JPH07245267A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a semiconductor device where silicon oxide film formed by the chemical vapor growth method has improved characteristics and manufacturing yield improves. CONSTITUTION:Silicon oxide film 12 is formed by the LPCVD method (Low pressure chemical vapor growth method) with TEOS (tetraethoxysilane) as a feed gas on Si substrate 11 and then the formed silicon oxide film 12 is heated for a specific amount of time in mixed gas atmosphere containing oxygen (O2) and hydrogen chloride (HCl), thus increasing the film density of the silicon oxide film 12 due to the oxygen in atmosphere on heat treatment, decreasing porosity, and increasing dielectric constant. Also, the getter operation of chlorine eliminates movable ions such as Na ion intruding into the silicon oxide film 12 and metal impurity such as adsorbed copper and aluminum and hence improving the characteristics of the silicon oxide film 12 and the yield for manufacturing a semiconductor device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device.

[0002]

As is well known, there are various methods for forming a silicon oxide film on a substrate when manufacturing a semiconductor device. Among them, in order to reduce the temperature during CVD (chemical vapor deposition) and thin the film to be formed, L
There is a method of forming a silicon oxide film using TEOS (tetraethoxysilane) as a source gas by the PCVD method (low pressure chemical vapor deposition method). Then, there is a method of manufacturing a semiconductor device in which the silicon oxide film thus formed is used as, for example, a gate oxide film or a post oxide film for covering electrodes.

A method of forming a gate portion in a conventional MOS transistor will be described below with reference to FIGS. 19 to 21. 19 to 21 are cross-sectional views showing each step of formation.

First, in the first step shown in FIG. 19, 600 to 70 using TEOS as a source gas on the surface of the Si substrate 1.
A silicon oxide film 2 is formed by LPCVD at a temperature of 0 ° C. so as to deposit silicon oxide in a thickness of 4 to 10 nm.

Then, in the second step shown in FIG. 20, the temperature is maintained at 600 to 700 ° C. and monosilane (S
Polycrystalline silicon is deposited on the silicon oxide film 2 to a thickness of 400 nm by the LPCVD method using iH ₄ ) as a source gas. Then, phosphorus (P) as an impurity is thermally diffused into the deposited polycrystalline silicon at a temperature of about 900 ° C. to form a polycrystalline silicon film 3.

Next, in a third step shown in FIG. 3, a photoresist is applied on the polycrystalline silicon film 3 and patterned by a photo-etching method to form a photo mask. Then, the polycrystalline silicon film 3 and the silicon oxide film 2 are etched by the dry etching method using the formed photomask until the Si substrate 1 is exposed.
Then, by removing the photoresist, a gate portion 4 having the silicon oxide film 2 as a gate oxide film and the polycrystalline silicon film 3 as a gate is formed on the Si substrate 1.

When the gate portion 4 is formed of the silicon oxide film 2 formed by CVD using TEOS as described above, the breakdown voltage leakage represented by the I (current) -V (voltage) characteristic immediately after the film formation. There is a problem that the characteristics become unstable as compared with the silicon oxide film formed by the thermal oxidation method.

That is, due to the film density and the porosity which are said to vary depending on the film forming conditions, the low electric field current leakage is large in the low film density or high porosity state, and the insulating performance of the silicon oxide film 2 is large. As the low temperature process and thin film formation further reduce metal impurities such as copper, aluminum, and iron adsorbed on the substrate to be deposited, vapor phase growth equipment, etc., and Na ions that have penetrated during the deposition process, Pinhole defects may occur due to the influence of mobile ions such as Ca ions.

Therefore, the semiconductor device having the silicon oxide film 2 formed by the CVD method in the gate portion 4 has a low manufacturing yield.

Similarly, when an oxide film is formed after covering the electrodes of the memory cell in the same manner, invasion of mobile ions and water cannot be prevented, which causes adverse effects such as fluctuation of the threshold value of the transistor. As a result, good characteristics could not be obtained.

[0011]

In the case where the silicon oxide film is formed by the chemical vapor deposition method as described above, the pressure resistance leak characteristic of the silicon oxide film is unstable, and therefore, the manufacturing process of the semiconductor device is difficult. The stay was low. The present invention has been made in view of such circumstances, and an object of the present invention is to manufacture a semiconductor device in which a silicon oxide film formed by a chemical vapor deposition method has good characteristics and a manufacturing yield is improved. To provide a method.

[0012]

A method of manufacturing a semiconductor device according to the present invention comprises a step of forming a silicon oxide film on a surface of a substrate by chemical vapor deposition, and a step of forming the formed silicon oxide film with oxygen and chlorine. And a step of performing heat treatment in an atmosphere containing oxygen for a predetermined time, wherein the atmosphere containing oxygen and chlorine is a mixed gas of oxygen, hydrogen chloride and an inert gas, or oxygen, chlorine and an inert gas. It is characterized by comprising a mixed gas of active gases, and a step of forming a silicon oxide film on a silicon substrate by chemical vapor deposition, and a silicon substrate on which the silicon oxide film is formed. Is heat-treated in a mixed gas of an inert gas containing oxygen and hydrogen chloride for a predetermined time, and the surface of the substrate formed of a polycrystalline silicon film is formed. A step of forming a silicon oxide film by chemical vapor deposition, and a step of heat-treating a silicon substrate on which the silicon oxide film is formed in a mixed gas of oxygen and an inert gas containing hydrogen chloride for a predetermined time. Further, the temperature during the heat treatment is higher than the temperature during the chemical vapor deposition when the silicon oxide film is formed.

[0013]

According to the method of manufacturing a semiconductor device configured as described above, a silicon oxide film is formed by chemical vapor deposition, and the formed silicon oxide film is heat-treated for a predetermined time in an atmosphere containing oxygen and chlorine. I am trying to do it. Therefore, oxygen in the atmosphere during the heat treatment increases the film density of the silicon oxide film, lowers the porosity, and increases the dielectric constant. Similarly, the gettering action of chlorine removes mobile ions penetrating into the silicon oxide film and adsorbed metal impurities. As a result, the characteristics of the silicon oxide film are improved, and the manufacturing yield of semiconductor devices is improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. First, a method of forming a gate oxide film, which is an essential part of the present invention, in the MOS transistor of the first embodiment will be described with reference to FIGS. 1 to 4 are cross-sectional views showing each step of formation.

In the first step shown in FIG. 1, Si (1
00) On the flatly finished surface of the substrate 11, the CVD method (chemical vapor deposition method), for example, the temperature is maintained at 600 ° C. within the range of 600 to 700 ° C. and the pressure is 0.4 to 0.
By the LPCVD method (low pressure chemical vapor deposition method) under the condition of 8 Torr, TEOS (tetraethoxysilane) as a raw material gas was caused to flow at 50 sccm and nitrogen (N ₂ ) at 200 sccm to deposit silicon oxide to a thickness of 10 nm. A silicon oxide film 12 is formed.

Then, in the second step shown in FIG.
CV the Si substrate 11 on which the silicon oxide film 12 is formed,
It is placed in a mixed gas atmosphere of nitrogen containing oxygen (O ₂ ) and hydrogen chloride (HCl) maintained at a temperature higher than the temperature at the time of film formation in D, for example, 800 ° C. Then, heat treatment is performed for about 30 minutes to perform thermal annealing of the silicon oxide film 12.

Next, in the third step shown in FIG. 3, the temperature is maintained at 600 to 630 ° C. and the pressure is 0.4 to 0.8.
By the LPCVD method under the conditions of Torr, monosilane (SiH ₄ ) as a source gas is caused to flow at 100 sccm to deposit polycrystalline silicon on the silicon oxide film 12 so as to have a thickness of 400 nm. Then, phosphorus (P) as an impurity is thermally diffused into the deposited polycrystalline silicon at a temperature of about 900 ° C. to form a polycrystalline silicon film 13.

Next, in a fourth step shown in FIG. 4, a photoresist is applied on the polycrystalline silicon film 13 and patterned by using a photoetching method to form a photomask. Then, the polycrystalline silicon film 13 and the silicon oxide film 12 are etched by the dry etching method using the formed photomask until the Si substrate 11 is exposed. Then, by removing the photoresist, the silicon oxide film 12 is used as a gate oxide film on the Si substrate 11,
A gate portion 14 having the polycrystalline silicon film 13 as a gate is formed.

The silicon oxide film 12 of the gate portion 14 formed through the above steps has a high film density due to oxygen by thermal annealing in a mixed gas containing oxygen and hydrogen chloride at a high temperature, and has a hole. The dielectric constant decreases and the dielectric constant increases. The gettering action of chlorine in hydrogen chloride removes mobile ions such as sodium and calcium that have entered the silicon oxide film 12 and adsorbed metal impurities such as copper, aluminum, and iron.

As a result, the initial breakdown voltage failure due to pinholes and the low electric field current leakage due to the low film density and high porosity can be reduced, and the insulating property of the silicon oxide film 12 can be improved. The instability of is resolved.
Then, since the characteristics of the silicon oxide film 12 are improved, MO
The manufacturing yield of the S transistor is also improved.

The getter action of chlorine is 80
Although a temperature of 0 ° C. or lower is possible, a temperature higher than the temperature at the time of film formation by CVD is required when increasing the film density by oxygen, and the getter action and the film density increase should be performed at different temperatures. However, if the temperature is 800 ° C. or higher, thermal annealing in a mixed gas can be performed at once.

Next, a method of forming the gate oxide film on the floating gate in the nonvolatile memory of the second embodiment will be described with reference to FIGS. 5 to 13 are cross-sectional views showing each step of formation.

In the first step shown in FIG. 5, Si (1
00) on the flat-finished surface of the substrate 21, approximately 900
The first silicon oxide film 22 having a thickness of 20 nm is formed by a thermal oxidation method which is usually performed by heating to a temperature of ℃.
To form a film.

Subsequently, in a second step shown in FIG. 6, a photoresist is applied on the first silicon oxide film 22,
A photomask is formed by patterning using a photo-etching method. Then, the first silicon oxide film 22 is etched by a wet etching method using the formed photomask, and the memory cell forming portion side 2 of the Si substrate 21 is etched.
Processing is performed so that the surface of No. 3 is exposed, and then the photoresist is removed. Regarding the select gate forming portion side 24, the first silicon oxide film 22 is left on the Si substrate 21.

Next, in the third step shown in FIG. 7, the second silicon oxide film 25 having a thickness of 10 nm is formed again by the thermal oxidation method performed by heating to a temperature of about 900.degree. As a result, on the surface of the Si substrate 21 on the memory cell forming portion side 23 from which the first silicon oxide film 22 is removed,
A silicon oxide film having a thickness of 10 nm is formed by the second silicon oxide film 25, and the first silicon oxide film 22 is not removed.
The first silicon oxide film 22 and the second silicon oxide film 25 form a silicon oxide film having a film thickness of 30 nm on the first layer 1.

Next, in the fourth step shown in FIG. 8, the temperature is maintained at 600 to 630 ° C. and the pressure is 0.4 to 0.8 T.
By the LPCVD method under the condition of orr, the source gas monosilane is caused to flow at 100 sccm to generate the second silicon oxide film 25.
Polycrystalline silicon is deposited thereon to a thickness of 200 nm. Then, phosphorus (P) as an impurity is thermally diffused into the deposited polycrystalline silicon at a temperature of about 900 ° C. to form a first polycrystalline silicon film 26.

Next, in the fifth step shown in FIG. 9, a temperature of 600 to 7 is applied to the surface of the first polycrystalline silicon film 26.
In the range of 00 ° C., for example, about 600 ° C. is maintained, and the pressure is 0.4 to 0.8 Torr.
Source gas TEOS 50sccm, nitrogen 200sc
Then, a third silicon oxide film 27 is formed so that silicon oxide is deposited to a thickness of 10 nm.

Next, in the sixth step shown in FIG.
Si substrate 21 on which the third silicon oxide film 27 is formed
Is higher than the temperature at the time of film formation by CVD, for example, 80
It is placed in a mixed gas atmosphere of nitrogen containing oxygen and hydrogen chloride maintained at 0 ° C. And heat treatment for about 30 minutes
The silicon oxide film 27 is thermally annealed.

Next, in a seventh step shown in FIG. 11, a photoresist is applied on the third silicon oxide film 27,
A photomask is formed by patterning using a photo-etching method. Then, the third silicon oxide film 27 is etched by a wet etching method using the formed photomask so that the surface of the first polycrystalline silicon film 26 on the select gate formation portion side 24 is exposed. ,
Then, the photoresist is removed.

Next, in an eighth step shown in FIG. 12, the temperature is maintained at 600 to 630 ° C. and the pressure is 0.4 to 0.8.
By the LPCVD method under the condition of Torr, monosilane as a source gas is caused to flow at 100 sccm to form polycrystalline silicon to a thickness of 4
It is deposited to have a thickness of 00 nm. Then, phosphorus (P) as an impurity is added to the deposited polycrystalline silicon at about 900.degree.
The second polycrystalline silicon film 28 is formed by thermal diffusion at the temperature of.

As a result, on the select gate formation portion side 24 where the third silicon oxide film 27 is removed, a polycrystalline silicon film having a thickness of 600 nm formed by the first polycrystalline silicon film 26 and the second polycrystalline silicon film 28. Are formed on the second silicon oxide film 25. The third silicon oxide film 2
A second polycrystalline silicon film 28 having a film thickness of 400 nm is formed on the third silicon oxide film 27 on the memory cell forming portion side 23 where 7 is not removed, and the second silicon oxide film 25 and the third polysilicon film 28 are formed. Film thickness of 200 n between the silicon oxide film 27 and
The first polycrystalline silicon film 26 of m is sandwiched between them.

Next, in the ninth step shown in FIG.
A photoresist is applied on the second polycrystalline silicon film 28 and patterned by using a photo-etching method to form a photo mask. Then, the first and second polycrystalline silicon films 26, 28 and the first, second and third silicon oxide films 22, 25, 27 are formed on the Si substrate 21 by a dry etching method using the formed photomask. Etching is performed until exposed. Then, by removing the photoresist, the first and second silicon oxide films 22 and 25 are used as gate oxide films and the first and second polycrystalline silicon films 26 and 28 are used as gates on the Si substrate 21. Select gate portion 29 is formed. In addition, the second silicon oxide film 2
5 is a first gate oxide film, a first polycrystalline silicon film 26
As a floating gate, and the third silicon oxide film 2
7 is a second gate oxide film and a second polycrystalline silicon film 28.
The gate portion 30 of the memory cell having the gate is formed.

The third silicon oxide film 27 of the gate portion 30 of the memory cell formed through these steps is subjected to the first annealing by thermal annealing in a mixed gas containing high temperature oxygen and hydrogen chloride. As in the example, oxygen increases the film density, lowers the porosity, and increases the dielectric constant. The getter action of chlorine in hydrogen chloride removes mobile ions such as sodium and calcium that have entered the third silicon oxide film 27 and adsorbed metal impurities such as copper, aluminum, and iron.

As a result, similarly to the first embodiment, the insulation characteristics of the third silicon oxide film 27 of the gate portion 30 can be improved, and the instability of the breakdown voltage leakage characteristics is eliminated. Then, the characteristics of the third silicon oxide film 27 are improved, so that the manufacturing yield of the nonvolatile memory is also improved.

Next, a method of forming a post oxide film on the gate of the polycrystalline silicon electrode of the MOS transistor of the third embodiment will be described with reference to FIGS. 14 to 18. 14 to 18 are cross-sectional views showing each step of formation.

In the first step shown in FIG. 14, Si
The (100) substrate 31 has approximately 9
The first silicon oxide film 32 having a thickness of 20 nm is formed by a thermal oxidation method which is usually performed by heating to a temperature of 00 ° C.

Then, in the second step shown in FIG.
The temperature is maintained at 600 to 630 ° C, and the pressure is 0.4 to 0.
By the LPCVD method under the condition of 8 Torr, a source gas of monosilane is caused to flow at 100 sccm to deposit polycrystalline silicon on the Si substrate 31 so as to have a thickness of 400 nm.
Then, phosphorus (P) as an impurity is thermally diffused into the deposited polycrystalline silicon at a temperature of about 900 ° C. to form a polycrystalline silicon film 33.

Next, in the third step shown in FIG.
A photoresist is applied on the polycrystalline silicon film 33 and patterned by using a photoetching method to form a photomask. Then, the polycrystalline silicon film 33 and the first silicon oxide film 32 are etched by the dry etching method using the formed photomask until the Si substrate 31 is exposed. Then, by removing the photoresist, a gate portion 34 having the first silicon oxide film 32 as a gate oxide film and the polycrystalline silicon film 33 as a gate is formed on the Si substrate 31.

Next, in the fourth step shown in FIG.
A temperature of 6 is applied on the gate portion 34 and the exposed Si substrate 31.
Maintained within the range of 00 to 700 ° C, for example, about 600 ° C,
By the LPCVD method under a pressure of 0.4 to 0.8 Torr, the source gas TEOS is 50 sccm and nitrogen is 20 sccm.
A second silicon oxide film 35 is formed so that silicon oxide is deposited to a thickness of 20 nm at a flow rate of 0 sccm.

Subsequently, in a fifth step shown in FIG. 18, the Si substrate 3 on which the second silicon oxide film 35 is formed
1 is higher than the temperature at the time of film formation by CVD, for example, 8
It is placed in a mixed gas atmosphere of oxygen and nitrogen containing hydrogen chloride maintained at 00 ° C. Then, heat treatment is performed for about 30 minutes to perform thermal annealing of the second silicon oxide film 35.

In this way, a post oxide film of the second silicon oxide film 35 is formed on the gate portion 34 having the polycrystalline silicon film 33 as a gate.

The second silicon oxide film 35 as a post oxide film of the gate portion 34 formed through the above process is
Thermal annealing in a mixed gas containing oxygen and hydrogen chloride at a high temperature causes oxygen to increase the film density, decrease the porosity, and increase the dielectric constant, as in the first and second embodiments. Becomes The gettering action of chlorine in hydrogen chloride removes mobile ions such as sodium and calcium that have entered the second silicon oxide film 35 and adsorbed metal impurities such as copper, aluminum, and iron.

As a result, similar to the first and second embodiments, the insulation characteristics of the second silicon oxide film 35 of the gate portion 34 can be improved, and the withstand voltage leak characteristic becomes unstable. Resolve. The improvement in the characteristics of the second silicon oxide film 35 also improves the manufacturing yield of the MOS transistor having the post oxide film in the gate formed of the polycrystalline silicon electrode.

In each of the above embodiments, TEOS is used.
Each of the silicon oxide films 12, 27 and 35 formed by the LPCVD method using as a raw material gas is heat-treated in a mixed gas atmosphere containing hydrogen chloride, but a gas that can obtain the same getter action instead of hydrogen chloride, Similar effects can be obtained by using chlorine, for example. In addition, in the second embodiment, the first and second silicon oxide films 22 and 25 are formed by the thermal oxidation method, but like the third silicon oxide film 27, they are formed by the LPCVD method using TEOS as a source gas. After that, it may be formed by heat treatment in a gas atmosphere containing oxygen and chlorine. Further, in the third embodiment, the first silicon oxide film 32 is formed by the thermal oxidation method, but similarly to the second silicon oxide film 35, it is formed by the LPCVD method using TEOS as a source gas, and then the oxygen is formed. It may be formed by heat treatment in a gas atmosphere containing chlorine.

[0045]

As is apparent from the above description, according to the present invention, a silicon oxide film is formed by chemical vapor deposition, and the formed silicon oxide film is heat treated for a predetermined time in an atmosphere containing oxygen and chlorine. With such a configuration, the characteristics of the formed silicon oxide film are improved and the manufacturing yield is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first step in a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second step in the first embodiment of the present invention.

FIG. 3 is a sectional view showing a third step in the first embodiment of the present invention.

FIG. 4 is a sectional view showing a fourth step of the first embodiment of the present invention.

FIG. 5 is a sectional view showing a first step in the second embodiment of the present invention.

FIG. 6 is a sectional view showing a second step in the second embodiment of the present invention.

FIG. 7 is a sectional view showing a third step in the second embodiment of the present invention.

FIG. 8 is a sectional view showing a fourth step of the second embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a fifth step in the second embodiment of the present invention.

FIG. 10 is a sectional view showing a sixth step in the second embodiment of the present invention.

FIG. 11 is a cross-sectional view showing a seventh step of the second embodiment of the present invention.

FIG. 12 is a sectional view showing an eighth step in the second embodiment of the present invention.

FIG. 13 is a sectional view showing a ninth step in the second embodiment of the present invention.

FIG. 14 is a sectional view showing a first step in the third embodiment of the present invention.

FIG. 15 is a sectional view showing a second step in the third embodiment of the present invention.

FIG. 16 is a sectional view showing a third step in the third embodiment of the present invention.

FIG. 17 is a sectional view showing a fourth step in the third embodiment of the present invention.

FIG. 18 is a sectional view showing a fifth step in the third embodiment of the present invention.

FIG. 19 is a sectional view showing a first step in a conventional example.

FIG. 20 is a cross-sectional view showing a second step in the conventional example.

FIG. 21 is a sectional view showing a third step in the conventional example.

[Explanation of symbols]

 11 ... Si substrate 12 ... Silicon oxide film

Claims (5)

[Claims] 1. A method comprising: a step of forming a silicon oxide film on the surface of a substrate by chemical vapor deposition; and a step of heat-treating the formed silicon oxide film in an atmosphere containing oxygen and chlorine for a predetermined time. A method for manufacturing a semiconductor device, comprising: 2. The atmosphere containing oxygen and chlorine is composed of a mixed gas of oxygen, hydrogen chloride and an inert gas, or a mixed gas of oxygen, chlorine and an inert gas. Of manufacturing a semiconductor device of. 3. A step of forming a silicon oxide film on a silicon substrate by chemical vapor deposition, and the step of forming the silicon substrate on which the silicon oxide film is formed in a mixed gas of an inert gas containing oxygen and hydrogen chloride. And a step of performing a heat treatment for a predetermined time. 4. A step of forming a silicon oxide film on the surface of a substrate formed of a polycrystalline silicon film by chemical vapor deposition, and the step of forming oxygen and hydrogen chloride on the silicon substrate formed with the silicon oxide film. And a step of performing heat treatment for a predetermined time in a mixed gas of an inert gas containing the semiconductor device. 5. The temperature during the heat treatment is higher than the temperature during the chemical vapor deposition when the silicon oxide film is formed, according to any one of claims 1 and 3 and 4. A method of manufacturing a semiconductor device according to any one of the above.