Method for improving ZDD of epitaxial wafer for BCD product and epitaxial machine

Abstract

The invention belongs to the technical field of semiconductor manufacturing, and particularly relates to a method for improving ZDD of an epitaxial wafer for a BCD product and an epitaxy machine, and the epitaxy machine comprises an epitaxy machine body which is internally provided with a working chamber; the heating base is arranged in the working chamber, a plurality of concentric annular cavities are sequentially formed in the heating base from inside to outside in the radial direction, and an independent heating element is correspondingly arranged in each annular cavity; the plurality of supporting seats are symmetrically distributed at the periphery of the top of the heating base and are used for supporting wafers; a mounting groove is formed in the top of each supporting seat, and a cushion block is detachably mounted in each mounting groove; according to the invention, more heat is supplemented to a low-growth-rate region through contact heat conduction, so that the growth rate of the region is improved; the high-growth-rate area obtains heat only through air heat conduction, overgrowth of the high-growth-rate area is restrained, and therefore the growth rates of different crystal orientation positions are effectively balanced, and ZDD Gap is reduced.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, specifically a method and epitaxial machine for improving ZDD of epitaxial wafers used in BCD products. Background Technology

[0002] With the continuous evolution of BCD (Bipolar-CMOS-DMOS) process technology and the increasing demands for device performance, more stringent requirements have been placed on the surface quality of epitaxial wafers, especially the flatness of the edge regions. The morphology and flatness of the epitaxial wafer edges directly affect the accuracy and consistency of subsequent key processes such as photolithography and etching, and are one of the important factors determining device performance and yield. The ZDD (Z-height Double Derivative) parameter, as a key indicator for quantitatively evaluating the second derivative (i.e., curvature change) of the Z-axis height change in the edge region of the epitaxial wafer, can sensitively reflect the local flatness and steepness of the edge. Its uniformity and stability have become one of the important specifications (SPECs) for high-end BCD products.

[0003] During epitaxial growth, the wafer edge region, being located at the edge of the reaction chamber's gas flow and temperature fields, presents more complex and difficult-to-control growth conditions compared to the central region. A significant technical challenge lies in the inherent differences in atomic density and surface energy at different crystal orientations along the edge of a single-crystal silicon wafer. This leads to varying vapor deposition and surface migration rates at different crystal orientations under the same epitaxial growth conditions, exhibiting anisotropic growth rates. This difference in growth rate caused by crystal orientation is further amplified at the wafer edge, ultimately resulting in non-uniform variations in deposition thickness and morphology at different azimuth positions within the edge annular region. This manifests as significant fluctuations in ZDD parameters along the circumferential direction, i.e., an excessively large ZDD gap. When this fluctuation exceeds the threshold allowed by the customer's process specifications, it will cause matching deviations in subsequent processes, severely impacting the uniformity of device performance and product yield.

[0004] Therefore, the present invention provides a method and epitaxial machine for improving ZDD of epitaxial wafers used in BCD products. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0006] The technical solution adopted by this invention to solve its technical problem is: an epitaxial machine for ZDD improvement of epitaxial wafers for BCD products, comprising: The epitaxial machine body has a working chamber inside; A heating base is disposed in the working chamber. Multiple concentric annular cavities are arranged radially from the inside to the outside on the heating base. Each annular cavity is provided with an independent heating element. Multiple support bases are symmetrically distributed around the top of the heating base to support the wafer; each support base has a mounting groove on its top, and a pad can be detachably installed in the mounting groove. A driving component, disposed on the heating base and connected to each of the support seats, is used to drive all the support seats to move synchronously so that each of the support seats can be positioned directly above any of the concentric annular cavities.

[0007] Preferably, a housing is fixed at the center of the heating base, and multiple crossbars are evenly distributed around the circumference of the housing. Each crossbar has a hollow structure and one end is fixedly connected to the outer wall of the housing. An installation block is slidably sleeved on the crossbar, and the support base is installed on the installation block.

[0008] Preferably, the drive assembly includes a lead screw, which is rotatably mounted inside the crossbar via a bearing seat. One end of the lead screw extends into the inner cavity of the housing and a gear is fixed to the end. A gear disk is rotatably disposed in the middle of the housing, and the gear disk meshes with the gears at all the ends of the lead screw. A drive motor for driving the gear disk to rotate is disposed on the heating base. A connecting block is threaded onto the lead screw, and the end of the connecting block away from the lead screw passes through a through slot opened on the side wall of the crossbar. The end of the connecting block is fixedly connected to the mounting block.

[0009] Preferably, the two side walls of the connecting block are slidably fitted with the inner wall of the through groove.

[0010] Preferably, the support base has a through hole in the middle, the crossbar passes through the through hole, and the height of the through hole is greater than the outer diameter of the crossbar; a magnetic block 1 is fixed at the bottom of the through hole, and multiple magnetic blocks 2 are fixed at intervals along the length direction at the bottom of the inner cavity of the crossbar, and the positions of the multiple magnetic blocks 2 correspond to the positions of the multiple annular cavities respectively.

[0011] Preferably, the support base and the mounting block are slidably engaged; a T-shaped limiting guide rail is fixed on the side wall of the support base, and a C-shaped slot is provided on the side wall of the mounting block, with the limiting guide rail being slidably positioned in the C-shaped slot.

[0012] Preferably, multiple fixing blocks are evenly distributed at the bottom of the multiple annular cavities, and the heating element is disposed between adjacent fixing blocks.

[0013] Preferably, each of the plurality of annular cavities is detachably fitted with a top cover.

[0014] A method for improving ZDD (zoom-dryness) in epitaxial wafers for BCD products, applicable to the aforementioned epitaxial machine for improving ZDD in epitaxial wafers for BCD products, includes the following steps: S1. Based on the size of the wafer to be processed, adjust the position of the support base through the drive component to accurately position it directly above the corresponding concentric annular cavity; S2. Place the wafer to be processed on top of the pad above the support base, so that the pad makes good contact with the low growth rate area of ​​the wafer. S3. Activate the heating element inside the corresponding concentric annular cavity in the heating base to heat different areas of the wafer; S4. By supplementing more heat to the low growth rate region through "contact heat conduction", the growth rate of the region is increased; the high growth rate region obtains heat only through "air heat conduction", which inhibits its excessive growth, thereby effectively balancing the growth rate of different crystal orientation positions and reducing the ZDD gap.

[0015] The beneficial effects of this invention are as follows: 1. The present invention discloses a method and epitaxial machine for improving ZDD of epitaxial wafers used in BCD products. The wafer to be processed is placed on top of a support base, so that the contact position is in contact with the low growth rate region. This allows more heat to be supplied to the region, increasing its growth rate. The high growth rate region obtains heat only through "air heat conduction" (low thermal conductivity), inhibiting its excessive growth. This effectively balances the growth rates of different crystal orientations, reduces the ZDD gap, and ensures that the wafer quality meets customer specifications.

[0016] 2. The method and epitaxial machine for improving ZDD of epitaxial wafers for BCD products described in this invention, through the precise control of the position of the support base by the drive component, can make each support base accurately correspond to and be positioned directly above any concentric annular cavity, thereby adapting to the processing needs of wafers of different sizes and meeting diverse production scenarios. Attached Figure Description

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 This is a perspective view of the present invention; Figure 2 This is a partial structural diagram of the present invention; Figure 3 This is a partial structural cross-sectional view of the present invention; Figure 4 yes Figure 3 Enlarged view of point A in the middle; Figure 5 yes Figure 3 Enlarged view at point B in the middle; Figure 6This is a schematic diagram of the internal structure of the annular cavity of the heating base in this invention; Figure 7 This is a side view of the support base in this invention; Figure 8 This is a schematic diagram of the method flow in this invention.

[0019] In the diagram: 1. Epitaxy machine body; 2. Base; 3. Top cover; 4. Shell; 5. Crossbar; 6. Support base; 7. Annular cavity; 8. Heating element; 9. Motor; 10. Gear disc; 11. Mounting groove; 12. Contact; 13. Mounting block; 14. Limiting guide rail; 15. Lead screw; 16. Through groove; 17. Connecting block; 18. Through hole; 19. Magnetic block one; 20. Magnetic block two; 21. Bearing seat; 22. Gear; 23. Fixing block. Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0021] Example 1: As Figures 1 to 7 As shown in the embodiment of the present invention, an epitaxial machine for ZDD improvement of epitaxial wafers for BCD products includes: The epitaxial machine body 1 has a working chamber inside; A heating base 2 is disposed in the working chamber. Multiple concentric annular cavities 7 are arranged radially from the inside to the outside on the heating base 2. Each annular cavity 7 is provided with an independent heating element 8. The sidewalls of the annular cavity 7 are made of a material with excellent heat insulation performance, which can effectively reduce heat loss. The top is made of a material with high thermal conductivity to improve heating efficiency.

[0022] Multiple support bases 6 are symmetrically distributed around the top of the heating base 2 to support the wafer; each support base 6 has a mounting groove 11 on its top, and a pad 12 can be detachably installed in the mounting groove 11. A driving component, disposed on the heating base 2 and connected to each of the support seats 6, is used to drive all the support seats 6 to move synchronously so that each of the support seats 6 can be positioned directly above any of the concentric annular cavities 7.

[0023] During operation, in the epitaxial growth process, the wafer to be processed is placed on top of the pad 12 above the support 6. Then, a quartz mask is placed on top of the heating base 2 to form a relatively closed reaction environment. A ring-shaped lamp is installed on the quartz mask to heat the top of the wafer, and process gas is introduced through the opening on the side of the quartz mask to promote the epitaxial growth of the wafer. The quartz mask, the ring-shaped lamp (not shown in the figure), and other structures adopt existing publicly available technologies and will not be described in detail here.

[0024] Simultaneously, during wafer placement, the pad 12 is positioned to abut against the low growth rate region. Both the support base 6 and the pad 12 are made of highly thermally conductive materials, such as copper and graphite, ensuring efficient heat transfer. This provides more heat to the low growth rate region, increasing its growth rate, while the high growth rate region obtains heat only through air heat conduction (which has low thermal conductivity), suppressing excessive growth. This effectively balances the growth rates at different crystal orientations, reduces the ZDD gap, and ensures the wafer quality meets customer specifications. Furthermore, precise control of the support base 6's position via the drive assembly allows each support base 6 to be precisely aligned and positioned directly above any concentric annular cavity 7, adapting to the processing needs of wafers of different sizes and meeting diverse production scenarios. Each annular cavity 7 is equipped with an independent heating element 8, which can employ common heating methods such as resistance wires or heating tubes. The heating temperature can be independently adjusted according to actual needs, further enhancing the precise control of the epitaxial growth process. In addition, the pad 12 is detachably connected to the support base 6. Different shapes and sizes of pads 12 can be selected according to the size of the low growth rate area of ​​the wafer, so as to completely cover the low growth rate area and ensure the uniformity and effectiveness of heat replenishment.

[0025] The heating base 2 has a housing 4 fixed at its center. Multiple crossbars 5 are evenly distributed around the circumference of the housing 4. Each crossbar 5 is hollow and one end is fixedly connected to the outer wall of the housing 4. An installation block 13 is slidably sleeved on the crossbar 5. The support base 6 is installed on the installation block 13.

[0026] During operation, the support base 6 is stably installed and flexibly moved in the horizontal direction by means of the crossbars 5 evenly distributed around the circumference of the housing 4 and the mounting blocks 13 slidably sleeved on them. This not only enhances the structural stability but also allows the support base 6 to slide precisely along the crossbars 5 to the designated annular cavity 7 under the action of the drive assembly, thereby adapting to the processing needs of wafers of different sizes.

[0027] The drive assembly includes a lead screw 15, which is rotatably mounted inside the crossbar 5 via a bearing seat 21. One end of the lead screw 15 extends into the inner cavity of the housing 4 and a gear 22 is fixed to the end. A gear disk 10 is rotatably disposed in the middle of the housing 4, and the gear disk 10 meshes with the gears 22 at the ends of all the lead screws 15. A drive motor 9 for driving the gear disk 10 to rotate is provided on the heating base 2. A connecting block 17 is threadedly connected to the lead screw 15. The end of the connecting block 17 away from the lead screw 15 passes through a through slot 16 opened on the side wall of the crossbar 5, and the end of the connecting block 17 is fixedly connected to the mounting block 13.

[0028] During operation, the drive motor 9 starts, causing the gear disc 10 to rotate. Since the gear disc 10 meshes with the gears 22 at the ends of all the lead screws 15, the rotation of the gear disc 10 synchronously drives the rotation of all the lead screws 15. When the lead screws 15 rotate, the connecting block 17, which is threaded to them, moves along the axial direction of the lead screws 15, thereby causing the mounting block 13 to slide along the crossbar 5. This achieves precise horizontal movement of the support base 6, allowing it to be positioned directly above any concentric annular cavity 7.

[0029] The two side walls of the connecting block 17 slide against the inner wall of the through groove 16.

[0030] During operation, the movement direction of the connecting block 17 is restricted, ensuring that the connecting block 17 can only move linearly along the axis of the through slot 16 under the drive of the lead screw 15. This avoids the connecting block 17 from swaying or shaking during movement, improves the accuracy and stability of the support seat 6 positioning, and thus ensures the precision and reliability of the wafer processing process.

[0031] The support base 6 has a through hole 18 in the middle, the crossbar 5 passes through the through hole 18, and the height of the through hole 18 is greater than the outer diameter of the crossbar 5; a magnetic block 19 is fixed at the bottom of the through hole 18, and multiple magnetic blocks 20 are fixed at intervals along the length direction at the bottom of the inner cavity of the crossbar 5, and the positions of the multiple magnetic blocks 20 correspond to the positions of the multiple annular cavities 7 respectively.

[0032] During operation, magnetic block 19 can be attracted to the side wall of the crossbar 5, and the opposing surfaces of magnetic block 19 and magnetic block 20 have opposite magnetic properties and repel each other. When the position of the support base 6 is adjusted by the drive component, magnetic block 19 is attracted to the bottom of the crossbar 5 under the action of attraction, and the support base 6 is moved upward simultaneously, so that the bottom of the support base 6 is separated from the upper surface of the heating base 2, thereby reducing wear between the two, so as to extend the service life of the equipment and reduce maintenance costs. When magnetic block 19 moves to directly below magnetic block 20, magnetic block 19 is separated from the crossbar 5 under the action of repulsion, and the support base 6 is pressed tightly against the surface of the heating base 2, ensuring close contact between the support base 6 and the heating base 2, and improving heat conduction efficiency.

[0033] The support base 6 is slidably engaged with the mounting block 13; a T-shaped limiting guide rail 14 is fixed on the side wall of the support base 6, and a C-shaped slot is provided on the side wall of the mounting block 13, and the limiting guide rail 14 is slidably positioned in the C-shaped slot.

[0034] During operation, the support base 6 can move up and down relative to the mounting block 13 through the sliding engagement of the limiting guide rail 14 and the C-shaped slot, and the support base 6 will move horizontally under the drive of the mounting block 13. At the same time, the limiting action of the limiting guide rail 14 in the C-shaped slot ensures that the support base 6 will not deviate or shake during the movement, thus ensuring the stability and accuracy of the movement of the support base 6.

[0035] Multiple fixing blocks 23 are evenly distributed at the bottom of the multiple annular cavities 7, and the heating element 8 is disposed between adjacent fixing blocks 23.

[0036] During operation, the fixing block 23 provides stable support and fixation for the heating element 8, so that the heating element 8 can be firmly set in the annular cavity 7, avoiding displacement or damage of the heating element 8 due to vibration or external force during operation.

[0037] Example 2: Figure 2 As shown in the comparative embodiment one, another embodiment of the present invention is that a top cover 3 is detachably installed on the top of each of the plurality of annular cavities 7.

[0038] During operation, when maintenance or replacement of heating element 8 is required, the top cover 3 can be easily removed from the top of the annular cavity 7, thereby opening the annular cavity 7 and allowing operators direct access to its interior. After completing the necessary operations, the top cover 3 is reinstalled on top of the annular cavity 7, ensuring that the annular cavity 7 is in a closed state. This guarantees the normal operation of the epitaxy machine during subsequent processes and also prevents external impurities from entering the annular cavity 7 and affecting wafer quality. This removable top cover 3 design greatly improves the maintainability and ease of use of the epitaxy machine.

[0039] like Figure 8 As shown, a method for improving ZDD (zoom-dryness) in epitaxial wafers for BCD products is applicable to the aforementioned epitaxial machine for improving ZDD in epitaxial wafers for BCD products, and includes the following steps: S1. Based on the size of the wafer to be processed, adjust the position of the support 6 through the drive component to accurately position it directly above the corresponding concentric annular cavity 7; S2. Place the wafer to be processed on top of the pad 12 above the support 6, so that the pad 12 makes good contact with the low growth rate region of the wafer. S3. Activate the heating element 8 inside the corresponding concentric annular cavity 7 in the heating base 2 to heat different areas of the wafer. S4. By supplementing more heat to the low growth rate region through "contact heat conduction", the growth rate of the region is increased; the high growth rate region obtains heat only through "air heat conduction" (low thermal conductivity), which inhibits its excessive growth, thereby effectively balancing the growth rate of different crystal orientation positions and reducing the ZDD gap.

[0040] The terms "front," "back," "left," "right," "top," and "bottom" all refer to the figures in the accompanying drawings. Figure 1 Based on the perspective of the observer, the side of the device facing the observer is defined as the front, the left side of the observer is defined as the left, and so on.

[0041] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An epitaxial machine for ZDD improvement of epitaxial wafers for BCD products, characterized in that: include: The epitaxial machine body (1) has a working chamber inside; A heating base (2) is disposed in the working chamber. Multiple concentric annular cavities (7) are arranged radially from the inside to the outside on the heating base (2). Each annular cavity (7) is provided with an independent heating element (8). Multiple support bases (6) are symmetrically distributed around the top of the heating base (2) to support the wafer; each support base (6) has a mounting groove (11) on its top, and a pad (12) can be detachably installed in the mounting groove (11). A driving component is disposed on the heating base (2) and connected to each of the support seats (6) for driving all the support seats (6) to move synchronously so that each of the support seats (6) can be positioned directly above any of the concentric annular cavities (7).

2. An epitaxial machine for ZDD improvement of epitaxial wafers for BCD products according to claim 1, characterized in that: The heating base (2) has a housing (4) fixed at its center. Multiple crossbars (5) are evenly distributed around the housing (4). The crossbars (5) are hollow and one end is fixedly connected to the outer wall of the housing (4). An installation block (13) is slidably sleeved on the crossbars (5). The support base (6) is installed on the installation block (13).

3. An epitaxial machine for ZDD improvement of epitaxial wafers for BCD products according to claim 2, characterized in that: The drive assembly includes a lead screw (15), which is rotatably mounted inside the crossbar (5) via a bearing seat (21). One end of the lead screw (15) extends into the inner cavity of the housing (4) and a gear (22) is fixed on the end. A gear disc (10) is rotatably arranged in the middle of the housing (4), and the gear disc (10) meshes with the gears (22) at the ends of all the lead screws (15). A drive motor (9) for driving the gear disc (10) to rotate is provided on the heating base (2). A connecting block (17) is threaded onto the lead screw (15). The end of the connecting block (17) away from the lead screw (15) passes through a through slot (16) opened on the side wall of the crossbar (5), and the end of the connecting block (17) is fixedly connected to the mounting block (13).

4. An epitaxial machine for ZDD improvement of epitaxial wafers for BCD products according to claim 3, characterized in that: The two side walls of the connecting block (17) slide against the inner wall of the through groove (16).

5. An epitaxial machine for ZDD improvement of epitaxial wafers for BCD products according to claim 2, characterized in that: The support base (6) has a through hole (18) in the middle, the crossbar (5) passes through the through hole (18), and the height of the through hole (18) is greater than the outer diameter of the crossbar (5); a magnetic block (19) is fixed at the bottom of the through hole (18), and multiple magnetic blocks (20) are fixed at intervals along the length direction at the bottom of the inner cavity of the crossbar (5), and the positions of the multiple magnetic blocks (20) correspond to the positions of the multiple annular cavities (7).

6. An epitaxial machine for ZDD improvement of epitaxial wafers for BCD products according to claim 2, characterized in that: The support base (6) is slidably engaged with the mounting block (13); a T-shaped limiting guide rail (14) is fixed on the side wall of the support base (6), and a C-shaped slot is provided on the side wall of the mounting block (13), and the limiting guide rail (14) is slidably positioned in the C-shaped slot.

7. An epitaxial machine for ZDD improvement of epitaxial wafers for BCD products according to claim 1, characterized in that: Multiple fixing blocks (23) are evenly distributed at the bottom of the multiple annular cavities (7), and the heating element (8) is disposed between adjacent fixing blocks (23).

8. An epitaxial machine for ZDD improvement of epitaxial wafers for BCD products according to claim 1, characterized in that: Each of the annular cavities (7) is detachably fitted with a top cover (3).

9. A method for improving ZDD (zoom-dryness) of epitaxial wafers for BCD products, the method being applicable to the epitaxial machine for improving ZDD of epitaxial wafers for BCD products as described in any one of claims 1-8, characterized in that: Includes the following steps: S1. According to the size of the wafer to be processed, adjust the position of the support base (6) by the drive component so that it is precisely positioned above the corresponding concentric annular cavity (7); S2. Place the wafer to be processed on top of the pad (12) above the support (6) so that the pad (12) is in good contact with the low growth rate region of the wafer. S3. Activate the heating element (8) inside the concentric annular cavity (7) corresponding to the heating base (2) to heat different areas of the wafer; S4. By supplementing more heat to the low growth rate region through "contact heat conduction", the growth rate of the region is increased; the high growth rate region obtains heat only through "air heat conduction", which inhibits its excessive growth, thereby effectively balancing the growth rate of different crystal orientation positions and reducing the ZDD gap.

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