JPS59105323A - Method of forming patter of material on substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION In many aspects of modern technology, such as the fabrication of integrated circuits, high precision
A copy of v or a main component of the pattern is required. The pattern is typically created by covering the entire substrate with a radiation-sensitive material, commonly referred to as a resist, and then exposing selected portions of the resist to radiation. This broadly exposed portion of the radiation becomes more or less soluble than the unexposed portion when treated with a suitable fluxing agent. After the more soluble portions of the resist are removed, the exposed substrate material may be modified, for example by doping or by removal of material. Depending on whether the exposed area has lower or higher solubility than the unexposed area,
Each is called negative or positive. The resist may be exposed directly to the radiation source, or a mask may be placed between the radiation source and the resist.

Several techniques have been developed to accomplish this phosphorographic copying or pattern generation. For example, photophosphorography and x-ray phosphorography have been developed. A third lithographic technique, electron beam lithography, has also been developed. This technique is a means of generating patterns for thin film devices and integrated circuits with high resolution and precision. However, generally it is a continuous process, one step at a time. That is, the pattern is written one step at a time. Writing with this technique is inherently slow and currently expensive. Fundamentally, due to these limitations, electron beam lithography generally requires direct viewing of the pattern for devices for research purposes, or very high resolution or precision to use this technique. used only occasionally.

Therefore, the current use of electron beam lithography is basically to form a master mask for lithography. Photolithography is currently most commonly used for device fabrication, and the expensive process of master masks is accepted. This is because such masks are currently used to fabricate hundreds, if not thousands, of wafers. Master masks currently used typically have a patterned layer of chromium on a glass substrate.

The aforementioned speed and cost limitations of current electron beam lithography techniques will be better understood from the following discussion. For example, when a pattern shape, that is, a rectangle is written in a positive resist, one of the usual exposure methods is
The entire area of the shape is scanned with an electron beam using several methods,
The beam remains at each point or location within the feature for the time necessary to expose the resist.

The time required to write the pattern depends on the time required to orient the beam to each shape and, for each shape, the time required to expose the shape. Once the beam is in place, the minimum time required to write the feature depends on the scan speed and/or dose required to expose the resist to the desired level at a given beam current. I'll decide. Writing speed and required dose are among the dominant considerations in the development and design of electron beam lithography machines and resists.

Considering the process just described, many writes will occur precisely in the pattern or location of the shape, unless the shape being written is as large as the minimum address dimension of each writing machine used. This results in the redundancy of exposing the resist, which is absolutely necessary for defining the external shape.

According to the present invention, most information about patterns is
It is recognized that proper communication will occur only if the periphery of each shape is exposed so as to fully define the position and shape of the shape. The color tone of the feature is usually determined by whether the resist in the periphery remains or is removed, and is determined by subsequent process steps.

According to the invention, therefore, a method is provided for fully patterning a material on a substrate, the material comprising a radiation-sensitive material, and comprising exposing at least a portion of the material forming the periphery of the shape of the pattern to radiation. and defining a first region exposed to radiation having different characteristics than a second region not exposed to radiation and not surrounding the material; includes the step of adding heights to the area, and the size of the heights is restricted by the first area.

Writing time may often be reduced by a process that exposes only the perimeter of the shape and then selectively colors the internal slopes in subsequent steps. Such a writing process may have other advantages. First, depending on the pattern, the radiation dose introduced to the substrate is essentially reduced and beneficial results are realized.
Good morning. In e-beam lithography, electrons scatter in both the resist and the substrate, and the scattering causes a p-background fog 9, resulting in an effective spatial variation in the optimal exposure dose. This deleterious effect, commonly referred to as the proximity effect, should be mitigated by some form of geometry. For example, if only the perimeter of a block is written, then two spatially adjacent and relatively large blocks are.

Furthermore, in some cases, exposure compensation will be more easily calculated due to the more localized nature of the writing process. Furthermore, in direct writing onto the substrate, the writing process may become more forgiving only when the periphery of the feature is exposed, resulting in electronic damage to the substrate and a reduction in the actual dose. be. Second, if the height control process is flexible enough, the same resist may be used for both positive and negative images without significantly changing writing times. Therefore, an optimal resist selected based on various conditions such as resolution may be used for any height pattern.

A method of patterning a material on a substrate comprises a defined step of exposing at least a portion of the material to radiation, thereby forming a perimeter of a feature, wherein the material is not exposed to the radiation. producing a first area exposed to radiation having a different percentage than a non-surrounding second head, and grading the material, the magnitude of the ridge being the same as the first area;
We have found that limited to the region of n, this is a desirable property.

According to one embodiment of the invention, the defining step 8 consists of exposing the positive resist coated substrate to an electron beam and then developing the resist, the time required for exposing the features and the total dose of radiation being , is decreased compared to Tsushiji's electron beam phosphorography. Exposure to radiation changes at least one property of the material in the exposed area. That is, the exposed material is radiation sensitive. The contouring process changes at least one property of the material, such as by removing material within or outside of the radiation-exposed area. At the end of this embodiment, the resist on the periphery of the shape is removed in a developing step, and then the entire window is formed in the resist. The elevation process may be accomplished by a self-sustaining chemical reaction that begins in the resist at points inside or outside the feature and is confined by windows in the resist. Therefore, the periphery or contour of the feature formed in the resist not only defines the edges of the feature, but also grooves that separate the interior of the feature from the elevation formation process starting from external nucleation, or vice versa. Or it can also be carved. The circumference is annular and does not shrink to arbitrarily small dimensions.

That is, the surroundings are not connected multiplexed. Because of the similarities between the phosphorography method of the present invention and trenches used in the field to limit the spread of wildfires, the lithography techniques described herein are conveniently referred to as "brushfire lithography" (B
rush Fire Lithography).

The foregoing and other aspects of the invention will be described by way of example with reference to the accompanying drawings.

The present invention will be described using a specific example, that is, patterning of a thin chromium film on an insulating material such as metal, e.g., glass. The insulating material may consist of a substrate or of a covering insulating layer. After describing this practical example, cancer practitioners will readily recognize that the method may be used in other embodiments as well.

Referring to FIG. 1, a perspective view of a structure comprising an insulating substrate 1 is shown, the substrate being covered with a layer 3, which layer is coated with a radiation sensitive material, generally referred to as a resist 5. It is.

The resist is, for example, a positive resist such as polymethyl methacrylate. Board 1f? :.

For example, it is made of glass, and 43 is made of metal, such as chromium. As shown, the perimeter of shape 7, which is rectangular, is outlined in the resist with a written area marked 9. The process of exposing or writing the shape is conveniently performed by scanning the electron beam and changing the characteristics of the exposed area. For details on beam generation and scanning, beam intensity, etc.
Since this is well known to those in the bucket industry, the details will be omitted. Other exposure techniques such as a focused ion beam can also be used, and of course other shapes can be written.

The exposed portions of the resist are removed in a suitable, well-known solution that is more soluble than the unexposed portions of the resist;
A structure as shown in FIG. 2 results. The now exposed portions of the chromium layer are removed from the exposed areas, for example by etching, resulting in the structure of FIG.

Next, the remaining resist is removed, and chromium island 7 is removed.
remains, which is separated from its surroundings by a groove in the ROM R film as shown in FIG. The steps of exposing a portion of the resist to radiation, developing the resist, and removing the exposed portions of the chromium layer define the perimeter of the shape and constitute the defining steps of this example.

Contouring processes that change the properties of the material require further etching or other process steps. The formation of high and low chromium can be done in several ways. For example, substrate total dilution Hf
When immersed in J and brought into contact with alumina, the desired shape of "
A positive "image", i.e. a rectangle of chrome, is produced as shown in Figure 5.Alternatively, a commercially available technology based on well-known flashing lenses can be used by continuing to make contact with the copper at one point outside the groove. When used, a negative slag with reversed brightness and darkness as depicted in FIG. 6 is produced. It will be clear to those skilled in the art that if exactly the same positive and negative images are to be produced, it will be necessary to fully adjust the dimensions of the initially exposed resist pattern. The structures depicted in FIGS. 5 and 6 may be used as a mask during patterning of a substrate.

The invention is advantageously applied to embodiments of thin metal films on insulating surfaces. This is because there is an easy way to carry out the entire brushfire phosphorography for this illustration. For example, one removal of the metal of a narrow band that defines the entire perimeter of each shape is Any lithographic process may be used, such as ion beam lithography followed by sputtering or electron beam lithography followed by chemical etching as described above.

After removing the entire perimeter of the shape, the contoured metal or conductive layer shapes are electrically isolated from their surroundings and subjected to a bundling height formation process that differs, for example, into individual discrete shapes. It is controlled by applying an electrical bias, ie, selectively biasing portions of the conductive layer. This fruit/iI! An example of this is the Brassy Fire Lingraphy, which can be simply called ECBFL. Such electrical biases may be phosphorographically patterned and used in various electrolytes to selectively etch, anodize, or electroplate different bias portions of the contoured thin metal film.

Additionally, in the specific embodiment of thin chromium films on insulating substrates, the activity of certain etches commonly used to etch chromium may be affected by contact with certain metals while etching. This can be inhibited or promoted by a suitable electrical bias, such as that occurring. For example, when immersed in dilution H, a thin chromium film initially exists or H
It has generally been found that it is formed in α and protected by a protective layer that is not etched. This behavior is a well-known phenomenon of passivation in chromium and other metals. Metals that are active during immersion, such as the previously mentioned Al'51, are
Physical, physical, and electrical contact with the electrode is useful for electrically biasing, thereby removing the passivation film in localized areas around the electrode. The chromium in this region becomes chemically inactive and begins to dissolve. This active region serves to electrically bias adjacent inactive regions to a lower potential, similar to when contacted with an active metal, making them also active. In this way, all areas of the chromium film that are in contact become active and dissolve, while areas that are not in electrical contact remain inactive and do not dissolve.

Furthermore, the activity of selenium-based etching, which is commonly used for etching thin chromium films mentioned above, is as follows:
It may be blocked by a suitable electrical bias, such as that provided by contacting the copper, while allowing both metals to be etched. Such electrical protection extends over a portion of the chromium film, the extent of which is determined by the voltage drop across the film caused by the current flow to the protective electrode. The thickness of the protected area may be inversely controlled by changing the properties of the thin film, such as resistivity, or the properties of the etchant, such as concentration. Multiple protected electrodes can be used to overlap the protected areas. These techniques may be used to minimize voltage fluctuations in the thin film, and protection over the entire mask dimension is easily achieved. As will be readily appreciated by those skilled in the art, electrical biases can be applied to a wide range of metals in addition to chromium on low resistance substrates in suitable electrolytes, and the high and low ranges desired using this electrical isolation technique are A pattern is generated.

Although these aspects of the invention are explicitly utilized in the embodiments described above using wet etching,
Similar results can be obtained with plasma-based etching or physical sputtering. In that case, a dry metal surface containing electrically isolating contours is created by applying different voltages to the various electrically isolating features, which attract or repel particles in the plasma to the bias region. In particular, high and low levels can be added as well.

Shima traders will recognize several characteristics of ECBFL. For example, a pattern of simply connected shapes, i.e., shapes that surround an external boundary and have no internal boundary, and all of these shapes outside their boundaries are bounded by a single common area, within which A general shape with all points connected together is easily obtained. Such a pattern can be obtained in a thin chromium film on an insulating substrate, for example by making electrodes in common areas with At or CLI as described above.

In many cases, ECBFL can also be implemented to obtain multi-connected geometries, ie geometries with external boundaries. In the case of a chromium layer on an insulator, the pattern of multiple contact shapes in a common bank ground can be completely written if a positive shape is required. That is, in the case of an ECBFL, the common areas are removed by exposing appropriate internal areas of each feature along with the external periphery and removing all of these areas in the first etching process, for example. The common areas are removed in a second etching process as described above.

But what about the general pattern of shapes? For processing purposes, it is desirable to have a means for positioning. In the case of a chromium layer on an insulator, one such means is to trace the entire contour of the feature in the etched grooves and then apply the Heavy 9 of Zn
Consists of forming layers. After this step, called "decorating", the structure is immersed in diluted HIJ,
The decorated shape is etched. Because - by decorating metals, they become less inert. This process is quite complex, as it requires a separate process to produce the decoration.

However, in a simple process such as those described for patterns of simply connected general shapes, many patterns, such as one solid level of an integrated circuit, can be made in this simple mold, which is already very advantageous. be.

Brushfire phosphorography, which has been described as advantageous, has several additional properties. ECB mentioned above
In the FL embodiment and in many other implementations of BFL, the etching of the entire circumference of the feature <gl requires strict linewidth control and K, just as in the conventional master mask fabrication process, for example. This is an etching process. In contrast, the grooves provide such an effective stop that there is little chance of over- or under-etching in the second, larger area etching process. Also, in brushfire lingraphy, only relatively fine lines are written for patterns that include many shapes and sizes. Pattern accuracy may be improved. This is because process steps such as resist development or wet etching often produce results that vary with feature size.

Furthermore, the occurrence of defects in BFL has a different quality than normal lamination.

In ECBFL, a pattern feature can disappear if there are point defects around it that electrically connect the feature to adjacent features.

If necessary, the problems associated with such defects can be alleviated by outlining the large shape with double width. However, some types of defects that are detrimental to normal lathography techniques, such as particles on the resist surface or point defects in the resist, can cause brushfire lithography if they are inside the feature. For many embodiments, no harmful effects occur.

Furthermore, in the intermediate stages of the ECBFL, where the perimeter has been defined but the elevations have not yet been formed, there is an opportunity to identify and correct various deficiencies in a straightforward manner. For example, the electrical isolation of simply connected shapes can be tested by observing the entire pattern with a scanning electron microscope (SEM) or some other means sensitive to their potentials. When using sEMi, the electrically isolated features become noticeably "brighter" due to the charging effect. Could you then try to turn the entire pattern, or even turn the entire pattern at this relatively early stage of the device process, before incurring further process costs? May be excluded. For example, if incomplete etching causes a minute short circuit beyond the periphery, further etching may remove the short circuit. In direct writing of complex circuits, this observation can be made early in the process and the pattern and therefore the device U can be recovered. Furthermore, in actual device processes, the amplification of defects that occur naturally in brushfire phosphorography is
If that's not the case, then it's advantageous. This is because defects at the edges of features cannot be seen by normal phosphorography observation but can often be fatal.

As previously mentioned, it will be appreciated by those skilled in the art that ECBFL may be extended to patterning other metals or conductive materials on other insulating substrates, where insulating substrates may be conductive or partially conductive substrates. Or it should be clear that it may be an insulating buffer layer or buffer layers formed on a substrate with already deposited device levels. Such a structure allows direct writing of device patterns by fi, ECBFL or other BFL embodiments. This is because the final metal pattern can be used as a mask for selective removal of the buffer layer and subsequent processing of the underlying substrate.

In addition, the present invention provides positive tone resist and line etching V
C Not limited. If a negative resist is used in a lift-off or negative relief process, the previously mentioned and near-patterns can be created by writing the same pattern all over, then electrolytically plating or depositing metal after development of this resist, followed by The resist is removed, leaving a pattern with the desired contour.

In the specific embodiment described above, the entire periphery of the shape is written, but it should be understood that in the present invention, it is not necessary to write the entire periphery. For example, accidental cuts can occur in the surroundings. However, the surrounding area must be written in essentially its entirety. That is, the surroundings must be filled in enough to clearly show the shape. Furthermore, the surroundings must be well written in order to control the entire height formation process. The perimeter may also be written to have a different width and internal structure. For example, can it be written twice, the line connecting the internal and external lines? It may also be possible to create a structure similar to a walkway.

The embodiments described herein use electron beam phosphorography. However, it should be understood that other radiations may be used to advantage in other embodiments. For example, in the field of phosphorography, the incident radiation is e.g.
It can be in the form of particles such as atoms, molecules, or photons such as glowing X-rays. The incident radiation may be a focused beam or beams, which are focused to a point or to a particular shape, such as a line segment or a rectangle. The radiation pattern on the substrate may be formed by a focused image or by a shadow created by a suitable mask. The radiation can be scanned over the radiation-sensitive material so that it is incident on different areas at different times or on all desired areas at the same time.

The effect of radiation on a radiation-sensitive material may be to erode the material, for example by physical sputtering or reactive ion etching, to change its chemical or physical properties, such as exposing a resist, or to ionize the material. Material may also be added, such as by injection or particle deposition of material. The radiation may also cause mixing or chemical reactions between the separate compounds of the surface layer.

It should be noted that the material covering the substrate may consist of multiple layers of material. These layers, singly or in combination, provide the necessary radiation sensitivity and also help define the height and height of the pattern. Additionally, the substrate is radiation sensitive to facilitate processes, such as doping of silicon with a focused ion beam. This doping changes the conductivity of the substrate and allows subsequent selective electrochemical treatments, such as etching of enclosed features.

The boundaries may be completely defined by radiation exposure, eg, focused ion beam etching, and may require additional steps, eg, %1M of resist. Additionally, several steps are required to fully define the boundaries for device fabrication purposes, such as developing the resist and subsequent removal or modification of the underlying layers, such as etching of the thin metal film. Sometimes.

The formation of elevations, i.e. the modification of the properties of a contoured feature in the material, may be accomplished by means of causing the material in the contoured feature to behave differently than the material outside the shape and to be modified in a different manner than adjacent features. It may consist of means using boundaries. The raised and lowered shapes may stop at the edges of the material. Electrical means of keeping different shapes at different potentials are described. Other techniques for creating differences between features during the elevation forming process include propagating through or over the material, but crossing around or across the boundaries of the feature because the properties of the boundary are different from those of adjacent materials. It includes any substance or phenomenon that does not exist. The propagating material may consist of diffusing solute atoms, molecules or ions, electrical charges or liquids that wet the surface or spaces of the material. The propagation phenomenon may consist of electric or magnetic fields, heat, sound waves or phase changes.

The latter tri may consist, for example, of changing the crystal structure, melting, melting, vitrification, cross-linking of polymers or scission of bonding chains.

In many embodiments, the spread of a substance or phenomenon can be limited by removing material at the boundaries of the shape. However, changing material properties at the interface can also be used to control the elevation formation process.

Although the embodiments described above were particularly related to the fabrication of semiconductor integrated circuits or other microcircuits, the method described herein may also be used in other fields of forming patterns k"IE on substrates. For example, it will be readily appreciated that the methods described herein facilitate the production of hard copies and displays.

Other embodiments are also possible. For example, the perimeter of the shape may be written in a positive resist, and the resist is then developed to form grooves that define the shape. The metal may be deposited at an angle so that the grooved areas, such as the bottom, are not coated. The resulting metal thin film is electrically isolated from each other by grooves in the resist and consists of features that can be contoured by ECBFL or other contour forming processes. The intact resist may be removed by plasma etching or other techniques, and then the entire substrate may be cleaned.

In yet another embodiment of the invention, two layers of positive resist may be deposited on the substrate. The shape may be drawn in the outline as described above and the resist may be developed. For certain selected shapes, high radiation exposures are made at points within the contour. This exposure is strong enough to render both resist layers insoluble in those areas. Next, a solvent is used to dissolve the entire underlying resist except for the insoluble areas, and the resist is then exposed to high radiation. 1. Substrate 3. Layer 5. ...Resist 7...Shape

Claims (1)

[Claims] 1. A method comprising the steps of: defining at least a part of a material forming the periphery of a pattern shape by exposing it to radiation; and forming heights and heights of the material; , producing a first region exposed to radiation, said first region having different characteristics than a second region not exposed to radiation and not forming a full circumference, said elevational extent being different from said first region; 1. A method of patterning a radiation-sensitive material on a substrate, the pattern being confined to one area. 2. The method of claim 1, wherein the material further comprises an electrically conductive layer between the radiation-sensitive material and the substrate. 3. The method of item 2 above, wherein the radiation-sensitive material comprises a resist. 4. The method according to item 3 above, characterized in that the radiation consists of electromagnetic radiation. 5. A method according to paragraph 3 above, characterized in that the radiation consists of a particle beam. 6. The method according to item 5 above, characterized in that the particle beam consists of electrons. 7. The method of claim 3, wherein the defining step further comprises developing the resist thereby exposing a portion of the electrically conductive layer. 8. The method according to item 7 above, characterized in that the electrically conductive layer comprises a thin metal film. 9. The method of claim 7, wherein the defining step further comprises removing portions of the electrically conductive layer exposed during the developing step. 10. The method of claim 9, wherein the drowsy conductive layer comprises chromium. 11 In the method described in paragraph 7 or 9 above,
A method further comprising the step of completely removing the resist. 12. The method of claim 11, wherein the step of forming the ridges comprises selectively biasing a portion of the electrically conductive layer and immersing it in an etchant. 13 In the method described in item 10 above, the step of forming the heights includes bringing a part of the chromium into contact with a metal;
A method characterized in that it consists of immersion in an etchant. 14. The method described in item 13 above, characterized in that the metal is made of At and the etchant is made of Hα. 15. The method of claim 13, wherein the metal comprises copper and the etchant comprises a chromium etch based entirely on selenium. 16. The method of item 9 above, wherein the step of forming the elevations comprises selective etching. 17. The method described in item 9 above, wherein step 1 of forming the entire height and height comprises anodization. 18. The method as described in item 9 above, wherein the step of forming all the heights and depressions comprises electrolytic plating.