BACKGROUND OF THE INVENTION [0002] Micro-electromechanical system (MEMS) may comprise movable micro- mirrors fabricated by microelectronic processing techniques on wafer substrates.

Electrostatic actuation is most commonly used to deflect micro-mirrors. In order to produce a force, a voltage is generated between two electrodes, one of which is stationary and the other of which is attached to an actuator for example the movable micro-mirror.

[0003] An SLM with an array of actuators used in for example a mask writing tool or a chip manufacturing tool is loaded with a specific pattern, where each actuator is in an addressed state or a non-addressed state before each stamp is printed.

This pattern may be a subset of the pattern to be printed on the mask or chip respectively. Each actuator mirror is deflected electrostatically by applying voltage between the mirror and an underlying address electrode, after which the actuator mirror is allowed to move into it's predetermined deflected state before an electromagnetic radiation source is triggered to print the stamp.

[0004] A deflection amplitude of the actuator mirror in a spatial light modulator (SLM) is determined by a number of factors such as an addressing voltage, mirror hinge material stiffness, mirror hinge thickness, electrode to mirror distance etc. With otherwise optimized parameters the addressing voltage is usually the determining free parameter for being able to reach the maximum required mirror deflection amplitude.

This, in turn, sets the requirements for a voltage span of an addressing CMOS circuit.

As a mirror area needs to shrink for future generations of SLM components to allow more mirrors per SLM chip, the addressing voltage will need to increase dramatically for otherwise unchanged parameters. A size of a pixel cell in the CMOS circuit is strongly dependent on the voltage span of the addressing CMOS circuit, why for

smaller mirror sizes, with increased addressing voltage span, the CMOS circuit becomes the limiting factor for future actuator sizes.

SUMMARY OF THE INVENTION [0005] Accordingly, it is an object of the present invention to provide a method of addressing microelements, which overcomes or at least reduces the above-mentioned problem of increased address voltages for smaller actuator sizes.

[0006] This object, among others, is according to a first aspect of the invention attained by a method for modulating at least one pulse of electromagnetic radiation with a spatial light modulator. At least one mechanically movable modulator element is provided. At least one actuating element capable to produce forces on said movable modulator element provided. A biasing signal is provided to said at least one movable modulator element. An address signal is providing to at least one first electrode belonging to said at lest one movable modulator element to move said movable element to a desired modulation state, where said electromagnetic radiation is impinged onto said at least one movable modulator element when being in said desired modulation state.

[0007] In another embodiment according the present invention, said biasing signal is to its absolute value greater than or equal to an absolute value of a maximum address signal.

[0008] In another embodiment according to the present invention, said maximum address signal causes said movable element to reach a state less than snap-in state but greater than 95% of snap in state.

[0009] In another embodiment according to the present invention, said maximum address signal causes said movable element to reach a state less than snap-in state but greater than 90% of snap in state.

[0010] In another embodiment according to the present invention, said maximum address signal causes said movable element to reach a state less than snap-in state but greater than 50% of snap in state.

[0011] In another embodiment according to the present invention, said movable modulator element is a multi-valued element capable to be in more than 2 modulation states.

[0012] The invention also relates to a method for patterning a workpiece arranged at an image plane and covered at least partly with a layer sensitive to electromagnetic radiation, by using at least one spatial light modulator (SLM) arranged at an object plane, where said SLM comprises at least one movable modulator microelement. A biasing signal is provided to said at least one movable modulator microelement. Said at least one movable modulator microelement is moved to a desired modulation state by providing an addressing signal to at least one first electrode belonging to said at least one movable modulator microelement. Electromagnetic radiation is emitting directed onto said object plane. Electromagnetic radiation is received by said spatial light modulator when at least one movable microelement being in said desired modulation state, where a modulated electromagnetic radiation is relayed by said spatial light modulator toward said work piece.

[0013] In another embodiment according to the present invention, said biasing signal is to its absolute value greater than or equal to a maximum address signal.

[0014] In still another embodiment according to the present invention, said movable modulator element is a multi valued element capable to be in more than 2 modulation states.

[0015] The invention also relates to an apparatus for patterning a workpiece arranged at an image plane and covered at least partly with a layer sensitive to electromagnetic radiation, by using at least one spatial light modulator (SLM) arranged at an object plane, where said SLM comprises at least one movable modulator microelement. Means for providing a biasing signal to said at least one movable modulator microelement. Means for moving said at least one movable modulator microelement to a desired modulation state by providing an addressing signal to at least one first electrode belonging to said at least one movable modulator microelement. Means for emitting electromagnetic radiation directed onto said object plane. Means for receiving said electromagnetic radiation by said spatial light modulator when at least one movable microelement being in said desired modulation state, where a modulated electromagnetic radiation is relayed by said spatial light modulator toward said work piece.

[0016] In another embodiment according to the present invention, said biasing signal is to its absolute value greater than or equal to a maximum address signal.

[0017] In another embodiment according to the present invention, said movable modulator element is a multi-valued element capable to be in more than 2 modulation states.

[0018] The invention also relates to an apparatus for patterning a workpiece arranged at an image plane and covered at least partly with a layer sensitive to electromagnetic radiation, by using at least one spatial light modulator (SLM) arranged at an object plane, where said SLM comprises at least one movable modulator microelement. An actuating element capable to move said at least one movable modulator microelement to a desired modulation state. At least one first electrode belonging to said at least one movable modulator microelement arranged to be addressed by an address signal when said movable modulator microelement being biased. A source to emit electromagnetic radiation directed onto said object plane when said at least one movable modulator microelement being in said desired modulation state, wherein a modulated electromagnetic radiation is relayed by said SLM toward said workpiece.

[0019] In another embodiment according to the present invention, said biasing signal is to its absolute value greater than or equal to a maximum address signal.

[0020] In another embodiment according to the present invention, said movable modulator element is a multi-valued element capable to be in more than 2 modulation states.

[0021] The invention also relates to a method for modulating at least one pulse of electromagnetic radiation with a spatial light modulator. At least one mechanically movable modulator element is provided. At least one actuating element capable to produce forces on said movable modulator element is provided. At least one first signal is provided having an absolute value greater than 0 to at least one electrode. said at least one movable modulator element is set to a desired modulation state by applying a second signal to the modulator element, and said electromagnetic radiation is impinged onto said at least one movable modulator element when being in said desired modulation state.

[0022] In another embodiment according to the present invention, said first signal is fixed and said second signal is capable to be altered to a predetermined value.

[0023] In another embodiment according to the present invention, an undeflected state is defined to be when an absolute value of said first signal provided to a single

electrode belonging to said movable element being essentially twice the absolute value of said second signal.

[0024] In another embodiment according to the present invention said movable modulator element is capable to deflect in a first and a second direction by decreasing or increasing said second signal, respectively, from said undeflected state.

[0025] In another embodiment according to the present invention, said movable modulator element is a multi-valued element capable to be in more than 2 modulation states.

[0026] In another embodiment according to the present invention, an undeflected state is defined to be when said second signal is essentially twice an absolute value of the first signal provided to a first electrode and essentially half an absolute value of a third signal provided to a second electrode, where said first and second electrodes belong to said movable element.

[0027] In another embodiment according to the present invention, said first and third signals are fixed and said second signal is capable to be altered to a predetermined value.

[0028] The invention also relates to a method for patterning a workpiece arranged at an image plane and covered at least partly with a layer sensitive to electromagnetic radiation, by using at least one spatial light modulator (SLM) arranged at an object plane, where said SLM comprises at least one movable modulator microelement. At least one first signal is provided having an absolute value greater than 0 to at least one electrode. Said at least one movable modulator microelement is moved to a desired modulation state by applying a second signal to the movable modulator microelement.

Electromagnetic radiation is emitted directed onto said object plane. Said electromagnetic radiation is received by said spatial light modulator when at least one movable modulator microelement being in said desired modulation state, where a modulated electromagnetic radiation is relayed by said spatial light modulator toward said work piece.

[0029] The invention also relates to an apparatus for patterning a workpiece arranged at an image plane and covered at least partly with a layer sensitive to electromagnetic radiation, by using at least one spatial light modulator (SLM) arranged at an object plane, where said SLM comprises at least one movable modulator microelement. Means for providing at least one first signal having an

absolute value greater than 0 to at least one electrode. Means for moving said at least one movable modulator microelement to a desired modulation state by applying a second signal to the movable modulator microelement. Means for emitting electromagnetic radiation directed onto said object plane. Means for receiving said electromagnetic radiation by said spatial light modulator when at least one movable modulator microelement being in said desired modulation state, where a modulated electromagnetic radiation is relayed by said spatial light modulator toward said work piece.

[0030] The invention also relates to an apparatus for patterning a workpiece arranged at an image plane and covered at least partly with a layer sensitive to electromagnetic radiation, by using at least one spatial light modulator (SLM) arranged at an object plane, where said SLM comprises at least one movable modulator microelement. Means for providing a biasing signal to said at least one movable modulator microelement. Means for moving said at least one movable modulator microelement to a desired modulation state by providing an addressing signal to at least one first electrode belonging to said at least one movable modulator microelement. Means for emitting electromagnetic radiation directed onto said object plane. Means for receiving said electromagnetic radiation by said spatial light modulator when at least one movable microelement being in said desired modulation state, where a modulated electromagnetic radiation is relayed by said spatial light modulator toward said work piece.

[0031] In another embodiment according to the invention, said biasing signal is to its absolute value greater than or equal to a maximum address signal.

[0032] In another embodiment according to the invention, said movable modulator element is a multi-valued element capable to be in more than 2 modulation states.

[0033] The invention also relates to an apparatus for patterning a workpiece arranged at an image plane and covered at least partly with a layer sensitive to electromagnetic radiation, by using at least one spatial light modulator (SLM) arranged at an object plane, where said SLM comprises at least one movable modulator microelement. An actuating element capable to move said at least one movable modulator microelement to a desired modulation state. At least one first electrode, belonging to said at least one movable modulator microelement, provided

with at least one first signal when said movable modulator microelement being provided with a predetermined signal capable to set said movable modulator element in a desired modulation state. A source to emit electromagnetic radiation directed onto said object plane when said at least one movable modulator microelement being in said desired modulation state, wherein a modulated electromagnetic radiation is relayed by said SLM toward said workpiece.

[0034] In another embodiment according to the present invention, said predetermined signal provided to said movable modulator microelement is capable to be altered to a predetermined value whereas said at least one first signal applied to said at least one first electrode is fixed at a predetermined value.

[0035] In still another inventive embodiment said movable element has a tilting action.

[0036] In still another inventive embodiment said movable element has a piston action.

[0037] In still another inventive embodiment said movable element modulates the intensity of said electromagnetic radiation.

[0038] In still another inventive embodiment said movable element modulates the phase of said electromagnetic radiation In another inventive embodiment said actuating element is a gap, comprising any kind of gaseous media.

[0039] In another inventive embodiment said actuating element is a dielectric medium.

[0040] In another inventive embodiment said dielectric medium is elastic.

[0041] In another inventive embodiment said actuating element is a piezoelectric medium.

[0042] In another inventive embodiment said actuating element is an electrostrictive medium.

[0043] Further characteristics of the invention, and advantages thereof, will be evident from the detailed description of preferred embodiments of the present invention given hereinafter and the accompanying Figs. 1-4b, which are given by way of illustration only, and thus are not limitative of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS [0044] Figure 1 illustrates schematically a side view of an actuator structure in an unaddressed state.

[0045] Figure 2 illustrates schematically a side view of the actuator structure in an addressed state.

[0046] Figure 3 is a schematic illustration of a deflection versus applied addressing signal for prior art addressing method and the inventive addressing method.

DETAILED DESCRIPTION OF EMBODIMENTS [0047] The following detailed description is made with reference to the figures.

Preferred embodiments are described to illustrate the present invention, not to limit its scope, which is defined by the claims. Those of ordinary skill in the art will recognize a variety of equivalent variations on the description that follows.

[0048] Further, the preferred embodiment is described with reference to a deflectable electrostatic driven micro-mirror. It will be obvious to one ordinary skill in the art that actuators other than deflectable and electrostatic driven microminors will be equally applicable; examples are piezoelectric actuators, electrostrictive actuators, and piston like actuators of circular or polygonal shape or similar devices.

Actuating material may be a gap of air, gas, vacuum, viscous, electrostrictive, viscoelastic or elastic material. I t may also be a combination of any of the medias above. The movement of the actuator element may be tilting or translational.

[0049] Figure 1 illustrates schematically a side view of a state of the art actuator structure 100. The structure 100 is depicted in an unaddressed state. Such an actuator structure 100 may for instance be a micro-mirror structure in a spatial light modulator (SLM). The actuator structure, depicted in figure 1, comprises a substrate 113, a first electrode 112 and a second electrode 114, a support structure 111 and a movable element 110. Said substrate may be made of semi-conducting material and may comprise one or a plurality of CMOS circuits. The first and second electrodes are made of an electrically conductive material, such as gold, copper, silver or alloys of said and/or other electrically conductive materials. Said electrodes are connectable to steering circuits, such as the above mentions CMOS circuit.

[0050] The support structure 111 is preferably manufactured of a relatively stiff material, such as single crystal silicon, but may of course be made of materials not having pronounced high stiffness. The movable element 110 is preferably manufactured of a material having good optical properties, such as aluminum.

However, if a material is selected not having the characteristics as desired, said material may be coated with one or a plurality of layers of other materials having more favorable characteristics, thereby creating a sandwich structure.

[0051] An electrostatic force may deflect the movable element 110. Applying different potentials on the movable element 110 and one of the first 112 and second 113 electrodes creates electrostatic force. In the event of applying a first potential on the movable element 110 and a second potential on said first and second electrodes, where said first and second potentials are different, creates an electrostatic force, but will not deflect said movable element. The reason for this is that the attractive force, which force is always attractive independently of the polarity of the potential difference, between the first electrode and the mirror is equivalent to the attractive force between the second potential and the same mirror. The two equal attractive forces equalize each other.

[0052] In figure 1 the actuator structure is illustrated to comprise two electrodes, the first 112 and second 113 electrodes. However, deflecting the movable element requires only one electrode, either the first 112 or second 113 one. There may be several reasons for having more than one electrode. One such reason is that it takes two electrodes arranged spaced apart from each other to deflect the mirror in two different directions. Other reasons become apparent from the description herein below describing different embodiments of the inventive method.

[0053] Figure 2 depicts the actuator structure 100 in an addressed state. The actuator structure 100 may be digital, i. e. , on-off, or multivalued, i. e. , having a plurality of states larger than two.

[0054] In a first inventive embodiment for reducing a required potential between the movable element 110 and the electrode 112,114 for a given deflection, said movable element 110 is biased to a first potential and one of the first or second electrode is addressed with a predetermined potential. For instance may said movable element be biased to-20 V and said first electrode be addressed to voltages varying between 0-5 V. For 0 volt on said first electrode there will be no deflection of said

movable element, since there are equal forces between said first electrode and said movable element and said second electrode (which is set to ground level) and said movable element 110. When increasing the potential on said first electrode the force will increase between said first electrode and said movable element compared to the force between said movable element and said second electrode.

[0055] The movable element can deflect in two opposite directions depending on which electrode is chosen as address electrode.

[0056] An undeflected state may be when said first and second potentials are set to any equal potentials different from ground potential and said movable element set to a biased state.

[0057] In figure 3 there is an illustration of a deflection versus potential curve for a prior art addressing method and the inventive method. 120 denote a curve according to a prior art method and 130 denote a curve according to the inventive method. In the prior art method it is assumed that the movable element is unbiased and one of the electrode is used as an addressing electrode. In the inventive method it is assumed that the movable element is biased, for instance to-20V, and at least one of the electrodes is used for addressing. As can be seen the inventive method requires much lesser potential on the address electrode for accomplishing the same degree of deflection.

[0058] Dashed line 140 in figure 3 indicates that for a potential of 5 V on the address electrode the deflection is several times grater for the biased movable element, indicated by curve 130, compared to the unbiased movable element indicated by curve 120.

[0059] The curvature of curve 130 can be deduced from the curve 120. If the movable element is biased to-20V and the address electrode is assumed to vary between 0-5V the curvature of 130 from 0-5V is essentially the same as the curvature of curve 120 between 20-25V. By biasing the movable element, a smaller address signal to one or a plurality of electrodes will result in a bigger deflection compared to if the movable element would have been unbiased. Having a biased movable element the voltage span on the electrode or electrodes for accomplishing a desired span in deflection of the movable element is much lesser than the unbiased movable element.

The movable element may be biased to any value different to zero, the bigger the biasing is the steeper the curvature of curve 120.

[0060] There is a maximum value to which the movable element can be biased, given by a snap-in state, which means that beyond a certain applied voltage to the movable element an infinitesimal change in addressing signal to one of the electrodes would cause the movable element to stuck into a fully deflected state possibly with its outer edge touching the substrate 113. The snap-in state is inter alia dependent on the structure and choice of material of the actuator structure 100.

[0061] In another embodiment, for reducing a required potential difference between the movable element 110 and the electrode 112,114 for a given deflection, a first fixed potential is applied to the first electrode 112 and a second variable potential is applied to the movable element 110. In one embodiment said variable potential is varying around an absolute value of x and said fixed potential is set to an absolute value of 2x. For instance may said movable element 110 vary around a potential of 10 Volt and said electrode be set to 20 Volt.

[0062] The attractive force between the electrode 112,114 and the movable element 110 is proportional to the square of the difference in potential between said electrode and said movable element.

[0063] F # (vm - Ve)2, where Ve is the voltage applied to the electrode and V, n is the voltage applied to the movable element. For instance the voltages applied to the electrodes are: [0064] If A, = 20V, A2 = 0V and V", = 0V (variable) [0065] The force induced by electrode 1 is: Fl # (Vm - A1)2 = Vm2-2VmA1 + A12 = 400 The force induced by electrode 2 is: F2 # (Vm + A2)2 =###= Vm2 + 2VmA2 + A22 = 0 [0066] The resulting force acting on the movable element in the direction of force F, is then: FYes = F-Fz = 400

When the element is in non-addressed state, i. e. V,, = 10, no resulting force exist and the mirror is in its equilibrium state [0067] Compared to the state of the art addressing method in which the electrode (s) functions as addressing means the resulting force will be as follows: |Vel = A, (VariableO-lOV) tVe2 = A2 (optional) [0068] If A, = 10V, A2 = 0V and V", = 0V (variable). This case illustrates the same amount of change in address voltage as described in connection with the inventive method above, i. e. in the inventive method the address voltage changed from 10V to 20V and in the prior art the address voltage change from 0V to 10V.

[0069] The force induced by electrode 1 is: F,- °' =V-2V,, + =100 The force induced by electrode 2 is: F2 # (Vm + A2)² = ### =Vm² + 2VmA2 + A2² = 0 [0070] The resulting force acting on the movable element in the direction of force F, is then: Fres = F1 - F2 = 100 [0071] In the inventive method of addressing the mirror instead of addressing one or a plurality of electrodes beneath the movable element, the force induced by the same amount of change in address voltage is increased by a factor of 4.

[0072] The inventive method for addressing actuators in an SLM, where the actuators are micro-mirror structures arranged in an array, may well be used in a pattern generator utilizing an SLM for patterning a workpiece. The array may comprise several million micro-mirror structures. A state of the art pattern generator for patterning a workpiece using lithography may make use of a pulsed laser source for imaging the pattern on the SLM onto a workpiece. Said stamps of the SLM on said workpiece may constitute only a fraction of the complete pattern to be imaged.

Between laser flashes a new pattern description is loaded into the SLM, i. e. individual micromirrors are set to new deflection states by applying a different potential difference between the mirror element and an underlying electrode.

[0073] By synchronizing the loading of new patterns on said actuator structure and a pulse rate of said laser source, a predictive pattern of the SLM can be imaged onto a workpiece.

[0074] While the preceding examples are cast in terms of a method, devices and systems employing this method are easily understood. A magnetic memory containing a program capable of practicing the claimed method is one such device. A computer system having memory loaded with a program practicing the claimed method is another such device.

[0075] While the present invention is disclosed by reference to the preferred embodiments and examples detailed above, it is understood that these examples are intended in an illustrative rather than in a limiting sense. It is contemplated that modifications and combinations will readily occur to those skilled in the art, which modifications and combinations will be within the spirit of the invention and the scope of the following claims.