JPH05152304A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To obtain a manufacturing method for a semiconductor substrate on which a gettering layer can be formed in the vicinity of a device active region in an excellent controllable manner. CONSTITUTION:First carbon is ion-implanted on the surface of a silicon wafer 11 under the condition of dosage 1X10<14> at m/cm<3>. At this point, the depth from the surface of the wafer of the high density carbon layer (gettering layer), which will be formed in the silicon wafer 11, is set at about 1mum by properly setting the energy amount of ion implantation. Then, an epitaxial layer (Si) 13 is grown in the thickness of 10 to 20mum. When an element is formed on the epitaxial layer of the semiconductor substrate formed as above, the gettering effect during processing or after formation can be maintained excellently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor substrate, and more particularly to a method for manufacturing a semiconductor substrate having a gettering layer at an appropriate position.

[0002]

2. Description of the Related Art Gettering is the ability to remove a defect in a device formation region or inactivate harmful impurities by performing a certain process on a silicon wafer during a device manufacturing process or in a state of a starting material. It is a technology that gives The defects and impurities targeted for gettering are
Although there are stacking faults, dislocations, heavy metal atoms, etc., the gettering technology is roughly classified into two methods.

One of them is intrinsic gettering (IG), which has a relatively high oxygen concentration in the crystal (>).
1 to 2 × 10 ¹⁸ atm / cm ³ ) A wafer is subjected to a specific heat treatment to precipitate oxygen in the crystal, and strain is formed along with the precipitation to form a gettering layer. It is a method of capturing (getter). In FIG. 2, this intrinsic gettering is applied to form a gettering layer 1A, which is a high-density defect region, inside the silicon wafer 1 (intermediate part between the front and back surfaces), and an epitaxial layer 2 is formed on the surface of the silicon wafer 1. An example is shown. In particular,
Recently, in CCD devices, as a countermeasure against white spots, there is a tendency to perform intrinsic gettering on a wafer having an epitaxial layer to increase the device yield, and gettering is indispensable in CCD devices.

Another method is extrinsic gettering (EG). This method intentionally forms a processing flaw or a CVD polycrystal layer on the back surface of the wafer to form a gettering layer, and has the same effect as the above-mentioned intrinsic gettering. FIG. 3 shows an example in which this extrinsic gettering is applied. A polycrystalline silicon film 3 and a SiO ₂ film 4 are intentionally formed on the back surface of the silicon wafer 1 by a CVD method to form a gettering layer. None, an example in which the epitaxial layer 2 is grown on the surface of the silicon wafer 1 is shown.

[0005]

However, such a conventional gettering type semiconductor substrate has the following problems.

That is, in the above-described intrinsic gettering semiconductor substrate, it is necessary to perform heat treatment including various steps so as to form a high density defect region therein. For example, a defect-free layer is formed at a high temperature. Then, the temperature is lowered to perform the nucleation, the temperature is further raised to perform the heat treatment for a long time, and the microdefects are formed around the oxygen atoms, which complicates the treatment process. In addition to this,
When the number of defects is small or the dissolved oxygen concentration is small, a more complicated heat treatment process is required, and these conditions and the like must be taken into consideration and set for each device, and there is a problem in controllability thereof. In addition, intrinsic gettering has a fundamental problem that the gettering effect is relatively low.

On the other hand, a semiconductor substrate subjected to extrinsic gettering has a problem that a gettering layer such as a polycrystalline layer is easily peeled off and dust is easily generated. Further, since the gettering layer is formed on the back surface of the wafer, the gettering layer is distant from the element forming region on the front surface side, so that there is a problem that the contamination and the like in the vicinity of the element forming region cannot be sufficiently absorbed. This problem also applies to a semiconductor substrate that has been subjected to intrinsic gettering. Also,
The gettering layer on the back surface is ground and removed after the wafer is processed into chips for the sake of packaging, so that the gettering effect cannot be maintained thereafter.

The present invention was devised by focusing on such conventional problems, and has a high gettering effect in the vicinity of the device active region (element forming region) and controllability of the gettering layer formation. It is intended to obtain a good method for manufacturing a semiconductor substrate.

[0009]

Therefore, according to the present invention, carbon is ion-implanted into the surface of a semiconductor wafer to form a gettering layer at a shallow position from the surface, and then a semiconductor epitaxial layer is formed on the surface of the semiconductor wafer. Growing up is the solution.

[0010]

By injecting carbon (C) into the surface of the semiconductor wafer, the gettering layer can be formed with good controllability. For example, the energy of ion implantation,
By properly setting the dose amount, the depth of the gettering layer and the gettering action can be controlled with high accuracy. Therefore, defects and harmful impurities generated in the epitaxial layer formed on the surface of the semiconductor wafer are easily absorbed by the gettering layer formed at a close position.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the method of manufacturing a semiconductor device according to the present invention will be described below with reference to the embodiments shown in the drawings.

First, as shown in FIG. 1A, carbon (C) is ion-implanted at a high concentration (for example, 1 × 10 ¹⁴ atm / cm ³ ) from the surface of a polished silicon wafer 11. As shown in FIG. 1B, a high-density garbon layer 12 as a gettering layer made of a crystal defect layer is formed at a depth of about 1 μm from the surface of the silicon wafer 11.

Next, 10 to 10 made of silicon (Si) is epitaxially grown on the surface of the silicon wafer 11.
The epitaxial layer 13 having a thickness of about 20 μm is formed.

The semiconductor substrate thus formed is
Since the epitaxial layer 13 serving as the element formation region and the high-density carbon layer 12 are close to each other, the getter effect can be reliably achieved. Particularly, by ion-implanting (ion-implanting) carbon into the surface of the silicon wafer 11, the high-density carbon layer 1 is formed near the surface of the silicon wafer 11.
2 can be formed with good controllability, and by setting the ion implantation energy and the dose amount in advance, it is possible to form a uniform gettering layer between the wafers. When the silicon wafer 11 is made into chips and assembled into a package after forming elements on the epitaxial layer 13, the lower surface of the chip is often ground to achieve close contact with the package. Since the layer 12 is located on the upper side, the getter effect can be maintained even after packaging without being removed.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various design changes are possible accompanying the gist of the configuration. For example, ion implantation conditions and other various Of course, the conditions can be changed.

[0016]

As is apparent from the above description, in the method for manufacturing a semiconductor substrate according to the present invention, carbon is ion-implanted into the surface of a semiconductor wafer to form a gettering layer at a shallow position from the surface, By growing the semiconductor epitaxial layer on the surface of the semiconductor wafer, the gettering layer performs gettering in the vicinity of the device active region, so that a high gettering effect is obtained and the device reliability is enhanced.

Further, according to the present invention, the gettering layer formation position and the gettering ability can be determined by setting the ion implantation conditions, so that there is an effect that the gettering can be performed quantitatively and with high controllability. ..

Further, according to the present invention, there is an effect that film peeling and dust generation as in the conventional extrinsic gettering semiconductor substrate can be avoided.

Further, the getter effect can be maintained even after the elements are formed on the semiconductor substrate manufactured by the method according to the present invention to form chips and packages.
This has the effect of increasing the durability of the semiconductor device.

[Brief description of drawings]

1A, 1B, and 1C are cross-sectional explanatory views showing each step of an embodiment of the present invention.

FIG. 2 is a cross-sectional explanatory view of a conventional example in which intrinsic gettering is applied.

FIG. 3 is a cross-sectional explanatory view of a conventional example to which extrinsic gettering is applied.

[Explanation of symbols]

11 ... Silicon wafer (semiconductor substrate), 12 ... High-density carbon layer (gettering layer), 13 ... Epitaxial layer.

Claims (1)

[Claims] 1. A semiconductor substrate comprising a semiconductor wafer, wherein carbon is ion-implanted into the surface of the semiconductor wafer to form a gettering layer at a shallow position from the surface, and then a semiconductor epitaxial layer is grown on the surface of the semiconductor wafer. Production method.