The present application generally relates to semiconductor processing and specifically to a cleaning process on a substrate using a first step of immersion in a first treatment chemical and concurrently irradiating the substrate with ultra-violet (UV) light and a second step using a wet clean process using a second treatment chemical.
In semiconductor processing, control of generation and lifetime of active chemical species is important to optimize cleaning processes with respect to removal efficiency of desired material, process time, and selectivity to other materials present on the substrate. In aqueous and plasma chemistry, generation of radicals is a convenient way to generate highly reactive and targeted species to remove material. Radicals are generated by mixing of two or more chemicals, (e.g. sulfuric acid and hydrogen peroxide to form hydroxyl radicals) or by application of energy, for example, light, heat, electrical/magnetic force, electrochemical, or mechanical energy. Ion implanted photoresist is challenging to remove because a hard crust layer forms during the implant process on the photoresist. When a certain range of doses and energies are used to implant ions on the resist, these hard crust layers have to be removed using a plasma ashing step. There are two methods known to remove ion implanted resist at levels of 1e15 atoms/cm2 and higher. The first method is a two-step process using oxidizing/reducing plasma ash and a 120-140° C. sulfuric and peroxide mixture (SPM) wet process to remove residual organics. The challenge with this process is oxidization of the silicon substrate leading to loss of dopant in subsequent wet cleans. The second method is an all wet removal approach using SPM chemistry.
The challenge with all wet process removal or wet benches is that the SPM has to be heated to temperatures approaching 250° C. to achieve the desired resist removal performance and at a removal rate that is practical for manufacturing. Wet benches typically operate with SPM temperatures up to 140° C. To reach SPM temperatures of 250° C., one-pass single substrate process tools are required. However, over time, the SPM loses its activity as the sulfuric acid is diluted by the continuous replenishment of hydrogen peroxide that is required to retain its cleaning activity. With SPM, the best cleaning performance is achieved above 100 wt % total acid in the SPM. SPM below 80 wt % total acid has very poor cleaning performance and a fresh batch of 108-96 wt % sulfuric acid is often used. Methods exist to remove the excess water from the recycled SPM or using electrolyzed sulfuric acid to extend the usage life of the sulfuric acid. Both methods significantly increase the complexity, capital cost, and operating costs of the resist strip process. Similar considerations are also applicable to cleaning of substrates after an ashing process.
Later approaches include cleaning techniques using a two-step process with hydrogen peroxide and ultra violet (UV) light followed by a wet stripping process. One such technique is U.S. Patent Publication No. 2012/0052687, by Raghaven, et al.,(Raghaven), “Use of Catalyzed Hydrogen Peroxide (CHP) Chemical System for Stripping of Implanted State-of-the-Art UV Resists”, filed on Dec. 29, 2010, where a catalyzed hydrogen peroxide solution is used with UV light to disrupt the crust of implanted photoresist and subsequently removing the underlying photoresist with a sulfuric acid peroxide mixture (SPM) in a wet etch process. Effectiveness of this technique is limited by the specific ranges of concentration of the catalyzed hydrogen peroxide, temperature of the treatment liquids, and speed of rotation of the substrate.
Another technique is contained in U.S. application Ser. No. 13/670,381, by Brown, I J, “METHOD OF STRIPPING PHOTORESIST ON A SINGLE SUBSTRATE SYSTEM”, filed on Nov. 6, 2012 (Brown). Brown introduced operating variables consisting of UV wavelength, UV power, first rotation speed, first flow rate, second process time, second rotation speed, percentage of residue removal, and dispense temperature. The additional operating variables provide some flexibility to control the cleaning process, but some issues develop as the process is used in a manufacturing environment. Some of the issues include: a) rotation of bigger size substrates require new and stronger motors and associated housing, b) time constraints involved in starting up and stopping rotation of substrate increases with increasing size and speed, c) time needed to perform the softening of the residue is a function of at least two or more operating variables such as thickness of the first chemical film, rotation speed of the substrate, and exposure time to the UV light, concentration of the first chemical, and intensity of the UV light. The position of the nozzle relative to the substrate and flow rate of the first chemical also affects the cleaning of the substrate. In order to make single substrate cleaning of substrates economically feasible, these issues and operating challenges must be addressed when the cleaning process is implemented in production volume environment.
The amount of treatment liquid used in cleaning systems is cost item that requires attention as more cleaning systems switch to single substrate systems. The challenge with reducing the amount of treatment liquid used is that the substrate needs to be wet all throughout during the process, that is, no dry spots as these causes some of residue or irregularity in the end product. Efforts to reduce the amount of treatment liquid used must be considered at the same time as ensuring the substrate is always wet. Another factor that requires attention is that with the advent of larger substrates, the temperature from the center to the edge of the substrate may drop to an extent that the reaction between the treatment liquid and the substrate at the edge is not the same as it is close to the center. All of these considerations need to be optimized concurrently to ensure the absolute wetting of the substrate, maintain a temperature gradient on the treatment liquid within an acceptable range, and use the least amount of treatment liquid. In addition, there is a need for a stripping method and system that makes single substrate process tools competitive in terms of cost of ownership and higher reliability in addition to expanding the process window for the stripping an ion implanted resist or cleaning or performing a post-ash cleaning.
Provided is a method for cleaning an ion implanted resist layer or a substrate after an ashing process. A duty cycle for turning on and turning off flows of a treatment liquid in two or more nozzles is generated. The substrate is exposed to the treatment liquid comprising a first treatment chemical, the first treatment chemical with a first film thickness, temperature, total flow rate, and first composition. A portion of a surface of the substrate is concurrently irradiated with UV light while controlling the selected plurality of cleaning operating variables in order to achieve the two or more cleaning objectives. The cleaning operating variables comprise two or more of the first temperature, first composition, first film thickness, UV wavelength, UV power, first process time, first rotation speed, duty cycle, and percentage of residue removal. Two or more cleaning operating variables are optimized to achieve the two or more cleaning objectives comprising at least two of: (1) complete wetting of the surface of the substrate, (2) minimum amount of treatment liquid used, and (3) a target temperature profile of treatment liquid from center to edge of the substrate.
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With regards to nozzles, the selected two or more dispense devices can have varying sizes of dispense width. In one embodiment, the selected two or more dispense devices are positioned above the substrate according to a selected pattern, the selected pattern including a height from the substrate surface to the dispense device and distance between a central dispense device and each additional dispense device of the selected two or more dispense devices. In another embodiment, the selected two or more dispense devices can comprise a central nozzle and one or more additional nozzles located at selected distances from the central nozzle towards an edge of the substrate, the central nozzle configured with a flow rate lower than any of the one or more additional nozzles. The dispense width of a nozzle requires sufficient size to allow a continuous dispense of the treatment liquid at the selected flow rate of the dispense device. For example, the first delivery device nozzles needs to be configured to support a treatment liquid flow rate in a range from 15 to 500 mL/min, 15 mL/min, or less than 15 mL/min. In still another embodiment, selection and placement, the selected two or more dispense devices comprising of nozzles can be connected to a single supply line and the duty cycle requires sequential turning on and turning off from a central nozzle towards a nozzle closest to the edge of the substrate and from the nozzle closest to the edge of the substrate towards the central nozzle. In yet another embodiment, each dispense device of the selected two or more dispense devices can be independently connected to a supply line and can be turned on and turned off independently; and/or wherein the selected two or more dispense devices are disposed in a line pattern, a cross pattern, a 3-ray star pattern configuration; and/or wherein the selected two or more dispense devices can be turned on and turned off independently.
In operation 808, two or more cleaning objectives are selected. The two or more cleaning objectives can comprise least two of: (1) complete wetting of the surface of the substrate, (2) minimum amount of treatment liquid used, (3) a target temperature profile of treatment liquid from center to edge of the substrate, (4) total cleaning time, and the like. In operation 812, two or more cleaning operating variables to be optimized for achieving the two or more cleaning objectives are selected. In operation 816, a surface of the substrate is exposed to the treatment liquid comprising a first treatment chemical, the first treatment chemical with a first film thickness, a first temperature, the first total flow rate, and a first composition, and concurrently irradiating a portion of a surface of the substrate with UV light, the UV light having a wavelength and having a UV power, the irradiating operationally configured to be completed in a first process time, the irradiating performed while the substrate is in a first rotation speed.
In operation 820, the substrate is exposed to a second treatment liquid, the second treatment chemical having a second temperature, the second flow rate, and a second composition, a second process time, and second rotations speed. In operation, 824, the selected plurality of cleaning operating variables are controlled in order to achieve the two or more cleaning objectives. In operation 828, optionally recycling the first and second treatment chemicals so as to reduce treatment liquid usage. In operation 832, if the two or more cleaning objectives are not met, adjusting one or more of cleaning operating variables in order to meet the two or more cleaning objectives.
The controller 1090 can include computer capabilities a) to obtain metrology measurements and/or process measurements used to calculate a value for the selected one or more cleaning objectives, b) if the one or more cleaning objectives are not met, to adjust the process operating variables including adjusting the flow rate of the selected two or more dispense devices, rotation speed of the substrate, duty cycle of each of the selected two or more dispense devices until the one or more cleaning objectives are met. Moreover, the controller 1090 also contains logic circuitry or computer code to concurrently optimize a selected flow rate, dispense flow type, position of a dispense device, height of dispense, and duty cycle for turning on or turning off each of the selected two or more dispense devices, pattern used in positioning the selected two or more dispense devices, and rotation speed of the substrate. Operating data obtained from optimization tests are incorporated into procedures and recipes for combinations of substrate cleaning processes and cleaning operating variables are loaded into the controller 1090. The cleaning system is configured to run in either online mode with metrology feedback or offline mode that does not require continuous metrology feedback, instead using the procedures and recipes.
The cleaning system 1004 can use two or more optical metrology devices 1008. An optical emission spectroscopy (OES) device 1070 can be coupled to the processing chamber 1010 at a position to measure the optical emission from the processing region 1015. In addition, another set of optical metrology devices 1060 can be disposed atop the processing chamber 1010. Although four optical metrology devices are shown, many other alternative and different configurations of the optical metrology devices can be positioned to implement design objectives using a plurality of optical metrology devices. The four optical metrology devices can be spectroscopic reflectometric devices and/or interferometric devices. The measurements from the two or more optical metrology devices, for example, the OES device 1070 and the set of optical metrology devices 1060, are transmitted to the metrology processor (not shown) where one or more critical dimension values are extracted. Measurements can be performed with the one or more optical metrology device OES 1070 and/or the set of optical metrology devices 1060 and one or more etch sensor devices, 1064 and 1068.
As mentioned above, a process sensor device, for example, can be a residue sensor device 1064 measuring the percentage of residue remaining, or measuring a cleaning operating variable with a substantial correlation to percentage of residue removal. Another process sensor device can include a device measuring the partial pressure of oxygen or the oxygen and ozone partial pressures or the total pressure of the process gas. Selection of at least one or more process sensor devices can be done using multivariate analysis using sets of process data, metrology data (diffraction signals) and process performance data to identify these inter-relationships. The measurements from the two or more optical metrology devices, for example, the OES device 1070 and the set of optical metrology devices 1060 and the measurement from the sensor device 1064 and/or 1068 are transmitted to the metrology processor (not shown) where the operating variable values are extracted. Another process sensor device is a temperature measurement device that is used to the temperature of the treatment liquid along the radial line in order to determine the temperature gradient of the treatment liquid from the center to an edge of the substrate. The controller can compare the measured temperature gradient to the set temperature gradient for the application and adjust one or more of the cleaning operating variables to get the temperature to the acceptable range.
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Although only certain embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of this invention. For example, although one exemplary process flow is provided for cleaning of substrates, other process flows are contemplated. As also mentioned above, the cleaning method and system of the present invention can be used in an FEOL or BEOL fabrication cluster. Accordingly, all such modifications are intended to be included within the scope of this invention.a
Pursuant to 37 C.F.R. §1.78(a)(4), this application claims the benefit of and priority to prior filed co-pending Provisional Application Ser. No. 61/728,359, entitled “METHOD OF CONTROLLING TREATMENT LIQUID DISPENSE FOR SPINNING SUBSTRATES”, filed on Nov. 20, 2012, which is expressly incorporated herein by reference.
Number | Date | Country | |
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20150136183 A1 | May 2015 | US |
Number | Date | Country | |
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61728359 | Nov 2012 | US |