UV-assisted wafer cleaning method and apparatus

Abstract

A method for removing post etch residue from the surface of a semiconductor wafer, comprising irradiating the patterned-side of the semiconductor wafer with ultraviolet radiation, the ultraviolet radiation having a wavelength of from 270 to 400 nm, and an apparatus for performing said method.

Description

[0001] Mewburn Ref: 8836553

[0002] 1

[0003] UV-ASSISTED WAFER CLEANING METHOD AND APPARATUS

[0004] This application claims priority from GB2417898.0 filed 06 December 2024, the contents and elements of which are herein incorporated by reference for all purposes.

[0005] FIELD OF THE INVENTION

[0006] The present invention relates to methods of cleaning semiconductor wafers. More specifically the present invention relates to methods of cleaning semiconductor wafers using a specific wavelength of UV-radiation.

[0007] BACKGROUND OF THE INVENTION

[0008] Advances in information and communication technologies have largely been predicated around increased computing power derived from constant miniaturisation of individual semiconductor components. There is consequently a need to develop efficient methods for patterning semiconductor wafers with critical dimensions of less than 20 nm.

[0009] During their manufacture semiconductor wafers are subjected to various surface treatment processes, such as etching, cleaning, polishing and material deposition. During the manufacture of semiconductor wafers, etching and / or deposition steps are used to build up or remove layers of different types of material on the semiconductor wafer. It is common to have a need to remove one type of material without removing a second type of material, such as a patterned underlying layer.

[0010] During etching processes in semiconductor fabrication processes undesirable residues such as polymeric fluorocarbons and hydroflurocarbons (CxFyHz) are formed and left on the surfaces and sidewalls (referred to as “post-etch residues”) of the resulting structures. These post-etch residues must be removed (cleaned) to prevent quality issues in subsequent deposition processes.

[0011] Various cleaning processes can be implemented to selectively remove or clean post-etch residues off a semiconductor wafer.

[0012] One common method for removing post-etch residues is plasma stripping; however, plasma stripping is often damaging to advanced low-k materials. Consequently, non-plasma methods for removing post-etch residues are needed.

[0013] Broadband UV lamps emitting wavelengths less than 260 nm have also been used for cleaning post etch residues. However, these methods can lead to a shift in properties such as dielectric constant and fall above the threshold for ozone generation, posing a risk of IC metal corrosion. Examples of methods using UV lamps with a wavelength of less than 260 nm are given in US6,800,142B1 and US 2015 / 0128991 A1.

[0014] Conventional methods for removal of post-etch residues also present numerous challenges. Traditional wet cleaning methods use solvents such as NMP (ZV-Methyl-2-pyrrolidone), along with amines (e.g., hydroxylamine) and hydrogen peroxide to strip polymers and remove sidewall Mewburn Ref: 8836553

[0015] 2 residue. However, as feature sizes are reduced and their aspect ratio increases, penetration of the liquid solvents into the features that have been etched into the dielectric becomes more challenging due to surface tension issues. Also, even if liquids do penetrate into such small features, then it becomes difficult to subsequently remove them. Therefore, these methods often require extensive exposure times and do not effectively remove all of the post etch residue.

[0016] Consequently, there is a need for improved methods for removing post-etch residues from semiconductor wafers with small critical dimensions.

[0017] In addition, whilst post-etch residues are reported to have a partially cross-linked structure containing active dangling bonds and functional groups when they are freshly deposited, post etch residues rapidly acquire nitrogen and release their fluoride content to attain a higher degree of cross-linking. This means that aged residues are even more difficult to remove than fresh post etch residues in particular from semiconductor wafers with small critical dimensions.

[0018] Consequently, there is a need to develop effective methods for removing aged post etch residue from semiconductor wafers; in particular semiconductor wafers with small critical dimensions.

[0019] SUMMARY OF THE INVENTION

[0020] The present invention has been devised in light of the above considerations. Accordingly, the present inventors have developed a process which helps to at least partially address the practical problems outlined above.

[0021] Accordingly, in a first aspect the present invention provides a method for removing post etch residue from the surface of a semiconductor wafer, comprising irradiating the patterned-side of the semiconductor wafer with ultraviolet radiation, the ultraviolet radiation having a wavelength of from 270 to 400 nm.

[0022] Preferably, the method further comprises the additional step of discharging a liquid onto the patterned-side of the semiconductor wafer to form a liquid layer on the surface of the patterned- side of the semiconductor wafer.

[0023] The process according to the present invention has a number of advantageous features

[0024] Firstly, the method according to the present invention can lead to the complete removal of post etch residue from a semiconductor wafer, whilst avoiding shifting the properties of the semiconductor wafer and avoiding ozone generation.

[0025] Secondly, the method according to the present invention facilitates removal of post etch residue from semiconductor wafers with critical dimensions of less than 20 nm. This Mewburn Ref: 8836553

[0026] 3 means that the method facilitates effective removal of post etch residue from features on the semiconductor wafer with small sizes and high aspect ratios.

[0027] Thirdly, the method according to the present invention allows aged post etch residue to be removed from semiconductor wafers, with the UV effectively activating the post etch residue for subsequent liquid removal.

[0028] Fourthly, the method according to the present invention allows the faster removal of post etch residue, with the UV irradiation step, reducing the time required to fully remove the post etch residue.

[0029] Fifthly, the use of higher wavelength UV irradiation in the irradiation step allows targeting of post-etch residue without excessive damage to adjacent materials within the patterned wafer.

[0030] Preferably, the method of irradiating the patterned-side of the semiconductor wafer is carried out while the liquid is present on the surface of the patterned-side of the semiconductor wafer.

[0031] This has a number of advantages.

[0032] Firstly, irradiating the surface of the patterned-side of the semiconductor wafer while liquid is present on the surface can reduce the time required for removal of post etch residue. Without being bound by any theory, it is believed that this may be because the UV radiation is able to activate the compounds of the liquid (i.e. cleaning liquid) in situ, or because the UV radiation is able to promote the photooxidation of the residues in the presence of the liquid (e.g. liquid oxidizers such as H2O2) when compared to air and components therein (e.g. gaseous O2 or H2O in air).

[0033] Secondly, the liquid present on the surface can act as a cooling layer avoiding the need for additional cooling systems and meaning that the surface of the semiconductor wafer is not exposed to extreme temperatures. This is because this approach helps to dissipate the heat generated by UV as the liquid can serve as a coolant preventing the semiconductor wafer from over-heating.

[0034] Thirdly, irradiating the surface of the patterned-side of the semiconductor wafer while liquid is present on the surface can also promote the removal of post etch reside over the detrimental swelling-up of partially cross-linked fluorocarbon polymers.

[0035] Also provided herein is an apparatus for carrying out a method according to the present invention, the apparatus comprising: a treatment chamber; a semiconductor wafer support for holding a semiconductor wafer; and Mewburn Ref: 8836553

[0036] 4 a light source configured to irradiate the patterned-side of the semiconductor wafer with ultraviolet radiation having a wavelength of from 270 to 400 nm from above.

[0037] The present invention will now be described with reference to preferred embodiments and other optional features.

[0038] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although, any methods and materials similar or equivalent to those described herein can be used in practice for testing of the present invention, the preferred materials and methods are described herein. In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below. Unless clearly indicated otherwise, use of the terms "a," "an," and the like refers to one or more.

[0039] While the invention is described in conjunction with the exemplary embodiments described below, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments set forth herein are considered to be illustrative and not limiting. Various changes may be made without departing from the scope of the invention which is defined by the claims. All references referred to herein are hereby incorporated by reference.

[0040] Each and every compatible combination of the embodiments described herein is explicitly disclosed herein, as if each and every combination was individually and explicitly recited. Additionally, where used herein, “and / or” is to be taken as a specific disclosure of each of the two specified features with or without the other.

[0041] Unless context dictated otherwise, the descriptions and definitions of the features set out herein are not limited to any particular aspect or embodiment and apply equally to all aspects and embodiments which are described where appropriate.

[0042] Where values are described as “at most” or “at least” it is understood that any of these values can be independently combined to produce a range.

[0043] Unless indicated otherwise, values provided are generally recorded at room temperature, that is, within the range 20-30°C for example 20°C.

[0044] Where non-SI units are provided, it will be understood that these can be converted easily into SI units by the skilled person.

[0045] The use of headings herein is intended to be to assist the understanding of the invention by the reader and does not imply any limitation on the invention as defined in the claims. Mewburn Ref: 8836553

[0046] 5

[0047] Semi-conductor wafer

[0048] The semiconductor wafer may be a silicon wafer. The wafer may have a diameter of 300 mm.

[0049] Suitably, the semiconductor wafer is a patterned semiconductor wafer. In other words, the semiconductor wafer includes surface structures. The surface structures may comprise or consist of pillars. Additionally, or alternatively, the surface structures may comprise or consist of trenches. Additionally, or alternatively, the surface structures may comprise or consist of vias. Preferably, the method is applied to semiconductor wafer having high aspect ratio (HAR) structures, for example, substrates having one or more structures (optionally, all structures) having an aspect ratio of at least about 5:1, at least about 8: 1 , or at least about 10:1 (trench depth : trench width). In the present specification, the “aspect ratio” refers to the ratio of height to width. Advantageously, the method of the present invention is particularly effective at removing post etch residue from surfaces with high aspect ratios.

[0050] The width of the one or more surface structures may be, for example, 100 nm or less, 80 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, or 20 nm or less. The pitch between features may be, for example, 200 nm or less, 150 nm or less, 100 nm or less, 80 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, or 30 nm or less. The height may be, for example, 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, 500 nm or more, 600 nm or more, 700 nm or more, 800 nm or more, or 1000 nm or more.

[0051] For semiconductor wafers incorporating an array of (optionally identical) surface structures, the pitch between structures (that is, the centre-to-centre distance between the structures) may be 500 nm or less, 400 nm or less, 300 nm or less 200 nm or less, 100 nm or less, 50 nm or less, 40 nm or less, or 30 nm or less. The structures’ pitch expressed as percentage of the structures’ height may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less. The structures’ pitch expressed as percentage of the structures’ width may be, for example, less than 500%, less than 400%, less than 300%, or less than 200%, or less 150%.

[0052] Post etch residue

[0053] The term “post etch residue” according to the present invention is not particularly limited, this term may refer to any type of residue or contaminant present on the semiconductor wafer surface following etching. Preferably, the term “post etch residue” refers to a material which comprises or consists of a fluorocarbon (CxFy) or hydrofluorocarbon (CxFyHz) deposit. Alternatively, the term post etch residue" may refer to a material which comprises or consists of a derivative of a fluorocarbon (CxFy) or hydrofluorocarbon (CxFyHz) material.

[0054] Without being bound by any theory, it is believed that the method according to the present invention is particularly effective at removing aged post etch residue. The term “aged” may refer to post etch residue which has been present on the surface of the semiconductor wafer for at least 1 day, optionally for at least 3 days, optionally for at least 4 days, optionally for at least 5 days, optionally for at least a week, optionally for at least two weeks, optionally for at least a month. Mewburn Ref: 8836553

[0055] 6

[0056] The removal of the post etch residue is believed to occur via photo activation of the post etch residue, optionally followed by removal of the residue in a liquid.

[0057] The term “patterned side” (of a semiconductor wafer) refers to the side that have been processed in order to create an electronic component.

[0058] UV

[0059] According to the method of the present invention the ultraviolet radiation has a wavelength of from 270 to 400 nm.

[0060] In general, the term wavelength in the present specification refers to the peak maximum of the wavelength. However, this term may also cover spectra where at least 90% of the energy intensity is between 270 and 400 nm, for example spectra where there are multiple peak maxima or diffuse spectra.

[0061] Preferably, the ultraviolet radiation has a wavelength of from 270 to 390 nm, more preferably, the ultraviolet radiation has a wavelength of from 275 to 385 nm, most preferably, the ultraviolet radiation has a wavelength of from 320 to 385 nm.

[0062] Preferably, the UV radiation has a monomodal peak intensity profile as a function of wavelength. In such a case, or in any other case, the term “wavelength” may refer to the wavelength of the peak intensity of the radiation - the “peak wavelength”.

[0063] Preferably, the ultraviolet radiation has a wavelength of from 315 to 400 nm. Preferably, the ultraviolet radiation has a wavelength of from 350 to 400 nm. Preferably, the ultraviolet radiation has a wavelength of from 360 to 390 nm. Preferably, the ultraviolet radiation has a wavelength of from 370 nm to 390 nm. Preferably, the ultraviolet radiation has a wavelength of from 380- 390 nm. Preferably, the ultraviolet radiation has a wavelength of about 385 nm. Suitably, the light source of the present invention is configured to irradiate the patterned-side of the semiconductor wafer with ultraviolet radiation having the above wavelengths.

[0064] Using UV radiation with the wavelength as set out herein results in the effective removal of post etch residue from low-k semiconductor wafers, whilst insignificantly impacting their k-value. In this way, the claimed wavelength range and those detailed herein represent a careful balance, and result in methods and apparatuses which are simultaneously efficacious and nondestructive. In particular, the wavelengths set out herein are particularly effective at removing post etch residue that comprises fluorocarbon or hydrofluorocarbon deposits.

[0065] According to the present invention the power density of the ultraviolet radiation may be from 1 W / cm2to 100 W / cm2, preferably from 3 W / cm2to 20 W / cm2, preferably from 8 W / cm2to 14 W / cm2at the surface of the patterned-side of the semiconductor wafer. Mewburn Ref: 8836553

[0066] 1

[0067] Alternatively, according to the present invention the power density of the ultraviolet radiation may be from 0.1 to 20 W / cm2, preferably from 0.2 to 15 W / cm2, preferably from 0.3 to 10 W / cm2, preferably from 0.4 to 5 W / cm2, preferably from 0.5 to 2.5 W / cm2at the surface of the patterned- side of the semiconductor wafer.

[0068] In order to achieve the above power densities at the surface of the patterned-side of the semiconductor wafer, the LED array will require a higher power density output, which will depend on at least the size of the LED array relative to the wafer, the distance of the wafer from the LED array, and the rotational velocity of the wafer

[0069] An advantage of the present process is that post etch residue can be removed more quickly than conventional processes. Therefore, the irradiation step in the present invention is preferably carried out for a period of from 1 to 60 seconds, preferably from 1 to 30 seconds, more preferably from 1 to 15 seconds.

[0070] Without, being bound by any theory, it is believed that by combining the UV-irradiation step with a liquid treatment step, it is possible to reduce the time required for complete removal of the post etch residue, due to activation of the liquid by UV and / or due to an enhanced rate of photooxidation of the residues by the liquid in the presence of UV.

[0071] In general, the method according to the present invention is carried out in an atmosphere containing oxygen. Without being bound by any theory, it is believed that oxygen is necessary to facilitate the degradation of the post etch residue. Preferably, the method is carried out in an atmosphere comprising at least 2 % oxygen, preferably at least 20 % oxygen, preferable at least 40 % oxygen and optionally up to a maximum of 60% oxygen. In some aspects, the present invention is carried out at ambient oxygen levels (e.g. around 21%).

[0072] Rotation

[0073] The semiconductor wafer may be spun during the method of the present invention, for example using a rotatable chuck that holds or supports the semiconductor wafer.

[0074] The rotational speed of the semiconductor wafer may be, for example, at least 30 rpm, more preferably at least 50 rpm, more preferably at least 100 rpm, more preferably at least 150 rpm and most preferably at least 200 rpm and optionally up to a maximum of 1000 rpm.

[0075] Rotating the semiconductor wafer means that the method according to the present invention may be carried out by having a UV light source configured to irradiation a portion of the patterned-side of the semiconductor wafer, with the method then involving rotating the wafer so Mewburn Ref: 8836553

[0076] 8 that the entire wafer is irradiated by the UV light source. For example, in the case of a circular semiconductor wafer the UV light source may be in the shape of a sector, with a radius the same as or similar to the radius of the semiconductor wafer (in this context the radius of a sector refers to the length of one of the non-curved sides). The UV light source may then be positioned above a sector of the semiconductor wafer and the semiconductor wafer may then be rotated to allow irradiation of all positions on the surface of the wafer.

[0077] Liquid

[0078] As set out above, the method according to the present invention preferably comprises the additional step of discharging a liquid onto the patterned-side of the semiconductor wafer in order to form a liquid layer on the surface of the patterned-side of the semiconductor wafer.

[0079] Preferably, the liquid is a cleaning liquid, which is preferably a liquid comprising hydrogen peroxide, a liquid comprising sulfuric acid, a mixture of sulfuric acid and hydrogen peroxide, a mixture of sulfuric acid and ozone, more preferably the cleaning liquid is a liquid comprising hydrogen peroxide for example a liquid comprising water and hydrogen peroxide. However, it is also possible to make use of alternative cleaning liquids or deionised water.

[0080] Preferably, the step of irradiating the patterned-side of the semiconductor wafer is carried out while the liquid is present on the surface of the patterned-side of the semiconductor wafer (so called “in-situ” treatment). This might be achieved by depositing liquid onto the patterned-side of the semiconductor wafer, whilst at the same time irradiating the patterned-side of the wafer with UV-radiation. Preferably, during this process, the liquid is deposited at one or more locations on the semiconductor wafer (away from the UV light source) the wafer is rotated to facilitate the diffusion of the liquid in order to give a layer of liquid over the semiconductor wafer surface.

[0081] Alternatively, the step of irradiating the patterned-side of the semiconductor wafer may be carried out at a different time to the step of discharging liquid onto the patterned-side of the semiconductor wafer (so called “ex-situ" treatment). For example, the irradiating step might be carried out first, followed by the step of discharging liquid onto the semiconductor wafer surface. It may be that the two steps are immediately sequential, or substantially immediately sequential (i.e. without an additional step between them and with minimal time between them, for example the step of discharging liquid onto the semiconductor wafer surface may happen shortly or immediately after the irradiating step). The time between the two steps may be less than 60 seconds, less than 30 seconds, less than 10 seconds or less than 1 second - such short times improve wafer cleaning throughput. However, the time between the two steps, may be at least 2 minutes, or at least 5 minutes, or at least 10 minutes, or at least 20 minutes, or at least 30 minutes, or at least 1 hour, or at least 2 hours, or at least 5 hours, or at least 12 hours, or at least 1 day, or at least 2 days, or at least a week and optionally up to a maximum of 1 year. Mewburn Ref: 8836553

[0082] 9

[0083] Optionally, the method according to the present invention comprises rotating the surface of the semiconductor wafer and discharging liquid onto the rotating surface of the patterned-side of the semiconductor wafer. This can assist with the distribution of the liquid over the surface of the semiconductor wafer. Preferably, the rotational velocity of the semiconductor wafer is sufficient to cause the deposited liquid to have a film thickness on the patterned-side of the semiconductor wafer of less than 1 mm, preferably less than 0.1 mm. For example, the deposited liquid may have a film thickness on the patterned-side of the semiconductor wafer of less than 500 pm, preferably less than 250 pm, preferably less than 100 pm. For example, when this present method involves dispensing a liquid at or adjacent to a centre of the semiconductor wafer, and the semiconductor wafer is spun so that the liquid is distributed over the whole surface of the semiconductor wafer, processing of narrow vias or other features towards the edge of the wafer may be reduced compared to corresponding processing towards the centre of the wafer.

[0084] Without being bound by any theory, it is believed that the thickness of the liquid is key to allowing UV radiation to reach the surface of the semiconductor wafer.

[0085] Cooling

[0086] The non-patterned side of the semiconductor wafer may be cooled during the ultraviolet irradiation step. Any appropriate cooling mechanism may be used. In one example, the cooling mechanism may involve flowing cooling fluids through piping in or adjacent to the non-patterned side of the semiconductor wafer. In another example, the cooling mechanism may involve dispensing coolant onto the non-patterned side of the semi-conductor wafer.

[0087] In general, cooling of the non-patterned side is particularly useful during ex situ treatment.

[0088] Without being bound by any theory, it is believed that when liquid is present on the surface of the semiconductor wafer, for example when the liquid is discharged at the same time as the irradiation step, cooling is not required.

[0089] Cleaning of UV light source

[0090] In the method according to the present invention, there may be a step of cleaning the UV light source (a light source cleaning step).

[0091] It may be that the step of cleaning the light source comprises applying a light source cleaning liquid to the light source. It may be that the light source cleaning liquid comprises water, for example de-ionised (DI) water. It may be that the light source cleaning liquid comprises an organic solvent. It may be that the step of cleaning the light source comprises applying a light source cleaning liquid to the light source, and then capturing the used or spent liquid once it has left or been removed from the light source. Mewburn Ref: 8836553

[0092] 10

[0093] It may be that the step of cleaning the light source comprises applying a light source cleaning gas to the light source. It may be that the light source cleaning gas comprises an inert gas, for example N2.

[0094] It may be that the step of cleaning the light source comprises applying both a light source cleaning liquid and a light source cleaning gas to the light source, simultaneously or sequentially. In such a case, the light source cleaning gas may act to dry the light source.

[0095] It may be that the step of cleaning the light source comprises contacting the light source with a light source cleaning implement, for example to wipe or brush the light source.

[0096] It may be that the step of cleaning the light source cleaning is carried out at a light source cleaning station, and so the method comprises delivering the light source to the light source cleaning station, and removing the light source from the light source cleaning station once cleaning is complete.

[0097] Suitably, the step of cleaning the light source may comprise cleaning of an enclosure which encloses the light source, for example including cleaning a UV transparent window between the light source and the patterned side of the semiconductor wafer.

[0098] The light source cleaning step advantageously works to remove contamination that has settled on the light source. For example, contamination may include liquid droplets from the application of liquid to the semiconductor wafer in the methods of the present invention. It may be that one or more components of the liquid applied to the semiconductor wafer are reactive, and can strongly adhere to the light source upon exposure to the ultraviolet radiation. Contamination may impact the optical output of the light source and may contaminate semiconductor wafers being processed. So, cleaning is important for the long-term performance of the light source.

[0099] Apparatus

[0100] The present invention also provides an apparatus for carrying out the method of the present invention. More specifically, the present invention provides an apparatus comprising: a treatment chamber; a semiconductor wafer support for holding a semiconductor wafer; and a light source configured to irradiate the patterned-side of the semiconductor wafer with ultraviolet radiation having a wavelength of from 270 to 400 nm from above. Mewburn Ref: 8836553

[0101] 11

[0102] Optional and preferably features of the apparatus will now be described. It should be understood that the options and preferences set out below also apply equally in respect of the first aspect of the present invention. Moreover, the options and preferences set out above for the method according to the present invention also apply equally for the apparatus according to the present invention.

[0103] Generally, the apparatus comprises a means for rotating the semiconductor wafer support.

[0104] The means for rotating the semiconductor wafer support may be a rotatable platform with suitable semiconductor wafer gripping means. The semiconductor wafer may be held by the rotatable platform by, for example, a vacuum chuck (or grip), edge gripping chuck or Bernoulli chuck (or grip).

[0105] Optionally, the semiconductor wafer support is a chuck. Preferably, the chuck may be a rotatable chuck which includes a chuck body which is rotatably mounted on a base. The chuck body is rotatable relative to the base about a rotational axis. Rotation of the chuck body relative to the base may be driven, for example, by a motor, which may itself be controlled by a controller. The chuck body may include grippers which are adapted to receive a wafer and hold the wafer securely in place. In this manner, when a wafer is mounted on the rotatable chuck via the gripping means, the wafer may be rotated by rotating the chuck body. In some embodiments, the grippers are gripping pins which exert a gripping force to hold the wafer in place. However, other suitable mechanisms may be used for holding the wafer in place instead, including but not limited to a clamp, screws, and a suction holder.

[0106] The chuck may include a transparent plate mounted on the chuck body. The transparent plate can be made of any suitable transparent material, for example quartz or sapphire. The transparent plate may be secured to the chuck body, such that when the chuck is a rotatable chuck the transparent plate rotates with the chuck body relative to the base. The transparent plate may be arranged such that it is substantially parallel to the wafer when the wafer is mounted on the chuck.

[0107] LEDs

[0108] The apparatus according to the present invention comprises a light source configured to irradiate the patterned-side of a semiconductor wafer with ultraviolet radiation having a wavelength of from 270 to 400 nm.

[0109] Preferably the light source is an array of light emitting diodes (LED-array). The term “array” may merely mean a plurality of LEDs, and does not necessarily mean that the LEDs are arranged in any particular order.

[0110] Optionally, the LED array is water-cooled, for example by being attached to a water-cooling apparatus. The LED-array may also be ventilated. Mewburn Ref: 8836553

[0111] 12

[0112] Optionally, the apparatus has an adjustable LED-sample distance. Preferably, the LED- semiconductor wafer distance is from 1 to 50 mm, preferably 3 to 50 mm, preferably 10 to 50 mm, preferably 30 to 50 mm.

[0113] The LED-array may have a packing density of from 1.0 to 8.0 diodes / cm2, preferably 1.0 to 5.0 diodes / cm2, preferably from 1.5 to 4.5 diodes / cm2, preferably from 2.0 to 3.0 diodes / cm2, most preferably about 2.5 diodes / cm2.

[0114] The arrangement of the LED-array depends on the configuration of the apparatus and the specific manner in which the device is being used.

[0115] The array of LEDs may be arranged to face towards the semiconductor wafer when the wafersemiconductor wafer is in the semiconductor wafer support.

[0116] The LEDs may be disposed on a substantially plane surface (e.g. on a board, such as a circuit board).

[0117] The array of LEDs may be arranged to face towards the patterned-side of the semiconductor wafer and the may be arranged to be substantially parallel to the semiconductor wafer when the semiconductor wafer is in the semiconductor wafer support.

[0118] The LEDs may be substantially uniformly distributed over the plane surface, to irradiate the semiconductor wafer in a uniform manner, which may result in uniform irradiation of the semiconductor wafer.

[0119] The array of LEDs may be arranged to cover an area that is substantially the same as an area of the semiconductor wafer, or an area that is within 10% of an area of the wafer-shaped article.

[0120] It may be that the LEDs cover an area that is at least 10% of the area of the semiconductor wafer, at least 15% of the area of the semiconductor wafer, at least 20% of the area of the semiconductor wafer, at least 25% of the area of the semiconductor wafer, at least 30% of the area of the semiconductor wafer, at least 35% of the area of the semiconductor wafer, or at least 40% of the semiconductor wafer.

[0121] All of the LEDs may be of the same type (e.g. they may all have the same characteristics).

[0122] Each of the LEDs may comprise a chip or die or diode of the LED that emits light, and a lens that focusses or directs the light emitted by the chip or die or diode. The lens may be a silica (SiCh) lens. The lens may be a hemispherical lens that is positioned over the chip or die or diode. Of course, other shapes and / or materials for the lens are possible. Each of the LEDs may further comprise a case or housing that houses the chip or die or diode and the lens. The Mewburn Ref: 8836553

[0123] 13 combination of the chip or die or diode, the lens and the case or housing may be referred to as an LED package, for example.

[0124] Where the semiconductor wafer support is rotatable, the LED-array may be mounted relative to the semiconductor wafer support such that it does not rotate together with the semiconductor wafer support when the semiconductor wafer support is rotated. In other words, the array of LEDs may remain stationary when the semiconductor wafer support is rotated. This may facilitate providing electrical connections to the array of LEDs.

[0125] The LEDs may be arranged in concentric arcs (concentric about a centre of the array).

[0126] The apparatus may comprise one or more reflectors for focussing or directing the light emitted by the LEDs, for example so as to focus or direct the light onto one or more specific regions of the semiconductor wafer.

[0127] In each concentric arc the LEDs may be bunched into different groups. In other words, the LEDs in a respective concentric circle may not be evenly distributed around that concentric arc.

[0128] Each of the different groups may contain the same number of LEDs.

[0129] The different groups of LEDs may be independently controlled, for example by different power being supplied to different groups of the LEDs, and / or by different groups of the LEDs being operated at different times.

[0130] The LEDs may have a power output of greater than or equal to 2W at maximum current, for example greater than or equal to 2.5W. However, the required power output will depend on the specific application so may be different to this.

[0131] In some embodiments, the LED array is a linear array. In the case, where the removal step is being carried out on a circular semiconductor wafer, which is being rotated during treatment the power of the LEDs may increase going from the centre to the outside of the array to ensure each section of the semiconductor wafer is exposed to the same level of UV-radiation when the semiconductor wafer is rotated.

[0132] Alternatively, the array may be a wedge-shaped array (i.e. equivalent to a sector of a circle of the same size as the semiconductor wafer), which is configured so that as the semiconductor wafer is rotated the patterned-side of the circular semiconductor wafer may be evenly irradiated by the wedge-shaped array.

[0133] It may be that the array is substantially shaped as a minor segment of a circle with radius the same as the radius of the circular semiconductor wafer. Suitably, the shape of the array may be altered or adapted to facilitate deployment in the apparatus of the present invention. For example, the shape of the array may be adapted to allow space for other components of the apparatus, such as one or more of the fluid dispensing nozzles. Therefore, whilst the array may Mewburn Ref: 8836553

[0134] 14 be substantially shaped as a minor segment of a circle, it may for example be that edges and corners are suitably truncated or extended as required. For example, it may be that one of the corners of the minor segment is truncated.

[0135] In the case that the LED array is substantially shaped as a minor segment of a circle with radius the same as the radius for the circular semiconductor wafer, the LEDs may be arranged in concentric arcs (concentric about the radial centre of the minor segment; that is the centre of a circle of which the LED array is a minor segment)

[0136] Preferably, the apparatus is configured such that during operation the clearance between the light source and the semiconductor wafer is from 1 to 50 mm, preferably from 3 to 50 mm, preferably 10 to 50 mm, preferably 30 to 50 mm.

[0137] Preferably, the apparatus comprises a UV-transparent window between the light source and the patterned-side of the semiconductor wafer. The UV-transparent window may optionally be quartz, sapphire or UV-transparent glass.

[0138] It may be that the light source is hermetically sealed. Sealing the light source protects sensitive components from damage, for example sensitive electrical or mechanical components.

[0139] Protection may specifically be achieved against damage through exposure to the liquids provided to the surface of the wafer, or from any gases produced on the surface of the wafer. It may be that the light source is sealed by including the light source in a hermetically sealed enclosure, the enclosure comprising a UV-transparent window, as described above.

[0140] Preferably, within the sealed light source the gas pressure is higher than a gas pressure outside of the sealed light source (i.e. the sealed light source is provided at an overpressure). The overpressure prevents and mitigates ingress of liquids and gases into the sealed light source, protecting sensitive components. Preferably, the overpressure is achieved by using a flow of gas into and out of the sealed light source. In such a case, the sealed light source comprises a gas inlet and a gas outlet. Preferably, within the sealed light source (for example, within the hermetically sealed enclosure) the gas substantially surrounds the light source, and other electrical components. For example, it may be that the gas is present between the light source and a UV-transparent window, as described above.

[0141] Preferably, the overpressure is achieved by using an inert gas. It may be that the inert gas is one or more gases selected from N2, He, Ne, and Ar. Preferably, the inert gas is or comprises N2. When the overpressure is achieved using a flow of gas, the flow also contributes to the thermal management of electronic components such as the light source. Preferably, the overpressure is monitored, for example by a pressure monitor. Monitoring the pressure enables detection of sealing failures or breaches, which would be seen through a drop in observed pressure. Mewburn Ref: 8836553

[0142] 15

[0143] The use of a hermetically sealed light source (for example by making use of a hermetically sealed enclosure) as set out above ensures a stable operating environment, the extension of component lifetime, and system reliability.

[0144] Regarding the homogeneity of the light source illumination across the wafer, and without wishing to be bound by theory, it is thought that the portions of semiconductor that are positioned beneath, or pass only beneath, peripheral regions of the LED array are liable to being under-exposed, due to the lack of (indirect) irradiation from any LEDs beyond the periphery of the LED array.

[0145] In more detail, it may be that the LEDs have a non-zero emission angle, meaning that in the context of the present invention they cast radiation onto regions of semiconductor wafer directly opposite them, as well as regions not directly opposite them but within their emission cone. As such, a region of semiconductor directly beneath a central region of the LED array will receive light from LEDs directly above it, and in all directions around it. In contrast, a region of semiconductor directly beneath a peripheral region of the LED array, or that only ever passes beneath a peripheral region, will receive light from LEDs directly above it, and only from LEDs towards a central region of the LED array.

[0146] Accordingly, it may be that in order to irradiate the semiconductor wafer in a uniform manner, the LEDs in the LED array are distributed with varying packing density across the array (i.e. the packing density varies across the surface of the LED array and is not constant across the array, that is it may be heterogenous). The exact arrangement of LEDs can vary and will depend in part on the shape of the LED array and its arrangement in the apparatus of the present invention.

[0147] It may be that the LEDs have a first packing density in a first region of the LED array, and a second packing density in a second region of the LED array, wherein the first packing density is higher than the second packing density.

[0148] In the case of a circular semiconductor wafer, it may be that the LED array comprises a higher packing density of LEDs at inner and / or outer edge regions (the first region(s)), as compared to an intermediate region between the inner and outer edge regions (the second region). Herein, “inner edge region” and “outer edge region” are defined relative to the circular semiconductor wafer, such that the “inner edge region” is towards the inner part (centre) of the wafer and the “outer edge region” is towards the outer part (perimeter) of the wafer. In this case, the intermediate region is at or adjacent to a point halfway along the radius of the circular semiconductor wafer. The intermediate region may be an arc portion that is at or adjacent to a point halfway along a radius of the circular wafer.

[0149] In the case that the LED array is shaped substantially as a minor segment of a circle with the same radius as the circular semiconductor wafer, the LED packing density is suitably higher at an inner edge region towards the middle of the substantially straight edge of the LED array, and Mewburn Ref: 8836553

[0150] 16 an outer edge region adjacent the curved edge of the LED array. The intermediate region with lower LED packing density may be shaped as a portion of an annular region or ring between the inner and outer edge regions.

[0151] It may be that the first region of the LED array has a packing density that is > 2.5 diodes / cm2and < 8.0 diodes / cm2. It may be that the first region of the LED array has a packing density that is > 2.5 diodes / cm2and < 6.0 diodes / cm2. It may be that the first region of the LED array has a packing density that is > 3.0 diodes / cm2and < 6.0 diodes / cm2. It may be that the first region of the LED array has a packing density that is > 3.5 diodes / cm2and < 6.0 diodes / cm2.

[0152] It may be that the second region of the LED array has a packing density that is < 2.5 diodes / cm2and > 1.0 diodes / cm2. It may be that the second region of the LED array has a packing density that is < 2.0 diodes / cm2and > 1.0 diodes / cm2. It may be that the second region of the LED array has a packing density that is < 1.5 diodes / cm2and > 1.0 diodes / cm2.

[0153] It may be that a difference in LED packing density between the first region of the LED array and the second region of the LED array is > 0.5 diodes / cm2, > 1.0 diodes / cm2, > 1.5 diodes / cm2, or > 2.0 diodes / cm2.

[0154] It may be that, in order to measure the LED packing density, a region of defined area is sampled, and the number of LEDs in that region is divided by the area of that region in cm2. In order to measure the packing density, the size of the region being probed can be set as 1 / 20ththe total area of the LED array. Alternatively, the total area of the LED array can be divided into 20 regions of equal area, and the LED packing density calculated for each. When calculating the LED packing density, the area being probed must be completely contained within the perimeter of the LED array (and not include an area outside of the perimeter of the LED array). The defined area may have a shape corresponding to the shape of the overall LED array. It may be that the areas are defined by dividing the LED array into a number of, for example 20, stacked and side-by-side arc segments of equal area, and the LED packing density calculated for each, wherein the curvature of the arc segments corresponds to the circular semiconductor wafer. Alternatively, it may be that the areas are defined by dividing the LED array into a number of, for example 5, 10 or 20 stacked arc segments of equal width, wherein the curvature of the arc segments corresponds to the circular semiconductor wafer.

[0155] As explained above, it may be that the LED array is liquid cooled, for example by being attached to a water-cooling apparatus. The LED-array may also be ventilated.

[0156] It may be that the apparatus further comprises a heat sink.

[0157] It may be that the heat sink is thermally coupled to the light source (for example, the LED array). It may be that the thermal coupling is direct, or indirect. It may be that the heat sink is thermally coupled to the light source via a thermal interface material (TIM). It may be that the TIM has a thermal conductivity of > 10 W / mK, or > 15 W / mK, > 20 W / mK, or > 25 W / mK. It may be that Mewburn Ref: 8836553

[0158] 17 the thermal conductivity of the TIM is in a direction between an axis connecting the light source and the heat sink.

[0159] It may be that the heat sink is thermally coupled to electronic components in addition to the light source, for example a driver I control board for the light source. It may be that such coupling is via a TIM. In such a case, the TIM may be as described above.

[0160] It may be that the heat sink is thermally coupled to both the light source, and additional electrical components (for example, a driver / control board).

[0161] It may be that the heat sink comprises a cooling channel through which fluids can flow, preferably the cooling channel is a liquid cooling channel. It may be that the heat sink comprises a plurality of cooling channels.

[0162] It may be that the cooling channel comprises an upstream portion and a downstream portion, wherein “upstream” and “downstream” are relative to a fluid flow direction. It may be that the upstream portion is thermally coupled (or more strongly thermally coupled than the downstream portion) to a first region of the light source (e.g. LED array) which has a higher thermal output than a second region of the light source. The higher thermal output may be due to a higher LED packing density. In such a case, the downstream portion is thermally coupled (or more strongly thermally coupled than the upstream portion) to a second region of the light source which has a lower thermal output (for example due to lower LED packing density). Such an arrangement ensures the fluid passing through the cooling channel is at it’s coolest when passing over the regions of the LED array that are at the highest temperature, improving thermal management.

[0163] In the case of a circular semiconductor wafer, it may suitably be the case that the upstream portion is thermally coupled to an outer edge portion or an inner edge portion of the LED array, where there is a higher packing density of LEDs than in an intermediate region of the LED array between the outer edge portion and the inner edge portion (as described above). The downstream portion may suitably be thermally coupled to an intermediate region of the LED array with a lower packing density of LEDs.

[0164] The introduction of a heat sink as described above, and optionally the use of one or more TIMs, regulates the temperature of the light source and other electronic components, ensuring their proper function. For example, LED junction temperature is important for achieving desired optical output.

[0165] It may be that the apparatus comprises a light source cleaning assembly for carrying out the light source cleaning step of the method according to the invention.

[0166] Suitably, the light source cleaning assembly may comprise a source of, or input for, light source cleaning liquid, and a light source cleaning liquid drain for collecting used or spent liquid. Mewburn Ref: 8836553

[0167] 18

[0168] Suitably, the light source cleaning assembly may comprise a source of, or input for, light source cleaning gas.

[0169] Suitably, the light source cleaning assembly may comprise a light source cleaning implement for physically contacting the light source to wipe, brush, etc the light source.

[0170] It may be that the light source cleaning assembly comprises a light source cleaning station, into which the light source can be situated for carrying out the light source cleaning step. Suitably, the light source cleaning station is situation away from the semiconductor wafer, so that the light source does not overlie the wafer when in the cleaning station. The light source cleaning station may be, or may be part of, the standby or rest position described elsewhere herein in relation to the delivery arm, and as such may comprise or exhibit the features described in relation to that standby or rest position.

[0171] Nozzles

[0172] The apparatus according to the present invention, optionally further comprises one or more fluid dispensing nozzles for delivering liquid onto the patterned-side of the semiconductor wafer. The nozzle(s) may be any suitable form for the delivery of streams / jets of a liquid at a suitable flow rate. The nozzles may alternatively be referred to as “outlets”. The nozzles may simply be the open ends of a liquid delivery tubing. Alternatively, the nozzles may be separate nozzles to guide the flow of the liquid. The nozzles may have the same internal diameter as the conduit through which liquid is delivered, or may have some different shape - e.g. a smaller crosssection to increase flow rate. The internal diameter of the nozzles will depend on the particular flow characteristics desired for a specific application, but may be, for example, at least 2 mm, at least 3 mm, at least 4 mm, at least 5 mm, or at least 10 mm.

[0173] Preferably, the one or more fluid dispensing nozzles are positioned off-centre on the semiconductor wafer; particularly preferably, the one or more fluid dispensing nozzles are positioned to one side of the LED-array, such that during operation the nozzle dispenses liquid onto the surface of the semiconductor wafer, which is then dispersed over the surface of the patterned-side of the semiconductor wafer.

[0174] However, it may be that one of the one or more fluid dispensing nozzles is positioned centrally on the semiconductor wafer. For example, when the LED array is in the shape of a minor segment of a circle of radius the same as the radius of the circular semiconductor wafer, there is room for one of the one or more nozzles to be positioned over the centre of the semiconductor wafer.

[0175] For example, when the semiconductor wafer is being rotated in a particular direction, having the fluid dispensing nozzles positioned to one side of the LED-array means that the liquid can be deposited onto the surface of the semiconductor wafer and then spun away from the LED-array, Mewburn Ref: 8836553

[0176] 19 allowing for the liquid to spread out on the surface of the LED-array to give a thin (less than 1 pm) uniform coating over the semiconductor wafer by the time the wafer reaches the LED-array under which UV-irradiation is carried out.

[0177] The nozzles are generally connected to a source of the liquid via a respective flow path.

[0178] The source of the liquid may comprise a container or reservoir of the liquid, for example.

[0179] The source of the liquid may comprise a source line, or supply line, or source flow path, or supply flow path, for example.

[0180] The source of the liquid may be a supply of the liquid.

[0181] The apparatus may comprise one or more valves to control the flow of liquid into the flow path.

[0182] Preferably, the apparatus according to the present invention comprises two nozzles: a first nozzle and a second nozzle.

[0183] In the case of two nozzles, as set out above, there may be a first flow path connected to the first nozzle and a second flow path connected to the second nozzle. In this case a first valve may be operable to control the flow of liquid in the first flow path, and a second valve may be operable to control the flow of liquid in the second flow path. For example, the first valve and / or the second valve may be operable to start or stop the flow of liquid in the respective flow path. In addition, or alternatively, the first valve and / or the second valve may be operable to control a flow rate of the liquid when the liquid is flowing in the respective flow path, for example to increase or decrease the flow rate.

[0184] Preferably, the first and second nozzles are configured to be positioned over the surface of the semiconductor wafer. The first and second nozzles being configured to be positioned over the surface of the semiconductor wafer may mean that the first and dispensing nozzles are mounted over the surface of the semiconductor wafer, or that the first and second nozzles are movable to over the surface of the semiconductor wafer.

[0185] Generally, there is a distance between the first nozzle and second nozzle. The distance between the first nozzle and the second nozzle may be measured in a horizontal plane, and / or in a plane of the wafer.

[0186] The distance between the first nozzle and the second nozzle may be a horizontal distance between the first nozzle and the second nozzle, and for example does not take into account any differences in height of the nozzles.

[0187] The distance between the first nozzle and the second nozzle may be measured between respective tips of the dispensing nozzles. Mewburn Ref: 8836553

[0188] 20

[0189] For example, the first and second nozzles may be viewed vertically from above, and the tips of the first and second nozzles projected into a horizontal plane. The distance between the projected tips in the horizontal plane may then be measured.

[0190] The first valve may be operable to shut-off, or stop, or block, or prevent a flow of the liquid thorough the first flow path.

[0191] The second valve may be operable to shut-off, or stop, or block, or prevent a flow of the liquid thorough the second flow path.

[0192] The first and / or second valve may have a closed state or configuration in which the valve prevents flow of liquid through the flow path, and an open state or configuration in which the valve allows flow of liquid through the flow path.

[0193] In addition to being usable to shut off the flow of liquid in the respective flow path, or as an alternative, the first and second valves may be configured to control a flow rate of the liquid in the respective flow path.

[0194] For example, the open state or configuration of the valve may be controllable or adjustable to control or adjust a flow rate of the liquid in the respective flow path while the flow of liquid is permitted or enabled by the valve.

[0195] Specifically, the first valve may be configured to control a flow rate of the liquid in the first flow path, and / or the second valve may be configured to control a flow rate of the liquid in the second flow path.

[0196] Controlling the flow rate in the respective flow path may comprise increasing or decreasing the flow rate of the liquid flowing in the flow path, for example from a first flow rate that is greater than 0 to a second flow rate that is greater than 0.

[0197] Such an arrangement enables independent control of the dispensing of the liquid from the first and second nozzles, enabling the dispensing of the liquid onto the surface of the wafer to be further optimised.

[0198] Alternatively, each of the flow paths could be provided with a shut-off valve for switching on or off the flow of the liquid in the respective flow path and a flow rate controlling device for controlling a flow rate in the respective flow path.

[0199] The first valve and / or the second valve may be a manual valve or an electronic valve, for example. Mewburn Ref: 8836553

[0200] 21

[0201] The first valve and / or the second valve may be manually adjustable or controllable, or may be controlled by a controller of the apparatus, for example electronically.

[0202] The first valve and / or the second valve may be a needle valve, for example.

[0203] The flow rate in the first flow path may be different to the flow rate in the second flow path. For example, the flow rate in the first flow path may be controlled to be different to the flow rate in the second flow path.

[0204] The flow rate of the liquid dispensed from the first nozzle may be different to the flow rate of the liquid dispensed from the second nozzle.

[0205] The ratio of the flow rate from the first nozzle to the flow rate from the second nozzle may be in the range of 2:1 to 1:4 inclusive, for example.

[0206] The ratio of the flow rate from the first nozzle to the flow rate from the second nozzle may be in the range of 1:1 to 1:4 inclusive, for example.

[0207] The ratio of the flow rate from the first nozzle to the flow rate from the second nozzle may be 1 :2, for example.

[0208] The first nozzle may be referred to as a primary nozzle, or a main nozzle, or a centre nozzle, for example. References to the first nozzle herein may therefore be replaced with any of these terms, unless incompatible.

[0209] The first nozzle may be configured to be positioned at, or adjacent to, or within a predetermined distance of the centre of the semiconductor wafer.

[0210] The second nozzle may be referred to as an auxiliary nozzle, or a secondary nozzle, or an edge nozzle, for example. References to the second nozzle herein may therefore be replaced with any of these terms.

[0211] The second nozzle may be configured to be positioned closer to an edge of the semiconductor wafer than the first nozzle.

[0212] The second nozzle may be configured to be positioned closer to an edge of the semiconductor wafer than to a centre of the semiconductor wafer.

[0213] Having different flow rates for the liquid dispensed from the first and second nozzles may facilitate optimising the flow conditions on the surface of the semiconductor wafer. In particular, the flow rate from the auxiliary nozzle (second nozzle) may need to be sufficiently large that it introduces sufficient shear into the liquid film on the surface of the semiconductor wafer provided by the liquid dispensed from the primary nozzle (first nozzle), but not so large that it causes splashing of the liquid to occur on the surface of the wafer, which may lead to ineffective Mewburn Ref: 8836553

[0214] 22 momentum transfer to the liquid film. The extent of the shearing may be modulated by setting the respective flow rates of the liquid in the first or second flow paths or the liquid dispensed from the primary and auxiliary nozzles.

[0215] The apparatus may further comprise: a first flow meter in the first flow path; and / or a second flow meter in the second flow path.

[0216] The first or second flow meter may be configured to measure a flow rate of the liquid in the respective flow path.

[0217] Therefore, the liquid flow rate to each of the nozzles can be independently measured.

[0218] The apparatus may comprise a controller or processor for controlling one or more operations of the apparatus.

[0219] The controller may be configured to control: the first valve based on an output of the first flow meter; and / or the second valve based on an output of the second flow meter.

[0220] For example, the controller may control the first or second valve to increase or decrease a flow rate in the respective flow path based on an output of the respective flow meter.

[0221] In other words, there may be a feedback loop for controlling the flow rate in the respective flow path, the feedback loop comprising the flow meter, the valve and the controller.

[0222] The controller may be configured to control: the first valve based on the output of the first flow meter and a first target flow rate; and / or the second valve based on the output of the second flow meter and a second target flow rate.

[0223] In particular, the respective valve may be controlled by the controller such that the flow rate measured by the respective flow meter is equal to the respective target flow rate.

[0224] There may be a fixed distance between the first nozzle and the second nozzle.

[0225] A position of the first nozzle relative to the second nozzle may be fixed. The first nozzle may be rigidly connected, directly or indirectly, to the second nozzle.

[0226] The first nozzle and the second nozzle may both be positioned, mounted or connected to a same part of the apparatus, for example a dispensing arm as discussed below.

[0227] A distance between the first nozzle and the second nozzle may be adjustable. For example, the first nozzle may be movable relative to the second nozzle, or the second nozzle may be movable relative to the first nozzle. Mewburn Ref: 8836553

[0228] 23

[0229] The first nozzle or the second nozzle may be adjustably or slidably mounted so as to change a position of the first dispensing nozzle or the second dispensing nozzle.

[0230] The distance between the first nozzle and the second nozzle may be greater than or equal to 65 mm and less than or equal to 120 mm, for example greater than or equal to 80 mm and less than or equal to 120 mm.

[0231] When processing a 300 mm wafer, if the primary nozzle (first nozzle) was positioned over the centre of the wafer, a distance of greater than 120 mm between the primary nozzle and the auxiliary nozzle (second nozzle) would mean that the auxiliary nozzle is located less than or equal to 30 mm from the edge of the wafer. In that case, most of the liquid dispensed from the auxiliary nozzle may merely flow off the wafer edge in the radial direction without being utilised for semiconductor wafer wetting and cleaning purposes over a significant area of the wafer. As to a specific example, if the separation between the primary and auxiliary nozzles was 140 mm, the liquid dispensed by the auxiliary nozzle would only impinge on a band of the semiconductor wafer between a radius of 140 mm and 150 mm, which would not be productive. Furthermore, larger separations between the two nozzles than 120 mm may be unfeasible to implement when moving the nozzles in / out to a periphery of the chamber module.

[0232] The first nozzle and the second nozzle may both be configured to dispense a jet or stream of liquid. This is different to dispensing a spray or mist of a liquid, for example.

[0233] The first nozzle and the second nozzle may be movable relative to a surface of a semiconductor wafer supported by the support. The first and second nozzles may be movable together, for example as a single unit, or may be independently movable.

[0234] Delivery arm

[0235] The apparatus may also comprise a delivery arm comprising the light source and optionally the fluid dispensing nozzle. Optionally, the delivery arm is configured to be freely adjustable to the desired radial location over the patterned-side of the semiconductor wafer when in use.

[0236] Preferably, the fluid dispensing nozzles are positioned or mounted on, or connected to, a separate dispensing arm (to the delivery arm comprising the light source).

[0237] The dispensing arm may be pivotable or rotatable. For example, the dispensing arm may be pivotable or rotatable around a first end of the arm (a proximal end). The dispensing arm may be pivotable or rotatable around a vertical axis.

[0238] When the apparatus comprises a first nozzle and a second nozzle. The first nozzle may be located at or adjacent to a tip of the dispensing arm. The second nozzle may be located on an auxiliary arm or auxiliary nozzle holder that is connected to the dispensing arm. Mewburn Ref: 8836553

[0239] 24

[0240] The auxiliary arm or auxiliary nozzle holder may be at an angle of greater than 0 degrees and less than 180 degrees to the dispensing arm, for example greater than 0 degrees and less than or equal to 90 degrees, for example greater than 0 degrees and less than or equal to 60 degrees.

[0241] The angle may be adjustable, so as to change or set a distance between the first nozzle and the second nozzle.

[0242] A length of the auxiliary arm or auxiliary nozzle holder may be adjustable, so as to change or set a distance between the first nozzle and the second nozzle.

[0243] A height of the first nozzle above a surface of a semiconductor wafer supported by the support may be adjustable, and / or a height of the second nozzle above a surface of a semiconductor wafer supported by the support may be adjustable.

[0244] The first nozzle or the second nozzle may able to be positioned over a centre of a semiconductor wafer supported by the support, or at a predetermined distance from the centre of the semiconductor wafer. For example, the first nozzle may be at the tip of a dispensing arm and may be able to be positioned over the centre of the wafer by rotating the dispensing arm to a suitable position.

[0245] Therefore, either the first or second nozzle that is positioned over the centre of the wafer, or adjacent to the centre, may be used to dispense liquid at the centre, or adjacent to the centre, of the wafer. The other nozzle may then be used to dispense the same liquid at a radially outwards position.

[0246] The first nozzle may be able to be positioned over the centre of the wafer. The first nozzle may therefore be referred to as a centre nozzle, for example.

[0247] The auxiliary nozzle (second nozzle) may have a different nozzle inner diameter to a nozzle inner diameter of the primary nozzle (first nozzle).

[0248] Typically, a nozzle inner diameter of the auxiliary nozzle (second nozzle) is less than or equal to a nozzle inner diameter of the primary nozzle (first nozzle). For example, the auxiliary nozzle may have a nozzle inner diameter of greater than or equal to 4mm and less than or equal to 6mm.

[0249] By tailoring the nozzle inner diameter of the primary nozzle and / or the auxiliary nozzle, the amount of shearing introduced into the liquid film on the surface of the wafer, provided by the liquid dispensed from the first nozzle, by the liquid dispensed from the auxiliary nozzle can be modulated so as to achieve a sufficient amount of shear while avoiding splashing of the liquid which may lead to ineffective momentum transfer to the liquid film. Mewburn Ref: 8836553

[0250] 25

[0251] The treatment chamber of the treatment apparatus of the invention may also comprise an annular liquid collector surrounding the rotating platform and substrate, to collect liquid flowing from the surface of the substrate.

[0252] BRIEF DESCRIPTION OF THE FIGURES

[0253] The present proposals are now explained further with reference to the accompanying figures in which:

[0254] Figure 1 is a simplified schematic illustration of an apparatus for processing a wafer according to an embodiment of the present invention.

[0255] Figure 2 is a simplified schematic illustration of an apparatus for processing a wafer according to an embodiment of the present invention.

[0256] Figure 3 is simplified schematic illustration of an apparatus for processing a wafer according to an embodiment of the present invention, shown in partial cross-section.

[0257] Figure 4 is a simplified schematic illustration of an LED array that can be used in embodiments of the present invention.

[0258] Figure 5 is a simplified schematic illustration of an apparatus for processing a wafer according to an embodiment of the present invention.

[0259] Figure 6 is a graph showing how with increased time between fluorocarbon polymer deposition and cleaning the amount of fluorocarbon polymer removed is reduced and the degree of C-C surface crosslinking increases.

[0260] Figure 7 is a graph showing how fluorocarbon polymer thickness varies depending on the oxygen content of the treatment atmosphere, both pre and post UV and liquid cleaning.

[0261] Figure 8 is a graph showing that the fluorocarbon polymer removal rate increases linearly with UV-exposure time

[0262] Figure 9 is a graph showing the XPS carbon signals for a fluorocarbon polymer pre-treatment (left), following irradiation at 275 nm (middle) and following irradiation at 385 nm (right).

[0263] Figure 10 is a graph showing how the thickness of a fluorocarbon polymer film is reduced following in situ and ex situ treatment.

[0264] Figure 11 is a graph showing the effect of irradiation of fluorocarbon polymer films at different UV wavelengths. Mewburn Ref: 8836553

[0265] 26

[0266] Figure 12 is a graph showing the difference in temperature between in-situ and ex-situ treatment of fluorocarbon polymer films.

[0267] Figure 13 is a graph showing the difference between treatment of fluorocarbon polymer at 275 nm and 385nm.

[0268] Figure 14 is a simplified schematic illustration of an apparatus for treatment of a semiconductor wafer, according to an embodiment of the present invention, including an enclosure.

[0269] Figure 15 includes two graphs which demonstrate that UV radiation with a peak wavelength of 160 nm causes an increase in dielectric constant (k) in low-k materials, whereas UV radiation with a peak wavelength of 385 nm does not.

[0270] Figure 16 is a graph of ozone concentration as a function of time during exposure of a low-k material to two different wavelengths of UV radiation (160 nm and 385 nm).

[0271] Figure 17 is a simplified schematic illustration showing a circular semiconductor wafer overlaid by a semicircular array of LEDs.

[0272] Figure 18 is a simplified schematic illustration showing a semicircular light source in the form of an array of LEDs. The array of LEDs is overlaid onto a heat sink.

[0273] Figure 19 is a simplified schematic illustration of an apparatus for processing a wafer according to an embodiment of the present invention.

[0274] Figure 20 is a simplified schematic illustration looking down at an apparatus for processing a wafer according to an embodiment of the present invention.

[0275] Figure 21 is a simplified schematic illustration looking down at an apparatus for processing a wafer according to an embodiment of the present invention.

[0276] DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS

[0277] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0278] FIG. 1 is a simplified schematic illustration of an apparatus for liquid treatment of a semiconductor wafer W, according to an embodiment of the present invention.

[0279] As shown in FIG. 1 , the apparatus comprises a chuck 2 (such as a rotary chuck) for holding or supporting a semiconductor wafer W. The chuck 2 may comprise a series of gripping pins that grip an outer edge of the semiconductor wafer W to hold the semiconductor wafer on the chuck Mewburn Ref: 8836553

[0280] 27

[0281] 2. The semiconductor wafer W may be supported by the chuck 2 spaced apart from the surface of the chuck 2. For example, the chuck 2 may be a Bernoulli chuck wherein the semiconductor wafer W is held spaced apart from the surface of the chuck 2 by a flow of gas from the surface of the chuck 2 according to the Bernoulli effect. However, other types of chuck or semiconductor wafer supports may be used in the present invention, and the manner in which the semiconductor wafer is supported or held in the apparatus is not essential to the present invention.

[0282] The chuck 2 is mounted on a rotatable shaft 3, which can be driven to rotate by a motor. The chuck 2 may therefore be referred to as a spin chuck, for example. Of course, alternative mechanisms may be provided for rotating the chuck 2 and the semiconductor wafer W.

[0283] In practice, the chuck 2 will be positioned within a processing chamber, to isolate the processing environment around the semiconductor wafer W from an external environment. As discussed in more detail below, the processing chamber may comprise a plurality of vertically arranged processing sub-chambers, and the chuck 2 and the processing chamber may be vertically movable relative to the semiconductor wafer W between the different processing sub-chambers. For example, each of the processing sub-chambers may be configured to collect and / or recycle a liquid dispensed on the semiconductor wafer W, and the semiconductor wafer W may be moved between the processing sub-chambers so that each of the processing sub-chambers collects and / or recycles a respective liquid when that liquid is used in the processing of the semiconductor wafer W.

[0284] As shown in FIG. 1 , a light source 4 (such as an array of LEDs) is positioned above the chuck. The light source 4 is arranged to illuminate the patterned-side (top or upper surface) of the semiconductor wafer W, when the apparatus is in use. The light source 4 is typically attached to a delivery arm 5 configured to be freely adjustable to the desired radial location over the patterned-side of the semiconductor wafer when in use.

[0285] FIG. 2 is a simplified schematic illustration of an apparatus for treatment of a semiconductor wafer W, according to an embodiment of the present invention. The apparatus shown in Figure 2 comprises all of the features of Figure 1, but also includes a liquid dispenser.

[0286] As shown in FIG. 2, a liquid dispenser 9 is positioned above the chuck 2, for selectively dispensing liquid onto an upper surface of the semiconductor wafer W.

[0287] The liquid dispenser 9 comprises a liquid dispensing arm 10 that is connected to a supply of a liquid. The supply of the liquid is generally indicated by element 11 in FIG. 2. For example, the supply of the liquid 11 may comprise a container of the liquid to which the liquid dispensing arm 10 is directly or indirectly connected, or a flow path such as a tube or pipe that supplies the liquid from a container of the liquid to the liquid dispenser arm 10. Mewburn Ref: 8836553

[0288] 28

[0289] In FIG. 2 the liquid dispensing arm 10 is illustrated as being directly connected to the supply of liquid 11. However, in practice the connection between the liquid dispensing arm 10 and the supply of liquid 11 may be via one or more pipes, tubes or other flow paths.

[0290] The dispensing arm 10 comprises a first nozzle 12 and a second nozzle 13, both of which are connected to the same supply of liquid 11. The first nozzle 12 and the second nozzle 13 are for dispensing the liquid onto the surface of the semiconductor wafer W supported by the chuck 2. Of course, in practice the positioning and / or arrangement of the first nozzle 12 and the second nozzle 13 will be different to that illustrated in a simplified form in FIG. 2.

[0291] The first nozzle 12 and the second nozzle 13 are both configured to dispense a continuous jet or stream of the liquid onto the surface of the semiconductor wafer W in operation, for example as opposed to a mist or a spray.

[0292] The first nozzle 12 may be referred to as a primary nozzle, or a main nozzle, or a centre nozzle, for example. The first nozzle 12 may be configured to be positioned at, or adjacent to, or within a predetermined distance of the centre of the wafer (above the wafer).

[0293] The second dispensing nozzle 13 may be referred to as an auxiliary nozzle, or a secondary nozzle, or an edge nozzle, for example. The second nozzle 13 may be configured to be positioned closer to an edge of the wafer than the first nozzle (above the semiconductor wafer).

[0294] The dispensing arm 10 comprises a shared flow passage for supplying liquid to the first nozzle 12 and the second nozzle 13. The shared flow passage then splits into a first flow path connected to the first nozzle 12 for supplying the liquid to the first nozzle 12, and a second flow path connected to the second nozzle 13 for supplying the liquid to the second nozzle 13. Such an arrangement may be referred to as split-flow dispensing, or a split-flow dispenser. This arrangement is discussed in more detail below. Of course, in an alternative embodiment separate flow paths for each of the first and second nozzles 12 and 13 may be provided in the liquid dispenser arm 10 instead of the shared flow passage. The separate flow paths may then be connected to a common or shared flow path, or separately to the supply of the liquid 11 , upstream of the liquid dispensing arm 10.

[0295] The liquid dispensing arm 10 is pivotable or rotatable to a standby position in which it does not overlie the semiconductor wafer W, to facilitate loading and unloading of the semiconductor wafer W on the chuck 2. The dispensing arm 10 is also pivotable across the surface of the semiconductor wafer W supported by the chuck 2, for dispensing liquid on different parts of the surface of the semiconductor wafer W. Typically, the liquid dispensing arm 10 is pivotable at a first end of the liquid dispensing arm 10 (a proximal end), and the first and second nozzles 12 and 13 are positioned at or adjacent to a second end of the dispensing arm (a distal end). The dispensing arm 10 may be referred to as a swing arm or a boom arm, for example. Mewburn Ref: 8836553

[0296] 29

[0297] Typically, the apparatus comprises a controller that controls the overall operation of the apparatus, including coordinating the action of the motor to rotate the chuck 2, the action of the light source 4 to irradiate the semiconductor wafer W, and the action of the liquid dispenser 9 to dispense liquid from the supply of the liquid 11, so that liquid is controllably dispensed onto the surface of the semiconductor wafer W while the semiconductor wafer W is rotated.

[0298] In the apparatus illustrated in FIG. 2, the flow of the liquid from the supply 11 is split between the first nozzle 12 and the second nozzle 13. As mentioned above, this may be referred to as split-flow dispensing, and the liquid dispenser arm 10 may be referred to as a split-flow dispenser (such an arrangement is set out in W02025082802A1).

[0299] The supply 11 may be a container or reservoir of the liquid, or may be a source flow path or supply flow path that is connected to such a container or reservoir of the liquid, for example one or more tubes or pipes. The supply 11 may therefore comprise a common source flow path or common supply flow path.

[0300] Fig. 3 shows the apparatus further comprising a processing chamber 17 surrounding the chuck 2 and semiconductor wafer W. The apparatus is shown schematically in partial cross-section for ease of understanding.

[0301] The processing chamber 17 may comprise three processing sub-chambers 17a-17c, which are vertically arranged. Each of the processing sub-chambers 17a- 17c is configured to collect a liquid that is dispensed onto the surface of the semiconductor wafer and that is discharged from an outer periphery of the semiconductor wafer when the semiconductor wafer is spun. The chuck 2 is vertically movable relative to the processing chamber 17 so as to position the semiconductor wafer W in each of the processing sub-chambers 17a- 17c. In particular, either the chuck 2 or the processing chamber 17 may be moveable vertically, so as to affect relative vertical movement between the chuck 2 and the processing chamber 17.

[0302] The liquid dispensing arm 10 may also be vertically movable relative to the processing chamber 17, for the purpose of setting an appropriate height of the first and second nozzles 12 and 13 above the surface of the semiconductor wafer when the semiconductor wafer is positioned in each of the processing sub-chambers 17a-17c.

[0303] Each of the processing sub-chambers 17a-17c comprises a gutter for collecting the liquid. The collected liquid may then be recycled or reused, for example.

[0304] In practice, when performing sequential processing using different liquids in the apparatus, each of the processing sub-chambers may be used to collect a respective liquid when that liquid is used in the processing. In particular, the chuck and semiconductor wafer may be moved to that processing sub-chamber when the specific liquid is used in the processing. Mewburn Ref: 8836553

[0305] 30

[0306] Of course, it is not essential to provide a plurality of processing sub-chambers 17a- 17c in this manner, for example if it is not intended to recycle the liquid. Therefore, as an alternative, only a single processing chamber may be provided in some embodiments.

[0307] As mentioned previously, the liquid dispensing arm 10 is pivotable / rotatable to move the first and second nozzles 12 and 13 relative to the semiconductor wafer W. For example, the liquid dispensing arm 10 may be referred to as a swing arm.

[0308] The apparatus may comprise one or more standby or rest positions 18 at the periphery of the apparatus 8 on an upper surface of the processing chamber 17. The standby or rest position 18 is on the arc of rotation / pivoting of the first and second nozzles 12 and 13 of the liquid dispensing arm 10, so that the first and second nozzles 12 and 13 can be rotated / pivoted to the standby or rest position 18 with the first and second nozzles 12 and 13 located above the standby or rest position 18. In this position, the first and second nozzles 12 and 13 do not overlay / overlap the semiconductor wafer W and therefore do not restrict loading or unloading of the semiconductor wafer from the chuck 2. The liquid dispensing arm 10 may therefore be moved to the standby or rest position 18 when loading or unloading a semiconductor wafer on the chuck 2. Of course, there may be more than one standby or rest position, for example two standby or rest positions may be provided at opposite ends of an arc of rotation of the first and second dispensing nozzles 12 and 13.

[0309] Similarly, the delivery arm 5 may be pivotable / rotatable to move the light source relative to the semiconductor wafer. The delivery arm may be pivoted to a standby or rest position (not shown). In this position the light source does not overlap / overlay the semiconductor wafer W and therefore does not restrict loading or unloading of the semiconductor wafer W from the chuck 2. The delivery arm 5 may therefore be moved to a standby position when loading or unloading a semiconductor wafer on the chuck 2. The delivery arm 5 may then be moved back into position so that the light source 4 overlays the semiconductor wafer W.

[0310] Fig. 4 shows an example of an LED array 20 that can be used in embodiments of the present invention.

[0311] As shown in FIG. 4, the LEDs 21 are arranged on substantially concentric arcs (concentric demi-circles) around the centre of the LED array 20. The arrangement of the LEDs 21 is rotationally symmetric around the centre of the LED array 20.

[0312] Within a given concentric arc, the LEDs 21 are bunched into discrete groups 22. In other words, the LEDs 21 in a given concentric arc are not evenly distributed around the concentric arc. The power to each of the groups 22 of LEDs 21 may be independently controlled.

[0313] In this example there are concentric arcs of LEDs 21, but of course in other embodiments the number of concentric arcs may be different. Mewburn Ref: 8836553

[0314] 31

[0315] Of course, the LED array 20 may be different to that illustrated in FIG. 4. In particular, the arrangement of the LEDs in the LED array 20 is not essential to the present invention. For example, it is not essential for the LEDs 21 to be arranged in concentric arcs, or for the LEDs in a given concentric arc to be bunched into groups.

[0316] As illustrated in FIG. 4 the array of LEDs 20 has a wedge shape (equivalent to a sector of a circle).

[0317] The radius of the LED array 20 (i.e. the radius of the sector - radius of the sector in this context means the length of the non-curved sides of the sector) may be the same as, or similar to, the radius of the semiconductor wafer W. The array of LEDs may be arranged to face towards the patterned-side of the semiconductor wafer and the may be arranged to be substantially parallel to the semiconductor wafer when the semiconductor wafer is in the semiconductor wafer support.

[0318] As mentioned above, a UV-transparent plate may be provided between the semiconductor wafer W and the LED array 20 to protect the LED array 20

[0319] Preferably, the LED array 20 includes a circuit board including driving circuitry for the LEDs 21 provided the delivery arm 5.

[0320] The LEDs 21 may have a power output of greater than or equal to 0.5W at maximum current, for example greater than or equal to 1.2W. For example, the LEDs 21 may have a power of approximately 1 ,6W at maximum current. Of course, in other applications different power LEDs may be used.

[0321] The LEDs 21 may have a width of less than or equal to 4mm, for example less than or equal to 3.5mm. In particular, a housing or case of the LED may have a width of less than or equal to 4mm, for example less than or equal to 3.5mm. Of course, other sizes of LEDs can also be used in the present invention.

[0322] Fig. 5 is a simplified schematic illustration of an apparatus for processing a wafer according to an embodiment of the present invention.

[0323] As discussed above, typically the first nozzle 12 and the second nozzle 13 are both used to dispense the same liquid onto the surface (i.e. patterned side) of the semiconductor wafer W simultaneously. The flow rates from the two nozzles 12 and 13 may be the same or may be different. Typically the flow rates from the two nozzles 12 and 13 are different in operation. The manner in which the liquid may be dispensed by the first and second nozzles 12 and 13 is discussed in more detail below. Mewburn Ref: 8836553

[0324] 32

[0325] Typically, the first nozzle 12 is positioned at or adjacent to a centre of the semiconductor wafer (above the wafer) and the second nozzle 13 is positioned closer to the edge of the semiconductor wafer than the first nozzle 12, when the nozzles are used to dispense the liquid.

[0326] The (liquid) dispensing arm 10 is rotatable / pivotable so as to move the first and second nozzles 12 and 13 over the surface of the semiconductor wafer. The first and second nozzles 12 and 13 may be moved while dispensing liquid on the surface of the semiconductor wafer W while the semiconductor wafer W is being rotated. In other words, the dispensing arm 10 may be swung over or across the surface of the semiconductor wafer W.

[0327] In addition, the dispensing arm 10 may be rotated / pivoted to move the first and second nozzles 12 and 13 to a periphery of the apparatus where they do not directly overlap with the semiconductor wafer receiving surface of the chuck 2, to facilitate loading and unloading of a semiconductor wafer on the chuck 2. For example, there may be a standby or rest area to which the first and second nozzles 12 and 13 can be moved when a semiconductor wafer is being loaded or unloaded on the chuck 2.

[0328] The first nozzle 12 and the second nozzle 13 may be the same or identical. Alternatively, the first nozzle 12 and the second nozzle 13 may be different, for example, a nozzle internal diameter of the second nozzle 13 may be different to a nozzle internal diameter of the first nozzle 12. The nozzle internal diameter of the second nozzle 13 may be greater than or equal to 4mm and less than or equal to 6mm, for example.

[0329] As discussed above, the light source 4 according to the present invention is preferably an LED array. The LED array is positioned above the chuck. The LED array may take the form of a wedge shape (equivalent to a sector of a circle), with a radius which may be the same as, or similar to, the radius of the semiconductor wafer. The LED array is typically attached to a delivery arm 5, which is configured to provide the LED array with a connection to electrical power.

[0330] Fig. 6 is a graph showing experimental data demonstrating that with increased time between fluorocarbon polymer deposition and removal the amount of fluorocarbon polymer removed is reduced and the degree of C-C surface crosslinking increases (this is a proxy for the amount of post etch residue that could be removed).

[0331] The data in fig. 6 was produced using a semiconductor wafer which had a fluorocarbon polymer layer applied to its surface using a C4F8, CH3F gas blend. The fluorocarbon polymer layer was then allowed to age for 2, 4 and 14 days under ambient atmospheric conditions. The semiconductor wafer was then exposed to UV (wavelength = 385nm; power = approximately 10W / cm2) for 180 seconds followed by application of a liquid (comprising hydrogen peroxide) for 60 seconds. The degree of C-C cross-linking of the fluorocarbon polymer to the wafer was determined by EDX and the degree of removed polymer was determined by LD10 ellipsometry. Mewburn Ref: 8836553

[0332] 33

[0333] The data in fig. 6 demonstrates that the longer that a fluorocarbon polymer is aged onto the surface of a semiconductor wafer, the more difficult it is to completely remove the polymer film. This is believed to be a result of increased surface crosslinking.

[0334] Fig. 7 is a graph showing that removal of aged fluorocarbon polymer is more effective at higher oxygen concentrations.

[0335] The data in fig. 7 was obtained by exposing a semiconductor wafer which had a fluorocarbon polymer layer applied to its surface using CH3F gas to UV (wavelength = 385nm; power = 10W / cm2) for 180 seconds under atmospheres comprising <2% O2; 21 % O2 and 40-45% O2 respectively followed by application of a liquid (comprising hydrogen peroxide) for 60 seconds. The fluorocarbon polymer thickness on the surface of the semiconductor layer was then determined using ellipsometry.

[0336] Fig. 7 reveals that having a higher level of oxygen present in the atmosphere leads to more effective removal of the fluorocarbon polymer (i.e. more efficient removal of post-etch residue). Without being bound by any theory it is believed that the UV-induced photo-oxidation process takes place through an irreversible process whereby oxygen atoms from the environment are built into the fluorocarbon polymer structure, fragmenting it into monomers that can be solubilised and removed in liquid solutions.

[0337] Fig. 8 is a graph showing that polymer removal rate increases linearly with UV-exposure time. Experiments were carried out as for fig. 7 in 21% O2 and the test semiconductor wafer was exposed to UV for varying amounts of time from 60 to 300 seconds.

[0338] Fig. 9 is a graph showing the XPS carbon signals for a fluorocarbon film pre-treatment (left), following irradiation at 275 nm (middle) and following irradiation at 385 nm (right).

[0339] Thinning of fluorocarbon films is known to occur upon extended UV-irradiation.

[0340] The data in fig. 9 was obtained by exposing a semiconductor wafer which had a fluorocarbon polymer layer applied to its surface using CH3F to UV from a distance of 2cm with a wavelength of 275 nm (160 mW / cm2) and 385 nm (10 W / cm2) for 180 seconds. The signals present in the polymer film, where then determined by XPS. It can be seen that following irradiation at both 275 nm and 385 nm the C=O signal increased suggesting increased incorporation of oxygen into the structure of the fluorocarbon polymer. As set out above, without being bound by any theory, it is believed that oxygen is important for the breakdown of fluorocarbon polymer films.

[0341] Fig. 10 shows how the thickness of a fluorocarbon polymer film is reduced following treatment with UV and a cleaning liquid.

[0342] The data in fig. 10 was obtained by exposing a semiconductor wafer which had a fluorocarbon polymer layer applied to its surface using C4F8 and CH3F to UV (power= 10W / cm2(max)) 385 Mewburn Ref: 8836553

[0343] 34 nm and liquid cleaning. The liquid used in liquid cleaning was a 1:1 waterhydrogen peroxide mix (at 59 °C), which was dispensed at 1.8 L / min using 25 mm off-centre dispensing at 300 rpm. The distance between the LEDs and the semiconductor wafer was 2 cm (with a quartz window) and the LED array was centred at 25 mm off-centre. The thickness measurement was carried out using LD10 ellipsometry and the temperature of the semiconductor wafer was controlled at 62 °C. During the ex-situ irradiation steps the temperature ramps up to 130 °C over the course of treatment.

[0344] In the context of this graph ex-situ refers to treatment with UV followed by treatment with a liquid cleaner, so for example “Ex-situ 10sec+10sec” refers to treatment with UV for 10 seconds followed by treatment with a liquid cleaner for 10 seconds. In situ refers to treatment with UV and liquid cleaner at the same time, so in-situ 10 sec refers to treatment with UV and liquid cleaner for 10 seconds.

[0345] Data in the graph shows that treatment with the solvent (1:1 water: hydrogen peroxide mix (at 59 °C)) only leads to the fluorocarbon polymer swelling - a negative effect. This effect is also seen for ex-situ treatment for up to 30 s. Ex-situ treatment for 60secs + 60 secs and for 120 secs + 120 secs leads to good removal of the fluorocarbon film (PER). However, it can be seen that in- situ treatment is more efficient at removing the PER film with similar results being seen following 10 seconds of treatment in situ to 60secs + 60 secs ex-situ and with almost complete removal of the film following 30 seconds of in-situ treatment. These results therefore suggest that in situ treatment is more efficient at removing fluorocarbon polymers (post etch residue).

[0346] Without being bound by any theory, it is believed that fluorocarbon polymers can be removed more efficiently using in-situ treatment as the UV may activate the hydrogen peroxide meaning that it is more reactive and hence able to remove the fragments of the fluorocarbon polymers produced by UV fragmentation.

[0347] Fig. 11 shows the effect on removal of a 3-month aged fluorocarbon polymer layer by irradiation at different UV wavelengths.

[0348] The data in fig. 11 was obtained by preparing a semiconductor wafer with a fluorocarbon polymer layer applied to its surface using C4F8 and CH3F and aging the polymer for 3 months. The semiconductor wafer with a fluorocarbon polymer layer was then exposed to UV and liquid cleaning. The liquid used in liquid cleaning was a 1:1 water: hydrogen peroxide mix (at 59 °C), which was dispensed at 1.8 L / min using 25 mm off-centre dispensing at 300 rpm. The distance between the LEDs and the wafer was 2 cm (with a quartz window) and the LED array was centred at 25 mm off-centre. The thickness measurement was carried out using LD10 ellipsometry and the temperature of the wafer was controlled at 62 °C. During the ex-situ irradiation steps the temperature ramps up to 130 °C over the course of treatment. Mewburn Ref: 8836553

[0349] 35

[0350] Test were carried out at various UV wavelengths and the tests were carried out “in situ” (with UV and liquid cleaning at the same time). The time for each test was the time taken to irradiate the surface of the semiconductor wafer with the specific amount of energy.

[0351] Fig. 12 shows the difference in temperature between in-situ and ex-situ treatment.

[0352] The data in fig. 12 was obtained by preparing a semiconductor wafer with a fluorocarbon polymer layer applied to its surface using C4F8 and CH3F. The semiconductor wafer with a fluorocarbon polymer layer was then exposed to UV only (the ex-situ approach, the data for which is shown in black) and UV in combination with liquid cleaning (the in-situ approach, the data for which is shown in grey). For the ex-situ approach, the LEDs turned on at t = 0 and turned off at t = 13 seconds; for the in-situ, the LEDs turned on at t = 10.5 seconds and stayed on. The liquid used in liquid cleaning was a 1 :1 water: hydrogen peroxide mix (at 59 °C), which was dispensed at 1.8 L / min using 25 mm off-centre dispensing at 300 rpm. The distance between the LEDs and the wafer was 2 cm (with a quartz window) and the LED array was centred at 25 mm off-centre. During the ex-situ irradiation steps the temperature ramps up to 130 °C over the course of treatment.

[0353] It is clear from fig. 12 that the temperature of the semiconductor wafer rises much more in ex situ treatment; whereas during in situ treatment the temperature of the semiconductor wafer remains roughly constant.

[0354] Fig. 13 is a graph showing the sensitivity of a polymer to wavelengths of 275 nm and 385nm.

[0355] The data in fig. 13 was obtained by preparing a semiconductor wafer with a fluorocarbon polymer layer applied to its surface using C4F8 and CH3F. The semiconductor wafer with a fluorocarbon polymer layer was then exposed to UV at the wavelength specified in the graph and liquid cleaning (using a solution comprising hydrogen peroxide based solvent). The maximum irradiation intensity for the irradiation step was less than 10 W / cm2and the wafer was exposed to UV for a time period of 5min.

[0356] The data in fig. 13 demonstrates that irradiation at both 275 nm and 385 nm leads to activation of the fluorocarbon film facilitating removal using the liquid cleaning solution. In contrast, irradiation at 405 nm does not activate the fluorocarbon film for removal. In addition, heating the wafer with IR radiation does not activate the fluorocarbon film for removal.

[0357] Fig. 15 provides two graphs which demonstrate that UV radiation with a peak wavelength of 160nm causes an increase in dielectric constant (k) in low-k materials, whereas UV radiation with a peak wavelength of 385nm according to the present invention does not.

[0358] To obtain the results in Fig. 15, areas on blanket low-k wafer (a SiOCH structure with k-value < 2.55 when pristine) were exposed to UV light at 160nm peak wavelength and 385nm peak wavelength. The shift in k-value in each area was assessed. The distance between UV source Mewburn Ref: 8836553

[0359] 36 and wafer was 2cm; exposure occurred in an environment of air. K-value was measured using Mercury Capacitance / Voltage probe. In each case, exposure to UV light was for a time sufficient to remove representative post-etch residue which had been determined previously, and depended in part on the power of the UV sources. Exposure to the 160 nm UV light (lower power) was for 30 minutes and exposure to the 385 nm UV light was for 5 minutes (higher power). For each area directly exposed to the UV radiation, an adjacent area (2.5cm away from centre of exposure) that was indirectly exposed was also probed. The shift in k-value observed in directly exposed and indirectly exposed areas was compared to areas that were unexposed.

[0360] It can be seen that the use of UV radiation with a peak wavelength of 160nm resulted in a shift (increase) in k-value for directly exposed and indirectly exposed areas. In contrast, no significant shift in k-value was observed for low-k material directly exposed or indirectly exposed to UV radiation with a peak wavelength of 385nm.

[0361] Without wishing to be bound by theory, it is thought that the 160nm light causes bond cleavage in the low-k material (demethylation of SiOCHs), thereby causing the k-value of the material to increase. The 160nm radiation also produces ozone (O3) in ambient conditions (in air) which is highly reactive and can cause low-k material oxidation (and k-value increases as a result). The 385nm radiation is not energetic enough to cause bond cleavage in the low-k material, nor does it lead to ozone formation in ambient conditions. Therefore, no significant damage is caused to the low-k material, which is seen through the lack of k-value deviation from non-exposed wafer areas.

[0362] In the context of the present invention, the light of 385nm is representative of the UV radiation wavelength range claimed and it is expected that no low-k material k-value shift would be seen at any of the wavelengths claimed.

[0363] Fig. 16 is a plot of ozone concentration as a function of time as a low-k material (a SiOCH structure with k-value < 2.55) is exposed to two different wavelengths of UV radiation. Measurements were carried out by using an ozone probe placed 1cm from the UV light sources in ambient conditions.

[0364] It can be seen that the 160nm radiation causes significant ozone production (after a measurement delay). In contrast, the UV radiation with peak wavelength at 385 nm causes no ozone production beyond background levels.

[0365] Fig. 14 is a simplified schematic illustration of an apparatus for treatment of a semiconductor wafer W, according to an embodiment of the present invention. The apparatus shown in Fig. 14 comprises all of the features of Fig. 2, but also includes an enclosure 6.

[0366] The light source is sealed by inclusion of an enclosure 6 in the apparatus, wherein the enclosure is hermetically sealed and comprises a gas inlet 62 and a gas outlet 64, through which a gas, such as an inert gas like N2, can be flowed. The inlet 62 and the outlet 64 are Mewburn Ref: 8836553

[0367] 37 respectively connected to inlet and outlet gas supplies when in use (not shown). The enclosure is configured such that the flow of gas substantially surrounds the light source 4, effectively protecting it from damage by gas or liquid ingress. In particular, the gas flow is able to flow between the light source 4 and the UV-transparent window 66.

[0368] Fig. 17 is a simplified schematic illustration showing a circular semiconductor wafer W overlaid by an array of LEDs 4 (overlaying shown by dotted lines). For brevity, only three representative arc portions of LEDs are shown in Fig. 17.

[0369] In Fig. 17, the array of LEDs is shaped substantially as the minor segment of a circle with radius equal to the radius of the circular semiconductor wafer W, and the LEDs face towards the wafer W. In the arc portion of LEDs shown that is at an outer edge region of the LED array 4, and the arc portion of LEDs shown that is at an inner edge region of the LED array 4, the packing density of LEDs is higher than in the arc portion of LEDs that is at an intermediate region between the inner and outer edge regions of the LED array 4. The intermediate region is a radially intermediate region, between the centre of the wafer W and its outer perimeter.

[0370] Fig. 18 is a simplified schematic illustration showing a light source 4 in the form of an array of LEDs, as in Fig. 17, except that the light source 4 is facing the other way to in Fig. 17. The array of LEDs 4 is overlaid onto a heat sink 8 such that the LEDs emit light away from the heat sink (overlaying shown by dotted lines). The heat sink 8 is thermally coupled to the LED array 4 via a TIM 82. The heat sink 8 comprises a cooling channel 84, of which only a portion is shown. The cooling channel has a fluid flow direction indicated by an arrow. The cooling channel 84 comprises an upstream portion 841 which precedes a downstream portion 842 in the fluid flow direction. The upstream portion 841 is thermally coupled to the region of higher LED packing in the LED array 4 (shown by dotted line), and the downstream portion 842 is thermally coupled to the region of lower LED packing in the LED array 4 (shown by dotted line).

[0371] Fig. 19 is a simplified schematic illustration of an apparatus for processing a wafer according to an embodiment of the present invention, like as is presented in Fig. 5, except that the light source 4 is an LED array that is shaped substantially as a minor segment of a circle with radius the same as the radius of the circular semiconductor wafer W. It can be seen that because the LED array is shaped as a minor segment, there is space for the first nozzle 12 to be directly above the centre of the wafer W.

[0372] Fig. 20 is a simplified schematic illustration of an apparatus for processing a wafer according to an embodiment of the present invention. Fig. 20 views the apparatus from above. The dashed arrows show the movement paths of the LED array 4, and of the first 12 and second 13 nozzles above a wafer W. The LED array 4 is shown in the process position above the wafer W, as well as in a rest position for when it is not in use, where is does not overlie the wafer W. The rest position may be a light source cleaning station, as described herein. It can be seen that the LED array 4 is substantially shaped as a minor segment of a circle with the same radius as the wafer W, and that as a result the first nozzle 12 is able to be positioned over the centre of the wafer Mewburn Ref: 8836553

[0373] 38

[0374] W, and the nozzles 12, 13 are able to move across the wafer unobstructed by the LED array 4 when the LED array is positioned above the wafer W and in the use position.

[0375] Fig. 21 is a simplified schematic illustration like in Fig. 20, but with an alternative LED array shape. The LED array in Fig. 21 has two curved edges, and is a crescent moon shape.

Claims

Mewburn Ref: 883655339Claims1. A method for removing post etch residue from the surface of a semiconductor wafer, comprising(a) irradiating the patterned-side of the semiconductor wafer with ultraviolet radiation, the ultraviolet radiation having a wavelength of from 270 to 400 nm.

2. The method according to claim 1, wherein the post etch residue comprises fluorocarbon or hydrofluorocarbon deposits.

3. The method according to claim 2, wherein the fluorocarbon deposit is at least 3 days old.

4. The method according to any one of the preceding claims, wherein the ultraviolet radiation has a wavelength of from 270 to 390 nm, preferably wherein the ultraviolet radiation has a wavelength of from 275 to 385 nm; more preferably wherein the ultraviolet radiation has a wavelength of from 320 to 385 nm.

5. The method any one of the preceding claims, wherein the method further comprises the additional step of(b) discharging liquid onto the patterned-side of the semiconductor wafer to form a liquid layer on the surface of the patterned-side of the semiconductor wafer.

6. The method of claim 5, wherein the step of irradiating the patterned-side of the semiconductor wafer is carried out while the liquid is present on the surface of the patterned-side of the semiconductor wafer.

7. The method according to claim 5 or 6, wherein the liquid is a liquid comprising hydrogen peroxide.

8. The method according to any one of the preceding claims wherein the method comprises rotating the semiconductor wafer whilst the patterned-side is irradiated; preferably, wherein the semiconductor wafer is rotated at a velocity of at least 30 rpm, more preferably at least 50 rpm, more preferably at least 100 rpm, more preferably at least 150 rpm and most preferably at least 200 rpm and optionally up to a maximum of 1000 rpm.Mewburn Ref: 8836553409. The method of claim 8, wherein the method involves spinning the semiconductor wafer at a rotational velocity sufficient to cause the deposited liquid to have a film thickness on the patterned-side of the semiconductor wafer of less than 1 mm, preferable less than 0.1 mm.

10. The method according to any one of the preceding claims, wherein the method is carried out in an atmosphere comprising at least 2 % oxygen, preferably at least 20 % oxygen, preferable at least 40 % oxygen.

11. The method according to any one of the preceding claims, wherein the power density of the ultraviolet radiation is from 0.1 W / cm2to 20 W / cm2, preferably from 0.3 W / cm2to 10 W / cm2, preferably from 0.5 W / cm2to 2.5 W / cm2at the surface of the patterned-side of the semiconductor wafer.

12. The method according to any one of the preceding claims, wherein the non- patterned-side of the semiconductor wafer is cooled during the ultraviolet irradiation step.

13. The method according to any one of the preceding claims, wherein the ultraviolet irradiation step is carried out for 1 to 60 seconds, preferably from 1 to 30 seconds, more preferably from 1 to 15 seconds.

14. Apparatus for carrying out a method according to any one of claims 1 to 13, the apparatus comprising: a treatment chamber; a semiconductor wafer support for holding a semiconductor wafer; and a light source configured to irradiate the patterned-side of the semiconductor wafer with ultraviolet radiation having a wavelength of from 270 to 400 nm, preferably wherein the ultraviolet radiation has a wavelength of from 270 to 390 nm, more preferably wherein the ultraviolet radiation has a wavelength of from 275 to 385 nm; more preferably wherein the ultraviolet radiation has a wavelength of from 320 to 385 nm.Mewburn Ref: 88365534115. Apparatus according to claim 14, further comprising a means for rotating the semiconductor wafer support.

16. Apparatus according to claim 14 or 15, wherein the light source is an LED-array.

17. Apparatus according to claim 16, wherein the LED-array has a packing density of 2.5 diodes / cm2.

18. Apparatus according to claim 16, wherein the LED-array has heterogenous LED packing density.

19. Apparatus according to claim 18, wherein the LED-array has first packing density in a first region of the LED array, and a second packing density in a second region of the LED array, wherein the first packing density is higher than the second packing density.

20. Apparatus according to claim 17 wherein the LED-array is attached to a watercooling apparatus.

21. Apparatus according to claim 18 or claim 19, wherein the apparatus further comprises a heat sink that is thermally coupled to the light source.

22. Apparatus according to claim 21, wherein the heat sink comprises a cooling channel through which fluids can flow.

23. Apparatus according to claim 22, wherein the cooling channel comprises an upstream portion and a downstream portion, wherein the upstream portion precedes the downstream portion in a fluid flow direction, and the upstream portion is thermally coupled to the first region of the LED array, and the downstream portion is thermally coupled to the second region of the LED array.

24. Apparatus according to any one of claims 14 to 23, wherein the LED-array is a linear array.

25. Apparatus according to any one of claims 15 to 24, wherein the LED-array is a wedge-shaped array and configured so that as the semiconductor wafer is rotated the patterned-side of the semiconductor wafer may be evenly irradiated by the wedge- shaped array.Mewburn Ref: 88365534226. Apparatus according to any one of claims 14 to 25, further comprising a fluid dispensing nozzle for delivering liquid onto the patterned-side of the semiconductor wafer.

27. Apparatus according to claims 26, wherein the apparatus comprises a delivery arm and wherein the delivery arm comprises the fluid dispensing nozzle and the light source and wherein, the delivery arm is configured to be freely adjustable to the desired radial location over the patterned-side of the semiconductor wafer when in use.

28. Apparatus according to claim 26 or 27, wherein the fluid dispensing nozzle is positioned to one side of the LED-array, such that during operation the nozzle dispenses liquid onto the surface of the semiconductor wafer, which is then dispersed over the surface of the patterned-side of the semiconductor wafer.

29. Apparatus according to any one of claims 14 to 28, wherein the apparatus is configured such that during operation the clearance between the light source and the semiconductor wafer is from 1 to 50 mm, preferably 3 to 50 mm.

30. Apparatus according to any one of claims 14 to 29, wherein the apparatus comprises a UV-transparent window between the light source and the patterned-side of the semiconductor wafer.

31. Apparatus according to any one of claims 14 to 30, wherein the light source is hermetically sealed.

32. Apparatus according to any one of claims 14 to 31, further comprising an enclosure which encloses the light source and includes a UV-transparent window, wherein the enclosure is hermetically sealed.

33. Apparatus according to claim 32, wherein the enclosure comprises a gas inlet and gas outlet.

34. Apparatus according to any one of claims 14 to 33, further comprising a light source cleaning assembly.

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