NL8304031A - PROCESS ACCORDING TO APPLYING MATERIAL ON A SUBSTRATE ACCORDING TO A PATTERN. - Google Patents

Description

Subject: Method according to the pattern-applying material on a substrate. ___ i J * • w- VO 5082

The invention generally relates to pattern formation.

Many aspects of modern technology, such as the manufacture of integrated circuits, require very precise replication or patterning. More specifically, the patterns are obtained by coating a substrate with a radiation-sensitive material, commonly referred to as a lacquer, and then exposing selected portions of the lacquer to radiation, which renders the exposed portion more or less soluble when subjected to a suitable developer is then subjected to the unexposed portion. After the more soluble portion of the lacquer has been removed, the now exposed substrate material can be changed, for example by doping or removing material. The lacquer is said to be negative or positive depending on whether the exposed portion becomes less or more soluble than the unexposed portion, respectively. The lacquer can be exposed directly to the radiation source or a mask can be placed between the source and the lacquer.

Several methods have been developed to accomplish this lithographic replication or patterning. For example, photolithography and X-ray lithography have been developed. A third lithographic method, electron beam lithography, has also been developed. This method is a high precision, high resolution means for patterning thin film devices and integrated circuits. However, the method is generally a series-25 process, i.e., the patterns are recorded step-by-step, and recording with this method is inherently slow and currently expensive. Substantially due to these limitations, the electron beam lithography is usually used only for directly registering cartridges for devices intended for research purposes or when the need for particularly high resolution or accuracy requires the use of this method. Therefore, the main use of the electrode beam lithography at present is in the manufacture of precision mother masks for photolithography. Photolithography is the method most widely used at the moment for device manufacturing and the expensive processing of master masks S 3 o 4 0 3 if ΐ - 2 - is justified because such masks are currently used for the manufacture of hundreds, if not thousands, of pictures.

More specifically, the master masks currently used have a patterned layer of chromium on a glass substrate.

The aforementioned speed and cost limitations associated with current electron beam lithography methods are better illustrated by the following considerations. When registering a pattern feature, for example a rectangle with a positive varnish, in a conventional exposure approach the electron beam is scanned in some way over the entire area of the feature, the beam in each point or address within the feature remains for the time required to expose the varnish. The time required to register a pattern is then determined by the time required to image the beam for each feature. positioning, and for each feature, the time required to expose the feature. The minimum time required to register a feature once the beam has been positioned is determined by the scanning speed and / or the dose required to illuminate the paint to the desired level with certain beam current . The registration rate and required dosage are among the central considerations for development design choice of electron beam lithography devices and lacquers.

Unless the feature to be recorded has a size 25 which is comparable to the minimum address size of the particular recording device used, consideration of the process just described leads to the realization that a large portion of the registration is redundant since more of the lacquer is exposed than is absolutely necessary to accurately define the pattern, ie, the positions and the shapes of the features.

The invention is based on the fact that most of the information pertaining to the pattern is adequately conveyed if only the outline of each feature has been exposed since it completely determines the position and shape of the feature. The tone of the characteristic, which is normally determined by whether the paint remains within the periphery or is removed, can be determined in a subsequent processing step.

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The invention therefore provides a method for applying material to a substrate according to a determined pattern, wherein this material comprises a radiation-sensitive material, wherein at least parts of the material are determined by adjusting the radiation. form features of the pattern, thereby obtaining radiation-exposed first regions having characteristics different from those of non-radiation-exposed, non-circumferential second regions, and showing the material, showing the extent of this is bounded by the first regions.

The method of exposing only the feature contours and selectively showing the interior areas in a subsequent step can in many cases reduce the recording time. Such a registration process can also have other advantages. Firstly, for some cartridges, the radiation dose applied to the substrate will be markedly reduced and favorable results can be achieved. In electron beam lithography, the electrons scatter in both the lacquer and the substrate, and the scattering leads to a background blur and an effective spatial variation in optimal exposure dose. This disturbing effect, commonly referred to as the proximity effect, should be reduced for some types of features, for example, two closely spaced and relatively large blocks, if only the outlines of the blocks are recorded. Furthermore, in some cases, exposure corrections can be calculated in a more simple manner because of the more local nature of the registration process. Furthermore, in the direct registration of substrates subject to electron damage, a reduction in the actual dose may make the registration process more permissible if only the feature effects 30 are exposed, Secondly, if the tone control process is sufficiently flexible, the same lacquer can be used for both positive and negative images without a significant change in the recording time. Therefore, an optimal lacquer chosen for various reasons, such as based on resolving power, can be used for each tone pattern.

It has been found that a method of patterning a material on a substrate, wherein exposure to 8 3 C 4 0 3 1 * * irradiation "determines at least portions of the material, thereby forming outlines of the features forming this determining radiation-exposed first regions having characteristics different from those of the non-exposed, non-peripheral second regions, and the material being shown, the extent of this tones are limited by the first areas, exhibits desirable properties.

In one embodiment of the invention, determining may include exposing a positive-lacquer coated substrate to an electron beam, after which the lacquer is developed, and the time required to expose the feature and the total radiation. single dose reduced compared to conventional electron beam lithography. Exposure to radiation changes at least one characteristic of the material in the exposed areas, i.e., the exposed material is radiation sensitive. The display modifies at least one property of the material by removing, for example, material located either within or outside the radiation exposed areas. In this embodiment, the lacquer is removed at the periphery of the feature during development, thereby forming an opening in the lacquer. Display can be done with a self-sustaining chemical reaction, which is introduced into the lacquer at a point either inside or outside the feature and which point is limited by the lacquer opening. Therefore, the outline of the feature which is formed in the lacquer serves not only to determine the geometry of the feature, but also as a slot insulating the inside of the feature from tone processes applied to the outside or inverted. The outline is an annular feature, which cannot be reduced to an arbitrarily small size, ie, the outline is "multiply connected". In connection with the analogy between the lithographic method of the invention and the use of on-site trenches to limit the spread of forest fires, the described lithography method is referred to as "forest fire lithography" for convenience.

The invention will be explained in more detail below with reference to the drawing, in which an exemplary embodiment is found, and in which Figures 1 - 6 show perspective steps in an embodiment of forest fire lithography, which form a set. 8 3 0 4 0 3 1 - 5 - lead with a certain pattern.

The invention will be described "with reference to a particular embodiment, n.1. Patterning a metal, for example chromium, which is present as a film on an insulating material, such as glass. The insulating material may comprise a substrate or may consist of an insulating layer covering a substrate. After this embodiment has been described, it is readily apparent to those skilled in the art that the method also applies to other embodiments.

Fig. 1 shows a perspective view of a system, 10 provided with an insulating substrate 1, coated with a layer 3, which in turn is coated with a radiation-sensitive material 5. which is usually called a lacquer. The paint is a positive paint, such as, for example, polymethyl methacrylate. The substrate 1 consists, for example, of glass and the layer 3 comprises, for example, a metal, such as chrome. As indicated -15, the outline of a feature 7, which is rectangular, is recorded on the lacquer, the registered area being indicated by 9 · The exposure, ie the treatment step, in which the feature is registered, is preferably done with a scanning electron beam, changing the characteristics of the exposed areas.

The details regarding the generation and scanning of the beam, the beam intensity, etc., are known to those skilled in the art and will not be described in detail. Other illumination methods, such as a focused ion beam method, can also be used, and it is clear that other geometries can be recorded.

The exposed portion of the lacquer, which is more soluble than the unexposed portion of the lacquer, is removed in a suitable and known developer to obtain the system shown in Figure 2. The newly exposed portion of the chromium layer is removed, for example, by etching in the exposed area, thereby obtaining the system of FIG. 3. The remaining lacquer is then stripped off, thereby obtaining an island 7 of chromium, which is relative to the environment thereof is insulated by a slit in the chrome film, as shown in fig.

4, The operations of exposing portions of the lacquer with radiation, developing the lacquer and removing the exposed portion of the chromium layer, therefore determine the outline of the feature and include the determining step for this embodiment.

The tone step, in which a characteristic of the material is modified 5304031 • ΐ -β-, requires a further etching or treatment step. The showing of chrome can be done on a number of screws. For example, if the substrate is dipped in dilute ICI and touched, for example, with an aluminum object somewhere outside the circumference, ie, at a point outside the slit, a "positive" image of the desired characteristic, for example, a chrome rectangle, is obtained as indicated in FIG. 5. The use of a known cerium-based commercially available etchant with continued contact with copper at a point outside the slit alternatively leads to the "negative" reverse tone image shown in FIG. 6. It will be apparent to those skilled in the art that obvious adjustments in the dimensions of the originally exposed resist pattern are required if accurately identical positive and negative images are to be formed. The systems depicted in FIGS. 5 and 6 can be used as masks in patterning substrates.

The invention has been successfully used in an embodiment of the metal film. on an insulating surface, because for this embodiment readily available means for realizing forest fire lithography are available. For example, the removal of the metal along a narrow strip defining the circumference of each characteristic can be accomplished by a lithographic procedure such as ion beam lithography followed by sputtering etc. as well as electron beam lithography followed by the chemical etching described. .

After removing the periphery of the features, the now delimited metal or conductive layer features are electrically insulated from their environment and accordingly tone processes can be performed, which are controlled, for example, by different electrical biases on individual, insulated features. to apply, ie selectively prestress a part of the electrically conductive layer. This embodiment can be referred to as an electrically controlled, transparent lithography or more simply as ECBPL. Such electric bias can be used in various electrolytic solutions to obtain preferred etching, anodizing, or electroplating of the differently biased portions. of the metal film, which has been given a pattern and outline by lithography.

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In addition, the specific embodiment of the chromium film on an insulating substrate lean the activity of certain etchants commonly used in chromium etching, or are hindered or promoted by appropriate electrical bias such as may be caused by contact with certain metals during etching. For example, upon immersion in dilute HCl, it appears that chromium films are usually protected by a pacifying layer, which is either initially present or is formed in the HCl and will not be etched. This behavior reflects the known phenomenon of passivity in chromium and other metals. Physical and electrical contact during immersion with an active metal, e.g., Al or Sn, as previously mentioned, conveniently provides an electrical bias that removes the passivation layer in a local area around the contact. Set chromium in this area becomes chemically active and starts to dissolve at 15. This active region serves to electrically bias adjacent passive regions to a low potential in a manner similar to that of the active metal contact, thereby also making them active. In this way, the entire bonded region of a chromium film is made active and dissolves while those areas which are not in electrical contact remain passive and do not dissolve.

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Furthermore, the activity of the aforementioned cerium-based etchants commonly used for etching chrome films can be hindered by an appropriate electrical bias such as may be caused by contact with copper, while both metals are in the etchant. Such electrical protection extends over a portion of the chrome film, the size of which is determined by the voltage drops in the film resulting from the current to the protective contact. The size of the protected area can be controlled by varying factors, for example, film properties, such as specific resistance, or etchant properties, such as concentration. Multiple protective contacts can be used to obtain overlapping protection areas. These methods can be used to minimize voltage variations in the films and full size mask protection can be easily obtained. As will be apparent to those skilled in the art, electrical bias to a wide variety of metals in addition to chromium on substrates with 8304031 - 8 -

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Ring conduction in appropriate electrolytes are applied to obtain patterns shown as desired using this electrical isolation method.

Although these aspects of the invention are explicitly used in the described embodiments using wet etching, similar results can be obtained for plasma based etching or physical spattering, wherein the dry metal surface containing the electrically insulating outlines is similarly, it can be shown by applying different voltages to the different electric gel insulators, thereby attracting or repelling charged particles in the plasma to the biased regions.

A number of features of ECBFL are clear to the skilled person. Thus, this method can be easily realized for patterns of easily connected features, ie features with one surrounding outer boundary and no inner boundaries, all these features outside their boundaries surrounded by a single common area , in which all points are connected. Such patterns can be obtained in chrome films on insulating substrates by, for example, contacting Al or Cu in the common region, as described above. In many cases, ECBFL can also be used for multiply linked features, ie features with internal boundaries . For a chrome layer on an insulator, patterns of multiply connected features on a common background, if necessary, can be fully registered for the "positive" case, ie the case where the common area is removed, by the respective internal areas. of each feature, as well as illuminating the external outline and removing these areas, for example, in the first etching procedure. The common area, as previously described, is removed in the second etching procedure,

However, it is desirable to have addressable means to treat more general patterns of features. For a chrome layer on an insulator, such a means involves outlining all features through etched slots and then applying Al or Zn coatings to a small portion of each feature, the removal of which is desired. Ha this step, which " decorating "are called, 8304031 # V - '- 9 - the system is immersed in dilute AC1 and the decorated features are etched, because the metal decorations lose their passivity.

This procedure is more complex since a separate lithographic operation is required to obtain the decorations. However, the more simple method described for patterns of simply connected features is already useful, because many patterns, such as individual levels of integrated circuits, are or can be made of this simple type.

There are several additional characteristics of forest fire lithography that it is preferable to mention.

In the described ECBFL embodiment and in many other embodiments of BCL, the first etching treatment, which defines the feature circumference, is the critical etching treatment for line width control, just as is the case, for example, in the conventional master mask manufacturing. In contrast, the second etching over a larger surface area has a low probability of either over-under or under-etching, since the slots act as very effective blocks. Furthermore, in forest fire lithography, only relatively thin lines are recorded for a pattern, which can contain numerous feature shapes and sizes. One can obtain improved accuracy in the pattern, because certain treatment steps, such as the lacquer development or wet etching treatment, often lead to results varying in feature size.

Furthermore, the occurrence of defects in BFL has different qualitative aspects than in conventional lithography. With ECBFL, a feature can be erased from a cartridge if a dot defect is present on the outline of the feature, thereby electrically connecting it to a neighboring feature. If necessary, problems associated with such defects can be alleviated, for example, by using double width contours with large characteristics. However, various types of defects, which are normally detrimental in conventional lithographic methods, such as, for example, a dust particle on the paint surface, or a point defect in a paint, do not result in detrimental effects in many embodiments of forest fire lithography, if they are in the interior of a feature are located.

Furthermore, in the intermediate step at ECBFL, in which the outlines have been determined, but the display has not been performed, some defects can be appropriately both determined and repaired. For example, the electrical isolation of the various features, which are easily connected, can be tested by observing the pattern with scanning electron microscopy (SEM) or other means sensitive to their electrical potential. When SEM is used, electrically insulated features will literally "light up" due to charging effects. One can then attempt to repair the cartridge, or at this relatively early stage of device treatment, shoot the cartridge out completely before additional treatment costs are incurred. For example, if there is a micro short circuit over a circumference as a result of an incomplete etching treatment, the short circuit can be eliminated by a further etching treatment. In the case of direct registration of a complicated chain, this diagnosis occurs at an early stage of the treatment, and it is likely that the cartridge and therefore the device can still be saved. Furthermore, in the actual device treatment, the enhancement of a defect, which occurs in a somewhat natural way in forest fire lithography, may be beneficial rather than otherwise, since a defect at the edge of a feature can often, though invisible, be fatal with the usual lithographic diagnosis.

As already mentioned, it is clear to those skilled in the art that ECBFL can be extended to pattern other metals or conductive materials on other insulating substrates, and that the insulating substrate may consist of an insulating buffer layer or insulating buffer layers, which are applied to conductive or partially conductive substrates or to substrates on which previously device levels have been applied. Such a system allows the direct registration of device patterns by ECBFL or other BFL embodiments, because the final metal pattern can be used as a mask for selectively removing the buffer layer and then treating the underlying substrate.

Moreover, the invention is not limited to positive lacquers and line etching. If a negative varnish is used in a lift-off or negative relief process, patterns similar to those already discussed can be treated by registering the identical pattern and then applying electrogalvanic or depositing metal after development of this varnish, followed by a 3304031 -, * - 11 - removal of the varnish, leaving desired certain metal patterns.

Although the particular embodiment described relates to recording the entire circumference of the features, it is clear that the invention does not require recording the entire circumference. For example, accidental breaks in the perimeter may be present. However, substantially the entire circumference must be recorded, i.e., sufficient circumference must be recorded to unambiguously indicate the feature shape. In addition, 10 of the outline must be registered to control the tone process. The perimeter can also be registered with different widths and with internal structures. For example, the perimeter can be recorded twice and include lines connecting the inner and outer lines, thereby obtaining a structure analogous to a sidewalk.

The described embodiment uses electron lithography. It is clear, however, that in other embodiments, different radiation can be successfully used. For example, in the field of lithography, incident radiation can be in the form of particles, such as electrons, ions, atoms, molecules or photons, such as those of light or X-rays. The incident radiation can be in the form of fused, single or multiple beams, which are focused to a spot or a certain shape, for example a line segment or a rectangle. The radiation pattern on the substrate can also be formed by focused images or by shadows cast by a suitable mask. The radiation can be made to scan the radiation-sensitive material, so that the radiation is incident at different times in different regions or at the same time incident in all desired regions.

The effect of the stroking on the radiation-sensitive material can be, for example, that the material is eroded, such as with physical splashing or reactive ion etching, thereby altering the chemical or physical properties of the material, such as with exposure of lacquers, or even material is added, such as in ion implantation or material precipitation by particles. The radiation can also lead to intermixing or chemical reactions between separated S3 0 4 0 3 1 - 12 components of the surface layers.

It is noted that the material with which the substrate is coated can comprise more than one material layer. These layers can serve individually or in combination to provide the required radiation sensitivity and can also help determine the tone of the pattern. Furthermore, the substrate may be radiation sensitive such that the process is promoted, such as, for example, doping of silicon by a focused ion beam, with which the substrate conductance is changed, in order to achieve a subsequent selective electrochemical treatment, for example etching, of the surrounding features.

The boundaries can be completely determined by the radiation exposure, such as, for example, with focused ion beam etching, or additional steps may be required, such as, for example, with the development of lacquers. In addition, a number of steps may be required to fully determine the device manufacturing boundary, such as, for example, in developing lacquers, followed by removing or modifying an underlying layer, such as etching metal films.

• Ions, ie changing a characteristic of the characteristics in the material, may include means where the material in the enclosed characteristic behaves differently than the material outside the characteristic, using the boundary to make it possible that adjacent features are modified in different ways. Tones can also be blocked by the edge of the material. Electric means in which the different characteristics are kept at different electric potentials have been described above. Other useful methods for differentiating between features in the tone process include a substance or phenomenon propagated through or on the material, but which cannot pass a feature outline or boundary, because the properties of the boundary are different from those of the adjacent material. The propagation of substances may include diffusion of dissolved atoms, molecules or ions, an electric charge or liquids which wet the surface of the material or its cavities. Propagation phenomena can include electric or magnetic fields, heat, sound or phase change. The latter may include, for example, a change in crystal structure, melting, vitrification, polymer cross-linking or chain interruption. In 8304031 to "3" - 13 - many embodiments, the dispersion of the substance or phenomenon can be limited by removing the material at the key mark boundaries. However, one can also use a modification of the material properties at the boundaries to control the tone process.

Although the more particularly described embodiment relates to an integrated semiconductor chain or other micro-chain fabrication, the described method can also be applied in other fields where patterns are formed on substrates. For example, it is clear that the provision of hard copies and displays can be simplified by the described method.

Other embodiments can also be realized. For example, the outlines of the features can be recorded with a positive varnish, and the varnish can then be developed to form slits that outline the features. Metal can be vapor-deposited at such an angle that some parts of the slots are not coated, such as, for example, the bottoms. The resulting metal film. includes features which are electrically insulated from one another by the lacquer slots and which may be displayed by ECBFL or other display procedures. The residual lacquer released by showing the metal film can be removed by plasma etching or some other method and the substrate can then be modified.

In yet another embodiment of the invention, two layers of a positive varnish can be applied to a substrate.

The characteristics can then be registered in the manner previously described and the lacquer can be developed. For some selected features, strong radiation exposure occurs at points within the outlines. This exposure is sufficiently strong to cause the two lacquer layers to become insoluble in these areas. Then, a solvent is used to dissolve all bottom coat layers except 30 in the insoluble areas, allowing the lacquer in the characteristics to be removed without the internal strong exposure. For example, the resulting system can be used as a mask for ion implantation or other targeted processes, whereby the substrate is modified.

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Claims (12)

1. Method for forming a material pattern on a substrate, the material comprising a radiation-sensitive material, wherein by exposure to radiation parts of the material, which form characteristics of the pattern, are determined, wherein in this determination radiation exposed first regions are provided which have properties different from those of non-radiated, non-circumferential second regions, characterized in that the first regions form at least part of only the outline of features of the pattern and further said material is shown, the extent of this showing being limited by the first regions. Method according to claim 1, characterized in that the material further comprises an electrically conductive layer between the radiation-sensitive material and the substrate. Method according to claim 2, characterized in that the radiation-sensitive material comprises a lacquer, k. Method according to claim 3, characterized in that the radiation comprises electromagnetic radiation. Method according to claim 3, characterized in that the radiation 20 comprises a particle beam. Method according to claim 5, characterized in that the particles comprise a beam of electrons. Method according to claim 3, characterized in that the lacquer is developed during the determination and parts of the electrically conductive layer are thereby released, Method according to claim 7, characterized in that the electrically conductive layer comprises a metal film. 9. Method according to claim 7, characterized in that when determining which parts of the electrically conductive layer are removed which are released during development. Method according to claim 9, characterized in that the electrically conductive layer comprises chromium. Π. Method according to claim 7 or 9, characterized in that the lacquer is stripped off. 12. A method according to claim 11, characterized in that part of the electrically conductive layer is selectively prestressed and immersed in an etchant in the toning process. Method according to claim 10, characterized in that a part of the chromium is contacted with a metal and d is immersed in an etchant. 1U. Method according to claim 13, characterized in that the metal comprises Al and the etchant comprises IICl. Method according to claim 13, characterized in that the metal comprises copper and the etchant comprises a cerium-based chromium etchant 10. Method according to claim 9, characterized in that the display comprises a preferred etching. 1T. Method according to claim 9, characterized in that the display comprises anodizing. 18. A method according to claim 9, characterized in that the display comprises electro-galvanizing, • i. * "" "\ '~ 83 04 0 3 1'