Diffusion deposition method based on a furnace tube apparatus and furnace tube apparatus

Abstract

The present disclosure provides a furnace tube device-based diffusion deposition method and furnace tube device. In the diffusion deposition method, each two wafers are a group, and are placed on a bearing position of a same plane of a wafer boat. Two wafers of a same group are stacked with deposition surfaces facing away from each other. A pre-prepared isolation material layer is placed between the two wafers. The isolation material layer is a soft material layer different from the wafer material, has a heat-resistant temperature not lower than a diffusion deposition temperature, and is not modified before a diffusion deposition process is completed. The furnace tube device is used to perform the diffusion deposition method. The isolation material layer can effectively improve production efficiency, reduce production cost, and effectively reduce wafer damage risk without directly processing the wafer surface. The isolation material layer and the wafer can be effectively avoided from being bonded, which is convenient for subsequent removal. The flexibility of the isolation material layer can not only avoid scratching the wafer, but also play a good buffering role between the wafers.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor technology, and in particular to a diffusion deposition method and furnace tube equipment based on furnace tube equipment. Background Technology

[0002] In related technologies, when using a vertical furnace tube for diffusion deposition of multiple wafers, the wafers are placed one by one on the grooves of each layer of a wafer boat with the deposition surfaces facing up or down. Reactive gases are then supplied to the deposition surfaces of the wafers, thereby depositing the desired thin film on the wafer surface. However, this method suffers from the problem that the non-deposition surfaces (the surfaces corresponding to the deposition surfaces) of each wafer are completely exposed to the gas environment, leading to the deposition of unwanted thin films. To address this issue, existing methods include depositing a protective layer such as a mask on the non-deposition surfaces of the wafers before diffusion deposition, and removing the thin film formed on the non-deposition surfaces of the wafers through processes such as cleaning after diffusion deposition. Both methods not only increase the process flow, further increasing production costs and reducing production efficiency, but also increase the risk of wafer damage and contamination. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this disclosure is to provide a diffusion deposition method and furnace tube equipment based on furnace tube equipment to solve the problems in the related technology.

[0004] The first aspect of this disclosure provides a diffusion deposition method, comprising:

[0005] In the diffusion deposition method, two wafers are placed together on the same plane of the carrier during the deposition process. The two wafers in the same group are stacked with their deposition surfaces facing away from each other. An isolation material layer is placed between the two wafers. The isolation material layer is a soft material layer that is different from the wafer material. Its heat resistance temperature is not lower than the diffusion deposition temperature, and it is not modified before the diffusion deposition process is completed.

[0006] In an embodiment of the first aspect, the diffusion deposition method is high-temperature deposition, and the insulating material layer is high-temperature resistant ceramic fiber cotton.

[0007] In an embodiment of the first aspect, the insulating material layer is porous ceramic fiber cotton.

[0008] In an embodiment of the first aspect, the diffusion deposition method is a low-temperature deposition at a temperature below 400 degrees Celsius, and the insulating material layer is a water-soluble polymer material layer.

[0009] In an embodiment of the first aspect, during initial placement, the circumferential edge of the isolation material layer is bonded to the two wafers by an adhesive, which is removed at high temperature during diffusion deposition or by cleaning after diffusion deposition.

[0010] In an embodiment of the first aspect, the two stacked wafers have opposing bowl-shaped warpages, and the thickness distribution of the insulating material layer is adapted to the warpage distribution of the two wafers.

[0011] In an embodiment of the first aspect, the isolation material layer is provided with a warp improvement structure that can be longitudinally deformed. The warp improvement structure is provided corresponding to the warp position of the two wafers and is used to improve wafer warp through longitudinal deformation during diffusion deposition.

[0012] In an embodiment of the first aspect, the warp-improving structure includes an inflatable bladder and a plurality of elastic columns disposed within the inflatable bladder that expand longitudinally upon heating.

[0013] In an embodiment of the first aspect, the warp-improving structure includes an inflatable bladder and an inert gas filled within the inflatable bladder.

[0014] A second aspect of this disclosure provides a furnace tube apparatus for performing the diffusion deposition method.

[0015] As described above, the diffusion deposition method provided by this invention arranges wafers in pairs, back to back, with an isolation material layer placed between each pair of wafers. This isolation material layer is not corroded or modified before or during diffusion deposition, and its heat resistance temperature is not lower than the diffusion deposition temperature. In other words, the isolation material layer has excellent high-temperature corrosion resistance and its properties remain unchanged before the diffusion deposition process is completed. Therefore, the isolation material layer does not cause process contamination during diffusion deposition, but it effectively prevents deposition gases from entering the back side of the wafer, thereby effectively improving the problem of thin film deposition on the back side of the wafer. Furthermore, this invention uses a pre-fabricated isolation material layer, and the fabrication of the isolation material layer is completely independent of the wafer (the isolation material layer is not directly fabricated on the wafer surface). Compared to existing methods that form protective layers such as masks on the wafer or use cleaning / grinding processes to remove the deposited thin film on the back side of the wafer, this invention can effectively improve production efficiency, reduce production costs, and eliminate the need for direct wafer surface treatment, effectively reducing the risk of wafer damage. This invention uses a soft material layer, different from the wafer material, which effectively avoids bonding between the isolation material layer and the wafer, facilitating subsequent removal. Its flexibility not only prevents scratches on the wafer but also provides good cushioning between wafers, preventing risks such as wafer drop and particle detachment under vibration. Furthermore, by selecting an isolation material compatible with the diffusion deposition method, it helps improve heat distribution and stress distribution on the wafer surface, thereby enhancing film deposition uniformity. Simultaneously, in this invention, the deposition surfaces of every two wafers are exposed to the same gas atmosphere, contributing to improved uniformity between wafers. The furnace tube equipment used to perform this invention is easier to manufacture and maintain, helping to reduce customer operating costs. Attached Figure Description

[0016] Figure 1 The diagram shown is a schematic representation of the structure of two wafers in one embodiment of this disclosure.

[0017] Figure 2 The diagram shown is a schematic representation of two wafers mounted on a crystal boat according to an embodiment of the present disclosure.

[0018] Figure 3 The diagram shown is a structural schematic of the isolation material layer in one embodiment of this disclosure.

[0019] Figure 4 The diagram shown is a schematic representation of the warping of two stacked wafers in one embodiment of this disclosure.

[0020] Figure 5 The diagram shown is a cross-sectional schematic of a warp-improvement structure according to an embodiment of the present disclosure.

[0021] Figure 6 The diagram shown is a cross-sectional schematic of a warp-improvement structure according to another embodiment of this disclosure.

[0022] Figure 7 The middle is shown as Figure 5 Example sectional view.

[0023] Figure 8 The middle is shown as Figure 5 The example shows cross-sectional views of multiple inflatable cysts after expansion.

[0024] Figure 9 The diagram shown is a cross-sectional schematic of a warp-improving structure in another embodiment of this disclosure.

[0025] Figure 10 The diagram shown is a cross-sectional schematic of a warp-improvement structure according to another embodiment of this disclosure.

[0026] Figure label:

[0027] 110. Wafer; 120. Isolation material layer; 140. Warp-corrected structure; 141. Expansion bladder; 142. Elastic pillar; 200. Crystal boat. Detailed Implementation

[0028] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the information disclosed herein. This disclosure can also be implemented or applied through other different specific embodiments, and various details in this disclosure can be modified or changed according to different viewpoints and application modules without departing from the spirit of this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be combined with each other.

[0029] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings, so that those skilled in the art to which this disclosure pertains can readily implement it. This disclosure may be embodied in many different forms and is not limited to the embodiments described herein.

[0030] In diffusion deposition of multiple wafers using a vertical furnace tube, wafers are placed one by one on the support sites of each layer of a wafer boat with the deposition surfaces facing either upwards or downwards. Reactive gases are then supplied to the deposition surfaces of the wafers, thereby depositing the desired thin film on the wafer surface. However, this method suffers from the problem that the non-deposition surfaces (the surfaces corresponding to the deposition surfaces) of each wafer are completely exposed to the gas environment, leading to the deposition of unwanted thin films. To address this issue, existing methods include depositing a mask of inorganic or organic materials such as silicon nitride on the non-deposition surfaces of the wafers before diffusion deposition, and removing the thin film formed on the non-deposition surfaces of the wafers through a grinding process after diffusion deposition. Both methods not only increase the process flow, further increasing production costs and reducing production efficiency, but also increase the risk of wafer damage and contamination. Therefore, this invention proposes an improved solution.

[0031] Figure 1 The diagram shown is a schematic representation of the structure of two wafers in one embodiment of this disclosure. At this point, combined with... Figure 1 This invention provides a diffusion deposition method based on a furnace tube device. In this diffusion deposition method, two wafers 110 are grouped together and placed on a support position on the same plane of a crystal boat 200 (e.g., a groove or a planar support position on the same circumferential surface). The two wafers 110 in the same group are stacked with their deposition surfaces facing away from each other (i.e., their non-deposition surfaces facing each other). An isolation material layer 120 is placed between the two wafers 110, and this same isolation material layer 120 is at least partially in contact with the non-deposition surfaces of the two wafers 110 in the same group. The isolation material layer 120 is a soft material layer, different from the material of the wafers 110, prefabricated before the diffusion deposition process. Its heat resistance temperature is not lower than the diffusion deposition temperature. Furthermore, it retains its original properties and is not modified before the diffusion deposition process, including during pretreatment processes such as cleaning (nitrogen purging) and preheating, as well as during the diffusion deposition process itself.

[0032] Specifically, this invention applies to single-sided deposition of all wafers 110. For example, the wafer 110 can be a silicon wafer, germanium wafer, germanium-silicon wafer, SOI wafer, silicon carbide wafer, or a non-semiconductor substrate, such as a glass substrate. The wafers 110 are placed back-to-back in pairs, with the non-deposition surfaces facing each other. Wafers 110 in the same group are typically of the same type, but this is not limited to this. For example, two wafers 110 in the same group can have different thicknesses or even different materials (provided they can withstand the diffusion deposition and pretreatment process conditions), but they are used to deposit the same thin film. An isolation material layer 120 is placed between wafers 110. The size of the isolation material layer 120 can be determined as needed, for example, usually based on the size of the wafers 110, and is generally no larger than the size of the wafers 110. Preferably, it is the same size as the wafers 110, or at least its circumferential direction can cover the circumferential direction of the two wafers 110, ensuring that the isolation material layer 120 is provided between the two wafers 110 in the circumferential direction. The longitudinal distance between the edge of the isolation material layer 120 and the two wafers 110 is as small as possible, preferably in a close fit, to prevent diffusion gas from entering the back side of the two wafers 110 through the edge during diffusion deposition and depositing a thin film on the back side of the wafers 110. In some other examples, when the size of the isolation material layer is smaller than the wafer size, such that the edge of the back side of the wafer does not contact the isolation material layer, a rigid barrier ring can be provided at the edge of the back side of the wafer to prevent gas from entering the back side of the wafer. The barrier ring can be made of the same material as the wafer boat, such as a quartz ring or a silicon ring. The ring is located on the back edge of each wafer group, while the isolation material layer is located inside it.

[0033] The isolation material layer 120 is prefabricated and is typically custom-made outside the fab. Its material must be strictly determined based on parameters such as the material of the wafer 110, diffusion deposition temperature, pretreatment process conditions, and gas type. It must be ensured that it will not be degraded by high temperatures, corroded, or bonded to the wafer 110 during the diffusion deposition process and during pretreatment processes such as cleaning and preheating before deposition. Simultaneously, the isolation material layer 120 also possesses a certain degree of flexibility to prevent hard collisions with the wafer 110 and to act as a buffer between the two wafers 110.

[0034] The diffusion deposition method of this invention can effectively block deposition gas from entering the back side of wafer 110, thereby effectively improving the problem of thin film deposition on the back side of wafer 110. Compared with existing methods that form protective layers such as masks on wafer 110 or use cleaning / grinding processes to remove the deposited thin film on the back side of wafer 110, this invention can effectively improve production efficiency, reduce production costs, and eliminate the need for direct treatment of the wafer 110 surface, effectively reducing the risk of wafer 110 damage. This invention uses an isolation material layer 120 different from the wafer 110 material, which can effectively prevent bonding between the isolation material layer 120 and the wafer 110, facilitating subsequent removal. Its flexibility not only avoids scratching the wafer 110 but also provides good buffering between wafers 110, preventing the wafer 110 from falling or particles from detaching under vibration. Furthermore, in this invention, the deposition surfaces of every two wafers 110 are exposed to the same gas atmosphere, which helps improve the uniformity between wafers 110.

[0035] Figure 2 The image shown is a schematic diagram illustrating two wafers mounted on a crystal boat according to an embodiment of this disclosure. This is in conjunction with... Figure 2 To illustrate, in specific operations, the stacking of the isolation material layer 120 between wafers 110 and its transfer to the crystal boat 200 of the furnace tube equipment can be completed entirely manually by staff or with the aid of mechanical equipment. For example, a robotic arm can first place a single wafer 110 with its deposition surface facing down on a hollow annular clamping rack, or place it entirely on a disk with a soft protective layer. Then, a staff member places the isolation material layer 120 on the wafer 110, and then the robotic arm places another wafer 110 with its deposition surface facing up on the isolation material layer 120, thus completing the stacking of a single set of wafers 110. The stacked wafers 110 are then transferred to the wafer boat 200 of the furnace tube equipment using a robotic arm (preferably an edge-lifting or edge-clamping type, with its clamping dimensions adjusted according to the thickness of the stacked wafer group 110). The vertical height of the grooves or slots in the wafer boat 200 that support the wafers 110 is also adjusted according to the thickness of the stacked wafer group 110. This operation is repeated until several batches of wafers 110 are placed. The top and bottom wafers 110 on the wafer boat 200 can be filled with dummy wafers, so that no reactive gas needs to be supplied to these two positions during the deposition process, and the dummy wafers can be reused multiple times. After diffusion deposition is completed, the wafers 110 are transferred to a cleaning tank using a robotic arm, during which the isolation material layer 120 is removed.

[0036] To prevent damage to the deposition surface of wafer 110 by transfer equipment such as robotic arms, wafer 110 can be moved by multiple soft chuck units. The chuck unit can be implemented as including multiple uniformly arranged chucks to improve the stability of wafer 110 when it is mounted in or removed from the slot.

[0037] This operation process is merely an example; in reality, the entire process can be carried out mechanically or manually, without any restrictions.

[0038] The thickness of the isolation material layer 120 can be determined based on its material and processing technology. A smaller thickness is better, for example, less than 100 micrometers, to minimize its weight, while ensuring sufficient mechanical strength during diffusion deposition. Its thickness can be the same or different at various locations, depending on the wafer 110. For example, if all wafers 110 are flat, the isolation material layer 120 preferably has a uniform thickness. If the wafers 110 are warped, the two stacked wafers 110 will have different longitudinal spacing at different positions, and the thickness distribution of the isolation material layer 120 can be adaptively adjusted, which will be further explained later.

[0039] In some examples, the diffusion deposition method is high-temperature deposition (greater than 500 degrees Celsius), and the isolation material layer 120 is a high-temperature resistant ceramic fiber cotton / fiber cloth. For example, if the diffusion deposition is a silicon oxide thin film deposition at temperatures greater than 900 degrees Celsius, then the isolation material layer 120 accordingly uses a high-temperature resistant ceramic material, such as fiber cotton whose main components are alumina and silicon oxide, so that it can maintain stable performance for a long time in high-temperature environments, is not easily deformed or damaged, and has good chemical stability. In addition, the thermal conductivity of the isolation material layer 120 can be optimized to enhance the thermal conduction within and between wafers of the wafer 110, improve the temperature uniformity within and between wafers of the wafer 110, thereby helping to improve the uniformity of thin film deposition.

[0040] In other examples, the diffusion deposition method is a low-temperature deposition below 400 degrees Celsius, and the isolation material layer 120 is a water-soluble polymer material layer. For example, if the diffusion deposition is a low-temperature deposition of silica with a deposition temperature not exceeding 300 degrees Celsius, then a polymer material layer such as polyimide with good chemical stability can be used. These polymer material layers are soluble in water or organic solvents such as ethanol, and are easily removed in subsequent cleaning processes. Furthermore, polymer materials have good elasticity, making it easy to process into the desired shape and thickness distribution. In addition, polymer materials have good adhesion, allowing them to adhere well to both sides of the wafer 110, not only providing better protection for the back side of the wafer 110, but also effectively preventing the wafer 110 from slipping during loading and unloading, reducing the risk of fragmentation. Therefore, polymer material layers that are compatible with the diffusion deposition temperature are preferred. It should be emphasized again that in this embodiment, cleaning before diffusion deposition can only be done using dry methods such as nitrogen purging, and not wet cleaning, to prevent residual moisture on the isolation material layer 120 from causing adverse effects.

[0041] Figure 3 The diagram shown is a structural schematic of the isolation material layer in one embodiment of this disclosure. Figure 3 In this example, the isolation material layer 120 may have a porous structure. Exemplarily, the surface of the isolation material layer 120 has a plurality of through-holes arranged in a ring array. For example, when using ceramic fiber cotton, the isolation material layer 120 is a porous ceramic fiber cotton. Using a porous isolation material layer 120 can reduce its weight while ensuring good isolation performance, helping to reduce pressure on the wafer 110 located below it and improving the support stability of the wafer 110. Simultaneously, its porous properties can be used to capture impurity particles entering between the two wafers 110, preventing backside contamination of the wafer 110 and localized hot spots caused by impurity particles. Furthermore, the porous structure can also reduce the contact area between the isolation material layer 120 and the wafer 110, thereby facilitating subsequent removal.

[0042] If the isolation material layer 120 itself has moderate adhesiveness, in some examples, an adhesive can be applied to one or both edges of the isolation material layer 120 during initial placement, i.e., when the isolation material layer 120 is stacked between two wafers 110. This allows the circumferential edges of the isolation material layer 120 to adhere to the two wafers 110 via the adhesive, effectively preventing the wafers 110 from slipping when loaded onto the wafer boat 200. The adhesive is removed at high temperature during diffusion deposition or by washing after diffusion deposition. For example, the adhesive can be a water-soluble or ethanol-soluble polymer material, or other materials that can decompose and volatilize at high temperatures. In other examples, the adhesive can also be applied to one or both sides of the isolation material layer 120, for example, by directly immersing the isolation material layer 120 in an adhesive solution before placement. In some other examples, an adhesive can be applied to the back of wafer 110 and then the isolation material layer 120 can be placed on wafer 110. However, this operation is more complicated and may damage wafer 110. Therefore, it is recommended to work on the isolation material layer 120.

[0043] Figure 4 The image shown is a schematic diagram illustrating the warping of two stacked wafers in one embodiment of this disclosure. Figure 4 In the example, the two stacked wafers 110 have opposing bowl-shaped warpages, and the thickness distribution of the isolation material layer 120 is adapted to the warpage distribution of the two stacked wafers 110. That is, the middle of the two stacked wafers 110 bulges towards each other, so the spacing between the two wafers 110 gradually decreases from the edge to the center. Accordingly, the isolation material layer 120 can be configured with a thickness that decreases from the edge to the center to maintain as much contact as possible with the wafers 110 at the edges. If the wafer 110 has a saddle-shaped warpage, the thickness distribution of the isolation material layer 120 is also adjusted accordingly. The wafer 110 warpage information can be known before diffusion deposition (or can be known in advance based on experience), and the isolation material layer 120 is prefabricated according to the wafer 110 warpage. Typically, the warpage distribution of wafers 110 of the same product and / or the same batch is similar. In each group of wafers 110, the lower wafer 110 will have its bowl-shaped warping slightly improved due to the deposition surface facing downwards under the influence of gravity, but the improvement is still limited.

[0044] Therefore, in a preferred embodiment provided by the present invention, the isolation material layer 120 is provided with a warp improvement structure 140 that can be longitudinally deformed. The warp improvement structure 140 is provided corresponding to the warp position of the two wafers 110, and is used to improve the warp of the wafers 110 through longitudinal deformation during the diffusion deposition process. That is, the warp improvement structure 140 is only provided locally in the isolation material layer 120, and is usually provided in the area where the warp is more severe.

[0045] Figure 5The image shown is a cross-sectional schematic diagram of a warp-improvement structure according to an embodiment of this disclosure. Figure 5 In the example, the warp-improving structure 140 includes an expansion bladder (not shown in the figure) and several elastic pillars 142 disposed within the expansion bladder that expand longitudinally upon heating. From the perspective of improving the stress-bearing surface, the elastic pillars 142 are preferably several cylindrical structures with large circular surfaces at both ends. Their height is determined by considering the sum of the warp of the two wafers 110 and the material's expansion and contraction properties, ensuring that their height after thermal expansion does not exceed the sum of the warp of the two wafers 110. For example, if the warp of a single wafer 110 is 500 micrometers, the height of the elastic pillars 142 can also be set to this height. The specific number of elastic pillars 142 depends on the size of the warp region; for example, it can be a single elastic pillar 142 with a large surface area, or it can be multiple elastic pillars 142 with smaller surface areas spaced apart.

[0046] Exemplarily, the expansion bladder is a cavity made of the insulating material layer 120, and the elastic pillar 142 is, for example, a high-temperature corrosion resistant rubber pillar that can stretch when heated, with its upper and lower ends connected to the two ends of the expansion bladder. During the diffusion deposition process, as the temperature rises, the elastic pillar 142 gradually stretches towards both ends. At the same time, the wafer 110 also exhibits a certain degree of deformation under high-temperature conditions. Therefore, the elastic pillar 142 pushes the opposing convex parts of the two wafers 110 towards opposite directions until the diffusion deposition ends, the temperature drops, and the elastic pillar 142 retracts. The degree of retraction depends on the elastomer material and the diffusion deposition temperature. At this point, the wafer 110 has been shaped, and the warpage is improved.

[0047] Figure 6 The diagram shown is a cross-sectional schematic of a warp-improvement structure according to another embodiment of this disclosure. Figure 7 The middle is shown as Figure 6 A schematic cross-sectional view of the example. Exemplarily, the warpage improvement structure 140 includes an expansion bladder 141 and an inert gas filled within the expansion bladder 141. For example, in a low-temperature diffusion deposition process, an expansion bladder 141 capable of sealing the gas can be fabricated using a polymer material layer. The size of the expansion bladder 141, particularly the size of its surface in contact with the wafer 110, can be determined according to the warpage of the wafer 110, while the amount of gas filled can be determined according to the gas volume expansion coefficient, without specific limitations. The inert gas is preferably a rare gas; in some examples, nitrogen can also be used. The gas gradually expands and lifts the wafer 110 as the chamber temperature increases, maintaining this state throughout the deposition process to promote warpage improvement of the wafer 110. Using an expansion structure with gas is relatively gentler and can effectively avoid damage to the wafer 110 while improving its warpage. Figure 6 and Figure 7In the example, the expansion bladders 141 are implemented in multiple forms, and the multiple expansion bladders 141 are distributed at intervals along the circumferential or radial direction of the wafer 110. Figure 6 and Figure 7 In the example, each of the expansion bladders 141 is implemented as a ring, and the plurality of expansion bladders 141 are distributed radially spaced along the wafer 110 with the radial direction gradually changing with the distribution direction.

[0048] Understandably, the depth of the depression in the center of the bowl-shaped warped wafer 110 gradually increases radially inward, especially in smaller wafers 110. Figure 8 The middle is shown as Figure 6 Cross-sectional schematic diagrams of multiple inflatable cysts after expansion, as shown in the example. Figure 8 In the example, the air pressure inside the plurality of radially distributed expansion bladders 141 gradually increases radially inward. Therefore, when the temperature rises to a specified temperature, the degree of expansion of the plurality of expansion bladders 141 gradually increases radially inward, thereby creating stress offsetting on the deformation regions of the wafer 110 with different radii, so that the wafer 110 tends to be flat and the warpage of the wafer 110 is improved.

[0049] Figure 9 The diagram shown is a cross-sectional schematic of a warp-improving structure according to another embodiment of this disclosure. Figure 9 In the example, multiple inflatable bladders 141 are implemented, each of which is linear. The multiple linear inflatable bladders 141 are distributed at intervals along the circumference of the insulating material layer 120 at its center. Exemplarily, the linearity of the inflatable bladders 141 is implemented as at least one of a straight line, a broken line, or a curve.

[0050] Figure 10 The image shown is a cross-sectional schematic diagram of a warp-improvement structure according to another embodiment of this disclosure. Figure 10 In this example, the inflatable bladder 141 is implemented as a single unit. The horizontal cross-section of the single inflatable bladder 141 is implemented as a vortex shape. Exemplarily, the inflatable bladder 141 is implemented as a gasbag filled with an inert gas.

[0051] Understandably, larger wafers (110) typically exhibit warping with warped edges and a flat central portion. However, when the edges are unable to warp due to resistance, the flat central portion will be concave relative to the edge area to release stress. Figure 10In this example, because the expansion bladder 141 is integrally formed, the internal air pressure at different locations of the expansion bladder 141 is the same. Therefore, when the temperature rises, the expansion degree at different locations of the expansion bladder 141 is the same, so as to achieve uniform stress compensation on the concave central flat portion of the large wafer 110, avoid local undulations in the central flat portion of the wafer 110, and improve the yield of the wafer 110.

[0052] Except for the placement of the wafer 110, the diffusion deposition method of this invention is not significantly different from the prior art in other steps, including heating, ventilation, cooling, and unloading. Since this part is not the focus of this invention, it will not be elaborated upon. After diffusion deposition is completed, the wafer 110 is transferred to a cleaning tank. First, the isolation material layer 120 is removed, and then cleaning is performed according to existing cleaning processes. This process will also not be elaborated upon.

[0053] The diffusion deposition method provided by this invention can be used in various furnace tube processes, such as high-temperature annealing, thin film deposition, oxidation, diffusion and other processes. Its advantages are particularly prominent when used in processes such as silicon oxide and silicon nitride, which are prone to causing deposition on the back side of the wafer.

[0054] The furnace tube apparatus for performing the diffusion deposition method of the present invention has a generally similar overall layout to existing vertical furnace tube apparatuses, with only minor adjustments to the details. Therefore, the present invention also provides a furnace tube apparatus for performing the diffusion deposition method as described in any of the above embodiments. As mentioned earlier, to perform the diffusion deposition method of the present invention, the height of the grooves or slots on the crystal boat 200 of the furnace tube apparatus for placing the wafers 110, and the clamping grooves of a single robotic arm, are adaptively adjusted to accommodate two wafers 110 plus the thickness of an isolation material layer 120. Since two wafers 110 are placed in a single bearing position, the number of bearing positions on the crystal boat 200 can be reduced while bearing the same number of wafers 110. Therefore, the processing difficulty of the crystal boat 200 is relatively lower, which helps to improve the processing yield of the equipment. On the other hand, the gas outlets of the gas supply line also need to be adjusted accordingly. They supply gas to the middle of two adjacent sets of wafers 110, and the gas from each outlet is sufficient for thin film deposition on two adjacent wafers 110. Therefore, the number of outlets can be reduced, but the outlet area and / or gas flow rate can be appropriately increased. Increasing the outlet area helps reduce the risk of blockage in the gas injection line (injector), which is crucial for improving process stability. Furthermore, the heater configuration can be adaptively adjusted according to the wafer 110 arrangement. Overall, the furnace tube equipment implementing the diffusion deposition method of this invention is less difficult to process than existing equipment and easier to clean and maintain, for example, with fewer dead zones during cleaning. This, from another perspective, demonstrates that the diffusion deposition method of this invention will have a cost advantage.

[0055] In summary, the diffusion deposition method provided by this invention arranges wafers in pairs, back to back, with an isolation material layer placed between each pair of wafers. This isolation material layer is uncorroded and unmodified before and during diffusion deposition, and its heat resistance temperature is not lower than the diffusion deposition temperature. That is, the isolation material layer has excellent high-temperature corrosion resistance and its properties remain unchanged before the diffusion deposition process is completed. Therefore, the isolation material layer does not cause process contamination during diffusion deposition, but it effectively prevents deposition gases from entering the back side of the wafer, thereby effectively improving the problem of thin film deposition on the back side of the wafer. Furthermore, this invention uses a pre-fabricated isolation material layer, and the fabrication of the isolation material layer is completely independent of the wafer (the isolation material layer is not directly fabricated on the wafer surface). Compared to existing methods that form protective layers such as masks on the wafer or use cleaning / grinding processes to remove the deposited thin film on the back side of the wafer, this invention can effectively improve production efficiency, reduce production costs, and eliminate the need for direct wafer surface treatment, effectively reducing the risk of wafer damage. This invention uses a soft material layer, different from the wafer material, which effectively avoids bonding between the isolation material layer and the wafer, facilitating subsequent removal. Its flexibility not only prevents scratches on the wafer but also provides good cushioning between wafers, preventing risks such as wafer drop and particle detachment under vibration. Furthermore, by selecting an isolation material compatible with the diffusion deposition method, it helps improve heat distribution and stress distribution on the wafer surface, thereby enhancing film deposition uniformity. Simultaneously, in this invention, the deposition surfaces of every two wafers are exposed to the same gas atmosphere, contributing to improved uniformity between wafers. The furnace tube equipment used to perform this invention is easier to manufacture and maintain, helping to reduce customer operating costs.

[0056] The above embodiments are merely illustrative of the principles and effects of this disclosure and are not intended to limit this disclosure. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this disclosure. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this disclosure should still be covered by the protection scope of this disclosure.

Claims

1. A diffusion deposition method based on furnace tube equipment, characterized in that, In the diffusion deposition method, two wafers are placed together on the same plane of a crystal boat during the deposition process. The two wafers in the same group are stacked with their deposition surfaces facing away from each other. A pre-fabricated isolation material layer is placed between the two wafers. The isolation material layer is a soft material layer different from the wafer material, and its heat resistance temperature is not lower than the diffusion deposition temperature. It is not modified before the diffusion deposition process is completed. The two stacked wafers have opposing bowl-shaped warpages. The thickness distribution of the isolation material layer is adapted to the warpage distribution of the two wafers. The isolation material layer is provided with a warpage improvement structure that can be deformed longitudinally. The warpage improvement structure is set corresponding to the warpage position of the two wafers and is used to improve the wafer warpage through longitudinal deformation during the diffusion deposition process.

2. The diffusion deposition method according to claim 1, characterized in that, The diffusion deposition method is high-temperature deposition, and the isolation material layer is high-temperature resistant ceramic fiber cotton.

3. The diffusion deposition method according to claim 2, characterized in that, The insulating material layer is porous ceramic fiber cotton.

4. The diffusion deposition method according to claim 1, characterized in that, The diffusion deposition method is a low-temperature deposition at a temperature below 400 degrees Celsius, and the isolation material layer is a water-soluble polymer material layer.

5. The diffusion deposition method according to claim 1, characterized in that, During initial placement, the circumferential edge of the isolation material layer is bonded to the two wafers by an adhesive, which is removed at high temperature during diffusion deposition or by cleaning after diffusion deposition.

6. The diffusion deposition method according to claim 1, characterized in that, The warp-correcting structure includes an expansion bladder and several elastic columns disposed within the expansion bladder that expand longitudinally upon heating.

7. The diffusion deposition method according to claim 1, characterized in that, The warp-correcting structure includes an inflatable bladder and an inert gas filled within the inflatable bladder.

8. A furnace tube device, characterized in that, The furnace tube apparatus is used to perform the diffusion deposition method as described in any one of claims 1-7.

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