Silicon through hole electroplating method

Abstract

The invention discloses a silicon through hole electroplating method. The method comprises the following steps: carrying out cleaning and surface activation treatment on a to-be-electroplated adapter plate; performing deep hole mask pattern transfer on the adapter plate; a TSV deep hole is machined in the surface of the adapter plate in a Bosch etching mode; a dry method and a wet method are combined to remove residual photoresist on the surface of the pinboard and in the holes after etching; removing the residual glue and the polymer in the deep hole of the adapter plate by combining SC1 cleaning and megasonic cleaning; generating an insulating layer on the surface of the adapter plate and in the deep hole by adopting a CVD (Chemical Vapor Deposition) mode; a uniform seed layer is deposited on the surface of the adapter plate and the side wall of the deep hole in a high-target-substrate-distance physical vapor deposition mode; putting the adapter plate into an electroplating bath of an electroplating system, and performing filling electroplating of the deep hole by using the electroplating system; and carrying out annealing treatment on the electroplated adapter plate. According to the method, the uniformity of TSV electroplating can be improved, copper particles on the surface of the adapter plate after electroplating can be reduced, the filling rate of TSV electroplating can be improved, the dishing value of a copper column after TSV electroplating can be reduced, and the service life of liquid medicine can be prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor packaging, and in particular relates to a through silicon via electroplating method. Background Art

[0002] With the increasing demand for high performance, miniaturization and high integration of electronic devices, 2.5D interposer packaging technology has been widely used. In 2.5D interposer packaging, TSV technology plays a key role, which can achieve vertical electrical connection, improve signal transmission speed and reduce power consumption. However, the current TSV electroplating method has some problems in 2.5D interposer packaging, such as poor electroplating uniformity, large copper nodules, low electroplating filling rate, large copper pillar dishing value after electroplating, and short service life of the solution. Summary of the invention

[0003] The object of the present invention is to provide a through silicon via electroplating method, which can improve the uniformity of TSV electroplating, reduce the copper particles on the surface of the adapter board after electroplating, improve the filling rate of TSV electroplating, reduce the dishing value of the copper column after TSV electroplating, and extend the service life of the solution.

[0004] In order to achieve the above object, one aspect of the present invention provides a through silicon via electroplating method, comprising: Pretreatment step: cleaning and surface activation of the transfer plate to be plated to remove impurities and oxides on the surface of the wafer and improve the adhesion of the seed layer; Photolithography step, transferring deep hole mask pattern to the adapter plate; In the deep hole etching step, a TSV deep hole is processed on the surface of the adapter plate by Bosch etching, and the TSV hole depth-to-width ratio is 7:1; The de-resisting step uses a combination of dry and wet methods to remove the residual photoresist on the surface of the adapter plate and in the hole after etching; In the deep hole cleaning step, SC1 cleaning and megasonic cleaning are combined to remove residual glue and polymer in the deep holes of the adapter plate; In the thermal oxidation step, an insulating layer is formed on the surface of the adapter plate and in the deep hole by ICPCVD; In the sidewall metallization step, a uniform seed layer is deposited on the surface of the adapter plate and the sidewall of the TSV hole by high target-substrate distance physical vapor deposition; In the TSV electroplating step, the adapter plate is placed in the electroplating tank of the electroplating system, and the deep hole filling electroplating is performed by the electroplating system. The filling rate of TSV electroplating is improved by optimizing the vacuum pre-treatment method, current density, electroplating time, temperature, circulation flow rate, and swing frequency; In the post-processing step, the transfer board after electroplating is annealed to improve the reliability of the through silicon via plating.

[0005] The through silicon via electroplating method according to the above aspects of the present invention can improve the uniformity of TSV electroplating, reduce the copper particles on the surface of the adapter board after electroplating, improve the filling rate of TSV electroplating, reduce the dishing value of the copper column after TSV electroplating, and extend the service life of the solution. DETAILED DESCRIPTION

[0006] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0007] An embodiment of the present invention provides a through silicon via electroplating method, comprising the following steps: Pretreatment: Clean and activate the surface of the transfer board to be electroplated to remove impurities and oxides on the surface of the wafer and improve the adhesion of the seed layer.

[0008] Photolithography: Deep hole mask pattern transfer to the adapter board.

[0009] TSV hole etching: Bosch etching is used to process TSV deep holes on the surface of the adapter board, and the TSV hole depth-to-width ratio is 7:1.

[0010] Removal of photoresist: Use a combination of dry and wet methods to remove the residual photoresist on the surface of the adapter board and in the holes after etching.

[0011] TSV deep hole cleaning: SC1 cleaning combined with megasonic cleaning is used to remove residual glue and polymer in the deep holes of the adapter board.

[0012] Thermal oxidation: Use CVD to generate an insulating layer on the surface of the adapter plate and in the deep holes.

[0013] TSV sidewall metallization: A uniform seed layer is deposited on the surface of the adapter and the sidewall of the TSV hole using a high target-to-substrate distance physical vapor deposition (PVD) method. The seed layer material is usually copper.

[0014] TSV electroplating: Place the adapter plate in the electroplating tank and use a specific electroplating solution to fill the TSV hole. During the electroplating process, the surface morphology and filling rate of TSV electroplating are improved by controlling parameters such as vacuum pre-treatment method, current density, electroplating time, temperature, circulation flow, and swing frequency.

[0015] Post-processing step: Anneal the plated adapter to improve the reliability of the coating.

[0016] The electroplating systems used in the TSV hole filling step include: Plating tank: Made of corrosion-resistant materials, with good sealing and temperature control functions; Vacuum pre-treatment system: It uses a combination of vacuum and ultrasound to remove dirt on the wafer surface and the bottom of the hole. Ultrapure water replaces the air in the TSV hole, making it easier for the plating solution to fully enter the bottom of the TSV hole during the subsequent electroplating process. Cathode hanger: a carrier for mounting the adapter plate to be plated, inputting a stable and uniform current to the adapter plate; Anode rack: a carrier for mounting anode plates to provide uniform metal ions to be plated for electroplating; Power supply system: provides stable current to meet the needs of TSV electroplating; Stirring device: Stirring the plating solution can improve the uniformity and fluidity of the plating solution, thereby improving the quality of electroplating; Temperature control system: accurately control the temperature in the electroplating tank to ensure that the electroplating process is carried out at the appropriate temperature; Monitoring system: Real-time monitoring of current, voltage, temperature and other parameters during the electroplating process in order to adjust the electroplating conditions in time.

[0017] In a specific embodiment, the TSV electroplating method of the embodiment of the present invention includes the following steps: 1. Pretreatment: Place the transfer board to be electroplated in the RCA tank cleaning machine, perform SPM cleaning to remove organic dirt; perform DHF cleaning to remove the native oxide layer; perform SC1 cleaning to remove particulate impurities; perform SC2 cleaning to remove metal dirt.

[0018] 2. Photolithography: Use AZP4620 photoresist for pattern masking.

[0019] 3.TSV hole etching: TSV deep hole etching is performed using a three-step cycle of etching, passivation, and re-etching.

[0020] 4. Degumming: Use a combination of argon and oxygen plasma dry method and DMSO degumming liquid wet method to remove the residual photoresist on the surface of the adapter plate and in the hole after etching.

[0021] 5. TSV deep hole cleaning: Use SC1 cleaning solution with a volume ratio of NH4OH:H2O2:H2O=1:1:5 to remove residual glue and polymer in the deep holes of the adapter board at 1MHz MegPie megasonic power.

[0022] 6. Thermal oxidation: Use ICPCVD to generate an insulating layer on the surface of the adapter plate and in the deep hole. The thickness of the insulating layer is about 2 microns.

[0023] 7. TSV sidewall metallization: A uniform barrier layer and seed layer are deposited on the surface of the adapter board and the sidewall of the TSV hole using a high target-substrate distance physical vapor deposition (PVD) method. The barrier layer is Ti with a thickness of about 50nm, which serves to block the seed layer from diffusing into silicon dioxide; the seed layer is Cu with a thickness of about 300nm, which serves to thicken the conductive layer through electroplating.

[0024] 8.TSV electroplating: Place the adapter plate in the electroplating tank and use a specific electroplating solution to fill and electroplate the TSV holes. During the electroplating process, the filling quality and uniformity of the TSV holes are ensured by controlling the vacuum pre-treatment method, current density, electroplating time, temperature, circulation flow, and swing frequency. The electroplating current parameters are the four-stage current method: the first stage current density is 0, the time is 1min; the second stage current density is 0.02ASD, the time is 15min; the third stage current density is 0.06ASD, the time is 4h; the fourth stage current density is 0.08ASD, the time is 1h, and the temperature is 24℃.

[0025] 9. Post-processing steps: Anneal the electroplated adapter plate to improve the quality and stability of the coating. The annealing temperature is 280°C and the time is 6 hours.

[0026] The through silicon via electroplating method of the embodiment of the present invention can be applied to 2.5D adapter board packaging, and has the following beneficial effects: 1) Improved the uniformity of TSV electroplating, and the uniformity of electroplating was increased to 10%; 2) Reduce the copper particles on the surface of the transfer board after electroplating, and the thickness of the surface copper particles is reduced from 50µm to 5µm; 3) Improve the filling rate of TSV electroplating from 75% to 99.99%; 4) Reduce the dishing value of the copper pillar after TSV electroplating. The dishing value of the copper pillar after TSV electroplating is optimized from -4µm to +2µm; 5) Extend the shelf life of the drug solution from 14 tablets to 19 tablets.

[0027] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that, for those skilled in the art, the described embodiments can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the above description is illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A through silicon via electroplating method, characterized in that: include: Pretreatment step: cleaning and surface activation of the transfer plate to be plated to remove impurities and oxides on the surface of the wafer and improve the adhesion of the seed layer; Photolithography step, transferring deep hole mask pattern to the adapter plate; In the deep hole etching step, a TSV deep hole is processed on the surface of the adapter plate by Bosch etching, and the TSV hole depth-to-width ratio is 7:1; The de-resisting step uses a combination of dry and wet methods to remove the residual photoresist on the surface of the adapter plate and in the hole after etching; In the deep hole cleaning step, SC1 cleaning and megasonic cleaning are combined to remove residual glue and polymer in the deep holes of the adapter plate; In the thermal oxidation step, an insulating layer is formed on the surface of the adapter plate and in the deep hole by ICPCVD; In the sidewall metallization step, a uniform seed layer is deposited on the surface of the adapter plate and the sidewall of the TSV hole by high target-substrate distance physical vapor deposition; In the TSV electroplating step, the adapter plate is placed in the electroplating tank of the electroplating system, and the deep hole filling electroplating is performed by the electroplating system. The filling rate of TSV electroplating is improved by optimizing the vacuum pre-treatment method, current density, electroplating time, temperature, circulation flow rate, and swing frequency; In the post-processing step, the transfer board after electroplating is annealed to improve the reliability of the through silicon via plating.

2. The method according to claim 1, characterized in that The electroplating system comprises: The electroplating tank is made of corrosion-resistant materials and has good sealing and temperature control functions; The vacuum pre-treatment system uses a combination of vacuum and ultrasound to remove dirt from the wafer surface and the bottom of the hole. Ultrapure water replaces the air in the TSV hole, making it easier for the plating solution to fully enter the bottom of the TSV hole during the subsequent electroplating process. Cathode hanger, used to install the adapter plate and input stable and uniform current to the adapter plate; Anode hanger, used to install anode plates and provide uniform metal ions to be plated for electroplating; A power supply system for providing a stable electric current; A stirring device, used to improve the uniformity and fluidity of the electroplating solution by stirring the electroplating solution; Temperature control system, used to accurately control the temperature in the plating tank; Monitoring system for real-time monitoring of current, voltage and temperature parameters during the electroplating process.

3. The method according to claim 1 or 2, characterized in that In the pretreatment step, the transfer board to be electroplated is placed in an RCA tank cleaning machine and subjected to SPM cleaning to remove organic contaminants; Perform DHF cleaning to remove the native oxide layer; Perform SC1 cleaning to remove particulate impurities; Perform SC2 cleaning to remove metal contaminants.

4. The method according to claim 1 or 2, characterized in that: In the deep hole etching step, the deep hole etching is performed in a three-step cycle of etching, passivation and re-etching.

5. The method according to claim 1 or 2, characterized in that: In the degumming step, the residual photoresist on the surface of the adapter plate and in the hole after etching is removed by combining a dry method using argon and oxygen plasma and a wet method using DMSO degumming solution.

6. The method according to claim 1 or 2, characterized in that: In the thermal oxidation step, the thickness of the insulating layer was 2 microns.

7. The method according to claim 1 or 2, characterized in that: In the sidewall metallization step, a uniform barrier layer and seed layer are deposited on the surface of the adapter plate and the sidewall of the TSV hole. The barrier layer is Ti with a thickness of 50 nm, and the seed layer is Cu with a thickness of 300 nm.

8. The method according to claim 1 or 2, characterized in that: In the TSV electroplating step, the electroplating current is divided into four sections: the first section has a current density of 0 and a time of 1 min; the second section has a current density of 0.02 ASD and a time of 15 min; the third section has a current density of 0.06 ASD and a time of 4 h; and the fourth section has a current density of 0.08 ASD and a time of 1 h.

9. The method according to claim 1 or 2, characterized in that: In the post-treatment step, the annealing temperature is 280° C. and the time is 6 h.

10. The method according to claim 1 or 2, characterized in that: The adapter board to be electroplated is a 2.5D adapter board.