How Advanced Ozone Cleaning Reduces Costs and Improves Wafer Yields When ozone is used to clean silicon wafers, it reduces the use of aggressive chemicals and it can decrease the wafer particle count. Modutek’s advanced ozone cleaning process can clean more quickly than many chemical-based processes and it delivers other benefits. Ozone is used to remove organic contaminants from wafer surfaces in either the Coldstrip sub ambient process or the Organostrip process. Either process can reduce overall wafer fabrication costs and improve manufacturing facility performance.

Advanced Ozone Cleaning Outperforms Chemical Stripping

With increased regulation of the use of dangerous chemicals and pressure on businesses to make their operations more environmentally friendly, Modutek developed the advanced ozone cleaning processes to help semiconductor manufacturers and research labs reduce chemical use. Ozone is introduced in Modutek’s DryZone system in compact units using the Coldstrip or Organo strip processes. Both cleaning methods also feature a reduced particle count compared to chemical cleaning methods.

In the Coldstrip process, wafers are first rinsed with deionized water to remove soluble non-organic contaminants. The process operates at four to ten degrees centigrade. After the rinsing, ozone is introduced into the chamber and combines with the carbon of the organic compounds on the wafer surfaces. The ozone-carbon reaction forms carbon dioxide, leaving wafers clean and almost free of particles.

The Organostrip process also uses ozone but operates at ambient temperature. Ozone is introduced into the process dissolved in acetic acid, a mild solvent in which ozone has a very high solubility. The wafers are rinsed with the ozone-acetic acid solution and the high level of ozone rapidly oxidizes the organic contaminants. The waste products of the process do not require special treatment. Both processes work quickly and feature excellent cleaning performance with low particle counts.

Changing to the Advanced Ozone Cleaning Process Delivers Substantial Benefits

The major benefits of changing from chemical cleaning to an advanced ozone cleaning process is a reduction in the use of toxic chemicals and improved cleaning performance with a lower particle count. These two factors are at the root of additional benefits resulting in cost savings, better yields and improved safety for employees.

Reduced Use of Chemicals

When the use of toxic chemicals is reduced, there are cost reductions in addition to savings resulting from fewer chemical purchases. Other savings include reduced costs for chemical storage, handling and disposal. Employees benefit from lower exposure to harmful chemicals and from increased workplace safety because there is less danger of spills or accidents.

Regulatory compliance costs are also reduced. As environmental regulations become more onerous, costs rise and compliance becomes more difficult. Reduced chemical use results in lower compliance costs, and a more environmentally friendly operation helps improve community relations and the environmental reputation of the business.

Lower Particle Contamination

Lower particle counts are the result of better cleaning performance. Particle counts play ang increasingly important role in wafer structures that are smaller and more tightly packed. Even a single particle can block a conducting path or the etching of a tiny detail. Fewer particles means a lower rate of defective products and higher yields. Product quality and longevity may also be improved.

Improved Cleaning Performance and Wafer Yields with Less Equipment

In addition to a lower particle count, the improved cleaning performance of the advanced ozone cleaning process results in shorter cleaning times within a smaller footprint. Modutek’s DryZone units used for the ozone cleaning process are compact and take up less space than the corresponding chemical cleaning stations. Cleaning is more rapid resulting in higher throughput. As a result of these benefits, the overall performance of the silicon wafer fabrication facility can improve substantially.

Modutek Provides Advanced Equipment for Manufacturers

As one of the leading semiconductor equipment manufacturers, Modutek can advise customers on how to implement a change to ozone cleaning. Modutek offers a free consultation and quote on their equipment, and ensures their equipment will support processes that meet customer requirements.

When silicon wafers are cleaned between manufacturing steps, it is critical to remove all contamination from the wafer surfaces. The remaining traces of process chemicals or microscopic particles can disrupt the etching process and result in defective or low-quality semiconductor devices.

Megasonic cleaning uses high-frequency sound waves in the cleaning tank to remove contaminants and particles from the silicon wafers. The technology can save time and money because it works quickly and does not require expensive chemicals. Silicon wafers cleaned with Megasonic cleaning are completely clean with a reduced particle count. As a result, the technology can improve the operation of semiconductor manufacturing lines for semiconductor fabricators and research labs.

Megasonic Cleaning Reduces the Use of Toxic Chemicals

The cleaning of silicon wafers after the completion of each semiconductor manufacturing step is accomplished by soaking the wafers in mixtures of chemicals including hydrochloric acid or sulfuric acid. In addition to the cost of the chemicals themselves, there are ongoing costs related to the storage, delivery, and disposal of these chemicals. The possibility of leaks and the disposal of the waste chemicals represent environmental hazards that are continuously being mitigated with tighter regulations. Reducing the use of aggressive chemicals can save money beyond their direct cost and can improve the environmental footprint of the semiconductor manufacturing facility.

With Megasonic cleaning, a frequency generator produces an electric signal in the MHz range that is transmitted to a transducer. The transducer that is immersed in the cleaning solution converts the signal to sound waves in the cleaning tank. The sound waves create microscopic cavitation bubbles that deliver a gentle scrubbing action against the surface of the silicon wafer. The cleaning intensity is strong enough to dislodge impurities and contaminants but will not damage the wafer surface or the microscopic structures that have been etched into it.

When Megasonic cleaning is used to replace some of the traditional cleaning steps, the use of chemicals is reduced. Megasonic cleaning uses plain water or water with the addition of mild detergents. The cost benefits and reduced environmental impact can be substantial, and the areas where Megasonic cleaning is used will have increased worker safety and reduced chemical exposure.

Megasonic Cleaning Can Deliver Improved Cleaning Performance

While acid baths work well for cleaning general contaminants from silicon wafer surfaces, ensuring low particle counts can be challenging. Contaminating particles can block etching and cause defects in the final semiconductor devices. As functions become more and more closely packed on the wafer and microscopic structures become smaller, a single particle can affect the etched shapes and current paths. A key factor for improving output quality and reducing defects is reducing particle counts to a minimum.

Microscopic particles can be difficult to remove from the surface of silicon wafers because they often develop a static charge that allows them to cling to the wafer. Chemicals can dissolve the substances that make the particle adhere to the wafer surface but the static charge often remains as an additional bond. With Megasonic cleaning, very small cavitation bubbles form and collapse in tune with the sound wave frequency in the MHz range. When a bubble collapses near the wafer surface, it emits a powerful jet that dislodges any particle still clinging to the surface. Wafers that have been cleaned with Megasonic cleaning systems have a lower particle count as well as a high degree of cleanliness.

Modutek Can Help with Megasonic Cleaning Integration

As a leading manufacturer of wet process semiconductor manufacturing equipment, Modutek can help customers integrate Megasonic cleaning into their wafer cleaning process. Modutek offers free consultation and can show customers how to realize the benefits of lower costs, better output quality, and improved yields.

SEMICONDUCTOR WET PROCESS EQUIPMENT AND WET BENCH MANUFACTURER

Tag Archives: reducing chemical usage

How Advanced Ozone Cleaning Reduces Costs and Improves Wafer Yields

How Megasonic Cleaning Improves Silicon Wafer Manufacturing