A method for improving adhesion of seed layers

Abstract

The present application belongs to the technical field of integrated circuit, and provides a method for improving the adhesion of seed layer. In the present application, a first Ti layer is deposited on a substrate with an opening, then the substrate is bombarded by plasma, atoms of the part of Ti layer in contact with the substrate are embedded into the substrate to form an alloy layer as an adhesion enhancement layer, then a TiCu seed layer is deposited, thus the adhesion between the substrate and the TiCu seed layer and between the sidewall of the via and the TiCu seed layer can be improved, then a plating photoresist layer is made on the surface of the Cu layer, a Cu layer is deposited at the gap of the pattern of the plating photoresist layer to form a Cu column, the plating photoresist layer is stripped, the Cu layer, the TiCu seed layer, the first Ti layer and the alloy layer at the original position of the plating photoresist layer are etched and removed, and finally the seed layer is completed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of integrated circuits, and more particularly, to a method for improving seed layer adhesion. BACKGROUND

[0002] The key to the development and integration of chiplet heterogeneous integration technology is to realize multi-scale and multi-dimensional chip interconnection, so as to improve power efficiency and reduce delay, and provide smaller size and higher performance chips for high-performance computing, artificial intelligence and smart terminals. The vertical interconnection of the chip depends on technologies such as through silicon via (TSV) or through glass via (TGV), and the horizontal interconnection is realized through the redistribution layer (RDL) technology.

[0003] The metal filling of TGV via and TSV via is generally to first deposit a Cu seed layer on the substrate and the via sidewall by using a magnetron sputtering method, and then electroplate Cu to fill the via with metal Cu. However, when depositing a TGV substrate with a high aspect ratio (the aspect ratio is generally 3:1-20:1), the energy of the sputtered metal particles reaching the sidewall is weakened, resulting in poor adhesion between the seed layer and the deep hole sidewall, and there is a risk of peeling.

[0004] Therefore, it is urgent to develop a method for improving the adhesion of the seed layer, which can improve the adhesion between the seed layer and the substrate and reduce the peeling risk between the seed layer and the deep hole sidewall even when depositing a TGV substrate with a high aspect ratio. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a method for improving the adhesion of the seed layer. The method provided by the present application can improve the adhesion between the seed layer and the substrate and the adhesion between the seed layer and the deep hole sidewall, and can reduce the peeling risk between the seed layer and the deep hole sidewall even when depositing a TGV substrate with a high aspect ratio.

[0006] The first aspect of the present application provides a method for improving the adhesion of the seed layer.

[0007] Specifically, a method for improving the adhesion of the seed layer comprises the following steps:

[0008] (1) Take a substrate and open a via;

[0009] (2) Deposit a first Ti layer on the surface of the substrate;

[0010] (3) Perform plasma treatment on the surface of the first Ti layer to form an alloy layer;

[0011] (4) Deposit a TiCu seed layer on the surface of the first Ti layer;

[0012] (5) making an electroplating photoresist layer on the surface of the TiCu seed layer;

[0013] (6) then electroplating Cu at the gap of the pattern of the electroplating photoresist layer, stopping the deposition when the through hole is filled with Cu and the pattern of the electroplating photoresist layer is not deposited with Cu, forming a Cu column;

[0014] (7) stripping the electroplating photoresist layer;

[0015] (8) etching in etching solution, stopping the etching when the Cu layer, the TiCu seed layer, the first Ti layer and the alloy layer at the position originally occupied by the electroplating photoresist layer are etched away and the Cu column is retained;

[0016] In step (3), the plasma treatment is Xe plasma treatment or Kr plasma treatment.

[0017] In the present application, a first Ti layer is deposited on a through hole substrate, and then Xe plasma treatment or Kr plasma treatment is performed. Since the radius of Xe atom or Kr atom is relatively large, the energy when bombarding onto the Ti layer above is large, which can embed the atoms of the part of the first Ti layer in contact with the substrate into the substrate, forming an alloy layer (TiSi alloy layer). Similar to the principle of using a hammer to drive a wooden pile into the ground, the alloy layer can be used as a connecting layer and a buffer layer between the seed layer and the substrate, thereby significantly improving the adhesion between the seed layer and the substrate, and between the seed layer and the sidewall of the through hole (especially the sidewall of a deep hole with a depth-to-width ratio of 3:3-20:1).

[0018] Preferably, in step (1), the substrate is a glass substrate.

[0019] Preferably, in step (1), the thickness of the substrate is 0.1-1 mm.

[0020] Further preferably, in step (1), the thickness of the substrate is 0.4-0.6 mm.

[0021] Preferably, in step (1), the aperture of the through hole is 10-200 μm, and / or the depth-to-width ratio of the through hole is 3:1-20:1.

[0022] Further preferably, in step (1), the aperture of the through hole is 80-100 μm, and / or the depth-to-width ratio of the through hole is 5:1-10:1.

[0023] Preferably, in step (2), the thickness of the first Ti layer is 5-20 nm.

[0024] Further preferably, in step (2), the thickness of the first Ti layer is 10-15 nm.

[0025] The thickness of the Ti layer is controlled to ensure that the energy of the bombardment can be transmitted to the Ti in contact with the substrate and embedded into the substrate. At the same time, when the plasma is bombarded, part of the Ti atoms are bombarded out, causing the thickness of the Ti layer to become thin and the local film layer to be discontinuous. If Cu is directly deposited on the discontinuous Ti film, the adhesion of the Cu layer will be poor. Therefore, a second Ti layer needs to be deposited again to ensure the continuity of the Ti barrier layer and the adhesion of the subsequently deposited Cu layer.

[0026] Preferably, in step (3), the thickness of the alloy layer is 1-10 nm.

[0027] Further preferably, in step (3), the thickness of the alloy layer is 1-5 nm.

[0028] Preferably, in step (3), the energy of the plasma treatment is 100-2000 eV.

[0029] Further preferably, in step (3), the energy of the plasma treatment is 500-1000 eV.

[0030] Preferably, in step (4), the TiCu seed layer is a Ti layer and a Cu layer deposited in sequence. The Ti layer and the Cu layer serve as a metal seed layer. Since there is an alloy layer buffer between the substrate and the TiCu seed layer, the adhesion between the substrate and the TiCu seed layer can be greatly improved.

[0031] Preferably, the thickness of the second Ti layer is 50-150 nm, and / or the thickness of the Cu layer is 250-350 nm.

[0032] Further preferably, the thickness of the second Ti layer is 100-150 nm, and / or the thickness of the Cu layer is 300-350 nm.

[0033] Preferably, in step (8), the Cu layer, the TiCu seed layer, and the first Ti layer are removed by etching in an etching solution, and then the alloy layer is removed by over-etching. In this way, the impedance of the surface of the substrate (the impedance between two Cu pillars of adjacent substrates is required to be >100 MΩ) can be improved, and signal interference between the two Cu pillars of adjacent vias can be avoided.

[0034] Preferably, in step (8), the etching solution is a hydrogen peroxide solution.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] The application is to deposit a first Ti layer on the substrate with a through hole, then bombard the substrate with plasma, embed the atoms of the first Ti layer in contact with the substrate into the substrate to form an alloy layer as a connecting layer, adhesion enhancement layer and buffer layer, then deposit a TiCu seed layer, which can greatly improve the adhesion between the substrate and the TiCu seed layer, the through hole sidewall and the TiCu seed layer, continue to make a plating photoresist layer on the surface of the Cu layer, deposit a Cu layer at the gap between the patterns on the surface of the plating photoresist layer, and the patterns on the surface of the plating photoresist layer do not deposit a Cu layer, and fill the through hole with Cu to form a Cu column, then strip the plating photoresist layer, etch the Cu layer, TiCu seed layer, first Ti layer and alloy layer on the original position of the plating photoresist layer, and finally complete the preparation of the seed layer on the substrate with a through hole, which not only greatly improves the adhesion between the seed layer and the substrate, the seed layer and the deep hole sidewall, but also reduces the risk of peeling between the seed layer and the deep hole sidewall, and can also make a seed layer with strong adhesion on the surface of the substrate with a high aspect ratio through hole. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The structure diagram of the substrate with a through hole completed by step (1) of embodiment 1 of the application is shown in the figure.

[0038] Figure 2 The schematic diagram of depositing a first Ti layer on the surface of the substrate in step (2) of embodiment 1 of the application is shown in the figure.

[0039] Figure 3 The schematic diagram of Xe plasma treatment of the Ti layer in step (3) of embodiment 1 of the application is shown in the figure.

[0040] Figure 4 The schematic diagram of depositing a TiCu seed layer in step (4) of embodiment 1 of the application is shown in the figure.

[0041] Figure 5 The schematic diagram of making a PR pattern in step (5) of embodiment 1 of the application is shown in the figure.

[0042] Figure 6 The schematic diagram of depositing a Cu layer in step (6) of embodiment 1 of the application is shown in the figure.

[0043] Figure 7 The schematic diagram of stripping the PR pattern in step (7) of embodiment 1 of the application is shown in the figure.

[0044] Figure 8 The schematic diagram of the substrate after removing the Cu layer, TiCu seed layer, first Ti layer and alloy layer on the original position of the plating photoresist layer in step (8) of embodiment 1 of the application is shown in the figure. DETAILED DESCRIPTION

[0045] In order to make the skilled in the art more clearly understand the technical solutions described in the present application, the following examples are listed for illustration. It should be noted that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0046] The raw materials, reagents or devices used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels, or can be obtained by existing known methods.

[0047] Example 1

[0048] A method for improving the adhesion of a seed layer, comprising the following steps:

[0049] (1) Take a substrate with a thickness of 0.4 mm, open a hole with a diameter of 80 μm and a depth-to-width ratio of 8 to obtain a TGV substrate with glass open holes completed; the substrate completed in step (1) is shown in Figure 1 , wherein Figure 1 A is a cross-sectional view of the glass substrate with open holes completed, Figure 1 B is a top view of the glass substrate with open holes completed;

[0050] (2) Deposit a first Ti layer with a thickness of 10 nm on the surface of the substrate; the substrate completed in step (2) is shown in Figure 2 ; and

[0051] (3) Perform Xe plasma treatment on the surface of the first Ti layer with an energy of 500 eV to form a TiSi alloy layer with a thickness of 1-5 nm; the substrate completed in step (3) is shown in Figure 3 ; and

[0052] (4) Deposit a second Ti layer with a thickness of 100 nm and a Cu layer with a thickness of 300 nm on the surface of the alloy layer in sequence as a metal seed layer (TiCu seed layer); the substrate completed in step (4) is shown in Figure 4 ; and

[0053] (5) Form a plating photoresist layer pattern (PR pattern) on the surface of the Cu layer by coating, exposure and development; the substrate completed in step (5) is shown in Figure 5 ; and

[0054] (6) Then, electroplate the Cu layer at the gap of the pattern of the plating photoresist layer (the place where the pattern of the plating photoresist layer is not electroplated with Cu), fill the TGV through hole with Cu, and form a Cu column; the substrate completed in step (6) is shown in Figure 6 ; and

[0055] (7) Strip the PR pattern by stripping liquid; the substrate completed in step (7) is shown in Figure 7 ; and

[0056] (8) Put the substrate into F-containing H2O2 etching solution, etch the Cu layer, TiCu seed layer and first Ti layer on the substrate above the position where the photoresist layer is located, then continue to etch the substrate until the TiSi alloy layer is also completely etched, and at this time the Cu column is reserved, then stop etching, and the impedance between the two adjacent Cu columns is > 100 MΩ. The substrate after step (8) is shown in Figure 8

[0057] Example 2

[0058] A method for improving the adhesion of the seed layer, which is different from example 1 is that the Xe plasma treatment in step (3) is replaced by Kr plasma treatment.

[0059] Comparative Example 1

[0060] This comparative example provides a method for making a seed layer, which is different from example 1 in that the Xe plasma treatment in step (3) is not performed.

[0061] Product effect test

[0062] 1. Test method

[0063] Tension test: It is a conventional test method in the industry, and the specific test method is as follows: the products finally prepared in each of the above examples and comparative examples are used as test substrates, the test spindles are respectively attached to the test substrates on which the seed layer film is deposited, and the film is cut along the circle where the spindle and the film contact. Then, the test spindle is stretched in the direction perpendicular to the substrate until the test spindle and the test substrate are separated, at which time the tension value converted into the tension per unit area is the adhesion value between the seed layer and the substrate.

[0064] 2. Test results

[0065] Table 1: Tension test results of each example and comparative example

[0066] Pull force (N / mm) Example 1 1.1 Example 2 1.0 Comparative Example 1 0.3

[0067] As can be seen from the above table, in the tension test, the tension of example 1 can reach 1.0-1.1 N / mm; while the tension of comparative example 1 is only 0.3 N / mm, which indicates that the method of the present application significantly improves the adhesion between the seed layer and the substrate.​

Claims

1. A method for improving the adhesion of a seed layer, characterized in that, Includes the following steps: (1) Take the substrate and make through holes; (2) A first Ti layer is deposited on the substrate surface; (3) Perform plasma treatment on the surface of the first Ti layer to form a TiSi layer; (4) Deposit a TiCu seed layer on the surface of the first Ti layer; (5) An electroplated photoresist layer is fabricated on the surface of the TiCu seed layer; (6) Next, Cu is electroplated and deposited in the gaps of the pattern of the electroplated photoresist layer until the through holes are filled with Cu and the pattern of the electroplated photoresist layer is not deposited with Cu, then the deposition is stopped to form Cu pillars. (7) Peel off the electroplated photoresist layer; (8) Place it in the etching solution for etching. When the Cu layer, TiCu seed layer, first Ti layer and TiSi layer at the original location of the electroplated photoresist are etched away and the Cu pillar is retained, stop etching. In step (3), the plasma treatment is either Xe plasma treatment or Kr plasma treatment; In step (4), the TiCu seed layer includes a second Ti layer and a Cu 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 thickness of the substrate is 0.1-1 mm.

4. The method according to claim 1, characterized in that, In step (1), the diameter of the through hole is 10-200μm, and / or the depth-to-width ratio of the through hole is 3:1-20:

1.

5. The method according to claim 1, characterized in that, In step (2), the thickness of the first Ti layer is 5-20 nm.

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

7. The method according to claim 1, characterized in that, In step (3), the energy of the plasma processing is 100-2000 eV.

8. The method according to claim 1, characterized in that, The thickness of the second Ti layer is 50-150 nm, and / or the thickness of the Cu layer is 250-350 nm.

9. The method according to claim 1, characterized in that, In step (8), the Cu layer, TiCu seed layer and first Ti layer are first removed by etching in the etching solution, and then the TiSi layer is removed by etching.

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