Crystal oscillator microbalance (QCM) sensor with rapid recording response

Abstract

A method of manufacturing a quartz crystal microbalance (QCM) sensor for monitoring semiconductor processes includes the steps of (i) providing a quartz crystal configured to measure the mass of material deposited on its surface, and (ii) increasing the surface area for rapid deposition of mass by modifying the surface of the quartz crystal by increasing the number of surface defects per unit area. The change in mass of the quartz crystal is recorded as a result of a change in the resonant frequency of the quartz crystal when pulsed with an AC power source. The surface modification enhances the recorded response of the QCM sensor when exposed to a deposition process.

Description

Technical Field

[0001] Cross - reference to Related Applications In accordance with 35 U.S.C. § 119 and the relevant parts of 37 CFR 1.53, this application claims the benefit and priority of U.S. Patent Application No. 63 / 223,333, filed on July 19, 2021, the entire content of which is incorporated herein by reference.

Background Art

[0002] Deposition processes and etching processes are two important steps in the manufacturing sites of numerous industries. In manufacturing factories, often an integrated group of sensors such as mass spectrometers, optical spectrometers, RF sensors, vacuum gauges, etc. are well - used to monitor these processes. These sensors provide detailed information about the materials deposited on or removed from the substrate, but it takes a great deal of effort to correlate the data collected by these sensors with each other to monitor the actual film accumulation or removal on the substrates within various chambers.

[0003] One of the most well - known and versatile sensors applied to monitor film growth rate is the Quartz Crystal Microbalance (QCM) sensor. These sensors are also known as Quartz MicroBalance (QMB) sensors and Quartz Crystal Nanobalance (QCN) sensors, and measure mass changes by measuring changes in the resonance frequency of a quartz crystal. The resonance frequency changes due to the addition or subtraction of mass on the crystal surface by film deposition / removal on the surface of the acoustic resonator.

[0004] In a typical deposition process, the material to be coated onto the target substrate arrives from a source by evaporation or sublimation and condenses on the substrate to form the desired film. Since the physical and electrical properties of this film are often determined by factors such as the substrate temperature and the condensation rate of the material, it is crucial to have complete control over the evaporation / sublimation rate before actual deposition on the substrate. QCM sensors, positioned near the substrate, serve as an alternative means of reflecting the deposition rate and accumulated thickness. Due to the strong correlation between the evaporation rate of the source and the QCM detection rate, QCM sensors have proven to be a passively or actively effective means of controlling the deposition process.

[0005] QCM sensors are consumable devices that need to be replaced periodically and routinely in a continuous substrate manufacturing process. Conventional QCM sensors function for a predetermined period (i.e., several minutes to several hours), and when one QCM sensor is used up, another QCM sensor needs to be replaced in place at the monitoring location while the deposition process continues. More specifically, several QCMs may be housed in a carousel and rotated in sequence to replace each crystal consumed during process monitoring. Generally, only one QCM is used to monitor a specific location at a specific time. When this QCM sensor reaches the end of its service life, it is replaced by a new QCM sensor that has been moved forward and positioned in place under the shuttered section of the carousel.

[0006] Theoretically, each newly replaced crystal should immediately record the evaporation rate of the previously defined source for optimal manufacturing control. Unfortunately for many deposition materials, QCM sensors typically exhibit a short but significant delay before reaching the response time required to accurately record the precise steady-state response—that is, the accurate rate of material deposition. Such delays can cause the power supply to react incorrectly, sending erroneous signals to the source control, resulting in a temporary increase in evaporation / sublimation capacity and significant errors in the actual film thickness of the substrate. While such errors are negligible for some materials, for others, various efforts to mitigate the problems caused by the monitoring delay by the QCM sensor have proven unsuccessful.

[0007] Magnesium is one of many materials that QCM sensors exhibit significant delays in initial detection. Currently, there is no available solution for rapidly responding to or recording the true magnesium deposition rate. To mitigate response delays, operators are known to pre-coat QCM crystal oscillators with a small amount of magnesium in the same process chamber before receiving actual measurements. This additional step is labor-intensive and adds material costs, making it impractical to perform as part of crystal oscillator manufacturing. Furthermore, the magnesium-precoated surface layer cannot withstand prolonged exposure to the atmosphere for the purpose of transportation and / or storage convenience. [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, there is a need for a QCM sensor that can rapidly detect or record the true source flux in the Mg coating deposition process. [Means for solving the problem]

[0009] One embodiment of the present disclosure provides a method for manufacturing a quartz crystal microbalance (QCM) sensor for monitoring a semiconductor process, comprising the steps of (i) providing a quartz crystal configured to measure the mass of material deposited on its surface, and (ii) increasing the surface area for rapid mass deposition by modifying the surface of the quartz crystal by increasing the number of surface defects per unit area. The mass change of the quartz crystal is registered as a result of a change in the resonant frequency of the quartz crystal when pulsed by an AC power supply. The surface modification enhances the registration response of the QCM sensor when exposed to the deposition process.

[0010] In another embodiment, a quartz crystal microbalance (QCM) sensor is used to monitor a thin film deposition process, with a quartz crystal disk positioned between a pair of conductive electrodes, and this quartz crystal disk is configured to measure the mass of the film deposited on its own surface. The surface of the quartz crystal disk is modified so that the number of defects increases beyond a threshold number per unit area along the surface. The mass change is recorded as a result of the change in the resonant frequency of the quartz crystal disk when pulsed by an AC power supply. The modified surface increases the surface area for rapid mass deposition and enhances the recording response of the QCM sensor.

[0011] In one embodiment of the present disclosure, the amount of surface defects on the electrode surface of the QCM ranging from nanometer to submillimeter scales is significantly increased. In a microscopic sense, the generated surface structural defects can take the form of pits, edges, islands, or any combination thereof.

[0012] In another embodiment, nonmetallic elements (such as hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon, radon, bromine, carbon, phosphorus, sulfur, selenium, and iodine) and metalloid elements (such as boron, silicon, germanium, arsenic, antimony, and tellurium) are adsorbed onto the surface of a crystalline electrode. The elements added to the surface may be a single species or any combination of nonmetallic and / or metalloid elements. Furthermore, the structure of these added nonmetallic and metalloid elements formed on the surface can be in any form, such as adsorbed atoms, clusters, regular or irregular nanopatterns, partial layers, complete layers, or multilayers.

[0013] The embodiments described above are merely illustrative. Other embodiments described herein are within the scope of the disclosed subject matter. [Brief explanation of the drawing]

[0014] To enable understanding of the features of this disclosure, specific embodiments are described in detail with reference, some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings only show specific embodiments and should not be considered limiting the scope, as the scope of the disclosed subject matter also encompasses other embodiments. The drawings are not necessarily to scale and are generally focused on illustrating the features of specific embodiments. In the drawings, similar reference numerals are used to indicate similar parts in different drawings.

[0015] [Figure 1] This is a separated perspective view of a quartz crystal microbalance (QCM) sensor having a quartz crystal disc positioned between conductive electrodes along each of its surfaces. [Figure 2A] Figure 1 is a bottom view of the quartz crystal microbalance (QCM) sensor. [Figure 2B] Figure 1 is a top view of the quartz crystal microbalance (QCM) sensor. [Figure 3]This is a magnified view of the surface of a processed quartz crystal microbalance (QCM) sensor manufactured according to the teachings of this disclosure, the sensor surface being topologically modified, the topological modification increasing surface defects within a fixed area and improving the response speed of the sensor. [Figure 4] This is a magnified view of a modified quartz crystal microbalance (QCM) sensor, in which the sensor surface on a square submicrometer scale has been treated by adsorption of nonmetallic and metalloid elements to improve the response speed of the QCM sensor. [Figure 5] This is a magnified view of a modified QCM sensor surface on a square submicrometer scale, where the sensor surface is (i) topologically modified to increase the amount of surface defects, and (ii) treated by adsorption of nonmetallic and semimetallic elements to improve the response speed of the QCM sensor. [Figure 6] This graph compares the response speed associated with a conventional QCM sensor with the response speed associated with a modified / processed QCM sensor manufactured according to the teachings of this disclosure. [Figure 7] This graph compares the response speed associated with multiple conventional QCM sensors with the response speed associated with the same number of modified / processed QCM sensors. [Figure 8] This graph compares the overall sensor stability of conventional QCM sensors and modified / processed QCM sensors over multiple time periods in monitoring deposition rates.

[0016] Corresponding reference letters indicate the corresponding parts through several figures. The examples described herein illustrate several embodiments but should not be construed as limiting the scope. [Modes for carrying out the invention]

[0017] In Figures 1, 2A, and 2B, the perspective, bottom, and top views of the quartz crystal microbalance (QCM) sensor 10 include conductive electrodes 20 and 24 positioned on each side of the quartz crystal disk 30, respectively. A pair of connectors 40a and 40b are positioned on each side of the quartz crystal disk 30 and connected to the conductive electrodes 20 and 24, respectively, thereby recording changes in the frequency of the quartz crystal as its mass changes, i.e., in response to deposition and / or etching processes. When in use, the QCM sensor 10 is positioned near an area or region being monitored within the process chamber of a semiconductor or organic light-emitting diode (OLED) manufacturing system. Changes on the surface of the QCM can be correlated with the same process being performed on the surface of the substrate material within the process chamber. More specifically, the QCM sensor 10 has resonant properties that change during material deposition. Changes in mass alter the resonant response of the QCM crystal, which indicates that expected changes are occurring on the substrate surface.

[0018] As described in the background art of the present invention, the QCM sensor 10 is a consumable item and needs to be replaced periodically during the manufacturing cycle. Furthermore, such a QCM sensor 10 typically requires a short but significant period of time to adapt to process conditions before it can record an accurate response. In efforts to improve the response speed of the QCM sensor 10, the inventors have recognized that surface modification of the QCM sensor 10 can significantly reduce the time required to adapt the QCM sensor 10 to process chamber conditions.

[0019] In FIG. 3, the first modified QC surface 100 of the crystal oscillator (QC) 30 is manufactured in accordance with the teachings of the present disclosure. Here, the QC surface 100 exhibits a plurality of topological depressions, defects, and contours / edges 104, 106, 108 (hereinafter collectively referred to as surface modifications or surface defects) over a sub-micrometer scale surface area. As shown, as the proportion of defects 104, 106, 108 within the fixed area increases, the ability of the sensor to efficiently and rapidly adhere deposited material is enhanced. More specifically, the surface modifications are on the scale of (i) angstroms to (ii) dozens of nanometers. At this extremely small size, comparable to the size of atoms and molecules, surface defects can effectively capture deposited atoms or molecules. The surface modification of the electrodes improves the efficiency and capacity of the QCM for monitoring deposited atoms or molecules.

[0020] In FIG. 4, another embodiment of the present disclosure includes a square sub-micrometer processing surface 102 having non-metallic elements 120 and / or semi-metallic elements 122 adsorbed by the QC to increase the response speed of the QCM sensor 30. The non-metallic element 120 may include elements selected from the group consisting of hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon, radon, bromine, carbon, phosphorus, sulfur, selenium, and iodine. The semi-metallic element 122 may include elements selected from the group consisting of boron, silicon, germanium, arsenic, antimony, and tellurium. The structures of these additional non-metallic elements 120 and semi-metallic elements 122 can be in various forms including adsorbed atoms, clusters, and regular or irregular nanopatterns. The surface distribution of the non-metallic elements and / or semi-metallic elements can also be in various forms including a random distribution, irregular groups 124 (shown in the lower left corner) or patterned groups 128 (shown in the upper right corner).

[0021] In FIG. 5, another embodiment shows a modified / processed QCM surface 103 including surface modifications 104, 106, 108, where the surface modifications 104, 106, 108 each represent the addition of pits (such as those shown in FIG. 3) with area dimensions spanning square sub-micrometers, in combination with adsorbed non-metallic elements 120 and / or semi-metallic elements 122 (such as those described in relation to FIG. 4). The QCM sensor surface 103 is modified by (i) increasing the amount of surface defects and (ii) treated by the adsorption of non-semimetallic elements 120, 122. Thus, at least one of the aforementioned surface treatments may be performed to improve the response speed of the QCM sensor 30.

[0022] In FIG. 6, the graph shows a comparison between a conventional QCM sensor and a modified QCM sensor. This graph plots the response speed (at a data collection rate of 10 Hz) against time (in minutes) for a first curve 200 related to a conventional QCM sensor of the prior art and a second curve 300 related to the modified QCM sensor. Examining curve 200, it is clear that the performance gradually improves over a period T200 of about 4 - 5 minutes. The steady-state condition is reached when curve 200 produces a steady response, at which point the performance is optimized. Examining curve 300, it is clear that the performance improves almost instantaneously over a period T300 of less than about 5 seconds and reaches the optimal performance condition. Thus, the modified QCM sensor has a significantly improved performance readiness compared to the conventional QCM sensor.

[0023] In Figure 7, the graph shows a comparison between several conventional QCM sensors and modified QCM sensors. The graph plots the response speeds of six conventional sensors and six modified sensors. Examining curves 200-1, 200-2, 200-3, 200-4, 200-5, and 200-6, it is clear that all six conventional QCM sensors 30 show a gradual improvement in performance over a TTR of 200 or approximately 4-5 minutes. On the other hand, curves 300-1, 300-2, 300-3, 300-4, 300-5, and 300-6, associated with the modified QCM sensors, show nearly instantaneous response speeds over a TTR of only a few seconds. As before, this graph shows the degree of consistency that can be achieved when a modified QCM sensor is applied.

[0024] In Figure 8, the graph shows the response speed over an entire manufacturing cycle of approximately 5 hours for several conventional QCM sensors and several modified QCM sensors. Specifically, the graph plots the response speeds of six conventional sensors and six modified sensors. Examining curves 200-1, 200-2, 200-3, 200-4, 200-5, and 200-6, it is clear that all six conventional QCM sensors exhibit stable speed monitoring performance over a TTC200 period of a 4-5 hour manufacturing cycle. Similarly, curves 300-1, 300-2, 300-3, 300-4, 300-5, and 300-6 show the same performance characteristics over the same period TTC300 (TTC300=TTC200). Therefore, there is no performance loss as a result of QCM sensor processing.

[0025] In summary, crystals produced by conventional methods have a surface roughness of one-tenth of the micrometer scale, i.e., too large compared to the size of the deposited atoms or molecules. In other words, within a randomly selected area on the nanometer scale, the electrode surface appears locally flat overall. In this disclosure, external impacts of atoms, molecules, and / or ions generate extremely small surface defects on the angstrom to tens of nanometer scales. At this extremely small size, i.e., comparable to the size of atoms and molecules, the defects can effectively trap the deposited atoms or molecules. This large number of surface defects increases the capacity of the QCM electrode when monitoring deposited atoms or molecules.

[0026] In one embodiment, defects of a desired size and quantity are fabricated on the crystal surface 30 while maintaining the underlying electrode-quartz interface, i.e., while having a conventionally smooth surface. External impacts of atoms, molecules, and / or ions are carefully selected and precisely controlled to impact the surface with a time and energy amount exceeding a threshold during the processing. Under certain conditions, if the impact energy is too low, defects cannot be effectively generated, and under other conditions, if the processing time is insufficient, the amount of surface defects per unit area may be insufficient. Under yet another condition, very high impact energy or excessively long processing may destroy the QCM electrode surface, causing sound waves to scatter randomly and become non-coherent. As a result, the QCM becomes unstable for precise velocity / thickness monitoring.

[0027] Additional embodiments include any one of the embodiments described above, wherein one or more of its components, functions, or structures are replaced, substituted, or enhanced with one or more of the components, functions, or structures of the different embodiments described above.

[0028] It should be understood that various modifications and alterations to the embodiments described herein will be obvious to those skilled in the art. Such modifications and alterations can be made without departing from the spirit and scope of this disclosure and without impairing the intended advantages. Accordingly, such modifications and alterations are intended to be covered by the appended claims.

[0029] While some embodiments of this disclosure are disclosed in the preceding specification, it will be understood by those skilled in the art that many modifications and other embodiments of this disclosure are conceivable within the scope of this disclosure, having a benefit of teaching presented in the foregoing description and the associated drawings. Therefore, it should be understood that this disclosure is not limited to any specific embodiments beyond those disclosed herein, and that many modifications and other embodiments are intended to be included within the scope of the appended claims. Furthermore, while certain terms are used herein and in the claims, they are used only in a general and descriptive sense and are not intended to limit the scope of this disclosure and the claims.

Claims

1. A method for manufacturing a quartz crystal microbalance (QCM) sensor used to monitor semiconductor processes, A step of providing a quartz crystal oscillator configured to measure the deposition mass on its own surface, wherein the mass difference is recorded as a result of a change in the resonant frequency of the quartz crystal oscillator, The step includes modifying the surface of the quartz crystal oscillator, A method for enhancing the recording response of the QCM sensor by increasing the amount of surface defects in the step of modifying the surface and rapidly capturing the mass.

2. The method according to claim 1, further comprising the step of depositing a nonmetallic element onto the modified surface.

3. The method according to claim 1, further comprising the step of depositing a metalloid element onto the modified surface.

4. The method according to claim 2, wherein the nonmetallic element is selected from the group consisting of hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon, radon, bromine, carbon, phosphorus, sulfur, selenium, and iodine.

5. The method according to claim 3, wherein the metalloid element is selected from the group consisting of boron, silicon, germanium, arsenic, antimony, and tellurium.

6. The method according to claim 2, wherein the step of attaching the nonmetallic element is performed by adsorption.

7. The method according to claim 3, wherein the step of attaching the metalloid element is performed by adsorption.

8. The method according to claim 1, wherein the step of modifying the surface includes increasing the amount of defects to a submicrometer scale.

9. The method according to claim 1, wherein the step of modifying the surface includes surface modification on the order of angstroms.

10. The method according to claim 1, wherein the step of modifying the surface includes surface modification on the order of one-tenth of a nanometer.

11. A quartz crystal microbalance (QCM) sensor used to monitor thin film deposition processes, A quartz crystal disk is positioned between a pair of conductive electrodes and configured to measure the accumulated mass on the surface of the quartz crystal. The mass change is recorded as a result of the change in the resonant frequency of the quartz crystal oscillator, A quartz crystal microbalance (QCM) sensor, wherein the surface of the quartz crystal is modified by increasing the amount of surface defects in order to enhance the recording response of the quartz crystal.

12. The QCM sensor according to claim 11, further comprising a metalloid element attached to the modified surface of the quartz crystal oscillator.

13. The QCM sensor according to claim 11, further comprising a non-metallic element attached to the modified surface of the quartz crystal oscillator.

14. The QCM sensor according to claim 11, further comprising a combination of a non-metallic element and a metallic element attached to the modified surface of the quartz crystal oscillator.

15. The QCM sensor according to claim 14, wherein the metalloid element includes an element selected from the group consisting of hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon, radon, bromine, carbon, phosphorus, sulfur, selenium, and iodine, and the nonmetalloid element includes an element selected from the group consisting of boron, silicon, germanium, arsenic, antimony, and tellurium.

16. A method for manufacturing a quartz crystal microbalance (QCM) sensor used to rapidly record a predetermined deposition rate, A method comprising the step of increasing the area ratio of defects on a QCM surface.

17. The method according to claim 16, further comprising the step of treating the QCM surface with a nonmetallic element.

18. The method according to claim 16, further comprising the step of treating the QCM surface with a metalloid element.

19. The method according to claim 17, wherein the nonmetallic element includes an element selected from the group consisting of hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon, radon, bromine, carbon, phosphorus, sulfur, selenium, and iodine.

20. The method according to claim 18, wherein the metalloid element includes an element selected from the group consisting of boron, silicon, germanium, arsenic, antimony, and tellurium.

21. The steps include treating the QCM surface with a nonmetallic element, The method according to claim 16, further comprising the step of treating the QCM surface with a metalloid element.

22. The method according to claim 21, wherein the step of treating the QCM surface includes thin film deposition selected from the group consisting of atomic layer deposition, chemical vapor deposition, atomic beam bombardment or ion beam bombardment and high-voltage sputtering.

23. The method according to claim 16, wherein the step of increasing the percentage of defects on the QCM surface is performed in a reaction environment including a liquid phase environment, a gas phase environment and a plasma phase environment.

24. The method according to claim 16, further comprising the step of modifying the surface of the quartz crystal oscillator by removing / peeling off a material from the surface of the quartz crystal oscillator.

25. The QCM sensor according to claim 15, wherein the precursor / reagent required to achieve surface adsorption can be one of a chemical form and a physical form, including atoms, ions, radicals and combinations thereof.

26. The QCM sensor according to claim 15, wherein the surface modification is performed on an existing quartz crystal oscillator.

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