JP2006114722A - Method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide such a method that an oxide film having a low plane direction dependency is formed and a rounding oxidation is efficiently made. <P>SOLUTION: In forming a groove in a silicon substrate, a plasma damage on the silicon substrate is decreased by utilizing a wet etching method, and a stress and an electric field concentration are decreased at a distal end by a shape control at the end of the groove by adjustment of an etching time period. By using an oxygen radical oxidation heat treating method when the rounding oxidation is made, a plane direction film thickness dependency of the oxide film to be formed can be considerably suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an etching technique using a chemical solution for a silicon substrate.

  In recent years, STI (Shallow Trench Isolation) technology has attracted attention as an element isolation process of CMOS-LSI. Hereinafter, a conventional STI formation method will be described (for example, see Patent Document 1).

  First, a groove is formed on a semiconductor substrate, and at least the groove is filled with an insulating film. Thereafter, the insulating film on the semiconductor substrate is removed by one or more planarization means, leaving the insulating film only in the trench. Of these one or more times of flattening, the final flattening means is flattened by the mirror polishing method without using the wet etching method.

For this reason, it is possible to prevent a concave portion generated at the end of the element isolation insulating film during the formation of the element isolation insulating film, reduce the number of manufacturing steps, and realize an STI formation method that is easy to form and has a high yield.
Japanese Patent Laid-Open No. 10-50822

  However, in the conventional formation method, the following problems remain when applied to a semiconductor device.

  First, when grooves are formed using dry etching in the entire etching process as in the conventional formation method, plasma damage to the substrate is large, and the formed grooves are physically used as part of the device. The problem of creating a vulnerability occurs.

  Further, the taper angle of the formed groove bottom portion is 87 to 90 °, and there is a problem that electric field concentration and stress concentration are likely to occur at a portion where the groove bottom surface and the groove side surface intersect.

  Further, in the technology at the time of filing of Patent Document 1, the furnace processing is generally used as the mass production technology in the rounding oxidation processing. However, in this method, the oxidation formed on the inner side walls of the silicon substrate grooves having different plane orientations. The variation in film thickness is very large, and it is difficult to form a uniform film, which causes a problem that electric field concentration and stress concentration tend to occur.

  Therefore, an object of the present invention is to provide a method for forming an STI that overcomes the above-described problems.

  The outline of the invention disclosed in the present application is as follows.

  First, the present invention reduces plasma damage to a silicon substrate by partially using wet etching using an alkaline solution instead of using only dry etching in the etching process as in the conventional formation method. Thus, the physical strength deterioration due to ion bombardment can be solved.

  In the present invention, an anisotropic etching process using an alkaline solution is allowed to proceed along the (111) plane, but the process is stopped before all of the etching exposed surfaces become the (111) plane, so that the groove tip The portion can be prevented from being V-shaped, thereby solving the problems of electric field concentration and stress concentration.

  In addition, since the present invention uses the oxygen radical oxidation method instead of the conventional furnace for the rounding oxidation after the formation of the separation groove, it is possible to greatly suppress the surface orientation film thickness dependency of the formed oxide film. Can also solve the problems of electric field concentration and stress concentration.

  According to the present invention, in the etching process of the separation groove, wet etching using an alkaline solution reduces plasma damage to the silicon substrate and the groove tip becomes trapezoidal, and stress concentration and electric field concentration at the groove tip. Can be avoided. In addition, in the oxidation treatment of the separation groove, rounding oxidation using the oxygen radical oxidation method greatly reduces the plane orientation dependency of the oxide film thickness, and forms a uniform oxide film. In addition, stress concentration can be further avoided. Therefore, it is possible to realize an STI that is easy to form and has a high yield.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1 to 2 are cross-sectional views showing respective steps of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

First, as shown in FIG. 1A, an SiO ₂ film (underlying film) 101, a polysilicon film 102, a silicon nitride film (antioxidation film) 103, an antireflection film are formed on a silicon substrate 100 on the (100) main surface. An (ARC film) 104 and a resist pattern 105 subjected to exposure opening processing are formed.

  FIG. 1A shows the state after the active region mask exposure step, and the groove shape formed by the etching process to be performed later varies depending on the diameter of the resist opening. Depending on the device to be applied, it is necessary to adjust the shape of the opening.

Next, as shown in FIG. 1B, the antireflection film 104, the silicon nitride film 103, the polysilicon film 102, and the SiO ₂ film 101 are removed by dry etching and oxygen ashing, so that the silicon substrate 100 is opened. It is formed so as to be exposed. Thereafter, the resist pattern 105 and the antireflection film 104 are removed.

  Next, as shown in FIG. 1C, the silicon substrate 100 is etched using sulfuric acid and ammonium hydroxide as wet etching using an alkaline solution. At that time, the anisotropic etching process is performed so that the process is stopped before all the exposed portions of the silicon substrate 100 become the (111) plane.

  Next, as shown in FIG. 2A, a trench deepening process of about 250 to 400 nm is performed along the (100) plane at the exposed portion of the silicon substrate 100 using dry etching.

  Next, as shown in FIG. 2 (b), after the wet etching process of one bath, the protective oxidation of the separation groove is performed at 1000 to 1150 ° C. using ISSG (In-Situ Steam Generation) annealing as an oxygen radical oxidation method. Oxidation treatment is performed to round the separation groove (not shown).

Next, as shown in FIG. 2C, after the isolation trench is filled with an insulating film (for example, a CVD-SiO ₂ film) 106 as in the prior art, the insulating film 106 on the semiconductor substrate is polished by a polishing method. And the insulating film 106 is left only in the isolation trench. Thereafter, the silicon nitride film 103 and the polysilicon film 102 are removed, and the STI of the element isolation layer according to the present invention is formed.

As described above, according to this embodiment, the following representative effects can be obtained.
(1) Rather than using only dry etching in the etching process, plasma damage to the silicon substrate can be reduced by partially using wet etching using an alkaline solution, thereby making physical damage due to ion bombardment possible. Strength deterioration can be prevented.
(2) Anisotropic etching process using an alkaline solution is allowed to proceed along the (111) plane, but the process is stopped before all of the exposed etching surface becomes the (111) plane, so that the groove tip becomes V It is possible to avoid the shape of the letter, thereby preventing electric field concentration and stress concentration.
(3) Since the oxygen radical oxidation method is used for the rounding oxidation after the formation of the separation groove, it is possible to greatly suppress the surface orientation film thickness dependency of the formed oxide film, and to prevent electric field concentration and stress concentration from now on. be able to.

  As described above, the present invention is useful for a method of forming an STI that is easy to form and has a high yield.

Sectional drawing which shows each process of the manufacturing method of the semiconductor device which concerns on embodiment of this invention Sectional drawing which shows each process of the manufacturing method of the semiconductor device which concerns on embodiment of this invention

Explanation of symbols

100 silicon substrate 101 SiO ₂ film 102 polysilicon film 103 a silicon nitride film 104 antireflection film 105 resist pattern 106 insulating film

Claims (3)

Forming a laminated film of a base film and an antioxidant film on a silicon substrate;
Selectively etching the laminated film to form an opening to expose the surface of the silicon substrate;
Etching the exposed portion of the silicon substrate to form a separation groove;
A step of embedding an insulating film in the isolation trench to form an element isolation layer,
The step of forming the separation groove is characterized in that after forming a trapezoidal groove on the exposed portion of the silicon substrate by wet etching, a groove deepening process is performed by maintaining the shape of the bottom of the groove by dry etching. A method for manufacturing a semiconductor device. In the wet etching, an anisotropic etching process of the (111) plane is performed on the exposed portion using an alkaline solution, and the process is stopped before all the etched exposed surfaces become the (111) plane,
The method of manufacturing a semiconductor device according to claim 1, wherein the dry etching is performed while maintaining the (111) plane. The method for manufacturing a semiconductor device according to claim 1, further comprising a step of performing rounding oxidation of the separation groove using an oxygen radical oxidation method after the step of forming the separation groove.

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