JPS5834932B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device using ion implantation.

When using ion implantation, it is possible to precisely measure the number of ions (dose) implanted into a semiconductor substrate, so it is possible to convert the conductivity type or conductivity of a semiconductor with extremely high precision, and even within the same substrate. Complementary field effect transistor (CMO8) which requires both p and n channels
) plays a particularly important role.

However, absolutely. When applying ion implantation to a semiconductor thin film formed on an insulating substrate, charge accumulates on the insulating substrate and the ion beam is disturbed, so the ion implantation cannot be carried out as accurately as when using ordinary bulk silicon. It is difficult to perform driving.

Single-crystal sapphire was selected as the insulating substrate, and a single-crystal silicon thin film was epitaxially grown on the sapphire.
FIGS. 1 and 2 show conventional examples of the case where e) is used.

In FIG. 1, an SO 8 is constituted by a sapphire substrate 2 and a single crystal silicon film 3.

A silicon oxide film 4 is formed on the single crystal silicon film 3 by thermal oxidation to a thickness of about 100 OA.

The oxide film 4 prevents channel ring during ion irradiation.

It is used to achieve uniform doping.

Next, after a mask material 5 is deposited over the entire surface, an opening 5' is formed and an ion beam 7 is irradiated to implant ions through the oxide film 4 to a predetermined depth in the silicon film.

The mask material 5 may be either a thick oxide film or a photoresist film.

If the mask material 5 is a photoresist, it is removed, and if the mask material 5 is a silicon oxide film, it is not removed as it is, but implanted ions are diffused in a diffusion furnace to determine the conductivity type of the predetermined region 8. Or conductivity conversion.

In FIG. 2, after forming a single crystal silicon film on a sapphire substrate 2 into an island shape, the oxide film 4 is provided, a mask material 5 is selectively formed, and ion implantation is subsequently performed. The diffusion of is as described above.

Now, after the diffusion is completed, the mask material 5 and the oxide film 4 are removed to proceed to the next step, but in the manufacturing method shown in FIG. The surface is almost flat with only a very small impact trace remaining, making it extremely difficult to align the photomask in the next step.

Therefore, some chips on the wafer must be sacrificed to leave the mask material 5 on the silicon surface 3, and the remaining mask material 5 must be used as a target for mask alignment, which has the disadvantage of complicating the process. was.

On the other hand, in the manufacturing method shown in FIG. 2, since the island-shaped single crystal silicon layers 9 and 10 are formed on the sapphire substrate 2, mask alignment is extremely easy.

However, with the manufacturing method explained in FIG. 2, it is difficult to accurately control the conversion of conductivity type or conductivity. Therefore, when configuring CMO8, the threshold voltage (1) fluctuates greatly, making it difficult to manufacture with high yield. could not.

The variation in VT is particularly remarkable in transistors whose conductivity type has been converted by ion implantation.

As a result of further studies on this point, the inventors of the present invention found that the manufacturing method shown in FIG. 1 allows conversion of conductivity type or conductivity to be relatively well controlled.

That is, in FIG. 1, since there is a conductive single crystal silicon film 3 over the entire surface of the sapphire substrate 2, the beam current passes through the silicon film 3 and the sapphire substrate 2 at a uniform current density. On the other hand, in FIG. 2, since the silicon film 9.10 separated into islands exists on the sapphire substrate, the beam current passes through the sapphire substrate 2 and reaches the sample holder 1. The current density is different when it flows to the sample holder 1 and when it flows to the sample holder 1 through the silicon island and the sapphire substrate 2, and when the charge is accumulated on the silicon island, the current density increases further. This is thought to be due to the increased disturbance.

In FIG. 1, reference numeral 6 denotes a metal piece for pressing the semiconductor substrate onto the sample holder 1 of the ion implanter.

The present invention solves the above problems, and is capable of converting the conductivity type or conductivity of a semiconductor layer on an insulating substrate with good reproducibility and sufficient accuracy, and is not affected by the shape of the semiconductor layer. It also has major features.

The details of the present invention will be explained with reference to the embodiments shown in FIG. 3 and below.

First, 50%
A silicon oxide film of approximately 00A is deposited, and subsequently a photoresist film is selectively left on the silicon oxide film by a well-known photo process.

Using the photoresist film as an etching mask, the silicon oxide film is etched to remove the resist.

Next, by etching the single crystal silicon film in a strong alkaline solution such as KOH using the silicon oxide film as a mask, a single crystal silicon island 9 having a trapezoidal cross section as shown in the figure is formed.
, 10 can be obtained.

After removing the silicon oxide film, a conductive thin film 1 is formed on the entire surface.
1 is precipitated.

The thin film 11 is made of Al, for example, 1200. If it is deposited to a thickness of A, the channeling prevention effect will be the same as that of a silicon oxide film with a thickness of 1.00 OA.

FIG. 3 shows a state in which a resist film is selectively formed as a mask material 5 for ion implantation.

It is sufficient that the thickness of the resist film is 5000A or more.

In FIG. 4, a silicon oxide film is selectively formed as a mask material 5 on a silicon film to a thickness of 5000 Å or more, and then a conductive thin film 11 is deposited on the entire surface.

In both FIGS. 3 and 4, the ion beam 7 is a conductive thin film;
ionized dopant atoms are implanted into the silicon island 9.

On the other hand, since the mask material 5 exists on the silicon island 10, dope atoms are not implanted into the silicon island 10.

After the ion implantation is completed, the mask material 5 and the conductive thin film are removed, a silicon oxide film for preventing contamination is deposited on the entire surface, and a heat treatment is performed in a diffusion furnace to complete the conversion of the conductivity type or conductivity of the desired region. do.

As is clear from the above explanation, in converting the conductivity type or conductivity of a semiconductor thin film on an insulating substrate using the ion implantation method according to the present invention, since there is a conductive thin film on the semiconductor thin film, No charge is accumulated in the semiconductor thin film,
In addition, the current density when the sample holder 1 heavy beam current flows through the semiconductor thin film and the sapphire substrate due to the shielding effect of the conductive thin film, and when the sample holder 1 heavy beam current flows through the sapphire substrate. will be the same.

Therefore, the doped atoms are uniformly implanted in the predetermined region where the ions are implanted, and in the SOS-CMO8 in which the ions are implanted according to the present invention, the variation in the threshold voltage V can be suppressed to less than ±0.1■. Ta.

In FIG. 1, even if 4 is a conductive thin film and the mask material 5 is a resist film, the object of the present invention can be achieved, and the conductivity type or conductivity change can be converted with much higher accuracy and reproducibility than in the past. However, the drawback is that mask alignment is difficult in the next process.

It is clear that the conductive thin film is not limited to AA, but may also be metals such as W or Mo, or carbon, and the deposition on the semiconductor substrate is not limited to vapor deposition, but may also be performed by spuck or electroless plating.

It is also possible to use spinel as the insulating substrate.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views of conventional ion implantation into a semiconductor thin film on an insulating substrate, and Figures 3 and 4 are sectional views of ion implantation into a semiconductor thin film on an insulating substrate using the method of the present invention. A cross-sectional view of the case is shown. 1... Sample holding stand of ion implanter, 2...
...Insulating substrate, 3...Semiconductor thin film, 4...
...Silicon oxide film for preventing channeling, 5...
...Mask material, 7...Ion beam, 9.10
・・・・・・Semiconductor device separated into islands

Claims (1)

[Scope of Claims] 1. A conductive thin film is deposited on a semiconductor thin film formed on an insulating substrate or a semiconductor thin film formed in island shapes on an insulating substrate, and a resist is applied to predetermined areas. 1. A method of manufacturing a semiconductor device, characterized in that after selectively depositing a semiconductor thin film, ions are implanted through the conductive thin film to convert the conductivity type or conductivity of the semiconductor thin film. 2 After selectively depositing an insulating film on a semiconductor thin film formed on an insulating substrate or on a semiconductor thin film formed in island-like manner on an insulating substrate, and depositing a conductive film on the entire surface. A method of manufacturing a semiconductor device, characterized in that the conductivity type or conductivity of the semiconductor thin film is converted by implanting ions through the conductive thin film. 3. The method of manufacturing a semiconductor device according to claim 2, wherein a silicon oxide film is used as the insulating film.