An ion implanter and a method of manufacturing an ion implanter liner

Abstract

The embodiment of the present application provides a kind of ion implanter and the manufacturing method of ion implanter lining, belong to semiconductor manufacturing and ion implantation field.The ion implanter at least includes: ion source and cavity, the ion source with the cavity is connected;The ion source is used to emit ion beam;The cavity is used to transport the ion beam;Inner wall of the cavity is equipped with lining;The lining is equipped with convex structure.The ion implanter disperses the impact effect of ion beam to the working surface of protective lining, prolongs the service life of protective lining, reduces the manufacturing cost of ion implantation.

Description

Technical Field

[0001] This invention relates to the fields of semiconductor manufacturing and ion implantation, and more specifically to an ion implanter and a method for manufacturing an ion implanter liner. Background Technology

[0002] Existing ion implanters typically use aluminum alloy or stainless steel as the cavity material. Ion impacts can sputter metal particles off the surface, causing serious metal contamination. To improve this, common methods include adding a high-density graphite protective liner or using a silicon-coated metal plate liner to isolate the metal from the beam. However, graphite has limited inherent strength and poor resistance to ion impacts, and the coating material is prone to peeling off under impact. Therefore, the protective liner needs to be replaced frequently during ion implantation, which significantly increases manufacturing costs. Summary of the Invention

[0003] The purpose of this invention is to provide an ion implanter and a method for manufacturing an ion implanter liner. The ion implanter disperses the impact of the ion beam on the working surface of the protective liner, extends the service life of the protective liner, and reduces the manufacturing cost of ion implantation.

[0004] To achieve the above objectives, embodiments of the present invention provide an ion implanter, which includes at least: an ion source and a cavity, wherein the ion source is connected to the cavity; the ion source is used to emit an ion beam; the cavity is used to transmit the ion beam; an inner liner is provided on the inner wall of the cavity; and the inner liner has a convex structure.

[0005] Optionally, in the region of the liner that is subjected to concentrated ion beam bombardment, the convex structure is a flange structure.

[0006] Optionally, the dimensions of the flange structure satisfy the following conditions: the height difference H2 between the highest and lowest points of the flange structure is: 0.5H1≤H2≤2H1; the radius R2 at the highest point of the flange structure is: 0.5R1≤R2≤5R1; the length L2 of the flange structure is: 0.5L1≤L2≤3L1; where H1 is the depth of the pit formed in the area without the convex structure liner during its service life under concentrated ion beam bombardment, R1 is the radius of the pit, and L1 is the length of the pit.

[0007] Optionally, in the region of the liner that is bombarded by the dispersed ion beam, the convex structure is a plurality of convex curved surface structures.

[0008] Optionally, the dimensions of each of the convex curved surface structures satisfy the following conditions: the distance L3 between the highest points of two adjacent convex curved surface structures is: 0.5ΔR≤L3≤6ΔR; the radius R3 at the highest point of the convex curved surface structure is: 0.5ΔR≤R3≤5ΔR; the height difference H3 between the highest and lowest points of the convex curved surface structure is: 0.5ΔR≤H3≤5ΔR; where ΔR is the average radius of the pits formed in the area without the convex structure liner during its service life under the dispersed bombardment of the ion beam.

[0009] Optionally, the liner is a graphite liner or a silicon-coated metal plate.

[0010] On the other hand, the present invention provides a method for manufacturing an ion implanter liner, the ion implanter comprising at least: an ion source and a cavity, the ion source being used to emit an ion beam; the cavity being used to transmit the ion beam; and an liner being provided on the inner wall of the cavity, characterized in that the manufacturing method comprises: providing a convex structure on the surface of the liner.

[0011] Optionally, providing a convex structure on the liner surface includes: operating an ion implanter with a liner without the convex structure for one liner life cycle, and determining the type and size of the convex structure based on the degree to which the surface of the liner is bombarded by the ion beam.

[0012] Optionally, the convex structure provided in the region of the liner that is subjected to concentrated ion beam bombardment is a flange structure.

[0013] Optionally, the dimensions of the flange structure satisfy the following conditions: the height difference H2 between the highest and lowest points of the flange structure is: 0.5H1≤H2≤2H1; the radius R2 at the highest point of the flange structure is: 0.5R1≤R2≤5R1; the length L2 of the flange structure is: 0.5L1≤L2≤3L1; where H1 is the depth of the pit formed in the area without the convex structure liner during its service life under concentrated ion beam bombardment, R1 is the radius of the pit, and L1 is the length of the pit.

[0014] Optionally, in the region of the liner that is bombarded by the dispersed ion beam, the convex structure is a plurality of convex curved surface structures.

[0015] Optionally, the dimensions of each of the convex curved surface structures satisfy the following conditions: the distance L3 between the highest points of two adjacent convex curved surface structures is: 0.5ΔR≤L3≤6ΔR; the radius R3 at the highest point of the convex curved surface structure is: 0.5ΔR≤R3≤5ΔR; the height difference H3 between the highest and lowest points of the convex curved surface structure is: 0.5ΔR≤H3≤5ΔR; where ΔR is the average radius of the pits formed in the area without the convex structure liner during its service life under the dispersed bombardment of the ion beam.

[0016] An ion implanter of the present invention includes at least: an ion source and a cavity, wherein the ion source is connected to the cavity; the ion source is used to emit an ion beam; the cavity is used to transmit the ion beam; an inner liner is provided on the inner wall of the cavity; and the inner liner has a convex structure. The ion implanter disperses the impact of the ion beam on the working surface of the protective liner, extends the service life of the protective liner, and reduces the manufacturing cost of ion implantation.

[0017] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 This is a schematic diagram of an existing ion implanter.

[0020] Figures 2a-2c This is a schematic diagram illustrating the flange structure of an ion implanter according to the present invention;

[0021] Figures 3a-3d This is a schematic diagram illustrating the convex curved surface structure of an ion implanter according to the present invention;

[0022] Figures 4a-4b This is a dimensional schematic diagram of the convex curved surface structure of an ion implanter according to the present invention;

[0023] Figures 5a-5b This is a schematic diagram showing the dimensions of a convex curved surface structure of another ion implanter according to the present invention.

[0024] Explanation of reference numerals in the attached figures

[0025] 1-Ion source;

[0026] 2-Quality analyzer;

[0027] 3-Ion beam focuser;

[0028] 4-Parallelizer;

[0029] 5-Electron Neutralizer;

[0030] 6-Accelerator and decelerator;

[0031] 7-Scanning chamber;

[0032] H - Height of the liner without a convex structure;

[0033] W - Width of the lining without a convex structure;

[0034] L - Length without the lining of the convex structure;

[0035] L1 - The length of the indentation;

[0036] R1 - the radius of the pit;

[0037] H1 - Depth of the pit;

[0038] R2 - Radius at the highest point of the flange structure;

[0039] The height difference between the highest and lowest points of the H2-flange structure;

[0040] L2 - Length of the flange structure;

[0041] R4 - Radius of the first erosion pit;

[0042] R5 - Radius of the second pit;

[0043] R6 - Radius of the third erosion pit;

[0044] R7 - Radius of the fourth erosion pit;

[0045] R8 - Radius of the fifth erosion pit;

[0046] R3 - The radius at the highest point of the convex curved surface structure;

[0047] L4 - The distance between the start and end points of the cross-sectional profile line of the convex curved surface parallel to the L or W direction;

[0048] L3 - The distance between the highest points of two adjacent convex curved surface structures;

[0049] The height difference between the highest and lowest points of the H3-convex curved surface structure;

[0050] E-ion beam. Detailed Implementation

[0051] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0052] The present invention proposes an ion implanter, which includes at least: an ion source 1 and a cavity, wherein the ion source 1 is connected to the cavity; the ion source 1 is used to emit an ion beam E; the cavity is used to transmit the ion beam E; the inner wall of the cavity is provided with an inner liner; the inner liner is provided with a convex structure.

[0053] Figure 1 This is a schematic diagram of an existing ion implanter, such as... Figure 1 As shown, the ion implanter includes: an ion source 1, a mass analyzer 2, an ion beam focuser 3, a parallelizer 4, an electron neutralizer 5, an accelerator / decelerator 6, and a scanning chamber 7. The ion source 1 ionizes the gaseous particles of the element to be implanted into ions, determining the type of ions and beam intensity to be implanted. Electrons generated by DC or high-frequency discharge from the ion source 1 act as bombardment particles. When the energy of the incoming electrons is higher than the ionization potential of the atom, they collide to ionize the element. After the collision, in addition to the original electrons, positrons and secondary electrons are also produced. The positive ions enter the mass analyzer 2 to select the desired ions, then sequentially pass through the ion beam focuser 3, parallelizer 4, electron neutralizer 5, and accelerator / decelerator 6 to obtain higher energy, and finally enter the scanning chamber 7 for ion implantation.

[0054] The cavity in the ion implanter of the present invention can be any one or more of the cavity of the mass analyzer 2, the cavity of the ion beam focuser 3, the cavity of the parallelizer 4, the cavity of the electron neutralizer 5, and the cavity of the acceleration / deceleration unit 6. Typically, the protective liners installed in the cavities of the ion beam focuser 3 and the acceleration / deceleration unit 6 are subjected to concentrated impact from the ion beam E, while the protective liners installed in the cavities of the mass analyzer 2 and the parallelizer 4 are subjected to dispersed impact from the ion beam E.

[0055] The lining of this invention has a convex structure, which may include a flange structure and a convex curved surface structure.

[0056] Specifically, in the region of the liner that is concentratedly bombarded by the ion beam E, the convex structure is a flange structure. Figures 2a-2c This is a schematic diagram of the flange structure of an ion implanter according to the present invention, as shown below. Figure 2a As shown, the cuboid is the liner to be tested without the convex structure, wherein the height of the liner is the height H of the liner without the convex structure, the width is the width W of the liner without the convex structure, and the length is the length L of the liner without the convex structure. The liner is subjected to concentrated bombardment by an ion beam E.

[0057] like Figure 2b As shown, after the liner is bombarded by a high-energy ion beam E for one lifetime, a pit will be formed on the failure part of the bombarded liner surface near the ion beam E. The size parameters of the pit include at least the length L1, the radius R1 and the depth H1 of the pit.

[0058] like Figure 2cAs shown, a flange structure is provided at the location of the deep pit, and the flange structure is a thickened flange. The dimensional parameters of the flange structure include at least the radius R2 at the highest point of the flange structure, the height difference H2 between the highest and lowest points of the flange structure, and the length L2 of the flange structure. The dimensions of the flange structure satisfy the following conditions: the height difference H2 between the highest and lowest points of the flange structure is: 0.5H1≤H2≤2H1; the radius R2 at the highest point of the flange structure is: 0.5R1≤R2≤5R1; the length L2 of the flange structure is: 0.5L1≤L2≤3L1; where H1 is the depth H1 of the pit formed by concentrated ion beam bombardment in the area without the convex structure during the service life of the liner (i.e., the erosion distance of the pit along the H direction of the liner), R1 is the radius R1 of the pit (i.e., the approximate radius of curvature at the deepest point), and L1 is the length L1 of the pit (i.e., the erosion distance of the pit along the L direction of the liner).

[0059] In addition, in the region of the liner that is bombarded by the dispersed ion beam E, the convex structure is a plurality of convex curved surface structures. Figures 3a-3c This is a schematic diagram illustrating the convex curved surface structure of an ion implanter according to the present invention, as shown below. Figure 3a As shown, the cuboid is the liner to be tested without the convex structure, wherein the height of the liner is the height H of the liner without the convex structure, the width is the width W of the liner without the convex structure, and the length is the length L of the liner without the convex structure. The liner is subjected to dispersed bombardment by an ion beam E.

[0060] like Figure 3b As shown, after the lining is bombarded by a high-energy ion beam E for one lifetime, multiple dispersed pits are formed on the surface of the bombarded lining. The radii of the pits may be different, for example: the radius of the first pit is R4, the radius of the second pit is R5, the radius of the third pit is R6, the radius of the fourth pit is R7, the radius of the fifth pit is R8, etc.

[0061] Figure 3c and 3d These are two types of convex curved surface structures, such as Figure 3c and 3d As shown, a convex curved surface structure is provided at the location of the etch pit. The dimensions of each convex curved surface structure satisfy the following conditions: the distance L3 between the highest points of two adjacent convex curved surface structures is: 0.5ΔR≤L3≤6ΔR; the radius R3 at the highest point of the convex curved surface structure is: 0.5ΔR≤R3≤5ΔR; the height difference H3 between the highest and lowest points of the convex curved surface structure is: 0.5ΔR≤H3≤5ΔR; where ΔR is the average radius of the etch pit formed in the area bombarded by the ion beam E during the service life without the lining of the convex structure. Figure 4a and Figure 4b for Figure 3cCross-sectional view, Figure 5a and Figure 5b for Figure 3d Cross-sectional view.

[0062] like Figure 4a and Figure 4b As shown, if we take L3 = L4 = 2ΔR and H3 = ΔR, then within the range of length L3 and width L4, the convex curved surface structure, when bombarded by a vertical ion beam E, will have a contact surface of πΔR with the ion beam E. 2 +4ΔR 2 The planar design has a contact surface with the ion beam E of 4ΔR. 2 Wherein, L4 is the distance between the start and end points of the cross-sectional contour line of the convex curved surface parallel to the L or W direction. The convex structure of the present invention has a larger contact area with the ion beam E, which can evenly distribute the impact of the ion beam E on the inner lining surface, thereby delaying the formation of defect pits.

[0063] When the smooth convex surface of the ion implanter of this invention is struck by an ion beam E, the impacting ions are more prone to eccentric elastic collisions, losing some energy and migrating away from the surface. Conversely, when ions impact a flat surface, they are more prone to inelastic collisions, losing energy and remaining in the liner. The kinetic energy of the ion impacts is converted into heat and vibration, thus damaging the liner. The independently and densely arranged convex structure of this invention divides the liner surface into multiple discontinuous small areas, which can avoid the problem of large-area peeling caused by the connection of multiple pitting pits during the use of the liner.

[0064] This invention also proposes a method for manufacturing an ion implanter liner. The ion implanter includes at least an ion source 1 and a cavity. The ion source 1 is used to emit an ion beam E; the cavity is used to transmit the ion beam E; and an liner is provided on the inner wall of the cavity. The method is characterized by comprising: setting a convex structure on the surface of the liner. Setting the convex structure on the surface of the liner includes: installing a standard flat liner on the ion implanter for one cycle of operation; determining the type and size of the convex structure based on the degree of bombardment of the ion beam E on the surface of the liner; and the liner without the convex structure being a conventional flat liner.

[0065] The convex structure provided in the area of ​​the liner subjected to concentrated bombardment by ion beam E is a flange structure. The dimensions of the flange structure satisfy the following conditions: the height difference H2 between the highest and lowest points of the flange structure is: 0.5H1≤H2≤2H1; the radius R2 at the highest point of the flange structure is: 0.5R1≤R2≤5R1; the length L2 of the flange structure is: 0.5L1≤L2≤3L1; where H1 is the depth H1 of the pit formed in the area of ​​the liner without the convex structure subjected to concentrated bombardment by ion beam E during its service life, R1 is the radius R1 of the pit, and L1 is the length L1 of the pit.

[0066] In the region of the liner subjected to dispersed bombardment by ion beam E, the convex structure comprises multiple convex curved surface structures. The dimensions of each of the convex curved surface structures satisfy the following conditions: the distance L3 between the highest points of two adjacent convex curved surface structures is: 0.5ΔR≤L3≤6ΔR; the radius R3 at the highest point of the convex curved surface structure is: 0.5ΔR≤R3≤5ΔR; the height difference H3 between the highest and lowest points of the convex curved surface structure is: 0.5ΔR≤H3≤5ΔR; where ΔR is the average radius of the pits formed in the region of the liner without the convex structure subjected to dispersed bombardment by ion beam E during its service life.

[0067] The specific implementation steps are as follows:

[0068] Step 1: Install ordinary flat protective liners on each protective module of the ion implanter and allow them to operate for a complete life cycle. When each protective liner fails or is about to fail, remove it and observe the failure mode. The failure mode may be that some areas of the liner are bombarded by concentrated ion beam E, forming deep pits that exceed the tolerance value, or that the ion beam E impact forms scattered pits on the surface, worsening the particle contamination of the machine and exceeding the tolerance value.

[0069] Step 2: Based on the lining failure mode and failure area confirmed in Step 1, measure the erosion distance L1 along the L direction of the lining in the area with deep pits formed by concentrated bombardment of ion beam E, the approximate radius of curvature R1 at the deepest point of the pit, and the erosion distance H1 along the H direction of the lining. Measure the average radius ΔR of the scattered pits in the area with dispersed pitting formed by the impact of ion beam E.

[0070] Step 3: Create a thickened flange with a smooth curved surface profile in the area where deep pits are formed by concentrated bombardment of ion beam E. Create continuous or independent densely arranged convex curved surfaces in the area where pitting pits are formed by ion beam E impact. When creating the thickened flange on the working surface of the lining, the length of the thickened flange L2 ≥ 0.5L1 and ≤ 3L1, the radius of curvature R2 at the highest point of the flange surface ≥ 0.5R1 and ≤ 5R1, and the height difference H2 between the highest and lowest points of the flange surface ≥ 0.5H1 and ≤ 2H1. When densely arranged convex curved surfaces are made on the working surface of the inner lining, the distance between the highest points of adjacent convex curved surfaces L3 ≥ 0.5ΔR and ≤ 6ΔR, the radius of curvature R3 at the highest point of a single convex curved surface R3 ≥ 0.5ΔR and ≤ 5ΔR, the height difference H3 between the highest and lowest points of a single convex curved surface H3 ≥ 0.5ΔR and ≤ 5ΔR, and the distance between the start and end points of the profile line of a single convex curved surface parallel to the L or W direction L4 ≥ 0.5ΔR and ≤ 6ΔR.

[0071] Compared to conventional ion implanter protective liners with flat working surfaces, this invention, by designing one or more convex curved surface profiles on the working surface, can disperse the impact of the ion beam E on the liner surface, resulting in a more stable surface structure. The smooth convex surface of the liner of this invention allows the impacting ions to undergo eccentric elastic collisions more easily when bombarded by ions. After losing some energy, they change their incident trajectory and migrate away from the surface, reducing damage to the liner. When the liner surface is divided into multiple discontinuous convex small areas, the problem of large-area peeling of the liner surface coating or graphite due to the connection of multiple pitting pits during use can be avoided. This invention determines the design scheme of the convex profile of the liner surface based on the failure mode of the protective liner in different parts of the ion implanter. In areas where the ion beam E is concentratedly bombarded, thickened flanges are used to extend the service life of the liner, and the flanges are designed as continuous smooth convex curved surfaces to disperse the impact. In areas where the ion beam E is dispersedly impacted, continuous or independently densely arranged convex curved surfaces are used to reinforce the surface. By creating a convex curved surface on the protective liner surface of the ion implanter, the service life of the liner can be effectively extended and the cost of ion implantation can be reduced.

[0072] The ion implanter of the present invention includes at least: an ion source 1 and a cavity, wherein the ion source 1 is connected to the cavity; the ion source 1 is used to emit an ion beam E; the cavity is used to transmit the ion beam E; an inner liner is provided on the inner wall of the cavity; the inner liner has a convex structure. The ion implanter disperses the impact of the ion beam E on the working surface of the protective liner, extends the service life of the protective liner, and reduces the manufacturing cost of ion implantation.

[0073] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0074] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0075] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0076] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An ion implanter, characterized in that, The ion implanter includes at least: an ion source and a cavity, wherein the ion source is connected to the cavity; The ion source is used to emit an ion beam; The cavity is used to transmit the ion beam; The inner wall of the cavity is lined; The lining is provided with a convex structure; In the region of the liner that is subjected to concentrated ion beam bombardment, the convex structure is a flange structure; In the region of the liner that is bombarded by a dispersed ion beam, the convex structure is a plurality of convex curved surface structures; The dimensional parameters of the flange structure include at least the radius at the highest point of the flange structure, the height difference between the highest and lowest points of the flange structure, and the length of the flange structure. The dimensions of the flange structure satisfy the following conditions: The height difference H2 between the highest and lowest points of the flange structure is: 0.5H1≤H2≤2H1; The radius R2 at the highest point of the flange structure is: 0.5R1≤R2≤5R1; The length L2 of the flange structure is: 0.5L1≤L2≤3L1; Wherein, H1 is the depth of the pit formed in the area of ​​the liner without the convex structure that is subjected to concentrated ion beam bombardment during its service life, R1 is the radius of the pit, and L1 is the length of the pit. The dimensions of each of the convex curved surface structures satisfy the following conditions: The distance L3 between the highest points of two adjacent convex curved surface structures is: 0.5ΔR≤L3≤6ΔR; The radius R3 at the highest point of the convex curved surface structure is: 0.5ΔR≤R3≤5ΔR; The height difference H3 between the highest and lowest points of the convex curved surface structure is: 0.5ΔR≤H3≤5ΔR; Wherein, ΔR is the average radius of the pits formed in the area of ​​the liner without the convex structure that is subjected to ion beam dispersion bombardment during its service life.

2. The ion implanter according to claim 1, characterized in that, The lining is a graphite lining or a silicon-coated metal plate.

3. A method for manufacturing a liner for an ion implanter, wherein the ion implanter comprises at least: An ion source and a cavity, wherein the ion source is used to emit an ion beam; The cavity is used to transmit the ion beam; The inner wall of the cavity is provided with an inner lining, characterized in that the manufacturing method includes: A convex structure is provided on the surface of the inner liner; The provision of the convex structure on the liner surface includes: operating an ion implanter with a liner without the convex structure for one liner life cycle, and determining the type and size of the convex structure based on the degree of ion beam bombardment on the surface of the liner; The convex structure provided in the region of the inner liner that is subjected to concentrated ion beam bombardment is a flange structure; In the region of the liner that is bombarded by a dispersed ion beam, the convex structure is a plurality of convex curved surface structures; The dimensional parameters of the flange structure include at least the radius at the highest point of the flange structure, the height difference between the highest and lowest points of the flange structure, and the length of the flange structure. The dimensions of the flange structure satisfy the following conditions: The height difference H2 between the highest and lowest points of the flange structure is: 0.5H1≤H2≤2H1; The radius R2 at the highest point of the flange structure is: 0.5R1≤R2≤5R1; The length L2 of the flange structure is: 0.5L1≤L2≤3L1; Wherein, H1 is the depth of the pit formed in the area of ​​the liner without the convex structure that is subjected to concentrated ion beam bombardment during its service life, R1 is the radius of the pit, and L1 is the length of the pit. The dimensions of each of the convex curved surface structures satisfy the following conditions: The distance L3 between the highest points of two adjacent convex curved surface structures is: 0.5ΔR≤L3≤ 6ΔR; The radius R3 at the highest point of the convex curved surface structure is: 0.5ΔR≤R3≤5ΔR; The height difference H3 between the highest and lowest points of the convex curved surface structure is: 0.5ΔR≤H3≤5ΔR; Wherein, ΔR is the average radius of the pits formed in the area of ​​the liner without the convex structure that is subjected to ion beam dispersion bombardment during its service life.

4. The manufacturing method according to claim 3, characterized in that, The lining is a graphite lining or a silicon-coated metal plate.

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