JPH09139408A - Method of sorting semiconductor substrate, having epitaxial growth semiconductor layer and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of sorting semiconductor substrates, wherein substrates that may eventually cause defective devices are rejected in an initial stage of a manufacturing process to prevent troubles from occurring in succeeding steps, so that the yield rate and reliability are improved with the result of the reduction in device costs. SOLUTION: A semiconductor material 3 comprising a semiconductor substrate 1 with an epitaxial layer 2 is selected so that Tepi/Tsub may take a predetermined value, where Tsub is the recombination life time of the semiconductor substrate 1 and Tepi is the recombination life time of the epitaxial layer.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method of selecting a semiconductor substrate having an epitaxially grown semiconductor layer, which is suitable for obtaining a semiconductor device or the like using a charge coupled device, a so-called CCD (charge coupled device) type solid-state imaging device. And manufacturing method of semiconductor device.

[0002]

2. Description of the Related Art In various semiconductor devices, if a crystal defect or metal impurity contamination is present in a semiconductor substrate on which the semiconductor element is formed, especially in an operation area of the semiconductor element, that is, an active area, the characteristics of the element are deteriorated and the life is shortened. Come on. Especially,
In the case of forming a solid-state image pickup device using a charge-coupled device so-called CCD (charge coupled device), the presence of this defect and metal impurities causes a so-called white defect in the captured image together with an increase in dark current.

In many semiconductor devices, the CZ method (Cz
ochralski method), MCZ method (Magnetic Field Applied C)
Z method), FZ method (Float Zone method), and a semiconductor substrate formed by epitaxially growing a required semiconductor layer on a semiconductor substrate obtained by cutting out a single crystal semiconductor grown by the MCZ method.

When a semiconductor substrate having this epitaxially grown semiconductor layer is used, a low resistance region can be formed by forming a buried region below the element formation portion or by using a low resistivity semiconductor substrate. It has advantages such as easy realization of low power consumption.

Further, in a solid-state image pickup device, for example, dopant concentration unevenness is called so-called striation.
n) to reduce the image contrast unevenness caused by
As the semiconductor substrate, a semiconductor substrate having an epitaxially grown semiconductor layer, generally a semiconductor substrate obtained by epitaxially growing a silicon semiconductor layer on a silicon single crystal semiconductor substrate is used.

As a practical method of epitaxial growth of this silicon (Si), CVD (Chemical Vapor Depo
sition) method is used. As this CVD method,
The following four types of source gas are mainly used.
The hydrogen reduction method is a method using SiCl ₄ . In this case, Si is epitaxially grown by the following reaction. SiCl ₄ + 2H ₂ → Si + 4HCl A method using SiHCl ₃ . In this case, Si is epitaxially grown by the following reaction. SiHCl ₃ + H ₂ → Si + 3HCl As the thermal decomposition method, a method using SiH ₂ Cl ₂ . In this case, Si is epitaxially grown by the following thermal decomposition reaction. A method using SiH ₂ Cl ₂ → Si + 2HCl SiH ₄ . In this case, Si is epitaxially grown by the following thermal decomposition reaction. There is SiH ₄ → Si + 2H ₂ .

Among them, as a semiconductor substrate used for a solid-state image pickup device, the above-mentioned method is generally used because it is inexpensive and has a high growth rate, that is, it is suitable for thick film epitaxy.

However, in any of the above methods (1) to (3), the impurities present in the source gas during the epitaxial growth or the impurities present in the CVD apparatus are mixed during the epitaxial growth, resulting in the generation of white defects due to dark current. That is, defective products may be generated or quality may be deteriorated.

In a semiconductor device such as a solid-state image pickup device, a semiconductor element such as a solid-state image pickup device such as a CCD is formed on a semiconductor substrate formed by epitaxially growing a semiconductor layer on a semiconductor substrate as described above. After forming the desired semiconductor device by forming the, to measure or observe its characteristics, for example, in a solid-state imaging device, by observing the white flaw defect of the captured image, the quality of the device is selected. ing. Therefore, in this case, a defective manufacturing process is taken for a defective product, and the labor, time, and cost associated with the manufacturing work are extremely wasteful, resulting in a high cost.

[0010]

SUMMARY OF THE INVENTION According to the present invention, when manufacturing a semiconductor device such as the above-described solid-state imaging device, the characteristics of the semiconductor device finally obtained in the state of the semiconductor substrate on which the epitaxially grown semiconductor layer is formed, that is, Based on the discovery of a method capable of predicting the deterioration of characteristics such as the occurrence of crystal defects and the occurrence of white scratches due to the presence of impurity metals, etc., a semiconductor device having the finally desired excellent characteristics is obtained. The present invention provides a method for selecting a semiconductor substrate having an epitaxially grown semiconductor layer that can be manufactured and a method for manufacturing a semiconductor device.

That is, according to the present invention, in a semiconductor substrate, a semiconductor substrate in which a finally obtained semiconductor device has a defective product is discriminated. Since it can be eliminated in the early stage of manufacturing a semiconductor device, unnecessary work after that can be eliminated, thereby improving the incidence of defective products, eventually reducing cost, and improving reliability. To be able to.

[0012]

In the present invention, a semiconductor substrate having an epitaxially grown semiconductor layer on a semiconductor substrate has a recombination lifetime of the semiconductor substrate as τ _sub, and a recombination lifetime of the epitaxially grown semiconductor layer is When τ _epi , τ _{ep i} / τ
_A semiconductor substrate whose _sub has a predetermined value is selected.

Specifically, a semiconductor substrate having τ _epi / τ _sub of 0.3 or more is selected and only a semiconductor substrate satisfying this condition is used as a semiconductor substrate for forming a target semiconductor device.

[0014]

Embodiments of the present invention will be described.
As shown in the process diagram of FIG. 1, a first conductivity type, for example, n-type Si substrate 1 obtained from a single crystal Si ingot grown by, for example, the CZ method is manufactured. Then, the recombination lifetime τ _sub of this Si substrate is measured. This recombination lifetime τ _sub is measured by forming a SiO ₂ film on the surface of the substrate by surface thermal oxidation and suppressing recombination on the surface, and measuring the recombination state of electron-hole pairs by microwaves. Obtained from measurement.

Next, on the Si substrate 1, for example, an n-type Si semiconductor layer 2 of the same conductivity type as that of the substrate 1 in the first conductivity type or the second conductivity type is shown.
A semiconductor substrate 3 in which the semiconductor layer 2 is epitaxially grown on the substrate 1 by epitaxial growth to a thickness of about 10 μm to 20 μm is manufactured. This semiconductor substrate 3
The recombination lifetime of the epitaxially grown semiconductor layer 2 was measured by a microwave in the same manner as described above to obtain the recombination lifetime τ _epi of this epitaxially grown semiconductor layer.

In this way, τ _epi / τ _sub for this semiconductor substrate 3 is obtained. In this case τ _epi / τ
_sub is actually smaller than 1. In the present invention, those having τ _{ep i} / τ _sub of 0.3 or more are selected,
Only with respect to the semiconductor substrate _satisfying τ _epi / τ _sub ≧ 0.3, a semiconductor device such as a solid-state imaging device in which a CCD is formed, or a semiconductor device such as a bipolar transistor, a DRAM (dynamic random access memory), or the like is configured.

The semiconductor device manufactured by the semiconductor substrate selected in this manner has excellent characteristics and can significantly reduce the incidence of defective products.

Further, an embodiment in which the present invention is applied to manufacture of a solid-state image pickup device will be described. In this case, the Si substrate 1 is prepared as described with reference to FIG. In this example,
Similar to the above, the single crystal S grown by the CZ method
Substrate 1 having a diameter of 4 inches was produced from an i ingot. This substrate 1 was a Si substrate having a (100) crystal plane in the plate surface direction and doped with n-type impurity phosphorus (P) and having a specific resistance of about 10 Ωcm.

Then, regarding this substrate 1,
As described above, the lifetime τ _{su b} is measured.

Next, the semiconductor layer 2 is epitaxially grown on the mirror surface, which is one main surface of the substrate 1, to form the semiconductor substrate 3. The semiconductor layer 2 is, for example, an n-type Si semiconductor layer having a specific resistance of 40 to 50 Ωcm and a thickness of about 12 μm. The semiconductor layer 2 is formed by epitaxial growth, for example, by the above-described method, that is, a CVD method using SiHCl ₃ as a source gas and PH ₃ as a doping gas of an impurity phosphorus (P).

The lifetime τ _epi of this semiconductor layer is measured by the same method as described above to calculate the lifetime τ _epi / τ _sub . And τ _epi / τ _sub
The solid-state image pickup device is manufactured only for the semiconductor substrate 3 of ≧ 0.3.

Actually, in the case of the microwave measurement, since the measurement depth extends to a depth of about 50 μm, the measurement of the lifetime τ _epi for the semiconductor layer 2 is
Although the lifetime of the region including the portion that has also entered the substrate 1 is measured, in the present invention, the relative lifetime of both the semiconductor layer 2 and the substrate of τ _epi / τ _sub. Since the values are targeted, it is not necessary to strictly measure the lifetime of only the semiconductor layer 2 as τ _epi .

Then, as described above, τ _epi / τ _sub
The solid-state imaging device is manufactured only for the semiconductor substrate 3 having ≧ 0.3.
As shown in the schematic sectional view of the main part of the finally manufactured structure, for example, a CCD type solid-state imaging device is used. In this case, p-type impurity B (boron) is added to the n-type semiconductor layer 2.
Are selectively ion-implanted to form a first well region 21, and a light receiving portion 22 is formed on the first well region 21 and a CCD for transferring charges generated by the light receiving portion 22 according to the amount of light received. A vertical shift register section 23 having a configuration,
A read gate section 24 for reading charges from the light receiving section 22 is formed in the shift register section 23.

The light receiving portion 22 is composed of the p-type first well region 2
1 and an n-type light receiving region 25 forming a pn junction to form a photodiode, and a p formed on the n type light receiving region 25.
A positive charge storage region 26 of the mold is formed. This light receiving section 22
2 are arranged in a direction orthogonal to the paper surface in FIG. 2, that is, a so-called vertical direction, and a plurality of rows of the light receiving portions are arranged in parallel.

The shift register section 23 is formed between each row of the light receiving sections 22 and along each row. Shift register unit 2
3, a p-type second well region 27 is formed, and an n-type transfer region 28 is formed thereon.

A light-transmissive SiO ₂ insulating film 29 formed by, for example, surface thermal oxidation is formed on the entire surface of the semiconductor layer 2 and extends over the shift register section 23 and the read gate section 24. An insulating film 31 made of, for example, Si ₃ N ₄ and an insulating film 32 made of SiO ₂ are laminated on the gate insulating film 13 to form the transfer electrode 30 thereon.
Is formed.

Then, a light-transmissive interlayer insulating layer 33 such as PSG (phosphosilicate glass) is formed on the entire surface, and a light-shielding film 34 made of an Al film or the like is formed except on the light receiving portion 22.

A p-type channel stopper region 35 is formed between the light receiving portions and outside the shift register portion.

Detailed steps of manufacturing the solid-state image pickup device shown in FIG. 2 will be described with reference to FIGS. As shown in FIG. 3, the semiconductor substrate 3 manufactured by the above-described method,
Particularly, the semiconductor layer 2 of the semiconductor substrate with τ _epi / τ _sub ≧ 0.3
A p-type first well region 21 is formed on the surface of the semiconductor layer 2, and an insulating film 29 made of SiO ₂ is formed on the surface of the semiconductor layer 2 by thermal oxidation. After that, the p-type second well region 27 and the n-type transfer region 28 are formed in the well region 21 by ion implantation, respectively, to thereby form the vertical shift register portion 23.
And a p-type channel stopper region 35 is formed by ion implantation.

As shown in FIG. 4, all over the insulating film 29.
To Si_ThreeN_FourInsulating film 31 and Si_ThreeN _FourInsulation film 32 is deposited
After forming, these insulating films 32 and 31 are sequentially and selectively selected.
Then, the portion forming the light receiving portion is removed by etching. This
The insulating films 29, 31 and 32 as described above.
The insulating film 13 is formed. And this gate insulation
A transfer electrode 30 made of polycrystalline Si having a low specific resistance is formed on the film 13.
To form The transfer electrode 30 is formed by using polycrystalline Si.
Photolithographically formed over the entire surface by CVD method
It can be formed by patterning with a mask.

As shown in FIG. 5, n-type impurity P (phosphorus) is added to the first well region 21 using the transfer electrode 30 as a mask.
In particular, ion implantation is performed to a depth of about 0.4 μm from the surface of the semiconductor layer 2, and annealing is then performed in an N ₂ atmosphere to form a light receiving region 25 of an n-type region. In this way, a photodiode having a pn junction is formed between the p-type well region 21 and the n-type light receiving region 25 to form the light receiving portion 22.

As shown in FIG. 6, a p-type impurity B (boron) is further ion-implanted into the surface of the light receiving region 25 using the transfer electrode 30 as a mask, and annealed in an N ₂ atmosphere to perform positive charge accumulation region 26. To form.

Thereafter, as shown in FIG. 2, the transfer electrode 30
An interlayer insulating layer 33 made of, for example, PSG (phosphosilicate glass) is deposited over the entire surface including the above, and a light shielding film 34 made of, for example, an Al vapor deposition film having an opening in the light receiving portion 22 is deposited thereon. In this way, the solid-state imaging device having the above-described configuration is configured.

The solid-state imaging device formed in this manner is a solid-state imaging device which has no problem in white defects, that is, a defective product is produced by a metal defect which becomes a crystal defect or a recombination center, or has a problem in image quality. The production could be effectively eliminated.

In the solid-state imaging device having the structure described with reference to FIGS. 2 to 6, as the semiconductor substrate 3, the P (phosphorus) -doped substrate 1 of 8 to 12 Ωcm is similarly provided. The 50 Ωcm epitaxial growth semiconductor layer 2 is changed by the epitaxial film forming conditions, that is, the selection of the source gas, the selection of the substrate temperature for the epitaxial growth, etc., and τ _epi / τ _sub is 0.1.
Each solid-state imaging device was manufactured by using a plurality of semiconductor substrates 3 having different values in the range of to 0.77, and the relationship between white defect and τ _epi / τ _sub was measured. FIG. 7 is a diagram showing the measurement results. As is clear from this, τ _epi / τ _sub
When ≧ 0.3, the number of white defects is sharply reduced. That is, τ
_It can be seen that according to the method of the present invention in which the semiconductor substrate 3 having _epi / τ _sub ≧ 0.3 is selected and used, white defect hardly occurs, that is, the defective product generation rate can be effectively suppressed.

In the above example, the semiconductor substrate 1 and the epitaxially grown semiconductor layer 2 are both of the first conductivity type, and the first conductivity type is the n type. However, the first conductivity type is the p type. You can do it, and semiconductor substrate 1
And the semiconductor layer 2 may have different conductivity types.

Further, in the CCD type solid-state image pickup device shown in FIGS. 2 to 6, the conductivity type of each part may be opposite conductivity type.

The semiconductor substrate 1 is usually C
Although it is formed by cutting out from a single crystal ingot formed by the Z method or the MCZ method, it may be formed by the FZ method or the like.

Further, the method of the present invention is not limited to the above-mentioned solid-state image pickup device, and various semiconductor devices including MOS transistors (insulated gate field effect transistors), bipolar transistors or semiconductor integrated circuits thereof can be formed. The present invention can be applied when obtaining a semiconductor substrate and a semiconductor device which are to

In the selection of the semiconductor substrate according to the present invention, for example, in a substrate having a plurality of epitaxially grown semiconductor layers in which the same process is performed by using the substrate 1 obtained from the same ingot, a part of the substrate is sampled to obtain τ. Measure _epi / τ _sub , and measure τ _{epi for} other substrates
It is also possible to adopt a method of estimating / τ _sub .

[0041]

As described above, according to the present invention, in a semiconductor substrate, a semiconductor substrate in which a finally obtained semiconductor device has a defective product is discriminated. It is possible to eliminate unnecessary semiconductor substrates at an early stage of manufacturing a semiconductor device, so that unnecessary work after that can be eliminated, thereby improving the defective product rate, eventually reducing cost, and improving reliability. It is possible to improve the sex.

[Brief description of the drawings]

FIG. 1 is a process diagram of a method for selecting a semiconductor substrate according to the present invention.

FIG. 2 is a schematic cross-sectional view of a main part of an example of a semiconductor device using a semiconductor substrate selected by the method of the present invention.

FIG. 3 is a schematic cross-sectional view in one manufacturing process of a semiconductor device using a semiconductor substrate selected by the method of the present invention.

FIG. 4 is a schematic cross-sectional view in one manufacturing process of a semiconductor device using a semiconductor substrate selected by the method of the present invention.

FIG. 5 is a schematic cross-sectional view in one manufacturing process of a semiconductor device using a semiconductor substrate selected by the method of the present invention.

FIG. 6 is a schematic cross-sectional view in one manufacturing process of a semiconductor device using a semiconductor substrate selected by the method of the present invention.

FIG. 7 is a diagram showing the dependency of the number of white defects in the solid-state imaging device on the recombination lifetime ratio used for explaining the method for selecting semiconductor substrates according to the present invention.

[Explanation of symbols]

 1 Substrate 2 Semiconductor Layer 3 Semiconductor Substrate 22 Light Receiving Section 23 Shift Register Section

Claims (4)

[Claims] 1. A semiconductor substrate having an epitaxially grown semiconductor layer on a semiconductor substrate has a recombination lifetime τ of the semiconductor substrate.
and _sub, when the recombination lifetime of the epitaxial semiconductor layer and tau _epi, the use as a semiconductor substrate τ _epi / τ _sub form a semiconductor device of interest by selecting a semiconductor substrate to be a predetermined value A method for selecting a semiconductor substrate having a characteristic epitaxially grown semiconductor layer. 2. The method for selecting a semiconductor substrate having an epitaxially grown semiconductor layer according to claim 1, wherein the semiconductor substrate having τ _epi / τ _sub of 0.3 or more is selected. 3. A semiconductor substrate having an epitaxially grown semiconductor layer on a semiconductor substrate has a recombination lifetime τ of the semiconductor substrate.
_{Let sub be the sub} -recombination lifetime of the epitaxially grown semiconductor layer be τ _epi , select a semiconductor substrate for which τ _epi / τ _sub has a predetermined value, and form a semiconductor element on this selected semiconductor substrate. A method for manufacturing a characteristic semiconductor device. 4. A semiconductor substrate having an epitaxially grown semiconductor layer on a semiconductor substrate has a recombination lifetime of the semiconductor substrate of τ.
_{When the} recombination lifetime of the epitaxially grown semiconductor layer is _{defined as sub} , and τ _epi is _defined as τ _epi , a semiconductor substrate having τ _epi / τ _sub of 0.3 or more is selected, and a solid-state imaging device is formed on the selected semiconductor substrate. A method for manufacturing a semiconductor device, comprising: