JPH05335320A - Silicon semiconductor substrate and manufacture thereof - Google Patents

Abstract

PURPOSE:To impart an effect of eliminating heavy metal impurities mixed in the manufacturing process of a semiconductor integrated circuit. CONSTITUTION:Carbon ions of more than 1X10<14> ions/cm<2> are implanted in the rear side of a silicon semiconductor substrate, and the semiconductor substrate forms crystal defects of more than 1X10<5> pieces/cm on the rear of the silicon semiconductor substrate by heat treatment of oxidizing atmosphere. On the basis of the defects generated at the time of ion implantation, secondary defects are generated by oxidizing heat treatment. By utilizing the rear of the semiconductor substrate as a gettering site, a gettering wafer can be manufactured with higher productivity than that of the conventional technology in which an ion-implantation layer is used as the gettering site.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon semiconductor substrate used for manufacturing semiconductor devices such as integrated circuits. In particular, the present invention relates to a silicon semiconductor substrate having an effect of removing heavy metal impurities received during device manufacturing from a device region in a silicon substrate, and a manufacturing method thereof.

[0002]

2. Description of the Related Art With the high integration of integrated circuits, reduction of a minute leak current in a dynamic memory (DRAM) has become an important issue. This minute leak current is caused by heavy metal impurities represented by iron, nickel, and copper that are mixed in during the manufacture of semiconductor integrated circuits.

A gettering method is used to remove the heavy metal impurities. As this gettering method, a method of implanting carbon ions is known (Japanese Patent Laid-Open No. 58-58-58).
93334, JP-A-62-235741, Appl. Phys.
Lett. Vol. 52,889 (1988), Appl. Phys. Lett. Vol. 5
7,798 (1988).

In Japanese Patent Application Laid-Open No. 58-93334, a total of 10 ¹⁷ / s of the front surface or the back surface of a silicon semiconductor substrate is partially or completely formed.
Carbon ions are implanted at a peak concentration exceeding cm ³ . The region where carbon is injected is used as the gettering site.

In Japanese Patent Laid-Open No. 62-235741, a silicon single crystal containing carbon is formed on the back surface of a silicon semiconductor substrate. The gettering site is a region containing carbon.

[0006] Appl. Phys. Lett. Vol. 52, 889 (1988) and Appl. Phys. Lett. It has been revealed that it has become a gettering site.

[0007]

The carbon ion implantation method is
Ion implantation can be performed at room temperature, and there is no side effect due to generation of particles from the ion implantation region. However, when the ion implantation is performed with low energy, the carbon ion implantation region is shallow, and in the method of using the carbon ion implantation region as the gettering site, the gettering site is formed by incorporating the carbon ion implantation region into the oxide film in the oxidation heat treatment step. There is a problem that disappears. In order to solve this problem, a protective film that is not oxidized such as a silicon nitride film or a silicon oxide film is formed on the back surface of the carbon ion implantation area to protect it, or the carbon ion implantation energy is increased to increase the carbon ion implantation area. It is formed in a region deeper than the surface so that it is not taken in even by an oxidative heat treatment. The method of forming the non-oxidizing film on the back surface includes an extra process and has poor productivity. The method of implanting carbon ions with high energy requires a large-sized implanter, resulting in poor productivity. It is an object of the present invention to provide a silicon semiconductor substrate having high productivity and high gettering ability, and a method for manufacturing the same.

[0008]

The above object can be achieved by a silicon semiconductor substrate having carbon and oxidation-induced crystal defects introduced by ion implantation into the back surface of the silicon semiconductor substrate.

The above problem is that after carbon is ion-implanted into the back surface of the silicon semiconductor substrate, heat treatment is performed in an oxidizing atmosphere, and the carbon introduced by the ion implantation and the defects caused by the ion implantation serve as nuclei for the oxidation-induced crystal defects. It is achieved by forming.

[0010]

In the silicon substrate according to the present invention, carbon ions of 1 × 10 ¹⁴ ions / cm ² or more are implanted into the silicon semiconductor substrate and the back surface of the substrate, and the implanted carbon and the defects caused by the ion implantation serve as nuclei. The silicon semiconductor substrate has 1 × 10 ⁵ / cm ² or more oxidation-induced crystal defects. 1 carbon ion on the back surface of silicon semiconductor substrate
× 10 ¹⁴ ions / cm ² or more is implanted. This silicon semiconductor substrate is heat-treated at a temperature of 800 ° C. or higher in a gas atmosphere containing oxygen gas or a gas atmosphere containing water vapor,
Oxidation-induced crystal defects of 1 × 10 ⁵ / cm ² or more are formed with the implanted carbon and the defects generated by the ion implantation as nuclei. When heat-treating silicon in an oxidizing atmosphere,
Interstitial silicon is injected into the silicon semiconductor substrate, and the concentration of interstitial silicon becomes higher than the thermal equilibrium concentration and becomes supersaturated. In the case where a lattice strain due to carbon atoms or minute crystal defects formed by ion implantation exist on the surface of the silicon semiconductor substrate, oxidation-induced crystal defects are formed with such defects as nuclei, and become effective gettering sites. Oxidation heat treatment of silicon is essential for implanting interstitial silicon.

When carbon ions are implanted into the back surface of the silicon semiconductor substrate at a dose of less than 1 × 10 ¹⁴ ions / cm ^2, only less than 1 × 10 ⁵ / cm ² of oxidation-induced crystal defects are formed, and the getter is used. Ring ability is weak.

[0012]

EXAMPLES Next, the present invention will be described in detail with reference to examples.

Under the condition that the carbon ion beam generated by using the vacuum arc discharge type ion generator is tilted by 7 degrees with respect to the plane orientation (100) on the back surface of the silicon semiconductor substrate, the acceleration voltage is 40 keV and the dose is. Amount 1 × 10 ¹³ ions / cm ² , 1 × 10 ¹⁴ ions / cm ² , 1 × 10 ¹⁵
Ions / cm ² , 1 × 10 ¹⁶ ions / cm ² , 1 × 10
Ion implantation of ¹⁷ ions / cm ² was performed. The ion-implanted substrate was heat-treated at 1100 ° C. in a steam gas atmosphere for 1 hour, and then the oxide film formed by the heat treatment was removed with an aqueous solution containing hydrofluoric acid.

This silicon substrate was selectively etched with a light etching solution, and the ion-implanted surface was observed and evaluated with an optical microscope. The results are shown in Table 1. Oxidation-induced crystal defects are generated along with the ion implantation.

[0015]

[Table 1]

Next, the gettering ability of the above-mentioned silicon semiconductor substrate is intentionally contaminated with copper, and after the diffusion heat treatment of copper,
The amount of copper captured by the oxidation-induced crystal defects was analyzed by an atomic absorption method and evaluated by the copper recovery rate. The intentional contamination of copper was performed by rotating a silicon substrate and dropping an aqueous solution containing copper onto the surface of the substrate. According to this method, it is possible to uniformly attach the substrate.

The initial surface contamination amount of copper is 1 × 10 ¹⁴ ions /
cm ² . Post-contamination diffusion treatment conditions are 1000 ° C,
5 minutes nitrogen atmosphere. The amount of copper gettered on the injection surface was determined by dissolving 10 μm from the injection surface with a mixed acid of hydrofluoric acid and nitric acid, and analyzing the copper concentration of this solution by an atomic absorption method.
The results are shown in Table 2. A case where the copper recovery rate exceeds 90% is considered to have a sufficient gettering effect. As is clear from Table 2, the carbon ion implantation amount is 1 × 10 ¹⁴ / cm 3.
It can be seen that ^two or more have a good gettering effect.

[0018]

[Table 2]

[0019]

As described above, according to the present invention, the oxidation-induced crystal defects, which are the secondary defects, are generated by the oxidation heat treatment using the implanted carbon and the defects generated by the ion implantation as the nuclei, and the gettering sites are generated there. Therefore, even if the ion implantation energy is as low as that, as in the prior art in which the carbon ion implantation layer itself is used as a gettering site, after the carbon ion implantation,
Since a good gettering ability can be imparted to the silicon substrate without requiring an extra process such as forming a non-oxidizing film, the productivity can be remarkably improved.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Kenji Sugiyama 5-10-1, Fuchinobe, Sagamihara-shi, Kanagawa Nippon Steel Corporation Electronics Research Laboratory

Claims (2)

[Claims] 1. A silicon semiconductor substrate and a back surface of the substrate,
1 × 10 carbon ions of 1 × 10 ¹⁴ ions / cm ² or more
A silicon semiconductor substrate having ⁵ or more oxidation-induced crystal defects formed per cm ² . 2. The back surface of the silicon semiconductor substrate is 1 × 10.
It is characterized by forming 14 × 10 ⁵ / cm ² or more oxidation-induced crystal defects on the back surface of a silicon semiconductor substrate by implanting ¹⁴ ions / cm ² or more of carbon ions and performing a heat treatment containing an oxidizing atmosphere. Manufacturing method of silicon semiconductor substrate.