Pre-infiltration method for electrochemical electroplating

Abstract

The invention provides a pre-infiltration method for electrochemical electroplating, which comprises the following steps of: providing a wafer, forming a through hole in the wafer, and depositing a diffusion barrier layer and a seed crystal layer in the through hole in sequence; placing the wafer in a process chamber to carry out a hot baking process; the process chamber is vacuumized, so that residual gas in the process chamber is removed; ammonia gas is introduced into the process chamber, and the air pressure in the process chamber is adjusted to the pre-infiltration process pressure; and stopping introducing the ammonia gas, and introducing water vapor into the process chamber to pre-infiltrate the through hole. According to the pre-infiltration method provided by the invention, ammonia gas is taken as a medium, the property that the ammonia gas is extremely easy to dissolve in water is utilized, and the contradiction of high-vacuum-degree exhaust and easy vaporization of water under a high vacuum degree in the prior art is solved through the steps of high-vacuum-degree exhaust, ammonia gas replacement, water vapor dissolution and the like, so that the filling reliability and the product yield are remarkably improved, and the production cost is reduced. And the method is simple to operate and high in process compatibility.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a pre-wetting method for electrochemical electroplating. Background Technology

[0002] In TSV manufacturing, metallization filling is a critical step, typically using electrochemical plating (ECP) to fill copper into high aspect ratio vias. However, unlike the shallow trench filling in back-end circuitry (BEOL) damascus processes, TSV high aspect ratio vias exhibit capillary action, leaving residual gas at the bottom. This prevents the plating solution from reaching the bottom of the via, easily leading to voids or via openings after filling.

[0003] To overcome this problem, existing technologies typically introduce a hot baking and pre-wetting process before electroplating. The hot baking aims to remove the moisture and some of the gas adsorbed in the through-hole. The subsequent pre-wetting process introduces water vapor (H2O) into the chamber under controlled pressure, causing it to condense on the inner wall of the through-hole to form a water film, which replaces the residual gas and facilitates the entry of the subsequent electroplating solution.

[0004] However, the vacuum required for the process contradicts the physical properties of the pre-wetting medium (H2O): in order to remove the gas remaining at the bottom of the through hole as thoroughly as possible, the process chamber needs to be evacuated to the highest possible vacuum level (far below 20 torr); but when the chamber pressure is below 20 torr, the introduced H2O will vaporize rapidly and the pre-wetting effect cannot be achieved.

[0005] Therefore, the existing pre-wetting process is forced to maintain a low vacuum level of more than 20 torr, which means that the gas in the through hole cannot be completely removed. The residual gas is trapped during electroplating and is still the main cause of TSV electroplating filling defects (such as ViaOpen).

[0006] There is an urgent need for a new pre-wetting method that can completely eliminate gas inside the through-hole without causing water vaporization. Summary of the Invention

[0007] The purpose of this invention is to provide a solution to the problem of residual gas in the through-hole during pre-wetting.

[0008] To solve the above-mentioned technical problems, the present invention provides a pre-wetting method for electrochemical electroplating, comprising the following steps:

[0009] A wafer is provided, wherein a via is formed on the wafer, and a diffusion barrier layer and a seed layer are sequentially deposited in the via;

[0010] The wafer is placed in a process chamber for a thermal baking process;

[0011] The process chamber is evacuated to remove residual gas from the process chamber.

[0012] Ammonia gas is introduced into the process chamber, and the gas pressure in the process chamber is adjusted to the pre-wetting process pressure;

[0013] Stop the supply of ammonia gas and introduce water vapor into the process chamber to pre-wet the through holes.

[0014] Optionally, the pre-impregnation process pressure is 20~50 torr.

[0015] Optionally, the vacuum pressure for the process chamber is 10. -12 ~10 -5 torr.

[0016] Optionally, before introducing ammonia into the process chamber, the method further includes maintaining the pressure in the process chamber continuously for a first time.

[0017] Optionally, the first time is configured to be greater than 10 seconds.

[0018] Optionally, the ammonia flow rate is 10~500 sccm.

[0019] Optionally, the temperature of the heat treatment is 100~400℃.

[0020] Optionally, the diffusion barrier layer and seed layer can be deposited by one of the following methods: atomic layer deposition, chemical vapor deposition, and physical vapor deposition.

[0021] Optionally, the aspect ratio of the through hole is 5 to 25.

[0022] Optionally, after pre-wetting the vias, the method further includes performing an electrochemical plating process and an edge washing process on the wafer.

[0023] In summary, the present invention provides a pre-wetting method for electrochemical electroplating, comprising the following steps: providing a wafer having through-holes formed thereon, and sequentially depositing a diffusion barrier layer and a seed layer within the through-holes; placing the wafer in a process chamber for a thermal baking process; evacuating the process chamber to a vacuum to remove residual gas; introducing ammonia gas into the process chamber and adjusting the gas pressure within the process chamber to the pre-wetting process pressure; stopping the introduction of ammonia gas and introducing water vapor into the process chamber to pre-wet the through-holes.

[0024] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0025] During the impregnation process, a high vacuum is first maintained to expel the residual gas in the through hole, and then ammonia is introduced while maintaining the vacuum at a level where water will not vaporize. Taking advantage of the fact that ammonia is highly soluble in water, the pre-impregnation of the through hole is completed, which significantly improves the integrity and reliability of the electroplating filling.

[0026] The method provided by this invention only requires adding an ammonia input step and is easy to integrate into existing processes, with strong process compatibility. Attached Figure Description

[0027] Figure 1 A schematic flowchart of the pre-wetting method for electrochemical electroplating provided in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of the process cavity used in the embodiments of the present invention;

[0029] 100 - Process chamber; 110 - Base; 120 - Vacuum pipeline; 130 - First pipeline; 140 - Second pipeline.

[0030] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention. Detailed Implementation

[0031] To make the objectives, advantages, and features of the present invention clearer, the pre-wetting method for electrochemical electroplating provided by the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention. Furthermore, the structures shown in the drawings are often part of the actual structure. In particular, different proportions are sometimes used because different figures need to show different emphases. It should be understood that relative terms such as "above," "below," "top," and "bottom" shown in the drawings can be used to describe the relationships between various elements. These relative terms are intended to cover different orientations of elements other than those depicted in the drawings. For example, if the device is inverted relative to the view in the drawings, an element described as "above" another element will now be below that element. It should also be understood that, unless specifically stated or indicated, the terms "first," "second," "third," etc., in the specification are only used to distinguish the various components, elements, steps, etc., in the specification, and are not used to indicate logical or sequential relationships between the various components, elements, steps, etc.

[0032] In existing processes, the aspect ratio of the through holes is typically 5 to 25. Due to the narrow internal space and significant capillary effect of through holes with high aspect ratios, existing pre-wetting processes cannot completely remove bottom gas.

[0033] To solve the above problems, refer to Figure 1 As shown, this embodiment of the invention provides a pre-wetting method for electrochemical electroplating, comprising the following steps:

[0034] S1, a wafer is provided, on which a via is formed, and a diffusion barrier layer and a seed layer are sequentially deposited in the via;

[0035] S2, the wafer is placed in the process chamber for a thermal baking process;

[0036] S3, Evacuate the process chamber to a vacuum level to remove residual gas from the process chamber;

[0037] S4, Ammonia gas is introduced into the process chamber, and the gas pressure in the process chamber is adjusted to the pre-wetting process pressure;

[0038] S5, stop the ammonia gas supply and introduce water vapor into the process chamber to pre-wet the through hole.

[0039] The method provided in this invention uses ammonia as a transition medium. First, the process chamber is evacuated to a high vacuum to completely remove residual gas from the through-hole. Then, ammonia is introduced and the gas pressure in the process chamber is adjusted to a preset pre-wetting process pressure, so that the through-hole is filled with ammonia. The preset pre-wetting process pressure can prevent water from vaporizing due to excessive vacuum during the pre-wetting process. Taking advantage of the property that ammonia is highly soluble in water, the ammonia in the through-hole is completely dissolved in water during pre-wetting, and finally, the residual gas in the through-hole can be completely removed. This solves the contradiction between high vacuum exhaust during pre-wetting and the easy vaporization of water under high vacuum in the prior art, and significantly improves the filling reliability and product yield. In addition, the method provided in this invention is simple to operate and has strong process compatibility.

[0040] The following combination Figure 2 The pre-wetting method for electrochemical plating provided in the embodiments of the present invention will be further described.

[0041] First, step S1 is performed, providing a silicon wafer. A TSV (Through-Video) is formed on the silicon wafer using an etching process. The aspect ratio of the TSV can be 10. The etching process may include dry etching. Subsequently, the wafer is wet-cleaned to remove etching residues. Next, one of atomic layer deposition (ALD), chemical vapor deposition (CVD), or physical vapor deposition (PVD) is used to sequentially deposit a diffusion barrier layer and a seed layer on the inner wall of the TSV and the surface of the wafer. The diffusion barrier layer and the seed layer conformally cover the sidewalls and bottom wall of the TSV.

[0042] Then refer to Figure 2As shown, in step S2, the wafer is placed on the base 110 in the process chamber 100 provided in this embodiment of the invention, and a thermal baking process is performed on the wafer through the process chamber 100 to eliminate water molecules on the inner wall of the via and the surface of the wafer. Preferably, in the actual process flow, to prevent oxidation of the copper layer connected to the via, the temperature of the thermal baking process should be controlled at 100~400℃, such as 150℃, 200℃, 250℃, 300℃, etc.

[0043] refer to Figure 2 As shown, the process chamber 100 provided in this embodiment of the invention is connected to a vacuum pipeline 120. Then, step S3 is executed, whereby the process chamber 100 is evacuated to a vacuum state through the vacuum pipeline 120 connected to it. When in the vacuum state, the pressure inside the process chamber 100 is 10... -12 ~10 -5 Torr, at this vacuum level, the residual gas in the trench is removed through the vacuum pipe. Preferably, to ensure that there is no gas residue at the bottom of the through hole, the embodiment of the present invention further includes: maintaining the pressure in the process chamber 100 for a first time. Preferably, the first time is configured to be greater than 10 seconds, for example, the first time is configured to be 15 seconds, 20 seconds, or 30 seconds. In the embodiment of the present invention, the pressure in the process chamber 100 is maintained for 20 seconds.

[0044] Continue to refer to Figure 2 As shown, the process chamber 100 is also connected to a first pipeline 130 and a second pipeline 140. After completely removing residual gas, step S4 is executed, in which high-purity ammonia gas is introduced into the process chamber 100 through the first pipeline 130 connected to the process chamber 100. During this process, the vacuum pipeline 120 is continuously operated, and the gas pressure in the process chamber 100 is adjusted to the pre-wetting process pressure by the pumping rate of the vacuum pipeline 120, and this pressure is maintained in the process chamber 100. As a preferred embodiment, the ammonia gas flow rate is 10~500 sccm. After completing the above steps, the ammonia gas introduced into the process chamber 100 replaces the gas that was pumped out of the through hole under vacuum and occupies the entire space inside the through hole.

[0045] In the process environment provided in this embodiment of the invention, water will vaporize under a vacuum of less than 20 torr, which will prevent the pre-wetting process from proceeding normally. Therefore, as a preferred solution, in order to ensure the smooth progress of pre-wetting, the preset pre-wetting process pressure is 20 to 50 torr. Preferably, in this embodiment of the invention, the pre-wetting process pressure in the process chamber is 30 torr, so that the vacuum degree in the process chamber 100 is higher than the vaporization vacuum degree of liquid water under this process condition (20 torr), which can ensure that the water participating in the pre-wetting process in subsequent steps can remain in a liquid state.

[0046] Finally, step S5 is executed, closing the first pipeline 130 to stop the supply of ammonia gas to the process chamber 100. In this embodiment of the invention, water vapor is supplied to the process chamber 100 through the second pipeline 140 connected to the process chamber 100. The water vapor condenses on the wafer surface and forms a liquid water film. The liquid water enters the inner wall of the through hole under the capillary force of the through hole structure. Due to the property that ammonia gas is highly soluble in water, the ammonia gas in the through hole quickly dissolves in the liquid water to form ammonia water. The liquid water fully fills the through hole, so that the through hole achieves a pre-wetting state without gas residue.

[0047] After completing the above pre-wetting step, the wafer is filled with metal through an electrochemical electroplating process, and then the wafer is subjected to an edge washing process. Excess copper layer on the wafer edge and back is removed by chemical mechanical polishing or wet etching to ensure that the wafer surface is planarized to meet the requirements of subsequent process steps.

[0048] In summary, this invention provides a pre-wetting method for electrochemical electroplating, comprising the following steps: providing a wafer with through-holes formed thereon, and sequentially depositing a diffusion barrier layer and a seed layer within the through-holes; placing the wafer in a process chamber for a thermal baking process; evacuating the process chamber to a vacuum to remove residual gas; introducing ammonia into the process chamber and adjusting the pressure within the process chamber to the pre-wetting process pressure; stopping the ammonia introduction and introducing water vapor into the process chamber to pre-wet the through-holes. The pre-wetting method provided by this invention uses ammonia as a medium and leverages the high solubility of ammonia in water. Through steps such as high-vacuum venting, ammonia replacement, and water vapor dissolution, it resolves the contradiction between high-vacuum venting and the easy vaporization of water under high vacuum in existing technologies, significantly improving filling reliability and product yield. Furthermore, the method is simple to operate and has strong process compatibility.

[0049] It should be noted that the above description is only a description of the preferred embodiment of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the present invention.

Claims

1. A pre-wetting method for electrochemical electroplating, characterized in that, Includes the following steps: A wafer is provided, wherein a via is formed on the wafer, and a diffusion barrier layer and a seed layer are sequentially deposited in the via; The wafer is placed in a process chamber for a thermal baking process; The process chamber is evacuated to remove residual gas from the process chamber. Ammonia gas is introduced into the process chamber, and the gas pressure in the process chamber is adjusted to the pre-wetting process pressure; Stop the supply of ammonia gas and introduce water vapor into the process chamber to pre-wet the through holes.

2. The pre-wetting method for electrochemical electroplating according to claim 1, characterized in that, The pre-impregnation process pressure is 20~50 torr.

3. The pre-wetting method for electrochemical electroplating according to claim 1, characterized in that, The vacuum pressure for the process chamber is 10. -12 ~10 -5 torr.

4. The pre-wetting method for electrochemical electroplating according to claim 1, characterized in that, Before ammonia is introduced into the process chamber, the method further includes maintaining the pressure in the process chamber continuously for a first time.

5. The pre-wetting method for electrochemical electroplating according to claim 4, characterized in that, The first time is configured to be greater than 10 seconds.

6. The pre-wetting method for electrochemical electroplating according to claim 1, characterized in that, The ammonia flow rate is 10~500 sccm.

7. The pre-wetting method for electrochemical electroplating according to claim 1, characterized in that, The heat treatment temperature is 100~400℃.

8. The pre-wetting method for electrochemical electroplating according to claim 1, characterized in that, The deposition of the diffusion barrier layer and seed layer can be achieved by one of the following methods: atomic layer deposition, chemical vapor deposition, and physical vapor deposition.

9. The pre-wetting method for electrochemical electroplating according to claim 1, characterized in that, The aspect ratio of the through hole is 5 to 25.

10. The pre-wetting method for electrochemical electroplating according to claim 1, characterized in that, After pre-wetting the vias, the method further includes performing an electrochemical electroplating process and an edge washing process on the wafer.

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