Method of making low dielectric constant films and semiconductor structures

Abstract

The present application provides a method for preparing a low dielectric constant film and a semiconductor structure. The method comprises: providing a mixture to a substrate surface in a plasma environment, the mixture comprising an alkylsiloxane precursor and a porogen, the mixture being used to generate a film on the substrate surface, the mixture having a first supply parameter; providing an oxygen-containing gas to the substrate surface, the oxygen-containing gas having a second supply parameter; obtaining a first film sample from the current film and measuring a first film thickness; irradiating the substrate with UV to remove at least a portion of the porogen to form a low dielectric constant film having pores; obtaining a second film sample from the low dielectric constant film and measuring a second film thickness, a film mechanical strength and a dielectric constant k value; determining whether the low dielectric constant film meets a preset process result, and in response to a determination result that the low dielectric constant film does not meet the preset process result, adjusting any of the first supply parameter, the second supply parameter, an environmental parameter of a process chamber and a UV parameter.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductors, and more particularly to a method for preparing a low dielectric constant film and a semiconductor structure. BACKGROUND

[0002] Low dielectric constant (low-k) materials, such as silicon oxide (SiOx), silicon carbide (SiCx), and carbon-doped silicon oxide (SiOCx), are widely used in semiconductor device manufacturing. The use of low-k materials as intermetallic and / or interlevel dielectrics between conductive interconnects reduces signal propagation delay due to capacitive effects. The lower the dielectric constant of the dielectric layer, the lower the capacitance of the dielectric, and the lower the RC delay of the integrated circuit (IC).

[0003] Traditionally, low-k materials are defined as materials having a dielectric constant k less than that of silicon dioxide, i.e., k < 4. Typical methods for obtaining low-k materials include doping silicon dioxide with various carbon- or fluorine-containing functional groups. Fluorosilicate glass (FSG) has a dielectric constant k of typically 3.5-3.9, while carbon-doping methods can further reduce k to about 2.5. Materials having a k value less than 2.5 are referred to as ultra-low-k (uLk) dielectric materials.

[0004] Pore-forming agents are typically used in forming low-k films on semiconductor substrates. After the film skeleton is formed, UV light is used to remove small molecules and leave pores, thereby reducing the k value. However, if there are too few pores and the porosity is too low, the k value cannot meet the requirements; if there are too many pores and the porosity is too high, the film structure is prone to collapse, resulting in insufficient strength of the film. In addition, the molecular combination is random and uncontrollable. Therefore, there is currently no effective method to regulate the density, porosity, and collapse rate of the film. SUMMARY

[0005] The present application provides a method for preparing a low dielectric constant film and a semiconductor structure, which can effectively obtain a low dielectric constant film that meets the k value requirements.

[0006] To solve the above technical problems, the present application provides a method for preparing a low dielectric constant film, comprising: providing a mixture to a substrate surface in a plasma environment, the mixture comprising an alkylsiloxane precursor and a pore-forming agent, the mixture being used to generate a film on the substrate surface, the film comprising a Si-O-Si-containing film skeleton, alkane end C m H 2m+1and the pore former, wherein the first supply parameters of the mixture include a flow rate of the alkyl siloxane precursor and / or a flow rate of the pore former, m is a positive integer greater than or equal to 1; providing an oxygen-containing gas to the substrate surface, oxygen-doping the thin film skeleton, wherein the second supply parameters of the oxygen-containing gas include an oxygen-containing gas flow rate and / or an oxygen-containing gas flow speed; obtaining a first thin film sample from the current thin film and measuring a first thin film thickness; irradiating the substrate with UV to remove at least a portion of the pore former, forming a low dielectric constant thin film having pores; obtaining a second thin film sample from the low dielectric constant thin film and measuring a second thin film thickness, a thin film mechanical strength, and a dielectric constant k value; determining whether the low dielectric constant thin film meets a preset process result, wherein the preset process result includes a thin film collapse rate, the thin film mechanical strength, and the dielectric constant k value, the thin film collapse rate being determined by the first thin film thickness and the second thin film thickness; and in response to a determination result that the low dielectric constant thin film does not meet the preset process result, adjusting any of the first supply parameters, the second supply parameters, environmental parameters of a process chamber, and UV parameters, wherein the environmental parameters include any of a power of a plasma generating device, a temperature in the chamber, and a pressure in the chamber, and the UV parameters include irradiation parameters of the UV.

[0007] In an embodiment of the present application, the first thin film sample is analyzed using a spectroscopy technique, and the second supply parameters are adjusted according to an analysis result so that the supply of the oxygen-containing gas meets the preset process result.

[0008] In an embodiment of the present application, the first thin film sample is analyzed using a spectroscopy technique, and the second supply parameters are adjusted according to an analysis result so that the supply of the oxygen-containing gas meets the preset process result, including: obtaining a first characteristic signal of the first thin film sample using a spectroscopy technique, the spectroscopy technique including solid-state nuclear magnetic resonance or Fourier transform infrared spectroscopy, the first characteristic signal including a first wave peak corresponding to Si-O2 in the first thin film sample and a second wave peak corresponding to Si-O3 in the first thin film sample; measuring an intensity of the first wave peak and an intensity of the second wave peak; and adjusting the second supply parameters so that the intensity of the first wave peak is less than a first threshold value and the intensity of the second wave peak is greater than a second threshold value, wherein the first threshold value is less than the second threshold value.

[0009] In an embodiment of the present application, the first thin film sample and the second thin film sample are analyzed using a spectroscopy technique, and the UV parameters are adjusted according to an analysis result so that the UV irradiation meets the preset process result.

[0010] In an embodiment of the present application, the first film sample and the second film sample are analyzed by using a spectrum analysis technique, and the UV parameters are adjusted according to the analysis results so that the UV irradiation meets the preset process result, including: obtaining a second characteristic signal of the first film sample by using a spectrum analysis technique, the spectrum analysis technique including solid-state nuclear magnetic resonance or Fourier transform infrared spectroscopy, the second characteristic signal including a third wave peak corresponding to -CH2 in the first film sample and a fourth wave peak corresponding to -CH3 in the first film sample; measuring the intensity of the third wave peak and the intensity of the fourth wave peak; obtaining a third characteristic signal of the second film sample by using the spectrum analysis technique, the third characteristic signal including a fifth wave peak corresponding to -CH2 in the second film sample and a sixth wave peak corresponding to -CH3 in the second film sample; measuring the intensity of the fifth wave peak and the intensity of the sixth wave peak; and adjusting the UV parameters so that the intensity of the fifth wave peak is less than the intensity of the third wave peak, and the intensity of the sixth wave peak is less than the intensity of the fourth wave peak.

[0011] In an embodiment of the present application, before judging whether the low dielectric constant film meets the preset process result, further comprising: adjusting the first supply parameter of the mixture so that the dielectric constant k value of the current film reaches a base value.

[0012] In an embodiment of the present application, the first supply parameter further includes any one of a flow rate of the alkyl siloxane precursor, a flow rate of the porogen, and a relative ratio of the porogen and the alkyl siloxane precursor, and the method further includes: in response to the film collapse rate not meeting the preset process result, adjusting the relative ratio of the porogen and the alkyl siloxane precursor.

[0013] In an embodiment of the present application, further comprising: in response to the film mechanical strength not meeting the preset process result, adjusting a film deposition rate and a temperature in the chamber, wherein the film deposition rate is related to any one or more of the first supply parameter, the second supply parameter, and the environmental parameter.

[0014] In an embodiment of the present application, the environmental parameter further includes any one of a substrate temperature, a showerhead temperature, and a distance between the substrate and the showerhead.

[0015] In an embodiment of the present application, the second supply parameter further includes a concentration of the oxygen-containing gas.

[0016] In an embodiment of the present application, the UV irradiation parameter includes any one of a UV intensity, a UV wavelength, and an irradiation time length, and the UV parameter further includes any one of a UV lamp power, a UV lamp number, and a reflective film effect.

[0017] In an embodiment of the present application, the thickness and material of the reflective film can affect the UV irradiation: for example, an anti-reflective film with a thickness of 50-200 nm is generally used to prevent UV light from irradiating the wafer surface and reducing the effect of UV light by reflecting energy. The specific film material can be, for example, a composite material that absorbs UV light.

[0018] In an embodiment of the present application, the preset process result is that the film collapse rate is in a range of 0-20%, the film mechanical strength is in a range of 5 GPa-10 GPa, and the dielectric constant k value is less than a threshold range of 2.5-2.6.

[0019] The present application also proposes a semiconductor structure formed by the method described above to solve the above technical problems.

[0020] The method for preparing a low dielectric constant film of the present application provides a mixture to a substrate surface in a plasma environment to form a film, provides an oxygen-containing gas to the substrate surface to perform oxygen doping on a film skeleton, and obtains film samples before and after UV irradiation of the substrate, respectively, to calculate and determine whether the film collapse rate, the film mechanical strength, and the dielectric constant k value of the film satisfy a preset process window. If not, any of the first supply parameter of the mixture, the second supply parameter of the oxygen-containing gas, the environmental parameter of the process chamber, and the UV parameter is adjusted, so that the skeleton reaction mode and balance can be accurately controlled, and a low dielectric constant film that satisfies the k value process requirement is obtained. Moreover, the method of the present application does not introduce adjustment molecules other than Si, O, and C, and does not cause pollution or other performance degradation in subsequent processes. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings are included to provide a further understanding of the present application, and they are collected and constitute a part of the present application. The drawings illustrate embodiments of the present application and, together with the specification, serve to explain the principles of the present application. In the drawings:

[0022] Figure 1 is an exemplary flowchart of the method for preparing a low dielectric constant film of an embodiment of the present application;

[0023] Figure 2 is a film skeleton structure before UV irradiation;

[0024] Figure 3 is a film skeleton structure after UV irradiation;

[0025] Figure 4 is a molecular structure fragment with 2 O and 2 CH3 on a Si;

[0026] Figure 5 is a molecular structure fragment of one Si bonding with three O and one CH3;

[0027] Figure 6 is a schematic diagram of a preset process window in an embodiment of the present application;

[0028] Figure 7 is a solid-state nuclear magnetic resonance spectrum obtained by analyzing the first thin film sample using silicon-29 solid-state nuclear magnetic resonance;

[0029] Figure 8 is a solid-state nuclear magnetic resonance spectrum obtained by analyzing the first thin film sample and the second thin film sample using carbon-13 solid-state nuclear magnetic resonance. DETAILED DESCRIPTION

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some examples or embodiments of the present application, and for those skilled in the art, the present application can also be applied to other similar scenarios without creative labor, unless it is obvious from the language environment or otherwise stated. In the drawings, the same reference numbers represent the same structures or operations, unless the context clearly indicates otherwise.

[0031] As shown in the present application, unless the context clearly indicates otherwise, the words "one", "a", "an", and / or "the" do not specifically refer to the singular, but can also include the plural. Generally speaking, the terms "comprise" and "include" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements.

[0032] Unless otherwise specifically stated, the relative arrangement of the components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that the sizes of the various parts shown in the drawings are not drawn in proportion to the actual proportions. The technology, methods and devices known to those skilled in the relevant art can not be discussed in detail, but under appropriate circumstances, the technology, methods and devices should be considered as part of the specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0033] In the description of the present application, it needs to be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicated orientation or position relationship generally based on the orientation or position relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, without making the opposite statement, these orientation words do not indicate and imply that the device or element indicated must have a particular orientation or be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the scope of protection of the present application; the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component itself.

[0034] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper" and the like can be used herein to describe the spatial position relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0035] In addition, it needs to be explained that the use of "first", "second" and the like to define parts is only for the convenience of distinguishing the corresponding parts, and the above words have no special meaning unless otherwise stated, therefore, it cannot be understood as a limitation on the scope of protection of the present application. In addition, although the terms used in the present application are selected from the commonly known and used terms, some terms mentioned in the specification of the present application may be selected by the applicant according to his or her judgment, and the detailed meaning of each term is described in the relevant part of the description. In addition, the present application is required to be understood not only by the actual terms used, but also by the meaning implied by each term.

[0036] Flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in sequence. On the contrary, various steps can be processed in reverse order or simultaneously. Meanwhile, or other operations are added to these processes, or one or more steps of operation are removed from these processes.

[0037] In the method for preparing low dielectric constant film of the present application, the film can be formed by CVD, PVD, ALD and the like. The present application does not limit the specific process.

[0038] Figure 1 is an exemplary flowchart of a method for preparing a low dielectric constant film according to an embodiment of the present application. Referring to FIG. 1, the method 100 according to the embodiment includes: Figure 1

[0039] Step S110: providing a mixture to a substrate surface in a plasma environment, the mixture including an alkylsiloxane precursor and a porogen, the mixture being used to generate a film on the substrate surface, the film including a Si-O-Si containing film skeleton, alkane end C m H 2m+1 and the porogen, wherein a first supply parameter of the mixture includes a flow rate of the alkylsiloxane precursor and / or a flow rate of the porogen, and m is a positive integer greater than or equal to 1;

[0040] Step S120: providing an oxygen-containing gas to the substrate surface, the oxygen-doping the film skeleton, wherein a second supply parameter of the oxygen-containing gas includes a flow rate of the oxygen-containing gas and / or a flow rate of the oxygen-containing gas;

[0041] Step S130: obtaining a first film sample from the current film and measuring a first film thickness;

[0042] Step S140: irradiating the substrate with UV light to remove at least a portion of the porogen, forming a low dielectric constant film having pores;

[0043] Step S150: obtaining a second film sample from the low dielectric constant film and measuring a second film thickness, a film mechanical strength, and a dielectric constant k value;

[0044] Step S160: determining whether the low dielectric constant film meets a preset process result, wherein the preset process result includes a film collapse rate, a film mechanical strength, and a dielectric constant k value, the film collapse rate being determined by the first film thickness and the second film thickness; and

[0045] Step S170: in response to a determination result that the low dielectric constant film does not meet the preset process result, adjusting any of the first supply parameter, the second supply parameter, an environmental parameter of a process chamber, and a UV parameter, wherein the environmental parameter includes any of a power of a plasma generating device, a temperature in the chamber, and a pressure in the chamber, and the UV parameter includes an irradiation parameter of the UV light.

[0046] According to the method 100, in the process of forming the low dielectric constant film, the mixture is provided to the substrate surface in the plasma environment to generate the film including the Si-O-Si containing film skeleton, the alkane end C m H 2m+1 ​The thin film and the pore-forming agent provide an oxygen-containing gas to the substrate surface to oxygen-dope the thin film skeleton, and a first thin film sample and a second thin film sample are obtained before and after the substrate is irradiated with UV, respectively, and whether the thin film collapse rate, the thin film mechanical strength and the k value meet the preset process results are calculated and judged, and if not, any one of the first supply parameter of the mixture, the second supply parameter of the oxygen-containing gas, the environmental parameter of the process chamber and the UV parameter is adjusted, so that the skeleton reaction mode and the balance can be accurately controlled, and the thin film meeting the k value process requirement is obtained. Moreover, the method 100 does not introduce adjustment molecules other than Si, O and C, and does not cause pollution or other performance degradation to subsequent processes.

[0047] The above steps S110-S170 are described below in conjunction with the drawings.

[0048] In step S110, the mixture includes an alkylsiloxane precursor and a pore-forming agent.

[0049] In some embodiments, the alkylsiloxane precursor is DEMS (Dimethylethoxysilane), and the pore-forming agent is ATRP (alpha-Terpinene). That is, the mixture is DEMS+ATRP.

[0050] In other embodiments, in addition to DEMS, the alkylsiloxane precursor can also be: methyltrimethoxysilane, dimethyldimethoxysilane, diethoxymethylsilane, hexamethylcyclotrisiloxane, etc. The alkylsiloxane precursor only includes elements Si, O, C and H. The pore-forming agent can also be an organic polymer (such as PS, PMMA) and a surfactant (such as P123) commonly used in the art.

[0051] The thin film skeleton with Si-O-Si structure is also called a siloxane skeleton.

[0052] The thin film includes an alkane end C m H 2m+1 , and m is a positive integer greater than or equal to 1. For example, when m=1, the alkane end is methyl-CH3. When m=2, the alkane end is ethyl-C2H5. When m=3, the alkane end is propyl-C3H7.

[0053] Figure 2 The thin film skeleton structure before being irradiated with UV is shown. As Figure 2 shown, some ends of the Si-O-Si skeleton form Si-CH3 structures and Si-O-C2H5 structures. Among them, -CH3 comes from DEMS. Figure 2 The PORE shown in FIG. 1C is a pore generated by ATRP.

[0054] In step S110, the first supply parameter of the mixture includes the flow rate of the alkylsiloxane precursor and / or the flow rate of the porogen. It is to be noted that the mixture can include multiple substances, such as the DEMS and ATRP described above. When adjusting the parameter, the flow rate of only one of the substances can be adjusted, or the flow rates of multiple substances can be adjusted simultaneously, all of which are within the scope of the present application. The mixture is usually introduced with a carrier gas, and thus the flow rate of the mixture is determined by the flow rate of the carrier gas.

[0055] In step S120, in some embodiments, providing the oxygen-containing gas to the substrate surface includes: introducing the oxygen-containing gas into the chamber by using a PECVD process, and exciting the gas to ionize by using an energy source such as radio frequency or microwave, so as to obtain an oxygen plasma.

[0056] In some embodiments, the oxygen-containing gas includes O2 or O3. The introduction of the oxygen-containing gas does not introduce other elements except O element, and does not cause contamination or other performance degradation in subsequent processes.

[0057] In some embodiments, the oxygen-containing gas can include CO2. The use of CO2 does not introduce other elements except C and O. However, since too much C element can cause particle problems in subsequent processes, it is preferred to use O2 or O3.

[0058] In step S120, the oxygen-containing gas is provided at the first supply parameter. The first supply parameter includes the flow rate of the oxygen-containing gas and / or the flow rate of the oxygen-containing gas. Taking O2 as an example of the oxygen-containing gas, the first supply parameter includes the flow rate of the oxygen and / or the flow rate of the oxygen. It is to be noted that when introducing a process gas such as O2 into the reaction chamber, a carrier gas is usually used. Therefore, the flow rate of the oxygen and the flow rate of the oxygen refer to the flow rate of the gas including the carrier gas.

[0059] In some embodiments, the first supply parameter can also include the concentration of the oxygen-containing gas. In an embodiment, the concentration of the oxygen can be obtained by the ratio of the oxygen and the carrier gas.

[0060] In step S130, since the thin film has been generated in step S110, and the thin film skeleton in the thin film has been doped with oxygen in step S120, the current thin film should be understood as the thin film after oxygen doping. The present application does not limit the method of obtaining the first thin film sample from the current thin film, and conventional means in the art can be used. The first thin film thickness of the thin film formed in the first thin film sample can be measured by slicing. The first thin film thickness can be obtained by image analysis, and the present application does not limit this. It can be understood that the first thin film sample includes the substrate itself, such as the substrate. Therefore, the first thin film thickness measured is the thickness of the thin film as expressed in the literal sense, and does not include the thickness of the substrate.

[0061] At step S140, the substrate is subjected to UV irradiation (UV cure) to remove at least a portion of the porogen and form a low-k film having pores. It is understood that the UV provided has certain UV parameters. The UV parameters include the irradiation parameters of the UV. For example, the irradiation intensity of the UV, the irradiation time, etc. The amount of porogen removed can be controlled by adjusting the UV parameters. The porogen is driven out of the film by the UV irradiation, while cross-linking reactions occur inside the film, thereby forming a porous structure. During this process, if the mechanical strength of the film skeleton is not strong enough to support the pore structure, or the internal stress cannot be balanced, the skeleton may collapse, the pores may close, i.e., the "collapse phenomenon" may occur. After the collapse, the thickness of the film changes.

[0062] In some embodiments, the UV parameters further include any of the UV lamp power, the number of UV lamps, and the effect of the reflective film. The thickness and material of the reflective film can affect the UV irradiation: for example, an anti-reflective film with a thickness of 50-200 nm is generally used to prevent the UV light from being reflected by the wafer surface to reduce the effect of the UV light by reflecting energy. The specific film material may, for example, be a composite material that absorbs UV light.

[0063] Figure 3 The film skeleton structure after UV irradiation is shown. As shown in Figure 3 Some Si-O-C cross-linking structures are formed inside the film. At the same time, some -CH3 are removed.

[0064] At step S150, a second film sample is obtained from the low-k film having pores after UV irradiation, and the second film thickness, the film mechanical strength, and the dielectric constant k value are measured. The second film sample can be obtained and the second film thickness can be measured in the same way as in step S130.

[0065] The film mechanical strength can include hardness and modulus, both of which can be measured by conventional methods. For example, the hardness of the film can be measured by a hardness tester, and the measurement methods include indentation, scratching, etc., which are not limited in the present application.

[0066] The measurement of the k value can be performed by conventional methods in the art, such as spectroscopic ellipsometry (SE), transmittance / reflectance spectroscopy, transmission electron microscopy (TEM) combined with electron energy loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS), etc.

[0067] In step S160, the film collapse rate can be calculated according to the first film thickness before UV irradiation and the second film thickness after irradiation. For example, the film collapse rate = (first film thickness - second film thickness) / first film thickness.

[0068] In step S160, the present application simultaneously considers the film collapse rate, the film mechanical strength, and the dielectric constant k value. If the three parameters simultaneously satisfy the preset process results, it indicates that the film meets the requirements. If the three parameters do not simultaneously satisfy the preset process results, in step S170, any one of the first supply parameter, the second supply parameter, the environmental parameter of the process chamber, and the UV parameter is adjusted, and steps S110-S170 are repeatedly executed until the three parameters simultaneously satisfy the preset process results.

[0069] It should be noted that in order to obtain a low-k film, it is generally necessary to increase the porosity of the film. However, when the porosity is too high, the mechanical strength of the film will decrease, and the film will collapse under the action of the porogen removal or stress. Therefore, while meeting the k value requirement, the film collapse rate and hardness also need to be considered, so that the obtained film can maintain the required characteristics in subsequent processes.

[0070] In some embodiments, according to steps S110-S170, the adjustment of the film collapse rate, the film mechanical strength, and the dielectric constant k value can be achieved only by adjusting the second supply parameter of the oxygen-containing gas, so that the three parameters simultaneously satisfy the preset process results.

[0071] Figure 4 is a structure in which one Si is connected to two O and two CH3, Figure 5 is a structure in which one Si is connected to three O and one CH3. In combination with Figure 4 and Figure 5 to explain the principle of adjusting the film collapse rate, the film mechanical strength, and the dielectric constant k value only by adjusting the first supply parameter of the oxygen-containing gas. Studies have shown that by introducing oxygen plasma, the ratio of Si-O-Si and Si-CH3 can be controlled. Referring to Figure 4 and Figure 5 When the amount of O is insufficient, the structure in which one Si is connected to two O and two CH3, i.e., the structure shown in Figure 4 tends to be generated in the film skeleton. When O increases, the reaction equilibrium can be pushed to one side, i.e., the structure in which one Si is connected to three O and one CH3, i.e., the structure shown in Figure 5 tends to be generated. Studies have shown that according to the structure characteristics shown in Figure 4 the effect of the porogen will be reduced, and the film collapse rate after subsequent UV irradiation will be large. According to Figure 5The structural features shown are conducive to the formation of holes after UV irradiation, and the skeleton is not prone to collapse. However, if the O content is increased blindly, the skeleton reaction may not be complete, the porogen may not be able to play a role, and the dielectric constant k value may be limited. Therefore, in this embodiment, the first supply parameters of the oxygen-containing gas are adjusted according to the film shrinkage rate, the film mechanical strength, and the dielectric constant k value, so that a film that meets the preset process window can be obtained.

[0072] Figure 6 is a schematic diagram of a preset process result in an embodiment of the present application. Referring to Figure 6 shown, which includes a double longitudinal axis graph, the horizontal axis is hardness, the unit is GPa, the left longitudinal axis is the dielectric constant k, and the right longitudinal axis is the film shrinkage rate, the unit is %. In this embodiment, the film shrinkage rate ranges from 0 to 20%, the hardness ranges from 5 GPa to 10 GPa, and the dielectric constant k value ranges from less than a threshold range, which is 2.5-2.6. In Figure 6 the embodiment shown, the dielectric constant k value ranges from less than 2.5. The three ranges form a range enclosed by the block 610 in Figure 6 . When the measured film shrinkage rate, hardness, and dielectric constant k value fall within the block 610, the preset process result is met. The current second supply parameters of the oxygen-containing gas can be used as standard parameters for the preparation method of the low dielectric constant film. At the same time, other parameters of the current process, such as the first supply parameters of the mixture, the environmental parameters, and the UV parameters, can also be stored as standard parameters.

[0073] In some embodiments, the environmental parameters further include any of a substrate temperature, a showerhead temperature, and a distance between the substrate and the showerhead.

[0074] In some embodiments, the method 100 further includes, in response to the film mechanical strength not meeting the preset process result, adjusting a film deposition rate and a chamber temperature, wherein the film deposition rate is related to any one or more of the first supply parameters, the second supply parameters, and the environmental parameters.

[0075] The present inventors have found through research that the film deposition rate and the chamber temperature have a strong correlation with the film mechanical strength. Therefore, the film deposition rate and the chamber temperature are also referred to as "mechanical strength most sensitive parameters". That is, when the mechanical strength does not meet the preset process result, the mechanical strength most sensitive parameters can be adjusted first, so that the mechanical strength can meet the preset process result quickly.

[0076] In some cases, if it is desired to know whether the oxygen-containing gas has played a role in time, the steps in the following embodiments can also be used.

[0077] In some embodiments, after obtaining the first film sample in step S130, further comprising: analyzing the first film sample by using a spectrum analysis technique, and adjusting the second supply parameter according to the analysis result, so that the supply of the oxygen-containing gas meets the preset process result. The spectrum analysis technique is a technique of analyzing the molecular structure, composition, content and dynamic change of a substance by detecting the "spectrum signal" (such as frequency, intensity, peak position) through the interaction of the substance and electromagnetic waves (from radio waves to X-rays). By using the spectrum analysis technique, the molecular structure, composition and content of various substances in the first film sample can be analyzed, and the analysis result of interest can be obtained. For example, in order to observe the effect of the oxygen-containing gas, the content of the oxygen-containing substance or chemical bond can be analyzed, and the second supply parameter of the oxygen-containing gas can be adjusted according to the result, so that the low dielectric constant film meets the preset process result.

[0078] In some embodiments, the first film sample is analyzed by using the spectrum analysis technique, the composition and content of the oxygen-containing chemical bond are analyzed, and the second supply parameter is adjusted according to the analysis result, so that the supply of the oxygen-containing gas meets the preset process result, comprising:

[0079] Step S210: obtaining a first characteristic signal of the first film sample by using a spectrum analysis technique, the spectrum analysis technique comprising solid-state nuclear magnetic resonance or Fourier transform infrared spectroscopy, the first characteristic signal comprising a first wave peak corresponding to Si-O2 in the first film sample and a second wave peak corresponding to Si-O3 in the first film sample;

[0080] Step S220: measuring the intensity of the first wave peak and the intensity of the second wave peak; and

[0081] Step S230: adjusting the second supply parameter so that the intensity of the first wave peak is less than a first threshold value, and the intensity of the second wave peak is greater than a second threshold value, wherein the first threshold value is less than the second threshold value.

[0082] The above steps S210-S230 are described below. Figure 7 The above steps S210-S230 are described below.

[0083] In step S210, the spectrum analysis technique comprises solid-state nuclear magnetic resonance (SSNMR) or Fourier transform infrared spectroscopy (FTIR). The present specification takes SSNMR as an example for description. When FTIR is used for analysis, those skilled in the art can make adaptive changes according to the characteristics of FTIR.

[0084] In some embodiments, in step S210, the first film sample is analyzed by using silicon-29 solid-state nuclear magnetic resonance.

[0085] Figure 7is a solid-state nuclear magnetic resonance spectrum obtained by analyzing the first thin film sample using silicon-29 solid-state nuclear magnetic resonance. The horizontal axis is chemical shift, with units of ppm (parts per million), and the vertical axis is intensity (Intensity), with arbitrary units (a.u., arbitrary units). The first peak Q2 corresponds to Si-O2, i.e. the structure of 2 O and 2 CH3 connected to 1 Si as shown in Figure 4 The second peak Q3 corresponds to Si-O3, i.e. the structure of 3 O and 1 CH3 connected to 1 Si as shown in Figure 5 The second peak Q3 corresponds to Si-O3, i.e. the structure of 3 O and 1 CH3 connected to 1 Si as shown in

[0086] Specifically, the present application adopts Q n represents a silicon atom that is completely connected to other silicon atoms through oxygen bridges (siloxane). n represents the number of these bridging oxygen atoms, ranging from 0 to 4. Therefore, Q2, Q3 and Q4 represent silicon with 2, 3 and 4 bridging oxygen atoms, respectively.

[0087] It should be noted that Figure 7 The two curves shown are two curves in extreme cases. Curve 710 represents a case where there is insufficient O, and mainly Si-O2 in the thin film, with only a small amount of Si-O3. Therefore, curve 710 has a clear first peak Q2, but almost no second peak Q3. Curve 720 represents a case where there is sufficient O, and mainly Si-O3 in the thin film, with only a small amount of Si-O2. Therefore, curve 720 has a clear second peak Q3, but almost no first peak Q2.

[0088] In step S230, after adjusting the second supply parameter, it is desired that the content of Si-O2 is reduced, and the content of Si-O3 is increased. The first threshold value is less than the second threshold value, indicating that after adjustment, the content of Si-O2 is less than the content of Si-O3. The first threshold value and the second threshold value can be set according to actual conditions, which are not limited by the present application.

[0089] In the process of performing steps S110-S170, after obtaining the first thin film sample each time, the intensity of the first peak Q2 and the intensity of the second peak Q3 can be observed according to steps S210-S230 first. If it is found that the intensity of Q2 is weakened and the intensity of Q3 is strengthened, it indicates that the provided oxygen-containing gas is playing its role, and the reaction equilibrium is being pushed towards more Si-O3. If it is found that the intensity of Q2 is not weakened and the intensity of Q3 is not strengthened, the second supply parameter of the oxygen-containing gas can be adjusted so that the intensity of Q2 is less than the first threshold value, and the intensity of Q3 is greater than the second threshold value.

[0090] As Figure 7As shown, in some embodiments, the first peak Q2 corresponds to a chemical shift range of -60ppm to -90ppm, and the second peak Q3 corresponds to a chemical shift range of -90ppm to -100ppm.

[0091] In some cases, if it is desired to know in time whether the UV irradiation has worked, the following embodiments can also be used.

[0092] In some embodiments, after the first film sample is obtained in step S130, the method further comprises: analyzing the first film sample and the second film sample by using a spectrum analysis technique, and adjusting the UV parameters according to the analysis result, so that the UV irradiation meets the preset process result. The first film sample is obtained before the UV irradiation, and the second film sample is obtained after the UV irradiation. According to these embodiments, the first film sample and the second film sample are analyzed, which means that the analysis results of the two samples can be compared, and the change amount of each different chemical bond before and after the UV irradiation can be analyzed according to the spectrum analysis technique, so as to reflect the influence of the UV irradiation on the film. Therefore, the UV parameters can be adjusted according to the analysis result, so as to achieve the purpose of making the low dielectric constant film meet the preset process result.

[0093] In some embodiments, the first film sample and the second film sample are analyzed by using a spectrum analysis technique, and the UV parameters are adjusted according to the analysis result, so that the UV irradiation meets the preset process result, comprising:

[0094] Step S310: obtaining a second characteristic signal of the first film sample by using a spectrum analysis technique, the spectrum analysis technique comprising solid-state nuclear magnetic resonance or Fourier transform infrared spectroscopy, and the second characteristic signal comprising a third peak corresponding to -CH2 in the first film sample and a fourth peak corresponding to -CH3 in the first film sample;

[0095] Step S320: measuring the intensity of the third peak and the intensity of the fourth peak;

[0096] Step S330: obtaining a third characteristic signal of the second film sample by using a spectrum analysis technique, the third characteristic signal comprising a fifth peak corresponding to -CH2 in the second film sample and a sixth peak corresponding to -CH3 in the second film sample;

[0097] Step S340: measuring the intensity of the fifth peak and the intensity of the sixth peak;

[0098] Step S350: adjusting the UV parameters so that the intensity of the fifth peak is less than the intensity of the third peak, and the intensity of the sixth peak is less than the intensity of the fourth peak.

[0099] In some embodiments, the spectrum analysis technique used in steps S310 and S330 is carbon-13 solid-state nuclear magnetic resonance.

[0100] Figure 8 are solid state nuclear magnetic resonance spectra obtained by analyzing the first film sample and the second film sample using carbon-13 solid state nuclear magnetic resonance. In which, curve 810 represents the solid state nuclear magnetic resonance spectrum of the first film sample, and curve 820 represents the solid state nuclear magnetic resonance spectrum of the second film sample. Referring to FIG. 8, before UV cure (Pre-cure), there are obvious third peaks 811 corresponding to -CH2and fourth peaks 812 corresponding to -CH3on the resonance spectrum, which are located on curve 810. After UV cure (Post-cure), the fifth peaks corresponding to -CH2on curve 820 are almost gone, and the intensity of the sixth peaks 821 corresponding to -CH3is obviously reduced. Figure 8 Figure 8 The results shown in FIG. 8 show that after UV irradiation, -CH2becomes weak or disappears, and -CH3also becomes weak, indicating that after UV irradiation, the -CH2and -CH3bonds are broken, indicating that the film has shrunk to a certain extent, and such breaking is usually caused by the energy of UV irradiation.

[0101] In step S350, the UV parameters include any of the irradiation intensity, the irradiation time length, the UV lamp power, the number of UV lamps, and the effect of the reflective film described above. In some embodiments of the present application, the thickness and material of the reflective film can affect the UV irradiation: for example, a 50-200 nm anti-reflective film is usually used to prevent UV light from irradiating the wafer surface through the reflection of energy to reduce the effect of UV light, and the specific film material can be selected, for example, a composite material that absorbs UV light.

[0102] According to steps S310-S350, the irradiation parameters of the UV irradiation can be adjusted in time in the film forming method to assist in more efficient formation of low dielectric constant films that meet the requirements.

[0103] In some embodiments, before determining whether the low dielectric constant film meets the preset process result in step S170, the method further includes:

[0104] Step S410: adjusting the first supply parameter of the mixture to make the dielectric constant k value of the current film reach a base value.

[0105] In some embodiments, the base value is less than 2.5. Step S410 can reduce the dielectric constant k value of the film to a value less than 2.5 by adjusting the first supply parameter of the mixture, which is equivalent to first reducing the dielectric constant k value to a relatively coarse range, and then adjusting each parameter in step S170 to make the film collapse rate, the film mechanical strength, and the dielectric constant k value meet the preset process result.

[0106] ​In some embodiments, the first supply parameter further comprises any of a flow rate of the alkyl siloxane precursor, a flow rate of the porogen, a relative ratio of the porogen and the alkyl siloxane precursor, and the method 100 further comprises adjusting the relative ratio of the porogen and the alkyl siloxane precursor in response to the thin film collapse ratio not satisfying the preset process window.

[0107] Similarly to the most sensitive parameter of the mechanical strength as described above, the inventors of the present application have found that, for the thin film collapse ratio, the most sensitive parameter is the relative ratio of the porogen and the alkyl siloxane precursor, i.e. the "most sensitive parameter of the thin film collapse ratio". In a specific embodiment, the relative ratio is the ratio of the contents of the ATRP / DEMS, i.e. the ratio of the two. The adjustment of the relative ratio can be achieved by adjusting the flow rates of the two.

[0108] According to the discovery of the most sensitive parameter of the thin film collapse ratio, before the adjustment of the oxygen-containing gas, the thin film collapse ratio can be adjusted by adjusting the ratio of the two in the mixture to satisfy the preset process result. Then, the thin film collapse ratio, the mechanical strength of the thin film, and the dielectric constant k value can be all satisfied by adjusting the second supply parameter of the oxygen-containing gas to satisfy the preset process result. According to these embodiments, the thin film can be adjusted in stages, and the low dielectric constant thin film satisfying the preset process result can be quickly and efficiently obtained.

[0109] The present application also provides a semiconductor structure formed by using the method for preparing a low dielectric constant thin film according to the embodiments of the present application, and thus the semiconductor structure has the beneficial effects of the method according to the present application. The relevant content can be referred to the above, and will not be repeated here. In some embodiments, the semiconductor structure is a thin film. In some embodiments, the semiconductor structure comprises a thin film.

[0110] The present application uses specific words to describe the embodiments of the present application. The words "one embodiment", "an embodiment", and / or "some embodiments" mean that a certain feature, structure, or characteristic described in relation to the one or more embodiments is related to at least one embodiment. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" or "one alternative embodiment" mentioned in different places in the specification does not necessarily refer to the same embodiment. In addition, some features, structures, or characteristics in one or more embodiments of the present application can be properly combined.

[0111] Aspects of the application can be implemented in, completely, in part, or otherwise in hardware, software (including firmware, resident software, micro-code, etc.), or combinations thereof. The foregoing hardware or software, as the case can be, can be referred to as a "data block", "module", "engine", "unit", "component", or "system". A processor can be one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DAPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, or combinations thereof. Furthermore, aspects of the application can be implemented as a computer product, which can include a computer-readable medium having computer program code embodied therein. The computer-readable medium can include, but is not limited to, magnetic storage devices (e.g., hard disk; floppy disk; magnetic strips...), optical disks (e.g., compact disk (CD); digital versatile disk (DVD)...), smart cards, and flash memory devices (e.g., card; stick; key drive...).

[0112] The computer program code can also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the code which implement the process is embodied on the computer readable medium. The computer readable medium can be a transmission line, a carrier wave transmitted on the transmission line, or a computer readable medium embodied in a computer program product. For example, a computer readable medium can be a magnetic storage device (e.g., a hard disk; a floppy disk; magnetic strips on a card; an educational card; a RAM; a ROM; or a compact disk (CD)), an electrical storage device (e.g., a resistor; a capacitor; transistors; or a circuit), an optical storage device (e.g., a compact disk (CD); a DVD; or a Blu-ray disk), a transmission line, a carrier wave transmitted on the transmission line, or a computer readable medium embodied in a computer program product. As used herein, a computer program product or computer readable medium can be one or more computer program code segments embodied on one or more computer readable media (e.g., floppy disks, CD-ROMs, hard disks, optical disks, memory cards, stick, key drive, etc.) that are readable and / or executable by a machine (e.g., a computer). The computer program code segments can also be downloaded into a computer from an external computer or external storage device or to be stored in a storage device (e.g., a hard disk drive, a floppy disk drive, a memory card, a stick, a key drive, etc.) that is connected to or accessible by the computer.

[0113] Accordingly, it should be noted that the description of the embodiments of the application herein does not specify a definitive number of features to be incorporated into an embodiment, figure, or description of an embodiment. Rather, the description of the embodiments of the application herein is presented to assist in the understanding of one or more embodiments, and the description of the embodiments of the application herein should not be interpreted to mean that an embodiment of the application requires more features than those described in the description of the embodiments of the application.

[0114] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used to describe embodiments are sometimes modified by the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in this application are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0115] Although this application has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are only used to illustrate this application, and various equivalent changes or substitutions can be made without departing from the spirit of this application. Therefore, any changes or modifications to the above embodiments within the scope of the essential spirit of this application will fall within the scope of this application.

Claims

1. A method for preparing a low dielectric constant thin film, characterized in that, include: A mixture comprising an alkylsiloxane precursor and a pore-forming agent is provided to a substrate surface in a plasma environment. This mixture is used to form a thin film on the substrate surface, the thin film comprising a Si-O-Si film framework and alkane-terminated C-terminated carbon atoms. m H 2m+1 The mixture includes the pore-forming agent, wherein the first supply parameter of the mixture includes the flow rate of the alkylsiloxane precursor and / or the flow rate of the pore-forming agent, and m is a positive integer greater than or equal to 1; Oxygen-containing gas is provided to the surface of the substrate to dope the thin film framework, wherein the second supply parameter of the oxygen-containing gas includes oxygen-containing gas flow rate and / or oxygen-containing gas velocity; Obtain a first film sample from the current film and measure the thickness of the first film; The substrate is irradiated with UV light to remove at least a portion of the pore-forming agent, forming a porous low-dielectric-constant thin film. A second film sample was obtained from the low dielectric constant film, and the thickness, mechanical strength, and dielectric constant k value of the second film were measured. Determine whether the low dielectric constant film meets the preset process results, wherein the preset process results include: film collapse rate, film mechanical strength, and dielectric constant k value, the film collapse rate being determined by the first film thickness and the second film thickness; and In response to the judgment result being unsatisfactory, any one of the first supply parameter, the second supply parameter, the environmental parameter of the process chamber, and the UV parameter is adjusted, wherein the environmental parameter includes any one of the power of the plasma generator, the temperature inside the chamber, and the pressure inside the chamber, and the UV parameter includes the UV irradiation parameter.

2. The method as described in claim 1, characterized in that, Also includes: The first thin film sample is analyzed using spectral analysis technology, and the second supply parameters are adjusted based on the analysis results to ensure that the supply of oxygen-containing gas meets the preset process results.

3. The method as described in claim 2, characterized in that, The first thin film sample is analyzed using spectroscopic analysis technology, and the second supply parameters are adjusted based on the analysis results to ensure that the supply of oxygen-containing gas meets the preset process results, including: The first characteristic signal of the first thin film sample is obtained by using spectral analysis technology, including solid-state nuclear magnetic resonance or Fourier transform infrared spectroscopy. The first characteristic signal includes a first peak corresponding to Si-O2 in the first thin film sample and a second peak corresponding to Si-O3 in the first thin film sample. Measure the intensity of the first peak and the intensity of the second peak; and The second supply parameter is adjusted so that the intensity of the first peak is less than the first threshold and the intensity of the second peak is greater than the second threshold, wherein the first threshold is less than the second threshold.

4. The method as described in claim 1, characterized in that, Also includes: The first and second thin film samples are analyzed using spectral analysis technology, and the UV parameters are adjusted based on the analysis results to ensure that the UV irradiation meets the preset process results.

5. The method as described in claim 4, characterized in that, The first and second thin film samples are analyzed using spectral analysis techniques, and the UV parameters are adjusted based on the analysis results to ensure that the UV irradiation meets the preset process results, including: The second characteristic signal of the first thin film sample is obtained by using spectral analysis technology, including solid-state nuclear magnetic resonance or Fourier transform infrared spectroscopy. The second characteristic signal includes a third peak corresponding to -CH2 in the first thin film sample and a fourth peak corresponding to -CH3 in the first thin film sample. Measure the intensity of the third peak and the intensity of the fourth peak; The third characteristic signal of the second thin film sample is obtained by using the spectral analysis technique. The third characteristic signal includes a fifth peak corresponding to -CH2 in the second thin film sample and a sixth peak corresponding to -CH3 in the second thin film sample. Measure the intensity of the fifth peak and the intensity of the sixth peak; and The UV parameters are adjusted so that the intensity of the fifth peak is less than the intensity of the third peak, and the intensity of the sixth peak is less than the intensity of the fourth peak.

6. The method as described in claim 1, characterized in that, Before determining whether the low dielectric constant film meets the preset process results, the process also includes: The first supply parameter of the mixture is adjusted so that the dielectric constant k of the current film reaches a base value.

7. The method as described in claim 1, characterized in that, The first supply parameters further include any one of the following: the flow rate of the alkylsiloxane precursor, the flow rate of the porogen, and the relative ratio of the porogen to the alkylsiloxane precursor; the method further includes: In response to the film collapse rate not meeting the preset process result, the relative ratio of the pore-forming agent and the alkylsiloxane precursor is adjusted.

8. The method as described in claim 1, characterized in that, Also includes: In response to the thin film mechanical strength not meeting the preset process result, the thin film deposition rate and the chamber temperature are adjusted, wherein the thin film deposition rate is related to any one or more of the first supply parameter, the second supply parameter, and the environmental parameter.

9. The method as described in claim 1, characterized in that, The environmental parameters also include any one of the following: substrate temperature, spray head temperature, and the distance between the substrate and the spray head.

10. The method as described in claim 1, characterized in that, The second supply parameter also includes the concentration of the oxygen-containing gas.

11. The method as described in claim 1, characterized in that, The UV irradiation parameters include any one of UV intensity, UV wavelength, and irradiation duration. The UV parameters also include any one of UV lamp power, number of UV lamps, and reflective film function.

12. The method according to any one of claims 1-11, characterized in that, The preset process results are as follows: the film collapse rate is in the range of 0-20%, the film mechanical strength is in the range of 5GPa-10GPa, and the dielectric constant k value is in the range of less than a threshold value, wherein the threshold value is 2.5-2.

6.

13. A semiconductor structure, characterized in that, The semiconductor structure is formed using the method described in any one of claims 1-12.

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