JPS60160009A - Production of thin film element - Google Patents

Abstract

PURPOSE:To obtain a thin film element having a stepped part with high accuracy by forming an org. resin on the surface of a thin film having the stepped part in such a way that the thickest part is thicker than the step, forming successively Al2O3 and photoresist layer on the resin. CONSTITUTION:An org. resin layer 71 of a novolak resin or the like is formed more thickly than a step on a ''Permalloy'' film 13 so that the thin film 13 deposited on the stepped part 12 on a substrate 11 of, for example, a thin film magnetic head is formed with a pattern of high accuracy on the surface including the stepped part of the thin film having the stepped part in production of an LSI, thin film magnetic head, liquid crystal element, etc. An Al2O3 layer 72 and a photoresist layer 33 are successively form thereon. The layer 33 is then exposed to a prescribed shape and is developed and patterned. A layer 72 is etched by using ion of gaseous fluorine compd. etc., with said layer as a mask then the layer 71 is etched by ionizing O2 and finally the layer 13 is etched with the layer 71 as a mask. The thin film element having high accuracy is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing a thin film device, and more particularly to a method for batting a thin film having steps.

[Background of the invention]

Thin film technology has been widely used in the production of thin film elements such as magnetic bubble memories, thermal display elements, thin film magnetic heads, and liquid crystal display elements, in addition to being used for wiring of semiconductors such as LSIs. One reason is that this thin film technology is being applied to fields that have traditionally been manufactured using machining or thick film technology, and there is a tendency to create products with complex structures. On the other hand,
As elements become smaller and more dense, it is becoming necessary to improve pattern accuracy. For these reasons, a technique for forming highly accurate patterns on steps caused by wiring patterns or through holes has become a common problem. This becomes a problem especially when this step is too large to be ignored with respect to the width of the pattern to be formed.

In order to form a high-precision pattern on a step, it is first necessary to pattern a mask material with high precision.

FIG. 1 shows an example of a cross section of the main part of a thin film magnetic head. A permalloy film 12 as a lower magnetic core is formed on the substrate 11, and forms a magnetic circuit together with a permalloy film 13 as an upper magnetic core which will be formed later. At the tip 14 of the head, that is, on the side facing the recording medium, an alumina film 15 is interposed between two layers of permalloy films 12 and 13 to form a magnetic gap, and this gap is used to write on the magnetic disk that is the recording medium. , and also reads information from the magnetic disk. The principle is the same even if the recording medium is magnetic tape. A conductor coil 16 is provided between the permalloy films, and is slightly insulated from the permalloy films 12 and 13 by an organic resin 17. This organic resin 17 needs to have a thickness of about 10 μm or more in order to prevent magnetic flux leakage between the permalloy films 12 and 13.

When manufacturing a magnetic head having such a configuration, the permalloy film 13 on the organic resin 17 must be patterned at locations with considerably large steps. On the other hand, the width of the track for writing and reading by the thin film magnetic head is determined by the patterning of the permalloy film 13. For this reason, as track width specifications become smaller, highly accurate patterning is required.The part that requires the most precision is the tip 14 in FIG. It has become.

When a photoresist is applied to such a stepped portion and exposed, the following problem occurs. FIG. 2 schematically shows a cross section of the photoresist 22 applied on the step 21, and the thickness of the photoresist 22 is different between the upper part 23 and the lower part 24 of the step, and the thickness of the photoresist at the lower part 24 of the step is 10 μm.
As the thickness increases to more than m, and the surface is not flat and does not come into close contact with the photomask in some areas, a state of proximity exposure occurs, resulting in a decrease in pattern accuracy in stepped portions. This means that even if projection type exposure is used, there will still be a partial defocus, and the accuracy will still be lower, just like with a contact type exposure machine.

Generally speaking, there are three ways to solve the above problem.
A resist film forming method called a layer resist method is known. This method is illustrated in FIG. First, an organic resin 31 is applied onto a substrate having a step 21. Next, this organic resin 31
An inorganic film 32 is deposited thereon, and a photoresist 33 is further formed (a). At this time, the organic resin 31 needs to have a flat surface. The flattening method uses a thermosetting resin such as a novolac resin, or a low molecular weight resin that is heated and fluidized, and after the film is formed, the unevenness of the surface is removed using an etch pack, etc. method is known. The latter has the advantage that various substances including inorganic substances can be used, but the former has the disadvantage of complicating the process, so the former is used. The inorganic film 32 should be made as thin as possible in order to perform etching with high precision, but on the other hand, it must be sufficiently durable as a mask material when the organic resin is dry etched using oxygen. For this reason, 81 compounds such as SI and 5ICh are often used. In addition, Mow T is resistant to oxygen plasma.
It is also possible to use metal films such as i + Or. The photoresist is novolac resin based U.

(2) A resist or other photosensitive resist, electron beam resist, X-ray resist, etc. can be used.

After laminating the three-layer film on the step, the photoresist 33 is exposed to light and developed to form a predetermined pattern (Fig. 3-b).
). Next, the inorganic film 32 is etched using the patterned photoresist 33 as a mask (FIG. 3-C).

This etching method can be either ordinary chemical etching or dry etching, and the choice of which method is appropriate depends on the material, precision, and other considerations. Generally speaking, dry etching, which can be performed using a non-uniform etching method, is more likely to achieve high accuracy.

Finally, the organic resin 31 is etched using the inorganic film 32 as a mask. This etching method requires anisotropic dry etching because it is necessary to accurately transfer the pattern of the inorganic mask 32, and more specifically, a reaction using a gas capable of selectively etching organic substances such as oxygen or oxygen mixed gas. The method is limited to dry etching methods, such as reactive sputter etching or reactive ion beam etching, in which ions are incident on the substrate from a limited direction.

The eight-layer resist method shown here is originally being studied as a method for forming submicron wiring on a step of about 1 to 2 μm in the formation of fine wiring for LSI. When trying to apply this method to a level difference on the order of 10 μm,
The following problems occur.

The first problem is the occurrence of cracks due to differences in the thermal expansion coefficients of the films. Since the level difference is as large as about 10 μm, the film thickness of the organic resin 31 must be increased to 10 μm or more, which increases stress. Generally, the coefficient of thermal expansion of an organic resin is large, on the order of 10-', so if the coefficient of thermal expansion of an inorganic film is small, cracks are likely to occur. Especially S10! This tendency is strong for films with a small thermal expansion coefficient of 5 x 101, such as
Cracks may be observed even when the thermal expansion coefficient is around 3 x 10''llK, such as sl. Cracks do not occur in metal films such as Mo, but this is because the thermal expansion coefficient is 5 x
In addition to being larger than 10-' and 81, S
This is because it has better adhesion to organic resins than 1 and 8i0*.

Considering only the above points, a metal film such as Mo is considered to be a good material for the inorganic film 32 of the three-layer resist.

The second problem is mask alignment. Normally, mask alignment is performed using alignment marks based on the unevenness of the base, but if an opaque film such as a metal film is used as the three-layer resist, the unevenness of the base cannot be detected at all. Therefore, in this case, it becomes necessary to expose the detection mark portion in advance, or to use a completely different detection method.

From the above results, the material to be applied to the inorganic film 32 of the three-layer resist formed on a high level difference is one that has a coefficient of thermal expansion close to that of an organic resin, has good adhesion to the organic resin, and is practically transparent. Things are desired. It is also important that the etching rate be sufficiently low in dry etching using oxygen ions.

An example of a material that satisfies the above points is an alumina film. The alumina film has a large coefficient of thermal expansion ((9
), which is characterized by high adhesion to organic resins. Furthermore, it is transparent and exhibits an etching rate of 1150 or less for organic films even by reactive sputter etching using oxygen or reactive ion beam etching, and has sufficient selectivity. However, until now, no method has been found that enables selective etching of this alumina film with high precision. For example, in conventional chemical etching, a sputtered alumina film can be etched with a hydrofluoric acid-based etching solution, but highly accurate patterning is difficult. On the other hand, even in dry etching, for example, reactive sputter etching using CF 4 hardly etches the material, and ion etching using Ar only physically etches it. Furthermore, even if this ion beam etching is used, an etching rate that is slower than that of photoresist can only be obtained. From the above point, in order to use the alumina film as the inorganic film 32 of the three-layer resist, the thickness of the photoresist 33 needs to be four to five times as thick as the alumina film in order to use ion beam etching. Increasing the thickness of the photoresist 33 in this way goes against the purpose of increasing the pattern accuracy of the three-layer resist.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing thin film confectionery that solves the problems of moisture in the conventional technique described above.

[Summary of the invention]

The present invention has confirmed through experiments that a transparent alumina film with excellent etching resistance can be selectively etched by ionizing a carbon fluoride gas such as CF4 with plasma, accelerating it, and irradiating it onto alumina. However, this effect and property are utilized to apply it to the middle layer of a three-layer resist. Specifically, an organic resin, alumina, and a photoresist are sequentially formed on the surface of a workpiece having steps, the photoresist is first patterned, and a fluorine compound gas or a mixed gas of a fluorine compound and hydrogen is applied using the patterned photoresist as a mask. The method is characterized in that alumina is patterned using ions obtained from a gas containing oxygen, an organic resin is patterned using ions obtained from an oxygen-containing gas using alumina as a mask, and a workpiece is patterned using the mask thus obtained.

[Embodiments of the invention]

Next, the present invention will be explained using specific examples.

FIG. 4 shows an example of an apparatus for etching alumina used in the present invention. The illustrated apparatus is called an ion beam etching apparatus or an ion milling apparatus. In the figure, a vacuum container 41 is an ion gas 42
The compartment is divided into a grid 44. and a sample chamber 43.
It is divided by 45. The gas used is boat 4.
6, and is evacuated through the exhaust port 47 by a vacuum pump. The ion gas 42 is the thermionic emission filament 4
8. The anode 49 and the coil 50 ionize the introduced gas to create a plasma 51, which is accelerated by the grids 44 and 45 to collide with the sample. The sample 52 is attached to a sample stage 53 that can be tilted and rotated. In addition, in order to prevent the sample 52 from being charged by ions, a neutralizing filament 5 is provided.
4 emits thermoelectrons.

FIG. 5 shows the respective etching rates when novolak photoresist and alumina are etched by introducing CF4 into the ion beam etching apparatus shown in FIG. 4. When the ion accelerating voltage is low, the alumina etching rate 61 is the same as the photoresist etching rate 62.
Although it is quite small, it reverses when the accelerating voltage is high. Ar
When a gas is introduced, the etching rate of photoresist does not change significantly, and the etching rate of alumina is about 1/2 or less than that of photoresist. This suggests that chemical action is involved in the etching of alumina when CF4 is used.

However, alumina is not practically etched by reactive sputter etching or plasma etching, which are one method of dry etching. The substance to be etched by the above-mentioned dry etching method needs to have a reaction product that evaporates easily. Tsuma J) When etching with 81 & CFa, the sublimation point of 81Fm is -95,50, and when etching A4 with CCLa, htcta
The boiling point of iE is 18L7C (755wxHg).

The product when etching alumina with CF4 is A7F.
m, but the boiling point of this substance is 1 at 1260C.
), plasma etching, etc. are difficult.

Considering the above, the etching characteristics of alumina shown in Figure 5 are considered to be an interaction between chemical action and physical action. Alumina has a melting point of 2015G.

It is a heat-resistant material with a boiling point of 3500 t:' and is physically difficult to be etched. Compared to alumina, ALFs can be considered to be a material that is easily etched. The reason for the strong dependence on accelerating voltage is not yet clear. At low ion accelerating voltages, the etching rate increases as the ion incidence angle increases, but at high voltages it tends to remain constant or decrease. Therefore, at low voltages, physical action is rate-determining, while at high voltages, the etching rate is the reaction to A L F g. It is thought that this is starting to play a role in determining the rate.

FIG. 6 shows the etching rate of photoresist and alumina when CF4 and Hs are introduced into the apparatus of FIG. The etching rate 66 of alumina is increased by adding hydrogen, but the etching rate 67 of photoresist is decreased. As a result, by further improving the etching selectivity of both, it becomes possible to reduce the thickness of the photoresist required for etching the sialumina film. Specifically, the thickness of the photoresist that forms an alumina pattern with a thickness of 0.5 μm is only 0.5 μm, which is about the same as the thickness of alumina, even considering the effect of side etching from the edge. Accurate patterning is possible.

The cause of the effect of H3 addition described above is not necessarily clear, but it is thought that the opposite effect described above occurred due to the reducing action of US on alumina, which becomes unstable in an oxidizing atmosphere, and organic matter, which becomes easily decomposed. It will be done. When O-wine is added to CPa, H! It was confirmed that, contrary to the addition, the etching rate of photoresist was far from that of alumina.

Since sialumina can be selectively etched by the above-described process, it can be inferred that it can be applied to photoresist patterning on steps. An outline of the patterning process is shown in FIG. It was found that it was possible to form a pattern with a line width of 3 .mu.m by depositing and patterning a 15 .mu.m thick layer of organic resin film, 0.5 .mu.m alumina layer, and 0.5 .mu.m thick photoresist layer on a flat part of the organic resin film with a step difference of 10 .mu.m. As the material of the organic resin film, a novolac resin heat-treated at 2000 and a low molecular weight polyimide resin were used, and the above results were confirmed for both. Novolak resin has good flatness, and polyimide resin has good heat resistance. For this reason, novolac resin is suitable when there are large steps and flatness is particularly required, and when the temperature of the substrate surface increases during alumina sputtering, for example when cooling of the substrate is poor, the substrate is thick and heat conduction is poor. Polyimide resin is suitable when the sample is small, when the sample is easily heated by conventional high-frequency sputtering, or when you want to deposit as fast as possible.

As a method for etching the organic resin, reactive sputter etching or reactive ion beam etching using oxygen or a gas prepared by adding a gas such as argon to oxygen for etching stability is preferable. Reactive sputter etching is suitable for large-scale processing because it allows patterning of large areas. On the other hand, since reactive ion beam etching has good ion directionality, an organic resin pattern with a good cross-sectional profile can be obtained with good reproducibility.

The alumina film used as an etching mask for the organic resin may be removed by reactive ion flame etching in the same manner as when patterning, or by lift-off when the organic resin is etched.

It is appropriate to remove the organic resin by incinerating it with oxygen plasma, dissolving it with an alkali or organic solvent, or using a combination of both.

The gas used for etching the alumina film is CF4
The explanation was given using a gas in which H2 is added to CF4, but it has been confirmed that alumina can be etched by a fluorine-based gas in principle, and can be etched by 6'), Cx Fs, CHF5, etc.

FIG. 7 shows a process in which the present invention is applied to manufacturing a thin film magnetic head. A permalloy film 13 serving as the upper magnetic core of the thin film magnetic head is deposited on the step 21 on the substrate 11. A novolac resin 71 typified by a positive type photoresist is applied thereon. The coating film thickness is 13 to 20 μm at the bottom of the step with respect to the step height of 10 μm. The unevenness of the surface of a positive photoresist depends on the coating film thickness and the heat treatment temperature after coating. When the coating film thickness is as thick as 20 .mu.m, the flatness can be improved even after heat treatment of about 900 degrees centigrade to evaporate the solvent. 150~ if the film thickness is thin
The softening point of the resin, which is approximately 250C, is exceeded and a heat treatment is required. When using a resin other than novolac, such as polyimide, it is a matter of course that heat treatment is required depending on the characteristics of each resin, as in the case of photoresist.

An alumina film 72 is placed on the novolac resin 71 to a thickness of 0.
Deposit 5 μm to 1 μm. A photoresist 33 is applied to a thickness of 0.5 to 1 μm on this alumina film 72 (Fig. 7-a).
. Next, the photoresist 33 is exposed using a photomask.
A is imaged and molded into a predetermined pattern (Fig. 7-b). It goes without saying that this photoresist patterning method is not limited to photoring 2-fi using a photomask, but can also be used with other methods such as electron beam lithography, but conditions such as coating film thickness should be matched to the characteristics of the resin used. be.

Next, the alumina film 72 is buttered and etched by reactive ion beam etching using a mixed gas of CF4 and hydrogen.

By etching for 10 minutes under the conditions of CFa 70' Its hydrogen 30% 1:t:/acceleration voltage of 800 V, the unnecessary portion of the alumina film 72 with a thickness of 0.5 μm is completely removed (Fig. 7- C). At this time, approximately 0.25 μm of the photoresist 33 is removed, but the thickness at the time of application is 0.5 μm.
Even at m, there are still 50 chips left.

Using the patterned alumina film 72 as a mask material, the novolac resin 71 is patterned to have vertical walls by reactive ion beam etching using oxygen (FIG. 7-d). The etching rate of the resin is 100 to 200'Hnr m/ even if the ion acceleration voltage is as low as 400V.
On the other hand, the etching rate of the alumina film is 115 mg I:, or higher than that of the resin.
Since the etching amount is as small as 0 or less, the etching amount in the process shown in Figure 7-d is 0.4 μm or less.j5.0.5 to 1 μm
A thin alumina film can be used as a mask. 7th
In the process of FIG. d, reactive sputter etching using oxygen or a gas mixture containing oxygen can be used. This method is characterized in that parallel plate type electrodes can be used, so a large number of substrates can be processed at once, and the structure of the apparatus is simple. On the other hand, in reactive ion beam etching, it is difficult for the radicals generated in the plasma to reach the sample, so most of the active chemical species that collide with the sample are limited to ions coming from one direction. Therefore, there is a characteristic that undercutting of the novolac resin 71 with respect to the alumina film 72 is small. In addition, since the plasma and sample are separated, novolac resin 71
It also has the characteristic of having little deterioration. 2 mentioned above
The characteristics of reactive ion beam etching are not limited to novolac resins, but are the same in principle for other polyimide resins, epoxy resins, etc., and have been confirmed through experiments.

The permalloy film 13 is etched using the novolac resin 71 patterned by the above process as a mask. As the etching method, chemical etching or dry etching such as ion beam etching is used.

Chemical etching has the feature of being able to pattern easily and in a short time, while ion beam etching has the feature of being able to obtain highly accurate patterns. For the purposes of the present invention, it is desirable to use anisotropic dry etching such as ion beam etching for turning the permalloy.

Finally, the novolac resin 71 is removed by plasma ashing, dissolution with a solvent such as acetone, or a combination of both, thereby completing the patterning of the upper magnetic core and shite permalloy film 13 of the thin film magnetic head.

As described above, by applying the present invention to the Nokumaq patterning process of a thin film magnetic head, it is possible to obtain a highly accurate pattern at the step portion.

FIG. 8 shows a process in which the present invention is applied to a process of forming a permalloy film 13 as an upper magnetic core of a thin film magnetic head by a frame deposition method as another embodiment of the present invention.

First, a thin permalloy film 81 of about 0.1 μm is deposited on the stepped portion 21 of the substrate 11 . This thin) Ku-malloy film 81
is the part that becomes the conductive layer in permalloy electroplating. Thereafter, novolac resin 71. Alumina membrane 72. Photoresist 33
are sequentially stacked (Fig. 8-a). Thereafter, photoresist 33. is applied according to the process of the embodiment shown in FIG. Alumina membrane 72. The novolac resin is sequentially turned (FIG. 8-b). The shape of the pattern is a frame 82 surrounding the desired permalloy pattern.

Next, permalloy films 83 and 84 are deposited on the inside and outside of the frame 82 by electroplating in an acid bath (Fig. 8-C).
). After this, a film other than the permalloy film 83 that is finally left inside the frame 82, that is, the alumina film 72 that constitutes the frame. Novo 2 Tsuku resin 71. The permalloy film 84 and thin permalloy film 81 on the outside of the frame are removed (FIG. 8-d). The novolac resin 71 is removed by a combination of good ashing and a solvent, and the alumina film 72 is removed by scrubbing. The permalloy film 81, 84 other than the bottom 85 of the frame 82 is removed by chemical etching. The lower portion 85 of the thin Permalloy [8107L/- membrane 82] is removed by sputter etching or ion milling.

According to the above method, the shape of the permalloy film 83 is determined by the highly precisely formed frame 82, and there is no deformation due to side etching, which is a problem when forming multiple layers by etching, so a highly accurate pattern can be easily formed. It has the characteristic that it can be obtained.

In this example, novolac resin was used for explanation, but similar effects can be obtained by using polyimide resin or other resins, and the surface flatness, chemical resistance, heat resistance, etc. should be selected taking into consideration the characteristics of

〔Effect of the invention〕

According to the present invention, a resist mask can be formed with high precision on a surface having a stepped portion, so that processing of a thin film element can be performed with high precision.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view to explain the structure of a thin-film magnetic head, Figure 2 is a cross-sectional view to explain the problems of the conventional process, Figure 3 is a diagram to explain the three-layer resist method, and Figure 4. is a schematic diagram for explaining an ion beam etching apparatus used in the present invention, FIGS. 5 and 6 are characteristic diagrams for explaining the present invention, and FIGS. 7 and 8 are diagrams for explaining a magnetic FIG. 3 is a process diagram for explaining a method for manufacturing a head. 12.13...Permanent film, 17,31...Organic resin, 22.23...Photoresist, 32...Inorganic film 1, 5/'7 20th Ga 3 Mouth 40 Kuzu 5 Ion pressure name 6 H2 da CF4 H2 No. 70 No. 70 Continued from page 1 ■ Inventor Katsuya Mitsuoka Inside 3-chome Saiwaimachi, Hitachi City @ Inventor Shinji Nari Inside 3-chome Saiwaimachi, Hitachi City 0 Inventor Masanobu Hanazono 3-chome Saiwaimachi, Hitachi City

Claims (1)

[Claims] 1. In a method for manufacturing a thin film element having a thin film having a stepped portion, the thickest organic resin layer is applied to the surface of the thin film including the stepped portion. A step of forming the alumina layer and a photoresist layer on the organic resin layer in order, and a step of patterning the photoresist layer into a predetermined shape by exposure and development. Using the patterned photoresist layer as a mask, the sialumina layer is patterned into a predetermined shape by accelerating ions obtained from a fluorine compound gas or a mixed gas of a fluorine compound and hydrogen and irradiating the exposed surface of the alumina layer. A step of patterning the organic resin layer into a predetermined shape by vertically irradiating the exposed surface of the organic resin layer with ions obtained from oxygen or a gas containing oxygen using the patterned alumina layer as a mask. A method for manufacturing a thin film element, comprising: