JPH05267480A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To prevent detrimental affect on device properties by reducing an amount of carbon atom taken into a silicon oxide film when a silicon oxide film is formed by plasma CVD method using organic oxysilane such as TEOS as a main material. CONSTITUTION:A silicon substrate 26 is arranged on a lower electrode 23 and heated by a lamp 22. Reaction gas is supplied through a gas supply port 29 and a high frequency voltage is applied between both electrodes 23, 24 from a high frequency power supply 28. Thereby, reaction gas reacts and a BPSG film or a PSG film is deposited on the silicon substrate 26. Conditions of plasma CVD are; a pressure inside a CVD reaction chamber 21 of 6.5Torr, a substrate temperature of 300 to 450 deg.C, a power of the high frequency power supply 28 of 100 to 500W. The BPSG film is deposited supplying TEOS kept at 40 deg.C together with oxygen, TMP and TMB as a reaction gas from a gas supply port 29 to the reaction chamber 21 while making helium gas flow. Ratio of O2 flow rate/TEOS flow rate is 2.0 or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a silicon oxide film as an interlayer insulating film, and a manufacturing method for depositing the silicon oxide film interlayer insulating film by a plasma CVD method.

[0002]

2. Description of the Related Art A method using TEOS (tetraethyl orthosilicate) as a main component by a plasma CVD method is used as an interlayer insulating film of a semiconductor device. The silicon oxide film formed by this method has better step coverage than the silicon oxide film formed by the atmospheric pressure CVD method using silane as the main raw material, and the silicon oxide film formed by the atmospheric pressure CVD method using TEOS as the main raw material. It has the advantage of stable film quality.

A silicon oxide film such as a BPSG film or a PSG film is widely used as an interlayer insulating film between the gate wiring (polysilicon or polycide) of the MOS type semiconductor device and the first layer metal wiring. As an interlayer insulating film, a plasma CVD method using TEOS as a main material is adopted for the purpose of providing good step coverage and improving flatness after reflow. However, in the silicon oxide film formed by the plasma CVD method using TEOS as a main raw material, the organic components generated in the process of forming the silicon oxide film have a strong tendency to be taken into the silicon oxide film. Silane (SiH ₄ ) which is a mainstream insulating film forming material at present does not contain an organic component in its molecular structure. Therefore, carbon is not contained in a silicon oxide film formed by using silane as a main raw material.

When a silicon oxide film formed by a plasma CVD method using TEOS as a main material is used as an interlayer insulating film between metal wirings, carbon atoms taken in the silicon oxide film are stable and the semiconductor It does not adversely affect the characteristics of the device. However, when the silicon oxide film is used as an interlayer insulating film between the gate wiring and the metal wiring, a heat treatment (reflow step) is usually performed after the CVD film for the purpose of planarization and activation of implanted impurities. The carbon atoms taken into the silicon oxide film formed from TEOS as a raw material diffuse into the semiconductor substrate due to the heat treatment, which adversely affects the device characteristics.

Therefore, TEOS is formed by the plasma CVD method.
Several methods have been proposed in order to prevent impurities such as carbon from being incorporated into a silicon oxide film formed by using as a main material. For example, a method of reducing the amount of carbon taken into the film by introducing TEOS into the CVD apparatus by aeration with nitrogen (see Japanese Patent Laid-Open No. 1-238024),
A method for reducing impurities in a film by annealing a silicon oxide film formed using TEOS as a main material in an ozone atmosphere or oxygen plasma (Japanese Patent Laid-Open No. 3-41).
No. 731232), a method of reducing impurities by reducing impurities by treating a silicon oxide film with oxygen plasma or oxygen radicals (Japanese Patent Laid-Open No. 2-219232).
(See Japanese Patent Laid-Open No. 2-285636), and a method of reducing the amount of carbon taken into the oxide film by mixing hydrogen or water vapor with TEOS (see Japanese Patent Laid-Open No. 2-285636).

[0006]

SUMMARY OF THE INVENTION The present invention provides a method of forming a silicon oxide film by a plasma CVD method using an organic oxysilane such as TEOS as a main raw material. It is an object of the present invention to provide a method for reducing the amount of carbon atoms taken in so as not to adversely affect device characteristics, and a semiconductor device having an interlayer insulating film thus formed.

[0007]

In the semiconductor device of the present invention, a silicon oxide film containing a small amount of carbon and containing organic oxysilane as a main component and deposited by plasma CVD is used as an interlayer insulating film formed under a metal wiring. It is used. In a preferred mode, the interlayer insulating film is an interlayer insulating film between the gate wiring and the metal wiring. In the manufacturing method of the present invention, when depositing the interlayer insulating film of the semiconductor device by the plasma CVD method, organic oxysilane is used as the main raw material, and the ratio of the oxygen flow rate to the organic oxysilane flow rate is expressed by the ventilation gas flow rate of the organic oxysilane. As a flow rate ratio at this time, O ₂ / (organooxysilane) is set to 2.0 or more.

Organooxysilane, which is a main raw material for forming a silicon oxide film by the plasma CVD method, includes C ₂ H ₅ Si (OC ₂ H ₅ ) ₃ and Si (OC ₃ H ₇ ) ₄ Si in addition to TEOS.
(OCH ₃ ) ₄ or the like can be used. In order to guide the organic oxysilane to the reaction chamber, an inert gas such as helium or oxygen is passed through the appropriately heated organic oxysilane to guide the gas together with the ventilation gas, or the organic oxysilane is heated to guide the vapor. Good. When venting in the case of TEOS, it is suitable to set the temperature of TEOS to 30 to 50 ° C.

[0009]

1 shows an embodiment of a semiconductor device of the present invention. Field oxide film 4 on silicon substrate 2
Form an active region, and a source region 6 and a drain region 8 are formed in the active region by impurity diffusion. Polysilicon is formed on the channel region between the source region 6 and the drain region 8 via a gate oxide film 10. Gate electrode 1
2 is formed. Gate electrode 12 and metal wiring 1
6 and 18, a BPSG film or a PSG film, which is a silicon oxide film containing TEOS as a main component and having a low carbon content and having a low carbon content, is formed as an interlayer insulating film 14 between the electrodes 6 and 18. Contact holes are formed in the interlayer insulating film 14, and the metal wirings 16 and 18 are connected to the source region 16 and the drain region 8, respectively.

FIG. 2 schematically shows a plasma CVD apparatus used in the manufacturing method of the present invention. In FIG. 2, a grounded lower electrode 23 whose temperature is controlled by a lamp 22 and an upper electrode 24 having a shower head for emitting a reaction gas and also serving as a high frequency applying electrode are arranged in the reaction chamber 21. The reaction chamber 21 is evacuated from the exhaust port 25.
A silicon substrate 26 on which a silicon oxide film is to be deposited is arranged on the lower electrode 23 so as to face the upper electrode 24. TEOS is aerated with an inert gas such as helium or oxygen, and is supplied to the reaction chamber 21 from the gas supply port 29 together with helium and oxygen as the aeration gas. From the gas supply port 29, oxygen and TMP (trimethyl phosphate; PO (OC
H ₃ ) ₃ ) and TMB (trimethylborate; B (OC
Impurity source gas such as H ₃ ) ₃ ) is also supplied to the reaction chamber 21. These reaction gases are uniformly supplied from the shower head of the upper electrode 24 onto the silicon substrate 26, and the exhaust port 25
Exhausted from. A high frequency power supply 28 applies a high frequency voltage of 13.56 MHz between the upper electrode 24 and the lower electrode 23.

In the CVD apparatus of FIG. 2, the silicon substrate 26 is placed on the lower electrode 23, and the substrate 26 is heated via the base electrode 23 by the light entering the reaction chamber 21 from the lamp 22 through the quartz glass 27. To be done. The reaction gas is supplied through the gas supply port 29, and the high frequency power supply 28 supplies the two electrodes 2 to each other.
When a high-frequency voltage is applied between 3 and 24, the reaction gas reacts and the BPSG film or PS on the silicon substrate 6.
G film is deposited.

As conditions for plasma CVD, the pressure in the CVD reaction chamber 21 is set to 2 to 12 Torr, for example, about 6.5 Torr, the substrate temperature is set to 300 to 450 ° C., and the high frequency power supply 28 is used.
Power of 100 to 500 W. Use TEOS with a purity of 99.9999%, keep it at about 40 ° C, and oxygen and TMP, TM while ventilating with helium gas.
FIG. 3A shows the relationship between the deposition rate of the BPSG film and the O ₂ flow rate / TEOS flow rate ratio when the BPSG film is deposited while being supplied to the reaction chamber 21 through the gas supply port 29 together with B. Here, the flow rate ratio of O ₂ and TEOS is expressed as a helium gas flow rate when TEOS is kept at 40 ° C. as a TEOS flow rate, and helium gas is aerated to vaporize the TEOS gas and lead the gas to the reaction chamber 21 together with the helium gas. ing. According to FIG. 3 (A), the smaller the O ₂ flow rate / TEOS flow rate ratio is, the higher the deposition rate of the BPSG film is. It is set and used in the range. However, it has been found that a large amount of carbon is incorporated into the BPSG film formed in such a range, which adversely affects the device characteristics. Figure 3 (B)
Is the ratio of O ₂ flow rate / TEOS flow rate during BPSG film formation and BP
It shows the relationship with the carbon content in the SG film.
The carbon content is measured by SIMS (secondary ion mass spectrometry), and the sample subjected to the reflow process (920 ° C., nitrogen atmosphere, 30 minutes) after forming the BPSG film is S
The peak concentration of carbon segregated at the interface between the BPSG film and the silicon substrate by IMS analysis is shown. In addition, the carbon concentration in the BPSG film made of silane as a main material is about 5.0 × 1.
0 ¹⁸ atoms / cc, which is almost the same as the background value of SIMS analysis.

The most notable effect of the carbon incorporated in the BPSG film on the device characteristics is CMO.
It is the resistance of the P-type diffusion layer of the S device, and the resistance of the P-type diffusion layer tends to increase as the amount of carbon taken in increases. FIG. 3C shows the relationship between the O ₂ flow rate / TEOS flow rate ratio and the sheet resistance value of the P-type diffusion layer. It can be seen that the sheet resistance value decreases as the O ₂ flow rate / TEOS flow rate ratio increases.

From the results of FIG. 3, the amount of carbon in the BPSG film formed by plasma CVD using TEOS as a main material depends on the O ₂ flow rate / TEOS flow rate ratio, and the influence on the device characteristics also depends on the ratio. Therefore, in order to reduce the influence of carbon in the BPSG film as much as possible, it is necessary to set the ratio as high as possible, and it is appropriate that the value is 2.0 or more.

Although TEOS is taken as the main raw material in the examples, other organic oxysilanes such as C ₂ H _{5 are used.}
Si (OC ₂ H ₅ ) ₃ , Si (OC ₃ H ₇ ) ₄ , Si (OCH
₃₎ can also be used as _4, there is a tendency that the carbon is incorporated in the same manner when those organic oxysilane as a main raw material, by the present invention even if their O ₂ flow /
(Organic oxysilane) By setting the flow rate ratio to be 2.0 or more, the amount of carbon taken in can be reduced.

[0016]

According to the present invention, a BPSG film or a PSG film is formed by TE
Plasma C mainly composed of organic oxysilane such as OS
When forming by the VD method, by setting the O ₂ flow rate / (organic oxysilane) flow rate ratio to 2.0 or more, BPS
It is possible to form a high-quality interlayer insulating film without reducing the amount of carbon taken into the silicon oxide film such as the G film or the PSG film and adversely affecting the device characteristics. Since this interlayer insulating film does not adversely affect the device characteristics, it can be used as an interlayer insulating film between the gate wiring and the metal wiring.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a semiconductor device of an embodiment.

FIG. 2 is a sectional view schematically showing an example of a plasma CVD apparatus to which the present invention is applied.

FIG. 3 is a diagram showing a relationship between an O ₂ flow rate / TEOS flow rate ratio, a film forming rate, a carbon concentration, and a sheet resistance value in one example.

[Explanation of symbols]

 2 Silicon substrate 6 Source 8 Drain 10 Gate oxide film 12 Gate electrode 14 Interlayer insulating film 16, 18 Metal wiring 21 Reaction chamber of CVD apparatus 22 Temperature control lamp 23 Lower electrode 24 Upper electrode 26 Silicon substrate 28 High frequency power supply

Claims (4)

[Claims] 1. A silicon oxide film containing organic oxysilane as a main component and having a low carbon content, which is deposited by a plasma CVD method, is used as an interlayer insulating film formed under a metal wiring of a semiconductor device. Semiconductor device. 2. The semiconductor device according to claim 1, wherein the interlayer insulating film is an interlayer insulating film between a gate wiring and a metal wiring. 3. A method of depositing an interlayer insulating film of a semiconductor device by a plasma CVD method, wherein organic oxysilane is used as a main raw material, and the ratio of the oxygen flow rate to the organic oxysilane flow rate is expressed by the gas flow rate of the organic oxysilane. O ₂ / (organooxysilane) is set to 2.0 or more as a flow rate ratio of the semiconductor device. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the interlayer insulating film is an interlayer insulating film between a gate wiring and a metal wiring.