JPH0642468B2 - Ion beam etching device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ion beam etching apparatus for etching a sample using an ion beam.

[Conventional technology]

FIG. 3 is a schematic diagram showing a conventional ion beam etching apparatus. A disk 34 that is rotated by a motor 36 is provided in the vacuum container 30, and a plurality of wafers (samples) 32 are mounted on the disk 34.
Then, the wafer 32 is etched by irradiating the ion beam 26 from the ion source 16. Ion source 16
Is an ECR type ion source in this example, a plasma chamber 6 for generating plasma, a gas supply source 10 for supplying an active gas (in some cases, an inert gas) to the plasma chamber 6, and a waveguide 4 through the plasma chamber 6. The microwave oscillator 2 for supplying microwave power, the magnetic field coil 8 for confining the plasma, the acceleration electrode 12 and the deceleration electrode 14 for extracting the ion beam 26 from the plasma chamber 6 are provided, and the acceleration electrode 12 and the deceleration electrode are provided. An acceleration voltage and a deceleration voltage are applied to 14 from an acceleration power supply 22 and a deceleration power supply 24, respectively. As a result, an ion beam 26 made of, for example, reactive ions (for example, CF ⁺ , CFx ⁺ , F ^*, etc.) is extracted from the ion source 16.

For example, as shown in FIG. 4, the wafer 32 has a surface of a substrate 321 made of silicon or the like covered with an insulating layer (material to be etched) 322 made of, for example, silicon oxide, polycrystalline silicon, or the like. It is covered with a patterned mask 323. Such a wafer 3
By irradiating 2 with the above-mentioned ion beam 26,
The insulating layer 322 is etched according to the pattern of the mask 323.

The etching state of the wafer 32 is monitored by the etching monitor 46 during the etching. The beam current of the ion beam 26 is measured by the Faraday cup 28.

[Problems to be solved by the invention]

In the conventional ion beam etching apparatus as described above, etching is performed while the acceleration voltage output from the acceleration power source 22 and the output of the microwave oscillator 2 are always constant, that is, the energy and beam current of the ion beam 26 are constant. Was there. In this case, the energy of the ion beam 26 needs to be set high in order to increase the etching rate, but if this is done, damage to the substrate 321 such as lattice defects gradually becomes a problem as the etching progresses. This is the thinned insulating layer 322
This is because the number of ion beams 26 passing through is increased. This becomes a very large problem near the end of etching, and for example, when the energy of the ion beam 26 is about 1 KeV, considerable lattice defects are observed on the surface of the substrate 321.

In this way, increasing the etching rate and the substrate 32
Reducing the damage of 1 is a mutually contradictory matter,
In the past, the etching rate was increased even if some damage was expected.

Therefore, an object of the present invention is to provide an ion beam etching apparatus that can realize both an improvement in etching rate and a reduction in damage to a substrate.

[Means for solving problems]

The ion beam etching apparatus of the present invention controls the monitoring means for monitoring the etching state of the sample and the energy of the ion beam extracted from the ion source in response to the monitoring means, being relatively high in the initial stage of etching and relatively low in the latter stage of etching. Beam energy control means, and beam current control means for suppressing a decrease in the beam current of the ion beam when the energy of the ion beam is lowered by the beam energy control means.

[Operation] The etching state of the sample is monitored by the monitoring means, and based on this, the beam energy control means controls the energy of the ion beam to be relatively high in the initial stage of etching and relatively low in the latter stage of etching. In this case, the decrease in beam current when the energy of the ion beam is lowered is suppressed by the beam current suppressing means. As a result, both the improvement of the etching rate and the reduction of damage to the substrate used as the sample are realized.

〔Example〕

FIG. 1 is a schematic diagram showing an ion beam etching apparatus according to an embodiment of the present invention. The same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

In this ion beam etching apparatus, the etching state of the wafer 32 is monitored by the etching monitor 46, and the data is taken into the control device 50 equipped with, for example, a microcomputer. Further, the current flowing through the disk 34, that is, the beam current I of the ion beam 26 is detected by the ammeter 48 and is taken into the control device 50. However, the detection of the ion beam I may be performed by the Faraday cup 28 as shown in FIG.

Specifically, the etching monitor 46 uses the ion beam 26.
The light emitted by the radicals (free atoms) contained in it is detected. For example, the emission intensity of F ^* (fluorine radical) is
For example, a change as shown in FIG. 2 is shown according to the progress of etching. This is because when etching starts, F
^{When *} is used, the emission intensity is reduced, and when the etching is almost finished, the consumption of F ^* is reduced and the emission intensity is increased. When the etching is finished, the consumption of F ^* is stopped and the emission intensity changes. This is because they are gone. Therefore, this F
By monitoring the change in the emission intensity of ^* , the etching monitor 46 can monitor the etching state of the wafer 32 and the end of etching.

Then, the controller 50 controls the energy of the ion beam 26 according to the progress status of the etching of the wafer 32. Specifically, by controlling the accelerating voltage supplied from the accelerating power supply 22 to the accelerating electrode 12, the energy of the ion beam 26 is maximized in the initial stage of etching to increase the etching rate, and the end of etching approaches. By gradually lowering the energy of the ion beam 26, the etching rate is improved and damage to the substrate 321 used for the wafer 32 is reduced.

A more specific example will be described with reference to FIG.
In general, an insulating layer 322 of silicon oxide or the like is provided on a substrate 321 of silicon or the like to have a thickness of about 1 μm, and a mask 323 is provided thereon. When etching such a wafer 32, even if the energy of the ion beam 26 is increased in the initial stage of the etching, the substrate 321
There are no lattice defects on the surface of. Therefore, when the etching progresses to some extent from the start of etching, for example, the insulating layer 3
Ion beam 2 is used to increase the etching rate until the remaining thickness of 22 reaches about 1000 to 2000Å.
6. Energy of 6 and beam current I are maximized. The remaining thickness of the insulating layer 322 can be roughly detected by monitoring the temporal change of the emission intensity of F ^* as shown in FIG. 2 by the etching monitor 46. Alternatively, it can be generally detected only by the passage of time from the start of etching. After that, the energy of the ion beam 26 is lowered a little and etching is continued.
Make the energy of as low as possible. By controlling the energy of the ion beam 26 in this manner, etching can be performed without damaging the crystal structure near the surface of the substrate 321. Therefore, for example, etching which requires low ion beam energy, such as GaAs, causes less damage.

On the other hand, if the energy of the ion beam 26 is lowered, the beam current I of the ion beam 26 inevitably decreases due to the nature of the ion source, and the etching rate accordingly decreases. Therefore, in order to prevent this, in the present invention, the acceleration electrode 12 and the deceleration electrode 14 are provided in the ion source 20.
An electrode gap adjusting mechanism 18 for adjusting the electrode gap between the electrodes is provided, and the controller 50 controls the electrode gap adjusting mechanism 18 and also controls the microwave oscillator 2, the acceleration power supply 22, and the deceleration power supply 24. The reduction of the beam current I is suppressed. Specifically, the maximum beam current I when the acceleration voltage is changed in the ion source 20
The deceleration voltage and the electrode interval for extracting the energy are stored in the control device 50 in advance, and the deceleration voltage and the electrode interval are optimized in accordance with the acceleration voltage at each time, that is, the energy of the ion beam 26. Control things. When the energy of the ion beam 26 is reduced, the microwave power output from the microwave oscillator 2 is increased. This prevents the etching rate from decreasing when the energy of the ion beam 26 is reduced.

In the ion beam etching apparatus of this embodiment, the disk 34 is rotated by the disk rotation / translation mechanism 44.
Is rotated at high speed as indicated by arrow A, and is translated as indicated by arrow B. That is, the disk 34 is rotated at a high speed by the motor (for example, an induction motor) 36, and the rotation of the motor (for example, a stepping motor) 38 is converted into its translational motion by the mechanism section 40 to translate the disk 34. Reference numeral 42 is a vacuum seal portion. Then, the control device 50 controls the disk 34
The motor 38 is controlled so that the translational motion velocity v of

v∝I / R where R is the distance between the center of the ion beam 26 and the center of the disk 34. As a result, the disk 34
Uniform etching is performed on each of the upper wafers 32.

〔The invention's effect〕

As described above, in the present invention, since the energy and the beam current of the ion beam applied to the sample are controlled according to the progress of the etching of the sample, it is possible to improve the etching rate and reduce the damage of the substrate used for the sample. Can be realized together.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an ion beam etching apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of temporal changes in the emission intensity of F ^* . Figure 3 shows
It is the outline which shows the conventional ion beam etching device.
FIG. 4 is a view partially showing a cross section of the wafer. 2 ... Microwave oscillator, 18 ... Electrode spacing adjusting mechanism, 20
… Ion source, 22… Acceleration power supply, 24… Deceleration power supply, 26…
Ion beam, 30 ... Vacuum container, 32 ... Wafer (sample), 34 ... Disk, 46 ... Etching monitor, 50
…Control device

Claims (1)

[Claims] 1. An ion beam etching apparatus for irradiating a sample housed in a vacuum container with an ion beam from an ion source to etch the sample, the monitoring means for monitoring the etching state of the sample, and the monitoring means. In response, the energy of the ion beam extracted from the ion source is controlled to be relatively high in the initial stage of etching and relatively low in the latter stage of etching, and the energy of the ion beam is reduced when the energy of the ion beam is lowered by the beam energy control unit. An ion beam etching apparatus comprising: a beam current suppressing unit that suppresses a decrease in beam current.