Dry etching method for molybdenum silicide layer

Abstract

The invention provides a dry etching method for a molybdenum silicide layer, and relates to the field of semiconductor mask plates. The method is used for performing dry etching pattern transfer on the molybdenum silicide phase shift layer in the phase shift mask. The method comprises the following steps of: 1, putting a patterned molybdenum silicide layer into an ICP (Inductively Coupled Plasma) dry etching machine; 2, mixed SF6 gas and Ar gas are introduced into the etching cavity; and 3, the plasma concentration is regulated and controlled by controlling the ICP source, the plasma bombardment kinetic energy is regulated and controlled through the RF source, and etching of the molybdenum silicide layer is completed. According to the dry etching method, SF6 and Ar are adopted as etching gas, a good etching selection ratio and good morphology can be obtained by controlling the gas proportion, the ICP power and the RF power, and the dry etching method has the advantages of being good in safety, low in production cost and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor processing, in particular to a dry etching method of molybdenum silicide layer. BACKGROUND

[0002] In the industry of large-scale integrated circuits, the essence of photolithography is to transfer the pattern on the mask to the wafer, so the mask is the link and bridge connecting the design end and the process manufacturing end, and its importance is not less than that of the photolithography machine and the photoresist. According to the specific needs of the photolithography process, common masks include binary masks, phase shift masks and EUV masks, etc. The binary mask refers to a photomask composed of two parts of light transmission and non-transmission, which is widely used in g-line and i-line photolithography.

[0003] When the process node is 0.18 μm, using the traditional chromium binary mask, optical diffraction will reduce the edge contrast of the pattern, thereby affecting the exposure resolution, so the industry begins to cut into the phase shift mask technology. That is, a phase shift layer is added to make the light wave produce a 180° phase difference after passing through the phase shift layer, and the pattern edge interference is cancelled, thereby improving the contrast and improving the exposure resolution. This three-layer structure mask is a phase shift mask (PSM, Phase Shift Mask). According to the phase conversion or the degree of light attenuation, the phase shift layer material is generally MoSi or its oxynitride. The practical phase shift layer must ensure that the incident light produces a 180° phase shift, so the phase value of the phase shift is related to the film thickness, refractive index and incident optical wavelength as follows: .

[0004] The manufacture of the phase shift mask requires two times of exposure, two times of development and two times of etching, and the cycle is long, the control points are many, and the manufacturing process flow is shown in Figure 1 . The main technical points are the control of the line width (CD) of the phase shift layer, the control of the defects of the phase shift layer, and the control of the phase angle of the phase shift layer, etc., which almost all depend on the dry etching process of the molybdenum silicide layer, that is, the MoSi etching profile has a nearly vertical sidewall, good etching depth uniformity and minimum roughness exposed to the quartz substrate.

[0005] The dry etching method of the molybdenum silicide phase shift layer is less reported. Its mechanism is to use fluorine-based or chlorine-based gas, such as chlorine (Cl2) or boron trichloride (BCl3), etc., under the action of high-energy magnetic field, the gas molecules are decomposed into Cl + , Cl -Active particles and groups participate in chemical reactions with silicon (Si) and molybdenum (Mo) in the molybdenum silicide to generate volatile products, realizing etching of the molybdenum silicide layer. The chlorine-based gas is generally toxic, and storage, use and tail gas emission will increase the safety hazard and production cost; the fluorine-based gas etching generally needs to be matched with high-cost inert gas such as He gas, which is relatively high in cost. It is necessary to propose a dry etching method of the molybdenum silicide layer to realize low-cost and high-safety production. SUMMARY

[0006] The present application is directed to the problems existing in the dry etching process of the molybdenum silicide phase shift layer in the phase shift mask, and provides a new dry etching method of the molybdenum silicide layer.

[0007] To achieve the above object, the present application adopts the following technical scheme, and the method steps are as follows: S1, the patterned molybdenum silicide is put into the etching machine; S2, the mixed SF6 and Ar gas is introduced into the cavity of the etching machine; S3, the radio frequency ignition is started, the ICP power, the RF power and the working gas pressure are adjusted, and the etching is carried out; S4, the etching time is reached, and the etching is completed; Optionally, in the step S1, the patterning can be implemented by a laser direct writing or electron beam direct writing photoetching machine; Optionally, in the step S2, the flow ratio of SF6 and Ar gas is controlled to be 5:1-3:1; Optionally, in the step S2, the flow rate of SF6 gas introduced into the cavity is 10-30sccm, and the flow rate of Ar gas is 2-10sccm; Optionally, in the step S3, the ICP power is adjusted to be 300-500W, and the RF power is adjusted to be 20-50W; Optionally, in the step S3, the working gas pressure is set to be 5-10mTorr; Optionally, in the step S3, the temperature of the sample stage is set to be 20-80℃.

[0008] Compared with the prior art, the technical scheme of the present application has at least one of the following beneficial effects: 1. The fluorine-based gas SF6 is used as the etching gas, the F free radicals in the plasma react with silicon and molybdenum in the molybdenum silicide to generate volatile products such as silicon tetrafluoride (SiF4), and there is no polymer by-product attached to the cavity wall, so that the molybdenum silicide layer can be effectively etched; 2. By adding a small amount of Ar gas as a diluent gas, the physical bombardment effect in the etching process is enhanced, the steepness of the sidewall of the molybdenum silicide layer is improved, and the lateral corrosion is effectively reduced; 3. The fluorine-based gas can improve production safety and effectively reduce production cost. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a phase shift mask processing flow; Figure 2 is a schematic diagram of dry etching of a molybdenum silicide layer; Figure 3 is an AFM diagram of a molybdenum silicide structure etched by the embodiment of the application; Figure 4 is a SEM diagram of a molybdenum silicide structure etched by the embodiment of the application. DETAILED DESCRIPTION

[0010] The application will be further described below in conjunction with the drawings and specific embodiments. It should be noted that the drawings are in a simplified form and non-precise scale, and only schematically illustrate the basic concept of the application, and the number, shape and scale of the components in actual implementation can be more complex, and therefore should not limit the protection scope of the application.

[0011] In addition, in the specific description of the following embodiments, specific details are provided to facilitate a more thorough understanding of the examples, and those skilled in the art can practice without these specific details.

[0012] The embodiment provides a dry etching method of a molybdenum silicide layer. An etching machine used in the etching process is an inductively coupled plasma etching machine (ICP), and the model is PlasmaPro100Cobra. The photoresist has completed exposure, development and other patterning operations, and the pattern is a grating structure with a line width of 800 nm.

[0013] The method specifically comprises the following steps. S1, placing the patterned molybdenum silicide into the etching machine.

[0014] In this step, the patterning specifically means that the photoresist coated on the molybdenum silicide layer is exposed by laser direct writing or electron beam direct writing, and developed.

[0015] S2, introducing the mixed SF6 and Ar gas into the cavity of the etching machine.

[0016] In this step, the flow ratio of SF6 and Ar gas is controlled to be 5:1-3:1, and more specifically, the flow rate of SF6 gas introduced into the cavity is 10-30sccm; the flow rate of Ar gas is 2-10sccm.

[0017] S3, radio frequency ignition ignition, adjusting ICP power, RF power and working gas pressure, and etching.

[0018] In this step, the ICP power regulation range is 300-500W; the RF power regulation range is 20-50; the working gas pressure setting range is 5-10mTorr; the sample stage temperature setting is 20-80℃.

[0019] S4, reach the etching time, complete etching.

[0020] In combination with the accompanying Figure 2 The basic principle of the dry etching method of the molybdenum silicide according to the present application is as follows: During the dry etching of the molybdenum silicide layer, fluorine-based gas SF6 is excited into plasma as etching gas in a high-vacuum cavity, which contains F + and F neutral particles and other active reaction ions. These active substances chemically react with the molybdenum silicide not protected by the photoresist to generate volatile substances such as SiF4, which are then pumped away. The added auxiliary inert gas Ar is ionized by high voltage to form Ar + , which carries a large kinetic energy to bombard the exposed molybdenum silicide layer under the direction of the electric field, on the one hand to break the chemical bonds of the molybdenum silicide to accelerate the chemical reaction, and on the other hand to reduce the lateral corrosion in the etching process due to its good directionality, which is conducive to obtaining a steep etching profile and a clean sidewall.

[0021] Under suitable etching parameters, an ideal etching profile, etching rate and high selectivity can be obtained.

[0022] The embodiment of the present application uses a standard phase shift mask substrate and implements direct writing exposure patterning using DUV laser with a wavelength of 266nm.

[0023] Based on the above steps S1-S4, the above steps are more specifically described based on the selected specific parameters, as follows: First, the 90nm thick patterned molybdenum silicide is transferred into the etching cavity through the Loadlock cavity, the sample stage (i.e. the lower electrode) temperature is set to 20℃, and the vacuum is extracted to 1×10 -6 mTorr.

[0024] The SF6 and Ar gas flow meters (MFC) are adjusted respectively, the SF6 flow is set to 15sccm, the Ar flow is set to 5sccm; the ICP power is set to 450W, the RF power is set to 30W; the working gas pressure is set to 8mTorr; the etching time is set to 30s; the radio frequency ignition is ignited, and the etching starts.

[0025] After the etching is completed, the sample is taken out and sent into the PMC1600 mask cleaning machine for stripping and cleaning.

[0026] Finally, the etching result is detected by atomic force microscope (AFM) and electron microscope (SEM).

[0027] Combine Figure 3 、 Figure 4 In the embodiment, the molybdenum silicide pattern prepared by dry etching has an RMS of about 0.561 nm, a sidewall steepness greater than 80°, and less sidewall deposition, which is conducive to obtaining a smooth sidewall.

[0028] In summary, the dry etching method for the molybdenum silicide layer of the above embodiment is suitable for etching the phase-shift layer in the phase-shift mask, can obtain a good etching selectivity and smooth and steep sidewalls, and has the advantages of good safety and low production cost.

[0029] It should be pointed out that the above embodiments are only for illustrating the technical ideas and features of the present invention and cannot limit the scope of protection of the present invention. Any equivalent substitutions or changes made based on the essential content of the present invention are within the scope of protection of the present invention.

Claims

1. A molybdenum silicide layer dry etching method for dry etching and pattern transfer of a molybdenum silicide phase shift layer in a phase shift mask; characterized in that: The following steps are involved: S1, placing the patterned molybdenum silicide layer into an etching machine; S2, introducing the mixed SF6 and Ar gas into the etcher chamber; S3, RF ignition, adjusting ICP power, RF power and working pressure to perform etching; S4. The etching time is reached and the etching is completed.

2. The dry etching method for a molybdenum silicide layer according to claim 1, wherein: In step S1 , the patterning method for the molybdenum silicide layer includes: exposing the photoresist coated on the molybdenum silicide layer by laser direct writing or electron beam direct writing, and developing.

3. The dry etching method for a molybdenum silicide layer according to claim 1, wherein: In step S1 , a patterned molybdenum silicide layer is located on a quartz substrate.

4. The dry etching method for a molybdenum silicide layer according to claim 1, wherein: In step S2, the purity of SF6 and Ar gases is greater than or equal to 99.999%.

5. The dry etching method for a molybdenum silicide layer according to claim 1, wherein: In step S2, the flow ratio of SF6 and Ar gas is set to a range of 5:1-3:

1.

6. The dry etching method for a molybdenum silicide layer according to claim 1, wherein: In step S2, the SF6 gas flow rate range is set to 10-30 sccm; the Ar gas flow rate range is set to 2-10 sccm.

7. The dry etching method for a molybdenum silicide layer according to claim 1, wherein: In step S3, the ICP power setting range is set to 300-500W; the RF power setting range is set to 20-50W.

8. The dry etching method for a molybdenum silicide layer according to claim 1, wherein: In step S3, the working pressure setting range is set to 5-10 mTorr.

9. The dry etching method for a molybdenum silicide layer according to claim 1, wherein: In step S3, the sample stage temperature is set to 20-80°C.

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