As AI and advanced semiconductor technologies continue to develop rapidly, circuits are becoming finer and package structures are becoming more complex. Accordingly, the importance of not only the materials included in finished products but also the materials required for manufacturing processes is increasing.

Among them, a stripper is a Wet Chemical process material that removes *photoresist (PR) and *residues generated during manufacturing processes. Although it does not remain in the final product, it plays a critical role in determining the quality and reliability of semiconductors and displays.

LG Chem, which has steadily built its technological capabilities in display strippers since 2004, has recently been successfully expanding into the advanced semiconductor packaging field.

In this interview, we spoke with Electronic Materials Process Technology Team 3 to learn what strippers are and how they enhance the quality of semiconductors and displays behind the scenes.

*Photoresist (PR): A photosensitive material used to form circuit patterns using light
*Residue: Fine organic and inorganic substances generated during manufacturing processes that remain on the surface without being removed
*Wet Chemical: Liquid chemical materials used in semiconductor and display manufacturing processes

Hello! Could you introduce your current responsibilities and your team?

Hello. We develop strippers used in display and semiconductor processes at Electronic Materials Process Technology Team 3.

Starting with the development of strippers for integrated aluminum (Al) and copper (Cu) display TFT processes in 2004, our team has built distinctive technological capabilities by supplying products to leading customers in Korea and overseas. More recently, based on these capabilities, we have expanded our development scope to include strippers for advanced semiconductor packaging.

Beyond simply developing materials, we comprehensively evaluate and validate our products to provide tailored solutions, ensuring they can be implemented reliably on our customers’ actual mass-production lines.

What is a stripper, and what role does it play in manufacturing?

Simply put, a stripper can be described as a “precision process cleaning agent.” In display and semiconductor manufacturing, desired circuits are formed through processes such as deposition, photolithography, and etching. Once these processes are complete, PR and various organic and inorganic residues remain on the surface. A stripper removes them cleanly so that the subsequent process can proceed reliably.

To use a simple analogy, if ordinary detergent is used to remove stains, a stripper is an “ultra-precision detergent that completely removes only the stains—PR and residues—without damaging the fabric, meaning the metal wiring and substrate, at all.”

As processes become finer, even very small residues or minor damage to the substrate can directly lead to defects and lower yields. For this reason, strippers are a key factor in determining the quality of advanced processes.

Although strippers do not remain in the final product, why are they considered a key material that determines product quality?

That is correct. Strippers are used during the manufacturing process and do not remain in the final product. However, product quality and reliability can vary significantly depending on how the removal is performed.

First, if PR and organic residues are not sufficiently removed, they can affect subsequent processes. This can cause poor contact, changes in the electrical characteristics of devices, or reduced reliability. Even microscopic residues that are difficult to see can cause defects in advanced processes, making removal performance extremely important.

On the other hand, excessive cleaning power can also cause problems. This is because if a stripper damages metal wiring, fine patterns, or surfaces, product reliability can be reduced. Therefore, the most important technical challenge in stripper development is achieving a balance between “how effectively it removes” and “how safely it protects.”

To achieve this, our team develops products by comprehensively considering not only stripping performance but also metal damage, residue control, and the management of trace metals and fine particles. In line with increasingly stringent quality management standards, we carefully manage even aspects that are not visible as we work to develop products that customers can trust.

Securing Approval from Global OSAT Company Amkor and
Accelerating Entry into the High-Value-Added Market

LG Chem has expanded into the semiconductor stripper market based on its expertise in display strippers.
What are the key achievements and background?

Two factors came together. The first was the need for a new growth engine beyond the display market, which had entered a mature stage, and the second was the explosive growth of the AI semiconductor market.

As strippers are a representative Wet Chemical process material, we were confident that the stripping performance, low-damage technologies, and customer-tailored formulation capabilities we had accumulated over the past 20 years could also become strong advantages in the semiconductor field.

As a result, we began developing customized strippers for advanced semiconductor packaging processes, including *Tall Bump, *RDL/*UBM, and *Deflux, in 2022, and this year, we achieved product approval from Amkor, a global semiconductor packaging (*OSAT) company. This is a highly meaningful milestone that demonstrates LG Chem’s Wet Chemical technological capabilities in the high-value-added semiconductor field.

💡 Mini Glossary

*Tall Bump: A tall metal bump structure formed to connect a semiconductor chip and substrate
*RDL (Redistribution Layer): A wiring layer that redistributes the input/output terminals of a semiconductor chip to desired positions
*UBM (Under Bump Metallization): A metal layer that improves adhesion and electrical connection between a bump and chip
*Deflux: A cleaning process that removes flux remaining after the soldering process
*OSAT (Outsourced Semiconductor Assembly and Test): A company specializing in outsourced semiconductor assembly, packaging, and testing

What are the technical differences between strippers for displays and those for semiconductors?

Both products serve the same role of removing PR and process residues, but their performance requirements differ.

First, display strippers are mainly used to remove *Positive PR. Because display substrates are very large, a considerable amount of stripper is also used in the process. Therefore, not only stripping performance but also cost competitiveness, versatility, and process convenience must be considered together. In other words, the key is to secure both productivity and economic efficiency while reliably processing large areas.

Semiconductor strippers require much more precise performance. This is because semiconductor circuits are extremely fine, while the metals, layered structures, and process conditions used are also diverse. They are mainly used to remove both *Negative PR and Positive PR. It is also important to protect sensitive metal layers and underlying structures while achieving the performance required for the specific purpose of each process.

In other words, while display strippers place greater emphasis on efficiency and versatility optimized for large-area processes, semiconductor strippers can be characterized more strongly as high-performance, high-precision, customized solutions tailored to fine processes and sensitive environments.

*Positive PR: A photosensitive material in which the areas exposed to light are removed by a developer to form the desired circuit pattern
*Negative PR: A photosensitive material in which the areas exposed to light are cured to form the desired circuit pattern

What are the R&D team’s strengths in collaborating with customers across different process environments?

A stripper is not a “one-size-fits-all” material. This is because the types of PR, metal wiring materials, and equipment used differ from customer to customer.

From the early stages of product development, we communicate with customers to identify key quality factors (*CTQs). No matter how good the results may be in the laboratory, unexpected variables can arise on actual mass-production lines. To resolve these issues, we collaborate with the marketing team, and the developers themselves enter customer production lines wearing cleanroom suits to analyze on-site variables together and set process conditions.

In addition, we have established an evaluation system within our R&D center that is similar to customers’ actual mass-production lines to maximize the completeness of pre-validation. This closely tailored approach is a unique differentiator for LG Chem.

*CTQ (Critical To Quality): The key quality factors that customers consider most important in products and processes

Could you share the most memorable technical challenge during the development process and how the team overcame it?

The most difficult part was resolving the dilemma mentioned earlier: “maximizing stripping performance while fully protecting the underlying metal.”

To resolve this issue, we adopted an Open Innovation approach together with the relevant organization and team members, flexibly considering a wide range of raw material candidates and technical ideas without limiting ourselves to internal researchers.

In particular, rather than simply increasing the number of experiments, we worked to fundamentally understand the interactions among various organic components and additives from the perspective of organic chemistry. By identifying the mechanisms by which certain molecular structures inhibit corrosion of specific metal films while effectively breaking down PR, we were able to find the optimal balance in the formulation.

What technical targets is the R&D team currently focusing on, and what is your vision for next-generation strippers?

We are currently devoting our efforts to developing strippers optimized for next-generation *3D DRAM and Advanced Packaging processes, which have recently been growing rapidly.

As structures become three-dimensionally stacked, interactions among materials have become much more sensitive. In response, we are expanding our portfolio of high-performance strippers with “High Selectivity” technology that selectively removes only the target material while protecting underlying devices even under harsh process conditions.

Our goal is to provide “proactive, process-tailored precision solutions” that customers can turn to first when developing new process technologies.

*3D DRAM: A next-generation DRAM technology that improves integration density and performance by vertically stacking memory cells or applying three-dimensional structures

Lastly, what does the R&D team find most rewarding, and what are your future goals?

Although strippers do not remain in the finished products and are invisible to end-users, they act as the backbone supporting the stability of multi-billion-dollar semiconductor manufacturing processes. We feel the greatest sense of accomplishment when the solutions we develop help improve our customers’ process yields.

Using the capabilities we have built in the existing display market to pioneer the new field of advanced semiconductor packaging is a source of great pride for all members of the team.

Going forward, we will expand the application scope not only into new display markets but also into semiconductor front-end processes, and develop the stripper into a representative Wet Chemical product for LG Chem that can compete confidently in global markets including the United States and Europe.

Semiconductors and displays are not completed by the finished products we can see alone. A single product is created only through the combination of numerous processes and materials that precisely form circuits and completely remove unnecessary residues.

Based on the stripper technologies accumulated over many years, LG Chem is expanding its business beyond displays into the advanced semiconductor packaging market and creating new possibilities. Going forward, through technologies that evolve together with customer processes, we will continue to deliver higher quality and reliability behind the scenes.

[Explore More from LG Chem’s Advanced Materials R&D Interview Series👉]

1) CCL R&D Team: Driving Semiconductor Performance in the AI Era: An Interview with LG Chem’s CCL R&D Team

2) DAF R&D Team: The Hidden Enabler of Advanced Semiconductor Packaging: LG Chem’s DAF(Die Attach Film) R&D Team

3) PID R&D Team: Pushing the Boundaries of Next-Generation Semiconductor Packaging: LG Chem’s PID (Photo Imageable Dielectric) R&D Team

4) BUF R&D Team: Designing the Core Layer of High-Performance Packages: LG Chem’s BUF (Build-Up Film) R&D Team