Tungsten filling method for silicon through hole

Abstract

The invention provides a tungsten filling method for a silicon through hole. The method comprises the following steps: carrying out at least one time of initial tungsten filling (depositing a first barrier layer and a first tungsten layer) on a substrate on which the silicon through hole is formed; subsequently performing at least one subsequent tungsten filling, wherein the subsequent filling comprises the following steps of: depositing a second barrier layer in the silicon through hole; transferring the substrate from the second barrier layer deposition chamber to a tungsten chemical vapor deposition chamber under the condition of not breaking vacuum; and depositing a second tungsten layer on the second barrier layer in the tungsten chemical vapor deposition chamber. Wherein the second barrier layer deposition chamber and the tungsten chemical vapor deposition chamber are integrated on the same equipment platform. The substrate is conveyed under the condition that vacuum is not broken, air residues in the hole are effectively avoided, uniform distribution of tungsten precursor gas is guaranteed, the tungsten filling capacity of the high-aspect-ratio silicon through hole is remarkably improved, the tungsten filling effect and the cavity problem are greatly solved, and the method is particularly suitable for a multi-step tungsten filling process on a 12-inch wafer, and the yield of the wafer is improved. And the yield and reliability of TSV manufacturing are improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a tungsten filling method for a through silicon via. Background Art

[0002] As semiconductor integrated circuit technology continues to advance, three-dimensional integrated circuit (3D IC) packaging has garnered widespread attention due to its potential to increase integration density, reduce power consumption, and shrink chip packaging size. Through-silicon via (TSV) technology is a key enabler of 3D IC packaging. It creates vertical conductive channels on the chip, enabling electrical interconnection within the chip, between chips, and between the chip and the packaging substrate.

[0003] During TSV manufacturing, through-silicon vias (TSVs) with micron-scale apertures (Critical Dimension, CD) and high aspect ratios (e.g., up to 30:1 or even higher) need to be filled with conductive material, with tungsten (W) being the most common material. However, the tungsten filling process faces many challenges. Particularly in 12-inch wafer manufacturing, to avoid excessive wafer warpage that could cause alarms in subsequent transfer and processing equipment, the thickness of the tungsten layer deposited in a single pass is strictly limited and typically cannot be too thick. This means that to completely fill TSVs with high aspect ratios, multiple cycles of tungsten deposition and etch-back are often required.

[0004] As the number of tungsten fillings increases, the effective aspect ratio of the unfilled portion of the TSV increases dramatically (for example, in a 12-inch fab, the aspect ratio may be 32:1 during the first tungsten filling, may increase to 60:1 during the second filling, and may be as high as 240:1 during the third filling), making subsequent tungsten filling increasingly difficult. In traditional processes, a barrier layer, such as titanium nitride (TiN) by physical vapor deposition (PVD), is usually deposited before each tungsten chemical vapor deposition (WCVD). However, if the vacuum is broken between the barrier layer deposition and the tungsten chemical vapor deposition, such as when the wafer is transferred from the PVD equipment to the WCVD equipment, air may remain in the TSV hole. In the subsequent WCVD process, these residual gases or problems caused by gas exchange will cause the tungsten precursor to be unevenly distributed in the TSV hole, especially at the bottom of the deep hole where the precursor concentration is insufficient, resulting in a slow growth rate at the bottom, while the top or middle of the hole may be sealed prematurely, resulting in filling defects such as voids or seams, seriously affecting the electrical performance and reliability of the device.

[0005] Therefore, the prior art urgently needs a method for improving the tungsten filling performance in high aspect ratio TSVs to meet the requirements of advanced three-dimensional integrated circuit packaging. Summary of the Invention

[0006] The technical problem to be solved by the present application is that the existing through-silicon via (TSV) tungsten filling technology, especially when processing through-silicon via with high aspect ratio (for example, greater than or equal to 30:1), faces the problem of poor filling effect and easy formation of voids (W seam). Specifically, in the conventional tungsten filling process, the barrier layer deposition and tungsten chemical vapor deposition (WCVD) are usually carried out in different equipment or require vacuum transfer between chambers, which can cause air to remain in the through-silicon via before tungsten deposition. The remaining air can exchange with the precursor gas during the subsequent tungsten chemical vapor deposition process, resulting in uneven distribution of the concentration of the precursor gas in the deep hole, especially insufficient supply of the precursor gas at the bottom of the hole. This can cause the tungsten growth rate at the bottom of the hole to be slow, while the hole opening or the middle part of the hole can be prematurely sealed, ultimately leading to tungsten filling failure and the formation of voids, which seriously affects the performance and reliability of the device. For 12-inch wafer manufacturing processes, due to the limitation of the thickness of a single tungsten deposition (to avoid wafer warping), more times of tungsten filling are usually required, which makes the above-mentioned problems more prominent and puts higher requirements on the tungsten filling capacity.

[0007] To solve the above technical problems, the present application provides a method for meeting the tungsten filling requirements of through-silicon via. The method significantly improves the tungsten filling performance of high aspect ratio through-silicon via by optimizing the selection of barrier layer material and the key transfer mode between chambers in the subsequent filling process.

[0008] According to one aspect of the present application, a method for meeting the tungsten filling requirements of through-silicon via is provided, characterized in that it comprises the following steps:

[0009] Step one, performing at least one initial tungsten filling process on a substrate with a through-silicon via, the initial tungsten filling process comprising depositing a first barrier layer and depositing a first tungsten layer thereon;

[0010] Step two, performing at least one subsequent tungsten filling process after the initial tungsten filling process, the subsequent tungsten filling process comprising:

[0011] Step two A, depositing a second barrier layer in the through-silicon via;

[0012] Step two B, transferring the substrate from the deposition chamber for depositing the second barrier layer to a tungsten chemical vapor deposition chamber under the condition of maintaining a vacuum state; and

[0013] Step two C, depositing a second tungsten layer on the second barrier layer in the tungsten chemical vapor deposition chamber;

[0014] Wherein, the deposition chamber for depositing the second barrier layer and the tungsten chemical vapor deposition chamber are integrated in the same equipment platform.

[0015] In some embodiments of the present invention, the first barrier layer may be a titanium nitride layer formed by physical vapor deposition.

[0016] In some embodiments of the present invention, the second barrier layer is preferably a tungsten nitride (WN) layer, which not only serves as an effective barrier layer but also as a good adhesion layer for subsequent tungsten layers.

[0017] In some embodiments of the present invention, the substrate is transferred from the deposition chamber where the second barrier layer is deposited to the tungsten chemical vapor deposition chamber through a buffer chamber within the equipment platform to ensure that the transfer is carried out in a vacuum state.

[0018] In some embodiments of the present invention, the thickness of the tungsten nitride layer may be 8 nanometers to 9 nanometers.

[0019] In some embodiments of the present invention, the thickness of the second tungsten layer may be approximately 600 nanometers (eg, 550 to 650 nanometers).

[0020] In some embodiments of the present invention, before step 2A, the through silicon via may be pre-cleaned to remove residues.

[0021] In some embodiments of the present invention, in step one, the initial tungsten filling process further includes etching back or chemical mechanical polishing the first tungsten layer after depositing the first tungsten layer; and / or, after step two (C), further includes etching back or chemical mechanical polishing the second tungsten layer.

[0022] In some embodiments of the present invention, the subsequent tungsten filling process may be repeated multiple times to achieve complete filling of the high aspect ratio through silicon via.

[0023] The method of the present invention is particularly suitable for filling through-silicon vias with an aspect ratio greater than or equal to 30:1.

[0024] The beneficial effects of the present invention are:

[0025] 1. Significantly improved tungsten filling performance: During the subsequent tungsten filling process, the chamber for depositing the second barrier layer (such as a tungsten nitride layer) and the tungsten chemical vapor deposition chamber are integrated into the same equipment platform, and the substrate is transferred between the two while maintaining a vacuum state, effectively avoiding residual air inside the through-silicon via. This ensures that during tungsten chemical vapor deposition, the precursor gas can be more evenly distributed throughout the through-silicon via, especially reaching the bottom of the deep hole, thereby promoting the effective growth of tungsten at the bottom of the hole, avoiding premature sealing of the hole mouth, and significantly improving the tungsten filling capacity and filling uniformity.

[0026] 2. Reduce or eliminate the void (W seam): due to the more uniform precursor distribution, the tungsten growth is more ideal, thus greatly reducing or eliminating the tungsten filling void (W seam) problem commonly seen in traditional processes, improving the filling quality and the reliability of the device.

[0027] 3. Improve the filling yield of high aspect ratio TSV: the method of the present application has excellent filling effect for through silicon vias with aspect ratio greater than or equal to 30:1, which can meet the filling needs of high aspect ratio TSV for advanced three-dimensional integrated circuits, and improve the manufacturing yield.

[0028] 4. Optimize the multi-step filling process: especially in the case of multiple tungsten filling (such as 12-inch wafer process), the present application ensures the high quality of each subsequent filling by maintaining the vacuum state of the subsequent filling step, so that the overall filling effect is guaranteed.

[0029] In summary, the present application solves the problem of tungsten filling of high aspect ratio through silicon via in the prior art by innovative process step combination, especially the vacuum state transfer and preferred barrier layer material in the subsequent filling process, which provides important technical support for realizing high-performance and high-reliability three-dimensional integrated circuits. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The process flow diagram of the present application is shown;

[0031] Figure 2 The deposition of the first barrier layer of the present application is shown;

[0032] Figure 3 The deposition of the first tungsten layer of the present application is shown;

[0033] Figure 4 The etching back or chemical mechanical polishing of the first tungsten layer after deposition of the first tungsten layer of the present application is shown;

[0034] Figure 5 The deposition of the second barrier layer in the through silicon via of the present application is shown;

[0035] Figure 6 The deposition of the second tungsten layer on the second barrier layer of the present application is shown;

[0036] Figure 7 The filling effect of tungsten in the through silicon via slot of the present application and the prior art is shown. DETAILED DESCRIPTION

[0037] Following, through specific concrete examples illustrate the embodiments of the present application, those skilled in the art can easily understand other advantages and effects of the present application from the disclosure of the present specification. The present application can also be implemented or applied by other different specific embodiments, and various modifications or changes can be made to the details in the specification based on different views and applications without departing from the spirit of the present application.

[0038] Referring to Figure 1 , the present application provides a method for meeting the demand of tungsten filling of through silicon via, characterized in that, comprising the following steps:

[0039] Step one, on the substrate 101 with through silicon via, at least one initial tungsten filling process is performed, the initial tungsten filling process includes depositing a first barrier layer 102 (forming a structure as shown in Figure 2 ) and depositing a first tungsten layer 103 (forming a structure as shown in Figure 3 ) on it;

[0040] In some embodiments, in step one, the first barrier layer 102 is a physical vapor deposition titanium nitride layer.

[0041] Step two, after the initial tungsten filling process, at least one subsequent tungsten filling process is performed, the subsequent tungsten filling process includes:

[0042] Step two A, depositing a second barrier layer 104 in the through silicon via, forming a structure as shown in Figure 5 ;

[0043] Step two B, under the condition of keeping vacuum state, the substrate 101 is transferred from the deposition chamber for depositing the second barrier layer 104 to the tungsten chemical vapor deposition chamber; and

[0044] Step two C, in the tungsten chemical vapor deposition chamber, depositing a second tungsten layer 105 on the second barrier layer 104, forming a structure as shown in Figure 6 ;

[0045] Wherein, the deposition chamber for depositing the second barrier layer 104 and the tungsten chemical vapor deposition chamber are integrated in the same equipment platform.

[0046] In some embodiments, in step two A, the second barrier layer 104 is a tungsten nitride layer.

[0047] In some embodiments, in step two B, the substrate 101 is transferred from the deposition chamber for depositing the second barrier layer 104 to the tungsten chemical vapor deposition chamber through the buffer chamber in the equipment platform.

[0048] According to the above method, the present application provides a technical solution for improving the filling performance of tungsten in a high aspect ratio TSV by optimizing the barrier material and deposition process. On the substrate 101 with a TSV, at least one initial tungsten filling process is first performed. This initial filling process includes depositing a first barrier layer 102, such as a physical vapor deposition titanium nitride layer, and then depositing a first tungsten layer 103 on the first barrier layer 102. The initial tungsten filling is to preliminarily fill the bottom of the TSV at a relatively shallow aspect ratio and provide a basis for subsequent filling.

[0049] After the initial tungsten filling process, at least one subsequent tungsten filling process is performed. The key of the subsequent tungsten filling process is the use of a second barrier layer 104 material and deposition process different from the conventional process. Specifically, in step two A, a second barrier layer 104 is deposited in the TSV. Unlike the conventional process, the second barrier layer 104 is preferably a tungsten nitride layer. Tungsten nitride has better filling and barrier properties than conventional physical vapor deposition titanium nitride, and has better adhesion with the subsequent tungsten layer.

[0050] In step two B, an important feature is that after depositing the second barrier layer 104 (such as a tungsten nitride layer), the substrate 101 is transferred from the deposition chamber for depositing the second barrier layer 104 to the tungsten chemical vapor deposition chamber under vacuum. This transfer process under vacuum is achieved by different chambers integrated on the same equipment platform. In some embodiments, the substrate 101 is transferred from the deposition chamber for depositing the second barrier layer 104 to the tungsten chemical vapor deposition chamber through a buffer chamber in the equipment platform. The transfer under vacuum is one of the core technical advantages of the present application. In the conventional process, the vacuum needs to be broken from the barrier layer deposition chamber to the tungsten chemical vapor deposition chamber, which will cause air to remain inside the TSV. These residual air will hinder the precursor gas from entering the bottom of the TSV during the subsequent tungsten chemical vapor deposition process, resulting in uneven distribution of the precursor in the TSV, insufficient precursor at the bottom, and thus slow growth rate at the bottom, premature sealing at the top or middle, and finally leading to tungsten filling failure and the formation of a W seam. By transferring under vacuum, air remaining inside the TSV can be effectively avoided, ensuring uniform distribution of the precursor gas during the subsequent tungsten chemical vapor deposition process, and significantly improving the filling ability of tungsten, especially in high aspect ratio TSVs.

[0051] In step two C, a second tungsten layer 105 is deposited on the second barrier layer 104 (such as a tungsten nitride layer) in the tungsten chemical vapor deposition chamber. As before, due to the avoidance of air remaining and uneven distribution of the precursor, the tungsten chemical vapor deposition process of the present application can more effectively fill the TSV.

[0052] In some embodiments, the tungsten nitride layer deposited in step 2A serves as an adhesion layer and barrier layer for the second tungsten layer 105. The tungsten nitride not only effectively prevents the precursors from reacting with the silicon substrate 101 during the subsequent tungsten deposition process, but also provides a good surface to promote the nucleation and growth of tungsten, enhancing the adhesion of the tungsten layer to the underlying structure.

[0053] In some embodiments, the thickness of the tungsten nitride layer deposited in step 2A is between 8 nm and 9 nm. This thickness range has been experimentally proven to provide sufficient barrier properties and adhesion, while not excessively reducing the effective diameter of the through-silicon via, affecting the subsequent tungsten filling.

[0054] In some embodiments, the thickness of the second tungsten layer 105 deposited in step 2C is about 600 nm. This thickness is to fill the through-silicon via as much as possible in a single subsequent filling process, while taking into account factors such as thin film stress to avoid excessive warping of the substrate 101, especially on 12-inch wafers.

[0055] In some embodiments, before step 2A, a pre-cleaning step is also included to remove residues. The pre-cleaning step can effectively remove polymers, particles or other contaminants that may remain after etching of the through-silicon via, ensuring good contact between the second barrier layer 104 and the subsequent tungsten layer and the sidewall of the through-silicon via, improving the reliability of the filling.

[0056] In some embodiments, in step 1, the initial tungsten filling process further includes a back-etching or chemical mechanical polishing of the first tungsten layer 103 after the deposition of the first tungsten layer 103, forming a structure as shown in Figure 4 and / or, after step 2C, a back-etching or chemical mechanical polishing of the second tungsten layer 105 is also included. Back-etching or chemical mechanical polishing is used to planarize the deposited tungsten layer, remove excess tungsten, and provide a flat surface for subsequent process steps, such as repeated subsequent filling or subsequent chip integration.

[0057] In order to completely fill the high aspect ratio through-silicon via, the subsequent tungsten filling process can be repeated multiple times. Each repetition includes the deposition of a second barrier layer 104 (such as a tungsten nitride layer) and the deposition of a second tungsten layer 105 thereon, and the transfer between the deposition of the second barrier layer 104 and the tungsten chemical vapor deposition is completed under vacuum conditions. By repeating the high filling performance of the subsequent tungsten filling process multiple times, the high aspect ratio through-silicon via can be gradually filled completely, effectively solving the problem of single filling that cannot be filled completely.

[0058] The method of the present application is particularly suitable for filling through-silicon vias with an aspect ratio greater than or equal to 30:1. For high aspect ratio vias with an aspect ratio greater than or equal to 30:1, the conventional tungsten filling method often has difficulty in achieving reliable filling due to precursor transport limitations and void problems.

[0059] The present application greatly improves the filling capacity of tungsten in high aspect ratio via by improving the barrier material and the key non-vacuum damage transmission process, effectively reduces or eliminates the generation of voids, thereby meeting the demand of TSV technology for reliable tungsten filling in high aspect ratio via, and improving the performance and yield of three-dimensional integrated circuit. Please refer to Figure 7 Compared with the existing process, the method of the present application can significantly improve the filling effect of W in TSV groove, and the W seam is also significantly improved, providing an effective solution for the manufacture of high aspect ratio TSV on 12-inch wafers.

[0060] It should be noted that the diagrams provided in the embodiments only illustrate the basic concept of the present application in a schematic manner, and only show the components related to the present application in the diagrams, not according to the number, shape and size of the components when actually implemented. The actual implementation of each component may be arbitrarily changed in type, number and proportion, and the component layout pattern may be more complex.

[0061] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A method for filling tungsten in a through silicon via, characterized in that: At least: Step 1: performing at least one initial tungsten filling process on a substrate having a through silicon via formed thereon, wherein the initial tungsten filling process includes depositing a first barrier layer and depositing a first tungsten layer thereon; Step 2: After the initial tungsten filling process, perform at least one subsequent tungsten filling process, wherein the subsequent tungsten filling process includes: Step 2A, depositing a second barrier layer in the through silicon via; Step 2B: while maintaining a vacuum state, transferring the substrate from the deposition chamber where the second barrier layer is deposited to a tungsten chemical vapor deposition chamber; Step 2C: depositing a second tungsten layer on the second barrier layer in the tungsten chemical vapor deposition chamber; The deposition chamber for depositing the second barrier layer and the tungsten chemical vapor deposition chamber are integrated into the same equipment platform.

2. The method for filling a through silicon via with tungsten according to claim 1, wherein: In step 1, the first barrier layer is a titanium nitride layer formed by physical vapor deposition.

3. The method for filling a through silicon via with tungsten according to claim 1, wherein: The method according to claim 1, characterized in that in step 2A, the second barrier layer is a tungsten nitride layer.

4. The method for filling a through silicon via with tungsten according to claim 1, wherein: In step 2B, the substrate is transferred from the deposition chamber where the second barrier layer is deposited to the tungsten chemical vapor deposition chamber through a buffer chamber in the equipment platform.

5. The method for filling through silicon via with tungsten according to claim 3, wherein: In step 2A, the tungsten nitride layer serves as an adhesion layer and a barrier layer for the second tungsten layer.

6. The method for filling through silicon vias with tungsten according to claim 1, wherein: In step 2A, the thickness of the tungsten nitride layer is 8 nm to 9 nm.

7. The method for filling through silicon vias with tungsten according to claim 1, wherein: In step 2C, the thickness of the second tungsten layer is 550 to 650 nanometers.

8. The method for filling a through silicon via with tungsten according to claim 1, wherein: Before step 2A, the through silicon via is pre-cleaned to remove residues.

9. The method for filling through silicon vias with tungsten according to claim 1, wherein: In step 1, the initial tungsten filling process further includes etching back or chemical mechanical polishing the first tungsten layer after depositing the first tungsten layer; and / or, after step 2C, further includes etching back or chemical mechanical polishing the second tungsten layer.

10. The method for filling through silicon vias with tungsten according to claim 1, wherein: The subsequent tungsten filling process is repeated multiple times.

11. The method for filling through silicon vias with tungsten according to claim 1, wherein: The aspect ratio of the through silicon via is greater than or equal to 30:1.

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