Specific Process Knowledge/Characterization/Sample imaging: Difference between revisions
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=== What kind of instrument to use === | === What kind of instrument to use === | ||
There is a lot of optical microscopes scattered around in the cleanroom because they are in great need. They are useful if, for instance, you need to | There is a lot of [[Specific Process Knowledge/Characterization/Optical microscope|optical microscopes]] scattered around in the cleanroom because they are in great need. They are useful if, for instance, you need to | ||
* inspect the quality of UV exposed photoresist when doing photolithography, | * inspect the quality of UV exposed photoresist when doing photolithography, | ||
* check for particles on wafers that have been processed in the furnaces or the PECVD's, | * check for particles on wafers that have been processed in the furnaces or the PECVD's, | ||
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One of the advantages of the optical microscopes is that they provide fast and easy accessible information about any sample without any kind of sample preparation. They do, however, also have some limitations. Since the depth of focus is quite limited, especially at high magnifications, one will experience problems when trying to image strucutures that have been etched more than some 10 µm: One cannot focus on both the top and the bottom at the same time. Another disadvantage is the physical limit to the resolution that makes it impossible to image structures below 1 µm. | One of the advantages of the optical microscopes is that they provide fast and easy accessible information about any sample without any kind of sample preparation. They do, however, also have some limitations. Since the depth of focus is quite limited, especially at high magnifications, one will experience problems when trying to image strucutures that have been etched more than some 10 µm: One cannot focus on both the top and the bottom at the same time. Another disadvantage is the physical limit to the resolution that makes it impossible to image structures below 1 µm. | ||
Both shortcomings of the optical microscopes mentioned above are addressed by the use of a beam of electrons (as you do in a SEM) instead of light. The depth of focus and the resolution of a SEM are at least one order of magnitude better. Another SEM advantage is the stage that allows you to image your sample from almost any angle. The SEM is, however, much more complicated in terms of | Both shortcomings of the optical microscopes mentioned above are addressed by the use of a beam of electrons (as you do in a SEM) instead of light. The depth of focus and the resolution of a [[Specific Process Knowledge/Characterization/SEM: Scanning Electron Microscopy|scanning electron microscope]] are at least one order of magnitude better. Another SEM advantage is the stage that allows you to image your sample from almost any angle. The SEM is, however, much more complicated in terms of | ||
* Operation: You need training and it takes some experience and skill to obtain good images. | * Operation: You need training and it takes some experience and skill to obtain good images. | ||
* Hardware: In order to work the SEM needs vacuum and sophisticated electronics. | * Hardware: In order to work the SEM needs vacuum and sophisticated electronics. | ||
Revision as of 12:24, 24 January 2008
The list of instruments for sample imaging available at Danchip includes 6 optical microscopes , three scanning electron microscopes (SEM's) and an atomic force microscope (AFM). These instruments cover a wide range of applications.
What kind of instrument to use
There is a lot of optical microscopes scattered around in the cleanroom because they are in great need. They are useful if, for instance, you need to
- inspect the quality of UV exposed photoresist when doing photolithography,
- check for particles on wafers that have been processed in the furnaces or the PECVD's,
- check the quality of KOH etched structures or
- generally verify any in batch process.
Using the different options such as bright/dark field, polarizer or transmitted/reflected light one can find a better signal for a specific need. Some of them have a camera that allows you to capture and store images.
One of the advantages of the optical microscopes is that they provide fast and easy accessible information about any sample without any kind of sample preparation. They do, however, also have some limitations. Since the depth of focus is quite limited, especially at high magnifications, one will experience problems when trying to image strucutures that have been etched more than some 10 µm: One cannot focus on both the top and the bottom at the same time. Another disadvantage is the physical limit to the resolution that makes it impossible to image structures below 1 µm.
Both shortcomings of the optical microscopes mentioned above are addressed by the use of a beam of electrons (as you do in a SEM) instead of light. The depth of focus and the resolution of a scanning electron microscope are at least one order of magnitude better. Another SEM advantage is the stage that allows you to image your sample from almost any angle. The SEM is, however, much more complicated in terms of
- Operation: You need training and it takes some experience and skill to obtain good images.
- Hardware: In order to work the SEM needs vacuum and sophisticated electronics.
- Sample preparation and mounting: You may have to prep your sample in several ways, either coating, cleaving or mounting on specific sample holders.
| Optical microscopes | SEM | AFM | |
|---|---|---|---|
| Magnification range | 25x to 1000x | 100x to 500.000x | Maximum scanned area 90x90 µm |
| Depth of focus | Low | Very high |