Method for implanting ions into a semiconductor structure - Patents.com

Abstract

A system is disclosed for implanting ions into a semiconductor structure. The semiconductor structure is placed on a heat sink 100 and ions are implanted through a front surface of the semiconductor structure to create a damaged region in the semiconductor structure. The coefficient of friction, e.g., the sliding angle, of the heat sink 100 is measured by a test fixture 300. The parameters are compared to a baseline range.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 132,156, filed December 30, 2020, which is incorporated by reference in its entirety. [Technical field]

[0002] The field of the disclosure relates to methods for implanting ions into semiconductor structures, and more particularly to methods in which a parameter related to the coefficient of friction of a heat sink on which the semiconductor structure is placed is measured. [Background technology]

[0003] Semiconductor structures can be implanted with ions to achieve desired physical, chemical, and electrical properties. For example, to form a silicon-on-insulator structure, a donor structure can be implanted with ions to form a damaged region in the structure, and then the structure can be cleaved.

[0004] During ion implantation, an ion beam (e.g., hydrogen atoms, helium atoms, or a combination of hydrogen and helium atoms) is directed at the semiconductor structures. A scan wheel may be used to support a batch of semiconductor structures during ion implantation. The semiconductor structures are arranged circumferentially about a central axis about which the scan wheel rotates. The scan wheel rotates to cause repeated passes of a stationary ion beam through the semiconductor structures, distributing the ions on the surface of the semiconductor structures. The temperature of the semiconductor structures during ion implantation is controlled to maintain a constant implantation.

[0005] During ion implantation, heat is generated in the semiconductor structure. A conventional method of controlling the temperature of the semiconductor structure is to dissipate the heat to a heat sink that is in contact with the semiconductor structure during ion implantation. The heat sink may be coated with a polymer coating, such as an elastomeric coating, to improve heat transfer between the semiconductor structure and the heat sink. The semiconductor structure may be removable from the heat sink so that the heat sink can be reused for multiple ion implantation processes. Over the life of the heat sink, mechanical wear and outgassing in the high vacuum environment of the ion processing system causes the elastomeric coating to deteriorate and wear out. Degradation of the coating reduces its ability to effectively transfer heat to the heat sink, causing variations in the temperature of the semiconductor structure, leading to production variations and loss.

[0006] What is needed is a method to evaluate the quality of a heat sink (e.g., a heat sink coating) and determine whether the heat sink is suitable for use during ion implantation or whether the heat sink needs to be reconditioned prior to the ion implantation process.

[0007] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below and / or claimed. This discussion is believed to be helpful in providing the reader with background information to better understand the various aspects of the present disclosure. As such, it should be understood that these statements are to be read in this light, and not as admissions of prior art. Summary of the Invention

[0008] One aspect of the present disclosure relates to a method for implanting ions into a semiconductor structure. The semiconductor structure has a front surface and a back surface opposite the front surface. The semiconductor structure is placed on a heat sink with the back surface of the semiconductor structure in contact with the heat sink. Ions are implanted through the front surface of the semiconductor structure while the semiconductor structure is placed on the heat sink to form a damage region in the semiconductor structure. A parameter related to a coefficient of friction of the heat sink is measured. The parameter is compared to a baseline range. If the parameter is outside the baseline range, the heat sink is reconditioned. If the parameter is within the baseline range, the heat sink is used during ion implantation of additional semiconductor structures.

[0009] Another aspect of the present disclosure relates to a method for evaluating the suitability of a heat sink for ion implantation of a semiconductor structure. The heat sink includes a substrate and an elastomeric coating disposed on at least one surface of the substrate. A parameter related to a coefficient of friction of the elastomeric coating is measured. The parameter is compared to a baseline range. If the parameter is outside the baseline range, the heat sink is reconditioned. If the parameter is within the baseline range, the heat sink is used during ion implantation of the semiconductor structure.

[0010] There are various refinements to the features described in relation to the above-mentioned aspects of the present disclosure. Additional features can be incorporated into the above-mentioned aspects of the present disclosure as well. These refinements and additional features can exist individually or in any combination. For example, the various features described below in relation to any of the illustrated embodiments of the present disclosure can be incorporated alone or in any combination into any of the above-mentioned aspects of the present disclosure. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic side view of a semiconductor structure. [Diagram 2] FIG. 2 is a top perspective view of a heat sink. [Diagram 3] FIG. [Figure 4]FIG. [Diagram 5] FIG. 2 is a front perspective view of the injection device. [Figure 6] FIG. 2 is a bottom perspective view of the injection device. [Figure 7] FIG. [Figure 8] FIG. 1 is a perspective view of a test fixture having a heat sink disposed thereon. [Figure 9] FIG. 2 is a perspective view of the test fixture and heat sink during testing. [Figure 10] 1 is a graph showing the change in coefficient of friction of a heat sink as a function of the number of cycles. [Figure 11] 1 is an interval plot of slip angle for a batch of implanter heat sinks. [Figure 12] 1 is a graph illustrating the heat sink friction coefficient and the temperature of an implanted semiconductor structure on a heat sink.

[0012] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Provisions of the present disclosure relate to a method for evaluating the quality of a heat sink used during ion implantation of a semiconductor structure. In general, the semiconductor structure may be any structure in which it is desired to implant ions. In some embodiments, the semiconductor structure is a layered structure, such as a donor structure used to fabricate a silicon-on-insulator structure. With reference to FIG. 1, an exemplary structure 10 is a layered structure including a donor wafer 12 and a dielectric layer 15 (e.g., silica), such as the structure disclosed in U.S. Pat. No. 10,679,908, which is incorporated herein by reference for all relevant consistent purposes. Ions (indicated by arrows) are implanted into the structure 10 through a surface 22, forming a cleavage plane 17. The ion-implanted structure 10 can be bonded to a handle structure and cleaved to form a silicon-on-insulator structure. Suitable structures that can be ion-implanted can be composed of silicon, germanium, silicon germanium, gallium nitride, aluminum nitride, gallium arsenide, indium gallium arsenide, and any combination thereof.

[0014] 5, to implant ions into the semiconductor structure 10, the structure 10 is placed on a heat sink 100 of an ion implanter 200. The structure 10 is positioned such that the backside surface 14 of the semiconductor structure 10 is in contact with the heat sink 100. The semiconductor structure 10 and heat sink 100 are rotated while an ion beam is directed at the structure 10 to form a cleave surface 17 in the semiconductor structure 10.

[0015] During ion implantation, heat is generated in the semiconductor structure 10. The heat sink 100 regulates the temperature of the semiconductor structure 10 during ion implantation by dissipating heat from the semiconductor structure 10 into the heat sink 100.

[0016] 2, the heat sink 100 includes a substrate 102 and an elastomeric coating 104 disposed at least partially on a surface 106 of the substrate 102. The surface 106 is sized and shaped to support the backside 14 of the semiconductor structure 10. The elastomeric coating 104 contacts the semiconductor structure 10 during ion implantation. The substrate 102 may be made of aluminum and / or stainless steel. The elastomeric coating 104 may be made of any suitable elastomer known to those skilled in the art. Exemplary elastomers include silicone elastomers, such as silicone elastomers made of polydimethylsiloxane (PDMS). The elastomeric coating 104 is applied to the surface 106 of the heat sink 100 to increase thermal contact between the heat sink 100 and the semiconductor structure 10. The elastomeric coating 104 is thermally conductive and facilitates heat transfer from the semiconductor structure 10 to the heat sink 100. In particular, the elastomeric coating 104 improves thermal conduction from the semiconductor structure 10 to the heat sink 100 during ion implantation, dissipating heat and controlling the temperature of the semiconductor structure 10 .

[0017] To load the semiconductor structure 10 into the implanter 200, the semiconductor structure 10 is loaded onto the heat sink 100 and the backside 14 is pressed against the elastomeric coating 104 using a spring-loaded clip (not shown) that holds the semiconductor structure 10 to the heat sink 100. The heat sink 100 may include one or more grooves 108 around the periphery of the heat sink. The grooves 108 are used to align and attach the spring-loaded clip to the heat sink 100. Other mechanisms or features may be used to initially hold the position of the semiconductor structure 10 on the heat sink 100.

[0018] 5, an ion implanter 200 (also referred to as a scan wheel) transports multiple semiconductor structures 10 during ion implantation, with a structure 10 disposed on each heat sink 100. The ion implanter 200 includes supports 202 (FIG. 6) that are removably connected to each heat sink 100. Each support 202 is disposed on a distal end 203 of an arm 204 that extends from a central hub 206. The supports 202 are aligned such that the semiconductor structures 10 and heat sink 100 rotate about a central axis Y extending through the central hub 206. 200 are arranged in the circumferential direction around the center.

[0019] The ion implantation apparatus 200 is arranged along a central axis Y 200 , and the semiconductor structures 10 are repeatedly passed through a stationary ion beam (not shown) to implant ions into each semiconductor structure 10. The ion implanter 200 may be located within a chamber (e.g., a vacuum chamber) during ion implantation.

[0020] The ion implantation apparatus 200 rotates about the central axis Y at a relatively high rotational speed, such as 500 rpm or more, 750 rpm or more, or 1000 rpm or more (e.g., 500 rpm to 2000 rpm). 200 The heat sink rotates about a rotation axis. Initially, the heat sink may be held in place by clips. The clips open when a threshold centrifugal force is reached during ramp-up of the implanter (e.g., when a threshold number of rotations is reached). Once the clips open, the semiconductor structure is held against the holding structure by centrifugal force without the use of additional fasteners to hold the semiconductor structure against the heat sink 100. In some embodiments, the heat sink is fluid-cooled, with channels formed through which a fluid can circulate.

[0021] The heat sink 100 can be used for multiple cycles of ion implantation. For example, the heat sink 100 can be reused for over 10,000 cycles of ion implantation. The ion implantation environment can degrade (e.g., harden and / or shrink) the elastomeric coating 104 of the heat sink 100.

[0022] In accordance with embodiments of the present disclosure, a parameter related to the coefficient of friction of the elastomeric coating 104 can be used to evaluate the wear of the elastomeric coating 104. The parameter related to the coefficient of friction may be used to evaluate the heat transfer capability of the heat sink 100. Alternatively or additionally, the parameter related to the coefficient of friction may be used to evaluate the peak temperature of the semiconductor structure 10 during ion implantation. The parameter related to the coefficient of friction may be used to determine whether the heat sink 100 may be used for further ion implantations or whether the heat sink 100 should not be used for subsequent ion implantations (e.g., should be reconditioned instead). In some embodiments, the parameter related to the coefficient of friction can be used to determine whether the temperature of the semiconductor structure held by the heat sink 100 during ion implantation has shifted and whether downstream process parameters should be adjusted to compensate for the temperature difference.

[0023] To evaluate a parameter related to the coefficient of friction of the elastomeric coating (e.g., to determine the temperature change of a semiconductor structure held by the heat sink 100 during ion implantation), the heat sink 100 is removed from the ion implantation apparatus 200 after one or more cycles of ion implantation into the semiconductor structure (e.g., at least 10 cycles, at least 100 cycles, at least 1000 cycles, or at least 5000 cycles, or at least 10000 cycles of ion implantation). The parameter related to the coefficient of friction is then experimentally determined (and may be compared to a baseline parameter, such as a parameter value of a new or reconditioned heat sink, as further described below). For example, referring to FIG. 7, one embodiment of a test apparatus 300 for determining a parameter related to the coefficient of friction is provided. As shown in FIG. 8, the heat sink 100 is placed on the test apparatus 300 after a cycle of ion implantation to measure a parameter related to the coefficient of friction of the heat sink 100.

[0024] The testing apparatus 300 includes a plate 302 having a plate surface 304. The plate 302 is supported by a frame 306 that is pivotally connected to a base 308 by a hinge 310 (FIG. 9). The plate surface 304 is aligned along a longitudinal axis X of the frame 306. 306 The frame 306 is parallel to the pivot axis Y 300 The frame 306 rotates around a pivot axis Y 300 and rotates about the longitudinal axis X of the frame 306 (and the plate surface 304). 306 is the base 308 and the horizontal axis X 300 The horizontal axis X may be inclined at an angle α. 300 is roughly parallel to the ground, and the pivot axis Y 300 The frame 306 and the plate 302 can be manually rotated about a hinge 310. Alternatively and / or additionally, a motor can be used to pivot the frame 306 and the plate 302.

[0025] The heat sink 100 may be placed on the plate surface 304 such that the elastomeric coating 104 (FIG. 2) is in contact with the plate surface 304. Thus, the coefficient of friction parameter of the heat sink 100 corresponds to the coefficient of friction between the elastomeric coating 104 and the plate surface 304.

[0026] The plate 302 may be made of any suitable material such that the plate surface 304 has properties that allow for the determination of parameters related to the coefficient of friction of the heat sink 100. The plate 302 may be made of a ceramic material and the plate surface 304 may be generally smooth. The plate surface 304 may be polished or have a low surface roughness.

[0027] When the tilt angle α is zero (FIG. 8), the plate surface 304 is aligned with the horizontal axis X 300 , and there is no friction between the plate surface 304 and the heat sink 100. The plate 302 rotates about the pivot axis Y until the heat sink 100 begins to slide on the plate surface 304. 300The one or more rotation sensors 312 detect the tilt angle α at which the heat sink 100 begins to slip (i.e., the "critical angle α c " or "Slip angle α c The parameter related to the coefficient of friction is this critical angle α c Alternatively, the critical angle α c may be used to determine a parameter related to the coefficient of friction.

[0028] Slippage of the heat sink 100 can be observed using visual inspection. In some embodiments, the critical angle α at which the heat sink 100 begins to slip is c One or more motion sensors (not shown) are used to detect the motion of the heat sink 100 to determine the critical angle α. In some embodiments, the rotation sensor 312 determines whether the slippage detection of the heat sink 100 is greater than the critical angle α by the rotation sensor 312. c The camera is linked to a motion detection sensor to trigger automatic recording of the subject.

[0029] In some cases, the parameter related to the coefficient of friction is related to the static friction of the heat sink 100. Alternatively and / or additionally, the parameter related to the coefficient of friction is related to the kinetic friction of the heat sink 100. In some embodiments, the parameter related to the coefficient of friction may be related to a breakaway force, which is the force at which slippage of the heat sink 100 begins (e.g., on a horizontal surface). For example, the parameter related to the coefficient of friction may be determined by application of a variable force F applied to the heat sink 100 resting on a horizontal surface. The variable force F may be increased until slippage of the heat sink 100 begins. The variable force F at which slippage begins (i.e., a critical force F) may be determined by application of a variable force F at which slippage begins (i.e., a critical force F). c ) is recorded. One or more motion sensors may be used to detect the movement of the heat sink 100. The fluctuating force F and / or the critical force F c A further load cell may be used to record the coefficient of friction. Parameters relating to the coefficient of friction may be determined using other experimental techniques.

[0030] In other embodiments, rather than a parameter related to the coefficient of friction, a parameter related to the hardness of the heat sink 100 or a parameter related to the color of the heat sink 100 is detected to determine whether the heat sink should be reconditioned or may be used to process additional semiconductor structures.

[0031] After measuring the parameter related to the coefficient of friction of the heat sink 100, the parameter is compared to a baseline range. In some embodiments, the baseline may be determined by evaluating the parameter related to the coefficient of friction of the elastomeric coating of the new or reconditioned heat sink 100 before mounting the new or reconditioned heat sink 100 on the implantation apparatus 200. The baseline range may be an acceptable deviation from the parameter related to the coefficient of friction of the heat sink. If the parameter falls outside the reference range, the heat sink 100 is reconditioned. If the parameter falls within the baseline range, the heat sink 100 is used during ion implantation of additional semiconductor structures 10. For example, the critical angle α at which the heat sink begins to slip is determined. c is less than the threshold angle, the heat sink 100 may be reconditioned. The baseline range may be determined by measuring a parameter related to the coefficient of friction of the heat sink 100 for heat sinks known to provide poor thermal properties (e.g., thermal conductance). The baseline may be age specific (e.g., expected degradation for a heat sink of a particular age, i.e., "intra-batch variation").

[0032] In some embodiments, to determine implant temperature conditions, each heat sink 100 is evaluated at regular intervals (e.g., 1000 cycles) to monitor the heat sink 100. The evaluation can be used to adjust downstream process parameters to accommodate temperature changes due to degradation of the heat sink coating.

[0033] If the material of the plate 302 or plate surface 304 is changed or altered, for example if the plate surface 304 is repolished, the plate 302 and heat sink 100 should be recalibrated to determine updated baseline ranges for parameters related to the coefficient of friction. Different baseline ranges may be used for different types of elastomeric coatings.

[0034] In preparation for determining the parameter related to the coefficient of friction, the plate surface and the elastomeric coating surface of the heat sink 100 may be cleaned and dried before the heat sink 100 is positioned on the plate 302 of the testing fixture 300. Cleaning the elastomeric coating 104 ensures that the contact surfaces are free of particulates or other debris that may affect the determination of the parameter related to the coefficient of friction.

[0035] If the heat sink falls outside the standard range (for example, the minimum inclination angle α c below 0.05° C.), the heat sink 100 may be reconditioned (e.g., an alternative heat sink 100 is used for the implanter 200 while it is being reconditioned). The heat sink 100 may be reconditioned by stripping the elastomeric coating 104 from the substrate 102 and depositing a second elastomeric coating 104 on the substrate 102. In some cases, the heat sink 100 may be discarded. The heat sink 100 may be evaluated periodically (e.g., during preventive maintenance or when process degradation indicates that the heat sink should be evaluated) depending on the age of the elastomeric coating and the stringency of the process temperature window (e.g., additional testing is performed during break-in of the heat sink).

[0036] Compared to conventional ion implantation methods, the disclosed method and system have several advantages. By determining a parameter related to the coefficient of friction and comparing the parameter to a baseline, wear and degradation of the elastomeric coating of the heat sink that affects the ability of the heat sink to dissipate heat from the semiconductor structure during ion implantation can be objectively evaluated. Determining a parameter related to the coefficient of friction provides a relatively repeatable, rapid, non-destructive, and cost-effective approach to evaluating the entire elastomeric coating. Periodic evaluation of the elastomeric coating by determining whether the coefficient-related parameter is greater than the baseline range and / or whether the rate of change follows the downstream process window provides valuable and practical guidance for quality control and process tuning. Reconditioning of the elastomeric coating prevents ion implantation misalignment. Evaluating a parameter related to the coefficient of friction provides relatively rapid feedback to enable downstream process parameter adjustments, reducing the risk of process window shifts and achieving high quality and high yield of semiconductor structures.

[0037] Working Example The processes of the present disclosure are further illustrated by the following examples, which should not be construed in a limiting sense.

[0038] Example 1: Baseline coefficient of friction for heat sinks The baseline coefficient of friction as a function of heat sink cycling is shown in Figure 10. As can be seen from Figure 10, the degradation rate of the elastomeric coating is faster early in the life of the heat sink.

[0039] Example 2: Detection of abnormally aged heat sinks in a batch A batch of heat sinks was mounted on the implanter wheel. The implanter was used for several cycles of ion implantation, and 5-6% of the wafers showed poor layer transfer yield. Commonality testing showed that the wafers were processed on the same heat sink. A coefficient of friction test (slide angle test) was performed on the entire batch of heat sinks on the implanter in the apparatus shown in Figures 7-9. The test showed that one of the heat sinks had an abnormal slide angle, as shown in Figure 11, so the bad heat sink was replaced.

[0040] Example 3: Detection of abnormal aging of heat sinks Aging of the heat sink causes a decrease in the sliding angle and coefficient of friction of the heat sink, which follow an exponential relationship with the number of cycles (Figure 10). In Figure 12, the change in the coefficient of friction is correlated with the temperature of the wafer, measured by a temperature indicator on the front side of the semiconductor structure. Figure 12 shows that as the sliding angle decreases, the temperature of the wafer increases due to the lack of effective heat transfer from the back side of the semiconductor structure to the heat sink. The coefficient of friction (e.g., sliding angle) can be used to quantitatively predict the process parameters (temperature) of the semiconductor during processing.

[0041] As used herein, the terms "about," "substantially," "essentially," and "approximately," when used in conjunction with a dimension, concentration, temperature, or other physical or chemical property or range of properties, are meant to cover variations that may exist at the upper and / or lower limits of the property or range of properties, including variations due to, for example, rounding, measurement method, or other statistical variations.

[0042] When introducing elements of the disclosure or embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," "containing," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of specific directional terms (e.g., "top," "bottom," "side," etc.) is for convenience of description and does not require a particular orientation of the items being described.

[0043] Since various changes may be made in the above-described structures and methods without departing from the scope of the present disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

Claims

1. 1. A method of implanting ions into a semiconductor structure, the semiconductor structure having a front surface and a back surface opposite the front surface, the method comprising the steps of: placing the semiconductor structure on a heat sink and contacting a backside of the semiconductor structure to the heat sink; implanting ions through a front surface of the semiconductor structure while the semiconductor structure is disposed on the heat sink to form a damaged region in the semiconductor structure; measuring a parameter related to the coefficient of friction of the heat sink; and comparing the parameter to a baseline range; Where: (1) if the parameter is outside the baseline range, the heat sink is retuned; and (2) if the parameters are within the baseline range, the heat sink is used during ion implantation of additional semiconductor structures.

2. The method of claim 1 , wherein the heat sink comprises a substrate and an elastomeric coating disposed on at least one side of the substrate, the elastomeric coating contacting the semiconductor structure during ion implantation.

3. 10. The method of claim 1, further comprising implanting ions into the plurality of semiconductor structures prior to measuring the parameter related to the coefficient of friction of the heat sink.

4. The method of claim 1 , wherein the semiconductor structure is a layer structure.

5. 10. The method of claim 1, wherein a heat sink is placed on the ion implanter during ion implantation, and the ion implanter rotates the heat sink during ion implantation, the method including removing the heat sink from the ion implanter after ions are implanted through the front side of the semiconductor structure and prior to measuring the parameter related to the coefficient of friction of the heat sink.

6. 6. The method of claim 5, further comprising placing the heat sink on a test fixture after ion implantation to measure a parameter related to the coefficient of friction of the heat sink.

7. The method of claim 1 , wherein the heat sink comprises a substrate and an elastomeric coating disposed on the substrate, and the parameter related to the coefficient of friction of the heat sink is related to the coefficient of friction of the elastomeric coating.

8. The method of claim 7 , wherein the substrate is formed from aluminum or stainless steel.

9. The method of claim 7 , wherein the elastomeric coating is a silicone elastomer.

10. The method of claim 1 , wherein the parameter related to the coefficient of friction is related to the static friction of the heat sink.

11. The method of claim 1 , wherein the parameter relating to the coefficient of friction relates to the kinetic friction of the heat sink.

12. The method of claim 1 , wherein the parameter related to the coefficient of friction is the sliding angle or breakaway force of the heat sink on the surface.

13. 10. The method of claim 1, wherein the heat sink comprises a substrate and an elastomeric coating disposed on the substrate, and the heat sink is reconditioned by peeling the elastomeric coating from the structure and depositing a second elastomeric coating on the substrate.

14. 1. A method for evaluating the suitability of a heat sink for ion implantation of a semiconductor structure, the heat sink including a substrate and an elastomeric coating disposed on at least one surface of the substrate, the method comprising the steps of: measuring a parameter related to the coefficient of friction of the elastomeric coating; and comparing the parameter to a baseline range; Where: (1) re-adjusting the heat sink if the parameters are outside the baseline range; and (2) If the parameters are within the baseline range, the heat sink is used during ion implantation of the semiconductor structure.

15. The method of claim 14 , wherein the substrate is formed of aluminum or stainless steel.

16. The method of claim 15, wherein the elastomeric coating is a silicone elastomer.

17. The method of claim 14, wherein the parameter relating to the coefficient of friction relates to the static friction of the elastomeric coating.

18. The method of claim 14, wherein the parameter relating to the coefficient of friction relates to the dynamic friction of the elastomeric coating.

19. The method of claim 14, wherein the parameter related to the coefficient of friction is the sliding angle or breakaway force of the heat sink on the surface.

20. The method of claim 14 , wherein the heat sink is reconditioned by stripping the elastomeric coating from the structure and depositing a second elastomeric coating on the substrate.

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