YPS / Products / Emitters

YPS Field Emitters: Thermal (TFE) & Cold (CFE)


YPS Schottky type field emission (FE) sources can be used in many brands of focused electron beam systems including SEM, TEM, AES, SAM, EPMA, E-BEAM LITHOGRAPHY and CD-SEM systems. We are also able to fabricate custom/bespoke emitters to customer specifications. These high quality FE sources are an excellent and cost effective drop-in alternative to FEI and Denka style FE sources. The YPS FE source is a thermal field emitter (TFE) cathode featuring a layer of zirconium oxide on an oriented single crystal tungsten wire with a very sharp tip. The tip is mounted on a hairpin filament that is used to maintain the tip at a temperature of around 1800K.

The tip just penetrates the aperture hole in a cylindrical suppressor electrode mounted around the assembly. Electrons are emitted from the tip due to both thermal excitation and an electrical field at the tip due to the potential difference between it and an extractor electrode. The YPS Schottky tip radii are typically 0.3-0.6µm to ensure high brightness of the source. Other specific customer requirements (including emitter radii) may also be supplied.

Zr07-99_after_remould_x40k_24-10-07.jpgCurrently there are three main types of FE sources available:

  • YPS-174;
  • YPS-184; and
  • YPS-M20 Mini Module

This product line is aimed at customers who are comfortable with changing field emission sources and have the capability to change, load and align the TFE cathodes in a clean environment. It is also an excellent product for developers building custom-designed electron beam columns using TFE sources. The operating vacuum for TFE sources is typically better than 1x10-9 mbar. This is higher than the operating vacuum for tungsten or LaB6 sources, but less stringent than for cold field emission sources.

Our product range of field electron emitters can fit a variety of instruments including SEMs, CD-SEMs, microprobes, as well as electron lithography machines etc. Other Schottky source dimensions can be fabricated to suit customer's requirements. 

Technical Product Specification:

Instrument Type

TFE Module Emitter Type

Amray

YPS-174-A

 

 

Applied / OPAL

 

 

YPS-M20-A

FEI (pre 2002)

YPS-174-F

 

 

FEI

 

YPS-184-F

 

Hitachi (TFE) SEM

YPS-174-H

 

 

Hitachi (TFE) CDSEM

YPS-174-C

 

 

JEOL (TFE)

YPS-174-J

 

 

LEO (Gemini)

YPS-174-L

 

 

PHI

YPS-174-P

 

 

Riber

YPS-174-R

 

 

Tescan

 

YPS-184-T

 

ZEISS (Gemini)

YPS-174-Z

 

 


Electron Source Performance Comparison:

Emitter Type

Thermionic

Thermionic

Schottky FE

Cold FE

Cathode material

W

LaB6

ZrO/W (100)

W(310)

Operating temperature [K]

2,800

1,900

1,800

300

Cathode radius [nm]

60,000

10,000

< 1,000

< 100

Effective source radius [nm]

>15,000

>5,000

~15 (*)

~2.5(*)

Emission current density [A/cm2]

3

30

5,300

17,000

Total emission current [µA]

200

80

100-500

5-10

Normalized brightness [A/cm2.sr.kV]

1 x 104

1 x 105

1 x 107

2 x 107

Maximum probe current [nA]

1000

Up to 10,000

Up to 1000

~2-5

Energy spread @ cathode [eV]

>0.59

>0.50

0.5-0.8

>0.23

Energy spread @ gun exit [eV]

1.5 - 2.5

1.3 - 2.5

0.5 - 0.8

0.3 - 0.7

Beam noise [%]

1

1

1

5 - 10

Emission current drift [%/h]

0.1

0.2

< 0.5

5

Operating vacuum mbar

< 1 x 10-5

< 1 x 10-6

< 1 x 10-9

< 1 x 10-10

Typical Cathode life [h]

100

> 1000

> 5000

> 2000

Cathode regeneration

not required

not required

not required

every 6 to 8 hours

Sensitivity to external influence

Minimal

minimal

low

high

* virtual source; 1hPa= hectopascals = 100 Pa