JP2518378B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device using a crystal defect due to oxygen precipitation nuclei in a silicon substrate as a gettering source.

[Conventional technology]

In recent manufacturing of high-density and highly integrated semiconductor devices, it is general to use some kind of gettering method to remove impurities in a silicon substrate. Among these, the gettering method that utilizes oxygen in the silicon substrate by utilizing precipitation nuclei is called intrinsic gettering (hereinafter referred to as IG). This is a technique for gettering contaminant impurities that infiltrate into a crystal defect region inside a silicon substrate during the manufacturing process of a semiconductor device.

As a method of intentionally applying IG, a method combining a long-term high-temperature heat treatment and a long-term low-temperature heat treatment is generally used. The high temperature heat treatment is for diffusing and releasing oxygen near the surface of the silicon substrate out of the silicon substrate (hereinafter referred to as outward diffusion), and the low temperature heat treatment is for growing defect nuclei inside the silicon substrate. In the outward diffusion of oxygen by high-temperature heat treatment, the precipitation of oxygen, which is the nucleus of crystal defect generation, should not occur on the silicon substrate surface by the next low-temperature heat treatment, so the oxygen concentration on the silicon substrate surface should be less than the solid solubility of oxygen. And have to. Therefore, when this kind of heat treatment is applied to a silicon substrate, the oxygen concentration at the outermost surface of the silicon substrate is 10 ^{-16 to} 10 ^-17 atoms / cm ³ (ASTM F-121-7
6) is generally used.

In addition, in the process of manufacturing semiconductor devices,
A similar phenomenon occurs. Particularly in the manufacturing process of the CMOS type semiconductor device, the oxygen concentration on the surface of the silicon substrate is lowered due to the outward diffusion of oxygen on the surface of the silicon substrate due to the high temperature heat treatment for forming the well.

[Problems to be Solved by the Invention]

Oxygen in the silicon substrate has the function of fixing dislocations and increasing the mechanical strength of the silicon substrate, but the oxygen concentration is 10 ¹⁸ atoms.
It is generally known that if it is lower than / cm ³ , its function is reduced.

In the above-described conventional method for manufacturing a semiconductor device, in order to reduce the oxygen concentration on the surface of the silicon substrate that is the semiconductor element forming layer, the thin film pattern end portion such as a silicon oxide film or a silicon nitride film that is a substance forming the semiconductor device is formed. Due to stress
There is a drawback that crystal defects such as dislocations are easily introduced into the surface of the silicon substrate.

Particularly in recent high-density and highly integrated semiconductor devices, the thin film pattern has become complicated and fine, so that crystal defects such as dislocations are likely to be introduced due to stress at the end of the pattern.

For example, element isolation is applied to the field silicon oxide film edge or the silicon substrate surface due to film stress at the silicon oxide film edge by the CVD method that is the gate sidewall material of the LDD (low-concentration drain) structure transistor for suppressing hot carriers. These are dislocations that occur.

The semiconductor device in which these crystal defects are introduced has a drawback that the electrical characteristics of the semiconductor element are deteriorated and the yield and reliability thereof are deteriorated.

An object of the present invention is to increase the mechanical strength of the surface of a silicon substrate while sufficiently maintaining the effect of IG, improve the electrical characteristics of semiconductor elements, and provide a method of manufacturing a semiconductor device with high yield and reliability. .

[Means for solving the problem]

According to the method of manufacturing a semiconductor device of the present invention, in a method of manufacturing a semiconductor device in which oxygen is precipitated in a silicon substrate by heat treatment to introduce crystal defects into the silicon substrate, oxygen precipitation nuclei are grown inside the silicon substrate. After introducing the crystal defects, a silicon nitride film is deposited on the surface of the silicon substrate, and then heat treatment is performed to make the oxygen concentration distribution in the entire silicon substrate uniform.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a distribution diagram in the depth direction when the oxygen concentration in the silicon substrate of one embodiment of the present invention is measured by SIMS (secondary ion mass spectrometry).

First, a silicon substrate containing 1.8 × 10 ¹⁸ atoms / cm ³ of oxygen is subjected to heat treatment at 1200 ° C. for 3 hours to outwardly diffuse oxygen near the surface of the silicon substrate. By this treatment, the oxygen concentration on the surface of the silicon substrate is 10 ¹⁶ atoms / c as shown by the curve L ₁ in FIG.
the m ^3. Next, heat treatment is performed at 700 ° C. for 4 hours to grow oxygen precipitation nuclei inside the silicon substrate having a high oxygen concentration.

Then, a known LPCVD (Low Pressure Vapor Deposition) method is used to deposit a silicon nitride film on the surface of a silicon substrate having a thickness of 50 nm, and heat treatment is performed at 1200 ° C. for 3 hours in an oxygen atmosphere. Oxygen diffuses to reach the concentration shown by the curve L ₂ in FIG. That is, the oxygen concentration on the surface of the silicon substrate is
^10/18 atoms / cm ^3, and the can have a sufficient mechanical strength against stress of the thin film pattern end portion.

After performing these treatments, the dislocation generated from the silicon oxide film end portion of the sample on which the field silicon oxide film was formed by the normal selective oxidation method was observed by the selective etching method. Was not observed at all. On the other hand, 10 for the sample prepared by the conventional method.
Dislocations of dislocations / cm ² were observed. In the conventional method, the field silicon oxide film is formed with the oxygen concentration on the surface of the silicon substrate kept at 10 ¹⁶ atoms / cm ³ .

As described above, according to this embodiment, no dislocation is generated from the end portion of the field silicon oxide film, and deterioration of the mechanical strength of the silicon substrate surface can be prevented. Therefore,
The semiconductor element provided in this region has no deterioration in electrical characteristics, and a high-quality semiconductor device can be obtained with high yield.

When the silicon nitride film is directly deposited on the surface of the silicon substrate, a crystal defect may occur on the surface of the silicon substrate in which a large strain has occurred depending on the deposition conditions. In such a case, a desirable result can be obtained by once depositing an oxide film of 10 to 50 nm and then providing a silicon nitride film.

FIG. 2 is a cross-sectional view of a semiconductor chip in another main step of applying the invention to a CMOS type semiconductor device composed of an LDD structure transistor.

First, as shown in FIG. 2A, an N-type silicon substrate 1
After the boron is ion-implanted on the surface of the substrate, the P well 2 is formed by heat treatment at 1150 ° C., and then the silicon oxide film 3 to be a field is selectively formed.

Next, as shown in FIG. 2 (b), a silicon nitride film 4 is deposited on the surface of the silicon substrate 1 to a thickness of 50 nm by the LPCVD method. Then, when heat treatment is performed at 200 ° C. for 3 hours in an oxygen atmosphere, oxygen diffuses from the inside of the silicon substrate to the surface.

Next, as shown in FIG. 2 (c), MO
The gate 5 of the S transistor, the silicon oxide film 6 serving as the gate sidewall material, and the source / drain 7 are formed by the CVD method.
Structure an OS type semiconductor device.

FIG. 3 is a diagram showing the reverse voltage-current characteristics of the PN junction of the CMOS type semiconductor device when the horizontal axis represents the reverse bias voltage (V) and the vertical axis represents the reverse current (A / cm ² ). Curve A in the figure
Is the characteristic of the CMOS type semiconductor device manufactured by the conventional method, and the curve B is the characteristic when manufactured by the method of the present embodiment. It should be noted that this conventional method is a method of immediately manufacturing a CMOS semiconductor device by forming a field silicon oxide film, and the oxygen concentration on the surface of the silicon substrate is 10 ¹⁶ to 10 ^{16.
It is of 17} atoms / cm ³ .

As is apparent from FIG. 3, in this embodiment (curve B), the reverse current with respect to the reverse bias is extremely small compared to the conventional example (curve A). This is because the conventional method has a low oxygen concentration on the surface of the silicon substrate, so that dislocations are introduced into the surface of the silicon substrate due to the stress at the edges of the silicon oxide film that is the gate sidewall material of the transistor.
The reason why the IG effect does not appear despite the formation of internal defects is that dislocations on the surface of the silicon substrate trap contaminant impurities.

When the crystal defects on the surface of the sample for which the measurement results of curves A and B were obtained were observed by the selective etching method, 5 dislocations / cm ² were observed in the sample prepared according to this example. Dislocations of 150 dislocations / cm ² were observed in the sample prepared by the method.

As described above, according to this embodiment, the reverse current of the PN junction is reduced, and a high-performance and high-quality semiconductor device can be obtained with a high yield.

〔The invention's effect〕

As described above, according to the present invention, in order to make the oxygen concentration of the defect-free layer on the surface of the silicon substrate equal to that of the inside, after introducing internal defects by the precipitation nuclei of oxygen, silicon nitride is prevented from diffusing outward. By depositing the film on the surface of the silicon substrate and subjecting it to heat treatment to diffuse the oxygen remaining in the interior to the surface of the substrate, the mechanical strength on the surface of the silicon substrate can be increased and the stress of the thin film, etc. can be increased. This has the effect of suppressing the crystal defects introduced on the surface of the silicon substrate. Therefore, it is possible to obtain a semiconductor device with improved yield and reliability without deterioration of the electrical characteristics of the semiconductor element.

[Brief description of drawings]

FIG. 1 is a distribution diagram of oxygen concentration in a silicon substrate in a depth direction for explaining the first embodiment of the present invention, and FIG. 2 is a CMOS type semiconductor device in which the present invention is composed of an LDD structure transistor. FIG. 3 is a cross-sectional view of a semiconductor chip in a main step when applied to FIG. 3, and FIG. 3 is a diagram showing reverse voltage-current characteristics of a PN junction in an example and a conventional example. 1 ... N-type silicon substrate, 2 ... P well, 3,6 ... silicon oxide film, 4 ... silicon nitride film, 5 ... gate,
7 ... Source / drain.

Claims (1)

(57) [Claims] 1. A method of manufacturing a semiconductor device in which oxygen is precipitated in a silicon substrate by heat treatment to introduce crystal defects into the silicon substrate. In the method, oxygen precipitation nuclei are grown in the silicon substrate to introduce crystal defects. After that, a silicon nitride film is deposited on the surface of the silicon substrate, and then heat treatment is performed to make the oxygen concentration distribution of the entire substrate in the silicon substrate uniform.