FLX Series Stress Measurement

Toho FLX Thin Film Stress Measurement Systems offer Industry Standard capabilities for mass production and research facilities that demand accurate stress measurements on various films and substrates. Incorporating KLA-Tencor’s patented “Dual Wavelength” technology, Toho FLX Series tools precisely determine and analyze surface stress caused by deposited thin films.

FLX systems resolve problems such as metal and dielectric film cracking, voiding, and lifting formation. Equipped with a heating element for stress monitoring at high temperatures and an optional cooling unit that allows a thorough understanding of film properties at temperatures from –65°C to 500°C, the Toho FLX systems offer outstanding value in a variety of comprehensive Stress Measurement Solutions.

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Spec Sheet
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Select a Spec Sheet:

FLX 2320-R

FLX 2320-S

FLX 3300-R

FLX 3300-T

Standard Features

KLA-Tencor Patented Dual Wavelength Technology (U.S. Patents 5134303, 5248889)

The FLX series feature KLA-Tencor’s patented dual wavelength technology, which enables the system to select the wavelength most suitable for the particular application. Pre-selecting the optimal wavelength minimizes destructive interference patterns from transparent films such as silicon nitride.

Simple, Stable and Robust Assembly

Only one moving element in the optical component ensures low vibration and high accuracy

Thermal Process Development

A key FLX feature is the ability to produce stress temperature correlations. In-situ stress measurements can be made from -65°C to 500°C at heating rates up to 30°C per minute (the cooling unit to -65°C is optional). An understanding of stress variations with temperature is essential for characterizing material properties such as stress relaxation, moisture evolution, and phase changes. In turn, this helps monitor and control process parameters such as sputtering power, furnace temperature, and gas flow rate.

Comprehensive Data Analysis

Intuitive Windows based analysis software displays any combination of stress, time, surface deflection, or reflected light intensity measurements. Data analysis features includes:

• Calculation of biaxial modulus of elasticity

• Calculation of linear expansion coefficient, stress uniformity, and file subtraction

• Trend plotting for Statistical Process Control (SPC)

• Calculation of water diffusion coefficient in dielectric films

• Automatic recalculation of stress when film or substrate thickness is corrected

• Two- and three-dimensional views of wafer topography

• Plotting of the measured stress-temperature curve

User Friendly FLX-Ability

Toho FLX systems all offer software leveling of the sample which provides more accurate results and also provide ease of use with the ability to customize parameters such as;

• Number of scan points

• Elastic modulus

• Substrate thickness

• Wafer diameter

• Specific heating and cooling cycles in the recipe for stress-temperature measurements

• Edit ready data records, plot graphs, and trend charts

• Automatic recalculation of stress when parameters of elastic modulus, wafer or film thickness are edited

Options & Accessories

• 3D Analysis Software Upgrade

• Calibration Mirror Standards

• Wafer Stress Pair Calibration Standards

• Auto-Rotation

• Low Temperature Module

• Odd size Substrate Locator Rings and Adaptors

• Gas Panel with all flow meters and pressure gauges installed

• Vibration Table and Accessories

• Extended Warranty and Service Agreements

The Toho FLX Series are engineered for outstanding Stress Measurement Accuracy and low cost of ownership. The table below provides all standard specifications for the four different systems we offer.

FLX Series Stress Measurement Specification                           FLX-2320-S
  Thermal Cycling
Performance  
Maximum Scan Diameter 200mm
Measurement Range 1 to 4,000MPa1  
Repeatability 1.3MPa2
Accuracy Less than 2.5% or 1 Mpa whichever is larger
Minimum Radius 2.0m
Maximum Radius 33km
Operating Temperature Room Temp to 500°C
(-65°C Cryo Option) Available 
Wafer Mapping Manual
3D Mapping Optional
Hardware Configuration  
Sample Size 75 to 200mm
50mm Option Available
Wafer Rotation Manual
Forced Gas Cooling Computer-controlled 3
Facilities Requirements  
Computer Power 100V AC, 50/60Hz, 6A
System Power 220V AC, 50/60Hz, 13A 
Purge Gas N² or Ar gas
Gas Flow 1.5L/min, 0.3kg/cm²
System Dimensions 566 x 450 x 488 (mm)
PC Dimensions 400 x 420 x 530 (mm)
PC Weight 20kg
System Weight 45.5kg
   
   
  Notes:
  1 725µm wafer thickness for 10,000Å thin film
  2 (1s): 1 x l07 dyne/cm2
  3(500°C to 100°C in 60 minutes) 30 w/ LN2)
   
FLX Series Stress Measurement Specification                           FLX-3300-T
  Thermal Cycling
Performance  
Maximum Scan Diameter 300mm
Measurement Range 1 to 3,500MPa1
Repeatability 1.3MPa2
Accuracy Less than 2.5% or 1 Mpa whichever is larger
Minimum Radius 2.0m
Maximum Radius 33km
Operating Temperature Room Temp to 500°C
(-65°C Cryo Option) Available
Wafer Mapping Manual
3D Mapping Optional
Hardware Configuration  
Sample Size 200 & 300mm
50mm Option Available
Wafer Rotation Manual 
Forced Gas Cooling Computer-controlled3
Facilities Requirements  
Computer Power 100V AC, 50/60Hz, 6A
System Power 220V AC, 50/60Hz, 13A 
Purge Gas N² or Ar gas
Gas Flow 1.5L/min, 0.3kg/cm²
System Dimensions 665 x 550 x 492 (mm)
PC Dimensions 400 x 420 x 530 (mm)
PC Weight 20kg
System Weight ~60kg
   
   
  Notes:
  1 725µm wafer thickness for 10,000Å thin film
  2 (1s): 1 x l07 dyne/cm2
  3(500°C to 100°C in 60 minutes) 30 w/ LN2)
   
FLX Series Stress Measurement Specification                           FLX-2320-R
  Auto-Mapping
Performance  
Maximum Scan Diameter 200mm
Measurement Range 1 to 4,000MPa1
Repeatability 1.3MPa2
Accuracy Less than 2.5% or 1 Mpa whichever is larger
Minimum Radius 2.0m
Maximum Radius 33km
Operating Temperature Room Temp
(-65°C Cryo Option) N/A
Wafer Mapping Automatic
3D Mapping Standard
Hardware Configuration  
Sample Size 75 to 200mm
50mm Option N/A
Wafer Rotation Automatic
Forced Gas Cooling N/A
Facilities Requirements  
Computer Power 100V AC, 50/60Hz, 6A
System Power 100V AC, 50/60Hz, 13A 
Purge Gas N/A
Gas Flow N/A
System Dimensions 566 x 450 x 488 (mm)
PC Dimensions 400 x 420 x 530 (mm)
PC Weight 20kg
System Weight 45.5kg
   
   
  Notes:
  1 725µm wafer thickness for 10,000Å thin film
  2 (1s): 1 x l07 dyne/cm2
   
FLX Series Stress Measurement Specification                           FLX-3300-R
  Auto-Mapping
Performance  
Maximum Scan Diameter 300mm
Measurement Range 1 to 3,500MPa1
Repeatability 1.3MPa2
Accuracy Less than 2.5% or 1 Mpa whichever is larger
Minimum Radius 2.0m
Maximum Radius 33km
Operating Temperature Room Temp
(-65°C Cryo Option) N/A
Wafer Mapping Automatic
3D Mapping Standard
Hardware Configuration  
Sample Size 200 & 300mm
50mm Option N/A
Wafer Rotation Automatic
Forced Gas Cooling N/A
Facilities Requirements  
Computer Power 100V AC, 50/60Hz, 6A
System Power 100V AC, 50/60Hz, 13A 
Purge Gas N/A
Gas Flow N/A
System Dimensions 665 x 550 x 492 (mm)
PC Dimensions 400 x 420 x 530 (mm)
PC Weight 20kg
System Weight ~60kg
   
   
  Notes:
  1 725µm wafer thickness for 10,000Å thin film
  2 (1s): 1 x l07 dyne/cm2
   

Theory: The FLX Systems Measure Curvature and then Calculate Stress:

The FLX tools are designed to measure the shape change caused by the film deposition and calculate the corresponding film stress.

The stress is calculated from the curvature change caused by the addition of the film. The key point is that the FLX tool measures the curvature of the wafer caused by the film deposition. The film stress is calculated using elasticity equations. Since stress is force normalized by area, it is a field variable, and therefore it cannot be measured directly; only the effect of stress is measurable.

From the measurement results, the field strength is calculated from an equation. The application of stress to any object will always be accompanied by some deformation, called strain. The deformation can be measured, and the stress that caused the deformation can be calculated if a theory exists to relate stress to strain for the system being measured. The tiny chemical or physical forces that develop in the thin film during the deposition will cause a stress in the film resulting in a slight bending of the wafer.

Theory: Scanning Mechanism

The FLX-2320-S determines stress by measuring the curvature change of pre- and post-deposition of the film. This difference in curvature is used to calculate stress by way of Stoney’s equation, which relates the biaxial modulus of the substrate, thickness of the film and substrate, and the radius of curvatures of pre- and post-process. Curvature is measured by directing a laser at a surface with a known spatial angle. The reflected beam strikes a position sensitive photodiode. The geometry of the film is recorded by scanning the surface.

Applications Thin Film Deposition

In general, stress is induced when materials of dissimilar coefficients of thermal expansion are bonded together. Films may behave similarly at high temperatures but as films are cooled, materials may contract/expand differently, thus causing stress in the film. With a stressed film, defects such as dislocations, voids, and cracking may occur. The FLX stress measurement system helps troubleshoot applications listed below:

• Aluminum stress-induced voids

• Passivation cracking (nitride, oxide)

• Stress-induced dislocations in silicon

• Electrical test yield degradation

• Tungsten silicide cracking

• Stress increase in oxides during temperature cycling

• Constant current stress test (CCST) degradation

• Matching metallization expansion on GaAs

• Silicon cracking due to high film stress

Application Notes

Toho Technology Provides Customers with Application Notes and Support for a variety of applications including;

• Thick Film Stress Measurement

• Improvement in Film Stress Measurement Using the Optical Cantilever Beam Technique

• Stress on Multiple Films

• Stress Mapping

• Silicon Wafer Deformation After Grinding

• Linear Thermal Expansion Coefficient and Biaxial Modulus

To accommodate a wide variety of applications, processes and budgets, Toho offers four FLX Models. Specifications are provided below.

Thermal cycling from -65°C to 500°C

FLX-2320-S : Sample size from 75mm to 200mm

FLX-3300-T : Sample size 200mm and 300mm

Automatic Wafer Mapping

FLX-2320-R : Sample size from 75mm to 200mm

FLX-3300-R : Sample size 200mm and 300mm