JP2002057213A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacturing method of a semiconductor device for improving adhesibility between a BPSG film and a resist, suppressing penetration of etchant into an interface and eliminating etching defects. SOLUTION: A BPSG film 2 as an inter-planarized insulating film is used on a metal wiring 11 in a Si wafer WF, as shown in Fig. (a). Then, although a system moves to a lithographic process, where a contact part with the metal wiring of an upper layer is formed. A cleaning process by a mixed liquid of sulfuric acid and hydrogen peroxide water, whose of specific gravity of sulfuric acid is 1.6 to 1.75 with respect to the PGSG film 12, as a pretreatment is inputted. Then, isotropic wet etching shown in Fig. (b) and dry etching as anisotropic etching shown in Fig.(c) are performed through the application of resist 13 and the formation of a resist pattern PTN.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device which is applied to a pre-treatment for applying a resist to the surface of a planarized interlayer insulating film.

[0002]

2. Description of the Related Art In recent years, large-scale integration of semiconductor devices and reduction of design rules have been remarkable. Along with this, the miniaturization of the metal wiring is promoted in the LSI process, and the contact portion with the upper metal wiring is being narrowed. A lithography technique is indispensable for forming such a contact portion. Therefore, the adhesion of the resist in the resist coating process is also regarded as important for realizing a fine pattern.

For example, in an LSI process, BP is used as a planarizing interlayer insulating film between metal wiring layers such as aluminum wiring.
An SG film is used. BPSG film consists of B (boron) and P
B ₂ O ₃ and P ₂ O ₅ (P ₂ O
_This is a SiO ₂ film to which ₃ ) is added. It is known that the BPSG film can be made to flow by heat treatment at a high temperature, thereby reducing the level difference of the base (reflow method).

FIG. 4 is a sectional view showing a conventional technique for forming a contact portion of a wiring provided on a semiconductor wafer. A flattened BPSG film 42 is provided on the metal wiring 41. When forming a contact portion connected to the lower metal wiring 41, first, a resist 43 is applied on the BPSG film 42 to form a resist pattern PTN.
After that, etching is performed in accordance with the resist pattern PTN by wet etching. Thereafter, as indicated by a broken line, dry etching is further performed according to the resist pattern PTN to perform anisotropic etching.

[0005] The wet etching is performed in order to relieve the step of the contact portion in advance. If only anisotropic etching by dry etching is performed, the step of the contact portion becomes steep as shown by the broken line. Therefore, the coverage of the upper metal wiring (not shown) formed later is deteriorated, which is not preferable. That is, wet etching is a measure taking into account the coverage of the upper metal wiring (not shown).

[0006]

Generally, the adhesion between the BPSG film and the resist is not always good, and as shown in FIG.
The etchant permeates the interface between the substrate and the resist 43. BP
An oxide film such as an SG film has a small wet etching rate and takes a corresponding time. For this reason, the degree of penetration into the interface is large, and the wet ratio (A / B) is large. As a result, there is a possibility that a problem such as a wiring short-circuit may occur between the arrangement of the contact portions in the high-density pattern, and this is treated as an etching defect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a semiconductor device that improves the adhesion between a BPSG film and a resist, suppresses the penetration of an etchant into an interface, and eliminates etching defects. It is intended to provide a method for producing the same.

[0008]

A method of manufacturing a semiconductor device according to the present invention is a method of forming a contact portion with a lower wiring layer by selectively etching a planarized interlayer insulating film provided on a semiconductor wafer. A step of applying a resist on the planarized interlayer insulating film to form a resist pattern, and an isotropic etching step of partially wet-etching the planarized interlayer insulating film exposed according to the resist pattern, Anisotropically etching the flattened interlayer insulating film according to the resist pattern after the isotropic etching process until the underlying wiring layer is exposed, and applying a resist on the planarized interlayer insulating film. As a pretreatment, washing with a mixed solution of sulfuric acid and hydrogen peroxide having a specific gravity of sulfuric acid larger than 1.60 and smaller than 1.75 is required. And butterflies.

According to the method of manufacturing a semiconductor device of the present invention, it is possible to remove contaminants on the planarized interlayer insulating film and clean the planarized interlayer insulating film by cleaning with a mixed solution of sulfuric acid and hydrogen peroxide having the above specific gravity. Improves the hydrophilicity of the insulating film. This improves the adhesion of the resist.

[0010]

1 (a) to 1 (c) are main parts of a method of manufacturing a semiconductor device according to an embodiment of the present invention, and show a part of a cleaning step and a lithography step for a wafer. It is sectional drawing.

As shown in FIG. 1A, a Si wafer WF
In step (1), a transistor element for forming an integrated circuit (not shown) and the like, and at least one or more metal wirings 11 corresponding thereto are formed. On this metal wiring 11, a BPSG film 12 is used as a planarizing interlayer insulating film.
The BPSG film 12 is made to flow by heat treatment at a high temperature,
Relieve the step on the base (reflow method).

Next, the process shifts to a lithography process for forming a contact portion with a metal wiring of an upper layer, and a cleaning process of the BPSG film 12 is provided as a pretreatment. This BPSG
For cleaning the membrane 12, a mixed solution of sulfuric acid and hydrogen peroxide (SP)
M: sulfuric acid / hydrogenperoxide / water mix
), So-called SPM cleaning is suitable. Thus, contaminants (organic matter and metal contamination) on the BPSG film 12 are removed.

In the present invention, the SPM cleaning of the BPSG film 12 is used to improve the adhesiveness of the resist. In the SPM cleaning, a mixed solution of sulfuric acid and hydrogen peroxide having a specific gravity of sulfuric acid larger than 1.60 and smaller than 1.75 is used. The processing temperature is about 120 ° C., and the processing time is about 10 minutes. With this, BPS
In addition to removing contaminants (organic matter and metal contamination) on the G film 12, the hydrophilicity of the planarized interlayer insulating film on the BPSG film 12 is improved. As a result, the adhesion of the resist is greatly improved.

Next, as shown in FIG. 1B, application of a resist 13 and formation of a resist pattern PTN are performed.
Then, according to the resist pattern PTN, the exposed B
The PSG film 12 is partially wet-etched. BPSG
Since the adhesion between the film 12 and the resist 13 is kept good,
The penetration of the etching solution at the interface is considerably suppressed. As a result, the wet ratio represented by A / B in the figure does not become too large, and the isotropic etching that guarantees a fine pattern can be achieved.

Next, as shown in FIG. 1C, after the isotropic etching step, the BPSG film 12 is anisotropically etched by dry etching according to the same resist pattern PTN until the underlying wiring layer 11 is exposed. I do.

FIG. 2 is a view showing the wet ratio according to the resist which affects the difference in the specific gravity of sulfuric acid in the SPM cleaning of the BPSG film 12 shown in FIG. FIG. 3 shows FIG.
FIG. 6 is a characteristic diagram showing a change in specific gravity of sulfuric acid with respect to the number of batches treated with the SPM cleaning liquid in FIG.

In FIG. 2, 96 before the SPM cleaning liquid is replaced.
The average of the first and eighth cleaning treatments and the average of the first and eighth cleaning treatments after the replacement of the SPM cleaning liquid are compared with each other after the wet etching according to the patterned resist. The inspection results of the wet ratio (that is, A / B shown in FIG. 1B) at five arbitrary positions in the wafer surface (not shown) are better before the former SPM cleaning liquid replacement. Further, it can be seen that this result is hardly affected before and after the replacement of the wet etching solution.

As shown in FIG. 3, the SPM cleaning solution is
As the number of treatments increases, the specific gravity of sulfuric acid gradually decreases due to the amount of sulfuric acid carried on the wafer surface and the replenishment of hydrogen peroxide. The hatched lines indicate the error range when hydrogen peroxide solution is replenished. The specific gravity of sulfuric acid may fall below 1.75 at least after the number of batches exceeds 60, and may fall below 1.65 by the time of liquid exchange.

In other words, the 96th and 100th cleaning processes before the replacement of the SPM cleaning solution shown in FIG. 2 can be said to be at least processes using an SPM cleaning solution having a sulfuric acid specific gravity smaller than 1.75.
Further, the first and eighth cleaning processes after the replacement of the SPM cleaning solution can be said to be processes using an SPM cleaning solution having a sulfuric acid specific gravity of more than 1.75.

From FIG. 2 and FIG. 3, when the number of treatments is not so large after the replacement of the SPM cleaning liquid, the deterioration of the wet ratio is observed, and the cleaning effect is taken into consideration. It is preferable to use a mixed solution of sulfuric acid and hydrogen peroxide having a specific gravity of sulfuric acid larger than 1.60 and smaller than 1.75. More preferably, SPM cleaning in which the specific gravity of sulfuric acid is maintained at around 1.7 may be performed. By cleaning with a mixed solution of sulfuric acid and hydrogen peroxide having such a specific gravity of sulfuric acid, contaminants are removed and the adhesion of the resist of the BPSG film is improved, and the wet ratio is improved.

According to the method of the above embodiment, the hydrophilicity of the BPSG film can be increased by SPM cleaning, and the adhesion to the resist can be improved. Thereby, at the time of wet etching using the resist pattern, the penetration of the etching solution into the interface between the BPSG film and the resist can be significantly reduced.

In general, the BPSG film has a low wet etching rate and takes a corresponding time. By suppressing the permeation into the interface, a predetermined isotropic etching is achieved, and a step relief portion that can cope with the arrangement of the contact portions in the high-density pattern can be formed.

[0023]

As described above, according to the method of manufacturing a semiconductor device according to the present invention, at least the specific gravity of sulfuric acid is larger than 1.60 and 1.7 in the step of cleaning the BPSG film.
Use a sulfuric acid-hydrogen peroxide mixture less than 5. As a result, the contaminant is removed, the adhesion of the BPSG film to the resist is improved, and the wet ratio is improved. As a result,
It is possible to provide a method for manufacturing a highly reliable semiconductor device capable of suppressing penetration of an etching solution into an interface between a BPSG film and a resist, eliminating etching defects, and realizing a high-density fine pattern.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views each showing a main part of a method for manufacturing a semiconductor device according to an embodiment of the present invention, and showing a part of a cleaning step and a lithography step for a wafer.

FIG. 2 is a diagram illustrating a wet ratio according to a resist which affects a difference in specific gravity of sulfuric acid in SPM cleaning of the BPSG film of FIG. 1;

FIG. 3 is a characteristic diagram showing a change in specific gravity of sulfuric acid with respect to the number of batches treated with the SPM cleaning solution in FIG. 1;

FIG. 4 is a cross-sectional view showing a conventional technique for forming a contact portion of a wiring provided on a wafer.

[Explanation of symbols]

 11, 41: metal wiring 12, 42: BPSG film 13, 43: resist PTN: resist pattern WF: Si wafer

Claims (1)

[Claims] 1. A method for selectively etching a planarized interlayer insulating film provided above a semiconductor wafer to form a contact portion with a lower wiring layer, wherein a resist is formed on the planarized interlayer insulating film. Applying a resist pattern to form a resist pattern; an isotropic etching step of partially wet-etching the planarized interlayer insulating film exposed according to the resist pattern; and the flattening according to the resist pattern after the isotropic etching step. Anisotropic etching step of dry-etching the patterned interlayer insulating film until a lower wiring layer is exposed, wherein the specific gravity of sulfuric acid is greater than 1.60 as a pre-treatment of resist application on the planarized interlayer insulating film; A method for manufacturing a semiconductor device, comprising performing cleaning with a mixed solution of sulfuric acid and hydrogen peroxide smaller than 1.75.