Method for improving cleaning efficiency before back hole electrogilding

Abstract

The invention discloses a method for improving cleaning efficiency before electrogilding of a back hole. The method comprises the following steps: detecting components of a to-be-etched position on a wafer by using an EDS; an etching machine is used for etching the wafer to form a back hole, in the etching process, signal detection is continuously carried out on the surface of the wafer until a gold signal appears, an etching end point is taken, and the etching process is ended; an EDS is used for detecting a signal of the etched position of the wafer, and back hole components are detected; checking the surface state of the side wall of the back hole and the gold surface roughness of the etching stop layer by using an SEM (Scanning Electron Microscope), wherein the surface state of the side wall is a smooth state or a rough state; configuring a shower head according to the signal type; and cleaning the back hole by using a configured shower head according to the signal type, the side wall surface state and the gold surface roughness until the side wall surface state is a smooth state, and the signals of the etching position only comprise the gold signal and the signal from the semiconductor material. The process can be simplified, and the cleaning efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device manufacturing, and particularly relates to a method for improving the cleaning efficiency before gold plating of back holes. Background Technology

[0002] For microwave semiconductor devices made of compound semiconductors to achieve higher operating frequencies and greater gain and bandwidth at high frequencies, heat dissipation is one of the most pressing issues that needs to be addressed. If the generated heat is not dissipated in time, the resistivity of the metal interconnects will continue to increase with rising temperature in the short term, which will significantly increase the signal delay on the metal interconnects, making it difficult to achieve the expected speed performance. If the device operates for a long time, it may burn out, potentially causing the entire circuit to fail.

[0003] Semiconductor materials are etched into back vias and then metallized. This not only ensures heat dissipation but also serves as a lead, significantly improving device reliability. A common method for back via metallization is electroplating. Typically, before electroplating, the inside of the back via needs to be cleaned to remove impurities generated during etching. These impurities include plasma ions, photoresist, etched area material, and the etch stop layer (gold). If these impurities are not completely removed, the back via metallization will be incomplete or nonexistent, preventing the device from dissipating heat effectively under high current, posing a risk of burn-out.

[0004] like Figure 1 As shown, the existing pre-cleaning method for gold plating of back holes involves cleaning the wafer surface, mask fabrication process, and back hole etching process, then cleaning gold residues with KI, cleaning residues with solvent, and finally depositing the plating layer and electroplating gold into the back holes.

[0005] The existing cleaning process has the following drawbacks: the process is complicated and the results are unpredictable. It requires first leaching gold with KI to treat the residue, and then using a solvent to remove the underlying organic residue. If stubborn residues are encountered, these two steps need to be repeated many times, resulting in low efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a method for improving the cleaning efficiency before back hole electroplating, which can simplify the process and improve cleaning efficiency.

[0007] To achieve the above objectives, one aspect of the present invention provides a method for improving the cleaning efficiency before back hole gold plating, comprising: Step S1: Use EDS to detect the composition of the location to be etched on the wafer; Step S2: Use an etching machine to etch the wafer to form back holes. During the etching process, signal detection is continuously performed on the wafer surface until a gold signal appears, which is the end point of the etching process. Step S3: Use EDS to detect the signal at the position after wafer etching to detect the composition of the back hole. The signal includes signals from the mask, signals from the semiconductor material, and gold signals. Step S4: Use SEM to inspect the surface condition of the back hole sidewall and the gold surface roughness of the etching stop layer, wherein the sidewall surface condition is either smooth or rough. Step S5: Configure the shower head according to the signal type in step S3. The shower head includes a central single-hole shower head, a star-shaped ultra-small hole shower head, and a cross-shaped small hole shower head. Step S6: Based on the signal type in step S3, the sidewall surface condition in step S4, and the gold surface roughness, use the shower head configured in step S5 to clean the back hole until the sidewall surface condition is smooth and the signals at the etching position are only gold signals and signals from semiconductor materials.

[0008] The method for improving the cleaning efficiency before gold plating of back holes according to the above-described aspects of the present invention can simplify the process and improve the cleaning efficiency. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 A flowchart of a prior art cleaning method for back hole gold plating before electroplating. Figure 2 This is a flowchart of a method for improving the cleaning efficiency before gold plating of back holes according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a shower head according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a device with transmission line metal according to an embodiment of the present invention; Figure 5 This is a schematic diagram of an automated production line according to an embodiment of the present invention. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0011] One embodiment of the present invention provides a method for improving the cleaning efficiency before back-hole gold plating. The method involves cleaning residual materials after wafer surface cleaning and mask fabrication processes, including steps S1 to S6, as described below. Figure 2 The flowchart below provides a detailed description of each step of the method according to an embodiment of the present invention.

[0012] In step S1, an EDS (energy dispersive spectroscopy) is used to detect the center position of the wafer before etching, and the composition of the position to be etched on the wafer is analyzed and detected. The detected materials include, but are not limited to, semiconductor materials, carbon and oxygen.

[0013] In step S2, an etching machine is used to etch the wafer to form back vias. During the etching process, the etching endpoint detection of the etching machine continuously detects the mask and semiconductor material byproduct signals on the entire wafer surface until an Au signal appears, at which point the entire etching process ends.

[0014] In step S3, EDS is used to detect the relevant signal values ​​of the center position, sidewall position and top edge position of the etched wafer, and to analyze and detect the composition of the back hole etched on the wafer.

[0015] The relevant signal sources include, but are not limited to, masks, semiconductor materials, and Au. The relevant signals from the mask source include inorganic signals and metallic signals. The inorganic signals include, but are not limited to, carbon and oxygen signals, and the metallic signals include, but are not limited to, nickel and copper signals. The semiconductor materials include, but are not limited to, Si, SiC, and GaAs. The semiconductor material source signals include Si signals, C signals, Ga signals, and As signals. The semiconductor material source signal range is 20% to 40%, preferably 20% to 30%.

[0016] In step S4, the surface condition of the sidewalls and the surface roughness of the etching stop layer gold are examined using SEM (scanning electron microscope).

[0017] The sidewall surface can be smooth or rough. The surface roughness of a smooth surface ranges from 0.6 μm to 9 μm, preferably from 0.6 to 4.5 μm. A rough surface includes, but is not limited to, areas with noticeable burrs, voids, and weed growth. These burrs, voids, and weed growth are all considered micromasking phenomena; if the micromasking rate exceeds 5%, subsequent actions will not be performed.

[0018] The gold surface roughness is 0~1μm. Preferably, the gold surface roughness is 160~500 Å.

[0019] In step S5, configure Figure 3The shower head shown is used. When the mask signal is an inorganic signal, shower head 33 is configured, and shower head 33 has a single central opening. When the mask signal is a metallic signal, shower head 31 or shower head 32 is configured, where shower head 31 is a star-shaped micro-hole and shower head 32 is a cross-shaped micro-hole. The opening size ratio of the star-shaped micro-hole, cross-shaped micro-hole, and single central opening is 1:2:4. Preferably, shower head 31 is configured when the nickel metal signal at the center of the etched wafer is in the range of 16~30%. When shower head 31 is configured, the rotation speed range is 100~140 RPM; when shower head 32 is configured, the rotation speed range is 50~100 RPM; when shower head 32 is configured, the rotation speed range is 10~50 RPM.

[0020] In step S6, back via cleaning is performed to remove residues, and the wafer back via cleaning results are confirmed using SEM equipment.

[0021] When the relevant signal from the mask source is an inorganic signal, if the sidewall surface is smooth and the gold surface roughness is 160–500 Å, the cleaning process involves acetone cleaning for 10 minutes, immersion in piranha solution for 1 minute, rinsing with deionized water for 20 seconds, and rinsing with anhydrous ethanol for 20 seconds. If the gold surface roughness is 500 Å–1 μm, the cleaning process involves ultrasonic cleaning with acetone for 10 minutes, immersion in piranha solution for 1 minute, and immersion in anhydrous ethanol for 10 minutes. If the sidewall surface is rough, the cleaning process involves DMSO cleaning for 10 minutes, immersion in EKC solution for 1 minute, and immersion in anhydrous ethanol for 10 minutes.

[0022] When the signal from the mask source is a metallic signal, and the metallic signal is a copper signal, the prepared solution composition includes one or more of HF, HNO3, H2SO4, and H3PO4. The solution is used for cleaning for 10 minutes, followed by immersion in EKC solution for 1 minute, and then immersion in anhydrous ethanol for 10 minutes. When the metallic signal is a nickel signal, the prepared solution composition includes a strong acid and additives. The strong acid includes one or more of hydrochloric acid, sulfuric acid, nitric acid, concentrated nitric acid, and concentrated hydrochloric acid. The additives include one or more of chloride ions, oxidants, and surfactants. The solution is used for cleaning for 10 minutes, followed by immersion in EKC solution for 1 minute, and then immersion in anhydrous ethanol for 10 minutes.

[0023] After cleaning, the sidewalls were inspected using SEM, and the sidewall surfaces were found to be smooth. EDS was used to confirm the back-hole cleaning results. EDS showed that the signal values ​​at the center location contained only gold signals; EDS showed that the signal values ​​at the sidewall and upper edge locations contained only semiconductor material signals.

[0024] After completing the pre-cleaning process for gold plating of the back vias, in order to achieve gold plating of the back vias, in step S7, the wafer is removed for initial plating deposition and back via gold plating. Initial plating deposition is performed on the back vias using a metal evaporation device, followed by back via gold plating using an electroplating device, thus obtaining the back-side transmission line structure, as shown below. Figure 4 The device 6 shown has a transmission line metal, where 62 is the transmission line metal and 61 is the etch stop layer.

[0025] The method for improving the cleaning efficiency before gold plating of back holes according to embodiments of the present invention can be applied to the machine controller of an automated device production line. The machine controller can interact with the device manufacturing equipment, controlling the robotic arm to pick up and place wafer devices from the equipment and controlling the equipment to perform corresponding processes. A schematic diagram of the automated production line is shown below. Figure 5 As shown, it includes robotic arm 5 and several surrounding device manufacturing equipment. This is only for illustrative purposes. In actual automated production lines, due to the large size of the device manufacturing equipment, it may be necessary to have robotic arms that can move over long distances and to have multiple robotic arms. In this case, the configuration can be made according to actual needs.

[0026] The method in this embodiment can be automated as follows: A robotic arm is controlled to grasp a wafer that has undergone masking; the robotic arm has a suction cup at its front end for picking up the wafer. For example... Figure 5As shown, the robotic arm is controlled to transfer the wafer to the SEM device 51; a SEM measurement command is sent to the SEM measurement device 511 to move the wafer to the monitoring position of the EDS device 512; a signal indicating that the wafer has moved to the monitoring position of the EDS device 512 is received; an EDS monitoring command is sent to the EDS device 512 to analyze and monitor the area of ​​the wafer to be etched; a monitoring completion signal is received from the EDS device; the robotic arm is controlled to remove the wafer and transfer it to the etching machine 52; an etching command is sent to the etching machine 52 to perform back hole etching; a back hole etching completion signal is received from the etching machine 52; the robotic arm is controlled to transfer the etched wafer to the SEM device 51; a SEM measurement command is sent to the SEM measurement device 511 to move the wafer to the monitoring position; an EDS monitoring back hole signal is sent to the EDS device 512 and a gold surface roughness confirmation command is sent to the SEM measurement device 512 sequentially. The device 511 performs testing; it receives EDS device monitoring completion signals and SEM measurement completion signals sequentially; it controls the robotic arm to remove the wafer and transfer it to the wafer cleaning device 53; it sends a processed cleaning signal, which is specifically assigned to the device configured with shower head 1 (531), shower head 2 (532), or shower head 3 (533) according to the previous steps; it receives a wafer cleaning completion signal from the wafer cleaning device; it controls the robotic arm to transfer the cleaned wafer to the SEM device 51 for result confirmation; it sends a SEM measurement command to the SEM measurement device 511 to move the wafer to the monitoring position of the EDS device 512; it receives a signal indicating that the wafer has moved to the monitoring position of the EDS device 512; it sends an EDS monitoring command to the EDS device 512 to analyze the wafer back via cleaning results; it receives an EDS device monitoring completion signal; and it controls the robotic arm to remove the wafer.

[0027] To realize the electroplating back gold fabrication transmission line, the following steps are also included: controlling the robotic arm to remove the wafer and transfer it to the metal evaporation equipment 54 for initial plating deposition; receiving the initial plating deposition completion signal from the metal evaporation equipment 54; controlling the robotic arm to remove the wafer and transfer it to the electroplating equipment 55 for back hole gold electroplating; receiving the back hole gold electroplating completion signal; controlling the robotic arm to remove the wafer and transfer it to the resist removal equipment 56; receiving the resist removal completion signal; controlling the robotic arm to remove the wafer.

[0028] Compared to other technologies, the method of this invention uses only one combination of cleaning solutions and operates entirely with equipment, improving cleaning efficiency and reducing human intervention, thereby increasing production efficiency and reducing risks. Furthermore, the method of this invention configures corresponding solutions and shower heads for cleaning based on EDS and SEM test results, eliminating the need for leaching residual gold with KI before performing other cleaning operations, simplifying the process. Moreover, the SEM equipment allows for confirmation of the pre- and post-cleaning conditions, enabling continuous process improvement.

[0029] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for improving the cleaning efficiency before gold plating of back holes, characterized in that, include: Step S1: Use EDS to detect the composition of the location to be etched on the wafer; Step S2: Use an etching machine to etch the wafer to form back holes. During the etching process, signal detection is continuously performed on the wafer surface until a gold signal appears, which is the end point of the etching process. Step S3: Use EDS to detect the signal at the position after wafer etching to detect the composition of the back hole. The signal includes signals from the mask, signals from the semiconductor material, and gold signals. Step S4: Use SEM to inspect the surface condition of the back hole sidewall and the gold surface roughness of the etching stop layer, wherein the sidewall surface condition is either smooth or rough. Step S5: Configure the shower head according to the signal type in step S3. The shower head includes a central single-hole shower head, a star-shaped ultra-small hole shower head, and a cross-shaped small hole shower head. Step S6: Based on the signal type in step S3, the sidewall surface condition in step S4, and the gold surface roughness, use the shower head configured in step S5 to clean the back hole until the sidewall surface condition is smooth and the signals at the etching position are only gold signals and signals from semiconductor materials.

2. The method as described in claim 1, characterized in that, Also includes: Step S7: Deposit a coating on the back hole of the wafer using a metal vapor deposition equipment, and perform gold electroplating on the back hole using an electroplating equipment.

3. The method as described in claim 1 or 2, characterized in that, In step S3, the signals originating from the mask include inorganic signals and metallic signals. The inorganic signals include carbon and oxygen signals, and the metallic signals include nickel and copper signals. The signals originating from semiconductor materials include Si, C, Ga, and As signals.

4. The method as described in claim 3, characterized in that, In step S5, when the mask signal is an inorganic signal, a shower head with a single central opening is configured; when the mask signal is a metallic signal, a shower head with a star-shaped ultra-small hole or a cross-shaped small hole is configured.

5. The method as described in claim 4, characterized in that, When the metal signal is a nickel signal and the range of the nickel signal is 16~30%, a star-shaped ultra-small hole shower head is configured.

6. The method as described in claim 1 or 2, characterized in that, The ratio of the opening sizes of the star-shaped ultra-small holes, cross-shaped small holes, and center single opening is 1:2:

4.

7. The method as described in claim 3, characterized in that, In step S6, when the signal from the mask is an inorganic signal, if the sidewall surface is smooth and the gold surface roughness is 160~500 Å, the following steps are performed sequentially: acetone cleaning, piranha solution immersion, deionized water rinsing, and anhydrous ethanol rinsing; if the sidewall surface is smooth and the gold surface roughness is 500 Å~1 μm, the following steps are performed sequentially: acetone ultrasonic cleaning, piranha solution immersion, and anhydrous ethanol immersion cleaning; if the sidewall surface is rough, the following steps are performed sequentially: DMSO cleaning, EKC solution immersion, and anhydrous ethanol immersion cleaning.

8. The method as described in claim 3, characterized in that, In step S6, if the signal originating from the mask is a metal signal, and the metal signal is a copper signal, a solution containing one or more of HF, HNO3, H2SO4, and H3PO4 is used for cleaning; if the metal signal is a nickel signal, a solution containing a strong acid and additives is used for cleaning, wherein the strong acid includes one or more of hydrochloric acid, sulfuric acid, nitric acid, concentrated nitric acid, and concentrated hydrochloric acid, and the additives include one or more of chloride ions, oxidants, and surfactants.

9. The method as described in claim 8, characterized in that, The automatic movement of wafers between SEM equipment, etching machine, and wafer cleaning equipment is achieved by a robotic arm. The SEM equipment includes SEM measurement equipment and EDS equipment. The wafer cleaning equipment is configured with a shower head to perform back hole cleaning based on the cleaning signal.

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