CN101593717B

CN101593717B - Preparation method of shallow trench isolation structure

Info

Publication number: CN101593717B
Application number: CN2008100434240A
Authority: CN
Inventors: 陈华伦; 陈雄斌; 熊涛; 陈瑜; 罗啸
Original assignee: Shanghai Hua Hong NEC Electronics Co Ltd
Current assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corp
Priority date: 2008-05-28
Filing date: 2008-05-28
Publication date: 2011-06-01
Anticipated expiration: 2028-05-28
Also published as: CN101593717A

Abstract

The invention discloses a preparation method of a shallow trench isolation structure, which comprises the following steps: forming a scalar silicon nitride appearance used as a mask for etching a shallow trench through three etching technologies, and realizing that a top angle is smoothed to prepare smoother silicon and silicon oxide interfaces by utilizing thinner silicon oxide with a poorer oxidation shielding property when the inner surface of a shallow trench is subsequently oxidized.

Description

The preparation method of fleet plough groove isolation structure

Technical field

The present invention relates to the preparation method of fleet plough groove isolation structure in a kind of semiconductor manufacturing.

Background technology

Fleet plough groove isolation structure (STI) is comparatively general isolation technology in the semiconductor manufacturing, and it mainly utilizes deposit silicon dioxide that the groove that etches is carried out backfill to form the isolation oxidation district.The preparation flow (referring to Fig. 1 to Fig. 6) of conventional fleet plough groove isolation structure is:

1) silicon oxide deposition and silicon nitride successively on silicon substrate;

2) carry out the shallow trench photoetching development, back etching forms shallow trench, carries out cleaning (see figure 3) after the etching;

3) oxidation processes of shallow trench inner surface forms the cushion oxide layer (see figure 4);

4) the silica-filled shallow trench (see figure 5) of high-density plasma;

5) planarization forms the fleet plough groove isolation structure (see figure 6).

Adopt above-mentioned traditional preparation method, because the shallow trench upper surface is covered by silicon nitride, and the side is exposed, lateral oxidation is fast when liner oxidation, surface oxidation is slow, oxidation rate difference maximum point is sharp corner in Fig. 4 just, cause oxidation herein easily after silicon face more sharp-pointed, problem such as cause that attenuation of grid oxygen and electric field are concentrated.On technology, existing device isolation need be carried out etching to silicon substrate, and what the slyness processing of vertical angles was leaned on basically is cushion oxide layer, how to utilize this one deck oxide layer to realize the drift angle slyness to greatest extent, is the problem that needs solution.

Summary of the invention

The technical problem to be solved in the present invention provides a kind of preparation method of fleet plough groove isolation structure, and it can prepare comparatively slick and sly silicon drift angle.

For solving the problems of the technologies described above, the preparation method of fleet plough groove isolation structure of the present invention comprises the steps:

Step 1, silicon oxide deposition and silicon nitride successively on silicon substrate;

Step 2, the coating photoresist carries out shallow trench photoetching and development, forms a photoresist opening;

Step 3 is the described silicon nitride of mask etching with described photoresist, removes the silicon nitride of part, and thickness can be 20～60% of described silicon nitride gross thickness;

Step 4, the horizontal reduction of photoresist is with the opening expansion 10～50% of the photoresist in the described step 2;

Step 5, with step 3 in the silicon nitride of identical etching technics etch step three back residual thickness to described silicon oxide surface or described surface of silicon;

Step 6 is that mask carries out etching formation shallow trench with the silicon nitride;

Step 7, shallow trench inner surface oxidation processes forms cushion oxide layer;

Step 8, the silica-filled shallow trench of high-density plasma;

Step 9 forms fleet plough groove isolation structure after the planarization.

The preparation method of fleet plough groove isolation structure of the present invention, the step before etch silicon nitride be with original consistent, in etch silicon nitride,, form as stair-stepping special appearance after making silicon nitride etch by the adjusting of etching parameters, and then deoxidation.Doing like this is to utilize silicon nitride thin more, and its shielding to oxide layer is poor more, and oxidized characteristic reaches the purpose of drift angle slyness easily.Because the thickness gradient of silicon nitride changes, therefore the most weak and strengthen in gradient the thinnest to the screening ability of oxidation near shallow trench drift angle place, that is the influence of oxidation rate is increased gradually by minimum.Thereby in the difference minimum of the oxidation rate of drift angle place upper surface and side, and because the silicon nitride progressive additive, the oxidized amount of silicon in the inner part reduces, and therefore prepares more smooth radian, avoids the formation of silicon drift angle place wedge angle.

Description of drawings

The present invention is further detailed explanation below in conjunction with accompanying drawing and embodiment:

Fig. 1 to Fig. 6 is the preparation flow structural representation of fleet plough groove isolation structure in the prior art;

Fig. 7 is the structural representation after photoresist is laterally reduced among the preparation method of the present invention;

Fig. 8 is the structural representation behind the etching remaining silicon nitride among the preparation method of the present invention;

Fig. 9 is the structural representation after the shallow trench etching among the preparation method of the present invention;

Figure 10 is a partial structurtes enlarged diagram after the shallow trench etching among the preparation method of the present invention;

Figure 11 is a partial structurtes enlarged diagram after the oxidation of shallow trench inner surface among the preparation method of the present invention.

Embodiment

The preparation method of fleet plough groove isolation structure of the present invention, it is integrated in the existing technology, mainly utilizes the etching technics etching to form a special silicon nitride pattern.Whole process of preparation is as follows:

1) silicon oxide deposition and silicon nitride successively on silicon substrate.

2) the coating photoresist carries out shallow trench photoetching and development, forms a photoresist opening.Similar in concrete setting in this two step and the prior art.

3) be the described silicon nitride of mask etching with described photoresist, remove the silicon nitride thickness of part, the silicon nitride thickness of removal can be 20～60% of silicon nitride layer gross thickness;

4) the horizontal reduction of photoresist, this process of opening expansion 10～50% (see figure 7)s of photoresist in the step 2 can be carried out in the etch chamber of silicon nitride etch, its etching parameters is adjusted into: fluorine carbon based compound is below 15% of consumption in the conventional silicon nitride dry etching, feed the oxygen of 10～20sccm, electrode applies electricity less than 70W.

5) with step 3 in identical etching technics etch step three back residual silicon nitride to silicon oxide surface or surface of silicon (among Fig. 8 for being etched to silicon oxide surface);

6) be mask etching silica and the silicon substrate under it with the silicon nitride, form the shallow trench (see figure 9).

7) shallow trench inner surface oxidation processes forms cushion oxide layer.Because silicon nitride has a thickness gradient, the thinnest near shallow trench drift angle place, thereby the most weak and strengthen in gradient to the screening ability of oxidation herein, that is the influence of oxidation rate is increased gradually by minimum.Thereby in the difference minimum of the oxidation rate of drift angle place upper surface and side, and because the silicon nitride progressive additive, the oxidized amount of silicon in the inner part reduces, and therefore prepares more smooth radian (seeing Figure 10 and Figure 11), avoids the formation of wedge angle.

8) the silica-filled shallow trench of high-density plasma.

9) form fleet plough groove isolation structure after the planarization, step 8 and nine processing mode are same as the prior art.

In the above-mentioned preparation flow, step 3 to the etch step of step 5 has formed the silicon nitride special appearance: traditional approach all is to adopt fluorocarbons to carry out etching, and the silicon nitride sidewall of formation is more straight, can't realize the gradient of oxidation screening ability is changed.Silicon nitride pattern among the present invention can obtain by the following method: at first adopt conventional method to etch away the silicon nitride of a part, for example 40% of the silicon nitride gross thickness; Switch etch step then, reduce to feed the amount (to 15% below) of fluorocarbons, feeds an amount of oxygen (about 10～20sccm), and the bias voltage (approximately less than 70W) that applies of reduction electrode, with the minimizing ion bombardment effects.Opening at the following photoresist of situation of less photoresist loss enlarges like this, by the time openings of sizes satisfy process specification (as, enlarge 20%) after, switch back the silicon nitride of main etching step removal residual thickness again.Be exposed in the etching environment at original silicon nitride with regard to some like this and accept etching without etching.When treating that the silicon nitride that is etched in advance has been etched substantially, it is very thin that the silicon nitride edge that newly comes out has also become.Owing to the characteristic of etching itself, the etch rate at the edge of outstanding bar always than comparatively fast, therefore forms the silicon nitride pattern that a thickness gradient changes simultaneously.

Claims

1. the preparation method of a fleet plough groove isolation structure is characterized in that, comprises the steps:

Step 3 is the described silicon nitride of mask etching with described photoresist, removes the silicon nitride of part;

Step 5, with step 3 in the silicon nitride of identical etching technics etch step three back residual thickness to described silica or described surface of silicon;

Step 8, the silica-filled shallow trench of high-density plasma;

Step 9 forms fleet plough groove isolation structure after the planarization.

2. according to the described preparation method of claim 1, it is characterized in that: the removal thickness of silicon nitride is 20～60% of described silicon nitride gross thickness in the described step 3.

3. according to claim 1 or 2 described preparation methods, it is characterized in that: dry etch process is adopted in the horizontal reduction of photoresist in the described step 4, it is below 15% of consumption in the conventional silicon nitride dry etching that its etching parameters is set at fluorine carbon based compound, feed the oxygen of 10～20sccm, electrode applies power less than 70W.