JP2003092301A - Method of manufacturing semiconductor substrate, and method of manufacturing solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a semiconductor substrate which can form a semiconductor device having an excellent quality and characteristic, and a solid-state image pickup device which has less white defect. SOLUTION: A semiconductor substrate having an oxygen concentration of 8×10<17> atom cm<-3> or more is manufactured at a crystal growth rate of 1.0 mm/min., and a semiconductor device such as a solid-state image pickup device is formed on the semiconductor substrate. The semiconductor substrate has inherently less point defects or clusters thereof introduced during crystal growth. And even when impurities and crystal defects are present on the substrate, these impurities and crystal defects can have a strong gettering ability and removed by the precipitated oxygen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor substrate and a method of manufacturing a solid-state image pickup device for forming a semiconductor device such as a solid-state image pickup device.

[0002]

2. Description of the Related Art As a semiconductor substrate for forming a semiconductor device, a CZ substrate grown by the CZ method, an MCZ substrate grown by the MCZ method, and an epitaxial layer on the surface of these CZ substrate and MCZ substrate. The formed epitaxial substrate or the like has been used conventionally.

On the other hand, the process of forming a semiconductor device is currently carried out in an ultra-clean room of class 100 or less, but it is necessary to completely avoid contamination of the semiconductor substrate by impurities such as gas, water and semiconductor manufacturing equipment. Can not. Moreover, the amount of impurities introduced into the semiconductor substrate in the step of forming the epitaxial layer on the surface of the semiconductor substrate is larger than the amount of impurities introduced in the step of forming the semiconductor device.

If impurities or crystal defects are present in the element active region of the semiconductor substrate, the quality and characteristics of the semiconductor device are significantly deteriorated. In addition, if impurities or crystal defects are present in the semiconductor substrate, the semiconductor substrate is susceptible to irradiation damage due to radiation such as α rays, which further deteriorates the quality and characteristics of the semiconductor device.

Therefore, in order to remove these impurities and crystal defects from the element active region, intrinsic gettering (IG) and extrinsic gettering (E) are used.
G) is conventionally performed. 2 and 3 show the characteristics of a semiconductor device formed on an epitaxial substrate or the like that has been subjected to these treatments.

In order to obtain the results shown in FIGS. 2 and 3, first, an epitaxial layer is simultaneously formed on a CZ substrate not subjected to gettering, a CZ substrate subjected to EG, and a CZ substrate subjected to IG. did. The EG in this case is 620
A polycrystalline Si film having a thickness of 1.5 μm was formed on the back surface of the CZ substrate by the CVD method at a temperature of ℃. Also, IG is 1
Heat treatment at 100 ° C. for 1.5 hours, heat treatment at 650 ° C. for 10 hours, and heat treatment at 1050 ° C. for 2 hours were sequentially added, and crystal defects were generated inside the CZ substrate by precipitation of oxygen. .

Then, on these epitaxial substrates,
A gate insulating film made of a SiO ₂ film having a thickness of 20 nm and A
A MOS capacitor having a gate electrode composed of an I film and a CCD image pickup device were formed. Figure 2 shows this MOS
The generation life obtained by the Ct method using a capacitor is
The measured value on the substrate is shown as a standardized value with 1. FIG. 3 shows the number of white defects in the CCD image pickup device as M
The measured value on the CZ substrate is shown as a standardized value with 1. The white defect corresponds to a dark current caused by impurities or the like.

[0008]

However, as is clear from FIGS. 2 and 3, in the epitaxial substrate, E
Even if G and IG are performed, the generation life is not much different from that of the CZ substrate, and the number of white defects cannot be reduced to the level of the MCZ substrate. On the other hand, CZ substrate and MCZ
There are defects in the substrate and not only in the substrate but also in the gate insulating film formed on the surface of the substrate. Due to current leakage and increase in interface state due to breakdown voltage deterioration of the gate insulating film, C
Transfer failure or the like has occurred in the CD imaging device.

[0009]

According to the method of manufacturing a semiconductor substrate of claim 1, a semiconductor substrate having an oxygen concentration of 8 × 10 ¹⁷ atom cm ⁻³ or more is manufactured at a crystal growth rate of 1.0 mm min ⁻¹ or less. . For this reason, the point defects and their clusters introduced during crystal growth are inherently small, and even if impurities and crystal defects are present, these impurities and crystal defects are strongly gettered by the precipitated oxygen. It is possible to manufacture a semiconductor substrate that can be manufactured.

[0010] manufacturing method of a solid-state imaging device according to claim 2, the oxygen concentration of the 8 × 10 ¹⁷ atoms cm ^-3 or more semiconductor substrate 1.
It is manufactured at a crystal growth rate of ⁰ mm min ^-1 or less, and a solid-state imaging device is formed on this semiconductor substrate. Therefore, the solid-state imaging device can be manufactured on a semiconductor substrate having a strong gettering ability and a long-term gettering ability.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference embodiments and embodiments of the invention of the present application will be described below with reference to FIGS. Figure 1
Shows a reference form. In this reference mode, FIG.
As shown in (a), a CZ substrate 11 which is a Si substrate grown by the CZ method is prepared. With this CZ substrate 11, <1
00> surface is the mirror surface 12, and the resistivity is 1 to 1
0 Ωcm and oxygen concentration of 1.5 × 10 ¹⁸ atom cm ^-3
Is. Then, the CZ substrate 11 is first set to NH ₄ OH.
/ H ₂ O ₂ aqueous solution, and further HCl / H ₂ O ₂ aqueous solution.

Next, dry oxidation is performed at a temperature of 1000.degree.
Therefore, as shown in FIG. 1B, S having a film thickness of about 20 nm is used.
iO₂A film 13 is formed on the mirror surface 12. And S
iO₂800 ke from the mirror surface 12 through the membrane 13
V acceleration energy and 1 × 10 ¹⁴cm^-2With the dose amount of
Carbon 14 is ion-implanted into the CZ substrate 11. At this time
The projected range of carbon 14 is about 1.3 μm, and
Concentration is 1 × 10¹⁸Atom cm^-3It is a degree.

Next, annealing is performed at 1000 ° C. for 10 minutes in an N ₂ atmosphere. As a result, as shown in FIG. 1C, a carbon-implanted region 15 having a peak concentration is formed at a position deeper than the mirror surface 12 of the CZ substrate 11. The peak concentration of carbon 14 in the carbon implantation region 15 is
It may be 1 × 10 ¹⁶ atoms cm ⁻³ or more.

After that, the SiO ₂ film 13 is removed with an HF / NH ₄ F aqueous solution. Then, using SiHCl ₃ gas,
At a temperature of about 1150 ° C., the Si epitaxial layer 16 having a resistivity of about 20 to 30 Ωcm is grown on the mirror surface 12 to a thickness of about 10 μm to complete the epitaxial substrate 17.

Carbon 1 in the carbon implantation region 15
The position of the peak concentration of 4 is deeper than the mirror surface 12 is that when the position of the peak concentration is set to the mirror surface 12, the crystallinity of the mirror surface 12 deteriorates and Si grown on this mirror surface 12 is deteriorated. This is because the crystallinity of the epitaxial layer 16 also deteriorates. Further, annealing in the N ₂ atmosphere after the ion implantation of carbon 14 causes Si epitaxial layer 16 to grow on the mirror surface 12 later, so that in the vicinity of the mirror surface 12 amorphized by the ion implantation. This is to restore the crystallinity.

Further, forming the SiO ₂ film 13 on the mirror surface 12 prevents channeling from occurring at the time of ion implantation of carbon 14, and at the same time, the mirror surface 12 is formed.
This is to prevent the sputtering. However, the SiO ₂ film 13 and the annealing in the N ₂ atmosphere are not always necessary depending on the acceleration energy and the dose amount when the carbon 14 is ion-implanted.

2 and 3 also show values measured using the epitaxial substrate 17 of this reference embodiment. The CZ substrate for forming the epitaxial substrate of the conventional example shown in FIGS. 2 and 3 and the CZ substrate 11 for forming the epitaxial substrate 17 of this reference embodiment are
It has the same specifications. As is clear from these FIGS.
The generation life is improved to about 1.4 times that of the CZ substrate.
The number of white defects is improved to about half that of the MCZ substrate. That is, in the epitaxial substrate 17, the gettering ability is effectively functioning even after the semiconductor device is formed.

In the above reference embodiment, 800 keV
Acceleration energy and 1 × 10¹⁴cm ^-2Dose of carbon
14 is ion-implanted into the CZ substrate 11, but FIG.
Of these conditions, only the dose amount can be changed variously.
The obtained dose amount of carbon 14 and the epitaxial substrate 17
The relationship with the number of white defects in the CCD image pickup device formed on
is doing.

Similarly to FIG. 3, FIG. 4 also shows a standardized value with the number of white defects of the CCD image pickup device formed on the MCZ substrate as 1. However, while FIG. 3 is a logarithmic graph, FIG. 4 is a linear graph. From FIG. 4, the number of white defects is smaller than that of the MCZ substrate if only carbon 14 is ion-implanted, but the number of white defects is particularly small when the dose amount is 5 × 10 ¹³ cm ⁻² or more. It can be seen that the gettering effect by the ion implantation of carbon 14 is large.

However, the dose amount of carbon 14 is 5 × 10 ¹⁵ c
When it exceeds m ⁻² , the crystallinity of the mirror surface 12 of the CZ substrate 11 deteriorates, and Si grown on the mirror surface 12 is deteriorated.
The crystallinity of the epitaxial layer 16 also deteriorates. Therefore, the dose amount of carbon 14 is 5 × 10 ^{13 to} 5 × 10 ¹⁵ c
A range of m ^-2 is preferred.

Further, in the above-mentioned reference embodiment, 800 keV
Carbon 14 is ion-implanted at an acceleration energy of 400 keV. Even if the acceleration energy is 400 keV, the gettering effect by the ion implantation of carbon 14 is the same as the case of 800 keV. It is considered to be the same as the case of 800 keV.

Therefore, if the carbon 14 is ion-implanted at a low energy, a commonly used high-current ion implanter can be used, and the ion implantation is about 1 compared to C ^2+.
Since C ⁺ that can obtain 0 times the current can be used, the throughput can be improved about 10 times.

The acceleration energy is 400 keV and 2
The projected range distances of carbon 14 in the case of 00 keV are about 0.75 μm and 0.40 μm, respectively, and in both cases, as in the case of 800 keV, CZ substrate 11
It is possible to form the carbon-implanted region 15 having a peak concentration at a position deeper than the mirror surface 12 of.

Further, in the above-described reference embodiment, the CZ substrate 11
The Si epitaxial layer 16 is temporarily grown on the mirror surface 12 of the above, but it is said that after the Si epitaxial layer 16 is grown to a predetermined film thickness at the epitaxial growth temperature, it is once cooled to a temperature of ½ or less of the epitaxial growth temperature. The Si epitaxial layer 16 having a desired film thickness may be formed by repeating a series of steps twice or more.

In this way, the Si epitaxial layer 1
Since heat history is applied twice or more when forming 6,
The crystal defects formed on the CZ substrate 11 by the ion implantation of carbon 14 grow further, and the gettering ability of the epitaxial substrate 17 further increases.

In addition, in the above-described reference embodiment, in order to enhance the gettering ability of the epitaxial substrate 17, carbon 1 is used.
Although only the ion implantation of No. 4 is performed, the gettering ability can be further improved by using the EG performed by forming a polycrystalline Si film or a phosphorus glass film on the back surface of the CZ substrate 11 together.

Further, in the above-mentioned reference embodiment, only carbon 14 is ion-implanted into the CZ substrate 11 which is a Si substrate, but group IV elements Ge, Sn, Pb and the like are ion-implanted instead of carbon 14. Alternatively, an element other than the group IV element may be ion-implanted simultaneously with the group IV element such as carbon 14.
Further, in this reference embodiment, the CZ substrate 11 that is a Si substrate is used.
Although the MCZ substrate may be used, a substrate other than the Si substrate may be used. When a substrate other than the Si substrate is used, at least an electrically neutral element that is different from the element forming the substrate but is in the same group as this element is ion-implanted.

Also, in the above-mentioned reference embodiment, SiHCl ₃
The Si epitaxial layer 16 is grown by using SiCl ₄ , SiH ₂ Cl ₂ , SiH ₃ Cl or Si.
H ₄ may be used instead of SiHCl ₃ , especially SiH
_It has been found that when ₄ is used, the characteristics of the semiconductor device are further improved.

Next, an embodiment will be described. In this embodiment, the growth rate of the Si crystal by the MCZ method is 0.5 mm.
Min is set to ^-1, the oxygen concentration is 1 × 10 ¹⁸ atoms cm ^-3, and the mirror surface <100> plane, resistivity 20Ωc
A Si substrate having a size of about m was prepared. Then, on this Si substrate, a MOS capacitor having a gate insulating film made of a SiO ₂ film and a gate electrode made of an Al film having a film thickness of 20 nm and a CCD image pickup device were formed.

When the Si substrate manufactured in this embodiment is compared with the Si substrate manufactured in the conventional example, the non-defective rate of the SiO ₂ film breakdown voltage of the MOS capacitor is improved to about 4 times, and the white flaw of the CCD image pickup device is improved. The number of defects is also improved to 1/5 or less. Although the Si crystal was grown by the MCZ method in this embodiment, the same effect can be expected by the CZ method.

FIG. 5 shows the relationship between the oxygen concentration of the Si substrate obtained by further changing the oxygen concentration of the Si substrate in the embodiment and the number of white defects in the CCD image pickup device formed on the Si substrate. Is shown. From this FIG. 5, it can be seen that the number of white defects is stable at a low level when the oxygen concentration is 8 × 10 ¹⁷ atoms cm ⁻³ or more. It is presumed that this is because impurities and crystal defects were gettered by the IG effect naturally introduced in the process of forming the CCD image pickup device.

FIG. 6 shows that the oxygen concentration of the Si substrate is 9 × 10 ^17.
The growth rate of the Si crystal obtained by variously changing the growth rate of the Si crystal with the atom cm ⁻³ fixed, the yield rate of the SiO ₂ film breakdown voltage of the MOS capacitor formed on this Si substrate, and the CCD image pickup device. Shows the relationship with the number of white scratch defects. From FIG. 6, it can be seen that if the growth rate is 1 mm min ⁻¹ or less, the yield rate of the SiO ₂ film is good and the number of white defects is good. It is presumed that this is because the growth rate is slow and the number of point defects and their clusters introduced during crystal growth is small.

Therefore, when the CCD image pickup device is formed on this Si substrate, not only are there few white defects, but also there are few transfer defects and the like due to the breakdown voltage deterioration of the gate insulating film. In addition, S
From the viewpoint of productivity, the growth rate of the i crystal has generally been about 1.5 mm min ⁻¹ .

[0034]

According to the method of manufacturing a semiconductor substrate of claim 1,
Since the number of point defects and their clusters that are introduced during crystal growth is inherently small, and it is possible to manufacture a semiconductor substrate that can strongly getter these impurities and crystal defects even if they exist, Also, a semiconductor substrate capable of forming a semiconductor device having excellent characteristics can be manufactured.

In the method of manufacturing a solid-state image pickup device according to claim 2,
Since the solid-state imaging device can be manufactured on a semiconductor substrate having a strong gettering ability and a long-term gettering ability, it is possible to manufacture a solid-state imaging device with few white defects.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a reference embodiment of the invention of the present application in the order of steps.

FIG. 2 is a graph showing the relationship between the type of semiconductor substrate and the generation life.

FIG. 3 is a graph showing the relationship between the type of semiconductor substrate and the number of white defects.

FIG. 4 is a graph showing the relationship between the dose of carbon and the number of white defects.

FIG. 5 is a graph showing the relationship between the oxygen concentration of the Si substrate and the number of white flaws.

FIG. 6 is a graph showing the relationship between the growth rate of Si crystal, the yield rate of SiO ₂ film breakdown voltage, and the number of white defects.

[Explanation of symbols]

11 ... CZ substrate, 12 ... Mirror surface, 14 ... Carbon, 16
... Si epitaxial layer, 17 ... Epitaxial substrate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takayoshi Higuchi             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Hideo Kobe             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Masanori Ohashi             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 4M118 AA05 AA10 AB01 BA10 EA01

Claims (2)

[Claims] 1. A method for producing a semiconductor substrate, which comprises producing a semiconductor substrate having an oxygen concentration of 8 × 10 ¹⁷ atoms cm ⁻³ or more at a crystal growth rate of 1.0 mm min ⁻¹ or less. 2. A semiconductor substrate having an oxygen concentration of 8 × 10 ¹⁷ atoms cm ⁻³ or more is manufactured at a crystal growth rate of 1.0 mm min ⁻¹ or less, and a solid-state imaging device is formed on the semiconductor substrate. Solid-state image pickup device manufacturing method.