JPH07335655A - Gettering method - Google Patents

Abstract

PURPOSE:To provide a thermal treating method by which unwanted heavy metal impurities are removed in a semiconductor integrated circuit manufacturing process. CONSTITUTION:A thermal treatment is carried out in a semiconductor device manufacturing process through such a method that it is carried out for 1 to 24 hours at a temperature of 600 to 650 deg.C, 30 minutes to 24 hours at a temperature of 650 to 700 deg.C, 15 minutes to 24 hours at a temperature of 700 to 750 deg.C, and 10 minutes to 24 hours at a temperature of 750 to 800 deg.C. By this setup, elements such as iron and the like slow in diffusion and weak in gettering effect are effectively gettered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to heat treatment in a semiconductor device manufacturing process such as an integrated circuit. In particular, the present invention is a heat treatment method for effectively removing contaminant impurities received during device manufacturing from device regions in a silicon substrate.

[0002]

2. Description of the Related Art With the high integration of integrated circuits, reduction of minute leak current has become an important issue in dynamic memories (DRAM). This minute leak current is caused by heavy metal impurities typified by iron, nickel and copper that are mixed in during the semiconductor integrated circuit manufacturing process. A gettering method is used to remove the contaminant impurities.

The gettering method is a method of performing phosphorus diffusion on the back surface during the semiconductor integrated circuit manufacturing process (Journal of
Electrochemical Society 1978 Vol. 122, p. 786),
Method of introducing mechanical strain on the back side (Japanese Journal of
Applied Physics, Vol. 23, 1984, p. 959), Method of depositing polycrystalline silicon film on backside (Journal of Electrochemical
Society 1982 Vol.129, p.1294), method of implanting ions such as argon on the back surface (Journal of Applied Physics
1975, 46, 600) is known.

Semiconductor devices are manufactured using such gettering-treated substrates. In a normal device process, as a gettering process, a heat treatment including a thin film forming process for manufacturing a device is performed, and then a wafer is pulled out of the furnace at a drawing temperature of 600 ° C. or more and a drawing speed of 50 mm / min or more. , Gettering is performed during cooling from the drawing temperature to room temperature.

[0005]

The heavy metal impurities to be gettered are copper, nickel, cobalt, iron, manganese, chromium and the like. After the heat treatment, which is the heat treatment condition in the normal device process, the temperature of drawing out from the furnace is 600.
When drawn out at a temperature of ℃ or more at a drawing speed of 50 mm / or more, the thermal history during which it is drawn out from the furnace and air-cooled at room temperature is 600 ° C. when converted as a diffusion distance.
It does not exceed the diffusion distance when held for 10 minutes. Even in this thermal history, gettering can be sufficiently performed with a metal such as copper, nickel, and cobalt which has a high diffusion rate in silicon. However, with slow-diffusing elements such as iron, manganese, and chromium, diffusion during cooling is rate-determining and gettering cannot be performed. It is an object of the present invention to provide a heat treatment method for promoting a gettering effect on a slow diffusion element represented by iron.

[0006]

The present invention provides a heat treatment method for enhancing the gettering effect for slow-diffusing elements represented by iron. In the semiconductor device manufacturing process, the present invention is 1 in the temperature range of 600 ° C. or higher and lower than 650 ° C.
In the temperature range of 650 ° C to less than 700 ° C, 30 minutes to 24 hours, 700 ° C to 75 hours
The gettering treatment method is a heat treatment of 15 minutes or more and 24 hours or less in a temperature range of less than 0 ° C., or 10 minutes or more and 24 hours or less in a temperature range of 750 ° C. or more and 800 ° C. or less.

[0007]

In the temperature range over 800 ° C., even heavy metals represented by iron, manganese, and chromium can sufficiently diffuse into silicon, but the capture energy of the gettering site is weak, so that the gettering site contains sufficient impurities. I can't capture. As for the trapping energy of the gettering site for the heavy metal, the trapping at the gettering site progresses as the temperature gets lower, so that the gettering site can sufficiently getter in the temperature range of 800 ° C. or lower. The trapping energy does not largely depend on the type of element, and therefore this temperature dependency is followed for all heavy metals. If a gettering site is formed on the back side, 60
In a low temperature region of less than 0 ° C., the diffusion is slow, and in fact the diffusion to the gettering site is insufficient, so an effective gettering effect cannot be expected. In the semiconductor device manufacturing process, 1 hour or more and 24 hours or less, preferably 3 hours or more and 20 hours or less in a temperature range of 600 ° C. or more and less than 650 ° C., 30 minutes or more and 24 hours or less in a temperature range of 650 ° C. or more and less than 700 ° C., preferably 2 hours to 16 hours,
15 minutes or more in the temperature range from 700 ° C to less than 750 ° C 2
Within 4 hours, preferably 60 minutes or more and 12 hours or in a temperature range of 750 ° C. or more and 800 ° C. or less, 10 minutes or more and 24 hours or less, preferably 15 minutes or more and 4 hours or less, iron, manganese , Gettering can be sufficiently performed even for elements with slow diffusion represented by chromium. Since the heat treatment time is 24 hours and the diffusion is sufficient, the gettering effect is not improved when the heat treatment time exceeds 24 hours.

There are no particular restrictions on the pressure conditions and atmosphere conditions during this heat treatment. Even if the pressure is normal pressure, or even if the pressure is reduced or increased, the effect is not different. Also, the atmosphere is, for example, nitrogen or oxygen,
There is no difference in the effect between argon and hydrogen.

The present gettering processing conditions are the same in the silicon nitride film deposition processing, thermal oxide film formation processing, polysilicon film deposition processing, silicon oxide film deposition processing, dopant diffusion and activation processing used in the semiconductor device manufacturing process. Can be done.

[0010]

[Example] The wafer used had a polysilicon film of 1 μm on the back surface.
m is a polysilicon gettering wafer deposited.
The substrate is P type 10 Ωcm and the oxygen concentration is 7 × 10 ¹⁷ / cm ^3.
Is. Fe was used as a contaminant element by spin coating to contaminate the surface with an amount of 1 × 10 ¹² / cm ² . Contamination diffusion treatment, gate oxidation treatment, gettering treatment,
Hydrogen annealing is performed, Al electrode MOS diode is mounted, and MOS. The gettering ability was evaluated by the occurrence lifetime by the Ct method. First, as the iron diffusion and gate oxidation conditions, diffusion treatment is performed in a nitrogen atmosphere at 1000 ° C. for 1 hour, and dry oxidation is continuously performed at 1000 ° C. for 25 minutes. The formed gate oxide film thickness is 30 nm. Gettering treatment at 600 ℃ to 800 ℃ under 1 atmosphere
Heat treatment up to. 4 as hydrogen annealing condition
The treatment was carried out at 00 ° C. for 1 hour in a 20% H ₂ / N ₂ atmosphere.

The gettering process was performed under the conditions 1 to 21. Condition 1 is a case where the gettering process is not performed. As the gettering treatment condition, condition 2 is 600 ° C. in a nitrogen atmosphere for 1 hour, and condition 3 is 600 ° C.
C. under nitrogen atmosphere for 24 hours, under condition 4 at 650.degree. C. under nitrogen atmosphere for 30 minutes, under condition 5 under 650.degree. C. under nitrogen atmosphere for 24 hours, and under condition 6 under 700.degree. C. under nitrogen atmosphere.
5 minutes, under condition 7 at 700 ° C. under a nitrogen atmosphere for 24 hours,
In condition 8, at 750 ° C. under a nitrogen atmosphere for 10 minutes, and in condition 9
At 750 ° C. under a nitrogen atmosphere for 24 hours, under condition 10 800 ° C. under a nitrogen atmosphere for 10 minutes, and under condition 11 800
C. in a nitrogen atmosphere for 24 hours, condition 12 at 600.degree. C. in a nitrogen atmosphere for 50 minutes, condition 13 at 600.degree. C. in a nitrogen atmosphere for 48 hours, and condition 14 at 650.degree. C. in a nitrogen atmosphere for 20 minutes. In No. 15, 48 hours at 650 ° C. in nitrogen atmosphere, and in Condition 16, 700 ° C. in nitrogen atmosphere for 1 hour
0 minutes, condition 17 at 700 ° C. under nitrogen atmosphere for 48 hours, condition 18 at 750 ° C. under nitrogen atmosphere for 5 minutes, condition 19 at 750 ° C. under nitrogen atmosphere for 48 hours, condition 2
0, 800 ° C. under nitrogen atmosphere for 5 minutes, condition 21 8
It was carried out at 00 ° C. under a nitrogen atmosphere for 48 hours. Table 1 shows the measurement results of the occurrence lifetime.

[0012]

[Table 1]

In Condition 2, Condition 3, Condition 4, Condition 5, Condition 6, Condition 7, Condition 8, Condition 9, Condition 10, and Condition 11, the occurrence lifetime is 500 μsec or more, and a sufficient gettering effect is recognized. In the temperature range of 700 ° C. or higher and lower than 750 ° C., the heat treatment is preferably 15 minutes or longer and within 24 hours and 10 minutes or longer and within 24 hours in the temperature range of 750 ° C. or higher and 800 ° C. or lower.

[0014]

Industrial Applicability According to the present invention, in a semiconductor device manufacturing process, 1 hour or more and 24 hours or less in a temperature range of 600 ° C. or more and less than 650 ° C., 30 minutes or more and 24 hours or less in a temperature range of 650 ° C. or more and less than 700 ° C., 700 ℃ or more 750 ℃
Less than 15 minutes and less than 24 hours in the temperature range of less than 750 ° C
In the temperature range of 800 ° C. or higher, heat treatment for 10 minutes or more and 24 hours or less enables effective gettering of elements such as iron, manganese, and chromium that have slow diffusion.

Claims (4)

[Claims] 1. In a semiconductor device manufacturing process, 600
A gettering treatment method by heat treatment for 1 hour or more and 24 hours or less in a temperature range of ℃ to 650 ℃. 2. In a semiconductor device manufacturing process, 650
A gettering treatment method by heat treatment for 30 minutes or more and 24 hours or less in a temperature range of ℃ to 700 ℃. 3. In a semiconductor device manufacturing process, 700
A gettering treatment method by heat treatment for 15 minutes or more and 24 hours or less in a temperature range of ℃ to 750 ℃. 4. In a semiconductor device manufacturing process, 750
A gettering treatment method by heat treatment for 10 minutes or more and 24 hours or less in a temperature range of ℃ to 800 ℃.