Integrated circuit bonding process

Abstract

The present invention discloses an integrated circuit bonding process, which belongs to the field of copper-copper bonding technology. The present invention first electroplates copper pillars on a chip and a carrier, and then uses laser welding to achieve copper-copper bonding between the copper pillars, so that the copper pillars can be successfully joined. Laser welding has the advantages of fast, local and precise heating. Rapid heating can reduce the risk of surface oxidation and shorten the process cycle, and laser local heating does not require additional measures to deal with thermal expansion like regional heating. The present invention uses infrared laser to irradiate the surface of the substrate. Because it can penetrate silicon, the energy can be converted into a local heat source for bonding, and the local heating is accurately controlled to achieve heating and bonding of the copper pillars. At the same time, pressure is applied to the substrate to make the copper pillars tightly connected after melting and cooling, reducing the thermal mismatch caused by material differences and reducing the internal stress and deformation of the material. Laser welding only requires a small pressure to complete copper-to-copper welding, and can achieve single crystal copper welding and polycrystalline copper welding, expanding the scope of welding application and flexibility.

Description

Technical Field

[0001] The invention belongs to the technical field of copper-copper bonding, and in particular relates to an integrated circuit bonding process. Background Art

[0002] As the demand for high-performance chip applications continues to rise, advanced packaging interconnect technology is developing rapidly towards high density and high reliability. At present, tin-based solder soldering process occupies a mainstream position in advanced packaging interconnect technology. However, this process has obvious limitations, such as poor contact or bump bridging. In recent years, a new copper-copper bonding method has emerged, which effectively avoids the above problems because it does not use tin.

[0003] At present, single crystal copper bonding is widely used in the industry. However, when electroplating copper pillars (Cupillar), as the thickness of the coating increases, the twinning phenomenon gradually appears, and the coating structure will also change to polycrystalline. As a result, epitaxial electroplating on traditional single crystal substrates can only obtain single crystal films of a few microns thick, and it is difficult to construct high copper pillar structures (≥20um). In high-density packaging scenarios, the copper content per unit volume increases, and the heat dissipation demand becomes more urgent. However, single crystal copper pillars are limited in height and cannot fully meet the heat dissipation requirements. In view of this, it is particularly critical to deeply explore the bonding technology between high copper pillars. Summary of the invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides two methods for copper-copper bonding.

[0005] In order to achieve the above object, the following technical solution is adopted: The present invention provides an integrated circuit bonding process, comprising the following steps:

[0006] Provide wafers;

[0007] Depositing a PI layer on the bumps of the wafer, and then exposing and developing the PI layer;

[0008] sputtering a metal seed layer on the PI layer;

[0009] Covering the metal seed layer with a dry film or a photoresist layer;

[0010] exposing and developing the dry film or photoresist layer;

[0011] Electroplating of copper pillars;

[0012] Stripping, removing dry film or photoresist layer;

[0013] etching the metal seed layer;

[0014] Aligning the wafer with other wafers or substrates;

[0015] Laser welding is performed by means of a laser source;

[0016] Complete copper-copper bonding.

[0017] The present invention also provides another integrated circuit bonding process, comprising the following steps:

[0018] Provide wafers;

[0019] Depositing a PI layer on the bumps of the wafer, and then exposing and developing the PI layer;

[0020] sputtering a metal seed layer on the PI layer;

[0021] Covering the metal seed layer with a dry film or a photoresist layer;

[0022] exposing and developing the dry film or photoresist layer;

[0023] Electroplating of copper pillars;

[0024] Aligning the wafer with other wafers or substrates;

[0025] Laser welding is performed by means of a laser source;

[0026] Complete copper-copper bonding;

[0027] Stripping, removing dry film or photoresist layer;

[0028] The metal seed layer is etched.

[0029] The beneficial effects of the present invention are as follows: the present invention aims at the bonding problem between high copper pillars, firstly electroplating copper pillars on the chip and the carrier through a series of process flows, and then realizing copper-copper bonding between the copper pillars by laser welding, so that the copper pillars are bonded with each other, and laser welding can realize fast and local precise heating. Fast heating can reduce the risk of surface oxidation and shorten the process cycle. Laser local heating does not require additional measures to reduce the impact of thermal expansion like regional heating. The present invention uses laser to irradiate the surface of the substrate, wherein the infrared laser can penetrate silicon, and its energy can be efficiently absorbed and converted into a local heat source in the bonding process. Local heating is achieved through precise control to achieve local copper column heating bonding. At the same time, pressure is applied to the substrate to cause the copper columns between the substrates to melt, and a tight connection is achieved after cooling. This method greatly reduces the thermal mismatch problem caused by material differences and effectively reduces the internal stress and deformation of the material. Laser welding only requires a small pressure to achieve welding between copper and copper, unlike the traditional process of single crystal copper and single crystal copper welding that relies on high temperature and high pressure. In addition, laser welding can not only achieve welding between single crystal copper, but also smoothly achieve welding between polycrystalline copper, significantly expanding the application range and flexibility of welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of an integrated circuit bonding process of the present invention Figure 1 ;

[0031] Figure 2 A schematic diagram of an integrated circuit bonding process of the present invention Figure 2 ;

[0032] Figure 3 A schematic diagram of an integrated circuit bonding process of the present invention Figure 3 ;

[0033] Figure 4 A schematic diagram of an integrated circuit bonding process of the present invention Figure 4 ;

[0034] Figure 5 A schematic diagram of an integrated circuit bonding process of the present invention Figure 5 ;

[0035] Figure 6 A schematic diagram of an integrated circuit bonding process of the present invention Figure 6 ;

[0036] Figure 7 A schematic diagram of an integrated circuit bonding process of the present invention Figure 7 ;

[0037] Figure 8 A schematic diagram of an integrated circuit bonding process of the present invention Figure 8 ;

[0038] Fig. 9 A schematic diagram of an integrated circuit bonding process of the present invention Figure 9 ;

[0039] Fig.10 A schematic diagram of an integrated circuit bonding process of the present invention Figure 10 ;

[0040] Fig.11 A schematic diagram of an integrated circuit bonding process of the present invention Figure 10 one;

[0041] Fig.12 A schematic diagram of an integrated circuit bonding process of the present invention Figure 10 two;

[0042] Fig.13 A schematic diagram of an integrated circuit bonding process of the present invention Figure 10 three. Fig.14 A schematic diagram of an integrated circuit bonding process of the present invention Figure 10 Four.

[0043] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0044] Legend: 1. Wafer; 2. Bump; 3. PI layer; 4. Metal seed layer; 5. Dry film or photoresist layer; 6. Copper pillar; 7. Wafer or substrate; 8. Laser source. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0046] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0047] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0048] Example 1

[0049] An integrated circuit bonding process comprises the following steps:

[0050] Providing a wafer 1;

[0051] As attached Figure 1 As shown, a PI layer 3 is deposited on the bump 2 of the wafer 1, and then the PI layer 3 is exposed and developed;

[0052] As attached Figure 2 As shown, a metal seed layer 4 is sputtered on the PI layer 3;

[0053] As attached Figure 3 As shown, a dry film or photoresist layer 5 is covered on the metal seed layer 4;

[0054] As attached Figure 4 As shown, the dry film or photoresist layer 5 is exposed and developed;

[0055] As attached Figure 5 As shown, a copper column 6 is electroplated;

[0056] As attached Figure 6 As shown, the film is stripped and the metal seed layer 4 is etched;

[0057] As attached Figure 7 As shown, the wafer 1 is aligned with other wafers or substrate 7;

[0058] As attached Figure 8 As shown, laser welding is performed by a laser source 8;

[0059] As attached Fig. 9 As shown, copper-copper bonding is completed.

[0060] Example 2

[0061] An integrated circuit bonding process, characterized in that it includes the following steps:

[0062] Providing a wafer 1;

[0063] As attached Figure 1 As shown, a PI layer 3 is deposited on the bump 2 of the wafer 1, and then the PI layer 3 is exposed and developed;

[0064] As attached Figure 2 As shown, a metal seed layer 4 is sputtered on the PI layer 3;

[0065] As attached Figure 3 As shown, a dry film or photoresist layer 5 is covered on the metal seed layer 4;

[0066] As attached Figure 4 As shown, the dry film or photoresist layer 5 is exposed and developed;

[0067] As attached Figure 5 As shown, a copper column 6 is electroplated;

[0068] As attached Fig.10 As shown, the surface of the dry film or photoresist layer 5 is ground and smoothed to obtain a correct copper profile;

[0069] As attached Fig.11 As shown, the wafer 1 is aligned with other wafers or substrate 7;

[0070] As attached Fig.12 As shown, laser welding is performed by a laser source 8;

[0071] As attached Fig.13 As shown, copper-copper bonding is completed;

[0072] The film is removed, and the metal seed layer 4 is etched to obtain Fig. 9 Same structure as shown.

[0073] Results Analysis

[0074] The present invention successfully solves the key problem that the height of single crystal copper pillars in the prior art cannot meet the demand by adopting an innovative method of laser welding at the positions where copper pillars are aligned. In the traditional bonding process between single crystal copper, due to the limitation of the twinning phenomenon during the electroplating process, it is difficult to obtain single crystal copper pillars of sufficient height, which leads to difficulties in heat dissipation and high-density packaging. However, the present invention first electroplates a higher copper pillar (whether a single crystal or a polycrystalline structure), and then uses laser welding to achieve the connection between the copper pillars, which not only breaks through the limitation of the height of the copper pillars, but also gives full play to the many advantages of laser welding.

[0075] The rapid heating characteristics of laser welding greatly reduce the risk of copper pillar surface oxidation during welding. Compared with traditional heating welding methods, laser welding can heat the copper pillar to above the melting point in a very short time, reducing the time the copper pillar is exposed to high temperature environment, thereby effectively inhibiting the occurrence of oxidation reaction. This not only helps to improve the quality and reliability of the welded joint, but also reduces the increase in contact resistance caused by the presence of the oxide layer, ensuring the stability of the electrical performance of the integrated circuit.

[0076] At the same time, the local precise heating capability of laser welding makes it unnecessary to take additional measures to deal with the impact of thermal expansion like regional heating. During the welding process, the laser beam is focused only on the joint of the copper pillars, so that the heat is highly concentrated in this area, and the surrounding materials are minimally affected by the heat. This local heating method can effectively avoid the stress concentration and deformation problems caused by uneven thermal expansion of materials due to large-area heating, thereby improving the stability and reliability of the entire integrated circuit structure. Especially in the case of high-density packaging, the spacing between the components inside the chip is small, and the control requirements for thermal expansion and stress are more stringent. The laser welding method of the present invention can better meet this demand.

[0077] In addition, the present invention utilizes the characteristic that infrared laser can penetrate silicon to efficiently convert laser energy into a local heat source in the bonding process. During the welding process, by accurately controlling the laser power, pulse frequency, welding time and other parameters, it is possible to achieve precise control of the copper column heating process, ensuring that the copper columns are melted and connected together under appropriate temperature and time conditions. At the same time, appropriate pressure is applied to the substrate to promote the copper columns between the substrates to fully fuse in a molten state, and form a tight and firm connection after cooling. This method greatly reduces the thermal mismatch problem caused by material differences (such as different materials between the wafer and the substrate), and effectively reduces the stress and deformation inside the material. Compared with traditional processes, traditional processes often require high temperature (350-450°C) and high pressure (2000-4000N) conditions to achieve better welding effects when welding single crystal copper to single crystal copper, while the laser welding of the present invention only requires a small pressure (e.g., 100-500N) to achieve high-quality welding between copper and copper. This not only reduces the requirements for equipment and process conditions, but also reduces the risk of damage to other components and structures inside the chip due to high temperature and high pressure, thereby improving the overall performance and reliability of the chip.

[0078] The laser welding method of the present invention can not only realize welding between single crystal copper, but also smoothly achieve welding between polycrystalline copper. This feature makes the present invention more widely applicable and flexible in practical applications. In the actual integrated circuit manufacturing process, due to the influence of factors such as electroplating process, the copper column may present a polycrystalline structure. Traditional welding methods may face many difficulties when dealing with polycrystalline copper welding, such as insufficient strength of the welding joint, decreased conductivity and other problems. The laser welding method of the present invention can effectively overcome these problems and provide a new solution for the bonding of polycrystalline copper columns.

[0079] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0080] The present invention and its implementation methods are described above, which is not restrictive. The drawings are only one of the implementation methods of the present invention, and the actual application is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. An integrated circuit bonding process, characterized in that: The steps include: Provide wafers; Depositing a PI layer on the bumps of the wafer, then exposing and developing the PI layer; sputtering a metal seed layer on the PI layer; Covering the metal seed layer with a dry film or a photoresist layer; exposing and developing the dry film or photoresist layer; Electroplating of copper pillars; Stripping, removing dry film or photoresist layer; etching the metal seed layer; Aligning the wafer with other wafers or substrates; Laser welding is performed by means of a laser source; Complete copper-copper bonding.

2. An integrated circuit bonding process, characterized in that: The steps include: Provide wafers; Depositing a PI layer on the bumps of the wafer, then exposing and developing the PI layer; sputtering a metal seed layer on the PI layer; Covering the metal seed layer with a dry film or a photoresist layer; exposing and developing the dry film or photoresist layer; Electroplating of copper pillars; Aligning the wafer with other wafers or substrates; Laser welding is performed by means of a laser source; Complete copper-copper bonding; Stripping, removing dry film or photoresist layer; The metal seed layer is etched.

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