Wafer coating device and wafer coating method for improving thickness uniformity of film layer

Abstract

The invention discloses a wafer coating device and a wafer coating method for improving the thickness uniformity of a film layer, and the device comprises a process chamber which is internally provided with a heater, and the heater comprises a heating disc and an upper cover plate; a plurality of mounting holes are formed in the heating disc, and an ejector pin is arranged in each mounting hole; a plurality of first through holes are formed in the upper cover plate; the bottom end of the thimble is connected with the thimble lifting mechanism; an enlarged wafer contact head is arranged at the top end of the ejector pin, the diameter of the wafer contact head is matched with the aperture of the first through hole, and when the ejector pin ascends and descends, the wafer contact head can pass through the first through hole; when the ejector pin descends to the lowest position, the top end of the wafer contact head is not higher than the upper surface of the top cover plate, at least part of the wafer contact head is located in the first through hole, and the wafer contact head is used for reducing airflow flowing through the first through hole. The problem that the thickness of a wafer coating film is not uniform due to heat loss of the ejector pin contact area can be solved, and the uniformity of the thickness of the coating film in the wafer coating process is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to a wafer deposition apparatus and a wafer deposition method for improving the uniformity of film thickness. Background Technology

[0002] Surface acoustic wave (SAW) filters play a crucial role in radio frequency (RF) transmitting and receiving systems. Traditional SAW filters based on interdigital transducers (IDTs) and piezoelectric substrates typically exhibit significant frequency shifts with temperature changes, leading to interference between adjacent frequency bands. Temperature-compensated SAW filters (TC-SAWs), designed by combining a piezoelectric layer and a low-thermal-expansion layer (temperature compensation layer), can compensate for this deficiency. The temperature compensation layer has a significant impact on the quality of TC-SAW devices; a suitable temperature compensation layer can provide better temperature stability and a wider bandwidth.

[0003] However, in reality, process fluctuations and window limitations can affect the performance of temperature compensation layers. For example, when using the P5000 equipment for SIN coating, uneven coating was observed at the four pins on a lithium niobate wafer during the deposition of the temperature compensation layer. Figure 1 As shown in the diagram. Comparative experiments revealed that the coating uniformity was good on ordinary silicon wafers, but significant non-uniformity appeared on lithium niobate wafers. Therefore, this problem is related to the low thermal conductivity of lithium niobate wafers. Furthermore, during coating, the lithium niobate wafer is placed on a heater, supported by four pins. The heater's heating plate and top cover are shown in the diagram. Figure 2 and Figure 3 As shown. Lithium niobate itself has poor thermal conductivity, and its temperature is mainly raised by thermal radiation from the heater below. However, at the pin support point, the gas flowing inside the chamber (close to room temperature) flows upward from the bottom of the heater through the pin via on the heater, thereby carrying away the heat from the pin support point on the back of the wafer, as shown. Figure 4 As shown, the temperature in these four regions is significantly lower than in other areas of the wafer. This temperature gradient is the root cause of the uneven film thickness deposition at the pin points on the wafer due to SIN film deposition. Currently, there is a lack of specific solutions to address this problem. Summary of the Invention

[0004] The purpose of this invention is to provide a wafer coating apparatus and a wafer coating method for improving the uniformity of film thickness, thereby solving the problem of uneven wafer coating thickness caused by heat loss in the contact area of ​​the ejector pins and improving the uniformity of coating thickness in the wafer coating process.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a wafer coating apparatus, comprising: a process chamber, wherein a heater is provided in the process chamber, and the heater includes a heating plate and an upper cover plate;

[0006] The heating plate has multiple mounting holes that penetrate the heating plate, and each mounting hole contains a ejector pin; the upper cover plate has multiple first through holes that penetrate the upper cover plate, and the multiple first through holes correspond one-to-one with the multiple mounting holes; a ejector pin lifting mechanism is provided below the heating plate, and the bottom end of the ejector pin is connected to the ejector pin lifting mechanism.

[0007] The top of the ejector pin is provided with an enlarged wafer contact head, the diameter of which matches the diameter of the first through hole. When the ejector pin moves up and down, the first through hole can accommodate the wafer contact head to pass through.

[0008] When the ejector pin descends to its lowest position, the top tip of the wafer contact head is not higher than the upper surface of the top cover plate, and at least part of the wafer contact head is located in the first through hole. The wafer contact head is used to reduce the airflow through the first through hole.

[0009] Optionally, the wafer contact head is cylindrical, spherical, oblate, or disc-shaped;

[0010] The diameter of the wafer contact head is larger than the diameter of the ejector pin and smaller than the diameter of the first through hole. The difference between the diameter of the first through hole and the diameter of the wafer contact head is in the range of 0.02mm–0.1mm.

[0011] Optionally, the wafer contact head is made of alumina ceramic or aluminum nitride ceramic, and the material of the wafer contact head is the same as that of the ejector pin.

[0012] Optionally, a guide sleeve is provided in the mounting hole, the outer diameter of the guide sleeve matches the diameter of the mounting hole, the inner diameter of the guide sleeve matches the diameter of the ejector pin, and the ejector pin passes through the guide sleeve.

[0013] The top of the guide sleeve is lower than the upper surface of the heating plate. When the ejector pin descends to its lowest position, the wafer contact head is located between the top of the guide sleeve and the upper surface of the upper cover plate.

[0014] Optionally, an annular protrusion is provided around the first through hole on the lower surface of the upper cover plate. When the upper cover plate is placed on the heating plate, the annular protrusion is embedded in the corresponding mounting hole.

[0015] Optionally, the upper surface of the upper cover plate is provided with multiple arc-shaped support protrusions for supporting the edge of the wafer, and the first through hole is disposed adjacent to the arc-shaped support protrusions and located inside the arc-shaped support protrusions.

[0016] In a second aspect, the present invention proposes a wafer deposition method for improving film thickness uniformity, utilizing the wafer deposition apparatus described in the first aspect, the method comprising:

[0017] The wafer to be processed is placed into the process chamber, and the ejector pins are raised to the wafer transfer position to support the wafer by the ejector pin lifting mechanism.

[0018] The multiple ejector pins are gradually lowered to their lowest position to place the wafer on the upper surface of the upper cover plate, and the wafer contact head on each ejector pin is retracted into the first through hole to block the first through hole.

[0019] To perform the coating process, process gas is introduced into the process chamber, protective gas is introduced into the heating plate, and the heating plate is heated to a set temperature on the wafer until a film layer of a set thickness is deposited on the wafer surface.

[0020] Optionally, the wafer includes a lithium niobate wafer.

[0021] Optionally, before transferring the wafer to be processed into the process chamber, the process further includes:

[0022] A metal layer is formed on the back side of the wafer to increase the wafer's thermal conductivity.

[0023] Optionally, the coating process includes a silicon nitride coating process.

[0024] The beneficial effects of this invention are as follows:

[0025] The wafer coating apparatus of the present invention adds a wafer contact head with a larger diameter at the top of the ejector pin. The diameter of the wafer contact head matches the inner diameter of the pin hole (first through hole) on the heater cover plate. When the ejector pin descends to the lowest position for coating, the wafer contact head can retract into the first through hole. The wafer contact head blocks the pin hole, preventing the flowing gas in the chamber from directly scouring the pin hole area on the back of the wafer, reducing heat loss and temperature drop in this area, thereby improving the uniformity of film deposition at the pin hole on the wafer.

[0026] Furthermore, the wafer deposition method for improving film thickness uniformity of the present invention utilizes the above-mentioned improved wafer deposition apparatus to improve the deposition uniformity of the thin film at the pin holes on the wafer; in addition, a metal layer is pre-formed on the back side of the wafer, which increases the thermal conductivity of the wafer (especially the back side). The metal layer can quickly and uniformly transfer heat from the heater to the entire wafer (including the pin contact area), which can effectively compensate for the local temperature drop at the pin point, thereby further improving the uniformity of the deposition thickness.

[0027] The system of the present invention has other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0028] The above and other objects, features and advantages of the present invention will become more apparent from the accompanying drawings, in which like reference numerals generally denote like parts.

[0029] Figure 1 This is a schematic diagram illustrating the uneven coating phenomenon in the pin contact area on a wafer.

[0030] Figure 2 This is a schematic diagram of the heating plate and pin of the heater in an existing wafer coating apparatus.

[0031] Figure 3 This is a schematic diagram of the top cover plate of the heater in an existing wafer coating apparatus.

[0032] Figure 4 This is a schematic diagram of the structure at the pin hole on the heater in an existing wafer coating apparatus and the gas flow at that location.

[0033] Figure 5 This is a schematic diagram of the heater pin structure in a wafer coating apparatus according to Embodiment 1 of the present invention.

[0034] Figure 6a and Figure 6b These are comparison figures showing the coating results of a conventional wafer coating apparatus and the coating results of the wafer coating method of Embodiment 2 of the invention.

[0035] Figure 7a and Figure 7b These are comparison figures showing the coating results of a conventional wafer coating apparatus and the coating results of the wafer coating method of Embodiment 3 of the invention. Detailed Implementation

[0036] The invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0037] Example 1

[0038] This embodiment provides a wafer coating apparatus. Compared with the prior art, the wafer coating apparatus of this embodiment improves the structure of the ejector pin by adding a wafer contact head with a larger diameter at the top of the ejector pin to block the pin hole on the heater and improve the coating effect.

[0039] Specifically, such as Figure 5 As shown, the wafer coating apparatus of this embodiment includes: a process chamber, wherein a heater is provided in the process chamber, the heater including a heating plate 1 and an upper cover plate 2; the heating plate 1 is provided with a plurality of mounting holes 6 penetrating the heating plate 1, and a ejector pin 3 is provided in each mounting hole 6; the upper cover plate 2 is provided with a plurality of first through holes 7 penetrating the upper cover plate 2, and the plurality of first through holes 7 correspond one-to-one with the plurality of mounting holes 6; an ejector pin lifting mechanism is provided below the heating plate 1, and the bottom end of the ejector pin 3 is connected to the ejector pin lifting mechanism;

[0040] The wafer deposition apparatus in this embodiment is a chemical vapor deposition (CVD) device. The process chamber, heating plate 1, upper cover plate 2 structure, and other supporting components such as the lifting mechanism are all consistent with existing CVD equipment. The overall structure of the heating plate 1 and upper cover plate 2 can be referenced. Figure 3 and Figure 4 .

[0041] refer to Figure 5 In this embodiment, the top of the ejector pin 3 is provided with an enlarged wafer contact head 4, the diameter of which matches the diameter of the first through hole 7. When the ejector pin 3 moves up and down, the first through hole 7 can accommodate the wafer contact head 4 to pass through.

[0042] When the ejector pin 3 descends to its lowest position, the top of the wafer contact head 4 is not higher than the upper surface of the top cover plate, and at least part of the wafer contact head 4 is located in the first through hole 7. The wafer contact head 4 is used to reduce the airflow through the first through hole 7.

[0043] The wafer contact head 4 can be cylindrical, spherical, oblate, or disc-shaped; in this embodiment, a cylindrical shape is preferred. The diameter of the wafer contact head 4 is larger than the diameter of the ejector pin 3 and smaller than the diameter of the first through hole 7. The difference between the diameter of the first through hole 7 and the diameter of the wafer contact head 4 is preferably 0.02mm–0.1mm. Specifically, the diameter of the wafer contact head 4 is slightly smaller than the diameter of the first through hole 7 to ensure that the wafer contact head 4 can smoothly pass through the first through hole 7 during the lifting and lowering of the ejector pin 3, while blocking the first through hole 7 when the ejector pin 3 descends to its lowest position, thereby minimizing the airflow through the first through hole 7.

[0044] In this embodiment, the wafer contact head 4 is made of alumina ceramic or aluminum nitride ceramic, and the material of the wafer contact head 4 is the same as that of the ejector pin 3. Preferably, the ejector pin 3 and the wafer contact head 4 are integrally formed.

[0045] In this embodiment, a guide sleeve 5 is provided inside the mounting hole 6. The outer diameter of the guide sleeve 5 matches the diameter of the mounting hole 6, and the inner diameter of the guide sleeve matches the diameter of the ejector pin 3. The ejector pin 3 passes through the guide sleeve 5. The top end of the guide sleeve 5 is lower than the upper surface of the heating plate 1. When the ejector pin 3 descends to its lowest position, the wafer contact head 4 is located entirely between the top end of the guide sleeve 5 and the upper surface of the upper cover plate 2.

[0046] In this embodiment, an annular protrusion is provided around the first through hole 7 on the lower surface of the upper cover plate 2. When the upper cover plate 2 is placed on the heating plate 1, the annular protrusion is embedded in the corresponding mounting hole 6.

[0047] In this embodiment, the upper surface of the upper cover plate 2 is provided with multiple arc-shaped support protrusions for supporting the edge of the wafer. The first through hole 7 is arranged adjacent to the arc-shaped support protrusions and is located inside the arc-shaped support protrusions.

[0048] In this embodiment, the wafer coating apparatus adds a wafer contact head 4 with a larger diameter at the top of the ejector pin 3. The diameter of the wafer contact head 4 matches the inner diameter of the first through hole 7 (pin hole) on the heater upper cover plate 2. When the ejector pin 3 descends to the lowest position for coating, the wafer contact head 4 can retract into the first through hole 7. The wafer contact head 4 blocks the first through hole 7, preventing the flowing gas in the chamber from directly scouring the area of ​​the first through hole 7 on the back of the wafer, reducing heat loss and temperature drop in this area, thereby improving the problem of uneven film deposition thickness at the pin hole on the wafer and improving the uniformity of the overall wafer coating.

[0049] Example 2

[0050] This embodiment provides a wafer deposition method for improving film thickness uniformity, utilizing the wafer deposition apparatus described in Embodiment 1. The method includes:

[0051] The wafer to be processed is placed into the process chamber, and the multiple ejector pins 3 are raised to the wafer transfer position to support the wafer by the ejector pin lifting mechanism.

[0052] The multiple ejector pins 3 are gradually lowered to their lowest position to place the wafer on the upper surface of the upper cover plate 2, and the wafer contact head 4 on each ejector pin 3 is retracted into the first through hole 7 to block the first through hole 7 through the wafer contact head 4.

[0053] To perform the coating process, process gas is introduced into the process chamber, and protective gas is introduced into the heating plate 1, which heats the wafer at a set temperature until a film layer of a set thickness is deposited on the wafer surface.

[0054] In this embodiment, the wafer is a lithium niobate wafer, and the coating process is a silicon nitride coating process.

[0055] The method of this embodiment is applicable to various wafer deposition processes, especially to the fabrication of silicon nitride temperature compensation layers for TC-SAW devices on lithium niobate wafers. The deposition apparatus with the improved pin structure of Example 1 can effectively improve the thickness uniformity of silicon nitride thin films (temperature compensation layers) deposited on lithium niobate wafers with poor thermal conductivity. Figure 6a The image shows the deposition effect of silicon nitride on a lithium niobate wafer using a traditional pin-structure wafer deposition device. It can be seen that there is obvious film thickness unevenness in the pin area on the wafer. Figure 6b The following is a sample of the deposition results of silicon nitride on a lithium niobate wafer using a deposition apparatus with an improved pin structure in this embodiment. It can be seen that the wafer contact head 4 added to the pin 3 blocks the airflow of the first through hole 7, reducing the heat loss at the wafer pin contact point. The problem of uneven coating thickness in the pin point area is significantly improved. The method in this embodiment can form a temperature compensation layer with uniform thickness on the wafer surface, thereby effectively improving the performance of the TC-SAW device.

[0056] In other embodiments, the wafer to be coated can also be a sapphire wafer, a silicon wafer, etc., and the coating process can also be a silicon oxide coating process, etc. This method can also improve the uniformity of wafer coating thickness.

[0057] Example 3

[0058] The difference between this embodiment and embodiment 2 is that, in this embodiment, a metal layer is pre-formed on the back side of the wafer before it is transferred into the process chamber to increase the thermal conductivity of the wafer. The subsequent steps are the same as in embodiment 2.

[0059] Specifically, since the back side of a lithium niobate wafer is exposed lithium niobate material with poor thermal conductivity, this embodiment adds a back-side metallization process before depositing a silicon nitride thin film (temperature compensation layer) on the front side of the wafer. A highly thermally conductive metal layer (e.g., titanium) is pre-deposited on the back side of the wafer. This back-side metal layer significantly improves the thermal conductivity of the entire wafer (especially the back side), enhancing the overall thermal uniformity of the wafer. Even if there is still localized heat dissipation at the pin points, the efficient metal layer can quickly and uniformly transfer heat from the heater to the entire wafer (including the pin contact area), effectively compensating for localized temperature drops at the pin points. This embodiment, by adding a metal layer to the back side of the wafer combined with an improved pin structure coating apparatus, can completely solve the problem of uneven coating thickness in the pin contact area during the lithium niobate wafer silicon nitride coating process. Figure 7a The image shows the coating effect using a traditional pin-structure wafer coating device. It can be seen that there is significant film thickness unevenness in the pin area on the wafer. Figure 7b The method in this embodiment, which involves forming a metal layer on the back side of a lithium niobate wafer and then using a deposition apparatus with an improved ejector pin structure to complete the silicon nitride deposition process, demonstrates that the addition of the wafer contact head 4 on the ejector pin 3 reduces heat loss due to airflow at the pin points. Simultaneously, the metal layer on the back side of the wafer improves the overall thermal conductivity of the wafer, resulting in a more thorough improvement in the uneven deposition thickness problem in the wafer pin contact area. This embodiment's method can form a more uniform temperature compensation layer on the wafer surface, further enhancing the performance of TC-SAW devices.

[0060] It should be noted that the method in this embodiment is not limited to the silicon nitride coating process of lithium niobate wafers. This method is also applicable to improving the uniformity of coating thickness of wafers made of other materials with poor thermal conductivity.

[0061] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A wafer coating apparatus, characterized in that, include: A process chamber, wherein a heater is provided in the process chamber, and the heater includes a heating plate and an upper cover plate; The heating plate has multiple mounting holes that penetrate the heating plate, and each mounting hole contains a ejector pin; the upper cover plate has multiple first through holes that penetrate the upper cover plate, and the multiple first through holes correspond one-to-one with the multiple mounting holes; a ejector pin lifting mechanism is provided below the heating plate, and the bottom end of the ejector pin is connected to the ejector pin lifting mechanism. The top of the ejector pin is provided with an enlarged wafer contact head, the diameter of which matches the diameter of the first through hole. When the ejector pin moves up and down, the first through hole can accommodate the wafer contact head to pass through. When the ejector pin descends to its lowest position, the top tip of the wafer contact head is not higher than the upper surface of the top cover plate, and at least part of the wafer contact head is located in the first through hole. The wafer contact head is used to reduce the airflow through the first through hole.

2. The wafer deposition apparatus according to claim 1, characterized in that, The wafer contact head is cylindrical, spherical, oblate, or disc-shaped; The diameter of the wafer contact head is larger than the diameter of the ejector pin and smaller than the diameter of the first through hole. The difference between the diameter of the first through hole and the diameter of the wafer contact head is in the range of 0.02mm–0.1mm.

3. The wafer deposition apparatus according to claim 1, characterized in that, The wafer contact head is made of alumina ceramic or aluminum nitride ceramic, and the material of the wafer contact head is the same as that of the ejector pin.

4. The wafer deposition apparatus according to claim 2, characterized in that, A guide sleeve is provided inside the mounting hole. The outer diameter of the guide sleeve matches the diameter of the mounting hole, and the inner diameter of the guide sleeve matches the diameter of the ejector pin. The ejector pin passes through the guide sleeve. The top of the guide sleeve is lower than the upper surface of the heating plate. When the ejector pin descends to its lowest position, the wafer contact head is located between the top of the guide sleeve and the upper surface of the upper cover plate.

5. The wafer deposition apparatus according to claim 4, characterized in that, The upper cover plate has an annular protrusion around the first through hole on its lower surface. When the upper cover plate is placed on the heating plate, the annular protrusion is embedded in the corresponding mounting hole.

6. The wafer deposition apparatus according to claim 1, characterized in that, The upper surface of the cover plate is provided with multiple arc-shaped support protrusions for supporting the edge of the wafer. The first through hole is arranged adjacent to the arc-shaped support protrusions and is located inside the arc-shaped support protrusions.

7. A wafer deposition method for improving film thickness uniformity, utilizing the wafer deposition apparatus according to any one of claims 1-6, characterized in that, The method includes: The wafer to be processed is placed into the process chamber, and the ejector pins are raised to the wafer transfer position to support the wafer by the ejector pin lifting mechanism. The multiple ejector pins are gradually lowered to their lowest position to place the wafer on the upper surface of the upper cover plate, and the wafer contact head on each ejector pin is retracted into the first through hole to block the first through hole. To perform the coating process, process gas is introduced into the process chamber, protective gas is introduced into the heating plate, and the heating plate is heated to a set temperature on the wafer until a film layer of a set thickness is deposited on the wafer surface.

8. The wafer deposition method for improving film thickness uniformity according to claim 7, characterized in that, The wafer includes lithium niobate wafers.

9. The wafer deposition method for improving film thickness uniformity according to claim 8, characterized in that, Before the wafer to be processed is transferred into the process chamber, the following steps are also included: A metal layer is formed on the back side of the wafer to increase the wafer's thermal conductivity.

10. The wafer deposition method for improving film thickness uniformity according to claim 7, characterized in that, The coating process includes a silicon nitride coating process.

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