GB2135776A - Film thickness measurement - Google Patents
Film thickness measurement Download PDFInfo
- Publication number
- GB2135776A GB2135776A GB08304594A GB8304594A GB2135776A GB 2135776 A GB2135776 A GB 2135776A GB 08304594 A GB08304594 A GB 08304594A GB 8304594 A GB8304594 A GB 8304594A GB 2135776 A GB2135776 A GB 2135776A
- Authority
- GB
- United Kingdom
- Prior art keywords
- film
- crystal
- deposited
- thickness
- source
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000005259 measurement Methods 0.000 title description 2
- 239000013078 crystal Substances 0.000 claims abstract description 32
- 230000008021 deposition Effects 0.000 claims abstract description 12
- 239000000463 material Substances 0.000 claims abstract description 12
- 239000010453 quartz Substances 0.000 claims abstract description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000000151 deposition Methods 0.000 description 11
- 239000000758 substrate Substances 0.000 description 9
- 238000012544 monitoring process Methods 0.000 description 6
- 238000000576 coating method Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 2
- 230000002596 correlated effect Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 230000001360 synchronised effect Effects 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000007738 vacuum evaporation Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
- G01B7/063—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using piezoelectric resonators
- G01B7/066—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using piezoelectric resonators for measuring thickness of coating
Abstract
Apparatus embodying a quartz crystal for measuring the thickness of deposited film evaporated or sputtered from a source of the film material, has a rotating shutter 8 interposed between the source and the crystal to regularly interrupt film deposition and thereby increase the operational life of the crystal. <IMAGE>
Description
SPECIFICATION
Improvements in film thickness measurement
This invention relates to measuring the thickness of deposited film and is particularly, though not exclusively, directed to the use of quartz crystals as detectors responsive to deposited film thickness.
The techniques of depositing film of various materials upon a substrate is now well established in a number of industrial processes.
Typical examples of the application of such films are in the production of semiconductor integrated circuits and as anti-reflection surfaces on lenses and other optical elements.
In each of these processes the thickness of film, which generally is deposited by a vacuum evaporation or sputtering technique, must be controlled within close tolerances to ensure that the film exhibits the required properties. It has been proposed to monitor and to measure the thickness of films deposited on a substrate by way of a detector such as a quartz crystal disposed adjacent the substrate. The natural frequency of the crystal when embodied in an oscillator circuit of known kind is modified by a film deposited upon its surface, the shift of oscillation frequency being a function of the thickness of the deposited film. Suitable calibration can compensate for different film materials enabling the quartz crystal detector to be used for measuring as well as for monitoring the thickness of films deposited.
In a number of applications, for example in the deposition of infra red coatings upon glass, the thickness of film deposited on the crystal is relatively large; it has been found that with such relatively thick films produced either by the deposition of one relatively thick coating or by a plurality of thinner coatings, the effective operational life of a quartz crystal detector and in some cases its accuracy is impaired.
It is one object of the present invention to attempt to overcome this deficiency.
The present invention according to its broadest aspect provides a method for monitoring the thickness of film deposited upon a suitable detector including repetitively interrupting the passage of film material from the source on to the detector active surface.
According to a further aspect of the present invention, apparatus for monitoring the thickness of film deposited upon a suitable detector includes means interposed between the detector and the source of film material and effective to repetitively interrupt the passage of film material onto the detector active surface.
In a preferred embodiment of the invention the repetition rate is regular so that the thickness of film which would have been deposited in the absence of any interruption can be calculated with reasonable accuracy.
Suitably, the detector comprises a crystal such as a quartz crystal which is embodied in an oscillator circuit of any type well known in the art. In this case, the natural oscillation frequency of the uncoated crystal will vary in accordance with the thickness of film deposited. Film thickness values obtained with regular interruption can accordingly be correlated to thickness under continuous deposition conditions by correction by the mark/space interruption ratio.
Conveniently, the deposition of film material is interrupted by a rotatable disc disposed adjacent the crystal, the disc having cut away portions adapted respectively to go into and out of register with the crystal active surface during rotation so that film deposition occurs only during register. A synchronous or like motor drive for the disc ensures that the interruption is regular to enable film thickness deposited on the crystal to be accurately correlated to that deposited on an adjacent substrate.
The embodiment of the invention will now be particularly described by way of example with reference to the accompanying drawing in which:- Fig. 1. Is a schematic side view of apparatus embodying a quartz crystal for monitoring the thickness of deposited film and, Fig. 2. is a schematic plan view of a rotating disc for interrupting the deposition of film on to the quartz crystal of Fig. 1.
Referring to the drawings the film thickness monitor comprises a holder 2 of any conventional type for releasably retaining a suitable quartz crystal 4 intended to be coupled into an oscillator circuit of known kind. Crystal 4 is retained within the recessed portion 6 of the holder 2 by way of resilient contacts (not shown) which engage the crystal surface and which form the connection to the remote oscillator.
Disposed adjacent the recess 4 of holder 2 is part circular disc 8 driven for rotation by synchronous or like constant speed motor 10.
The disc 8 has cut away portions 1 2 which are disposed symetrically about its axis of rotation and which move into and out of register with the exposed active surface of crystal 4 retained in holder 2.
The monitoring apparatus shown in Figs. 1 and 2 is located adjacent the substrate upon which film material evaporated or sputtered from a suitable source is to be deposited. The film may be a dielectric material for non reflectively coating optical elements such as lenses or may be of metal for producing a reflecting surface upon lamp reflectors. The juxta position of the monitoring apparatus is such that film material migrating from the source to the substrate will also migrate to the quartz crystal 4 but will be partially but regularly interrupted by the rotating disc 8; this film material will deposited on the crystal only when the cut away portion 1 2 is in register with the crystals active surface.The rate of deposition on the crystal will accordingly be reduced in accordance with the total angular width of the cut away portion 12 and may be increased or decreased respectively by increasing or decreasing this angular width.
Since the effective operational life of the crystal before replacement or cleaning is limited by the thickness of deposited film, a substantial extension of operational life can be produced by the present invention.
The rate of film deposition is not dependent upon disc angular velocity. However as previously recited disc volicity must be maintained substantial constant to enable film thickness deposited on the crystal to be related with sufficient accuracy to that deposited on the substrate. This is necessary to enable substrate film thickness to be monitored by reference to the frequency variation of the oscillator circuit in which the crystal is embodied.
The constant rate of rotation of the disc 10 must however be selected to avoid modulation of the instrumentation by which the oscillator frequency is monitored.
It will be appreciated that with the angular width of the cut away portions of the disc known the actual film thickness deposited upon the substrate can be measured in addition to being monitored with the instrumentation suitably calibrated.
It will also be appreciated that while the invention has been described with reference to an appertured or cut away disc for interrupting deposition of film material on to the quartz crystal it is equally applicable to alternative film thickness detectors and with the use of other means for interrupting film deposition.
Claims (1)
1. Apparatus embodying a quartz crystal for measuring the thickness of deposited film evaporated or sputtered from a source of the film material, has a rotating shutter interposed between the source and the crystal to regularly interrupt film deposition and thereby increase the operational life of the crystal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08304594A GB2135776A (en) | 1983-02-18 | 1983-02-18 | Film thickness measurement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08304594A GB2135776A (en) | 1983-02-18 | 1983-02-18 | Film thickness measurement |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8304594D0 GB8304594D0 (en) | 1983-03-23 |
| GB2135776A true GB2135776A (en) | 1984-09-05 |
Family
ID=10538234
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08304594A Withdrawn GB2135776A (en) | 1983-02-18 | 1983-02-18 | Film thickness measurement |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2135776A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2237640A (en) * | 1989-11-02 | 1991-05-08 | Leybold Inficon Inc | Multiple crystal head for deposition thickness monitor |
| FR2771810A1 (en) * | 1997-11-28 | 1999-06-04 | Sgs Thomson Microelectronics | Monitoring procedure for application of deposit by evaporation |
| WO2011039191A1 (en) * | 2009-10-02 | 2011-04-07 | Applied Materials, Inc. | Coating thickness measuring device and method |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB896934A (en) * | 1959-05-21 | 1962-05-23 | Ass Elect Ind | Improvements relating to diffraction gratings |
-
1983
- 1983-02-18 GB GB08304594A patent/GB2135776A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB896934A (en) * | 1959-05-21 | 1962-05-23 | Ass Elect Ind | Improvements relating to diffraction gratings |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2237640A (en) * | 1989-11-02 | 1991-05-08 | Leybold Inficon Inc | Multiple crystal head for deposition thickness monitor |
| GB2237640B (en) * | 1989-11-02 | 1993-04-14 | Leybold Inficon Inc | Multiple crystal head for deposition thickness monitor |
| FR2771810A1 (en) * | 1997-11-28 | 1999-06-04 | Sgs Thomson Microelectronics | Monitoring procedure for application of deposit by evaporation |
| WO2011039191A1 (en) * | 2009-10-02 | 2011-04-07 | Applied Materials, Inc. | Coating thickness measuring device and method |
| EP2309220A1 (en) * | 2009-10-02 | 2011-04-13 | Applied Materials, Inc. | Coating thickness measuring device and method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8304594D0 (en) | 1983-03-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |