APPARATUS AND METHOD TO ASSESS SUB-MICRON PARTICLE LEVELS OF A SAMPLE

Abstract

The present invention provides systems and methods for determining the cleanliness of a sample, the method including impinging high pressure fluid pulses on a sample disposed in a chamber to liberate particles therefrom and quantifying a number of the liberated particles to determine the cleanliness of the sample.

Claims

1-27. (canceled)

28. A method for determining a quantity of particles on a surface of a sample, the method comprising: a. continuously introducing a flow of clean air or other gas into a chamber in such a manner that said air flows in a downwards spiral motion on an internal side walls of the chamber; b. impinging high pressure air or other gas pulses on the sample, disposed in said chamber to release particles therefrom; and c. quantifying a number of the released particles to determine the cleanliness of the sample using one or more particle counters, wherein said downwards spiral motion prevents said particles from escaping upwards.

29. A method according to claim 28, wherein said impinging step comprises providing air or another gas at a pressure in a range of 5-20 bar of said air or said other gas at a velocity of 400-2000 m/s at an exit of a nozzle orifice.

30. A method according to claim 29, wherein said impinging step comprises providing said air from two or more nozzles disposed at different locations within said chamber.

31. A method according to claim 30, wherein said two or more nozzles are disposed at the lower side of the chamber, at an angle of 60-180 degrees.

32. A method according to claim 30, wherein said two or more nozzles are disposed at perimeter of the circular chamber and at different heights on a side of the chamber, at an angle of 60-180 degrees between the nozzles.

33. A method according to claim 30, wherein said air comprises ionized air.

34. A method according to claim 28, further comprising generating vibrations on at least one of a wall of the chamber and on other units attached to the chamber thereby removing particles adhered to the chamber.

35. A method according to claim 34, wherein said generating vibrations step is performed utilizing ultrasonic energy.

36. A method according to claim 28, wherein said quantifying step comprises collecting said released particles for further analysis by at least one of SEM, EDS and XRF.

37. A method according to claim 28, wherein said continuous flow of clean air moves spirally around an inner surface of walls of said chamber enables concentration of the particles into a small volume of air.

38. A method according to claim 28, wherein said sample is selected from the group consisting of a metal part, glass, quartz part, ceramic part, and plastic part and materials among others such as elastomers, fluorocarbon polymers and combinations thereof.

39. A method according to claim 28, wherein said sample is selected from the group consisting of a machine part, a tool, a clean room gown, a clean room glove a clean room towel, a clean room paper, a silicon wafer, and a magnetic media disk.

40. A method according to claim 28, wherein said method is a non-destructive method.

41. A system for determining a quantity of particles on a surface of a sample to determine its cleanliness, the system comprising: a. a cylindrical chamber and a closable lid; b. at least one clean gas port controlled by a controller/processor/computer for continuously introducing a flow of pre-filtered clean air under pressure into the chamber in such a manner that said air flows spirally on the internal side walls of the cylindrical chamber, in a downwards spiral motion, adapted to prevent said particles from escaping upwards; c. a sample holder for holding the sample; d. at least one nozzle in fluid connection with a clean air provision unit, said at least one nozzle configured to provide high pressure pulses of clean air onto the sample, thereby releasing particles therefrom; and e. at least one particle counter in fluid connection with a vacuum pump, the at least one particle counter configured to receive said particles from said sample and further to quantify a number of said particles to determine said cleanliness of said sample.

42. A system according to claim 41, wherein said at least one clean gas port is configured to provide air at a pressure of in a range of 5-20 bar, at an air velocity of 400-2000 m/s at an exit of a nozzle orifice.

43. A system according to claim 41, wherein said gas inlet comprises at least two nozzles, disposed at different locations within said chamber.

44. A system according to claim 43, wherein said at least two nozzles comprise one nozzle disposed at a lower side of the chamber and at least another nozzle disposed at a vertical side of the chamber, at an angle of 60-180 degrees.

45. A system according to claim 43, wherein said at least one nozzle comprises two nozzles disposed on an inner perimeter of the cylindrical section at different heights on a vertical side of the chamber, with an angle of 60-180 degrees between the two nozzles.

46. A system according to claim 41, wherein said air comprises ionized air.

47. A system according to claim 41, further comprising a vibration generating apparatus, disposed on at least one of a wall of the chamber and on other units attached to the chamber, the vibration generating apparatus configured to release particles adhered to the chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0097] The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

[0098] With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the drawings:

[0099] FIG. 1A is a simplified pictorial illustration showing a side view of a system for quantifying sub-micron particles present in a sample, in accordance with an preferred embodiment of the present invention;

[0100] FIG. 1B is a simplified pictorial illustration showing a vertical cross-sectional view of a system for measuring and quantifying sub-micron particles present in a sample, in accordance with an embodiment of the present invention;

[0101] FIG. 1C is a simplified pictorial illustration showing a three-dimensional perspective view of a system for measuring and quantifying sub-micron particles present in a sample, in accordance with an embodiment of the present invention;

[0102] FIG. 1D is a simplified diagram of a clean air inlet in accordance with an embodiment of the present invention;

[0103] FIG. 1E is a simplified diagram of a high pressure pulse system in accordance with an embodiment of the present invention;

[0104] FIG. 2 is a simplified schematic block drawing of a system for analyzing sub-micron particles, present in a sample, in accordance with an embodiment of the present invention; and

[0105] FIG. 3 is a simplified flow chart of a method for analyzing sub-micron particles, present in a sample, in accordance with an embodiment of the present invention. In all the figures similar reference numerals identify similar parts.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0106] In the detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that these are specific embodiments and that the present invention may be practiced also in different ways that embody the characterizing features of the invention as described and claimed herein.

[0107] Reference is now made to FIG. 1A, which is a simplified pictorial illustration showing a side view of a system 100 for quantifying sub-micron particles present in a sample, in accordance with an preferred embodiment of the present invention.

[0108] FIG. 1A shows schematically a chamber 106 with all the units, which are connected to it, including:

[0109] A flap (door) 108 or lid, that allows access into the chamber. The opening of the flap may be activated manually or automatically. The chamber comprises several HEPA/ULPA filter unit components 110, 104 and 118, 114 for filtering air/gases entering the chamber. The system further comprises a controlled air exhaust 130 activated mechanically by a system of springs (not shown), or similar devices, or electronically by pressure sensors (not shown).

[0110] The system further comprises at least one particle counter 120 connected to the round or conical bottom 121 of the chamber 106.

[0111] Additional (optional) particle counters 122, 123 are connected to the side of the round or conical bottom of the chamber 106. Typically at least one particle counter is located at to the bottom of the chamber and at least one to a cylindrical side wall 125 thereof.

[0112] At least one clean air inlet 102, 116 is configured to allow air to flow on the inner walls 151 (FIG. 1B) of the chamber though sub-micron filters 104, 118, typically having a gauge of 0.03 μm (or less) at inlets A & B respectively on the upper side 127 and lower side 129 of the chamber. The air may enter the chamber in a continuous, semi-continuous or pulsed fashion. According to some preferred embodiments, the air is passed through two or more nozzles 130 (FIG. 1F) at different angles to the sides of the chamber.

[0113] An optional particle collection unit 124, equipped with a vacuum pump 126 to collect and further determine the nature and chemical composition of the particles.

[0114] Turning to FIG. 1B, there is seen a simplified pictorial illustration showing a vertical cross-sectional view 120 of system 100 for analyzing quantifying sub-micron particles present in a sample, in accordance with an embodiment of the present invention.

[0115] FIG. 1B shows three high pressure pulse units 160, 162 and 164, for providing airflow to the chamber. Further details of the high pressure air units 199 appear in FIG. 1D.

[0116] These are connected to the sides of the cylindrical chamber at different heights via respective filter units 154, 150 and 152. Additionally, the system comprises of the two high pressure air pulse units 166, 168, connected to the bottom 121 of the cylindrical chamber, each via its respective filter 158, 156, respectively. These two high pressure air pulse units 166, 168 are for providing pulsed air under high pressure to a sample (not shown). Further details of the high pressure air pulse units 199 appear in FIG. 1D.

[0117] Additional high pressure units may be attached to the chamber 106 at different locations, not shown in the Figure.

[0118] FIG. 1C is a simplified pictorial illustration showing a three-dimensional perspective view 170 of a system for quantifying sub-micron particles present in a sample, in accordance with an embodiment of the present invention. FIG. 1C is a three dimensional pictorial view 170 of chamber 106 showing the suggested location of the nozzles (showers) attached to the high-pressure pulse units 160, 162, 164 (FIG. 1C). Three showers are located on the sides of the chamber 172 and two nozzles 166, 168 on the bottom. The sample holding apparatus further comprises a grid 176, vertical support elements 178 and a lid 179.

[0119] FIG. 1D is a schematic diagram of the clean air inlet unit 102 showing a valve 101, a pressure regulator 103 a sub-micron filter 104 and a rectangular nozzle 130 attached to the chamber at inlets A & B. Both the valve 101 and the pressure regulator 103 may be of the mechanical type or electrical controlled type. All valves described in the present invention may be manual and/or electrical.

[0120] FIG. 1E is a schematic diagram of the high-pressure pulse unit 199 showing a valve 107, a pressure regulator 105, electrical controlled valves 109, a reservoir (100-500 ml) 113 a sub-micron filter 115 attached to the five nozzles (showers) and attached to the chamber 106. Both the valve 107 and the pressure regulator 105 may be of the mechanical type or electrically-controlled type.

[0121] Reference is now made to FIG. 2, which is a simplified schematic block drawing of a system 200 for quantifying sub-micron particles, released from a sample, in accordance with an embodiment of the present invention. The block diagram depicted in FIG. 2 shows the main components of the system.

[0122] The system typically comprises a cylindrical chamber 106 made of stainless steel, or other metal such as aluminum, or conductive glass/plastic, or any other appropriate material, a clean air unit 204 equipped with filters and electrical valves 207 controlled by a programmable controller or computer 220 and appropriate software 230. The system further comprises a source of air 202 that may be a compressor, a compressed air or other gas reservoir, a liquefied nitrogen or air reservoir, each of these being equipped with a suitable filtration units, valves, pressure regulators etc. (not shown).

[0123] The clean air unit 204 supplies clean air to the clean air supply unit 208 that supplies clean air to the chamber 106 that flows on the chamber walls as shown in FIG. 1A (locations A & B).

[0124] Clean air unit 204 also supplies clean air to the high pressure pulse system 210 equipped with nozzles, showers and similar accessories to generate short pulses of high velocity air/gas to impinge upon the sample.

[0125] The system typically further comprises a HEPA/ULPA filter unit 206 that receives air/gas from the supply system 202 that is used for flushing and cleaning the chamber 106 before the measurements and one or more particle counters 214 attached to the chamber 106 through isokinetic probes 212.

[0126] According to some embodiments, the entire operation of the chamber, air inlets, air flow rates, nozzles, meters, pumps and flow regulators are computer controlled. Typically the computer/processor 220 performs ongoing calculations to optimize air flow rates and to control the system working parts.

[0127] Turning to FIG. 3, there is seen a simplified flow chart of a method 300 for quantifying sub-micron particles, released from a sample, in accordance with an embodiment of the present invention. Cleaning Chamber Step 302 - Before a working session or if the cleanliness of the chamber 106 is so required, the HEPA/ULPA filter unit 206 is activated to flush, clean and prepare the chamber for testing.

[0128] Activating clean air flow step 304—The clean air unit 208 is activated to ensure positive pressure in the chamber 106 at inlet ‘A’.

[0129] Further activate clean air flow step 306—The clean air unit 208 is activated to ensure positive pressure in the chamber 106 at inlet ‘B’. This is performed to avoid entry of exterior air into the chamber. According to some embodiments, the air flow is in a downwards spiral motion, largely around the inner sides of the chamber. The air flow may be pulsed air, controlled by a controller/processor/computer such that the air flow or air stream is focused to prevent particles from escaping upwards. This methodology enables concentration of the particles into a small volume of air. The chamber is designed to have no electrostatic charge (such as from stainless steel, plastic, glass, aluminum and combinations thereof).

[0130] Sample delivery step 308—Open the flap (door) 108 and place the sample (not shown) to be tested, into the chamber and take readings of the particle counter or particle counters.

[0131] Pulsing air step 310—Start the sequence of short pulses of high-velocity air (gas) to impinge upon the sample and remove particles and taking readings of the particle counter or particle counters.

[0132] Repeating pulsing air step 312—Step 310 is repeated as many times as required by the programed testing sequence determined by the user according to the nature and type of the tested sample.

[0133] All steps of the method described above as well as calculating total particle steps 314 and a display results step 316. These two steps are controlled and performed by a previously programed testing sequence (“recipe”) as created previously by the user established according to the sample to be tested.

[0134] For example, here are some working, non-limiting exemplary parameters to be measured: directed pulses of air, air velocity m/s, air flow l/s, direction of flow and number of air inlets to chamber. In one example with two air inlets the exemplary parameters appear below.

TABLE-US-00001 1- CLEAN AIR FLOW: FLOW RANGE= 2-6 CFM Velocity @ nozzle exit= 1000-3000 cm/sec 2- AIR PULSE FLOW: container range volume 100-500 cm.sup.3 # orifices range 20-50 pressure range  5-15 bar flow range @ 1 bar 10,000-30,000 cm.sup.3/sec total velocity/pulse range 20,000-60,000 cm/sec velocity @ orifice exit (range)  40,000-200,000 cm/sec

[0135] The references cited herein teach many principles that are applicable to the present invention. Therefore the full contents of these publications are incorporated by reference herein where appropriate for teachings of additional or alternative details, features and/or technical background.

[0136] It is to be understood that the invention is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Those skilled in the art will readily appreciate that various modifications and changes may be applied to the embodiments of the invention as hereinbefore described without departing from its scope, defined in and by the appended claims.