Single inhibitor for high aspect ratio TSV copper plating and electroplating process

Abstract

The invention discloses a single inhibitor for high aspect ratio TSV copper plating and an electroplating process. The TSV copper electroplating solution and the additive comprise four components, namely CuSO4. 5H2O, H2SO4, Cl <-> and a single inhibitor. The single inhibitor is a block polymer which is connected by silane and has a symmetrical structure. The electroplating process comprises the steps of plasma cleaning, vacuum wetting pretreatment, pre-stirring, current density measurement and the like. According to the single inhibitor for copper plating of the TSV with the high aspect ratio and the electroplating technology, the TSV with the high aspect ratio can be completely filled from bottom to top only through one inhibitor, 100% of defects are avoided, operation is easy and convenient, liquid medicine maintenance is convenient, the single inhibitor and the electroplating technology are suitable for filling of the TSV with different sizes, the liquid medicine adjusting technology is simple, and the single inhibitor and the electroplating technology are economical and applicable.

Description

Technical Field

[0001] The invention relates to the technical field of copper electroplating, and in particular to a single inhibitor and an electroplating process for high aspect ratio TSV copper plating. Background Art

[0002] Through Silicon Via (TSV) technology is an important technology in 3D packaging. It realizes vertical electrical interconnection of through silicon vias by filling conductive materials such as copper, tungsten and polysilicon. The advantages of 3D integration based on TSV technology mainly include: better electrical interconnection performance, wider bandwidth, higher interconnection density, lower power consumption, smaller size and lighter weight.

[0003] Copper plating is a common method for achieving TSV interconnection. During the micro-hole electroplating process, defects such as seams and voids are easily formed, especially when copper is plated in micro-holes with high aspect ratios. Achieving void-free filling is a very severe challenge. An important aspect of achieving TSV filling is to ensure that the deposition rate at the hole mouth is lower than the deposition rate at the bottom of the hole, thereby promoting a bottom-up filling mode. Therefore, the introduction of additives is a necessary factor for achieving TSV void-free filling. Additives usually added to the TSV plating solution include accelerators, inhibitors, and levelers. Small molecule accelerators can diffuse and adsorb at the bottom of the hole in advance, which accelerates the deposition of copper at the bottom of the hole, while large molecule inhibitors diffuse slowly and quickly adsorb at the hole mouth during the diffusion process, inhibiting the deposition of copper at the top of the hole. Levelers are similar to inhibitors. The ratio of additives is an important factor in TSV copper filling. In the absence of accelerators and levelers, using a single inhibitor to fill TSV, it is necessary to consider the concentration of the inhibitor, the rotation speed, the current density and other aspects. If there is an imbalance, it will lead to defects such as holes and gaps in the filling. In the technical background, it is emphasized that the current methods all use three doses. The additive ratio needs to be adjusted for TSVs of different sizes. The adjustment of the three-dose formula is complex and there are many factors to consider. A single inhibitor can solve this problem and achieve defect-free TSV filling. Summary of the invention

[0004] The present invention aims to provide a single inhibitor and electroplating process for high aspect ratio TSV copper plating to solve the TSV copper electroplating problem mentioned in the above background technology.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A single inhibitor for high aspect ratio TSV copper plating, the single inhibitor is a block polymer of a symmetrical structure connected by silane, and the structure of the inhibitor is as follows: ; The range of x is 120-165, and the range of y is 25-125; more preferably, the range of x is 120-140, and the range of y is 25-45.

[0006] The block polymer with symmetrical structure connected by silane has a left-right symmetrical structure and an average molecular weight of 14000-16000, wherein ethylene oxide:propylene oxide = 8-12:1-2, and this ratio is the ratio of the number of ethylene oxide and propylene oxide.

[0007] In some preferred cases, the block polymer with a symmetrical structure connected by silane has a left-right symmetrical structure and an average molecular weight of 14600, wherein ethylene oxide: propylene oxide = 8:2 (EO: PO = 8:2).

[0008] A single inhibitor and electroplating process for high aspect ratio TSV copper plating, comprising the following steps: Step S1: Wafer preparation: a plasma cleaning machine is used to treat the wafer to improve the hydrophilicity of the wafer; Step S2: Wafer pretreatment: fix the wafer treated in step S1 on a carrier, immerse it in pure water under vacuum conditions, and make the holes fully wetted; Step S3: Setting up the experimental device: preparing the electroplating recipe, including the copper electrolyte and the inhibitor, fixing the cathode (wafer to be electroplated) and the anode (phosphorus copper anode) in the electrolytic cell, and connecting the upper electrode in the electroplating recipe; Step S4: pre-stirring: stirring without applying current to allow water in the TSV through-hole to be fully exchanged with the electroplating solution; Step S5: TSV copper electroplating: TSV copper electroplating is performed using a constant current method.

[0009] Among them, the wafer hole size used in step S1 is 100-120μm in depth and 5-1μm in width. The specific conditions for plasma cleaning are: vacuum degree is 10-30Pa, volume flow ratio of air to argon is 3:1-5:1, power is 90-120w, time is 10-20min, and after the plasma cleaning machine finishes working, wait for 5-10min to take out the wafer.

[0010] The copper electrolyte in step S3 includes 150-200 g / L CuSO4·5H2O, 10-40 g / L H2SO4, 50-80 ppm Cl - ; Among them, the addition amount of a single inhibitor is 50-200ppm, and more preferably 100-200ppm.

[0011] Wherein, the speed of pre-stirring in step S4 is 500-1000RPM, and the pre-stirring time is 10-30s; The current density of the constant current electroplating in step S5 is 0.03 A / dm 2 -0.2 A / dm 2 , the speed during electroplating is 500-1000RPM.

[0012] The single inhibitor and electroplating process for high aspect ratio TSV copper plating of the present invention have the following advantages: (1) The present invention uses a block polymer with a symmetrical structure connected by silane as a single inhibitor to achieve high aspect ratio TSV non-void and defect-free filling, and the filling method is bottom-up filling.

[0013] (2) The electroplating process described in the present invention can fully realize defect-free filling of TSVs with high aspect ratios. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0015] Figure 1 This is a cross-sectional view of the complete filling under an ultra-depth-of-field microscope after electroplating in Example 1.

[0016] Figure 2 This is a cross-sectional view of the complete filling under a scanning electron microscope after electroplating in Example 1.

[0017] Figure 3 This is a cross-sectional view taken under a scanning electron microscope after electroplating in Comparative Example 1.

[0018] Figure 4 This is a cross-sectional view taken under a scanning electron microscope after electroplating in Comparative Example 2.

[0019] Figure 5 This is a cross-sectional view taken under a scanning electron microscope after electroplating in Comparative Example 3.

[0020] Figure 6 This is a cross-sectional view taken under a scanning electron microscope after electroplating in Example 2.

[0021] Figure 7 This is a cross-sectional view of TSV copper filling in Example 3.

[0022] Figure 8 This is a cross-sectional view of TSV copper filling in Example 4.

[0023] Fig. 9 This is a cross-sectional view of TSV copper filling in Example 5.

[0024] Fig.10 This is a cross-sectional view of TSV copper filling of the comparative example in Example 5.

[0025] Fig.11 This is a cross-sectional view of TSV copper filling in Example 6.

[0026] Fig.12 This is a cross-sectional view of TSV copper filling of the comparative example in Example 6. DETAILED DESCRIPTION

[0027] In order to more clearly describe the present invention, the following is a detailed description with reference to the accompanying drawings. The single inhibitor of the high aspect ratio TSV copper plating used in this embodiment is a block polymer of a symmetrical structure connected by silane, and the structure of the inhibitor is as follows: ; The range of x is 120-140 and the range of y is 25-45.

[0028] Embodiment 1: A single inhibitor and electroplating process for high aspect ratio TSV copper plating, comprising the following steps: Step S1: Wafer preparation: a plasma cleaning machine is used to treat the wafer to improve the hydrophilicity of the wafer; Step S2: Wafer pretreatment: fix the wafer treated in step S1 on a carrier, immerse it in pure water under vacuum conditions, and make the holes fully wetted; Step S3: Setting up the experimental device: preparing the electroplating recipe, including the copper electrolyte and the inhibitor, fixing the cathode (wafer to be electroplated) and the anode (phosphorus copper anode) in the electrolytic cell, and connecting the upper electrode in the electroplating recipe; Step S4: pre-stirring: stirring without applying current to allow water in the TSV through-hole to be fully exchanged with the electroplating solution; Step S5: TSV copper electroplating: TSV copper electroplating is performed using a constant current method.

[0029] In this embodiment, the vacuum degree during plasma cleaning is 20Pa, the volume flow ratio of air to argon is 4:1, the power is 100W, the time is 10min, and the composition of the copper electrolyte mainly includes 180g / L CuSO4·5H2O, 30g / L H2SO4, 70ppm Cl -The inhibitor used in this embodiment is a block polymer of a symmetrical structure connected by silane in the present invention, the left-right symmetrical structure is a polymer with an average molecular weight of 14600 (EO:PO=8:2), x in the structure is 124, y is 31, the addition amount is 100ppm, the electroplating speed is 800RPM, and the current density is 0.15 A / dm 2 , the electroplating time is 120min.

[0030] In this embodiment, the electroplated test piece was embedded with epoxy resin, wet-ground with 800-grit sandpaper, and polished with alumina polishing powder, and observed under an ultra-depth microscope. Figure 1 As shown, it can be observed that TSV copper plating under a single inhibitor can achieve void-free and defect-free filling. Figure 2 This is a scanning electron microscope image after the TSV is completely filled and embedded.

[0031] Comparative Example 1: A single inhibitor and electroplating process for high aspect ratio TSV copper plating. This test is a comparative test. The electroplating steps are the same as those in Example 1. In this test example, the inhibitor is poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), with an average molecular weight of 8400, EO:PO=4:1, and a concentration of 100 ppm. The cross-sectional morphology of the wafer is as follows: Figure 3 , TSV copper filling appears sealed at the hole opening.

[0032] Comparative Example 2: A single inhibitor and electroplating process for high aspect ratio TSV copper plating. This test is a comparative test. The electroplating steps are the same as those in Example 1. In this test example, the inhibitor is poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), with an average molecular weight of 2900, EO:PO=2:3, and a concentration of 100 ppm. The cross-sectional morphology of the wafer is as follows: Figure 4 , TSV copper filling appears sealed at the mouth, and the grains of the filled copper are coarse.

[0033] Comparative Example 3: A single inhibitor and electroplating process for high aspect ratio TSV copper plating. This test is a comparative test. The electroplating steps are the same as in Example 1. In this test example, the inhibitor is poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), with an average molecular weight of 2000, EO:PO=1:9, and a concentration of 100 ppm. The cross-sectional morphology of the wafer is as follows: Figure 5 , TSV copper is filled on the hole wall.

[0034] Embodiment 2: The specific experimental steps in this example are the same as those in Example 1. The inhibitor used in this example is a block polymer with a symmetrical structure connected by silane, wherein the average molecular weight of the block polymer is 15800 (EO:PO = 9:3), x is 123, y is 41, the addition amount is 100 ppm, the electroplating time is 120 min, and the other conditions are the same as those in Example 1. Figure 6 This is the cross-sectional morphology of the TSV copper filling after electroplating. The TSV copper filling appears sealed near the hole mouth.

[0035] Embodiment 3: The specific experimental steps in this example are the same as those in Example 1. The inhibitor used in this example is a block polymer with a symmetrical structure connected by silane, wherein the average molecular weight of the block polymer is 16000 (EO:PO = 5:1), x is 140, y is 28, the addition amount is 100 ppm, the electroplating time is 120 min, and the other conditions are the same as those in Example 1. Figure 7 This is the cross-sectional morphology of TSV copper filling after electroplating. The TSV copper filling is filled on the wall.

[0036] Embodiment 4: The specific experimental steps in this embodiment are the same as those in Embodiment 1, and the purpose is to explore the filling mode of TSV copper filling. In this embodiment, the additive is the single inhibitor described in the present invention, the concentration is 100 ppm, and the electroplating time is 30 min. Figure 8 This is the cross-sectional morphology of the TSV copper filling after electroplating. It can be seen that the TSV copper filling grows in a bottom-up mode.

[0037] Embodiment 5: The specific experimental steps in this example are the same as those in Example 1. In this example, the additive is the single inhibitor described in the present invention, the concentration is 100 ppm, the electroplating speed is 500 RPM, and the electroplating time is 120 min. Fig. 9 It can be seen from the morphology image that at lower rotation speeds, holes appear in the lower middle part of the TSV copper filling.

[0038] Comparative Example 4: A single inhibitor and electroplating process for high aspect ratio TSV copper plating. This test is a comparative test. The steps are the same as those in Example 1. In this test example, the additive is the single inhibitor described in the present invention, the concentration is 100ppm, the electroplating time is 120min, the speed is 1000RPM, and the Fig.10 It can be seen from the morphology image that at higher rotation speeds, TSV copper filling will have holes and gaps.

[0039] Embodiment 6: The specific experimental steps in this example are the same as those in Example 1. The concentration of the single inhibitor added in this example is 50 ppm. Fig.11 This is a cross-sectional view after electroplating. When the additive concentration is low, the hole mouth is filled with copper, resulting in a filled seal.

[0040] Comparative Example 5: A single inhibitor and electroplating process for high aspect ratio TSV copper plating. This test is a comparative test. The steps are the same as those in Example 1. The added concentration of the single inhibitor in this test example is 200 ppm. Fig.12 It can be seen that the TSV copper filling does not reach the bottom-up filling, but is filled on the wall. Based on the above embodiments and comparative examples, it can be concluded that the present invention achieves void-free and defect-free filling of TSV with high aspect ratio by using a single inhibitor, and the TSV copper filling grows in a bottom-up manner.

Claims

1. A single inhibitor for high aspect ratio TSV copper plating, characterized in that: The single inhibitor is a block polymer of a symmetrical structure connected by silane, and the structure of the inhibitor is as follows: ； In the structure of the inhibitor, the range of x is 120-165, and the range of y is 25-125.

2. The single inhibitor for high aspect ratio TSV copper plating according to claim 1, characterized in that: The block polymer with symmetrical structure connected by silane, the left-right symmetrical structure is a polymer with an average molecular weight of 14000-16000, wherein ethylene oxide: propylene oxide = 8-12: 1-2.

3. An electroplating method using the single inhibitor for high aspect ratio TSV copper plating according to claim 1 or 2, characterized in that: The electroplating process includes the following steps: Step S1: Wafer preparation: a plasma cleaning machine is used to treat the wafer to improve the hydrophilicity of the wafer; Step S2: Wafer pretreatment: fix the wafer treated in step S2 on the cathode plate and immerse it in pure water under vacuum conditions to achieve sufficient wetting in the hole; Step S3: Step S3: Construction of experimental device: preparing an electroplating recipe, including a copper electrolyte and a single inhibitor as claimed in claim 1 or 2, fixing the cathode and anode in an electrolytic cell, and connecting an electrode in the electroplating recipe; Step S4: pre-stirring: stirring without applying current to allow water in the TSV through-hole to be fully exchanged with the electroplating solution; Step S5: TSV copper electroplating: TSV copper electroplating is performed using a constant current method.

4. The method according to claim 3, characterized in that: The wafer hole size used in step S1 is 100-120μm in depth and 5-15μm in width. The plasma cleaning conditions include a vacuum degree of 10-30Pa, a volume flow ratio of air to argon of 3:1-5:1, a power of 90-120w, and a time of 10-20min. After the plasma cleaning machine finishes working, wait for 5-10min to remove the wafer.

5. The method according to claim 3, characterized in that: The single inhibitor addition amount is 50-200 ppm.

6. The method according to claim 3, characterized in that: The copper electrolyte in step S3 includes 150-200 g / L CuSO4·5H2O, 10-40 g / L H2SO4, 50-80 ppm Cl - .

7. The method according to claim 3, characterized in that: In step S4, the pre-stirring speed is 500-1000 RPM, and the pre-stirring time is 10-30 s.

8. The method according to claim 3, characterized in that: In step S5, the current density of the constant current electroplating is 0.03 A / dm 2 -0.2 A / dm 2 , the speed during electroplating is 500-1000RPM.

Images