Process for electron beam evaporation deposition of solder in wafer level packaging and wafer level packaging process

Abstract

The present disclosure provides a process of electron beam evaporation deposition of solder in wafer level packaging and a wafer level packaging process. The process of electron beam evaporation deposition of solder in wafer level packaging comprises the following steps: step S1, putting Au material and Sn material with a mass ratio of 4:1 into a crucible to form an original gold-tin mixture; step S2, vacuumizing the chamber and maintaining the vacuum; step S3, starting an electron beam evaporation source, evaporating the original gold-tin mixture by the electron beam to form a first layer of gold-tin mixture to be deposited on a wafer substrate to form a first layer of coating; step S4, evaporating a second layer of gold-tin mixture in the crucible by the electron beam to be deposited on the first layer of coating to form a second layer of coating; step S5, evaporating a third layer of gold-tin mixture in the crucible by the electron beam to be deposited on the second layer of coating to form a third layer of coating; in steps S3 to S5, the power of the electron beam in step S3 is the smallest, and the power of the electron beam in step S5 is the largest; after steps S3 to S5 are completed, the accumulated coating forms a gold-tin solder.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor technology, and more specifically to a process for electron beam evaporation deposition of solder in wafer-level packaging and a wafer-level packaging process. Background Technology

[0002] Gold-tin solder has advantages such as high strength, good oxidation resistance, fatigue resistance, and excellent creep performance. It is increasingly used in hybrid integrated circuits, especially in high-power, high-reliability integrated circuits, where eutectic bonding is used to reduce package thermal resistance and improve chip soldering reliability.

[0003] Due to the wide application of gold-tin solder, numerous deposition methods have been developed, such as: alternating electron beam evaporation of gold and tin layers to form a gold / tin solder layer structure, electron beam evaporation of gold-tin eutectic solder, alternating electroplating of gold and tin layers to form a gold / tin solder layer structure, and electroplating of gold-tin eutectic solder. Electron beam evaporation for solder preparation involves exposing the evaporated metal to the electron beam in a high-vacuum chamber, where the metal vapor is deposited onto the substrate metal. There are two main methods for preparing gold-tin solder: one is alternating evaporation of gold and tin metal layers followed by annealing to obtain gold / tin solder; the other is simultaneous evaporation of gold and tin metals.

[0004] Whether through electron beam evaporation or electroplating, the gold / tin solder layer structure formed by alternating gold and tin deposition requires annealing to allow gold and tin to diffuse into each other, forming a highly consistent gold / tin solder layer. However, in wafer-level packaging, the annealing temperature can cause photoresist to deform and collapse, leading to difficulties in subsequent stripping and affecting the process. Furthermore, when depositing gold / tin eutectic solder, the gold / tin eutectic solder is easily affected by the current or electron beam power, making it difficult to obtain Au. 80 Sn 20 Eutectic deposition phase. To eliminate the influence of deposited gold / tin eutectic solder, some manufacturers typically use up to 18 crucibles (9 crucibles for gold evaporation and another 9 crucibles for tin evaporation, with the 18 crucibles performing electron beam evaporation sequentially to achieve alternating evaporation and deposition) to deposit the solder layer during the electron beam evaporation process. Each crucible uses the same electron beam evaporation power, which results in high manufacturing costs. Some manufacturers even use multiple vacuum evaporation devices during the manufacturing process, further increasing manufacturing costs, time, and risks, leading to a high product scrap rate. Summary of the Invention

[0005] In view of the problems existing in the background art, one object of this disclosure is to provide a process for electron beam evaporation deposition of solder in wafer-level packaging and a wafer-level packaging process, which can achieve close to Au 80 Sn 20The eutectic gold-tin solder, when bonded to gold, can precipitate AuSn and Au5Sn at the corresponding edge and middle parts respectively to obtain the required AuSn and Au5Sn, thereby meeting the quality requirements of the bonding process for the formed solder ring.

[0006] Another objective of this disclosure is to provide a process for electron beam evaporation deposition of solder in wafer-level packaging and a wafer-level packaging process, which is beneficial for saving the preparation cost of gold-tin solder and shortening the production time.

[0007] Therefore, a process for electron beam evaporation deposition of solder in wafer-level packaging includes the following steps: Step S1, placing Au and Sn materials in a mass ratio of 4:1 into a crucible within the chamber of a vacuum evaporation apparatus, and stirring to mix the Au and Sn materials to form a raw gold-tin mixture; Step S2, evacuating and maintaining a vacuum in the chamber of the vacuum evaporation apparatus; Step S3, activating the electron beam evaporation source within the chamber of the vacuum evaporation apparatus, and evaporating the first layer of gold-tin mixture from the surface inwards in the raw gold-tin mixture within the crucible, so that the first layer of gold-tin mixture evaporated by the electron beam is deposited onto the wafer substrate to form a first coating layer; Step S4, after the first coating layer formed on the wafer substrate reaches a first thickness, continuing to... After the first layer of gold-tin mixture in the crucible is used up, the second layer of gold-tin mixture is subjected to electron beam evaporation so that the electron beam evaporated second layer of gold-tin mixture is deposited on the first layer of the wafer substrate to form the second layer of the coating; in step S5, after the second layer of the coating formed on the wafer substrate reaches the second thickness, the third layer of gold-tin mixture in the crucible after the second layer of gold-tin mixture is used up is subjected to electron beam evaporation so that the electron beam evaporated third layer of gold-tin mixture is deposited on the second layer of the coating on the wafer substrate to form the third layer of the coating; in steps S3 to S5, the electron beam power in step S3 is the minimum and the electron beam power in step S5 is the maximum; after steps S3 to S5 are completed, the accumulated coating on the wafer substrate forms gold-tin solder.

[0008] A wafer-level packaging process includes the following steps: Step 1, providing a cap wafer and a chip wafer, wherein the cap wafer has gold-tin solder formed according to the aforementioned electron beam evaporation deposition solder process in wafer-level packaging, and the chip wafer has patterned bonding material required for wafer-level packaging with at least a gold surface layer, the patterned bonding material surrounding the corresponding chip; Step 2, performing patterned stripping of the gold-tin solder to form a gold-tin solder packaging pattern required for wafer-level packaging; Step 3, aligning the cap wafer completed in Step 2 with the chip wafer provided in Step 1, so that the gold-tin solder... Step 4: The solder and bonding material are aligned and made in contact; Step 5: Under vacuum, heat, and pressure, the gold-tin solder and bonding material are bonded to form a solder ring that encloses the corresponding chip; Step 6: The cap wafer and chip wafer after Step 4 are X-rayed to detect whether there are voids or overflow in the solder ring; Step 7: The cap wafer and chip wafer, which are sealed and connected together by the solder ring after Step 5, are cut to form independent devices with chip packages; Step 8: The devices with chip packages are subjected to vibration overflow detection and leakage rate detection.

[0009] The beneficial effects of this disclosure are as follows: In the electron beam evaporation deposition of solder process in the wafer-level packaging of this disclosure, using this power configuration, it is possible to achieve near-Au power. 80 Sn 20 Eutectic gold-tin solder, based on the ability to obtain near-Au 80 Sn 20 In wafer-level packaging processes, eutectic gold-tin solder, when bonded to gold, can precipitate AuSn and Au5Sn at the corresponding edge and center locations to obtain the required AuSn and Au5Sn, thereby meeting the quality requirements of the solder ring formed by the bonding process. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of an exemplary vacuum evaporation apparatus used in the electron beam evaporation deposition process for wafer-level packaging according to the present disclosure.

[0011] Figure 2 This is a schematic diagram of the electron beam evaporation process for a single crucible in the process of electron beam evaporation deposition of solder in wafer-level packaging according to the present disclosure.

[0012] Figure 3 This is a photograph of the SEI morphology of the gold-tin solder formed by electron beam evaporation deposition in Example 1.

[0013] Figure 4 Is with Figure 3 The corresponding EDS morphological photograph.

[0014] Figure 5 yes Figure 4The distribution of EDS elements in the corresponding parts of the image.

[0015] Figure 6 This is a schematic diagram of the cap wafer used in wafer-level packaging technology.

[0016] Figure 7 This is a schematic diagram of the chip wafer used in wafer-level packaging technology.

[0017] Figure 8 This is a schematic diagram showing the alignment and contact between bonding materials and gold-tin solder in a wafer-level packaging process.

[0018] Figure 9 This is a photograph of the SEI morphology of the solder ring after step four of the wafer-level packaging process is completed.

[0019] Figure 10 Is with Figure 9 The corresponding EDS morphology image of the solder ring is taken after the solder ring is formed in step four of the wafer-level packaging process and before the X-ray inspection in step five.

[0020] Figure 11 yes Figure 10 The distribution of EDS elements in a corresponding part of the image.

[0021] Figure 12 yes Figure 10 The distribution of EDS elements in the corresponding other part of the image.

[0022] Figure 13 This is an overall X-ray photograph taken during step five of the wafer-level packaging process.

[0023] Figure 14 This is an X-ray photograph of a device with solder overflow around the solder ring, taken before vibration testing after step six of the wafer-level packaging process.

[0024] Figure 15 yes Figure 14 An X-ray photograph of the overflow material taken after the device underwent vibration testing. Detailed Implementation

[0025] The accompanying drawings illustrate embodiments of this disclosure, and it will be understood that the disclosed embodiments are merely examples of this disclosure, which can be implemented in various forms. Therefore, the specific details disclosed herein should not be construed as limiting, but are intended only as the basis for the claims and as an illustrative basis to teach those skilled in the art how to implement this disclosure in various ways.

[0026] [Electron beam evaporation deposition process for solder in wafer-level packaging]

[0027] Reference Figure 1 and Figure 2 The process for electron beam evaporation deposition of solder in wafer-level packaging according to this disclosure includes the following steps:

[0028] Step S1: Place Au material and Sn material with a mass ratio of 4:1 into a crucible in the chamber of the vacuum evaporation device, and stir to mix Au material and Sn material to form original gold-tin mixture;

[0029] Step S2: Evacuate the chamber of the vacuum evaporation apparatus and maintain the vacuum.

[0030] Step S3: Start the electron beam evaporation source in the chamber of the vacuum evaporation device. The electron beam emitted by the electron beam evaporation source evaporates the first layer of gold-tin mixture from the surface to the inside of the original gold-tin mixture in the crucible, so that the first layer of gold-tin mixture evaporated by the electron beam is deposited on the wafer substrate to form the first layer of coating.

[0031] Step S4: After the first layer of coating formed on the wafer substrate reaches the first thickness, the second layer of gold-tin mixture in the crucible after the first layer of gold-tin mixture has been used up is subjected to electron beam evaporation so that the second layer of gold-tin mixture evaporated by electron beam is deposited on the first layer of coating on the wafer substrate to form the second layer of coating.

[0032] Step S5: After the second layer of film formed on the wafer substrate reaches the second thickness, the third layer of gold-tin mixture in the crucible after the second layer of gold-tin mixture has been used up is subjected to electron beam evaporation so that the electron beam evaporated third layer of gold-tin mixture is deposited on the second layer of film on the wafer substrate to form the third layer of film.

[0033] In steps S3 to S5, the power of the electron beam in step S3 is the lowest, and the power of the electron beam in step S5 is the highest (that is, the power of the electron beam in step S4 is between the power of the electron beam in step S3 and the power of the electron beam in step S5).

[0034] After steps S3 to S5 are completed, the accumulated coating on the wafer substrate forms gold-tin solder.

[0035] In the electron beam evaporation deposition solder process of the wafer-level packaging disclosed herein, in step S3, the electron beam emitted by the electron beam evaporation source first strikes the surface of the original gold-tin mixture in step S3. The electron beam heats the first layer of gold-tin mixture until it evaporates. During the heating (including the process of the electron beam emitted by the electron beam evaporation source reaching a predetermined power) to evaporation process, the first layer of gold-tin mixture first forms a molten liquid. The gold and tin in the molten liquid will settle due to the density difference between them. As the first layer of gold-tin mixture evaporates... The process is gradual. As the first layer of gold-tin mixture evaporates, the proportion of tin increases. This process continues throughout the evaporation of the first layer of gold-tin mixture. When the electron beam evaporation of the first layer of gold-tin mixture approaches the second layer, the deposited gold will enter the lower layer of gold-tin mixture (i.e., the second layer of gold-tin mixture, because the interface between the second and first layers of gold-tin mixture is also molten due to the heating of the electron beam). This results in a decrease in the proportion of gold and an increase in the proportion of tin in the first layer of gold-tin solder that is evaporated from the first film. The aforementioned gold deposition also occurs in the second gold-tin mixture, resulting in the highest gold content in the third gold-tin mixture. Based on the changes in the tin and gold ratios in the first, second, and third gold-tin mixtures, the first gold-tin mixture has the highest tin content, and the third gold-tin mixture has the highest gold content. Therefore, the electron beam power in step S3 is the lowest, the electron beam power in step S5 is the highest, and the electron beam power in step S4 is between that in step S3 and step S5. As demonstrated in Example 1 of the subsequent test process, in the wafer-level packaging electron beam evaporation deposition solder process of this disclosure, such a power configuration can achieve close to Au. 80 Sn 20 Eutectic gold-tin solder. And as demonstrated in Example 1 of the subsequent testing process, based on the ability to obtain near-Au... 80 Sn 20 In the wafer-level packaging process described later, the eutectic gold-tin solder, when bonded to gold, can precipitate AuSn and Au5Sn at the corresponding edge and middle parts respectively to obtain the required AuSn and Au5Sn, thereby meeting the quality requirements of the bonding process for the formed solder ring.

[0036] Compared to alternating evaporation of gold in one crucible and tin in another, the electron beam evaporation deposition process for wafer-level packaging disclosed herein reduces the number of crucibles and simplifies power control by using a gold-tin mixture in the same crucible for electron beam evaporation, combined with the aforementioned power configuration. This helps to save on the preparation cost of gold-tin solder and shorten production time.

[0037] Based on the total thickness of the accumulated coating deposited on the wafer substrate, the number of crucibles required is determined. When the number of crucibles required is greater than one, the weight of the original gold-tin mixture in all crucibles in step S1 is equal. After the electron beam evaporates the original gold-tin mixture in the first crucible, the electron beam evaporates the original gold-tin mixture in the second crucible. The electron beam evaporation of the original gold-tin mixture in all crucibles is the same in each step of steps S3 to S5. Figure 1 As shown, more than one crucible is arranged on a crucible tray, and the crucible tray can be rotated by a rotating mechanism (not shown) to rotate the corresponding crucibles to a relative position. Figure 1 The designated location of the electron beam evaporation source.

[0038] In the electron beam evaporation deposition solder process for wafer-level packaging disclosed herein, in steps S3 to S5, the first thickness of the first layer, the second thickness of the second layer, and the third thickness of the third layer can be determined by mounting... Figure 1 A crystal-controlled film thickness gauge on a planetary cooker, which revolves and rotates, is used to monitor the deposition of film on the wafer substrate on the planetary cooker. This means the crystal-controlled film thickness gauge and... Figure 1 The operation of the electron beam evaporation source is controlled by communicating with the electron beam evaporation source.

[0039] In one example, in step S1, both Au and Sn materials are in block form with a purity of 5N or higher. Further, the Au material is cylindrical with a diameter of 3mm and a length of 3mm; the Sn material is spherical with a diameter of 1-5mm.

[0040] In one example, during steps S2 to S5, the vacuum evaporation apparatus is at room temperature (e.g., 20-30°C), and there are no other heating devices inside the chamber besides the electron beam evaporation source; during steps S2 to S5, the chamber of the vacuum evaporation apparatus is maintained at 5.0 × 10⁻⁶. -3 Below Pa, that is, through Figure 1 The vacuum port is connected to an external vacuum device (not shown) to maintain a vacuum.

[0041] In one example, in steps S3 to S5, the first thickness in step S3 is the smallest, and the third thickness in step S5 is the largest, that is, the second thickness in step S4 is between the first thickness in step S3 and the third thickness in step S5.

[0042] In one example, in steps S3 to S5, the upper limit of the power of the electron beam in step S3 is not higher than the lower limit of the power of the electron beam in step S4; the upper limit of the power of the electron beam in step S4 is not higher than the lower limit of the power of the electron beam in step S5.

[0043] Specifically, in one example, in step S3, the electron beam power is 1000-1300W, and the deposition rate is... The initial deposition thickness is 500±200 nm; in step S4, the electron beam power is 1300-1500 W, and the deposition rate is... The second thickness achieved by deposition is 1000±400 nm; in step S5, the electron beam power is 1500-1800 W, and the deposition rate is... The third deposition thickness is 1000±200 nm. Further, in step S3, the electron beam power is 1000 W, and the deposition rate is... The initial deposition thickness reached was 500 nm; in step S4, the electron beam power was 1300 W, and the deposition rate was... The second thickness achieved by deposition is 1000 nm; in step S5, the electron beam power is 1500 W, and the deposition rate is... The third thickness achieved by deposition is 1000 nm.

[0044] In steps S3 to S5, the wafer substrate may be a silicon substrate.

[0045] In steps S3 to S5, the electron beam evaporation source 4 can be commercially available from ULVAC ESZ-R in Japan.

[0046] [Wafer-level packaging process]

[0047] Reference Figures 6 to 8 and combined Figures 1 to 2 The wafer-level packaging process according to this disclosure includes the following steps:

[0048] Step 1: Provide a cap wafer and a chip wafer. The cap wafer has gold-tin solder formed according to the electron beam evaporation deposition solder process in the aforementioned wafer-level packaging. The chip wafer has patterned bonding material required for wafer-level packaging with at least a gold surface layer. The patterned bonding material surrounds the corresponding chip.

[0049] Step 2: Pattern the gold-tin solder by stripping it to form the gold-tin solder packaging pattern required for wafer-level packaging.

[0050] Step 3: Align the capped wafer completed in Step 2 with the chip wafer provided in Step 1 so that the gold solder and bonding material are aligned and in contact.

[0051] Step four: Under vacuum, heat, and pressure, the gold-tin solder is bonded to the bonding material to form a solder ring that seals the corresponding chip.

[0052] Step 5: After completing Step 4, the capped wafer and the chip wafer are subjected to X-ray imaging to detect whether there are voids or overflow in the solder ring;

[0053] Step six: The cap wafer and chip wafer, which were sealed and connected together by solder rings in step five, are cut to form their own independent devices with chip packages.

[0054] Step 7: Perform vibration overflow detection and leakage rate detection on the device containing the chip.

[0055] Based on the test process demonstrated in Example 1, the electron beam evaporation deposition solder process in wafer-level packaging of this disclosure can achieve near-Au levels. 80 Sn 20 Eutectic gold-tin solder, as demonstrated in Example 1 of the subsequent testing process, is based on the ability to obtain near-Au... 80 Sn 20 In wafer-level packaging processes, eutectic gold-tin solder, when bonded to gold, can precipitate AuSn and Au5Sn at the corresponding edge and center locations to obtain the required AuSn and Au5Sn, thereby meeting the quality requirements of the solder ring formed by the bonding process.

[0056] In one example, in step one, the bonding material consists of a titanium layer, a nickel layer, and a gold layer, starting from the wafer substrate of the chip wafer, as follows: Figure 8 As shown. Further, the thickness of the titanium layer is 40-60 nm, the thickness of the nickel layer is 100-120 nm, and the thickness of the gold layer is 180-200 nm.

[0057] In one example, in step four, the heating temperature is 285±5℃, the pressure is 3500±500N, and the vacuum degree is 5.0×10⁻⁶. -3 Below Pa. The pressure operation involves supporting the aligned cap wafer and chip wafer on the support surface via the chip wafer, and then pressing down on the cap wafer with a pressure plate.

[0058] In step seven, vibration overflow detection is performed using Aerospace Hill's electrical vibration testing system and operating requirements to test whether the overflow of solder rings has fallen off. If it does not fall off, it is considered qualified, for example, the IPA60H / LS437A / GT500M model; leak rate detection can be performed using a helium mass spectrometer leak detector.

[0059] In one example, the device is a detector.

[0060] [test]

[0061] Example 1

[0062] A. Electron beam evaporation deposition process for solder in wafer-level packaging

[0063] The electron beam evaporation deposition process for solder in wafer-level packaging employs the following steps:

[0064] Step S1: Au material and Sn material with a mass ratio of 4:1 are placed into two crucibles in the chamber of the vacuum evaporation device. The original gold-tin mixture in the two crucibles has an equal weight. The mixture is stirred to form the original gold-tin mixture. The purity of Au material and Sn material is 5N. Au material is cylindrical with a diameter of 3mm and a length of 3mm. Sn material is spherical with a diameter of 3mm.

[0065] Step S2: Evacuate the chamber of the vacuum evaporation apparatus and maintain the vacuum at 5.0 × 10⁻⁶. -3 Below Pa;

[0066] Step S3: The electron beam evaporation source in the vacuum evaporation apparatus is activated. The electron beam emitted by the source evaporates the first layer of gold-tin mixture from the surface inwards in the first crucible, depositing this first layer onto the wafer substrate to form the first film. The electron beam evaporation source is a commercially available ULVAC ESZ-R from Japan, the wafer substrate is a capped silicon wafer, the electron beam power is 1000W, and the deposition rate is... The first thickness achieved by deposition is 500 nm, and the deposition of the wafer substrate on the planetary pot is monitored by a crystal-controlled film thickness gauge on the planetary pot.

[0067] Step S4: After the first layer of gold-tin mixture formed on the wafer substrate reaches a first thickness, electron beam evaporation is performed on the second layer of gold-tin mixture in the first crucible after the first layer of gold-tin mixture has been used up. This allows the electron beam-evaporated second layer of gold-tin mixture to be deposited onto the first layer of gold-tin mixture on the wafer substrate to form the second layer of gold-tin mixture. The electron beam power is 1300W, and the deposition rate is... The second thickness achieved by deposition is 1000 nm;

[0068] Step S5: After the second layer of coating formed on the wafer substrate reaches the second thickness, electron beam evaporation is performed on the third layer of gold-tin mixture in the first crucible after the second layer of gold-tin mixture has been used up. This allows the electron beam-evaporated third layer of gold-tin mixture to deposit onto the second layer of coating on the wafer substrate to form the third layer of coating. The electron beam power is 1500W, and the deposition rate is... The third thickness achieved by deposition is 1000 nm;

[0069] In steps S2 to S5, the vacuum evaporation apparatus is at room temperature of 25°C, and there are no other heating devices in the chamber except for the electron beam evaporation source;

[0070] After the first crucible is completed, the crucible tray is rotated to rotate the second crucible to a predetermined position relative to the electron beam evaporation source, and steps S3 and S5 are repeated.

[0071] After steps S3 to S5 in the second crucible are completed, the accumulated coating on the wafer substrate forms gold-tin solder.

[0072] Figure 3 This is a photograph of the SEI morphology of gold-tin solder formed by electron beam evaporation deposition after the electron beam evaporation deposition solder process in the wafer-level packaging of Example 1 is completed. Figure 4 Is with Figure 3 Corresponding EDS morphological images, Figure 5 yes Figure 4 The distribution of EDS elements in the corresponding parts of the spectrum is shown in Table 1. Figure 10 EDS elemental distribution of gold-tin solder deposited by electron beam evaporation (spectral) Figure 10 ).

[0073] Table 1. EDS elemental distribution of gold-tin solder deposited by electron beam evaporation (spectral analysis). Figure 10 )

[0074] element Line type wt% Wt%Sigma At% C K-line system 10.16 0.47 60.51 Si K-line system 1.06 0.05 2.7 Sn L-line system 18.92 0.25 11.41 Au M-line system 69.87 0.43 25.39 Total 100 100

[0075] from Figure 3 It can be seen that the gold-tin solder film is relatively uniform. From Table 1, we can see that the mass ratio of Au to Sn eutectic is 69.87:18.92, which is close to the ideal Au content. 80 Sn 20 Eutectic.

[0076] B. Wafer-level packaging process

[0077] The wafer-level packaging process employs the following steps:

[0078] Step 1: Provide a cap wafer and a chip wafer. The cap wafer has gold-tin solder formed by the electron beam evaporation deposition process in the aforementioned wafer-level packaging. The chip wafer has patterned bonding material required for wafer-level packaging. The patterned bonding material surrounds the corresponding chip. The bonding material consists of a titanium layer, a nickel layer, and a gold layer, starting from the wafer substrate of the chip wafer. The thickness of the titanium layer is 50 nm, the thickness of the nickel layer is 110 nm, and the thickness of the gold layer is 190 nm.

[0079] Step 2: Pattern the gold-tin solder by stripping it to form the gold-tin solder packaging pattern required for wafer-level packaging.

[0080] Step 3: Align the capped wafer completed in Step 2 with the chip wafer provided in Step 1 so that the gold solder and bonding material are aligned and in contact.

[0081] Step four involves bonding the gold-tin solder to the bonding material under vacuum, heat, and pressure to form a solder ring that seals the corresponding chip. The heating temperature is 295°C, the pressure is 4000N, and the vacuum level is 5.0 × 10⁻⁶.-3 Below Pa, the pressure operation involves supporting the aligned cap wafer and chip wafer on the support surface via the chip wafer, and then pressing down on the cap wafer with a pressure plate.

[0082] Step 5: After completing Step 4, the capped wafer and the chip wafer are subjected to X-ray imaging to detect whether there are voids or overflow in the solder ring;

[0083] Step six: The cap wafer and chip wafer, which were sealed and connected together by solder rings in step five, are cut to form independent devices with their own chips. The devices are detectors.

[0084] Step 7: Perform vibration overflow detection and leakage rate detection on the device with the packaged chip. The vibration overflow detection is carried out using the Aerospace Hill electric vibration testing system (IPA60H / LS437A / GT500M model) and the operating requirements to detect whether the solder ring overflow has fallen off. The leakage rate detection is carried out using a helium mass spectrometer leak detector.

[0085] Figure 9 This is a photograph of the SEI morphology of the solder ring after step four of the wafer-level packaging process is completed. Figure 10 Is with Figure 9 The corresponding EDS morphology image of the solder ring is taken after the solder ring is formed in step four of the wafer-level packaging process and before the X-ray inspection in step five. Figure 11 yes Figure 10 Table 2 shows the EDS element percentage distribution for a corresponding part in the graph, and the solder ring formed after bonding is shown in Table 2. Figure 11 Corresponding EDS elemental distribution table (spectrum) Figure 1 ). Figure 12 yes Figure 10 Table 3 shows the EDS element percentage distribution of the corresponding part in the figure, and is a diagram of the solder ring formed after bonding. Figure 12 Corresponding EDS elemental distribution table (spectrum) Figure 2 )

[0086] Table 2. EDS elemental distribution of the solder ring formed after bonding (spectral analysis). Figure 1 )

[0087]

[0088]

[0089] Table 3. EDS elemental distribution of the solder ring formed after bonding (spectral analysis). Figure 2 )

[0090] element Line type wt% Wt%Sigma At% C K-line system 14.69 0.74 59.42 O K-line system 3.09 0.3 9.38 Si K-line system 6.55 0.11 11.33 Sn L-line system 7.44 0.26 3.04 Au M-line system 68.22 0.68 16.82 Total 100 100

[0091] After bonding, as shown in Table 2, the ratio of Au to Sn atoms in the edge layer is 16.9:20.69, which is close to the ideal AuSn. As shown in Table 3, the ratio of Au to Sn atoms in the middle layer is 16.82:3.04, which is close to the ideal Au5Sn.

[0092] Figure 13 This is an overall X-ray image of step five in the wafer-level packaging process. From Figure 13 It can be seen that after bonding, the solder ring has no void defects.

[0093] Figure 14 This is an X-ray photograph of a device with solder overflow around the solder ring, taken before vibration testing after step six of the wafer-level packaging process. Figure 15 yes Figure 14 An X-ray photograph of the spillage taken after the device underwent vibration testing. Combined with... Figure 13 and Figure 14 After bonding, there was solder overflow in the solder ring. Figure 15 It can be seen that after the device was vibrated, there was no overflow of material, which meets the process requirements.

[0094] Furthermore, leak rate was detected using a helium mass spectrometer, and no gas leakage was found in the device.

[0095] Several exemplary embodiments have been described in detail above, but this document is not intended to limit itself to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined to form several other combinations, which are not shown for simplicity.

Claims

1. A process for electron beam evaporation deposition of solder in wafer-level packaging, characterized in that, Including the following steps: Step S1: Place Au material and Sn material with a mass ratio of 4:1 into a crucible in the chamber of the vacuum evaporation device, and stir to mix Au material and Sn material to form original gold-tin mixture; Step S2: Evacuate the chamber of the vacuum evaporation apparatus and maintain the vacuum. Step S3: Start the electron beam evaporation source in the chamber of the vacuum evaporation device. The electron beam emitted by the electron beam evaporation source evaporates the first layer of gold-tin mixture from the surface to the inside of the original gold-tin mixture in the crucible, so that the first layer of gold-tin mixture evaporated by the electron beam is deposited on the wafer substrate to form the first layer of coating. Step S4: After the first layer of coating formed on the wafer substrate reaches the first thickness, the second layer of gold-tin mixture in the crucible after the first layer of gold-tin mixture has been used up is subjected to electron beam evaporation so that the second layer of gold-tin mixture evaporated by electron beam is deposited on the first layer of coating on the wafer substrate to form the second layer of coating. Step S5: After the second layer of film formed on the wafer substrate reaches the second thickness, the third layer of gold-tin mixture in the crucible after the second layer of gold-tin mixture has been used up is subjected to electron beam evaporation so that the electron beam evaporated third layer of gold-tin mixture is deposited on the second layer of film on the wafer substrate to form the third layer of film. In steps S3 to S5, the power of the electron beam is the lowest in step S3 and the power of the electron beam is the highest in step S5. After steps S3 to S5 are completed, the accumulated coating on the wafer substrate forms gold-tin solder; in, In step S3, the power of the electron beam is 1000-1300W, the deposition rate is 4-6 Å / s, and the first thickness achieved by deposition is 500±200nm. In step S4, the power of the electron beam is 1300-1500W, the deposition rate is 4-6Å / s, and the second thickness achieved by deposition is 1000±400nm. In step S5, the electron beam power is 1500-1800W, the deposition rate is 4-6 Å / s, and the third thickness reached by deposition is 1000±200nm.

2. The process for electron beam evaporation deposition of solder in wafer-level packaging according to claim 1, characterized in that, In step S1, both Au and Sn materials are in block form with a purity of 5N or higher.

3. The process for electron beam evaporation deposition of solder in wafer-level packaging according to claim 2, characterized in that, Au material is cylindrical, with a diameter of 3mm and a length of 3mm; Sn material is spherical, with a diameter of 1-5mm.

4. The process for electron beam evaporation deposition of solder in wafer-level packaging according to claim 1, characterized in that, In steps S2 to S5, the vacuum evaporation apparatus is at room temperature, and there are no other heating devices in the chamber except for the electron beam evaporation source; In steps S2 to S5, the chamber of the vacuum evaporation apparatus is maintained at 5.0 × 10⁻⁶. -3 Below Pa.

5. The process for electron beam evaporation deposition of solder in wafer-level packaging according to claim 1, characterized in that, In step S3, the power of the electron beam is 1000W, the deposition rate is 5Å / s, and the first thickness achieved by deposition is 500nm. In step S4, the power of the electron beam is 1300W, the deposition rate is 5Å / s, and the second thickness achieved by deposition is 1000nm. In step S5, the electron beam power is 1500W, the deposition rate is 5Å / s, and the third thickness reached by deposition is 1000nm.

6. The process for electron beam evaporation deposition of solder in wafer-level packaging according to any one of claims 1-5, characterized in that, The number of crucibles required is determined based on the total thickness of the accumulated film deposited on the wafer substrate. When the number of crucibles required is greater than one, the weight of the original gold-tin mixture in all crucibles in step S1 is equal. After the original gold-tin mixture in the first crucible is evaporated by electron beam, the original gold-tin mixture in the second crucible is evaporated by electron beam. The electron beam evaporation of the original gold-tin mixture in all crucibles is the same in each step of steps S3 to S5.

7. A wafer-level packaging process, characterized in that, Including the following steps: Step 1: Provide a cap wafer and a chip wafer. The cap wafer has gold-tin solder formed by the electron beam evaporation deposition process in wafer-level packaging according to any one of claims 1-6. The chip wafer has patterned bonding material required for wafer-level packaging with at least a gold surface layer. The patterned bonding material surrounds the corresponding chip. Step 2: Pattern the gold-tin solder by stripping it to form the gold-tin solder packaging pattern required for wafer-level packaging. Step 3: Align the capped wafer completed in Step 2 with the chip wafer provided in Step 1 so that the gold solder and bonding material are aligned and in contact. Step four: Under vacuum, heat, and pressure, the gold-tin solder is bonded to the bonding material to form a solder ring that seals the corresponding chip. Step 5: After completing Step 4, the capped wafer and the chip wafer are subjected to X-ray imaging to detect whether there are voids or overflow in the solder ring; Step six: The cap wafer and chip wafer, which were sealed and connected together by solder rings in step five, are cut to form their own independent devices with chip packages. Step 7: Perform vibration overflow detection and leakage rate detection on the device containing the chip.

8. The wafer-level packaging process according to claim 7, characterized in that, In step one, the bonding material consists of a titanium layer, a nickel layer, and a gold layer, starting from the wafer substrate of the chip wafer.

9. The wafer-level packaging process according to claim 8, characterized in that, The thickness of the titanium layer is 40-60nm, the thickness of the nickel layer is 100-120nm, and the thickness of the gold layer is 180-200nm; In step four, the heating temperature is 285±5°C, the pressure is 3500±500N, and the vacuum degree is 5.0×10⁻⁶. -3 Below Pa.

Images