Method for preparing electrodes of semiconductor devices

Abstract

The present application provides a method for preparing an electrode of a semiconductor device. The method for preparing the electrode includes: providing a semiconductor substrate and a donor substrate, the semiconductor substrate having a first surface with a boss structure therein, and the donor substrate having a second surface; forming a transfer film on the second surface, the material of the transfer film including a conductive material; attaching the transfer film to the top surface of the boss structure; separating the semiconductor substrate from the donor substrate by using a transfer technique so that the top surface picks up the conductive material in the transfer film that is attached to the top surface, wherein the transfer technique realizes the picking up by controlling the peeling speed; curing the conductive material on the top surface to obtain the electrode of the semiconductor device. Through the present application, the problem of low patterning uniformity of the mesa electrode of the semiconductor device in the prior art is solved.

Description

Technical Field

[0001] This application relates to the technical field of semiconductor chip process preparation, and more specifically, to a method for preparing an electrode of a semiconductor device. Background Art

[0002] High-power devices such as IGCTs and IGBTs are key modules in DC power grid transmission and transformation technologies. The cathode of the device has a special mesa structure (or boss structure, and the surface of the mesa structure or boss structure includes a top mesa and an inclined sidewall), which undertakes the function of gate-cathode electrical isolation during crimping. To ensure effective insulation isolation, the mesa height of the cathode mesa structure should reach 15 µm. Therefore, the gate-cathode structure needs to be designed into a so-called "quasi-mesa" grooved structure.

[0003] To meet the requirements of high voltage withstand of power devices, the thickness of the mesa electrode can reach more than 20 µm and the consistency of the electrode morphology also needs to be satisfied. However, during the preparation process of the mesa electrode, due to the height difference between the mesa structure and the grooved structure, the thickness of the photoresist on the top mesa of the mesa structure and the bottom of the above grooved structure is uneven (the photoresist thickness on the top mesa is lower). The top mesa will be overexposed under the same exposure dose and time, resulting in a decrease in exposure uniformity and thus affecting the uniformity of the photoresist line width. In addition, the light scattering phenomenon caused by the inclined sidewall of the mesa structure will cause the offset of the exposure pattern position at the mesa structure and thus misalignment, reducing the uniformity of the line width and patterning of the metal electrode (including the mesa electrode), and even causing the phenomenon of gate-cathode short circuit.

[0004] In summary, the current patterning preparation technology of the mesa electrode faces problems such as low lithography uniformity, difficult etching process, and low efficiency, seriously affecting the reliability, processing efficiency, and yield of power devices. Summary of the Invention

[0005] The main purpose of this application is to provide a method for preparing an electrode of a semiconductor device to solve the problem of low patterning uniformity of the mesa electrode of a semiconductor device in the prior art.

[0006] To achieve the above object, according to one aspect of this application, a method for preparing an electrode of a semiconductor device is provided, including: providing a semiconductor substrate and a donor substrate, the semiconductor substrate having a first surface with a boss structure therein, and the donor substrate having a second surface; forming a transfer film on the second surface, the material of the transfer film including a conductive material; fitting the transfer film to the top mesa of the boss structure; separating the semiconductor substrate from the donor substrate by using a transfer technique so that the top mesa picks up the conductive material in the transfer film that fits the top mesa, wherein the transfer technique realizes the pick-up by controlling the peeling speed; curing the conductive material on the top mesa to obtain the electrode of the semiconductor device.

[0007] Optionally, the conductive material is liquid metal, and a transfer film is formed on the second surface, including: dissolving the liquid metal and a polymer matrix material to prepare a composite conductive slurry, wherein the polymer matrix material includes nanoclay or hydrogel; and coating the composite conductive slurry on the second surface to form a transfer film.

[0008] Optionally, the electrode preparation method further comprises: before the step of laminating the transfer film to the top table of the boss structure, forming an interface modification layer on the first surface, wherein the material of the interface modification layer has hydrogen bonds.

[0009] Optionally, the conductive material is solid metal, and forming a transfer film on the second surface includes: using a thin film deposition technology to deposit the solid metal on the second surface to form the transfer film.

[0010] Optionally, the conductive material is solid metal, and the transfer film is bonded to the top surface of the boss structure to obtain a bonded structure. The electrode preparation method also includes: heat treating the bonded structure at a temperature higher than the melting point of the solid metal.

[0011] Optionally, laminating the transfer film with the top surface of the boss structure includes: transferring the semiconductor substrate to a surface of the transfer film facing away from the donor substrate; and applying pressure to the semiconductor substrate to laminarly fit the transfer film with the top surface of the boss structure.

[0012] Optionally, when the conductive material is liquid metal, a first pressure is applied to the semiconductor substrate, and the first pressure is 5-10N.

[0013] Optionally, when the conductive material is solid metal, a second pressure is applied to the semiconductor substrate, and the second pressure is 50-100N.

[0014] Optionally, the semiconductor substrate has a first end and a second end relative to each other, and the direction in which the first end points to the second end is parallel to the first surface. The semiconductor substrate is separated from the donor substrate by using a transfer technology, including: lifting the semiconductor substrate from the first end; peeling the semiconductor substrate and the conductive material in the transfer film that is in contact with the top table from the donor substrate until the second end is separated from the donor substrate.

[0015] Optionally, a first peeling speed is used to peel the semiconductor base and the conductive material in the transfer film that is in contact with the top table from the donor substrate, and the first peeling speed is 10-30 cm / s.

[0016] Applying the technical solution of the present application, a method for preparing an electrode of a semiconductor device includes: providing a semiconductor substrate and a donor substrate, the semiconductor substrate having a first surface with a boss structure therein, and the donor substrate having a second surface; forming a transfer film on the second surface, the material of the transfer film including a conductive material; attaching the transfer film to the top surface of the boss structure; separating the semiconductor substrate from the donor substrate by using a transfer technique so that the top surface picks up the conductive material in the transfer film that is attached to the top surface, wherein the transfer technique realizes the picking up by controlling the peeling speed; curing the conductive material on the top surface to obtain the electrode of the semiconductor device. Through the present application, the transfer film formed on the second surface of the boss structure and the donor substrate is attached and separated by the transfer technique, so that the conductive material can automatically align with the boss structure, achieving the purpose of picking up the conductive material through a stamping self-alignment technique, and avoiding lithography and etching problems such as low exposure uniformity and CD uniformity caused by light scattering at the boss and uneven glue thickness due to the special structure of the boss structure of the semiconductor substrate, thereby enabling the obtaining of an electrode (a mesa electrode) with higher uniformity. In summary, the present application solves the problem of low patterning uniformity of the mesa electrode of a semiconductor device in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings forming a part of this application are used to provide a further understanding of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0018] Figure 1 FIG. 9 shows a schematic structural diagram of a semiconductor substrate provided in a method for preparing an electrode of a semiconductor device according to an embodiment of the present application;

[0019] Figure 2 FIG. 13 shows a schematic structural diagram of a donor substrate with a transfer film and a flipped semiconductor substrate provided in a method for preparing an electrode of a semiconductor device according to an embodiment of the present application;

[0020] Figure 3 FIG. 17 shows a schematic structural diagram of a donor substrate and a semiconductor substrate after the top surface picks up the conductive material in the transfer film that is attached to the top surface in a method for preparing an electrode of a semiconductor device according to an embodiment of the present application.

[0021] Among them, the above-mentioned drawings include the following reference numerals:

[0022] 10. Semiconductor substrate; 101. Boss structure; 20. Donor substrate; 30. Transfer film; 40. Conductive material. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0024] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so as to implement the embodiments of the present invention described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0026] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element can be directly on the other element or there can also be intermediate elements. Moreover, in the description and claims, when an element is described as "connected" to another element, the element can be "directly connected" to the other element or "connected" to the other element through a third element.

[0027] As introduced in the background art, in the prior art, during the preparation of the mesa electrode, due to the height difference between the mesa structure and the trench structure, the thickness of the glue on the top mesa of the mesa structure and the bottom of the trench of the above trench structure is uneven (the glue thickness on the top mesa is lower). The top mesa will be overexposed under the same exposure dose and time, resulting in a decrease in exposure uniformity and thus affecting the uniformity of the photoresist line width. In addition, the light scattering phenomenon caused by the inclined sidewalls of the mesa structure will cause the offset of the exposure pattern position at the mesa structure and thus cannot be aligned, reducing the uniformity of the line width and patterning of the metal electrode (including the mesa electrode), and even causing the phenomenon of gate cathode short circuit. To solve the problem of low patterning uniformity of the mesa electrode of semiconductor devices in the prior art, the embodiments of the present application provide a method for preparing an electrode of a semiconductor device.

[0028] A method for preparing an electrode of a semiconductor device provided by the present application includes:

[0029] Providing a semiconductor substrate and a donor substrate, the semiconductor substrate having a first surface with a boss structure therein, and the donor substrate having a second surface; forming a transfer film on the second surface, the material of the transfer film including a conductive material; attaching the transfer film to the top surface of the boss structure; separating the semiconductor substrate from the donor substrate by using a transfer technique so that the top surface picks up the conductive material in the transfer film that is attached to the top surface, wherein the transfer technique realizes the pickup by controlling the peeling speed; curing the conductive material on the top surface to obtain an electrode of the semiconductor device.

[0030] In the above embodiment, the transfer film formed on the second surface of the boss structure and the donor substrate is attached and separated by the transfer technique, so that the conductive material can be automatically aligned with the boss structure, achieving the purpose of picking up the conductive material by the stamp-type self-alignment technique, and avoiding lithography and etching problems such as low exposure uniformity and CD uniformity caused by light scattering at the boss and uneven glue thickness due to the special structure of the boss structure of the semiconductor substrate. Therefore, an electrode (mesa electrode) with higher uniformity can be obtained. In summary, the present application solves the problem of low patterning uniformity of the mesa electrode of the semiconductor device in the prior art.

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0032] In some embodiments, as Figure 1 shown, a boss structure 101 can be prepared on one side surface of the semiconductor substrate to obtain a semiconductor substrate 10, so that the boss structure 101 protrudes in the first surface to generate a height difference, serving as an acceptor or a receiver of the transfer film on the donor substrate. Among them, a plurality of boss structures 101 spaced apart can be provided in the first surface of the semiconductor substrate 10. Further, the plurality of boss structures 101 can be presented as a comb-shaped boss structure evenly distributed in the first surface.

[0033] Specifically, as Figure 1 shown, the boss structure 101 can be prepared and formed by a dry / wet etching method:

[0034] For the wet etching process, as Figure 1As shown, based on the patterned mask layer prepared by lithography process first, by selecting a silicon etching solution with a specific ratio (a mixture of hydrofluoric acid, concentrated nitric acid and hydrogen peroxide), and based on the tooling clamping and rotating etching process, at a specific etching time (such as 1 - 3 minutes) and process temperature (such as 15 - 25 °C), the wet etching process of the semiconductor substrate is completed. The mesa height is 15 - 20 µm, and a uniformly distributed comb-shaped convex structure is formed with an etching uniformity of less than 3%. After the mesa structure is prepared, the surface mask is removed through plasma dry stripping or inorganic wet stripping process, and the preparation of the convex structure 101 is completed.

[0035] For the dry etching process, based on the patterned mask layer prepared by lithography process first, by selecting an etching gas with a specific ratio and flow rate (sulfur hexafluoride and oxygen), and based on the deep silicon etching process, at a specific etching time, upper electrode power, chamber pressure and process temperature, the dry etching process of the semiconductor substrate is completed. The mesa height is 15 - 20 µm, and a uniformly distributed comb-shaped convex structure is formed with an etching uniformity of less than 3%. After the mesa structure is prepared, the surface mask is removed through plasma dry stripping or inorganic wet stripping process, and the preparation of the convex structure 101 is completed.

[0036] In some alternative embodiments, the conductive material is a liquid metal, and a transfer film 30 is formed on the second surface, including: dissolving the liquid metal and the polymer matrix material to prepare a composite conductive paste, where the polymer matrix material includes nano-clay or hydrogel; coating the composite conductive paste on the second surface to form the transfer film 30.

[0037] Specifically, as Figure 2 shown, when the conductive material is a liquid metal, first provide the above-mentioned semiconductor substrate 10, the above-mentioned donor substrate 20 and prepare the composite conductive paste, and then coat the composite conductive paste on the second surface of the donor substrate 20 to form the transfer film 30. It should be noted here that the order of the steps of preparing the composite conductive paste, providing the semiconductor substrate and providing the donor substrate 20 is not limited, and the step of coating the composite conductive paste on the second surface is after providing the donor substrate 20. Then, the transfer film 30 is attached to the top mesa of the convex structure 101, and then the semiconductor substrate 10 and the donor substrate 20 are separated by using a transfer technique, so that the top mesa picks up the conductive material (composite conductive paste) in the transfer film 30 that is attached to the top mesa. Furthermore, the electrode of the semiconductor device can be obtained by curing the conductive material (composite conductive paste) on the top mesa.

[0038] In the above-described embodiments, when the conductive material of the transfer film 30 is a liquid metal, by dissolving the liquid metal with the polymer matrix material, a composite conductive paste with a surface tension smaller than that of the liquid metal and high viscosity can be formed. Thus, when the composite conductive paste is coated on the second surface, the difficulty of laying and extending the transfer film 30 is reduced, and a transfer film 30 with better film layer quality can be obtained.

[0039] Specifically, as Figure 2 shown, the thickness of the transfer film 30 in this embodiment can be 20 - 40 µm.

[0040] Specifically, as Figure 2 shown, the transfer film 30 can be prepared from the above composite conductive paste, that is, the material of the transfer film 30 includes the above liquid metal and polymer matrix material. It should be noted here that since the composite conductive paste contains conductive liquid metal, the composite conductive paste is also a conductive material.

[0041] The liquid metal is a low melting point alloy and can include gallium-based liquid metal or mercury-based liquid metal.

[0042] In some examples, the above liquid metal includes, but is not limited to, one or more of metal elements such as Ga, In, Sn, Bi, Mg, Zn, and Hg.

[0043] Specifically, when the conductive material is a liquid metal and the polymer matrix material is nano clay, the steps for preparing the composite conductive paste can be: adding nano clay powder to the liquid metal and high-speed stirring to form a high-viscosity paste-like conductive nano clay, that is, the composite conductive paste.

[0044] Specifically, when the conductive material is a liquid metal and the polymer matrix material is a hydrogel, the steps for preparing the composite conductive paste can be: first, ultrasonic treatment of the liquid metal, dispersing and precipitating to extract the liquid metal sediment, and mixing it into the hydrogel. After stirring and curing, a liquid metal hydrogel "ink paste" is obtained, that is, the composite conductive paste. Among them, the hydrogel can include, but is not limited to, polyvinyl alcohol (PVA), poly(acrylic acid) (PAA), (PAAm), and biopolymers.

[0045] It should be noted here that the viscosity of the composite conductive paste can be regulated by adjusting the volume ratio of the polymer matrix material. Among them, the higher the proportion of the polymer matrix material, the greater the viscosity, and the better the overall support degree and film-forming property of the composite conductive paste, which is more conducive to its being picked up by the top table of the boss structure of the semiconductor substrate as an "ink paste" material; the higher the proportion of the liquid metal, the better the conductivity of the composite conductive paste. Those skilled in the art can adjust the proportions of the polymer matrix material and the liquid metal in the composite conductive paste according to actual needs, which are not limited herein.

[0046] In addition, in order to coat the composite conductive paste on the second surface to form a transfer film, the composite conductive paste can be spread on the second surface by any one of spin coating, drop coating, spraying, dip coating, and brush coating means. In this step, the thickness of the transfer film can be regulated by regulating process parameters such as spin coating. For example, by adjusting the rotation speed of spin coating, increasing the rotation speed can obtain a thinner transfer film; alternatively, a customized polymer hard brush can be used to dip a certain amount of the composite conductive paste and evenly brush it on the second surface. To adjust the thickness of the transfer film, it is gradually thinned by multiple scraping coatings, and the thickness of the transfer film is tested by a thickness measuring tool to ensure that the thickness of the transfer film is controlled within the optimal range.

[0047] In some alternative embodiments, the method for preparing the electrode of the semiconductor device further includes: before the step of fitting the transfer film to the top table of the boss structure, an interface modification layer is formed on the first surface, and the material of the interface modification layer has hydrogen bonds.

[0048] Specifically, the transfer film can be prepared from the above-mentioned composite conductive paste, that is, the material of the transfer film includes the above-mentioned liquid metal and polymer matrix material.

[0049] It can be understood that the interface modification layer is formed on the first surface, and the first surface has a boss structure, so that the material of the interface modification layer covers the top table of the boss structure.

[0050] In the above-described embodiments, first, the above semiconductor substrate and the above donor substrate are provided. Then, a transfer film is formed on the second surface of the donor substrate, and an interface modification layer is formed on the first surface of the semiconductor substrate. After that, the transfer film is bonded to the top surface of the boss structure. Here, it should be emphasized that since the interface modification layer is formed on the first surface, the bonding of the transfer film to the top surface of the boss structure can be regarded as bonding the transfer film to the top surface of the boss structure through the interface modification layer. Further, since the material of the interface modification layer has hydrogen bonds and the material of the transfer film includes a polymer matrix material, hydrogen bond bonding is formed between the material of the interface modification layer and the polymer matrix material between the boss structure and the transfer film. Therefore, the adhesion of the conductive material in the transfer film that is bonded to the top surface of the boss structure to the top surface is strengthened. Next, a transfer technique is used to separate the semiconductor substrate from the donor substrate so that the top surface picks up the conductive material in the transfer film that is bonded to the top surface. Here, it is mentioned that since the interface modification layer strengthens the adhesion of the conductive material in the transfer film that is bonded to the top surface, it can also improve the success rate and adhesion of the top surface picking up the conductive material in the transfer film that is bonded to the top surface.

[0051] In some alternative embodiments, as Figure 2 shown, the conductive material in the transfer film is a solid metal. Forming the transfer film 30 on the second surface includes: depositing the solid metal on the second surface by a thin film deposition technique to form the transfer film 30. The thin film deposition techniques include electron beam evaporation, thermal evaporation, magnetron sputtering, pulsed laser deposition, electroplating, etc.

[0052] Specifically, as Figure 2 shown, in the case where the conductive material is a solid metal, the above transfer film 30 can be directly deposited and formed.

[0053] In some examples, the solid metal may include, but is not limited to, one or more of aluminum, copper, silver, platinum, gold, palladium, and iridium.

[0054] Here, it is explained that, as Figure 2 shown, in this embodiment, the thickness of the transfer film 30 can be adjusted by adjusting the deposition time in the thin film deposition technique. Those skilled in the art can make reasonable selections according to actual needs, and the embodiments of the present application do not make specific limitations.

[0055] Similarly, as Figure 2 shown, the thickness of the transfer film 30 in this embodiment can be 20 - 40 µm.

[0056] In the above-described embodiments, first, the semiconductor substrate 10 and the donor substrate 20 are provided, and then a solid metal is deposited on the second surface by a thin film deposition technique to form a transfer film 30. Next, the transfer film 30 is bonded to the top surface of the boss structure 101, and then the semiconductor substrate 10 and the donor substrate 20 are separated by a transfer technique, so that the top surface picks up the conductive material (solid metal) in the transfer film 30 that is bonded to the top surface. Furthermore, an electrode of the semiconductor device can be obtained by curing the conductive material (solid metal) on the top surface.

[0057] In some embodiments, before the step of forming the transfer film on the second surface, a plurality of spaced-apart bonding portions can also be formed on the second surface by a dispensing process. The method for preparing the electrode of the semiconductor device in this embodiment can further include: measuring the distance between two adjacent boss structures of the semiconductor substrate. Furthermore, the distance between two adjacent bonding portions can be made less than or equal to the length of the boss structure (the length direction of the boss is the connection direction of two adjacent bonding portions, and is also the connection direction of two adjacent boss structures). It can be understood that after the transfer film is formed on the second surface, the plurality of bonding portions can enhance the bonding strength between the transfer film and the donor substrate. Then, during the process of bonding the transfer film to the top surface of the boss structure, each bonding portion corresponds to the groove between two adjacent boss structures. Since the plurality of bonding portions enhance the bonding strength between the transfer film and the donor substrate, the process of separating the semiconductor substrate from the donor substrate can make the transfer film easier to be torn at the boundary bonded to the bonding portion, which is beneficial to the pickup of the top surface of the boss structure.

[0058] In some other alternative embodiments, when the conductive material is a solid metal, after bonding the transfer film to the top surface of the boss structure to obtain a bonded structure, the method for preparing the electrode of the semiconductor device further includes: performing a heat treatment on the bonded structure, and the temperature of the heat treatment is higher than the melting point of the solid metal.

[0059] Specifically, first, the semiconductor substrate and the donor substrate are provided, and then a solid metal is deposited on the second surface by a thin film deposition technique to form a transfer film. Next, the transfer film is bonded to the top surface of the boss structure to obtain a bonded structure. Then, the above heat treatment is performed on the bonded structure, so that the solid metal in the transfer film is transformed into a molten paste-like material. After that, the semiconductor substrate and the donor substrate are separated by a transfer technique, so that the top surface picks up the conductive material (molten solid metal) in the transfer film that is bonded to the top surface. Furthermore, an electrode of the semiconductor device can be obtained by curing the conductive material (molten solid metal) on the top surface.

[0060] Exemplarily, the heat treatment of the bonded structure is achieved by placing the bonded structure on a hot plate and heating the hot plate.

[0061] Specifically, if the solid metal is aluminum, and thus the transfer film is an aluminum film, after the aluminum film is bonded to the top surface of the boss structure to obtain a bonded structure and placed on a hot plate, the heating temperature of the hot plate can be 600 - 800 °C. The heating time can be 1 - 2 min.

[0062] In this embodiment, since the heat treatment temperature is higher than the melting point of the solid metal, the transfer film is in a flowing metastable state at the donor substrate interface, reducing the overall stiffness and internal stress of the transfer film. This makes the conductive material of the transfer film more likely to become unstable and break under an external force, making it more similar to the composite conductive paste or "ink paste" material mentioned above. Thus, it is more conducive to the top table picking up the conductive material that fits the top table in the transfer film.

[0063] In some alternative embodiments, in combination Figure 2 and Figure 3 as shown, the step of bonding the transfer film 30 to the top table of the boss structure 101 includes: transferring the semiconductor substrate 10 to the surface of the transfer film 30 facing away from the donor substrate 20; applying pressure to the semiconductor substrate 10 to bond the transfer film 30 to the top table of the boss structure 101.

[0064] It can be understood that, as Figure 2 shown, before transferring the semiconductor substrate 10 to the surface of the transfer film 30 facing away from the donor substrate 20, the semiconductor substrate 10 can be flipped so that the side of the semiconductor substrate 10 with the boss structure 101 faces the transfer film 30. Then transferring the semiconductor substrate 10 to the surface of the transfer film 30 facing away from the donor substrate 20 can make the top table of the boss structure 101 bond to the transfer film 30.

[0065] After the top table of the boss structure 101 contacts the transfer film 30, in order to make the top table of the boss structure 101 contact and bond to the transfer film 30, pressure can be applied to the semiconductor substrate 10. It should be noted that the transfer film 30 only bonds seamlessly to the top table of the boss structure 101 and does not contact the part of the first surface of the semiconductor substrate 10 other than the above-mentioned top table. Thus, after separating the semiconductor substrate 10 from the donor substrate 20 using the transfer technology, the top table can pick up the conductive material 40 that fits the top table in the transfer film 30, as Figure 3 shown.

[0066] In some optional embodiments, when the conductive material is liquid metal, in order to ensure that the top table surface of the boss structure is in seamless contact and fit with the transfer film without contacting the first surface of the semiconductor substrate other than the top table surface, a first pressure is applied to the semiconductor substrate, and the first pressure is 5~10N.

[0067] In some optional embodiments, when the conductive material is solid metal, in order to ensure that the top table surface of the boss structure is in seamless contact and fit with the transfer film without contacting the first surface of the semiconductor substrate other than the top table surface, a second pressure is applied to the semiconductor substrate, and the second pressure is 50~100N.

[0068] In some optional embodiments, such as Figure 2 and Figure 3 As shown, the semiconductor substrate 10 has a first end (not marked in the figure) and a second end (not marked in the figure) opposite to each other, and the direction pointing from the first end to the second end is parallel to the first surface. The semiconductor substrate 10 is separated from the donor substrate 20 by using a transfer technology, including: lifting the semiconductor substrate 10 from the first end; peeling off the semiconductor substrate 10 and the conductive material 40 in the transfer film 30 that is in contact with the top table from the donor substrate 20 (or in other words, peeling off the conductive material 40 in the transfer film 30 that is in contact with the top table of the boss structure 101 and the semiconductor substrate 10 from the donor substrate 20), until the second end is separated from the donor substrate 20.

[0069] Specifically, Figures 1 to 3 As shown, the semiconductor substrate 10 may be a hard structure.

[0070] In the above embodiment, by following the process of lifting from the first end of the semiconductor substrate and starting to peel off until the second end of the semiconductor substrate is separated from the donor substrate, the success rate of the top table picking up the conductive material in the transfer film that is attached to the top table can be improved.

[0071] In addition, in some examples, in order to ensure that there are sufficient force points when lifting the semiconductor substrate, a gripper can be adsorbed on the surface of the semiconductor substrate on the side away from the donor substrate. The gripper can include but is not limited to a movable suction pen, a vacuum suction pen, a clamping tool, and an adhesive tool.

[0072] According to the kinetic counterbalance relationship between the energy release rate and the tearing rate at the interface, the peeling speed of the top surface of the boss structure from the donor substrate directly affects the adhesion between the top surface and the transfer film. If the top surface of the boss structure is lifted from the donor substrate at a relatively high peeling speed, the adhesion of the top surface of the boss structure to the transfer film is strong enough to transfer the conductive material of the transfer film (it can be understood that the conductive material here can be the above-mentioned composite conductive paste including liquid metal or the above-mentioned solid metal) from the donor substrate to the top surface of the boss structure. Thus, in some alternative embodiments, in order to improve the success rate of the top surface picking up the conductive material that fits the top surface in the transfer film, the semiconductor substrate and the conductive material that fits the top surface in the transfer film are peeled off from the donor substrate at a first peeling speed, and the first peeling speed is 10 - 30 cm / s.

[0073] In some embodiments, if the conductive material is liquid metal, the steps of curing the conductive material on the top surface to obtain the electrode of the semiconductor device may include: curing the conductive material on the top surface by photo-curing or thermal-curing. Among them, for photo-curing: it can be irradiated by an ultraviolet lamp to crosslink and cure the free radicals, monomers, oligomers, etc. in the composite conductive paste, so that the composite conductive paste hardens and maintains its shape to obtain the electrode. For thermal-curing: it can be heated to form bonds between polymer molecules in the composite conductive paste and form a three-dimensional network structure, so that the polymer is cured, and the composite conductive paste hardens and maintains its shape to obtain the electrode.

[0074] In some embodiments, if the conductive material is solid metal, the steps of curing the conductive material on the top surface to obtain the electrode of the semiconductor device may include: after the molten conductive material (solid metal) is picked up on the top surface of the boss structure, through cooling treatment, it can be hardened and maintained its shape by standing at room temperature or accelerating cooling and hardening at low temperature to obtain the electrode.

[0075] Specifically, in order to achieve the electrical isolation effect of the boss structure during the crimping and encapsulation process, there is a thickness difference between the top surface of the boss structure and the part of the first surface of the semiconductor substrate other than the boss structure, and this thickness difference can be more than 25 µm.

[0076] In some alternative embodiments, the above semiconductor device is an IGCT device, and the top surface of the boss structure is the cathode surface of the IGCT device.

[0077] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0078] Applying the technical solution of the present application, a method for preparing an electrode of a semiconductor device includes: providing a semiconductor substrate and a donor substrate, the semiconductor substrate having a first surface with a boss structure therein, and the donor substrate having a second surface; forming a transfer film on the second surface, the material of the transfer film including a conductive material; attaching the transfer film to the top surface of the boss structure; separating the semiconductor substrate from the donor substrate by using a transfer technique so that the top surface picks up the conductive material in the transfer film that is attached to the top surface, wherein the transfer technique realizes the picking up by controlling the peeling speed; curing the conductive material on the top surface to obtain the electrode of the semiconductor device. Through the present application, the transfer film formed on the second surface of the boss structure and the donor substrate is attached and separated by the transfer technique, so that the conductive material can automatically align with the boss structure, achieving the purpose of picking up the conductive material through a stamping self-alignment technique, and avoiding lithography and etching problems such as low exposure uniformity and CD uniformity caused by light scattering at the boss and uneven glue thickness due to the special structure of the boss structure of the semiconductor substrate, thereby enabling the electrode ( mesa electrode) with higher uniformity to be obtained. In summary, the present application solves the problem of low patterning uniformity of the mesa electrode of the semiconductor device in the prior art.

[0079] The foregoing are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for preparing an electrode of a semiconductor device, characterized in that: The semiconductor device is an IGCT device, and the electrode preparation method comprises: A semiconductor base and a donor substrate are provided, wherein the semiconductor base has a first surface, the semiconductor base has a first end and a second end opposite to each other, the direction in which the first end points to the second end is parallel to the first surface, the first surface has a boss structure, the boss structure has a table height of 15 to 20 μm, and the donor substrate has a second surface; forming a transfer film on the second surface, wherein the material of the transfer film includes a conductive material; Transferring the semiconductor substrate to a surface of the transfer film facing away from the donor substrate; Applying pressure to the semiconductor substrate so that the transfer film is in contact with the top surface of the boss structure, wherein when the conductive material is liquid metal, a first pressure is applied to the semiconductor substrate, and the first pressure is 5-10N; when the conductive material is solid metal, a second pressure is applied to the semiconductor substrate, and the second pressure is 50-100N; lifting the semiconductor substrate from the first end; The semiconductor substrate and the conductive material in the transfer film that is attached to the top table are peeled off from the donor substrate using a first peeling speed until the second end is separated from the donor substrate, so that the top table picks up the conductive material in the transfer film that is attached to the top table, wherein the transfer technology realizes the picking up by controlling the peeling speed, and the first peeling speed is 10-30 cm / s; The conductive material on the top mesa is solidified to obtain an electrode of the semiconductor device, wherein the top mesa is a cathode mesa of the IGCT device, and the electrode is a cathode.

2. The electrode preparation method according to claim 1, characterized in that: The conductive material is liquid metal, and a transfer film is formed on the second surface, including: Dissolving liquid metal and polymer matrix material to prepare a composite conductive slurry, wherein the polymer matrix material includes nanoclay or hydrogel; The composite conductive paste is coated on the second surface to form the transfer film.

3. The electrode preparation method according to claim 2, characterized in that: The electrode preparation method further comprises: Before the step of laminating the transfer film to the top mesa of the boss structure, an interface modification layer is formed on the first surface, and the material of the interface modification layer has hydrogen bonds.

4. The electrode preparation method according to claim 1, characterized in that: The conductive material is solid metal, and a transfer film is formed on the second surface, including: The solid metal is deposited on the second surface by using a thin film deposition technique to form the transfer film.

5. The electrode preparation method according to claim 1, characterized in that: The conductive material is solid metal, the transfer film is laminated to the top table of the boss structure to obtain a laminated structure, and the electrode preparation method further includes: The bonded structure is subjected to heat treatment, wherein the temperature of the heat treatment is higher than the melting point of the solid metal.

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