JP3348262B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a MIS (metal
Insulator semiconductor) A process suitable for forming a sacrificial oxide film used for forming a gate insulating film in a field effect transistor is included.
And a method of manufacturing a semiconductor device .

At present, a gate insulating film in a MIS field-effect transistor has been developed in accordance with high integration of an integrated circuit device.
It is getting thinner.

In order to improve the dielectric breakdown resistance of the thinned gate insulating film by keeping the threshold voltage constant, it is necessary to increase the uniformity of the thickness of the gate insulating film. It is important not to thin locally, and the present invention addresses this need.

[0004]

2. Description of the Related Art Generally, when manufacturing an integrated circuit device including a MIS field-effect transistor, a field insulating film is formed for element isolation.
aloxidation of silicone: LO
COS) method is applied.

FIG. 2 is a cutaway side view showing a main part of an integrated circuit device including a MIS field-effect transistor at a key point in a process for explaining a conventional technique.

In the figure, 1 is a silicon semiconductor substrate, 2
Is a pad oxide film made of SiO ₂ , 3 is a nitride film made of Si ₃ N ₄ , 4 is a field insulating film made of SiO ₂ ,
Numeral 5 indicates a nitride.

When the field insulating film 4 is formed by the LOCOS method, (1) the pad oxide film 2 is formed on the surface of the silicon semiconductor substrate 1; (2) the pad oxide film 2
(3) exposing the silicon semiconductor substrate 1 in the field region, and (4) forming the field insulating film 4 by performing field oxidation.

In the above process, when field oxidation is performed,
Since the nitride film 3 is also oxidized, N or NH ₃ is generated and reaches the surface of the field region of the silicon semiconductor substrate 1 to form S or S 3.
Nitride 5 composed of i ₃ N ₄ or nitride 5 composed of SiON
Generate This is what is called a so-called white ribbon.

When the white ribbon is generated, the nitride film 3 and the pad oxide film 2 are removed later, and then, when a gate insulating film is formed again, the edge of the gate insulating film on the field insulating film side becomes thin. As a result, the breakdown voltage is degraded.

Therefore, removal of the white ribbon has been performed. That is, before the gate insulating film is formed, a sacrificial oxide film is formed in an oxygen atmosphere to oxidize and wrap the nitride 5, and the sacrificial oxide film is removed together with the nitride with hydrofluoric acid. Thereafter, a gate insulating film is formed again.

[0011]

Generally, the thickness of the sacrificial oxide film is required to be at least 20 [nm] or more. The reason for this is that a nitride that is difficult to oxidize must be incorporated into the oxide film.

However, since the thickness of the gate insulating film and the thickness of the field insulating film are becoming thinner as the integration density of integrated circuit devices becomes higher, a thicker sacrificial oxide film is formed and the controllability is improved. It is impossible to remove by uniform etching.

For example, when the sacrificial oxide film is etched, the field insulating film may be damaged, and thereafter, the gate insulating film to be formed may not be thin and uniform. There is also a problem that the dopant profile of the substrate is changed due to the necessity of a long-time high-temperature heat treatment for forming GaN.

According to the present invention, even a thin sacrificial oxide film formed at a low temperature in a short time can be easily oxidized and taken in the nitride to be easily removed.

[0015]

According to the present invention, the problem is solved by appropriately selecting an atmosphere for forming a sacrificial oxide film. That is, in the method of manufacturing a semiconductor device according to the present invention,

(1) A nitride (for example, a nitride 5 made of Si ₃ N ₄ or a nitride 5 made of SiON: see FIG. 2) formed on a silicon semiconductor substrate (for example, silicon semiconductor substrate 1: see FIG. 2) is used. A sacrificial oxide film (eg, SiO
Including the step of forming a ₂ film) in an atmosphere containing ozone
Or wherein the non-thing, or,

(2) Step of forming pad oxide film on silicon semiconductor substrate surface
Forming a nitride film on the oxide film;
Patterning, and applying a hot acid to the surface of the silicon substrate.
Forming a nitrided film, and oxidizing the nitride film and the pad.
Removing the film, and in an atmosphere containing ozone,
Forming a sacrificial oxide film on the silicon substrate surface
Is characterized by becoming , or

(3) In the above (1) or (2) , the sacrificial oxide film is
Characterized in that a step of immersion and removal in hydrofluoric acid is added , or

(4) In any one of the above (1) to (3), the silicon half
The feature is that the conductor substrate is heated in a reduced pressure ozone atmosphere
I do.

[0020]

[0021]

According to the present invention, ozone gas is decomposed to generate oxygen radicals and becomes a strong oxidizing species, so that oxidation of nitrides that are difficult to oxidize is promoted, and oxidation treatment is performed at a low temperature for a short time. However, the white ribbon can be satisfactorily removed.

[0022]

The steps of an embodiment of the present invention will be described.

(1) By applying the thermal oxidation method,
At a temperature of, for example, 850 ° C., a pad oxide film made of SiO ₂ having a thickness of, for example, 3 [nm] is formed on the surface of the silicon semiconductor substrate.

(2) Chemical vapor deposition (chemical vapor deposition)
By applying a vapor deposition (CVD) method, the temperature is set to, for example, 800 ° C.
Si ₃ having a thickness of, for example, 100 nm is formed on the pad oxide film.
A nitride film made of N ₄ is formed.

(3) By applying a wet etching method using phosphoric acid as an etchant, a nitride film is patterned to expose a portion where a field insulating film is to be formed.

(4) By applying the thermal oxidation method,
At a temperature of, for example, 900 ° C., wet oxidation is performed to form a field insulating film made of SiO ₂ with a thickness of, for example, 350 nm.

(5) The nitride film used as the oxidation-resistant mask and the underlying pad oxide film are removed to expose the active region of the silicon semiconductor substrate.

(6) By applying the thermal oxidation method,
A sacrificial oxide film made of SiO ₂ having a thickness of, for example, 10 [nm] is formed on the surface of the active region in an ozone atmosphere at a temperature of, for example, 1000 [° C.] by performing normal pressure lamp heating and for a time of, for example, 4 [min]. Form.

(7) The sacrificial oxide film is removed by immersion in hydrofluoric acid.

(8) By applying the thermal oxidation method,
At a temperature of, for example, 1000 [° C.], a gate insulating film made of SiO ₂ having a thickness of, for example, 7 [nm] is formed on the surface of the active region.

Thereafter, an ordinary technique was applied to form an amorphous silicon electrode on the gate insulating film, and the breakdown voltage was measured.

At the same time, in the step (6),
As in the conventional case, the withstand voltage was measured for a sample prepared under the same conditions except that the sacrificial oxide film was formed in an HCl / O ₂ gas atmosphere.

FIG. 1 is a diagram showing a breakdown voltage histogram in which the results obtained by measuring the breakdown voltage are summarized.

In the figure, (A) shows the data on the sample of the present invention, and (B) shows the data on the sample of the comparative example. The horizontal axis indicates the electric field strength.

As is apparent from the figure, in the case of the present invention, the reduction of the A-mode deterioration and the B-mode deterioration, which could not be improved by forming the sacrificial oxide film having a thickness of 10 nm by the conventional technique, was achieved. You can see what is being realized.

In the above description of the process, the atmosphere in which the sacrificial oxide film is formed is simply an ozone atmosphere. However, various features appear due to the means for generating ozone.

When an atmosphere in which ozone is generated by high-voltage discharge is used, ozone that does not contain moisture, which causes a trap, can be used.

When an atmosphere in which ozone is generated by electrolysis is used, ozone having less particles can be used.

When an atmosphere in which ozone is generated by UV irradiation is used, ozone can be generated directly above the wafer, so that high-concentration ozone can be used.

In the above description of the process, the temperature of the atmosphere for forming the sacrificial oxide film is merely a numerical value, but various characteristics appear due to the heating means. , It will be described.

In the case of forming a sacrificial oxide film by performing hot wall heating in an ozone atmosphere, batch processing is easy and good in-plane uniformity is obtained.

When the sacrificial oxide film is formed by performing lamp heating in an ozone atmosphere, the wafer is mainly heated and the heating of ozone can be suppressed, so that high-concentration ozone can be used.

Further, although the pressure of the ozone atmosphere is not mentioned in the above description of the process, when the ozone atmosphere is depressurized and a sacrificial oxide film is formed by, for example, lamp heating, the ozone atmosphere is depressurized. Long life.

[0044]

In the method of manufacturing a semiconductor device according to the present invention, a sacrificial oxide film for oxidizing and including and removing nitride generated on a silicon semiconductor substrate is formed in an atmosphere containing ozone. It is characterized by including a film forming step .

Ozone gas is decomposed to generate oxygen radicals and becomes a strong oxidizing species by adopting the above-mentioned structure, so that oxidation of nitride which is difficult to oxidize is promoted, and oxidation treatment is performed at low temperature and for a short time. Even in this case, the nitride can be oxidized and removed satisfactorily, and is particularly effective for removing the white ribbon. Therefore, for example, the gate insulating film in the MIS field-effect transistor does not become thinner at the side of the field insulating film, and the deterioration of the breakdown voltage can be prevented, so that the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a breakdown voltage histogram in which results obtained by measuring a breakdown voltage are summarized.

FIG. 2 shows M at a process key point for explaining a conventional technique.
FIG. 2 is a cutaway side view of an essential part showing an integrated circuit device including an IS field effect transistor.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 silicon semiconductor substrate 2 pad oxide film made of SiO ₂ 3 nitride film made of Si ₃ N _{4 4} field insulating film made of SiO ₂ 5 nitride

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 29/78

Claims (4)

(57) [Claims] 1. A half of a sacrificial oxide film for removing nitride produced in a silicon semiconductor substrate by oxidation and encompass, characterized in that it comprises a step of forming in an atmosphere containing ozone
A method for manufacturing a conductor device. 2. A pad oxide film is formed on a surface of a silicon semiconductor substrate.
Forming, forming a nitride film on the oxide film, patterning the nitride film, forming a thermal oxide film on the surface of the silicon substrate, and forming the nitride film and the pad oxide film. Removing and sacrifice the silicon substrate surface in an atmosphere containing ozone.
And characterized in that it contains the extent factory to form a牲酸monolayer
Semiconductor device manufacturing method. 3. The sacrifice oxide film is immersed in hydrofluoric acid.
Characterized in that a step of removing by adding
Item 3. The method for manufacturing a semiconductor device according to item 1 or 2. 4. A silicon semiconductor substrate is placed in a reduced pressure ozone atmosphere.
4. The method according to claim 1, wherein the heating is performed by:
The manufacturing method of the semiconductor device described in the above.