CN102543819A - Method for preventing STI (Shallow Trench Isolation)-CMP (Chemical-Mechanical Polishing) scratching - Google Patents

Abstract

The invention provides a method for preventing STI-CMP from scratching, comprising the steps of: the first step, grinding away the HDP-OX (high-density plasma silicon oxide) on the surface of the active area of the wafer, and at this time the surface of the wafer will form and be poured out The sharp corners; the second step is to grind the SiN and grind the SiN to a certain thickness, and add a high-pressure cleaning step between the first and second steps to remove the sharp corners that fall, so as to prevent scratches on the wafer surface. Compared with the prior art, the high-pressure cleaning step can wash away the fallen sharp corners in time to achieve the effect of cleaning the wafer surface, thereby preventing STI-CMP scratches.

Description

A Method of Preventing STI-CMP from Scratching

【Technical field】

The invention relates to the technical field of semiconductor production technology, in particular to an improved STI-CMP (Shallow Trench Isolation Planarization) method.

【Background technique】

STI (Shallow Trench Isolation) has now become a key technology for isolation between devices and has replaced LOCOS (Local Oxidation of Silicon) technology. The main steps include etching shallow trenches on pure silicon wafers, silicon dioxide deposition, and finally surface planarization with CMP (Chemical Mechanical Polishing) technology. The CMP (Chemical Mechanical Polishing) process was introduced into the integrated circuit manufacturing industry by IBM in 1984, and was first used in the planarization of the IMD (Intermetal Insulation Dielectric) in the subsequent process, and then used for the planarization of tungsten through the improvement of equipment and processes , subsequently used for planarization of STI and copper. CMP is the fastest growing and most valued technology in IC manufacturing process in recent years. The main reason is that VLSI has a strong demand for planarization with the continuous miniaturization of line width. The process goal of STI-CMP is to grind away all oxide layers higher than the SiN (silicon nitride) layer, otherwise the process performed after STI polishing cannot use hot phosphoric acid to peel off SiN to achieve planarization.

Therefore, traditional STI-CMP is generally carried out in the following two steps: the first step is to grind off the HDP-OX (high-density plasma silicon oxide) in the active area, and the second step is to grind off the SiN in the active area. The thickness (for example, 400A), and these two steps are carried out continuously, as shown in Figure 1. However, in the semiconductor manufacturing process, there is a HDP-OX precipitation process before the STI-CMP process. This step will complete the filling of the STI trench, but sharp corners will be formed on the surface of the active region after filling. Therefore, during STI-CMP grinding, there may be scratches on the wafer surface due to the falling of large sharp corners on the surface, and because the grinding process of STI-CMP is carried out continuously, the large sharp corners that fall away exist on the wafer and The middle of the grinding pad cannot be removed, so it is easy to form scratches after grinding.

In order to solve the above problems, it is necessary to provide an improved STI-CMP method.

【Content of invention】

Aiming at the deficiencies of the prior art, the technical problem solved by the present invention is to provide an improved STI-CMP method, which can prevent and alleviate the scratches on the wafer surface caused by the sharp corners formed by HDP-OX.

The object of the present invention is achieved by providing the following technical solutions:

A method for preventing STI-CMP scratches, comprising the steps of: the first step, grinding away the HDP-OX (high-density plasma silicon oxide) on the surface of the active region of the wafer, and at this time the surface of the wafer will form a sharp angle that falls ; The second step is to grind the SiN and grind the SiN to a certain thickness, and add a high-pressure cleaning step between the first step and the second step to remove the sharp corners that fall, thereby preventing the wafer surface from being scratched.

Further, the grinding of SiN can remove the accidental scratches formed on the wafer surface.

Still further, the certain thickness mentioned in the polishing step of SiN is 400 Å.

Still further, the first step, the second step and the high-pressure cleaning step between them are carried out continuously.

Furthermore, the poured sharp corner is HDP-OX (High Density Plasma Oxide of Silicon).

Compared with the prior art, the beneficial effect of the present invention is that the high-pressure cleaning step can wash away the fallen sharp corners in time to achieve the effect of cleaning the surface of the wafer, thereby preventing STI-CMP scratches.

【Description of drawings】

The present invention will be further described below in conjunction with accompanying drawing:

FIG. 1 is a flow chart of STI-CMP in the prior art.

Fig. 2 is a flow chart of the method for preventing STI-CMP scratches of the present invention.

【Detailed ways】

The best mode for carrying out the present invention will be described below with reference to the drawings.

As shown in FIG. 2, the present invention provides a method for preventing STI-CMP (shallow trench isolation planarization scratch). In the semiconductor manufacturing process, there is a deposition process of HDP-OX (high-density plasma silicon oxide) before the STI-CMP process. This step will complete the filling of the STI trenches, but after filling, the surface of the active region of the wafer will be form sharp corners. The first step of the present invention is to grind away the HDP-OX on the surface of the active area of the wafer. At this time, the sharp corners on the surface of the active area of the wafer will be poured out, and other by-products will be formed simultaneously. These fallen sharp corners and by-products are located between the wafer surface and the polishing pad. If they are not cleaned in time, they will cause scratches on the wafer surface during the subsequent grinding process. And the present invention is provided with a high-pressure cleaning step just after the first step is completed, and by high-pressure cleaning, the sharp corners and by-products poured away will be washed away, and the wafer surface is also cleaned. Subsequently, the grinding step of SiN will be carried out, and the grinding will be continued according to the specified thickness. This step can weaken or even remove the scratches accidentally formed on the wafer surface. At this time, the thickness of SiN that is ground away is generally 400A. It should be pointed out that the above steps are performed continuously.

Compared with the prior art, the beneficial effect of the present invention is that the high-pressure cleaning step can wash away the fallen sharp corners and other by-products in time to achieve the effect of cleaning the wafer surface, thus preventing STI-CMP scratches.

Although preferred embodiments of the present invention have been disclosed for illustrative purposes, those of ordinary skill in the art will appreciate that various Improvements, additions, and substitutions are possible.

Claims (5)

1. take precautions against the method that STI-CMP scratches for one kind, comprise step: the first step, the HDP-OX (high-density plasma silica) of wafer surfaces of active regions is ground off, at this time wafer surface can form the wedge angle of outwelling; Second step, carry out the grinding of SiN and SiN is ground off certain thickness, it is characterized in that: add the wedge angle that the high-pressure wash step drops to removing in the first step with between second step, thereby prevent that wafer surface from scratching.

2. the method that strick precaution STI-CMP according to claim 1 scratches is characterized in that: the grinding of SiN can be removed the accidental scuffing that forms of wafer surface.

3. the method that strick precaution STI-CMP according to claim 2 scratches, it is characterized in that: the certain thickness described in the grinding steps of SiN is 400A.

4. according to the method for claim 1 or 2 or 3 described strick precaution STI-CMP scuffings, it is characterized in that: said first step, second step and high-pressure wash step are between the two carried out continuously.

5. the method that strick precaution STI-CMP according to claim 4 scratches, it is characterized in that: the said wedge angle of outwelling is HDP-OX (a high-density plasma silica).

Images