JP3196373B2 - Method for manufacturing semiconductor device - Google Patents

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 having a capacitor having a lower electrode formed of a polycrystalline silicon film containing impurities.

[0002]

2. Description of the Related Art FIG. 2 shows a method which has been conventionally carried out by the present applicant for manufacturing a stacked capacitor type DRAM. In this method, as shown in FIG.
SiO ₂ film 1 by LOCOS method on P-type Si substrate 11
2 and the like, an element isolation region is formed, and Si as a gate oxide film is formed on the surface of the element active region surrounded by the SiO ₂ film 12.
An O ₂ film 13 is formed. Then, the W polycide film 14 and the like are patterned to form a gate electrode serving as a word line in the memory cell.

After that, using the W polycide film 14 and the SiO ₂ film 12 as a mask, an N-type impurity such as Phos or As is ion-implanted into the Si substrate 11 at a dose of 10 ¹² to 10 ¹³ cm ^-2. By performing a heat treatment, the N ⁻ type diffusion layer 15 is formed.
To form Thus, the transistor 16 forming the memory cell is completed. Then, the peripheral circuit transistor (not shown) in order to LDD structure, depositing a SiO ₂ film 17 by the CVD method, the entire surface of the SiO ₂ film 17 is anisotropically etched, the SiO ₂ film 17 LD
D spacers are formed on the side walls of the W polycide film 14.

After that, a SiO ₂ film, a PSG film, a reduced pressure CV
An interlayer insulating film 21 is formed from a SiN film or the like deposited by the method D, and a contact hole 22 for a storage node electrode is opened in the interlayer insulating film 21. Then, a polycrystalline Si film 23 is deposited by a low pressure CVD method so as to contact one of the diffusion layers 15 through the contact hole 22.

[0005] Thereafter, a predeposition method of thermally diffusing Phos from the vapor by exposing it to POCl ₃ vapor is carried out, or As or Phos is ion-implanted to a dose of 10 ¹⁵ cm ^-2 or more and subjected to a heat treatment. And polycrystalline Si
After adding impurities to the film 23, the polycrystalline Si film 23 is processed into a pattern of a storage node electrode.

By the way, a capacitor dielectric film is formed on the surface of the patterned polycrystalline Si film 23, and the surface of the polycrystalline Si film 23 is formed as shown in FIG.
The natural oxide film (SiO _X film) 24 is grown. If the natural oxide film 24 is present, the capacitor dielectric film cannot be made thinner and the capacity of the capacitor cannot be increased. In addition, since the natural oxide film 24 has poor film quality, Increase the leakage current of the capacitor and also reduce the reliability of the capacitor.

[0007] Therefore, rapid thermal nitridation (RTN), which is nitridation by infrared lamp annealing in an NH ₃ atmosphere, is performed on the surface of the polycrystalline Si film 23.
As shown in (c), the natural oxide film 24 is changed to an oxynitride film (SiO
_X N _Y film) to 25, while suppressing the growth of new native oxide film 24, the natural oxide film by etching with dilute hydrofluoric acid 2
4 had been removed.

Then, a polycrystalline Si film 23 is formed by a low pressure CVD method.
A SiN film is formed thereon, and the surface of the SiN film is oxidized to form a SiO ₂ film on the surface.
The iO ₂ film is used as a capacitor dielectric film. Thereafter, through a conventionally known process, the multilayer capacitor type DRAM is completed.

[0009]

By the way, polycrystalline Si
If the film 23 contains no impurities, the thickness of the natural oxide film 24 is small, so that the natural oxide film 24 can be removed by the above-described etching with dilute hydrofluoric acid. However, since the actual polycrystalline Si film 23 is doped with As or Phos at a high concentration as an impurity, the natural oxide film 24 has a thickness of 1.0 nm.
It grows to the above thick film thickness.

On the other hand, the thickness of the nitride film grown by rapid thermal nitridation has a saturation amount depending on the temperature. If the thickness of the natural oxide film 24 is as thick as 1.0 nm or more, FIG. As described above, the surface of the polycrystalline Si film 23 is not nitrided, and the native oxide film 24 remains on the polycrystalline Si film 23.

In order to remove the natural oxide film 24, the oxynitride film 25 must be removed. However, if the oxynitride film 25 is completely removed to expose the natural oxide film 24, Oxide film 24 grows again. That is, in the above-described method, the effect of rapid thermal nitridation is not obtained, and the natural oxide film 24 remains. Therefore, a stacked capacitor type DRAM having a capacitor with high reliability and a large capacity cannot be manufactured.

By performing rapid thermal nitridation at a temperature of 1000 ° C. or more to increase the saturation of the grown film thickness of the nitride film,
Since the surface of the polycrystalline Si film 23 can be nitrided, even if the oxynitride film 25 is removed by etching with dilute hydrofluoric acid, the natural oxide film 24 does not grow again. However, lamp annealing at a temperature of 1000 ° C. or more deteriorates the film quality of the SiO ₂ film 13 or the like serving as a gate oxide film, and lowers the reliability and yield of the stacked capacitor type DRAM.

[0013]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device having a capacitor having a lower electrode formed of a polycrystalline silicon film containing impurities. A step of performing a first etching with dilute hydrofluoric acid on the surface of the silicon film 23, and a step of nitriding the surface by irradiating the surface with infrared rays in an ammonia gas atmosphere after the first etching; A step of repeating a process of performing a second etching with dilute hydrofluoric acid on the nitrided surface, and a step of forming a silicon nitride film on the surface by a low pressure CVD method after the step of repeating the process a plurality of times. The surface of the silicon nitride film is oxidized to form a silicon oxide film on the surface, the silicon nitride film 26 formed by the infrared irradiation, and the low pressure CVD method. The formed and the silicon nitride film and the silicon oxide film and a step of the capacitor dielectric film 27 of the capacitor 32.

According to a second aspect of the present invention, in the method of manufacturing a semiconductor device of the first aspect, the thickness for performing the second etching is 1 nm or less in terms of a thermal oxide film.

According to a third aspect of the present invention, in the method of manufacturing a semiconductor device of the first aspect, cleaning with an acid is performed instead of the first etching with dilute hydrofluoric acid.

According to a fourth aspect of the present invention, in the method of manufacturing a semiconductor device of the first aspect, only the nitriding by infrared irradiation is performed in the last of the steps repeated a plurality of times.

[0017]

According to the method of manufacturing a semiconductor device of the first aspect, the polycrystalline silicon film forming the lower electrode of the capacitor is formed.
Even if a thick native oxide film 24 is grown on the surface of the native oxide film 3 because it contains impurities, at least a part of the native oxide film 24 in the thickness direction is nitrided and then the nitrided natural oxide film is formed. Since the process of removing a part of the film 25 in the film thickness direction is repeated a plurality of times, the surface of the polycrystalline silicon film 23 can be nitrided to completely remove the natural oxide film 24.

In the method of manufacturing a semiconductor device according to the second aspect, the nitrided natural oxide film 25 on the surface of the polycrystalline silicon film 23 forming the lower electrode of the capacitor 32 is completely removed by the second etching. Therefore, the native oxide film 24 remaining without being nitrided is not exposed, and the growth of a new native oxide film 24 can be prevented when the native oxide film 24 is removed while being nitrided.

In the method of manufacturing a semiconductor device according to the third aspect, when the natural oxide film 24 on the surface of the polycrystalline silicon film 23 forming the lower electrode of the capacitor 32 is removed, particles such as silicon and metal are formed on the surface. Is difficult to adhere.

In the method of manufacturing a semiconductor device according to the present invention, since the silicon nitride film formed by the irradiation of infrared rays is left as it is, the thickness of the silicon nitride film is large and the quality of the film is low despite the small number of manufacturing steps. Good capacitor dielectric film 2
7 can be formed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to the manufacture of a stacked capacitor type DRAM will be described below with reference to FIG. The components corresponding to those shown in FIG. 2 are denoted by the same reference numerals.

Also in this embodiment, as shown in FIG. 1A, steps similar to those in the method shown in FIG. 2 are executed until the polycrystalline Si film 23 is processed into a pattern of the storage node electrode. I do. Accordingly, a natural oxide film 24 grows on the surface of the polycrystalline Si film 23 as shown in FIG.

In this embodiment, from this state, only cleaning with acid to remove particles such as silicon and metal is performed, or both cleaning with acid and etching with dilute hydrofluoric acid are performed. It should be noted that although cleaning only with an acid is more difficult to attach particles and improving the yield, the natural oxide film 24 becomes thicker, and the number of times of rapid thermal nitridation and etching with dilute hydrofluoric acid, which will be described later, is reduced. I need to do more.

Then, by performing rapid thermal nitriding,
As shown in FIG. 1B, the surface of the natural oxide film 24 having a thickness of 1.0 to 2.0 nm is changed to an oxynitride film 25. Also in this case, the thickness of the nitride film grown by rapid thermal nitridation has a saturation amount, and as in the case shown in FIG.
The surface of the i-film 23 is not nitrided, and the native oxide film 24 remains on the polycrystalline Si film 23.

Then, after a part of the oxynitride film 25 in the thickness direction is removed by etching with dilute hydrofluoric acid, it is removed again.
Rapid thermal nitridation at a temperature of 50 to 1000 ° C. is performed to remove a part of the remaining native oxide film 24 in the thickness direction from the oxynitride film 25.
To As a result, the oxynitride film 25 becomes the polycrystalline Si film 23.
And the part of the native oxide film 24 in the thickness direction has been removed. However, when the natural oxide film 24 is exposed by completely removing the oxynitride film 25, the natural oxide film 24 grows again as described above. To 1 nm or less.

In this embodiment, the above-described diluted hydrofluoric acid is used until the natural oxide film 24 is completely removed, and the surface of the polycrystalline Si film 23 is nitrided to form the SiN film 26 (FIG. 1C). Etching and rapid thermal nitridation are repeated. Thereafter, etching with dilute hydrofluoric acid is performed to completely remove the oxynitride film 25 as shown in FIG. 1C, and if necessary, rapid thermal nitridation is performed.

Next, S is deposited on the SiN film 26 by a low pressure CVD method.
An iN film (not shown) is deposited to a thickness of several nm,
By oxidizing the surface of the iN film to form a SiO ₂ film, FIG.
As shown in (d), a laminated film of the SiN film and the SiO ₂ film is used as the capacitor dielectric film 27. And CV
A polycrystalline Si film 31 is deposited to a thickness of several tens to several hundreds of nm by the D method, and an N-type impurity is added to the polycrystalline Si film 31 at a high concentration by a predeposition method using POCl _3. The polycrystalline Si film 31 is processed into a plate electrode pattern,
The capacitor 32 constituting the memory cell is completed.

Then, a SiO ₂ film, a PSG film, a BPSG film
The interlayer insulating film 33 is formed of a film or a SiN film, and if necessary, the interlayer insulating film 33 is formed by a method such as etch back, reflow, or the like.
After smoothing 3, a contact hole 34 for a bit line is opened in the interlayer insulating film 33. Then, the W polycide film 3
5. A bit line is formed of a high melting point metal film such as a polycrystalline Si film, an Al film or a W film, and the multilayer capacitor type DRA is formed.
Complete M.

Although the embodiments described above apply the invention of the present application to the manufacture of a stacked capacitor type DRAM, the invention of the present application can also be applied to the manufacture of semiconductor devices other than the stacked capacitor type DRAM.

[0030]

According to the method of manufacturing a semiconductor device of the first aspect,
Since the natural oxide film on the surface of the polycrystalline silicon film forming the lower electrode of the capacitor can be completely removed, a capacitor dielectric film of good quality consisting of a silicon nitride film and a silicon oxide film thereover can be formed. It is possible to reduce the thickness of the capacitor dielectric film. Therefore, a semiconductor device having a capacitor with high reliability and large capacity can be manufactured.

In the method of manufacturing a semiconductor device according to the second aspect, the growth of a new native oxide film is prevented when the native oxide film on the surface of the polycrystalline silicon film forming the lower electrode of the capacitor is removed while nitriding. Therefore, the natural oxide film can be efficiently removed. Therefore, a semiconductor device having a capacitor with high reliability and large capacity can be manufactured efficiently.

In the method of manufacturing a semiconductor device according to the third aspect, since particles such as silicon and metal hardly adhere to the surface of the polycrystalline silicon film forming the lower electrode of the capacitor, the capacitor has high reliability and a large capacitance. Can be manufactured with high yield.

According to the method of manufacturing a semiconductor device of the present invention, a capacitor dielectric film having good film quality can be formed despite the small number of manufacturing steps, so that a semiconductor device having a highly reliable capacitor can be efficiently manufactured. Can be manufactured.

[Brief description of the drawings]

[1] Ru side sectional view showing an embodiment in the order of steps of the present invention.

[2] the present applicant is Ru side sectional view showing a method implemented conventionally in the order of steps.

[Explanation of symbols]

 Reference Signs List 23 polycrystalline Si film 24 natural oxide film 25 oxynitride film 26 SiN film 27 capacitor dielectric film 32 capacitor

Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01L 27/108 H01L 21/318 H01L 21/822 H01L 21/8242 H01L 27/04

Claims (4)

(57) [Claims] 1. A method of manufacturing a semiconductor device having a capacitor in which a lower electrode is formed of a polycrystalline silicon film containing impurities, wherein a first surface of the polycrystalline silicon film is made of dilute hydrofluoric acid.
A step of irradiating the surface with infrared rays in an ammonia gas atmosphere to nitride the surface after the first etching, and a second process using diluted hydrofluoric acid on the nitrided surface. A step of repeating a process of performing etching a plurality of times; a step of forming a silicon nitride film on the surface by a low-pressure CVD method after the step of repeating the process a plurality of times; Forming a silicon oxide film on the substrate, and using the silicon nitride film formed by the infrared irradiation and the silicon nitride film and the silicon oxide film formed by the low pressure CVD method as a capacitor dielectric film of the capacitor. A method for manufacturing a semiconductor device, comprising: 2. The method according to claim 1, wherein a thickness at which the second etching is performed is 1 nm or less in terms of a thermal oxide film.
The manufacturing method of the semiconductor device described in the above. 3. The method of manufacturing a semiconductor device according to claim 1, wherein cleaning with an acid is performed instead of said first etching with dilute hydrofluoric acid. 4. The method of manufacturing a semiconductor device according to claim 1, wherein in the last of the steps repeated a plurality of times, only the nitridation by irradiating infrared rays is performed.