JPH0159736B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a pattern forming processing method using a lift-off method.

Conventionally, semiconductor integrated circuits, Josephson integrated circuits, etc. have been manufactured using, for example, a semiconductor substrate 1 as shown in FIG. 1A.
Using this resist film 2 as a mask, a metal layer 3 is applied to the pattern area surrounded by the resist film 2 formed above.
Pattern formation is performed by a so-called lift-off method in which a resist film 2 and a metal layer 32 formed thereon are removed by forming a resist film 1 and immersing it in an organic solvent such as acetone.

However, a thin sidewall adhesion layer 33 is formed on the sidewall portion of the resist film 2 due to scattering and diffusion of deposited metal particles during the vacuum deposition process for forming the metal layers 31 and 32. This sidewall adhesion layer 33 prevents the removal action of the resist film 2 by the organic solvent. For this reason, a method is usually adopted in which mechanical force such as ultrasonic vibration is applied while the semiconductor substrate 1 is immersed in an organic solvent to promote destruction of the sidewall adhesion layer 33.

However, in such a pattern forming method using lift-off processing, the lift-off processing requires a long time, and as shown in FIG.
1, a part of the sidewall adhesion layer 33 that was not completely removed may adhere as a burr 33a, or the metal layer 31
may adhere to the surface of the semiconductor substrate 1 near the 33
a′, or 33a″ that may remain in a protruding state near the metal layer 31.Furthermore, in severe cases, burrs may remain in the form of bridges covering the metal layer 31.As a result, multilayer wiring Occasionally, there was a problem that the wiring pattern was disconnected or short-circuited.In order to solve these problems, in particular, applying ultrasonic vibration to the positive photoresist film 2 in a good solvent for the positive photoresist film 2, Alternatively, a method has been adopted in which the sidewall adhesion layer 33 of the connection portion 4 between the positive photoresist film 2 and the semiconductor substrate 1 is cut and destroyed by applying mechanical force such as by spraying a solvent. However, since a process for cutting and destroying the bottom portion of the positive type photoresist film 2 is required, there is a problem in that the lift-off process time is lengthened.

The present invention has been made in view of these points,
The present invention has discovered a pattern forming processing method using a lift-off method that can shorten the lift-off processing time and prevent the occurrence of burrs associated with the lift-off processing.

Examples of the present invention will be described below.

First, as shown in FIG. 1A, a positive photoresist film 2 made of quinone diazide ester and novolak resin is formed in a predetermined pattern on the surface of a semiconductor substrate 1 to a thickness of about 1 μm. Next, this positive type photoresist film 2 is irradiated with ultraviolet rays to chemically decompose the photoresist film 2. Next, using the positive photoresist film 2 as a mask, metal layers 31 and 32 made of, for example, a lead alloy are applied to the exposed surface of the semiconductor substrate 1 and on the positive photoresist film 2 to a thickness of about 0.4 μm.
Form. At this time, a thin sidewall adhesion layer 33 is formed on the sidewall portion of the positive photoresist film 2.

Here, the positive photoresist film 2 made of quinone diazide ester and novolak resin is as follows:
AZ-1470 (Shitsupray company product name) resist, AZ
It is preferable to use -1350J resist, AZ-1450J resist (all trade names of Shippray Co., Ltd.), OFPR series resist (trade name of Tokyo Ohka Co., Ltd.), or the like. Further, an insulating layer made of a predetermined material may be formed instead of the metal layers 31 and 32.

Next, using the positive photoresist film 2 as a mask, the semiconductor substrate 1 on which the metal layer 31 of a predetermined pattern has been formed is immersed in a resist film swelling treatment solution for about 5 minutes to form a positive photoresist film as shown in FIG. 21
to swell. Here, the resist film swelling treatment liquid is a good solvent for the positive photoresist film 2 consisting of a lower alcohol such as ethyl alcohol, methyl alcohol, and isopropyl alcohol, and an aromatic hydrocarbon solvent such as chlorobenzene, xylene, toluene, and promobenzene. The positive type photoresist film 2 is made of a mixture of poor solvents such as .
The ratio of good solvent to poor solvent is set so that the amount of good solvent is 2 to 5% by volume and the remainder is poor solvent, and more preferably, the amount of good solvent is set in the range of 2.5 to 3.5% by volume. is desirable. If the amount of good solvent is less than 2% by volume, the positive photoresist film 2 cannot be sufficiently dissolved and the positive photoresist film 2
swelling cannot be achieved. Further, if the amount of the good solvent exceeds 5% by volume, the positive photoresist film 2 will be dissolved more than necessary, and the positive photoresist film 2 will not be able to swell to the extent that cracks will occur in the metal layers 31 and 32.

Next, the positive photoresist film 21 is immersed in a resist solvent consisting of the swelling-treated semiconductor substrate 1 and acetone for about 5 minutes, and in this state, for example, ultrasonic waves (frequency 45 KHz) with an output of 200 W are applied. The positive photoresist film 21 and the metal layer 32 formed thereon are lifted off.

In this way, the pattern forming treatment method using the lift-off method applies swelling treatment to the positive photoresist film 2 in a swelling treatment solution for the resist film to form the metal layer 3.
2 and the sidewall adhesion layer 33,
In particular, the sidewall adhesion layer 33 near the surface of the semiconductor substrate 1
After the photoresist film 2, metal layer 32, and sidewall adhesion layer 33 are easily destroyed and cut, a lift-off treatment using a resist solvent is performed to prevent the sidewall adhesion layer 33 from remaining and causing burrs. It can be completely removed in a very short time.

In addition, the amount of swelling of the positive photoresist film 2 by the resist film swelling treatment solution was varied by changing the proportion of ethyl alcohol, which is a good solvent, in the range of 0 to 6% by volume (the remainder being chlorobenzene), and the swelling amount of the positive photoresist film 2 due to this was varied. When the volume increase rate was investigated, the results shown by curve a in FIG. 3 were obtained. Here, the positive photoresist film 2 used was an AZ-1470 resist film having a film thickness of about 1 μm and prebaked at 70° C. for 30 minutes. In addition, this positive photoresist film 2 is coated with ultraviolet rays that are equivalent to or higher than that required for pattern formation (for example, energy at a wavelength of 436 nm is approximately
100 mJoule/cm ² cm ² or more) was applied. For comparison, the volume increase of the positive photoresist film 2 in the case of a treatment solution in which the proportion of ethyl alcohol was similarly varied in the range of 0 to 6% by volume was applied to the positive photoresist film 2 that was not irradiated with ultraviolet rays. When the ratio was investigated, the results shown by curve b in the figure were obtained.

As is clear from the figure, in the case where the swelling treatment liquid is applied to the positive photoresist film 2 that has been irradiated with ultraviolet rays, the positive photoresist film 2 is exposed especially when the proportion of ethyl alcohol, which is a good solvent, is 2.5 to 3.5% by volume. It can be seen that exhibits an extremely large volume increase rate of 150 to 200%. In other words, the metal layer 32 and sidewall adhesion layer 33 formed on the surface of the positive photoresist film 2, which has swollen at an extremely high volume increase rate, can easily undergo cracking, cutting, and destruction treatments. It can be easily applied by swelling the membrane 2.

Furthermore, when the lift-off completion rate of the positive photoresist film 21 lifted off according to the above-mentioned example was investigated for each ultrasonic application time (0 to 60 minutes), the results shown by curve c in FIG. 4 were obtained. Ta. For comparison, the lift-off completion rate of the positive photoresist film 2 was measured using the conventional method under the same conditions as in the example except that the positive photoresist film 2 was not subjected to the swelling treatment. (0~
60 minutes), the results shown by curve d in the figure were obtained.

As is clear from the figure, in the example, it is possible to obtain a 100% lift-off completion rate by ultrasonic vibration treatment in acetone for 5 minutes, but in the conventional method, Even after 60 minutes of ultrasonic treatment inside the chamber, a 100% lift-off completion rate could not be obtained, and it was confirmed that burrs were generated after the lift-off treatment.

As explained above, according to the pattern forming processing method using the lift-off method according to the present invention, it is possible to significantly shorten the lift-off processing time, prevent the occurrence of burrs accompanying the lift-off processing, and produce high-quality metal with extremely high shape accuracy. It has remarkable effects such as being able to easily form layers.

[Brief explanation of drawings]

FIG. 1A is a cross-sectional view showing a state in which a metal layer is formed using a positive photoresist film formed on a semiconductor substrate as a mask, and FIG. FIG. 2 is an explanatory diagram showing a state in which a positive resist film is subjected to swelling treatment by the method of the present invention;
FIG. 3 is a characteristic diagram showing the relationship between the volume increase rate of a positive photoresist film and the proportion of ethyl alcohol;
FIG. 4 is a characteristic diagram showing the relationship between lift-off completion rate and ultrasound application time. 1... Semiconductor substrate, 2... Positive photoresist film,
31, 32...metal layer, 33...side wall adhesion layer.

Claims (1)

[Claims] 1. A predetermined pattern of a positive photoresist film made of quinone diazide ester and novolak resin is formed on a semiconductor substrate, and then, after irradiating the resist film with ultraviolet rays, a metal layer or an insulating film is formed on the resist pattern. A layer is deposited, and then the resist film is immersed in a swelling treatment solution for the resist film to undergo a swelling treatment, and then the resist film is immersed in a good resist solvent to remove the resist film and the resist. A pattern forming processing method using a lift-off method, which is characterized by removing a metal layer or an insulating layer deposited on a film. 2. The resist film swelling treatment solution contains chlorobenzene, xylene, toluene, bromobenzene or a mixture thereof, and a lower alcohol consisting of ethyl alcohol, methyl alcohol, isopropyl alcohol, or a mixture thereof. 2. The pattern forming method using a lift-off method according to claim 1, wherein a mixed solvent added in an amount of % by volume is used.