With the rapid development of science and technology, integration and ever-increasing, decreasing line width, so the quality of silicon substrate films have become increasingly demanding, especially on polished wafers of silicon surface quality requirements become more stringent. This is mainly the surface at the end of particles and metallic impurities contamination will seriously affect the device yield, at present, demand for polished wafers at the end of the end of the surface is larger than 0.2μm particle number should be less than 20 / piece. In the IC manufacturing process, almost every process has a cleansing, cleaning semiconductor devices important and most frequent steps, and cleaning effect a direct impact on device yield, performance and reliability, so at home and abroad in the ongoing cleaning process.
Wet chemical cleaning
Most of the cleaning methods can be roughly divided into wet cleaning and dry cleaning, in the past three decades, wet cleaning wafer cleaning technology has been the mainstream, it is the use of solvents, a variety of acid and alkali, surface active agents and water, through corrosion, dissolution, chemical reaction into the solution and hot and cold), the washing and other methods to remove the chip surface staining material, each time after the use of chemical reagents are applied ultrapure water to wash, to remove the remnants of chemical reagents . Although there is no What kind of cleaning method can be applied to all cleaning requirements, but the past three decades has formed its own wet cleaning a typical cleaning sequence.
(1) Common chemical reagents, washing fluid nature of the
Chemical reagents and cleaning liquid decontamination capability, for wet chemical cleaning of the cleaning efficiency will have a decisive affect 9 to, wet chemical cleaning of the first step is based on wafer cleaning purposes and asked to select the appropriate reagents and cleaning fluid. Commonly used in silicon wafer cleaning chemicals and cleaning fluids are mainly inorganic acid, oxidants, complexing agent, hydrogen peroxide cleaning fluid, organic solvents, synthetic detergents, electronics cleaning agents for several major categories. Their primary role in the chemical cleaning and chemical properties in Table 1.
(2) solution immersion method
Soaking solution will be cleared through silicon immersed into the solution to remove surface contamination to reach the purpose of a method of wet chemical cleaning which is the most commonly used methods. It is mainly through the solution and the pollution of the surface of silicon impurities in the immersion process of dissolution of a chemical reaction and to achieve the clear silicon surface impurities. Choose a different solution to soak up to clear the different types of silicon surface contamination impurities. A simple solution immersion method's efficiency is often unsatisfactory, so the introduction of immersion, while often also accompanied by heat, ultrasound, mixing and other physical measures.
(3) Mechanical scrubbing method
When the silicon surface stained particles or organic residues often used method of cleaning wipe film. Brush France is considered to remove the chemical mechanical polishing liquid residue of the most effective methods. This cleaning method in Japan, Korea and Taiwan are very common in Europe and the United States also been widely applied. Mechanical scrubbing method is generally divided into hand-scrubbing method and mechanical scrubbing method in two ways.
Hand-scrubbing method is the simplest kind of scrub, common clamp the clip to take soaked toluene, acetone, ethanol and other organic solvents, cotton balls, in the silicon surface graze along the same direction in order to remove the wax film, dust and other solid particles Secretary adhesive residue. However, this method could easily lead to scratches, pollution is serious.
The brush used to scrub film machine can be divided into a purely mechanical brush cleaning machines and high-pressure rub rub-chip-chip machines. Purely mechanical film machine mechanical rotating brush, so soft brush or wool roller brush brush brush the surface of silicon. The Act created a more hand-washing greatly reduce the silicon scratch. The high-pressure cleaning machine because there is no mechanical friction film, it will scratch the surface of silicon, but can meet clean stains inside the slot marks, silicon wafer scrubbing machine scrubbing is the trend.
(4) The ultrasonic cleaning method
Ultrasonic cleaning is widely used in cattle conductor industry as a cleaning method, the method's advantages are: a good washing effect, simple operation, for miscellaneous devices and containers can also be removed, but the method is relatively noisy, easily broken transducer shortcomings.
The method of cleaning works as follows; in a strong ultrasonic effects (commonly used in ultrasonic frequency is 20 kH2 to 40kHz or so), the liquid will be produced within a dense sparse and the Department of the Ministry, the Ministry of generated sparse near-vacuum cavity bubbles disappear when the bubble cavity an instant, in the vicinity will have a strong local pressure to break the chemical bonds within the fools, thus making the surface of silicon impurity desorption. Lan sound wave frequency and the cavity resonance frequency of bubbles, the mechanical action as large as the largest gathering of a large number of heat inside the bubble, so that higher temperatures promote the reaction from occurring. The effect of ultrasonic cleaning and ultrasonic conditions (such as temperature, pressure, ultrasound frequency, power, etc.) related to, but Jane is often beneficial for improving ultrasonic cleaning effect of the increase.