Variable-tilt specimen holder and method and for monitoring milling in a charged-particle instrument

• US 8,227,781 B2
• Filed: 07/23/2010
• Issued: 07/24/2012
• Est. Priority Date: 07/24/2009
• Status: Active Grant

• Current Assignee: Oxford Instruments America Incorporated (Oxford Instruments PLC)
• Original Assignee: Omniprobe Inc. (Oxford Instruments PLC)
• Inventors: Zaykova-Feldman, Lyudmila, Moore, Thomas M., Amador, Gonzalo
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US12/842,105
• Publication Number:
  US 20110017927A1
• Time in Patent Office: 732 Days
• Field of Search: 250/559.4, 250/559.27, 250/239, 250306-311, 250/492.21, 250/492.3, 738/648.1
• US Class Current: 250/559.4
• CPC Class Codes: G01N 1/32 Polishing; Etching
• CPC Class Codes: H01J 2237/20207 Tilt
• CPC Class Codes: H01J 2237/2482 Optical means
• CPC Class Codes: H01J 2237/30466 Detecting endpoint of process for plasma apparatus H01J37/32963, for sputtering apparatus H01J37/3479
• CPC Class Codes: H01J 2237/31745 for preparing specimen to be viewed in microscopes or analyzed in microanalysers
• CPC Class Codes: H01J 37/304 Controlling tubes by information coming from the objects or from the beam, e.g. correction signals
• CPC Class Codes: H01J 37/3056 for microworking, e.g. etching of gratings, trimming of electrical components trimming of resistors H01C17/22

Abstract

An apparatus for monitoring sample milling in a charged-particle instrument has a variable-tilt specimen holder attached to the instrument tilt stage. The variable-tilt specimen holder includes a first pivoting plate having a slot for holding a specimen rotatably supported in the specimen holder. The first pivoting plate has a range of rotation sufficient to move the axis of thinning of the specimen from a first position where the tilt stage is placed at its maximum range of tilt and the angle between the preferred axis of thinning of the specimen and the axis of the ion beam column of the instrument is greater than zero, to a second position where the axis for thinning of the specimen is substantially parallel to the axis of the ion-beam column. A light detector intercepts light passing through the specimen as it is thinned to determine an endpoint for milling of the specimen.

Claims

1. An apparatus for monitoring sample milling in a charged-particle instrument;

the charged-particle instrument having a tilt stage, where the tilt stage has a maximum range of tilt; and

an ion-beam column for producing an ion beam;

the ion beam column having an ion-beam column axis;

the apparatus comprising;

a variable-tilt specimen holder attached to the tilt stage;

the variable-tilt specimen holder further comprising;

a first pivoting plate rotatably supported in the variable-tilt specimen holder;

the first pivoting plate having a slot for holding a specimen from a sample, where the specimen has a preferred axis for thinning by the ion beam;

the first pivoting plate having a range of rotation sufficient to move the preferred axis of thinning of the specimen from;

a first position where the tilt stage is placed at its maximum range of tilt and the angle between the preferred axis of thinning of the specimen and the axis of the ion beam column is greater than zero to;

a second position where the preferred axis for thinning of the specimen is substantially parallel to the ion-beam column axis;

a second pivoting plate;

the second pivoting plate rotatably supported adjacent to the first pivoting plate;

a light detector;

the light detector supported on the second pivoting plate;

a light source;

the light source directed so as to pass light through the specimen and to the light detector when the specimen is positioned by the first pivoting plate to a preferred axis of thinning and the second pivoting plate is positioned to intercept light passing through the specimen.

2. The apparatus of claim 1 further comprising:

the light detector having an output signal responsive to the intensity of light passing through the specimen.

3. The apparatus of claim 1 further comprising:

the light detector having an output signal responsive to the intensity of light passing through the specimen;

the output signal of the light detector coupled to a programmed computer;

the programmed computer having instructions for comparing the amplitude of the output signal of the light detector to the amplitude of an output signal from the light detector previously received and recorded.

5. The apparatus of claim 1 further comprising:

the light detector having an output signal responsive to the intensity of light passing through the specimen.

6. The apparatus of claim 1 further comprising:

the light detector having an output signal responsive to the intensity of light passing through the specimen;

the output signal of the light detector coupled to a programmed computer;

the programmed computer having instructions for comparing the amplitude of the output signal of the light detector to the amplitude of an output signal from the light detector previously received and recorded.

4. An apparatus for monitoring sample milling in a charged-particle instrument;

the charged-particle instrument having a tilt stage, where the tilt stage has a maximum range of tilt; and

an ion-beam column for producing an ion beam;

the ion beam column having an ion-beam column axis;

the apparatus comprising;

a variable-tilt specimen holder attached to the tilt stage;

the variable-tilt specimen holder further comprising;

a first pivoting plate rotatably supported in the variable-tilt specimen holder;

the first pivoting plate having a slot for holding a specimen from a sample, where the specimen has a preferred axis for thinning by the ion beam;

the first pivoting plate having a range of rotation sufficient to move the preferred axis of thinning of the specimen from;

a first position where the tilt stage is placed at its maximum range of tilt and the angle between the preferred axis of thinning of the specimen and the axis of the ion beam column is greater than zero to;

a second position where the preferred axis for thinning of the specimen is substantially parallel to the ion-beam column axis;

a second pivoting plate;

the second pivoting plate rotatably supported adjacent to the first pivoting plate;

a mirror supported on the second pivoting plate;

a light detector;

the light detector positioned to intercept light reflected from the mirror;

a light source;

the light source directed so as to pass light through the specimen and to the light detector by way of the mirror when the specimen is positioned by the first pivoting plate to a preferred axis of thinning and the second pivoting plate is positioned to intercept light passing through the specimen.

7. A method for monitoring sample milling in a charged-particle instrument;

the charged-particle instrument having a tilt stage, where the tilt stage has a maximum range of tilt; and

an ion-beam column for producing an ion beam;

the ion beam column having an ion-beam column axis;

the method comprising;

placing a specimen for milling in a holder in a first pivoting plate;

rotating the first pivoting plate so that the specimen is positioned to a preferred axis for thinning with respect to the ion beam column axis;

milling the specimen;

positioning a light detector so as to intercept light passing through the specimen;

passing a light beam through the specimen to the light detector;

comparing the output signal of the light detector to an output signal from the light detector previously recorded; and

,

stopping the milling of the specimen when the output signal from the light detector reaches a pre-determined amplitude.

8. The method of claim 7 further comprising:

continuing the milling of the specimen when the output signal from the light detector has not reached a pre-determined amplitude.