EP3811153A1

EP3811153A1 - Method and device for exposing pixels

Info

Publication number: EP3811153A1
Application number: EP18734150.8A
Authority: EP
Inventors: Bernhard THALLNER; Boris Povazay
Original assignee: EV Group E Thallner GmbH
Current assignee: EV Group E Thallner GmbH
Priority date: 2018-06-19
Filing date: 2018-06-19
Publication date: 2021-04-28
Also published as: SG11201910818PA; US20210247697A1; WO2019242840A1; JP7309759B2; TW202401173A; JP2021534440A; KR102604859B1; KR20210021966A; US11681228B2; CN112236721A; TW202014803A

Abstract

The invention relates to a method for exposing pixels (1) of a photosensitive layer (19) made of a photosensitive material (18) on a substrate, by means of an optical system, having the following features: - the pixels (1) are continuously moved relative to the optical system, - multiple secondary beams (16) are individually controlled by means of the optical system to individually expose each pixel (1) by switching the secondary beams (16) into either an ON state or an OFF state, wherein a) secondary beams (16) in an ON state individually expose the pixel (1) associated with each secondary beam (16), and b) secondary beams (16) in an OFF state do not individually expose the pixel (1) associated with each secondary beam (16), - wherein in order to produce pixels (1) with grey tones n>1, individual exposures are made using different secondary beams (16) with individual doses D, the grey tone G of each pixel (1) being defined by the sum of the individual doses D. The present invention further relates to a corresponding device.

Description

Method and device for the exposure of pixels

Description

The present invention relates to a method according to claim 1 and an apparatus according to claim 7.

The semiconductor industry is looking for better and more efficient ones

Process for micro and nano structuring of surfaces. Most surfaces are structured using lithography. The

Lithographic techniques in the semiconductor industry can be roughly divided into two major areas, imprint lithography and

Photolithography. In most cases, masks are used in photolithography to reproduce a structure in a photosensitive material. These masks can either be scaled down onto the photosensitive material layer using projection techniques or the mask structure can be transferred into the photosensitive material without optical scaling. The production of the masks is time-consuming, cost-intensive and prone to errors.

In recent years, so-called maskless ones have also become

Lithography techniques developed. These techniques are based on the

Principle that at least one pixel, but especially several

Pixels, are exposed simultaneously and after exposure there is a relative shift between the photosensitive material and the optical system that is responsible for the pixel exposure. In particular, these are scanning methods.

An increasingly important area in, in particular maskless, photolithography is the possibility of a controllable exposure of the photosensitive material in the third direction, which is normal to the plane of relative movement. These procedures are called

Gray-tone lithography has recently been used to enable a three-dimensional or 2.5-dimensional photolithographic exposure of a photosensitive material and thus a structuring of the

Materials.

Structures in the semiconductor industry have been manufactured using photolithographic processes for decades. To three-dimensional

In order to be able to produce structures, it is generally necessary to produce several masks for several exposure processes. Each

Exposure step is preceded by a coating process and each

Exposure step follows a development step. Only after the

After successful exposure, the masks made of the photosensitive material can be used for etching or for the metal coating.

With the maskless exposure technologies mentioned above, the mask itself is saved, but for the generation of one

three-dimensional structure, a multi-layer process is required.

The maskless exposure technologies were expanded to include black-and-white or gray-tone lithography, with the help of which a photosensitive material could be exposed not only two-dimensionally but three-dimensionally. Experience has shown, however, that the used

Methods did not give optimal results. In particular, the quality of the exposed profiles and / or the duration for the exposure were insufficient. In black and white lithography, a pixel is either exposed or is not exposed.

In gray-tone lithography, a micromirror device (Digital Micromirror Device, hereinafter: DMD) is fixed in relation to the photosensitive material layer, after which the individual mirrors of the DMD are switched for well-defined times so that they deliver a desired dose to the respective pixel. This process is very time consuming.

The methods mentioned in the prior art in particular require the use of step processes (step-and-repeat).

The problem in the prior art is therefore that there are no efficient, inexpensive methods for structuring a photosensitive material three-dimensionally.

It is therefore an object of the present invention to provide an apparatus and a method in which an at least 2.5-dimensional, preferably three-dimensional, photolithographic exposure of a photosensitive material can be carried out efficiently and with the simplest and cheapest possible means.

This object is achieved with the features of claims 1 and 7. Advantageous developments of the invention are specified in the subclaims. All fall within the scope of the invention

Combinations of at least two of those in the description

Claims and / or the features specified. at

specified ranges of values should also be disclosed as limit values within the stated limits and be usable in any combination. The invention is based on the idea of specifying a method for exposing image points of a photosensitive layer consisting of a photosensitive material on a substrate by means of an optical system with the following features:

the image points are continuously moved in relation to the optics, several secondary beams are controlled individually by means of the optics for individual exposures of each image point by the

Secondary beams are placed in either an ON or an OFF state, with

a) secondary beams in the ON state a single exposure of the

effect the image point assigned to the respective secondary beam and b) secondary rays in the OFF state do not effect individual exposure of the image point assigned to the respective secondary beam, with n> l being used to generate image points with gray tones

Individual exposures are carried out using different secondary beams with individual doses D, the gray tone G of each pixel being defined by the sum of the individual doses D.

According to an alternative, more complex embodiment of the aforementioned invention, a plurality of secondary beams are controlled individually by means of the optics for individual exposures of each pixel, the secondary beams being defined in an ON or an OFF state or in a state between the ON and the OFF state Intermediate state.

Furthermore, the invention relates to a device for exposing image points of a photosensitive layer consisting of a photosensitive material on a substrate by means of an optical system with the following features: Means for the continuous movement of the pixels

compared to the optics,

Control means for the individual control of a plurality of secondary beams by means of the optics for individual exposures of each pixel, in that the secondary beams can be set either in an ON or in an OFF state, with a) secondary beams in the ON state providing a single exposure of the associated secondary beam

Effect pixel and

b) Secondary beams in the OFF state none

Effect single exposure of the pixel assigned to the respective secondary beam,

Single exposure means for generating pixels with gray tones by n> l single exposures

different secondary beams with single doses D, the gray tone G of each pixel by the sum of the

Individual doses D can be defined.

The invention particularly describes several methods and one

Device for at least 2.5 dimensional, preferably

three-dimensional, photolithographic exposure of a photosensitive material. The invention is based primarily on several different methods for producing this photolithographic exposure. The basic idea is based on (i) multiple exposure of a pixel by, in particular, immediately following mirrors of a DMD s and / or (ii) the use of a mathematical algorithm for setting a pixel pattern and / or (iii) on variation / control of the radiation intensity of the Light source and / or the dose per pixel. 2.5 dimensional and three-dimensional photolithographic exposure are subsequently used synonymously for the further dimension of the gray levels or multiple exposure of individual pixels.

In other words, a core of the invention consists in particular of a plurality of methods which are independent of one another but can be used together, by means of which a 2.5-dimensional, photolithographic exposure is made possible. The procedures differ technically

from each other, but can be combined with one another in any way in order to be able to implement corresponding combination methods with optimized results.

All of the methods described in accordance with the invention have in common that they can be used to perform a targeted, locally resolved, 2.5-dimensional exposure of a photosensitive material. The individual, in particular to be considered or used in any combination

preferably independent, core aspects of the entire invention are:

(i) The generation of a higher positioning accuracy of the individual pixels, in particular by inclination and / or distorted imaging of the exposure grid, and / or

(ii) continuous exposure process as opposed to

Step process (no step-and-repeat), and / or

(iii) superimposing the intensity profiles of adjacent pixels, and / or

(iv) binary control of DMD levels, i.e. each mirror can only be switched between two states (ON-OFF) and / or

(v) Control of the dose in one pixel by a combined switching of several DMD mirrors to different

Points in time, in particular by oversampling and / or (vi) using mathematical algorithms to generate a pattern and / or

(vii) Control the primary / light source dose.

A main idea of the invention is, above all, that the generation of a gray tone lithography by using at least one of the processes according to the invention, in particular under simultaneous

Sacrifice / reduction of the positioning accuracy is made possible.

The methods according to the invention, as well as those described

Requirements to be able to carry out the method have several advantages over the prior art.

In contrast to the prior art, in which step-and-repeat techniques are predominantly used, the method according to the invention preferably uses a scanning method, i.e. a continuous

Relative movement between the DMD and the photosensitive material. Through the use of scanning methods, the throughput is significantly increased, since the relative movement between the DMD and the photosensitive material is not stopped or at least slowed down after each step, in order to control the exposure of the DMDs in the photosensitive material by, in particular, individually controlling the mirrors

To provide pixels with the respective dose. So they are

Plants and methods according to the invention in particular for

High volume manufacturing (HVM) suitable.

Another important advantage and aspect of the invention

The method consists in particular in that all mirrors of the DMD are switched simultaneously / synchronously, i.e. all mirrors will be

at the same time either in one or in the other of only two

Conditions. This can affect the photosensitive material projected dose can be set to be spatially resolved. The DMD s therefore do not have to be set individually at one position, ie the mirrors of the DMD are always switched in synchronism.

An essential aspect is the possibility of the targeted adjustment of a gray tone in a pixel by the repeated exposure of several mirrors, which are located along a line parallel to the relative movement direction. Through this aspect of the invention, the targeted

Setting a shade of gray allows.

Another, additional aspect of the invention is not only the targeted adjustment of the gray tone by oversampling, but also

especially in the superimposition of the pixels due to finite broad intensity profiles.

An, in particular additional superimposition of the image points in the lateral direction (normal to the direction of the relative movement) takes place

at the same time due to the relatively broad intensity profiles. The methods disclosed according to the invention enable gray-tone exposure in different and / or combined ways.

The methods according to the invention can be used in particular to replace gray tone masks and / or multiple exposures.

According to the invention, the substrate holder is precisely controlled and positioned, in particular during the continuous exposure, the position of the optics (DMD) and the layer to be exposed, preferably continuously, being checked, in contrast to the step process. Exposure, movement and, if appropriate, also the measurement of the areas already exposed are in particular carried out, monitored and simultaneously controlled. The control electronics and / or software must be set up for this.

To the extent that algorithms for generating an averaged gray tone are used over a pixel area, positioning accuracy is at least partially lost.

To control the exposure intensity of each pixel or gray tone, the behavior of the lacquer over a wide intensity range is, in particular, relevant to the control in order to obtain further optimized results.

In order to obtain a higher number of gray tones in one pixel according to the invention, correspondingly more mirrors in one

Mirror exposure column arranged. By driving a large number of mirrors, the maximum switching rate of the DMD drops and the data volume to be transmitted increases, the maximum

Scanning speed decreases.

The number of gray tones is therefore limited by the number of

Mirror exposure lines that sweep over a pixel. One can imagine the mirror exposure lines grouped into blocks. The set of all mirror exposure lines that can be used to set a gray tone are referred to as the mirror exposure line block. The following example is given as an example. Using a DMD with 900 mirror exposure lines, a pixel with one of 900 shades of gray or 900 different shades of gray can be generated. If you group the 900 mirror exposure lines into three blocks of 300 mirror exposure lines each, a pixel can only take on one of 300 shades of gray, but three pixels can do the same

to be discribed. The methods according to the invention serve to produce exposed 2.5-dimensional structures in a photosensitive material. The

Photosensitive material is known from the prior art

Process applied to a substrate.

The invention shows several methods to image pixels in the

To expose photosensitive material laterally and vertically. Lateral exposure means the exposure of a pixel in the plane parallel to the surface of the photosensitive material. Vertical exposure is an exposure of the photosensitive material at a pixel to a defined depth. Through the

The method according to the invention shown thus makes it possible

three-dimensional structures in a photosensitive material

expose. In the further course of the text, the terms 3D or three-dimensional are always used, since they are more general.

The structures exposed in this way can proceed in further processes

are developed and thus result in a three-dimensional, topographical photosensitive material structure which is used for further coating and / or etching processes. On the further ones

Process steps are not discussed further here.

The methods according to the invention are described with the aid of a DMD. It would also be conceivable to use LCDs (liquid crystal displays), LCoS (liquid crystal on silicon), GLVs (grating light valve) or similar optical elements that can be used analogously to the DMDs described.

All mentioned methods according to the invention can also be used to ensure the quality of the classic, binary, maskless To improve exposure lithography. In particular, edge effects can be reduced by the methods mentioned. On such

Optimization properties will not be discussed in more detail, however.

definitions

In the further section, some important terms are defined in order to be able to describe the method according to the invention more efficiently.

In the further course of the text, a pixel is understood to be a defined, exposed position in the photosensitive material, which is generated by a single mirror of the DMD. The image point is thus a spatially limited area on the photosensitive material to be exposed. In each pixel, the photosensitive material can be exposed to a defined depth. Each pixel thus has not only a lateral, but also a vertical extension. The pixel is therefore three-dimensional. The vertical extent, i.e. the depth of the

Pixel, depends in particular on the dose received

electromagnetic radiation together. Setting this dose for each pixel is an essential aspect of the present invention. The depth in which the photosensitive material is exposed is determined in particular by the dose. One of the most important methods according to the invention for defining the dose of a pixel is repeated exposure through several DMD mirrors. These DMD mirrors are arranged, in particular in a line parallel to the relative direction of movement of the DMD mirrors, one after the other, in each case being alignable on the same image point. The DMD levels can be controlled in such a way that s either projects the same defined dose onto the pixel per unit of time or not (ON-OFF). A shade of gray results from the amount of photosensitive material of the pixel that has received a defined dose and has been chemically modified accordingly. The higher the dose received, the more photosensitive material was chemically and / or physically altered in depth.

A pixel line means a set of pixels that are distributed along a straight line normal to the relative direction of movement on the photosensitive material, in particular equidistantly.

A pixel column means a set of pixels which are distributed along the straight line parallel to the relative movement direction on the photosensitive material, in particular equidistantly.

A pixel area is understood in the further course of the text to be a set of, in particular neighboring, pixels. The

Pixels of the pixel area are exposed in particular by a mathematical algorithm in such a way that the resulting one

Pixel area has an averaged gray tone value. This averaged gray tone value is based in particular on the algorithm used, with which the individual gray tone values of the pixels are controlled. When using mathematical algorithms to determine a

The pixel area (and not the pixel) represents the actual pixel in gray tones. By the lateral extension of the

The greatest possible resolution is defined in the pixel areas.

In particular, it is an aspect of the invention that the lateral

The magnitude of the pixel area and the dimensions of a DMD mirror, more precisely the projection of the DMD mirror, are approximately the same. The area of the pixel region is in particular greater than 0.5 times, preferably greater than 0.75 times, more preferably exactly 1.0. times, most preferably greater than 1.5 times, most preferably greater than 2.0 times the area of the projected DMD area.

An exposure strip describes a set of pixels along a direction, in particular in the direction of the longest movement distance of the DMD. For example, with a meandering raster path, the DMD is always moved along a longest possible movement path, which extends in particular to the edge of a substrate, and by a short lateral movement from one movement path to the next

Movement distance driven.

A primary beam is understood to mean that through a

Radiation source / primary source / light source generated light beam before it strikes the DMD. The primary beam originates in the light source and in particular passes through several optical elements before it strikes the DMD.

A secondary beam is understood to mean that part of the primary beam which is reflected, in particular, by a, preferably individual, mirror of the DMD. A primary beam is therefore broken down into several secondary beams by the DMD. The secondary beam has its origin in a mirror of the DMD and can pass through several optical elements before it strikes the photosensitive material.

In the further course of the text, an intensity profile is understood to mean the cross-sectional intensity distribution of a secondary beam which, in particular with its predominant intensity component of the intensity profile, illuminates a pixel. The intensity profiles of a plurality of secondary beams lying next to one another preferably overlap, the point of inflection of an intensity profile in each case lying within an intensity profile of an adjacent secondary beam. This results in a particularly high homogeneity of the exposure of the

Pixels, especially at the edge of the pixels, are reached.

The dose of a pixel is understood to mean the amount of electromagnetic radiation with which the photosensitive material in one

Pixel was applied at any time during the maskless writing process (exposure).

The optical power of the primary beam is between 0.01 W and 1000W, preferably between 0.1W and 750W, more preferably between 1W and 500W, most preferably between 10W and 250W, most preferably between 20W and 50W. The optical power attributed to a secondary beam is then approximately the ratio between the optical power of the primary beam and the number of DMD mirrors irradiated. For example, a DMD has 1000x 1000 pixels. Accordingly, the optical performance of the

Primary beam of 25W an optical power of 0.000025 watts on a secondary beam. Assuming an irradiation time of 20 p s per pixel, an energy of 5 * 10 ¹⁰ J or 500 pJ per single secondary beam would be transferred to one pixel. By the

Oversampling can increase this energy per pixel accordingly when passing through the DMD.

The pixel energy is in particular between 10 J and 1 J, preferably between 10 - 1 2 J and 10 -2 J, more preferably between 10 - 12

J and 10 ⁴ J, most preferably between 10 ¹² J and 10 ⁶ J, am

most preferably between 10 J and 10 J.

The irradiation time is in particular between 10 ⁹ s and 1 s,

preferably between 10 ⁹ s and 10 ² s, more preferably between 10 ⁹ s and 10 ⁴ s, most preferably between 10 ⁹ s and 10 ⁴ s,

most preferably between 10 ⁹ s and 10 ⁶ s.

The individual dose D is therefore, in particular, the energy with which a pixel is acted upon in a single exposure.

The cumulative is taken under the entire dose of a pixel

understood electromagnetic radiation, which the photosensitive material received in a pixel at the end of a completely completed maskless writing process. By the above, preferred

Overlapping the intensity profiles, each pixel receives part of the dose from secondary rays of neighboring pixels. The cumulative dose specifies in particular the gray tone of a pixel.

Under a mirror line is a set of mirrors of a DMD

understood, which are positioned along a first axis of the DMD reference system. If the DMD is not rotated in relation to the direction of movement, this axis is normal to the direction of movement.

A mirror column is understood to be a set of mirrors of a DMD that are positioned along a second axis of the DMD reference system. The second axis is normal to the first axis of the DMD reference system.

By rotating the DMD relative to the direction of movement, which is preferred according to the invention, the mirror lines do not become normal or

Mirror columns are not arranged parallel to the direction of movement.

A mirror exposure line is understood to be a set of mirrors of a DMD that lie along a line normal to the direction of movement. If the DMD is not rotated in relation to the direction of movement, The exposure line and mirror line are identical in relation to the lateral arrangement.

A mirror exposure column is understood to be a set of mirrors of a DMD that lie along a line parallel to the direction of movement. If the DMD is not rotated in relation to the direction of movement, the exposure slits and mirror slits would be identical in relation to the lateral arrangement.

A mirror exposure line block is a set of mirror exposure lines that are used for the complete exposure of all

Pixels are necessary.

If a DMD is equipped with more lines than are necessary for a mirror exposure block, the additional DMD mirrors can perform additional functions. In particular, they can be used as redundancy or additional ones can be used

Mirror exposure line blocks for be formed. Advantageously, the amount of mirror exposure lines per mirror exposure line block is constant, i.e. the number of mirror exposure line blocks is an integral divisor of the number of mirror exposure lines. The number of gray tones is then by the number of mirror exposure lines per

Mirror exposure s line block limited.

In the further course of the text, different parameter sets are disclosed, which also relate to the static characteristics of accuracy and precision.

Accuracy is understood as a systematic error. A systematic error is the deviation of the statically from the

Sample quantity determined expected value of a parameter from true value of the population. The greater the accuracy, the smaller the value of the deviation, the smaller the systematic error.

Precision is understood to mean the scatter of a measurement variable around the expected value of the sample quantity. The greater the precision, the smaller the spread.

Positioning accuracy is the accuracy with which a pixel in the photosensitive material can be driven congruently through the center of a DMD mirror. This positioning accuracy is particularly due to an inclined position of the DMD

Direction of movement between the DMD and the photosensitive material increased.

contraption

The device according to the invention consists of a substrate holder and an optical system. The substrate holder has technical features known in the prior art for fixing and / or aligning and / or moving a substrate.

The fixations are used to hold the in the device

processing substrates. The fixations can be

mechanical fixations, especially clamps and / or

Vacuum fixings, in particular with individually controllable or interconnected vacuum paths, and / or

electrical fixations, in particular electrostatic fixations, and / or

magnetic fixations, and / or

act adhesive fixations, in particular Gel-Pak fixations and / or fixations with adhesive, in particular controllable, surfaces. The fixings can be controlled electronically in particular. Vacuum fixation is the preferred type of fixation. The vacuum fixation consists preferably of several vacuum paths that emerge on the surface of the sub-holder. The vacuum tracks can preferably be controlled individually. In a technically preferred realizable application, some vacuum tracks are combined to form vacuum track segments that can be individually controlled, and therefore can be evacuated or flooded. each

Vacuum segment is preferably independent of the others

Vacuum segments, ie preferably from individually controllable

Vacuum segments. The vacuum segments are preferably constructed in a ring shape. This enables a specific, radially symmetrical, in particular fixation and / or detachment of a substrate from the substrate holder to be carried out from the inside out.

The substrate holder can preferably be actively moved relative to a fixed coordinate system. In particular, the position of the substrate holder is continuously tracked, measured and stored during the movement.

The precision of the positioning is described by the confidence interval of the variance. The precision possesses for a three sigma

Confidence level of 99.7%, a confidence interval between 1 nm and 10 pm, preferably between 1 nm and 10 pm, more preferably between 1 nm and 10 pm, more preferably between 1 nm and 10 nm, most preferably between 1 nm and 1 nm, most most preferred between 1 nm and 5 nm.

The optical system of the device consists in particular of at least one light source and in particular a DMD. Optical elements for homogenizing the primary beam are preferably located in the optical path, in particular at least or only in the path of the

Primary beam. All optical elements are preferably fixedly mounted in relation to a base, so that a relative movement, at least during the exposure, only by moving the substrate by means of the Substrate holder is done. All optical elements can preferably be calibrated in six spatial directions. The foundation or base on which the substrate holder is moved is preferably vibration-damped. The vibration damping can take place actively and / or passively. The foundation is preferably a granite block. Even more preferred around an active vibration damping granite block.

method

In the method described below, the DMD mirrors are designed as binary switching elements, which corresponds to a preferred embodiment of the invention, with which the invention can be described more easily. Each mirror of the DMD can be in a single state of the following two states at a certain point in time: either it reflects its part of the primary beam onto the photosensitive material or it reflects its part of the primary beam so that it does not hit the photo sensitive material , The two states of a mirror are accordingly referred to as "on" (English: ON, the photosensitive material is hit) and "off" (English: OFF, the photosensitive material is not hit). The two binary states are accordingly spoken of more precisely. This term simplifies reading the text. It is also conceivable according to the invention to use mirrors which can carry out continuous tilting. From a technical point of view, these mirrors then represent a generic term for the binary switchable mirrors, but are much more complex and expensive in terms of production and control technology.

The mirrors of a DMD can preferably only be switched all at the same time, with the choice between ON and OFF. The switching frequency for the simultaneous switching of all mirrors is in particular greater than 1 Hz, preferably greater than 100 Hz, more preferably greater than 1 kHz, most preferably greater than 100 kHz, most preferably greater than 1 MHz.

According to an advantageous, important aspect for all of the methods described in accordance with the invention, an increase in the positioning accuracy is achieved in particular by tilting the DMD in relation to the relative direction of movement.

Alternatively or in addition, an increase in

Positioning accuracy can be achieved by using optical elements that distort the secondary beams. There are other methods in the prior art for increasing the positioning accuracy, but not all of them are listed individually here. Exemplary, but not restrictive, are the benefits of increasing the

Positioning accuracy described using the inclination of the DMD.

For a simple maskless (or correct, dynamically structured) exposure system with a scanning imaging principle, a DMD with a single mirror line would be sufficient according to the invention. DMDs that are common and available on the market usually have a large number

Mirror rows (e.g. 1080 mirror rows with 1920 mirror columns each in a Full HD DMD). Such DMDs with more than one mirror line are preferably used according to the invention. The additional mirror lines are used in particular to increase the position accuracy by means of oversampling. Oversampling is described, for example, in US4700235A regarding printing technology.

However, if you choose a special angle of rotation, a higher number of pixels per length can be exposed normally to the direction of movement. The angle of rotation cc is especially with the formula n

a = arctan—

m

calculated and defined, where n is the distance between the pixel rows and m is the distance between the pixel columns between two nearest mirror centers.

In a first method according to the invention, the desired dose of each pixel over several points in time is determined cumulatively. In particular, each individual exposure is carried out with the same

Single dose D.

The cumulative exposure of one of the pixels is carried out by

different DMD levels that are in the same

Mirror exposure column are located. The first idea according to the invention is therefore based on the idea that during a relative movement between the DMD and the photosensitive layer, a pixel that has a gray tone level n, at least n times of n different mirrors of a DMD that split along the mirror exposure are exposed. For example, if you choose a maximum

Grayscale depth of 128, and if a pixel should get a gray tone n = l 3, then 13 mirrors must be within one

Mirror exposure split all mirrors exactly 1/128 of the maximum

Dispense the maximum intensity available as a dose. All mirrors therefore emit a total dose of 13/128 of the intensity that would be necessary for 100% exposure of the image point to the substrate surface.

With this method according to the invention, the gray tone of a single pixel can be set in a targeted manner. In general, the number of gray tones that can be generated per pixel is in the first invention

Method equal to the number of mirror exposure line blocks.

Since the DMD generally consists of several mirrors and

accordingly also several pixels simultaneously with each same pattern can be exposed, this method can be used to generate entire patterns at the same time. The aspect of this method according to the invention can therefore also be summarized in such a way that a temporal averaging of similar exposure steps with different patterns is carried out with each exposure step.

In a second method according to the invention which can be combined with the first, the desired dose of a pixel is generated by the fact that s a precisely adjustable dose acts on the desired pixel at each exposure time. There are several basic options for obtaining a precisely adjustable dose.

In a first embodiment according to the invention, the intensity of the radiation source of the primary beam is specifically changed while the DMD is over a position to be exposed. The shade of gray for one

Pixel is then defined by the dose that arrives at the pixel at the given point in time. Since the intensity of the radiation source can be specifically set and changed, the dose can also be changed in a targeted manner. The method according to the invention is suitable for setting the radiation intensity of the source to a defined value at a time and for illuminating several pixels simultaneously with this dose by the resulting dose per DMD mirror in accordance with the switching state of each mirror.

In particular, the frequency of the radiation from the radiation source can be changed or multiple radiation sources are used, each of which can generate radiation with a different frequency. The frequency of the radiation from a radiation source should in particular harmonize with the photosensitive material used, ie it should be able to change it chemically and / or physically as efficiently as possible. Through the In particular, the grayscale can also be varied using radiation with different intensities.

In a first embodiment of the second according to the invention

Process is the maximum number of gray tones that can be generated per

Pixel equal to 2 ^k , where k is the number of used

Represents mirror exposure lines per mirror exposure line block.

Accordingly, a pixel of k-mirror exposure lines of one and only one mirror exposure line block is exposed or not exposed.

In a second embodiment of the second invention

Process is the maximum number of gray tones that can be generated per

Pixel equal to 2 ^k , where k is the number of used

Represents mirror exposure line blocks. Accordingly, an image point from one and only one mirror exposure line of each k-mirror exposure line block is exposed or not exposed.

In particular, it is possible with the method according to the invention to adapt the dose for the respective mirror exposure line, preferably to change the dose according to a mathematical law with changing mirror exposure line. The first mirror exposure line can preferably receive the full dose, the two mirror exposure lines the half dose, the next mirror exposure line the fourth dose, and the kth mirror exposure line the (1/2) ^k dose.

The frequency at which the intensity of the radiation source can be changed is in particular greater than 10 Hz, preferably greater than 100 Hz, more preferably greater than 1 kHz, most preferably greater than 100 kHz, most preferably greater than 1 MHz. In a third method which is most preferred according to the invention and which can be combined with the above-described methods, a dithering algorithm is used in order to generate an, in particular averaged, dose in a pixel region which is in particular larger than a single pixel , The principle of the algorithm is to set the gray tones of pixels lying next to one another in such a way that there is an averaged gray tone value for the pixel area.

The method mentioned can in particular be based on several, in the state of

Already known technology use algorithms that control the generation of a gray tone gradient. In particular, the algorithms

Ordered and / or

Floyd-Steinberg and / or

Jarvis and / or

be applied. In addition to these preferred algorithms, there are countless other algorithms that cannot be fully listed here.

The aspect of this method according to the invention can also be so

are summarized that s is a relative local subsampling, the original oversampled pixels, for the purpose of

Variation possibility of the dose is carried out.

The method according to the invention generates a pixel area that is larger than the individual pixels. Accordingly, the advantage of positioning accuracy achieved in the event of an inclination of the DMD is at least partially lost for the gray tone resolution obtained by the mathematical algorithm.

Another important feature of the method according to the invention is a continuous (that is, at least along an exposure strip uninterrupted) relative movement between the photosensitive material and the DMD during the application of the method according to the invention. The methods according to the invention therefore preferably do not represent step process methods, but continuous motion methods.

According to the invention, it is advantageous in all methods according to the invention if the reflected rays generated by the mirrors

Have cross-sectional profiles that are at least partially superimposed.

All of the methods according to the invention can also be used in classic, binary lithography in order to improve the homogeneity of the illumination and thus to improve the process stability and image quality. For this purpose, the intensity distribution of the entire DMD image is first recorded (e.g. with a CCD chip in the exposure plane or test exposures using a gray tone varnish, or several

Exposures in step-selective varnishes) and then the writing data (raster data) corrected so that the exposure intensity of the individual imaging points is more homogeneous.

Furthermore, it is possible to use all of the methods according to the invention in order to improve the imaging quality for critical structures

improve by in particular increasing or decreasing the dose for individual pixels if these are not in the lithography process

sufficiently resolved (see OPC, optical proximity correction). In this method, knowledge of the chemical and physical behavior of the paint used and knowledge of the optical behavior, in particular in the near field, are particularly advantageous. This knowledge can be theoretically as well as empirically (e.g. about

Test exposures) can be determined in Lorm from data series. Applications / Uses

The methods according to the invention can in particular be used to produce the following products.

In a first application according to the invention, the

Methods according to the invention can be used to generate a lot of optical elements, in particular lenses, in the photosensitive material. Fresnel, convex or concave lenses have pronounced three-dimensional shapes that can be produced with the aid of the method according to the invention. With a particularly advantageous

According to the embodiment of the invention, these optical elements are produced as part of a monolithic lens substrate (MLS).

According to a second application according to the invention, the

Methods according to the invention can be used to generate a stamp. The stamps created are in particular directly as

Work stamp and / or used as a master stamp in imprint lithography. These stamps have pronounced 2.5 dimensional structures.

After a third application according to the invention, the

Methods according to the invention are used to generate lithographic masks or at least to serve as a negative for lithographic masks.

In a fourth application according to the invention, the

Methods according to the invention are used to structure a, in particular wavy and non-planar and / or homogeneous, layer of the photosensitive material using the methods according to the invention. The gray tones are generated in relation to the ripple so that s the ripple of the photosensitive material has no influence on the topography that develops after development. This makes it possible to expose a photosensitive material without having to remove the waviness beforehand using complicated processes and methods

Compensation only to a certain extent. According to the invention, this results in a time and cost saving in particular.

In a fifth embodiment according to the invention, the

Methods of the invention are used to create a flat surface. In general, each substrate has a certain ripple and / or roughness. A layer that is applied to such a substrate partially takes on the waviness and / or the roughness of the underlying substrate. There are many techniques in the prior art for planarizing this wavy layer. Using the methods according to the invention, after the waviness of the layer was measured, a lithography according to the invention could be carried out in such a way that the wave crests of the layer were treated lithographically in such a way that after the exposure and development process, the wave crests were removed or planarized Layer takes place. A method according to the invention for planarization of the layer is thus available, which is not based on mechanical, but purely photolithographic methods.

In a sixth application according to the invention, the

Methods according to the invention can be used to generate MEMS structures.

All technically possible combinations and / or permutations as well as multiplications of the functional and / or material parts of the device and the associated changes in at least one of the method steps or methods are considered as disclosed. To the extent that device features are disclosed in the present and / or in the subsequent description of the figures, these are also intended as

Process features disclosed apply and vice versa.

Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments and from the drawings. These show in:

FIG. 1 shows a schematic representation of an embodiment of a device according to the invention with optics and a photosensitive layer to be exposed arranged on a substrate,

FIG. 2 shows a schematic illustration of an embodiment of a method according to the invention with several,

successive procedures,

Figure 3 a is a schematic representation of an embodiment of the

Apparatus according to the invention in one method step in an exposure through a radiation source with a first intensity spectrum,

Figure 3b is a schematic representation of an embodiment of the

Apparatus according to the invention in one method step in an exposure through a radiation source with a second intensity spectrum,

FIG. 4 shows a schematic illustration of a photosensitive layer exposed with an embodiment of the invention, and

Figure 5 is a schematic cross-sectional view of a section of the substrate with the photosensitive layer to be exposed.

In the figures, the same components or components with the same

Function marked with the same reference numerals. FIG. 1 shows a simplified schematic illustration of a set of pixels 1. The pixels 1 are with the following

described method on a surface of a photosensitive

Materials 1 8 of a photosensitive layer 19, which is applied to a substrate 6, produced (see in particular FIG. 5)

or exposed. At least some of the

Pixels 1 exposed.

Above the pixels 1, the amount of which defines an exposure strip 2, is the micromirror device (DMD 3) rotated relative to the direction of movement v of the pixels 1. In Figure 1

Simplification of the display does not show the DMD 3 itself, but its projection onto the photosensitive layer 19. For the sake of simplicity, a distinction is no longer made between the actual DMD 3 and its actual elements and their projections. Mirror 4,

4 ‘, 4 ″ of the DMD 3 are in mirror rows 9z and mirror columns 9s

arranged.

The mirror lines 9z are arranged rotated by the angle cc with respect to the direction of movement v. The relative direction of movement v takes place along the y axis. The substrate 6 on which the photosensitive material 18 is located is fixed on a substrate holder 14 and moved with it in the negative y-direction, the DMD 3 preferably being fixed statically at least during the exposure.

For some applications according to the invention, the DMD 3 can be designed to be movable, this being a less preferred embodiment. Accordingly, with v the relative direction of movement between the DMD 3 and the photosensitive material 18 or

Denoted pixels 1. The pixels 1 represent the positions which can be illuminated by secondary beams 16 deflected by the mirrors 4, 4 ', 4 ". The width of the secondary beams 16 is preferably at least as large as the mirrors 4, 4 ', 4 ". The secondary rays 16 have a characteristic, in particular Gaussian, intensity profile 5, 5 '. The characteristic intensity profile 5, 5 'defines the intensity distribution in the photosensitive material 18 or in the respective pixel 1.

It can be seen that the DMD 3 has been rotated relative to the direction of movement v such that each mirror center 4c of a mirror 4 of the DMD 3 is congruent with one of the image points 1, which - as described below - are exposed in a targeted manner with regard to their exposure profile.

The relative movement is understood to mean that the DMD 3 and the photosensitive layer 19 to be exposed are moved relative to one another, preferably either the DMD 3 or the photosensitive layer 19 being moved while the non-moving part is statically fixed. Technically, the photosensitive layer 19, which is located on the substrate 6, is preferably moved actively in relation to a spatially fixed coordinate system, while the DMD 3 and all other optical elements (not shown) are moved relative to the spatially fixed

Coordinate system are static.

As an example, it is shown that during the course of the, in particular continuous, relative movement, the image point 1 is first under the mirror 4, then under the mirror 4 ″ and finally under the mirror 4 ″. At each of these times, one of the mirrors 4, 4 ″, 4 “could be switched in such a way that it directs a secondary beam onto the photosensitive

Material 18 reflects, so that the photo sensitive material 18 with a (Further) Do sis is applied to generate a gray tone G. Each exposure leads to an increase in gray tone G.

Mirror exposure lines l Oz, l 0z ‘, l Oz” are each one

corresponding pixel line and are normal to the direction of movement v. A mirror exposure column l Os represents a column of pixels 1 running in the direction of movement v

(for example pixel column l l s), which with the in the

Mirror exposure column l Os arranged mirrors 4 can be exposed.

It can be seen in FIG. 1 that there are a total of four mirrors 4, 4 ″, 4 ″ on the mirror exposure column l Os, whose

Mirror centers 4c are congruent to the mirror exposure column l Os. In this specific case, only the three mirrors 4, 4 ″, 4 “can thus be used

Exposure of the pixel 1 can be used during a

Relative movement between the DMD 3 and the photosensitive material 18 takes place.

The three mirror exposure lines l Oz, l 0z ‘, l Oz” become one

Mirror exposure line block 17 assigned. If the DMD 3 exists

For example, from six hundred mirror exposure lines l oz, the six hundred mirror exposure lines l oz can, for example and advantageously, be combined to form two hundred mirror exposure line blocks 17.

In the example shown here, each of the

Mirror exposure line blocks 17 are used to expose a pixel 1 with one of four gray tones G (no exposure at all, exposure with one dose, with two doses or with three doses). The frame in the lower right part of the exposure strip 2 symbolizes a pixel area 8, consisting of a total of nine pixels 1. The pixel area 8 is preferably approximately the same size as the mirror 4 of the DMD 3. By using an unrest algorithm, an averaged gray tone is set in this image area 8.

A further, essential aspect according to the invention consists in the fact that an inclination of the optics, in particular the DMD 3, relative to the direction of movement v and / or the pixel lines 11z increases the positioning accuracy, but this in favor of producing an averaged gray tone in the Image area 8 is again at least partially abandoned.

The resolution of the structures in the photosensitive material 1 8 cannot be greater than the resolution of the mirrors in the DMD 3. By increasing, on the one hand, in particular due to the inclination

Positioning accuracy takes place and on the other hand gray tones G are summarized as averaged gray tones of a pixel area, a very efficient gray tone lithography can be carried out.

FIG. 2 shows a series of exposure steps of part of an exposure strip 2 with several pixels 1. The illustrated

Series of images represents, in particular, the combination of the first and second methods according to the invention. The intensity profiles 5, as in FIG. 1, are not shown for the sake of clarity, since otherwise the different gray tones G of the pixels 1 cannot be recognized. Each exposure step consists of several, in particular synchronously executed, individual exposures of individual pixels 1.

The DMD 3, here represented in a simplified manner by only nine mirrors 4, is moved relative to the pixels 1, with actually a movement of the Photosensitive layer 19 takes place and the DMD 3, which is preferably mounted with vibration damping as possible, is fixed.

Every time a mirror 4 is switched (controlled) in such a way that it reflects the secondary beam onto the photosensitive material 18, this is symbolized by a black dot in the interior of the mirror 4. The first image in the series consists of part of an exposure strip 2, in which some pixels 1 of the bottom five lines have already been exposed. Each exposed pixel 1 was exposed only once, so that a gray tone value of 1 can be assigned to each exposed pixel 1. The gray tone values are described according to their strength by a natural number including the zero. Through the continuous relative

Shift between the DMD 3 and the one below

Photosensitive layer 19 can expose subsequent mirrors 4 of the DMD 3 pixels 1 that have already been exposed, provided that the algorithm provides for the exposure of the respective pixel.

If you look at the last picture in the series, you can see that the algorithm has been set so that a dithering pattern results in the pixel area 8. As an example, the pixel 1 in the third image of the series is shown with a gray tone G = 1, while, by using the method according to the invention, the same pixel in the twelfth image of the series has the gray tone G = 2, that is to say it has received a stronger dose. He received this from an exposure (not shown) with a subsequent DMD mirror 4 from the same mirror exposure column 1 Os.

The picture series shows on the one hand the use of a dithering algorithm, on the other hand the setting of a gray tone G by multiple exposure of mirror elements connected in series. The method according to the invention for generating an averaged pixel area 8 by using a corresponding one

mathematical algorithm would of course also work with black and white (b / w) lithography, i.e. when using only two shades of gray. However, the depth resolution of the resulting pixel region 8 would also be much lower due to the reduced gray tone depth. By combining a high-resolution gray depth spectrum with the use of the algorithms according to the invention, a very good depth resolution can take place with respect to the exposure.

Figures 3 a and 3b show schematic representations of a

Embodiment of the method according to the invention, in which the dose which is used for the exposure of the pixels 1 is varied by changing the radiation intensity of a radiation source 12. In order to keep the illustration simple, a state is shown in which in turn only a mirror 4 of a DMD 3 is switched so that it exposes a pixel 1 on a photosensitive material 18.

The radiation source 12 generates a primary beam 15, which can be influenced by optical elements 13 before it strikes the DMD 3. There, the individual mirrors 4 of the DMD 3 generate a corresponding number of individual secondary beams 16 for generating individual pixels 1. The intensity of the radiation source 12 influences and defines the strength of the dose, the shape of the intensity profiles 5, 5 'and thus the gray tone G. The definition can be determined empirically or by physico-chemical processes. The optics is the sum of the optical elements 13 and the DMD 3.

FIG. 4 shows a gray tone gradient created from the averaged gray tones by the method according to the invention, the gradient of which decreases from left to right. There will be a section consisting of 5 lines and 4 columns of pixel areas 8, 8 ', 8 ", 8'" are shown. Each pixel area comprises 8, 8 ', 8 ", 8'" nine pixels (not

shown), then there are a total of 15 x 12, i.e. 1 80 pixels.

The pixel area 8 has the strongest, averaged gray tone (from the nine gray tones G of the individual pixels, not shown). The averaged gray tones of the pixel areas 8 ″, 8 ″ and 8 ″ “decrease continuously from left to right. Each averaged gray tone of a pixel area 8, 8 ″, 8 ″, 8 ″ ”was created using mathematical algorithms in connection with the gray tone adjustment of individual pixels 1 (not shown for the sake of clarity) according to the inventive method described above.

FIG. 5 shows part of a cross section of a substrate 6 on which a photosensitive layer 19 consisting of a photosensitive material 18 has been deposited. An image point 1 is also shown, with an exposure profile depth t. It can be seen that the exposure profile depth t makes up approximately one third of the total thickness of the photosensitive layer 19.

Method and device for the exposure of pixels

B e z u g s z e i c h e n l i s t e

1 pixel

2 exposure strips

3 micromirror device (DMD)

4, 4 ', 4 "mirror

4c mirror center

5, 5 'intensity profile

6 substrate

8, 8 \ 8 ", 8" 'pixel area

9z mirror line

9s mirror column

lOz, l0z ‘, lOz“ mirror exposure line

lOs mirror exposure column

llz pixel line

11 s pixel column

12 radiation source

13 optical elements

14 substrate holder

15 primary beam

16 secondary beam (s)

17 mirror exposure line block

18 photosensitive material

19 photosensitive layer

G shade of gray

D single dose

cc angle

v Direction of movement (speed)

t Depth of exposure profile

n Distance of the pixel lines

m Distance of the pixel columns

Claims

Method and device for exposing pixels P at entansp rü che

1. Method for the exposure of pixels (1) one out of one

layer (19) consisting of photosensitive material (18) on a substrate (6) by means of an optical system with the following features:

the pixels (1) are continuously moved relative to the optics,

a plurality of secondary beams (16) are controlled individually by means of the optics for individual exposures of each pixel (1), in that the secondary beams (16) are placed either in an ON or in an OFF state, whereby

a) secondary beams (16) in the ON state

Single exposure of the image point (1) assigned to the respective secondary beam (16) and

b) secondary beams (16) in the OFF state none

Single exposure of the image point (1) assigned to the respective secondary beam (16), individual exposures being carried out using different secondary rays (16) with individual doses D to produce pixels (1) with gray tones n> l, the

Gray tone G of each pixel (1) by the sum of the

Single doses D is defined.

2. The method according to claim 1, wherein the gray tones by a) n single exposures with constant individual doses D and / or b) n individual exposures by changing one

Radiation intensity of the secondary rays (16)

different single doses D and / or

To be defined .

3. The method of claim 1 or 2, wherein shades of gray several

Adjacent pixels (1) combined to form a pixel area (8), in particular by means of an unrest algorithm, for defining an average gray tone value of the pixel area (8).

4. The method according to any one of the preceding claims, wherein the

Secondary beams (16) are generated from a primary beam (15) generated by a radiation source (12) by means of the optics, in particular a micromirror device (Digital Micromirror Device, DMD 3).

5. The method according to any one of the preceding claims, wherein the

Secondary beams (16) can be controlled synchronously by means of the optics, in particular finally.

6. The method according to any one of the preceding claims, wherein a maskless optics is used.

7. Device for exposing pixels (1) of a photosensitive layer (19) consisting of a photosensitive material (18) on a substrate (6) by means of an optical system with the following

features:

Means for the continuous movement of the pixels (1) relative to the optics,

Control means for the individual control of a plurality of secondary beams (16) by means of the optics for individual exposures of each pixel (1), in that the secondary beams (16) can be set either in an ON or in an OFF state, whereby

a) secondary beams (16) in the ON state

b) secondary beams (16) in the OFF state none

Cause individual exposure of the image point (1) assigned to the respective secondary beam (16),

Single exposure means for the generation of pixels (1) with gray tones by n> l single exposures

different secondary beams (16) with individual doses D, the gray tone G of each pixel (1) being definable by the sum of the individual doses D.

8. The device according to claim 7, wherein the device is an optical system for generating the secondary beams (16) from one of one

Radiation source (12) generated primary beam (15), in particular a micromirror device (Digital Micromirror Device, DMD 3).

9. The device according to claim 7 or 8, wherein the secondary beams (16) by means of the optics, in particular exclusively, can be controlled synchronously.

10. Device according to one of claims 7 to 9 with a maskless optics.