JP2003051536A - Wafer treatment method and production method for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer treatment method with which the corner of a rugged pattern formed on the surface of a wafer can be sufficiently rounded without damaging the relevant wafer, and a production method for semiconductor device for performing such a treatment method. SOLUTION: After a groove pattern 7 is formed on the surface layer of a silicon wafer 1, an oxidized film 9 is grown on the inner wall of the groove pattern 7 by wet treatment using an oxidized solution. Next, the oxidized film 9 is selectively removed by wet etching. Afterwards, element separating materials 13 are buried in the groove pattern 7 through a thermal oxidized film 11, the excessive element separating materials 13 are removed from the surface of the silicon wafer 1, and an element separating area 15 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing a substrate and a method of manufacturing a semiconductor device, and more particularly, to a method of processing a surface of a substrate on which a concavo-convex pattern such as an electrode for a capacitor or a groove pattern for element isolation is formed. The present invention relates to a method for manufacturing a semiconductor device that performs this processing method.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a so-called STI (Shallow Trench I) is used as a trench type element isolation region.
When forming a solation), first, a pad oxide film is formed on the surface of the silicon substrate 1 by thermal oxidation, and then CVD
A silicon nitride film is formed by the (chemical vapor deposition) method. After that, a resist pattern is formed on the silicon nitride film, the silicon nitride film and the pad oxide film are etched using this resist pattern as a mask, and the resist pattern is removed. Then, the silicon substrate 1 is etched using the silicon nitride film as a mask to form a groove pattern for element isolation on the surface layer of the silicon substrate 1.

After that, the inner wall of the groove pattern is covered with an oxide film, and then an element isolation material is formed in a state where the inside of the groove pattern is buried, and then the excess element isolation material and the silicon nitride film on the silicon substrate are removed. Then, a groove type element isolation region is formed by filling the inside of the groove pattern with an element isolation material.

By the way, in a semiconductor device having an element isolation region formed in this way, if there is a corner at the boundary between the element regions separated by the groove pattern, the electric field concentrates at this corner. However, the reliability of the gate insulating film formed on the element region may be reduced, or leakage current may occur. Therefore, in the step of forming the element isolation region described above, a thermal oxide film is formed after the groove pattern is formed so that corners are not formed in the groove pattern,
A step of blunting the corners is performed by removing the thermal oxide film by dry etching.

[0005]

However, in the method of forming a thermal oxide film on the inner wall of the groove pattern and removing it by dry etching, damage due to dry etching easily enters the inner wall of the groove pattern, which results in leakage current. Will increase. Moreover, when the temperature of thermal oxidation when forming the thermal oxide film is high, a corner remains at the bottom of the groove pattern. Therefore, it is not possible to prevent the electric field concentration at the bottom of the groove. On the other hand, when the temperature of thermal oxidation is low, the opening upper part of the groove pattern becomes overhung, so that, for example, the embedded state of the element isolation material in the groove pattern deteriorates, and the characteristics of the semiconductor element formed in the element region are reduced. There is a problem of causing deterioration.

Therefore, the present invention provides a substrate processing method capable of sufficiently blunting the corners of an uneven pattern formed on the surface of a substrate without damaging the underlying surface layer, and a semiconductor device performing this processing method. It aims at providing the manufacturing method of.

[0007]

The present invention for achieving the above object is a method for treating a surface of a substrate having an uneven pattern, wherein a surface layer of the substrate is oxidized by a wet treatment using an oxidizing solution. After the film is grown, the oxide film is selectively removed by wet etching.

In the above processing method, an oxide film is grown on the surface layer of a substrate having an uneven pattern by a wet process using an oxidizing solution. Here, the growth of the oxide film by the wet treatment using the oxidizing solution is controlled by the supply of oxygen from the oxidizing solution. Therefore, on the surface of the substrate having the concavo-convex pattern, oxygen is sufficiently supplied to the convex corners as compared with the flat portions, and the oxidation easily progresses, and the thickness of the oxide film in this portion is large. Become. On the other hand, since the amount of oxygen supplied to the concave corners tends to be insufficient, it is difficult for the oxidation to proceed, and the thickness of the oxide film at this portion becomes thin. That is, an oxide film having a thick convex corner and a thin concave corner is formed on the surface of the substrate. Therefore, by removing such an oxide film by wet etching, the convex corners and the concave corners on the surface of the substrate are blunted without damaging the surface layer of the underlying substrate.

The present invention is also a method of manufacturing a semiconductor device having a groove-type element isolation region, in which a groove pattern is formed on a surface layer of a substrate and then an inner wall of the groove pattern is formed by a wet process using an oxidizing solution. An oxide film is grown on the substrate, and the oxide film is selectively removed by wet etching. After that, the inside of the groove pattern is filled with an element isolation material.

In such a manufacturing method, an oxide film is grown on the surface layer of the groove pattern by a wet process using an oxidizing solution, and the oxide film is selectively removed by wet etching. Similar to the treatment method, the convex corners and the concave corners in the groove pattern are blunted without damaging the surface layer of the substrate.

Further, the present invention is also a method of manufacturing a semiconductor device having a capacitor, in which the surface of the first electrode is formed by wet processing using an oxidizing solution after forming the first electrode on the substrate in a standing state. An oxide film is grown on the layer and then the oxide film is selectively removed by wet etching. Then, a dielectric film and a second electrode film are formed in a state of covering the first electrode.

In such a manufacturing method, an oxide film is grown on the surface layer of the first electrode erected on the substrate by using an oxidizing solution, and the oxide film is selectively removed by wet etching. Therefore, similarly to the substrate processing method described above, the convex corners and the concave corners of the first electrode are blunted without damaging the underlying substrate or the surface layer of the first electrode.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(First Embodiment) FIG. 1 shows, as a first embodiment of the present invention, a groove type element isolation region (so-called STI).
FIG. 6 is a cross-sectional process diagram for describing the method for manufacturing the semiconductor device including the above. Hereinafter, the first embodiment of the present invention will be described with reference to this drawing.

First, as shown in FIG. 1A, the surface of the silicon substrate 1 is thermally oxidized to form a pad oxide film 3 made of silicon oxide, and then silicon nitride is formed on the pad oxide film 3 by a CVD method. The film 5 is formed.

Next, a resist pattern (not shown here) is formed on the silicon nitride film 5 by the lithography method, and the silicon nitride film 5 and the pad oxide film 3 are etched using this resist pattern as a mask.
Here, the silicon nitride film 5 and the pad oxide film 3 in the element isolation region portion formed on the surface layer of the silicon substrate 1 are removed by etching in the following steps. After this etching is completed, the resist pattern is peeled and removed.

Next, using the silicon nitride film 5 as a mask,
The surface layer of the silicon substrate 1 is anisotropically etched by dry etching to form a groove pattern 7 (concave pattern) on the surface layer of the silicon substrate 1.

Next, as shown in FIG. 1B, the pad oxide film 3 is selectively wet-etched by, for example, a treatment using an aqueous solution of hydrofluoric acid to expose the pad oxide film 3 exposed on the etching side wall. Are recessed in the depth direction to form an undercut under the silicon nitride film 5. As a result, the upper surface of the convex corner portion A located at the upper end of the opening of the groove pattern 7 formed in the silicon substrate 1 is exposed. Further, in this wet etching, the pad oxide film 3 is etched by a desired retreat amount by adjusting the concentration and temperature of the hydrofluoric acid aqueous solution, and further by adjusting the etching time.

In this wet etching,
In addition to the hydrofluoric acid aqueous solution, an ammonium fluoride aqueous solution, a mixed aqueous solution of hydrofluoric acid and ammonium fluoride, a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide solution, and a hydrofluoric acid and hydrochloric acid solution. A mixed aqueous solution or an aqueous solution containing hydrofluoric acid such as a mixed aqueous solution of hydrofluoric acid and a surfactant may be used as the etching solution.

Then, the following steps are the steps peculiar to the first embodiment. That is, first, as shown in FIG. 1 (3), by a wet process using an oxidizing solution,
The exposed surface of the silicon substrate 1 including the inner wall of the groove pattern 7 is oxidized, and the oxide film 9 is grown on the inner wall of the groove pattern 7.
The oxidizing solution used at this time is, for example, ozone water (a solution in which ozone O ₃ is dissolved in pure water).

This wet treatment is performed, for example, with an ozone concentration of 2
In the case of using ozone water of 0 ppm and 23 ° C., an oxide film having a thickness of about 1 nm grows on the exposed surface of the silicon substrate 1 within about 10 seconds after starting the treatment, and the treatment time is further extended. However, the thickness of the oxide film 9 does not increase so much from 1 nm. Therefore, when this wet treatment is performed with ozone water at room temperature (23 ° C.), the treatment time is set to about 10 seconds to 3 minutes in order to perform the treatment efficiently.

The wet treatment is not limited to using ozone water as the oxidizing solution, and oxidizing solutions other than ozone water may be used. As the oxidizing solution other than ozone water, hydrogen peroxide solution, a mixed solution of hydrochloric acid and hydrogen peroxide solution, a mixed solution of hydrogen peroxide solution and sulfuric acid, and the like are used. Also, improving the growth rate of the oxide film,
The oxidizing solution may be heated and used for the purpose of increasing the thickness of the oxide film.

After the oxide film 9 is formed by the wet treatment as described above, this oxide film (9) is selectively removed by wet etching as shown in FIG. 1 (4). At this time, for example, a hydrofluoric acid aqueous solution (hydrofluoric acid concentration 1%, 24 ° C.) is used as the etching solution to selectively remove the oxide film (9) made of silicon oxide with respect to the silicon substrate 1. . At this time, if the etching time is lengthened, the pad oxide film 3 and the silicon nitride film 5 are etched. Therefore, if the etching of these films is not desired, it is necessary and sufficient to remove only the oxide film 9. Set the appropriate etching time. For example, when a hydrofluoric acid aqueous solution (hydrofluoric acid concentration 1%, 24 ° C.) is used as the etching solution, the oxide film 9 is necessary and sufficiently etched and removed in about 10 seconds. On the other hand, the pad oxide film 3 may be intentionally set back by making the etching time at this time longer than the time for removing the oxide film (9).

The etching solution used for this wet etching is not limited to the hydrofluoric acid aqueous solution, and the pad oxide film 3 described with reference to FIG.
The etching solution used for the wet etching can be used.

After this wet etching is completed, a pure water rinse is performed, and then a drying process is performed.

If necessary, a pure water rinse step may be inserted between the oxidation step by the wet process shown in FIG. 1 (3) and the wet etching step shown in FIG. 1 (4). Further, in the case where a mixed solution of highly viscous sulfuric acid and hydrogen peroxide solution is used as an oxidizing solution in the oxidizing step by wet treatment, it is preferable to perform a pure water rinse step after the oxidizing step.

After the above, as shown in FIG. 1 (5), a thermal oxide film 11 is formed on the inner wall of the groove pattern 7 by heat treatment, and is then made of silicon oxide in a state of filling the groove pattern 7 by the CVD method. The element isolation material film 13 is formed. In the step described with reference to FIG. 1D, when the pad oxide film 3 is made to recede, it is continued from the inner wall of the groove pattern 7 to the upper surface of the convex corner located at the upper end of the opening of the groove pattern 7. The thermal oxide film 11 can be grown effectively.

After the element isolation material film 13 is formed, the element isolation material film 13 on the silicon nitride film 5 is polished and removed using the silicon nitride film 5 as a stopper, and further nitrided by wet etching using hot phosphoric acid. After removing the silicon film 5, the pad oxide film 3 on the silicon substrate 1 is removed by wet etching using an aqueous solution of hydrofluoric acid. As a result, as shown in FIG. 1 (6), the element isolation material film 13 is formed in the groove pattern 7 via the thermal oxide film 11.
Trench type element isolation region (so-called ST
I) Form 15.

In the method of manufacturing a semiconductor device as described above, as described with reference to FIG. 1C, the oxide film 9 is formed on the inner wall of the groove pattern 7 by a wet process using an oxidizing solution. ing. In the wet process using such an oxidizing solution, the oxidation reaction proceeds due to the rate of the oxidation reaction in the initial stage of the process, and oxygen atoms gradually pass through the oxide film 9 formed on the surface of the silicon substrate 1. In the case of diffusing at the interface between the silicon substrate 1 and the silicon substrate 1, the reaction is controlled by the diffusion (that is, the supply rate control). As a result, the oxide film 9 initially formed on the exposed surface of the silicon substrate 1 is The oxidation reaction of the silicon substrate 1 is rate-controlled by the film thickness.

Therefore, on the flat surface of the silicon substrate 1,
Oxygen is supplied uniformly in the initial stage of the oxidation reaction,
Oxide film 9 having a uniform film thickness is formed. On the other hand, since the oxygen is sufficiently supplied to the convex corner portion A at the upper end of the groove pattern 7 in the initial stage of the oxidation reaction as compared with the flat surface, the oxidation easily proceeds, and the oxide film 9 in this portion is The film thickness increases.
Further, in the concave corner portion B at the bottom of the groove pattern 7, the oxygen supply amount tends to be insufficient at the initial stage of the oxidation reaction as compared with the flat surface, so that the oxidation is difficult to proceed, and the oxide film 9 in this portion The film thickness becomes thin.

That is, on the exposed surface of the silicon substrate 1,
Thus, the oxide film 9 having a thick convex corner portion A and a thin concave corner portion B is formed. Therefore, in the step described below with reference to FIG. 1D, the oxide film 9 is removed by wet etching to expose the silicon substrate 1 without damaging the surface layer of the silicon substrate 1. The convex corners and concave corners on the surface, that is, the inner wall of the groove pattern 7 are blunted.

At this time, since excessive heat treatment is not applied, it is possible to prevent thermal stress and thermal deformation from being applied to the silicon substrate 1. Further, since the process is wet etching, the silicon substrate 1 is not damaged unlike the case of performing dry etching.

As a result, it is possible to form the groove-type element isolation region 15 in which the electric field concentration is prevented from occurring by blunting the corner portion where the electric field concentration is likely to occur, without damaging the silicon substrate 1. .

If the convex corners A and the concave corners B on the inner wall of the groove pattern 7 are not sufficiently blunted by only one oxidation process and subsequent etching of the oxide film, FIG. The process described with reference to FIG. 1 and the process described with reference to FIG. 1D are repeated a plurality of times. As a result, the convex corner portion A and the concave corner portion B can be further sufficiently blunted.

Further, in the above first embodiment, as described with reference to FIG. 1B, after the pad oxide film 3 is receded, the oxide film is grown by the wet process and thereafter. Was performed. However, in the formation of the groove pattern 7 described with reference to FIG. 1A, when the pad oxide film 3 recedes due to the etching conditions, the pad oxide film described with reference to FIG. It is not necessary to perform the step of retracting 3.

Further, in the above first embodiment,
The oxide film 9 was grown by the wet treatment described with reference to FIG. 1C while the pad oxide film 3 and the silicon nitride film 5 were provided on the silicon substrate 1. However, in the present invention, after the step described with reference to FIG. 1A is completed and then the silicon nitride film 5 and the pad oxide film 3 are removed, the step described with reference to FIG. You may make it perform the above-mentioned each process following.

(Second Embodiment) FIG. 2 is a sectional process view for explaining a method of manufacturing a semiconductor device having a cylinder type capacitor used as a capacitor for DRAM, for example, as a second embodiment of the present invention. is there. The second embodiment of the present invention will be described below with reference to this drawing.

First, as shown in FIG. 2A, silicon oxide is formed on a substrate 21 in which MOS transistors, bit contacts (not shown), etc. are covered with a planarization insulating film whose outermost surface is made of silicon nitride, for example. Insulating film 23
And an opening 25 is formed in the insulating film 23. The opening 25 is formed at a position reaching a contact (not shown) connected to the MOS transistor. Then, the silicon layer 2 made of polysilicon or amorphous silicon is covered with the inner wall of the opening 25.
7 is formed, and the silicon layer is left only on the inner wall of the opening 25 by CMP polishing, and this is erected on the substrate 1 as the first electrode 27a of the cylinder type capacitor.

Next, as shown in FIG. 2B, the insulating film (23) made of silicon oxide is selectively removed, and the substrate 2
Cylinder-shaped first electrode 27a (concave pattern) on 1
Is formed vertically.

Then, as shown in FIG. 2C, the exposed surface of the first electrode 27a is oxidized by a wet process using an oxidizing solution, and an oxide film 29 is formed on the surface of the first electrode 27a.
Grow. At this time, the same oxidizing solution as that used in the first embodiment (for example, ozone water) is used.

Next, as shown in FIG. 2D, the oxide film (29) on the surface of the first electrode 27a is selectively removed by wet etching. At this time, the etching solution may be, for example, a hydrofluoric acid aqueous solution (hydrofluoric acid concentration 1%, 24%
C.) is used to selectively remove the oxide film (29) made of silicon oxide with respect to the first electrode 27a made of polysilicon or amorphous silicon and the surface layer of the substrate 21 made of silicon nitride. At this time, if the etching time is lengthened, the underlying silicon nitride film is etched. Therefore, if etching of these films is not desired, it is necessary and sufficient to remove only the oxide film (29). Set the time. For example, when a hydrofluoric acid aqueous solution (hydrofluoric acid concentration 1%, 24 ° C.) is used as the etching solution, the oxide film 9 is necessary and sufficiently etched and removed in about 10 seconds.

In this wet etching,
In addition to the hydrofluoric acid aqueous solution, an ammonium fluoride aqueous solution, a mixed aqueous solution of hydrofluoric acid and ammonium fluoride, a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide solution, and a hydrofluoric acid and hydrochloric acid solution. A mixed aqueous solution or an aqueous solution containing hydrofluoric acid such as a mixed aqueous solution of hydrofluoric acid and a surfactant may be used.

After this wet etching is completed, a pure water rinse is performed, and then a drying process is performed.

If necessary, between the above-described oxidation process by the wet process of FIG. 2C and the wet etching process of FIG. 2D, as described in the first embodiment, may be performed. A pure water rinse step may be included.

After the above, as shown in FIG. 2 (5), the first
A dielectric film 31 is formed in a state of covering the electrode 27a, and then a second electrode film 33 is formed on the dielectric film 31.
Then, the second electrode film 33 is patterned into a predetermined shape, whereby the cylinder type capacitor 35 is formed.

In the method of manufacturing a semiconductor device as described above, as described with reference to FIG. 2C, the surface layer of the cylinder-shaped first electrode 27a standing on the substrate 21 is oxidized. Oxide film 2 by wet treatment using solution
9 is formed. Therefore, as in the first embodiment,
An oxide film 29 having a thick convex corner portion A and a thin concave corner portion B is formed on the surface layer of the first electrode 27a made of silicon. Therefore, in the step described below with reference to FIG. 2D, by removing such an oxide film 29 by wet etching, the convex shape of the cylindrical first electrode 27a can be obtained without damaging the base. Corners and concave corners are blunted.

At this time, since excessive heat treatment is not applied, it is possible to prevent heat stress and thermal deformation from being applied to the base. Further, since the processing is wet etching, the underlying layer is not damaged unlike the case of performing dry etching.

As a result, the corner portion where electric field concentration is likely to occur is blunted, the electric field concentration is prevented from occurring, and the cylinder type capacitor 35 can be formed without damaging the base.

When the blunting of the convex corners A and the concave corners B of the first electrode 27a is not sufficient with only one oxidation treatment and subsequent etching of the oxide film, the process shown in FIG. By repeating the process described above and the process described in FIG. 2 (4) a plurality of times, the convex corner portion A and the concave corner portion B are sufficiently blunted.

Further, in the second embodiment, the case where the capacitor is a cylinder type is illustrated, but the procedure of the second embodiment can be applied to a capacitor having a shape other than the cylinder type, and the same effect is obtained. It is possible to obtain

In the above, in the first and second embodiments, the embodiments in which the present invention is applied to the manufacture of a semiconductor device have been described. However, the present invention is not limited to the production of semiconductor devices, and for example, in the production of micromachines, it can be applied to treatment for blunting the convex corners and concave corners of the substrate surface having an uneven shape. It can be effectively applied and the same effect can be obtained.

[0052]

As described above, according to the substrate processing method of the first aspect of the present invention, the oxide film is formed on the surface layer of the substrate having the concavo-convex pattern by the wet process using the oxidizing solution and the wet process is performed. By selectively removing by etching, it is possible to make the convex corners and the concave corners of the concavo-convex pattern blunt without damaging the substrate.

According to a second aspect of the present invention, when the groove type element isolation region is formed in the manufacture of the semiconductor device,
Since the convex corners and the concave corners in the groove pattern can be blunted, it is possible to prevent problems due to electric field concentration at these corners, and to improve the reliability of the semiconductor device. be able to.

Similarly, according to claim 3 of the present invention, when forming a capacitor in the manufacture of a semiconductor device, for example, the convex corners and the concave corners of the cylinder-type first electrode can be blunted. Therefore, it becomes possible to prevent the occurrence of defects due to electric field concentration at these corners,
The reliability of the semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is a sectional process diagram for explaining a first embodiment.

FIG. 2 is a sectional process diagram for explaining the second embodiment.

[Explanation of symbols]

1 ... Silicon substrate (substrate), 7 ... Groove pattern, 9, 29
... oxide film, 13 ... element isolation material film, 15 ... element isolation region, 21 ... substrate, 27a ... first electrode, 31 ... dielectric film,
33 ... Second electrode film, 35 ... Capacitor

Claims (3)

[Claims] 1. A method for treating a surface of a substrate having a concavo-convex pattern, wherein an oxide film is grown on a surface layer of the substrate by wet treatment using an oxidizing solution, and then the oxide film is selectively etched by wet etching. A substrate processing method, characterized in that the substrate is removed. 2. A method of manufacturing a semiconductor device comprising an element isolation region in which a groove pattern formed in a surface layer of a substrate is filled with an element isolation material, wherein the groove pattern formed in the surface layer of the substrate is formed. An oxide film is grown on the inner wall by a wet process using an oxidizing solution,
Next, the oxide film is selectively removed by wet etching, and then the groove pattern is filled with the element isolation material. 3. A method of manufacturing a semiconductor device comprising a capacitor, which is formed by sequentially laminating a dielectric film and a second electrode film on a substrate in a state of covering a first electrode erected on the substrate. Then, an oxide film is grown on the surface layer of the first electrode formed on the substrate by a wet process using an oxidizing solution, and then the oxide film is selectively removed by wet etching. A method of manufacturing a semiconductor device, wherein the dielectric film and the second electrode film are sequentially laminated in a covered state.