JP2802702B2 - Evaluation and management method of sandblast condition in 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 method for evaluating and managing conditions in a sand blast method as a means for imparting an extrinsic gettering effect to a silicon single crystal wafer (hereinafter abbreviated as "wafer"). It is.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have become smaller and more highly integrated, quality requirements for wafers used as substrate materials for semiconductor devices have become more stringent. In the manufacturing process, there is a problem that generation of crystal defects due to contaminants on the element formation surface of the wafer is suppressed.

As a means for suppressing such crystal defects, there is known a gettering method in which contaminant impurities mainly composed of heavy metals are collected in a strain field formed outside an element formation region in an element formation step. The gettering method is roughly classified into intrinsic gettering (IG) and extrinsic gettering (EG).

The method classified as the extrinsic gettering mainly applies mechanical strain to the back surface opposite to the device forming surface of the wafer, and the sand blast method is one of the methods. The magnitude of the backside damage formed on the back surface of the wafer by the sandblasting method is an important factor of the gettering technique, and the oxidation induced stacking fault (oxidation induced stacking fault) generated by the oxidation heat treatment of the sandblasted wafer.
ng fault (hereinafter abbreviated as OSF)).

In the sand blast method, a wafer 2 is placed on a conveyor belt 3 by a loader 1 as schematically shown in FIG . The wafer 2 on the conveyor belt 3 is shown in FIG.
It is conveyed in the direction of the arrow, and a jet blast 5 of quartz particles or alumina particles collides from the feeder 4 during the conveyance to perform sandblasting. The wafer 2 after the sandblasting process is lowered from the conveyor belt 3 by the unloader 6, and is moved to the next processing step. The main conditions that determine the effect of sandblasting are the strength and the processing time. Factors for imparting strength include the pressure and flow rate when the jet 5 containing particles is blown from the feeder 4, and the discharge port of the feeder and the wafer 2 to be processed.
And the hardness and particle size distribution of the particles used and their concentration are related. The processing time is adjusted by the belt speed of the conveyor belt 3, and the reciprocal thereof corresponds to the processing time.

[0006]

By the way, the current wafer is cut out from a single crystal grown in the <100> orientation in order to increase the yield at the time of manufacturing a semiconductor device.
Wafers having the <100> plane as the main surface are used in an overwhelming majority, and therefore, most of the wafers subjected to sandblasting also have the <100> plane as the main surface. By the way, even under the same sand blast condition, the above-mentioned OS depends on the crystallographic orientation of the surface subjected to sand blast.
Since it is known that the generation density of F is different, <10
The monitor at the time of sandblasting the wafer having the <0> plane as the main surface is at least <10 of the same crystallographic orientation.
It is desirable to use a wafer whose main surface is the 0> plane.

However, in the case of a wafer having a <100> plane as a main surface, when the OSF density is measured by performing an oxidizing heat treatment after sandblasting, the measured value of the OSF density is very unstable and has poor reproducibility. There was a problem that sandblasting conditions could not be set correctly.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to improve the reproducibility of the density of OSF introduced by the sand blast conditions and the subsequent oxidizing heat treatment.
It is an object of the present invention to provide a method capable of performing an accurate evaluation, and further to provide a management method capable of setting conditions for sandblasting a wafer by applying the evaluation method.

[0009]

According to the present invention, a method for evaluating a sand blast condition on a silicon single crystal wafer is to perform an oxidizing heat treatment after sand blasting one side surface of the silicon single crystal wafer, and then perform a sand blasting one side surface of the wafer. A method for evaluating the conditions of sandblasting by introducing oxidation-induced stacking faults thereon and measuring the surface defect density thereof, wherein a wafer having a <111> plane as a main surface is used as the wafer.

Further, the method for managing sandblast conditions for controlling the oxidation-induced stacking fault density of a silicon single crystal wafer according to the present invention provides a method for evaluating the above sandblast conditions when sandblasting a silicon single crystal wafer.
The relationship between the sandblast condition and the oxidation-induced stacking fault density is measured in advance for a silicon single crystal wafer having the <111> plane as a principal surface by a valence method, and the sandblast condition is set based on this relationship. And

[0011] Further, the evaluation of the sandblasting conditions of the present invention.
In the method for controlling the sand blast condition according to the present invention , a silicon single crystal wafer having a <111> plane as a main surface is used as a monitor when sand blasting a silicon single crystal wafer.

The wafer to which the present invention is applied is <100
After cylindrical polishing with the pulling axis of the silicon single crystal rod grown in the> axis direction or <111> axis direction as the center of rotation,
A disk obtained by slicing in the vertical direction of the pull-up shaft, chamfering the edge of the disk and lapping the main surface, and then performing etching to remove residual processing strain. , Usually called a chemically etched wafer (CW wafer). That is, a wafer to which the present invention is applied is exactly such a CW wafer. The sandblasting is performed thereafter, and the mirror-finished wafer is finally mirror-polished to be a mirror-polished wafer (PW wafer) to be shipped as a product.

There are various methods for evaluating the degree of mechanical strain on the surface of a sandblasted wafer. In the case of the present invention, however, in the case of the EG effect, it occurs when a wafer after sandblasting is subjected to thermal oxidation treatment. A method of measuring the OSF density is adopted. That is, the wafer subjected to the sandblast treatment is heat-treated in a wet oxidizing atmosphere at 1100 ° C. for 1 hour, then cooled, the surface oxide film is removed by a hydrofluoric acid treatment, and the single crystal surface is reduced by a zirtolu etchant to remove the surface oxide film. 1 μm-etched, washed and dried, the sandblasted surface of the wafer was observed with an optical microscope (NIKON IC microscope), and the OS
Measure F. In the OSF measurement, the measurement magnification was set to 1000 times, and the OSF present in the visual field was measured using a counter at three points obtained by equally dividing the arbitrary radial direction of the wafer into three, and the density was converted to × 10 ⁴ / cm ^2. By doing so.

[0014]

[Function] O introduced by subjecting a wafer having a <111> plane as a main surface to sand blasting and then performing thermal oxidation treatment.
Regarding the density of SF, a constant OSF density is reproduced under a constant sandblasting condition regardless of a wafer (CW wafer) manufactured under any conditions. Therefore, if a wafer having the <111> plane as the main surface is employed as a monitor, the sandblast can be quantitatively set. Therefore, at the time of sandblasting a wafer having an arbitrary main surface, at least the sandblast conditions must be set. Or it can be used for control.

[0015]

Next, the present invention will be described in more detail with reference to examples. Example 1 and Comparative Example 1 As a sandblast condition for a wafer etched by various etching allowances, OSF for the strength was used.
The relationship of occurrence is shown by the <111> main surface wafer (Example 1)
And <100> main surface wafer (Comparative Example 1).

[Test conditions and method] [111]
> And <100> as main surfaces (resistivity of about 1
(Normal resistance product of Ωcm), the etching amount of the wafer having the <111> plane as the main surface was 25 μm and 3 μm, respectively.
Etching to 8 μm and 55 μm, <1
With respect to the wafer having the main surface of 00>, three wafers (CW wafers) each having been subjected to an etching treatment so as to have an etching amount of 25 μm, 38 μm, and 48 μm were prepared. For each of these wafers, the setting conditions of the sandblast strength (evaluated as the amount of OSF generated after sandblasting, pieces / cm ² ) using the P-type wafer of the <111> main surface as a monitor were 300,000, 500,000 and 700,000. At three levels.

[Test Results] Each sample after sandblasting
OS for 3 observation points (total 9 points)
Inspection of the F density was performed, and the relationship between the OSF generation amount, which is the average value, the set sandblasting strength, and the wafer etching amount was shown in FIG. 1 (Example 1) and FIG. 2 (Comparative Example 1).

It is clear from FIGS. 1 and 2 that <11
Both the 1> main surface wafer and the <100> main surface wafer correspond to the strength of the sandblast strength, and the same tendency is observed in that the occurrence of OSF increases and decreases. In the case of the first embodiment (FIG. 1), the influence of the etching amount of the wafer is small and the value is close to the setting condition for the same setting conditions of the sandblast strength in each case. On the other hand, Comparative Example 1
In the case of (FIG. 2), the occurrence of OSF shows an exponential increase corresponding to the etching amount of the wafer. This fact shows that in the case of the <111> main surface wafer, the etching amount of the wafer has almost no effect, and therefore, no matter what etching amount of the CW wafer is used, if the setting conditions of the sandblasting strength are constant, a constant OSF is required. In the case of the <100> main surface wafer, the OSF occurrence value varies greatly with the etching amount, whereas the quality condition as a CW wafer including the etching amount is controlled. Unless otherwise, the reproducibility of the OSF occurrence value cannot be obtained. In other words, this fact is the reason that the <100> main surface wafer could not be adopted as a monitor conventionally. Although the data is omitted, it has been confirmed that the same result as that of the P-type wafer is obtained in the case of the N-type wafer.

Example 2 and Comparative Example 2 The relationship between the amount (defined by the sandblasting time) and the generation of OSF as the sandblasting conditions for the wafers etched with various etching margins was determined by using the <111> main surface wafer (implemented). Example 2) and a wafer having a <100> main surface (Comparative Example 2) were examined. [Test Conditions and Methods] Wafers manufactured from the same single crystal used in Example 1 and Comparative Example 1, that is, crystal orientations <111> and <1
From a P-type single crystal having a principal surface of 00> (a normal resistance product having a resistivity of about 1 Ωcm), the etching amount of a wafer having a principal surface of <111> is 25 μm, 38 μm, and 55 μm, respectively.
μm, and the etching amount of the wafer having the <100> plane as the main surface is 25 μm,
Three wafers (CW wafers) and three mirror-finished wafers (PW wafers) each having been etched to 38 μm and 48 μm were prepared. Each wafer is <1
11> The sandblasting strength of the P-type monitoring wafer on the main surface was set to a constant value of 500,000 pieces / cm ² , and the sandblasting amount was set to a conveyor belt speed (m) in a sandblasting apparatus schematically shown in FIG. 6.
/ Min), sandblasting is performed at 1.8, 1.2, 0.8, and 0.6, and the reciprocal ( min / min)
m: equivalent to the processing time ) was taken as the sandblast amount.

[Test Results] OSF density was inspected at three observation points (a total of 9 points) for each of the three wafers after sandblasting, and the average value of the amount of OSF generation and the set amount of sandblasting (time 3) (Example 2) and FIG. 4 (Comparative Example 2). 3 and 4 have a clear proportional relationship between the increase in the amount of sandblasting (processing time) and the amount of OSF generation.
In the case of FIG. 3, the sandblasting time and the amount of OSF generation show a constant relationship regardless of the wafer etching amount, that is, the CW wafer under any manufacturing conditions, while the comparative example shows a comparative example. 2 (FIG. 4) shows Comparative Example 1
As in the case of the above, there is a remarkable difference between the sandblast time and the amount of OSF generation for wafers of various etching amounts. Therefore, a wafer having a <100> plane as a main surface cannot be used as a monitor for evaluating or managing sandblasting conditions unless the cause is clarified and a management standard is established.

Example 3 A wafer having a <111> main surface was used as a monitor for sandblast control for 20 days, and its suitability as a monitor was examined.

[Test conditions and method] A wafer having the same conductivity type and resistivity as those used in Examples 1 and 2 having a <111> plane as a main surface (etching amount: about 37 μm)
m) 20 sheets were prepared. In the test, each of the monitoring wafers each having the <111> plane as a main surface was subjected to sandblasting simultaneously with the other wafers each morning, and then the monitoring wafers were inspected for OSF generation by a predetermined method. In addition, as sandblast conditions, the set intensity is 500,000 pieces / cm when using a <111> monitor
² and the belt speed was 1.2 m / min.

[Test Results] The test results are shown in FIG. It can be seen that the wafer used for the monitor has a reproducible value with a level value corresponding to the sandblast strength set at 500,000 wafers / cm ² .

[0024]

According to the method for evaluating sandblast conditions of the present invention, sandblast conditions can be evaluated with good reproducibility. Further, according to the method for managing sandblast conditions of the present invention, sandblast conditions can be controlled so that the OSF density of a silicon single crystal wafer becomes a predetermined value.

[Brief description of the drawings]

FIG. 1 shows the etching amount and OS of a <111> P-type wafer
It is a graph which shows the relationship of F density.

FIG. 2 <100> P-type wafer etching amount and OS
It is a graph which shows the relationship of F density.

FIG. 3 is a graph showing a relationship between an OSF density of a <111> P-type wafer, a reciprocal of a belt speed (a sandblast amount), and a wafer etching amount.

FIG. 4 is a graph showing a relationship between an OSF density of a <100> P-type wafer, a reciprocal of a belt speed (a sandblast amount), and a wafer etching amount.

FIG. 5 is a graph showing a change in OSF density in the number of operating days in Example 3.

FIG. 6 is an explanatory view schematically showing a sand blast method.

[Explanation of symbols]

 1 Loader 2 Wafer 3 Conveyor Belt 4 Feeder 5 Jet 6 Unloader

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Yamamoto 1393 Yashiro, Yashiro, Nagano Prefecture Nagano Denshi Kogyo Co., Ltd. (72) Inventor Moriaki Torigoe 2 Inside Naoetsu Electronics Co., Ltd. (72) Katsuyoshi Yamamoto Inventor Katsuyoshi Yamano, Nakakushiro-gun, Niigata Prefecture 596-2 Naoetsu Electronics Co., Ltd. Odakura Ohira 150 Shin-Etsu Semiconductor Co., Ltd. Shirakawa Plant (56) References JP-A-4-93177 (JP, A) JP-A-61-131869 (JP, A) (58) Fields investigated (Int. Cl) . ^6, DB name) B24C 1/00 B24C 3/32

Claims (4)

(57) [Claims] 1. After sandblasting one surface of a silicon single crystal wafer, oxidation heat treatment is performed to introduce oxidation-induced stacking faults on the sandblasted one surface of the wafer, and the surface defect density is measured. The method for evaluating sand blast conditions in a silicon single crystal wafer, wherein a silicon single crystal wafer having a <111> plane as a main surface is used as the wafer. 2. The method according to claim 1, wherein said silicon single crystal wafer is sandblasted.
1> measuring the relationship between the sandblast condition and the oxidation-induced stacking fault density in advance on a silicon single crystal wafer having a main surface as a main surface, and setting the sandblast condition based on this relationship. A method for managing sandblast conditions for controlling the oxidation-induced stacking fault density of a crystal wafer. 3. The method according to claim 1, wherein a silicon single crystal wafer having a <111> plane as a main surface is used as a monitor when sand blasting the silicon single crystal wafer.
The method for evaluating sandblast conditions according to claim 1. 4. A silicon single crystal wafer is sand blasted.
Silicon bonding with <111> plane as the main surface
Characterized by using a crystal wafer as a monitor
The method for managing sandblast conditions according to claim 2.