Method and apparatus for monitoring layer erosion in a dry-etching process
First Claim
1. A method for monitoring layer erosion of layers on at least one substrate in a dry-etching process, having a first electrode that electrically contacts the substrate to be etched and a second electrode that is located above the first electrode, both electrodes being situated inside a process chamber, comprising the steps of:
- placing an optical photometer outside of the process chamber and reflecting a light beam off of the substrate in the process chamber by means of the photometer, signals output by the optical photometer being amplified by an electrical circuit and being edited and displayed by means of a Fourier transformation.
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Abstract
A method and apparatus for monitoring layer erosion in a dry-etching process. The apparatus has a first electrode that is electrically connected to a substrate to be etched, as well as a second electrode that is located above the first electrode. Both electrodes are situated inside a process chamber. An optical photometer is positioned outside of the process chamber and directed onto the substrate in the process chamber. Signals received from the optical photometer are amplified by an electrical circuit and are edited and displayed with a Fourier transformation. The etching process can be automatically interrupted when received periodic signals having essentially constant amplitude and frequency undergo a significant change during the etching process of the upper layer. That is, they are received as signals signficantly deviating from one another, this being identified by the electrical circuit as the passage from one layer to another layer of the substrate during the dry-etching process.
51 Citations
14 Claims
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1. A method for monitoring layer erosion of layers on at least one substrate in a dry-etching process, having a first electrode that electrically contacts the substrate to be etched and a second electrode that is located above the first electrode, both electrodes being situated inside a process chamber, comprising the steps of:
- placing an optical photometer outside of the process chamber and reflecting a light beam off of the substrate in the process chamber by means of the photometer, signals output by the optical photometer being amplified by an electrical circuit and being edited and displayed by means of a Fourier transformation.
- View Dependent Claims (2, 3, 4)
- 5. An apparatus for monitoring layer erosion of layers on at least one substrate in a dry-etching process, having a first electrode that electrically contacts the substrate to be etched and a second electrode that is located above the first electrode, both electrodes being situated inside a process chamber, an optical photometer being outside of the process chamber and reflecting a light beam off of the substrate in the process chamber, signals representive of the reflected light beam and output by the optical photometer being amplified and being edited and displayed by means of a Fourier transformation, the optical photometer having at least one measuring light source for producing the light beam with an associated receiver for receiving the reflected light beam, and an electrical circuit for processing of the signals from the associated receiver, comprising the measuring light source located outside of the process chamber and above a first glazed, pressuretight opening in the process chamber, the measuring light source directing the light beam onto the substrate which is reflected by the substrate onto the associated receiver, the associated receiver also being located outside of the process chamber.
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9. A method for monitoring layer erosion of layers on at least one substrate in a dry-etching process, having a first electrode that electrically contacts the substrate to be etched and a second electrode that is located above the first electrode, both electrodes being situated inside a process chamber, comprising the steps of:
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in a first preliminary step placing an optical photometer outside of the process chamber and reflecting a light beam off of the substrate in the process chamber by means of the photometer, signals output by the optical photometer being amplified by an electrical circuit and said signals being received in chronologically short succession by the electrical circuit and thereby form a reflection curve; in a first calculating step, storing a plurality of data points from the signals read by the photometer in the electrical circuit up to a prescribed point in time, an amplitude of one frequency being obtained via a Fourier transformation calculation; in a second calculating step, reducing the plurality of data points by one point and a second Fourier transformation being carried out; in a third calculating step, incrementing the plurality of data points by a further data point and a third Fourier transformation being carried out; in a fourth calculating step, identifying the frequency with the maximum amplitude; in a fifth calculating step, adding a further data point to those data points already recorded and the data point that was stored first being simultaneously eliminated, whereupon a frequency search is carried out with this data point set that has advanced by one data point on the time axis, that is, a time window that progresses in the direction of the time axis is placed over the reflection curve with respect to the acquisition of the data points; and in a sixth calculating step, identifying an amplitude change that indicates a transition of a shortwave signal of the signals into a long-wave signal of the signals and forming a final point curve representative of the amplitude change. - View Dependent Claims (10, 11)
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- 12. An apparatus for monitoring layer erosion of layers on at least one substrate in a dry-etching process, having a first electrode that electrically contacts the substrate to be etched and a second electrode that is located above the first electrode, both electrodes being situated inside a process chamber, an optical photometer being outside of the process chamber and reflecting a light beam off of the substrate in the process chamber, signals representive of the reflected light beam and output by the optical photometer being amplified and being edited and displayed by means of a Fourier transformation, the optical photometer having at least one measuring light source for producing the light beam with an associated receiver for receiving the reflected light beam, and an electrical circuit for processing of the signals from the associated receiver, comprising the measuring light source located outside of the process chamber and above a first glazed, pressuretight opening in the process chamber, the measuring light source directing the light beam onto the substrate which is reflected by the substrate onto the associated receiver, the associated receiver also being located outside of the process chamber, the second electrode located above the substrate having an aperture for the passage of the light beam of the measuring light source.
Specification