A method for removing polymer in dry etching

Abstract

The application provides a method for removing polymer in dry etching, comprising etching a hard mask by using a gas containing CF group at an initial temperature in a hard mask etching process; over-etching the hard mask after the hard mask etching, adjusting the initial temperature to a target temperature in the hard mask over-etching process, so that the polymer generated in the hard mask etching process sublimates, and maintaining the first time after the opening state of the exhaust device is adjusted to discharge the sublimated polymer from the processing chamber. In the hard mask etching process of the wafer, the temperature in the processing chamber is adjusted to the target temperature, so that the polymer remaining on the hard mask sublimates and is discharged outward through the exhaust device, thereby effectively removing the polymer remaining on the hard mask and improving the product yield.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more particularly to a method for removing polymers during dry etching. Background Technology

[0002] Dry etching is a technique that uses plasma for thin-film etching. When gases exist in plasma form, they possess two key characteristics: firstly, the chemical reactivity of these gases in plasma is much stronger than under normal conditions. Depending on the material being etched, selecting the appropriate gas allows for a faster reaction with the material, achieving the etching removal purpose; secondly, an electric field can be used to guide and accelerate the plasma, giving it sufficient energy. When this energy bombards the surface of the material being etched, it ejects atoms from the material, thus achieving the etching purpose through physical energy transfer. Therefore, dry etching is the result of a balance between physical and chemical processes on the wafer surface.

[0003] However, in existing processes, Ti-containing polymers remain on the wafer surface after dry etching, and subsequent wet cleaning cannot remove Ti-containing polymers while maintaining the morphology. These residual polymers may cause leakage current between interlayer dielectric (ILD) layers, affecting yield.

[0004] Therefore, it is necessary to provide a novel method for removing polymers in dry etching to solve the aforementioned problems in the prior art. Summary of the Invention

[0005] The purpose of this invention is to provide a method for removing polymers in dry etching, which can effectively remove titanium polymers in the dry etching process and improve product yield.

[0006] To achieve the above objective, the method for removing polymers in dry etching according to the present invention includes:

[0007] During the hard mask etching process, the hard mask is etched using a gas containing CF base at an initial temperature;

[0008] After the hard mask is etched, the hard mask is over-etched. During the hard mask over-etching process, the initial temperature is adjusted to the target temperature so that the polymer generated during the hard mask etching process sublimates. At the same time, the opening state of the vacuum equipment is adjusted and maintained for a first moment to discharge the sublimated polymer.

[0009] The beneficial effect of the method for removing polymers in dry etching described in this invention is that, during the hard mask over-etching process of the wafer, the temperature in the processing chamber is adjusted to the target temperature, so that the polymers remaining on the hard mask sublimate and are discharged outward through the vacuum equipment, thereby effectively removing the polymers remaining on the hard mask and improving product yield.

[0010] Optionally, the polymer includes at least one of F3Ti, TiF4, and Ti.

[0011] Optionally, the target temperature is determined based on relevant information about the polymer and a preset pressure value, wherein the preset pressure value is the pressure value inside the processing chamber after the vacuum device is turned on.

[0012] Optionally, the polymer-related information includes the latent heat of phase change, molar mass, and density of the polymer.

[0013] Optionally, the calculation process for the target temperature satisfies the following formula:

[0014]

[0015] Wherein, L is the latent heat of phase change of the polymer, R is the universal gas constant, M is the molar mass of the polymer, p is the preset pressure value, T is the target temperature, including the first target temperature and the second target temperature, and ρa is the average of the zero-pressure density and the density of the polymer at the preset pressure value p.

[0016] Optionally, the first time interval is 30 to 40 seconds. The advantage of this is that it ensures the residual polymer is fully sublimated during the second time interval.

[0017] Optionally, the polymer-related information is determined based on the proportion of the CF-based gas. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method for removing polymers in dry etching according to the present invention.

[0019] Figure 2 This is a comparison image showing the process of removing polymers in dry etching as described in this invention, before and after polymer removal. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed following the word and its equivalents, but do not exclude other elements or objects.

[0021] To address the problems existing in the prior art, embodiments of the present invention provide a method for removing polymers during dry etching, referring to... Figure 1 It includes the following steps:

[0022] S101. During the hard mask etching process, the hard mask is etched using a gas containing CF base at the initial temperature;

[0023] S102. After the hard mask is etched, the hard mask is over-etched. During the hard mask over-etching process, the initial temperature is adjusted to the target temperature so that the polymer generated during the hard mask etching process sublimates. The opening state of the vacuum equipment is adjusted and maintained for a first moment to discharge the sublimated polymer from the processing chamber.

[0024] In this embodiment, due to the continuous input of etching gas and the continuous generation of gaseous reactants during the etching process, the evacuation equipment operates continuously throughout the etching process to maintain the pressure in the chamber at a low level. During the dry etching of the wafer, when using CF-based gas to etch the hard mask on the titanium nitride layer, titanium nitride reacts with CF-based plasma to form titanium-containing polymer residues on the surface of the hard mask, which cannot be effectively removed in subsequent processes. Therefore, in this solution, after the hard mask etching is completed, during the over-etching process, the temperature in the processing chamber is adjusted from the initial temperature to the target temperature, which is beneficial for the generated polymer to fully sublimate in the next step. Then, the plasma excitation and gas intake are stopped, and the opening state of the evacuation equipment is adjusted. The swing valve of the evacuation equipment is opened to the maximum value to achieve the minimum gas pressure in the chamber, i.e., the preset pressure value. At the same time, the target temperature and preset pressure value are maintained for the first moment to ensure that the sublimated polymer is fully discharged, thereby completing the polymer removal process and effectively reducing polymer residue.

[0025] It should be noted that the target temperature is determined based on the relevant information of the polymer and a preset pressure value. The preset pressure value is the pressure value in the processing chamber after the vacuum device is turned on. Since the target temperature is calculated based on the relevant information of the polymer and the preset pressure value in the processing chamber after the vacuum device is turned on, the polymer is under good sublimation conditions after the vacuum device is turned on, so as to improve the sublimation efficiency of the polymer and ensure that the sublimated polymer is completely extracted by the vacuum device.

[0026] In some embodiments, the polymer includes at least one of F3Ti, TiF4, and Ti, and the three usually coexist. Some of the F3Ti undergoes a disproportionation reaction, but the amount of the reaction is small. The sublimation point of TiF4 is much lower than that of F3Ti, while the remaining Ti usually comes from the disproportionation reaction. The main component is F3Ti, and the contents of the other TiF4 and Ti are small. The polymer-related information includes the latent heat of phase transition, molar mass, and density of the polymer.

[0027] In some other embodiments, the polymer-related information is obtained by performing TEM sample preparation and EDS composition analysis on the wafer after the process is completed. Since the above processes are all existing technologies, this solution does not impose any special limitations on them and will not be described in detail here.

[0028] Furthermore, the polymer-related information is determined based on the proportion of the CF-based gas. Since polymers generally contain one or more of F3Ti, TiF4, and Ti, the latent heat of phase change, molar mass, and density values ​​of the polymer are all average values ​​among the corresponding parameters of F3Ti, TiF4, and Ti, to ensure the accuracy of subsequent calculation results.

[0029] refer to Figure 2 , Figure 2 The left side shows a schematic diagram of the wafer structure without using this method to remove the polymer, while the right side shows a schematic diagram of the structure with this method to remove the polymer axis. It can be clearly seen that the polymer 2 on the hard mask layer 1 is effectively removed, and the hard mask layer is not affected, which effectively improves the wafer processing yield.

[0030] In some other embodiments, the calculation process of the target temperature satisfies the following formula (1):

[0031]

[0032] Wherein, L is the latent heat of phase change of the polymer, R is the universal gas constant, M is the molar mass of the polymer, p is the preset pressure value, T is the target temperature, and ρa is the average of the zero-pressure density and the density at the preset pressure value p of the polymer.

[0033] Specifically, the target sublimation temperature T of the polymer and the preset pressure value p satisfy the following formula (2):

[0034]

[0035] Where L is the latent heat of phase change of the polymer, and v2 and v1 are the specific volumes of the polymer before and after the phase change, respectively.

[0036] That is, it satisfies formula (3).

[0037]

[0038] Where v = v2 - v1, formula (1) can be obtained after derivation.

[0039] In some embodiments, the first time interval is 30 to 40 seconds to ensure that the remaining polymer is fully sublimated within the second time interval.

[0040] During the hard mask over-etching process of the wafer, the temperature in the processing chamber is adjusted to the target temperature, causing the polymer remaining on the hard mask to sublimate and be discharged outward through the vacuum equipment, thereby effectively removing the polymer remaining on the hard mask and improving product yield.

[0041] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A method for removing polymers during dry etching, characterized in that, include: During the hard mask etching process, the hard mask is etched using a gas containing CF base at the initial temperature, and the gas extraction equipment operates continuously throughout the etching process. After the hard mask is etched, the hard mask is over-etched. During the hard mask over-etching process, the initial temperature is adjusted to the target temperature so that the polymer generated during the hard mask etching process sublimates. Then, the plasma excitation and gas intake are stopped, and the opening state of the pumping equipment is adjusted simultaneously. The swing valve of the pumping equipment is opened to the maximum value to achieve the preset pressure value. At the same time, the target temperature and preset pressure value are maintained for a first moment so that the sublimated polymer is discharged from the processing chamber. The target temperature is determined based on relevant information about the polymer and a preset pressure value, wherein the preset pressure value is the lowest air pressure in the processing chamber after the vacuum device is turned on.

2. The method for removing polymers in dry etching according to claim 1, characterized in that, The polymer includes at least one of F3Ti, TiF4, and Ti.

3. The method for removing polymers from dry etching according to claim 1, characterized in that, The relevant information of the polymer includes its latent heat of phase change, molar mass, and density.

4. The method for removing polymers in dry etching according to claim 3, characterized in that, The calculation process for the target temperature satisfies the following formula: Wherein, L is the latent heat of phase change of the polymer, R is the universal gas constant, M is the molar mass of the polymer, p is the preset pressure value, and T is the target temperature. This is the average of the zero-pressure density and the density at a preset pressure value p of the polymer.

5. The method for removing polymers in dry etching according to claim 1, characterized in that, The first moment is 30 to 40 seconds.

6. The method for removing polymers in dry etching according to claim 1, characterized in that, The relevant information of the polymer is determined based on the proportion of the CF-based gas.

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