JP3252386B2 - Manufacturing method of silicon single crystal wafer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon single crystal wafer used for a semiconductor material.
Z method), the silicon single crystal wafer obtained at a low pulling rate to improve the initial dielectric breakdown characteristics has poor dielectric breakdown characteristics over time, that is,
In particular, the present invention relates to a method for manufacturing a silicon single crystal wafer that solves such a problem by performing a specific heat treatment in a non-oxidizing atmosphere in view of the fact that the time-dependent dielectric breakdown characteristics are particularly poor when the gate oxide film thickness is small.

[0002]

2. Description of the Related Art Along with the high integration of MOS devices, it has become an important issue to improve the reliability of a gate oxide film. A membrane is required.

[0003] The oxide film insulation properties of a silicon single crystal wafer are determined by forming a large number of MOS diodes having the structure shown in FIG.
The gate electric field is increased stepwise, and the breakdown strength is determined based on the strength of the electric field when the leak current reaches a certain value, and the breakdown strength is determined based on an initial breakdown (time zero dielectric).
c breakdown: TZDB) characteristic (hereinafter referred to as TZDB characteristic).

[0004] Further, the oxide film is broken down with the lapse of time under the application of a constant electric field, and the dielectric breakdown with time (time dependent) is performed.
dielectric breakdown: TD
DB) characteristic (hereinafter referred to as TDDB characteristic), which is a very important factor from the viewpoint of device reliability.

In recent years, it has been revealed that the oxide film breakdown voltage defect of a silicon single crystal wafer depends on the method of growing a silicon single crystal, and it has been proposed to reduce the crystal growth rate for the purpose of reducing the defect. , Diameter 100mm
In the above method of manufacturing a silicon single crystal, it has been proposed that the crystal growth rate be 0.8 mm / min or less (Japanese Patent Application Laid-Open No. 2-267195).

[0006]

The silicon single crystal grown by the CZ method has a ring-shaped OSF generation region formed when a wafer is thermally oxidized in a high-temperature oxidizing atmosphere. There is a correspondence between the crystal growth rate and the position where the ring-shaped OSF is generated in the wafer. As the growth rate is reduced, the diameter of the ring-shaped OSF is reduced, and when the crystal growth rate is further reduced, the ring-shaped OSF is formed at the center of the wafer. Disappear.

TZDBs inside and outside the ring-shaped OSF
The characteristics are significantly different, and the outside of the OSF on the ring is TZDB
The characteristics are very good, and the inside of the ring-shaped OSF is TZ
This is a part where the DB characteristics are inferior. Here, the T of the slow pulling crystal
The reason why the ZDB characteristics are excellent is that the diameter of the ring-shaped OSF is small and the area outside the ring-shaped OSF having the excellent TZDB characteristics is large (S. Shinoyam).
a, M.A. Hasebe, and T.S. Yamau
chi: Oyo Buturi 60 (1991)
766).

By the way, when a thermal oxidation process is performed in a high-temperature oxidizing atmosphere, a low-speed pulling silicon single crystal wafer in which a ring-shaped OSF generation region disappears at the center of the crystal is:
Although the TZDB characteristic is very good, the TDDB characteristic is such that the defect rate is low when the gate oxide film thickness is as large as 100 to 300 °, but increases rapidly when the gate oxide film thickness is as thin as 50 to 70 °. was there. Further, the TDDB characteristics and the leak characteristics after thermal processing of a CMOS or the like are deteriorated, so that the actual device yield is low and the device has not been put to practical use.

The present invention relates to the Czochralski method (CZ).
Method), the silicon single crystal wafer produced by
A silicon single crystal that eliminates the drawbacks of a low-speed pulled silicon single crystal wafer with good TZDB characteristics, and that can provide a silicon single crystal wafer with excellent TDDB characteristics even when the oxide film is thin and after a thermal process. It aims to provide a method of manufacturing a wafer.

[0010]

The inventor of the present invention has conducted various investigations on the cause of the degradation of the TDDB characteristic, which is a drawback of a low-speed pulling silicon single crystal wafer having a good TZDB characteristic, as a result. Focusing on the fact that defects of a size that did not affect the characteristics previously grew to a size that affected the characteristics during the thermal process, reducing or eliminating small-sized defects in the slowly pulled crystal As a result of further study on a method for causing the defects, it was found that the defects can be reduced and eliminated by performing a heat treatment at a specific temperature in a non-oxidizing atmosphere, and the present invention was completed.

That is, according to the present invention, in a method of manufacturing a silicon single crystal by the Czochralski method, a ring-shaped OSF generation region which is generated in a ring shape when subjected to thermal oxidation treatment in a high-temperature oxidizing atmosphere disappears at the center of the crystal. The silicon single crystal wafer pulled under the conditions is subjected to a heat treatment in a non-oxidizing atmosphere at a temperature of 1000 ° C. or more and 1250 ° C. or less for a time of 10 seconds or more. A method for manufacturing a silicon single crystal wafer having excellent reliability of an oxide film.

Further, the present invention provides a silicon single crystal wafer in which a ring-shaped OSF generation region which is generated in a ring shape when subjected to thermal oxidation treatment in a high-temperature oxidizing atmosphere disappears at the center of the crystal. Crystal growth rate) is 0.5
It is intended for wafers of not more than mm / min.

[0013]

According to the present invention, the TD in the case where the gate oxide film is thin is used.
The cause of the deterioration of the DB characteristics is that the characteristics are not affected when the oxide film thickness is sufficiently large with respect to the defect size, but the oxide film thickness becomes thin and the silicon thickness of the silicon wafer surface taken into the oxide film becomes defective. Deterioration of TDDB characteristics when the size is about the same as above, and deterioration of TDDB characteristics and leakage characteristics after thermal processing are caused by defects of a size that did not affect the characteristics before thermal processing. It was found that it was grown to a size that affected the properties during the thermal process, and this was resolved by a specific heat treatment.

That is, a low-speed pulled silicon single crystal wafer by the CZ method has many small-sized defects.
The DDB characteristic is deteriorated, and the TDDB characteristic can be improved by eliminating or reducing the defect having the small size. According to the present invention, in order to reduce or eliminate small-sized defects in a low-speed pulled silicon single crystal wafer, a temperature of 90 ° C. in a non-oxidizing atmosphere is used.
A heat treatment of 0 ° C. or more, 1250 ° C. or less and a time of 10 seconds or more is performed, and the temperature increase rate and the temperature decrease rate at the time of the heat treatment are set to 1 ° C./second or more. However, there is no deterioration in TDDB characteristics and leak characteristics, and it is possible to realize the manufacture of a wafer having extremely excellent reliability of an oxide film.

In the present invention, the lower limit of the heat treatment temperature is 9
The temperature is set to 00 ° C., because defects cannot be eliminated below 900 ° C. The upper limit of the heat treatment temperature is set at 1250 ° C. If it exceeds 1250 ° C., there is a problem of wafer slip and contamination, and depending on the cooling conditions, rapid cooling defects may newly occur and adversely affect the characteristics. Because there is. The lower limit of the heat treatment time is set to 10 seconds, which is the minimum time required for shrinking defects during heat treatment. The reason why the heating rate and the cooling rate during the heat treatment are set to 1 ° C./second or more is that if the heating rate and the cooling rate are lower than this rate, defects grow at the time of temperature change, which adversely affects the characteristics.

In the heat treatment of the present invention, a preferable temperature range is 1050 ° C. to 1200 ° C., and a preferable heat treatment time is 2 hours to 5 hours. The upper limit of the heat treatment time is not particularly defined. However, although a defect-free layer can be formed on the wafer surface by a long-term heat treatment at a high temperature in a non-oxidizing atmosphere, the long-term treatment has cost and productivity problems. It is desirable to determine the time as needed according to the heat treatment conditions. Further, the preferable temperature increase and decrease rates are 5 ° C / sec to 100 ° C.
° C / sec.

[0017]

【Example】

Example 1 A CZ silicon single crystal wafer (diameter 6 inches, boron-doped P-type, pulled at a growth rate of 0.43 mm / min,
Specific resistance 4.5-6 Ωcm, oxygen concentration 14-16 × 10 ¹⁷
atoms / cc, plane orientation (100)), that is, a low-speed pulling silicon single crystal wafer in which a ring-shaped OSF generation region disappears at the center of the crystal when subjected to thermal oxidation treatment, using a heat treatment furnace. 850 ° C. to 1300 ° C. at a rate of 5 ° C./sec in a non-oxidizing atmosphere
Table 1 shows the state of occurrence of slip after heat treatment for 3 hours at temperatures up to and a defect density of 0 to 10 μm from the wafer surface by infrared interferometry after heat treatment corresponding to the heat process of the CMOS device shown in FIG. Shown in It can be seen from Table 1 that the heat treatment at 1300 ° C. causes a slip and the heat treatment at 850 ° C. does not reduce defects.

[0018]

[Table 1]

Example 2 CZ silicon single crystal wafer (diameter 6 inches, boron-doped P-type, pulled at a growth rate of 0.43 mm / min)
Specific resistance 4.5-6 Ωcm, oxygen concentration 14-16 × 10 ¹⁷
(atoms / cc, plane orientation (100)) was subjected to a heat treatment at 1200 ° C. for 2 hours at a rate of 5 ° C./sec in a nitrogen atmosphere containing 2% oxygen using a heat treatment furnace. As an evaluation of the wafer, M of the structure shown in FIG.
The OS diode was manufactured by performing gate oxidation at 900 ° C. in dry oxygen, an oxide film thickness of 70 °, boron-doped polysilicon as an electrode at 5000 ° thickness, and an electrode area of 8 mm ² . The measurement condition of the TDDB characteristic is that the current density is 1 m
The constant current TDDB characteristics were evaluated with A / cm ² , a temperature of room temperature, a determination voltage of 5 V or less, and a gate oxide film thickness of 70 °.

The CMO of the heat pattern shown in FIG.
After performing the heat treatment corresponding to the thermal process of the S device,
The constant current TDDB characteristic when the gate oxide film thickness was 70 ° was evaluated. For comparison, an evaluation of a conventional low-speed pulled crystal wafer without heat treatment was also performed. Table 2 summarizes the evaluation results of the conventional example and the wafer of the present invention. Where TDD
The 20% Qbd indicating the B characteristic is the amount of passing charge (C / cm ² ) until the cumulative failure rate reaches 20%, and the larger the value, the better the TDDB characteristic.

As apparent from Table 2, when the gate oxide film thickness is 70 °, the 20% Qbd is 70 in the conventional low-speed pulling crystal wafer (Sample A), whereas the wafer of the present invention ( In sample B), it has increased to 150. Further, after the CMOS heat treatment, the 20% Qbd is 6 in the conventional low-speed pulling crystal wafer (sample C), while it is increased to 132 in the wafer of the present invention (sample D). To confirm the effect of reducing defects, samples C and D in Table 2 were evaluated in a region of 0 to 10 μm from the wafer surface by infrared interferometry. In sample C of the comparative example, a defect of 3.6 × 10 ⁷ / cm ³ was observed, whereas in sample D of the present invention, 1.2 × 10 ⁷ / cm ^3.
The number was reduced to ⁵ / cm ^3, and a correspondence with the TDDB characteristic was observed.

Example 3 A CZ silicon single crystal wafer pulled up at a growth rate of 0.48 mm / min (diameter: 6 inches, boron-doped P type, specific resistance: 4.5 to 6 Ωcm, oxygen concentration: 14 to 16 × 10 ¹⁷ a)
tomos / cc, plane orientation (100)), in a nitrogen atmosphere using a lamp annealing furnace, a lamp annealing treatment was performed at 1100 ° C. for 20 seconds at a temperature increase / decrease rate of 100 ° C./second. Example 2 for wafer evaluation
Under the same measurement conditions as those described above, the constant current TDDB characteristic was evaluated with a gate oxide film thickness of 70 °.

For comparison, a conventional low-speed pulled crystal wafer without lamp annealing was also evaluated. Table 4 summarizes the evaluation results of the conventional example and the wafer of the present invention. As is clear from Table 4, the gate oxide film thickness was 70 °
In the case of, the wafer of the conventional slow pulling crystal (Sample E)
In this case, the 20% Qbd is 63, whereas the wafer (sample E) of the present invention has increased to 169.

[0024]

[Table 2]

[0025]

According to the present invention, a small-sized defect in a low-speed pulled crystal that grows to a size that affects properties during a thermal process can be subjected to a heat treatment at a specific temperature in a non-oxidizing atmosphere as shown in the embodiment. The method according to the present invention can provide a silicon single crystal wafer having excellent TDDB characteristics even when the gate oxide film thickness is small and after the thermal process. High quality wafers that could not be obtained can be easily obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a structure of a MOS diode.

FIG. 2 is a heat pattern diagram showing CMOS heat treatment conditions as a function of time and temperature.

Continuation of the front page (56) References JP-A-7-14755 (JP, A) JP-A-5-213696 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21 / 02 C30B 15/00 C30B 33/00

Claims (2)

(57) [Claims] In a method of manufacturing a silicon single crystal by a Czochralski method, a ring-shaped OSF generation region which is generated by thermal oxidation treatment in a high-temperature oxidizing atmosphere is pulled up under such a condition that it disappears at the center of the crystal. A temperature of 900 ° C. or more in a non-oxidizing atmosphere
A method for producing a silicon single crystal wafer, wherein a heat treatment is performed at a temperature of 250 ° C. or less for a time of 10 seconds or more, and a temperature increasing rate and a temperature decreasing rate during the heat treatment are set to 1 ° C./sec or more. 2. The method according to claim 1, wherein the pulling speed (crystal growth speed) of the silicon single crystal wafer is 0.5 mm / mi.
n. A method for producing a silicon single crystal wafer, wherein n is equal to or less than n.