PLASMA PROCESSING APPARATUS AND FOREIGN PARTICLE DETECTING METHOD THEREFOR

• US 20110146908A1
• Filed: 01/29/2010
• Published: 06/23/2011
• Est. Priority Date: 12/18/2009
• Status: Abandoned Application

• Current Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Inventors: KOBAYASHI, Hiroyuki, Maeda, Kenji
• Application Number:
  US12/696,072
• Publication Number:
  US 20110146908A1
• Time in Patent Office: Days
• US Class Current: 156/345.24
• CPC Class Codes: G06V 20/69 Microscopic objects, e.g. biological cells or cellular parts
• CPC Class Codes: H01J 37/32192 Microwave generated discharge H01J37/32357, H01J37/32366, H01J37/32394, H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32981 Gas analysis

Abstract

The present invention provides a plasma processing apparatus including: a processing chamber; a gas exhaust unit for reducing the pressure of the inside of the processing chamber through a gas exhaust line; and a laser light source for allowing laser light to transmit through an exhaust gas flowing in the gas exhaust line; an I-CCD camera for detecting scattered light caused by foreign particles passing in the laser light; and a foreign particle determination and detection unit for detecting the foreign particles from an image measured by the I-CCD camera, wherein the foreign particle determination and detection unit determines that the foreign particles are detected from the measured image when plural pixels with signals having a predetermined intensity or larger are connected in a substantially straight line.

Claims

1. A plasma processing apparatus including a processing chamber, a high-frequency electric power that generates plasma, a gas supplying unit that supplies a gas, a gas exhaust unit that reduces the pressure of the inside of the processing chamber through a gas exhaust line, a pressure-adjusting valve that adjusts the pressure of the inside of the processing chamber, and a sample stage on which a processing target is placed, the apparatus comprising:

a laser light source that allows laser light to transmit through an exhaust gas flowing in the gas exhaust line;

an I-CCD camera that detects scattered light caused by foreign particles passing in the laser light; and

a foreign particle determination and detection unit that detects the foreign particles from an image measured by the I-CCD camera, wherein

the foreign particle determination and detection unit determines that the foreign particles are detected from the measured image when a plurality of pixels with signals having a predetermined intensity or larger are connected in a substantially straight line.

2. The plasma processing apparatus according to claim 1, wherein

in the case where the pixels with the predetermined signal intensity or larger are present across a predetermined length at predetermined pitches or shorter in a rectangular area with a predetermined width along an arbitrary axis in the measured image, the foreign particle determination and detection unit determines that the plurality of pixels with signals having the predetermined intensity or larger are connected in a substantially straight line.

3. The plasma processing apparatus according to claim 1, wherein

if the image measured by the I-CCD camera is processed by an image processing program and a substantially-straight pixel line is detected on the basis of the states of signal intensities of the respective pixels, the foreign particle determination and detection unit determines that the foreign particles are present.

4. The plasma processing apparatus according to claim 1, wherein

in the case where the pixels with the predetermined signal intensity are arranged at substantially-equal intervals on a substantially straight line in the measured image, the foreign particle determination and detection unit determines that the foreign particles are detected.

5. The plasma processing apparatus according to claim 4, wherein

when the pixels with signals having the predetermined intensity or larger are connected in a substantially straight line in the measured image, the foreign particle determination and detection unit estimates the velocity of the foreign particles on the basis of intervals of the pixels with signals having the predetermined intensity or larger in the pixels on the substantially straight line, and determines that the foreign particles are detected when the estimated velocity of the foreign particles is similar to the velocity of gas flow.

6. The plasma processing apparatus according to claim 1, wherein

on the basis of determination on whether or not the total value of the signal intensities of all pixels exceeds a certain threshold value, the foreign particle determination and detection unit detects the foreign particles before determination on whether or not the plurality of pixels with signals having the predetermined intensity or larger are connected in a substantially straight line.

7. The plasma processing apparatus according to claim 1,

wherein the intensity of Rayleigh scattering light caused by a gas existing in the processing chamber is estimated in accordance with the pressure of the inside of the processing chamber, a threshold value that distinguishes a signal by the foreign particles from a noise signal is adjusted,

wherein the laser light is allowed to transmit immediately beneath a gap generated when the pressure-adjusting valve adjusts the pressure of the inside of the processing chamber, and

wherein the scattered light caused by the foreign particles passing in the laser light is measured by the I-CCD camera.

8. The plasma processing apparatus according to claim 1,

wherein the power density of the laser light in an observed area is at least 10 mW/mm² or larger at a position where the power density is the largest, pulse oscillation laser is used for the laser light source, and

wherein the laser power density, a position where a light collecting optical system is provided, and the diameter of an objective lens of the light collecting optical system are adjusted, so that the average number of photons entering the light collecting optical system for detecting the scattered light caused by particles with a particle diameter of 80 nm is 1 in one laser pulse.

9. A foreign particle detecting method in a plasma processing apparatus including a processing chamber, a high-frequency electric power that generates plasma, a gas supplying unit that supplies a gas, a gas exhaust unit that reduces the pressure of the inside of the processing chamber through a gas exhaust line, a pressure-adjusting valve that adjusts the pressure of the inside of the processing chamber, and a sample stage on which a processing target is placed, the plasma processing apparatus comprises,

a laser light source that allows laser light to transmit through an exhaust gas flowing in the gas exhaust line;

an I-CCD camera that detects scattered light caused by foreign particles passing in the laser light; and

a foreign particle determination and detection unit that detects the foreign particles from an image measured by the I-CCD camera,

wherein the foreign particle detecting method comprising steps of;

allowing the laser light to transmit immediately beneath a gap generated when the pressure-adjusting valve adjusts the pressure of the inside of the processing chamber;

measuring the scattered light caused by the foreign particles passing in the laser light using the I-CCD camera; and

determining that the foreign particles are detected from the measured image when a plurality of pixels with signals having a predetermined intensity or larger are connected in a substantially straight line.

10. The foreign particle detecting method in a plasma processing apparatus according to claim 9,

when the pixels with the predetermined signal intensity or larger are present across a predetermined length at predetermined pitches or shorter in a rectangular area with a predetermined width along an axis corresponding to the flow of the exhaust gas in the measured image, determining that the plurality of pixels with signals having the predetermined intensity or larger are connected in a substantially straight line.