CN105374840A - Method to reduce metal pollution in work area of contact-type image sensor - Google Patents

Abstract

The invention provides a method for reducing metal pollution in the working area of a contact image sensor, comprising: performing etching in the working area, the etching in the working area includes etching in the pixel area and partial etching in the logic control area; etching in the working area Follow-up cleaning of the wafer after etching; for the wafer after subsequent cleaning, use the in-situ water vapor generation process to grow a high-density oxide layer for surface oxidation; use photoresist to cover the pixels grown with a high-density oxide layer In the area, the logic control area is etched; the wafer is deglued; and the high-density oxide layer is removed.

Description

A Method for Reducing Metal Contamination in Working Area of Contact Image Sensor

technical field

The invention relates to the field of semiconductor manufacturing, and more specifically, the invention relates to a method for reducing metal pollution in a working area of a contact image sensor.

Background technique

CIS (Contact Image Sensor) is a photoelectric conversion device that uses a row of built-in LED light-emitting diodes for illumination. Because of its small size and light weight, it is widely used in mobile devices such as smartphones with camera functions.

The camera function of this kind of contact sensor is particularly sensitive to the increase of leakage and white spots caused by metal pollution, especially the pollution of the work area, which leads to low yield and even scrapping of a large number of wafers.

Specifically, while contact sensors are used more and more widely, there are some problems as follows:

1) Contact sensors are extremely sensitive to metal pollution, especially heavy metal pollution; however, the metal pollution test cycle is long and there are many interference factors, making it difficult to accurately interpret the results;

2) Because the etching chamber uses plasma for the etching process in the working area, the inherent characteristics of high metal precipitation inevitably produce metal contamination on the working area of the contact sensor; resulting in serious white spots and poor wafer quality. Low rate or even large-scale scrapping.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method that can solve the problem of metal contamination of the wafer caused by the etching process of the etching chamber on the working area in view of the above-mentioned defects in the prior art, thereby reducing the contact image Methods of metal contamination of the sensor working area.

In order to achieve the above technical purpose, according to the present invention, a method for reducing metal pollution in the working area of a contact image sensor is provided, including: performing etching of the working area, the etching of the working area includes etching of the pixel area and etching of the logic control area Partial etching; perform subsequent cleaning on the wafer after etching in the working area; for the wafer that has undergone subsequent cleaning, use an in-situ water vapor generation process to grow a high-density oxide layer 10 for surface oxidation; use photoresist to cover The part of the pixel area where the high-density oxide layer is grown, etch the logic control area; remove the glue from the wafer; and remove the high-density oxide layer.

Preferably, the etching chamber uses plasma to etch the logic control area.

Preferably, after the logic control area is etched, metal ions are deposited on the surface of the oxide layer in the pixel area.

Preferably, a wet cleaning process is used for subsequent cleaning of the wafer.

Preferably, the photoresist does not cover the logic control area.

Preferably, the degumming is high temperature degumming.

Preferably, after the wafer is degummed, the degummed wafer is further cleaned.

Preferably, the deglued wafer is cleaned by wet cleaning.

Preferably, the high-density oxide layer is removed by a hydrofluoric acid wet process.

In the present invention, before etching the wafer working area of the touch sensor, a high-density oxide layer is grown in the pixel area by oxygen oxidation to protect the pixel area, and the high-density oxide layer/silicon nitride/silicon oxide It is denser than the photoresist, and it is difficult for metal ions to penetrate, and the dense characteristics of the high-density oxide layer further better block metal ions, so that the subsequent etching process chamber precipitates metal ions only on the surface of the oxide layer, avoiding Metal ions are attached to the surface of the silicon source in the working area, and then cleaned with a wet method containing hydrofluoric acid to remove the oxide layer containing metal ions, avoid metal pollution on the surface of the silicon source in the pixel area, reduce pixel white spots, and improve sensor yield the goal of.

Description of drawings

A more complete understanding of the invention, and its accompanying advantages and features, will be more readily understood by reference to the following detailed description, taken in conjunction with the accompanying drawings, in which:

1 to 6 schematically illustrate various steps of a method for reducing metal contamination in a working area of a contact image sensor according to a preferred embodiment of the present invention.

It should be noted that the accompanying drawings are used to illustrate the present invention, but not to limit the present invention. Note that drawings showing structures may not be drawn to scale. And, in the drawings, the same or similar elements are marked with the same or similar symbols.

detailed description

In order to make the content of the present invention clearer and easier to understand, the content of the present invention will be described in detail below in conjunction with specific embodiments and accompanying drawings.

1 to 6 schematically illustrate various steps of a method for reducing metal contamination in a working area of a contact image sensor according to a preferred embodiment of the present invention.

As shown in Fig. 1 to Fig. 6 to Fig. 6, the method for reducing metal pollution in the working area of a contact image sensor according to a preferred embodiment of the present invention includes performing the following steps in sequence:

A semiconductor structure is provided, wherein a silicon oxide layer 2 and a silicon nitride layer 3 are sequentially arranged on a silicon substrate 1; on the basis of the structure, etching of the working area is performed, and the etching of the working area includes etching of the pixel area 100 and a partial etching of the logic control area 200; for example, the structure shown in FIG. 1 is formed after performing the etching of the working area.

Subsequent cleaning is performed on the wafer after etching in the working area; preferably, a wet cleaning process is used for subsequent cleaning of the wafer.

For the wafer after subsequent cleaning, a high-density oxide layer 10 is grown by an in-situ water vapor generation process (ISSG) for surface oxidation, as shown in Figure 2; the high-density oxide layer protects the pixel area and prevents subsequent processes from Metal pollution to the pixel area;

Use a photoresist 30 to cover the pixel area part (the photoresist does not cover the logic control area) that grows a high-density oxide layer, as shown in Figure 3; subsequently, the logic control area is etched; wherein, the etching cavity Use plasma to etch the logic control area. The etching process is shown in Figure 4, where the black origin represents metal ions; after etching the logic control area, in the pixel area, the metal ions are only deposited on the oxide layer surface, as shown in Figure 5.

Degumming the wafer (such as high-temperature degumming); preferably, further cleaning the degummed wafer (for example, using wet cleaning to clean the degummed wafer);

Remove the highly dense oxide layer. Preferably, the high-density oxide layer is removed by a hydrofluoric acid wet process. The resulting structure is shown in Figure 6.

In the prior art, during the etching process of the logic area, metal ions are deposited on the photoresist covered by the pixel area and the silicon source surface of the logic area. Due to the soft physical properties of the photoresist, the metal ions gradually migrate to the surface of the silicon source or even inside. ; while the pixel area is extremely sensitive to metal ions, the metal contamination will lead to increased white spots and decreased yield;

However, in the present invention, an oxide layer is grown on the surface of the silicon source in the pixel area, and this oxide layer will block the migration of metal ions to the surface and interior of the silicon source, so that the metal ions only deposit in the oxide layer, and the oxide layer will In the process, it is directly cleaned with a wet method containing hydrofluoric acid, so as to prevent the metal ion from contaminating the silicon source in the pixel area.

Therefore, the present invention grows a high-density oxide layer in the pixel area by oxygen oxidation before etching the wafer working area of the touch sensor to protect the pixel area, and the high-density oxide layer/silicon nitride /Silicon oxide is denser than photoresist, and it is difficult for metal ions to penetrate, and the dense characteristics of the high-dense oxide layer further better block metal ions, so that metal ions can only be deposited in the cavity of the subsequent etching process. The surface of the oxide layer prevents metal ions from adhering to the surface of the silicon source in the working area, and then cleans it with a wet method containing hydrofluoric acid to remove the oxide layer containing metal ions, avoiding metal pollution on the surface of the silicon source in the pixel area, so as to reduce the white point of the pixel , The purpose of improving the sensor yield.

In addition, it should be noted that, unless otherwise specified or pointed out, the terms “first”, “second”, “third” and other descriptions in the specification are only used to distinguish each component, element, step, etc. in the specification, and It is not used to represent the logical relationship or sequential relationship between various components, elements, and steps.

It can be understood that although the present invention has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or be modified to be equivalent to equivalent changes. Example. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention, which do not deviate from the technical solution of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims (9)

1. A method for reducing metal pollution in the working area of a contact image sensor, characterized in that it comprises: performing etching in the working area, the etching in the working area includes etching in the pixel area and partial etching in the logic control area; Subsequent cleaning of the wafer after etching in the work area; For the subsequently cleaned wafers, a high-density oxide layer is grown by an in-situ water vapor generation process for surface oxidation; Use photoresist to cover the part of the pixel area where the highly dense oxide layer is grown, and etch the logic control area; Deglue the wafer; Remove the highly dense oxide layer. 2. The method for reducing metal contamination in the working area of the contact image sensor according to claim 1, wherein the etching chamber uses plasma to etch the logic control area. 3. The method for reducing metal pollution in the working area of a contact image sensor according to claim 1 or 2, characterized in that, after the logic control area is etched, metal ions are deposited on the surface of the oxide layer in the pixel area. 4. The method for reducing metal contamination in the working area of a contact image sensor according to claim 1 or 2, wherein a wet cleaning process is used for subsequent cleaning of the wafer. 5 . The method for reducing metal pollution in the working area of a contact image sensor according to claim 1 or 2 , wherein the photoresist does not cover the logic control area. 6 . The method for reducing metal pollution in the working area of a contact image sensor according to claim 1 , wherein the degumming is high-temperature degumming. 7 . 7. The method for reducing metal contamination in the working area of a contact image sensor according to claim 1 or 2, characterized in that after the wafer is deglued, the wafer after degluing is further cleaned. 8. The method for reducing metal contamination in the working area of a contact image sensor according to claim 1 or 2, wherein the wafer after deglue is cleaned by wet cleaning. 9. The method for reducing metal pollution in the working area of a contact image sensor according to claim 1 or 2, characterized in that the high-density oxide layer is removed by a hydrofluoric acid wet process.