Preparation method of semiconductor device
By coating the organic coating on the front of the substrate of the semiconductor device and curing at high temperature, the problem of the organic passivation layer releasing water vapor and small organic molecules in the high-temperature process is solved, reducing the water absorption performance and improving the performance stability of the device.
Patent Information
- Application Number
- CN202311381715.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-24
- Publication Date
- 2025-04-25
AI Technical Summary
The organic passivation layer is prone to release a large amount of water vapor and small organic molecules during high-temperature processes, resulting in the contamination of the substrate structure and affecting the performance of the device.
By coating the organic coating on the front of the substrate and curing at a temperature higher than the subsequent process temperature, the water vapor and organic small molecules in the organic passivation layer are fully released during the curing process, reducing the water absorption performance, and avoiding the release of water vapor and organic small molecules caused by secondary curing or multiple curing in subsequent high-temperature processes.
Effectively prevent the organic passivation layer from releasing water vapor and small organic molecules in high-temperature processes, reduce pollution to device structure and processing equipment, and improve the performance stability of semiconductor devices.
Smart Images
Figure CN119890056A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for preparing a semiconductor device. Background Art
[0002] In the semiconductor field, passivation layers are widely used on the surface of semiconductor devices to passivate and protect the device structure underneath. Covering with a passivation layer helps to enhance the stability and reliability of the device and improve the device packaging yield.
[0003] In the prior art, a passivation layer can be formed by coating an organic material. The passivation layer of the organic material has good fluidity and can cover the surface of the device structure well. For example, in an IGBT device, an organic passivation layer is usually formed on the substrate to cover the device structure below it, which greatly improves the reliability of the product and increases the diversity of application scenarios. However, when the passivation layer of the organic material is exposed to the external environment for a long time or undergoes a wet process, it is very easy to absorb a certain amount of water vapor. Then, in the subsequent high-temperature process, the organic passivation layer is easy to release a large amount of water vapor and small organic molecules instantly, resulting in the contamination of the substrate structure, causing the performance parameters of the prepared device to diverge and deteriorate, or even result in low-quality scrap. Summary of the invention
[0004] The object of the present invention is to provide a method for preparing a semiconductor device to solve the problem that a large amount of water vapor and small organic molecules are easily released instantly in the organic passivation layer during the subsequent high-temperature process and pollute the device structure.
[0005] In this regard, the present invention provides a method for preparing a semiconductor device, comprising: processing the front side of a substrate to form a front side structure; and processing the back side of the substrate to form a back side structure. After processing the front side of the substrate and before processing the back side of the substrate, the method further comprises: coating an organic coating on the front side of the substrate, and curing the organic coating to form a passivation layer, and the curing temperature of the organic coating is higher than the highest temperature of the process for processing the back side of the substrate.
[0006] Optionally, the curing temperature of the organic coating is 10° C. to 50° C. higher than the highest temperature of the backside processing process.
[0007] Optionally, the material of the organic coating includes polyimide.
[0008] Optionally, processing the back side of the substrate to form a back side structure includes: depositing a back side metal layer on the back side of the substrate, and before depositing the back side metal layer, further includes baking the substrate structure.
[0009] Optionally, the baking temperature is 20° C. to 150° C. lower than the curing temperature of the organic coating.
[0010] Optionally, the baking temperature is, for example, 200°C-380°C.
[0011] Optionally, after baking the substrate structure and before depositing the back metal layer, the method further includes: performing a degassing process on the substrate structure to remove moisture in the substrate structure, wherein the process temperature of the degassing process is, for example, 120°C to 250°C.
[0012] Optionally, after performing the degassing process and before depositing the back metal layer, the method further includes: cleaning the back side of the substrate with an inert gas, wherein the inert gas is used for micro-etching the back side of the substrate to remove oxides and other contaminants on the back side of the substrate.
[0013] Optionally, the inert gas etches the substrate to a thickness of 10 angstroms to 30 angstroms.
[0014] In the method for preparing a semiconductor device provided by the present invention, when preparing a passivation layer of an organic material, the curing temperature of the organic coating is made higher than the process temperature of the subsequent process (i.e., the process temperature for processing the back of the substrate), so that the water vapor and small organic molecules in the organic passivation layer can be fully released under high-temperature curing, and the fully cured organic passivation layer has lower water absorption performance, which is conducive to alleviating its absorption of water vapor in the subsequent process. At the same time, since the curing temperature is higher than the highest temperature of the subsequent process, the problem of the passivation layer of the organic material releasing water vapor and small organic molecules during secondary curing or multiple curing in the subsequent high-temperature process is effectively alleviated, thereby preventing the released water vapor and small organic molecules from contaminating the device structure and processing equipment, and improving the performance stability of the prepared semiconductor device. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 It is a schematic flow chart of a method for manufacturing a semiconductor device in one embodiment of the present invention.
[0016] Figure 2 A schematic diagram of the structure of a field effect transistor.
[0017] Figure 3 The figure is a schematic diagram of the structure of a field effect transistor with a back metal layer.
[0018] Figure 4 It is a schematic flow chart of a method for manufacturing a field effect transistor in one embodiment of the present invention.
[0019] Figure 5 A schematic diagram of defect distribution obtained by conducting electrical property testing on a semiconductor device formed on a substrate after the substrate is processed using a conventional method.
[0020] Figure 6 The defect distribution diagram is obtained by performing electrical inspection on a semiconductor device formed on a substrate after the substrate is processed by the method provided by an embodiment of the present invention.
[0021] The reference numerals are as follows:
[0022] 100-substrate;
[0023] 100a-front;
[0024] 100b - back;
[0025] 200G-gate structure;
[0026] 200S-source doping region;
[0027] 200D-drain doping region;
[0028] 300-Back metal layer. DETAILED DESCRIPTION
[0029] As described in the background art, during the preparation of semiconductor devices, a passivation layer of organic material is covered on the surface of the device structure to passivate and protect the structure below. However, after the passivation layer is formed, since the passivation layer easily absorbs water vapor, a large amount of water vapor and small organic molecules are easily released instantly in the subsequent high-temperature process, resulting in contamination of the substrate structure and processing equipment.
[0030] In this regard, the present invention optimizes the preparation method of semiconductor devices to improve the problem that the passivation layer of organic materials is easy to release water vapor and organic molecules in the subsequent high-temperature process and contaminate the substrate structure and processing equipment. Figure 1 As shown, a method for preparing a semiconductor device in an embodiment of the present invention includes: processing the front side of a substrate to form a front side structure; then, coating an organic coating on the front side of the substrate, and curing the organic coating to form a passivation layer; and then, processing the back side of the substrate to form a back side structure. The curing temperature of the organic coating is higher than the highest temperature of the process for processing the back side of the substrate.
[0031] That is, in the present invention, by increasing the curing temperature of the organic coating so that the curing temperature of the organic coating is higher than the process temperature of the subsequent process, it can not only ensure that the water vapor and organic small molecules in the organic passivation layer can be fully released during the curing process, but also the fully cured organic passivation layer has a lower efficiency in absorbing water vapor, thereby reducing the water absorption performance of the organic passivation layer; at the same time, since the curing temperature is higher than the highest temperature of the subsequent process, the organic passivation layer can avoid secondary curing or multiple curing in the subsequent high-temperature process to release a large amount of water vapor or organic molecules.
[0032] The following is a further detailed description of the method for preparing a semiconductor device proposed in the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will become clearer. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. It should be recognized that relative terms such as "above", "below", "top", "bottom", "above" and "below" shown in the drawings can be used to describe the relationship between various elements. These relative terms are intended to cover different orientations of elements other than the orientations depicted in the drawings. For example, if the device is inverted relative to the view in the drawing, an element described as being "above" another element will now be below the element.
[0033] A specific example is given below to explain the method for preparing the semiconductor device in this embodiment. The semiconductor device in this example is, for example, a field effect transistor, which can be further an insulated gate bipolar transistor (IGBT) or a shielded gate field effect transistor (SGT), etc.
[0034] For details, please refer to Figure 2 and Figure 3 The structural diagram of the field effect transistor shown in FIG. Figure 2 and Figure 3 As shown, the field effect transistor in this embodiment includes a front structure formed on the front side 100a of the substrate and a back structure formed on the back side 100b of the substrate. The front structure includes a gate structure 200G and a source doping region 200S formed on the front side 100a of the substrate 100; the back structure includes a drain doping region 200D formed on the back side 100b of the substrate 100. Specifically, the source doping region 200S can be formed in the substrate 100 by performing an ion implantation process on the front side 100a of the substrate, and the drain doping region 200D can be formed in the substrate 100 by performing an ion implantation process on the back side 100b of the substrate. And, in Figure 2 In the example, the gate structure 200G is embedded into the substrate 100 from the front side 100a of the substrate 100; while in other examples, the gate structure may also be formed above the front side of the substrate, which will not be described in detail here.
[0035] In a further solution, the front structure formed on the front side 100a of the substrate further includes: an interconnection structure (not shown in the figure), which is connected to the source doping region 200S and the gate structure 200G, and is used to electrically lead out the source doping region 200S and the gate structure 200G. Specifically, the interconnection structure includes, for example, a plurality of conductive plugs, a source metal layer, and a gate metal layer, wherein the plurality of conductive plugs include a conductive plug electrically connected to the source doping region 200S and a conductive plug electrically connected to the gate structure 200G, the source metal layer is electrically connected to the source doping region 200S through the conductive plug, and the gate metal layer is electrically connected to the gate structure 200G through the conductive plug.
[0036] Next reference Figure 3 As shown, the back structure formed on the back side 100 b of the substrate further includes a back metal layer 300 . The back metal layer 300 covers the back side 100 b of the substrate 100 and is electrically connected to the drain doping region 200D.
[0037] As described above, after the front side of the substrate 100 is processed, and before the back side of the substrate 100 is processed, it also includes: forming a passivation layer (not shown in the figure) on the front side 100a of the device 100 to passivate and protect the front side structure below it. Specifically, the preparation method of the passivation layer includes: coating an organic coating on the front side 100a of the substrate 100, and curing the organic coating to form a passivation layer, wherein the curing temperature of the organic coating is higher than the subsequent process temperature of processing the back side 100b of the substrate 100. Since the passivation layer is cured under high temperature conditions, the moisture and small organic molecules therein can be fully removed, which can reduce the absorption performance of the passivation layer to water vapor in the subsequent process on the one hand, and can also effectively improve the problem that the passivation layer is easily released instantly due to secondary curing or multiple curing in the subsequent high temperature process.
[0038] Combine the following Figure 4 The method for preparing the semiconductor device in this example is specifically described by taking the method for preparing a field effect crystal as an example, and the specific preparation process is described as follows.
[0039] First, the front device is processed to form the front structure. Figure 2 As shown, it includes: etching the front side 100a of the substrate 100 to form a gate trench, and then filling the gate material in the gate trench to form a gate structure 200G; and performing an ion implantation process on the front side 100a of the substrate 100 to form a source doping region 200S (for constituting the emitter of the IGBT device).
[0040] Furthermore, the processing of the front side 100a of the substrate may also include: forming an interconnection structure on the front side 100a of the substrate 100, wherein the interconnection structure is connected to the source doping region 200S and the gate structure 200G for electrically leading out the source doping region 200S and the gate structure 200G.
[0041] Next, a passivation layer is formed on the front side 100a of the substrate 100. The preparation method of the passivation layer specifically includes: coating an organic coating, and the organic coating in this embodiment is, for example, a polyimide coating (PI); then, performing a curing process to cure the organic coating, so that the water vapor and organic small molecules in the polyimide coating are fully released, and the water absorption performance of the polyimide coating after high-temperature curing can be greatly reduced to avoid the introduction of a large amount of water vapor. Among them, the curing temperature of the organic coating is higher than the highest temperature of the subsequent process, for example, the curing temperature of the organic coating can be 10°C to 50°C higher than the highest temperature of the back processing process.
[0042] In this way, the back side of the substrate 100 can be processed under the protection of the passivation layer, thereby preventing the front side structure of the substrate 100 from being affected by the subsequent processes.
[0043] Continue to refer Figure 4 As shown, the device processing on the back side is performed, wherein the process of processing the back side 100b of the substrate 100 includes: thinning the back side of the substrate 100. The thinning step can be specifically thinned by a grinding process. In the grinding and thinning process, an aqueous solution including a grinding liquid, a cleaning liquid, etc. is usually used. Therefore, during the thinning process, the passivation layer is exposed to the solution, which easily causes the risk of the passivation layer absorbing water vapor. However, compared with the traditional passivation layer, the passivation layer in this embodiment has a greatly reduced water absorption performance due to the high-temperature cured polyimide coating, which can effectively reduce the absorption of water vapor. In a further scheme, the substrate 100 can be further thinned by corrosion.
[0044] Next, continue combining Figure 2 and Figure 4 As shown, an ion implantation process and a thermal annealing process are performed on the back side of the substrate 100 to form a drain doping region 200D on the back side 100b of the substrate 100. The ions in the drain doping region 200D are activated and uniformly diffused by the thermal annealing process. The annealing temperature of the thermal annealing process is lower than the curing temperature of the organic coating, thereby reducing the risk of water vapor and small organic molecules in the passivation layer being released.
[0045] Next, combine Figure 3 and Figure 4 As shown, a back metal layer 300 is formed on the back side 100 b of the substrate 100 . The back metal layer 300 may specifically constitute a drain metal layer and be electrically connected to the drain doped region 200D.
[0046] In one example, before depositing the back metal layer 300, the back side 100b of the substrate 100 is also cleaned to remove impurities and contaminants on the back side, so that the subsequently formed back metal layer 300 can fully contact the drain doping region 200D on the back side 100b of the substrate, which is conducive to achieving the fusion of the back metal layer 300 and the substrate 100 at the interface and improving the performance of the device. It should be noted that in this step, the substrate 100 can be wet cleaned with a cleaning liquid. At this time, the passivation layer will also be exposed to the cleaning liquid and easily absorb water vapor. The passivation layer in this embodiment is cured at high temperature, which is conducive to reducing its water absorption performance.
[0047] Furthermore, before the back metal layer 300 is deposited, the substrate structure is baked, and the baking temperature is lower than the curing temperature of the organic coating. Specifically, the baking temperature can be 20°C to 150°C lower than the curing temperature of the organic coating, for example, the baking temperature can be 200°C to 380°C. Specifically, before the back metal layer 300 is deposited, the substrate 100 formed with the device structure is exposed to the air for a long time, and also undergoes multiple wet processes (including a thinning process and a cleaning process of the substrate 100), so that a small amount of water vapor is absorbed in the substrate structure. The water vapor in the substrate structure (including the water vapor in the passivation layer) is removed by baking, so as to avoid the water vapor and small organic molecules in the passivation layer being released instantly during the high-temperature process of depositing the back metal layer 300, thereby affecting the quality of the back metal layer 300 and contaminating the device structure.
[0048] After the substrate structure is baked and before the back metal layer 300 is deposited on the back of the substrate, the substrate structure can also be subjected to a degassing process (degassing) to further remove moisture in the substrate structure (including moisture in the passivation layer). Also, after the substrate structure is subjected to the degassing process, the back side 100b of the substrate can be cleaned with an inert gas (e.g., argon), which can slightly etch the back side of the substrate (e.g., the thickness of the back side of the substrate etched by the inert gas is about 10 angstroms to 30 angstroms) to remove oxides and other contaminants on the back side of the substrate. Afterwards, the back metal layer 300 can be deposited on the back side of the substrate, and its deposition temperature is also lower than the curing temperature of the organic coating, and the deposition temperature is, for example, 320°C to 400°C, and the material of the back metal layer 300 includes, for example, aluminum.
[0049] It should be noted that a large amount of heat will be released in the process of cleaning the back side of the substrate with an inert gas as described above. Therefore, in this embodiment, the process temperature of the degassing process can be appropriately lowered during the degassing process (for example, the process temperature of the degassing process can be controlled at 120°C-250°C) to reduce the total heat generated by the degassing process and the heat generated in the process of cleaning the back side of the substrate with an inert gas. This ensures that the total heat generated by the degassing process and the cleaning process of the back side of the substrate with an inert gas is less than the heat generated by the organic coating during the curing process, thereby further improving the problem of water vapor and small organic molecules in the passivation layer being released and splashing back onto the surface of the substrate.
[0050] To sum up, in the preparation method of the semiconductor device provided in this embodiment, on the one hand, the curing temperature of the organic coating is adjusted accordingly in combination with the process temperature of the post-process of the semiconductor device (i.e., the process temperature of the back side of the substrate). At this curing temperature, the organic coating can be fully cured while avoiding carbonization of the organic coating, and it can also be ensured that the curing temperature is not lower than the highest temperature of the process temperature in the subsequent process. On the other hand, before depositing the back metal layer, the substrate structure is baked to remove the water vapor absorbed by the substrate structure when it is exposed to the air and undergoes the wet process; and the substrate structure can also be subjected to a degassing process to remove the water vapor in the substrate structure to a greater extent. On this basis, a cleaning process for the back side of the substrate can be added (specifically, the back side of the substrate is cleaned using an inert gas) to remove oxides and other contaminants on the back side of the substrate by micro-etching the back side of the substrate. At this time, the process temperature of the degassing process can be further reduced (for example, the process temperature of the degassing process can be controlled at 120°C-250°C) to control the total heat generated by the degassing process and the heat generated in the process of cleaning the back side of the substrate using an inert gas. In this way, the risk of causing the passivation layer to release a large amount of water vapor and contaminating the device structure and processing equipment during the deposition of the back metal layer can be reduced to a greater extent.
[0051] For example, you can refer to Figure 5 and Figure 6 The defect distribution diagram shown in Figure 5 This is a schematic diagram of defect distribution obtained by conducting electrical testing on a semiconductor device formed on a substrate after substrate processing using a conventional method. Figure 6 This is a schematic diagram of defect distribution obtained by conducting electrical property testing on a semiconductor device formed on a substrate after substrate processing using the method provided in this embodiment. By comparison, it can be clearly found that Figure 5 The defect rate of the semiconductor devices formed on the substrate (wafer) shown is relatively high, especially in the peripheral area of the substrate other than the central area, which is more susceptible to water vapor. Therefore, the defect rate of the semiconductor devices formed in the peripheral area is even higher. Figure 6 The semiconductor devices formed on the substrate (wafer) shown have lower defects and the product yield is significantly improved.
[0052] It should be noted that, although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belongs to the scope of protection of the technical solution of the present invention.
[0053] It must be noted that as used herein and in the appended claims, the singular forms "a," "an," and "an" include plural references unless the context clearly indicates otherwise. For example, reference to "a step" or "a device" means reference to one or more steps or devices and may include secondary steps as well as secondary devices. All conjunctions used should be interpreted in the broadest sense. Also, the word "or" should be interpreted as having the definition of a logical "or" rather than a logical "exclusive or" unless the context clearly indicates otherwise.
Claims
1. A method for preparing a semiconductor device, characterized in that: include: Processing a front surface of a substrate to form a front surface structure; and, processing the back side of the substrate to form a back side structure; Among them, after processing the front side of the substrate and before processing the back side of the substrate, it also includes: coating an organic coating on the front side of the substrate and curing the organic coating to form a passivation layer, and the curing temperature of the organic coating is higher than the highest temperature of the process for processing the back side of the substrate.
2. The method for preparing a semiconductor device according to claim 1, wherein: The curing temperature of the organic coating is 10° C. to 50° C. higher than the highest temperature of the backside processing process.
3. The method for preparing a semiconductor device according to claim 1, wherein: The material of the organic coating layer includes polyimide.
4. The method for preparing a semiconductor device according to claim 1, wherein: Processing the back side of the substrate to form a back side structure includes: depositing a back side metal layer on the back side of the substrate, and before depositing the back side metal layer, further includes baking the substrate structure.
5. The method for preparing a semiconductor device according to claim 4, characterized in that: The baking temperature is 20° C. to 150° C. lower than the curing temperature of the organic coating.
6. The method for preparing a semiconductor device according to claim 4, wherein: The baking temperature is 200°C-380°C.
7. The method for preparing a semiconductor device according to claim 4, wherein: After baking the substrate structure and before depositing the back metal layer, the method further includes: performing a degassing process on the substrate structure to remove moisture in the substrate structure.
8. The method for preparing a semiconductor device according to claim 7, wherein: The process temperature of the degassing process is 120°C to 250°C.
9. The method for preparing a semiconductor device according to claim 7, wherein: After performing the degassing process and before depositing the back metal layer, the method further includes: cleaning the back side of the substrate with an inert gas, wherein the inert gas is used for micro-etching the back side of the substrate to remove oxides and other pollutants on the back side of the substrate.
10. The method for preparing a semiconductor device according to claim 9, characterized in that: The thickness of the substrate etched by the inert gas is 10 angstroms to 30 angstroms.