Method for measuring the concentration of a photoresist in a stripping liquid

The present invention relates to a method for measuring the concentration of a photoresist in a stripping liquid.

Photoresist (PR) is widely used as mask patterns for form layers in TFT technologies. There are two types photoresist, i.e. positive photoresist and negative photoresist. When exposed, the exposed areas of the positive photoresist are made to be solvable in a developer, and the unexposed areas are left as a pattern.

The concentration of a photoresist in a stripping liquid (also be called as stripper) is usually measured by UV-VIS (Ultraviolet and Visible Spectrophotometer). In this method, the absorbance are read directly and stored in a database to measure the concentration of a photoresist in a stripping liquid. In this method, the operation is complicated and it is not suitable to put into practice.

The present invention provides a method for measuring the concentration of a photoresist in a stripping liquid, which can measure the concentration of a photoresist in a stripping liquid accurately.

The present invention is realized in such a way that: A method for measuring the concentration of a photoresist in a stripping liquid, the method for measuring the concentration of a photoresist in a stripping liquid comprising the steps of:

S 102 : preparing standard photoresist samples; S 104 : collecting the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample; and S 106 : taking the nth derivative of the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample, wherein n is an integer equal to or greater than 1, and storing the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample; S 108 : establishing a standard curve based on the nth derivative curves and calculating the concentration of the test photoresist sample.

Preferably, in step S 102 , photoresist is coated on a glass, an exposure process, a developing process and an etching process are performed, and a stripping process is simulated in a beaker by stripping the photoresist with a target weight, such as to obtain the standard photoresist samples with target concentrations.

Preferably, in step S 104 , the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample are collected by ultraviolet and visible spectrophotometer.

Preferably, the step S 104 comprises the steps of:

solvent preparing step: selecting a solvent as the reference solution;

the spectrum of the stripping liquid collecting step: diluting the stripping liquid with the reference solution, collecting the spectrum of the stripping liquid in the predetermined wavelength;

the spectrum of the standard photoresist samples collecting step: diluting a plurality of standard photoresist samples with the reference solution, collecting the spectrum of the plurality of standard photoresist samples in the predetermined wavelength;

the spectrum of the test photoresist sample collecting step: diluting the test photoresist sample with the reference solution, collecting the spectrum of the test photoresist sample in the predetermined wavelength.

Preferably, in step S 106 , taking the nth derivative of the spectrum of the stripping liquid, the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample, wherein n is 1, 2, 3 or 4, and storing the nth derivative curves of the nth derivative of the spectrum of the stripping liquid, the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample.

Preferably, in step S 108 , if the absorbance of the nth derivative curves of the nth derivative of the spectrum of the stripping liquid at a first wavelength is zero, and both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples at the first wavelength and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist sample at the first wavelength are at respective troughs, then establishing the standard curve based on the respective troughs and the concentration of the photoresist of the standard photoresist samples.

Preferably, in step S 108 , if the absorbance of the nth derivative curves of the nth derivative of the spectrum of the stripping liquid at a second wavelength is zero, and both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples at the second wavelength and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist sample at the second wavelength are at respective peaks, then establishing the standard curve based on the respective peaks and the concentration of the photoresist of the standard photoresist samples.

Preferably, in step S 108 , if the absorbance of the nth derivative curves of the nth derivative of the spectrum of the stripping liquid between a third wavelength and a fourth wavelength is zero, both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist samples at the third wavelength are at respective troughs, and both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist samples at the fourth wavelength are at respective peaks, then establishing the standard curve based on the difference of the absorbance between the third wavelength and the fourth wavelength and the concentration of the photoresist of the standard photoresist samples.

Preferably, the stripping liquid is organic amine stripping liquid.

Preferably, the photoresist is a phenolic resin positive type photoresist.

According to the present invention, in the method for measuring the concentration of a photoresist in a stripping liquid, a plurality of standard photoresist samples are prepared at first, then the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample are collected, and the nth derivative of the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample are taken, wherein n is an integer equal to or greater than 1, a standard curve based on the nth derivative curves and calculating the concentration of the test photoresist sample is established, the concentration of a photoresist in a stripping liquid can be measured accurately according to the standard curve.

For more clearly and easily understanding above content of the present invention, the following text will take a preferred embodiment of the present invention with reference to the accompanying drawings for detail description as follows.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a schematic view illustrating the step of preparing standard photoresist samples according to an embodiment of the present invention;

FIG. 2 is a schematic view illustrating that both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist sample at the first wavelength λ 1 are at respective troughs in another embodiment of the present invention;

FIG. 3 is a schematic view illustrating that both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist sample at the second wavelength λ 2 are at respective peaks in another embodiment of the present invention;

FIG. 4 is a schematic view illustrating that both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist samples at the third wavelength λ 3 are at respective troughs, and both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist samples at the fourth wavelength λ 4 are at respective peaks in yet another embodiment of the present invention; and

FIG. 5 is a flowchart of the method for measuring the concentration of a photoresist in a stripping liquid according to yet another embodiment of the present invention.

The embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1 to FIG. 5 , the method for measuring the concentration of a photoresist in a stripping liquid in the present embodiment comprises the steps of:

S 102 : preparing standard photoresist samples; S 104 : collecting the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample; and S 106 : taking the nth derivative of the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample, wherein n is an integer equal to or greater than 1, and storing the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample; S 108 : establishing a standard curve based on the nth derivative curves and calculating the concentration of the test photoresist sample according to the standard curve.

In the present embodiment, the stripping liquid is organic amine stripping liquid. And the photoresist is a phenolic resin positive type photoresist.

As shown in FIG. 1 , in step S 102 , photoresist is coated on a glass (step A), an exposure process (step B), a developing process (step C) and an etching process (step D) are performed, and a stripping process (step F) is simulated in a beaker by stripping the photoresist with a target weight, such as to obtain the standard photoresist samples with target concentrations. The difference between the step S 102 and the practical photo lithography of TFT array process, metal layers and non-metal layers are not deposited on the glass in step S 102 .

In step S 104 , the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample are collected by ultraviolet and visible spectrophotometer.

The step S 104 comprises the steps of:

solvent preparing step: selecting a solvent as the reference solution, the solvent can be selected based on the dissolution performance, economic factor and safety factor;

baseline scanning step: scanning the reference solution in visible light region and ultraviolet light region;

the spectrum of the stripping liquid collecting step: diluting the stripping liquid with the reference solution, collecting the spectrum of the stripping liquid in the predetermined wavelength;

the spectrum of the standard photoresist samples collecting step: diluting a plurality of standard photoresist samples (3˜5 standard photoresist samples for example) with the reference solution, collecting the spectrum of the plurality of standard photoresist samples in the predetermined wavelength;

the spectrum of the test photoresist sample collecting step: diluting the test photoresist sample with the reference solution, collecting the spectrum of the test photoresist sample in the predetermined wavelength.

In step S 106 , the nth derivative of the spectrum of the stripping liquid, the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample are taken wherein n is 1, 2, 3 or 4, and storing the nth derivative curves of the nth derivative of the spectrum of the stripping liquid, the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample. The nth derivative of the spectrum of the stripping liquid, the spectrum of the standard photoresist samples and the spectrum of the test photoresist sample maybe taken by a operation software or drawing software. In FIG. 2 , FIG. 3 and FIG. 4 , the reference mark Fresh stripper means the nth derivative curves of the nth derivative of the spectrum of the stripping liquid, the reference mark Sample means the nth derivative curves of the nth derivative of the spectrum of the test photoresist sample, the reference mark STD 1 means the nth derivative curves of the nth derivative of the spectrum of the first standard photoresist sample, the reference mark STD 2 means the nth derivative curves of the nth derivative of the spectrum of the second standard photoresist sample.

In step S 108 , if the absorbance of the nth derivative curves of the nth derivative of the spectrum of the stripping liquid at a first wavelength λ 1 is zero, and both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist sample at the first wavelength λ 1 are at respective troughs, then establishing the standard curve based on the respective troughs and the concentration of the photoresist of the standard photoresist samples.

In step S 108 , if the absorbance of the nth derivative curves of the nth derivative of the spectrum of the stripping liquid at a second wavelength λ 2 is zero, and both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist sample at the second wavelength λ 2 are at respective peaks, then establishing the standard curve based on the respective peaks and the concentration of the photoresist of the standard photoresist samples.

In step S 108 , if the absorbance of the nth derivative curves of the nth derivative of the spectrum of the stripping liquid between a third wavelength λ 3 and a fourth wavelength λ 4 is zero, both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist samples at the third wavelength λ 3 are at respective troughs, and both the absorbance of the nth derivative curves of the nth derivative of the spectrum of the standard photoresist samples and the absorbance of the nth derivative curves of the nth derivative of the spectrum of the test photoresist samples at the fourth wavelength λ 4 are at respective peaks, then establishing the standard curve based on the difference of the absorbance between the third wavelength λ 3 and the fourth wavelength λ 4 and the concentration of the photoresist of the standard photoresist samples.

The concentration of a photoresist in a stripping liquid can be measured accurately according to the standard curve. The standard curve is usually a straight line. By this way, the concentration of a photoresist in a stripping liquid can be obtained visually and directly. Thus, the time of the exchange of stripping liquid can be known in practical photo lithography of TFT array process. The life span of the stripping liquid can be extended. The method for measuring the concentration of a photoresist in a stripping liquid according to the present invention may be widely used in TFT technical field.

While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.