Back End of Line

When stripping a photoresist via plasma, some residues, known as „ash,“ remain on the surface. Multiple options are available for cleaning these residues, including the use of SicOzone or a solvent-based media, as well as a mixture of sulfuric acid and peroxide.

Polymers generated during dry etching are removed using solvent-based media.

Highly treated photoresists can be challenging to remove. A mixture of sulfuric acid and peroxide is deployed because of its high temperature and strong acidity, which effectively removes the photoresist. Compatibility with the underlying material is crucial.

Regardless of resist type (negative, positive, implanted, or treated), solvent-based solutions are used for stripping these resists.

The most cost-effective method for removing photoresist is ozone-based stripping. Ozone-based photoresist stripping is also applicable to exposed metals. Most metals are not affected by ozone as an oxidizer. With various parameter options and expertise, SicOzone can be utilized in the BEOL process.

When wet etching AlSi or AlSiCu, the silicon grains of the alloy can remain on the surface. To remove them, a freckle etch process is performed.

To electroplate copper, a seed layer is essential. After growth and photoresist removal, it becomes necessary to etch the seed layer. There are several methods available to achieve this removal.

Oxide etching is a crucial step in chip manufacturing. Common etching mixtures include BOE 7:1 or 10:1, BHF, and HF at varying concentrations. The typical uniformity values for this process are as follows: <1% within the wafer, <2% wafer-to-wafer, and <2% batch-to-batch.

In BEOL processes, materials such as Au, Ag, Al, Cu, Cr, Mo, Ni, Ta, Pt, or salicides are commonly used to establish connections or create various functions. The BATCHSPRAY^® processing of these materials combines uniformity, efficiency, and effective process control.

Ti, TiN, TiW, and W are common materials used to create barriers. Often, a stack of more than two layers is used. Various methods are available for removing these layers, and an advantage is achieved by conducting an in-situ etch that addresses all layers in a single, straightforward etch step.

Typical stacks, such as Ag, Ni, Ti, or Au Ni, Ti, or Au Cu, Ni, Ti, are deployed to enhance the conductive performance from the chip to the bump. Achieving selective etching of all layers and perfect undercut performance are crucial factors in this process.

Photomasks, essential in lithography for wafer patterning, need periodic cleaning. Contaminated photoresists on masks up to 9″ square are removed using a sulfuric-peroxide mixture.

The most common method for developing the resist is immediately after patterning. However, in certain applications, batch development of multiple wafers can be done using typical solutions such as 2.6% TMAH or 3.6% KOH.

In the world of compound semiconductors, materials like GaAs, GaInP, AlInP, InP, GaN, and others are commonly used. When it comes to shaping, cutting, and removing these materials, various options are available.