Plating Apparatus with Auxiliary Cathode for Uniform Copper Film
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Solution Overview
Problem
The challenge in semiconductor manufacturing is forming copper interconnects with uniform thickness, especially in smaller trenches and contact holes, where conventional seed layers can block openings and lead to voids, and thinner seed layers result in uneven film thickness profiles due to higher sheet resistance, requiring additional components and increased processing time.
Innovation Solution
A plating apparatus with a ring-shaped seal member and an auxiliary cathode that redirects excessive current from the peripheral region, combined with a high-resistance structure between the anode and substrate to ensure uniform current distribution, allowing for in-plane uniformity of the plated film without changing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thickness seed layer is formed on smaller-sized trenches and contact holes, then the seed layer provides sufficient conductivity, but it blocks the openings and narrows the trenches, impeding electrodeposition and causing voids
Solution Approach 1:
The invention changes the physical-chemical parameters of the plating solution by adding specific additives (leveling agents, brighteners, and complexing agents) to enable successful plating on ultra-thin seed layers. This allows the seed layer thickness to be reduced to 1-10 nm while maintaining adequate conductivity for electrodeposition, thereby preventing trench blocking while ensuring sufficient electrical conductivity for uniform copper deposition.
2Reliability
If a thick plated film is formed in the peripheral region due to higher current flow, then the seed layer conductivity issue is addressed, but additional CMP processing time is needed to remove the extra film and flatten the surface, lowering productivity
Solution Approach 1:
The invention changes the electrical parameters of the plating system by adding conductive additives to the plating solution. These additives increase the solution's ionic conductivity, reducing the voltage drop across the thin seed layer and enabling more uniform current distribution. This results in uniform plated film thickness across the entire substrate surface, eliminating the need for extended CMP processing to remove peripheral excess material.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the formation of uniformly thick copper films across the substrate surface, improving manufacturing efficiency and reducing costs by maintaining component consistency and simplifying maintenance, while ensuring high-quality interconnects.
Implementation Method 1
the sheet resistance R2 of the seed layer 7 between its center and its peripheral electricity-feeding portion becomes relatively higher than the resistance R1 of a plating solution 202
Implementation Method 2
copper plating is performed onto a surface of the seed layer 7 of the substrate W to fill the contact holes 3 and the trenches 4 with copper
Data Source
AI summary
A plating apparatus can form a plated film having a uniform thickness over the entire surface of a substrate without a change of members. The plating apparatus includes a substrate holder, a cathode contact for contacting a conductive film formed on the substrate so that the conductive film serves as a cathode, a ring-shaped seal member for covering the cathode contact and bringing its inner circumferential portion into contact with the peripheral portion of the substrate to seal the peripheral portion of the substrate, an anode disposed so as to face the conductive film formed on the substrate, and an auxiliary cathode disposed with respect to the seal member such that at least part of the auxiliary cathode is exposed on a surface of the seal member. Plating is carried out by bringing the conductive film, the anode and the auxiliary cathode into contact with a plating solution.