Water-based pretreatment for photoresist scum removal

Abstract

Methods, apparatus, and systems for removing photoresist scum from a substrate are described. After the photoresist scum is removed, the substrate can be electroplated. In various embodiments, the method involves receiving a substrate in a processing chamber, the substrate including a photoresist layer having patterned features therein, where photoresist scum is present in the features; and exposing the substrate to a solution comprising water and one or more chemicals capable of removing at least a portion of the photoresist scum from the feature.

Description

Incorporated by Reference

[0001] The PCT application form is filed concurrently with this specification as a part of this application. Each application identified in the concurrently filed PCT application form to which this application claims the benefit or priority is incorporated herein by reference in its entirety and for all purposes. Background Art

[0002] As semiconductor device dimensions continue to shrink, the fabrication of such devices becomes increasingly challenging. One area where problems arise is the patterning of features on semiconductor substrates, and electroplating within the patterned features.

[0003] The background description provided here is for the purpose of generally presenting the background of the present disclosure. The work of the currently designated inventors within the scope described in this background section and aspects of the specification that were not determined to be prior art at the time of filing the application are neither explicitly nor implicitly admitted to be prior art against the present disclosure. Summary of the invention

[0004] Various embodiments herein relate to methods, devices and systems for removing photoresist scum on a substrate. The substrate is typically a semiconductor substrate. In many cases, the photoresist scum is removed after the photoresist is developed to form features and before metal is electroplated into the features.

[0005] Various embodiments herein relate to methods, apparatus and systems for processing a substrate to remove photoresist scum. The photoresist scum is present in recessed features formed in a photoresist on a substrate. The photoresist scum is removed without substantially removing the bulk of the photoresist. After the photoresist scum is removed, the features may be filled, such as by electroplating to fill the features with metal. Typically, the photoresist scum is removed by exposing the substrate to a solution with a specific chemical substance.

[0006] In one aspect of the disclosed embodiment, a method for processing a substrate is provided, the method comprising: receiving a substrate in a processing chamber, the substrate comprising a photoresist layer having a patterned feature therein, wherein photoresist scum is present in the feature; and exposing the substrate to a solution comprising water and one or more chemicals, the solution being capable of removing at least a portion of the photoresist scum from the feature.

[0007] In various embodiments, the solution is an ozone solution comprising water and ozone. In some such embodiments, the ozone solution has an ozone concentration between about 5 ppm and about 500 ppm.

[0008] In various embodiments, the solution is a free radical initiator solution comprising water and a free radical initiator. In some such embodiments, the free radical initiator comprises one or more chemical substances selected from the group consisting of peroxide, azo compound, alkyl halide compound, and combinations thereof. In some embodiments, the free radical initiator comprises one or more chemical substances selected from the group consisting of hydrogen peroxide, benzoyl peroxide, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and combinations thereof. In some embodiments, the free radical initiator solution has a free radical initiator concentration between about 5ppm and about 1000ppm. In various embodiments, the free radical initiator decomposes to form free radicals, which remove at least a portion of the photoresist scum from the feature, and the free radical initiator preferentially decomposes near the bottom of the feature compared to the top of the feature.

[0009] In some embodiments, more than one solution may be used. For example, in various embodiments, exposing the substrate to a solution comprises exposing the substrate to a first solution, followed by exposing the substrate to a second solution, wherein the first solution is a free radical initiator solution comprising water and a free radical initiator, and the second solution is an ozone solution comprising water and ozone. In some embodiments, in some embodiments, the free radical initiator decomposes to form free radicals, and wherein the free radicals formed by the free radical initiator interact with the ozone to form hydroxyl radicals.

[0010] In some embodiments, the solution contains both a free radical initiator and ozone, such that the substrate is exposed to both the free radical initiator and ozone simultaneously.

[0011] Various techniques can be used to provide the solution to the substrate. For example, in some embodiments, exposing the substrate to the solution includes spraying or flowing the solution onto the substrate, or immersing the substrate in the solution. In these or other embodiments, the photoresist can be a negative photoresist or a positive photoresist. In any one of the embodiments herein, the method also includes electroplating the metal into the feature after exposing the substrate to the solution.

[0012] In another aspect of the disclosed embodiment, a substrate processing apparatus is provided, the apparatus comprising a processing chamber; an inlet to the processing chamber, the inlet being configured to provide a solution to the processing chamber; and a controller configured to: receive the substrate in the processing chamber, the substrate comprising a photoresist layer having patterned features therein, wherein photoresist scum is present in the features; and provide the solution to the processing chamber via the inlet and expose the substrate to the solution, the solution comprising water and one or more chemicals capable of removing at least a portion of the photoresist scum from the features.

[0013] In various embodiments, the apparatus further comprises a nozzle fluidly connected to the inlet, wherein the nozzle sprays or flows the solution onto the substrate. In some embodiments, the substrate support is configured to immerse the substrate in the solution.

[0014] The device may include hardware of a specific material that is resistant to the chemicals used during processing. For example, in various embodiments, the inlet may include one or more materials selected from the group consisting of polycarbonate, polyetheretherketone (PEEK), polyurethane, polytetrafluoroethylene (PTFE), glass, titanium, stainless steel, and combinations thereof.

[0015] In some embodiments, the device further comprises a mixing container and / or conduit to prepare the solution by combining (i) the water and (ii) the one or more chemicals capable of removing at least a portion of the photoresist scum. In various embodiments, the controller is further configured to prepare the solution by combining (i) the water and (ii) the one or more chemicals capable of removing at least a portion of the photoresist scum no more than about 10 minutes before exposing the substrate to the solution.

[0016] In various embodiments, the apparatus further comprises a second processing chamber configured for electroplating, wherein the processing chamber and the second processing chamber are arranged together so that the substrate is transferred from the processing chamber to the second processing chamber under a controlled atmosphere without removing the substrate from the apparatus.

[0017] In another aspect of the disclosed embodiment, a system is provided, the system comprising: a first processing chamber; an inlet to the first processing chamber, the inlet configured to provide a solution to the first processing chamber; an outlet of the first processing chamber, the outlet configured to remove the solution from the first processing chamber; a second processing chamber configured for electroplating; and a controller configured to: receive the substrate in the first processing chamber, the substrate comprising a photoresist layer having a patterned feature in the photoresist layer, wherein photoresist scum is present in the feature; provide the solution to the first processing chamber via the inlet and expose the substrate to the solution, the solution comprising water and one or more chemicals capable of removing at least a portion of the photoresist scum from the feature; receive the substrate in the second processing chamber; and electroplate a metal into the feature while the substrate is in the second processing chamber.

[0018] These and other aspects are further described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figures 1A-1C Depicted is a feature formed in photoresist showing some of the problems that can occur when photoresist scum is present in the feature.

[0020] Figure 2 and Figure 3 Features (eg, lines) formed in the photoresist are depicted. Figure 2 shows the features before any photoresist scum is removed, and Figure 3 Features after photoresist scum removal are shown.

[0021] Figure 4A and 4B Shows damage and other problems that can occur during a plasma-based photoresist descum process.

[0022] Figure 5 Flowcharts according to various embodiments herein are shown.

[0023] Figure 6 Depicted are the structures of specific free radical initiators used in various embodiments herein.

[0024] Figure 7 Shown is a processing chamber that can be used to perform the liquid-based processing operations described herein, such as exposing a substrate to an ozone solution and / or a free radical initiator solution.

[0025] Figure 8 Shown is a processing chamber that may be used to perform electroplating according to various embodiments herein.

[0026] Fig. 9 Depicted are apparatuses configured to perform the liquid-based processing operations described herein (eg, exposing a substrate to an ozone solution and / or a free radical initiator solution), and further configured to perform electroplating, according to various embodiments herein.

[0027] Fig.10 and Fig.11 Examples are presented that illustrate the effectiveness of the photoresist scum removal process described herein.

[0028] Figures 12A-12D Features plated at different quality levels due to the presence of different levels of photoresist scum are depicted.

[0029] Fig.13 The effectiveness of the photoresist scum removal process described herein is shown in Figures 12A-12D The different quality levels shown in .

[0030] Fig.14 The disclosed method is shown to be able to be performed in negative photoresist without increasing the feature diameter. DETAILED DESCRIPTION

[0031] In the following, numerous specific details are set forth to provide a thorough understanding of the embodiments presented. The disclosed embodiments may be practiced without some or all of these specific details. In other cases, well-known process operations are not described in detail so as not to unnecessarily obscure the disclosed embodiments. Although the disclosed embodiments will be described in conjunction with specific embodiments, it should be understood that this is not intended to limit the disclosed embodiments.

[0032] Photolithography is commonly used to pattern semiconductor substrates. Such a process typically involves selectively exposing a photoresist layer on a substrate to radiation, and then developing the photoresist to selectively remove exposed or unexposed portions, thereby forming recessed features in the photoresist. One case where photolithography is used is through mask electroplating, in which metal is electroplated into features formed in the photoresist. Through mask electroplating is achieved by a process flow generally referred to as a semi-additive process (SAP). In general, SAP involves (i) depositing a photoresist on a seed layer on a substrate; (ii) selectively exposing the substrate to radiation to define features, such as lines, pads, etc., on the photoresist; (iii) selectively developing exposed or unexposed portions of the photoresist to form features in the photoresist; (iv) electroplating metal into features in the photoresist; and (v) stripping the remaining photoresist.

[0033] When the photoresist is developed, there is usually a certain amount of photoresist scum that remains at the bottom of the feature, especially near the sidewalls. This photoresist scum can cause problems in subsequent electroplating processes. For example, the photoresist scum can prevent deposition in the area where it is located, resulting in defects ranging from feature undercuts to electroplating failures.

[0034] Figures 1A-1C Shows the problems that can occur during electroplating due to photoresist scum. In particular, Figure 1A The substrate with the seed layer 102 and the photoresist 104 is shown after patterning a feature 106 with sidewalls 108 into the photoresist 104. Photoresist scum 110 is present at the bottom of the feature 106, near the sidewalls 108. Figure 1B The substrate is shown after it has been through a plating process and features 106 have been filled with metal 112. Figure 1A Unfortunately, photoresist scum 110 remains on the substrate. Figure 1C Depicted is a similar Figure 1B The substrate shown in FIG. Figure 1CIn FIG. 1 , metal 112 is copper, which has been electroplated into feature 106. Defects caused by photoresist scum 110 are clearly present.

[0035] To solve this problem, a photoresist descum operation is performed. Before the photoresist descum operation, there is a large amount of photoresist scum at the bottom corner of the feature. After the photoresist descum operation, the photoresist scum in this area is significantly less. The photoresist descum operation is also commonly used to widen the critical dimensions of the feature. Figure 2 and Figure 3 Depicts the photoresist before descumming operation ( Figure 2 ) and after photoresist descum operation ( Figure 3 ). Before descumming, the critical dimension of the feature in this example was about 2.2 μm. After descumming, the feature had a critical dimension of about 3.2 μm.

[0036] In conventional processing, photoresist descumming is usually completed by exposing the substrate to plasma. In many cases, oxygen plasma or oxygen-containing plasma is used. Although this strategy is applicable to many applications, there are some disadvantages, particularly in the case of developing packaging applications. For example, in the case of removing photoresist scumming from very small features or features with a large depth:width aspect ratio, the photoresist descumming operation based on plasma is usually invalid. The oxygen plasma commonly used for photoresist descumming operation is very reactive (reactive), and tends to react anywhere where atoms contact with photoresist. During descumming, compared with the top of the feature, the bottom of the feature is more shielded by the sidewall, and is significantly less exposed to plasma. The photoresist scumming of the bottom of the feature can be completely removed and can be exposed to plasma for a long time, which may cause the undesirable increase of the feature size at the top of the feature.

[0037] Another problem with plasma-based photoresist descum operations is that the etch process is isotropic. This means that photoresist is removed from the bottom of the feature and the sidewalls of the feature. This results in widening of the feature, as discussed above with respect to Figure 2 and Figure 3 As discussed. When the feature size is small (for example, in the case of fine-line redistribution layer (RDL) patterns), this widening may significantly change the feature size. For example, a 1 μm line separated by 1 μm photoresist may become a 1.5 μm or wider line after descumming, which is only separated by 0.5 μm or less photoresist. These changes in feature geometry can affect electrical characteristics and, in some cases, may even cause electrical shorts in the plated circuit. In addition to changing feature size, plasma-based descum operations may also result in changes in feature shape. Figure 4A and4B Features in photoresist 404 on a substrate are depicted as the substrate undergoes a plasma-based photoresist descum operation. Figure 4A shows a substrate during a descum operation when the substrate is exposed to an oxygen plasma 444, and Figure 4B Shows the substrate after the descum operation. Figure 4B As shown, the photoresist descum operation results in damage to the photoresist 404 , an increase in critical dimensions near the top of the features, and incomplete removal of the photoresist scum 410 .

[0038] Plasma-based photoresist descum operations are also difficult to control. For example, in many cases, a short plasma exposure time is required. However, the formation of the plasma requires a finite time. Therefore, a plasma-based descum operation will always damage or remove some minimum amount of photoresist from the substrate. Historically, this has not been considered a big problem. However, as feature sizes continue to shrink, this problem has become more and more problematic.

[0039] In order to overcome these problems, a new photoresist descum operation and device are provided. The new photoresist descum operation is not a plasma-based process, but a liquid-based process. The liquid-based process involves exposing the substrate to a solution containing a chemical substance that contributes to the removal of the photoresist scum. In various embodiments, the photoresist descum operation can be performed in the case of wafer-level packaging applications. In various embodiments, the photoresist descum operation can be performed in the case of a semi-additive process (Semi-Additive Process) as described above. For example, the photoresist descum operation can be performed after the photoresist is developed and before the metal is electroplated into the feature. It has been found that the photoresist descum operation based on liquid described herein can be used for negative photoresist and positive photoresist, as well as ion implanted photoresist. In general, any type of photoresist can be used.

[0040] Figure 5 A flow chart is presented that describes a photoresist descum and electroplating process according to various embodiments herein. The method begins at operation 502, where a substrate is provided to a processing chamber. The substrate typically includes a conductive seed layer (e.g., a metal seed layer) and a photoresist layer that has been patterned to include recessed features, such as Figure 1AAs shown. The seed layer is typically partially exposed and partially covered by the photoresist scum. In some embodiments, the feature may have a critical dimension (e.g., width) between about 1 μm-500 μm. In some embodiments (e.g., in the case of fine-line RDL), the feature may have a smaller critical dimension, such as about 1 μm or less (in some cases, between about 0.5 μm-1 μm). In various embodiments, the feature may have a depth-to-width ratio of about 1:1 or greater, in some cases about 2:1 or greater. The depth of the feature is defined by the thickness of the photoresist. In various embodiments, the photoresist may have a specific thickness. For example, the thickness may have a minimum value of about 0.5 μm, or about 10 μm. In these or other embodiments, the thickness may have a maximum value of about 5 μm or about 250 μm. The thickness of the photoresist may depend on the type of feature patterned into the photoresist. For example, in the case of RDL patterns, the photoresist typically has a thickness of about 5 μm or less, and more advanced patterns have a thickness of about 0.5 μm to 1 μm. In contrast, in the case of wafer-level packaging (WLP) patterning applications, the photoresist typically has a thickness of about 10 μm or more, up to about 250 μm for very large structures. In general, the benefits described herein are greatest (compared to conventional plasma-based descum processes) when the features have relatively small critical dimensions and / or have relatively high aspect ratios. However, the processes described herein can be performed on features of any size and shape.

[0041] In one example, the processing chamber is an electroplating chamber in which a subsequent electroplating process is performed. In another example, the processing chamber is a stand-alone device configured for a photoresist descum operation as described herein. In a similar example, such a processing chamber can be further configured to perform other limited liquid-based processing operations, including but not limited to pre-wetting or otherwise pre-treating the substrate with a liquid. In another example, the processing chamber can be incorporated into a larger processing device or system configured for additional purposes. For example, such a device or system may include one or more processing chambers configured to perform a photoresist descum operation and one or more processing chambers configured to perform electroplating and / or related processes. In such an embodiment, the processing chambers can be implemented as modules that are combined to provide enhanced functionality and a controllable processing and substrate transfer environment. It should be understood that Figure 5 The operations described in the description may independently occur in any type of processing chamber, module, or device described herein, and such processing chambers, modules, or devices may be combined into, for example, devices or systems as needed for specific applications.

[0042] In operation 504, the process chamber is sealed and the pressure in the process chamber is reduced by applying a vacuum. For example, in various embodiments, the pressure can be reduced to about 100 Torr or less. Such a reduction in pressure allows for improved penetration of solutions into features during subsequent processing steps, as well as ensuring that there is no trapped air within the features that would prevent the solution from reaching the bottom of the features.

[0043] Next, at operation 506, the substrate undergoes one or more water-based cleaning operations. For example, as described in operation 506a, the substrate may be exposed to a free radical initiator solution. Alternatively or additionally, as described in operation 506b, the substrate may be exposed to an ozone solution. Any of these operations, alone or in combination, may result in the removal of photoresist scum from the substrate. In some embodiments, operation 506a is omitted so that operation 506 only involves operation 506b. In other embodiments, operation 506b may be omitted so that operation 506 only involves operation 506a. In other embodiments, operation 506 may involve both operations 506a and 506b. In some such embodiments, operation 506a is performed before operation 506b. In some embodiments, operation 506a may be performed after operation 506b. In various embodiments, operations 506a and 506b are repeated at least once. In some embodiments, operations 506a and 506b may be performed cyclically. In another embodiment, operations 506a and 506b are performed once. In another embodiment, operation 506a is performed twice, which is separated by operation 506b. Generally speaking, any one or both of operations 506a and 506b can be repeated any number of times. In addition, operations 506a and 506b can occur sequentially or simultaneously. After any one or both of operations 506a and 506b, the substrate can be rotated to remove excess solution. The (multiple) processes involved in operation 506 can be selected based on a variety of factors, including but not limited to: the composition and molecular structure of the photoresist and photoresist scum (for example, ozone reacts more with C=C bonds, and the OH generated by the free radical initiator will react with any CC bonds), the size of the feature, and the depth of the feature. In addition, such selectivity may be affected by the following items: the need for additional free radicals, whether to use water to clean the substrate after operation 506, and any impact on processing time / yield.

[0044] With regard to operation 506a, a plurality of processing conditions can be controlled. For example, exposure conditions can be adjusted to provide a desired free radical initiator solution flow rate and a desired exposure time period. In various embodiments, the free radical initiator solution is sprayed onto the surface of the substrate. In other examples, the substrate can be immersed in the free radical initiator solution. The substrate can be rotated while being exposed to the free radical initiator solution. The decompression realized in operation 504 allows the free radical initiator solution to penetrate deeply into the feature. The substrate is exposed to the free radical initiator solution for a desired time period. In various embodiments, the time period can have a minimum value of about 5 seconds or about 30 seconds. In these or other embodiments, the time period can have a maximum value of about 60 seconds or about 10 minutes. When the free radical initiator solution is washed off from the substrate (for example, when the substrate is exposed to an ozone solution in operation 506b, or when the substrate is exposed to water to clean the substrate in operation 508 without operation 506b), the exposure time period ends.

[0045] In certain embodiments, the radical initiator solution may have a specific concentration. For example, in some embodiments, the radical initiator in the radical initiator solution may have a minimum concentration of about 5ppm, about 10ppm, about 50ppm or about 100ppm. In these or other embodiments, the radical initiator in the radical initiator solution may have a maximum concentration of about 100ppm, about 200ppm, about 500ppm or about 1000ppm. Typically, a solution of a lower concentration and a longer exposure period can be used, and a solution of a higher concentration and a shorter exposure period can be used. Concentration should be high enough to effectively remove photoresist scum, and low enough to avoid substantial damage to photoresist. An advantage of relatively high concentration is that the processing time is faster. An advantage of relatively low concentration is that the removal of photoresist scum can be more easily controlled to provide uniform results on the entire substrate surface.

[0046] In some embodiments, the temperature of the substrate, substrate holder and / or free radical initiator solution can be controlled. For example, the temperature of one or more of the substrate, substrate holder and / or free radical initiator solution may have a minimum value of about 0°C or about 10°C. In these or other embodiments, the temperature may have a maximum value of about 30°C or about 50°C. In some cases, active heating or cooling is not used. In some cases, the treatment occurs at about room temperature. Typically, lower temperatures result in lower reaction rates, which increase the possibility of generating free radicals at the surface (e.g., photoresist surface). In contrast, higher temperatures increase the generation of free radicals and accelerate the treatment of substrates.

[0047] As used herein, a free radical initiator is a chemical substance that decomposes and produces free radicals when exposed to UV radiation, heat or a catalyst. In various embodiments herein, the metal surface of the seed layer serves as a suitable catalyst for a free radical initiator. As a substitute or supplement for a metal seed layer catalyst, exposure to UV radiation and / or heat can be used to drive the formation of free radicals. Examples of free radical initiators include, but are not limited to, peroxides (such as hydrogen peroxide, benzoyl peroxide (benzoyl peroxide) etc.), azobisisobutyronitrile (AIBN, azobisisobutyronitrile), 2,2'-azobis (2-methylpropionamidine) dihydrochloride (2,2'-Azobis (2-methylpropionamidine) dihydrochloride) and other azo compounds (azocompound), and alkyl halide compounds. AIBN is commonly used as a free radical initiator. However, it is insoluble in water, and therefore may not be the best candidate for use based on an aqueous solution. In contrast, many other identified free radical initiators are soluble in water or miscible in water, and may be better candidates. For reference, the structure of 2,2'-azobis(2-methylpropionamidine) dihydrochloride is as follows Figure 6 As shown. When exposed to the appropriate conditions described above, 2,2'-azobis(2-methylpropionamidine) dihydrochloride decomposes in water to form two molecules with nitrogen and carbon radicals. Similarly, peroxide decomposes in water to form hydroxyl radicals. In general, azo compounds are chemical compounds with the formula RN=N-R', where R and R' can independently be any aryl or alkyl group. Alkyl halide compounds have the formula RX, where R is an alkyl group and X is a halogen.

[0048] The free radicals formed by the free radical initiator can react with the photoresist scum to remove it from the substrate surface. In addition, in embodiments where operation 506 involves both exposure to a free radical initiator solution in 506a and exposure to an ozone solution in 506b, the free radicals formed by the free radical initiator in 506a can react with ozone in 506b to produce hydroxyl radicals. These hydroxyl radicals can react directly with the photoresist scum and remove it, or they can react with ozone to produce additional hydroxyl radicals.

[0049] An advantage of operation 506a is that the decomposition of the free radical initiator can be controlled. For example, the decomposition can be adjusted by applying ultraviolet radiation, heat or being exposed to a catalyst to reach a desired free radical concentration. The amount of UV radiation, heat and catalyst provided to the free radical initiator solution can be easily controlled to promote the formation of free radicals of a desired degree. In addition, the free radical initiator decomposed when exposed to a metal catalyst (such as the metal of a seed layer) can preferably promote the decomposition at a desired position in the feature. Compared with a plasma-based photoresist descumming process, this is a significant advantage. Since the photoresist scum is concentrated at the bottom of the feature, this is the most useful place for free radicals. When free radicals are selectively or preferably produced at the bottom of the feature (compared with the top or bulk solution of the feature), the scum can be effectively removed from the bottom of the feature while minimizing the damage to the remaining photoresist. While plasma-based processes typically result in more removal near the top of a feature and less removal near the bottom of the feature, the liquid-based solutions described herein can have the opposite effect: more removal at the bottom of the feature (where such removal is desired) and less removal near the top of the feature (where such removal is not desired). This improvement is significant.

[0050] With regard to operation 506b, multiple processing variables can be controlled. For example, exposure conditions can be adjusted to provide required ozone solution flow rate and required exposure time period. In various embodiments, ozone solution is sprayed onto the surface of substrate. In other examples, substrate can be immersed in ozone solution. Substrate can be rotated while being exposed to ozone solution. The decompression realized in operation 504 allows ozone solution to penetrate deeply into features. Substrate is exposed to ozone solution for a desired time period. In various embodiments, the time period can have a minimum value of about 5 seconds or about 30 seconds. In these or other embodiments, the time period can have a maximum value of about 60 seconds or about 10 minutes. When ozone solution is cleaned off from substrate (for example, when substrate is exposed to water to clean substrate in operation 508), the exposure time period ends.

[0051] In certain embodiments, ozone solution can have specific concentration.For example, in some embodiments, ozone in ozone solution can have the minimum concentration of about 5ppm, about 10ppm, about 30ppm, about 50ppm or about 100ppm.In these or other embodiments, ozone in ozone solution can have the maximum concentration of about 50ppm, 100ppm, about 200ppm, about 300ppm, about 500ppm.In various embodiments, ozone can be present in ozone solution with the concentration of about 5ppm, about 30ppm or about 50ppm.Usually, solution of lower concentration and longer exposure time period can be used, and solution of higher concentration and shorter exposure time period can be used.Concentration should be high enough to effectively remove photoresist scum, and low enough to avoid substantial damage to photoresist.Similar to free radical initiator solution, one advantage of relatively high concentration is that processing time is faster, and one advantage of relatively low concentration is that the removal of photoresist scum can be more easily controlled, to provide uniform result on the whole substrate surface.

[0052] In some embodiments, the temperature of the substrate, substrate holder and / or ozone solution can be controlled. For example, the temperature of one or more of the substrate, substrate holder and / or ozone solution can have a minimum value of about 0°C or about 10°C. In these or other embodiments, the temperature can have a maximum value of about 30°C or about 50°C. In some cases, active heating or cooling is not used. In some cases, the treatment occurs at about room temperature.

[0053] Ozone in the ozone solution can directly interact with the photoresist scum on the substrate and remove it. Ozone is a strong oxidant, and can remove the photoresist scum in a manner similar to oxygen plasma. In addition, in operation 506, the substrate is exposed to the free radical initiator solution in operation 506a and the embodiment of the ozone solution in operation 506b, the free radical produced by the free radical initiator can interact with ozone to cause the formation of hydroxyl radicals. These hydroxyl radicals can directly interact with the photoresist scum on the substrate and remove it. In addition, these hydroxyl radicals can interact with additional ozone molecules to cause the formation of additional hydroxyl radicals. Hydroxyl radicals are more reactive than molecular ozone, so the reactivity of ozone solution can be regulated by promoting or suppressing free radical formation. For example, a free radical initiator is provided to increase the rate at which ozone forms hydroxyl radicals, thereby increasing the reactivity of solution. As mentioned above, free radical initiators produce free radicals under certain controllable conditions (e.g., exposure to radiation, heat and / or catalysts). By selecting a free radical initiator that forms free radicals when exposed to a metal surface (e.g., a metal seed layer beneath a patterned photoresist), the free radical generation reaction can occur preferentially or selectively near the bottom of the feature, where the photoresist scum is located. The generated free radicals can then promote the decomposition of nearby ozone molecules into more reactive hydroxyl radicals.

[0054] Either of operations 506a and 506b may be used alone or in combination to facilitate photoresist scum removal.While either strategy alone may effectively remove photoresist scum, it is believed that these strategies work synergistically to allow for substantial optimization and tuning of photoresist scum removal.

[0055] Back to Figure 5 In some embodiments, the method continues with operation 508, wherein the substrate is optionally cleaned, for example, with water. Cleaning removes reactive free radicals and / or ozone chemicals from the substrate so that the chemicals do not interfere with subsequent processes, such as electroplating. At operation 510, the pressure in the processing chamber can be increased to, for example, atmospheric pressure. In some embodiments, this pressure increase can be omitted, or the pressure can be increased to a level other than atmospheric pressure. For example, in the case where the processing apparatus includes a load lock to transfer substrates between related modules / chambers under controlled conditions (e.g., controlled pressure), such a pressure change may not be required.

[0056] At operation 512, optional post-processing may be performed. Such post-processing may include, for example, drying the substrate in operation 512a, and / or electroplating the substrate in operation 512b. Drying the substrate may be particularly beneficial in cases where the substrate will be stored for a period of time before further processing. The substrate may be dried in the same or different processing chambers in which operations 506 and / or 508 are performed. In cases where further processing such as electroplating is performed to the substrate immediately after any one of operations 506, 508, or 510, such drying may be omitted. The substrate may be transferred to an electroplating chamber before electroplating in operation 512b. Electroplating processes and devices are discussed further below.

[0057] Compared with plasma-based substrate exposure, an advantage of using aqueous solution to remove photoresist scum is that liquid-based substrate exposure is easier to control. In addition, the reactivity of aqueous solution can be fine-tuned by the concentration of active species in the control solution (for example, the concentration of free radical initiator and / or ozone). When using plasma, it is substantially more difficult to adjust the reactivity. By using the free radical initiator that produces free radicals when exposed to metal, reactivity can be further adjusted and positioned at the bottom of feature. The increase of such localization / preference of reactivity causes improved selectivity and feature shape, for example, because less photoresist is undesirably removed from the sidewall of feature while removing photoresist scum from the bottom of feature.

[0058] Another advantage of the disclosed embodiments is that they can be implemented on an electroplating apparatus. In general, liquid-based processing modules are simpler and easier to incorporate into an electroplating apparatus than modules configured to perform plasma processing. For example, certain electroplating apparatuses (e.g., the ELECTRONIC ... 3D tools) are usually equipped with a module called an advanced pre-treatment module (APT), which is configured to perform liquid-based electroplating. The process that such a module is usually configured to perform is to pre-wet the substrate surface before electroplating, for example to ensure that the electrolyte can sufficiently penetrate into the recessed features. The pre-wetting liquid is usually transmitted through a nozzle, which is sprayed on the substrate surface. The substrate can be rotated to promote uniform liquid transmission. The embodiments of this article can be performed in the same type of module. However, it should be noted that the hardware (for example, the processing chamber and any components therein, and the fluid delivery system coupled to the processing chamber, or some subsets of these components) can withstand the chemicals used. For example, in the case of using a free radical initiator solution, the hardware should be able to withstand exposure to the free radical initiator, and any free radicals generated therefrom. Similarly, in the case of using an ozone solution, the hardware should be able to withstand exposure to ozone, and any free radicals generated therefrom. These chemicals are highly corrosive. Suitable materials for fabricating the hardware include, but are not limited to, polycarbonate, polyetheretherketone (PEEK), polyurethane, polytetrafluoroethylene (PTFE), glass, titanium, and some grades of stainless steel (eg, 316). Device

[0059] The methods herein can be performed on many devices and systems. Suitable devices or systems include treatment chambers configured for liquid-based treatment. Additionally, in various embodiments, the device or system may also include a treatment chamber configured for electroplating, which may be separated from but connected to the treatment chamber configured for liquid-based treatment. The device or system may also include a controller configured to cause any one or more of the methods described herein.

[0060] Figure 7 A process chamber configured for liquid-based processing is shown. The process chamber can be used Figure 5 Any one or more of the operations described in . In this example, the processing chamber is configured to spray or flow the solution onto the substrate. As described above, in other examples, immersion can be used instead of spraying or flowing the solution.

[0061] exist Figure 7 , a substrate 701 is held face-up in a processing chamber 703 by a substrate holder 702. In some embodiments, the substrate holder is configured to hold the substrate in a substantially horizontal orientation (e.g., "face-up" or "face-down") during processing. In other embodiments, the substrate holder is configured to hold the substrate in a substantially vertical orientation during processing. The substrate holder can be temperature controlled to allow the substrate to be heated and / or cooled as desired.

[0062] In a typical operation, a vacuum is first drawn on the process chamber 703 through a vacuum port 709 connected to a vacuum system (not shown). This reduces the pressure in the process chamber 703 to a pressure below atmospheric pressure. After most of the gas in the process chamber is removed by vacuum, a solution (e.g., a free radical initiator solution, an ozone solution, and / or a cleaning solution) is delivered onto the substrate surface from a nozzle 705 or other mechanism.

[0063] The solution is provided to the nozzle 705 by a pipeline (not shown). Part or all of the pipeline can be shared between different solutions. In some cases, a separate pipeline can be provided for different solutions. The pipeline system can include one or more mixing vessels, which are used to prepare one or more solutions. In some cases, a first mixing vessel is provided for preparing an ozone solution, and a second mixing vessel is provided for preparing a free radical initiator solution. The mixing vessel can be fluidically connected to a water source and one or more reactant sources. The reactant source can be a gas, a liquid or a solid, depending on the chemical substance used to prepare a specific solution. Many mixing methods can be used. The mixing vessel, the reactant source and / or the related pipeline can be temperature controlled. In some embodiments, one or more of these elements can be heated and / or cooled.

[0064] In a plurality of embodiments, it may be advantageous to mix the solutions shortly before the solutions are transferred to the treatment chamber for treatment on the substrate. This can maximize the lifetime of the chemical substance being active in the solution. For example, ozone can be mixed into water to produce an ozone solution, which is then immediately transferred to the treatment chamber, where the substrate is exposed to the ozone solution. Similar mixing and solution transfer can be used for free radical initiator solutions. In some embodiments, one or more solutions are degassed before contacting the substrate surface to avoid the gas being released when the solution enters a vacuum environment. Degassing can be performed before or after the solution is mixed. In some embodiments, degassing can be performed before the solution is mixed to ensure that the relevant chemical substances are not removed during degassing. The water used to clean the substrate can be degassed similarly. As described above, many hardware such as pipelines, mixing vessels, nozzles 705, and any other components in the treatment chamber 703 are made of materials that can withstand the chemical substances used for deslagging.

[0065] Motor 707 can be utilized to rotate substrate during processing, to ensure that substrate is fully wetted and exposed to relevant solution. In some embodiments, solution first contacts the rotating substrate within the scope of about 3cm from the center of substrate. After wetting substrate with solution, motor 707 can be used to rotate substrate with low rotation speed, to remove incidental solution. In some cases, thin layer of solution may be left on substrate surface. Excessive solution is discharged, and leaves vacuum chamber through port 711. Substrate can be transferred to electroplating chamber or other treatment chambers then. Treatment chamber 703 will also include controller 713 usually, and this controller 713 includes program instructions and / or logic for performing many aspects of method described herein.

[0066] Figure 8 An apparatus in which the electroplating step can be performed is shown in FIG. The apparatus includes one or more electroplating cells in which a substrate (e.g., a wafer) is processed. For clarity, Figure 8 A plating cell is shown in FIG. In order to optimize bottom-up electroplating, additives (e.g., promoters and inhibitors) are often added to the electrolyte. However, the electrolyte with additives may react with the anode in an undesirable manner. Therefore, the anode and cathode regions of the plating cell are sometimes separated by a membrane so that plating solutions of different compositions can be used in each region. The plating solution in the cathode region is called the catholyte, and the plating solution in the anode region is the anolyte. A variety of engineering designs can be used to introduce the anolyte and catholyte into the electroplating device.

[0067] Reference Figure 8 , shows a schematic cross-sectional view of an electroplating apparatus 801 according to an embodiment. An electroplating bath 803 contains an electroplating solution, which is shown at a liquid level 805. The cathode portion of the container is adapted to receive a substrate in a catholyte. A wafer 807 is immersed in the electroplating solution and is held by, for example, a (e.g., clamshell) substrate holder 809, which is mounted on a rotatable spindle 811 that allows the substrate holder 809 to rotate with the wafer 807. A general description of a clamshell electroplating apparatus having aspects suitable for use with the present invention is described in detail in U.S. Pat. Nos. 6,156,167 and 6,800,187, issued to Patton et al., which are incorporated herein for all purposes.

[0068] Anode 813 is disposed below the wafer in electroplating bath 803 and is separated from the wafer area by membrane 815 (preferably an ion selective membrane). For example, Nafion TMCation exchange membrane (CEM). The area below the anode membrane is generally referred to as the "anode chamber". Membrane 815 allows ions to be communicated between the anode region and the cathode region of the electroplating unit while preventing particles generated at the anode from entering the vicinity of the wafer and contaminating the wafer. The anode membrane can also be used to redistribute current during the electroplating process, and thereby improve electroplating uniformity. A detailed description of suitable anode membranes is provided in U.S. Patents Nos. 6,126,798 and 6,569,299 issued to Reid et al., both of which are incorporated herein for all purposes for reference. Ion exchange membranes, such as cation exchange membranes, are particularly suitable for these applications. These membranes are typically made of ionomeric materials, such as perfluorinated copolymers (such as Nafion) containing sulfonic acid groups. TM ), sulfonated polyimide, and other materials known to those skilled in the art that are suitable for cation exchange. Suitable Nafion TM Selected examples of films include N324 and N424 films available from Dupont de Nemours Company.

[0069] During electroplating, ions from the plating solution are deposited on the substrate. The metal ions must diffuse through the diffusion boundary layer and enter the TSV hole. A common way to assist diffusion is convection of the plating solution provided by pump 817. In addition, vibration stirring or sonic stirring components and wafer rotation can be used. For example, a vibration transducer 808 can be attached to the substrate holder 809.

[0070] The plating solution is continuously provided to the plating bath 803 by pump 817. Typically, the plating solution flows upward through membrane 815 and diffusion plate 819 to the center of wafer 807, and then radially outward and across the range of wafer 807. The plating solution can also be provided from the side of the plating bath 803 to the anode area of ​​the bath. The plating solution then overflows the plating bath 803 to the overflow reservoir 821. The plating solution is then filtered (not shown) and returned to pump 817 to complete the recirculation of the plating solution. In some configurations of the plating cell, different electrolytes are circulated through the portion of the plating cell that contains the anode, while using a sparingly permeable membrane or an ion selective membrane to prevent mixing with the main plating solution.

[0071] The reference electrode 831 is located outside the plating bath 803, in a separate chamber 833 that is replenished by overflow from the plating bath 803. Alternatively, in some embodiments, the reference electrode is positioned as close to the substrate surface as possible, and the reference electrode chamber is connected to the side of the wafer substrate or directly below the wafer substrate via a capillary tube or another method. In some preferred embodiments, the device also includes a contact sensing lead that is connected to the periphery of the wafer and is configured to sense the potential of the metal seed layer at the periphery of the wafer, but does not transmit any current to the wafer.

[0072] When it is desired to electroplat at a controlled potential, a reference electrode 831 is typically employed. The reference electrode 831 can be one of many commonly used types, such as mercury / mercuric sulfate, silver chloride, saturated calomel, or copper metal. In addition to the reference electrode, contact sensing leads in direct contact with the wafer 807 can also be used in some embodiments for more accurate potential measurement (not shown).

[0073] A power supply 835 (e.g., a DC power supply) can be used to control the current flowing to the wafer 807. Power supplies that can provide pulsed current or apply pulsed voltage are also applicable, and the pulses can be many combinations of forward (plating), off (no plating), and reverse (deplating) stages of different time periods, repeated and / or adjusted during the process. The power supply 835 has a negative output lead 839, which is electrically connected to the wafer 807 through one or more slip rings, brushes, and contacts (not shown). The positive output lead 841 of the power supply 835 is electrically connected to the anode 813 located in the plating bath 803. The power supply 835, the reference electrode 831, and the contact sensing lead (not shown) can be connected to a system controller 847, which, among other functions, can also allow the current and potential of the components provided to the plating unit to be adjusted. For example, the controller can allow plating to be performed under potential control and current control. The controller can include program instructions that specify the current and voltage levels that need to be applied to the various components of the plating unit, as well as the time when these levels need to be changed. When a forward current is applied, power supply 835 biases wafer 807 to have a negative potential relative to anode 813. This causes current to flow from anode 813 to wafer 807 and electrochemical reduction (e.g., Cu 2+ +2e - =Cu 0 ) occurs on the wafer surface (cathode), which results in the deposition of a conductive layer (e.g., copper) on the wafer surface.

[0074] Device may also include heater 845, which is used to maintain the temperature of the plating solution at a specific level. The plating solution may be used to transfer heat to other elements of the plating bath. For example, when wafer 807 is loaded into the plating bath, heater 845 and pump 817 may be opened to circulate the plating solution through the plating device 801 until the temperature of the entire device becomes substantially uniform. In one embodiment, the heater is connected to a system controller 847. The system controller 847 may be connected to a thermocouple to receive feedback of the plating solution temperature in the plating device, and to determine whether additional heating is needed.

[0075] As mentioned above, Figure 8 The electroplating unit shown may be incorporated into a larger substrate processing apparatus. The apparatus may be configured to perform a number of process operations in addition to electroplating. For example, the apparatus may include one or more process chambers configured for water-based processes (e.g., Figure 7 The invention relates to a process chamber for treating a substrate by exposing the substrate to an ozone solution and / or a free radical initiator solution, as described herein. Including these different types of process chambers in a single apparatus provides many benefits, including but not limited to providing a controlled atmosphere for transferring substrates between related operations. In addition, such an apparatus eliminates the need for a separate plasma-based photoresist scum removal tool, thereby minimizing capital costs.

[0076] Fig. 9 One embodiment of an electrodeposition apparatus 900 is schematically shown. In this embodiment, the electrodeposition apparatus 900 has a set of electroplating cells 907, each of which may include a pair of electroplating baths or electroplating baths configured in multiple "duets." In addition to electroplating itself, the electrodeposition apparatus 900 may perform many other electroplating-related processes and sub-steps, such as spin cleaning, spin drying, metal and silicon wet etching, electroless deposition, pre-wetting and pre-chemical treatment (e.g., using the solutions described herein), reduction, annealing, electro-etching and / or electro-polishing, photoresist stripping, and surface pre-activation. Fig. 9 The electrodeposition apparatus 900 is schematically shown from top to bottom in the figure, and only a single level or "floor" is disclosed in the figure, but it is readily understood by those of ordinary skill in the art that such an apparatus (e.g., Lam Sabre TM A 3D tool) may have two or more layers "stacked" one above the other, each of which may have the same or different types of processing stations.

[0077] Reference again Fig. 9, the substrate 906 to be plated is typically supplied to the electrodeposition apparatus 900 via a front loading FOUP 901, and in this example, the substrate 906 is brought from the FOUP to the main substrate processing area of ​​the electrodeposition apparatus 900 via a front robot 902, which can retrieve and move the substrate 906 driven by a spindle 903 in multiple dimensions to from one station to another accessible station, in this example, two front accessible stations 904 and two front accessible stations 908 are shown. The front accessible stations 904 and 908 can include, for example, a pre-treatment station (e.g., using a solution described herein) and a spin cleaning and drying (SRD) station. The lateral movement of the front robot 902 from one side to the other side is achieved using a robot track 902a. Each substrate 906 can be held by a cup / cone assembly (not shown), which is driven by a spindle 903 connected to a motor (not shown), and the motor can be attached to a mounting bracket 909. Also shown in this example are four "doubles" of electroplating cells 907, for a total of eight electroplating cells 907. A system controller (not shown) may be coupled to the electrodeposition apparatus 900 to control some or all characteristics of the electrodeposition apparatus 900. The controller may be programmed or otherwise configured to execute instructions according to the processes described herein.

[0078] In some implementations, the controller is part of a system, which can be part of the above examples. Such a system can include a semiconductor processing device, which includes one or more processing tools, one or more chambers, one or more platforms for processing, and / or specific processing components (wafer pedestals, gas flow systems, etc.). These systems can be integrated with electronic devices for controlling their operation before, during, and after the processing of semiconductor wafers or substrates. The electronic device can be referred to as a "controller", which can control various components or subcomponents of one or more systems. Depending on the processing requirements and / or the type of system, the controller can be programmed to control any process disclosed herein, including the delivery of process gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and operation settings, wafer transfer in and out tools and other transfer tools and / or load locks connected or docked with a specific system.

[0079] Broadly speaking, a controller can be defined as an electronic device having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operations, enable cleaning operations, enable endpoint measurements, etc. The integrated circuit can include a chip in the form of firmware that stores program instructions, a digital signal processor (DSP), a chip defined as an application specific integrated circuit (ASIC), and / or one or more microprocessors or microcontrollers that execute program instructions (e.g., software). The program instructions can be instructions sent to the controller in the form of various individual settings (or program files) that define operating parameters for performing a specific process on or for a semiconductor wafer or system. In some embodiments, the operating parameters can be part of a recipe defined by a process engineer to complete one or more processing steps during the manufacture of one or more (kinds of) layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or dies of a wafer.

[0080] In some implementations, the controller may be part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the "cloud" or all or part of a wafer fab host system that may allow remote access to wafer processing. The computer may enable remote access to the system to monitor the current progress of a manufacturing operation, check the history of past manufacturing operations, check trends or performance criteria for multiple manufacturing operations, change parameters of a current process, set processing steps to follow the current process, or start a new process. In some examples, a remote computer (e.g., a server) may provide a process recipe to the system via a network (which may include a local network or the Internet). The remote computer may include a user interface that enables input or programming of parameters and / or settings, which are then sent from the remote computer to the system. In some examples, the controller receives instructions in the form of data that specify parameters for each processing step to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus, as described above, the controller may be distributed, for example, by including one or more discrete controllers networked together and working toward a common purpose, such as the processes and controls described herein. An example of a distributed controller for such a purpose is one or more integrated circuits on a chamber that communicate with one or more integrated circuits remotely (e.g., at a platform level or as part of a remote computer), which combine to control the process on the chamber.

[0081] Example systems may include, but are not limited to, plasma etch chambers or modules, deposition chambers or modules, spin rinse chambers or modules, metal plating chambers or modules, cleaning chambers or modules, chamfer edge etch chambers or modules, physical vapor deposition (PVD) chambers or modules, chemical vapor deposition (CVD) chambers or modules, atomic layer deposition (ALD) chambers or modules, atomic layer etch (ALE) chambers or modules, ion implantation chambers or modules, track chambers or modules, and any other semiconductor processing system that may be associated with or used in the manufacture and / or preparation of semiconductor wafers.

[0082] As described above, depending on one or more processing steps to be performed by the tool, the controller can communicate with one or more other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout the factory, a host computer, another controller, or tools used in material transport to transport wafer containers to and from tool locations and / or load ports in a semiconductor manufacturing facility. Example

[0083] Numerous working examples have shown that the methods described herein can be used to remove photoresist scum from substrates with high quality results, including for both positive and negative photoresists. Fig.10 Describe one such example. Fig.10 Defect density is shown for a substrate patterned with a positive photoresist exposed to a standard oxygen plasma photoresist descum process or to a liquid water based photoresist descum process. The liquid water based process involves exposing the substrate to an ozone solution. Fig.10 The curves in reflect different ozone concentrations and exposure times. The ozone concentrations range from a few ppm to about 50 ppm, and the time periods range from about 1 minute to several minutes. After descumming, the substrates were electroplated and then analyzed for defects. Fig.10 Results are also shown for a substrate that was electroplated without any prior descum process and demonstrates the effectiveness of the descum process. Fig.10 In each of the graphs, the x-axis corresponds to the distance from the center of the substrate (radius, r), and the y-axis corresponds to the defect density measured at that radius. A low defect density indicates a relatively successful photoresist scum removal process, while a high defect density indicates that a large amount of photoresist scum remains on the substrate surface, which interferes with subsequent electroplating and causes defect formation.

[0084] Fig.10 The graphs on the left side of show the results for: (i) a substrate that has not undergone any descum process, and (ii) a substrate that has undergone descum. The substrate that has not undergone descum exhibits an extremely high defect density.

[0085] For the sake of clarity, Fig.10The right part of the chart shows Fig.10 The results for the substrates that were only descummed fit within this range. Even a short exposure to the ozone solution resulted in substantial removal of the photoresist scum, and minimization of related defects after plating.

[0086] Table 1 below shows the average increase in feature CD of substrates with a variety of different standardized features after a liquid water photoresist scum removal process involving exposure of the substrate to an ozone solution or a photoresist scum removal process based on an oxygen plasma involving exposure of the substrate to an oxygen plasma. In this embodiment, the photoresist is a positive photoresist. Each substrate includes many features (e.g., circular pads, square pads, and lines with a critical dimension range of about 5 μm and about 100 μm) with different geometries. Compared to other substrates, each substrate has the same feature layout.

[0087] A substrate that has not been subjected to any photoresist descum process is used as a baseline to show the extent to which the critical dimensions of many features change during the photoresist descum process. [Table 1]

[0088] For all substrates that were subjected to the photoresist scum removal process, there was a small but detectable increase in the critical dimension. The increase in critical dimension was expected because the liquid water based process and the oxygen plasma based process were chosen to completely remove the photoresist scum with the least amount of processing. It is worth noting that the liquid water based process and the oxygen plasma based process resulted in very similar increases in critical dimension.

[0089] A subset of this example is in Fig.11 In particular, Fig.11 Displays the line width for the 10μm line feature type. Fig.11 The results in show that exposing a substrate to either a liquid water based photoresist descum process or to an oxygen plasma based photoresist descum process results in a slight but measurable increase in the critical dimensions of features thereon. The increase in critical dimensions between the two types of photoresist descum processes is comparable.

[0090] In another example, a set of substrates having features patterned as negative photoresist and having a large amount of photoresist scum remaining in the features were analyzed to show the effectiveness of the liquid water based photoresist scum removal process described herein. The photoresist was relatively thick. Half of the substrates (e.g., wafers 1, 4, 5, and 7) were not subjected to any photoresist scum removal process. The remaining half of the substrates (e.g., wafers 2, 3, 6, and 8) were subjected to a liquid water based photoresist scum removal process that involved exposing the substrates to an ozone solution. All substrates were electroplated before analysis. Many features on each substrate were inspected. The features were inspected to determine whether the electroplating process was successful. Each feature was classified as good, poor, defective, or missing. Good fill showed no visible defects and the feature edges were clean. Photoresist residue may be present but is not considered a defect in this analysis. Examples of good fill are shown in FIG. Fig. 12A , shown from top to bottom. Poor fill shows small defects on the surface of the feature. These defects can increase resistance during electroplating, resulting in uneven or low-quality electroplating results. An example of poor fill is Fig. 12B , shown from top to bottom. Defective fill includes large defects that prevent a large portion of the feature surface from being plated. These features are often not fully plated and / or undesirably fall off the substrate during the subsequent photoresist stripping step. Examples of defective fill are shown in FIG. Fig. 12C , shown from top to bottom. Missing fill corresponds to features that are completely or almost completely unplated. An example of missing fill is shown in Fig.12D Shown, displayed from top to bottom.

[0091] Fig.13 It is shown that all inspected features on substrates that have not been subjected to any photoresist scum removal process show poor, defective or missing fill results. In contrast, Fig.13 It was shown that all inspected features on the substrate that were subjected to a liquid water based photoresist removal process (eg, involving exposure to an ozone solution) showed good filling results with no visible defects attributable to photoresist scum.

[0092] In a related example, a set of substrates having features patterned as negative photoresist and having a large amount of photoresist scum in the features were analyzed to show the effectiveness of the liquid water based photoresist scum removal process described herein. The photoresist was relatively thick. Half of the substrates (e.g., wafers 1, 4, 5, and 7) were not subjected to any photoresist scum removal process. The remaining half of the substrates (e.g., wafers 2, 3, 6, and 8) were subjected to a liquid water based photoresist scum removal process that involved exposing the substrates to an ozone solution. The substrates were analyzed to determine the diameter of the features. The diameter of the features associated with this example is shown in FIG. Fig.14As shown. Notably, there was no detectable difference between the feature diameters for any of the substrates. In other words, exposing the substrates to the ozone solution did not result in a widening of the feature diameters. In contrast, conventional processes that effectively remove photoresist scum generally also remove a certain amount of photoresist, resulting in wider features. Therefore, it is believed that the disclosed method is particularly beneficial when used in combination with a negative photoresist (although positive photoresists may also be used).

[0093] The examples described herein show that the disclosed method can be effectively used to remove scum on both negative photoresists and positive photoresists. In addition, the examples show that the disclosed method can be used even for relatively thick photoresists. In the past, similar liquid-based photoresist removal processes were used, which were generally limited to positive photoresists where the photoresist was relatively thin (e.g., <1 μm).

[0094] These promising examples provide unexpected results.Previous liquid-based ozone water treatments have been used in the following situations: (1) completely remove a photoresist layer, or (2) completely remove photoresist residues after another process removes the bulk photoresist. Such treatments have not been used before to remove photoresist scum while maintaining the bulk of the photoresist (e.g., while maintaining features formed in the photoresist). Therefore, surprisingly, the disclosed treatment can be used to remove photoresist scum while maintaining features formed in the bulk of the photoresist. In addition, previous attempts to remove bulk negative photoresists using ozone solutions have not been successful. Therefore, surprisingly, such treatments can successfully remove photoresist scum produced by negative photoresists. Although ozone has been used to remove photoresist scum in very limited situations, these methods have only been practiced or considered in the context of gas-based treatments, where ozone is provided to the substrate in gaseous form. As discussed above, at least in part because previous attempts to remove bulk negative photoresist using ozone solutions have been unsuccessful, it is believed that liquid-based ozone solution treatments are less likely to be successful than gas-based methods. in conclusion

[0095] Although the above embodiments have been described in some detail for the purpose of clarity of understanding, it is apparent that certain changes and modifications may be implemented within the scope of the appended claims. It should be noted that there are many alternative ways to implement the processes, systems, and devices of the embodiments of the present invention. Therefore, the embodiments of the present invention should be considered illustrative rather than restrictive, and these embodiments are not limited to the details provided herein.

Claims

1. A method for processing a substrate, the method comprising: receiving the substrate in a processing chamber, the substrate comprising a photoresist layer having features patterned therein, wherein photoresist scum is present in the features; as well as The substrate is exposed to a solution comprising water and one or more chemicals capable of removing at least a portion of the photoresist scum from the features.

2. The method of claim 1, wherein the solution is an ozone solution comprising water and ozone.

3. The method of claim 2, wherein the ozone solution has an ozone concentration between about 5 ppm and about 500 ppm. The method according to claim 1 , wherein the solution is a free radical initiator solution comprising water and a free radical initiator.

5. The method of claim 4, wherein the free radical initiator comprises one or more chemical species selected from the group consisting of peroxides, azo compounds, alkyl halide compounds, and combinations thereof.

6. The method of claim 5, wherein the free radical initiator comprises one or more chemical species selected from the group consisting of hydrogen peroxide, benzoyl peroxide, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and combinations thereof.

7. The method of claim 4, wherein the free radical initiator solution has a free radical initiator concentration between about 5 ppm and about 1000 ppm.

8. The method of claim 4, wherein the free radical initiator decomposes to form free radicals that remove at least a portion of the photoresist scum from the feature, and wherein the free radical initiator preferentially decomposes near a bottom of the feature as compared to a top of the feature.

9. The method of claim 1 , wherein exposing the substrate to the solution comprises: The substrate is exposed to a first solution and subsequently exposed to a second solution, wherein the first solution is a free radical initiator solution comprising water and a free radical initiator and the second solution is an ozone solution comprising water and ozone.

10. The method of claim 9, wherein the free radical initiator decomposes to form free radicals, and wherein the free radicals formed by the free radical initiator interact with the ozone to form hydroxyl radicals.

11. The method of claim 1, wherein the solution comprises both a free radical initiator and ozone, such that the substrate is exposed to both the free radical initiator and ozone simultaneously.

12. The method of claim 1 , wherein exposing the substrate to the solution comprises: The solution is sprayed or flowed onto the substrate, or the substrate is immersed in the solution.

13. The method of claim 1, wherein the photoresist is a negative photoresist or a positive photoresist.

14. The method of claim 1 further comprising electroplating a metal into the feature after exposing the substrate to the solution.

15. An apparatus for processing a substrate, the apparatus comprising: Processing room; an inlet to the process chamber, the inlet configured to provide a solution to the process chamber; as well as A controller configured to: receiving the substrate in the processing chamber, the substrate comprising a photoresist layer having features patterned therein, wherein photoresist scum is present in the features; as well as The solution is provided to the processing chamber via the inlet and the substrate is exposed to the solution, the solution comprising water and one or more chemicals capable of removing at least a portion of the photoresist scum from the feature.

16. The apparatus of claim 15, further comprising a nozzle fluidly connected to the inlet, wherein the nozzle sprays or flows the solution onto the substrate.

17. The apparatus of claim 15, further comprising a substrate support configured to immerse the substrate in the solution.

18. The device of claim 15, wherein the inlet comprises one or more materials selected from the group consisting of polycarbonate, polyetheretherketone (PEEK), polyurethane, polytetrafluoroethylene (PTFE), glass, titanium, stainless steel, and combinations thereof.

19. The apparatus of claim 15, further comprising a mixing container and / or conduit to prepare the solution by combining (i) the water and (ii) the one or more chemicals capable of removing at least a portion of the photoresist scum.

20. The apparatus of claim 15, wherein the controller is further configured to cause the solution to be prepared by combining (i) the water and (ii) the one or more chemicals capable of removing at least a portion of the photoresist scum no more than about 10 minutes prior to exposing the substrate to the solution.

21. The apparatus of claim 15, further comprising a second processing chamber configured for electroplating, wherein the processing chamber and the second processing chamber are arranged together so that the substrate is transferred from the processing chamber to the second processing chamber under a controlled atmosphere without removing the substrate from the apparatus.

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