JPS60136218A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve manufacturing yield and reliability and to contrive a high density by reducing leakage current by generating crystal defects in a semiconductor substrate and forming a defectless layer on a surface of the substrate and forming semiconductor elements in an epitaxial layer arranged in the defectless layer. CONSTITUTION:After treating an N type Si substrate 1 with high temperature, a low temperature treatment is performed step by step to generate a plurality of crystal defects 3 inside the Si substrate. At this time, a defectless layer 2 of about 3 pieces/cm<-2> or less is formed on a surface of the Si substrate 1 by IG effect. Oxygen concentration is desirably reduced to about 1-5X10<17>cm<-3> in a surface defectless layer after performing the heat treatment even if it is of about 16X10<17>cm<-3> in the Si substrate at the beginning. Next, an N type epitaxial layer 5 is formed on the defectless layer 2. The epitaxial layer 5 does not include oxygen so that minute defects caused by oxygen as in the Si substrate 1 are not generated and the layer becomes a defectless layer. Next, after solid state image pick-up element are formed in the epitaxial layer 5, a solid state image pick-up device is completed according to a common method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a semiconductor device with extremely low leakage current and a method for manufacturing the same.

It is well known that micro-defects that occur on the surface of semiconductor substrates and in the active region of epitaxial layers deteriorate the electrical characteristics of devices, and effectively suppressing micro-defects is a key factor in the yield rate of semiconductor devices. This leads to improvement.

The main causes of these microdefects are believed to be crystal defects such as dislocations and stacking faults existing in the semiconductor substrate (silicon substrate will be explained below) and contamination by heavy metal elements generated during the device manufacturing process. In addition, various suppression methods, so-called gettering methods, have been introduced into the manufacturing process of semiconductor devices.

Conventionally known gettering methods include (1) mechanically forming high-density defects on the back surface of a silicon substrate by sandblasting, etc., and (2) applying impurities such as high concentrations of phosphorus or boron. (3) Method of forming υ high-density defects in unnecessary parts of a silicon substrate by ion implantation; (4) Intrinsic gettering effect using crystal defects inside a silicon substrate (hereinafter referred to as the IG effect) are common, and the purpose of suppressing micro defects has been achieved to some extent by these methods.

However, due to recent demands for higher density semiconductor devices, larger diameter crystals, higher quality, lower prices, etc., it has become increasingly important to suppress micro defects in the active region of a silicon substrate. In particular, in solid-state imaging devices, which are being developed recently, it is necessary to form a large number of picture elements at high density in a large chip area, and if even one microscopic defect exists in a picture element, leakage current will occur. occurs, causing a defective surface. For this reason, a high-quality silicon substrate with no defects in the active region is required. However, as shown in Figure 1 (al) and (b), in the semiconductor manufacturing method using the conventional gettering method, the active region In other words, as shown in FIG. 1(a), the silicon substrate 1 manufactured by the Cz method is heated at 1200 degrees.
When low-temperature treatment is performed for 30 hours at 550° C. to 800° C. after 3 hours of high-temperature treatment, many crystal defects 3 are generated inside the silicon substrate 10, and a defect-free layer 2 is formed on the surface of the silicon substrate 10 due to the IG effect. . However, when a semiconductor element was formed in the defect-free layer 2 on the surface, a few minute defects 3' generated during the manufacturing process were observed in the active region 4, as shown in FIG. 1(b).

Further, as shown in FIG. 2(a), after forming a defect-free epitaxial layer 5 on the silicon substrate 1.

Even when a semiconductor element was formed in this epitaxial layer 5, a few minute defects 3' were generated in the active region 6, as shown in FIG. 2(b).

As described above, in the conventional semiconductor device manufacturing method 2, it is not possible to reduce the active region to a defect level below the desired level, so it is difficult to manufacture semiconductor devices with good electrical characteristics, especially solid-state imaging devices. Rushi, there was a drawback of not being able to obtain it.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks, form an epitaxial layer on a semiconductor surface having a defect-free layer, and form a semiconductor element on this epitaxial layer, thereby reducing leakage current to an extremely low level and improving manufacturing yield. An object of the present invention is to provide a high-density semiconductor device with improved reliability and a method for manufacturing the same.

[Structure of the invention]

A semiconductor device of the present invention includes a semiconductor substrate having a defect-free layer on its surface, an epitaxial layer formed on the defect-free layer of the semiconductor substrate, and a semiconductor element provided on the epitaxial layer. be done.

Further, the method for manufacturing a semiconductor device of the present invention includes a step of forming crystal defects in a semiconductor substrate, a step of heat-treating the semiconductor substrate to form a defect-free layer on the surface thereof, and a step of forming a defect-free layer on the surface of the semiconductor substrate. and forming an epitaxial layer.

[Explanation of Examples]

Next, embodiments of the present invention will be described using the drawings.

FIGS. 3(a) to 3(C) are cross-sectional views of main steps for explaining an embodiment of the present invention.

First, as shown in FIG. 3(a), an N-type silicon substrate 1 manufactured by the C2 method was subjected to high temperature treatment at 1200°C for 3 hours, and then heated in stages at 550°C to 750°C for 3θ hours. A large number of crystal defects 3 are generated inside the silicon substrate 1 by performing the low temperature treatment. At this time, a defect-free layer 2 of about 3 cass-2 or less is formed on the surface of the silicon substrate 1 due to the IG effect.

Even if the oxygen concentration is about 16 x 3 101'IcIrL in the initial silicon substrate, it will be 1 to 5 x 101 in the surface defect-free layer after the heat treatment.
It is desirable that the reduction is about 7crrc-''.

Next, as shown in FIG. 3(b), on the defect-free layer 2, a layer 5 with seven N-type layers 5 having a thickness of about 35 μm is formed. Since this epitaxial layer 5 does not contain oxygen, minute defects caused by oxygen do not occur as in the silicon substrate 1, so that it becomes a defect-free layer.

Next, as shown in FIG. 3(C), a solid-state imaging device is formed on the epitaxial layer 5, and then a solid-state imaging device is completed according to a conventional method. In such a case, there are only a few minute defects 3 in the defect-free layer 2.
' may occur, but no microdefects are observed in the active region 6 of the epitaxial layer in which the solid-state imaging device is formed. This is caused by IG due to crystal defects in the silicon substrate 1.
This is due to the effect.

As described above, according to the manufacturing method of the present invention, the active region in which a semiconductor element can be formed is formed by the IG effect due to crystal defects formed in the silicon substrate and by the prevention of defect transfer by the defect-free layer formed on the surface of the silicon substrate. In addition to the effects, since a defect-free state is maintained, the leakage current of the semiconductor device becomes extremely small.

〔Effect of the invention〕

As explained in detail above, according to the present invention, crystal defects are generated in a semiconductor substrate to form a defect-free layer on the surface thereof, and a semiconductor element is formed in an epitaxial layer provided on the defect-free layer. By doing so, the leakage current is extremely low.
The effect is great because a high-density semiconductor device and its manufacturing method with improved manufacturing yield, reliability, etc. can be obtained.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views for explaining a conventional method of manufacturing a semiconductor device, and FIG. 3 is a process cross-sectional view for explaining an embodiment of the present invention. l... Silicon substrate, 2... Defect-free layer, 3... Crystal defect, 3'... Micro defect, 4
... Active region, 5 ... Epitaxial layer, 6 ... Active region. Atsushi 7 Illustration 3 Illustration

Claims (2)

[Claims] (1) A semiconductor substrate having a defect-free layer on its surface, an epitaxial layer formed on the defect-free layer of the semiconductor substrate, and a semiconductor element bonded to the epitaxial layer. Semiconductor equipment. (2) a step of forming crystal defects in a semiconductor substrate; a step of heat-treating the semiconductor substrate to form a defect-free layer on its surface; and a step of forming an epitaxial layer on the defect-free layer of the semiconductor substrate. A method of manufacturing a semiconductor device, comprising: