Copper-copper bonding method and bonding structure

Abstract

The invention discloses a copper-copper bonding method and a bonding structure, and relates to the technical field of microelectronics. The bonding method comprises the following steps: growing an insulating layer on the surface of a substrate layer through a plasma enhanced chemical vapor deposition method; spin-coating a substrate layer on the surface of the insulating layer, and sequentially performing exposure treatment, developing treatment and curing treatment to respectively form a concave structure with an inclined side wall and a convex point structure; and respectively depositing an adhesion layer and a bonding layer on the concave structure and the convex point structure through a stripping process and physical vapor deposition to form a convex point bonding structure and a concave bonding structure with inclined side walls. By means of the inclined side wall, high-precision alignment can be spontaneously achieved in the approaching process of the concave body and the convex body.

Description

Technical Field

[0001] The present invention relates to the field of microelectronics technology, and in particular to a copper-copper bonding method and bonding structure. Background Art

[0002] With the rapid development of technologies such as autonomous driving, cloud computing, and artificial intelligence, the demand for high-performance chips is becoming increasingly urgent. However, as transistor feature sizes approach physical limits, improving chip performance through traditional scaling alone is becoming increasingly difficult. Furthermore, the increasing density and variety of devices on chips place higher and more stringent demands on manufacturing equipment and processes, inevitably leading to higher costs. Therefore, new solutions are needed to improve chip performance.

[0003] Three-dimensional integration (3D integration), relying on the through-silicon via structure inside the chip and inter-chip bonding, can stack and interconnect multiple chips in the vertical direction, so that the package has a smaller volume, higher interconnection density, lower latency and greater bandwidth. Therefore, this technology is an effective solution to continue Moore's Law and improve chip performance. However, current inter-chip bonding is often achieved in the form of alloy solder balls (bumps) in conjunction with pads (pads), which has potential risks such as solder overflow (causing short circuits) and electromigration (causing open circuits). What's more troublesome is that the volume of alloy solder balls is usually large, which is not conducive to further improving the interconnection density.

[0004] Copper-copper bonding (Cu-Cu bonding) is an emerging wafer-level interconnection technology. It promotes direct bonding of copper atoms through solid-state diffusion by precisely controlling the bonding temperature, applying pressure and optimizing the environmental atmosphere. Compared with traditional intermetallic compound contact interconnection technology, this technology has the following significant advantages: First, the copper material itself has extremely low resistivity and excellent anti-electromigration properties; second, thanks to advanced micromachining technology, copper contacts with a size of 1 to 10 μm can be prepared. These characteristics are expected to make copper-copper bonding technology an ideal solution for the three-dimensional integration of a new generation of high-density, high-performance chips. However, the industrial application of this technology still faces two key challenges: First, in the existing process, copper contacts are only formed through a limited area on the top (typical value 5-20 μm 2 ) to achieve contact, significantly limiting bond strength. Second, the alignment accuracy of current bonding equipment (typically ±1μm) hinders the full potential of micro- and nanoscale interconnects. These technical bottlenecks urgently need to be overcome through innovative bonding interface designs or high-precision alignment systems (at the submicron level). Summary of the Invention

[0005] The object of the present invention is to provide a copper-copper bonding method and bonding structure, aiming to solve or improve at least one of the above-mentioned technical problems.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A copper-copper bonding method comprising:

[0008] growing an insulating layer on the surface of the substrate layer by a plasma enhanced chemical vapor deposition method;

[0009] Spin coating a base layer on the surface of the insulating layer, and sequentially performing exposure treatment, development treatment and curing treatment to form a concave structure and a convex structure with inclined sidewalls respectively;

[0010] An adhesion layer and a bonding layer are deposited on the recessed structure and the convex structure respectively through a lift-off process and physical vapor deposition to form a convex bonding structure and a recessed bonding structure with inclined sidewalls.

[0011] Optionally, the base layer is made of photosensitive polyimide.

[0012] Optionally, the base layer has a thickness of 3 to 10 μm.

[0013] Optionally, the exposure dose of the exposure treatment is 800 to 1300 mJ / cm 2 .

[0014] Optionally, the developing solution for the development treatment is 2.38% concentration of tetramethylammonium hydroxide.

[0015] Optionally, the development process takes 360 to 600 seconds.

[0016] Optionally, the sidewall inclination angles of the concave structure and the convex structure are 30 to 60°.

[0017] Optionally, the material of the adhesion layer is titanium or chromium, and the material of the bonding layer is copper.

[0018] Optionally, the thickness of the adhesion layer is 100-500 nm, and the thickness of the bonding layer is 1-5 μm.

[0019] The present invention also provides a copper-copper bonding structure, which is prepared by the bonding method as described above, and includes: a bump bonding structure and a recessed bonding structure with inclined sidewalls; wherein the top area of ​​the bump bonding structure, the bottom area of ​​the recessed bonding structure and the inclined sidewalls on both sides are in contact and connected.

[0020] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0021] The present invention discloses a copper-copper bonding method and bonding structure. The bonding method comprises growing an insulating layer on the surface of a substrate layer using plasma-enhanced chemical vapor deposition; spin-coating a base layer on the surface of the insulating layer, and sequentially performing exposure, development, and curing processes to form a recessed structure and a convex structure with inclined sidewalls, respectively; and depositing an adhesion layer and a bonding layer on the recessed structure and the convex structure, respectively, using a lift-off process and physical vapor deposition to form a convex bonding structure and a recessed bonding structure with inclined sidewalls. Due to the inclined sidewalls, the present invention enables spontaneous high-precision alignment of the recessed and convex structures as they approach. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Schematic diagram of the traditional bonding structure in this embodiment;

[0024] Figure 2 Schematic diagram of the copper-copper bonding structure of the present invention;

[0025] Figure 3 Schematic diagram of the preparation process of the copper-copper bonding structure in the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] The object of the present invention is to provide a copper-copper bonding method and bonding structure, aiming to solve or improve at least one of the above-mentioned technical problems.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1-Figure 3 As shown, the present invention provides a copper-copper bonding method for compensating for the following problems: Figure 1The defects of the traditional bonding method shown in the figure. The traditional bonding method is a regular cylinder or a rectangular parallelepiped; the alignment accuracy of the two is completely dependent on the performance of the alignment equipment, and the bonding interface is a plane. This bonding form has two major drawbacks: first, the performance requirements of the bonding equipment are too high; second, the bonding area may be insufficient, resulting in insufficient bonding strength. The present invention proposes a copper-copper bonding structure with self-alignment capability and high bonding strength, such as Figure 2 As shown, the bonding body features sloped sidewalls that mate with the concave and convex parts. During alignment, the sloped sidewalls automatically align the two parts, enabling precise alignment. During bonding, the sloped sidewalls not only contact and bond the bottom of the concave and top of the convex parts, but also enhance bond strength.

[0030] The shapes of the concave and convex parts are complementary, and the processing flow is consistent, providing Figure 3 The preparation process shown:

[0031] Step 1: Grow a 1 μm thick silicon oxide as an insulating layer on the surface of the silicon substrate by plasma enhanced chemical vapor deposition (PECVD). Figure 3 Middle (a).

[0032] Step 2: First, spin-coat photosensitive polyimide (PSPI) on the surface of the silicon substrate for more than 2 minutes. The spin-coating speed can be adjusted between 1000 rpm and 5000 rpm according to actual needs. Then, bake it on a hot plate at 100 to 200°C for no less than 120 minutes. Then, expose it on a contact exposure machine with an exposure dose of 800 mJ / cm2 according to actual needs. 2 to 1300mJ / cm 2 Finally, the development is carried out in a developer solution of 2.38% TMAH, and the duration is adjusted between 360s and 600s according to actual needs. After the above steps, a PSPI substrate with inclined sidewalls can be obtained, such as Figure 3 (b) and Figure 3 Middle (c).

[0033] Step 3: First, spin-coat photoresist S1805 on the surface of the PSPI substrate as a peeling layer and pattern it by photolithography, such as Figure 3 As shown in (d). 200nm thick titanium and 1μm thick copper were deposited on the surface of the PSPI substrate by physical vapor deposition (PVD). Figure 3(e). Finally, the stripping is carried out in a degumming solution. After the above steps, concave and convex bodies can be obtained, such as Figure 3 As shown in (f).

[0034] Therefore, the present invention has the following beneficial effects:

[0035] First, during the bonding process, even without high-performance alignment equipment, the inclined sidewalls allow the concave and convex parts to spontaneously achieve high-precision alignment as they approach. Second, compared to traditional regular flat bonding, the sidewalls of the concave and convex parts also contact and adhere to each other, helping to improve overall bond strength.

[0036] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0037] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A copper-copper bonding method, characterized in that: include: growing an insulating layer on the surface of the substrate layer by a plasma enhanced chemical vapor deposition method; Spin coating a base layer on the surface of the insulating layer, and sequentially performing exposure treatment, development treatment and curing treatment to form a concave structure and a convex structure with inclined sidewalls respectively; An adhesion layer and a bonding layer are deposited on the recessed structure and the convex structure respectively through a lift-off process and physical vapor deposition to form a convex bonding structure and a recessed bonding structure with inclined sidewalls.

2. The copper-copper bonding method according to claim 1, characterized in that The base layer is made of photosensitive polyimide.

3. The copper-copper bonding method according to claim 1, characterized in that The thickness of the base layer is 3 to 10 μm.

4. The copper-copper bonding method according to claim 1, characterized in that The exposure dose of the exposure treatment is 800-1300 mJ / cm 2 .

5. The copper-copper bonding method according to claim 1, characterized in that The developer for the development treatment is 2.38% tetramethylammonium hydroxide.

6. The copper-copper bonding method according to claim 1, characterized in that: The development treatment time is 360 to 600 seconds.

7. The copper-copper bonding method according to claim 1, characterized in that: The sidewall inclination angles of the concave structure and the convex structure are 30 to 60 degrees.

8. The copper-copper bonding method according to claim 1, wherein: The material of the adhesion layer is titanium or chromium, and the material of the bonding layer is copper.

9. The copper-copper bonding method according to claim 1, characterized in that: The thickness of the adhesion layer is 100-500 nm, and the thickness of the bonding layer is 1-5 μm.

10. A copper-copper bonding structure, prepared by the bonding method according to claims 1-4, characterized in that: include: A bump bonding structure and a recessed bonding structure with inclined sidewalls; wherein the top area of ​​the bump bonding structure, the bottom area of ​​the recessed bonding structure and the inclined sidewalls on both sides are in contact and connected.

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