JP2006317442A - Method for quantification of hydrophilicity of porous material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-destructive method for quantifying the hydrophilicity of porous material such as low dielectric constant (low-k) material having vacancies, and to provide a method for determining the depth of damage of the porous material. <P>SOLUTION: A typical method includes a step of performing first polarimetry about the porous material using first adsorbate having a first wetting angle. This typical method further includes a step of performing second polarimetry about the porous material using second adsorbate having a second wetting angle, and the first and second wetting angles to the porous material are different from each other. The hydrophilicity of the porous material is determined at least partly based on the first and second adsorbates. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  This application claims the benefit set forth in Section 119 (e) of the US Patent Act for US Provisional Patent Application No. 60 / 680,665, dated May 12, 2005. Furthermore, this application claims priority based on European Patent Application No. 05015412.9 dated 15 July 2005. The entire disclosures of US Provisional Patent Application No. 60 / 680,665 and European Patent Application No. 05015412.9 are hereby incorporated by reference herein.

  The present invention relates to a method for quantifying the hydrophilicity of a porous material, such as a low dielectric constant (low-k) material having pores. Typical methods can also be used to determine the depth of damage after patterning for such porous materials.

  In semiconductor processing, one of the major problems in incorporating porous materials, such as low dielectric constant materials, is the degradation of the dielectric properties of those materials, for example during plasma etching and / or resist stripping. The plasma used in such processes typically contains oxygen-containing species. The main cause of the deterioration of the dielectric properties of the porous material is that the carbon-containing hydrophobic groups are removed by using these oxygen-containing plasmas.

Carbon depletion occurs, for example, when Si—CH ₃ bonds are broken and carbon is replaced by silicon dangling bonds. This carbon depletion leads to the formation of silanol (Si—OH) through various intermediate reactions. This leads to an increase in the relative dielectric constant (k-value) at the damaged portion of the porous material, and converts the inherently hydrophobic low dielectric constant material into a hydrophilic material. Thereafter, moisture such as water and other polar molecules having a high polarizability are absorbed and mediated by hydrogen bonds, so that the actual relative permittivity of these materials is, for example, “relative permittivity >> There is a possibility of a large increase to 80 ”. The degree and depth of damage by the plasma depends on the pore size and continuity of the pores in the porous material, and thus has relatively large sized pores, for example a relative dielectric constant of Ultra low dielectric constant materials below 2.6 will suffer much more plasma damage than microporous materials with relative dielectric constants above 2.6. The degree of damage to the insulating material on the sidewalls of the etched material is also expected to increase as the porosity of the porous material increases, and the effect of such damage on the overall electrical performance is It becomes increasingly important as the interval is reduced. That is, the insulator damage on the side wall greatly affects the performance of the advanced wiring, and a reliable analysis method for evaluating the degree of such damage is desired.

  In general, the depth and characteristics of carbon depletion can be determined, for example, by time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), energy filter transmission electron microscopy (EFTEM), etc. It has been evaluated using complex analytical techniques or has been evaluated using the so-called HF immersion test. TOF-SIMS is a type of SIMS that uses a very low current incident ion beam to obtain information about the chemical composition of the outermost surface of a solid. EFTEM is a technique that detects variations in atomic concentrations of elements such as C, O, and Si through cross-sections of morphology.

  Using TOF-SIMS, only the concentration of carbon affects the hydrophobicity that determines the dielectric constant of the film, regardless of how they are incorporated and incorporated into the structure of the porous material. Is assumed. The TOF-SIMS data used to determine the depth of damage for low dielectric constants is related to the carbon concentration in the surface region of the low dielectric constant porous material. Compared with Thus, depletion of carbon in the surface region after etching and stripping is an indicator of damage to low dielectric constant. However, when performing HF immersion tests on such low dielectric constant materials such as films, there is no obvious correlation between carbon depletion and plasma damage.

The HF immersion test is based on the fact that damaged low dielectric constant insulating materials exhibit higher etch rates than undamaged materials. Usually, this test more directly reflects the hydrophilicity of the porous material, but the autocatalytic mechanism in the reaction of HF and SiO ₂ is dependent on the rate of etching and the depth of damage obtained by calculation. Depends on the concentration of HF, making this test unreliable.

  Carbon depletion may not always correlate directly with plasma damage. For example, when advanced polymerization chemistry is used (eg, CxFyHz plasma), carbon depletion is compensated by CFx polymer deposition, resulting in the same carbon concentration on the surface of the low dielectric constant porous material, or To increase. According to conventional interpretation of TOF-SIMS results, this surface is considered to be the most hydrophobic (no “damage”). However, when the HF immersion test is performed on this sample, the etching rate is higher than that of a low dielectric constant reference material that is generally not naturally damaged. That is, a fluorocarbon polymer formed in the etching process and filling the pores of the porous material cannot provide the same hydrophobicity as the original hydrophobizing factor. These facts indicate the importance of developing special measurement procedures that provide a more direct analysis of the degree of internal hydrophilization associated with plasma damage.

  In addition, the existing methods described above and all other methods available in the prior art are all destructive and / or relatively complex and have the greatest impact on the insulating properties of the porous material. It cannot provide directly correlated information about sexual loss. That is, existing methods for determining damage to low dielectric constants have serious drawbacks and deficiencies. Therefore, a method that can determine the depth of damage and the exact hydrophobicity of a low dielectric constant material is desired. Furthermore, there is a need for simple non-destructive methods for use in the development and screening of various low dielectric constant materials, particularly ultra low dielectric constant materials that will be used in future technologies.

  The examples of background art described above and the limitations associated therewith are intended to be illustrative and not exhaustive. Other limitations of the background art will become apparent to those skilled in the art upon reading this specification and studying the drawings.

  The following embodiments and aspects thereof are described and illustrated with respect to systems, tools, and methods that are given by way of example, are meant to be illustrative, and are not intended to limit the scope. In various embodiments, one or more of the problems described above are reduced or eliminated, while other embodiments are directed to other improvements.

An example of a non-destructive method for quantifying the hydrophilicity of a porous material is disclosed. For example, typical methods are disclosed for quantifying the hydrophilicity / hydrophobicity of a porous material, and these hydrophilicity / hydrophobicity can be indicative of the degree of damage to the porous material. The material may be a porous low dielectric constant material or may be an ultra low dielectric constant material. This typical method takes advantage of the adsorption / desorption characteristics in the pores of the porous material. Further, this method utilizes first and second adsorbates having different contact angles (also referred to as wetting angles) with respect to the inner surface of the pores of the porous material. In this exemplary method, the first adsorbate is an adsorbate having a contact angle or wetting angle substantially equal to zero and the second adsorbate is substantially with respect to the porous material. An adsorbate having a non-zero contact angle or wetting angle and polarity. Examples of first adsorbates (which have a substantially zero contact angle with low dielectric constant materials or porous films containing organic molecules) are nitrogen, toluene, methanol, and benzene; These adsorbates exhibit good wettability with porous materials such as low dielectric constant materials. Examples of second adsorbates (which have a substantially non-zero contact angle for low dielectric constant materials or porous films containing organic molecules) are water, thionyl (SOCl ₂ ), or organic molecules Or any other suitable inorganic solvent having a non-zero contact angle for porous films.

  An exemplary method provides for the quantification of the hydrophilicity of the porous material and includes at least a first and second polarimetry, wherein the first polarimetry is performed using the first adsorbate. And a second polarimetry is performed using the second adsorbate, wherein the first and second adsorbates have different wetting angles with respect to the porous material.

  In another exemplary method, a method is provided for determining the degree of damage of a porous material, eg, a low dielectric constant material, and more specifically, the internal surface energy (effective contact angle) in the porous material. And a method for determining the extent and depth of damage is provided. Here, damage is defined as the loss of hydrophobicity of a porous material, for example a low dielectric constant material, and is related to plasma etching and / or stripping processes. More specifically, a method is disclosed that includes at least three polarization measurements. In this exemplary method, the polarimetry is an ellipsometric adsorption measurement. Similar to the first exemplary method described above, the first and second adsorbates are used in this method, and each adsorbate has a different wetting angle with respect to the inner surface of the pores of the porous material. Have. For example, the first adsorbate is an adsorbate having a contact angle or wetting angle substantially equal to zero with respect to the porous material, and the second adsorbate is substantially different with respect to the porous material. It is an adsorbate having a non-zero contact (wetting) angle and polarity.

  In addition to the steps of the first example described above, the method of the second example includes a second material having a second wetting angle with respect to the porous material with respect to the porous material before damage processing. It further includes performing a third polarization measurement using the adsorbate. For purposes of this disclosure, damage processing means a processing step (eg, a plasma etching step) that causes damage to the porous material. The third polarization measurement is performed on a reference porous material having almost no hydrophilicity, such as a porous material before damage treatment or a reference low dielectric constant film. Natural insulating materials are often used as reference materials. Furthermore, the third polarimetry in this method uses a second adsorbate with polar molecules so that intrinsic hydrophilicity within the pores of a reference material, such as a reference low dielectric constant film, can be obtained. .

  Such a method can be used, for example, to determine damage after dry etching and peeling treatment of a porous material which is a low dielectric constant film. For example, the low dielectric constant material may be a SiOC (H) material, such as an ultra low dielectric constant material having a pore size of 2-10 nm. Using such a method, quantification of the hydrophobicity of the porous material can be used to determine the depth of damage caused to the porous material by the etching and / or stripping process.

  Exemplary embodiments are illustrated in the cited figures of the drawings. The embodiments and drawings disclosed herein are to be considered illustrative and should not be construed as limiting the invention.

Overview Porous materials can be damaged during certain semiconductor processing steps for the manufacture of devices containing porous materials, such as etching and / or stripping steps. For example, porous materials such as porous low dielectric constant films can lose organic hydrophobic groups during plasma etching and / or stripping processes. As a result, they become hydrophilic and absorb moisture and other polar molecules that adversely affect the dielectric properties. During plasma etching and / or stripping processes, the degree of damage caused by the plasma to porous materials, such as low dielectric constant materials, is currently limited to depths using, for example, XPS, TOF-SIMS, EFTEM, etc. -It is evaluated using techniques such as feature analysis.

  In these methods, plasma damage is correlated with carbon depletion. However, as already explained, carbon depletion is not always directly related to plasma damage. For example, when a highly polymerized plasma, such as CxFyHz plasma, is used, carbon depletion is compensated by the deposition of CFx polymer, but in determining the extent of damage, such porous materials may be, for example, porous low It must have different properties compared to a non-damaged reference porous material which is a dielectric material.

  Another approach at this time is the HF immersion test, which is based on the fact that plasma damage correlates with etch depth. However, the depth of etching with HF depends strongly on the concentration of HF due to the autocatalytic etching mechanism of silica with HF.

FIG. 1 shows TOF-SIMS data for the atomic concentration of carbon as a function of etching, eg, ion sputtering time, which is a CF ₄ containing plasma (curve 1) at low power (eg, 27 MHz). _C 4 _{F 8} containing plasma at 600W) at 300W and 2MHz (curve 2), an intermediate output (e.g., _C 4 _{F 8} containing plasma (curve 3 in 1800W) in 800W and 2MHz at 27 MHz), and high power (27 MHz Is proportional to the etching depth of the SiOC (H) low dielectric constant material after etching with a C ₄ F ₈ containing plasma (curve 4) at 1000 W and 2000 W at 2 MHz.

As shown in FIG. 1, in this example, a CF ₄ based plasma (curve 1) results in the most pronounced carbon depletion in the surface region. A high power C ₄ F ₈ based plasma (curve 2) also shows a decrease in carbon concentration in the surface area of the low dielectric constant material, but to a lesser extent. When this result is interpreted as a TOF-SIMS flow, the depth of damage is reduced. The intermediate power C ₄ F ₈ based plasma (curve 3) shows a small surface area showing a decrease in carbon concentration and some enrichment of carbon concentration. The low power C ₄ F ₈ based plasma (curve 4) shows a large increase in carbon concentration in the surface regions and masses of low dielectric constant materials, especially in the region corresponding to 30-50 nm from the top surface of the film. . This can be determined from the fact that the depth of etching is proportional to the time of etching, for example ion sputtering. If the film thickness and etching time are known, the etching depth can be calculated as a function of time, assuming that the etching rate is constant.

  However, the observation of an increase in carbon concentration in a damaged material that is higher than the carbon concentration in a normally undamaged material is the original SiOC (H) in an example that assumes a natural reference material. Rather than being related to the carbon concentration of the material (CCS in Japan, NCS (nanocrystalline silica), initial porosity is 31%), it is also referred to as the hydrofluorocarbon polymer deposited during etching. This is caused by the CFx polymer. These CFx polymers are by-products of the etching process and do not represent damage to the porous material. For example, according to conventional interpretation of TOF-SIMS results, this material is the most hydrophobic (substantially “not damaged”). However, the HF immersion test shows a faster etch rate compared to the baseline natural sample for this sample. The deposited CFx polymer tends to increase the relative dielectric constant of the low dielectric constant material and tends to change at least the material properties from hydrophobic (original material) to hydrophilic. That is, a fluorocarbon polymer that is formed during the etching process and fills the pores of the porous material cannot provide the same hydrophobicity as the original hydrophobic group that is lost during the etching process. The above is more direct regarding the degree of hydrophilization inside a porous material such as a low dielectric constant material, and more specifically, the degree of hydrophilization within the pores of a porous material such as a low dielectric constant material. It shows that a method of providing information is desirable.

Method for Determining the Hydrophilicity / Hydrophobicity of a Porous (Low Dielectric Constant) Material The following describes an exemplary method for determining the hydrophilicity and / or hydrophobicity of a porous material of a low dielectric constant material . However, it will be understood that this example is illustrative only and does not limit the scope of the claims. For example, this exemplary method can be applied to other porous materials such as, for example, porous membranes (eg, zeolite membranes).

  This exemplary method provides a determination of the hydrophilicity and / or hydrophobicity of a porous material, such as a low dielectric constant material or a porous membrane. The porous material may be a porous low dielectric constant material or an ultra low dielectric constant material. This exemplary method takes advantage of the adsorption and / or desorption properties in the pores of the porous material. Various polarization pore distribution measurements (hereinafter referred to as “polarization measurements”), various adsorbates or gaseous forms with various contact angles (also referred to as wetting angles) to porous materials By performing while using the material, the hydrophilicity / hydrophobicity of the porous material is determined.

Polarimetry is based on the analysis of the hysteresis loop that appears due to the process of capillary condensation during vapor adsorption and desorption in the pores of the porous material. This hysteresis loop appears because the effective radius of curvature of the condensed liquid meniscus differs between the adsorption process and the desorption process. The adsorptive vapor condenses in the pores of the porous material even if the vapor pressure P is less than the parallel pressure P ₀ of the flat liquid surface. The dependence of the relative pressure P / P _{0 on} the meniscus curvature is described in the following Kelvin equation.

Where γ and V _L are the surface tension and molar volume of the adsorbate or gaseous substance used, respectively. The principal radii of curvature r ₁ and r ₂ (elliptical radii) define the size of the holes. In the case of a cylindrical hole, r ₁ = r ₂ , and equation (1) can be written as equation (2) below. Here, r _k is often referred to as the Kelvin radius.

  Kelvin's equation (2) directly gives the pore radius, assuming that the wetting angle of the adsorbate or gaseous material to the surface of the porous material is substantially zero. However, according to the present invention, adsorbates or gaseous substances with different contact angles or wetting nuclei to the porous material are used and therefore the contact angle or wetting angle must be taken into account. Therefore, the equation (2) can be written as the following equation (3).

Here, theta is the contact angle or wetting angle adsorptive or gaseous substance to the porous material, r _k is the average radius of the pores present in the porous material. Polarization measurements are performed using single wavelength or multiple wavelength ellipsometry.

  Initial experimental data for the calculation of the adsorption isotherm are the polarization characteristics Δ (phase difference between p-polarized light and s-polarized light (see FIG. 2)) and Ψ (shown in FIG. 3). In general, polarization measurement can be expressed by the following equation (4) with respect to these parameters.

Where r _p and r _s are the complex Fresnel reflection coefficients of the sample for p-polarized (in the plane of incidence) and s-polarized (perpendicular to the plane of incidence) (see FIG. 2). The change in refractive index of the porous material upon adsorption and desorption can then be calculated by special software developed at the Institute of Semiconductor Physics in Novosibirsk, Russia. Next, from this change in refractive index, the change in adsorption volume or pore volume can be calculated using the following equation (5).

Where n _b is the dense part of the material with volume polarizability B _b , ie the refractive index of the matrix, n _p is the refractive index measured for the vacancies, and B _p is from n _p Calculated volume polarizability. The dependence of the adsorption volume on the relative pressure P / P ₀ results in an adsorption isotherm.

  As already mentioned, the method according to the first embodiment of the present invention provides a first contact angle or wetting angle for two different adsorbates or gaseous substances, ie the surface of the porous material to be examined. First adsorbate or gaseous substance having a second contact angle or wetting angle with respect to the surface of the porous material to be examined Is used. According to the present invention, the first contact angle or the wetting angle is different from the second contact angle or the wetting angle. According to the first embodiment of the invention, the first wetting angle is substantially equal to zero. Here, substantially equal to zero means that the first wetting angle may be less than 5 °, may be less than 3 °, or may be less than 1 °. The second contact angle or wetting angle is substantially different from zero. Preferably, the difference between the first and second contact angles or wetting angles may be as large as possible. Preferably, the second contact angle or wetting angle may be 90 ° or more.

Examples of adsorbates having a contact angle or wetting angle substantially equal to zero for low dielectric constant materials or porous films containing organic molecules that can be used in accordance with the present invention include, for example, nitrogen, toluene, methanol , And benzene. In this case, cos θ = 1 in Kelvin's equation (3) (because θ = 0), and it was adsorbed in the pores of the porous material by the adsorption / desorption cycle using the method already described. The volume of adsorbate can be calculated and thus corresponds to the volume of open pores present in the porous material. Examples of adsorbates having a contact angle substantially different from zero for low dielectric constant materials or porous films containing organic molecules include, for example, water, thionyl (SOCl ₂ ), or organic molecules And any other suitable inorganic solvent having a non-zero contact angle with the low dielectric constant material or porous film.

  To perform polarimetry, a substrate having a porous material such as a low dielectric constant film on the top surface is placed in a pressurizable chamber filled with a first adsorbate or gaseous substance. . A second measurement is then performed in the same manner, but this time in a pressurizable chamber filled with a second adsorbate or gaseous substance.

  In the following, the method according to the preferred embodiment of the invention will be further described by way of example only. It should be understood that this example does not limit the invention. The method according to the first embodiment of the present invention can be applied to any porous material having any porosity, such as a low dielectric constant material or a porous film.

  In the following example, the hydrophilicity / hydrophobicity of a low dielectric constant material is determined. In the first step, a first polarization measurement is performed using, for example, toluene as the first adsorbate. From the measured values for Ψ and Δ, the change in the refractive index n of the porous material is determined, and from this change in the refractive index n, the change in the volume of adsorbed toluene is determined using the method described above. It is.

In FIG. 4, the toluene adsorption / desorption cycle is shown for the given example low dielectric constant film (curves 5 and 6, respectively). From curves 5 and 6, it can be determined that the example low dielectric constant film given in FIG. 4 has a porosity of about 31%. This porosity value is determined by the amount of adsorbate adsorbed in the pores of the porous material at a relative pressure P / P ₀ equal to 1, ie at a pressure P = P ₀ . At this pressure, the adsorbate or gaseous substance is completely condensed into the pores of the porous material, although in this example the pores of the low dielectric constant material. That is, the amount of adsorbate adsorbed is equal to the amount of pores present in the porous material, although this is a low dielectric constant material in this example.

  It should be noted that this first step can be performed on at least one of a damaged porous material or an undamaged porous material. Processing can create defects that can behave as vacancies, and defects that can behave as vacancies can increase the porosity of the porous material during processing. Conveniently, the first measurement is advantageously performed on both the undamaged (pre-treatment) material and the damaged (post-treatment) material. In this way, the porosity of the starting material can be determined, and damage caused by the processing step can be accurately determined.

  In a second step, a second polarization measurement using a second adsorbate or gaseous material in which the damaged material has a contact angle or wetting angle with respect to the porous material that is substantially different from zero. To be served.

Non-damaged low dielectric constant dielectrics are generally hydrophobic, which is a contact that is substantially different from zero to a porous material, for example water, in this example a low dielectric constant material. When a polar adsorbate having corners or wetting angles is used, it means that cos θ is close to zero in Kelvin's equation (3). Thus, when these adsorbates are water, for example in these porous materials which are low dielectric constant films, water condensation does not occur virtually. From the second polarization measurement, the values of Ψ and Δ are determined, from which the change in the refractive index of the porous material, which in this example is a low dielectric constant material, and the change in the amount of water adsorbed, Determined using the method described above. Further, FIG. 4 shows water vapor adsorption / desorption cycles for the damaged low dielectric constant films (curves 7 and 8, respectively). From these curves 7, 8, it can be determined that the amount of water adsorbed is about 18.5%. This value is determined by determining the volume of water adsorbed at a pressure of P = P ₀ (or P / P ₀ = 1). From the amount of adsorbed water, the concentration of the damaged part can be calculated as follows. From the proportion of adsorbed water, the volume of adsorbed water can be determined. By multiplying the adsorbed water volume by the density of the water, the weight of the adsorbed water is obtained. Dividing by the molecular weight of the water results in the molar amount of water adsorbed. By multiplying this result by the Avogadro number, the number of sites where water is adsorbed can be obtained.

  Furthermore, FIG. 4 shows the water vapor adsorption / desorption cycle (curves 9 and 10, respectively) for a reference material that is intact in this example. The reference material can be viewed as a porous material prior to being damaged by etching and / or stripping. In the natural film shown in FIG. 4, there is no large condensation, little water adsorption occurs, and there is only a small amount of sites (constitutive defects) where water adsorption can occur. Reflects. When the number of these parts is limited, the contact angle or the wetting angle remains large because the adsorbed water molecules do not form a continuous layer on the wall surface. FIG. 4 shows that the natural film adsorbs only 4% of the total film volume of water. Measurements on a reference material, for example an undamaged porous material, determine the damage caused by the etching and / or delamination process and distinguish them from the total number of sites measured and are present in the material from the outset It is performed to distinguish it from constitutive hydrophilic sites.

  However, the situation is different for damaged low dielectric constant films. The surface area of the damaged low dielectric constant film becomes hydrophilic due to the loss of hydrocarbon groups, thus greatly increasing the amount of water adsorbed. The water adsorption / desorption isotherm for the damaged low dielectric constant film is also shown in FIG. 4 (curves 7 and 8, respectively, as already shown). The water adsorption / desorption isotherm on a damaged low dielectric constant film determines the amount of water adsorption (this value increases as a result of plasma damage) and the relative pressure corresponding to the onset of water condensation. enable. The relative pressure at which this water begins to condense allows calculation of the internal contact angle using equation (4).

  In order to determine the degree of hydrophilicity (hydrophilic / hydrophobic), the two Kelvin equations (6) and (7) are combined. The first Kelvin equation (6) has a value obtained after a first polarization measurement with an adsorbate (eg, toluene, benzene) having a contact angle to the porous material of substantially zero, Kelvin's equation (7) has a value obtained after a second polarization measurement with an adsorbate (eg, toluene, benzene) with a non-zero contact angle to the porous material, where the second adsorption The quality is polar (eg water). The combination of the two Kelvin equations (6) and (7) can be performed as follows.

By combining these Kelvin equations (6) and (7), an effective “contact angle” for a porous material of adsorbate or gaseous material having a “non-zero” contact angle, such as water, can be determined. The effective contact angle or effective wetting angle gives information about the surface energy that correlates with the hydrophilicity of the porous material. Contact angle is a measure of surface energy. The equilibrium situation is the Young's equation γ _SV −γ _SL = γ _LV cos θ (8)
Where γ _SV , γ _SL , and γ _LV are the surface energy of the solid, the surface energy of the interface, and the surface energy of water, respectively. Using equation (8), the difference between the two quantities on the left side can be determined. In order to separate these two quantities, for example the surface energy of the solid and the surface energy of the interface, a model is used based on how the liquid and solid adhere together.

  Equation (6) is the Kelvin equation for a first adsorbate or gaseous material having a first contact angle or wetting angle substantially equal to zero. Equation (7) is the Kelvin equation for a second adsorbate or gaseous material having a second contact angle or wetting angle that is not zero. In equations (6) and (7), the subscripts a1 and a2 represent the first adsorbate or gaseous substance and the second adsorbate or gaseous substance, respectively. The result of the combination of equations (6) and (7) is the following equation (9).

  According to the method described above, it is possible to determine the effective contact angle of a porous material that is extremely difficult to actually measure by any other method. Furthermore, the effective contact angle directly reflects the hydrophilicity / hydrophobicity that is important for the relative dielectric constant of porous materials such as low dielectric constant materials. The difference between the method of the present invention and prior art techniques such as TOF-SIMS / XPS is that the present invention does not use assumptions such as equating the degree of carbon depletion and hydrophilization. Furthermore, this typical method is non-destructive to porous materials, in contrast to existing methods.

  As described above, in order to determine the hydrophilicity / hydrophobicity of a porous material, such as a low dielectric constant film with pores, an exemplary method is to use at least two polarizations using first and second adsorbates. Measurements are included, and the contact angle or wetting angle of each adsorbate with respect to the porous material is different. In certain embodiments, these polarization measurements can be performed using pressures that vary from zero to the equilibrium vapor pressure of the adsorbate used. As already described, in a typical method, the first adsorbate may be an adsorbate having a contact angle or wetting angle substantially equal to zero, the second adsorbate comprising polar molecules. The adsorbate may have a second non-zero second contact angle or wetting angle.

  Examples of the first adsorbate (the contact angle to the porous material is substantially equal to zero) include nitrogen, toluene, methanol, and in the case of low dielectric constant materials and porous films containing organic molecules, and Benzene is mentioned. These adsorbates have good wettability in porous materials such as porous low dielectric constant materials and porous films containing organic molecules.

Examples of the second adsorbate has a contact angle or wetting angle is not zero with respect to low-k materials or porous membranes comprising organic molecules, include water, SOCl 2, or an organic _molecule, Any other suitable inorganic solvent that has a non-zero contact angle to the low dielectric constant material or porous film may be mentioned.

Method for Quantifying Low Dielectric Damage or Low Dielectric Film Damage Depth In another embodiment, a method is provided for determining damage depth for a porous material such as a low dielectric constant film. Is done. The method includes determining the internal surface energy or effective contact angle and the extent and depth of damage for a porous material, such as a low dielectric constant material, and more specifically, plasma etching and / or It includes determining the depth of damage in a porous material such as a low dielectric constant material after release treatment. Here, damage caused by plasma is defined as, for example, a loss of hydrophobicity of a porous material due to a loss of organic hydrophobic groups, although it is a hydrocarbon group in the case of a low dielectric constant material. This damage can be caused by plasma etching and / or stripping of the porous material.

  To determine the depth of damage to the porous material in this exemplary method, a film made of a porous low dielectric constant film containing two layers with different properties is used. The first layer, that is, the upper layer, exhibits a damaged region of the porous low dielectric constant film. The first or top layer is more hydrophilic than the second or bulk layer of the porous low dielectric constant film. The bulk layer is considered undamaged. Taking this fact into account, the depth of plasma damage in such a porous low dielectric constant film can be determined.

  In the same way as described above, the amount of water adsorbed in the pores of the porous low dielectric constant material is calculated to calculate the degree of damage, more specifically the depth of damage in the porous low dielectric constant film. Therefore, it can be used in this exemplary method.

  In order to determine the depth of damage in a damaged low dielectric constant film, this typical method uses adsorption within the pores of a porous film at pressures ranging from zero to the equilibrium vapor pressure of the adsorbate used. To determine the characteristics, at least three polarization measurements are included. To perform these polarization measurements, a substrate having a porous low dielectric constant film on the top surface is placed in a pressurizable chamber filled with a first adsorbate (which can be a gaseous substance). Be placed. A second measurement is then performed in the same manner as described above, but in a pressurizable chamber filled with a second adsorbate (which can be a gaseous substance).

  In order to obtain the porosity and / or pore size of the porous low dielectric constant film in the first polarization measurement performed on the porous low dielectric constant material that has not been damaged, A first adsorbate or gaseous material having a contact angle or wetting angle equal to zero is used. For purposes of the examples described herein, substantially equal to zero means that the first contact angle or wetting angle may be less than 5 °, less than 3 °, or less than 1 °. It means that it may be. Pore size determination in adsorption porosity measurement (eg, using polarized porosity (EP) measurement) is based on Kelvin's equation (2), which correlates relative pressure with hole radius.

In order to make such measurements accurate, adsorbates or gaseous substances are used whose contact angle or wetting angle to the surface of the porous film is substantially equal to zero. Examples of such adsorbates are nitrogen, toluene, methanol, and benzene. In this case, cos θ = 1 in Kelvin equation (3) (because θ = 0 °), and the volume of adsorbed toluene (volume of open pores) is calculated by the adsorption / desorption cycle. be able to. Preferably, the contact angle or wetting angle of the selected adsorbate or gaseous substance is substantially the same for an undamaged reference material, i.e., a natural material and a damaged low dielectric constant material. Should be the same. The value obtained from this measurement is referred to as the porosity of the porous low dielectric constant film as measured by P _a1 or an adsorbate or gaseous substance with a contact angle or wetting angle substantially equal to zero.

In this exemplary method, a second polarization measurement is performed on a damaged porous low dielectric constant film, where a second contact angle or wetting angle with respect to the porous material is present. Two adsorbates or gaseous substances are used. The second adsorbate can include polar molecules so that the adsorption of the second gaseous material in the pores of the damaged low dielectric constant film can be measured. The second gaseous substance or adsorbate can have a contact angle of 90 ° or greater. By way of example, the second gaseous substance may be water, SOCl ₂ , and any other suitable inorganic solvent having a non-zero contact angle for low dielectric constant materials or organic films including organic molecules It may be. The value obtained from this second _polarimetry is referred to as _Pa2,1 , or a damaged porous low dielectric constant measured by a second adsorbate or gaseous material such as water or other polar material. It is referred to as the porosity of the film.

In this exemplary method, a third polarimetric measurement is performed on an undamaged low dielectric constant film (also referred to as a reference low dielectric constant film or “natural material”), for example, etching that causes damage to the film. And / or on a porous low dielectric constant film prior to being subjected to a stripping process. The non-damaged low dielectric constant film has little hydrophilicity with respect to the second gaseous substance (adsorbate), and therefore the adsorption of the second gaseous substance in the pores of the reference low dielectric constant film. Can be obtained. The value obtained from this third polarization measurement is referred to as _Pa2,2 , or the _{porosity of an undamaged} low dielectric constant film as measured by water or other polar material.

The above three polarization measurements are combined in the following equation (10) and then used to determine the depth of damage in the low dielectric constant film.
P _a2,2 * d ₀ = P _a1 * d + P _a2,1 * (d ₀ −d) (10)
Here, P _a2,2 is the porosity (volume of adsorbed liquid) of the damaged porous low dielectric constant film measured by the polar gaseous substance, and P _a2,1 is (measured by water The porosity of the porous low dielectric constant film before damage (volume of the adsorbed liquid), and P _a1 is the porosity of the porous low dielectric constant film without damage measured using toluene, d ₀ is the thickness of the film and d is the depth of wetting.

As already mentioned, the value P _a1 is such that the contact angle or wetting angle with respect to the porous material is substantially zero for the low dielectric constant film so that the porosity and / or pore size of the low dielectric constant film can be obtained. Obtained from a first polarization measurement performed with an equal first gaseous substance. The first adsorbate may be nitrogen, toluene, methanol, or benzene. The values _Pa2,2 are obtained from a second polarization measurement performed on a damaged low dielectric constant film with a second adsorbate or gaseous substance having polar molecules. The second adsorbate or gaseous substance may be water. The value P _a2,1 is from a third polarization measurement performed with a second adsorbate or gaseous material having polar molecules for a low dielectric constant film (before plasma etching and / or stripping) without damage. Has been obtained.

Example 1
Determining the amount of water adsorbed on a porous low dielectric constant film FIGS. 5A-5E are reference non-damaged low dielectric constant materials (as is) and SiOC (H) after various plasma etching treatments. The adsorption / desorption isotherm is shown for a low dielectric constant material (NCS).

  FIG. 5A shows the amount of water adsorbed on a non-damaged reference low dielectric constant material, also referred to as natural material. In the reference material (in this example, the natural material), there is little water adsorption, no large condensation, reflecting a small amount of water adsorption sites. Yes. When the number of these portions is limited, the contact angle remains large because the adsorbed water molecules do not form a continuous layer on the wall surface. FIG. 5A shows that the film adsorbs only 4% water relative to the film volume.

FIG. 5B shows the amount of water adsorbed on the SiOC (H) low dielectric constant material (NCS) after CF ₄ / O ₂ plasma etching. The amount of water adsorbed on the low dielectric constant film due to plasma damage is 18%.

FIG. 5C shows the amount of water adsorbed on the SiOC (H) low dielectric constant material (NCS) after C ₄ F ₈ plasma etching. The amount of water adsorbed on the low dielectric constant film due to plasma damage is 9.5%.

FIG. 5D shows the amount of water adsorbed on the SiOC (H) low dielectric constant material (NCS) after CF ₄ standard plasma etching. The amount of water adsorbed on the low dielectric constant film due to plasma damage is 9%.

  FIG. 5E shows the amount of water adsorbed on the SiOC (H) low dielectric constant material (NCS) after HMDS treatment. The amount of water adsorbed on the low dielectric constant film due to plasma damage is 2.7%.

(Example 2)
Determining the degree and depth of damage in porous low dielectric constant films Anisotropically etching vias and trenches for interconnect processing into porous low dielectric constant materials deposited on wafers (eg, (dual) damascene structures A standard etching process is applied. The etching plasma used in this example includes CF ₄ , O ₂ , N ₂ and Ar.

Using the method described above and the following equation, the depth of damage in the low dielectric constant film can be obtained.
P _a2,2 * d ₀ = P _a1 * d + P _a2,1 * (d ₀ −d) (11)
Here, P _a2,2 is the porosity of the low dielectric constant film with damage measured using the second adsorbate, for example, water, and P _a2,1 is (second adsorbate, Is the porosity of the low dielectric constant film before damage), and P _a1 is the porosity of the non-damaged low dielectric constant film measured using the first adsorbate, for example toluene. Degrees, d ₀ is the thickness of the film, and d is the depth of wetting. The value P _a1 has been obtained from a first polarization measurement performed on the low dielectric constant film with the first adsorbate so that the porosity and / or pore size of the low dielectric constant film can be obtained. The values _Pa2,2 are obtained from a second polarization measurement performed on the second adsorbate for a damaged low dielectric constant film. The value _PWl is obtained from a third polarization measurement performed on the second adsorbate for a low dielectric constant film (before plasma etching and / or stripping) without damage.

As a result of the polarization measurement, 14.2% P _a2,2 value, 4.2% P _a2,1 value, and 30% P _a1 value were obtained. By using the Lorentz-Lorentz equation, the following equation (12) is obtained.

Here, V is the volume of adsorbed water, and n _rl , n _ads , and n ₂ are the refractive indexes of the film on which water is adsorbed, water, and the film itself, respectively. By dividing the value obtained by equation (12) by the volume of the film and multiplying it by 100, a damage of 38.5% is obtained. This indicates that 38.5% of the total thickness of the low dielectric constant film was damaged.

CONCLUSION Various configurations and embodiments have been described herein. However, one of ordinary skill in the art appreciates that modifications and variations can be made to these configurations and embodiments without departing from the true scope and spirit of the invention as defined by the following claims. You will understand.

CF ₄ containing plasma, _C 4 _{F 8} containing plasma at low power, _C 4 _{F 8} containing plasma, and after etching by _C 4 _{F 8} containing plasma at high output SiOC (H) low-k material in the intermediate output FIG. 5 shows TOF-SIMS data on the atomic concentration of carbon as a function of time. It is a figure explaining the principle of polarization measurement. It is a figure explaining the principle of polarization measurement. Toluene adsorption / desorption cycle for (damaged) low dielectric constant films, water vapor adsorption / desorption cycle for (damaged) low dielectric constant films, and water vapor adsorption for intact reference materials FIG. 5 is a diagram showing a desorption cycle. It is a figure which shows the quantity of the water adsorb | sucked to the low dielectric constant material used as the standard which has not received the natural damage. FIG. 4 is a diagram showing the amount of water adsorbed on a SiOC (H) low dielectric constant material (NCS) after CF ₄ / O ₂ plasma etching. FIG. 3 is a diagram showing the amount of water adsorbed on a SiOC (H) low dielectric constant material (NCS) after C ₄ F ₈ plasma etching. FIG. 5 shows the amount of water adsorbed on a SiOC (H) low dielectric constant material (NCS) after CF ₄ standard plasma etching. It is a figure which shows the quantity of the water adsorb | sucked to the SiOC (H) low dielectric constant material (NCS) after a hexamethyldisilazane (HMDS) process.

Claims (10)

A method for quantifying the hydrophilicity of a porous material, comprising:
Performing a first polarization measurement on the porous material using a first adsorbate having a first wetting angle;
Performing a second polarization measurement on the porous material using a second adsorbate having a second wetting angle different from the first wetting angle for the porous material;
Determining the hydrophilicity of the porous material based at least in part on the first and second polarization measurements.   The method of claim 1, wherein the first wetting angle is substantially zero and the second wetting angle is substantially different from zero. Further comprising performing a third polarization measurement on the porous material prior to damage treatment;
The method of claim 1, wherein the third polarization measurement is performed using the second adsorbate. The hydrophilicity of the porous material is determined based at least in part on the first, second, and third polarization measurements;
4. The method of claim 3, further comprising determining an indication of the damage depth of the porous material from the hydrophilicity.   The method of claim 1, wherein the first wetting angle is one of (i) less than 5 °, (ii) less than 3 °, and (iii) less than 1 °.   The method of claim 1, wherein the first adsorbate is one of nitrogen, toluene, methanol, and benzene.   The method according to claim 1, wherein the second wetting angle is 90 ° or more.   The method of claim 1, wherein the second adsorbate contains polar molecules. The method of claim 8, wherein the second adsorbate is one of water, SOCl ₂ , and an inorganic solvent. The method of claim 1, wherein the porous material is a low dielectric constant material.

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