The invention relates to an integrated electro-mechanical actuator and to a method for manufacturing such an integrated electro-mechanical actuator.
As power and energy constraints in microelectronic applications become more and more challenging one is seeking constantly alternative and more power efficient ways of switching and computing. A typical switching device used in the semi-conductor industry is a CMOS transistor. To overcome power related bottle necks in CMOS devices novel switching devices operate on fundamentally different transport mechanisms such as tunnelling are investigated. However, combining the desirable characteristics of high on-current, very low off current, abrupt switching, high speed as well as a small footprint in a device that might be easily interfaced to a CMOS device is a challenging task. Mechanical switches such as Nano-Electro-Mechanical switches (NEM Switches) are promising devices to meet these kinds of criteria. A Nano-Electro-Mechanical switch having a narrow gap between electrodes is controlled by electrostatic actuation. In response to an electrostatic force a contact electrode can be bent to contact another electrode thus closing a switch. The control of the narrow gap for the electrostatic actuation and for the electrical contact separation is a main issue in designing and operating Nano-Electro-Mechanical switches. The NEM Switch has to meet both the requirement of high switching speed and low actuation voltage. Typically to achieve an actuation voltage in the range of 1 V and a switching speed approaching 1 ns the provided gap between the electrodes has to be in the range of about 10 nm. However to define and control the dimension of a 10 nm spacing between electrodes is difficult even when applying state of the art lithography technology.
The invention provides an integrated electro-mechanical actuator comprising
an electrostatic actuator gap between actuator electrodes,
an electrical contact gap between contact electrodes,
wherein an inclination with an inclination angle is provided between said actuator electrodes and said contact electrodes.
In a possible embodiment of the integrated electro-mechanical actuator according to the present invention, a thickness of said electrical contact gap is equal to the thickness g0 of a sacrificial layer.
In a possible embodiment of the integrated electro-mechanical actuator according to the present invention, the gap gA of said electrostatic actuator gap depends on the thickness of said electrical contact gap and said inclination angle α as follows:
g
A
=g
0·cos(α).
In a possible embodiment of the integrated electro-mechanical actuator according to the present invention, the electro-mechanical actuator is an in-plane actuator.
In a further possible embodiment of the integrated electro-mechanical actuator according to the present invention, the electro-mechanical actuator is an out-of-plane actuator.
In a further possible embodiment of the integrated electro-mechanical actuator according to the present invention said electro-mechanical actuator is a vertical actuator.
In a possible embodiment of the integrated electro-mechanical actuator according to the present invention the thickness of the contact gap is in a range of 5-50 nm.
In a possible embodiment of the integrated electro-mechanical actuator according to the present invention said inclination angle is in a range of 15-60 degrees.
In a possible embodiment of the integrated electro-mechanical actuator according to the present invention the electro-mechanical actuator comprises at least one electro-mechanical switch.
In an embodiment of the integrated electro-mechanical actuator according to the present invention in an actuated switching state of the electro-mechanical switch the contact gap is closed and in a not actuated switching state of the electro-mechanical switch the contact gap is not closed.
In an embodiment of the integrated electro-mechanical actuator according to the present invention in the actuated switching state of the electro-mechanical switch a structured contact beam fixed to a contact electrode is bent or moved in response to an electrostatic force generated by an electrical field between the structured contact beam and an actuator electrode.
In a possible embodiment of the integrated electro-mechanical actuator according to the present invention the structured contact beam comprises a flexible portion fixed to the contact electrode and a rigid portion connected to the flexible portion and having at its distal end an electrical contact surface separated by the electrical contact gap from an electrical contact surface of another contact electrode.
In an embodiment of the integrated electro-mechanical actuator according to the present invention the flexible portion of the structured contact beam comprises a spring constant in the range of 0.1 to 10 N/m.
In a possible embodiment of the integrated electro-mechanical actuator according to the present invention the electro-mechanical actuator comprises
an input electrode for applying an input voltage,
an output electrode for providing an output voltage,
a first supply voltage electrode to which a first structured contact beam is fixed,
a second supply voltage electrode to which a second structured contact beam is fixed,
wherein if the input voltage applied to the input electrode corresponds to the first supply voltage the second structured contact beam fixed to the second supply voltage electrode is bent or moved in response to an electrostatic force generated by an electrical field between the second structured contact beam and the input electrode to provide a contact between the second supply voltage electrode and the output electrode,
wherein if the input voltage supplied to the input electrode corresponds to the second supply voltage the first structured contact beam fixed to the first supply voltage electrode is bent or moved in response to an electrostatic force generated by an electrical field between the first structured contact beam and the input electrode to provide a contact between the first supply voltage electrode and the output electrode.
The invention further provides a method for manufacturing an integrated electro-mechanical actuator comprising
an electrostatic actuator gap between actuator electrodes,
an electrical contact gap between contact electrodes,
wherein an inclination with an inclination angle is provided between said actuator electrodes and said contact electrodes,
wherein each gaps are formed by etching a single sacrificial layer having a thickness corresponding to said electrical gap.
In a possible embodiment of the method for manufacturing an integrated electro-mechanical actuator according to the present invention, the sacrificial layer is formed by atomic layer deposition (ALD).
In an alternative embodiment of the method for manufacturing an integrated electro-mechanical actuator according to the present invention, the sacrificial layer is formed by chemical vapour deposition (CVD).
In a still further embodiment of the method for manufacturing an integrated electro-mechanical actuator according to the present invention, the sacrificial layer is formed by plasma enhanced chemical vapor deposition (PECVD).
In a possible embodiment of the method for manufacturing an integrated electro-mechanical actuator according to the present invention, the method comprises the steps of:
etching silicon on insulator to provide beam bodies,
performing a selective silicidation of said beam bodies,
deposition of a sacrificial layers on said beam bodies,
performing a metal deposition,
performing a CMP, and
etching the sacrificial layers and said insulator to separate the beam bodies from a substrate.
In the following possible embodiments of an integrated electro-mechanical actuator and of a method for manufacturing such an integrated electro-mechanical actuator are described with reference to the enclosed figures.
As can be seen from
Both structured contact beams 6, 7 of a flexible portion 6A, 7A can comprise a predetermined spring constant in a range of 0.1 to 10 N/m. In the embodiment shown in
In the embodiment shown in
If the input voltage supplied to the input electrode 2 correspond to the second supply voltage V2 (e.g. GND) the first structured contact beam 6 fixed to the first supply voltage electrode 4 is bent or moved in response to an electrostatic force generated by an electrical field between the first structured contact beam 6 and the input electrode 2 to provide a contact between the first supply voltage electrode 4 and the output electrode 3. Accordingly, the embodiment shown in
Both gaps, i.e. the actuator gap gA and the contact gap g0 are gaps between electrodes measured in a motion direction. The difference between the electrode angles of the contact and the actuator electrode is α. The gap gA of the electrostatic actuator gap depends on the thickness of the electrical contact gap g0 and on the inclination angle α as follows:
g
A
=g
0·cos(α)
By choosing the predetermined inclination angle α the motion gap difference can be provided by design.
In a preferred embodiment the thickness g0 of the electrical contact gap is equal to the thickness of a sacrificial layer in the manufacturing process. In a possible embodiment the thickness of the contact gap g0 is in a range of 5 to 50 nm. In a preferred embodiment the thickness g0 of the contact gap is in a range of 5 to 15 nm preferably about 10 nm.
In a possible embodiment the inclination angle α between the actuator electrodes and the contact electrodes is in a range of 15 to 60 degrees. In a preferred embodiment the inclination angle α is in a range between 25 and 35 degrees in particular about 30 degrees.
The parallel bars of the flexible portions 6A, 7A of the structured beams 6, 7, can comprise an aspect ratio of about 1 to 2 such that they perform no rotational but only a translational motion when actuated. In a possible embodiment the thickness g0 of the electrical contact gap is about 10 nm and the inclination angle α has 30 degrees so that the thickness gA of the electrostatic actuator gap is about 11.5 nm so that there is a slight difference of about 1.5 nm between the gap g0 of the electrical contact gap and the gap gA of the electrostatic actuator gap. Such a slight difference would very hard to create by conventional lithography methods. The integrated electromechanical actuator 1 according to the present invention having an inclination angle between the actuator electrodes and the contact electrodes allows to define a different gap with the same spacer. In a possible embodiment the input electrode 2 and the output electrode 3 are formed by Platinum electrodes. Depending on a length L of the flexible beam portion 6A, 7A it is possible to adjust a spring constant for the structured contact beams 6, 7 which can vary in a range of 0.1 to 10 N/m. By increasing the length of the flexible portion the structured contact beam are easier to be bent or moved by electrostatic forces. Accordingly, by increasing the length L of the flexible portion the necessary switching voltages can be reduced. In a possible embodiment the switching voltages are in a range between 0.5 and 5 V. In a preferred embodiment the switching voltages are in a range lower than 1 V. Accordingly, the actuation voltage for performing an actuation, in particular a switching, is less than 1 V in a preferred embodiment.
In a first step S1 of the manufacturing process a silicon on insulator (SOI) is etched to provide beam bodies. As can be seen in
In a further step S2 a selective silicidation is performed as shown in
In a further step S3 sacrificial layer is deposited on the beam bodies as shown also in
In a further step S4 a metal deposition is performed as also shown in
In a further step S5a CMP step, i.e. a mechanical polition step is performed as shown in
Finally, in a step S6 the sacrificial layer deposited in step S3 is etched as well as the insulator of the SOI structure to separate the beam bodies of the electro-mechanical actuator from the substrate as can be seen in
The integrated electro-mechanical actuator 1 according to the present invention which can be manufactured by a manufacturing process as shown in
While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims. For example, the gaps are not necessary obtained by sacrificial layer. Furthermore, in embodiments, the said electrostatic actuator gap may be designed irrespective of the thickness of said electrical contact gap and said inclination angle. It may still depend on these two quantities but not necessarily according to the law gA=g0.cos(α). Also, the actuator may have configurations other than in-plane, out-of-plane or vertical. Similarly, in embodiments, the thickness of said contact gap is not necessarily in the range of 5-50 nm and the inclination angle does not necessarily need to be in the range of 15-60 degrees, depending on a particular application sought. Furthermore, the extent into which the contact gap is actually closed depends on detailed circumstances. Also, other means than a structured contact beam can be relied upon. Still, should a contact beam (or a contact part, or the like) be used, various design can be contemplated as to its exact structure. More generally, embodiments of the integrated electro-mechanical actuator according to the invention may be implemented in digital electronic circuitry or in computer hardware.
Number | Date | Country | Kind |
---|---|---|---|
10158391.2 | Mar 2010 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/IB11/51322 | 3/29/2011 | WO | 00 | 9/28/2012 |