JP3234054B2 - Silicon wafer for semiconductor device and method of manufacturing the same - 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 wafer for a semiconductor device and a method for manufacturing the same, and more particularly to a silicon wafer suitable for use in highly integrated and miniaturized advanced semiconductor devices and a method for manufacturing the same.

[0002]

2. Description of the Related Art Crystals prepared for silicon wafers are:
More or less contaminated during processes such as oxidative heat treatment. Particularly contaminating impurities are alkali metals such as Na and K and heavy metal atoms such as Fe and Au. Alkali metal exists in SiO2 or at the interface between Si and SiO2,
Vary the threshold voltage. In addition, heavy metals are precipitated in the crystal, causing dislocations and stacking faults, and the heavy metal atoms themselves also form carrier traps to reduce the lifetime.

[0003] Collecting these contaminating impurities on a portion other than the element active region such as the back surface of the wafer or the inside of the crystal and removing the adverse effect is collectively called gettering. Gettering technology includes extrinsic gettering (EG) that collects contaminating impurities in a processing strained layer or an impurity diffusion layer formed on the back surface of a wafer, and minute defects (hereinafter abbreviated as BMD, surface minute defects, bulk) generated inside the wafer. Intrinsic gettering (IG) utilizing both small defects). In particular, in the latter intrinsic gettering, BMD caused by oxide precipitate nuclei formed by heat treatment in a crystal containing oxygen in supersaturation exhibits a gettering effect by trapping contaminant impurities. As the IG process conditions, for example, the silicon wafer was heat-treated at 650 ° C. for 3 hours (donor killer heat treatment).

As described above, in the conventional silicon wafer device process, since the gettering effect can be used, it has been considered that it is better to form a BMD within a certain density range in the wafer.

[0005]

However, with the progress and improvement of the clean technology in the device process, the number of metal impurities to be gettered has been drastically reduced, so that the need for the gettering effect of the BMD is losing its necessity. Conversely, the BMD on the surface layer of the wafer deteriorates the quality of the gate oxide film, so that the BMD generates a leak current, which may cause a reduction in the reliability and yield of the product device. The adverse effects as crystal defects have become noticeable. In particular, the higher the degree of integration and miniaturization, the stronger the tendency.

Accordingly, an object of the present invention is to reduce the BMD (bulk micro defect and surface micro defect) density due to oxygen precipitation in silicon crystal by controlling the amount of decrease in oxygen concentration in the crystal before and after the treatment, thereby reducing the wafer density. It is an object of the present invention to provide a semiconductor silicon wafer having a high reliability by preventing a decrease in device yield due to the above, and a method for manufacturing the same.

[0007]

SUMMARY OF THE INVENTION The present invention provides an initial oxygen concentration of 10.0-1.
6.0 × 10 ¹⁷ atoms / cm ³ (old ASTM converted value, AST
M code: F128-81, F1188, and so on) two-stage heat treatment performed on a silicon wafer, that is, heating at 600 to 800 ° C. for 2 to 6 hours, and then 1000 ° C.
The amount of oxygen loss before and after heating for 10 to 20 hours is less than 1 × 10 ¹⁷ atoms / cm ³ (former ASTM) (however, the measurement limit by infrared spectroscopy is about 0.1 × 10 ¹⁷ atoms / cm ³ cm ³ ).

Further, the present invention relates to a method for producing an initial oxygen concentration of 10.0 to
A silicon wafer of 16.0 × 10 ¹⁷ atoms / cm ³ is subjected to an inert gas atmosphere at 1000 to 1200 ° C. for 30 to 300
A method for producing a silicon wafer for a semiconductor device, characterized by obtaining a silicon wafer having the above characteristic value by heating for 2 seconds.

The silicon wafer of the present invention is subjected to a heat treatment in a specific temperature range in order to reduce the BMD density in the wafer. That is, under an inert gas atmosphere,
The initial precipitate disappears by the donor killer heat treatment at 00 to 1200 ° C. for 30 to 300 seconds, and the formation of precipitation nuclei (BMD) does not progress even during the subsequent two-step heat treatment. 3
Even if the donor killer heat treatment is performed for more than 00 seconds, the BM
The decrease in D becomes saturated and the effect is the same. If the donor killer heat treatment condition is less than 1000 ° C, especially 600 to 9
If the temperature is not higher than 00 ° C., the heat treatment for 30 to 60 seconds will result in BM
The D density does not change (does not decrease), and the BMD density increases in proportion to time even after a long-time heat treatment. In place of the inert gas, a non-oxidizing atmosphere,
For example, a hydrogen atmosphere may be used.

When the value of the initial oxygen concentration in the wafer is below the above range, the BMD density is obviously reduced. However, when the initial oxygen concentration is too low, the dislocation movement cannot be prevented, and the FZ (floating zone) ) Like a crystal, warping and slippage due to heat treatment tend to occur. Therefore, the present invention provides an initial oxygen concentration range (10.0
１６16.0 × 10 ¹⁷ atoms / cm ³ ) and B
The MD density is kept low.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a method for manufacturing a semiconductor silicon wafer according to the present invention and results of comparison of various characteristics between the present invention and a conventional silicon wafer will be described below with reference to the accompanying drawings.

The initial oxygen concentration obtained by the CZ method (pulling method) (former ASTM; the same applies hereinafter) 15 × 10 ¹⁷ atoms / cm
As grown silicon wafer (n-type, plane orientation (100)) of No. ³ in N2 atmosphere at 1000.degree.
A second heat treatment was performed to produce a silicon wafer [C] according to the present invention. Thereafter, heat treatment at 800 ° C. for 4 hours (first heat treatment) and heat treatment at 1000 ° C. for 16 hours (second heat treatment) were performed. Here, the donor killer heat treatment condition must be 1000 ° C. or higher. The two-step heat treatment (first and second heat treatment) steps were performed under general conditions for evaluating the BMD density.

On the other hand, [A] having different initial oxygen concentrations,
[B] ([A] is 15.5 × 10 ¹⁷ atoms / cm ³ , [B]
Is a donor killer heat treatment at 650 ° C. for 30 minutes on a 14 × 10 ¹⁷ atoms / cm ³ CZ silicon wafer (n-type, plane orientation (100)) according to a conventional general gettering method. A first heat treatment at 800 ° C. for 4 hours and a second heat treatment at 1000 ° C. for 16 hours were sequentially performed to obtain a comparative sample.

First, the BMD densities of these three kinds of wafers after the heat treatment and the oxygen reduction amount before and after the two-step heat treatment step (oxygen concentration before the first heat treatment-oxygen concentration after the second heat treatment) were measured. 1 and 2 are shown in FIGS. Looking at the BMD density, [C] was the lowest and was 100,000 / cm ² or less (however, a measured value when the cleavage plane was removed by 2 μm with a selective etching solution). As for the oxygen reduction amount before and after the two-step heat treatment, [C] is significantly lower than [A] and [B]. That is, according to the silicon wafer manufacturing method of the present invention, the generation of oxygen-induced precipitation nuclei, that is, BMD, is effectively suppressed. In addition, the BMD density of [C] is lower than that of [A] whose initial oxygen concentration is lower than [C]. This is considered to be due to the difference in the donor killer heat treatment conditions for the wafer. Conventional 65
It is considered that BMD precipitate nuclei remain under the donor killer heat treatment condition of about 0 ° C., but at 1000 ° C. or higher, the initial precipitate dissolves and no precipitate nuclei are formed.

Next, using these three silicon wafers [A], [B] and [C], an oxide film thickness of 25 nm was used.
MOS diode is formed, and the capacitor area is 10 mm
² and the capacitor area 1 mm ²
TDDB (dielectric breakdown) measurement was carried out in FIG. [C] was the best for both the initial oxide film breakdown voltage and the TDDB characteristics. Therefore, it was confirmed that the decrease in the BMD density contributed to the improvement of the breakdown voltage and the TDDB characteristics.

FIG. 5 shows a BMD formation model in the two-step heat treatment step. As described above, in [C], the initial precipitate disappeared due to the high-temperature donor killer heat treatment, and the formation of precipitate nuclei did not progress even during the subsequent two-step heat treatment.
In [A] and [B], it is considered that the two-stage heat treatment is performed in a state where some precipitates remain, and the formation of BMD proceeds.

In order to reduce the BMD density, there is a method of lowering the initial oxygen concentration. The effect is remarkable as shown in FIG. 6. However, if the initial oxygen concentration is too low, the dislocation movement cannot be prevented. As in the case of the FZ crystal, warpage and slip due to the heat treatment are likely to occur. Therefore, the present invention intends to keep the BMD density at a low value within the oxygen concentration range where there is no problem in strength.

FIG. 7 shows the wafer 100 in the wafer depth direction before and after the two-step heat treatment in the conventional and the present invention.
A SIMS profile up to μm is shown, and a portion having a large amplitude in this profile indicates a position where a minute defect occurs. After the two-step heat treatment, it was found that BMD caused by oxygen precipitates was present at high density in the conventional wafer, but the generation of BMD was small in the wafer according to the present invention.

[Brief description of the drawings]

FIG. 1 is a graph showing initial oxygen concentration and BMD density after two-step heat treatment of a silicon wafer [C] according to the present invention and conventional silicon wafers [A] and [B].

FIG. 2 shows a silicon wafer [A] before and after a two-step heat treatment,
It is a graph which shows each oxygen reduction amount of [B] and [C].

FIG. 3 is a graph showing an initial oxide film breakdown voltage distribution of each of silicon wafers [A], [B], and [C].

FIG. 4 is a graph showing TDDB characteristics of silicon wafers [A] and [C].

FIG. 5 is an explanatory diagram showing a BMD formation model in a two-step heat treatment step for each of the silicon wafers [A], [B], and [C].

FIG. 6 is a graph showing a relationship between an initial oxygen concentration and a BMD density in a conventional silicon wafer.

FIG. 7 is a graph showing SIMS profiles of silicon wafers [A] and [C] before and after a two-step heat treatment up to 100 μm in a depth direction.

[Explanation of symbols]

 Reference Signs List 1 silicon wafer cross section 2 precipitation nucleus 3 BMD (bulk minute defect and surface minute defect)

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/324 C30B 29/06 H01L 21/322

Claims (3)

(57) [Claims] 1. An initial oxygen concentration of 10.0 to 16.0 × 10 ¹⁷
Two-stage heat treatment performed on a silicon wafer of atoms / cm ³ (former ASTM), that is, 600 to 800 ° C.
After heating for 2 to 6 hours, and then heating at 1000 ° C. or lower for 10 to 20 hours, the oxygen reduction amount before and after 1 × 10 ¹⁷ atoms / cm
^A silicon wafer for a semiconductor device, wherein the silicon wafer is less than ³ (old ASTM equivalent). 2. The density of minute defects in a silicon wafer after a two-step heat treatment is 100,000 / cm ² or less.
The silicon wafer for a semiconductor device according to claim 1. 3. An initial oxygen concentration of 10.0 to 16.0 × 10 ^17.
2. A silicon wafer for a semiconductor device according to claim 1, wherein the silicon wafer of atom / cm < ³ > is heated at 1000 to 1200 [deg.] C. for 30 to 300 seconds in an inert gas atmosphere. Method.