JP2004247643A - Method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that in a method for forming a stacked capacitor, a conductive film of an upper interlayer insulating film, as the conductive film formed near an opening of a trench is also simultaneously etched in dry-etching, and a decrease (capacitance loss) of the capacitor capacitance is caused. <P>SOLUTION: A protection film is formed in the upper interlayer insulating film, whereby after the diameter of the trench is widened by wet-etching the interlayer insulating film, the conductive film is formed. Therefore, it is possible to prevent a decrease at an upper end of the opening of the conductive film formed in the trench by the dry-etching and to prevent the capacitance loss. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a capacitor technology applied to a DRAM (Dynamic Random Access Memory).
[0002]
[Prior art]
LSIs (Large Scale Integrated Circuits), which are known as representatives of semiconductor devices, are roughly classified into memory products and logic products. With the recent progress in semiconductor manufacturing technology, the former is particularly remarkable. In addition, memory products are classified into DRAM and static random access memory (SRAM). Most of these memory products are constituted by MOS (Metal Oxide Semiconductor) transistors which are excellent in integration degree. . In addition, DRAMs are widely applied to various storage devices such as information devices, because the cost can be reduced because the advantages of high integration can be made greater than SRAMs.
[0003]
A semiconductor device composed of a DRAM uses a capacitor as a capacitance element for storing information and stores information depending on the presence or absence of electric charge. However, as the element is miniaturized, the area occupied by individual capacitors formed on a semiconductor substrate is reduced. Will be.
[0004]
In order to compensate for the decrease in the area per unit cell and increase the capacitance of the capacitor, the two-dimensional structure of the conventional planar capacitor is changed to a three-dimensional electrode such as a stack type, a fin type and a trench type, and an HSG structure (Hemispherical). Grained silicon: an electrode structure in which minute irregularities are formed and roughened on the silicon surface serving as the lower electrode, and the surface area is substantially increased without increasing the dimensions of the lower electrode. A three-dimensional and three-dimensional structure has been realized. In addition, the problem of securing the capacity has been overcome by changing the insulating film material of the capacitor from SiO ₂ to a high dielectric constant material.
[0005]
The three-dimensional structure of the capacitor is classified into a trench type and a stack type depending on the manufacturer, but the stack type is superior from the viewpoint of introducing a high dielectric constant material. Since a high-temperature process of 900 ° C. or more in the transistor manufacturing process continues after the formation of the capacitor, it is difficult to secure the heat resistance of the metal oxide film and the high dielectric constant material. However, in the case of a stack type, it is usually sufficient to have a heat resistance of about 800 ° C. in order to form a capacitor after forming a transistor. For this reason, a stacked capacitor structure has been developed aiming at higher integration (for example, see Patent Document 1).
[0006]
Hereinafter, a conventional method for forming a stacked capacitor will be described with reference to the drawings. 4 and 5 are cross-sectional views showing a conventional manufacturing method.
[0007]
First, as shown in FIG. 4A, a BPSG film 1 is deposited on a semiconductor substrate (not shown). After that, the groove 2 is formed by dry etching.
[0008]
Next, as shown in FIG. 4B, a polysilicon film 3 containing an impurity (for example, phosphorus) is formed. Thereafter, as shown in FIG. 4C, the inside of the groove 2 is filled with a photoresist film 4.
[0009]
Next, as shown in FIG. 5A, the polysilicon film 3 formed on the BPSG film 1 is removed by dry etching. Thereafter, as shown in FIG. 5B, a Si ₃ N ₄ film 5 is deposited as a capacitance insulating film.
[0010]
Finally, as shown in FIG. 5C, a polysilicon film 6 containing an impurity (for example, phosphorus) is deposited as an upper electrode. Thus, a three-dimensional stacked capacitor is formed.
[0011]
[Patent Document 1]
JP 2001-15712 A
[Problems to be solved by the invention]
However, the conventional stacked capacitor structure has the following problems in processing the polysilicon film 3 serving as the lower electrode.
[0013]
As shown in FIG. 6A, when the polysilicon film 3 is dry-etched, the polysilicon film 3 formed near the opening of the groove 2 is simultaneously etched. For this reason, a decrease in the capacitance value of the capacitor (capacity loss) is caused.
[0014]
In addition, the deterioration of the processed shape due to dry etching causes an increase in leak current. In particular, as shown in FIG. 6B, when the HSG-converted silicon film 7 is used as the lower electrode material, this problem becomes conspicuous. Since the volume ratio of silicon of the HSG-converted silicon film 7 is reduced, the etching time near the surface is inevitably shortened. This is because, as shown in FIG. 6C, the processed shape of the silicon film 7 formed near the opening of the groove becomes angular and unstable.
[0015]
In view of the above, the present invention has been made in view of the above problems, and an object of the present invention is to reliably form a conductive film, which is a lower electrode material, up to the upper end of an opening of a groove in a step of forming a lower electrode of a capacitor. An object of the present invention is to provide a method for manufacturing a semiconductor device.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device having a stacked capacitor, comprising the steps of: sequentially depositing an interlayer insulating film and a protective film on a semiconductor substrate; A step of forming a groove reaching the semiconductor substrate in the film and the interlayer insulating film, a step of etching the interlayer insulating film using the protective film as a mask to increase the diameter of the groove, and a step of forming a conductive film inside the groove having the increased diameter. A step of depositing, a step of filling the inside of the groove where the conductive film is deposited with a coating film, a step of etching the conductive film above and on the side of the protective film using the coating film as a mask, and a step of removing the protective film And characterized in that:
[0017]
According to this configuration, in etching the conductive film serving as the lower electrode of the stacked capacitor, the conductive film in the groove opening is not etched by the protective film, so that the conductive film is reliably formed up to the upper end of the groove opening. Therefore, it is possible to form a good capacitor with a small leak current while preventing a decrease or variation in the capacitance value of the capacitor.
[0018]
In the above method for manufacturing a semiconductor device, in the step of increasing the diameter of the groove, etching is preferably performed using a liquid containing HF.
[0019]
In the above method for manufacturing a semiconductor device, the step of etching the conductive film is preferably performed under a condition that the etching rate of the protective film with respect to the conductive film is low.
[0020]
In the above method for manufacturing a semiconductor device, the step of removing the protective film may include a step of filling the inside of the groove with another coating film and a step of etching the protective film using the other coating film as a mask. preferable.
[0021]
In the above method for manufacturing a semiconductor device, in the step of removing the protective film, it is preferable that the etching is performed under a condition that an etching rate of the conductive film and the interlayer insulating film with respect to the protective film is small.
[0022]
In the above method for manufacturing a semiconductor device, it is preferable that the interlayer insulating film is a silicon oxide film, the protective film is a silicon nitride film, and the conductive film is a silicon film.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a method of manufacturing a semiconductor device having a stacked capacitor according to the present invention will be described with reference to the drawings. 1 to 3 are cross-sectional views illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention.
[0024]
First, as shown in FIG. 1A, an interlayer insulating film 8 and a protective film 9 are sequentially formed on a semiconductor substrate (not shown). The interlayer insulating film 8 is preferably a film having a high wet etching rate, for example, a silicon oxide film made of a BPSG film. The protective film 9 is preferably a film that is not etched in the wet etching of the interlayer insulating film 8 performed later. Further, in the dry etching of the conductive film 11 performed later, the protective film 9 is entirely etched, and has a sufficient film thickness so as not to etch the conductive film 11 formed immediately below the protective film 9. It is preferable to form them. For this reason, it is preferable that the etching rate in the dry etching is lower in the protective film 9 than in the conductive film 11.
[0025]
It is assumed that the material of such a protective film 9 is a film that can be dry-etched, or has a condition of wet etching described later. For example, silicon nitride (Si ₃ N ₄ ), aluminum (Al), tungsten (W), titanium (Ti), titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (WN), and the like are used. .
[0026]
Thereafter, a groove 10 is formed by dry etching from the surface of the protection film 9 to the surface of the semiconductor substrate through the interlayer insulating film 8.
[0027]
Next, as shown in FIG. 1B, using the protective film 9 as a mask, the interlayer insulating film 8 inside the groove 10 is wet-etched to increase the diameter of the groove 10. The length of the diameter to be expanded is preferably about the thickness of the conductive film 11 to be formed later. The cleaning liquid for wet etching is preferably a liquid containing HF.
[0028]
Next, as shown in FIG. 1C, a conductive film 11 is formed inside the groove 10 and above the protective film 9. The conductive film 11 is preferably formed by a low pressure CVD method having good step coverage. The conductive film 11 is made of polysilicon containing impurities (for example, phosphorus), titanium nitride (TiN), ruthenium (Ru), ruthenium oxide (RuO), iridium (Ir), iridium oxide (IrO), platinum (Pt), or the like. And
[0029]
Next, as shown in FIG. 2A, the inside of the groove 10 is filled with a photoresist film 12 as a coating film. This method is formed by the following method. A photoresist film 12 is applied on the entire surface. Next, the entire surface of the photoresist film 12 is irradiated with exposure light to expose the photoresist film 12 outside the groove 10. At this time, the photoresist film 12 inside the groove 10 is not exposed because the exposure amount is insufficient. Next, the photoresist film 12 is developed to remove the exposed photoresist film 12 outside the groove 10.
[0030]
Next, as shown in FIG. 2B, using the photoresist film 12 as a mask, the conductive film 11 formed above and on the side of the protective film 9 is removed by dry etching. At this time, the entire protective film 9 is not etched so that the conductive film 11 formed immediately below the protective film 9 is not etched.
[0031]
Next, as shown in FIG. 2C, the protective film 9 is removed by etching. At this time, the etching removal method has two options (dry etching or wet etching).
[0032]
First, in the case of performing dry etching, a necessary condition is that the protective film 9 can be dry-etched. As an etching procedure at this time, similarly to the dry etching of the conductive film 11, the trench 10 is filled with the photoresist film 12 to perform etching. For example, when TiN is used for the protective film 9, polysilicon is used for the conductive film 11, and BPSG is used for the interlayer insulating film 8, dry etching can be performed.
[0033]
In the case of removal by wet etching, the necessary conditions are that the protective film 9 is a film that is easily wet-etched, and that the conductive film 11 and the interlayer insulating film 8 are films that are hardly wet-etched. For example, when Si ₃ N ₄ is used for the protective film 9, polysilicon is used for the conductive film 11, and BPSG is used for the interlayer insulating film 8, wet etching can be performed by using phosphoric acid (H ₃ PO ₄ ) as the cleaning liquid.
[0034]
Next, as shown in FIG. 3A, a capacitance insulating film 13 is formed. The capacitance insulating film 13 is made of silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), tantalum oxide (Ta ₂ O ₅ ), aluminum oxide (Al ₂ O ₃ ), BST [(Br, Sr) TiO ₂ ], STO [SrTiO ₃ ], and the like.
[0035]
Finally, as shown in FIG. 3B, a conductive film 14 is formed as an upper electrode. The conductive film 14 is made of polysilicon containing impurities (for example, phosphorus), titanium nitride (TiN), ruthenium (Ru), ruthenium oxide (RuO), iridium (Ir), iridium oxide (IrO), platinum (Pt), or the like. And As described above, the stacked capacitor of the present invention is formed.
[0036]
In the conventional method for forming the lower electrode, when the conductive film on the interlayer insulating film is dry-etched, the conductive film at the upper end of the opening of the groove is also etched at the same time, resulting in a decrease in the capacitance value of the capacitor.
[0037]
On the other hand, in the present invention, by forming the protective film 9 on the interlayer insulating film 8, the conductive film 11 is formed after the groove diameter of the interlayer insulating film 8 is increased by wet etching. Thus, even if the conductive film 11 on the interlayer insulating film 8 is dry-etched, the protective film 9 prevents the conductive film 11 formed near the opening of the groove from being etched. Therefore, it is possible to reliably form the conductive film 11 as the lower electrode material up to the upper end of the opening of the groove. As a result, it is possible to prevent a decrease (capacity loss) and variation in the capacitance value of the capacitor.
[0038]
In addition, since the lower electrode made of the conductive film 11 formed near the opening of the groove has a conformal processed shape and is stable, a good capacitor with little leakage current can be formed.
[0039]
【The invention's effect】
As described above, according to the method for manufacturing a semiconductor device of the present invention, since the conductive film serving as the lower electrode of the stacked capacitor is reliably formed up to the upper end of the opening of the groove, the reduction or variation in the capacitance value of the capacitor can be prevented. Thus, a good capacitor having a small leakage current can be formed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a manufacturing process of a semiconductor device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a manufacturing process of a semiconductor device according to an embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a manufacturing process of a conventional semiconductor device. FIG. 5 is a cross-sectional view illustrating a manufacturing process of a conventional semiconductor device. FIG. Sectional view showing a problem in a method of manufacturing a semiconductor device according to the present invention.
DESCRIPTION OF SYMBOLS 1 BPSG film 2 Groove 3 Polysilicon film 4 Photoresist film 5 Si ₃ N ₄ film 6 Polysilicon film 7 HSG-converted silicon film 8 Interlayer insulating film 9 Protective film 10 Groove 11 Conductive film 12 Photoresist film 13 Capacitive insulating film 14 Conductive film

Claims (6)

In a method of manufacturing a semiconductor device having a stacked capacitor,
A step of sequentially depositing an interlayer insulating film and a protective film on the semiconductor substrate,
Forming a groove reaching the semiconductor substrate in the protective film and the interlayer insulating film;
Etching the interlayer insulating film using the protective film as a mask to increase the diameter of the groove;
Depositing a conductive film inside the groove having the increased diameter;
Filling a coating film inside the groove where the conductive film is deposited,
Etching the conductive film above and on the side of the protective film using the coating film as a mask,
Removing the protective film. The method for manufacturing a semiconductor device according to claim 1,
The method of manufacturing a semiconductor device, wherein the step of increasing the diameter of the groove is performed by etching using a liquid containing HF. The method for manufacturing a semiconductor device according to claim 1, wherein
The method of manufacturing a semiconductor device, wherein the step of etching the conductive film is performed under a condition that an etching rate of the protective film with respect to the conductive film is small. The method for manufacturing a semiconductor device according to claim 1, 2 or 3,
A semiconductor device, wherein the step of removing the protective film includes a step of filling the groove with another coating film, and a step of etching the protective film using the other coating film as a mask. Manufacturing method. The method for manufacturing a semiconductor device according to claim 1, 2 or 3,
The method of manufacturing a semiconductor device, wherein the step of removing the protective film is performed under a condition that an etching rate of the conductive film and the interlayer insulating film with respect to the protective film is small. The method for manufacturing a semiconductor device according to claim 5,
A method of manufacturing a semiconductor device, wherein the interlayer insulating film is a silicon oxide film, the protective film is a silicon nitride film, and the conductive film is a silicon film.

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