High aspect ratio tsv structures, methods of making and applications thereof

Abstract

The application discloses a high-depth-width-ratio TSV structure, a preparation method and application thereof. The preparation method comprises the following steps: providing a hole structure, the depth-width ratio of the hole structure is greater than 2 and the aperture is smaller than 100 um; and forming a TSV structure in the hole structure by adopting a pulse reverse electrodeposition method, the pulse reverse electrodeposition comprises a forward current and a reverse current, the current density of the forward current is 1.0 mA / cm 2 The preparation method provided by the application eliminates the protrusions at the through-hole openings by the pulse reverse electrodeposition, and then deposits the dense TSV structure. In the pulse reverse electrodeposition, specific deposition conditions and processes are set, so that the hole structure with high depth-width ratio and small diameter is fully filled, and the holes are avoided. The preparation method provided by the application can be widely applied to the processing and manufacturing processes of various MEMS devices and semiconductor devices, and has wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device fabrication technology, and in particular to a high aspect ratio TSV structure, its fabrication method and application. Background Technology

[0002] Through-silicon vias (TSVs) are vertical interconnect structures that penetrate silicon wafers or chips. TSV technology has important applications in micro / nano device manufacturing, 3D packaging, and 3D integrated circuits, and is quite advantageous for entering the 3D IC market.

[0003] High aspect ratio TSV structures are commonly used in semiconductor devices and integrated circuit interconnects. With the continuous development of Moore's Law, chip integration density is rapidly increasing, and conventional placement, routing, and interconnection methods can no longer meet the requirements. 3D high aspect ratio TSV structures can further improve chip integration density.

[0004] Among the methods for preparing TSV structures, electroplating has become the most promising method due to its fast deposition rate and low cost.

[0005] However, in the electroplating deposition of high aspect ratio TSV structures, traditional DC electroplating is commonly used to fill the TSV structure. This method has two drawbacks: 1) The TSV structure has a large aspect ratio and a narrow opening. Due to the tip discharge effect, protrusions easily form at the opening, causing blockage and resulting in voids in the TSV structure. The specific process is as follows... Figure 1 As shown. Especially for pore structures with a high aspect ratio and a small diameter, as deposition continues, the protrusions will seal the opening, preventing metal ions from depositing into the deep pores, which will easily lead to the formation of voids; 2) After long-term continuous deposition, the surface roughness of the TSV structure will continue to increase, which will affect the electrical performance.

[0006] The aforementioned issues will significantly affect the conductivity and stability of the TSV structure, thereby adversely impacting the performance of the final micro / nano products. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a high aspect ratio TSV structure, its fabrication method, and its applications. The objective is to provide a simple method: using a pulsed reverse current method specific to high aspect ratio and small diameter hole structures, protrusions at the via openings are eliminated, preventing hole formation, while simultaneously depositing a smooth and dense TSV structure.

[0008] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0009] In a first aspect, the present invention provides a method for fabricating a high aspect ratio TSV structure, comprising:

[0010] A hole structure is provided, wherein the aspect ratio of the hole structure is greater than 2 and the pore diameter is less than 100 μm;

[0011] A pulsed reverse electrodeposition method is used to fill the void structure with metal to form a TSV structure. The pulsed reverse electrodeposition includes periodically cyclically applying forward and reverse currents, with the forward current density being 1 mA / cm². 2 the following.

[0012] Secondly, the present invention also provides the application of the above-mentioned preparation method in the field of micro-nano device or integrated circuit manufacturing.

[0013] Thirdly, the present invention also provides a TSV structure prepared by the above preparation method, wherein the aspect ratio of the TSV structure is greater than 2 and the diameter is less than 100 μm; and the TSV structure is free of voids.

[0014] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least the following:

[0015] The preparation method provided by this invention eliminates the protrusions at the opening of the via through by pulsed reverse electrodeposition, thereby depositing a dense TSV structure. In pulsed reverse electrodeposition, specific deposition conditions and processes are set to achieve full filling of void structures with high aspect ratio and small diameter, thereby avoiding the formation of voids.

[0016] The preparation method provided by this invention can be widely applied in the fabrication processes of various MEMS devices and semiconductor devices, and has broad application prospects.

[0017] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the preparation state of the TSV structure preparation method provided in the background art of this invention;

[0019] Figure 2 This is a schematic diagram of a photolithographic pattern for forming a hole structure, provided in a typical embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the pulse current waveform in the preparation method provided in a typical embodiment of the present invention;

[0021] Figure 4a This is a cross-sectional scanning electron microscope image of a TSV structure prepared by the preparation method provided in a typical comparative case of the present invention;

[0022] Figure 4b This is a cross-sectional scanning electron microscope image of a TSV structure prepared by the preparation method provided in a typical comparative case of the present invention;

[0023] Figure 4c This is a cross-sectional scanning electron microscope image of a TSV structure prepared by a preparation method provided in another typical embodiment of the present invention;

[0024] Figure 4d This is a cross-sectional scanning electron microscope image of a TSV structure prepared by a preparation method provided in another typical embodiment of the present invention. Detailed Implementation

[0025] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate the technical solution, its implementation process, and its principles.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0027] This invention provides a method for fabricating a high aspect ratio TSV structure, comprising the following steps:

[0028] A hole structure is provided, wherein the aspect ratio of the hole structure is greater than 2 and the hole diameter is less than 100 μm.

[0029] A pulsed reverse electrodeposition method is used to fill the void structure with metal to form a TSV structure. The pulsed reverse electrodeposition includes periodically cyclically applying forward and reverse currents, with the forward current density being 1 mA / cm². 2 the following.

[0030] The aspect ratio can be around 2, such as 1.7, or as high as around 10. The common applicable aspect ratio range is 1.5-10, but it is not limited to this.

[0031] In the prior art, the application of pulsed reverse current for high-quality electroplating has been developed in the macroscopic field. For example, some prior art provides the application of pulsed reverse electroplating in copper plating of through-holes in circuit boards. However, unlike the prior art, the present invention is aimed at TSV structures in the microscopic field. Given the huge difference in scale, it is impossible to achieve high-quality electrodeposition of TSV structures in the microscopic field by simply copying the pulsed reverse electroplating method in the prior art.

[0032] One crucial difference lies in the order-of-magnitude difference in current density. Specifically, the inventors discovered that due to the completely different application directions of macroscopic and microscopic processes, the parameters used in macroscopic through-hole pulse reverse electroplating are entirely inapplicable; the required current densities are not even on the same order of magnitude. Because the "protrusion" effect does not affect structural formation at the macroscopic scale, it only causes sealing problems in microscopic aspect ratio structures, preventing the filling of micro / nano structures. Therefore, it is necessary to specifically adjust parameters such as current density to effectively eliminate voids.

[0033] Specifically, some existing pulsed reverse electroplating techniques use a current density of 20-30 mA / cm². 2 However, the inventors of this invention discovered that even with the above-mentioned current density, voids could not be avoided. Therefore, it was necessary to specifically reset the pulse-reverse deposition conditions.

[0034] Specifically, during the research process of this invention, it was discovered that when the forward current time is shorter than the reverse current time, it is easier to prepare a dense TSV structure, which is significantly different from the teachings of the prior art. At the same time, a small reverse current and a long reverse time are needed to better remove the protrusions at the sealing point, thus better solving the technical problem discovered by the inventors.

[0035] Therefore, in some implementations, the duration of the forward current is preferably shorter than the duration of the reverse current.

[0036] In some implementations, the current density of the reverse current is preferably less than the current density of the forward current.

[0037] In some implementations, the ratio of the time of the forward current to the time of the reverse current can be 1:(7-11).

[0038] In some implementations, the duration of the forward current can be 1-3 s, and the duration of the reverse current can be 9-27 s.

[0039] In some implementations, the current density of the forward current can be 0.2-0.8 mA / cm². 2 .

[0040] In some embodiments, the current density of the reverse current is preferably 8-40% of the current density of the forward current, more preferably 8-12%, and most preferably 10%.

[0041] In addition to the significant difference in current density compared to existing pulsed reverse currents, the inventors have also discovered that, for TSV structures with high aspect ratios, due to the special nature of their dimensions, the relationship between the magnitudes of the forward and reverse currents and the forward and reverse times cannot be set in the manner taught in the prior art.

[0042] For example, in the prior art, it is generally taught that the forward current is less than the reverse current, and the forward time is longer than the reverse time. For instance, some prior art teaches that the forward current is 2.0 A / dm. 2 The forward plating time is 20 seconds; the reverse current is 6.0 A / dm². 2 The reverse electroplating time is 1 second; however, after the inventors set it according to the above teachings, they found that its effect of eliminating voids and reducing the roughness of the TSV structure was not ideal. After a lot of research and innovation, the inventors found that the forward current time should be less than the reverse current time, and the current density of the reverse current should be less than the current density of the forward current. By adopting a setting method that is opposite to the teachings in the prior art, a better overall effect was achieved.

[0043] Specifically, research has found that in some specific application examples, such as Figure 3 As shown, a value of 0.2-0.8 mA / cm is used. 2 The optimal combination of current density and 10% reverse current ratio can eliminate voids and achieve the best TSV filling effect while ensuring dense filling of micro / nano high aspect ratio structures.

[0044] In some implementations, the relationship between the ratio of reverse current to forward current and the aspect ratio is as follows:

[0045] Aspect ratio ≈ (forward current / reverse current - 1), specifically, aspect ratio = (0.8~1.2) × (forward current / reverse current - 1).

[0046] The inventors have discovered that, in order to ensure the comprehensive effect of eliminating voids and reducing roughness for different void structures, it is necessary to select appropriate pulse current density and reverse current filling of the TSV structure based on its aspect ratio. Therefore, through long-term practice, the above-mentioned correlation has been summarized. Using the value range in the above correlation can achieve better results for different void structures.

[0047] In some embodiments, the metal filling the hole structure may include any one or a combination of two or more of copper, silver, gold, and nickel.

[0048] In some implementations, the pore wall material of the hole structure can be either silicon or quartz.

[0049] In some embodiments, the pulsed reverse electrodeposition is performed in an electrolyte that may include metal ions and additives.

[0050] In some embodiments, the preparation method further includes the following steps:

[0051] The step of depositing a seed layer in the porous structure prior to the pulse reverse electroplating.

[0052] In some embodiments, the seed layer is deposited by vapor deposition, and the deposition method is more preferably electron beam vapor deposition.

[0053] In some implementations, the seed layer is made of any one of Au, Cr, Ag, Ti, and Cu.

[0054] In some implementations, the thickness of the seed layer is 30-100 nm.

[0055] As a typical application example of the above exemplary technical solution, the fabrication of a high aspect ratio TSV structure can be carried out by the following specific steps:

[0056] 1. As follows Figure 2 The original photolithographic pattern of the target design shown is etched by photolithography and deep silicon etching (BOSCH) processes to obtain a high aspect ratio hole structure.

[0057] 2. After the lift-off process, the seed layer is deposited by electron beam evaporation.

[0058] 3. Based on the aspect ratio of the TSV structure, select appropriate pulse current density and reverse current filling to form the TSV structure. The filling situation is as follows: Figure 4c and 4d As shown.

[0059] The embodiments of the present invention also provide the application of the preparation method provided in any of the above embodiments in the field of micro-nano device or integrated circuit manufacturing.

[0060] As a specific example of the above applications, this embodiment of the invention also provides a TSV structure prepared by the preparation method provided in any of the above embodiments, wherein the aspect ratio of the TSV structure is greater than 2 and the diameter is less than 100 μm; and the TSV structure has no voids.

[0061] The technical solution of the present invention will be further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0062] Example 1

[0063] This embodiment illustrates the fabrication process of a high aspect ratio TSV structure, as shown below:

[0064] 1) Using a silicon wafer as a substrate, a photoresist patterning etching method is used to form an array of multiple holes with a diameter of 30μm and a depth of 87μm.

[0065] 2) The substrate with the above-mentioned porous structure is placed in an electron beam evaporation equipment and a seed layer of Au material with a thickness of 50 μm is deposited at a high temperature of 180°C.

[0066] 3) The substrate with the seed layer is then immersed in a commercial copper plating electrolyte; the seed layer acts as the cathode, with an electrode current of 0.8 mA / cm. 2 A forward current density of 2 s was used for deposition; then it was used as the anode at 0.25 mA / cm². 2 The current density was reverse electrolysis for 18 seconds; the total electrodeposition time was 2 hours, and the current cycle of electrodeposition was as follows: Figure 3 As shown, IA+ represents the forward current and IA- represents the reverse current. The forward current is significantly greater than the reverse current, and the duration of the forward current is significantly shorter than the duration of the reverse current; until the deposited TSV structure fills the pore structure.

[0067] The cross-sectional electron microscope image of the high aspect ratio TSV structure obtained in this embodiment is as follows: Figure 4c As shown, the high aspect ratio TSV structure has a uniform texture, is solid and pore-free, and has a surface roughness of 10 nm as determined by atomic force microscopy.

[0068] Example 2

[0069] The fabrication process of the high aspect ratio TSV structure in Example 1 of this embodiment is largely the same as that in Example 1, with the main difference being:

[0070] In step 1), during patterning etching, the diameter of the resulting hole structure is 50 μm and the depth is 102 μm.

[0071] The diameter of the hole structure is increased compared to Example 1, but it is still a TSV structure with a high aspect ratio.

[0072] Furthermore, due to the change in aspect ratio, in this embodiment, the forward current density is adjusted to 1 mA / cm² to achieve the optimal filling effect. 2The forward time is 2 s, and the reverse current density is adjusted to 0.5 mA / cm². 2 The reverse time is adjusted to 18 seconds.

[0073] The cross-sectional electron microscope image of the high aspect ratio TSV structure obtained in this embodiment is as follows: Figure 4d As shown, the high aspect ratio TSV structure has a uniform texture, is solid and pore-free, and has a surface roughness of 17 nm as determined by atomic force microscopy.

[0074] Example 3

[0075] The fabrication process of the high aspect ratio TSV structure in Example 1 of this embodiment is largely the same as that in Example 1, with the main difference being:

[0076] Replace the electrolyte with a commercial silver plating electrolyte.

[0077] By observing the cross-sectional electron microscope images of the high aspect ratio TSV structure prepared in this embodiment, it can be seen that the high aspect ratio TSV structure has a uniform texture and is solid without pores.

[0078] Example 4

[0079] The fabrication process of the high aspect ratio TSV structure in Example 1 of this embodiment is largely the same as that in Example 1, with the main difference being:

[0080] The diameter of the pore structure is 300 μm, and the aspect ratio is 10.

[0081] The reverse current density was adjusted to 0.08 mA / cm². 2 .

[0082] By observing the cross-sectional electron microscope images of the high aspect ratio TSV structure prepared in this embodiment, it can be seen that the high aspect ratio TSV structure has a uniform texture and is solid without pores.

[0083] This demonstrates that the method provided by the present invention still achieves good results in filling TSVs with high aspect ratio holes.

[0084] Comparative Example 1

[0085] This comparative example is largely the same as Example 1, with the only difference being:

[0086] In step 3), a similar growth template was used, and the same constant forward current density was used for DC electrodeposition until the pore structure was filled. Instead of using the pulsed reverse current method, TSV structures were filled in the pore structures of 30 μm and 50 μm respectively.

[0087] The resulting TSV structures are as follows: Figure 4a and Figure 4bAs shown, it is clear that there are voids and the surface is uneven, making it impossible to perform roughness testing under an atomic force microscope.

[0088] Comparative Example 2

[0089] This comparative example is largely the same as Example 1, with the only difference being:

[0090] In step 3), the forward current density is set to 2.0 A / dm², following the common practice in existing technologies. 2 That is, 20mA / cm 2 The forward plating time is 20 seconds; the reverse current density is 6.0 A / dm³. 2 That is, 60mA / cm 2 The reverse electroplating time is 1 second.

[0091] In this comparative example, the forward current density is less than the reverse current density, and the forward current time is greater than the reverse current time.

[0092] Although the cross-sectional void phenomenon of the resulting TSV structure is improved compared to Comparative Example 1, voids still exist, only in smaller size.

[0093] Comparative Example 3

[0094] This comparative example is largely the same as Example 1, with the only difference being:

[0095] In step 3), the magnitudes of the forward current and the reverse current are interchanged so that the intensity of the forward current is actually less than the intensity of the reverse current, thus preparing a sample.

[0096] The process is repeated, but the durations of the forward and reverse currents are swapped so that the duration of the forward current is longer than that of the reverse current. Another sample is then prepared.

[0097] Although the cross-sectional void phenomenon of the formed TSV structure in both samples was improved compared with Comparative Example 1, voids were still clearly present, only in smaller size.

[0098] Comparative Example 4

[0099] This comparative example is largely the same as Example 2, with the only difference being:

[0100] In step 3), the electrodeposition parameters from Example 1 are continued without any adaptive adjustments based on the change in aspect ratio.

[0101] Although the cross-sectional void phenomenon of the resulting TSV structure is improved compared to Comparative Example 2, voids still exist, only in smaller size.

[0102] Based on the above embodiments and comparative examples, it can be clearly seen that the preparation method provided by the present invention eliminates the protrusions at the opening of the via by pulsed reverse electrodeposition, thereby depositing a dense TSV structure. In pulsed reverse electrodeposition, specific deposition conditions and processes are set to achieve full filling of void structures with high aspect ratio and small diameter, thereby avoiding the formation of voids.

[0103] In particular, for pore structures with high aspect ratios and small diameters, electrodeposition parameters and the relationship between forward and reverse pulses, which differ from those used in conventional pulse reversal, are required to achieve better pore elimination. Furthermore, the aforementioned electrodeposition parameters should ideally be adaptively adjusted according to the aspect ratio to maintain the best results.

[0104] It is understood that the preparation method provided by this invention can be widely applied in the fabrication processes of various MEMS devices and semiconductor devices, and has broad application prospects.

[0105] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for fabricating a high aspect ratio TSV structure, characterized in that, include: A hole structure is provided, wherein the aspect ratio of the hole structure is greater than 2 and the pore diameter is less than 100 μm; A pulsed reverse electrodeposition method is used to fill the porous structure with metal to form a TSV structure. The pulsed reverse electrodeposition includes periodically cyclically applying a forward current and a reverse current. The ratio of the forward current time to the reverse current time is 1:(7-11), the forward current time is 1-3 s, the reverse current time is 9-27 s, and the forward current current density is 0.2-0.8 mA / cm². 2 The current density of the reverse current is less than the current density of the forward current. The relationship between the ratio of the forward current to the reverse current and the aspect ratio is: Aspect ratio = (0.8~1.2) × (forward current / reverse current - 1).

2. The preparation method according to claim 1, characterized in that, The metal filling the hole structure includes any one or a combination of two or more of copper, silver, gold, and nickel.

3. The preparation method according to claim 1, characterized in that, The wall material of the hole structure is either silicon or quartz.

4. The preparation method according to claim 1, characterized in that, The pulsed reverse electrodeposition is performed in an electrolyte comprising metal ions and additives.

5. The preparation method according to claim 1, characterized in that, Also includes: The step of depositing a seed layer in the porous structure prior to the pulse reverse electroplating.

6. The preparation method according to claim 5, characterized in that, The seed layer is deposited using electron beam evaporation.

7. The preparation method according to claim 6, characterized in that, The seed layer is made of any one of Au, Cr, Ag, Ti, and Cu. And / or, the thickness of the seed layer is 30-100 nm.

8. The application of the preparation method according to any one of claims 1-7 in the field of micro / nano device or integrated circuit manufacturing.

9. The TSV structure prepared by the method according to any one of claims 1-7, characterized in that, The TSV structure has an aspect ratio greater than 2 and a diameter less than 100 μm; The TSV structure has no voids.

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