JPS5874041A - Etchant for polyimide resin - Google Patents

Abstract

PURPOSE:To stably and reliably form a micro-miniature through hole which is required for multi-layer wirings of LSI, by using the alcohol liquid of methylammonium tetrahydride as an etchant. CONSTITUTION:An etchant consisting of the alcohol liquid of methylammonium tetra hydride is used for the etching of polyimide resin. In this case, the preferable concentration of alcohol liquid of methylammonium tetra hydride should be in the range 5-35wt% from the point of view of etching capability for the polyimide resin film and solubility of etchant. It is also preferable that this etchant is used for a polyimide resin film having imidation ratio of 5-90%. When the polyimide resin film 2 formed over the substrate 1 is etched with this etchant using the photo resist, while the etching is carried out in the shape having almost linear inclination and a swelling region cannot be recognized at all. This shape is desirable for formation of wiring conductor of the second layer.

Description

[Detailed description of the invention] The present invention relates to an etching solution for polyimide resins.

In recent years, semiconductor parts made of polyimide resin with excellent insulation properties and heat resistance, especially wiring board insulation films in semiconductor integrated circuits, and monolithic L8I protection! Its use in I films, multilayer wiring insulating films, etc. is increasing. Among these, when a polyimide resin film is used as an interlayer insulating film for multilayer wiring on an FM board or on a monolithic LaI board, fine etching processing is required in order to improve the degree of integration.

Conventionally, as a method for etching a polyimide resin film, polyamic acid, which is a precursor of the polyimide resin film, is baked at a temperature of 200° C. or higher, and etching is performed in a state where the imidization rate is 90 or higher. A method is used in which the material is baked at a temperature of about 130 DEG C. and then etched in a state where it is imidized to about 5 to 101.

As one of the etching methods for polyimide resin films, a film of polyamic acid, which is its precursor, is formed, and a positive type photoresist is used in nine steps. A method of etching the film is known. This method is described in, for example, Japanese Patent Publication No. J1147-12609.

In this method, first, polyamide a is prepared using N-methyl-2-bits IJ ton, dimethylacetamide, etc. as a solvent.
The solution was applied to the substrate, and then dried at 82° C. for 3 minutes to form a polyamic acid film. As a positive type photoresist, for example, 5hipley's A213
00 was applied, dried at 82° C. for 15 minutes, and exposed using a photomask. The gL image solution of AZ1300 is alkaline and has the ability to dissolve polyamic acid as well, so when it is immersed in the #4 solution of AZ1300, the exposed portion of Person 21300 dissolves and at the same time the polyamic acid also dissolves.

The procedure is then to dissolve only AZ1300 by immersing it in acetone.

In this method, boriadic acid is heated at a temperature of no more than 82°C.

Moreover, solvents with high boiling points such as N-methyl-2-pyrrolidone, which has a boiling point of 202°C and dimethylacetamide, which has a boiling point of 167°C, are not completely evaporated. Further, the etched shape is unstable, the reproducibility is poor, and the size that can be practically processed is several tens of μm or more.

Furthermore, as a method for etching a polyimide resin film, there is also a method using a concentrated aqueous solution of quaternary ammonium hydroxide, or a method using Ohto solution, in which an aqueous solution of quaternary ammonium hydroxide is mixed in a non-aqueous solvent. ing. Tetramethylammonium hydroxide as quaternary ammonium hydroxide,
Examples include sodium 2-ethylammonium hydroxide, butylammonium hydroxide, and examples of non-aqueous solvents include dimethysulfoxide, sulfolane, dimethylformamide, and pyridine. In the etching using the above two methods, polyamic acid, polyimide iso, indoroquinazolinedione (polyimide is
ndroqu inago I 1ned 1one.

Hereinafter referred to as PIQ. It is possible to etch a prepolymer film (PIQ is a trademark of Hitachi Chemical Co., Ltd.) that has been betatized at a temperature of 200"C and is imidized, but the imidized film swells during etching. 1
The figure shows the results of investigating the change in film thickness of a polyimide resin film when polyamic acid or PIQ prepolymer OjI was baked at a temperature of 200°C to imidize, photoresist escape was performed using a 9-shaped resin, and the film was immersed in an etching solution. It is something. Curve a shows the case where an aqueous solution of 10% by weight of tetramethylammonium hydroxide was concentrated to about 30% by weight and a 9% solution was used as the etching solution. The curve 9 shows the case in which a solution # was used as an etching solution, which was prepared by mixing an approximately 30% aqueous solution of sodium dimethylammonium hydroxide (the same as above) in a sulfone solution at a ratio of 50 volumes.

In the case where a concentrated aqueous solution of tetramethylammonium hydroxide is applied to the etching solution, the polyimide resin film swells as the etching solution penetrates, as shown in curve a, and the film thickness increases by approximately 20 -. . In the case where a concentrated solution of tetramethylammonium hydroxide is mixed with sulfolane and the solution is used as an etching solution, the swelling will not be large and the film thickness will increase to about aOS. is also suitable.

When the cross-sectional shape of this IIIIIIL9 section is observed, it has a shape as shown in FIG. 2(a). That is, after etching the polyimide resin film 2 formed on the substrate 1 using a photoresist as a mask, the photoresist was removed and the cross section was polished and observed. A raised portion 3 at the periphery of the pattern caused by swelling can be clearly seen. This rise is caused by, for example, multi-layer wiring.

This has the disadvantage that it not only hinders the formation of the second layer wiring conductor, but also reduces the stability and reliability in subsequent steps, such as a decrease in heat resistance.

On the other hand, if a prepolymer of polyamic acid or PIQ is baked at a temperature of 200°C or less9, e.g. 130-150°C, the etching rate is too high;
Since etching is completed in 0 to 20 seconds, it is difficult to manage the etching time, and the etching accuracy and reproducibility are also poor.

Ethylenediamine and diethylenetriamine are also used as an etching method for polyimide resin films.

A method using triethyltetramine and the like is also known.

However, even if any of the above is used as an etching solution, if a polyimide resin film cured at a temperature of 180°C or higher is etched using a polyamic acid or PIQ prepolymer, the polyimide resin film will only swell after being immersed in the etching solution and will not be etched. temperature below 180°C.

For example, when a nine-bolyide resin film is cured at 100 to 130° C. and etched, the etched shape is poor, the reproducibility is poor, and the above-mentioned etching solution is highly toxic.

Further, as a method for etching a polyimide resin film, there is a method of using a mixed slag of hydrazine or hydrazine and a boriaone compound such as ethylenediamine or diethylenetriamine.

Ff this etching liquid! In the case of 1 or 9, it is possible to bake the polyamic acid or PIQ prepolymer at a temperature of 200°C or higher to imidize it and etch it even in good condition, but the side etch is thick and the through-hole design value differs from the actual etching value. Due to the difference in the opening dimensions of the
Poor etching stability in mΩ. All below 200℃
Beta with tL and etching with imidized material.

The etching ability of the above etching solution is very high.
Since the etching time is short, the width of the appropriate etching time is extremely narrow, making it difficult to bury the etching. Further, the reproducibility and stability of etching are poor, and the size that can be practically processed is several tens of μm or more. 9 and Drazin are soul 4 wheels 11
11. Ginseng is highly toxic.

It is an object of the present invention to provide an etching solution that can be formed stably and reliably over the conventional etching solution.

The present invention relates to an etching solution for polyimide resins comprising an alcoholic solution of tetramethylammonium hydroxide.

The polyimide resin to which the present invention can be applied will be explained.

'-Repeating unit represented by the general formula (where R1 is a tetravalent group having an aromatic ring, - is a divalent group having an aromatic ring)
A polyimide resin having the following properties is used. This is a polymer synthesized from an aromatic diamine and an aromatic acid dianhydride.
Manufactured using Lenise (manufactured by Toshisha). More details are described in US Lil' Patent No. 11 & 17@634.

PIQ represented by the general formula % (in which Ar1, Arl, Arc and Ar4 represent aromatic residues, Y represents SO, and t+ represents CO) is also used.

This is shown by the general formula (in the formula, Ar represents an aromatic residue, Y represents 80., and 9 represents CO; one amino group and the Y-Nl circle group are located at ortho positions to each other). υ can be produced by reacting a diaminoamide compound with a diamine and a tetracarboxylic dianhydride to produce a polyamide lid intermediate, and then dehydrating and drifting the intermediate.

For example, general formula It is a highly heat-resistant polymer having a trivalent group).

^ For more information on PIQ, please refer to the Special Publication Publication No. 48-285
This is stated in Publication No. 6. This etching solution can also be applied to etching polyamide-imide, polyester-imide, and other polyamide-based resin films having imide groups.

The etching solution of the present invention is polyamic acid or PIQ.
It is preferable to bake the prepolymer at a temperature of 130 to 200° C. and use it for a polyimide resin film having an imidization rate of 5 to 90 −.

Imidization rate and Hiro are complete! The imide group of the imidized polyimide resin film on the silkworm (for example, 1775 (1'jll)
, or 1375aI-”) as the reference KL,
The initial value is 0, which is the logarithm of the imide group absorption intensity of the polyamic acid precursor or the PIQ prepolymer itself divided by the above-mentioned standard imide group absorption intensity. The imide group absorption intensity is divided by the standard imide group absorption and the 9-logarithm value is taken as the indization rate of the polyimide resin film at the heat treatment temperature.

Etching ability for polyimide resin films.

From the viewpoint of the solubility of the etching solution, the concentration of the alcohol solution of sodium dimethylammonium hydroxide is preferably 5 to 35% by weight.

Examples of alcohol solutions of tetramethylammonium hydroxide include methanol solutions and ethanol solutions.

Etching is carried out by patterning a resist layer with openings on the surface of a polyimide resin heat-treated at 130 to 200°C, for example, using a method similar to that used for ordinary photolithography. It can be removed by immersing it in an etching solution or by spraying it with a shower of etching solution. After etching the polyimide resin in the openings of the resist layer, the resist layer is removed.

We investigated the change in film thickness of the polyimide resin film when etching was performed using a 20% methanol solution of tetramethylammonium hydroxide, which is a typical etching solution of the present invention.The results are shown in curve C in Figure 1. show. The etching conditions at this time are that a film of polyamic acid or PIQ prepolymer is baked at a temperature of 150°C, imidized, subjected to photoresist treatment in good condition, and immersed in an etching solution at 25°C. - Line C shows an increase in the thickness of the two-curve mid-based resin film (
There is no swelling. fact.

Observing the cross section of a polyimide resin film etched with 20 weight of tetramethylammonicum hydroxide and 1 solution of methanol, as shown in Figure 2 (bl), it was etched in a round shape with an almost straight slope. Moreover, the swelling region seen in the etching solution of a concentrated solution of sodium dimethylammonium hydroxide alone is not observed at all.

Such a shape is very suitable for the formation of the second layer wiring conductor 1. For example, it can be said that accidents such as disconnection at the step of the conductor do not occur at all.

Next, the etching solution of the present invention will be described from the viewpoint of etching stability. Figure 3 (11) shows the relationship between etching time and finished dimensions of etched through holes.
b) shows the finished dimensions of the etched through-holes relative to the design values of the through-hole dimensions. Here, the through-hole finishing dimension refers to the opening dimension of the resin film.

The composition of the etching solution, the imidization temperature, and the etching temperature of the lines c, d, and e shown in FIG. 4 are as follows.

Imide temperature: 50℃, etching temperature: 4o℃d Hydrazine hydrogen hydride 80 - aqueous solution imide temperature: 00
℃, etching temperature 25℃, 10 weight of tetramethylammonium hydroxide - aqueous solution imidization temperature 150℃, etching temperature 40℃ When etching a polyimide resin film with hydrazine, if the photoresist film is thin, the hydrazine may damage the photoresist film. Because the etching is done by going all the way to the bottom, the side etch becomes large, and the etched through hole expands quickly, resulting in areas where there are both large and small through holes. When etching large through-holes, there is a difference between the through-hole design value and the actual finished size after etching, as shown in Figure 4(b). Stability is poor.

Before, sodium 2 methyl ammonium hydroxide:: 10 weight - aqueous solution alone /d,, s''22 te 2g capacity 1
After treatment at 50°C and idization, the through-holes expand at a high speed as shown in Figure 4(a)K for the polyimide resin film, but as shown in Figure 4(b), the through-holes expand rapidly. There is a large difference between the hole design value and the actual finished through-hole dimension, and etching stability is poor, making microfabrication difficult.

On the other hand, in the case of a methanol solution of tetramethylammonium hydroxide, which is an etching solution according to an embodiment of the present invention, the through-holes expand at a high speed as shown in FIG. 4 (al). ), the relationship between the through-hole dimension design values and the through-hole finished dimensions is extremely good. This shows that even if large through holes and small through holes coexist, it is possible to form through holes that are uniform compared to the design value.

Furthermore, it is possible to etch fine through holes as small as 3 μm. Because the through hole has a large expansion speed,
Since the etching time is short, it is suitable for mass production.

Also, for fine processing = 1. ,,F Important etching factor (FIC) is 1.3~1.4 and 1.0~1.2°0 respectively for etching liquids C and Le.
．． It becomes 85-1.0. The etching factor is determined by the thickness d of the film to be etched and the width W of the slope, as shown in Figure 4.
It is expressed as against. Therefore, the larger the etching 7 actor is, the more the slope of the slope becomes perpendicular to the substrate, and the design value of the wiring width when forming the subsequent two-layer wiring can be made smaller, making microfabrication easier. becomes. In this respect, a methanol solution of tetramethylammonium hydroxide is superior to other etching solutions.

The etching effect of an alcoholic solution of dimethylammonium hydroxide on a polyimide resin film is determined by the etching effect of an alcoholic solution of dimethylammonium hydroxide when imidizing boria-containing acid, PIQ prepolymer, etc. It varies depending on the temperature of the etching solution, the temperature of the etching solution, etc. First, regarding the temperature at which the oxidizing process is performed, it is preferable to carry out the process at a temperature of 130 to 200 DEG C. in view of the etching rate, the etching stability of through holes, and the like. Further, the temperature of the etching solution is preferably 25 to 30 DEG C. from the viewpoint of etching speed and stability of the etching solution.

The photoresist that can be used as an etching mask is preferably a cyclized rubber negative type photoresist, such as KMER or KTFR manufactured by Kodak.

OMR manufactured by Tokyo Ohka Kogyo Co., Ltd. or the like is used.

After finishing the etching, the photoresist is processed by a manufacturer, for example, an industrial chemical laboratory (Industry Chemical Laboratory).
It can be removed using a removal agent such as J-loo manufactured by -Ri-chem-Laboratory). J
When using J-100, the polyimide resin film baked at a temperature of 200° C. or lower may not be completely imidized and may be rounded, and the polyimide resin film may be slightly damaged in J-100. Therefore, after etching of the polyimide resin film is completed, it is necessary to bake the polyimide resin film at a temperature of 200 to 220° C. before removing the photoresist. The photoresist is removed, and then a second
At least 250% of
It is preferable to re-bake the polyimide resin film at a temperature of 0.degree. C. or higher to completely imidize it. It should be noted that during this re-baking, the through-hole pattern formed using the etching solution of the present invention suffers from deformation or deformation, whereas there is almost no development.

The through-hole pattern formed by etching with an active solution of positive photoresist, a concentrated solution of aqueous tetramethylammonium hydroxide, or hydrazine has the disadvantage that its shape is significantly distorted and distorted. this is,
The swollen region penetrated by the etching solution is rounded and is thermally unstable.

Next, the present invention will be specifically explained with reference to Examples.

Example 1 The following prepolymer solutions of polyamic acid and PIQ were prepared.

Le Pyre-ML, RC-5057 DuPont (
Prepolymer of B manufactured by DuPont), Lenise C manufactured by Toshi Co., and PIQ The prepolymer of PIQ manufactured by Hitachi Chemical Co., Ltd. was obtained as follows.

9100 equipped with temperature needle, stirrer and calcium chloride tube
4,4'-diaminodiphenyl ether-3-carbonamide 2.43), 44'-
Diaminodiphenyl ether λOf and N-methyl-
Add 60 co of 2-pyrrolidone.

Stir well. In this, biromellitic dianhydride 4
．． Add 36 P gradually. After the addition was completed, the reaction was continued for 5 hours with stirring, and the PIQ prepoly 1 was heated to a barrel shape (imidization rate a).
OS). N-methyl-2-pyrrolidone was added to each of A, B, and C to adjust the viscosity to 1.000 cps. A whose viscosity was adjusted as described above.

The surfaces of B and C were thermally oxidized and then dropped onto silicon wafer 1 for semiconductor devices, and coated every minute using a photoresist spin coater (Spinner'-IH-DS type, manufactured by Mikasa Corporation). "Coating was carried out at a rotational speed of 00 to 4,000 revolutions.

This was dried at 150° C. for 60 minutes, and then a photoresist was spin-coated on the resin film using a 39 cps solution of OMB-83 manufactured by Tokyo Ohka Kogyo. Apply at a rotational speed of 4000 rpm.

The photoresist film thickness was 1.0 μm.

The photoresist was dried at 90° C. for 20 minutes, then exposed to ultraviolet light with a photomask attached, and then immersed in OMRI @ Current Solution (Tokyo Ohka Kogyo) to dissolve the unexposed photoresist. Furthermore, the photoresist film that remained on the resin film and formed a predetermined pattern by exposure to light was cured at 140° C. for 20 minutes, and a post-baking process was performed.

The film thicknesses of the polyimide resin films were A, 26 μm, B, 25 μm, and hsμm, respectively. Then, tetramethylammonyl hydroxide 1
Etching into 30 weight bags of methanol solution at a liquid level of 5 at 30℃.
Immersed for 0 seconds and mourned.

The following results were obtained regarding the opening dimensions and pattern dimensional accuracy when etching was performed under the above etching conditions.

That is, the thickness of each of A, B, and C is 15 to 16
With a dimensional accuracy of 3 to 0.4 μm for an opening of 10/Am' and 74 m' for a 4 m resin film, 54 m
', 4 prno, 0.2 to 34 m° aperture
Etching was possible with a dimensional accuracy of 0.3 μnlo tolerance. Note that the opening dimension is the dimension of the bottom surface of the polyimide resin film relative to the mask dimension. The shape of the pattern is A, B,
Both Cs have a 3μm0 opening with almost no roundness and a good shape with 6x9.

Also, when the etching factor was measured, A and B
, C are both in the range of 1.30 to 1.40.

The slope of the pattern end is 52 to 55 degrees. The fact that a 3 μm' through hole can be etched into a good shape and the taper angle is 52 to s5 can be said to have extremely excellent characteristics for microfabrication.

Comparative Example 1 The same polyimide resin jlA used in Example 1,
When B and C were etched with a 10-weight bag aqueous solution of tetramethylammonium hydroxide, an overetched pattern 11 was obtained with the same spacing. In addition, the etching 7 actors of the through-hole that are connected are α for A, B, and C.
85 to 1.0.

Comparative Example 2 When the same polyhydric resin used in Example 1 was used to etch A, B, and C with an etching solution containing ethylene diamine alone, 74 m' or less was not opened in the same time; Through holes 4 of 910 μm are rounded and etched.

Example 2 The same solutions A, B and C as in Example 1 were added at 1,000% each.
0 cps viscosity to 4ooo rpm
Spin coating onto a specified substrate at 160°C for 60 minutes.

It was heat-cured and imidized. The thickness of the resin film is 26
〜27μm and nine. Next, a photoresist pattern with a pattern size of 104 m' to 3 μm' was formed in the same manner as in Example 1, and then etched in an etching solution containing 25 weight of tetramethylammonium hydroxide-methanol solution at a temperature of 28°C for 80 seconds or at a temperature of 25°C. So 10
Immerse for 0 seconds.

Similar results were obtained under the two etching conditions.
For both B and C, openings were formed within a range with almost no significant difference in pattern dimensional accuracy from Example 1.

Example 3 ・：、、 The same one liquid as in Example 1, 1 each of B and C.

The viscosity of each Looocp is &000~400゜r
It was spin-coated onto a predetermined substrate at 150° C. and heat-cured at 150° C. for 60 minutes to imide. Resin film O film thickness is 27
It was ~29 μm. Then, in the same manner as in Example 1, the pattern size was 10 μm and 0 to 3 sm.

After forming a photoresist pattern, it was immersed in an etching solution containing 30% by weight of tetramethylammonium hydroxide-ethanol solution for 80 seconds at an etching temperature of 30°C.

The pattern dimensions are 1Qμm' and 74m' for A, B, and C.

For 5 μm and 0.4 μm OK, the accuracy is within α3 μm, and for 3 μm, the opening size is 25 am.

Met.

According to the etching solution of the present invention, when etching polyimide resin, conventional polyandroic acid or PIQ
When etching with the current solution of positive type photoresist at the prepolymer stage or imidization and conventional quaternary ammonium hydroxide solution at the nine stage, the quaternary
Compared to the case where a grade ammonium hydroxide solution is mixed and etched with a diluent solution or hydrazine, the etching speed is dramatically higher, and extremely precise fine processing is possible without swelling during etching.

Also, the time required for etching polyimide resin is 50
Since the etching time is 100 seconds, which is shorter than that using other conventional etching solutions, it is characterized by excellent mass productivity. The rounding and etching method can be changed from batch processing to individual sheet processing using spray etching.In this case, by automating the etching process, it is possible to achieve excellent mass production, high etching accuracy, and highly safe etching. Be able to do this.

[Brief explanation of the drawing]

Figure 1 shows the etching characteristics of the etching solution, Figure 2 shows the etching characteristics of the etching solution.
The figure is a cross-sectional view of an etched nine-bolyide resin film, and FIG.
b) is a diagram showing the relationship between the design value of the through hole and the actual through hole opening size, and FIG. 4 is a diagram explaining the etching factor. Explanation of symbols 1... Base 2... Polyimide resin film 3... Embossed upper part lb 1 day 0/234567 δ 9 1 7th position 2 Diagram (d)

Claims (1)

[Claims] 1. An etching solution for polyimide resins comprising an alcoholic solution of tetramethylammonium hydroxide. 2 The concentration of tetramethylammonium hydroxide in the alcohol solution of tetramethylammonium hydroxide is 5 to 3.
5. The etching solution for polyimide resin according to claim 1, which has a weight of 5. & Claim 1 and Claim 2, wherein the polyimide resin is a polyimide resin with an imidization rate of 5 to 90.
Etching liquid for bolioid resin as described in .