JP3232663B2 - Method for manufacturing semiconductor device - 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 of manufacturing a semiconductor device in which elements are separated only by different conductive regions such as various types of semiconductor memories.

[0002]

2. Description of the Related Art At present, element isolation in a semiconductor device is S
LOC formed by causing partial thermal oxidation on i-substrate
A configuration performed by an OS (Local Oxidation of Silicon) has become mainstream. For example, element isolation by LOCOS is performed in all elements such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), and CCD (Charge Coupled Device).

However, LOCOS due to this thermal oxidation
In the separation, distortion occurs at an edge portion of the SiO ₂ film, that is, a bird's beak, and impurities such as heavy metals and alkali metals are easily accumulated, so that GR (Generation and Recombination) is performed.
It has been pointed out that this causes an increase in current (eg, A. Ohsawa, R. Takizawa et al., Semiconductor Sili-co
n 1990, p601 (1990).

[0004] Therefore, for example, in a CCD which is extremely susceptible to GR current and contamination, element isolation is often performed by using only a different conductive region, that is, a channel stopper region, instead of the LOCOS.

In this case, as a countermeasure against contamination during the manufacturing process, so-called gettering for removing contamination and defects by providing a defect absorption region in a part of the substrate is performed. This getter rig is made of alkali metals such as Na and K, Fe, Cu
This is a process for removing impurities such as heavy metals and crystal defects, etc., by segregating in a defect absorption region provided outside the active region of the element by high-temperature treatment.

As the gettering method, for example, a polycrystalline Si region is formed on the back surface of the substrate, a phosphorus absorption layer is formed by diffusing phosphorus to form a defect absorbing region, or oxygen is previously formed. A so-called intrinsic gettering (IG) or the like is performed in which a high-temperature heat treatment is performed on a substrate containing a relatively high concentration to out-diffuse oxygen on the surface and oxygen remaining in the substrate is precipitated by the heat treatment. In the case of this IG, the surface layer forming the element becomes a denuded zone where neither oxygen precipitation nor crystal defects occur, while oxygen precipitates and crystal defects are formed at high density inside the substrate, and these have a gettering effect. With.

In these conventional gettering methods, if the distance between the element active region and the above-mentioned defect absorption region is short, a leak current may occur. Even in the case of trinic gettering, it is provided at a relatively large distance of about 10 to 30 μm, and it is difficult to perform sufficiently effective gettering.

Further, at the time of lowering the temperature of the process in the manufacture of semiconductor devices, there is a problem that the diffusion length of contaminant impurities during the process becomes shorter and the gettering effect is reduced.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a semiconductor device as described above, in particular, in a semiconductor device in which element isolation is performed by using different kinds of conductive regions, a defect absorption region is formed closer to the element active region and the gettering is performed. It is an object of the present invention to provide a method of manufacturing a semiconductor device in which the effect is sufficiently obtained and the defect absorption region itself does not become a source of leakage current.

[0010]

According to a method of manufacturing a semiconductor device according to the present invention, a method of manufacturing a semiconductor device in which element isolation is performed only by using different types of conductive regions is performed. A substrate separate from the substrate is directly bonded so as to cover the absorption region, and a defect absorption region is formed only immediately below a deep portion of a region where a heterogeneous conductive region is to be formed.

[0011]

According to the method of manufacturing a semiconductor device of the present invention, the substrate is bonded by direct bonding after forming the defect absorption region. In this case, after bonding, grinding and polishing are performed from the back side of the substrate. By performing the processing, a desired distance can be selected from the surface of the bonded substrate, that is, the distance from the element active region to the defect absorption region, and a sufficient gettering effect can be obtained without generating a leak current. Can be formed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a semiconductor device according to the present invention will be described below in detail with reference to FIGS. In this case, C
An example in which the present invention is applied to a CD image sensor will be described.

FIG. 1 shows an example of a CCD image pickup device according to the present invention. Referring to FIG. 1, reference numeral 1 denotes a substrate made of, for example, n-type Si or the like having a resistivity of about 50 Ω · cm formed by a CZ (Czochralski) method and having a high concentration of, for example, p
As shown in FIG. 2, a channel stopper region formed by ion implantation of boron or the like, that is, a heterogeneous conductive region 3 is, for example, a square so as to surround the light receiving region 9 and the vertical shift register unit 10. The elements are formed in an eye shape to perform element isolation. Into the light receiving region 9, a low-concentration impurity of a conductivity type opposite to that of the substrate 1, that is, a p-type impurity in this case is implanted to form the carrier generation region 4. On this, a gate electrode 6 made of polycrystalline Si or the like and a wiring 8 made of Al or the like are formed so as to extend vertically in FIG. 2 via an insulating film 5 made of SiO ₂ or the like. Is configured. Reference numeral 7 denotes an interlayer insulating film made of PSG (phosphosilicate glass) or the like.

In particular, in this case, the defect absorbing region 2 is selectively formed only under the deep portion of the heterogeneous conductive region 3 over a range of the depth d of 2 to 5 μm. As described above, since the defect absorption region 2 is provided close to the element active region on the substrate surface, in this case, the light receiving region 9 and the vertical shift register portion 10, the gettering effect can be sufficiently obtained, The white spot defect due to the generation of the GR current, which is more resistant to contamination than the CCD element and is generally a problem in the CCD image sensor, can be reduced. In this case, the gettering effect can be further improved by providing a defect absorption region on the back surface of the substrate or combining intrinsic gettering as in the conventional semiconductor device.

Next, an example of a method for forming such a defect absorption region will be described in detail with reference to FIGS. 3A and 3B. In this case, direct bonding technique of the Si substrate (e.g., "Shimbo, Applied Physics 56, 337 (1987)") in the example that applies, prepared Si substrate 1A and 1B of the pair, as shown in Figure 3A, one of its A groove 11 is selectively formed on the substrate 1A, and for example, a polycrystalline S
After depositing i by CVD or the like, the surface is flattened by etch back or the like to form a defect absorption region 2. In this case, a SiO ₂ or Si ₃ N ₄ film may be formed instead of the polycrystalline Si, and the surface 1AS of the substrate 1A is selectively irradiated with a laser beam to locally form the polycrystalline Si. Can also. Defects can also be formed by high-concentration ion implantation.

Thereafter, the surface 1AS of the substrate 1A and the surface 1BS of the other substrate 1B are mirror-finished to produce an arrow c.
3A, the substrates 1A and 1A are annealed at about 1 hour, respectively.
And 1B can be joined. Alternatively, after subjecting surfaces 1AS and 1BS to hydrophilic treatment, they are superimposed,
The bonding can also be performed by annealing at about 1200 ° C. in oxygen. In the case of performing the electrostatic pressure bonding, a strong adhesion can be obtained more easily.

At this time, the defect absorption region 2
In this case, due to the difference in the thermal expansion coefficient between the polycrystalline Si and the surrounding substrate material, ie, Si, dislocation defects occur at the interface as shown by hatching in FIG. 3B, and these form the defect absorption region 2. .

After bonding, the substrate 1A or 1B, for example, the substrate 1
B is thinned to a thickness t of about 2 μm by grinding and polishing, and a different kind of conductive region is formed immediately above the defect absorption region 2 on the defect absorption region 2 as described with reference to FIG. A CCD image pickup device is formed by forming a carrier generation region, a gate electrode, and the like.

In this case, stress is generated at the interface between the polycrystalline Si or SiO ₂ or Si ₃ N ₄ film and the Si substrate due to the difference in the coefficient of thermal expansion, and defects such as distortion and crystal transition are formed. Therefore, a sufficient gettering effect can be obtained, and the defect absorption region 2 can be formed at an arbitrary depth, for example, at a depth of about 2 μm from the surface as described above. Gettering can be performed effectively.

In this example, the defect absorbing region 2 is provided by embedding in the substrate 1A. However, the defect absorbing region 2 may be formed on the other substrate 1B or both the substrates 1A and 1B.

FIG. 4 shows a comparative example of a method for forming the above-described defect absorption region. In this example, a defect absorption region is formed by a high energy ion implantation method. For example, before forming a heterogeneous conductive region, in this case, a channel stopper region, on a substrate 1 made of oxygen-containing Si formed by the CZ method, a strain-generating impurity is ionized as indicated by an arrow I just below the deep portion of this portion. inject. In this example, the thickness of the resist is determined greater than the thickness at the time of the conventional ion implantation, approximately after patterned by exposure and development the thickness of 4μm, 1 × 10 ¹⁵ cm carbon at 2 MeV ^- Implantation was performed at a density of ² and recrystallization annealing was performed at 1000 ° C. for 60 minutes to form a defect absorption region 2. As a result, it was confirmed by observation with an electron microscope that a defect absorption region 2 was formed in a region having a depth d of about 3 μm from the surface and no defect was generated on the surface side.

In this comparative example, a Si substrate formed by the CZ method is used.
m (for example, about 30 ppm), oxygen is precipitated when impurities are implanted into the substrate 1 and the above-described IG
A gettering effect can be obtained by the same operation as (intrinsic gettering).

Although carbon was used as the ion species in the comparative example, B was used as the other p-type material.
(Boron), Al, Ga, etc., and n-type material is P
(Phosphorus), As, Sb, etc. can be used, and when forming a neutral defect absorption region, various materials such as oxygen and Ge can be used. Further, the substrate 1 is not limited to the CZ method, and may be a magnetic-field-applied CZ
An Si substrate or the like formed by the i) method can also be used.

The method of manufacturing a semiconductor device according to the present invention is not limited to the above-described embodiment, and it goes without saying that various other material configurations can be adopted.

[0025]

As described above, according to the method for manufacturing a semiconductor device of the present invention, the depth of the defect absorption region can be formed with good controllability, and a semiconductor device having a sufficient gettering effect can be obtained. be able to.

In the semiconductor device thus obtained, a sufficient gettering effect can be obtained because the defect absorbing region is provided without being separated from the element active region and without generating a leak current. In particular, even if the diffusion length of metal impurities becomes small due to the future low-temperature processing of the device, gettering can be sufficiently performed.

[Brief description of the drawings]

FIG. 1 is a schematic enlarged cross-sectional view of a main part of an example of a semiconductor device applied to the present invention.

FIG. 2 is a schematic enlarged plan view of a main part of the semiconductor device of FIG. 1;

FIG. 3 is a manufacturing process diagram showing an example of a method for manufacturing a semiconductor device according to the present invention.

FIG. 4 is a manufacturing process diagram showing a method for manufacturing a semiconductor device according to a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Defect absorption area 3 Heterogeneous conductive area 4 Carrier generation area 6 Gate electrode 9 Light receiving area 10 Vertical shift register section

Claims (1)

(57) [Claims] In a method of manufacturing a semiconductor device in which element isolation is performed only by using different types of conductive regions, a defect absorbing region is formed on a substrate, and then a substrate separate from the substrate is formed so as to cover the defect absorbing region. A method of manufacturing a semiconductor device, wherein the defect absorption region is formed only directly below a deep portion of a region where the heterogeneous conductive region is to be formed by direct bonding.