Patent Application
20200194285
This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2018-235399, filed on Dec. 17, 2018, and Japanese Patent Application No. 2019-94425, filed on May 20, 2019, the entire contents of which are incorporated herein by reference.
The present application relates to a catalyst used for catalyst-referred etching, a processing pad provided with catalyst, and a catalyst-referred etching device.
In manufacturing semiconductor devices, a Chemical Mechanical Polishing (CMP) device for polishing a substrate surface has been known. The CMP device has a polishing surface formed by attaching a polishing pad onto an upper surface of a polishing table. This CMP device presses a surface to be polished of a substrate, which is held by a top ring, against a polishing surface; and rotates the polishing table and the top ring while supplying slurry as a polishing liquid to the polishing surface. Accordingly, the polishing surface and the surface to be polished are relatively moved in a sliding manner, thereby polishing the surface to be polished.
In recent years, there have been a wide range of materials to be polished and polishing performances (in such as planarity and polishing damages, and further for productivity) of a planarization technique including CMP have been more severely required. In such a background, new planarization methods have been proposed and a catalyst-referred etching (hereinafter, CARE) method is also one of them. In the CARE method, a reactive species with a surface to be processed is generated from within a processing liquid only in the proximity to a catalyst material under the presence of processing liquid, and the catalyst material and the surface to be processed are brought close to or into contact with each other, thereby allowing selective generation of an etching reaction of the surface to be processed on a surface close to or in contact with the catalyst material. For example, on a surface to be processed which has a concave and convex, a convex part and a catalyst material are brought close to or in contact with each other so as to enable selective etching for the convex part, thereby allowing planarization of the surface to be processed. This CARE method originally has been proposed in planarization of next-generation substrate materials such as SiC and GaN that are not easy to planarize with high efficiency by CMP due to their chemical stabilities (for example, Japanese Patent Laid-Open No. 2008-121099, Japanese Patent Laid-Open No. 2008-136983, Japanese Patent Laid-Open No. 2008-166709, and Japanese Patent Laid-Open No. 2009-117782). However, it has been confirmed in recent years that silicon oxide or the like are also processable, and there is a possibility of application to semiconductor device materials such as a silicon oxide film and the like on a silicon substrate (for example, International Publication No. WO 2013/084934).
In the CARE method, a chemical species derived from water adsorbed on a surface of a catalyst material continuously chemically reacts with a surface to be processed, thereby removing an element to be processed. At this point, if the removed element or a compound derived from the removed element remains on a surface of a catalyst, an active site of the catalyst may be deactivated. In the CARE method, deactivation of the active site of the catalyst may cause a phenomenon which decreases the removal rate of a surface to be processed in etching according to use time (number of times). Such a phenomenon is called “poisoning.” A significantly poisoned catalyst causes a significant decrease in the removal rate of the surface to be processed in etching with increasing number of use times; and therefore, it is difficult to apply the CARE method to manufacturing of semiconductor devices. It is one object of the present application to provide a catalyst that is less poisoned.
A catalyst used for catalyst-referred etching is provided. This catalyst includes: a first element for promoting etching of a processing object; and a second element for preventing an etching product generated by the etching from being adsorbed.
Hereafter, embodiments of a catalyst used for catalyst-referred etching (CARE), processing pad provided with the catalyst, and catalyst-referred etching device (CARE device) of the present invention will be described with attached drawings. In the attached drawings, identical or similar elements are denoted by the same or similar reference signs; and in the description of each of the embodiments, a repeated explanation of the identical or similar elements may be omitted. In addition, characteristics indicated by each of the embodiments can be applied to the other embodiments as long as there is no mutual inconsistency.
The CARE device 10 shown in
In addition, in this embodiment, the table 20 includes, as a mechanism for holding the wafer Wf, a vacuum suction mechanism having a vacuum suction plate for vacuum suction of a rear surface of the wafer Wf (surface opposite to the surface to be processed). As a vacuum suction method, either of the following methods can be used: a point suction method using a suction plate having a plurality of suction holes, which are connected to a vacuum line, on a suction surface; and a surface suction method of sucking through a connection hole to a vacuum line provided within a groove (for example, concentrically shaped) which is included in the suction surface.
Further, for stabilization of a suction state, a backing material may be attached to a surface of the suction plate so as to suck the wafer Wf through this backing material. It is noted that a mechanism for holding the wafer Wf can be any publicly known mechanism. For example, it may be a clamp mechanism for clamping a front surface and rear surface of the wafer Wf at least at one part of a peripheral edge part of the wafer Wf; or may be a roller chuck mechanism for holding a side surface of the wafer Wf at least at one part of the peripheral edge part of the wafer Wf. The table 20 is constituted so as to be rotatable around an axial line AL1 by a driving unit motor, an actuator (not illustrated).
In addition, in the embodiment shown in
In one embodiment, the processing liquid PL can be a basic chemical solution having a pH higher than 7. According to the embodiment, hydrolysis involved in the CARE method is promoted. In adjustment of the pH, chemical agents used therefor are not limited; however, a strong base is preferable in order to increase a processing speed. Further, a base not being adsorbed on a metal surface is preferable. In one embodiment, the processing liquid PL can be a chemical solution including sodium hydroxide (NaOH) or potassium hydroxide (KOH). Moreover, though the wall 21 in this figure is fixed to an outer periphery of the table 20, it can be constituted separately from the table. In this case, the wall 21 can be constituted so as to be movable up and down. The wall 21 which is movable up and down allows the holding amount of the processing liquid PL to be changed. In addition, for example, in cleaning a substrate surface after etching process, the wall 21 is lowered so as to allow a cleaning liquid to be efficiently discharged to an outside of the wafer Wf.
The head 30 in the embodiment shown in
Next, the nozzle 40 is constituted so as to supply the processing liquid PL to the surface of the wafer Wf. It is noted that in the illustrated embodiment, the nozzle 40 is provided singly; however, it may be in plurality. In this case, a different processing liquid PL may be supplied from each of the nozzles. In addition, in cleaning the surface of the wafer Wf in the CARE device 10 after etching processing, a chemical liquid for cleaning and water may be supplied from the nozzles 40. Further, the nozzle 40 may be constituted so as to supply the processing liquid PL from the processing pad and a surface of the catalyst 31 via an inside of the head 30 (see
Next, the swing arm 50 is constituted so as to be swingable around a rotation center 51 by a driving unit, that is, an actuator (not illustrated) and is also constituted so as to be movable up and down. At a tip end (an end part on an opposite side of the rotation center 51) of the swing arm 50, the head 30 is rotatably attached. It should be noted that in performing CARE processing, the rotation speed per unit time of the head 30 and the rotation speed per unit time of the table 20 are preferably different from each other. In addition, those rotation speeds per unit time are preferably coprime. Due to those characteristics of the rotation speeds, an uneven wear of the wafer Wf to be processed can be prevented.
The shaft 310 is connected to the swing arm 50 as shown in
At an inner side of the outer peripheral member 304, a head body 306 is arranged. At a lower side of the head body 306, a base plate 308 is arranged. The base plate 308 is detachably attached to the head body 306 with, for example, screws or the like. The base plate 308 is formed of, for example like a metal material, a material having a high rigidity equal to or higher than 50 GPa, preferably equal to or higher than 100 GPa with excellent machinability and surface finish, so as to provide a flat surface and prevent deformation. The base plate 308 can be formed of, for example, ceramic, stainless steel (SUS), or the like.
On a lower side surface of the base plate 308, an elastic member 32 is arranged. In the illustrated embodiment, the elastic member 32 is formed by an elastic film and inside the elastic member (elastic film) 32, a pressure chamber 33 is formed. The pressure chamber 33 is configured so that a fluid (for example, air or nitrogen gas) supplied to the pressure chamber 33 by a fluid source (not illustrated) is controlled so as to control a contact pressure between the region to be processed of the wafer Wf and the catalyst 31. As one example, the pressure of the pressure chamber 33 is controlled within a range of 0.1 psi to 3.0 psi. On a lower surface of the elastic film 32, a processing pad 314 is provided. The processing pad 314 is closely adhered to a lower surface of the elastic film 32 with, for example, a double-sided tape, an adhesive, welding, or the like. The processing pad 314 is preferably formed from a metal material in light of: maintaining surface roughness and shape accuracy still after application of the catalyst; maintaining strength against deformation by the elastic film 32; and applying a voltage to the catalyst. For example, the processing pad 314 can be formed from a metal foil having a thickness of 100 μm or less, such as an SUS foil. On a lower surface of the processing pad 314, the catalyst 31 is provided. Preferably, on a surface of the processing pad 314 for holding the catalyst 31, a groove (not illustrated) is provided. By providing the groove, the processing liquid PL used for CARE processing passes through an inside of the groove, thereby promoting the introduction and discharge of the processing liquid PL to between a surface of the catalyst and a surface of the wafer Wf as a processing object. A pattern of the groove provided on the surface of the processing pad 314 is freely selected; however, it may be, for example, a pattern of a groove radially extending from the surface of the processing pad 314, a pattern in which a plurality of concentrically shaped grooves are formed, or a combination of them.
As shown in
In one embodiment, the head 30 includes a passage 335 for supplying the processing liquid PL, as shown in
In one embodiment, the catalyst 31 used for the CARE device 10 includes: a first element for promoting etching of the substrate as a processing object; and a second element for preventing an etching product generated by the etching from being adsorbed. The first element and the second element can be metals. For example, the catalyst 31 can be an alloy composed of the first element and second element of metals. As one example, the first element can be nickel (Ni) or ruthenium (Ru). As one example, the second element, being alloyed with the first element, is selected from elements capable of adjustment of a d-band center of the catalyst. As one example, the second element can be titanium (Ti), chromium (Cr), molybdenum (Mo), tungsten (W), vanadium (V), zirconium (Zr), aluminum (Al), iridium (Ir), rhodium (Rh), copper (Cu), platinum (Pt), or the like. In addition, the catalyst 31 using the first element and the second element can also be said to be: the first element that promotes etching and has a removal rate relatively higher than the second element; and the second element that does not cause a decrease in the removal rate when being singly used. Further, as one example, the catalyst 31 includes an alloy of: an element having an electron occupation rate of 50% or higher in a d orbital; and an element having an electron occupation rate of 50% or lower in a d orbital. Elements having the electron occupation rate of 50% or higher in a d orbital include elements with atomic numbers 26-30, 44-48, and 76-80. Elements having the electron occupation rate of 50% or lower in a d orbital include elements with atomic numbers 21-25, 39-43, and 72-75. In creating an alloy of a plurality of elements, the created alloy should have a band structure significantly different from any of the elements constituting the alloy; and therefore, elements adopted may be selected from elements whose energy levels are sufficiently separate from one another, that is, whose element numbers are sufficiently separate from one another. The alloy thus obtained has a wider band structure even in comparison with a single metal and therefore, it changes adsorption energy with a compound such as silicon oxide which has been removed from the substrate by the CARE method. In addition, when the catalyst 31 is an alloy, the content of the second element in the alloy is preferably from 5 atomic weight % (at. %) to 80 atomic weight %, and is further preferably from 10 atomic weight % to 50 atomic weight %.
In one embodiment, the catalyst 31 is formed as a film on, for example, a surface of the processing pad 314. For example, the catalyst 31 can be formed as a film on the surface of the processing pad 314 by a sputtering method, a chemical vapor deposition method, a vapor deposition method or the like. In using the sputtering method, a plurality of metals may be sputtered at a time or sputtering may be performed with a chip, frame or the like of one element installed on a target of another element, or an alloy film may be formed by sputtering alloy materials. Further, an alloy film may be formed by thermal treatment after laminating films of heterogeneous elements. Still further, the catalyst 31 may be formed on the processing pad 314 by other film forming methods such as electro plating and electroless plating. The thickness of the catalyst 31 is preferably about from 100 nm to several 10 μm. This is because when the catalyst comes into contact with the substrate and performs a relative motion, a degradation due to wear occurs and if the catalyst is extremely thin, the frequency of replacing the catalyst increases. In addition, the catalyst 31 which is plate-shaped may be fixed to the processing pad 314. Further, a layer of the catalyst 31 may be formed on the surface of the processing pad 314 by impregnating the processing pad 314 with a solution containing the catalyst.
Catalyst-referred etching was performed for a substrate by using a plurality of alloy catalysts of different kinds and a single metal catalyst. First, a substrate including an SiO2 film of 1000 nm on its surface was used as a processing object. The SiO2 film was formed on an Si substrate by a chemical vapor deposition method. The diameter of the substrate was approximately 50 mm. As a processing liquid, 200 ml of 0.1 mol/L potassium hydroxide (KOH) solution was prepared. In addition, the KOH solution had a pH=13. Single metals used were nickel (Ni), ruthenium (Ru), chromium (Cr), titanium (Ti), tungsten (W), aluminum (Al), copper (Cu), platinum (Pt), rhodium (Rh), and iridium (Ir). In addition, as an alloy catalyst used, an alloy catalyst containing any of titanium (Ti), chromium (Cr), molybdenum (Mo), and tungsten (W) in nickel (Ni) (hereinafter, Ni—Ti alloy, Ni—Cr alloy, Ni—Mo alloy, Ni—W alloy) was created. Further, as an alloy catalyst used, an alloy catalyst containing any of titanium (Ti), zirconium (Zr), and vanadium (V) in ruthenium (Ru) (hereinafter, Ru—Ti alloy, Ru—Zr alloy, Ru—V alloy) was created. In the catalyst-referred etching, a head for holding each of the catalysts was slid in a state where both the substrate including the SiO2 film and the catalyst were being brought into contact with each other while being rotated under the presence of a potassium hydroxide solution. In this example, time for single CARE processing was set to one minute. That is, in single processing, the catalyst and the SiO2 film were being brought into contact for a minute while being relatively moved under the presence of the processing liquid. After completion of the processing, the substrate and the catalyst were quickly separated. In addition, after completion of the processing, the processing liquid was quickly removed and the surface of the substrate was cleaned with ultrapure water. After that, the substrate was quickly dried and the thickness of the SiO2 film was measured by using an optical interference film thickness meter. Such CARE processing for one minute was performed five times for each of the catalysts. By measuring the film thickness of the SiO2 film before and after the CARE processing, the removal amount and removal rate (Removal Rate) of the SiO2 film in single processing can be obtained.
As can be seen from
As described above, in comparison with when using Ni alone as a catalyst, when each of the Ni—Mo alloy, Ni—Cr alloy, and Ni—W alloy, which are prepared by adding Mo, Cr, and W, respectively, is used as a catalyst, the removal rate is stable and a decrease in the removal rate of a surface to be processed due to, so-called, poisoning can be moderated or prevented. In addition, in comparison with when using Ni alone as a catalyst, when each of the Ni—Mo alloy and Ni—Cr alloy, which are prepared by adding Mo and Cr respectively, is used as a catalyst, the average removal rate becomes higher and therefore, in performing CARE processing for a plurality of substrates, the overall processing rate increases.
When Ni is used alone as a catalyst for substrate processing, it may occur that: a chemical species derived from water adsorbed on a catalyst surface causes a nucleophilic substitution reaction to Si on a surface of an oxide film, causing bonding with Si; and a silicon oxide or a compound derived from silicon remains on the catalyst surface, thereby causing the deactivation of a reactive site of the catalyst. However, it is considered that when an alloy prepared by adding Mo or Cr to Ni was used, the deactivation of the reactive site was reduced due to an effect of preventing a decrease in the removal rate of Mo or Cr, that is, an effect of making it difficult for a compound derived from silicon to remain.
In addition, when Ru is used alone as a catalyst for substrate processing, it may occur that: a chemical species derived from water adsorbed on a catalyst surface causes a nucleophilic substitution reaction to Si on a surface of an oxide film, causing bonding with Si; and a silicon oxide or a compound derived from silicon remains on the catalyst surface, thereby causing the deactivation of a reactive site of the catalyst. However, it is considered that when an alloy prepared by adding Ti, V, or Zr to Ru was used, the deactivation of the reactive site was reduced due to an effect of preventing a decrease in the removal rate of Ti, V, or Zr, that is, an effect of making it difficult for a compound derived from silicon to remain.
From such a viewpoint, it is preferable to select, as elements constituting an alloy catalyst, at least two elements from among transition metals; and it is preferable that at least one of the selected plurality of elements is an element having a relatively high removal rate for promoting etching and at least another one of the selected plurality of elements is an element not causing an decrease in the removal rate in attempting etching by itself.
From the present disclosure, at least the following technical ideas can be grasped. [Embodiment 1] According to Embodiment 1, a catalyst used for catalyst-referred etching is provided. This catalyst includes: a first element for promoting etching of a processing object; and a second element for preventing an etching product generated by the etching from being adsorbed and/or for preventing the first element from being altered.
[Embodiment 2] According to Embodiment 2, the catalyst of Embodiment 1 is an alloy or mixture including the first element and the second element.
[Embodiment 3] According to Embodiment 3, the first element in the catalyst of Embodiment 2 is nickel (Ni) or ruthenium (Ru).
[Embodiment 4] According to Embodiment 4, the second element in the catalyst of any one of Embodiment 1 to Embodiment 3 is an element such that the amount of reduction in the removal rate with processing time in a case where catalyst-referred etching processing is performed using the second element alone as a catalyst is less than the amount of reduction in the removal rate with processing time in a case where catalyst-referred etching processing is performed using the first element alone as a catalyst.
[Embodiment 5] According to Embodiment 5, the second element in the catalyst of any one of Embodiment 1 to Embodiment 4 is selected from a group consisting of aluminum, titanium, vanadium, chromium, copper, molybdenum, rhodium, tungsten, iridium, and platinum.
[Embodiment 6] According to Embodiment 6, a head used for catalyst-referred etching is provided. This head includes a processing pad and a surface of the processing pad has the catalyst according to any one of claims 1 to 5.
[Embodiment 7] According to Embodiment 7, the processing pad of the head of Embodiment 6 includes an inelastic member and the catalyst is arranged on the inelastic member.
[Embodiment 8] According to Embodiment 8, the head of Embodiment 7 includes an elastic member for defining a pressure chamber and the inelastic member is attached to the elastic member.
[Embodiment 9] According to Embodiment 9, the head of any one of Embodiment 6 to Embodiment 8 includes an opening for supplying a processing liquid onto a processing object.
[Embodiment 10] According to Embodiment 10, a catalyst-referred etching method is provided. This catalyst-referred etching method includes the steps of: preparing the catalyst according to any one of Embodiment 1 to Embodiment 5; and bringing the catalyst into contact with or close to a processing object under the presence of a processing liquid.
[Embodiment 11] According to Embodiment 11, the processing liquid in the catalyst-referred etching method of Embodiment 10 is basic.
[Embodiment 12] According to Embodiment 12, the catalyst-referred etching method of Embodiment 10 or Embodiment 11 includes a step of applying a voltage to the catalyst.
[Embodiment 13] According to Embodiment 13, the catalyst-referred etching method of any one of Embodiment 10 to Embodiment 12 includes a step of making the catalyst and the processing object perform a relative motion while being brought into contact with or close to each other.
| Number | Date | Country | Kind |
|---|---|---|---|
| 235399/2018 | Dec 2018 | JP | national |
| 094425/2019 | May 2019 | JP | national |
