JPS58123721A - Impurity doping method onto semiconductor crystal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in impurity doping techniques in semiconductor devices.

In the manufacture of diodes, transistors, and integrated circuits, the most basic and important technique is to selectively dope a predetermined region of a semiconductor crystal with a predetermined impurity by diffusion or ion implantation. There are ion implantation methods and diffusion methods for doping only a predetermined region with impurities. For example, in ion implantation, it is most common to apply photoresist to a wafer, then provide a photoresist window in a predetermined area, and perform ion implantation through this window.

For diffusion, a mask material such as 5ins, Si@N4, etc. is normally used, and diffusion through the window of this mask material is utilized.

In any case, the doping mask must have windows formed at precisely predetermined positions, but in conventional methods, the pattern of the photomask depends on how accurately the windows can be opened at the positions of the predetermined areas. It is determined by the positioning accuracy when exposing and transferring the image to the photoresist, but with conventional exposure equipment, the limit is ±1 μm, and it has been difficult to obtain higher accuracy. In recent years, the demand for improved high-frequency characteristics and increased integration of semiconductor devices has become stronger and stronger, but in order to meet these demands, it is necessary to reduce the size of the devices. There is an increasing demand for highly accurate positioning in even smaller areas.

The present invention was made in view of this situation.
The purpose is to perform doping with two types of impurities with highly accurate alignment of 1 μm or less.

The present invention will be explained in detail below using figures.

In FIG. 1, 1 is a semiconductor crystal, for example semi-insulating GaA
s crystal substrate. A conductive type region 2 is formed by doping impurities by ion implantation using a mask pattern 3 formed on the surface of the substrate. In the example, 7 with a thickness of 1.5 μm
A mask pattern 8 was formed by forming a pattern on the photoresist using ordinary glue lithography.

As for the ion implantation conditions, 6×101' daughter Si ions were implanted with an implantation energy of 200 KeV.

As a result, the density was 3.2×10 at a depth of 0.17 μm.
A conductivity type region having a peak of 1 mm/ffi'' was obtained.

Next, as shown in FIG. 2, a thin film 4' is formed on the entire surface of the sample, and the mask pattern 3 is removed to obtain a mask pattern 4 as shown in FIG. In the example, a 0.3 μm thick SiOs film was deposited on the entire surface of the sample by vacuum evaporation, and 7 photoresist patterns 8 were removed with acetone.

This apprentice 2 is doped with impurities to form a new conductivity type region 2'. For example, Si ions are implanted with an implantation energy of 50KeV and an implantation amount of 1.8XIQts dose/ffi", and a concentration of 2X 10" is implanted at a depth of 0.04μm.
A conductivity type region 2' having a peak of α8 was obtained. Finally, by activating the implanted element by annealing, impurity doping with two types of conductivity type regions is realized.

In the present invention, the essential element is to dope the impurity by reversing the mask pattern, and as a result, the conductivity type regions are in contact with each other as shown in FIG. 8 without any advanced alignment. It is characterized by the formation of These conductivity type regions are expanded laterally by high temperature treatment such as annealing and automatically and dynamically overlap, so that electrical connection can be easily obtained.

Obviously, the present invention can be modified and applied in various ways other than the above examples. -For example, photoresist 3 is made of Ti, Mo,
Other metals that can be etched with high precision, such as Ta and At, or insulators made of inorganic compounds such as SiOs, or organic compounds such as polyimide may also be used.

In addition, the thin film 4' serves as a mask for ion implantation and thermal diffusion.
And if the mask in step 3 is made of a material that can be selectively removed, this meets the requirements of the present invention! Tasu. For this purpose, any material and formation method are possible. For example, inorganic compound films such as silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, zirconium oxide, titanium oxide, At, Ti, W,
It is possible to use a metal film such as Mo or the like, which is made into an insulating film by an anodic oxidation method or the like. Further, the impurity to be doped is not limited to Si, but any N-type or P-type impurity can be used, and in combination with a mask material, other impurity doping methods such as thermal diffusion are also possible. Further, the crystal is not limited to GaAs, and materials such as Si, Ge, and InP can be used.

As described above, according to the present invention, after the first doping is performed for the first seven turns, the second doping is performed while maintaining the positional relationship of the patterns. Because the relative positions of the first and second doping can be set extremely precisely, two conductive layers with different depths, concentrations, conductivity types, etc. can be placed adjacent to each other with high accuracy. can be formed with.

[Brief explanation of the drawing]

1 to 8 are cross-sectional views showing one embodiment of the present invention. 1...Semiconductor crystal substrate 2...-Conductivity type region 2'...Second conductivity type region 3...Mask material 4...1 Mask/pattern 4'...Thin film for mask

Claims (1)

[Claims] 11 In a method of selectively doping impurities into a semiconductor crystal, a mask material is formed on the surface of the semiconductor crystal, and this is used as a mask to perform the first impurity doping, and then the mask material is reversely reversed. An impurity doping method for semiconductor crystal characterized by performing a second impurity doping after forming a mask pattern