JPH08213403A - Semiconductor substrate and manufacture thereof - Google Patents

Abstract

PURPOSE: To always effectively maintain the strength and gettering capacity by incorporating platelike SiO2 deposit due to dislocation in a specific density in a region separated at a specific distance or more from the surface of a semiconductor substrate. CONSTITUTION: A platelike SiO2 deposit 11b is contained in a density of 10<10> to 10<12> particles/cm<3> in an Si matrix 11a in a region separated at about 50μm or more from the surface of a semiconductor substrate 10, and oxygen between lattices is contained in a concentration of (8 to 12)×10<17> particles/cm<3> . Thus, a non-defect layer 12 is formed on an active region near the surface of the substrate, a defective layer 11 including the SiO2 deposit and dislocation is effectively formed therein, gettering capacity for contaminant substance is enhanced, and maintained. The decrease in the strength due to the oxygen between the lattices is prevented in the substrate. As a result, the increase in a leakage current, the decrease in an oxide film pressure resistance and the deformation can be prevented as well.

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 manufacturing method thereof, and more particularly to a single crystal Si (silicon) semiconductor substrate used as a substrate for forming an integrated circuit such as an LSI and a manufacturing method thereof.

[0002]

2. Description of the Related Art Most of semiconductor substrates used as substrates for forming integrated circuits such as LSIs are made of single crystal Si, and this single crystal Si spins a Si melt filled in a quartz crucible. It is formed by a pulling method called the Czochralski method (CZ method) of pulling up while allowing it to move.

When single crystal Si is grown using such a CZ method, the quartz crucible itself dissolves in the Si melt and elutes oxygen, and this oxygen is generally introduced from the solid-liquid interface into the Si ingot ( 13 to ¹⁷ ) × 10 ¹⁷ particles / cm ³ are taken in at a concentration of.

On the other hand, for example, at 1000 ° C. which is a typical heat treatment temperature during LSI manufacturing, the solid solubility of oxygen in single crystal Si is about 3 × 10 ¹⁷ pieces / cm ³ , and even below 1000 ° C. Therefore, single crystal Si
The oxygen contained therein is always saturated. For this reason, oxygen is converted into single crystal S during heat treatment in LSI manufacturing.
It is deposited in an i semiconductor substrate (hereinafter simply referred to as a semiconductor substrate) and changes into a SiO ₂ structure. Then, the volume may expand and strain may occur around this, and when the strain exceeds a certain critical value, dislocation occurs.

If these SiO ₂ 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 and the generation of leak current will occur, which will cause LSI failure. It is harmful. On the other hand, when the dislocations exist only inside the semiconductor substrate sufficiently distant from the surface, the dislocations are Fe (iron), Ni (nickel), Cu.
A so-called gettering action of adsorbing a heavy metal pollutant such as (copper) and removing the pollutant from the active region of the element is useful in manufacturing a high-quality LSI.

For the above-mentioned reason, a defect-free layer (hereinafter referred to as a DZ (Denuded Zone) layer) free of the SiO ₂ precipitates and dislocations is formed on the surface of the semiconductor substrate, and the SiO ₂ is formed inside the layer. ₂ Heat treatment is performed to form a defect layer (hereinafter, referred to as an IG (Internal Gettering) layer) in which precipitates and dislocations exist. Specifically, for example, the semiconductor substrate is heated to 1100 ° C. in a nitrogen atmosphere.
Then, heat treatment is performed for about 4 hours, and oxygen is diffused outward to reduce the oxygen concentration near the surface (D
Formation of Z layer). Then, a heat treatment at a temperature lower than 1100 ° C. is performed in a nitrogen atmosphere (for example, heating at 700 ° C. for 4 hours and then heating at 1000 ° C. for 16 hours) to generate the SiO ₂ precipitates and dislocations inside the semiconductor substrate ( I
Formation of G layer).

[0007]

In the above-described conventional semiconductor substrate and the method for manufacturing the same, (1) the density of SiO ₂ precipitates is as low as 10 ⁹ pieces / cm ³ or less, and the gettering ability may be poor. . (2) Density of SiO ₂ precipitates is 10 ¹⁰ to 10 ¹² pieces / cm
Although it is as high as ³ , gettering ability may be inferior. (3) While the gettering ability is excellent, the strength of the semiconductor substrate is liable to be lowered, which may cause a hindrance to the lithography process of the device process. There was a problem.

The present invention has been made in view of the above problems, and the gettering ability can be always reliably maintained and the strength can be maintained. As a result, an increase in leak current and an oxide film can be achieved. It is an object of the present invention to provide a semiconductor substrate and a method for manufacturing the same that can prevent the breakdown voltage from being lowered and can prevent deformation and damage.

[0009]

In order to achieve the above object, a semiconductor substrate according to the present invention is a semiconductor substrate containing oxygen, which has a plate-like shape with dislocations in a region 50 μm or more away from the surface of the semiconductor substrate. SiO ₂ precipitate is 10 ¹⁰ to 10
It is characterized in that it is contained at a density of ¹² pieces / cm ³ .

Further, in the method of manufacturing a semiconductor substrate according to the present invention, the semiconductor substrate containing oxygen is added to the semiconductor substrate in a nitrogen gas atmosphere at 110
After heat treatment at 0 to 1200 ° C. for 2 to 4 hours, temperature T (° C.) and time t (H) are 750 ≦ T ≦ 95, respectively.
0, 8 ≦ t ≦ 32, and 1000 ≦ T ≦ 1050, 8 ≦
The method is characterized by performing a two-step heat treatment in the range of t ≦ 32.

[0011]

The present inventor has found that the heat treatment temperature T (° C.) in the two-stage heat treatment (first-stage heat treatment and second-stage heat treatment)
And the relationship between the time t (H) and the formation state of plate-like SiO ₂ precipitates and dislocations were investigated. (1) First stage heat treatment (a) Effect of heat treatment temperature T When the heat treatment temperature T is lower than 750 ° C., the plate-like SiO 2
₍₂ ) Since the rate of nucleation of precipitates is slow, the heat treatment requires a long time, resulting in a significant decrease in production efficiency. On the other hand, when the heat treatment temperature T is higher than 950 ° C, the plate-like SiO ₂
Since the generation density of the precipitate nuclei is reduced, the generation density of the plate-like SiO ₂ precipitates growing from the nuclei and the dislocations accompanied therewith becomes small during the second heat treatment, and the gettering ability is reduced. It will be inferior.

(B) Effect of heat treatment time t When the heat treatment time t is shorter than 8H, the nuclei of the plate-like SiO ₂ precipitates are small in size. It easily dissolves and disappears inside. Therefore, the density of the plate-like SiO ₂ precipitates growing at this time and the dislocations accompanying it is reduced, and the gettering ability is deteriorated. On the other hand, the heat treatment time t is 32H
When the length is longer, the interstitial oxygen concentration is lowered, so that the strength is lowered, the semiconductor substrate is apt to be deformed, and the production efficiency is lowered. (2) Second stage heat treatment (a) Effect of heat treatment temperature T When the heat treatment temperature T is lower than 1000 ° C., it is difficult for the plate-like SiO ₂ precipitates to grow to a predetermined size by using the nuclei as a generation source, and strain is generated. Since the dislocations are small, dislocations are hard to occur, and even if the plate-like SiO ₂ precipitates of a predetermined density are formed, they are not accompanied by dislocations, resulting in poor gettering ability. On the other hand, when the heat treatment temperature T is higher than 1050 ° C, S
The shape of the iO ₂ precipitate tends to be a polyhedron, the strain around the SiO ₂ precipitate in this case is small, and dislocations are difficult to occur, resulting in poor gettering ability. (B) Effect of heat treatment time t When the heat treatment time t is shorter than 8H, it is difficult for the plate-like SiO ₂ precipitates to grow to a predetermined size and the strain is small.
Dislocations are less likely to occur, and even if the plate-like SiO ₂ precipitates of a predetermined density are formed, they do not accompany dislocations, resulting in poor gettering ability. On the other hand, the heat treatment time t is 32
When it is longer than H, the interstitial oxygen concentration is lowered, so that the strength is lowered, the semiconductor substrate is deformed at the time of dislocation formation, and the production efficiency is lowered.

According to the semiconductor substrate having the above structure, a plate-like SiO ₂ precipitate accompanied with dislocations is contained in a region of 50 μm or more from the surface of the semiconductor substrate at a density of 10 ¹⁰ to 10 ¹² pieces / cm ^3. Since the SiO ₂ precipitate has a plate-like shape, distortion is likely to occur, and this distortion causes the SiO 2
₂ Loop-shaped dislocations will occur around the precipitate. Therefore, the LS near the surface of the semiconductor substrate
The DZ layer is formed in the active region of the I element, and the IG layer containing the predetermined density of SiO ₂ precipitates and dislocations is surely formed inside the semiconductor substrate, and the gettering ability with respect to contaminants is enhanced. Will be maintained. Further, the interstitial oxygen concentration inside the semiconductor substrate is 8 to
Since it is maintained at about 12 × 10 ¹⁷ pieces / cm ³ , it is possible to prevent the decrease in the substrate strength due to the decrease in the interstitial oxygen concentration. As a result, it is possible to prevent an increase in leak current and a decrease in breakdown voltage of the oxide film in the semiconductor substrate and prevent deformation.

Further, according to the method of manufacturing a semiconductor substrate having the above structure, the semiconductor substrate containing oxygen is placed in a nitrogen gas atmosphere 11
After heat treatment (hereinafter referred to as pre-heat treatment) at 00 to 1200 ° C. for 2 to 4 hours, temperature T (° C.), time t (Hr)
Are 750 ≦ T ≦ 950, 8 ≦ t ≦ 32 (first-stage heat treatment), and 1000 ≦ T ≦ 1050, 8 ≦ t ≦, respectively.
Since the two-step heat treatment in the range of 32 (second heat treatment) is performed, oxygen is diffused outward by the preheat treatment,
DZ within a range of about 50 μm from the surface of the semiconductor substrate
The layers will be composed. On the other hand, when the temperature of the preheat treatment is less than 1100 ° C., it is difficult for oxygen to diffuse outward,
The width of the DZ layer does not increase. On the other hand, when the temperature exceeds 1200 ° C., the surface of the semiconductor substrate becomes rough due to contamination from the heat treatment apparatus. Further, even if the preheat treatment time is less than 2 hours, it is difficult for oxygen to diffuse outward.
The width of the Z layer does not increase. On the other hand, even if the pre-heat treatment is performed for more than 4 hours, the action is saturated and the productivity is lowered.

[0015] The by first-stage heat treatment, 10 ^{of 10} to the remote or 50μm from the surface of the semiconductor substrate region
Nuclei of plate-like SiO ₂ precipitates having a density of 10 ¹² / cm ³ are formed reliably and efficiently, and the interstitial oxygen concentration is (8 to 12) × 10 ¹⁷ / cm ^3. Will be maintained. Further, by the heat treatment in the second step, a plate-like SiO ₂ precipitate having the predetermined density grows from the nuclei to locally generate strain, and the strength is maintained by the presence of the interstitial oxygen. Therefore, while preventing the deformation of the semiconductor substrate, loop-shaped dislocations are surely formed around the SiO ₂ precipitate.

[0016]

EXAMPLES AND COMPARATIVE EXAMPLES Examples 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 cross-sectional view schematically showing an embodiment of a semiconductor substrate according to the present invention, which is a sketch of a photograph of a cross section of the semiconductor substrate taken by an infrared tomography method. In a region away from the surface of the semiconductor substrate 10 by about 50 μm or more, plate-like SiO ₂ precipitates 11b are contained in the Si matrix 11a at a density of 10 ¹⁰ to 10 ¹² pieces / cm ³ , and
Interstitial oxygen (not shown) is (8-12) × 10 ¹⁷ pieces / c
It is contained at a concentration of m ³ . Further, as shown in FIG. 2, the SiO ₂ precipitate 11b is surrounded by two {100} planes and is formed into a substantially plate shape having a thickness d of about 40Å, with loop-like dislocations 11c around the periphery. And these Si matrix 11a, plate-like SiO ₂ precipitate 11b, dislocation 1
The IG layer 11 includes 1c, interstitial oxygen, and the like. In the region within about 50 μm from the surface of the semiconductor substrate 10, oxygen is contained in the Si matrix 12a and plate-like SiO _{2 is used.}
The DZ layer 12 contains almost no precipitates and dislocations. The semiconductor substrate 10 is configured to include the IG layer 11 and the DZ layer 12.

FIG. 3 is a perspective view schematically showing a heat treatment apparatus used in the method of manufacturing a semiconductor substrate according to the embodiment. In the figure, reference numeral 21a indicates a substantially hollow cylindrical quartz tube having a predetermined length. . A plurality of heaters (not shown) are arranged around the quartz tube 21a, and the heaters are used to set predetermined locations in the quartz tube 21a to predetermined temperatures. 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.
A Si wafer 10a to be a semiconductor substrate is housed inside. The Si wafer 10a is inserted into slit portions 22c formed on both side wall portions of the tray 22b and installed in the vertical direction, and the wafer supporting means 22 is constituted by including the quartz board 22a and the tray 22b. Tray 2
2b is inserted from the inlet portion 21b of the heat treatment furnace 21 in the direction of the arrow in the drawing, is conveyed in the quartz tube 21a at a predetermined constant speed, and is taken out again from the inlet portion 21b. The heat treatment apparatus 20 is configured to include the support means 22.

When the semiconductor substrate 10 is manufactured using the apparatus 20 having the above structure, first, the quartz tube 21a is used.
After introducing nitrogen gas into the chamber, the current applied to the heater is controlled to control the temperature of the quartz tube 21a from 1100 to 120.
Set to 0 ° C. Next, the Si wafer 10a accommodated in the wafer support means 22 is placed in the heat treatment furnace 21 for about 50 mm, for example.
Insert at a predetermined speed of / min. Then, as shown in the heat treatment pattern of FIG.
Pre-heat treatment at 00 ° C for 2-4H (hours), then 75
The first stage heat treatment of 0 to 32H at 0 to 950 ° C is performed,
After the second stage heat treatment at 1000 to 1050 ° C. for 8 to 32 H, the semiconductor substrate 10 is treated as a heat treatment furnace 21.
Take out from.

Regarding the relationship between the density of plate-like SiO ₂ precipitates, the presence or absence of dislocations, the density of surface defects, the interstitial oxygen concentration and the substrate strength, and the temperature and time of each heat treatment in the semiconductor substrate 10 according to the examples below. The results of the investigation will be explained. The wafer 10a has a diameter of about 150 mm and a thickness of about 0.
A 63 mm Si wafer was used. The density of plate-like SiO ₂ precipitates was obtained by observing a plurality of sample surfaces using a TEM, counting the number of plate-like SiO ₂ precipitates, and converting this to the number per observed area. The presence or absence of dislocations was observed and measured at the same time when the density of the plate-like SiO ₂ precipitate was measured. The surface defect density is determined by the semiconductor substrate 10
For about 0.3 hours in nitrogen atmosphere at about 900 ℃ Fe
(Iron) diffusion treatment is applied, and further in oxygen atmosphere about 1100
A sample that had been subjected to an oxidation treatment at a temperature of about 16 hours was used.
Then, the sample surface was subjected to selective etching treatment, and the surface defect density was determined by an observation method using an optical microscope. When the surface defect density was low, it was determined that the gettering ability was high. The interstitial oxygen concentration was determined by FTIR (Fourier transform infrared absorption method). Further, the substrate strength is measured by measuring the amount of warpage of the semiconductor substrate 10 after manufacturing the substrate with a thickness gauge, and the amount of warpage does not affect the subsequent steps.
The following items were evaluated as “OK” and those exceeding 5 μm were evaluated as “Fail”.

As comparative examples, those for which the pre-heat treatment time is short (Comparative Examples 1 to 9), those for which the pre-treatment time is long (Comparative Examples 10 to 18), and the temperature or time for the first-stage heat treatment are carried out. Those outside the range of the examples (Comparative Examples 2 to 7, 11)
˜16, 21 to 26), and the temperature or time of the second stage heat treatment is out of the range according to the example (Comparative example 3 to
4, 6-9, 12-13, 15-22, 24-25) were selected. The results of the investigations relating to Examples 1 to 8 and Comparative Examples 1 to 26 are also shown in Table 1 below.

[0021]

[Table 1-1]

[0022]

[Table 1-2]

As is clear from the results shown in Table 1, Comparative Example 1
The semiconductor substrates manufactured by the methods No. 26 to (26) have a low density of plate-like SiO ₂ precipitates and are free from dislocations. (2) The density of the SiO ₂ precipitate is high, but the shape of the SiO ₂ precipitate is not plate-like, so that it does not cause dislocation. (3) The interstitial oxygen concentration is low. Either of these states, or the heat treatment time became longer and the productivity decreased. On the other hand, in each of the semiconductor substrates 10 manufactured by the methods of Examples 1 to 8, 5
The plate-like SiO ₂ precipitates 11b are contained in a region separated by 0 μm or more at a density of 10 ¹⁰ to 10 ¹² pieces / cm ³ , and
The SiO ₂ precipitate 11b was accompanied by dislocations 11c. Further, in each case, the surface defect density was low, the gettering ability was excellent, and the reduction in strength (deformation) was small.

As is clear from the above results, according to the method of manufacturing the semiconductor substrate 10 of the example, oxygen is diffused outward by the pre-heat treatment, and about 5% of oxygen is diffused from the surface of the semiconductor substrate 10.
A substantially complete DZ layer 12 is formed in the range of 0 μm.
Further, by the first-stage heat treatment, 10 ¹⁰ to 10 ¹² pieces / cm ³ are formed in a region 50 μm or more away from the surface of the semiconductor substrate 10.
The generation nuclei of the plate-like SiO ₂ precipitates 11b having a density of 1 are reliably and efficiently formed, and the interstitial oxygen concentration is maintained at about (8 to 12) × 10 ¹⁷ pieces / cm ³ .
Further, by the second stage heat treatment, a plate-like SiO ₂ precipitate 11b having a predetermined density grows from the generated nuclei, a local strain is generated around this, and the existence of interstitial oxygen of a predetermined concentration is maintained. It Further, loop-shaped dislocations 11c are surely formed around the SiO ₂ precipitates 11b. As a result, in the semiconductor substrate 10 according to the example, strain is likely to occur because the SiO ₂ precipitate 11b has a plate shape, and this strain causes loop-shaped dislocations around the SiO ₂ precipitate 11b. Therefore, a substantially complete DZ layer 12 is formed in the active region of the LSI element near the surface of the semiconductor substrate 10, and the IG layer 11 containing SiO ₂ precipitates 11b and dislocations 11c of a predetermined density is formed inside the semiconductor substrate 10.
Are reliably formed, and the gettering ability for contaminants such as Fe is enhanced. Further, since the interstitial oxygen concentration inside the semiconductor substrate 10 is maintained at about 8 to 12 × 10 ¹⁷ oxygen atoms / cm ³ , the decrease in strength due to the reduction in the interstitial oxygen concentration is prevented. As a result, it is possible to prevent an increase in leak current in the semiconductor substrate 10 and a decrease in breakdown voltage of the oxide film, and also to prevent deformation.

In the manufacturing method according to the above-described embodiment, the case where the heat treatment furnace 21 of the type having the quartz tube 21a built therein is used has been described, but the heat treatment furnace of the type is not limited to the heat treatment furnace of a predetermined type. The heat treatment atmosphere, temperature and time may be controlled.

Further, in the manufacturing method according to the above-described embodiment, the case where the wafer 10a is housed in the wafer supporting means 22 has been described. However, the wafer supporting means 22 is not limited to the wafer supporting means having this structure, and the stress is applied to the wafer 10a. Does not take
The wafer 10a and the atmospheric gas are sufficiently contacted, and the wafer 1
Any structure may be used as long as 0a is uniformly heated.

Further, in the manufacturing method according to the above-described embodiment, the wafer 10a is heat-treated in the heat treatment furnace 21 at a speed of about 50 mm / min.
The case where it was inserted into the inside was explained, but there is no 50mm.
It is not limited to / min.

[0028]

As described above in detail, in the semiconductor substrate according to the present invention, a plate-like SiO ₂ precipitate accompanied by dislocations is formed in the region of 50 μm or more from the surface of the semiconductor substrate.
Since it is contained at a density of ¹⁰ to 10 ¹² pieces / cm ³ , the S
Since the shape of the iO ₂ precipitate is plate-like, distortion is likely to occur, and this distortion causes loop-shaped dislocations around the SiO ₂ precipitate. Therefore, the DZ layer is formed in the active region of the LSI element near the surface of the semiconductor substrate, and the SiO 2 having the predetermined density is formed inside the semiconductor substrate.
_{2 The} IG layer containing precipitates and dislocations is surely formed, and the gettering ability for contaminants is enhanced and maintained. Further, since the interstitial oxygen concentration inside the semiconductor substrate is maintained at about 8 to 12 × 10 ¹⁷ oxygen atoms / cm ³ ,
A decrease in strength due to a decrease in the interstitial oxygen concentration is prevented. As a result, it is possible to prevent the increase of the leak current and the decrease of the withstand voltage of the oxide film in the semiconductor substrate and the deformation.

Further, in the method of manufacturing a semiconductor substrate according to the present invention, the semiconductor substrate containing oxygen is preheated in a nitrogen gas atmosphere at 1100 to 1200 ° C. for 2 to 4 hours, and then the temperature T (° C. ), And time t (Hr) is 750 ≦
Since the two-stage heat treatment in the range of T ≦ 950, 8 ≦ t ≦ 32 (first-stage heat treatment) and 1000 ≦ T ≦ 1050, 8 ≦ t ≦ 32 (second-stage heat treatment) is performed, Oxygen is diffused outward by the pre-heat treatment, and a DZ layer is formed within a range of about 50 μm from the surface of the semiconductor substrate. Further, by the first-stage heat treatment, 10 ¹⁰ to 10 ¹² pieces / cm 2 are formed in a region 50 μm or more away from the surface of the semiconductor substrate.
Generation nuclei of plate-like SiO ₂ precipitates having a density of ³ are formed reliably and efficiently, and the interstitial oxygen concentration is maintained at (8-12) × 10 ¹⁷ pieces / cm ³ . Further, by the heat treatment in the second step, a plate-like SiO ₂ precipitate having the predetermined density grows from the nuclei to locally generate strain, and the strength is maintained by the presence of the interstitial oxygen. Therefore, the semiconductor substrate is prevented from being deformed, and loop-shaped dislocations are surely formed around the SiO ₂ precipitate.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an embodiment of a semiconductor substrate according to the present invention, in which a cross-section of a semiconductor substrate is photographed by an infrared tomography method and this photograph is sketched.

FIG. 2 is a schematic view showing plate-like SiO ₂ precipitates and dislocations formed inside a semiconductor substrate according to an example.
It is the figure which sketched the photograph image | photographed by M (equivalent electron microscope).

FIG. 3 is a perspective view schematically showing a heat treatment apparatus used in the method for manufacturing a semiconductor substrate according to the example.

FIG. 4 is a schematic view showing a heat treatment pattern in a method for manufacturing a semiconductor substrate according to an example.

Claims (2)

[Claims] 1. A semiconductor substrate containing oxygen, containing plate-like SiO ₂ precipitates accompanied with dislocations at a density of 10 ¹⁰ to 10 ¹² / cm ³ in a region 50 μm or more away from the surface of the semiconductor substrate. A semiconductor substrate characterized in that. 2. A semiconductor substrate containing oxygen is subjected to heat treatment at 1100 to 1200 ° C. for 2 to 4 hours in a nitrogen gas atmosphere, and then temperature T (° C.) and time t (H) are each 750 ≦.
T ≦ 950, 8 ≦ t ≦ 32, and 1000 ≦ T ≦ 105
2. The method of manufacturing a semiconductor substrate according to claim 1, wherein the heat treatment is performed in two stages within a range of 0, 8≤t≤32.