Thin film deposition method and thin film deposition apparatus

Abstract

The application provides a thin film deposition method and a thin film deposition device, which comprises the following steps: introducing a reducing gas into a pre-cleaning chamber to remove an oxidation layer on a surface to be deposited of a wafer by a reduction reaction with the oxidation layer; and depositing a first metal layer capable of inter-diffusion with the wafer on the surface to be deposited of the wafer in a first deposition chamber by a first magnetron sputtering method; wherein an inter-diffusion structure of the first metal layer and the wafer is obtained by controlling a substrate temperature of the first magnetron sputtering method. The thin film deposition method and the thin film deposition device provided by the application can reduce wafer surface damage, improve the inter-diffusion effect of the metal and the wafer, and obtain a more ideal inter-diffusion structure, so that the chip contact resistance can be reduced, the product performance can be improved, the process steps can be simplified, and the production capacity can be improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and more specifically, to a thin film deposition method and a thin film deposition apparatus. Background Technology

[0002] Backside metallization plays a crucial role in the performance of power device chips. Currently, the mainstream backside metallization process used in IGBTs (Insulated Gate Bipolar Transistors) primarily employs magnetron sputtering to deposit multilayer metals, such as aluminum / titanium / nickel-vanadium / silver stacks.

[0003] In existing thin film deposition methods, during the pre-cleaning step of the wafer backside (i.e., the silicon wafer), plasma bombardment is used to remove the native oxide layer on the silicon wafer surface. Then, an aluminum metal layer is deposited on the pre-cleaned wafer backside using magnetron sputtering at room temperature (e.g., 20°C). The wafer with the deposited aluminum metal is then removed from the magnetron sputtering equipment and passed to a high-temperature annealing unit to obtain an aluminum-silicon intermetallic structure. Finally, it is passed back to the magnetron sputtering unit for titanium / nickel-vanadium / silver metal deposition, thus completing the aluminum / titanium / nickel-vanadium / silver stacked backside metallization process.

[0004] The above-mentioned thin film deposition method inevitably suffers from the following problems in practical applications:

[0005] Firstly, because the pre-cleaning step uses plasma bombardment of the back side of the wafer to remove the natural oxide layer on the silicon substrate surface, the bombardment activates atoms on the silicon wafer surface, leading to the formation of [something] at the interface between the silicon wafer and the aluminum metal. Figure 1 The abnormal silicon bump failure morphology shown cannot form a normal aluminum-silicon intersolubility structure, resulting in high contact resistance of the prepared chip and reduced product performance.

[0006] Secondly, the plasma bombardment of the back of the wafer in the above pre-cleaning step can easily cause some damage to the surface of the silicon wafer, affecting the aluminum-silicon intersolubility effect and thus affecting product performance.

[0007] Third, the above-mentioned thin film deposition method requires removing the wafer from the magnetron sputtering equipment and transferring it to the annealing equipment for annealing, and then returning it to the magnetron sputtering equipment for titanium / nickel vanadium / silver three-layer metal deposition. This results in complicated process steps, affecting production capacity. Moreover, the aluminum metal layer is easily oxidized when exposed to the atmospheric environment, which will also have a certain impact on the bonding force between aluminum and titanium, resulting in low product yield. Summary of the Invention

[0008] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a thin film deposition method and thin film deposition equipment, which can reduce wafer surface damage, improve the mutual solubility effect between metal and wafer, obtain a more ideal mutual solubility structure, thereby reducing chip contact resistance, improving product performance, and simplifying process steps and increasing production capacity.

[0009] To achieve the objectives of this invention, a thin film deposition method is provided, comprising:

[0010] A reducing gas is introduced into the pre-cleaning chamber to remove the oxide layer by reducing it with the oxide layer on the surface of the wafer to be deposited.

[0011] In a first deposition chamber, a first magnetron sputtering method is used to deposit a first metal layer that is miscible with the wafer on the surface to be deposited.

[0012] Specifically, by controlling the base temperature used in the first magnetron sputtering method, a mutually soluble structure between the first metal layer and the wafer is obtained.

[0013] Optionally, the base temperature in the first magnetron sputtering method is controlled to be greater than or equal to 300°C and less than or equal to 380°C.

[0014] Optionally, after depositing a first metal layer miscible with the wafer on the surface to be deposited on the wafer using a first magnetron sputtering method in the first deposition chamber, the thin film deposition method further includes:

[0015] In the second deposition chamber, a second magnetron sputtering method is used to deposit a second metal layer on the wafer on which the first metal layer has been deposited.

[0016] Specifically, the wafer is cooled by controlling the base temperature used in the second magnetron sputtering method, and the wafer is controlled at a first wafer temperature after the deposition of the second metal layer is completed, so as to promote the mutual solubility between the first metal layer and the wafer.

[0017] Optionally, after depositing a second metal layer on the wafer on which the first metal layer has been deposited using a second magnetron sputtering method in the second deposition chamber, the thin film is deposited...

[0018] Product methods also include:

[0019] In the third deposition chamber, a third magnetron sputtering method is used to deposit a third metal layer on the wafer on which the second metal layer has been deposited;

[0020] Specifically, the wafer is cooled by controlling the base temperature used in the third magnetron sputtering method, and the wafer is controlled at a second wafer temperature after the deposition of the third metal layer is completed, so as to promote the mutual solubility between the first metal layer and the wafer.

[0021] Optionally, after depositing a third metal layer on the wafer on which the second metal layer is deposited using a third magnetron sputtering method in the third deposition chamber, the thin film deposition method further includes:

[0022] The wafer is cooled in a cooling chamber and its temperature is controlled at a third wafer temperature to promote the intersolubility of the first metal layer with the wafer.

[0023] Optionally, after cooling the wafer in the cooling chamber, the thin film deposition method further includes:

[0024] In the fourth deposition chamber, a fourth magnetron sputtering method is used to deposit a fourth metal layer on the wafer on which the third metal layer has been deposited;

[0025] Specifically, by controlling the base temperature used in the fourth magnetron sputtering method, the wafer is cooled, and the wafer after the deposition of the fourth metal layer is controlled at the fourth wafer temperature to promote the mutual solubility between the first metal layer and the wafer.

[0026] Optionally, the temperature of the first wafer is greater than or equal to 250°C and less than or equal to 300°C; the temperature of the second wafer is greater than or equal to 300°C and less than or equal to 330°C; the temperature of the third wafer is greater than or equal to 210°C and less than or equal to 240°C; and the temperature of the fourth wafer is greater than or equal to 300°C and less than or equal to 330°C.

[0027] Optionally, the substrate temperature in the second magnetron sputtering method is controlled to be below 0°C; the substrate temperature in the third magnetron sputtering method is controlled to be below 0°C; and the substrate temperature in the fourth magnetron sputtering method is controlled to be below 0°C.

[0028] Optionally, the wafer is made of silicon; the first metal layer is aluminum; the second metal layer is titanium; the third metal layer is nickel-vanadium; and the fourth metal layer is silver.

[0029] As another technical solution, the present invention also provides a thin film deposition apparatus applied to the thin film deposition method provided by the present invention. The thin film deposition apparatus includes the pre-cleaning chamber and the first deposition chamber, wherein the first deposition chamber is provided with a base and a deposition ring surrounding the base. The deposition ring has an annular support portion, the top of which is higher than the upper surface of the base, for supporting the lower surface edge region of the wafer; the base in the first deposition chamber has a heating function.

[0030] A cooling channel for conveying the cooling medium is provided in the deposition ring. The inlet and outlet of the cooling channel are connected to the cooling circulation system through two flexible pipes, respectively.

[0031] Optionally, the thin film deposition apparatus may further include a second deposition chamber, a third deposition chamber, a fourth deposition chamber, a cooling chamber, and a loading / unloading chamber, or may further include a second deposition chamber, a third deposition chamber, a fourth deposition chamber, and a loading / unloading chamber with cooling function; wherein the base in the second deposition chamber, the third deposition chamber, and the fourth deposition chamber has a cooling function.

[0032] The present invention has the following beneficial effects:

[0033] The thin film deposition method and equipment provided by this invention employ a reduction pre-cleaning technique. This involves introducing a reducing gas into the pre-cleaning chamber to reduce the oxide layer on the wafer's surface to be deposited, thereby removing the oxide layer with minimal damage and avoiding activation of atoms on the silicon wafer surface, thus preventing abnormal silicon bump failure morphologies. Furthermore, when depositing a first metal layer that is miscible with the wafer on the wafer's surface using a first magnetron sputtering method, controlling the substrate temperature allows for the acquisition of a miscible structure between the first metal layer and the wafer. This eliminates the need for the annealing process in existing technologies, and consequently, eliminates the need to transfer the wafer between the magnetron sputtering equipment and the annealing equipment. This not only simplifies the process and increases production capacity but also prevents the first metal layer from being exposed to the atmosphere, ensuring the bonding strength between metals and ultimately improving product performance. Attached Figure Description

[0034] Figure 1 This is a scanning electron microscope image of the abnormal silicon protrusion failure morphology generated at the interface between silicon wafer and aluminum metal in the prior art.

[0035] Figure 2 A flowchart of a thin film deposition method provided in an embodiment of the present invention;

[0036] Figure 3Another flowchart of the thin film deposition method provided in an embodiment of the present invention;

[0037] Figure 4 The scanning electron microscope (SEM) image of the interface between the silicon wafer and aluminum metal obtained after steps S1 to S6 of the thin film deposition method provided in this embodiment of the invention.

[0038] Figure 5 This is a schematic diagram of the structure of the first deposition chamber of the thin film deposition apparatus provided in an embodiment of the present invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions of the present invention, the thin film deposition method and thin film deposition equipment provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0040] Please see Figure 2 The thin film deposition method provided in this embodiment of the invention is applied, for example, to a back-side metallization process, i.e., depositing a multilayer metal, such as an aluminum / titanium / nickel / vanadium / silver multilayer, on the back side of a silicon wafer. This thin film deposition method includes:

[0041] S1. A reducing gas is introduced into the pre-cleaning chamber to remove the oxide layer by reducing it with the oxide layer on the surface of the wafer to be deposited.

[0042] The aforementioned pre-cleaning chamber is a chamber in a thin film deposition apparatus used for pre-cleaning.

[0043] In step S1 above, a plasma-free reduction pre-cleaning technique is used to remove the oxide layer with minimal damage, while avoiding activation of atoms on the silicon wafer surface, thereby preventing abnormal silicon bump failure morphologies. The oxide layer mentioned above is, for example, the native oxide layer on the silicon wafer.

[0044] Optionally, the substrate temperature in the first magnetron sputtering method is controlled to be greater than or equal to 300°C and less than or equal to 380°C. By controlling the substrate temperature within this range, it is beneficial for the reducing gas to undergo a reduction reaction with the oxide layer on the surface of the wafer to be deposited.

[0045] Optionally, the reducing gas may include, for example, hydrogen. The chamber pressure is greater than or equal to 3 mT and less than or equal to 4 mT.

[0046] For back-side metallization, the surface to be deposited on the wafer is the back side, that is, the front side of the wafer is opposite to the surface of the substrate used to support the wafer. Of course, in practical applications, the surface to be deposited can also be the front side of the wafer, and the embodiments of the present invention do not have any particular limitation on this.

[0047] Optionally, before performing step S1 above, the thin film deposition method may further include:

[0048] S01. Clean the surface of the wafer to be deposited;

[0049] S02. Bake the wafer to dry it.

[0050] Optionally, the baking temperature is greater than or equal to 150°C and less than or equal to 200°C.

[0051] S2. In the first deposition chamber, a first metal layer that is miscible with the wafer is deposited on the surface to be deposited of the wafer using a first magnetron sputtering method.

[0052] The aforementioned first deposition chamber is a magnetron sputtering chamber in a thin-film deposition apparatus used for depositing a first metal layer. For example, the thin-film deposition apparatus includes, but is not limited to, a transfer chamber, the aforementioned pre-cleaning chamber, the first deposition chamber, and a load-lock chamber. The pre-cleaning chamber, the first deposition chamber, and the load-lock chamber surround the transfer chamber, and a robotic arm in the transfer chamber can transfer the wafer between these chambers. A liftable base is provided in the first deposition chamber to support the wafer, and this base integrates a heating device to heat the wafer. Furthermore, a target (made of the same material as the first metal layer) is provided at the top of the first deposition chamber. This target is electrically connected to a sputtering power source, which applies sputtering power to the target to excite the sputtering gas in the first deposition chamber to form plasma. This sputtering power source is, for example, a DC power source. The first magnetron sputtering method described above includes: introducing a process gas (e.g., argon) into a first deposition chamber and turning on a sputtering power supply to excite the process gas to form plasma; the plasma bombards the target material to cause target atoms to escape from the target surface and deposit on the wafer to form a first metal layer.

[0053] In step S2 above, the substrate temperature used in the first magnetron sputtering method is controlled to obtain a mutual fusion structure between the first metal layer and the wafer.

[0054] When using step S2 above, i.e., depositing a first metal layer that is miscible with the wafer on the surface to be deposited using the first magnetron sputtering method, a miscible structure between the first metal layer and the wafer can be obtained by controlling the substrate temperature. In other words, while depositing the first metal layer, heating the wafer by controlling the substrate temperature can increase the wafer temperature, promoting the miscibility of the first metal layer and the wafer to obtain a miscible structure. The presence of this miscible structure can reduce chip contact resistance and improve product performance. Therefore, the thin film deposition method provided by this embodiment of the invention can eliminate the annealing process in the prior art, thus eliminating the need to transfer the wafer between the thin film deposition equipment and the annealing equipment. This not only simplifies the process steps and increases production capacity but also avoids exposing the first metal layer to the atmospheric environment, thereby ensuring the bonding force between metals and improving product performance.

[0055] In some optional embodiments, in step S2 above, the base temperature used in the first magnetron sputtering method is greater than or equal to 300°C and less than or equal to 380°C. By setting the base temperature within this range, not only can the mutual solubility between the first metal layer and the wafer be promoted to obtain a more ideal mutual solubility structure, but also, by using a higher base temperature, the annealing process in the prior art can be replaced, and a basis is provided for ensuring that the wafer temperature reaches a reasonable range when depositing the stacked metals. This ensures that after all metal layers are deposited, the wafer temperature is always controlled within the temperature range that can promote the mutual solubility between the first metal layer and the wafer, further simplifying the process steps and increasing production capacity.

[0056] In some alternative embodiments, please refer to Figure 3 The thin film deposition method provided in this embodiment of the invention can be applied to depositing multilayer metals on a wafer. That is, after the deposition of the first metal layer is completed in step S2 above, the thin film deposition method further includes:

[0057] S3. In the second deposition chamber, a second magnetron sputtering method is used to deposit a second metal layer on the wafer on which the first metal layer has been deposited.

[0058] The aforementioned second deposition chamber is a magnetron sputtering chamber in a thin-film deposition apparatus used for depositing a second metal layer. For example, the thin-film deposition apparatus includes, but is not limited to, a transport chamber, the aforementioned pre-cleaning chamber, a first deposition chamber, a second deposition chamber, and a loading / unloading chamber. These chambers surround the transport chamber, and a robotic arm within the transport chamber can transport wafers between them. The second deposition chamber has a structure largely the same as the first deposition chamber, but the target material and the structure and function of the base differ. Specifically, the target material in the second deposition chamber is the same as that of the second metal layer, and the base in the second deposition chamber integrates a cooling device for cooling the wafer. The aforementioned second magnetron sputtering method is the same as the aforementioned first magnetron sputtering method, used to form the second metal layer.

[0059] In this method, by controlling the substrate temperature used in the second magnetron sputtering, the wafer can be cooled, and the temperature of the first wafer after the deposition of the second metal layer can be controlled to promote the intersolubility of the first metal layer and the wafer. In other words, controlling the wafer temperature to the first wafer temperature is beneficial for further increasing the formation of the intersolubility structure. Optionally, the first wafer temperature is greater than or equal to 250°C and less than or equal to 300°C; alternatively, the substrate temperature is below 0°C to cool the wafer. When depositing the second metal layer using the second magnetron sputtering method, the particle energy is higher during magnetron sputtering, and the deposition time is longer than that of the first metal layer deposition using the first magnetron sputtering method. This leads to an increase in wafer temperature. In this case, it is necessary to use the substrate to cool the wafer to control the wafer temperature at the aforementioned first wafer temperature.

[0060] In some alternative embodiments, please refer to Figure 3 After the deposition of the second metal layer is completed in step S3 above, the thin film deposition method further includes:

[0061] S4. A third metal layer is deposited on the wafer on which the second metal layer has been deposited using a third magnetron sputtering method in the third deposition chamber;

[0062] The aforementioned third deposition chamber is a magnetron sputtering chamber in a thin-film deposition apparatus used for depositing a third metal layer. For example, the thin-film deposition apparatus includes, but is not limited to, a transport chamber, the aforementioned pre-cleaning chamber, a first deposition chamber, a second deposition chamber, a third deposition chamber, and a loading / unloading chamber. These chambers surround the transport chamber, and a robotic arm within the transport chamber can transport the wafer between them. The third deposition chamber has a structure substantially similar to the second deposition chamber, but the target material differs; that is, the target material in the third deposition chamber is the same as that of the third metal layer. The third magnetron sputtering method is the same as the second magnetron sputtering method used to form the third metal layer. Furthermore, the base in the third deposition chamber integrates a cooling device for cooling the wafer.

[0063] Specifically, by controlling the substrate temperature used in the third magnetron sputtering method, the temperature of the second wafer after the deposition of the third metal layer is controlled, thereby promoting the intersolubility of the first metal layer and the wafer. In other words, controlling the wafer temperature to the second wafer temperature is beneficial for further increasing the formation of the intersolubility structure. Optionally, the second wafer temperature is greater than or equal to 300°C and less than or equal to 330°C. Optionally, the substrate temperature is below 0°C to cool the wafer. When depositing the third metal layer using the third magnetron sputtering method, the particle energy is higher during magnetron sputtering, and the deposition time is longer than that of the first metal layer deposition using the first magnetron sputtering method. This leads to an increase in wafer temperature. In this case, it is necessary to use the substrate to cool the wafer to control the wafer temperature at the aforementioned second wafer temperature.

[0064] After depositing metals such as nickel and vanadium, the wafer needs to be cooled due to its high temperature to meet the requirements of subsequent processes. In some optional embodiments, after the deposition of the third metal layer is completed in step S4 above, please refer to... Figure 3 Thin film deposition methods also include:

[0065] S5. Cool the wafer in the cooling chamber and control the wafer temperature at the third wafer temperature to promote the mutual dissolution of the first metal layer with the wafer.

[0066] By controlling the wafer temperature at the third wafer temperature, it is beneficial to further increase the formation of intermetallic structures while meeting the requirements of the fourth metal layer deposition process. Optionally, the third wafer temperature is greater than or equal to 210°C and less than or equal to 240°C.

[0067] Optionally, the aforementioned cooling chamber can be a separate chamber within the thin film deposition equipment, or it can be a load-lock chamber with integrated cooling functionality. For example, the thin film deposition equipment includes, but is not limited to, a transfer chamber, the aforementioned pre-cleaning chamber, a first deposition chamber, a second deposition chamber, a third deposition chamber, a cooling chamber, and a load-lock chamber. These chambers surround the transfer chamber, and a robotic arm within the transfer chamber can transfer wafers between them. Alternatively, the thin film deposition equipment may include, but is not limited to, a transfer chamber, the aforementioned pre-cleaning chamber, a first deposition chamber, a second deposition chamber, a third deposition chamber, a cooling chamber, and a load-lock chamber with integrated cooling functionality.

[0068] In some optional embodiments, after cooling the wafer in the cooling chamber in step S5 above, please refer to... Figure 3 Thin film deposition methods also include:

[0069] S6. Deposit a fourth metal layer on a wafer on which a third metal layer has been deposited using a fourth magnetron sputtering method in the fourth deposition chamber;

[0070] The aforementioned fourth deposition chamber is a magnetron sputtering chamber in a thin-film deposition apparatus used for depositing a fourth metal layer. For example, the thin-film deposition apparatus includes, but is not limited to, a transport chamber, the aforementioned pre-cleaning chamber, a first deposition chamber, a second deposition chamber, a third deposition chamber, a fourth deposition chamber, a cooling chamber, and a loading / unloading chamber. These chambers surround the transport chamber, and a robotic arm in the transport chamber can transport wafers between them. Alternatively, the thin-film deposition apparatus includes, but is not limited to, a transport chamber, the aforementioned pre-cleaning chamber, a first deposition chamber, a second deposition chamber, a third deposition chamber, a fourth deposition chamber, and a loading / unloading chamber with integrated cooling functionality. The fourth deposition chamber has a structure substantially the same as the aforementioned second and third deposition chambers, but the target material is different; that is, the target material in the fourth deposition chamber is the same as the material of the fourth metal layer. The fourth magnetron sputtering method described above is the same as the second and third magnetron sputtering methods described above, and is used to form the fourth metal layer. In addition, the substrate in the fourth deposition chamber integrates a cooling device for cooling the wafer.

[0071] Specifically, by controlling the substrate temperature used in the fourth magnetron sputtering method, the wafer is cooled, and the temperature of the fourth wafer after the deposition of the fourth metal layer is controlled to promote the intersolubility between the first metal layer and the wafer. In other words, controlling the wafer temperature at the fourth wafer temperature is beneficial for further increasing the formation of the intersolubility structure. Optionally, the fourth wafer temperature is greater than or equal to 300°C and less than or equal to 330°C. Optionally, the substrate temperature is below 0°C to cool the wafer. When depositing the fourth metal layer using the fourth magnetron sputtering method, the particle energy is higher during magnetron sputtering, and the deposition time is longer than that of the first metal layer deposition using the first magnetron sputtering method. This leads to an increase in wafer temperature. In this case, it is necessary to use the substrate to cool the wafer to control the wafer temperature at the aforementioned fourth wafer temperature.

[0072] As can be seen from the above, in steps S1 to S6, after all the metal layers have been deposited, the wafer temperature is always controlled within the temperature range that can promote the mutual solubility between the first metal layer and the wafer. That is, by controlling the wafer temperature throughout the deposition process and keeping the wafer temperature between 210°C and 350°C, the mutual solubility effect between the first metal layer and the wafer can be improved, and a more ideal mutual solubility structure can be obtained, thereby reducing the chip contact resistance and improving product performance.

[0073] In one specific embodiment, the wafer is a silicon wafer; the first metal layer is aluminum; the second metal layer is titanium; the third metal layer is nickel-vanadium; and the fourth metal layer is silver. The thin film deposition method provided in this embodiment includes the steps S1 to S6 described above. In this case, in step S2, the substrate temperature is greater than or equal to 300°C and less than or equal to 380°C; the chamber pressure is greater than or equal to 2 mT and less than or equal to 3 mT; and the thickness of the first metal layer is greater than or equal to... and less than or equal to The wafer temperature after the process is completed is greater than or equal to 300℃ and less than or equal to 320℃.

[0074] After completing step S2, step S3 can be executed directly without the annealing process in the prior art. This eliminates the need to transfer wafers between the thin film deposition equipment and the annealing equipment, thereby simplifying the process steps, increasing production capacity, and preventing the first metal layer from being exposed to the atmospheric environment. This ensures the bonding force between the metals and improves product performance.

[0075] In step S3 above, the base temperature is below 0°C, for example, -20°C; the process gas includes argon; the chamber pressure is greater than or equal to 2 mT and less than or equal to 3 mT; the thickness of the second metal layer is... The temperature of the first wafer after the process is completed is greater than or equal to 250°C and less than or equal to 300°C.

[0076] In step S4 above, the base temperature is below 0°C, for example, -30°C; the process gases include argon and nitrogen; the chamber pressure is greater than or equal to 2 mT and less than or equal to 3 mT; the thickness of the third metal layer is greater than or equal to... and less than or equal to The temperature of the second wafer after the process is completed is greater than or equal to 300℃ and less than or equal to 330℃.

[0077] In step S5 above, the wafer is cooled in the cooling chamber. That is, a cooling chamber is added to the thin film deposition equipment or the loading and unloading chamber with integrated cooling function is used to cool the wafer. This can enhance the cooling capacity and improve the cooling efficiency. Compared with the cooling step in the magnetron sputtering chamber in the prior art, no additional cooling time is required, thereby shortening the process time of the third deposition chamber and increasing the machine's capacity.

[0078] In step S5 above, the method of cooling the wafer in the cooling chamber includes: directly transferring the wafer into the cooling chamber after the nickel-vanadium deposition process is completed, introducing a certain amount of argon gas, and letting the wafer stand for 30s-60s while maintaining the chamber pressure at 0.5T, thereby completing the cooling of the wafer. The temperature of the third wafer after the process is completed is greater than or equal to 210℃ and less than or equal to 240℃.

[0079] In step S6 above, the base temperature is below 0°C, for example, -20°C; the process gas includes argon; the chamber pressure is greater than or equal to 2 mT and less than or equal to 3 mT; the thickness of the fourth metal layer is greater than or equal to... and less than or equal to The temperature of the fourth wafer after the process is completed is greater than or equal to 300℃ and less than or equal to 330℃.

[0080] Figure 4 This refers to the scanning electron microscope (SEM) image of the interface between the silicon wafer and aluminum metal obtained after completing steps S1 to S6. (Example:) Figure 3 As shown, the thin film deposition method provided in this embodiment of the invention can obtain an ideal intersoluble structure (i.e., an aluminum-silicon intersoluble structure), thereby reducing the contact resistance of the chip and effectively improving product performance.

[0081] As another technical solution, this embodiment of the invention also provides a thin film deposition apparatus, which is applied to the thin film deposition method provided in this embodiment of the invention. The thin film deposition apparatus includes a pre-cleaning chamber and a first deposition chamber, wherein the pre-cleaning chamber is used to perform the above-mentioned step S1, that is, to remove the oxide layer by undergoing a reduction reaction with the oxide layer on the surface to be deposited on the wafer.

[0082] Please see Figure 5The first deposition chamber 1 contains a base 2 and a deposition ring 3 surrounding the base 2. The base 2 has a heating function, i.e., it integrates a heating device for heating the wafer. The deposition ring 3 has an annular support portion 31, the top of which is higher than the upper surface of the base 2, for supporting the lower surface edge region of the wafer 5. For the back-side metallization process, the surface to be deposited on the wafer 5 is the back side of the wafer, i.e., the front side of the wafer is opposite to the surface of the base used to support the wafer. In this case, to avoid damage to the front side of the wafer due to contact with the base, the top of the annular support portion 31 supports the lower surface edge region of the wafer 5, forming a gap between the front side of the wafer and the base surface to protect the front side pattern of the wafer. Optionally, this gap is greater than or equal to 2 mm.

[0083] However, during continuous mass production, as the high-energy target atoms accumulate energy and heat up in the grooves under the deposition ring, the temperature of the deposition ring 3 near the annular support 31 becomes abnormally high. This results in a significant temperature difference between the wafer edge and the center, leading to greater warping of the wafer 5 after the magnetron sputtering process. Greater warping also increases the risk of fragmentation. To address this issue, optionally, a cooling channel 32 for conveying a cooling medium (e.g., cooling water) is provided in the deposition ring 3. The inlet and outlet of this cooling channel 32 are connected to a cooling circulation system (not shown in the figure) via two flexible pipes 4. Since the base 2 is generally liftable, the two flexible pipes 4 ensure that the lifting movement of the base 2 can proceed normally. During the magnetron sputtering process, by circulating the cooling medium into the cooling channel 32, the surface temperature of the deposition ring 3 can be kept stable at a relatively low level, solving the wafer warping problem caused by the accumulated temperature of the deposition ring 3.

[0084] In one specific embodiment, wafer 5 is a silicon wafer; the first metal layer is aluminum; the second metal layer is titanium; the third metal layer is nickel-vanadium; and the fourth metal layer is silver. The semiconductor process equipment provided in this embodiment of the invention is applied to a thin film deposition method including the above-described steps S1 to S6. In this case, the semiconductor process equipment further includes a transfer chamber, a second deposition chamber, a third deposition chamber, a fourth deposition chamber, a cooling chamber, and a loading / unloading chamber. The aforementioned pre-cleaning chamber, first deposition chamber, second deposition chamber, third deposition chamber, fourth deposition chamber, cooling chamber, and loading / unloading chamber surround the transfer chamber. A robotic arm in the transfer chamber can transfer the wafer between the aforementioned pre-cleaning chamber, first deposition chamber, second deposition chamber, third deposition chamber, fourth deposition chamber, cooling chamber, and loading / unloading chamber. The aforementioned first to fourth deposition chambers are used to deposit an aluminum / titanium / nickel-vanadium / silver stack on the back side of the silicon wafer. Alternatively, it may also include a transfer chamber, a second deposition chamber, a third deposition chamber, a fourth deposition chamber, and a loading / unloading chamber with integrated cooling function.

[0085] Optionally, the structures of the second, third, and fourth sedimentation chambers can be the same as described above. Figure 5 The structures of the first deposition chambers shown are generally the same, but the materials of the target and the structure and function of the base are different. Specifically, the materials of the target in each deposition chamber are the same as the materials of the metal layers to be deposited. The bases in the second, third and fourth deposition chambers have cooling functions, that is, they are integrated with cooling devices for cooling the wafer, while the base in the first deposition chamber has heating functions, that is, it is integrated with heating devices for heating the wafer.

[0086] In summary, the thin film deposition method and equipment provided in this invention employ reduction pre-cleaning technology. Specifically, a reducing gas is introduced into the pre-cleaning chamber to reduce the oxide layer on the wafer's surface to be deposited, thereby removing the oxide layer with minimal damage. This avoids activating atoms on the silicon wafer surface, preventing abnormal silicon bump failure morphologies. Furthermore, when depositing a first metal layer that is miscible with the wafer on the wafer's surface using the first magnetron sputtering method, controlling the substrate temperature allows for the acquisition of a miscible structure between the first metal layer and the wafer. This eliminates the need for the annealing process in existing technologies, thus eliminating the need to transfer the wafer between the magnetron sputtering equipment and the annealing equipment. This simplifies the process, increases production capacity, and prevents the first metal layer from being exposed to the atmosphere, ensuring the bonding strength between metals and improving product performance.

[0087] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A thin film deposition method, characterized in that, include: A reducing gas is introduced into the pre-cleaning chamber to remove the oxide layer by reducing it with the natural oxide layer on the surface of the wafer to be deposited. In a first deposition chamber, a first magnetron sputtering method is used to deposit a first metal layer that is miscible with the wafer on the surface to be deposited; wherein, by controlling the base temperature used in the first magnetron sputtering method, a miscible structure between the first metal layer and the wafer is obtained; the base temperature in the first magnetron sputtering method is greater than or equal to 300°C and less than or equal to 380°C. In the second deposition chamber, a second magnetron sputtering method is used to deposit a second metal layer on the wafer on which the first metal layer has been deposited. In this method, the wafer is cooled by controlling the substrate temperature used in the second magnetron sputtering method; the substrate temperature in the second magnetron sputtering method is below 0°C. A third metal layer is deposited on the wafer on which the second metal layer has been deposited in a third deposition chamber using a third magnetron sputtering method; wherein the wafer is cooled by controlling the substrate temperature used in the third magnetron sputtering method; the substrate temperature in the third magnetron sputtering method is below 0°C.

2. The thin film deposition method according to claim 1, characterized in that, The step of depositing a second metal layer on the wafer on which the first metal layer has been deposited using a second magnetron sputtering method in a second deposition chamber further includes: The wafer is controlled at a first wafer temperature after the deposition of the second metal layer is completed, so as to promote the mutual solubility of the first metal layer and the wafer.

3. The thin film deposition method according to claim 2, characterized in that, The step of depositing a third metal layer on the wafer on which the second metal layer has been deposited using a third magnetron sputtering method in a third deposition chamber further includes: The wafer is heated to a second wafer temperature after the deposition of the third metal layer is completed, in order to promote the mutual solubility of the first metal layer and the wafer.

4. The thin film deposition method according to claim 3, characterized in that, After depositing a third metal layer on the wafer on which the second metal layer has been deposited using a third magnetron sputtering method in the third deposition chamber, the thin film deposition method further includes: The wafer is cooled in a cooling chamber and its temperature is controlled at a third wafer temperature to promote the intersolubility of the first metal layer with the wafer.

5. The thin film deposition method according to claim 4, characterized in that, After cooling the wafer in the cooling chamber, the thin film deposition method further includes: In the fourth deposition chamber, a fourth magnetron sputtering method is used to deposit a fourth metal layer on the wafer on which the third metal layer has been deposited; Specifically, by controlling the base temperature used in the fourth magnetron sputtering method, the wafer is cooled, and the wafer after the deposition of the fourth metal layer is controlled at the fourth wafer temperature to promote the mutual solubility between the first metal layer and the wafer.

6. The thin film deposition method according to claim 5, characterized in that, The temperature of the first wafer is greater than or equal to 250°C and less than or equal to 300°C; the temperature of the second wafer is greater than or equal to 300°C and less than or equal to 330°C; the temperature of the third wafer is greater than or equal to 210°C and less than or equal to 240°C; and the temperature of the fourth wafer is greater than or equal to 300°C and less than or equal to 330°C.

7. The thin film deposition method according to claim 5, characterized in that, The temperature of the base in the fourth magnetron sputtering method is controlled to be below 0°C.

8. The thin film deposition method according to claim 5, characterized in that, The wafer is made of silicon; the first metal layer is aluminum; the second metal layer is titanium; the third metal layer is nickel-vanadium; and the fourth metal layer is silver.

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