JPH07335656A - Gettering method - Google Patents

Abstract

PURPOSE:To provide a thermal treatment through 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 at a cooling rate of 0.1 deg.C/minute to 1.0 deg.C/minute in a temperature range of 790 deg.C to 750 deg.C from 800 deg.C, 0.1 deg.C/minute to 2.0 deg.C/minute in a temperature range of 750 deg.C to 700 deg.C from soot, and 0.1 deg.C/minute to 3.0 deg.C/minute in a temperature range of voov to 600 deg.C from 800 deg.C. By this setup, elements such as iron 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 E).
lectrochemical Society 1975 Vol. 122, p. 786), Method of introducing mechanical strain on the back surface (Japanese Journal of Ap
plied Physics, Vol. 23, 1984, p. 959), a method of depositing a polycrystalline silicon film on the back surface, (Journal of Electrochemic
al Society 1982 Vol. 129, p. 1294), Method of implanting ions such as argon on the back surface (Journal of Applied Phy
sics 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 from the furnace and cooled to room temperature by air cooling at a drawing speed of 50 mm / or more at a temperature of ℃ or more, the thermal history during that time is the diffusion distance when converted to a diffusion distance and held at 600 ° C. for 10 minutes. It does not exceed. Metals such as copper, nickel, and cobalt, which diffuse rapidly in silicon, can be sufficiently gettered by their thermal history. 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. The present invention, in the semiconductor device manufacturing process, after the heat treatment at 800 ℃ or more, from 800 ℃ to 75
Heat treatment for cooling a temperature range from 0 ° C to 790 ° C or lower at a cooling rate of 0.1 ° C / min to 1.0 ° C / min, and 0.1 ° C / 800 ° C to 700 ° C to 750 ° C or lower Min to 2.0 ° C./min cooling rate or 800 ° C. to 600 ° C. to 700 ° C. cooling range 0.1 ° C./min to 3.0 ° C./min cooling rate Is.

[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, after heat treatment at 800 ° C or higher, 800 ° C to 750 ° C
Heat treatment for cooling the temperature range from ℃ to 790 ℃ or less at a cooling rate of 0.1 ℃ / min to 1.0 ℃ / min, 800 ℃
To a temperature range of 700 ° C to 750 ° C.
Heat treatment for cooling at a cooling rate of 1 ° C./min to 2.0 ° C./min, preferably 0.2 ° C./min to 1.0 ° C./min, or 8
The temperature range of 00 ° C to 600 ° C to 700 ° C is 0.1 ° C / min to 3.0 ° C / min, preferably 0.1 ° C / min.
By performing the heat treatment of cooling at a cooling rate of 0.5 to 0.5 ° C./minute, gettering can be sufficiently performed even for elements with slow diffusion represented by iron, manganese, and chromium. Slow cooling rate of 0.1 ° C / min is sufficient for gettering 0.1
Improvement in gettering effect cannot be expected under cooling conditions slower than ° C / min.

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. It can be carried out.

[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 pollutant 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,
After hydrogen annealing, the Al electrode MOS diode is mounted and the MOS. The gettering ability was evaluated by the occurrence lifetime by the Ct method. First, the iron diffusion and gate oxidation conditions are dry oxidation at 1000 ° C. for 25 minutes, followed by diffusion treatment at 1000 ° C. for 1 hour in a nitrogen atmosphere. The formed gate oxide film thickness is 30 nm. As gettering treatment, cooling after gate oxidation is performed at 1000 ° C. to 80 ° C.
It was performed at 0 ° C. at 3.0 ° C./min, and at 800 ° C. to 600 ° C. at 0.05 ° C./min to 4.0 ° C./min. The pressure during gettering was 1 atm and the atmosphere was N ₂ atmosphere. As hydrogen annealing conditions, 400 ° C for 1 hour 20
It was performed treated with% H ₂ / N ₂ atmosphere.

The gettering process was performed under the conditions 1 to 33. Condition 1 is a case where the material is pulled out of the furnace as it is at 800 ° C.

The condition 2 was that the temperature from 800 ° C. to 790 ° C. was cooled at 1.0 ° C./min and the sample was taken out from the furnace at 790 ° C. Condition 3 is that the temperature from 800 ° C. to 775 ° C. is 1.
It was cooled at 0 ° C / min and withdrawn from the furnace at 775 ° C. In the condition 4, the temperature from 800 ° C. to 760 ° C. was cooled at 1.0 ° C./min, and the sample was taken out from the furnace at 760 ° C. Condition 5 is 8
The temperature from 00 ° C. to 750 ° C. was cooled at 2.0 ° C./min, and the sample was taken out from the furnace at 750 ° C. Condition 6 is that the temperature from 800 ° C to 730 ° C is cooled at 2.0 ° C / min to 730 ° C.
I pulled it out of the furnace. Condition 7 is 800 ° C to 710
The temperature up to ℃ was cooled at 2.0 ℃ / min, and the furnace was pulled out at 710 ℃. The condition 8 was that the temperature from 800 ° C. to 700 ° C. was cooled at 3.0 ° C./min and then pulled out from the furnace at 700 ° C. The condition 9 was that the temperature from 800 ° C. to 650 ° C. was cooled at 3.0 ° C./min and then pulled out from the furnace at 650 ° C.
Condition 10 is that the temperature from 800 ° C to 600 ° C is 3.0.
It was cooled at 0 ° C / min and pulled out of the furnace at 600 ° C. Condition 1
In No. 1, the temperature from 800 ° C. to 790 ° C. was cooled at 0.1 ° C./min and pulled out from the furnace at 790 ° C. Condition 12 is
The temperature from 800 ° C. to 760 ° C. was cooled at 0.1 ° C./min and the product was pulled out from the furnace at 760 ° C. Condition 13 is 800
The temperature from ℃ to 750 ℃ is cooled at 0.1 ℃ / min.
Pulled out of furnace at 0 ° C. The condition 14 was to cool the temperature from 800 ° C. to 710 ° C. at 0.1 ° C./min, and pull out from the furnace at 750 ° C. Condition 15 is 800 ° C to 700
The temperature up to 0 ° C was cooled at 0.1 ° C / min, and it was pulled out of the furnace at 700 ° C. The condition 16 was that the temperature from 800 ° C. to 650 ° C. was cooled at 0.1 ° C./min, and was withdrawn from the furnace at 650 ° C. The condition 17 was to cool the temperature from 800 ° C. to 600 ° C. at 0.1 ° C./min and draw it from the furnace at 600 ° C.

The condition 18 was that the temperature from 800 ° C. to 790 ° C. was cooled at 2.0 ° C./min, and the sample was taken out from the furnace at 790 ° C. The condition 19 was to cool the temperature from 800 ° C. to 775 ° C. at 2.0 ° C./min, and pull out from the furnace at 775 ° C.
Condition 20 is that the temperature from 800 ° C to 760 ° C is 2.0.
It was cooled at 0 ° C / min and pulled out of the furnace at 760 ° C. Condition 2
In No. 1, the temperature from 800 ° C. to 750 ° C. was cooled at 3.0 ° C./min and pulled out from the furnace at 750 ° C. Condition 22 is
The temperature from 800 ° C. to 730 ° C. was cooled at 3.0 ° C./min and the product was taken out from the furnace at 730 ° C. Condition 23 is 800
Cooling the temperature from ℃ to 710 ℃ at 3.0 ℃ / 71
Pulled out of furnace at 0 ° C. The condition 24 was that the temperature from 800 ° C. to 700 ° C. was cooled at 4.0 ° C./min and then pulled out from the furnace at 700 ° C. Condition 25 is 800 ° C to 650
The temperature was lowered to 4.0 ° C / min at 4.0 ° C / min, and the furnace was withdrawn at 650 ° C. The condition 26 was that the temperature from 800 ° C. to 600 ° C. was cooled at 4.0 ° C./min, and the sample was pulled out from the furnace at 600 ° C.

The condition 27 was that the temperature from 800 ° C. to 790 ° C. was cooled at 0.05 ° C./min and the sample was taken out from the furnace at 790 ° C. The condition 28 was that the temperature from 800 ° C. to 760 ° C. was cooled at 0.05 ° C./min, and the sample was taken out from the furnace at 760 ° C. The condition 29 was that the temperature from 800 ° C. to 750 ° C. was cooled at 0.05 ° C./min and then pulled out from the furnace at 750 ° C. The condition 30 was that the temperature from 800 ° C. to 710 ° C. was cooled at 0.05 ° C./min, and the sample was taken out from the furnace at 710 ° C. The condition 31 was that the temperature from 800 ° C. to 700 ° C. was cooled at 0.05 ° C./min, and the temperature was pulled out from the furnace at 700 ° C. The condition 32 was that the temperature from 800 ° C. to 650 ° C. was cooled at 0.05 ° C./min, and the sample was taken out from the furnace at 650 ° C. The condition 33 was to cool the temperature from 800 ° C. to 600 ° C. at 0.05 ° C./min, and pull out from the furnace at 600 ° C. Table 1 shows the measurement results of the occurrence lifetime.

[0015]

[Table 1]

Condition 2, Condition 3, Condition 4, Condition 5, Condition 6, Condition 7, Condition 8, Condition 9, Condition 10, Condition 11, Condition 12, Condition 13, Condition 14, Condition 15, Condition 16, Condition 17 Then, the occurrence lifetime becomes 500 μsec or more, and a sufficient gettering effect is recognized.

[0017]

According to the present invention, in a semiconductor device manufacturing process, after heat treatment at 800 ° C. or higher, 800 ° C. to 750 ° C.
Temperature range up to less than 790 ° C from 0.1 ° C / min to 1.0
Heat treatment for cooling at a cooling rate of ℃ / min, 800 ℃ to 70
Heat treatment for cooling a temperature range of more than 0 ° C and less than 750 ° C at a cooling rate of 0.1 ° C / min to 2.0 ° C / min, and a temperature range of 800 ° C to 600 ° C or more and 700 ° C or less at 0.1 ° C / min.
By heat treatment for cooling at a cooling rate of 3.0 to 3.0 ° C./min, elements such as iron, manganese, and chromium that have slow diffusion can be effectively gettered.

Claims (3)

[Claims] 1. In a semiconductor device manufacturing process, 800
A gettering treatment method in which a temperature range from 800 ° C. to more than 750 ° C. and less than 790 ° C. is cooled at a cooling rate of 0.1 ° C./min to 1.0 ° C./min after heat treatment at a temperature of ≧ ° C. 2. In the semiconductor device manufacturing process, 800
A gettering treatment method of cooling from 800 ° C. to a temperature range of more than 700 ° C. and less than 750 ° C. at a cooling rate of 0.1 ° C./min to 2.0 ° C./min after heat treatment at a temperature of ≧ ° C. 3. In a semiconductor device manufacturing process, 800
After heat treatment at ℃ or more, 800 ℃ to 600 ℃ to 700 ℃
A gettering method in which the following temperature range is cooled at a cooling rate of 0.1 ° C./min to 3.0 ° C./min.