Method for solving problem that large amount of dirt is attached to chromium shading film

Abstract

The invention relates to a method for solving the problem that a large amount of dirt is attached to a chromium shading film, which comprises the following steps: washing with hot deionized water after cleaning with tetramethylammonium hydroxide liquid to enhance the surface affinity with amine chemical residues, and then removing the residual amine chemical residues by using nano-scale tiny blasting bubbles generated by ultrasonic oscillation. According to the method, the chromium shading film is washed by deionized water, so that the amine chemical residues are separated from the chromium shading film and are finally washed away by deionized water, the amine chemical residues are prevented from being oxidized into complex nitrogen oxides in an ozone environment measured by a subsequent critical dimension measuring machine CDSEM, and the problem of dirt on the chromium shading film is also solved.

Description

Technical Field

[0001] The invention relates to the technical field of phase transfer masks, and in particular to a method for solving the problem of a large amount of dirt adhering to a chrome light-shielding film. Background Art

[0002] Phase Shift Mask (PSM) is a resolution enhancement technology that uses both the intensity and phase of light to create an image and obtain a higher resolution. As chip graphics design becomes more and more complex and sophisticated, in order to reduce the minimum resolution of the pattern, the key layers of the high-end process need to use phase shift masks.

[0003] In the process of phase transfer mask manufacturing, as the pattern design becomes more complex, the types of dirt appear more and more diverse. These abnormal types of dirt will cause waste of the inspection machine's production capacity, delay delivery, and cause losses such as scrap.

[0004] In the existing phase transfer mask manufacturing process, there is a type of abnormal dirt that is distributed in large quantities on the outer Cr light shielding film (such as Figure 1 As shown in the figure, the size of the dirt is about 200-700nm and the height is about 20nm. Moreover, the dirt is difficult to remove by conventional cleaning process, which greatly affects the yield of the product. Summary of the invention

[0005] The invention aims to provide a method for solving the problem of a large amount of dirt adhering to a chrome light-shielding film.

[0006] The specific plan is as follows:

[0007] A method for solving the problem of a large amount of dirt attached to a chrome light shielding film, the method is to remove amine chemical residues on the chrome light shielding film of a phase transfer mask, and the method comprises the following steps:

[0008] S1, pre-cleaning with deionized water;

[0009] S2, using ozone water for cleaning;

[0010] S3, using tetramethylammonium hydroxide solution for cleaning;

[0011] S4, rinse with hot deionized water, the hot deionized water temperature is 60-100°C;

[0012] S5, using ultrasonic vibration;

[0013] S6. Rinse with deionized water;

[0014] S7. Drying.

[0015] Furthermore, in step S4, the flow rate of the hot deionized water is 1000-1800 ml / min, and the flushing time is 200-300 s.

[0016] The method provided by the present invention for solving the problem of a large amount of dirt adhering to the chrome shading film has the following advantages compared with the prior art: the method provided by the present invention for solving the problem of a large amount of dirt adhering to the chrome shading film is, after the cleaning with tetramethylammonium hydroxide solution is completed, hot deionized water is used for rinsing to enhance the surface affinity with the residual amine chemicals, and then ultrasonic vibration is used to generate nano-scale tiny bursting bubbles to remove them, so that the residual amine chemicals can be separated from the chrome shading film, and finally rinsed away with deionized water, thereby avoiding these residual amine chemicals from being oxidized into complex nitrogen oxides in the ozone environment of the subsequent critical dimension measuring machine CDSEM measurement, thereby also solving the problem of dirt on the chrome shading film. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A picture showing a phase-shift mask made by a conventional process with a large amount of dirt detected on the Cr light-shielding film on its periphery.

[0018] Figure 2 Show Figure 1 A magnified image of the area in the middle.

[0019] Figure 3 The schematic diagram shows the structure of a phase-shift mask manufactured by the conventional manufacturing process, in which the Cr light-shielding film on the periphery thereof is dirty.

[0020] Figure 4 The picture shows that no dirt is detected on the Cr light shielding film on the periphery of the phase-shift mask obtained by the method provided by the present invention. DETAILED DESCRIPTION

[0021] To further illustrate the various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, a person of ordinary skill in the art should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0022] The present invention will now be further described with reference to the accompanying drawings and specific implementation methods.

[0023] like Figure 3As shown, the basic structure of the existing phase transfer mask includes a substrate 1, a MoSi layer 2 as a mask image is provided on the substrate 1, and a Cr layer 3 is covered on the MoSi layer 2 in the non-main image area. It should be noted here that the substrate is usually made of quartz glass, and the formation of the MoSi layer and the Cr layer on the substrate, as well as the pattern drawing, exposure, and development processes are all existing technologies, and the specific process technology will not be described in detail here.

[0024] It was found in the process that there is a type of dirt 4 distributed on the outer Cr light shielding film. The size of the dirt 4 is mostly distributed in the range of 200-700nm, the height is about 20nm, and it is difficult to remove by conventional cleaning processes. Research has found that in the process flow of existing phase transfer masks, there will be amine chemical residues in the photoresist removal process after dry etching, and these amine chemical residues are removed by using tetramethylammonium hydroxide (TMAH) and deionized water in the cleaning process of the cleaning machine. However, in the actual process, these amine chemical residues are attached to the Cr layer due to their surface hydrophilicity and are difficult to be completely removed. These amine chemical residues are oxidized into complex nitrogen oxides in the ozone environment measured by the critical dimension measurement machine CDSEM. These nitrogen oxides are detected in the optical inspection machine, that is, they become the above-mentioned dirt 4 distributed on the Cr light shielding film.

[0025] In this regard, the present invention provides a method for solving the problem of a large amount of dirt attached to the chrome light shielding film, wherein the amine chemical residue is removed by the following method in the cleaning process after the photoresist is removed, and specifically includes the following steps:

[0026] S1. Pre-clean with deionized water to wash away the residual liquid and some obvious granular residues in the photoresist removal process. The flow rate of deionized water in step S1 is 500-1500 ml / min, and the temperature is 22.5-23.5°C.

[0027] S2. Use ozone water for cleaning to remove most of the organic residues (organic oil stains). In step S2, the flow rate of ozone water is 800-1500 ml / min, the temperature is 22.5-23.5° C., and the cleaning time is 15-60 seconds.

[0028] S3, using tetramethylammonium hydroxide (TMAH) solution for cleaning to remove residual organic matter (photoresist residue). In step S3, the flow rate of the tetramethylammonium hydroxide solution is 800-2000 ml / min, the temperature is 22.5-23.5° C., and the cleaning time is 500-1000 seconds.

[0029] S4. Rinse with hot deionized water to enhance the surface affinity with the byproducts of the reaction with the amine chemicals (TMAH) during the photoresist removal (PRstrip) process, which are oxidized into complex nitrogen oxides (EDX (X-ray energy dispersive spectrometer) detection results C / N / O) in an ozone (O3) environment. The flow rate of the hot deionized water in step S4 is 500-1500 ml / min, the temperature is 60-80°C, and the rinsing time is 200-500 seconds.

[0030] S5. Use ultrasonic vibration to generate nano-scale tiny burst bubbles to shake off the amine chemical residues attached to the Cr layer so that they no longer adhere to the Cr layer;

[0031] S6. Rinse with deionized water to rinse off the amine chemical residues shaken in step S5, wherein the flow rate of the hot deionized water in step S6 is 500-1500 ml / min, the temperature is 60-80° C., and the rinsing time is 200-500 seconds.

[0032] S7, drying the phase transfer mask after step S6, that is, completing the cleaning process.

[0033] According to research, the temperature of the hot deionized water in step S4 has a decisive influence on the chemical residues. When the temperature of the hot deionized water is greater than 80° C., a large amount of dirt remains on the photomask, making it unusable.

[0034] When the hot DI water temperature was >60°C, the final fouling count was 385, a significant improvement over the baseline of >2000 fouling counts for the unchanged process.

[0035] When the temperature of hot deionized water is between 70℃ and 80℃, the final number of dirt is <10, which basically solves this type of dirt problem.

[0036] In addition, by optimizing other steps, the occurrence of such problems can be effectively eliminated; preferably, the following conditions are used to remove dirt in steps S2-S6:

[0037]

[0038] The method provided by the present invention for solving the problem of a large amount of dirt attached to the chrome light-shielding film is to use hot deionized water to rinse after the tetramethylammonium hydroxide (TMAH) solution cleaning is completed to enhance the surface affinity with the amine chemical residues, and then use ultrasonic vibration to generate nano-scale tiny burst bubbles to remove them, so that the amine chemical residues can be separated from the chrome light-shielding film, and finally rinsed off with deionized water, thereby avoiding these amine chemical residues from being oxidized into complex nitrogen oxides in the ozone environment of the subsequent critical dimension measurement machine CDSEM measurement, thereby also solving the problem of dirt on the chrome light-shielding film.

[0039] like Figure 4 As shown, it is an image after cleaning by the cleaning process provided by the present invention, measured by the critical dimension measuring machine CDSEM, and finally detected by the optical inspection machine. It can be seen that after cleaning by the cleaning process provided by the present invention, no dirt is detected on the Cr shading film distributed on the periphery of the phase transfer mask, which proves that the method provided by the present invention can solve the problem of a large amount of dirt adhering to the chromium shading film.

[0040] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined by the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A method for solving the problem of a large amount of dirt adhering to a chrome light-shielding film, characterized in that: The method is to remove the amine chemical residue on the chrome light shielding film of the phase transfer mask, and comprises the following steps: S1, pre-cleaning with deionized water; S2, using ozone water for cleaning; S3, using tetramethylammonium hydroxide solution for cleaning; S4, rinse with hot deionized water, the temperature of the hot deionized water is 60-80°C; S5, using ultrasonic vibration; S6. Rinse with deionized water; S7. Drying.

2. The method according to claim 1, characterized in that: In step S4, the flow rate of hot deionized water is 800-2000 ml / min, and the flushing time is 200-500 s.

3. The method according to claim 1, characterized in that: In step S1, the flow rate of deionized water is 500-1500 ml / min, and the temperature is 22.5-23.5°C.

4. The method according to claim 1, characterized in that: In step S2, the flow rate of ozone water is 800-1500 ml / min, the temperature is 22.5-23.5° C., and the cleaning time is 15-60 seconds.

5. The method according to claim 1, characterized in that: In step S3, the flow rate of tetramethylammonium hydroxide solution is 800-2000 ml / min, the temperature is 22.5-23.5° C., and the cleaning time is 500-1000 seconds.

6. The method according to claim 1, characterized in that: In step S6, the flow rate of hot deionized water is 500-1500 ml / min, the temperature is 60-80° C., and the flushing time is 200-500 seconds.

Images