Device for processing a wafer and method for controlling the device

Abstract

An apparatus for processing a wafer comprises: a rotatable chuck adapted to receive a wafer; a heating assembly comprising an array of heating elements configured to heat the wafer received by the rotatable chuck; an image sensor configured to detect electromagnetic radiation from a surface of the wafer; and a controller configured to control power supplied to the array of heating elements based on a measurement output of the image sensor.

Description

Technical Field

[0001] The present invention relates to a device for processing a wafer and a method for controlling the device. Background Art

[0002] Semiconductor wafers may undergo various surface treatment processes, such as etching, cleaning, grinding, and material deposition. In order to perform such processes, the wafer may be mounted on a rotatable chuck so that various processes may be performed on the surface of the wafer.

[0003] For example, the surface of the wafer can be cleaned by applying a cleaning liquid or a rinsing liquid (e.g., isopropyl alcohol or deionized water) to the surface of the wafer. Subsequently, the cleaning liquid or the rinsing liquid can be evaporated by rotating the wafer using a rotatable chuck and heating the wafer to dry the wafer surface. This cleaning process is generally referred to as a "spin cleaning process."

[0004] An example of an apparatus that can be used to clean a wafer surface is described in US 2017 / 0345681 A1, the contents of which are incorporated herein by reference.

[0005] The apparatus described in US2017 / 0345681A1 includes a rotatable chuck on which a wafer can be mounted, and a liquid dispenser for dispensing liquid onto the upper surface of the wafer when the wafer is mounted on the rotatable chuck. The apparatus also includes a heating element array disposed below the wafer when the wafer is mounted in the rotatable chuck and configured to heat the wafer. After the liquid is dispensed onto the surface of the wafer, the heating element array is controlled to heat the wafer, causing the liquid to evaporate. Summary of the Invention

[0006] In most general terms, the present invention provides an apparatus for processing a wafer, the apparatus comprising: a plurality of heating elements configured to heat a wafer mounted in the apparatus; and an image sensor configured to detect electromagnetic radiation from a surface of the wafer, wherein power supplied to the heating elements is controlled based on a measured output of the image sensor.

[0007] The processes performed on the wafer can be highly sensitive to processing conditions, such as temperature. The present invention enables more precise control of the wafer temperature during processing because the heating element used to heat the wafer is controlled based on the measured output of an image sensor that detects electromagnetic radiation from the surface of the wafer.

[0008] For example, the measurement output of the image sensor may indicate the current temperature distribution of all or a portion of the wafer, and the power supplied to the heating element may then be controlled based on the measurement output to achieve a desired temperature distribution of all or a portion of the wafer.

[0009] A conventional technique for attempting to achieve a desired temperature distribution across the entire wafer during wafer processing is to manually set the power supplied to each heating element based on the desired temperature distribution. However, this is a lengthy and cumbersome procedure. In addition, the technique is not robust to disturbances in the temperature distribution. For example, the heating caused by the heating elements may change over time, for example due to defects or degradation of one or more heating elements. This can result in incorrect heating conditions being applied to the wafer and / or variations in heating conditions between different processing steps and / or from wafer to wafer. Other environmental factors that are difficult or impossible to properly consider in advance can also affect the temperature distribution across the wafer. For example, when a liquid is present on the surface of the wafer, the properties or characteristics of the liquid may vary across the wafer surface and thereby affect the temperature distribution across the wafer surface.

[0010] The apparatus of the present invention can be used to address this problem by controlling a heating element that heats a wafer based on the measurement output of an image sensor that detects electromagnetic radiation from the wafer's surface. For example, differences between the wafer's actual temperature distribution and a target temperature distribution can be identified based on the image sensor's measurement output, and the power applied to the heating element can be controlled to eliminate or reduce any such differences, thereby achieving or substantially achieving the target temperature distribution.

[0011] Therefore, according to a first aspect of the present invention, there is provided an apparatus for processing a wafer, the apparatus comprising: a rotatable chuck adapted to receive a wafer; a heating assembly comprising an array of heating elements configured to heat the wafer received by the rotatable chuck; an image sensor configured to detect electromagnetic radiation from a surface of the wafer; and a controller configured to control power supplied to the array of heating elements based on a measurement output of the image sensor.

[0012] As explained above, the image sensor is configured to detect electromagnetic radiation from the wafer surface. The power supplied to the heating element is then controlled based on the image sensor's measured output. This information, indicating the current temperature distribution of the wafer, can thus be measured in situ, for example, in real time, and used to control the heating element, thereby, for example, changing the temperature distribution of the wafer in real time.

[0013] Thus, by means of the present invention, the temperature distribution of a wafer can be more accurately controlled during wafer processing.

[0014] The device according to the first aspect of the invention may have any one of the following optional features or any combination of the following optical features where compatible.

[0015] In practice, the electromagnetic radiation detected by the image sensor represents or indicates the temperature of the wafer surface. For example, the intensity of the electromagnetic radiation may depend on the temperature of the wafer surface. For example, there may be a fixed mathematical relationship between the intensity of the electromagnetic radiation and the temperature of the wafer surface.

[0016] The term "rotatable chuck" (rotate chuck) may simply mean a wafer holder that is designed to hold a wafer as well as rotate the wafer.

[0017] The rotatable chuck may be configured to rotate the wafer about an axis of rotation of the rotatable chuck, wherein the axis of rotation is substantially perpendicular to a surface of the wafer.

[0018] The rotatable chuck may be substantially circular when viewed from above.

[0019] The rotatable chuck may include a mechanism (eg, a clamp, screws, vacuum holder, etc.) adapted to receive a wafer and securely hold the wafer in position relative to the chuck.

[0020] The rotatable chuck may be adapted to receive a wafer of a predetermined size, for example a wafer having a diameter of 300 mm or 450 mm.

[0021] The rotatable chuck may include a motor for driving the chuck to rotate relative to the rotation axis.

[0022] Alternatively, the rotatable chuck may be caused to rotate by an external drive tool (eg, via magnetic induction).

[0023] The heating assembly is used to heat a wafer mounted on the rotatable chuck. The heating assembly includes an array of heating elements configured to heat the wafer received by the rotatable chuck.

[0024] The term "array" may simply mean a plurality of heating elements, and does not necessarily mean that the heating elements are arranged in any particular order.

[0025] The array of heating elements may be configured to face the wafer when the wafer is received by the rotatable chuck.

[0026] The array of heating elements can be configured to face a first surface of a wafer, the first surface being opposite a second surface of the wafer on which processing (eg, cleaning, deposition of material, etc.) is performed.

[0027] The heating element may be disposed on a substantially flat surface (eg, on a board such as a circuit board).

[0028] The plate may be configured to be substantially parallel to the wafer when the wafer is received by the rotatable chuck.

[0029] The heating elements may be distributed substantially evenly over the planar surface, thereby heating the wafer in a uniform manner.

[0030] The heating assembly may have a circular shape when viewed from above.

[0031] The array of heating elements may be configured to cover an area that is substantially the same as the wafer area or within 10% of the wafer area.

[0032] All heating elements may be of the same type (eg they may all have the same characteristics).

[0033] The heating element can be mounted relative to the rotatable chuck so that it does not rotate with the rotatable chuck as the rotatable chuck rotates about the rotation axis. In other words, the array of heating elements can remain stationary as the rotatable chuck rotates about the rotation axis. This can facilitate providing electrical connections to the array of heating elements.

[0034] The heating elements may be arranged in concentric circles within the heating assembly (concentrically around the center of the heating assembly).

[0035] In each concentric circle, these heating elements can be divided into different groups.In other words, the heating elements located in each concentric circle may not be evenly distributed around the concentric circle.

[0036] Each different group may contain the same number of heating elements, for example 16 heating elements.

[0037] In some embodiments, individual groups of heating elements in the array can be controlled separately.

[0038] Similarly, in some embodiments, each individual heating element can be controlled separately.

[0039] Generally, a heating element is an element (or component) operable to heat a wafer received by a rotatable chuck.

[0040] Any type of heating element may be used, such as radiant, conductive, or convection.

[0041] In some embodiments of the present invention, the heating element may be a light emitting heating element configured to illuminate the wafer to heat the wafer.

[0042] Generally, a luminescent heating element is an element (or component) that uses light to perform radiative heating.

[0043] The light emitted by the light emitting heating element may be visible light.

[0044] Here, the light emitting heating element may refer to a light source that emits light of a wavelength suitable for heating the wafer. For example, the light emitting heating element may emit light having a maximum intensity in a wavelength range of 380 nm to 650 nm.

[0045] In some embodiments, one or more light emitting heating elements may be light emitting diodes (LEDs).

[0046] The use of LEDs can be beneficial because they can be highly efficient and produce relatively little waste heat. LEDs emit light at a wavelength or within a wavelength range suitable for heating the wafer. For example, LEDs can emit light having a wavelength in the range of 380 nm to 650 nm. Other wavelength ranges may also be suitable.

[0047] The image sensor is configured to detect electromagnetic radiation from the surface of the wafer.

[0048] As mentioned above, in practice, the electromagnetic radiation detected by the image sensor is electromagnetic radiation that may be indicative of (eg, correlated with or proportional to) the temperature of the wafer.

[0049] The term "image sensor" may simply mean a two-dimensional array of sensors or sensing elements that is used to measure the intensity distribution of electromagnetic radiation in two dimensions.

[0050] The image sensor may output an image of a two-dimensional intensity distribution of the electromagnetic radiation, or information (eg, a data stream) indicative of such a two-dimensional intensity distribution.

[0051] Electromagnetic radiation can be emitted by the wafer itself or by one or more substances on the wafer surface. For example, electromagnetic radiation can be emitted by liquid on the wafer surface. References herein to electromagnetic radiation emitted by the wafer surface explicitly include electromagnetic radiation emitted by other substances on the wafer surface (e.g., liquid on the wafer surface).

[0052] The controller is configured to control power supplied to the array of heating elements based on the measured output of the image sensor.

[0053] The controller may be a computing device having software installed thereon to control the power supplied to the array of heating elements and to receive the output of the image sensor.

[0054] The controller can be connected to a power supply that supplies power to the array of heating elements via a communication interface (e.g., USB, Ethernet, etc.). The controller can be configured to transmit instructions to the power supply to control the amount of power supplied by the power supply to the array of heating elements. Similarly, the controller can be connected to the image sensor via a communication interface (e.g., USB, Ethernet, etc.) to receive measurement output from the image sensor.

[0055] For example, the controller may be configured to control the power supplied to the array of heating elements based on the measurement output of the image sensor until the measurement output indicates that a desired temperature distribution across a portion or the entire wafer has been achieved or substantially achieved.

[0056] The controller may be configured to compare the measured output of the image sensor, or information derived therefrom, with a reference and, based on the comparison, adjust power supplied to one or more heating elements in the array of light-emitting heating elements.

[0057] The reference may be related to the desired temperature distribution, for example, corresponding to a predicted measurement output or a previously measured measurement output of a wafer having the desired temperature distribution, or corresponding to a target measurement output.

[0058] The controller may be configured to store the reference in a memory.

[0059] The image sensor may be, for example, a thermal image sensor, an infrared image sensor, or a thermographic image sensor.

[0060] The image sensor may be configured to detect infrared radiation.

[0061] The image sensor can be a camera. For example, a camera can produce an image of the electromagnetic radiation detected by the image sensor.

[0062] The camera may be, for example, a thermal image camera, an infrared camera, or a thermographic camera.

[0063] The image sensor may be adapted to detect electromagnetic radiation having a wavelength in the range of 3 to 14 μm. This wavelength range corresponds to the so-called medium-wavelength infrared and long-wavelength infrared (which may be indicative of temperature).

[0064] The image sensor may be adapted to detect electromagnetic radiation having a wavelength in the range of 3 to 5 μm. This wavelength range corresponds to the so-called mid-wavelength infrared.

[0065] The image sensor may be adapted to detect electromagnetic radiation having a wavelength in the range of 8 to 14 μm. This wavelength range corresponds to the so-called mid-wavelength infrared.

[0066] This type of electromagnetic radiation can provide precise information about (or be indicative of) the temperature of the wafer, and the measurement output of the image sensor can therefore be used to precisely control the temperature of the wafer.

[0067] The image sensor can be adapted to detect electromagnetic radiation having a wavelength within a range in which the transmittance of isopropyl alcohol (IPA) is less than 80%. When IPA is present on the surface of the wafer, this provides an advantage in that some, most, or all of the electromagnetic radiation from beneath the IPA may be shielded by the IPA and therefore not detected by the image sensor. For example, the image sensor can be adapted to selectively detect a wavelength range that includes wavelengths within a range in which the transmittance of isopropyl alcohol (IPA) is less than 80%. Alternatively, as discussed below, a filter can be provided that selectively transmits electromagnetic radiation having a wavelength within a range in which the transmittance of isopropyl alcohol (IPA) is less than 80%.

[0068] The image sensor may be configured to detect a wavelength of electromagnetic radiation having a peak corresponding to an emission intensity spectrum of isopropyl alcohol (IPA) or a minimum (local or absolute minimum) corresponding to a transmission spectrum of isopropyl alcohol (IPA).

[0069] The apparatus may include a liquid dispenser to dispense the liquid onto the surface of the wafer.

[0070] For example, the liquid dispenser can be used to dispense isopropyl alcohol or deionized water onto the surface of the wafer to clean or rinse the wafer surface.

[0071] The liquid dispenser may be configured to dispense liquid onto a surface of the wafer opposite a surface of the wafer facing the array of heating elements.

[0072] The liquid dispenser can be moved to dispense the liquid at different locations on the wafer surface. Thus, during the cleaning process, the liquid can be dispensed onto the surface of the wafer received by the rotatable chuck.

[0073] The liquid dispenser may include an arm having a dispensing nozzle.

[0074] The arm can pivot at one end so that the dispensing nozzle can be moved in an arc across the surface of the wafer by rotating the arm about the pivot point.

[0075] The dispensing nozzle is movable between a first position at the center of rotation of the wafer and a second position outside the circumference of the wafer.The dispensing nozzle is thus movable across the entire radius of the wafer.

[0076] The surface of the wafer may be dried by rotating the wafer using a rotatable chuck and heating the wafer to cause evaporation of the liquid.

[0077] The apparatus of the present invention may thus be a spin cleaning apparatus for spin cleaning wafers.

[0078] The controller may be configured to determine the temperature or information related to the temperature at one or more locations on the wafer surface based on the measurement output of the image sensor, and to control the power supplied to the heating element array based on the determined temperature or information related to the temperature.

[0079] Power supplied to the array of heating elements can be controlled to vary the temperature at one or more locations on the wafer surface.

[0080] For example, the temperature or information related to the temperature can be compared with a reference benchmark that is previously measured or predicted for a wafer having a desired temperature distribution, or is related to a target value. Any discrepancies can be identified, and the power supplied to the array of heating elements can be controlled to reduce or eliminate the identified discrepancies. In this way, the temperature distribution of the wafer can be controlled in real time to equal or approximate the desired temperature distribution.

[0081] The controller may be configured to determine a temperature distribution or information related to a temperature distribution across the entire or portion of the wafer surface based on the measurement output of the image sensor, and to control the power supplied to the array of heating elements based on the determined temperature distribution or information related to the temperature distribution.

[0082] Each heating element of the array of heating elements can be individually controlled, and the controller can be configured to individually control the power supplied to each heating element. This can enable more precise control of the temperature distribution across the wafer.

[0083] Alternatively, the array of heating elements may comprise a plurality of individually controllable groups of heating elements, and the controller may be configured to individually control the power supplied to each of the plurality of groups of heating elements.

[0084] In this way, each of the plurality of groups of heating elements can be individually activated by the controller by supplying power to the group. This can reduce the complexity of the device relative to individually controlling each of the heating elements.

[0085] Each set of heating elements may be configured to heat a different region of the wafer when the wafer is received by the rotatable chuck.

[0086] The plurality of groups of heating elements can be configured concentrically around the axis of rotation of the rotatable chuck so that each group occupies a separate radial position. In this way, different radial regions of the wafer can be heated by activating different groups of heating elements.

[0087] The apparatus may comprise a filter adapted to selectively transmit electromagnetic radiation having a predetermined wavelength or range of wavelengths.

[0088] This may facilitate detection of electromagnetic radiation having a predetermined wavelength by the image sensor, as the filter may block electromagnetic radiation of other wavelengths, eg caused by ambient noise.

[0089] “Selectively transmit” may mean that the filter transmits only a predetermined wavelength, and / or wavelengths less than the predetermined wavelength but not less than a predetermined percentage or a predetermined amount of the predetermined wavelength, and / or wavelengths greater than the predetermined wavelength but not greater than a predetermined percentage or a predetermined amount of the predetermined wavelength.

[0090] The filter may be, for example, a low-pass filter, or a high-pass filter, or a band-pass filter.

[0091] The predetermined wavelength may be selected based on the thermal emission spectrum of the liquid used in wafer processing.

[0092] The filter may be adapted to selectively transmit thermal radiation emitted by a liquid used in wafer processing.

[0093] The filter may be adapted to selectively transmit thermal radiation emitted by the isopropyl alcohol.

[0094] For example, the filter may be adapted to selectively transmit thermal radiation having a characteristic wavelength emitted by isopropyl alcohol (IPA), such as a wavelength that is a peak in the emission intensity spectrum of isopropyl alcohol.

[0095] The filter may be adapted to selectively transmit electromagnetic radiation having a wavelength in the range of 3.3 to 3.5 μm or in the range of 8.6 to 9.1 μm.Such wavelengths may be characteristic wavelengths emitted by isopropyl alcohol (IPA).

[0096] The filter can be adapted to selectively transmit electromagnetic radiation having a wavelength within a range in which the transmittance of isopropyl alcohol (IPA) is less than 80%. This provides an advantage when IPA is present on the surface of the wafer, in that some, most, or all of the electromagnetic radiation from beneath the IPA may be blocked by the IPA and, therefore, not detected by the image sensor.

[0097] The filter may be configured to selectively transmit electromagnetic radiation having a wavelength corresponding to a peak in an emission intensity spectrum of isopropyl alcohol (IPA).

[0098] The filter may be configured to selectively transmit electromagnetic radiation having a wavelength corresponding to a minimum (local or absolute minimum) of the transmission spectrum of isopropyl alcohol (IPA).

[0099] In a spin cleaning apparatus, when the rotatable chuck is rotated, the rotation of the wafer causes the liquid on the wafer surface to move radially outward across the entire wafer surface. Thus, a dry line is formed at the transition area between the dry area and the wet area on the wafer surface, which moves radially outward across the entire wafer surface.

[0100] As liquid is continuously dispensed onto the wafer surface by the liquid dispenser, the position of the drying line will be correlated with the position of the liquid dispenser. For example, if the dispensing nozzle of the liquid dispenser remains in a fixed position, the position of the drying line will also be substantially fixed, and in fact, the position of the drying line will be slightly radially inward of the position of the liquid dispenser. As the dispensing nozzle moves, the position of the drying line will move with the movement of the dispensing nozzle.

[0101] When performing the spin cleaning of wafer, the dispensing nozzle can be moved so that it moves radially outwards across the wafer surface. In this case, the drying line can also move radially outwards across the wafer surface following the movement of the dispensing nozzle.

[0102] As discussed in US 2017 / 0345681 A1, it is beneficial to preferentially heat the wafer adjacent to the drying line (on the drying side of the drying line) to a higher temperature than the rest of the wafer surface. This can result in faster liquid drying at the drying line, which can avoid pattern collapse that would otherwise occur during drying.

[0103] In an embodiment of the present invention, the controller can be configured to analyze the measurement output of the image sensor or information derived from the measurement output to determine the position of a dry line on the wafer surface, which dry line corresponds to a transition zone between a dry area and a wet area on the wafer surface, and control the power supplied to the heating element array based on the determined position of the dry line.

[0104] The drying line may be substantially circular shaped with the rotation axis of the wafer as the center.

[0105] As mentioned above, the radial position of the drying line can be the same as, correspond to, or be related to the radial position at which the liquid is dispensed onto the wafer surface. Therefore, if the position at which the liquid is dispensed onto the wafer surface moves radially outward across the wafer surface, the drying line can similarly move radially outward across the wafer surface.

[0106] The controller may be configured to use an edge detection algorithm to determine the position of the drying line.Many suitable edge detection algorithms are known to be usable.

[0107] The controller can be configured to control the power supplied to the array of heating elements so that the wafer is heated to a higher temperature near the drying line than elsewhere on the wafer. As mentioned above, this can help avoid pattern collapse during drying of the wafer when the wafer is spun clean.

[0108] The controller can be configured to control the power supplied to the array of heating elements so that the wafer adjacent to the drying line (on the drying side of the drying line) is heated to a higher temperature than elsewhere on the wafer. As mentioned above, this can help avoid pattern collapse during drying of the wafer.

[0109] The controller may be configured to control the heating element to cause heating of the wafer surface along the radially movable circumferential front end.

[0110] The radially movable circumferential front end can maintain a fixed orientation relative to the drying line. For example, the radially movable circumferential front end can maintain a fixed radial distance from the drying front end and, for example, can be a drying front end immediately adjacent to the drying side of the drying front end. The radially movable circumferential front end can track the radial movement of the dispensing nozzle dispensing liquid onto the wafer surface.

[0111] The controller may additionally control the array of heating elements to heat some or all other components of the wafer to lower temperatures.

[0112] The array of heating elements may be configured to heat a surface of the wafer that is on an opposite side of the wafer than a surface of the wafer imaged by the camera.

[0113] When the wafer is received by the rotatable chuck, the apparatus may further comprise a disk disposed between the array of heating elements and the wafer. The disk may be used to protect the array of heating elements from being affected by a process performed on the surface of the wafer.

[0114] The disk may be transparent, for example made of quartz or sapphire.

[0115] When the heating element is a luminescent heating element, the transparent disc is transparent to the light emitted by the luminescent heating element.

[0116] The wafer may be a semiconductor wafer.

[0117] According to a second aspect of the present invention, there is provided a method of controlling an apparatus according to the first aspect of the present invention. The method of the second aspect may comprise features as discussed above in relation to the first aspect of the present invention; these features are therefore not repeated.

[0118] The method may include dispensing liquid onto a surface of a wafer received by a rotatable chuck; rotating the rotatable chuck to remove the liquid from the surface of the wafer; supplying power to the array of heating elements to heat the surface of the wafer during the rotation; detecting electromagnetic radiation from the surface of the wafer with the image sensor; and adjusting the power supplied to the array of heating elements based on the measured output of the image sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0119] Embodiments of the present invention are discussed below with reference to the accompanying drawings, in which:

[0120] Figure 1 is a schematic cross-sectional view of an apparatus according to an embodiment of the present invention;

[0121] Figure 2a is a schematic diagram of the formation of drying lines on the surface of a wafer in one embodiment of the present invention;

[0122] Figure 2b In one embodiment of the present invention, Figure 2a Schematic diagram of the heating temperature profile in the configuration shown;

[0123] Figure 3 is an example of an image of infrared radiation from a wafer captured by an infrared camera in one embodiment of the present invention;

[0124] Figure 4a It is from Figure 3 An exemplary graph of temperature versus radial distance obtained from an image of

[0125] Figure 4b is the differential of temperature with respect to radial distance and Figure 4a A relationship diagram of radial distances in an exemplary diagram of ; and

[0126] Figure 5 is an example of a heating element that may be used in embodiments of the present invention. DETAILED DESCRIPTION

[0127] Figure 1 FIG. 1 is a schematic cross-sectional view of an apparatus 100 for processing a wafer according to a first embodiment of the present invention. Figure 1 , a wafer 101 is mounted in the apparatus 100 .

[0128] The apparatus 100 includes a rotatable chuck 102 adapted to receive a wafer. The rotatable chuck 102 includes a chuck body 104 rotatably mounted on a base 106. The chuck body 104 is rotatable relative to the base 106 about an axis of rotation indicated by reference numeral 108. The rotation of the chuck body 104 relative to the base 106 can be driven, for example, by a motor (not shown), which can itself be controlled by a controller. The chuck body 104 includes a set of clamping pins 110 adapted to receive the wafer 101 and securely hold the wafer in place. In this manner, when the wafer 101 is mounted on the rotatable chuck 102 via the clamping pins 110, the wafer 101 can be rotated by rotating the chuck body 104 relative to the base 106.

[0129] exist Figure 1In the illustrated configuration, clamping pins 110 apply a clamping force to hold the wafer 101 in place. However, other suitable mechanisms may be used to hold the wafer 101 in place (e.g., clamps, screws, suction holders, etc.).

[0130] The rotatable chuck 102 also includes a disk 112 mounted on the chuck body 104. The disk 112 is fixed to the chuck body 104 so that it rotates with the chuck body 104 relative to the base 106. Figure 1 As shown, disk 112 is configured so that it is substantially parallel to wafer 101 when wafer 101 is mounted on rotatable chuck 102. In this embodiment, disk 112 is a transparent disk, such as made of quartz or sapphire.

[0131] The apparatus also includes a heating assembly 114. In this embodiment, the heating assembly 114 includes an array of LEDs 116 configured to illuminate a wafer mounted on the rotatable chuck 102. The LEDs 116 serve as light-emitting heating elements for heating the wafer 101 received by the rotatable chuck 102.

[0132] In this embodiment, LED 116 is configured to emit light in the wavelength range of 380 nm to 650 nm. For example, LED 116 may emit light having a maximum intensity in the wavelength range of 380 nm to 650 nm. Such a wavelength range is suitable for heating semiconductor wafers.

[0133] The transparent disc 112 is arranged such that it is substantially transparent to the wavelengths emitted by the LEDs 116 , ie all or most of the light emitted by the LEDs 116 is transmitted by the transparent disc 112 .

[0134] The heating assembly 114 also includes a disk 118. The array of LEDs 116 is mounted on the upper surface of the disk 118, and the disk 118 acts as a heat sink for the array of LEDs 116 to dissipate the heat generated by the LEDs 116. For example, the disk 118 can be made of a metal such as aluminum. A circuit board 120 including a drive circuit (not shown) for the LEDs 116 is provided on the lower surface of the disk 118. The interconnection between the array of LEDs 116 and the drive circuit on the circuit board is achieved via the disk 118. The disk 118 is mounted on a fixing rod 122. The fixing rod 122 is not connected to the chuck body 104 so that it does not rotate with the chuck body 104. The disk 118 is substantially parallel to the transparent disk 112.

[0135] When the wafer is mounted in the rotatable chuck 102, the LED 116 array is configured to face the wafer 101. Figure 1As shown, when wafer 101 is mounted in rotatable chuck 102, transparent disk 112 is located between the array of LEDs 116 and wafer 101. Therefore, light emitted by the array of LEDs 116 can be transmitted by transparent disk 112 and illuminated on wafer 101 to heat wafer 101. When wafer 101 is mounted on rotatable chuck 102, transparent disk 112 can be used to protect the array of LEDs 116 from the effects of processes performed on wafer 101.

[0136] The array of LEDs 116 is configured to illuminate a first surface 103 of the wafer 101, which is opposite a second surface 105 of the wafer 101. The second surface 105 of the wafer 101 is exposed so that processes can be performed on the second surface 105 of the wafer 101.

[0137] The array of LEDs 116 can be positioned substantially symmetrically about the axis of rotation 108 of the rotatable chuck 102. In this manner, the array of LEDs 116 can illuminate the wafer substantially symmetrically about the axis of rotation 108.

[0138] The apparatus 100 further includes a liquid dispenser for dispensing liquid onto the second surface 105 of the wafer 101, for example, to clean the second surface 105. In this embodiment, the liquid dispenser includes an arm 128 having a discharge nozzle 130. The arm 128 is supplied with process liquid and / or rinse liquid, which is discharged downwardly onto the second surface 105 of the wafer 101 via the discharge nozzle 130.

[0139] The arm 128 is a swing arm 128 that is pivotally mounted at an end of the arm 128 opposite to the end where the exhaust nozzle 130 is located, such that the arm 128 can be rotated about the pivot mount to change the position of the exhaust nozzle 130 relative to the second surface 105 of the wafer 101. In particular, by rotating the arm 128 about the pivot mount 128, the radial position of the exhaust nozzle 130 relative to the second surface 105 of the wafer 101 can be changed, for example, between a first position located at the center of the second surface 105 of the wafer 101 and a second position located radially outward from the outer periphery of the wafer 101. The exhaust nozzle 130 moves in an arcuate manner across the second surface 105 of the wafer 101.

[0140] The above-described configuration of the liquid dispenser, together with the rotation of the wafer 101 by the rotatable chuck 102, means that the liquid dispenser can be operated to dispense liquid over the entire second surface 105 of the wafer 101 by pivoting the arm 128 from the center of the second surface 105 to the edge of the second surface 105 while the wafer 101 is rotating.

[0141] Of course, in other embodiments, other suitable liquid dispensers may be used in place of this particular liquid dispenser.

[0142] like Figure 2a As shown, as the discharge nozzle 130 of the arm 128 moves from the center of the second surface 105 of the wafer 101 to the edge of the second surface 105 while dispensing liquid L and rotating the wafer 101, a drying line 201 (which is the transition area between the dry area 202 of the wafer and the wet area 203 of the wafer) is generated. The drying line 201 moves radially outward across the second surface 105 of the wafer 101 in association with the movement of the discharge nozzle 130. For example, the drying line can be a substantially circular shape centered on the rotational axis of the wafer 101. The radial position of the drying line 201 at any given time can correspond to the radial position of the discharge nozzle 130. In practice, the drying line is likely located slightly radially inward of the radial position of the discharge nozzle 130.

[0143] As discussed in US 2017 / 0345681, when spin cleaning a wafer surface having high aspect ratio surface features (e.g., silicon-doped fins), drying of the liquid used for spin cleaning can cause a phenomenon known as pattern collapse, in which the high aspect ratio surface features are damaged.

[0144] For example, the surface tension of a cleaning or rinsing liquid, such as isopropyl alcohol (IPA), and the high aspect ratios of structures formed on the wafer surface can mean that the cleaning or rinsing liquid leaves the spaces between the high aspect ratio structures more slowly, which can cause menisci to form in the spaces between the structures. As drying continues, the surface tension of the cleaning or rinsing liquid can pull the structures toward each other, thereby changing their shape and / or damaging or destroying them, which can impair or hinder the precise performance of the associated semiconductor device.

[0145] US2017 / 0345681 describes that the pattern collapse phenomenon can be reduced or avoided by preferentially heating the wafer surface adjacent to the drying line to a higher temperature. This local higher temperature heating can be used to fully and quickly evaporate the cleaning liquid or rinsing liquid at the drying line between the high aspect ratio structures where no crescent shape is formed, thereby avoiding the pattern collapse phenomenon. As the drying line moves radially outward across the wafer surface following the radial movement of the distribution nozzle, the local higher temperature heating also moves radially outward across the wafer surface to follow the movement of the drying line. Thus, a local higher temperature front is generated (which moves radially outward across the wafer surface following the radial movement of the distribution nozzle).

[0146] This type of heating is used in some embodiments of the present invention.

[0147] Figure 2bIt is shown that in one embodiment of the present invention, it can be applied to Figure 2a Examples of heating profiles for the configurations shown.

[0148] Figure 2b The relationship between the temperature T to which the wafer 101 is heated by the heating assembly 114 and the radial position R on the wafer 101 is shown. The radial position R is the distance along the radial direction of the wafer 101 from the rotation axis of the wafer 101.

[0149] Figure 2b The radial position of the dryness line 201 is shown using a dashed line.

[0150] Figure 2b The temperature profile along a single radial direction is shown. In practice, the temperature profile may be the same or substantially the same along all radial directions (i.e., the temperature profile of the wafer is rotationally symmetric or substantially rotationally symmetric). However, due to environmental factors, etc., the temperature profile may be different in different radial directions.

[0151] like Figure 2b As shown, in the wetting region 203, the liquid on the wafer 101 is heated to an elevated temperature 204, but the temperature 204 does not cause premature drying of the liquid.

[0152] In contrast, in the drying region 202 adjacent to the drying line 201, the temperature of the wafer 101 is substantially raised to a temperature 205, thereby causing the evaporation rate of the cleaning liquid or rinse liquid to be sufficiently high so that no meniscus (or flat or 90-degree meniscus) is formed between the high aspect ratio features to avoid pattern collapse as discussed above.

[0153] like Figure 2b As shown, in the remainder of the drying area 202, the dried wafers are maintained at a lower, but still elevated, temperature 206 to ensure complete evaporation of the rinsing liquid and to avoid condensation on the dried wafer surfaces.

[0154] Thus, in the present invention, a localized higher temperature front can be generated that moves radially outward across the wafer surface.

[0155] The localized higher temperature front may have a substantially annular shape on the second surface 105 of the wafer 101 .

[0156] The radial position of the leading end of the locally higher temperature may correspond to the radial position of the drying line on the wafer surface.

[0157] The radial position of the leading end of the locally higher temperature may correspond to the radial position of the discharge nozzle 130 .

[0158] The apparatus 100 also includes an image sensor in the form of an infrared camera 124 configured to detect infrared light from the second surface 105 of the wafer 101 .

[0159] exist Figure 1 , infrared camera 124 is shown positioned above the rotation axis of wafer 101. This positioning of infrared camera 124 may mean that infrared camera 124 can easily detect infrared radiation from the entire second surface 105 of wafer 101. However, in other embodiments, infrared camera 124 may be provided at a different location to detect infrared radiation from part or all of second surface 105 of wafer 101.

[0160] The infrared camera 124 detects a two-dimensional infrared intensity distribution from the second surface 105 of the wafer 101 .

[0161] Infrared camera 124 may be configured to detect infrared radiation having a wavelength in the range of 3 to 14 μm, or 3 to 5 μm, or 8 to 14 μm, or infrared radiation having virtually any suitable wavelength range.

[0162] The device 100 may also include a controller (not shown) to control the power supplied to the array of LEDs 116 and to receive measurement output from the infrared camera 124 .

[0163] The controller can be any suitable computing device having software installed thereon to perform the desired functions. For example, the controller can be connected to the circuit board 120 via a communication interface (e.g., USB, Ethernet, etc.) to control the amount of power supplied to the array of LEDs 116. Similarly, the controller can be connected to the infrared camera 124 via a communication interface to receive measurement output from the infrared camera 124. The controller can include a memory in which various control parameters (e.g., power levels) for the array of LEDs 116 are stored. The controller can also store measurement data received from the infrared camera 124.

[0164] The LEDs 116 can be configured into multiple groups of individually controllable LEDs 116. Power can be supplied independently to each of the multiple groups of LEDs 116, for example, via circuitry on the circuit board 120, so that each group of LEDs 116 can be independently controlled (e.g., turned on or off). Each group of LEDs 116 can be configured to heat a specific area of the wafer 101, so that different areas of the wafer 101 can be controllably heated. The multiple groups of LEDs 116 can be concentrically arranged about the rotational axis 108 of the rotatable chuck 102, so that each group occupies a respective radial position. In this manner, different radial areas of the wafer 101 can be heated by activating different groups of LEDs 116.

[0165] The controller can be used to automatically control the power supplied to the array of LEDs 116 based on the measurement output received from the infrared camera 124. For example, the controller can adjust the power supplied to the array of LEDs 116 until the measurement output indicates a desired temperature distribution on the second surface 105 of the wafer 101. When the array of LEDs 116 includes multiple groups of individually controllable LEDs 116, the controller can automatically adjust the power supplied to each group of LEDs 116 so that the desired output of each group is obtained to achieve the desired temperature distribution on the surface 105 of the wafer 101.

[0166] In this embodiment, the controller is configured to determine a temperature distribution across some or all of the surface 105 of the wafer 101, or information related to such a temperature distribution, based on the measurement output from the infrared camera 124. The controller is also configured to control the power supplied to the array of LEDs 116 based on the determined temperature distribution or information related to the temperature distribution.

[0167] For example, the controller may store in memory a target temperature distribution for the second surface 105 of the wafer 101, or information related to such a target temperature distribution. Based on the measurement output from the infrared camera 124, any differences between the current temperature distribution and the target temperature distribution may be identified. The power supplied to the LEDs 116 may then be controlled to substantially remove or reduce any identified differences so that the current temperature distribution substantially matches or corresponds to the target temperature distribution.

[0168] When each LED 116 is individually controllable, the controller may individually control the power supplied to each LED 116 .

[0169] In contrast, when the LEDs are arranged into multiple individually controllable groups, the controller can individually control the power supplied to each of the multiple groups of LEDs 116 .

[0170] In one embodiment of the present invention, the target temperature distribution for the second surface 105 of the wafer 101 may be Figure 2b For example, the target temperature distribution may include a local (in the radial direction) region of higher temperature immediately adjacent to the drying line 201 to heat the wafer 101 to a higher temperature adjacent to the drying line 201, thereby avoiding or reducing pattern collapse.

[0171] In one embodiment of the present invention, the measurement output of the infrared camera 124 can be analyzed to determine the location of the drying line 201 on the wafer surface. For example, the location of the drying line 201 can be determined by applying an edge detection algorithm to the measurement output of the infrared camera 124.

[0172] Figure 3is an example of the measurement output of the infrared camera 124 in one embodiment of the present invention. Figure 3 The x-axis and y-axis in the figure show the distance in the perpendicular x-direction and y-direction on the surface of the chip 101, and the gray represents the infrared radiation of different intensities detected from the surface of the chip 101 (the lighter the gray, the higher the temperature).

[0173] Figure 4a Shows the temperature variation along Figure 3 The distance between the solid lines. Figure 4b Shows the temperature Figure 4a Differentiate the distance in .

[0174] At the position of the drying line 201 ( Figure 4a and 4b ), the temperature of the second surface 105 of the wafer 101 has an abrupt change due to the transition region between the dry area of the surface and the wet area of the surface.

[0175] So, if Figure 4b As shown, the position of the drying line can be determined by determining the position of the maximum value of the differential of temperature with respect to radial distance.

[0176] Of course, in other embodiments, different techniques may be used to identify the location of the drying line.

[0177] The power supplied to the array of LEDs 116 can then be controlled based on the determined location of the drying line 201. For example, as discussed above, the power supplied to the array of LEDs 116 can be controlled to produce a localized higher temperature region proximate the determined location of the drying line 201 (on the dry side of the drying line).

[0178] As the drying line 201 moves radially outward across the surface 105 of the wafer 101, for example following radial movement of a dispensing nozzle, the power supplied to the LED 116 array can also be controlled to cause the localized higher temperature region to move radially outward across the surface 105 of the wafer 101 corresponding to the movement of the drying line 201.

[0179] In this manner, a higher temperature radially moving circumferential front end may be generated by the LED 116 .

[0180] In an embodiment of the present invention, the liquid dispensed on the second surface 105 of the wafer 101 is isopropyl alcohol (IPA), which can be used to clean or rinse the second surface 105 of the wafer 101 .

[0181] Infrared radiation emitted by objects other than the surface of wafer 101 may also be detected by infrared camera 124, which may interfere with the detection of infrared radiation from the surface of wafer 101. For example, infrared radiation may also be emitted by other components of apparatus 100 or by other objects in the environment surrounding apparatus 100.

[0182] To more easily and / or more accurately detect infrared radiation from the surface 105 of the wafer 101, the apparatus 100 may include a filter (not shown) adapted to selectively transmit infrared radiation having a predetermined wavelength range. The filter is attached to or positioned adjacent to the opening of the infrared camera 124 so that all or most of the infrared radiation entering the opening of the infrared camera 124 first passes through the filter.

[0183] Preferably, the filter is a bandpass filter which transmits only infrared radiation of a predetermined wavelength range.However, the filter may alternatively also be a low-pass filter or a high-pass filter.

[0184] In practice, the wavelength transmitted by the filter will be selected based on the thermal emission spectrum of the liquid dispensed on the wafer.In particular, the filter will be adapted to selectively transmit thermal radiation emitted by the liquid dispensed on the wafer.

[0185] Thus, when the liquid dispensed onto the surface 105 of the wafer 101 is isopropyl alcohol (IPA), the filter will be adapted to selectively transmit thermal radiation emitted by the isopropyl alcohol.

[0186] For example, the filter may be adapted to selectively transmit thermal radiation having a characteristic wavelength emitted by isopropyl alcohol (eg, the wavelength of a peak in the emission intensity spectrum of isopropyl alcohol).

[0187] The filter may be adapted to selectively transmit electromagnetic radiation having a wavelength in the range of 3.3 to 3.5 μm or in the range of 8.6 to 9.1 μm.Such wavelengths may be characteristic wavelengths emitted by isopropyl alcohol.

[0188] In practice, the semiconductor wafer is typically a semiconductor wafer.

[0189] In some embodiments of the present invention, an exemplary configuration of the heating assembly 114 is shown in FIG. Figure 5 middle.

[0190] like Figure 5 As shown, the LEDs 116 are arranged in concentric rings around the center of the heating element 114. The arrangement of the LEDs 116 is rotationally symmetric about the center of the heating element 114.

[0191] Within a given concentric ring, the LEDs 116 are divided into groups, for example, with 16 LEDs 116 in each group 501. In other words, the LEDs 116 within a given concentric ring are not evenly distributed around the concentric ring.

[0192] As discussed above, the power supplied to each group 501 of LEDs 116 may be independently controlled.

[0193] In this example, there are 20 concentric rings of LEDs 116, but of course in other embodiments the number of concentric rings may be different.

[0194] exist Figure 5 In the embodiment, the heating assembly 114 is divided into four sector-shaped bodies 502 , and these sector-shaped bodies 502 are connected together by connecting members 503 .

[0195] Each LED may have a power consumption of 10 watts and provide 3 watts of power.

[0196] Of course, the heating element 114 can be used with Figure 5 In particular, the arrangement of the LEDs in the heating assembly is not critical to the invention.

Claims

1. An apparatus for processing a wafer, the apparatus comprising: a rotatable chuck adapted to receive the wafer; a heating assembly comprising an array of heating elements configured to heat the wafer received by the rotatable chuck; an image sensor configured to detect electromagnetic radiation from liquid on a surface of the wafer; as well as a controller configured to control power supplied to the array of heating elements based on the measured output of the image sensor, The controller is configured to analyze the measurement output of the image sensor to determine a location of a dryness line on the surface of the wafer, the dryness line corresponding to a transition between a dry area and a wet area on the surface of the wafer. The device of claim 1 , wherein the image sensor is a camera.

3. The apparatus of claim 2, wherein the camera is a thermal imaging camera. 4 . The device of claim 1 , wherein the image sensor is adapted to detect electromagnetic radiation having a wavelength in the range of 3 to 14 μm.

5. The apparatus of claim 1, wherein the apparatus comprises a liquid dispenser for dispensing the liquid onto the surface of the wafer.

6. The apparatus of claim 1, wherein the apparatus is a spin washing apparatus.

7. The apparatus of claim 1 , wherein the controller is configured to: determining a temperature or information related to the temperature at one or more locations on the surface of the wafer based on the measurement output of the image sensor; and Power supplied to the array of heating elements is controlled based on the determined temperature or information related to the temperature.

8. The apparatus of claim 1 , wherein the controller is configured to: determining a temperature distribution or information related to the temperature distribution across part or all of the surface of the wafer based on the measurement output of the image sensor; and Power supplied to the array of heating elements is controlled based on the determined temperature distribution or information related to the temperature distribution.

9. Apparatus according to any one of the preceding claims, wherein: Each heating element in the array of heating elements is individually controllable; and The controller is configured to individually control the power supplied to each of the heating elements.

10. The apparatus according to any one of claims 1 to 8, wherein: The heating element array comprises a plurality of groups of heating elements that are individually controllable; as well as The controller is configured to individually control power supplied to each of the plurality of individually controllable groups of heating elements.

11. The device according to any one of claims 1 to 8, wherein the device comprises a filter adapted to selectively transmit electromagnetic radiation having a predetermined wavelength or wavelength range.

12. The apparatus of claim 11, wherein the filter is a bandpass filter.

13. The apparatus of claim 11, wherein the filter is adapted to selectively transmit thermal radiation emitted by isopropyl alcohol.

14. The apparatus according to claim 11, wherein the filter is adapted to selectively transmit electromagnetic radiation having a wavelength in the range of 3.3 to 3.5 μm or in the range of 8.6 to 9.1 μm.

15. The apparatus according to any one of claims 1 to 8, wherein the controller is configured to: Power supplied to the array of heating elements is controlled based on the determined position of the drying line.

16. The apparatus of claim 15, wherein the controller is configured to determine the position of the drying line using an edge detection algorithm.

17. The apparatus of claim 15, wherein the controller is configured to control power supplied to the array of heating elements such that the wafer is heated to a higher temperature adjacent the drying line than elsewhere on the wafer.

18. The apparatus of any one of claims 1 to 8, wherein the controller is configured to control the heating element to cause heating of the surface of the wafer to occur along a radially moving circumferential front end.

19. The apparatus of any one of claims 1 to 8, wherein the array of heating elements is configured to heat a surface of the wafer that is on an opposite side of the wafer than a surface of the wafer imaged by the image sensor.

20. The apparatus of any one of claims 1 to 8, wherein the heating element is a light emitting heating element configured to illuminate the wafer to heat the wafer.

21. The apparatus of claim 20, wherein the light emitting heating element is an LED.

22. A method of controlling a device according to any preceding claim, the method comprising: dispensing a liquid onto a surface of a wafer received by the rotatable chuck; rotating the rotatable chuck to remove the liquid from the surface of the wafer; supplying power to the array of heating elements to heat the surface of the wafer during the rotating; detecting electromagnetic radiation from the liquid on the surface of the wafer with the image sensor; as well as The power supplied to the array of heating elements is adjusted based on the measured output of the image sensor.

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