Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
2000-01-05
2002-06-11
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C204S298360, C204S192340, C216S066000, C216S094000, C438S712000
Reexamination Certificate
active
06402882
ABSTRACT:
DEVICE AND METHOD FOR ION BEAM ETCHING
This invention concerns a device and a method for ion beam etching for producing an etched surface on a semiconductor or an insulant.
Ion beam etching calls for good spatial control of the etching zones on the etched surface. A mask comprising several holes can be used for this purpose. These holes can be several microns in size and enable optimum etching accuracy, in the order of a fraction of a micron, if not smaller. A shortcoming of this technology lies in the fact that it involves realising a mask for each etching pattern.
Another method consists of direct control of the relative position of the incident beam on the etched surface. This control is for example carried out using electric and/or magnetic guiding means and by cooling the beam down, i.e. reduction of the seed component perpendicular to the propagation direction of the beam. The accuracy of this method is further enhanced while associating the direct control with the usage of micro or nano holes. For etching, the semiconductor or the insulant is moved under the beam. This technique improves the accuracy significantly, which reaches a few nm to 100 nm. The reliability of this method is however limited, because of the problems raised by the selection of the exposure duration and the displacement velocity of the semiconductor.
The present invention relates to a highly reliable device and method for ion beam etching, enabling accurate spatial control of the etching process, a control that can be performed electronically.
The invention concerns notably a device and a method for ion beam etching enabling a one-nanometer etching accuracy.
The invention relates to such a device and such a method that can be economical and easy to implement.
To this end, the invention concerns a device for ion beam etching that enables producing an etched surface on a semiconductor or an insulant. The device comprises:
a positive ion source,
means for guiding an ion beam thereby directing the beam to the etched surface, and
means for displacing the etched surface relatively to the ion beam.
According to the invention, the device comprises:
a system for space-time detection of ion interactions of the beam with the etched surface,
means for interrupting the ion beam, and
a processing unit linked to the displacement means, to the detection system and the beam interruption means, controlling the successive operations of: detecting the interruptions of the ions in the beam with the etched surface, beam interruption, relative displacement of the etched surface in relation to the position of the beam and restoring the beam.
Preferably, the processing unit controls the operations mentioned above repeatedly.
In this context, the word (<<surface>> means a superficial part of the semiconductor or insulant, generally cut approximately along a crystallographic plane. The surface is advantageously plane, but can also be curved.
The operations performed with the ion beam are performed under vacuum. This vacuum may correspond to relatively high pressure, for example in the order of 10
−9
Pa. It can also be an ultra-vacuum.
The means of relative displacement of the etched surface with respect to the ion beam may involve displacement of the semiconductor or insulant or displacement of the beam, by varying their positions or their orientations. Etching is then carried out in succession, one zone after the other. According to an embodiment, several beams are directed simultaneously towards the surface.
The space-time detection system detects the positions and the timing of interactions, simultaneously.
The etching device according to the invention enables, with respect to the existing devices, reducing the exposure durations of the etched surface and the relative displacements of the etched surface with respect to the ion beam. This control improves the reliability of the system quite considerably. Indeed, the main difficulty of ion beam etching lies in the fact that the ions reach the target erratically, spatially as well as temporally. The device according to the invention enables suiting the etching process to these erratic phenomena.
The positive ions sent by the source are preferably multicharged, i.e. each of them has three positive charges at least.
Preferably, interactions of the beam ions with the etched surface are carried out one ion after the other.
The etched semiconductor is for instance formed of a material selected among Si, AsGa, InP and Ge. The etched insulant is, for its own part, formed by SiO
2
or LiF.
Preferably, the etching device comprises a system for spatial localisation of the ion beam, interposed between the ion source and the etched surface.
This spatial location system consists advantageously of one or several beam collimators.
It is also advantageous that the etching device should be fitted with a system for controlling the position of the beam, and with means for cooling the beam down. It is also interesting that the device should comprise a system for monokinetic selection of the ions (between the ion source and the etched surface).
The beam interrupting means comprise advantageously means for applying an electric field that is more or less parallel to the etched surface.
This electric field is capable of diverting the beam and of preventing, thus, a new ion from reaching the surface. The use of the beam interrupting electric field is advantageously combined with that of a collimator, whereas a weak electric field is sufficient for interrupting the beam.
According to a preferred embodiment of the guiding means, the former may comprise means for applying a magnetic field, thereby diverting the ion beam by a certain angle.
Advantageously, this magnetic field is uniform and the deviation angle is 90°.
In a first variation, the guiding means comprise means for applying an electric field causing an electric deviation.
In a second variation, the guiding means implement at the same time a combined magnetic and electric field, for example in a Wien filter.
The means for relative displacement of the etched surface with respect to the ion beam comprise advantageously at least one element selected among a piezoelectric quartz and a ceramic, thereby displacing the semiconductor with respect to the ion beam incident on the etched surface.
Such displacing means enable controlled movement with accuracy in the order of one nanometer. The presence of several additional displacing means, such as two piezoelectric quartzes or two ceramics, enables moving the semiconductor or the insulant into two directions perpendicular to one another, which enables realising any etching pattern. It is then possible to create, along a rectilinear or circular line, insulating points on a semiconductor or semiconducting points on an insulant at regular intervals in order to produce digital encoding.
Preferably, displacement of the semiconductor is perpendicular to the incident ion beam.
It can also be performed with any angle with respect to the incident beam.
It is interesting that the etching device should comprise a tunnel effect and/or atomic strength microscope, performing local topographic and/or electric conductivity control of the etched surface processed.
Generally, such a microscope enables reading an etched pattern.
The etching device according to the invention is applicable to any etched surface, passivated or not, and is valid for any etching principle according to which the electrical or chemical nature or the topography of the surface is modified locally by an ion beam.
According to a first preferred embodiment of the etching device of the invention, the surface is occupied by first molecules of the semiconductor or insulant having a first chemical or topographic nature. The ion source is a source of highly charged and low energy positive ions and the etching device comprises means for applying a deceleration voltage, conferring the ions of the beam an average controlled velocity, enabling these ions, without contacting the etched surface, transforming a number of the first molecules of
Arent Fox Kintner & Plotkin & Kahn, PLLC
Crowell Michelle
Mills Gregory
Universite Pierre et Marie Curie
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