JPH0574729A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To avoid the billard phenomena of O ions thereby enabling a high quality diffused layer to be formed by using poly Si or amorphous Si as the covering film of a silicon substrate. CONSTITUTION:A multitude of element formation regions 3 encircled by separation insulating films 2 comprising SiO2 are formed on a phosphorus-doped N type Si substrate 1. A covering film 4 comprising phosphorus-doped poly-Si is formed on this substrate 1 using CVD process. Next, this substrate is ion- implanted with boron fluoride to form P type well in the element formation region 3 and then the substrate 1 is annealed for activation in N2 current to form a semiconductor region 5. Next, the whole body is immersed in a water solution using KOH, isopropanol and ethylenediaminepyrocatechol as a solute to remove the N type covering film 4. Through these procedures, such a problem of quality deterioration in a diffused layer due to the billiard phenomena of O ions during the ion implantation step can be solved thereby enabling a high quality semiconductor region to be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a semiconductor region (diffusion layer) by an ion implantation method. A semiconductor device is one in which a semiconductor region having different conductivity types is formed by diffusing ions capable of controlling electron valence on a semiconductor substrate, and the device is formed using this semiconductor region.

Here, as a method of forming a semiconductor region, initially, a thermal diffusion method in which a gas containing an impurity element or an impurity element is brought into contact with a semiconductor substrate to perform solid phase-vapor phase diffusion or solid phase-solid phase diffusion. Although it was used, the ion implantation method (Ion Implantation), which ionizes the impurity element and gives high energy to it to implant it into the semiconductor substrate, is now mainly used because it is easy to control the concentration and depth of the impurity element. It is being used.

[0003]

2. Description of the Related Art Conventional ion implantation methods perform ion implantation.
A silicon dioxide (SiO ₂ ) film is provided on a Si substrate, and ion implantation is performed using this as a cover film.

[0004] Specifically, making the dried oxygen (O ₂₎ SiO ₂ film having a thickness of several 100 Å on the Si substrate by heat-treating the Si substrate at a temperature of about 900 ° C. in a gas atmosphere, the SiO ₂ Ion implantation is performed using the film as a cover film, and subsequently, heat treatment is performed in an atmosphere of an inert gas such as nitrogen (N ₂ ) to form a stable lattice structure, thereby forming a semiconductor region.

This heat treatment is generally called activation annealing. After this process is completed, the cover film made of SiO ₂ is removed using hydrofluoric acid (HF) to expose the semiconductor region.

The feature of using the cover film is to prevent contamination by impurities penetrating from the outside during the process of heat treatment during ion implantation and the subsequent heat treatment. However, when ion implantation is performed using the SiO ₂ film as a cover film, a phenomenon occurs in which O ions forming SiO ₂ are hammered into the Si substrate due to a beading phenomenon, and the O ions form donor-type impurities, Problems such as forming defects in the semiconductor region and changing the diffusion coefficient of ion-implanted impurity ions have occurred.

[0007]

Ion implantation is carried out through a cover film made of SiO _2. However, due to accelerated collision of ions, a beading phenomenon of O ions constituting SiO ₂ is generated and the ions are hit into the Si substrate. As a result, there is a problem that the quality of the diffusion layer deteriorates, and the solution is a problem.

[0008]

[Means for Solving the Problems] The above problems are not applicable to Si substrates.
Ion implantation of pure ions to form semiconductor region on Si substrate
In the process of
Poly Si or amorphous Si containing ON is a cover film for this substrate.
Or on top of this SiO₂Membrane or Si ₃N_FourThe membrane
Constructing a method of manufacturing a semiconductor device by using it as a coating
Can be solved by.

[0009]

The present invention uses poly-Si or amorphous Si as the cover film as a method of eliminating the beading phenomenon of O ions constituting the cover film when performing ion implantation.

By adopting such a method, the conventional problems can be eliminated because the O ions are not driven in and the cover film and the substrate are made of the same material. However, the problem that occurs when using poly-Si or amorphous-Si as the cover film is that the cover film needs to be removed after the activation annealing is finished, but since the substrate is the same material, selective dissolution does not occur. Have difficulty. Unlike the SiO ₂ film, the poly Si film or the amorphous Si film is inferior in the effect of preventing the diffusion of impurities from the outside in the processing steps such as activation annealing.
Contamination of the semiconductor region is more likely to occur than when a SiO ₂ film is used as the cover film. And so on.

As a countermeasure against the above problem, the present invention enables selective dissolution by making the conductivity type of the cover film different from the injection species. That is, when boron (B) is implanted into an N-type Si substrate to form a P-type diffusion layer, a poly-Si film or an amorphous Si film containing an N-type impurity should be formed as a cover film. For example, since the semiconductor region becomes P-type by ion implantation, only the cover film can be removed by immersing it in an aqueous solution of caustic potassium (KOH), isopropanol, and ethylenediaminepyrocatechol, which hardly dissolve B and Si.

As a countermeasure against the above problem, in the present invention, if necessary, a thin film of SiO ₂ or Si ₃ N ₄ conventionally used as a cover film is laminated on a cover film made of poly-Si or amorphous Si. It is a thing.

If this is done, it is necessary to increase the acceleration voltage for ion implantation, which seems to be disadvantageous, but the thickness of the SiO ₂ film or Si ₃ N ₄ film may be several tens of Å.
Therefore, the acceleration voltage can be slightly increased.

Next, the poly-Si film or amorphous Si film containing impurity ions of a type different from that of the implanted species according to the present invention is C
It can be formed using a conventional film forming method such as a VD method, a plasma CVD method, a sputtering method.

Here, in order to form poly-Si or amorphous Si by the CVD method, the material used and the Si substrate temperature may be selected. For example, in order to form a poly-Si film, silane ( SiH ₄ ) may be used at a substrate temperature of about 650 ° C., and disilane (Si ₂ H ₆ ) may be used at a substrate temperature of about 450 ° C. to form an amorphous Si film.

The substrate temperature can be further lowered by using the plasma CVD method.

[0017]

EXAMPLE 1 FIG. 1 is a cross-sectional view showing the steps for carrying out the present invention, which is an N-type Si substrate 1 doped with phosphorus (P).
A plurality of element forming regions 3 are formed on the upper surface of the device and surrounded by the isolation insulating film 2 made of SiO ₂ .

A cover film 4 made of P-doped poly-Si having a thickness of 200Å was formed on such a substrate by the CVD method. The processing conditions are H ₂ as a carrier gas, SiH ₄ as a source gas, and phosphine (P) as a dopant.
Using H ₃ ), the substrate temperature was kept at 650 ° C. and the gas phase reaction was carried out for 2 minutes. Next, boron fluoride ion (BF ₂ ⁺ ) was ion-implanted into this substrate to form a P-type well in the element formation region 3.

The implantation conditions are an energy of 60 KeV and a dose of 4 × 10 ¹⁵ / cm ² . Next, the substrate in an N ₂ stream 1200
Activation annealing was performed at 6 ° C. for 6 hours to form the semiconductor region 5. Next, the N-type cover film 4 was removed by immersing it in an aqueous solution containing KOH, isopropanol, and ethylenediaminepyrocatechol as solutes. Example 2 Using the same substrate as that used in Example 1, a cover film 4 made of P-doped poly-Si having a thickness of 200 Å is formed by the same CVD method as in Example 1. Formed.

Next, PH ₃ is switched to oxygen gas (O ₂ ),
Use a SiH ₄ -O ₂ reaction system and keep the substrate temperature at 425 ℃.
CVD was performed for a period of time to form a SiO ₂ film having a thickness of about 50Å.

Next, an ion implanter was used for this substrate, and BF ₂ ⁺ was added at an energy of 60 KeV and a dose of 4 × 10 ¹⁵ / c.
After performing ion implantation under m ² condition, activation annealing was performed at 1200 ° C. for 6 hours in N ₂ gas flow to form a semiconductor region.

Next, the SiO ₂ film forming the cover film is dissolved and removed by immersing in an HF aqueous solution, and then the N type poly-Si film is removed by immersing in an aqueous solution containing KOH, isopropanol and ethylenediaminepyrocatechol as solutes. It was

[0023]

As a result of the practice of the present invention, SiO _{2 is used} as the cover layer.
When using, it is possible to eliminate defects and deterioration of electrical characteristics that occur in the semiconductor region, and it is possible to form a good-quality semiconductor region.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a process of the present invention.

[Explanation of symbols]

 1 Si substrate 3 element formation region 4 cover film 5 semiconductor region

Claims (2)

[Claims] 1. In the step of implanting impurity ions into a silicon substrate to form a semiconductor region in the silicon substrate, the substrate is covered with polysilicon or amorphous silicon containing impurity ions of a type different from the implantation species. A method for manufacturing a semiconductor device, which is used as a film. 2. The polysilicon or amorphous silicon used as the cover film is further covered with a silicon dioxide film or a silicon nitride film for use.
A method of manufacturing a semiconductor device according to claim 1.