. Function: The core function of this solution is to remove metal contaminants. Hydrochloric acid can form soluble chlorine complexes with a variety of metal ions, so as to effectively dissolve and remove heavy metal impurities such as alkali metals and transition metals.

II．SPM cleaning

SPM is a powerful cleaning solution used to remove stubborn organic matter

Composition: Sulfuric acid and hydrogen peroxide are mixed in a ratio of H₂SO₄:H₂O₂,=5∶1 Process conditions: carried out at a high temperature of 130±5°C,

Function: Mainly used to remove photoresist and other complex organic pollutants High-temperature concentrated sulfuric acid provides strong oxidation and dehydration, and can effectively decompose organic substances.

0010-20351 6 INCH DEGAS LAMP MODULE 350C PVD

III.Silica etching: DHF and BHF/BOE

This series of processes is used for controlled etching of silica media layers.

1.DHF

Introduction: That is, diluted hydrofluoric acid.

Typical ratio: Dilution by volume ratio HF (49%): H₂O=1:100 or 1:10.

Process conditions: Typically performed at 25±1°C.

Function: For etching thermally grown silica and removing the native oxide layer from the silicon surface. The reaction equation is: SiO₂+6HF=H₂SiF₆. +2H₂O. After removing the primary oxide layer, the silicon surface becomes hydrophobic.

2.BHF/BOE

Introduction: That is, buffered hydrofluoric acid, composed of hydrofluoric acid and ammonium fluoride Typical ratio: NH₄F:HF=10:1 (commonly used)

Process conditions: The temperature is usually controlled at 25/26.5±1°C

Function and principle: Used to achieve uniform and stable silica etching. The buffering effect of ammonium fluoride maintains the concentration of HFz ions in solution, stabilizes the etch rate, and prevents process repeatability problems caused by fluctuations in HF concentration. At the same time, its stable pH value can avoid erosion of the photoresist mask.

IV. HPO cleaning: Silicon nitride selective etching

Thermal phosphoric acid is used to selectively remove the silicon nitride layer

Process conditions: Phosphoric acid with a concentration of 86% is used, treated at a high temperature of 160±5°C°C.

Function: This process can evenly etch silicon nitride with a low etch rate on silica, so it has a high silicon nitride/silicon oxide etch selection ratio, and is often used to selectively remove silicon nitride masks or stop layers on silicon oxide layers.

V. Solvent cleaning

Solvent cleaning is used for organic pollutants that cannot be treated with water-based solutions.Composition: It usually contains hydroxylamine and complexing agent, and often uses IPA (isopropyl alcohol) or NMP (N-methylpyrrolidone) as a co-solvent to improve cleaning efficiency.

Process conditions: at 75±5°C, treatment for about 20 minutes,

Function: Specially designed to remove polymer residues and stubborn photoresists formed after dry etching and ion implantation.

Note: This process will slightly etch metal films such as aluminum and copper, and its impact on the metal layer needs to be considered in the integration process.