JPH09190954A - Semiconductor substrate and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure that a slip is hard to arise and that the strength of a sub strate is hard to drop by making the semiconductor substrate contain oxygen in the range of specified pieces and oxygen deposits of polyhedrons in the speci fied range of density, in the specified extent from the surface of itself. SOLUTION: Oxygen ions of 10<18> -10<20> pieces/cm<3> are implanted only into the extent of 10mm or under from the periphery of an Si water 10a, which contains oxygen in the range of (5-10)×10<17> pieces/cm<3> , by controlling an X scan 5a and a Y scan 5b, using an ion implantation device. Furthermore, in nitrogen gas atmosphere, it is heat-treated in two stages of 8-16 hours at 750-850 deg.C and 1-4 hours at 1-50-1150 deg.C. Then, in the extent of 10mm or under from the periphery of the Si water 10a, it is made to contain the SiO2 deposits of the polyhedrons in the density of 10<8> -10<10> /cm<3> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate and a method for manufacturing the same, and more particularly to a semiconductor substrate in which the density of oxygen precipitates in the outer peripheral portion is controlled and a method for manufacturing the same.

[0002]

2. Description of the Related Art Most of semiconductor substrates used as substrates for forming integrated circuits such as LSI are manufactured from Si single crystals, and the Si single crystals are filled in a quartz crucible.
It is formed by a pulling method called the Czochralski method (CZ method) of pulling the melt while rotating it.

When a Si single crystal is grown by the CZ method, the quartz crucible itself dissolves in the Si melt to dissolve out oxygen, and this oxygen is introduced from the solid-liquid interface into the Si single crystal (5 to 2).
0) It is taken in at a concentration of about 10 ¹⁷ pieces / cm ³ . Of these, the oxygen concentration in the Si single crystal is approximately 10 × 10 ¹⁷ /
When it is at least ³ cm ³ , oxygen precipitates in the Si semiconductor substrate (hereinafter, simply referred to as a semiconductor substrate) during the heat treatment in the LSI manufacturing, and changes into a SiO ₂ structure. As a result, the volume may expand and strain may occur around the oxygen precipitates, and dislocation occurs when the strain exceeds a certain critical value. When these oxygen precipitates and dislocations are present within a range of several μm from the surface of the semiconductor substrate (active region of the LSI element), the breakdown voltage of the oxide film is reduced and leak current is generated, which is harmful to the LSI.

Due to the above reasons, in recent years, the oxygen concentration is (5
-10) × 10 ¹⁷ / cm ³ semiconductor substrates (so-called low oxygen concentration semiconductor substrates) have begun to be used as substrates for forming integrated circuits such as LSIs. In this low oxygen concentration semiconductor substrate, there is almost no precipitation of oxygen during the heat treatment in the LSI manufacturing, and therefore the manufacturing yield of the LSI becomes very high.

[0005]

However, in the above-mentioned low oxygen concentration semiconductor substrate, slip (dislocation) occurs from the outer peripheral portion due to local thermal stress that occurs during heat treatment in LSI manufacturing (particularly during substrate unloading from the heat treatment furnace). There is a problem that defects called "slip bands formed by sliding motion" tend to occur and the substrate strength is likely to decrease.

The present invention has been made in view of the above problems, and in a semiconductor substrate containing oxygen in the range of (5 to 10) × 10 ¹⁷ pieces / cm ³ , the slip is unlikely to occur and the substrate strength is high. It is an object of the present invention to provide a semiconductor substrate that does not easily deteriorate and a manufacturing method thereof.

[0007]

[Means for Solving the Problem and Its Effect] It is generally considered that the occurrence of slip is due to the mechanism described below.

During the heat treatment in the LSI manufacturing,
Generally, a temperature difference occurs between the outer peripheral portion and the central portion of the semiconductor substrate, and particularly when the semiconductor substrate is unloaded from the heat treatment furnace, the temperature of the outer peripheral portion of the semiconductor substrate becomes considerably lower than the temperature of the central portion.
Therefore, the contraction rate of the outer peripheral portion becomes larger than the contraction rate of the central portion, and tensile stress acts on the outer peripheral portion. Therefore, in order to alleviate the tensile stress, the movement of 60 ° dislocations parallel to the surface of the semiconductor substrate and the movement of the screw dislocations inside the semiconductor substrate occur.

The above-mentioned temperature difference between the outer peripheral portion and the central portion becomes remarkable especially when the diameter of the semiconductor substrate is 200 mm or more, and the movement of the dislocation tends to occur due to the large temperature difference.

The shape of the slip formed as a result of the movement of the dislocations is generally linear as shown in FIG. Here, FIG. 6 is a schematic plan view sketching an X-ray topographic image of the semiconductor substrate shown for explaining the slip, and the linear slip 12 described above is formed on the outer peripheral portion of the semiconductor substrate 10. . As a dislocation source when the slip 12 is formed, processing strain of the chamfered portion on the outer periphery of the semiconductor substrate 10 is considered.

It is considered that whether or not the generated dislocation moves until it becomes a slip 12 depends on the oxygen concentration inside the semiconductor substrate 10 and the state of precipitation of oxygen.

The oxygen existing inside the semiconductor substrate 10 is usually present at the interstitial position of the Si single crystal, but the oxygen present at this interstitial position (hereinafter referred to as interstitial oxygen) suppresses the movement of the generated dislocations. Has the effect of (Koji Sumino:
Mechanical Behavior of Semiconductors, Elsevier S
cience BV pp139-142, (1994)). Therefore, the oxygen concentration is (5 to 10) × 10 ¹⁷ pieces / cm ³ (old ASTM:
In the low oxygen concentration semiconductor substrate of 4.81 × 10 ¹⁷ atoms / cm ² ), the suppression effect is small, so that LS
Slip is likely to occur from the outer peripheral portion during heat treatment in manufacturing I.

Regarding the oxygen precipitate, its morphology,
It is known that the susceptibility to slip varies depending on the size and the presence or absence of dislocation. In particular, when the form of the oxygen precipitates is plate-like, dislocations often occur and slips easily occur. On the other hand, the morphology of the oxygen precipitates is, for example, the {111} plane of Si and the {10}
In the case of a SiO ₂ precipitate which is an 8 to 14-faced (henceforth simply referred to as a polyhedron) surrounded by the 0} plane, dislocations are often not generated and slip is less likely to occur. It is believed that this is because the oxygen precipitates of the polyhedron suppress the movement of dislocations that cause slips (Yasutake Kiyoshi: C
Research on micro lattice defects and mechanical properties of Z-Si crystals, p102 (1982)).

The present inventor has completed the present invention based on the above findings. That is, in order to achieve the above object, the semiconductor substrate according to the present invention is (5-10) × 10 ¹⁷ pieces /
It contains oxygen in the range of ³ cm ³ and contains 10 ⁸ to ¹⁰ 10 polyhedral oxygen precipitates / c in the range of 10 mm or less from the outer periphery of the substrate.
It is characterized by containing at a density in the range of m ³ .

According to the above semiconductor substrate, 10 ⁸ to 10 ¹⁰
Since the oxygen precipitates of the polyhedron contained at a density of pcs / cm ³ suppress the movement of dislocations that cause slip,
It is possible to suppress the occurrence of slip from the outer peripheral portion during the heat treatment in I manufacturing.

The content of polyhedral oxygen precipitates is 10 ⁸ /
If it is less than ³ cm ³ , the effect of suppressing the movement of dislocations is not sufficient, and on the other hand, polyhedral oxygen precipitates can precipitate only a saturable portion of the interstitial oxygen concentration, and thus 10 ¹⁰ / c
It is difficult to give a density of m ³ or more.

Since the oxygen concentration remains low in the region of 10 mm or more from the outer periphery of the semiconductor substrate, the breakdown voltage of the oxide film, the generation of leak current, etc. do not occur, and the manufacturing yield cannot be reduced. Absent.

A method of manufacturing a semiconductor substrate according to the present invention
Is (5-10) × 10¹⁷Pieces / cm ^Three Range of oxygen
10 mm from the outer periphery of the semiconductor substrate to have
10 in the following range¹⁸-10²⁰Pieces / cm^Three Range of oxygen
Ion implantation is performed, and further, in a nitrogen gas atmosphere,
8 to 16 hours at 850 ° C and 1 at 1050 to 1150 ° C
Characterized by a two-step heat treatment for up to 4 hours
You.

According to the method for manufacturing a semiconductor substrate, the oxygen concentration can be increased only within a range of 10 mm or less from the outer circumference of the semiconductor substrate by the ion implantation.
By the heat treatment of the stage, the generation nuclei of SiO ₂ precipitates (oxygen precipitates) having a density of 10 ⁸ to 10 ¹⁰ / cm ³ are surely generated in a region away from the surface of the semiconductor substrate by a predetermined distance or more,
And can be formed efficiently. In addition, by the second-stage heat treatment, the polyhedron S having the above-mentioned predetermined density based on the above-mentioned nuclei is generated.
The iO ₂ precipitate can be grown reliably and efficiently. Therefore, polyhedral SiO ₂ precipitates can be contained at a density of 10 ⁸ to 10 ¹⁰ / cm ³ within a range of 10 mm or less from the outer circumference of the semiconductor substrate.

In the first heat treatment, if the heat treatment temperature is lower than 750 ° C. or the heat treatment time is shorter than 8 hours, the SiO ₂ precipitate is hard to be generated, while
The generated nuclei generated when the heat treatment temperature is higher than 850 ° C. do not become polyhedra during the second heat treatment. In addition, the effect of the heat treatment for more than 16 hours is small, resulting in an increase in production cost.

In the second heat treatment, the heat treatment temperature is lower than 1050 ° C. or the heat treatment time is 1
When the time is less than the time, the SiO ₂ precipitate does not become polyhedral, while the heat treatment at a temperature higher than 1150 ° C. delays the growth of the SiO ₂ precipitate. Moreover, the effect of the heat treatment for more than 4 hours is small, and the production cost is increased.

Since the above-mentioned steps do not generate the SiO ₂ precipitate in the region of 10 mm or more from the outer periphery of the semiconductor substrate, the manufacturing yield of LSI is not reduced.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a semiconductor substrate and a method of manufacturing the same according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view schematically showing an ion implantation apparatus for ion-implanting oxygen or the like used for manufacturing the semiconductor substrate according to the embodiment.

Reference numeral 1 in the figure shows an ion source for ionizing the element to be implanted. An extraction electrode 2 is arranged at a predetermined position in front of the ion source 1, and an analyzer 3 for selecting the ions by mass spectrometry of the ions extracted through the extraction electrode 2 is arranged in front of the extraction electrode 2.
Is arranged. The ions selected by the analyzer 3 are taken into an accelerator 4 which accelerates with a high voltage, and the ion beam by the ions taken into the accelerator 4 is uniformly scanned into a predetermined position of a sample (Si wafer 10a) by a scanning system 5. Will be introduced to. The scanning system 5 is an X scan 5a which is a scanning system in the X direction and a Y scan 5 which is a scanning system in the Y direction.
b and, for example, the X scan 5a is the accelerator 4
Located on the side. Ions whose implantation position is controlled by the scanning system 5 are implanted into the Si wafer 10a in the sample chamber 6 having a function as an ion measuring instrument (Faraday cup). The implanted ions are
The energy is lost due to the interaction with Si atoms, and the silicon wafer stops in the Si wafer 10a.

In the present embodiment, the above-mentioned ion implanting device is used, and the X scan 5a and the Y scan 5b are used.
From the outer periphery of the Si wafer 10a by controlling
Implantation of 10 ¹⁸ to 10 ²⁰ oxygen ions / cm ³ is performed only in the range of 0 mm or less.

Next, the Si wafer 10a into which oxygen is ion-implanted by the above method is subjected to the heat treatment described below.

FIG. 2 is a perspective view schematically showing a heat treatment apparatus used for manufacturing a semiconductor substrate according to the embodiment. In the figure, 21a shows a substantially hollow cylindrical quartz tube having a predetermined length. There is. A plurality of heaters (not shown) are arranged around the quartz tube 21a, and the heater is used to set the temperature distribution in the quartz tube 21a to be substantially constant at the inlet, the central portion, and the outlet. There is. A gas supply system (not shown) is connected to the quartz tube 21a, and the atmosphere inside the quartz tube 21a is controlled by introducing nitrogen or oxygen through this gas supply system. The heat treatment furnace 21 is configured to include the quartz tube 21a, a heater, a gas supply system, and the like. On the other hand, a substantially box-shaped quartz tray 22b is placed on the substantially plate-shaped quartz board 22a, and the Si wafer 10a which is a semiconductor substrate is accommodated in the tray 22b. Si wafer 10a is tray 2
The quartz boards 22 are inserted vertically into the slit portions 22c formed on both side wall portions of the quartz board 22b.
The wafer supporting means 22 is constituted by including a and the tray 22b. The tray 22b is the inlet 21 of the heat treatment furnace 21.
It is designed to be inserted from b in the direction of the arrow in the figure, transported inside the quartz tube 21a at a predetermined constant speed, and taken out again from the inlet part 21b. The heat treatment furnace 21 and the wafer supporting means 22 are included in the heat treatment apparatus. 20 are configured.

In the case of manufacturing a semiconductor substrate using the apparatus 20 thus constructed, first, nitrogen gas is introduced into the quartz tube 21a, and then the current supplied to the heater is controlled to control the temperature of the quartz tube 21a. Set to 750 ° C.
Next, the Si wafer 10a housed in the wafer supporting means 22.
Is inserted into the heat treatment furnace 21 at a predetermined speed of, for example, about 5 cm / min. Next, the first stage heat treatment is performed at 750 to 850 ° C. for 8 to 16 hours, and further the second stage heat treatment is performed at 1050 to 1150 ° C. for 1 to 4 hours.
After depositing polyhedral SiO ₂ in the range of 10 mm or less from the outer periphery of a, it is taken out of the heat treatment furnace 21 at a speed of 5 cm / min.

[0030]

Examples and Comparative Examples In the examples, the semiconductor substrate 10 (Si
Wafer 10a) was manufactured under the following conditions.

Ion implantation source: oxygen Ion-implanted oxygen amount: 10 × 10 ¹⁷ ions / cm ³ Accelerating voltage in accelerator 4: 200 keV First stage heat treatment temperature: 800 ° C. First stage heat treatment time: 16 hours Second stage Heat treatment temperature: 1100 ° C. Second stage heat treatment time: 1 hour Further, as a comparative example, a Si wafer pulled by the CZ method as in the example was used. A semiconductor substrate that has not been subjected to the heat treatment of 1 was manufactured.

A range of 10 mm or less from the outer circumference of the semiconductor substrate according to the example and the comparative example is TEM (transmission electron microscope).
As a result, the size of the semiconductor substrate 10 according to the example surrounded by the {111} plane of Si was about 500.
Å Polyhedral SiO ₂ precipitates (Fig. 3) are 10 ⁹
It was confirmed with a density of pieces / cm ³ . In addition, the semiconductor substrate 10
The presence of the above-mentioned SiO ₂ precipitate was not confirmed in a range of 10 mm or more from the outer periphery of the.

On the other hand, in the semiconductor substrate according to the comparative example, the polyhedron of SiO ₂ precipitates was 10 ⁶ / cm.
Confirmed at a density of ³ . This value is a very small value as compared with the case of the example. On the other hand, the presence of the SiO ₂ precipitate was not confirmed within a range of 10 mm or more from the outer circumference of the semiconductor substrate.

As described above, in the semiconductor substrate 10 according to the example, much more polyhedral oxygen precipitates (SiO ₂ precipitates) were confirmed in the range of 10 mm or less from the outer periphery than the semiconductor substrate according to the comparative example. We were able to.

Next, with respect to the Si wafers according to the examples and the comparative examples, the easiness of occurrence of slip when heat-treated was compared. The interstitial oxygen concentration of both semiconductor substrates was about 8 × 10 ¹⁷ / cm ³ . The easiness of slippage is 1100 after inserting both semiconductor substrates into the heat treatment furnace 21.
After heat treatment at ℃ for 30 minutes, from the heat treatment furnace 21 15cm /
It was carried out at a speed of min and then compared by the X-ray topography method. According to the X-ray topography method, it is possible to directly observe the dislocations forming the slip existing in the semiconductor substrate, and the dislocations are observed as a bright linear contrast with respect to the perfect crystal part.

FIG. 4 is a photograph showing the X-ray topographic image of the semiconductor substrate 10 according to the example. As is clear from FIG. 4, the dislocations were hardly observed in the semiconductor substrate 10 according to the example, and it was found that slips were hardly generated.

FIG. 5 is a photograph showing an X-ray topographic image of a semiconductor substrate according to a comparative example. As is clear from FIG. 5, in the semiconductor substrate according to the comparative example, the dislocations were confirmed at a high density within a range of 10 mm or less from the outer peripheral portion, and it was found that slips occurred.

As described above, it was confirmed that in the semiconductor substrate 10 according to the example, slip did not occur even by the heat treatment, and slip did not occur even during the heat treatment in the LSI manufacturing.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing an ion implantation apparatus used for manufacturing a semiconductor substrate according to an embodiment of the present invention, for example, used for ion-implanting oxygen.

FIG. 2 is a perspective view schematically showing a heat treatment apparatus used for manufacturing a semiconductor substrate according to an embodiment.

FIG. 3 is a TE of polyhedral oxygen precipitates existing in a range of 10 mm or less from the outer circumference of the semiconductor substrate according to the example and the comparative example.
It is an M photograph.

FIG. 4 is an X-ray photograph of a semiconductor substrate according to an example.

FIG. 5 is an X-ray photograph of a semiconductor substrate according to a comparative example.

FIG. 6 is a schematic plan view sketching an X-ray topographic image of a semiconductor substrate shown for explaining slip.

[Explanation of symbols]

 10 semiconductor substrate 10a Si wafer

Claims (2)

[Claims] 1. Containing oxygen in the range of (5 to 10) × 10 ¹⁷ pieces / cm ³ and forming polyhedral oxygen precipitates in the range of 10 ⁸ to 10 ¹⁰ pieces / cm ³ within a range of 10 mm or less from the outer periphery of the substrate. A semiconductor substrate characterized by being contained at a density of. 2. A semiconductor substrate containing oxygen in the range of (5 to 10) × 10 ¹⁷ pieces / cm ^{3 and} a range of 10 ¹⁸ to 10 ²⁰ pieces / cm ³ within 10 mm or less from the outer periphery of the semiconductor substrate. Oxygen is ion-implanted, and further in a nitrogen gas atmosphere at 750 to 850 ° C. for 8 to 16 hours, and 1050 to 11
The method for manufacturing a semiconductor substrate according to claim 1, wherein the heat treatment is performed in two stages at 50 ° C. for 1 to 4 hours.