Method for preventing oxidation of seed layer

Abstract

The invention belongs to the technical field of integrated circuits, and provides a seed layer anti-oxidation method. According to the method, the through hole is firstly formed in the substrate, then the seed layer is deposited on at least one surface of the substrate, then the ruthenium and / or tungsten anti-oxidation layer is deposited on the seed layer through ALD, then subsequent photoetching, microetching and electroplating are carried out, the ruthenium and / or tungsten anti-oxidation layer plays a role in protecting the seed layer, the seed layer can be prevented from being oxidized in the subsequent manufacturing process, and therefore the yield is improved. The thickness of the seed layer does not need to be increased to meet the electroplating requirement, the deposition efficiency of the seed layer is improved, and meanwhile the stability of the metal hole filling process is improved.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and more specifically, to a method for preventing oxidation of a seed layer. Background Technology

[0002] The key to the development and integration of chiplet heterogeneous integration technology lies in the fusion of multi-scale and multi-dimensional chip interconnects, thereby improving power efficiency and reducing latency, and providing smaller and higher-performance chips for high-performance computing, artificial intelligence and smart terminals.

[0003] Vertical interconnects of chips rely on technologies such as through-silicon vias (TSVs) or through-glass vias (TGVs), while horizontal interconnects are achieved through redistribution systems (RDLs). Among these, TGV technology offers advantages such as high frequency response, high insulation, and high thermal stability on glass substrates, making it a disruptive solution for 5G communications, optoelectronics, and advanced packaging.

[0004] Currently, physical vapor deposition (PVD) is commonly used to prepare the TGV seed layer (including the Cu layer). Then, a photoresist pattern needs to be fabricated on top of the TGV seed layer. This process can cause slight corrosion or oxidation (such as the developer solution during photolithography, and dilute H2O2 solution or dilute H2SO4 solution during micro-etching, all of which can easily lead to Cu layer oxidation). The Cu seed layer in the middle of the via is thinner, so the impact is more obvious. Moreover, the longer the exposure time to the atmospheric environment, the more severe the oxidation of the Cu seed layer. In particular, for TGV seed layers with high aspect ratios (generally 5:1-20:1), moisture is easily retained in the vias, which further worsens the oxidation of the Cu seed layer in the middle of the vias.

[0005] Generally, micro-etching is required before electroplating to remove the corroded or oxidized Cu seed layer on the surface of the through-hole sidewalls. The typical depth of micro-etching is [insert depth here]. Therefore, during TGV PVD seed layer deposition, the seed layer needs to be deposited to a sufficiently thick thickness to meet subsequent electroplating requirements. However, this affects the efficiency of TGV PVD seed layer deposition.

[0006] Therefore, there is an urgent need to develop a method for fabricating a seed layer on the substrate surface that can prevent the seed layer from being oxidized and corroded during the fabrication process. Summary of the Invention

[0007] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a method for preventing oxidation of the seed layer. After depositing the seed layer, this invention further deposits an antioxidant layer on the seed layer using atomic layer deposition (ALD), which effectively prevents the seed layer from being oxidized in subsequent processes, thus eliminating the need for an excessively thick seed layer and improving production efficiency.

[0008] The first aspect of the present invention provides a method for preventing oxidation of the seed layer.

[0009] Specifically, a method for preventing oxidation of the seed layer includes the following steps:

[0010] (1) Take a substrate with completed through holes, wherein the substrate with completed through holes includes a planar area and through holes;

[0011] (2) A seed layer is deposited on at least one surface of the substrate to obtain a substrate containing a seed layer;

[0012] (3) An antioxidant layer is deposited on the surface of the seed layer using atomic layer deposition (ALD), wherein the antioxidant layer is made of ruthenium (Ru) and / or tungsten (W);

[0013] (4) Photolithography, micro-etching and electroplating are performed on the surface of the antioxidant layer.

[0014] After completing the via opening and seed layer deposition, this invention further deposits a ruthenium (Ru) and / or tungsten (W) anti-oxidation layer on the seed layer surface using ALD deposition. Because ALD deposition has excellent step coverage capabilities, the anti-oxidation layer thickness is consistent between the center of the via and the substrate plane area. Furthermore, the film exhibits excellent density and few defects, effectively protecting the underlying seed layer from external moisture and oxygen interference. Therefore, in subsequent processes, the presence of the ruthenium (Ru) and / or tungsten (W) anti-oxidation layer prevents oxidation and corrosion of the seed layer, improving process stability. Thus, there is no need to increase the seed layer thickness to meet subsequent electroplating requirements, while also significantly improving the production efficiency of PVD deposition.

[0015] Preferably, in step (1), the substrate is a glass substrate.

[0016] Preferably, in step (1), the through hole is an X-shaped hole.

[0017] Preferably, in step (1), the depth-to-width ratio of the through hole is 5:1-20:1.

[0018] More preferably, in step (1), the depth-to-width ratio of the through hole is 5:1-15:1.

[0019] More preferably, in step (1), the depth-to-width ratio of the through hole is 8:1-10:1.

[0020] More preferably, in step (1), the depth-to-width ratio of the through hole is 10:1.

[0021] Preferably, in step (2), the seed layer is obtained by physical vapor deposition.

[0022] Preferably, in step (2), a seed layer is deposited on the upper and lower surfaces of the substrate using physical vapor deposition.

[0023] Preferably, in step (2), the seed layer includes a Ti layer and a Cu layer (the Ti layer and the Cu layer can be collectively referred to as the TiCu seed layer).

[0024] Preferably, in step (2), the substrate planar region contains, in sequence, a Ti layer, a Cu layer, a substrate, a Cu layer, and a Ti layer.

[0025] This invention utilizes a Ti layer as a barrier functional layer and a Cu layer as a conductive functional layer.

[0026] Preferably, the thickness of the Ti layer in the planar region of the substrate is 100-200 nm.

[0027] More preferably, the thickness of the Ti layer in the planar region of the substrate is 110-180 nm.

[0028] More preferably, the thickness of the Ti layer in the planar region of the substrate is 120-150 nm.

[0029] Preferably, the thickness of the Cu layer in the planar region of the substrate is 400-1600 nm.

[0030] More preferably, the thickness of the Cu layer in the planar region of the substrate is 500-1500 nm.

[0031] More preferably, the thickness of the Cu layer in the planar region of the substrate is 800-1000 nm.

[0032] Preferably, the thickness of the Ti layer within the via of the substrate is 1-10 nm.

[0033] More preferably, the thickness of the Ti layer within the through-hole of the substrate is 2-8 nm.

[0034] More preferably, the thickness of the Ti layer within the via of the substrate is 3-5 nm.

[0035] Preferably, the thickness of the Cu layer within the through-hole of the substrate is 25-55 nm.

[0036] More preferably, the thickness of the Cu layer within the through-hole of the substrate is 30-50 nm.

[0037] More preferably, the thickness of the Cu layer within the through-hole of the substrate is 40-45 nm.

[0038] Preferably, in step (3), the material of the antioxidant layer is ruthenium, and the precursor used in the atomic layer deposition (ALD) is Ru(EtCp)2 (diethylcyclopentadienyl ruthenium).

[0039] Preferably, in step (3), the reducing agent used in the atomic layer deposition (ALD) is H2.

[0040] Preferably, in step (3), the atomic layer deposition (ALD) is performed for 1-5 cycles.

[0041] More preferably, in step (3), the atomic layer deposition (ALD) is performed for 1-3 cycles.

[0042] More preferably, in step (3), the atomic layer deposition (ALD) is performed for 1-2 cycles.

[0043] Preferably, in step (3), the thickness of the antioxidant layer is 0.1-2 nm.

[0044] More preferably, in step (3), the thickness of the antioxidant layer is 0.1-1 nm.

[0045] More preferably, in step (3), the thickness of the antioxidant layer is 0.5-0.8 nm.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] The present invention first creates vias on a substrate, the substrate having created vias includes a planar area and vias. Then, a seed layer is deposited on at least one surface of the substrate to obtain a substrate containing a seed layer. Next, an ALD deposition is performed on the seed layer to deposit a ruthenium (Ru) and / or tungsten (W) antioxidant layer on the surface of the seed layer, wherein the antioxidant layer is made of ruthenium (Ru) and / or tungsten (W). Then, subsequent photolithography, micro-etching and electroplating are performed on the surface of the antioxidant layer. After completing the via opening and seed layer deposition, this invention further deposits a ruthenium (Ru) and / or tungsten (W) anti-oxidation layer on the seed layer surface using ALD deposition. Because ALD deposition has excellent step coverage capabilities, the anti-oxidation layer thickness is consistent between the center of the via and the substrate plane area. Furthermore, the film exhibits excellent density and few defects, effectively protecting the underlying seed layer from external moisture and oxygen interference. Since the ruthenium (Ru) and / or tungsten (W) anti-oxidation layer protects the seed layer, oxidation and corrosion of the seed layer are effectively prevented during subsequent photolithography, micro-etching, and electroplating processes. The seed layer thickness remains almost unchanged, significantly improving the stability of the metal via filling process. Moreover, it eliminates the need to thicken the seed layer to meet subsequent electroplating requirements, thus also greatly improving the production efficiency of PVD deposition. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the structure of the glass substrate with the through hole opened in step (1) of Embodiment 1 of the present invention;

[0049] Figure 2 This is a schematic diagram of the glass substrate with deposited Ti and Cu layers in step (2) of Embodiment 1 of the present invention;

[0050] Figure 3 This is a schematic diagram of the structure of the glass substrate with the anti-oxidation layer deposited in step (3) of Embodiment 1 of the present invention;

[0051] Figure 4 This is a schematic diagram of the structure of the glass substrate that has been electroplated with Cu in step (4) of Embodiment 1 of the present invention.

[0052] In the figure, 100 is the glass substrate, 200 is the through hole, 300 is the Ti layer, 400 is the Cu layer, 500 is the anti-oxidation layer, and 600 is the electroplated Cu. Detailed Implementation

[0053] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0054] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0055] Normally, the seed layer is thinner closer to the center of the through hole. Therefore, the "thickness of the seed layer inside the through hole" described in this invention refers to the thickness of the thinnest part of the seed layer at the center of the through hole.

[0056] Example 1

[0057] A method for preventing oxidation of the seed layer includes the following steps:

[0058] (1) Take a TGV glass substrate and make through holes. The through holes are “X” type holes with a depth-to-width ratio of 10:1. The substrate obtained after making the holes includes a planar area and through holes.

[0059] (2) Using TGV PVD sputtering equipment, Ti layer and Cu layer are deposited sequentially on both sides of the substrate obtained in step (1) (Ti layer and Cu layer are combined and called seed layer);

[0060] After PVD sputtering, the thickness of the Ti layer in the substrate planar region is 150 nm, the thickness of the Cu layer in the substrate planar region is 1000 nm, the thickness of the Ti layer in the middle of the via is about 5 nm, and the thickness of the Cu layer is about 45 nm; the seed layer becomes thinner towards the middle of the via.

[0061] (3) Place the substrate obtained in step (2) in an ALD (atomic layer deposition) chamber and deposit a Ru antioxidant layer, wherein Ru(EtCp)2 (diethylcyclopentadienylruthenium) is used as a metal precursor and H2 is used as a reducing agent. Deposit for 1-2 cycles until a Ru antioxidant layer with a thickness of about 0.5 nm is obtained.

[0062] In the ALD deposition process, the precursor is Ru(EtCp)2 and the reducing agent is H2. The precursor and the reducing agent react to generate Ru.

[0063] Ru(EtCp)2+H2→Ru.

[0064] (4) The substrate obtained in step (3) is subjected to subsequent photolithography, micro-etching and electroplating processes to obtain electroplated Cu;

[0065] In the photolithography process, the developing solution used is a tetramethylammonium hydroxide (TMAH) aqueous solution with a solute concentration of 2.38% (0.26N), a process temperature of 25℃, and a processing time of 90s.

[0066] In the micro-etching process, the components and their mass concentrations in the solution used are: 8% H2SO4 and 2% H2O2, the process temperature is 25℃, and the processing time is 20s.

[0067] The results showed that in Example 1, due to the presence of the Ru antioxidant layer, the thickness of the seed layer did not change during the micro-etching process, resulting in high process stability.

[0068] In step (1) of Example 1, the TGV glass substrate (100) after the through hole (200) is as follows: Figure 1 As shown, the TGV glass substrate (100) contains an "X"-shaped through hole (200).

[0069] In step (2) of Example 1, the TGV glass substrate (100) after PVD sputtering is as follows: Figure 2 As shown, Ti layer (300) and Cu layer (400) are deposited sequentially inside the via of the substrate, on the front substrate plane area, and on the back substrate plane area. Ti layer (300) and Cu layer (400) can be combined and referred to as seed layer (or TiCu seed layer). Moreover, the seed layer becomes thinner towards the center of the via.

[0070] In step (3) of Example 1, the TGV glass substrate (100) with ALD deposition completed is as follows: Figure 3 As shown, Ru antioxidant layers (500) are deposited inside the vias of the substrate, on the front substrate plane area, and on the back substrate plane area. ALD deposition continues until the thickness of the Ru antioxidant layer (500) is approximately 0.5 nm.

[0071] In step (4) of Example 1, the TGV glass substrate (100) after completing the subsequent photolithography, micro-etching, and electroplating processes is as follows: Figure 4 As shown, electroplated Cu (600) fills the through-hole (200), and electroplated Cu (600) is also deposited on the substrate planar area.

[0072] As can be seen from the above results, in Example 1 of the present invention, by depositing a Ru antioxidant layer, the film has excellent density and few defects, which can effectively protect the underlying seed layer from interference by external moisture and oxygen. Given the protective effect of the Ru antioxidant layer on the seed layer, the seed layer can be well prevented from being oxidized and corroded in subsequent photolithography and micro-etching processes, and the thickness of the seed layer hardly changes.

[0073] Example 2

[0074] Example 2 provides a seed layer anti-oxidation method, which differs from Example 1 in that the aspect ratio of the through-hole is replaced with 8:1, and the thickness of the seed layer deposited by PVD sputtering is different.

[0075] The above-mentioned seed layer anti-oxidation method includes the following steps:

[0076] (1) Take a TGV glass substrate and complete the through hole opening. The through hole is an "X" shaped hole with a depth-to-width ratio of 8:1. The substrate obtained after the opening includes a planar area and a through hole.

[0077] (2) Using TGV PVD sputtering equipment, Ti layer and Cu layer are deposited sequentially on both sides of the substrate obtained in step (1) (Ti layer and Cu layer are collectively referred to as seed layer);

[0078] After PVD sputtering, the thickness of the Ti layer in the substrate planar region is 100 nm, the thickness of the Cu layer in the substrate planar region is 800 nm, the thickness of the Ti layer in the middle of the via is about 3 nm, and the thickness of the Cu layer is about 40 nm; the seed layer becomes thinner towards the middle of the via.

[0079] (3) Place the substrate obtained in step (2) in an ALD (atomic layer deposition) chamber and deposit a Ru antioxidant layer, wherein Ru(EtCp)2 (diethylcyclopentadienylruthenium) is used as a metal precursor and H2 is used as a reducing agent. Deposit for 1-2 cycles until a Ru antioxidant layer with a thickness of about 0.5 nm is deposited.

[0080] In the ALD deposition process, the precursor is Ru(EtCp)2 and the reducing agent is H2. The precursor and the reducing agent react to generate Ru.

[0081] Ru(EtCp)2+H2→Ru.

[0082] (4) The substrate obtained in step (3) is subjected to subsequent photolithography, micro-etching and electroplating processes to obtain electroplated Cu.

[0083] In the photolithography process, the developing solution used is a tetramethylammonium hydroxide (TMAH) aqueous solution with a solute concentration of 2.38% (0.26N), a process temperature of 25℃, and a processing time of 90s.

[0084] In the micro-etching process, the components and their mass concentrations in the solution used are: 8% H2SO4 and 2% H2O2, the process temperature is 25℃, and the processing time is 20s.

[0085] The results showed that in Example 2, due to the presence of the Ru antioxidant layer, the thickness of the seed layer did not change during the micro-etching process, thus improving the process stability.

[0086] As can be seen from the above results, in Example 2 of the present invention, by depositing a Ru antioxidant layer, the film has excellent density and few defects, which can effectively protect the underlying seed layer from external moisture and oxygen interference. Since the Ru antioxidant layer plays a protective role for the seed layer, the seed layer can be well avoided from being oxidized and corroded in subsequent photolithography and micro-etching processes, and the thickness of the seed layer hardly changes.

[0087] Comparative Example 1 (without Ru antioxidant layer)

[0088] Comparative Example 1 provides a method for preparing a seed layer, which differs from Example 1 in that, in step (3), no Ru antioxidant layer is deposited.

[0089] A method for preparing a seed layer includes the following steps:

[0090] (1) Take a TGV glass substrate and complete the through hole opening. The substrate includes a planar area and through holes. The through holes are “X” shaped holes with a depth-to-width ratio of 10:1.

[0091] (2) Using TGV PVD sputtering equipment, Ti layer and Cu layer (Ti layer and Cu layer are collectively referred to as seed layer) are deposited sequentially on both sides of the substrate; wherein, the thickness of Ti layer in the substrate planar area is 150nm, the thickness of Cu layer in the substrate planar area is 1000nm, the seed layer becomes thinner towards the middle of the via, the thickness of Ti layer in the middle of the via is about 5nm, and the thickness of Cu layer is about 45nm.

[0092] (3) The substrate is subjected to subsequent photolithography, micro-etching and electroplating processes in sequence to obtain electroplated Cu.

[0093] The results showed that, after photolithography and micro-etching processes, the Cu layer in the middle of the through-hole in Comparative Example 1 was thinned by 6 nm.

[0094] In Comparative Example 1, the Cu layer was thinner and corroded due to the absence of a Ru antioxidant layer. This is because the chemicals used in the process of Comparative Example 1 (developer during photolithography, and dilute H2O2 and dilute H2SO4 solutions during micro-etching) corroded the Cu layer, causing it to be thinned.

[0095] Compared with Comparative Example 1, it can be seen that in Examples 1 and 2 of the present invention, the Ru anti-oxidation layer is deposited, which effectively protects the seed layer below from interference by external moisture and oxygen. Since the Ru anti-oxidation layer plays a protective role for the seed layer, the seed layer can be well prevented from being oxidized and corroded in subsequent photolithography and micro-etching processes. Therefore, the Cu film layer in the middle of the via remains unchanged.

Claims

1. A method for preventing oxidation of the seed layer, characterized in that, Includes the following steps: (1) Take a substrate with completed through holes, wherein the substrate with completed through holes includes a planar area and through holes; (2) A seed layer is deposited on at least one surface of the substrate to obtain a substrate containing a seed layer; (3) An antioxidant layer is deposited on the surface of the seed layer by atomic layer deposition, wherein the antioxidant layer is made of ruthenium and / or tungsten; (4) Photolithography, micro-etching and electroplating are performed on the surface of the antioxidant layer.

2. The method according to claim 1, characterized in that, In step (1), the substrate is a glass substrate.

3. The method according to claim 1, characterized in that, In step (1), the through hole is an X-shaped hole, and / or the depth-to-width ratio of the through hole is 5:1-20:

1.

4. The method according to claim 1, characterized in that, In step (2), the seed layer is obtained by physical vapor deposition.

5. The method according to claim 4, characterized in that, In step (2), a seed layer is deposited on the upper and lower surfaces of the substrate using physical vapor deposition.

6. The method according to claim 4, characterized in that, In step (2), the seed layer includes a Ti layer and a Cu layer.

7. The method according to claim 6, characterized in that, The thickness of the Ti layer in the planar region of the substrate is 100-200 nm, and / or the thickness of the Cu layer in the planar region of the substrate is 400-1600 nm.

8. The method according to claim 6, characterized in that, The thickness of the Ti layer in the through-hole of the substrate is 1-10 nm, and / or the thickness of the Cu layer in the through-hole of the substrate is 25-55 nm.

9. The method according to claim 1, characterized in that, In step (3), the material of the antioxidant layer is ruthenium, and the precursor used for the atomic layer deposition is Ru(EtCp)2.

10. The method according to claim 1, characterized in that, In step (3), the thickness of the antioxidant layer is 0.1-2 nm.

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