Method for bonding semiconductor dies to a substrate

Abstract

A method for bonding a semiconductor die onto a substrate is provided. The method includes: applying a bonding assist layer in a first state to a press head; picking up a semiconductor die via the press head by adhering the semiconductor die to the bonding assist layer; displacing the press head to place the semiconductor die on a substrate; pressing the semiconductor die against the substrate by the press head; emitting a laser beam to the semiconductor die to heat the solder bumps between the semiconductor die and the substrate and bond the semiconductor die to the substrate; transitioning the bonding assist layer to a second state, wherein the adhesion of the bonding assist layer to the press head in the second state is lower than the adhesion of the bonding assist layer to the press head in the first state; displacing the press head to separate the bonding assist layer from the press head.

Description

Technical Field

[0001] This application generally relates to semiconductor technology, and more specifically, to a method for bonding semiconductor dies to a substrate. Background Technology

[0002] Semiconductor packaging is one of the most important parts of semiconductor manufacturing and design. The semiconductor packaging process affects the power, performance, cost, and basic functionality of a semiconductor package. In a typical packaging process, semiconductor dies are first fabricated at the wafer level, and then each die is mounted onto a substrate to form an integrated semiconductor package or device.

[0003] In recent years, laser compression bonding (LCB) technology has been widely adopted for bonding semiconductor dies to substrates due to its high bonding accuracy and efficiency. During the LCB bonding process, a laser beam is emitted to heat the bonding material between the semiconductor die and the substrate, and a pressure head is used to press the semiconductor die against the substrate to assist the bonding process. However, existing bonding heads may cause uneven heat distribution on the semiconductor die, which adversely affects the bonding formed between the semiconductor die and the substrate.

[0004] Therefore, there is a need for a method to bond semiconductor dies to a substrate with improved bonding quality. Summary of the Invention

[0005] The objective of this application is to provide a method for bonding semiconductor dies to a substrate with improved bonding quality.

[0006] According to one aspect of this application, a method for bonding a semiconductor die to a substrate is provided. The method includes: applying a bonding aid layer in a first state to a pressure surface of a crimp connector; picking up a semiconductor die via the crimp connector by adhering a semiconductor die to the bonding aid layer; displacing the crimp connector relative to a substrate to place the semiconductor die on the substrate, wherein a plurality of solder bumps are mounted between the semiconductor die and the substrate; pressing the semiconductor die against the substrate via the crimp connector, during which the bonding aid layer remains in the first state; emitting a laser beam through the crimp connector and the bonding aid layer toward the semiconductor die to heat the plurality of solder bumps between the semiconductor die and the substrate and to bond the semiconductor die to the substrate via the plurality of solder bumps; changing the bonding aid layer from the first state to a second state, wherein the adhesion of the bonding aid layer to the crimp connector in the second state is lower than the adhesion of the bonding aid layer to the crimp connector in the first state; displacing the crimp connector relative to the substrate to separate the bonding aid layer from the crimp connector; and removing the bonding aid layer from the semiconductor die.

[0007] According to another aspect of this application, a method for bonding a semiconductor die to a substrate is provided. The method includes: applying a bonding aid layer in a first state to a top surface of a semiconductor die; picking up the semiconductor die via a crimp connector by adhering the bonding aid layer to a crimp connector; displacing the crimp connector relative to a substrate to place the semiconductor die on the substrate, wherein a plurality of solder bumps are mounted between the semiconductor die and the substrate; pressing the semiconductor die against the substrate via the crimp connector, during which the bonding aid layer remains in the first state; emitting a laser beam through the crimp connector and the bonding aid layer toward the semiconductor die to heat the plurality of solder bumps between the semiconductor die and the substrate and to bond the semiconductor die to the substrate via the plurality of solder bumps; changing the bonding aid layer from the first state to a second state, wherein the adhesion of the bonding aid layer to the crimp connector in the second state is lower than the adhesion of the bonding aid layer to the crimp connector in the first state; displacing the crimp connector relative to the substrate to separate the bonding aid layer from the crimp connector; and removing the bonding aid layer from the semiconductor die.

[0008] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and not intended to limit the invention. Furthermore, the accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with this specification, serve to explain the principles of the invention. Attached Figure Description

[0009] The accompanying drawings referenced herein form part of this specification. Unless the specific embodiments clearly indicate otherwise, the features shown in the drawings illustrate only some embodiments of this application, not all embodiments of this application, and readers of this specification should not draw the contrary inferences.

[0010] Figures 1A to 1H The steps of a method for bonding a semiconductor die to a substrate according to a first embodiment of this application are illustrated.

[0011] Figures 2A to 2G The following describes the steps of a method for bonding a semiconductor die to a substrate according to a second embodiment of this application.

[0012] The same reference numerals will be used throughout the accompanying drawings to refer to the same or similar parts. Detailed Implementation

[0013] The following detailed description of exemplary embodiments of this application takes into account the accompanying drawings, which form a part of the description. The drawings illustrate specific exemplary embodiments in which this application may be practiced. The detailed description, including the drawings, describes these embodiments in sufficient detail to enable those skilled in the art to practice this application. Those skilled in the art may further utilize other embodiments of this application and make logical, mechanical, and other changes without departing from the spirit or scope of this application. Therefore, the reader of the following detailed description should not interpret the description in a limiting sense, and the scope of the embodiments of this application is defined only by the appended claims.

[0014] In this application, unless otherwise expressly stated, the use of the singular includes the plural form. In this application, unless otherwise stated, the use of “or” means “and / or”. Furthermore, the use of the term “comprising” is not restrictive. Additionally, unless otherwise expressly stated, terms such as “element” or “assembly” cover both elements and assemblies comprising one unit and elements and assemblies comprising more than one sub-unit. Furthermore, the section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described.

[0015] As used herein, for ease of description, spatial relative terms such as “below,” “under,” “above,” “upper,” “upper,” “lower,” “left,” “right,” “vertical,” “horizontal,” and “side” may be used to describe the relationship between an element or feature and another element (or feature) or feature (or feature), as shown in the diagrams. In addition to the orientations depicted in the diagrams, the spatial relative terms are intended to cover different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein shall be interpreted accordingly. It should be understood that when an element is referred to as “connected to” or “coupled to” another element, the element may be directly connected to or coupled to the other element, or there may be intermediate elements present.

[0016] As mentioned above, during the LCB bonding process, a press-fit device with vacuum channels can be used to bond semiconductor dies to a substrate. More specifically, vacuum pressure is applied through these vacuum channels so that the press-fit device can pick up the semiconductor die and bond it to the substrate via solder bumps. When the bonding process begins, a laser beam can be emitted towards the semiconductor die to heat the solder bumps between the semiconductor die and the substrate. Simultaneously, the press-fit device can press the semiconductor die against the substrate, thereby forming the desired bonding connection between the semiconductor die and the substrate. However, during the laser heating process, the vacuum channels within the press-fit device may adversely affect the transmittance of the laser beam to the solder bumps. That is, the laser irradiation reaching the semiconductor die area below the vacuum channels may be less compared to other semiconductor die areas not below the vacuum channels. Therefore, the temperature distribution on the semiconductor die may lack uniformity, which adversely affects the bonding quality between the semiconductor die and the substrate.

[0017] To address the aforementioned issues, a method for bonding semiconductor dies to a substrate is provided. The method introduces a bonding aid layer that enables a crimp connector to pick up the semiconductor die without applying vacuum pressure. The bonding aid layer can transition between a first state and a second state. When in the first state, the bonding aid layer exhibits adhesiveness, allowing it to adhere to the pressure surface of the crimp connector, thus providing adhesion to the crimp connector. In this manner, when the semiconductor die adheres to the bonding aid layer, it can be picked up by the crimp connector and further placed and pressed against the substrate. Once the LCB bonding process is complete and the semiconductor die is bonded to the substrate, the bonding aid layer transitions to the second state. The adhesion of the bonding aid layer to the crimp connector in the second state is lower than that in the first state, allowing the crimp connector to be separated from the bonding aid layer. Finally, the bonding aid layer can be removed from the semiconductor die, and the crimp connector can be reused in subsequent LCB bonding processes. Due to the use of the bonding aid layer, the crimp connector no longer requires a conventional vacuum channel. Therefore, the problem of insufficient laser beam transmittance through the crimp connector caused by the vacuum channel can be successfully eliminated. This promotes uniform thermal distribution on the semiconductor die and improves the bonding quality between the semiconductor die and the substrate.

[0018] Figures 1A to 1H The steps of a method for bonding a semiconductor die to a substrate according to a first embodiment of this application are illustrated.

[0019] like Figure 1A As shown, a bonding aid layer 110 is formed or applied on the processing platform 101. The bonding aid layer 110 can be used in the bonding process to facilitate the bonding of the semiconductor die to the substrate using a crimp connector. At this stage, the bonding aid layer 110 is provided in a first state, such as a liquid state. Furthermore, the bonding aid layer 110 is transparent to achieve high transmittance of the laser beam during subsequent bonding processes.

[0020] In some embodiments, the bonding aid layer 110 comprises polydimethylsiloxane (PDMS). PDMS materials possess excellent properties in their liquid state, such as high transparency, superior flexibility, excellent lubricity, and hydrophilicity, thereby making them ideal bonding aid materials for press-fit processes. In some preferred embodiments, the bonding aid layer 110 comprises ultraviolet-curable polydimethylsiloxane (UV PDMS). More specifically, the UV PDMS comprises an elastomeric substrate (e.g., a silicone elastomeric substrate) and a curing agent. For example, the ratio (e.g., weight ratio) between the elastomeric substrate and the curing agent can range from 30:1 to 10:1, or preferably from 20:1 to 15:1. In some preferred embodiments, the UV PDMS may comprise a commercially available product such as SYLGARD. TM 184 silicone elastomer complete set of materials.

[0021] In some other embodiments, the bonding aid layer 110 may comprise an ultraviolet-curable silicone having properties similar to UV PDMS. Alternatively, the bonding aid layer 110 may also comprise a liquid crystal polymer having low friction and high chemical resistance. These materials are suitable for use during subsequent pressing processes.

[0022] In some embodiments, the bonding aid layer 110 in a first state can be formed on the processing platform 101 by jetting, spraying, inkjet printing, or any suitable deposition technique. Before forming the bonding aid layer 110 on the processing platform 101, the platform 101 can be cleaned to remove any potential contaminants. In some preferred embodiments, the processing platform 101 may include a cavity. The bonding aid layer 110 may be formed on the region including the cavity. The cavity may be filled with water or air to cool the bonding aid layer 110 during its formation.

[0023] Next, as Figure 1BAs shown, a crimp connector 121 is provided. The crimp connector 121 is used to apply the required pressing force to bond a semiconductor die to a substrate. The crimp connector 121 may also include a base and a protrusion extending upward from the base. The protrusion may be attached to or formed together with the base. During subsequent processes, when the semiconductor die is picked up by the crimp connector 121, the bottom surface of the protrusion may be close to the semiconductor die, or specifically indirectly in contact with the semiconductor die via a bonding aid layer 110. In some embodiments, the size of the protrusion may be substantially equal to or smaller than the size of the base. In some embodiments, the protrusion may have a rectangular layout, which may resemble the shape of the semiconductor die. In some other embodiments, the protrusion may have other shaped layouts, such as circular, hexagonal, or octagonal. In some embodiments, the base may have a stepped layout, that is, a portion of the base closer to the protrusion may have a smaller size compared to a portion of the base farther from the protrusion. In some other embodiments, the base may have the same size or layout as the protrusion. It is understood that the protrusion can be formed separately from the base or integrally formed as a single piece with the base. In this embodiment, the crimp connector 121 comprises a material transparent to laser irradiation, which may include at least one material selected from the group consisting of Al2O3, sapphire, quartz, and glass. The crimp connector 121 allows the laser beam applied in subsequent processes to substantially pass through the crimp connector 121 and reach the semiconductor die. Additionally, a compression retainer 122 is provided on the outside of the crimp connector 121, which is matched in size and shape to the crimp connector 121 to securely hold the crimp connector 121. When the compression retainer 122 is used in the bonding process, it can provide mechanical support for the crimp connector 121. In some embodiments, the compression retainer 122 may include a light-shielding material that blocks the laser beam from passing through it. It should be noted that a vacuum channel is not required inside the crimp connector 121, thereby simplifying the formation process of the crimp connector 121 and reducing production costs. The crimp connector 121 and the compression retainer 122 together form the crimp member 120. Furthermore, the track is coupled to the crimping member 120, allowing the crimping member 120 to move vertically and / or horizontally relative to the work platform. In some embodiments, a drive mechanism may be mounted on the track to control the movement of the crimping member 120.

[0024] In some embodiments, the bonding auxiliary layer 110 in the first state may have a strength in the range of 30 mJ / m 2 Up to 40mJ / m 2 The surface energy between them exhibits hydrophilicity. Furthermore, the bottom surface of the crimp connector 121 can have a surface energy in the range of 45 mJ / m. 2 Up to 60mJ / m 2 The surface energy between them also exhibits hydrophilicity. For example... Figure 1BAs shown, the crimp connector 121 moves downward toward the bonding aid layer 110 until it contacts the bonding aid layer 110. Due to the hydrophilicity of the bonding aid layer 110, the bonding aid layer has relatively high adhesion to the crimp connector 121, thus the bonding aid layer 110 can firmly adhere to the bottom surface (i.e., the pressurized surface) of the crimp connector 121. Furthermore, the adhesion of the bonding aid layer 110 to the processing platform 101 can be lower than its adhesion to the crimp connector 121. Therefore, as the crimp connector 121 moves upward away from the processing platform 101, the bonding aid layer 110 can be released from the processing platform 101 and attached to the bottom surface of the crimp connector 121.

[0025] Next, as Figure 1C As shown, the crimp connector 121 moves toward the carrier 125 on which the semiconductor die 130 is placed. The carrier 125 can be used in previous manufacturing processes, such as a flipper 125. In some embodiments, the semiconductor die 130 may include a flip chip or some large-scale semiconductor chip, such as a system-on-a-chip (SOC) die. Conductive pads 131 may be formed on the bottom surface of the semiconductor die 130, and solder bumps 132 are formed on the conductive pads 131. Furthermore, the semiconductor die 130 may include, for example, a silicon wafer die with an oxide top surface. The top surface of the semiconductor die 130 may have a surface area in the range of 40 mJ / m². 2 Up to 60mJ / m 2 The surface energy between them exhibits hydrophilicity.

[0026] In some embodiments, the crimp connector 121 having the bonding aid layer 110 can be positioned directly above the semiconductor die 130 for optimal attachment between them. Next, the crimp connector 121 is moved downward toward the semiconductor die 130 until the bonding aid layer 110 contacts the top surface of the semiconductor die 130. Due to the adhesion of the bonding aid layer 110 to the semiconductor die 130, the top surface of the semiconductor die 130 adheres to the bonding aid layer 110. Therefore, the semiconductor die 130 is indirectly attached to the pressure surface of the crimp connector 121 via the bonding aid layer 110. Next, as... Figure 1D As shown, the crimp connector 121 and the semiconductor die 130 attached thereto move together and away from the carrier 125, so that the crimp connector 121 picks up the semiconductor die 130.

[0027] In some embodiments, the thickness of the bonding aid layer 110 can range from 200 micrometers to 1500 micrometers to provide sufficient adhesion to the semiconductor die 130. It is understood that the thickness of the bonding aid layer 110 can be proportional to the weight of the semiconductor die 130. For example, for a medium-sized semiconductor die 130 (approximately 30 mm in both length and width), the thickness of the bonding aid layer 110 can range from 200 micrometers to 500 micrometers to ensure stable pickup of the semiconductor die 130. For a larger-sized semiconductor die 130 (approximately 60 mm in both length and width), the thickness of the bonding aid layer 110 can range from 800 micrometers to 1500 micrometers to ensure uniform adhesion between the semiconductor die 130 and the crimp connector 121, thereby enabling stable pickup of the semiconductor die 130.

[0028] In some preferred embodiments, the semiconductor die 130 can be weighed before being picked up, and algorithms can be used to calculate the required thickness of the bonding aid layer 110 to provide sufficient adhesion for picking up the die.

[0029] Next, as Figure 1EAs shown, a semiconductor die 130 is moved to a position above a substrate 140 via a crimp connector 121. The semiconductor die 130 can be bonded to the substrate 140 in a subsequent bonding process. In some embodiments, the substrate 140 may be made of silicon or other semiconductor materials, or may include a printed circuit board (PCB), a ceramic substrate, a laminated interposer, a bridging interposer, a lead frame, or other suitable substrate. In some examples, the substrate 140 may include a redistribution layer or structure having one or more dielectric layers and one or more conductive layers located between and through the dielectric layers. Thus, various elements and other structures on one or both sides of the substrate 140 can be electrically coupled to each other to form an integrated electronic system. In this embodiment, the substrate 140 is placed on a substrate carrier 128 for mechanical support. In some embodiments, the substrate carrier 128 may have vents (e.g., holes) fluidly coupled to a vacuum source to apply vacuum pressure to the substrate 140 when it is placed on the substrate carrier 128. The attractive force exerted on the substrate 140 by the vacuum pressure can reduce warpage of the substrate 140 during subsequent bonding processes. Multiple sets of conductive pads can be formed on the top surface of the substrate 140 for mounting the semiconductor die 130 onto the substrate 140. In some other embodiments, additional solder paste can be applied to the multiple sets of conductive pads to facilitate subsequent bonding processes. Next, the crimp connector 121 moves downward toward the substrate carrier 128 together with the semiconductor die 130 to place the semiconductor die 130 onto the substrate 140, wherein solder bumps 132 are installed between the semiconductor die 130 and the substrate 140.

[0030] Next, a laser beam is emitted from a laser source (not shown) positioned above the pressure connector 121 toward the substrate carrier 128 to perform the bonding process. The laser beam passes through the pressure connector 121 and the bonding aid layer 110 to reach the semiconductor die 130, thereby heating the semiconductor die 130 and the solder bumps 132 located between the semiconductor die 130 and the substrate 140. In some embodiments, pressure can also be applied to the semiconductor die 130 through the pressure connector 121 to assist the bonding process.

[0031] In some embodiments, the semiconductor die 130 may be gradually heated by a laser beam. For example, the semiconductor die 130 may first be preheated to a temperature between 85°C and 150°C. In some preferred embodiments, the semiconductor die 130 may be preheated to a temperature of approximately 90°C. The preheating process may last for 2 to 20 seconds, or preferably for a period of 10 to 20 seconds. In this embodiment, the preheating process can release thermal stress within the semiconductor die 130, thus reducing warpage of the semiconductor die 130 caused in previous processes. For example, the preheating process can transform the semiconductor die 130, which has a convex or concave shape, into an almost flat shape, which is beneficial for subsequent processes. In addition, the preheating of the semiconductor die 130 and the solder bumps 132 can also reduce the heat energy and heating duration required in subsequent bonding processes. Next, the laser beam may continue to heat the semiconductor die 130 and the solder paste or solder bumps, such that all the solder paste is sufficiently heated, for example, to a temperature above its melting temperature, which may be referred to as a bonding heating process. During the bonding heating process, the semiconductor die 130 is pressed against the substrate 140 by pressure applied via the pressure connector 121 to reshape the solder bump 132 and fully wet the substrate 140. This allows the solder bump 132 to electrically connect the semiconductor die 130 to the substrate 140, thereby bonding the semiconductor die 130 to the substrate 140 via the solder bump 132. During this pressing process, the bonding aid layer 110 in a first state (e.g., liquid) can act as a buffer layer to mitigate collisions between the pressure connector 121 and the semiconductor die 130. Therefore, mechanical damage to the semiconductor die 130 and solder bump 132 during pressing is reduced, thereby further improving the reliability of the formed bonding connection. Subsequently, the pressure applied by the pressure connector 121 can be gradually reduced to allow the solder bump 132 to solidify. In some other embodiments, a preheating process is not required, and the process of pressing the semiconductor die 130 against the substrate 140 can be performed simultaneously with the entire process of emitting a laser beam onto the semiconductor die 130. During the pressing process, the semiconductor die 130 is bonded to the substrate 140 via solder bumps 132 using an in-situ bonding mechanism, without the need for self-alignment of the solder bumps 132 with the conductive pads on the substrate 140. This can provide higher bonding efficiency and accuracy compared to conventional thermal bonding or laser-assisted bonding processes. It should be noted that when the semiconductor die 130 is pressed against the substrate 240 to facilitate the pressing process, the bonding aid layer 110 remains in a first state, such as a liquid state.

[0032] During the bonding process, since the bonding aid layer 110 is used for the pressurization process, a conventional vacuum channel is no longer needed in the crimp connector 121. Therefore, the laser beam emitted from the laser source can effectively penetrate through the crimp connector 121. Furthermore, the bonding aid layer 110 is transparent to the laser beam, allowing the laser beam to penetrate through the crimp connector 121 and the bonding aid layer 110 with almost no energy loss to reach the semiconductor die 130 and the solder bump 132. In this way, all areas of the semiconductor die 130 and the solder bump 132 can receive sufficient and uniform laser irradiation for the bonding process. This promotes uniform heat distribution on the semiconductor die 130 and improves the bonding quality between the semiconductor die 130 and the substrate 140. Moreover, during the laser heating process, the bonding aid layer 110 has relatively stable properties when exposed to the laser beam, which allows the bonding aid layer 110 to remain in a first state (e.g., liquid state) to facilitate the implementation of the entire crimping process, thereby achieving an improved bonding connection.

[0033] Next, after the solder bumps 132 between the semiconductor die 130 and the substrate 140 have solidified, the laser source can be turned off. Then, the heating process applied to the semiconductor die 130 and solder bumps 132 is terminated, and the temperatures of the semiconductor die 130 and solder bumps 132 can begin to decrease to a lower temperature, such as room temperature or above room temperature. During the cooling of the solder bumps 132, the crimp connector 121 can be held in the bonding position for a period of time to help the solder bumps 132 solidify to the desired bump height. Afterward, the force applied by the crimp connector 121 can be removed, and the shape of the solder bumps 132 can remain unchanged, enabling a stable bonding connection between the semiconductor die 130 and the substrate 140, thereby completing the bonding process.

[0034] Next, as Figure 1F As shown, after the bonding process, ultraviolet (UV) irradiation is emitted from a light source above the crimp connector 121. The UV irradiation passes through the crimp connector 121 to reach the bonding aid layer 110, transforming it from a first state (e.g., liquid) to a second state. In some embodiments, for example... Figure 1FIn the illustrated embodiment, the liquid bonding aid layer 110 is cured and transformed into a solid cured bonding aid layer 115. More specifically, when ultraviolet light irradiation is applied to the bonding aid layer 110, the material of this layer (e.g., PDMS material) can undergo a crosslinking reaction to form covalent bridges within the material, and a 3D network can be established within the material. In this way, the PDMS material can be transformed from a viscous liquid to an elastic solid. During the curing process of the bonding aid layer 110, the surface energy of the bonding aid layer 110 decreases, and therefore the surface of the bonding aid layer 110 may gradually change from a hydrophilic surface to a hydrophobic surface. Therefore, the adhesion of the bonding aid layer 110 to external surfaces, such as the pressure surface of the crimp connector 121, is also reduced. In some embodiments, the adhesion of the bonding aid layer 110 can be reduced to at least a certain extent such that the adhesion of the cured bonding aid layer 115 to the crimp connector 121 is lower than the adhesion of the cured bonding aid layer 115 to the semiconductor die 130. In some preferred embodiments, the surface energy of the cured bonding auxiliary layer 115 can be reduced to 19 mJ / m 2 Up to 22mJ / m 2 Thus, the curing process is completed, resulting in a cured bonding auxiliary layer 115 with a hydrophobic surface and low adhesion.

[0035] In some other embodiments, the bonding aid layer 110 may include a UV-curable silicone, which can be cured using a process similar to PDMS. In some alternative embodiments, the bonding aid layer 110 may include a liquid crystal polymer. The liquid crystal polymer may be cured using a UV irradiation process or a heating process.

[0036] Next, as Figure 1G As shown, the crimp connector 121 is displaced relative to the substrate 140. Specifically, the crimp connector 121 moves upward away from the substrate carrier 128. Since the adhesion of the cured bonding aid layer 115 to the crimp connector 121 is lower than its adhesion to the semiconductor die 130, the cured bonding aid layer 115 can separate from the crimp connector 121 at the pressure surface when exposed to external forces, but still maintains adhesion to the semiconductor die 130.

[0037] Next, as Figure 1H As shown, the cured bonding aid layer 115 is removed from the semiconductor die 130. In some preferred embodiments, a flux removal process is performed to remove the cured bonding aid layer 115, which can simultaneously remove residual flux from the solder bumps 132. By applying the flux removal process to the semiconductor die 130 and the cured bonding aid layer 115, the pressure surface of the crimp connector 121 can remain uncontaminated, thereby ensuring reliable performance of subsequent bonding processes. In this way, the semiconductor die 130 is bonded to the substrate 140 with improved bonding quality for subsequent processes.

[0038] In some other embodiments, the adhesion of the bonding aid layer 115 to the semiconductor die 130 may be less than its adhesion to the crimp connector 121. Therefore, the bonding aid layer 115 can be separated from the semiconductor die 130 but still remain adhered to the crimp connector 121. The bonding aid layer 115 can then be removed from the crimp connector 121 to re-expose the pressurized surface for subsequent bonding processes.

[0039] Figures 2A to 2G The following describes the steps of a method for bonding a semiconductor die to a substrate according to a second embodiment of this application. Figures 2A to 2G The methods shown in the article are largely the same as Figures 1A to 1H The method shown is the same, the difference lies in... Figure 2A First, a bonding aid layer is applied to the semiconductor die, rather than as... Figures 1A to 1C As shown in the diagram, a bonding auxiliary layer is applied to the crimp connector.

[0040] like Figure 2A As shown, a semiconductor die 230 is placed on a carrier 225 (e.g., a flipper). In some embodiments, conductive pads 231 may be formed on the bottom surface of the semiconductor die 230, and solder bumps 232 are formed on the conductive pads 231. When the bonding aid layer 210 is in a first state (e.g., in a liquid state), the bonding aid layer 210 is formed on the top surface of the semiconductor die 230. In some embodiments, the bonding aid layer 110 comprises polydimethylsiloxane (PDMS). In some preferred embodiments, the liquid bonding aid layer 210 can be formed on the semiconductor die 230 by a spraying process. Specifically, the raw material for the bonding aid layer 210 can first be provided in a storage block 235, then the raw material is liquefied and sprayed from the outlet of the storage block 235. The liquid bonding aid layer 210 can have sufficient ductility to extend uniformly across the entire top surface of the semiconductor die 230, which provides maximum contact area for subsequent attachment with a crimp connector. Additionally, the bonding aid layer 210 can be formed according to the dimensions and layout of the top surface of the semiconductor die 230, which also facilitates subsequent attachment to the crimp connector 221. In some other embodiments, the bonding aid layer 210 can be formed by spraying, inkjet printing, or any suitable deposition technique. The liquid bonding aid layer 210 can have a strength in the range of 30 mJ / m 2 Up to 40mJ / m 2 The surface energy between them exhibits hydrophilicity. Additionally, the top surface of the semiconductor die 230 can have a surface energy in the range of 40 mJ / m². 2 Up to 60mJ / m 2The surface energy between them also exhibits hydrophilicity. Due to the hydrophilicity of the bonding aid layer 210 and the semiconductor die 230, the bonding aid layer 210 adheres well to the semiconductor die 230, thus allowing the bonding aid layer 210 to firmly adhere to the top surface of the semiconductor die 230. It should be noted that details regarding the materials, properties, and structure of the semiconductor die 230 and the bonding aid layer 210 can be found in [contact information]. Figures 1A to 1C The examples shown are similar to those illustrated, and for the sake of simplicity, they will not be described in detail here.

[0041] Next, as Figure 2B As shown, a crimp connector 221 is provided. The bottom surface (i.e., the pressure surface) of the crimp connector 221 can have a strength in the range of 45 mJ / m. 2 Up to 60mJ / m 2 The surface energy between them. The crimp connector 221 moves downward toward the bonding aid layer 210 and the semiconductor die 230 until it contacts the surface of the bonding aid layer 210. Similarly, due to the adhesion of the bonding aid layer 210 to the crimp connector 221, the bonding aid layer 210 adheres to the pressing surface of the crimp connector 221. Therefore, the semiconductor die 230 is indirectly attached to the pressing surface of the crimp connector 221 through the bonding aid layer 210. Next, as Figure 2C As shown, the crimp connector 221 moves upward together with the semiconductor die 230 attached thereto, so that the crimp connector 221 picks up the semiconductor die 230.

[0042] Next, as Figure 2D As shown, the semiconductor die 230 is moved to a position above the substrate 240 via the crimp connector 221. Next, the crimp connector 221 and the semiconductor die 230 move downward toward the substrate 240 to place the semiconductor die 230 onto the substrate 240, wherein solder bumps 232 are installed between the semiconductor die 230 and the substrate 240.

[0043] Next, a laser beam is emitted from a laser source (not shown) positioned above the crimp connector 221 toward the substrate 240 to perform a bonding process. The laser beam passes through the crimp connector 221 and the bonding aid layer 210 to reach the semiconductor die 230, thereby heating the semiconductor die 230 and the solder bumps 232. During the bonding process, the semiconductor die 230 is pressed against the substrate 240 via the crimp connector 221 to reshape the solder bumps 232, ensuring they fully wet the substrate 240. This allows the solder bumps 232 to electrically connect the semiconductor die 230 to the substrate 240, thereby bonding the semiconductor die 230 to the substrate 240 via the solder bumps 232. It should be noted that while the semiconductor die 230 is pressed against the substrate 240 to facilitate the crimping process, the bonding aid layer 210 remains in a first state, such as a liquid state. Details of the crimping process can be found in... Figure 1EThe examples shown are similar to those illustrated, and for the sake of simplicity, they will not be described in detail here.

[0044] Next, as Figure 2E As shown, after the bonding process, ultraviolet (UV) irradiation is emitted from a light source above the crimp connector 221. The UV irradiation passes through the crimp connector 221 to reach the bonding aid layer 210, transforming it from a first state (e.g., liquid) to a second state. In some embodiments, for example... Figure 2E In the illustrated embodiment, the liquid bonding aid layer 210 is cured and transformed into a solid (i.e., second state) cured bonding aid layer 215. More specifically, when ultraviolet irradiation is applied to the bonding aid layer 210, the material of this layer (e.g., PDMS material) can transform from a viscous liquid to an elastic solid. The cured bonding aid layer 215 can have a low surface energy hydrophobic surface, thereby exhibiting lower adhesion to the crimp connector 221 than its adhesion in the liquid state. More specifically, the adhesion of the cured bonding aid layer 215 to the crimp connector 221 can be lower than its adhesion to the semiconductor die 230.

[0045] In some other embodiments, the bonding aid layer 210 may include a UV-curable silicone that can be cured using a process similar to PDMS. In some alternative embodiments, the bonding aid layer 210 may include a liquid crystal polymer. The liquid crystal polymer may be cured using a UV irradiation process or a heating process.

[0046] Next, as Figure 2F As shown, the crimp connector 221 is displaced relative to the substrate 240. Specifically, the crimp connector 221 moves upward away from the substrate 240. Since the adhesion of the cured bonding aid layer 215 to the crimp connector 221 is lower than its adhesion to the semiconductor die 230, the cured bonding aid layer 215 can separate from the crimp connector 221 at the pressure surface when exposed to external force, but still maintains adhesion to the semiconductor die 230.

[0047] Next, as Figure 2G As shown, the cured bonding aid layer 215 is removed from the semiconductor die 230 by, for example, a flux removal process. In this way, the semiconductor die 230 is bonded to the substrate 240 with improved bonding quality for subsequent processes.

[0048] Further details regarding the steps for transitioning the bonding auxiliary layer 210 from the first state to the second state, the properties of the bonding auxiliary layer 215 in the second state, and the steps for separating the bonding auxiliary layer 215 from the crimp connector 221 can be found in... Figures 1F to 1H The examples shown are similar to those illustrated, and for the sake of simplicity, they will not be described in detail here.

[0049] Although an exemplary method for bonding a semiconductor die to a substrate has been described in conjunction with the accompanying drawings, those skilled in the art will understand that modifications and adjustments can be made to the method without departing from the scope of the invention.

[0050] Various embodiments have been described herein with reference to the accompanying drawings. However, it will be apparent that various modifications and alterations can be made thereto, and other embodiments can be practiced, without departing from the broader scope of the invention as set forth in the appended claims. Furthermore, other embodiments will be apparent to those skilled in the art upon consideration of the description and practice of one or more embodiments of the invention disclosed herein. Therefore, the examples in this application and herein are intended to be considered exemplary only, and the true scope and spirit of the invention are indicated by the list of exemplary claims appended.

Claims

1. A method for bonding a semiconductor die to a substrate, characterized in that, The method includes: The bonding aid layer in its first state is applied to the pressure surface of the pressure joint; The semiconductor die is picked up via the crimp connector by adhering the semiconductor die to the bonding aid layer; The crimping connector is displaced relative to the substrate to place the semiconductor die on the substrate, wherein a plurality of solder bumps are mounted between the semiconductor die and the substrate; The semiconductor die is pressed against the substrate using the crimp connector, during which the bonding aid layer remains in the first state; A laser beam is emitted through the crimp connector and the bonding aid layer toward the semiconductor die to heat the plurality of solder bumps between the semiconductor die and the substrate and to bond the semiconductor die to the substrate via the plurality of solder bumps; The bonding auxiliary layer is changed from the first state to the second state, wherein the adhesion of the bonding auxiliary layer to the crimp connector in the second state is lower than the adhesion of the bonding auxiliary layer to the crimp connector in the first state; Displace the crimp connector relative to the substrate to separate the bonding auxiliary layer from the crimp connector; and Remove the bonding auxiliary layer from the semiconductor die.

2. The method according to claim 1, characterized in that, The surface energy of the bonding auxiliary layer in the first state is higher than that in the second state.

3. The method according to claim 2, characterized in that, The first state of the bonding auxiliary layer is liquid, and the second state of the bonding auxiliary layer is solid.

4. The method according to claim 3, characterized in that, The bonding auxiliary layer comprises UV-curable polydimethylsiloxane.

5. The method according to claim 4, characterized in that, The UV-curable polydimethylsiloxane comprises a silicone elastomer substrate and a curing agent.

6. The method according to claim 5, characterized in that, The ratio of the silicone elastomer substrate to the curing agent is 20:1 to 15:

1.

7. The method according to claim 1, characterized in that, The step of changing the bonding auxiliary layer from the first state to the second state further includes: Reduce the adhesion of the bonding aid layer until the adhesion of the bonding aid layer to the crimp connector is lower than the adhesion of the bonding aid layer to the semiconductor die.

8. The method according to claim 1, characterized in that, The steps of pressing the semiconductor die against the substrate and emitting the laser beam at the semiconductor die are performed simultaneously, wherein the bonding aid layer remains in the first state during the step of emitting the laser beam at the semiconductor die.

9. The method according to claim 1, characterized in that, The step of changing the bonding auxiliary layer from the first state to the second state is performed after the step of emitting the laser beam to the semiconductor die.

10. The method according to claim 4, characterized in that, The process of changing the bonding auxiliary layer from the first state to the second state includes: curing the bonding auxiliary layer from the first state to the second state by applying ultraviolet light irradiation to the bonding auxiliary layer.

11. The method according to claim 3, characterized in that, The bonding auxiliary layer comprises UV-curable silicone.

12. The method according to claim 3, characterized in that, The bonding auxiliary layer comprises a liquid crystal polymer.

13. The method according to claim 11, characterized in that, The process of changing the bonding auxiliary layer from the first state to the second state includes: curing the bonding auxiliary layer from the first state to the second state by applying ultraviolet light irradiation or heat to the bonding auxiliary layer.

14. The method according to claim 1, characterized in that, The bonding aid layer in the first state is formed using a processing platform including a cavity, wherein the cavity is configured to apply air or water to cool the bonding aid layer.

15. A method for bonding a semiconductor die to a substrate, characterized in that, The method includes: The bonding aid layer in its first state is applied to the top surface of the semiconductor die; The semiconductor die is picked up via the crimp connector by adhering the bonding aid layer to the crimp connector; The crimping connector is displaced relative to the substrate to place the semiconductor die on the substrate, wherein a plurality of solder bumps are mounted between the semiconductor die and the substrate; The semiconductor die is pressed against the substrate using the crimp connector, during which the bonding aid layer remains in the first state; A laser beam is emitted through the crimp connector and the bonding aid layer toward the semiconductor die to heat the plurality of solder bumps between the semiconductor die and the substrate and to bond the semiconductor die to the substrate via the plurality of solder bumps; The bonding auxiliary layer is changed from the first state to the second state, wherein the adhesion of the bonding auxiliary layer to the crimp connector in the second state is lower than the adhesion of the bonding auxiliary layer to the crimp connector in the first state; Displace the crimp connector relative to the substrate to separate the bonding auxiliary layer from the crimp connector; and Remove the bonding auxiliary layer from the semiconductor die.

16. The method according to claim 15, characterized in that, The surface energy of the bonding auxiliary layer in the first state is higher than that in the second state.

17. The method according to claim 16, characterized in that, The first state of the bonding auxiliary layer is liquid, and the second state of the bonding auxiliary layer is solid.

18. The method according to claim 17, characterized in that, The bonding auxiliary layer includes UV-curable polydimethylsiloxane, UV-curable silicone, or liquid crystal polymer.

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