Back-Contact Solar Cell Contacts With Recast-Aligned Laser Openings

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Solution Overview

Problem

Conventional methods for forming metal contacts in semiconductor and solar industries require multiple process operations, often leading to damage and efficiency losses due to laser treatment, especially in single-crystal substrates, which increases contact resistance and recombination at the emitter/metal junction.

Innovation Solution

The use of a poly-crystalline material layer above a single-crystalline substrate, combined with a dielectric material stack, allows for direct-fire laser ablation to form contact holes without a patterned mask, confining any damage within the poly-crystalline layer and reducing recombination sites, using ultra-short pulse lasers or commercially available lasers with wavelengths less than 1064 nanometers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional laser treatment is used to form contact openings, then contact formation is achieved, but laser-induced damage occurs leading to increased contact resistance and recombination

Engineering Contradiction:

Improvecontact resistanceVSAvoidlaser-induced damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A sacrificial poly-crystalline silicon layer is introduced as an intermediary between the single-crystal substrate and the contact opening formation process. This sacrificial layer absorbs the laser-induced damage that would otherwise affect the single-crystal substrate, preventing damage propagation and maintaining low contact resistance and recombination rates.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The poly-crystalline silicon layer is deposited beforehand to serve as a protective cushion during subsequent laser treatment. This pre-positioned layer confining damage within itself protects the underlying single-crystal substrate from harmful laser effects, enabling reliable contact formation without compromising device performance.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Manufacturing precision

If multiple process operations are used for contact formation, then precise contact openings can be formed, but process complexity and manufacturing costs increase

Engineering Contradiction:

Improvecontact opening precisionVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The method combines multiple functions into a single laser treatment step. The laser process simultaneously forms contact openings through the dielectric layer and creates recast signatures in the poly-crystalline silicon layer for alignment, eliminating the need for separate masking, etching, and alignment processes while maintaining precision.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The recast signatures in the poly-crystalline silicon layer serve as copies or templates that guide subsequent contact formation steps. These signatures capture the precise locations where contacts should be formed, enabling accurate contact placement without requiring complex external alignment systems.

Inventive Principle:

Principle #26Copying

3Reliability

If conventional laser wavelengths are used, then laser treatment can be performed, but damage propagates to the single-crystal substrate increasing recombination

Engineering Contradiction:

Improverecombination rateVSAvoiddamage propagation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the physical parameters of the laser treatment by using ultra-short pulse durations (femtosecond to picosecond range). This parameter change confines the thermal and mechanical damage to the poly-crystalline silicon layer by limiting heat diffusion time, preventing damage propagation to the single-crystal substrate and reducing recombination sites.

Inventive Principle:

Principle #35Parameter changes

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 approach simplifies contact formation, reduces manufacturing costs and complexity, minimizes laser-induced damage, and maintains low contact resistance, thereby enhancing solar cell efficiency without the need for post-laser etching processes.

Implementation Method 1

A plurality of contacts holes is formed in the dielectric material stack by laser ablation

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

forming, by laser ablation, a plurality of contacts holes in the dielectric material stack

Methodology Applied

Scientific EffectAblation: Ablation

Implementation Method 3

using ultra-short pulse lasers or commercially available lasers with wavelengths less than 1064 nanometers

Methodology Applied

Scientific EffectUltra-short pulse laser: Laser

Data Source

PatentUS12191404B2Solar cell having conductive contacts in alignment with recast signatures

Publication Date: 2025.01.07 MAXEON SOLAR PTE LTD

AI summary

The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.