JPH02278818A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a shallow diffusion region with good accuracy without a restriction that a crystal silicon film must be left after a diffusion operation by a method wherein a polycrystalline carbon film is formed on a substrate, impurities are implanted into the carbon film by an ion implantation operation, the impurities are diffused into the substrate by a heat treatment and an impurity diffusion region is formed. CONSTITUTION:An SiO2 field insulating film 2 and a polycrystalline Si gate electrode 3 are formed on a p-Si substrate 1; a polycrystalline carbon film 4 is formed on the whole surface on them by a CVD method by pyrolyzing a hydrocarbon; As<+> ions are implanted. Then, a heat treatment is executed in an atmosphere of nitrogen; As in the carbon film is diffused to the substrate 1 and the gate electrode 3; a source/drain region 5 as an impurity diffusion region is formed in the substrate 1. Then, the carbon film 4 is removed by a mixed solution of heated concentrated sulfuric acid and hydrogen peroxide. Thereby, a shallow diffusion region can be formed with good accuracy without a restriction that a polycrystalline silicon film used as a solid diffusion source must be left after a diffusion operation.

Description

[Detailed Description of the Invention] [Summary] Regarding a method of manufacturing a semiconductor device, particularly a method of forming an impurity diffusion region on the surface of a semiconductor substrate, a polycrystalline silicon film serving as a solid phase diffusion source is not left behind after diffusion. The purpose of this method is to form a shallow diffusion region with high precision without any constraints such as not being able to obtain the desired results, by forming a polycrystalline carbon film on a semiconductor substrate and implanting impurities into the carbon film by ion implantation. and a step of diffusing the impurity in the carbon film into the substrate by heat treatment to form an impurity diffusion region in the substrate.

[Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming an impurity diffusion region in a surface portion of a semiconductor substrate.

In the impurity diffusion region formed on the surface of the semiconductor substrate,
Examples include source/drain regions of field effect transistors (FETs), base regions and emitter regions of bipolar transistors.

As semiconductor devices become more highly integrated and elements become thinner, these diffusion regions are required to be formed with shallower and shallower depths.

[Conventional technology]

The methods for forming the above-mentioned diffusion regions are divided into two types: (1) a method using ion implantation, and (2) a method using a method other than ion implantation.

■The method using ion implantation has high accuracy,
It is widely used because of its low distribution variation. However, since this method uses the principle of accelerating ions and implanting them, the implanted impurity ions enter the substrate at a depth and spread in the depth direction, reducing the depth of the diffusion region to, for example, 1,500 mm. There is a problem in that it is difficult to form a structure smaller than that of a human.

In method (2), a polycrystalline silicon film is formed on the substrate, impurities are implanted into the polycrystalline silicon film by ion implantation, and the impurities are removed by subsequent heat treatment. There is a method of diffusing it onto a substrate (solid-phase diffusion). According to this method, it is easier to form the diffusion region with good precision (and its depth is shallower than in method (2)).

However, this method has the problem that it is difficult to selectively remove the polycrystalline silicon film with respect to the substrate, so the polycrystalline silicon film used as a source of sales must be left as is.

Other methods for (2) include using an impurity gas as a diffusion source and using a film containing impurities during growth (for example, a PSG film) as a diffusion source for solid-phase diffusion, but none of these methods work. This method is inferior to method (2) in terms of precision and distribution, and is hardly used for forming diffusion regions in highly integrated semiconductor devices that require precision.

[Problem to be solved by the invention]

From the above, the present invention provides a method for manufacturing a semiconductor device, particularly a method for forming an impurity diffusion region on the surface of a semiconductor substrate, in which a polycrystalline silicon film serving as a solid phase diffusion source must be left after diffusion. The purpose of this invention is to enable formation of shallow diffusion regions with high precision without such constraints.

[Means to solve the problem]

The above purpose is to form a polycrystalline carbon film on a semiconductor substrate, to inject impurities into the carbon layer by ion implantation, and to diffuse the impurities in the carbon film into the substrate by heat treatment. This is achieved by the manufacturing method of the present invention in which an impurity diffusion region is formed in the substrate.

[For production]

In this method, the polycrystalline silicon film is replaced with polycrystalline carbon in the previously described method in which a polycrystalline silicon film is used as a solid-phase diffusion source. Since this carbon film is polycrystalline, it can serve as a solid phase diffusion source similar to a polycrystalline silicon film, and can be easily removed selectively with respect to the substrate by oxidation.

That is, the impurity concentration distribution diagrams in Figures 1(a) to (C) explain the principle of forming an enlarged rPI LR region by this method, where the vertical axis is the impurity concentration (log scale) and the axis of detection is the depth. The distance in the horizontal direction, A is the polycrystalline carbon film, B is the semiconductor substrate, C is the impurity diffusion region, (a) is the state after ion implantation, (b) is the state after heat treatment, (C) shows the state in which the carbon film has been removed after heat treatment.

In the state of (a), impurities are in the carbon film A and in the substrate B.
It's not included. This can be easily achieved by making the thickness of the carbon l1uA about 2,000 or more, for example, and adjusting the acceleration energy of ion implantation appropriately.

Since carbon film A is a polycrystalline structure composed of microcrystals, impurities diffuse quickly inside the carbon film A due to heat treatment.
Due to the heat treatment, the impurities therein quickly reach the interface between the carbon film A and the substrate B, and diffuse into the substrate B using the carbon film A as a solid-phase diffusion source, forming a diffusion region C as shown in FIG. The depth of the diffusion region C can be adjusted by selecting the concentration of ion implantation into the carbon film A and the heat treatment conditions, and since the ion implantation can be performed uniformly, there is little distribution variation.

The removal from the carbon film to the state (C) involves oxidation (C+oz
=CO□) can be easily performed selectively to the substrate B and without roughening the surface of the substrate B. This means that
This method differs greatly from the previously described method in which a polycrystalline silicon film is used as a solid-phase diffusion source.

From the above, according to the present method, it is possible to form a shallow diffusion region with high precision without the above-mentioned restrictions.

〔Example〕

An embodiment of the present invention will be described below with reference to step-by-step side sectional views of FIGS. 2(a) to 2(e).

This embodiment is a case where the present invention is applied to an n-channel MO5FET. That is, in Fig. 2, first (
Referring to a), a 4000-thick StO□ field isolation 8i film 2,
3000mm thick polycrystalline Si with gate insulating film interposed
A gate electrode 3 is formed.

Next, referring to (b), a hydrocarbon (
For example, CHa, Cz Hb, C3Hll, C2H
, , C, H, , Cz H2, etc.) by thermal decomposition of
A polycrystalline carbon film 4 with a thickness of 3000 μm is formed by the VD method, and As'' ions are implanted at an acceleration energy of 100 KeV and a dose of 14 It is a Gaussian distribution with about 520 people and a standard deviation of about 130 people.

Then, referring to (C), heat at 850°C3 in a nitrogen atmosphere.
Heat treatment for 1O is applied to diffuse As in the carbon film 4 into the substrate 1 and the gate electrode 3. As a result, source/drain regions 5, which are impurity diffusion regions, are formed in the FiI base to a depth of approximately 1000 nm.

Next, referring to (d), the carbon film 4 is removed using a heated mixed solution of concentrated sulfuric acid and hydrogen peroxide. The carbon film 4 is selectively removed without roughening the underlying surface.

Next, referring to (e), an interlayer insulating film 6 and an At electrode 7 are formed by a conventional method to complete the FET.

Conventionally, in the manufacture of such FETs, direct ion implantation has been used to form the source/drain regions 5, but it is difficult to achieve a depth of about 1000 using this conventional method. This is made possible by the method of the present invention described in the Examples. However, according to the method of the present invention, the depth of the source/drain region 5 can be made even shallower by appropriately selecting the conditions for ion implantation and heat treatment, as described above. This facilitates further miniaturization of the FET.

Although the above embodiment takes an example of an FET formed on a Si substrate, the present invention can also be applied to other devices such as bipolar transistors, and is further applicable to solid phase expansion transistors.
Since the polycrystalline carbon film sourced from No. 1 can be selectively removed not only from Si but also from other semiconductors without damaging the underlying layer, new developments in conventional semiconductor devices are expected by application of the present invention. can do.

[Effects of the Invention] As explained above, according to the configuration of the present invention, in a method for manufacturing a semiconductor device, particularly in a method for forming an impurity diffusion region in a surface portion of a semiconductor substrate, polycrystalline silicon as a solid phase diffusion source is used. It is now possible to form shallow diffusion regions with high accuracy without the constraints of leaving a film behind after diffusion, which facilitates further miniaturization of FETs, for example.
This has the effect of enabling new developments in conventional semiconductor devices.

[Brief explanation of drawings]

FIGS. 1(a) to (C) are impurity concentration distribution diagrams for explaining the present invention, and FIGS. 2(a) to (e) are side cross-sectional views of one embodiment in the order of steps. In the figure, A is a polycrystalline carbon film, B is a semiconductor substrate, C is an impurity motion region tPIM region, l is a Si substrate, 4 is a polycrystalline carbon film, and 5 is a source/drain region (impurity diffusion region). .

Claims (1)

[Claims] The process includes forming a polycrystalline carbon film on a semiconductor substrate, injecting impurities into the carbon film by ion implantation, and diffusing the impurities in the carbon film into the substrate by heat treatment. A method of manufacturing a semiconductor device, comprising forming an impurity diffusion region in a substrate.