Bath system and method

Abstract

A method for processing a plurality of substrates includes immersing a plurality of substrates in a bath solution contained in a bath, generating gas bubbles in the bath solution, projecting light from a light source toward the bath, generating light sensor data by capturing light emitted from the bath after interaction with the gas bubbles with a light sensor, and converting the light sensor data into a metric of the bath solution.

Description

[Technical field]

[0001] Cross-references to related patents and applications This application claims priority to the filing date of U.S. Non-Provisional Patent Application No. 17 / 341,105, filed June 7, 2021, the entire contents of which are incorporated herein by reference.

[0002] Technical Field FIELD OF THEINVENTION The present invention relates generally to systems and methods for monitoring bath processes, and in embodiments to bath systems and methods thereof. [Background technology]

[0003] Wafer baths with circulating fluids are commonly used in semiconductor manufacturing to perform substrate surface preparation steps such as surface cleaning, resist stripping, and thin film etching on batches of multiple wafers simultaneously.

[0004] Across-wafer and wafer-to-wafer uniformity is important to provide integrated circuit components such as transistors, capacitors, and resistors with narrow electrical distributions across all wafers in a lot. For large diameter wafers, such as 12-inch wafers, it is difficult to achieve across-wafer and wafer-to-wafer uniformity in the bath.

[0005] Insufficient cleaning or etching of the substrate in the surface preparation bath can result in reduced yields due to resist or thin film residues left on the wafer, or from non-uniformity of the etched thin film left on the wafer. Excessive cleaning increases cycle times and generates excess hazardous waste. Excessive cleaning can also reduce yields if excessive etching causes thin film thickness or critical dimensions to be off target. Summary of the Invention [Means for solving the problem]

[0006] In one embodiment, a method for processing a plurality of substrates includes immersing a plurality of substrates in a bath solution contained in a bath, generating gas bubbles in the bath solution, projecting light from a light source toward the bath, generating light sensor data by capturing light emitted from the bath after interaction with the gas bubbles with a light sensor, and converting the light sensor data into a metric of the bath solution.

[0007] In one embodiment, the bath treatment tool includes a bath with a loading arm and configured to hold a bath solution, a light source mounted on a light source mounting assembly for projecting light toward the bath, and a light sensor mounted on a sensor mounting assembly for capturing light emitted from the bath after interaction with air bubbles in the bath solution.

[0008] In one embodiment, a bath processing tool includes a bath for wet processing wafers, an electromagnetic radiation sensor for capturing electromagnetic signals from a bath solution in the bath, a processor, and a non-transitory memory storing a program and coupled to the processor, the program including instructions, when executed in the processor, for determining a metric of the bath solution based on the electromagnetic signal, and identifying that a target specification for processing the wafer has been reached based on the metric of the bath solution.

[0009] In one embodiment, an endpoint detection method includes processing a wafer with a wet process, capturing an electromagnetic signal from a bath solution in a bath during processing at an electromagnetic radiation sensor, determining an endpoint metric of the bath solution based on the electromagnetic signal, and stopping the wet process in response to identifying that an endpoint of the process has been reached based on the endpoint metric of the bath solution.

[0010] In one embodiment, a process control method includes processing a wafer with a wet process, capturing an electromagnetic signal from a bath solution in a bath during processing at an electromagnetic radiation sensor, determining a process target specification for the bath solution based on the electromagnetic signal, and adjusting the bath solution in response to the determination of the process target specification based on the process target specification for the bath solution.

[0011] For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions which should be read in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0012] [Figure 1A] FIG. 1 illustrates a cross-sectional view of a bath with a fluid injector and a gas injector, according to an embodiment. [Figure 1B] FIG. 1 is a cross-sectional view of a bath with a fluid injector and a heating element, according to an embodiment. [Diagram 2] FIG. 1 is a cross-sectional view of a system for monitoring and controlling a bath with bubble mixing according to one embodiment. [Diagram 3] FIG. 1 is a cross-sectional view of a system for monitoring and controlling a bath with bubble mixing according to one embodiment. [Figure 4] FIG. 1 is a perspective view of a system for monitoring and controlling a bath with bubble mixing, according to one embodiment. [Diagram 5] FIG. 1 is a cross-sectional view of a system for monitoring and controlling a bath with bubble mixing according to one embodiment. [Figure 6] FIG. 1 is a perspective view of a system for monitoring and controlling a bath with bubble mixing, according to one embodiment. [Figure 7] FIG. 1 is a cross-sectional view of a system for monitoring and controlling a bath with bubble mixing according to one embodiment. [Figure 8] FIG. 13 is a cross-sectional view of a light source for a bath with the light source integrated within a gas injector, according to one embodiment. [Figure 9] 1 is a cross-sectional view of a light source including a light pipe with an internal reflector for illuminating multiple zones within a bath, according to one embodiment. [Figure 10] FIG. 2 is a projection diagram of a bath light source including a circular illuminator, according to one embodiment. [Figure 11] 1 is a diagram of a photosensor including a rectangular array of pixels, according to one embodiment. [Figure 12] FIG. 2 is a diagram of a photosensor including strips of pixels, according to one embodiment. [Figure 13] FIG. 1 is a perspective view of a system for monitoring and controlling a bath with bubble mixing, according to one embodiment. [Figure 14] 1 is a projection diagram of a system for determining a bath endpoint and controlling a process in a bath, according to one embodiment. [Figure 15A] FIG. 2 illustrates an ethanol molecule and an infrared spectrum of an ethanol molecule, according to one embodiment. [Figure 15B] FIG. 2 illustrates an ethanol molecule and an infrared spectrum of an ethanol molecule, according to one embodiment. [Figure 16A] FIG. 2 illustrates a water molecule and an infrared spectrum of a water molecule, according to one embodiment. [Figure 16B] FIG. 2 illustrates a water molecule and an infrared spectrum of a water molecule, according to one embodiment. [Figure 17] 1 is a projection diagram of a system for determining a bath endpoint and controlling a process in a bath, according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Although the present invention has been described with reference to exemplary embodiments, this specification is not intended to be construed in a limiting sense. Various modifications and combinations of those exemplary embodiments, as well as other embodiments of the present invention, will become apparent to those skilled in the art upon reference to this specification. It is therefore intended that the appended claims cover any such modifications or embodiments.

[0014] Embodiments of this application disclose systems and methods for monitoring bath processes involving gas bubbles.Embodiments of this application disclose methods for monitoring mixing uniformity across the bath and uniformity of the surface preparation process.Embodiments of this application disclose methods for accurately determining the end point of a process in a surface preparation bath.

[0015] A cross-sectional view of a bath tool 10 including a bath for a surface preparation bath 100 for processing a plurality of wafers 104 is shown in FIGS. 1A and 1B.

[0016] In FIG. 1A, the surface preparation bath 100 includes an outer bath 100A and an inner bath 100B. The outer bath 100A and the inner bath 100B are typically Pyrex or quartz. Bath solution 102 flows into the bath 100 from a fluid injector 103 near the bottom of the bath 100. The bath solution 102 fills the inner bath 100B and overflows into the outer bath 100A. A wafer 104 is lowered into the bath solution 102 and supported within the bath 100 on a wafer loading arm 106. In FIG. 1A, gas bubbles 110 (usually nitrogen) are injected into the bath solution 102 from an orifice 109 along the length of a gas injector 108 near the bottom of the bath 100. The gas bubbles 110 rise through the bath solution 102 faster than the bath solution 102 flows into the bath 100, providing vigorous mixing. The bubbles 110 continuously replenish the bath solution 102 above the surface of the wafer 104 .

[0017] 1B , gas bubbles 110 are generated in the bath solution 102 by the heating element 107, which locally heats the bath solution 102 around the heating element 107, causing boiling near the bottom of the bath 100. The localized boiling of the bath solution 102 causes gas bubbles to form around the heating element 107. Thus, in various embodiments, the bath tool 10 includes a gas bubble injector including a heating element 107 and / or a gas injector 108 for generating gas bubbles (110) in the bath solution located below the loading arm. For purposes of illustration, the heating elements are shown in this arrangement, however, other arrangements and other types of heating elements 107 can be used.

[0018] The heat to boil the bath solution 102 may also be generated by exothermic reactions between reactants in the bath solution 102. For example, the temperature of a piranha bath (sulfuric acid + hydrogen peroxide) may be controlled by the rate at which hydrogen peroxide is added to the sulfuric acid. For example, the boiling temperature of a hot phosphoric acid / water bath used for stripping silicon nitride may be controlled by keeping the ratio of phosphoric acid to water in the bath 100 constant.

[0019] As further shown in FIG. 1A and FIG. 1B, the bath tool 10 includes a light mounting assembly 20 designed to illuminate selected areas of the bath 100 and to be customized to select a particular type of light. In addition, the light mounting assembly 20 can be designed to direct light at different angles of incidence to the inner bath 100A and the outer bath 100B. The light mounting assembly 20 can include a mechanical system, a circuit, a controller, and one or more light sources. The bath tool 10 includes a sensor mounting assembly 30 for detecting light scattered from the bath solution 102. The sensor mounting assembly 30 can include one or more light sensors mounted on the mechanical system and designed to detect light scattered from one or more areas of the bath solution 102. Various embodiments of the light mounting assembly 20 and the sensor mounting assembly 30 are described in more detail below.

[0020] A system for monitoring the mixing uniformity and homogeneity of the bath solution 102 across the bath by capturing and analyzing light scattered from the gas bubbles 110 is shown in FIG.

[0021] A light source 112 projects light into the bath 100. Multiple light sources 112 can project light into multiple zones across the length and width of the bath 100. Light scattered from the bubbles 110 can be captured by a light sensor 114 or multiple light sensors 114. The amount of light scattered from the bubbles 110 in a first zone within the bath 100 can be compared to the amount of light scattered from the bubbles in a second zone to determine the uniformity between zones across the bath 100. Various bubble characteristics indicative of the condition and uniformity of the bath solution 102 can be calculated from the light sensor data. The various bubble characteristics include static bubble number and size density, dynamic bubble number and size density, static bubble uniformity, dynamic bubble uniformity, bath solution uniformity, and bubble generation rate.

[0022] In FIG. 2, the light source 112 and the light sensor 114 are disposed below the bath 100 and are mounted, for example, on the light mounting assembly 20 and the sensor mounting assembly 30, respectively. The light source 112 can be an LED or a laser. The light sensor 114 can be a charge-coupled device (CCD) camera with an array of CCD pixels, a complementary metal-oxide semiconductor (CMOS) image sensor with an array of CMOS pixels, or the light sensor 114 can be a photodiode or an array of photodiode pixels. The light sensor 114 can transmit light data to a processor 180 for analysis. The processor 180 can be a controller for the bath tool 10 or a common controller for a group of tools. The processor 180 can increase or decrease the flow of gas from the gas injector 108 to improve mixing uniformity across the inner bath 100B. The processor 180 can increase or decrease the amount of fluid injected from the fluid injector 103 into the bath 100. The processor 180 can also adjust the intensity of the light source 112, turn the light source 112 on and off, and synchronize the light source 112 with the light sensor 114. The processor 180 can increase or decrease the power to the heating element 107 to increase or decrease boiling. The processor 180 can adjust the flow of components that cause an exothermic reaction to control the temperature of the bath 100. For example, an increase in the reaction rate of the exothermic reaction can cause localized heating within the bath 100 that results in boiling of the bath solution 102, thereby increasing the formation of gas bubbles that can be detected.

[0023] FIG. 3 shows an alternative embodiment in which a light sensor 114 positioned at an angle to the light path from the light source 112 into the bath captures the scattered light.

[0024] As shown, in various embodiments, the light sources 112 in FIG. 3 are distributed, for example evenly, across the underside of the bath 100. The light sensors 114 directed toward the sides of the bath 100 capture light scattered horizontally from the bubbles 110 from the sides of the bath 100. In one embodiment, the light sensors 114 are positioned orthogonal to the path of light from the light sources 112 into the bath 100. In other embodiments, the light sensors 114 may be positioned in other locations to capture light scattered at different angles from the bath 100. In one embodiment, the light sensors 114 may be scanned horizontally or vertically, for example from the bottom of the bath 100 to the top of the bath 100, while light is being shone from the light sources 112 to capture a video or series of images. The captured video or series of images may then be analyzed together to determine various bubble parameters, which in turn may be used to improve bath uniformity and other process metrics.

[0025] In various embodiments, the light sources 112 may have different wavelengths (colors). Different color light sources 112 may illuminate different zones within the bath 100. The light sensor 114 may be a CCD camera, a CMOS image sensor, or a photodiode array with color filters to separate the different colored light. This method may eliminate intensity errors that occur when light from two or more light sources 112 scatters from the same bubble 110. Bubble characteristics from two adjacent zones may be compared without interference using this method.

[0026] The light source 112 may be cycled on and off in synchronization with or with the light sensor 114. The frequency, duty cycle, and power of the light source 112 may be varied to produce flashes of light similar to a strobe light. The flashes of light allow the light sensor 114 to capture clear still images of the bubbles 110. Static bubble patterns may be analyzed to compare bubble sizes in various bath zones and to determine bubble uniformity and bubble density across and between zones. A series of static bubble patterns may be captured and analyzed over time to determine changes in bubble uniformity and bubble density in a zone. By alternating flashes of the first light source 112 and the second adjacent light source 112, the uniformity of the bath solution 102 in two adjacent bath zones may be determined without interference.

[0027] As an example, in the arrangement shown in Figure 3, mixing uniformity in corresponding zones on the left and right halves of the wafer 104 may be analyzed by comparing light scattered from a bubble 110 in a first zone on the left half of the wafer with light scattered from a bubble 110 in a second zone on the right half of the wafer. In the arrangement of Figure 3, light from a first light source 112A under the first zone is scattered horizontally from the bubble into a first light sensor 114A oriented to the left side of the bath 100. Light from a second light source 112B under the second zone is scattered horizontally from the bubble into a second light sensor 114B oriented to the right side of the bath 100.

[0028] FIG. 4 shows a perspective view of a bath tool, according to one embodiment. The bath tool of FIG. 4 shows an arrangement for analyzing and monitoring the mixing uniformity in the bath solution 102 by capturing light reflected from droplets emitted into the air above the surface of the bath 100 as the bubbles 110 rise to the surface and burst. A laser 116 can sweep a beam of laser light above the surface of the bath solution 102, forming (over time) a plane 118 of laser light. Laser light scattered from droplets emitted from the bursting bubbles can be captured by a light sensor 114 above the plane 118 of laser light. The light sensor 114 can be a CCD camera or a photodiode camera. The intensity and uniformity of the light captured by individual pixels 152 (FIG. 11) of a CCD or photodiode pixel array 150 can be analyzed to determine the uniformity and speed of the bursting bubbles 110 across the surface of the bath solution 102. The processor 180 can increase or decrease the gas injection rate from the gas injectors 108 to increase or decrease mixing, and can balance the gas bubbles 110 emitted from the individual gas injectors 108 to improve mixing uniformity across the bath 100. Alternatively, the processor 180 can increase or decrease the power to the heating elements 107 to increase or decrease mixing, and can balance the gas bubbles 110 formed around the individual heating elements 107 to improve mixing uniformity across the bath 100. The processor 180 can adjust the flow of components in the exothermic reaction to control the temperature of the bath 100, and therefore the boiling. FIG. 5 shows a cross-sectional view of a bath tool, according to one embodiment.

[0029] 2 and 3, light source 112 is positioned to monitor bath mixing uniformity across the width of bath 100. Light source 112 illuminates multiple bath zones across a major surface of the wafer.

[0030] In another embodiment shown in FIG. 5, a light source 112 is positioned to monitor bath mixing uniformity over the length of the bath 100. The light source 112 illuminates multiple bath zones along the length of the gas injector 108 or multiple zones along the length of the heating element 107. The light source 112 illuminates corresponding surface areas on all wafers 104 in the batch. Bubbles 110 are emitted from orifices 109 along the length of the gas injector 108 or from hot surfaces along the length of the heating element 107. The wafers 104 in the batch are aligned along the gas injector 108 and spaced above the gas injector 108 on the wafer loading arm 106. In FIG. 5, a light sensor 114 is below the bath 100. The light sensor 114 captures light reflected from bubbles rising between the wafers 104. Alternatively, the light sensor 114 may be positioned to capture light scattered from the sides of the bath 100, as shown in FIG.

[0031] FIG. 6 shows a projection view of a bath tool, according to one embodiment.

[0032] In the arrangement shown in Figure 6, a laser beam 124 is projected into the bath and redirected by a prism 122 towards a light sensor 114. The prism 122 may be placed in any convenient location within the bath 100. In Figure 5, the prism 122 serves a dual purpose, both for light refraction and as the wafer loading arm 106.

[0033] In a first example, the laser 116 projects the laser beam 124 horizontally onto the side of the bath 100 towards the prism 122. The prism 122 redirects the light 90 degrees downward towards the light sensor 114 below the bath 100. As the laser beam 124 travels through the bath solution 102, the light from the laser beam 124 is scattered off the bubbles 110, decreasing the intensity of the laser beam 124. The decrease in intensity of the laser beam 124 can be correlated to bubble characteristics such as bubble density, bubble uniformity, and bubble generation rate. Alternatively, the laser 116 can be above or below the bath and the light sensor 114 can be on the side of the bath 100.

[0034] In a second example, the laser 116 projects the laser beam 124 vertically from below the bath 100 toward a first prism 121 in the bath 100. The first prism 121 redirects the laser beam 124 horizontally 90 degrees toward a second prism 123. The second prism 123 redirects the laser beam 124 downward 90 degrees toward a light sensor 114 below the bath 100. As the laser beam 124 travels through the bath solution 102, light from the laser beam 124 is scattered from the bubbles 110, reducing the intensity of the laser beam. The intensity can be translated into bubble characteristics such as bubble uniformity, bubble density, and bubble generation rate. Alternatively, the laser 116 and light sensor 114 can be located on the side of the bath 100 by changing the positions of the first prism 121 and the second prism 123.

[0035] FIG. 7 is a cross-sectional view of the length of a surface preparation bath 100 filled with bath solution 102.

[0036] A wafer 104 supported by a wafer loading arm 106 is oriented vertically and spaced horizontally above a gas injector 108. Gas bubbles 110 are emitted from orifices 109 spaced along the length of the gas injector 108. In this arrangement, a plurality of light sources 112 are disposed below the bath 100 and spaced along the length of the bath 100. A plurality of light sensors 114 are also disposed below and along the length of the bath 100. If desired, each of the plurality of light sensors 114 may be configured to sense light from a respective one of the plurality of light sources 112.

[0037] 8 illustrates an embodiment in which a gas injector in the bath 100 includes a light source 112. As shown in FIG. 8, or in further embodiments, the gas injector 108 includes the light source 112. In one embodiment, multiple LEDs or lasers may be integrated into the gas injector 108. In this arrangement, the light source 112 is affixed to the inside surface of the bottom of the gas injector 108, which may be made of quartz, for example. In alternative embodiments, other arrangements are possible. For example, the light source 112 may be located elsewhere in the gas injector 108, or may be located outside of the gas injector 108 and protected from the bath solution 102 in an integrated gas injector 108 / light source 112 module.

[0038] FIG. 9 illustrates an embodiment in which the bath tool is illuminated with a single light source.

[0039] 9, one light source 112 is configured to illuminate multiple zones within bath 100. A light beam 125, which may be a laser beam, is projected into a light pipe 107 made of a transparent material such as Pyrex or quartz. Spaced along the inside of light pipe 107 are reflective surfaces 140 that redirect portions 142 of light beam 125 into multiple zones of bath 100. Light pipe 107 may be designed to be placed within bath 100, while light source 112 may be located outside of bath 100.

[0040] FIG. 10 shows an embodiment in which the bath tool is illuminated with light sources positioned around the light sensor.

[0041] 10, a donut-shaped light source 146 illuminates the bath 100. In one embodiment, the donut-shaped light source 146 is shaped like a ring. The donut-shaped light source 146 may be located either above or below the bath 100. The donut-shaped light source 146 may provide uniform illumination of the bath 100 when positioned around a light sensor 114, which may be located in the center of the donut-shaped light source 146.

[0042] An exemplary light sensor 114 arrangement is shown in FIGS.

[0043] 11 shows a top view of an array 150 of pixels 152, such as charge-coupled device (CCD) pixels, CMOS sensor pixels, or photodiode pixels. Such a pixel array 150 may be in a CCD camera, a CMOS sensor camera, or a photodiode camera. An arrangement of these photosensors 114 may be used to capture a two-dimensional image of the bath 100. Pixels 152 from two different locations in the image may be analyzed to compare uniformity in two different zones in the bath 100.

[0044] 12 shows a side view of a light sensor 114 having a rectangular strip 154 ​​of pixels 152. This type of light sensor 114 may be positioned adjacent to the bath 100 to capture light along the length of the gas injector 108. This arrangement may be used to monitor the velocity of gas bubbles 110 ejecting from orifices 109 along the gas injector 108 and determine if any orifices 109 have enlarged or become clogged. The rectangular strip 154 ​​of pixels 152 may be made up of elements of a charge-coupled device (CCD) image sensor, a photodiode image sensor, or a CMOS array sensor.

[0045] 13 shows an arrangement in which light sources 112 are evenly spaced across the bottom surface of bath 100 and light sensors 114 are spaced along the length and width on the sides of bath 100. Different numbers of light sources 112 and light sensors 114 than shown can be used.

[0046] The light sources 112 can be LEDs or lasers. The LEDs or lasers can all be the same color or can be different colors. The light sources 112 can be continuous or can flash on and off with a duty cycle synchronized with the light sensor 114. Data from the light sensor 114 can be communicated to the processor 180 and converted into information about bath conditions such as mixing and uniformity by executing a program in the processor 180, as known to those skilled in the art. The processor 180 can adjust the gas injection rate to increase or decrease mixing. The processor 180 can adjust the gas injection from the individual gas injectors 108 to improve mixing uniformity. Alternatively, the processor 180 can adjust the power to the heating elements 107 to increase or decrease mixing, and can locally adjust the power to individual heating elements 107 to improve mixing uniformity. The processor 180 can adjust the flow of components in the exothermic reaction to control the temperature of the bath 100 and therefore the boiling. The processor 180 can also regulate the rate at which the bath solution 102 is injected into the bath through the fluid injector 103.

[0047] A system and method for controlling the process variables and determining the endpoint of the surface preparation process in bath 100 is shown in FIG.

[0048] The electromagnetic radiation sensor 115 captures electromagnetic radiation 176 emitted from the bath 100 (such as long-wavelength infrared radiation to measure temperature, visible light to measure properties such as color, transparency, and turbidity, and short-wavelength infrared (IR) radiation from which the concentrations of various components in the fluid mixture can be determined from the intensity of IR absorption peaks in the IR spectrum of the fluid mixture).

[0049] Data from the electromagnetic radiation sensor 115, such as a CCD sensor, photodiode sensor, or microbolometer, can be sent to a processor 180. The processor 180 can analyze the data and compare it to a first endpoint specification 184 and a second endpoint specification 186 stored in a non-volatile memory 182. When the sensor data matches the first endpoint specification 184, the processor can adjust the process or terminate the process. For example, if the surface preparation process is resist stripping, the wafer 104 can be removed from the stripping bath and transferred into a rinse bath when the electromagnetic radiation sensor 115 no longer detects resist molecules in the stripping solution. If the wet batch process is etching a thin film, the processor can terminate the etching process and initiate transfer of the wafer 104 to a rinse tank when the bath temperature or bath color indicates etching completion. If the process is preparation of an etching solution, the processor 180 may compare the temperature of the bath to a first endpoint specification 184 if the mixture is exothermic, or may compare the concentration of a component in the etching solution as determined from an IR spectrum to a second endpoint specification 186. Once the endpoint specification is met, the processor 180 may then terminate the solution preparation step and begin lowering the wafer 104 into the bath 100.

[0050] The processor 180 can also analyze the data and compare it to process variable target specifications stored in the non-volatile memory 182. The processor can then make adjustments to the surface preparation process to keep the process variables on target. For example, during the silicon nitride stripping process, the processor 180 can add water as needed to the hot phosphoric acid / water mixture to keep the boiling temperature on target.

[0051] The electromagnetic radiation sensor 115 used for endpoint determination can be a short-wavelength infrared (IR) detector including a spectrometer. The spectrometer can sweep across a range of wavelengths and measure the intensity of the IR light at each wavelength. The concentration of organic molecules in the solution can be determined from the intensity of absorption peaks in their characteristic IR spectrum. The IR spectrum of the fluid mixture can be compared to a first endpoint specification 184 and a second endpoint specification 186 stored in non-volatile memory 182 to determine if the current surface preparation process step should be adjusted or terminated.

[0052] Figures 15B and 16B show schematic IR spectra of ethanol and water, respectively. Figures 15A and 16A show ethanol and water molecules. The unit of wavelength used in IR spectroscopy is the inverse centimeter (cm -1 In FIG. 15B, the wave number is the reciprocal of the wavelength in units of 4000 cm to 900 cm along the x-axis. -1 The percent transmission of IR light is recorded on the y-axis as the wavelength is swept from 3391 cm to 3391 cm. -1 At 1055 cm, the OH bonds in ethanol stretch and absorb IR energy, reducing the IR transmission by about 40%. -1 At 100 nm, the IR transmission is reduced to about 45% because the C-O bonds in ethanol stretch and absorb IR energy. The percent transmission at these wavenumbers depends on the concentration of ethanol in the mixture.

[0053] FIG. 16B is an IR spectrum of water. At 3266 cm, trough 224 is shown. -1 At 1634 cm, the IR transmission is reduced to about 45% because the OH bonds in the water stretch and absorb IR energy. -1 At 300 nm, the IR transmittance is reduced to about 70% because the scissor motion of the OH bonds in water absorbs the IR energy.

[0054] A spectrum of the fluid mixture in the bath 100 can be obtained by scanning wavelengths with the electromagnetic radiation sensor 115 using a spectrometer. The processor 180 can then compare the IR spectrum of the fluid mixture to a reference second endpoint specification 186, which can be a spectrum, stored in memory 182, and can initiate changes to the process if the spectrum matches. For example, if a fluid mixture of ethanol 200 and water 220 is prepared, the spectrum of the fluid mixture can be repeatedly obtained and compared to the reference second endpoint specification 186 stored in memory 182. When the IR spectrum of the mixture matches the reference second endpoint specification 186, the desired ratio of ethanol to water is achieved. The ratio of ethanol to water can also be monitored throughout the process, and the processor 180 can recommend adding water or ethanol as needed to keep the composition on target.

[0055] FIG. 17 shows an alternative apparatus and method for determining the concentration of components in the bath solution 102 using short wavelength IR spectra. Instead of using a spectrometer, an IR source 190 having wavelengths at the absorption peaks that uniquely identify the fluid components can be projected through the bath solution 102 mixture and captured by an electromagnetic radiation sensor 115 sensitive to these wavelengths. Filters can be added to allow independent measurement of the transmittance at the two wavelengths. Alternatively, the IR source 190 can be flashed on and off in sync with the electromagnetic radiation sensor 115 to independently measure the transmittance at the different wavelengths. This apparatus and method is less costly than a spectrometer.

[0056] For example, a mixture containing 200 parts ethanol and 220 parts water has a mean of 3391 cm -1 The broad absorption peaks (troughs) of ethanol at 210 and 3266 cm -1 The broad absorption peak (trough) of water at 1055 cm interferes with this and therefore cannot be used. -1 The absorption peak (trough) at 212 is specific to ethanol and at 1634 cm-1 The absorption peak (trough) 226 at is unique for water. The intensity of the transmitted radiation from the two IR sources 190 at these two wavelengths can be captured by the electromagnetic radiation sensor 115 and compared by the processor 180 to the reference first endpoint intensity 194 and the reference second endpoint intensity 196 stored in the memory 182. When the electromagnetic radiation sensor 115 data matches the reference first endpoint intensity 194, the desired ratio of ethanol to water has been achieved. This example is for illustrative purposes only. Other fluid mixtures containing components with unique infrared absorption peaks at other wavelengths can be used as well.

[0057] Here, exemplary embodiments of the present invention are summarized. Other embodiments may be understood from the entire specification and claims filed herewith. Reference numbers are added below for illustrative purposes only, and various examples may be implemented in different ways and should not be construed as being limited to only these examples.

[0058] Example 1. A method for processing a plurality of substrates includes immersing a plurality of substrates in a bath solution (102) contained within a bath (100), generating gas bubbles (110) in the bath solution (102), projecting light from a light source (112) toward the bath, capturing light emanating from the bath after interaction with the gas bubbles (110) with a light sensor (114) to generate light sensor data, and converting the light sensor data into a metric of the bath solution.

[0059] Example 2. The method of example 1, wherein generating the gas bubbles (110) comprises injecting the gas bubbles (110) through a gas injector (108) or boiling the bath solution.

[0060] Example 3. The method of example 1 or 2, wherein the bath solution metric comprises static bubble size and count density, dynamic bubble size and count density, static bubble uniformity, dynamic bubble uniformity, bath solution uniformity, or bubble generation rate.

[0061] Example 4. The method of any one of Examples 1-3, wherein projecting light from a light source (112) toward the bath includes illuminating multiple zones of the bath solution with multiple light sources spaced across an outer dimension of the bath; generating light sensor (114) data by capturing light emanating from the bubbles (110) includes capturing light emanating from a first zone of the multiple zones with a first light sensor (114A) of the light sensor (114) and capturing light emanating from a second zone of the multiple zones with a second light sensor (114B) of the light sensor (114); and converting the light sensor data to a metric of the bath solution includes comparing bubble characteristics in the first zone to bubble characteristics in the second zone based on the light sensor data.

[0062] Example 5. The method of any one of Examples 1-4, wherein an outer dimension of the bath is parallel to the major surfaces of the plurality of substrates, the first zone includes a first portion of the major surfaces of the plurality of substrates, and the second zone includes a second portion of the major surfaces of the plurality of substrates.

[0063] Example 6. The method of any one of Examples 1-4, wherein an outer dimension of the bath is perpendicular to a major surface of the plurality of substrates, the first zone includes a first portion of a gas injector (108) having a first orifice, and the second zone includes a second portion of a gas injector (108) having a second orifice.

[0064] Example 7. The method of any one of Examples 1-6, wherein illuminating the multiple zones of the bath solution with the multiple light sources includes illuminating the first zone with a first light at a first wavelength and illuminating the second zone with a second light at a second wavelength, the second wavelength being different from the first wavelength, and capturing the light further includes using a first filter to capture the light of the first wavelength and using a second filter to capture the light of the second wavelength.

[0065] Example 8. The method of any one of Examples 1 to 6, wherein the multiple light sources include lights configured to be periodically turned on and off with a duty cycle, and illuminating the multiple zones includes flashing the first zone at a first frequency synchronized with a first light sensor, and flashing the second zone at a second frequency synchronized with a second light sensor.

[0066] Example 9. The method of any one of Examples 1-6, wherein projecting light from the light source (112) toward the bath includes forming a plane of laser (116) light above the surface of the bath solution, and generating light sensor data further includes capturing light emitted from droplets generated by bubbles (110) bursting at the surface of the bath solution, and the bath solution metrics include bubble burst uniformity across the surface of the bath solution or bubble burst rate at the surface of the bath solution.

[0067] Example 10. The method of any one of Examples 1-6, 9, wherein projecting light from the light source toward the bathtub includes redirecting the light with a prism bar (122).

[0068] Example 11. A bath processing tool (10) includes a bath with a loading arm and configured to hold a bath solution (102), a light source (112) mounted on a light source mounting assembly for projecting light toward the bath, and a light sensor (114) mounted on a sensor mounting assembly (30) for capturing light emanating from the bath after interaction with air bubbles (110) generated in the bath solution (102).

[0069] Example 12. The bath processing tool of Example 11, further comprising a gas injector (108) having an orifice (109) for releasing air bubbles (110) disposed beneath the loading arm, or a heating element (107) for causing boiling of the bath solution, or an inlet (103 / 108) for flow of reactants into the bath solution, the inlet being configurable to cause boiling of the bath solution.

[0070] Example 13. A bath processing tool as described in Example 11 or 12, wherein the light source (112) includes a quartz gas injector with integrated light emitting diodes (LEDs), a quartz gas injector rod configured to redirect light into multiple zones of the bath, a quartz loader arm with integrated LEDs, a quartz loader arm configured to redirect light into multiple zones of the bath, or a ring illuminator surrounding a light sensor.

[0071] Example 14. A bath treatment tool described in any one of Examples 11 to 13, wherein the light source (112) includes multiple light sources spaced across the exterior dimensions of the bath to illuminate different zones of the bath solution, and the light sensor (114) includes multiple light sensors configured to sense light from the multiple light sources.

[0072] Example 15. The bath treatment tool of any one of Examples 11 to 14, wherein the light source (112) comprises a plurality of light sources having different wavelengths.

[0073] Example 16. A bath processing tool described in any one of Examples 11 to 13, wherein the light source (112) includes a laser (116) configured to generate a plane of laser light above the surface of the bath solution in the bath, and the light sensor (114) includes a charge-coupled device (CCD) image sensor or a CMOS array sensor positioned above the plane of the laser light and configured to capture light emitted from gas bubbles bursting on the surface of the bath solution.

[0074] Example 17. A bath treatment tool described in any one of Examples 11 to 13, wherein the light source (112) includes a first prism bar configured to redirect light toward a light sensor or to redirect light toward a second prism bar configured to redirect light toward a light sensor.

[0075] Example 18. A bath processing tool includes a bath for wet processing a wafer (104), an electromagnetic radiation sensor for capturing electromagnetic signals from a bath solution in the bath, a processor (180), and a non-transitory memory (182) storing a program and coupled to the processor (180), the non-transitory memory including instructions that, when executed in the processor, determine a metric of the bath solution based on the electromagnetic signal, and identify that a target specification for processing the wafer has been reached based on the bath solution metric.

[0076] Example 19. The bath processing tool of example 18, wherein the metric is an endpoint metric and the processor is configured to terminate the process.

[0077] Example 20. A bath processing tool as described in Example 18 or 19, wherein the metric is a process target specification and the processor is configured to make adjustments to the flow of gas, make adjustments to the power to the heating element, or make adjustments to the flow of bath solution components to keep the bath at the process target specification.

[0078] Example 21. A bath processing tool described in any one of Examples 18 to 20, wherein the electromagnetic radiation sensor includes a long-wavelength infrared camera or a visible light camera, and the instructions for determining an endpoint metric of the bath solution further include instructions for determining the temperature of the bath solution with the long-wavelength infrared camera or determining the color of the bath solution with the visible light camera.

[0079] Example 22. A bath processing tool described in any one of Examples 18 to 20, wherein the electromagnetic radiation sensor includes a short wavelength camera or a short wavelength camera having a variable wavelength filter, and the instructions for determining an endpoint metric of the bath solution further include instructions for determining the concentration of a component in the bath solution with the short wavelength camera or determining the spectrum of a component in the bath solution with the short wavelength camera having a variable wavelength filter.

[0080] Example 23. The bath processing tool of any one of Examples 18-22 further includes an electromagnetic radiation source configured to generate an electromagnetic signal, the electromagnetic radiation source including a plurality of electromagnetic radiation sources, each of the plurality of electromagnetic radiation sources having a different short infrared wavelength configured to project the short infrared wavelength through the bath solution, an electromagnetic radiation sensor configured to capture the short infrared wavelengths transmitted through the bath solution, and an endpoint metric of the bath solution includes a spectrum of components in the bath solution.

[0081] Example 24. An endpoint detection method comprising: processing a wafer with a wet process; capturing an electromagnetic signal (176) from a bath solution (102) in a bath during processing with an electromagnetic radiation sensor (115); determining an endpoint metric of the bath solution based on the electromagnetic signal; and stopping the wet process in response to identifying that an endpoint of the processing has been reached based on the endpoint metric of the bath solution.

[0082] Example 25. The method of Example 24, wherein determining the endpoint metric of the bath solution includes determining the temperature of the bath solution with a long wavelength infrared camera, determining the color of the bath solution with a visible light camera, determining the concentration of a component in the bath solution with a short wavelength camera, or determining the spectrum of a component in the bath solution with a short wavelength camera having a variable wavelength filter.

[0083] Example 26. A process control method comprising: processing a wafer with a wet process; capturing an electromagnetic signal (176) from a bath solution (102) in a bath during processing with an electromagnetic radiation sensor (115); determining a process target specification for the bath solution based on the electromagnetic signal; and adjusting the bath solution in response to the determination of the process target specification based on the process target specification for the bath solution.

[0084] Example 27. The method of example 26, wherein adjusting the bath solution includes adjusting the flow of gas, adjusting power to the heating element (107), or adjusting the flow of a bath solution component to maintain the bath within a process target specification.

[0085] Although the present invention has been described with reference to exemplary embodiments, this specification is not intended to be construed in a limiting sense. Various modifications and combinations of those exemplary embodiments, as well as other embodiments of the present invention, will become apparent to those skilled in the art upon reference to this specification. It is therefore intended that the appended claims cover any such modifications or embodiments.

Claims

1. 1. A method for processing a plurality of substrates, comprising: immersing the plurality of substrates in a bath solution contained within a bath; generating gas bubbles in the bath solution; projecting light from a plurality of light sources toward the bath, each of a plurality of precursor substrates extending across a plurality of zones, the plurality of zones being illuminated by two or more of the plurality of light sources; generating light sensor data by capturing light emitted from the bathtub after interaction with the air bubbles with a light sensor; converting the light sensor data to a metric of the bath solution, comprising generating zone comparison data across the wafer based on comparing light emitted from one of the plurality of zones to light emitted from another of the plurality of zones; The method comprising:

2. The method of claim 1 , wherein generating the gas bubbles comprises injecting the gas bubbles through a gas injector or boiling the bath solution.

3. The method of claim 1 , wherein the metrics of the bath solution include static bubble size and count density, dynamic bubble size and count density, static bubble uniformity, dynamic bubble uniformity, bath solution uniformity, or bubble generation rate.

4. projecting the light from a plurality of light sources toward the bath comprises illuminating the plurality of zones of the bath solution with a plurality of light sources spaced across an outer dimension of the bath; The step of generating light sensor data by capturing light emitted from the air bubble includes: capturing light emitted from a first one of the zones with a first one of the light sensors; capturing light emitted from a second one of the plurality of zones with a second one of the light sensors; having 2. The method of claim 1, wherein converting the optical sensor data into the metric of the bath solution comprises comparing a bubble characteristic in the first zone to a bubble characteristic in the second zone based on the optical sensor data.

5. the outer dimension of the bath is parallel to major surfaces of the substrates; the first zone includes first portions of the major surfaces of the plurality of substrates; The method of claim 4 , wherein the second zone comprises a second portion of the major surfaces of the plurality of substrates.

6. the outer dimension of the bath is perpendicular to major surfaces of the substrates; the first zone includes a first portion of a gas injector having a first orifice; The method of claim 4 , wherein the second zone comprises a second portion of the gas injector having a second orifice.

7. illuminating a plurality of zones of the bath solution with a plurality of light sources comprises illuminating the first zone with a first light at a first wavelength and illuminating the second zone with a second light at a second wavelength; the second wavelength is different from the first wavelength; The step of capturing the light further comprises: capturing light at the first wavelength with a first filter; capturing light at the second wavelength with a second filter; 5. The method of claim 4, comprising:

8. the plurality of light sources having illumination configured to be periodically turned on and off in a duty cycle; The step of irradiating the plurality of zones comprises: flashing the first zone at a first frequency synchronous with the first photosensor; flashing the second zone at a second frequency synchronous with the second photosensor; 5. The method of claim 4, comprising:

9. projecting light from the plurality of light sources toward the bath includes forming a plane of laser light above a surface of the bath solution; generating light sensor data further comprises capturing light emitted from a droplet created by the bursting of the gas bubble at the surface of the bath solution; The method of claim 1 , wherein the metric of the bath solution comprises a bubble burst uniformity across the surface of the bath solution or a bubble burst rate at the surface of the bath solution.

10. The method of claim 1 , wherein projecting the light from the multiple light sources toward the bathtub comprises redirecting the light with a prism bar.

11. The method of claim 1, wherein the step of capturing light emitted from the bath includes scanning the optical sensor along a diameter of the plurality of substrates.

12. The method of claim 1, wherein generating the bubbles comprises injecting the bubbles through a plurality of gas injectors oriented along a first direction; each of the plurality of gas injectors has a plurality of orifices having openings oriented along a second direction orthogonal to the first direction; The method of claim 1 , wherein the light beams from the multiple light sources are directed along the second direction.

13. A method for processing a plurality of substrates, comprising the steps of: immersing the plurality of substrates in a bath solution contained within a bath having a wafer loading arm extending along a first direction; holding the plurality of substrates in the bath solution with the wafer loading arm, wherein adjacent substrates of the plurality of substrates are held along the first direction and each of the plurality of substrates has a diameter along a second direction orthogonal to the first direction; generating gas bubbles in the bath solution from a plurality of gas injectors oriented along the first direction; projecting light from a plurality of light sources toward the plurality of substrates, the plurality of light sources having a first light source emitting light at a first wavelength toward a first zone and a second light source emitting light at a second wavelength toward a second zone, the second wavelength being different from the first wavelength, the first zone and the second zone having different volumes of bath solution along the first direction, each of the plurality of gas injectors having a plurality of orifices with openings oriented along a third direction orthogonal to the first direction and the second direction, and light beams from the plurality of light sources being directed along the third direction; generating optical sensor data based on capturing light emitted from air bubbles in the bath solution at an optical sensor, the capturing of light further comprising capturing light of the first wavelength from the first zone using a first optical sensor and a first filter and capturing light of the second wavelength from the second zone using a second optical sensor and a second filter; converting the optical sensor data into a metric of the bath solution; The method comprising:

14. The method of claim 13, wherein the metrics of the bath solution include static bubble size and count density, dynamic bubble size and count density, static bubble uniformity, dynamic bubble uniformity, bath solution uniformity, or bubble occurrence rate.

15. A method for processing a plurality of substrates, comprising the steps of: immersing the plurality of substrates in a bath solution contained within a bath having a wafer loading arm extending along a first direction; holding the plurality of substrates in the bath solution with the wafer loading arm, wherein adjacent substrates of the plurality of substrates are held along the first direction and each of the plurality of substrates has a diameter along a second direction orthogonal to the first direction; generating gas bubbles in the bath solution from a plurality of gas injectors oriented along the first direction; projecting light from a plurality of light sources toward the plurality of substrates, the plurality of light sources having a first light source emitting light at a first wavelength toward a first zone and a second light source emitting light at a second wavelength toward a second zone, the second wavelength being different from the first wavelength, and the first zone and the second zone having different volumes of bath solution along the first direction; generating optical sensor data based on capturing light emitted from air bubbles in the bath solution at an optical sensor, the capturing of light further comprising capturing light of the first wavelength from the first zone using a first optical sensor and a first filter and capturing light of the second wavelength from the second zone using a second optical sensor and a second filter; converting the optical sensor data into a metric of the bath solution; having The method, wherein the plurality of light sources are disposed within the plurality of gas injectors, and projecting light from the plurality of light sources comprises projecting light of a different wavelength from each of the plurality of gas injectors.

16. The plurality of light sources having illumination configured to be periodically turned on and off in a duty cycle; The step of projecting light from a plurality of light sources includes: flashing the first zone at a first frequency synchronous with the first photosensor; flashing the second zone at a second frequency synchronous with the second photosensor; 14. The method of claim 13, comprising:

17. The method of claim 15, wherein the metrics of the bath solution include static bubble size and count density, dynamic bubble size and count density, static bubble uniformity, dynamic bubble uniformity, bath solution uniformity, or bubble occurrence rate.

18. The plurality of light sources include illumination configured to be periodically turned on and off in a duty cycle; The step of projecting light from a plurality of light sources includes: flashing the first zone at a first frequency synchronous with the first photosensor; flashing the second zone at a second frequency synchronous with the second photosensor; 16. The method of claim 15, having the following structure:

19. The gas injectors, each of which has a plurality of orifices having openings oriented along a third direction orthogonal to the first direction and the second direction; The method of claim 15 , wherein the light beams from the multiple light sources are directed along the third direction.

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