PN junction passivation process of low-medium voltage mesa TVS product

Abstract

The invention discloses a PN junction passivation process of a low-medium voltage mesa TVS chip. The PN junction passivation process of the low-medium voltage mesa TVS chip is low in production cost,and the voltage endurance capability and reliability of the TVS product are effectively improved. The process comprises the following steps of S1, diffusing; depositing a layer of phosphorus and boronon the surface of a wafer to form a P+-N-N+ structure; S2, carrying out selective photoetching; regionalizing the wafer into crystal grains, exposing regions to be etched on the surfaces of the crystal grains, and protecting other regions by photoresist; S3, etching a groove; etching the exposed areas on the surface of the crystal grains; S4, preparing an SIPOS film; S5, carrying out insulation passivation; forming a layer of compact SIO2 film on the surface of the SIPOS film; S6, removing an oxide film on an electrode surface; and S7, metallizing, namely plating a layer of electrode metal onthe surface of the wafer to finish processing. According to the present invention, in the working process, SIPOS film passivation and SiO2 film passivation are combined, after the SIPOS film is deposited, a layer of compact SiO2 film continues to grow on the surface of the SIPOS film through LPCVD, and the product capacity is improved.

Description

technical field [0001] The invention relates to the field of chip processing, in particular to a PN junction passivation of a low-medium voltage mesa TVS chip [0002] craft. Background technique [0003] A transient suppressor diode ("TVS" for short) is a high-efficiency surge protection device. Because it has the advantages of fast response time, large transient power, low leakage current, small breakdown voltage deviation, and easy control of clamping voltage. At present, it has been widely used in various fields such as precision electronic components and communication equipment. [0004] At present, low and medium voltage mesa TVS diode products usually use SIPOS film + glass or pure SiO2 or simple glass as the PN junction passivation insulating layer. The above three passivation methods mainly have the following problems: 1) When SIPOS film + glass passivation , due to the semi-insulation and electrical neutrality of the SIPOS film, the charge induced in the externa...

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Problems solved by technology

[0004] At present, low and medium voltage mesa TVS diode products usually use SIPOS film + glass or pure SiO2 or simple glass as the PN junction passivation insulating layer. The above three passivation methods mainly have the following problems: 1) When SIPOS film + glass passivation , due to the semi-insulation and electrical neutrality of the SIPOS film, the charge induced in the external environment can flow into the semi-insulation polysilicon, relieve the surface electric field in the barrier region, and improve the product PN junction voltage resistance, reliability and stability. However, this process needs to be combined with glass passivation, and the production cost is high; 2) Simply using insulating films such as SiO2 or glass for insulating passivation, the passivation layer will be interfered by the external electric field and the movable charge on the surface of the PN junction, which cannot effectively prevent the device from The accumulation of surface charges and metal ion contamination, and the injection of carriers into silicon dioxide insulators can be stored and long-term residence, which changes the conductivity of the device surface area and deteriorates the reverse characteristics of the PN junction. , which ultimately affects the overall pressure resistance, high temperature characteristics and reliability of the TVS tube, resulting in a decline in product quality

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