Optimizing IC Interconnection: A Functional Approach to Innovation (Stay updated on the project's progress)

Exciting result - the most functional component for current providing is not a metal line but a component that keeps the metal line:

• If we assign that "Barrier Keeps Metal Line" (see the basic version) - the most functional component becomes Barrier
• If we assign that "ILD Keeps Metal Line" (next version) - the most functional component becomes ILD

The conclusion - the carrier has higher functionality than the metal line that provides electrical current.

So, we need to think about how to eliminate barriers and delegate its functions to another component - small air gaps between Cu metal lines and ILD seem to be very perspective from the standpoint of both Cu diffusion prevention and RC-delay reduction

The possible configuration can be as shown below:

The Functional Model is in the Proposed Version

The Air Gaps model seems much better and also helps to prevent void formation due to Cu electromigration - the void already exists. It might happen that due to very strong Cu-electromigration, the shape of the via and metal line will be slightly affected, but no voids will be created within the metal line or within the metal via.

Summary of the process functional modeling:

1. At least 16 operations, including 3 metrology operations, are needed to build one interconnection layer.
2. The process's average effectiveness is close to 70%, which is excellent. However, only about 30% of operations contribute value to the product. Therefore, the rest of the operations should be eliminated or simplified.

Some directions for the process development:

1. Etch Stop is needed only above Cu to prevent Cu diffusion from the bottom Cu metal line to the top ILD. Instead of depositing the Etch Stop material with CVD, it is proposed that a process of selective deposition of PMMA with dissolved SiC or SiN be developed. The liquid can be spun on the wafer and removed from the ILD (SiO2) areas.
2. Photolithography - Perform development of the exposed resist in wet etch equipment. More than that, why do we need to develop exposed PR at all? Exposed PR is removed by an aqueous solution, meaning it can be removed by plasma. So, the idea is to apply plasma etch directly after exposure.
3. Wet cleaning after dry etch - Why do we need to develop exposed PR at all? Exposed PR is removed by an aqueous solution, meaning it can be removed by plasma. So, the idea is to apply plasma etch directly after exposure. The aim is to eliminate expensive wet etch operations.
4. Polish (CMP) - To simplify the polish (CMP) operation, it is proposed that the bulk of the Cu be removed at the electroplater just after the completion of the electrodeposition. It is a straightforward process to reverse the polarity to make the wafer an anode and give (-) to the anode. This will dissolve the main affected part of the Cu and simplify the following operation - polish.

It is exciting results:

Plasma is the most functional component - we have to think about plasma for effective improvement of the process

The vacuum pump came out as the most problematic component of the system - we have to think about how to eliminate or replace the vacuum pump - Interesting.

Overall:

Etch stop Deposition is not a valuable operation. The operation's main purpose is to create a barrier between the Cu metal line and the top of ILD. Actually, we cover the surface of the wafer with Etch stop material, while we need it only on the top of Cu metal line.

Maybe we need to think about the material that is adsorbed bu Cu only and is not adsorbed by SiO2 - ILD. The process could be done as follows: spinon liquid, removing the liquid from the wafer at high-speed rotation (the liquid should remain only on the metallic parts), and thermal treatment of the liquid to create a top barrier layer.

So we need to develop a liquid that is adsorbed selectively by Cu and is converted to solid material after a thermal treatment.

Possible example:

A suitable liquid material that selectively adsorbs on Cu and converts to a solid after thermal treatment is Poly(methyl methacrylate) (PMMA) in a suitable solvent. Here’s how it works:

Liquid Material: PMMA Solution

1. Composition: PMMA can be dissolved in organic solvents such as toluene or acetone to create a liquid solution. The choice of solvent can influence the adsorption characteristics on Cu and SiO2.
2. Selective Adsorption: PMMA has a higher affinity for Cu due to its ability to interact with the metal surface, while it exhibits lower adhesion to SiO2. This allows for selective adsorption on the Cu parts of the wafer.
3. Thermal Treatment: Upon heating, the solvent evaporates, and the PMMA undergoes a polymerization process, leading to the formation of a solid PMMA film on the Cu areas. The thermal treatment can also help in cross-linking the PMMA, enhancing its mechanical properties.

Process Steps:

1. Spin Coating: Apply the PMMA solution onto the wafer and spin it to achieve a uniform layer. The centrifugal force will help remove excess material from the SiO2 areas.
2. Thermal Treatment: After spin coating, subject the wafer to a thermal treatment (e.g., baking at around 100-150°C) to evaporate the solvent and convert the PMMA into a solid film.

Advantages:

1. Selective Adsorption: The liquid selectively adheres to Cu, allowing for precise patterning.
2. Solid Film Formation: The conversion to a solid film provides structural integrity and can be further processed for various applications in semiconductor manufacturing.

Considerations:

1. Temperature Control: Ensure that the thermal treatment does not damage the underlying structures or materials on the wafer.
2. Solvent Choice: The choice of solvent is crucial for achieving the desired selectivity and should be tested for compatibility with both Cu and SiO2 surfaces.

This approach allows for effective selective adsorption and subsequent solidification, making it suitable for applications in wafer fabrication.

Stupid question. Why do we need a vacuum for ILD deposition? I see only one possible reason - to create a free pathway that is long enough for plasma creation. OK. We need to think about how to ensure plasma and avoid deep vacuum. ILD that is SiO2 or modifications of SiO2 do not need a vacuum. More than that, the lack of oxygen

There are too many components. It would be easier and more effective to use hot air to solidify the Sacrificial Light Absorbing Material when it is on the wafer. So, the process seems to be like this: Wafer is kept in the chuck and rotated. The liquid stuff is poured on the rated wafer, and hot air solidifies the material on the wafer. The local flow of the air will preserve the wafer from the contamination of the layer. A chamber filter and Fan will not be needed.