Application

OFFLINE PROCESS CONTROL

The best quality control can be achieved by inline process monitoring to check every wafer in the manufacturing process. However, in some cases the short cycle time (usually less than 1 second) does not allow to realize detailed analysis of the wafer, which may include full wafer mapping and techniques requires mechanical contacts.

The measurement tools were designed to include non-destructive techniques and favor non-contact methods where possible.

Fast measurements
User friendly operation
Low cost of ownership

The applications include the followings:

Incoming wafer characterization
Measurement of electrical parameters in different manufacturing steps
Characterization of deposited layer parameters
Monitoring surface passivation efficiency and homogeneity

Technology

PHOTOLUMINESCENCE IMAGING

Photoluminescent Imaging is an excellent tool for monitoring of multicrystalline, monocast or monocrystalline wafers. During the measurement, the laser illuminates the silicon block and the generated photoluminescent signal is detected by an IR camera. The illumination effects the recombination of charge carriers. If not, the defects are present and there is a chance of radiative recombination. During the radiative recombination, a photon is emitted which can be detected by an IR camera. PL intensity is inversely proportional to defect density and impurity concentration.

System features:

High quality fast imaging even for as cut wafers
Advanced on-the-fly lifetime calibration method
Flexible classification according to the particular requirements
Detection of wafers with broken edge
Capability to measure solar wafers at any processing stage providing full process control
Accurate tool matching capability
Cell efficiency forecast capability at as-cut stage
Flexible configurability from stand-alone to integration in fully automated systems

TYPES OF DETECTABLE DEFECTS:

1. Material (as-cut wafers):

General

High contamination density
Edge (corner) contaminations

Multi wafers

High dislocation density
Active grain boundaries

Mono wafers

Ring defects (for different reasons)
Pinholes
Cracks

2. Passivation control (double side passivated samples)

Optional on-the-fly Jo and iVoc mapping

3. Wiring (finished cells):

Shunt

Edge isolation defect

Bad finger

PL IMAGES AT DIFFERENT PROCESSING STAGES:

COMPARISON OF PLI AND LIFETIME FEATURES:

Good correlation between PL and μ-PCD data allows calibration between PL intensity and lifetime:

PL image

μ-PCD image

Point-to-point correlation of Multicrystalline wafers with lifetime:

PL image

μ-PCD image

CORRELATION BETWEEN FORECASTED AND MEASURED CELL EFFICIENCY

Semilab’s sorting solution provides good consistency between multicrystalline wafers and efficiency of final cells.

COMPARISON OF J₀ AND IMPLIED V_OC MAPPING BY QSS µ-PCD

FEATURES

Reflection side photoluminescence on finished cells, processed and as-cut wafers
On the fly lifetime map from µ-PCD calibrated PL image
Applicable for R&D usage

Quality description by calibrated lifetime map and customizable classification parameters
Cell efficiency forecast from PL images as-cut multi/monocast wafers (calibration required)
Measurement capability both on slurry and diamond-cut wafers

Product Line

PLI

Photoluminescence tool for wafer and cell inspection is a fast and reliable solution for non-destructive measurement of wafer and cell quality at any stage of processing from as-cut wafers to finished cells.
Provides full control of material quality during the whole production.
Higher quality wafers create higher efficiency cells making the production more cost-efficient.

Products

PLI-1001/A, PLI-1003/A

Photoluminescence tool for wafer and cell inspection

Inline photoluminescence tool is a fast and reliable solution for non-destructive measurement of wafer and cell quality at any stage of processing from as-cut wafers to finished cells.
Provides full control of material quality during the whole production.
Higher quality wafers create higher efficiency cells making the production more cost-efficient.

Features and System specifications:

Fully automated inline photoluminescence imaging and inspection
Reflection side photoluminescence on finished cells, processed and as-cut wafers
On the fly lifetime calibration
Quality description by calibrated lifetime map and custom classification parameters
Sample size: PLI-1001/A up to 156 mm
PLI-1003/A up to 162 mm

Types of detectable defects:

PLI-1001, PLI-1003

Material:

High dislocation density
Cracks
High contamination density
Edge (corner) contaminations
High vacancy density (for mono wafers)
Low lifetime