JPS62213266A - Pattern formation - Google Patents

Abstract

PURPOSE:To remove completely adhering unnecessary films without reducing the thicknesses of deposited films by a method wherein a protective film against etching is deposited by an evaporation method with high orientation on the deposited films which are not to be etched before the unnecessary films on side walls are removed and then the unnecessary films are etched. CONSTITUTION:A stencil 32 which has overhangs at its shoulder parts is formed on a substrate 31 and then an Nb layer 33(1), an Al2O3 layer 33(2) and an Nb layer 33(3) are formed on the substrate 31. Unnecessary films 34 formed on both of the side walls of the stencil 32 are shown in the figure. Then, an Nb/Al2O3/Nb layer can be formed on the substrate 31 by removing the films deposited on the stencil and an Si protective film formed on the Nb layer 33. The Nb/Al2O3/Nb laminated films 33(1)-(3) are formed by magnetron sputtering and the Si protective film 36 is formed by electron beam evaporation. The unnecessary films 34 which adhere to the side walls are completely removed by etching the whole substrate by BGl3+CCl4 of 15 Pa for 2 minutes in a parallel plate type reactive ion etching apparatus. With this constitution, the unnecessary films adhering to the side walls can be removed completely without damaging deposited films so that the yield of multilayer interconnection can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming patterns for multi-hesitant interconnections in the manufacture of semiconductors such as superconducting elements with high yield.

(Prior art and problems to be solved by the invention) Conventionally,
In pattern formation using the lift-off method, an overhang structure 2a is formed on the stencil 2 as shown in FIG. 3, and a directional strong, the desired 114 in the iai method (3 indicates the NI! direction)
methods have been used to deposit Since the non-T1 film adhering to the sidewalls of the fibers formed by such a method is not very thick, it can be easily removed by unnecessary film removal methods such as ultra-fine treatment. However, highly directional vapor deposition methods cannot be applied to all materials;
In the case of a film formed by reacting during film formation, such as a superconducting material such as Nb or a Nb compound or a nitride, which generates a loud noise and easily incorporates impurities in the atmosphere into the film, sputtering is suitable for film formation. By the way, it is well known that in film formation by sputtering, the material particles that fly onto the substrate on which the film is to be deposited are extremely random. Therefore, even if an overhang structure is formed on the stencil, the irregular film always adheres thickly to the wall of the stencil, and it is difficult to completely remove it even with ultrahigh wave treatment technology.

In FIG. 4, (a) shows a state in which a first wiring 1m21 is formed on a substrate (not shown) using the stencil 2 as a mask. In this case, since an overhang 2a is formed around the shoulder of the stencil 2, the stencil 2
An unnecessary portion 1121' is formed on the side wall of. However, for bonds with lift-off stencils, unnecessary 1 is shown in (b) figure.
A portion 121' remains as a burr 22. Next, the first arrangement 1
The state in which the absolute #R1123 is formed on the aM21 is shown in Figure (c). On this insulating film 23, a second wiring @f1424
The state in which it has been formed is shown in Figure (d). However, Bali 2
2, the first wiring 1121 and the second wiring [11124
will be short-circuited. (e) The figure shows an ideal case in which Paris does not occur.

Figure 5 shows the case where nine through holes are formed in the gap between the upper and lower wiring layers, and the through holes are filled with a conductive material to connect both wiring layers. K
Figure (A) shows the state in which the stencil 2 is formed on A@25. Next, a state in which an interlayer insulating film for forming through holes is formed on the third wiring gap 25 is shown in FIG. The state in which the stencil 2 is then lifted off is shown in FIG.

The state in which the fourth wiring gap 28 is then formed is shown in FIG. In the mouth-like state, Paris 27 is interposed in the through hole.
Because of this, both wirings [11125 and 28 are isolated and cannot be electrically connected. (e) The figure shows an ideal state.

If a mouth-like irregularity remains on the pattern like this, the height of the unnecessary 1122 is equal to the height of the stencil and usually reaches several hundred 0-1μ-, so in the case of Fig. 4! IIIJ insulation becomes incomplete and shows 1~ between the wires occur, and in the case of Figure 5, 1! The power line connection is not made. Conventionally, when lifting off a layer deposited by sputtering, the deposited film is etched before lift-off to completely remove the unnecessary film adhering to the sidewalls, or the unnecessary film adhering to the sidewalls is either completely removed or Methods have been used to facilitate removal by sonication. However, when the thickness of the deposited film exceeds 1100n, the sidewalls are exposed to f1.
The thickness of II also increases, and the thickness of the deposited film decreases while etching the unnecessary film. In order to compensate for this decrease in the deposited film thickness, attempts have been made to reduce the thickness of the deposited film in advance by etching it to make it thicker. There was a limit to the increase in film thickness because the stencil itself could not withstand the stress of training and would peel off.

As explained above, the #I layered film using the sputtering method can be removed by conventional methods using only ultrasonic waves or by etching.
In the method of removing 1Q, unnecessary films on the side walls of the stencil cannot be completely removed, and therefore, there is a large amount of unavoidable reduction in yield due to short circuits and disconnections between wiring lines.

(Means for Solving the Problems) The present invention has been proposed in order to improve the above-mentioned problems, and provides a method for completely removing unnecessary films attached to side walls without reducing the thickness of the deposited film. The purpose is to provide mouths.

To achieve the above object, the present invention comprises the steps of pre-forming a stencil on a substrate, depositing a first layer of a desired material on said substrate, and after depositing said film.
Deposit and preserve highly condensable and etching-removable materials using a well-directed evaporation method before lift-off:
! A step of forming a film, and using the above-mentioned protective film as a mask,
The gist of the invention is a pattern forming method characterized by comprising a step of removing an unnecessary film adhering to the side wall of the stencil when forming the first film, and then a step of performing lift-off. It is.

The feature of the present invention is that, prior to removing the unnecessary film on the sidewall, the deposited film, which should not be etched, is protected against etching using a vaporization method with good directionality.Then, the unnecessary film is etched. There is a particular thing.

In this case, the protective fall does not necessarily have to be resistant to etching to remove the unnecessary film, but only needs to be thick enough to not disappear until the unnecessary film on the side wall is etched. In addition, the material used for the protective film may be the same as or different from the deposited film.
Must be completely removed before turning off. According to the present invention, unlike the conventional technology, unnecessary films on the sidewalls can be completely removed without damaging the a-film, so the yield of multi-threshold wiring can be improved.

Next, the present invention will be explained in detail. It should be noted that the embodiments are merely illustrative, and it goes without saying that various changes and improvements may be made without departing from the spirit of the present invention.

[Example 1] FIG. 1 shows a first embodiment of the invention.

(A) In the figure, a stencil 32 with an overhang on the shoulder is formed on a substrate 31, and then Nb 33 (1), Al10333 (21, Nbl1!33 (21), Nbl1!33 (
3) Form.

34 indicates a hole 11134 formed on both side walls of the stencil 32 in this case. Next, a state in which a 3i bond:1!1136 during etching is formed on the above-mentioned integrated layer is shown.

(B) The figure shows the state in which the unnecessary film attached to the side wall has been lifted off by etching. Next, by removing the film deposited on the stencil 32 and the S1 protective film on Nbl1!3, Nil/AI and 03'NbFR are deposited on the male plate 31.
A mouth can be formed.

At this C, Nb, 'AI□03. 'Nb laminated film 33 (1),
+21. (3) was deposited by the IIc magnetron sputtering method, and the Si protective film 3G was deposited by the electron beam vaporization method. Nh
,,'AI□03. 'The thickness of the Nb deposited film is 400no+
At the time, the informal film thickness 34 of the − sidewall was 150 ni. In this case, the Si protective film thickness 3G was set to 200+V, and the etching process was performed at 15 Pa in a parallel plate type reactive ion etching (former) apparatus.
After etching with Icl3+CH4 for 2 minutes, the unnecessary $34 adhering to the side wall was completely removed, and the necessary Nb/Al2O3/Nb film was not etched as it was protected by Si. This 11(i) remaining Si layer is removed and lifted off using the reactive ion etching method (formerly [) of 6[4], a superconducting tunnel junction is formed, and the 1iil unnecessary film is removed only by ultrasonic processing. When removed, (iii) the characteristics were compared with those of tunnel junctions formed by etching without 3i protection II, and as a result, the junctions formed by the method of the present invention did not have one short circuit out of 100 junctions measured.
The leakage 7Ii current was also small, whereas when only ultrasonic waves were used, 20 out of 100 connections were shorted, and Si
When etched without a protective film, 12 out of 100 connections were achieved.
While the junctions were short-circuited, an increase in leakage current was observed in most of the junctions. This is because the necessary Nb is removed when removing unnecessary films.
, 'AI□03 /Nb product IIm! This is because the upper Nb film was etched at the same time, making the film too thick. To reduce this film thickness, the upper Nb is set to 40001, and the total i! When Fj was set to 6000 ■, the stencil peeled off from the substrate and patterning could not be performed. In this way, the method of the present invention achieves a good yield without causing insulation defects.
A Nb/^1□03z'Nb junction was formed.

[Example 2] FIG. 2 shows a second embodiment of the invention.

(a) In the figure, Nb wiring @42 is formed in advance on the root of Sio241. Next, a resist stainless steel 43 is formed on the wiring layer 42 to form a through hole having an overhang at the shoulder portion, and then a 5i02 deposit 44 is formed. In this case, burrs 45 are formed on the side walls of the stencil 43. Next, from etching when removing the burr 45 from the mouth, S! This shows the state in which Pd47 is deposited to protect 02II. (B) The figure shows a state in which the burr 45 attached to the side wall of the stencil 43 has been removed by etching. Next, SiO □ discipline 44. on the stencil 43. P
d1147 and I'd film 47 on threshold interval 1i11144
By removing this, interlayer insulation (2) having through holes is formed. (c) The figure shows this state. Note that ① an upper wiring [48] is formed on the insulation @44. This condition is shown in cause (d).

In order to investigate the yield of 5i02 contact 1 ~ hole formed by lift-off method (Sin 2 @ thickness 300 nl) of contact 1 ~ of upper Nb wiring and lower Nb wiring with GL thickness of 400 nm (+vt Pd retention!! film according to the present invention). 02F of 151'a using reactive ion etching method (
RIE) to remove unnecessary film and then pickle to remove Pd and perform lift-off, (V) lift-off using only ultrasound (vi) Preservation: 1! As a result of comparing the case of etching without a film, the method (iv) of the present invention had a yield of 100%, but the conventional method (v) had a yield of 95%, and the yield was lowered to 95%. A decrease in superconducting critical current was observed even when This is because the upper Nb electrode was cut off by the unnecessary film or became very loose. Also, in (vi) the yield is 10
096, but a decrease in breakdown voltage between both voltages was observed. According to the method of the present invention, the spatter 5i0
When through-holes are formed by lifting off 2, contacts can be formed with a high yield. In Example 2, Pd
When Au is used instead of , and it is removed by Ar sputter etching instead of acid cleaning after the role as a YL film is completed,
A similar effect was obtained when SiO was used instead of Pd and removed by reactive etching with C[4-based gas.

(Effects of the Invention) As explained above, according to the method of the present invention, it is possible to completely remove the non-Al film attached to the sidewall of the stencil and lift-off, so that it is possible to completely remove the non-Al film attached to the side wall of the stencil. It has the advantage of eliminating short-circuits and wire breaks, and can form multi-wiring structures and contacts, such as superconducting tunnel junctions, with high yield.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment of the method of the present invention, FIG. 2 shows a second embodiment of the same, and FIGS. 3, 4, and 5 show a conventional method. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Stencil having A-bar hang structure, 3... Vapor deposition particles, 4... Film to be deposited, 21... First wiring ■, 22 ...lI
23...Gap insulating film, 24...Second wiring-125...Third wiring line, 26...Through A discontinuous It film for hole formation, 21... an unnecessary film of an insulating film, 28... a fourth wiring III, 31... a substrate, 32... having an overhang shape Stencil, 33...Nb/At
20:, ,'Nb1i, 34-・-ste>shiL@M
D attached unnecessary film, 35... unnecessary film, 36...
Si protection'':!!Film, 41...5i (12 substrates, 42
...Nb wiring@, 43...Resist stencil, 44...5i (l□deposition layer, 45...Unnecessary film attached to side wall, 41...Pd protective film, 48...
・Upper Nb1S [! Line Figure 1 (A) (B) Car°-s- Section Figure 2 (A) (B) Figure 3

Claims (2)

[Claims] (1) forming a stencil on a substrate in advance; depositing a first film of a desired material on the substrate; and after depositing the film and before lift-off, the film has a strong condensation property;
and forming a protective film by depositing a material that can be removed by etching using a well-directed evaporation method; A pattern forming method comprising the steps of removing an unnecessary film attached to the substrate, and then performing lift-off. (2) Claim 1, characterized in that any one of Si, Au, Pd, and SiO is used as the material for the protective film.
Pattern formation method described in section.