Method for improving deposition uniformity of seed layer

Abstract

The invention belongs to the technical field of semiconductors, and provides a method for improving deposition uniformity of a seed layer. According to the method, the dotted pattern layers are designed in the through-hole-free areas of the upper surface and the lower surface of the substrate with the through holes, and then the seed layers are deposited, so that the film stress of the seed layers can be buffered, the warping of the substrate can be reduced (the warping can be as low as 0.4-0.8 mm), the through-hole substrate of the whole substrate is perpendicular to a substrate table, the step coverage rate of the seed layers in corner areas can be increased, and the yield of the substrate is increased. And the seed layer coverage rate difference of the middle area and the corner area of the substrate is small, so that the subsequent metal filling yield of the through hole is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and more specifically, to a method for improving the uniformity of seed layer deposition. Background Art

[0002] In the context of AI (artificial intelligence) with high computing power requirements and increasingly difficult front-end process miniaturization, advanced packaging technology with chiplet heterogeneous integration as the core integrates multi-scale and multi-dimensional chip interconnection, thereby improving power efficiency and reducing latency, and can provide smaller size and higher performance chips, becoming a key path and breakthrough in the development of integrated circuits. Typical advanced packaging technologies involved in chiplet heterogeneous integration include Through Silicon Via (TSV) and Through Glass Via (TGV).

[0003] Compared with planar interconnection, TSV and TGV can reduce the interconnection length and signal delay, reduce parasitic capacitance and inductance, achieve low power consumption and high-speed communication between chips, increase bandwidth and realize miniaturization of packaging. TGV seed layer deposition is the most important link in the through-hole metallization process. During the sputtering process of the seed layer, as the deposition thickness increases, due to the lattice mismatch and thermal expansion coefficient mismatch between the seed layer (Ti layer and Cu layer) and the glass substrate (Glass), there will be huge stress in the seed layer. The thin films of the Ti layer and Cu layer are characterized by tensile stress. These stresses are released during the deposition process, which will promote the expansion of cracks at the film-substrate interface, causing the film to warp quickly on all four sides or even fall off. There is an angle offset between the through hole in the warped area of ​​the substrate and the direction of the electric field. In this way, the sputtered Cu atoms or Cu ions are difficult to deposit inside the through hole, and the film uniformity is poor, resulting in the inability to form an effective connection between the metal film inside and outside the through hole, affecting the TGV yield. As the substrate size increases and the deposition thickness increases, when the substrate size reaches 200-300mm, slight warping may occur during high-temperature processing and multi-layer packaging structure; when the substrate size is greater than 300mm, the risk of warping is even greater, especially the stress distribution in the middle area is uneven, resulting in a high risk of warping.

[0004] Therefore, there is an urgent need to develop a method that can reduce film stress, reduce warping, and improve the uniformity of seed layer deposition. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method for improving the uniformity of seed layer deposition. The present invention sets a dot pattern layer on both sides of the substrate before deposition, so that the warping degree of the substrate during the deposition process is reduced (warping 0.4-0.8mm), the difference in seed layer coverage between the middle area and the corner area of ​​the substrate is small, the uniformity of seed layer coverage is improved, and thus the through-hole filling yield is improved.

[0006] A first aspect of the present invention provides a method for improving the uniformity of seed layer deposition.

[0007] Specifically, a method for improving the uniformity of seed layer deposition includes the following steps:

[0008] (1) Take a substrate having a through hole;

[0009] (2) providing dot pattern layers on the non-through-hole regions of the upper and lower surfaces of the substrate having through-holes to obtain a substrate having dot pattern layers on both sides;

[0010] (3) depositing a seed layer on one of the surfaces of the substrate having the dot pattern layer on both sides.

[0011] The present invention sets a dot pattern layer on the surface of the substrate with through holes. In the subsequent deposition process, the dot pattern layer can absorb and disperse stress through its own flexibility and thermal expansion characteristics, thereby reducing the warping of the substrate, weakening the stress generated by the large difference in thermal expansion coefficient (CTE) between the substrate and the seed layer, and improving the uniformity of seed layer coverage. In addition, the dot pattern layer is set on both surfaces of the substrate to provide support and balance stress, so as to achieve symmetrical stress distribution and reduce warping.

[0012] Preferably, the dot patterns on the upper and lower surfaces are precisely aligned to ensure uniform stress distribution on both sides and meet the requirements of high precision and high flatness.

[0013] Preferably, in step (1), the length, width and height of the substrate are 450-520 mm, 460-525 mm and 0.1-2 mm, respectively.

[0014] Further preferably, in step (1), the length, width and height of the substrate are 500-520 mm, 505-525 mm and 0.3-1.5 mm, respectively.

[0015] More preferably, in step (1), the length, width and height of the substrate are 510-520 mm, 515-525 mm and 0.5-1.5 mm, respectively.

[0016] Preferably, in step (1), the substrate is one of a glass substrate, a silicon substrate, a copper substrate, a ceramic substrate, and an organic substrate.

[0017] Preferably, in step (1), the substrate containing the through-holes is cleaned to remove organic and inorganic pollutants on the surface to ensure the adhesion of the subsequent dot pattern layer.

[0018] Preferably, in step (1), the aspect ratio of the through hole is (5-10):1.

[0019] Further preferably, in step (1), the aspect ratio of the through hole is (6-8):1.

[0020] Preferably, in step (2), the material of the dot pattern layer is an organic polymer and / or an inorganic substance.

[0021] Further preferably, in step (2), the material of the dot pattern layer is an organic polymer.

[0022] Preferably, the organic polymer is at least one of polyimide (PI), epoxy resin, acrylic resin, and polystyrene.

[0023] Preferably, the inorganic substance is BaTiO 3 、SiO 2 、Si 3 N 4 , SiC, graphene, and ZnO.

[0024] Preferably, in step (2), the total area of ​​the dot pattern layer accounts for 10%-30% of the total area of ​​the substrate, and / or the diameter of the dot pattern layer is 50-500 μm, and / or the thickness of the dot pattern layer is 10-50 μm. If the total area of ​​the dot pattern layer accounts for too much, it will increase the complexity and cost of the process and may also affect the flatness of the substrate surface; but if the total area of ​​the dot pattern layer accounts for too little, the pressure cannot be fully dispersed, resulting in an insignificant effect of alleviating warpage and failure to achieve the expected pressure balance.

[0025] Further preferably, in step (2), the substrate is a glass substrate, the material of the dot pattern layer is polyimide, and the total area of ​​the dot pattern layer accounts for 15%-20% of the total area of ​​the substrate. When the substrate is a glass substrate and the material of the dot pattern layer is polyimide, the effect of relieving stress warping is best when the total area of ​​the dot pattern layer reaches 15%-20%.

[0026] Preferably, in step (2), the size of each dot pattern in the dot pattern layer is kept consistent. The size of the pattern is kept consistent, which can better maintain a good effect of relieving stress warpage and reduce the impact of the pattern design on other packaging functional layers in subsequent use.

[0027] Preferably, in step (2), the shape of the dot pattern layer is one or more of a circle, a square, a rectangle, an ellipse, a triangle, an annular dot, and a multi-layer dot. The shape design of the pattern needs to take into account the actual effect of processability and stress relief. For example, an ellipse has two squares to provide different stress dispersion effects, and the stress distribution can be optimized by adjusting the ratio and direction of the major and minor axes. An annular dot pattern can provide additional stress dispersion and support in the central area. A multi-layer dot pattern is a pattern in which multiple layers of dots of different shapes and sizes are coated on the surface of the substrate to provide a more complex stress dispersion effect.

[0028] Preferably, in step (2), the seed layer comprises a stacked Ti layer and a Cu layer, the Ti layer is in contact with the substrate, and the Cu layer covers the surface of the Ti layer. The main function of the Ti layer is to improve the adhesion between the Cu layer and the substrate to prevent it from falling off.

[0029] Preferably, in step (3), before the deposition, the substrate containing the dot pattern layer on both sides is subjected to pre-cleaning and roughening treatment in sequence. The purpose of pre-cleaning is to thoroughly remove dirt, debris and other contaminants attached to the surface of the substrate and inside the through hole, so as to improve the quality and adhesion of the subsequent coating. The purpose of roughening treatment is to improve the microstructure of the substrate surface, increase the roughness, and further increase the adhesion of the film.

[0030] Preferably, the roughening treatment is performed by anodizing or plasma etching.

[0031] Preferably, in step (3), the deposition method is one of physical vapor deposition, chemical vapor deposition and atomic layer deposition.

[0032] Further preferably, in step (3), the deposition method is physical vapor deposition (PVD).

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] The present invention first sets a dot pattern layer in the non-through-hole area of ​​the upper and lower surfaces of the substrate containing through-holes, and then deposits a seed layer on one of the surfaces of the substrate. The dot pattern layer can buffer the film stress of the seed layer and reduce the warping of the substrate (the warping can be as low as 0.4-0.8mm), so that the through-hole substrate of the entire substrate is perpendicular to the substrate stage, which helps to improve the step coverage of the seed layer in the corner area. The difference in seed layer coverage between the middle area and the corner area of ​​the substrate is small, thereby improving the metal filling yield of the subsequent through-holes. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The glass substrate having the TGV through hole in step (1) of Example 1 of the present invention;

[0036] Figure 2 The cross-sectional view and top view of the substrate having dot pattern layers on both sides in step (2) of Example 1 of the present invention;

[0037] Figure 3 The glass substrate containing the Ti layer in step (3) of Example 1 of the present invention;

[0038] Figure 4 The glass substrate comprising a Ti layer and a Cu layer in step (3) of Example 1 of the present invention;

[0039] Figure 5 It is a diagram of substrate warpage values, a diagram of seed layer coverage, and a schematic diagram of the division of various regions of the substrate for Examples 1-5 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0040] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0041] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0042] Example 1

[0043] A method for improving the uniformity of seed layer deposition comprises the following steps:

[0044] (1) Take the glass substrate (glass) on which the TGV through-holes have been opened Figure 1 ), wherein the length, width and height are 510mm*515mm*0.5mm, and the through hole (X-shaped through hole) has a depth-to-width ratio of 6:1, and the glass substrate is cleaned;

[0045] (2) Customizing a mask according to the pattern of the dot pattern layer to ensure the uniformity and dot position of the pattern, then spin coating PI on the non-through-hole areas on the upper and lower surfaces of the glass substrate containing through holes, and heat curing at 300°C to improve the mechanical strength and chemical stability of the organic matter, removing the mask to obtain a dot pattern layer, wherein the dot pattern is a circle with a diameter of 50 μm, and obtaining a substrate ( Figure 2 );

[0046] (3) Pre-cleaning the substrate containing the dot pattern layer on both sides; then treating the glass substrate by plasma etching; then placing the glass substrate in a vacuum environment of a Ti chamber (the metal target material is Ti), coating the upper surface of the glass substrate by PVD, and after completion, obtaining a glass substrate containing a Ti layer ( Figure 3); finally, the glass substrate is transferred to the Cu chamber (the metal target is Cu), and a Cu layer is obtained by PVD coating on the surface of the Ti layer, and finally a glass substrate ( Figure 4 ).

[0047] Example 2

[0048] A method for improving uniformity of seed layer deposition, which differs from Example 1 in that the dot pattern is a circle with a diameter of 100 μm, and the material PI is replaced by epoxy resin.

[0049] Example 3

[0050] A method for improving uniformity of seed layer deposition is different from Example 1 in that the dot pattern is a circle with a diameter of 100 μm.

[0051] Example 4

[0052] A method for improving uniformity of seed layer deposition, which differs from Example 1 in that the circular shapes of the dot pattern layers on both sides are replaced with square shapes, and the side length of the square is 35 μm.

[0053] Example 5

[0054] A method for improving the uniformity of seed layer deposition, which is different from Example 4 in that the material of the dot pattern layer on both sides is replaced with BaTiO 3 .

[0055] Comparative Example 1 (no double-sided dot pattern layer)

[0056] A seed layer method, which differs from Example 1 in that step (2) is not performed.

[0057] Product effect testing

[0058] The substrate warping conditions of each embodiment and comparative example were detected respectively, and the seed layer coverage (calculated according to the following formula (1)) of different areas of the substrate on which the seed layer deposition was completed (the substrate is divided into: corner area, edge area and middle area. The present invention adopts a substrate with a size of 510mm*515mm, the corner area is 51mm*51mm, the edge area is a rectangular strip with a width of 51mm, and the middle area is 408mm*413mm.) was detected. The results are as follows: Figure 5 (a) Figure 5 (b) shows the schematic diagram of the division of each area of ​​the substrate. Figure 5 (c) as shown.

[0059] Seed layer coverage (%) = film thickness at the bottom of the through hole ÷ film thickness on the plane outside the through hole × 100% Formula (1).

[0060] The results show that during the deposition process of Example 1, the substrate warpage is small, only 0.5 mm, the seed layer coverage in the middle area of ​​the test substrate is 4.6%, and the seed layer coverage in the corner area is 4.1%.

[0061] During the deposition process of Example 2, the substrate warpage was small, only 0.4 mm, the seed layer coverage in the middle of the test substrate was 4.5%, and the seed layer coverage in the corner area was 4.3%.

[0062] During the deposition process of Example 3, the substrate warpage was small, only 0.4 mm, the seed layer coverage in the middle of the test substrate was 4.6%, and the seed layer coverage in the corner area was 4.2%.

[0063] During the deposition process of Example 4, the substrate warpage was small, only 0.7 mm, the seed layer coverage in the middle of the test substrate was 4.5%, and the seed layer coverage in the corner area was 3.6%.

[0064] During the deposition process of Example 5, the substrate warpage was small, only 0.8 mm, the seed layer coverage in the middle of the test substrate was 4.4%, and the seed layer coverage in the corner area was 3.2%. Comparison between Example 4 and Example 5 shows that the improvement effect of the organic polymer dot pattern layer is better than that of the inorganic dot pattern layer.

[0065] The results of the above embodiments 1-5 show that the coverage uniformity of different regions of the substrate is significantly improved, which is conducive to the subsequent complete filling of the TGV through-hole metal.

[0066] In Comparative Example 1, no dot pattern layer was set, and the seed layer was directly deposited on the glass substrate containing the TGV through hole. During the deposition process, due to the stress of the seed layer film, the substrate was severely warped, with the warping reaching 1.5 mm. The seed layer coverage in the middle area was 4.5%, while the seed layer coverage in the corner area was 2.1%, that is, the seed layer thickness in the deep through hole of the corner area was thin, resulting in the inability to form effective connectivity.

Claims

1. A method for improving the uniformity of seed layer deposition, characterized in that: The steps include: (1) Take a substrate having a through hole; (2) providing dot pattern layers on the non-through-hole regions of the upper and lower surfaces of the substrate having through-holes to obtain a substrate having dot pattern layers on both sides; (3) depositing a seed layer on one of the surfaces of the substrate having the dot pattern layer on both sides.

2. The method according to claim 1, characterized in that In step (1), the length, width and height of the substrate are 450-520 mm, 460-525 mm and 0.1-2 mm respectively.

3. The method according to claim 1, characterized in that In step (1), the substrate is one of a glass substrate, a silicon substrate, a copper substrate, a ceramic substrate, and an organic substrate.

4. The method according to claim 1, characterized in that: In step (2), the material of the dot pattern layer is organic polymer and / or inorganic substance.

5. The method according to claim 4, characterized in that The organic polymer is at least one of polyimide, epoxy resin, acrylic resin and polystyrene.

6. The method according to claim 4, characterized in that The inorganic substance is at least one of BaTiO3, SiO2, Si3N4, SiC, graphene, and ZnO.

7. The method according to claim 1, characterized in that In step (2), the total area of ​​the dot pattern layer accounts for 10%-30% of the total area of ​​the substrate, and / or the diameter of the dot pattern layer is 50-500 μm, and / or the thickness of the dot pattern layer is 10-50 μm.

8. The method according to claim 1, characterized in that In step (2), the shape of the dot pattern layer is one or more of a circle, a square, a rectangle, an ellipse, a triangle, a ring-shaped dot, and a multi-layer dot.

9. The method according to claim 1, characterized in that: In step (2), the seed layer includes a Ti layer and a Cu layer which are stacked, the Ti layer is in contact with the substrate, and the Cu layer covers the surface of the Ti layer.

10. The method according to claim 1, characterized in that In step (3), the deposition method is one of physical vapor deposition, chemical vapor deposition and atomic layer deposition.

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