阅读说明：本技术 一种硅片背面金属化结构及其制造工艺 (Silicon wafer back metallization structure and manufacturing process thereof ) 是由 高瑞峰 周骏贵 于 2020-01-02 设计创作，主要内容包括：本发明属于半导体器件和集成电路工艺技术领域,具体涉及硅器件背面金属化结构和工艺。所述结构在背面衬底硅片的表面至少沉积有第一金属层铪,然后沉积其他层。所述工艺包括正面保护、背面减薄、背面抛光、清洗、物理气相沉积等工艺步骤。本发明利用铪与硅形成欧姆接触的特点,在硅片的背面制备一层铪,具有更低的接触电阻和更好的粘附性,同时具有良好的导电性、导热性和合适的热膨胀系数,有效提高硅器件制造过程中的良率和使用中的可靠性。(The invention belongs to the technical field of semiconductor device and integrated circuit processes, and particularly relates to a back metallization structure and a back metallization process of a silicon device. According to the structure, at least a first metal layer hafnium is deposited on the surface of a back substrate silicon wafer, and then other layers are deposited. The process comprises the process steps of front protection, back thinning, back polishing, cleaning, physical vapor deposition and the like. The method utilizes the characteristic that the hafnium and the silicon form ohmic contact, prepares a layer of hafnium on the back of the silicon wafer, has lower contact resistance and better adhesion, simultaneously has good electrical conductivity, thermal conductivity and proper thermal expansion coefficient, and effectively improves the yield and the reliability in use in the manufacturing process of the silicon device.)

1. A silicon chip back metallization structure is characterized in that: according to the structure, at least a first metal layer is sequentially deposited on the surface of a back substrate silicon wafer from near to far, and the first metal layer is made of hafnium.

2. A silicon wafer backside metallization structure as in claim 1 wherein: the structure is characterized in that a first metal layer and a second metal layer are sequentially deposited on the surface of a back substrate silicon wafer from near to far, and the second metal layer is made of any one of gold, nickel or gold-germanium alloy.

3. A silicon wafer backside metallization structure as in claim 1 wherein: the structure is characterized in that a first metal layer, a second metal layer and a third metal layer are sequentially deposited on the surface of a back substrate silicon wafer from near to far, and the third metal layer is made of any one of silver, gold-germanium alloy and gold-tin alloy.

4. A silicon wafer backside metallization structure as in claim 1 wherein: the thickness of the first metal layer is 30 nm-300 nm.

5. A silicon wafer backside metallization structure as in claim 2 wherein: the thickness of the second metal layer made of gold is 500 nm-2000 nm, the thickness of the second metal layer made of nickel is 100 nm-600 nm, and the thickness of the second metal layer made of gold-germanium alloy is 100 nm-500 nm.

6. A silicon wafer backside metallization structure as in claim 3 wherein: the thickness of the third metal layer made of silver is 100 nm-2000 nm, the thickness of the third metal layer made of gold is 100 nm-1500 nm, and the thickness of the third metal layer made of gold-germanium alloy or gold-tin alloy is 300 nm-1500 nm.

7. A process for preparing the silicon wafer backside metallization structure of claim 1, wherein: the first metal layer is prepared by magnetron sputtering or electron beam evaporation, wherein the magnetron sputtering rate is 5-15 nm/s, and the electron beam evaporation rate is 0.5-3 nm/s.

8. A process for preparing a metallization structure on the back side of a silicon wafer according to claim 2 or 3, characterized in that: the second metal layer and the third metal layer are prepared by evaporation or magnetron sputtering, the evaporation rate is 0.5-3 nm/s, and the magnetron sputtering rate is 5-15 nm/s.

Technical Field

The invention belongs to the technical field of semiconductor device and integrated circuit processes, and particularly relates to a back metallization structure and a back metallization process of a silicon device.

Background

With the development of large-scale and ultra-large scale integrated circuits, the feature size of chips is smaller and smaller, the integration level is higher and higher, and electronic systems and complete machines are continuously developed towards miniaturization, high performance, high density and high reliability, which puts higher requirements on chip interconnection materials, component soldering materials and packaging materials.

The back side metallization system is an important component of the transistor. It has two main functions, one is a large current path, and the other is a path for transferring and dissipating a large amount of heat generated by the collector of the transistor. The backside metallization system has a large impact on the performance and reliability of the transistor.

A good backside metallization system requires low ohmic contact resistance, low contact resistance and good reliability. In order to form a good ohmic contact with the silicon substrate, it is generally required to select: 1) a metal material having a low Schottky barrier height; 2) a substrate material of high doping concentration; 3) substrate with high recombination centers.

In order to provide the transistor backside metallization with good thermal conductivity and reliability, thermal stress between the silicon chip and the backside metallization is minimized. When the transistor is in an intermittent operation state, the device undergoes periodic high and low temperature processes, forming a thermal cycle. Because the linear expansion coefficients of the silicon chip, the solder and the materials of all layers of the base in the transistor are different, thermal stress is generated in the system during thermal circulation, thermal resistance is increased, and the transistor is locally overheated and fails. Moreover, a silicon chip with a thickness of about 200 μm is a very thin brittle material, the chip has a large stress and is prone to chipping during ion implantation, and when the linear expansion coefficients of the materials of the layers are not well matched, the silicon chip may warp and crack after being subjected to multiple thermal cycles during use, and thus the silicon chip fails.

The structures of the back side metallization systems currently used in practical devices generally consist of three parts: an ohmic contact layer, a diffusion barrier layer, and a conductive layer. The ohmic contact layer is also called an adhesion layer. The metal used for the adhesion layer is generally titanium or vanadium or chromium or gold-arsenic alloy. The metal used for the barrier layer is generally nickel or gold, or copper-tin alloy, or gold-germanium-antimony alloy. The metal used for the conductive layer is typically gold or silver. The existing structure and process can not meet the comprehensive requirements of low cost, high stability, high reliability and good matching with the subsequent packaging process, and also have the problems of poor matching with the subsequent packaging process, warping or fragments, low yield and the like.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides the silicon wafer back metallization structure with low contact resistance and the manufacturing process thereof, has the advantages of high electrical conductivity, high thermal conductivity and better matching between the thermal expansion coefficient and the medium, and improves the yield of products.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: according to the structure, at least first metal hafnium is sequentially deposited on the surface of a back substrate silicon wafer from near to far. Preferably, a second metal layer may be deposited, and the material of the second metal layer is any one of gold, nickel or gold-germanium alloy. Preferably, a third metal layer may be deposited, and the material of the third metal layer is any one of silver, gold-germanium alloy, and gold-tin alloy.

Preferably, the thickness of the first metal layer is 30nm to 300 nm.

Preferably, the thickness of gold used as the second metal layer is 500nm to 2000nm, the thickness of nickel used as the second metal layer is 100nm to 600nm, and the thickness of gold-germanium alloy used as the second metal layer is 100nm to 500 nm.

Preferably, the thickness of silver used as the third metal layer is 100nm to 2000nm, the thickness of gold used as the third metal layer is 100nm to 1500nm, and the thickness of gold-germanium alloy or gold-tin alloy used as the third metal layer is 300nm to 1500 nm.

A processing technology of a silicon wafer back metallization structure comprises the following steps: the method comprises the steps of front protection, back thinning, back polishing, cleaning, magnetron sputtering or electron beam evaporation to prepare a first metal layer, and evaporation or sputtering to prepare other metal layers. The front protection is to stick a layer of protective film on the front of the silicon chip. And the back thinning is to thin the back of the silicon chip to the required thickness. And the back polishing is to remove a damaged layer generated by the grinding sheet. And the cleaning is to clean the polished silicon wafer. The first metal layer is prepared by magnetron sputtering or electron beam evaporation, wherein the magnetron sputtering rate is 5-15 nm/s, and the electron beam evaporation rate is 0.5-3 nm/s. The second metal layer and the third metal layer are prepared by evaporation or magnetron sputtering, the evaporation rate is 0.5-3 nm/s, and the magnetron sputtering rate is 5-15 nm/s.

The electron beam evaporation method is one of vacuum evaporation coating, and is a method for directly heating an evaporation material by using an electron beam under a vacuum condition, so that the evaporation material is gasified and transported to a substrate, and is condensed on the substrate to form a film. In the electron beam heating device, the heated substance is placed in a water-cooled crucible, so that the evaporation material can be prevented from reacting with the crucible wall to influence the quality of the film. The electron beam evaporation can evaporate high-melting-point materials, and has high thermal efficiency, high beam density and high evaporation speed compared with common resistance heating evaporation; the prepared film has the advantages of high purity, good quality and accurately controlled thickness.

The magnetron sputtering is one of physical vapor deposition, and has the advantages of simple equipment, easy control, large film coating area, strong adhesive force and the like. This technology includes, among other things, the target, the power supply, and the mode of operation of the target, of which the target is critical. Usually, the target is connected to a negative potential of 400V-600V, the substrate is grounded, and the target and the substrate form a discharge field with the target as a cathode and the substrate as an anode. And a magnetic circuit module which can be a permanent magnet or an electromagnet is arranged in the cathode target, and provides a magnetic flux density of 0.03T-0.06T for the target surface. The magnetic force lines are parallel to the surface of the target and are orthogonal to the electric field, and the space enclosed by the magnetic force lines and the surface of the target is the plasma region which generates the binding effect on electrons. Taking argon as an example, after Ar positive ions generated by glow discharge are accelerated, the Ar positive ions continuously bombard the surface of the target material, so that target material atoms are sputtered out to be deposited on a substrate opposite to the target, and a sputtered film layer is formed.

After the technical scheme is adopted, the invention has the following positive effects:

compared with the existing titanium or gold arsenic, the hafnium and the silicon substrate form better ohmic contact, have lower contact resistance and better adhesiveness, simultaneously have good electrical conductivity, thermal conductivity and proper thermal expansion coefficient, and effectively improve the yield and the reliability in use in the manufacturing process of the silicon device. The hafnium layer can realize ohmic contact without increasing the surface doping concentration of the substrate when applied to an n-type silicon substrate. Meanwhile, the design of the second metal layer and the third metal layer effectively improves the stability of the silicon device, and the silicon device is suitable for eutectic soldering occasions and has a wide application range. The processing technology of the invention ensures the realization of the back metallization structure.

Drawings

FIG. 1 is a schematic diagram of a silicon wafer backside metallization structure of the present invention. Wherein: 101, a silicon wafer; 102 hafnium, the first metal layer of the structure; 103 gold, is the second metal layer of the structure.

FIG. 2 is a schematic diagram of a silicon wafer backside metallization structure of the present invention. Wherein: 201 a silicon wafer; 202 hafnium, the first metal layer of the structure; 203 nickel, the second metal layer of the structure; 204 silver or gold, is the third metal layer of the structure.

FIG. 3 is a schematic diagram of a silicon wafer backside metallization structure of the present invention. Wherein: 301 a silicon wafer; 302 hafnium, the first metal layer of the structure; 303 gold germanium alloy, which is the second metal layer of the structure; 304 silver or gold, is the third metal layer of the structure.

FIG. 4 is a schematic diagram of a silicon wafer backside metallization structure of the present invention. Wherein: 401 silicon chip; 402 hafnium, the first metal layer of the structure; 403 nickel, the second metal layer of the structure; 404 gold germanium alloy or gold tin alloy, is the third metal layer of the structure.

FIG. 5 is a schematic diagram of a silicon wafer backside metallization structure of the present invention. Wherein: 501, silicon chip; 502 hafnium, the first metal layer of the structure; 503 nickel, which is the second metal layer of the structure; 504 gold, is the third metal layer of the structure.

Detailed Description

The backside metallization structure and process of the present invention will be described in more detail in conjunction with schematic drawings, in which preferred embodiments of the present invention are shown, it being understood that one skilled in the art may modify the invention described herein while still achieving the advantageous effects of the present invention. Accordingly, the following description is to be construed as broadly as possible to those skilled in the art and not as limiting the invention. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely intended to facilitate the clear description of the embodiments of the invention.