JP2576361B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a dry etching method for etching an insulating film or a polysilicon film by using plasma.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device, in a dry etching method for forming a contact hole in an insulating film formed on a semiconductor substrate, CHF ₃ + O ₂ , CH
F ₃ + CF ₄ + (+ O ₂ ) or CHF ₃ + C ₂ F ₆ (+
Gas systems such as O ₂ ) have been used. When etching is performed on silicon or polysilicon using such a gas system under conditions that provide a high selectivity, each time the etching process is repeated, it is formed by polymerization of process gas and photoresist in the etching chamber. The deposits adhered, and particles were generated due to the detachment of the deposits. Therefore, it is necessary to frequently open the etching chamber of the dry etching apparatus to the atmosphere and clean the etching chamber.

In recent years, as a method for reducing the frequency of cleaning the etching chamber, a method of adding an O ₂ gas in an amount of about 10% of the total flow rate (Japanese Patent Laid-Open No. 1-241128).
And a method of inserting a cleaning sequence of an etching chamber in connection with etching and etching of a wafer.

[0004] The deposition of deposits in the etching chamber occurs even when the polysilicon film is etched using HBr gas, as in the case of the insulating film.

[0005]

In the method of preventing the deposition of a polymer film by increasing the amount of O ₂ gas added to the etching of an insulating film, the etching for silicon or polysilicon underlying the oxide film or the nitride film is selected. There is a problem that a large ratio cannot be obtained. That is, FIG.
As shown in ( ₂₎ , in a CHF ₃ + O ₂ gas system, the selectivity of SiO ₂ to Si decreases as the amount of O ₂ added increases. In recent semiconductor devices, there are many cases where a plurality of contact holes have different depths and sizes, and a higher selectivity is required than ever before, so that it is impossible to cope with the method by simply increasing the amount of added O ₂ gas. ing.

Further, when HBr gas is used alone or under nearly independent conditions (80% or more of the total flow rate ratio) as a dry etching gas for a polysilicon film, a large amount of deposits are generated in the etching chamber. For this reason, when it is used normally, it is used by mixing with Cl ₂ or SF ₆ gas. When a gas system of HBr + SF ₆ is used, in order to obtain a selectivity with SiO ₂ of 20 or more, as shown in FIG.
The flow rate ratio of Br must be 75% or more. Under this condition, the etching chamber needs to be cleaned every time about 2,000 wafers are processed.

[0007] SF ₆ gas has a strong property of removing deposits and is also used as a cleaning gas for an etching chamber. However, when used alone or under nearly independent conditions (60% or more of the total flow ratio), an anisotropic processed shape is obtained. Unobtainable SiO ₂
And the selectivity with them is also low.

Further, in the method of inserting a dry cleaning sequence between the etching of the insulating film and the polysilicon film,
Problems arise, such as a decrease in throughput due to an increase in process time, and costs associated with remodeling of software and hardware of equipment.

[0009]

According to a method of manufacturing a semiconductor device of the present invention, an insulating film or a polysilicon film formed on a semiconductor substrate is etched with a deposit formed during etching.
In a method of manufacturing a semiconductor device which is etched by a plasma etching method using a mixed gas containing a gas to be etched, the deposit in the mixed gas is etched during the etching .
Is characterized in that the ratio of the gas for etching is reduced.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an etching apparatus used in an embodiment of the present invention. A case where a contact hole is formed in an insulating film will be described as a first embodiment.

First, after an element pattern is formed on a silicon substrate by diffusion or the like, a silicon oxide film having a thickness of about 1 μm is formed on the surface. Next, after forming a photoresist film having an opening on the silicon oxide film, the silicon substrate 3 is set on the lower electrode 2 facing the upper electrode 1 of the etching apparatus shown in FIG. Next, CHF ₃ (6
0% to 70%) and O ₂ (the mixed gas flow rate of 30-40%) to about 100 SCCM, the plasma is generated at a frequency of 13.56MH _Z, although the silicon oxide film is etched to form a contact hole, a silicon oxide Immediately before the film is etched and the silicon of the substrate is exposed, O ₂ of the mixed gas is reduced to 0.
The contact hole is completed by reducing the silicon oxide film to an etching selectivity of the silicon oxide film while improving the etching selectivity.

As described above, the ratio of O ₂ in the mixed gas is 30
When it is set to ４０40%, the amount of deposits in the etching chamber decreases as shown in FIG. According to the first embodiment, even though 1000 wafers were processed, almost no deposits were found in the chamber,
When the treatment was performed only with the HF ₃ gas, adhesion of a deposit having a thickness of about 10 μm was observed.

According to the present embodiment, the generation of particles of 3 μm or more can be reduced by half, and the cleaning cycle of the etching chamber can be extended by 50% or more. Further, since the state in the etching chamber is kept almost the same, the variation in the etching rate can be reduced from about 10% to 5% of the conventional one.

Next, the etching of a polysilicon film used for an electrode, a wiring and the like will be described as a second embodiment.

First, a polysilicon film for a lower electrode of a capacitor is formed to a thickness of about 1 μm on a silicon substrate via an insulating film such as silicon oxide. Next, after a photoresist film for a mask is formed on the polysilicon film, the substrate is set on the lower electrode 2 of the etching apparatus shown in FIG. Next, HBr (60-70%) and SF
₆ (30-40%) mixed gas flow rate about 100 SCC
M. Plasma is generated under the condition of a frequency of 13.56 MHz, and the polysilicon film is etched. Then, when the thickness of the polysilicon film becomes 0.1 μm, the mixture ratio of HBr is set to 80 to 90%, and the polysilicon film is etched.

As described above, by first increasing the mixing ratio of SF ₆ gas and then decreasing the mixing ratio of SF ₆ , the amount of deposits deposited in the chamber is reduced, and the selection with the underlying insulating film is reduced. Anisotropic etching with a high ratio can be performed, and a lower electrode having a good shape can be formed.

In each of the above embodiments, a case where a parallel plate type etching apparatus is used has been described. However, other types such as a magnetron type and an ECR type may be used.

[0018]

As described above, according to the present invention present invention, etching
When etching an insulating film or a polysilicon film using a mixed gas containing a gas for etching a deposit formed at the time of etching, the deposition in the mixed gas during etching is performed.
By reducing the proportion of gas that etches things,
There is an effect that a high selection can be made and the amount of deposits in the etching chamber can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an etching apparatus used in an embodiment of the present invention.

FIG. 2 is a view showing a relationship between a ratio of O _{2 in} a mixed gas and a selectivity.

FIG. 3 is a diagram showing the relationship between the ratio of O _{2 in} a mixed gas and the deposition rate of deposits.

FIG. 4 is a diagram showing a relationship between a ratio of SF _{6 in} a mixed gas and a selectivity.

[Explanation of symbols]

 Reference Signs List 1 upper electrode 2 lower electrode 3 silicon substrate 4 high frequency power supply

Claims (3)

(57) [Claims] An insulating film or a polysilicon film formed on a semiconductor substrate is removed from a deposit formed at the time of etching.
In a method of manufacturing a semiconductor device which is etched by a plasma etching method using a mixed gas containing a gas to be etched, the deposit in the mixed gas is etched during the etching.
A method for manufacturing a semiconductor device, characterized in that a ratio of a gas for etching a product is reduced . _2. The method according to claim 1, wherein a mixed gas of CHF ₃ and O ₂ is used for etching the insulating film. 3. The method of manufacturing a semiconductor device according to claim 1, wherein a mixed gas of HBr and SF ₆ is used for etching the polysilicon film.