CN101567312A

CN101567312A - Method for producing ONO structure

Info

Publication number: CN101567312A
Application number: CNA2008100432777A
Authority: CN
Inventors: 杨华; 吕煜坤
Original assignee: Shanghai Hua Hong NEC Electronics Co Ltd
Current assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corp
Priority date: 2008-04-22
Filing date: 2008-04-22
Publication date: 2009-10-28

Abstract

The invention discloses a method for producing an ONO structure, comprising the following steps: (1) depositing a lower-layer oxide film, a middle-layer nitric-oxide film and an upper-layer oxide film on a silicon substrate in sequence to form an ONO thin film, and then depositing a nitride film on the formed ONO thin film; (2) coating an anti-reflection coating and photoresist on the nitride film, and then using a photoetching technique to expose a position to be etched; (3) carrying out plasma etching at the position to be etched, and stopping on the lower-layer oxide film; (4) removing the residual photoresist and the anti-reflection coating; (5) further using a wet etching technique to etch the lower-layer oxide film; and (6) removing the residual nitride film by the wet etching technique to form the ONO structure. The structure can solve the problem of peeling off the photoresist, ensure uniformity of etching and effectively control side etching.

Description

The method for preparing the ONO structure

Technical field

The present invention relates to a kind of preparation method of semiconductor structure, be specifically related to prepare in a kind of semiconductor SONOS product the method for ONO (oxide-film-nitrogen oxidation film-oxide-film) structure.

Background technology

In the SONOS product, need prepare the ONO structure in specific zone.Shown in Figure 1 is that common ONO technology obtains the ONO structural representation.In this structure, size 5 has been represented the decrease of ONO effective dimensions in ONO technology.Operation window or increase ONO density of texture in order to increase subsequent technique flow process and device require size 5 the smaller the better.

Industry ONO structure formation method commonly used comprises photoetching, plasma etching and wet chemical technology.The first step is utilized lithographic definition photoresist figure, and ONO line size in the technology thereafter changed compensates.Second step, adopt plasma etching industrial successively with the photoresist figure transfer to antireflecting coating, upper strata oxide-film and middle nitride film, and rest on the lower-layer oxide film.In the 3rd step, utilize wet chemical technology to open lower-layer oxide film, and, can be good at stopping at the silicon substrate surface by means of the good selectivity of wet chemical to oxide-film and silicon substrate.At last, remove remaining photoresist and antireflecting coating, promptly obtain the ONO structure.

The 3rd step wet chemical technology can cause lateral corrasion to upper strata oxide-film and lower-layer oxide film section, obtains the ONO structure as shown in Figure 1.As seen, the size of size 5 mainly is subjected to the influence of wet chemical technology.In order to reduce size 5, essential control wet chemical technology is to the lateral corrasion of upper strata oxide-film.

What existing technology adopted when opening surface oxidation film with wet chemical is the photoresist mask, kind and the quantity of handling soup all have considerable restraint, if the long photoresist lift off problem that causes easily of processing time, the soup oxide-film etch rate that uses causes the problem, particularly upper strata oxide film sidewall of etching homogeneity difference to cross the serious increased in size 5 of conference to etching again too soon easily.

Summary of the invention

Technical problem to be solved by this invention provides a kind of method of the ONO of preparation structure, and it can eliminate the photoresist lift off problem, guarantees the uniformity of etching, effectively controls the side direction etching.

In order to solve above technical problem, the invention provides a kind of method of the ONO of preparation structure, comprise the steps:

(1) deposit lower-layer oxide film successively, intermediate layer nitrogen oxidation film and upper strata oxide-film on silicon substrate form the ONO film, deposit nitride film again on the ONO film that forms;

(2) coating antireflecting coating and photoresist on nitride film utilize the position that photoetching process exposes needs etching then;

(3) on the position of need etching, carry out plasma etching, and on the lower-layer oxide film that stops at;

(4) remove residual photoresist and antireflecting coating;

(5) further use wet corrosion technique etching lower-layer oxide film;

(6) remove remaining nitride film with wet corrosion technique, form the ONO structure.

Because the present invention's method that increases nitride film, can eliminate the photoresist lift off problem, use the slower BOE of speed can guarantee etching homogeneity simultaneously, effectively control the side direction etching, improve the window of ONO manufacturing process, improved performances such as the electricity of structure and reliability.

Description of drawings

Below in conjunction with the drawings and specific embodiments the present invention is described in further detail.

Fig. 1 is the ONO structural representation that existing technology obtains;

Fig. 2 is a flow chart of the present invention;

Fig. 3 is the structural representation after the present invention carries out plasma etching;

Fig. 4 is the structural representation after the present invention removes residual photoresist and antireflecting coating;

Fig. 5 is the structural representation after the present invention uses the wet etching lower-layer oxide film;

Fig. 6 is the ONO structural representation after the present invention removes nitride film.

Embodiment

For fear of peeling off of photoresist, the present invention in the end during oxidation step film etching, adopts nitride film to serve as hard mask layer, after all definition finishes, peels off the nitrogenize rete at figure again, forms the ONO structure.Technological process of the present invention as shown in Figure 2.

The first step, the lower-layer oxide film 2 of on silicon substrate 1, growing successively, intermediate layer nitrogen oxidation film layer 3, upper strata oxide-film 4 and nitride film 6.When NONO grew, the thickness of nitride film 6 should reduce intermembranous stress less than 200 dusts, also can shorten last nitride film and remove the time.

Second the step, utilize photoetching with the figure transfer on the light shield in photoresist 8.Cause loss in order to remedy etching technics and wet chemical technology thereafter, can compensate line size during photoetching size 5.Need to determine the position of etching after the exposure.This step etching wishes that directivity preferably can be arranged.For example, utilize dijection frequency power etching machine, source power is 200-600W, and deflection power is 30W-300W, and gas pressure is 2-20mT, the Cl2 flow is 0-100SCCM, the CF4 flow is 0-150SCCM, and the O2 flow is 0-50SCCM, and the Ar flow is 0-180SCCM, CHF3 etc. other to contain the C/F gas flow be 0-100SCCM, total gas couette 50-250SCCM.

The 3rd step, on the described position that needs etching, carry out plasma etching, successively with the photoresist figure transfer on antireflecting coating 7, nitride film 6, upper strata oxide-film 4 and intermediate layer nitrogen oxidation film 3, and stop at lower-layer oxide film 2 surfaces (as shown in Figure 3).The mode that plasma ashing adopts can comprise that high temperature (240-270 degree) or low temperature (100-140 degree) remove glue, and the gas that uses is oxygen O ₂, and follow chemical cleaning technology thereafter.The ratio of dioxysulfate water can be controlled at 2: 1-20: 1, and temperature can be used 110 ℃-160 ℃ scope.After removing, photoresist can increase the cleaning of the lower ammoniacal liquor hydrogen peroxide of temperature (volume ratio of ammoniacal liquor, hydrogen peroxide and water 1: 1: 5-1: 2: 60, temperature was lower than 45 ℃) short time.

In the 4th step, adopt plasma ashing technology or wet chemical stripping adhesive process to remove remaining photoresist 8 and antireflecting coating 7 (as shown in Figure 4).

In the 5th step, adopt wet chemical technology that lower-layer oxide film 2 is removed.Owing to adopted nitride film can serve as the hard mask plate, having avoided adopting photoresist is the photoresist lift off problem that mask may cause, therefore this technology can adopt the slower buffer oxide film etching agent (BOE) of speed, oxide-film speed is less than 30 dusts/min, thereby guaranteed the uniformity of etching, control the side direction etching effectively, avoided the excessive increase (Fig. 5) of size 5.

The 6th step, remove remaining top nitride film 6 with wet chemical, form ONO structure (Fig. 6).This technology is general to adopt hot phosphoric acid to remove nitride film.The treatment temperature of phosphoric acid can be between 140 ℃ to 160 ℃, and the processing time decides on top nitride film thickness, requires over etching about 100%, forms the ONO structure at last.

Claims

1, a kind of method for preparing the ONO structure; It is characterized in that, comprise the steps:

(1) deposit lower-layer oxide film successively, intermediate layer nitrogen oxidation film and upper strata oxide-film on silicon substrate form the ONO film, deposit one deck nitride film again on the ONO film that forms;

(2) coating antireflecting coating and photoresist on described nitride film utilize the position that photoetching process exposes needs etching then;

(3) need carry out plasma etching on the position of etching described, and stop on the described lower-layer oxide film;

(4) remove residual photoresist and antireflecting coating;

(5) further use wet corrosion technique etching lower-layer oxide film;

2, the method for preparing the ONO structure as claimed in claim 1 is characterized in that, the thickness of described nitride film is less than 200 dusts.

3, the method for preparing the ONO structure as claimed in claim 1 is characterized in that, the mode that step (4) adopts plasma ashing technology or dioxysulfate water to peel off is removed residual photoresist and anti-reflecting layer.

4, the method for preparing the ONO structure as claimed in claim 3 is characterized in that, the ratio of described dioxysulfate water can be controlled at volume ratio 2: 1 to 20: 1, and temperature is 110 ℃ to 160 ℃.

5, the method for preparing the ONO structure as claimed in claim 4 is characterized in that, can increase the ammoniacal liquor hydrogen peroxide cleaning that temperature is lower than 45 ℃ after photoresist is removed, and wherein the volume ratio of ammoniacal liquor, hydrogen peroxide and water is 1: 1: 5 to 1: 2: 60.

6, the method for preparing the ONO structure as claimed in claim 1 is characterized in that, step (5) adopts the oxide etching buffer solution of oxide-film etch rate 30 dusts/min to carry out wet etching.

7, the method for preparing the ONO structure as claimed in claim 1 is characterized in that, step (6) adopts hot phosphoric acid to peel off remaining nitride film, and the treatment temperature of described phosphoric acid is 140 ℃ to 160 ℃, and over etching is 100%.