JPH07120636B2 - Method for manufacturing semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device having improved uniformity of impurity content in an impurity diffusion source in a thermal diffusion process such as an integrated circuit. Is.

2. Description of the Related Art In order to obtain a high-performance element in a semiconductor device, it is necessary to form a junction by shallow irregular substance diffusion. For example,
It is a general method to deposit a polycrystalline semiconductor thin film on a semiconductor substrate, ion-implant impurities into the thin film, and heat-treat to diffuse the impurities into the semiconductor substrate to form a desired shallow impurity diffusion region. Is coming.

Problems to be Solved by the Invention Generally, when depositing a polycrystalline semiconductor thin film, the deposited polycrystalline semiconductor thin film is caused by non-uniformity of temperature distribution in a reaction part, infrared reflection on a semiconductor substrate surface, or the like. The size of the crystal grains is likely to be nonuniform in the plane of the semiconductor substrate. A part of the impurity atoms implanted into such a polycrystalline semiconductor thin film is taken into a boundary between crystal grains, that is, a grain boundary, and inactivated by a heat treatment after implantation. The crystal grain boundary is large in the small crystal grain portion and many impurity atoms are inactivated, and the crystal grain boundary is small in the large crystal grain portion and many impurity atoms are activated in the crystal grain. Therefore, if the crystal grain size of the polycrystalline semiconductor thin film is not uniform, the concentration distribution of the impurities diffused from this film into the semiconductor substrate will be uneven. That is, a bond with poor homogeneity is formed. This has reduced manufacturing yield and product quality. For example, in 1984, the pre-annealing method, in which a polycrystalline semiconductor thin film is heat-treated to uniformize the crystal grain size before ion implantation of atoms that determine the conductivity type, is described in the Journal of Electrochemical Society.
Chemical Society), Vol. 131, No. 1, pp. 216-217, but in order to obtain sufficient uniformity, heat treatment at a high temperature of 1000 ° C. or higher is required, and the actual manufacturing of semiconductor devices. It is not always preferable to apply it to the process. In addition, in the heat-treated polycrystalline semiconductor thin film, the size of the crystal grains becomes larger toward the portion closer to the surface, and it can be seen in 1984 that the Journal of Vacuum Science Technology (Journal of Vacuum Science Technology
logy), B, Vol. 2, No. 4, pages 698-706. If such a crystalline state is assumed, if the polycrystalline semiconductor thin film surface is made amorphous by ion implantation,
In the subsequent heat treatment, small crystal grains in the lower layer of the polycrystalline semiconductor thin film serve as seeds and the surface is recrystallized, resulting in non-uniform crystal grain size, making it difficult to form a highly uniform diffusion source. it is conceivable that.

The present invention solves such a problem by alleviating the nonuniformity of the crystal grain size of the polycrystalline semiconductor to improve the uniformity of the impurity concentration distribution in the polycrystalline semiconductor and to improve the impurity diffusion in the thermal diffusion process. The present invention provides a method for manufacturing a semiconductor device aiming at improving the uniformity of the impurity concentration distribution in a region and improving the quality.

Means for Solving the Problems In order to solve this problem, the present invention provides a step of depositing a polycrystalline semiconductor thin film on the main surface of a semiconductor substrate, and amorphizing the surface in the polycrystalline semiconductor thin film. A step of ion-implanting atoms whose conductivity type is not determined, a step of heat-treating a semiconductor thin film containing atoms whose conductivity type is not determined, and a step of ion-implanting atoms that determine a conductivity type into the heat-treated semiconductor thin film. ,
A structure having a step of heat-treating a semiconductor thin film containing atoms that determine the conductivity type, using the semiconductor thin film as a diffusion source, and making the atoms forming the polycrystalline semiconductor thin film and the atoms not defining the conductivity type the same atom Has become.

By the method of the present invention, in order to reduce the non-uniformity of the crystal grain size of the polycrystalline semiconductor, after the polycrystalline semiconductor thin film deposition,
By ion-implanting electrons that do not determine the conductivity type without making the surface amorphous and making the lower layer amorphous, and then performing heat treatment, ion-implanting atoms that determine the conductivity type and performing heat treatment again By unifying the crystal grains of the whole polycrystalline semiconductor thin film with large crystal grains on the surface, the uniformity of the impurity concentration distribution in the polycrystalline semiconductor is enhanced, and the irregular distribution of impurity concentration in the impurity diffusion region in the thermal diffusion process is excellent and uniform. It has become possible to provide semiconductor devices with high yield and high quality that have realized high reliability. Furthermore,
By implanting atoms that determine the conductivity type without amorphizing the surface, higher uniformity can be obtained.

Examples Hereinafter, the manufacturing method of the present invention will be described in detail with reference to examples using polycrystalline silicon.

Approximately 3000 on a semiconductor substrate by the low pressure CVD method with a reaction temperature of 610 ℃
A Å polycrystalline silicon thin film was deposited, and 1 × 10 ¹⁵ cm ^-2 of silicon was ion-implanted into the polycrystalline silicon thin film at an acceleration voltage of 70 kV. Then, the polycrystalline silicon thin film in which silicon was ion-implanted was heat-treated (pre-annealed) at a temperature of 800 ° C. to 1000 ° C. for 30 minutes in a nitrogen atmosphere. Next, 1 × 10 ¹⁵ cm ^-2 boron was accelerated at an acceleration voltage of 40 kV or 1 × 10 ¹⁶ cm ^-2 arsenic was injected at an acceleration voltage of 160 kV into this polycrystalline silicon thin film.
A desired impurity diffusion source was formed by the above series of steps. Then, heat treatment was performed for 30 minutes at a temperature of 950 ° C. in a nitrogen atmosphere. A desired impurity diffusion region was formed by the above series of steps.

On the other hand, as a sample showing the conventional example, the reaction temperature on the semiconductor substrate
Immediately after depositing a polycrystalline silicon thin film of about 3000 Å by the low pressure CVD method at 610 ° C., immediately after this, the polycrystalline silicon thin film is boron of 1 × 10 ¹⁵ cm ^{-2 at} an accelerating voltage of 25 kV or an accelerating voltage of 60
Arsenic of 1 × 10 ¹⁶ cm ^-2 was injected at kV, and then heat treatment was performed for 30 minutes at a temperature of 950 ° C. in a nitrogen atmosphere.

The uniformity of the impurity concentration distribution of the sample was evaluated by measuring the sheet resistance at 45 points on the polycrystalline silicon thin film and measuring the deviation of the distribution. FIG. 1 shows the deviation of the resistance value distribution in the polycrystalline silicon thin film between the conventional example and the example of the present invention in the sample implanted with boron. Further, FIG. 2 shows the deviation of the resistance value distribution in the polycrystalline silicon thin film between the conventional example and the example of the present invention in the arsenic-implanted sample. In either case, it is clear that the deviation of the resistance value in the plane of the substrate is reduced. Especially, the deviation after pre-annealing at 1000 ° C is about 1/2 to 1/3.

EFFECTS OF THE INVENTION The manufacturing method according to the present invention can alleviate the non-uniformity of the grain size of the polycrystalline semiconductor thin film and improve the uniformity of the impurity concentration distribution in the impurity diffusion region in the thermal diffusion process by the ion-implanted polycrystalline semiconductor thin film. It is possible to provide a semiconductor device with high yield and high reliability.

[Brief description of drawings]

FIG. 1 is a curve diagram showing a deviation of a resistance value distribution in a polycrystalline silicon thin film between a conventional example and an example of the present invention in a boron-implanted sample, and FIG. 2 is a conventional diagram in an arsenic-implanted sample. It is a curve figure which shows the deviation of the resistance value distribution in a polycrystalline silicon thin film between an example and the Example of this invention.

Claims (2)

[Claims] 1. A step of depositing a polycrystalline semiconductor thin film on a main surface of a semiconductor substrate, and a step of ion-implanting atoms whose conductivity type is not determined without amorphizing the surface into the polycrystalline semiconductor thin film. A step of heat-treating the semiconductor thin film containing atoms that do not determine the conductivity type; a step of ion-implanting atoms that determine the conductivity type into the heat-treated semiconductor thin film; Has a step of heat treatment,
A method of manufacturing a semiconductor device, wherein the semiconductor thin film is used as a diffusion source, and the atoms constituting the polycrystalline semiconductor thin film and the atoms whose conductivity types are not determined are the same. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the ion implantation of atoms that determine the conductivity type is performed without amorphizing the surface.