Device and method for maskless AFM microlithography
View Patent ↗The invention relates to a device and a method for maskless microlithography. Several microstructured cantilevers ( 2 ) are arranged in an array ( 26 ) and an actuator is integrated in each of the cantilevers ( 2 ) of the array ( 26 ). A power supply and control unit ( 24 ) is provided, said unit adjusting the distance of the cantilevers ( 6 ) relative to a surface ( 4 ) that is to be structured by means of an appropriate voltage. Every point of the needles ( 6 ) is connected to said power supply and control unit ( 24 ). In order to implement the inventive method, an array ( 26 ) with cantilevers, each of which carries a point of a needle ( 6 ), is brought into contact with a surface ( 4 ) to be structured in such a way that the points of the needles ( 6 ) are arranged close to the surface ( 4 ) to be structured.
1. Device for maskless microlithography with a microstructured cantilever 2 , which bears a needlepoint 6 at a free end 2 a , characterized in that a plurality of microstructured cantilevers 2 are arranged in an array 26 ; in that each cantilever 2 of the array 26 contains a bimorphic thermal actuator 50 , a piezoelectric resistance sensor 14 , and a heating element 15 ; and in that a power supply and control unit 24 is provided that is connected with the needlepoint 6 , the heating element 15 , and the piezoelectric resistance sensor 14 , and the needlepoint 6 and the heating element 15 are suitably powered and receive the voltage generated by the piezoelectric resistance sensor 14 .
2. Device according to claim 1 , characterized in that the needlepoint 6 consists of a point 10 and a ring 12 , and in that a cathode voltage V C is applied between the ring 12 and the point 10 , which acts as standby voltage.
3. Device according to claim 2 , characterized in that the ratio between the cathode voltage V c and an anode voltage V a regulates the spot size of electron radiation E on a surface 4 to be structured.
4. Device according to claim 1 , characterized in that the power supply and control unit 24 consists of a power source 60 , a voltage generator 61 , a phase inhibition circuit 62 , and a PID controller 63 , in which case the power source 60 includes an alternating voltage source 64 , a PID voltage source 65 , and a direct voltage source 66 .
5. Device according to claim 1 , characterized in that the phase inhibition circuit 62 receives the voltage measured by the piezoelectric resistance sensor 14 , and the phase inhibition circuit 62 receives voltage from the voltage generator 61 , and the phase inhibition circuit 62 delivers a signal to the PID controller 63 and, in turn, the PID controller 63 delivers a signal to the PID power source 65 that is provided for in the power source, and the voltage generator 61 delivers an alternating voltage signal to the alternating voltage source 64 that is provided for in the power source 60 .
6. Device according to claim 5 , characterized in that the an accumulator 67 is provided for in the power source 60 that accumulates the voltage from the alternating voltage source 64 , the voltage from the PID power source 65 , and the voltage from the direct voltage source 66 , and is connected to a heating element 15 by means of an electrical connection 19 .
7. Device according to claim 1 , characterized in that the power supply and control unit 24 determines the phase shift of the cantilever 2 , and in that the power supply and control unit 24 adjust and keep constant the distance of the needlepoint 6 relative to the surface 4 of the substrate 5 to be structured, in which case the phase shift is kept at a constant size.
8. Device according to claim 1 , characterized in that the surface 4 to be structured represents the surface of a wafer that is covered with a layer of a material to be structured.
9. Device according to claim 7 , characterized in that the arrangement of the cantilevers 2 in an array 26 is in the form of a row, and in that the length of the row approximates the diameter of the wafer that bears the layer to be structured.
10. Device according to claim 7 , characterized in that the arrangement of the cantilevers 2 in the array 26 is in the form of a spatial matrix.
11. Device according to claim 10 , characterized in that a plurality of spatial matrix arrangements of the cantilevers 2 in the array 26 are arranged like a mosaic, and wherein the mosaic-like arrangement corresponds approximately to the area of the surface 4 , the second wafer, or the substrate to be structured.
12. Device according to claim 1 , characterized in that the cantilevers 2 are provided with structured conductors 18 a and 19 a to regulate and control the cantilever 2 , and in that each cantilever 2 is provided with a base part 16 on which a plurality of electrical connections 19 , 20 , 21 , 22 are structured.
13. Device according to claim 1 , characterized in that the bimorphic thermal actuator 50 consists of three layers, in which case a first layer 30 is made of silicon (Si), a second layer 32 is of silicon dioxide (SiO 2 ), and a third layer 34 is of aluminum (Al).
14. Device according to claim 1 , characterized in that a plurality of arrays 26 are arranged on a silicon wafer, in which case the individual arrays 26 are separated from each other by partitions 28 made of silicon, and in that the connection to the power supply and control unit 24 is via the passageways 29 in the partitions.
15. Method for maskless lithography, consisting of the following steps:
Bringing together at least one array 26 with cantilevers 2 , of which each bears a needlepoint 6 , with a surface to be structured 4 such that the needlepoints 6 are arranged close to the surface 4 to be structured;
Adjusting and regulating a phase shift of the cantilevers 2 in the arrays 26 with a power supply and control unit 24 , in which case a constant phase shift corresponds to a constant distance of the needlepoint 6 that is provided on each cantilever 2 relative to the surface 4 to be structured;
Implementation of a relative movement between the minimum of one array 26 with cantilevers 2 and the surface 4 to be structured;
Application of an electrical voltage to the needlepoint 6 in order to generate an electrical field between the needlepoint and the surface 4 to be structured; and
Regulation of the voltage, in accordance with the pattern to be generated on the surface 4 to be structured.
16. Method according to claim 15 , characterized in that the distance between the needlepoint 6 of the cantilever 2 and the surface 4 to be structured is changed by means of a heating element 15 provided for in the cantilever 2 , and in which a bimorphic thermal actuator 50 is integrated into the cantilever 2 .
17. Method according to claim 15 , characterized in that the power supply and control unit 24 consists of a power source 60 , a voltage generator 61 , a phase inhibition circuit 62 , and a PID controller 63 , in which case the power source 60 includes an alternating voltage source 64 , a PID voltage source 65 , and a direct voltage source 66 .
18. Method according to claim 15 , characterized in that the phase inhibition circuit 62 receives the voltage measured by the piezoelectric resistance sensor 14 and the phase inhibition circuit 62 receives voltage from the voltage generator 61 , and the phase inhibition circuit 62 delivers a signal to the PID controller 63 and, in turn, the PID controller 63 delivers a signal to the PID power source 65 that is provided for in the power source, and the voltage generator 61 delivers an alternating voltage signal to the alternating voltage source 64 .
19. Method according to claim 16 , characterized in that the power from the alternating voltage source 64 , the power from the PID voltage source 65 , and the power from the direct voltage source 66 are delivered to the heating element 15 by way of an accumulator 67 in the power source 60 .
20. Method according to claim 15 , characterized in that the power supply and control unit 24 determines the phase shift of the cantilever 2 , and in that the power supply and control unit 24 adjust and keep constant the distance of the needlepoint 6 relative to the surface 4 of the substrate 5 to be structured, in which case the size of the phase shift is kept constant.
21. Method according to claim 15 , characterized in that the application of electrical voltage to the needlepoint 6 is implemented by means of a power supply and control unit 24 .
22. Method according to claim 21 , characterized in that the individual power supply and control unit 24 operates such that alternating voltage is applied to the heating element 15 such that the cantilever 2 is made to oscillate at a frequency of 1–15 MHz.
23. Method according to claim 22 , characterized in that the resonance frequency and at least three eigenmodes of the cantilevers 2 lie within the range of frequencies at which the cantilevers 2 oscillate.