JP2550561B2 - Method for manufacturing insulator thin film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an insulator thin film such that a thin film such as a tunnel insulating film is formed on the surface of a semiconductor substrate.

[Prior Art] Some semiconductor integrated circuits and the like are required to have higher integration, and it is required to further downsize the semiconductor circuit element portion. And for example DRAM
In this case, in order to effectively secure the capacitance, it is required that the insulating film formed on the semiconductor substrate and made of, for example, silicon oxide (SiO ₂ ) be made thinner.

In a floating gate type EEPROM, the tunnel insulating film is composed of an oxide film of 80 to 150 Å or an oxynitride film, and the Fowler Nordheim tunnel current is used to generate electrons. Data is taken in and out, and data storage and erasing operations are executed. In such an operation, the tunnel insulating film is exposed to a stress of a strong electric field and a high current every time data is written and erased. Therefore, in order to secure the reliability of this EEPROM, it is necessary to form an insulating film of sufficiently good quality, and the insulating film must be formed to be sufficiently thin.

Conventionally, for example, to form a thin film of SiO ₂ such as about 100 Å that is used as a tunnel insulating film of EEPROM, etc., the oxidation temperature is lowered in a normal electric furnace to form the oxide film. It is considered to control. However, if an oxide film is formed by oxidizing at a low temperature, the quality of the film is deteriorated, and there is a problem that the dielectric breakdown voltage is lowered.

Further, it is also considered that oxygen (O ₂ ) introduced into a reaction chamber heated in an electric furnace is diluted with an inert gas and the diluted gas is used for oxidation. When the dilution gas is introduced into the electric furnace in this way, the oxidation state can be controlled in a relatively high temperature state, but the semiconductor substrate is heated in a high temperature state for a long time. When the product is put in or taken out of the electric furnace, a failure may occur due to heat history or the like. For example, in a semiconductor device having a fine structure such as a VLSI, redistribution of impurities occurs, which causes a problem in electrical characteristics.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and is to be effectively used, for example, as a tunnel insulating film of an EEPROM without giving a long thermal history. An extremely thin insulating film is formed in such a manner that its film thickness can be easily controlled, and an insulating film thin film manufacturing method that can be effectively used in the manufacturing process of various semiconductor integrated circuits is provided. To do.

[Means for Solving the Problems] That is, the method of manufacturing an insulating thin film that requires the Fowler-Nordheim tunnel current to flow according to the present invention is a semiconductor substrate having a dose of 2 × 10 ^{15 to} 5 × 10 ¹⁵ arsenic. (A
s) is injected, the semiconductor substrate is set in a reaction vessel, a reaction gas for oxidizing or nitriding the surface of the semiconductor substrate is introduced, and the semiconductor substrate set in the reaction gas atmosphere is exposed to light. Irradiating, and the surface of the semiconductor substrate is heated by the light irradiation.

[Action]

In the method of manufacturing a thin film as described above, in a semiconductor substrate made of single crystal silicon or polycrystalline silicon, 2 ×
Arsenic of 10 ^{15 to} 5 × 10 ¹⁵ doses is ion-implanted, this semiconductor substrate is set in a reaction vessel, and a reaction gas for oxidizing or nitriding the surface of the semiconductor substrate is introduced into the reaction vessel. A thin insulating film is effectively formed, and its life can be effectively extended. In this case, by irradiating light, the surface portion of the semiconductor substrate is heated, which enables thin film production in a high temperature state.
Moreover, in this case, no long-term thermal history is given to the semiconductor substrate. Therefore, a high-quality insulating film whose thickness is reliably controlled is formed, and even when a VLSI is configured, reliability can be easily obtained in its electrical characteristics. is there.

[Examples of the Invention] Hereinafter, a method for manufacturing a thin film according to an example of the present invention will be described. FIG. 1 shows the structure of an apparatus for forming an insulating thin film on a semiconductor substrate. A semiconductor substrate 12 is set in the reaction chamber 11 so as to be supported by a jig. The semiconductor substrate 12 is, for example, a single crystal silicon semiconductor substrate or a silicon semiconductor thin film, and a thin film of SiO ₂ , for example, is to be formed on the surface thereof.

Then, inside the reaction chamber 11, oxygen (O ₂ ) is introduced as a reactive gas for forming an oxide film, and further an inert gas such as nitrogen (N ₂ ) is introduced. The reactive gas is diluted with an inert gas.

Here, the reaction chamber 11 is configured to be light transmissive, for example, a heating light source 13 such as a halogen lamp is set on the outer peripheral portion of the reaction chamber 11, and the light from the heating light source 13 is By irradiating the semiconductor substrate 12, the surface of the semiconductor substrate 12 is heated.

That is, light irradiation energy from the heating light source 13 is applied to the semiconductor substrate 12 so that high-temperature rapid oxidation is performed on the surface of the semiconductor substrate 12 in a short time of, for example, 10 seconds to several minutes. In this case, the atmosphere in the reaction chamber 11 is in a state of being diluted with an inert gas by a reactive gas, and the diluted reactive gas forms an oxide film on the surface of the semiconductor substrate 12. The rate at which this oxide film is formed is set according to the concentration of the reactive gas in the reaction chamber 11, and therefore, the semiconductor substrate 12 is diluted by the inert gas diluted with the reactive gas. It becomes possible to control the thickness of the thin film formed on the surface of the.

That is, the surface of the semiconductor substrate 12 is oxidized at a high temperature, and its oxidation rate is controlled by the diluted inert gas.
After activation of the ion-implanted layer using the S oxide film, light energy is applied to oxidize the ion-implanted layer in a reactive gas atmosphere diluted with an inert gas. is there.

By thus oxidizing at a high temperature, the breakdown voltage breakdown life of the generated insulating film can be extended, and the higher the oxidation temperature is, the longer the breakdown voltage breakdown life can be.

In Figure 2 is a constant current TDDB current density 64mA / cm ^2, about
By examining the dielectric breakdown life of a 100 Å oxide film, it can be seen that the higher the oxidation temperature, the longer the life. In this figure, FO _X shows the case of an oxide film formed in a normal electric furnace, RTO _X is due to high-temperature rapid oxidation heated by a halogen lamp, and diluted with an inert gas nitrogen. This is the result when the oxygen concentration is 1 to 100%.

Here, as a sample of the above breakdown voltage breakdown test, there is shown a result when an N type 3 to 5 Ω · cm (100) silicon substrate is used to form a MOS diode.
A positive voltage is applied to the polycrystalline silicon as (+), and a negative voltage is applied to the polycrystalline silicon gate (-).

In the above embodiments, the semiconductor substrate is assumed to be single crystal silicon or polycrystalline silicon, but the semiconductor substrate is made to contain arsenic (As) at a high concentration. This is 5 × 10 ^{14 at} 100 kev on a silicon substrate.
An ion implantation of As at a dose of ˜1 × 10 ¹⁶ As was performed in a reactive gas atmosphere by applying light energy to form an insulating film.

Fig. 3 shows the state of breakdown voltage breakdown life when an oxide film is formed on a silicon substrate containing As in this way. The oxide film generated by including As in a high concentration It turned out that the life is very long.

That is, in the case of this example, the dielectric breakdown life of the generated oxide film is improved, and the optimum substrate concentration is observed. That is, as can be seen from FIG. 3, in the breakdown voltage breakdown test, the impurity concentration of As was 2 × 10 ¹⁵
It can be understood that when the dose is set to ˜5 × 10 ¹⁵ doses, the life is longest in both the case where a positive voltage is applied and the case where a negative voltage is applied. Also, the oxidation temperature is 1000 ℃ ~
At 1300 ° C, the effect becomes remarkable.

Further, the effect is exhibited not only in the high temperature rapid oxidation but also in other oxidations, and it is considered that the life of this oxide film is extended when an appropriate amount of As or the like in the oxide film is introduced. This As is considered to be introduced as an oxide in SiO ₂ , and in the oxide film formed on the above-mentioned silicon substrate on which As is introduced, about 10 ¹⁷ to 10 ²⁰ / cm ³ As is added.
Is estimated to be included.

Further, when the doped polycrystalline silicon containing phosphorus is oxidized to form the insulating film, the oxidation rate changes according to the phosphorus concentration. Further, the change in the oxidation rate between the crystal grains is also reduced by the high temperature oxidation, the surface morphology of the generated oxide film is smoothed, and the breakdown voltage is effectively improved.

[Effects of the Invention] As described above, according to the method for manufacturing an insulating thin film of the present invention, a high-quality oxide insulating film can be effectively formed in a high temperature oxidation state, and a 2 × 10 ¹⁵ ~
By implanting 5 × 10 ¹⁵ doses of arsenic (As), the life of the produced insulator is extended. Therefore, a particularly thin oxide film can be easily and surely obtained with high quality, and, for example, a floating gate EEPROM or the like can be effectively manufactured. In particular, since it is heated by light energy from a halogen lamp or the like, it is possible to perform high temperature oxidation without causing a long time high temperature heat history on the semiconductor substrate.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an apparatus for carrying out a method of manufacturing a thin film according to an embodiment of the present invention, and FIGS. 2 and 3 show the state of dielectric breakdown life of an insulating film thin film manufactured by the present invention. It is a figure explaining. 11 ... Reaction container, 12 ... Semiconductor substrate, 13 ... Heating light source (halogen lamp).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshifumi Okabe 1-1, Showa-cho, Kariya city, Aichi Japan Denso Co., Ltd. (56) References JP 62-45129 (JP, A) JP 55- 38068 (JP, A)

Claims (2)

(57) [Claims] 1. Fowler Nord
heim) A method of manufacturing an insulator thin film that requires a tunnel current to flow, comprising a step of injecting arsenic (As) at a dose of 2 × 10 ^{15 to} 5 × 10 ¹⁵ into a semiconductor substrate, and the semiconductor substrate in a reaction vessel. And a step of introducing a reaction gas for oxidizing or nitriding the surface of the semiconductor substrate, and a step of irradiating the semiconductor substrate in the reaction gas atmosphere with light. A method for producing an insulating thin film, characterized in that the insulating thin film is heated by light irradiation. 2. The production of an insulating thin film according to claim 1, wherein the step of irradiating the semiconductor substrate with light is a step of heating the surface temperature of the semiconductor substrate to be irradiated with light to 1000 ° C. to 1300 ° C. Method.