JPS5857908B2 - Method of forming thin film structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a film forming method using a masking method.

The coating is formed under vacuum by sputtering or vacuum deposition.

The invention also relates to masks for depositing thin films on various substrates by vacuum deposition and sputtering methods.

This mask may be formed by electrodeposition, electroless deposition, or other methods.

Recently, masks having overhangs (hereinafter referred to as overhangs) have become widely used in forming desired patterns of materials in semiconductor structures.

A layer of material deposited through an opening defined by a mask material having an overhang will form a gap between it and the mask, which is due to the overhang and the geometry of the evaporation source, and is larger than the deposited layer. This is because the mask is thick.

IBM Technical Dis published in May 1974
Closure Bulletin Vol. 16
' Li by Bohg et al., page 3954 of A12.
The document entitled "f toffMask" discloses a lift-off mask with an overhang made of pyrolytic silicon oxide, which has advantages not achievable with photoresist.

According to this document, in order to form an overhang by changing the etching rate of silicon oxide to promote etching, silicon oxide is generated at a temperature of 300 to 500° C. by gradually increasing the temperature.

Use a photoresist layer as a temporary mask for the hydrofluoric acid.

A thin film of metal is then deposited on the substrate through the mask after removing the photoresist.

Next, the silicon oxide is lifted off.

The actual maximum thickness of this mask material is approximately 1 to 3 microns.

If the mask material is too thick, cracks and damage will occur.

U.S. Pat. No. 3,849,136 shows a substrate with a photoresist coating.

Overexposure of the photoresist layer through an opening in the metal layer above the photoresist layer results in the metal layer overhanging the photoresist layer.

The use of photoresists is said to be undesirable because of the tendency of photoresists to flow when heated to high temperatures during vacuum deposition.

If the photoresist layer is very thick, on the order of 7μ, the openings formed after exposure and development through a mask will be
It has a taper that tends to negate the value of overbangs as shown in FIG. 1E of the above-mentioned US patent.

In the case of such a very thick resist, the taper will be large as well, so that an aperture consisting of a fairly narrow groove of about 7 microns in depth will actually have an increasingly narrower aperture.

Accordingly, it is an object of the present invention to provide a method of forming a thin film structure on a substrate.

According to the invention, the top surface of the mask is approximately the same size or smaller than the opening in the bottom surface of the mask, in order to make it possible to form a fine pattern in good proximity to the lift-off mask material during the subtractive processing step. A lift-off mask is provided having a sidewall that intersects an opening in the lift-off mask.

The present invention differs from conventional lift-off methods in that the metal layer with overlapping edges is not supported by photoresist or the like, can withstand high temperatures, and is removed from the substrate surface by a metal lift-off method that has not been attempted in the prior art. I can do it.

Furthermore, the additive process of forming the lift-off mask by electroplating is also different from the prior art.

In fact, this process is the reverse of the prior art, which utilizes subtractive methods to form overburdens of photoresist or glass structures with or without an overlayer of metal.

According to the present invention, a method is provided for forming thin film structures by depositing desired materials under vacuum.

A layer of a first material is formed on a substrate and a pattern of openings is formed in the layer of material.

A second material, a lift-off mask material, is then deposited over the opening with a greater overhang at the top than at the bottom of the opening.

After removing the first material layer, the desired coating material is then applied to the substrate surface in a manner substantially less than the thickness of the first material layer, leaving a gap between the sidewalls of the exposed or foot-off mask material. It adheres thinly.

Finally, the structure is treated with a chemical acid solution effective to remove the lift-off mask material and any coatings deposited thereon by etching or similar methods. Remove material.

Reference examples will be described below with reference to the drawings.

First, referring to FIGS. 1A to 1G, a metal layer 11 is formed on a substrate 10. As shown in FIG.

This layer 11 may be a layer of materials that can be formed adhesively to the substrate 10 and serve as a plating substrate for electroplating.

When depositing metals such as Fe, Ni, Cr or Cd to the substrate 10 at high temperatures, both adhesion and plating substrates are achieved without the need for any intermediate adhesive layer.

However, Au with any hot nitrogen as a plating base material,
When depositing Cu, Pd or Pt, or Co or NiFe at room temperature, Ti, Ta is deposited on the substrate before depositing the plating substrate.

It is necessary to form an intermediate adhesive layer of a reactive metal such as Al or Cr.

A layer of photosensitive organic resist 12 is then formed on the layer 11, and the resist layer 12 is exposed and developed using ultraviolet light, electron beams or X-rays to form longitudinal grooves that reach the surface of the substrate 10. Openings 14 and 15 are formed.

The openings 14 and 15 are for forming the boundaries of a pattern such as an electrode lead pattern or a thin line pattern.

The openings 14 and 15 are then filled with an electroplated layer 25 of metal to form a strip having a mushroom-shaped overhang extending beyond the openings 14 and 15 in both vertical and horizontal directions, as shown in FIG. 1B. Mask materials 16 and 17 in the mold
form.

It goes without saying that the openings 14 and 15, that is, the mask materials 16 and 1γ, may be formed extremely wide or narrow as necessary.

As described below in connection with FIGS. 1D and 1E, in order to achieve a more satisfactory removal rate of the mask material to be removed from the substrate 10, the width ratio of the wide areas to be removed to the narrow passages is approximately 25. : It is preferable to make it smaller than 1.

This helps achieve uniform removal of layers 25 and 19, as shown in Figure 1E.

Next, as shown in FIG. 1C, after exposure and development treatment with an organic solvent or plasma ashing treatment or organic stripping @
The electroplating mask material 16 having an overhang 18 is removed by removing the resist I 12 using a conventional method such as a solution.
and 17 are left as is.

The electroplating metal must be deposited uniformly and the electroplating bath must have good macro and micro throwing power.

Measure the uniformity of plating using throwing power.

As a modification, an electroless plating method may be used.

The electroplated metal must be able to withstand well the deposition temperatures of the desired coating material (50-7000G).

The electroplated pattern masking materials 16 and 17 must have a uniform overhang (about 0.1 micron to 5 micron mushroom-shaped cavities).

The size of the overbang is mainly determined by this lift-off.
It is determined by the lateral and thickness dimensions of the final pattern 7 designed to be achieved in the process.

The thickness of the resist 12 is adjusted to be at least about 20 φ thicker (i.e., at least about 0.25 μ thicker if a thick film is used) than the desired thickness of the material to be deposited in the next step as shown in FIG. 1D. Be careful what you choose.

For very small geometries, as shown in FIG. 1C, overhangs O and protrusions P of plating material on the top surface of the resist 12 are formed to be approximately 5 to 10 times the thickness of the resist; Moreover, it is necessary to make O and P equal.

After removing the resist 12, sputter etching method,
The layer 11 in areas where the masking materials 16, 17, etc. are not present may be removed using a chemical etching method, a reactive plasma etching method, a reactive plasma spackle etching method, or the like.

1D, layers 11, 17 are then used as vacuum coating masks to form a layer of desired coating material 19, such as a metal or dielectric, by vapor deposition or bathbatter deposition. Mask materials 16 and 17
A coating material 19 is applied over the .

Overbang 18 leaves sidewalls 20 of masking materials 16 and 17 exposed with little coverage of coating material 19.

After depositing coating material 19, the electroplated metal comprising masking materials 16 and 17 is selectively etched using chemical etching, reactive plasma etching, or other methods, as shown in FIG. 1E. to form the desired pattern, which is largely unaffected by corrosion.

In this manner, mask material 16 and undesired metal of the JT are lifted off from layer 11.

When forming fine strips or removing a certain portion of the coating material 19, a resist layer 20' is formed except for the portion 21 of the coating material to be removed, as shown in FIG. 1F, and then , subtractive methods such as chemical etching methods,
Alternatively, a dry process such as spuck etching, reactive spuck etching, ion milling, plasma etching, and other suitable methods may be used to remove the portion 21 as shown in FIG. 1G. Good too.

Electroplating metals are for example (a) group Au l P
t HPd, Ag or (b) group Cu, Zn)
Ni, Co.

It may be Fe, Cr, Sn, W, or a binary, ternary or quaternary alloy of any of the above elements or any of the above elements and another element.

(a) Group metals are primarily used as lift-off masks for metallic or non-metallic patterns, in which case mask patterns consisting of noble metals or metals are selected using other methods such as heating or chemical reactions. It may be removed temporarily.

Group (b) metals are non-noble metals and are therefore widely used.

This group (b) metal may be used as a lift-off mask for dielectrics and various noble metals.

Although examples of typical structures are shown in this specification,
The method of the invention can be used to manufacture all types of magnetic structures, all types of semiconductor structures such as integrated circuits, second level packaging, optical and electro-optical structures, and other structures. Needless to say.

When forming the desired pattern 19 using a dielectric material,
Preferably, the metallization layer is removed using sputter etching, ion milling, plasma etching or chemical etching prior to depositing the desired coating material.

Although the method of the present invention can be applied to a fairly wide range of applications, it is especially suitable for use in shielding electromagnetic heads, M-R heads, shielding for other purposes, etc.
chott glass, 5in2. Si, Ti or Cr
It is effective for forming a laminated permalloy structure.

In this case, a copper plating bath can be used to form the electroplated structures into fairly fine strips, as shown in FIGS. 2A-2I.

In this case, ammonium persulfate was used to remove Fe.

Although the Cu may be selectively etched in the presence of NiFe, NiFeCr, NiFePd, etc., the final layer is a 5chott glass that serves as an additional protective layer for the desired structure.

Optionally, forming the desired structure in such a way that the edges of the desired structure are beveled (tapered) facilitates isolation of the connecting leads of the overlay structure during subsequent manufacturing steps. be able to.

This is distantly related to the use of sputter deposition methods rather than methods of depositing relatively thick layers while agitating the sample in an appropriate manner.

Permalloy laminate i.e. permalloy/shot glass/
A dry process is used to form an inorganic structure made of permalloy.
Another reference example using the process is shown in FIGS. 2A to 2-2.

As shown in FIG. 2A, a metallized thin film 1 on a glass substrate 10
1, a layer 12 of 5hipley resist is formed which is about 1 micron thicker than the desired thickness of the permalloy and glass laminate.

As shown in FIG. 2B, the resist is exposed and developed to form a thick resist 12 of preferably 4 to 6 μm.
．． A wide opening 24 of 2 to 0.4 μm is formed.

An electroplated metal layer 25 is then formed in the opening 24, as shown in FIG. 2C.

The metal selected must be one that can be readily etched selectively in the presence of permalloy.

Copper satisfies this condition and can be etched using ammonium persulfate (high pH 7 to 9) in which Ni--Fe does not dissolve.

Other metals such as Cr, Zn, Cd and Sn are also suitable for plating.

The metal is plated to a thickness of about 3 to 7 microns to form a mushroom-shaped cross-sectional mask material 25, preferably with an overhang of 0.25 to 3 microns.

The resist is then removed using a solvent (acetone in the case of Shipley) to form a structure as shown in Figure 2D.

Next, as shown in FIG. 2E, a permalloy layer 19, a shot glass layer 29, and a permalloy layer 39 are deposited over the mask material 25 and the exposed surface 11 to a total thickness of 2 to 3 cm.
Form it so that it becomes μ.

To prevent corrosion of the permalloy layer 39, a protective layer of shot glass (not shown) is preferably formed over the layer 39.

Permalloy and 5iFe and W, Cr, Pd or Mo
An alloy with etc. may also be used.

The sandwich-like laminate may be constructed as shown in Table 1.

As a modified example, 5endust (Si9.6 in weight ratio)
%Fes 5%, A15.41%) may be sputter deposited with or without lamination.

FIG. 2F then shows the structure resulting from lifting off the permalloy sandwich structure on the masking material from the substrate by etching away the masking material 25. FIG.

If the mask materials are made from copper, these mask materials are etched as described above.

When the mask material is made of Zn, ammonium sulfite is used as the etching liquid (pH 7 to 9).

In addition, when the mask material is made of Cr, Z is used as the etching liquid.
Use n-doped AlCl3 or other suitable Cr etchant.

In order to protect the permalloy sand inch structure that constitutes the yoke of the head, an opening 40 is provided as shown in Fig. 2G.
and 42 and a layer 20' of 5hipley resist is formed over the strips 41 between these openings.

Undesired portions 43 and 44 are then etched away using FeCl3 and HF separately or a mixture of HF and FeCl3 to form a structure as shown in FIG. 2H.

Next, the resist is removed to form a desired yoke structure having a desired pattern as shown in FIG.

In this case, there is no need to remove the dummy structure since it is not present or remains intact without damaging the desired structure.

3A-3C, various methods can be used to illuminate the positive resist 12 through the mask 53 to form a pattern of openings 50 having sloped sidewalls as shown in FIG. 3A. Techniques can be used.

Resist that can be used is 5hipley photor
esist, KTFR and PMMA (polymeth
ylmethacrate).

FIG. 3A shows a representative example of multiple processing steps from exposure to development.

When PMMA is used as a resist, a pattern as shown in FIG. 3A can be formed by weakening the electron beam irradiation, lengthening the development time, and/or increasing the concentration of the developer.

Next, as shown in FIG. 3B, metal is attached to form the mask material 2.
form 5.

Next, after removing the resist 12, a metal 19 is vacuum-deposited as shown in FIG. 3C.

Although not shown, the mask material 25 is
etching away.

When the electron beam resist is a negative resist, such an inclined edge pattern can be formed by adjusting the electron beam intensity and development time.

When PMMA and PMMA copolymer are used as resists, by appropriately changing the intensity of the electron beam and developing appropriately, a pattern of openings having sloped sidewalls as shown in FIG. 4A can be formed.

As is clear from FIGS. 3B, 3C, 4B, and 4C, both of the above methods require the use of suitable patterns (e.g., openings) used to form the inorganic material hot mask used for lift-off. 50 or 60).

In the case of a 5hipley resist or other positive resist, the sloped sidewalls as shown in FIG. 3A are formed according to the following section.

That is, (1) blur the focus or shift the aim of the ultraviolet light.

(2) Remove the mask that is in close contact with the resist.

(3) Use a fairly thick resist, ie, about 2 microns or more even if the light beam is not defocused or misaimed and if there is good contact between the mask and the resist.

(4) Use a dispersed (unaimed) light source.

(5) Use any one method of (i) + (2) and/or (3) and (4) above, or a combination thereof.

When using KTFR, KOR (resists manufactured by Eastman Kodak) and other negative resists, the methods shown in FIGS. Slanted side walls as shown in FIGS. 3C, 4B, and 4C are formed.

As shown in FIGS. 3A to 3C and 4A to 4C, after forming a resist pattern having such inclined edges, electroplating, electroless plating, vapor deposition, sputtering, etc. Fill the openings in the resist using a suitable deposition method such as.

The metal 25 or dielectric is deposited to a thickness equal to about 2/3 of the desired final deposited layer formed by lift-off or within about 0.25 microns from the top surface of the final deposited layer.

As shown in FIGS. 3B and 4B, the metal or dielectric material such as Cu, Zn, A1, etc. is formed into an inverted trapezoidal shape.

Because of the sloped sidewalls, there is no need to continue electrodepositing the metal or dielectric 25 until the mushroom shape is formed on the resist.

To achieve lift-off, depending on the shape of the inverted trapezoidal apertures 50 or 60, they may or may not be formed in a mushroom-shaped pattern.

After removing the resist, a desired metal layer, dielectric-magnetic stack, or dielectric layer is deposited using vapor deposition, ion gun plating, and/or sputtering.

The lift-off process is performed as shown in FIGS. 2E-2-2 or FIGS. 1D-1G.

It is necessary to select an inorganic lift-off material that can be selectively dissolved, corroded or etched without corroding the desired final pattern formed by the high temperature lift-off process.

In the method of the embodiment of the present invention shown in FIGS. 5A to 5E, first, S h i p l e y, KTFR, P
MMA.

exposing and developing a resist 12 such as PMMA copolymer or any other thermally deformable polymer;
Next, a desired pattern is formed by etching using a reactive plasma etching method, a chemical etching method, or the like.

The structure is then heated to a temperature high enough so that the resist 12 flows (deforms due to surface tension) to form the shape shown in FIG. 5B.

In the case of Sh i p I ey resists, this is
The structure can be rapidly heated to about 1.50-160'C and then cooled, or gradually heated to about 100-130'C and then slowly cooled (for a period of time that still allows the 5hiply resist to be easily removed). temperature production factor).

The Sh i p I ey resist is exposed to ultraviolet light and then developed using a conventional 5hipley resist developer or the resist is removed using a conventional etchant such as acetone.

It will be appreciated that the desired shape may be formed by heating the resist, which is useful for forming even slight overhangs on sloped sidewalls or masks of inorganic materials.

The subsequent processing steps are substantially the same as those described above in connection with FIGS. 1B-1G or 2C-2-2.

A circular etch or beveled edge may be formed by simply exposing the organic resist using reactive plasma etching or sputter etching.

As shown in FIG. 5C, the lift-off structure 25
As in the case of FIG. There is no need to do this, and it is sufficient to plate to a thickness that is equal to or less than the thickness of the resist 12.

A layer of patterned material 19 is deposited on the metal layer 11 to leave a gap between the exposed sidewalls of the lift-off structure 25 after the layer of resist 12 is removed, as shown in FIG. 5E. It is deposited substantially thinner than the thickness of the layer of resist 12.

Next, in the method of the reference example shown in FIGS. 6A to 6D,
Two resists with different sensitivities are used.

The high-sensitivity resist 70 on the top surface is a positive resist, and the resist 12 below it is a negative resist.

The lower resist layer 12 is formed approximately 25 mm thicker than the thickness of the material to be formed by lift-off.

After exposure to ultraviolet light, electron beams, or X-rays and development, a structure as shown in FIG. 6B is formed.

Next, the 6th C is applied using an electrodeposition method or an electroless deposition method.
A mask of inorganic material is formed with the desired overhang as shown in the figure.

After removing the resists 12 and 70, the subsequent steps of depositing the desired coating material 19 as shown in FIG. 6D are substantially the same as those described above.

As a variant, a highly sensitive resist may be used as the lower negative resist layer 12.

[Brief explanation of the drawing]

Figures 1A to 1G are diagrams showing a first process of forming a thin film by the lift-off method of the reference example using an overhang formed by plating to a depth considerably greater than the thickness of the resist, and Figures 2A to 21. Figures 3A-3C illustrate a second process in the reference column similar to the process of Figures 1A-1G, and Figures 3A-3C depict a reference process for forming an overhang in the lift-off material by forming a tapered opening in the resist. Figures illustrating the third example process, Figures 4A to 4
Figure C is a diagram showing the third reference example process of forming an overhang in the lift-off material by forming a tapered opening in the resist, and Figures 5A to 5E are similar to Figures 3A, 4A, and 5A. Figures 6A-6D illustrate a process according to the present invention for forming large overhangs by heating the resist in the form used and curving the edges of the resist; Figures 6A-6D are references for forming overhangs using two resists; FIG. 2 is a diagram illustrating an example process. 10...Substrate, 12...Resist layer,
14゜15...Opening, 16.17...
Lift-off mask material, 1 B-----"Overhang edge, 19... Desired coating material, 2
0...Side wall.

Claims (1)

[Claims] 1. Applying a thermally deformable resist on a metallic substrate, exposing the resist to light to form a pattern of openings with tapered sidewalls in the opposite form of overhangs, and heating the resist to shape the edges of the openings. The process of giving roundness to
a step of plating a metallic lift-off forming material to a thickness less than the thickness of the resist to form an overhang-shaped lift-off structure that is thicker at the top than the bottom of the opening; a resist portion without the lift-off structure; a step of vacuum-depositing a coating material on the thus formed structure to a thickness equal to or greater than the thickness of the resist 1-, and a step of removing the lift-off material with an etching agent. How to form structures.