JPS6370417A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent damages or the like to the surface of a semiconductor, by providing a layer of a material containing a required dopant on the surface of the semiconductor by means of application or the like, and applying plasma to the layer from above for injecting the dopant into the semiconductor. CONSTITUTION:On a semiconductor, there is provided a layer having a predetermined thickness of a material containing a dopant serving as a P-or N-type semiconductor. Plasma of a sellected gas is applied to this layer from above so that the dopant in the layer is injected into the semiconductor to form a P-or N-type semiconductor. According to this method, increase in temperature due to collision of electrons can be avoided. Further, a substrate to be processed can be prevented from being damaged since the surface of the substrate is not contacted directly with the plasma.

Description

[Detailed Description of the Invention] [Summary] In a doping method in which impurities (dopants) are implanted to form a P-type semiconductor or an N-type semiconductor, a layer containing a desired dopant is provided on the semiconductor surface by coating or the like, and this Dopants are injected into the semiconductor by irradiating plasma from above the layer.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a doping method for injecting impurities (dopants) into a semiconductor.

[Problems to be solved by conventional technology and invention] Conventionally,
A thermal diffusion method and an ion implantation method are known as methods for implanting impurities (dopants) into a semiconductor to form a P-type semiconductor or an N-type semiconductor.

The thermal diffusion method heats the semiconductor to a high temperature of 600°C or more,
This is a technique in which dopants are diffused into a semiconductor from a diffusion source. In this method, the semiconductor must be heated to a high temperature as mentioned above, so there are problems with peeling off the oxide film or nitride film, heat resistance of the mask, etc., and it is difficult to perform selective diffusion to select the location to be doped. When diffusion is performed, impurities in the diffusion layer formed by the previous diffusion enter deeper and wider, causing problems such as the profile being distorted. Further, the stress applied to the glabella of the semiconductor substrate when the temperature is raised or lowered cannot be ignored because it causes warping of the wafer. Furthermore, since the diffusion rate of the device is basically slow, it is difficult to process branches and leaves, making it unsuitable for automation and miniaturization, and cleaning the reactor requires time.

On the other hand, the i-on implantation method is a technology in which a dopant is ionized, electrostatically accelerated, and implanted into a semiconductor, and is currently the mainstream. Since the ion implantation method does not require heating the semiconductor substrate to high temperatures, selective diffusion can be performed using the resist as a mask, and the diffusion layer does not spread laterally.
It has many advantages such as being able to perform multiple implants and increasing processing speed. However, since ionized dopants are basically implanted into the semiconductor at high speed, the semiconductor crystal may be damaged, and the surface layer of the implanted portion may lose its crystallinity and become amorphous due to the impact. In addition, since ions are naturally implanted into the mask material, the mask material also suffers considerable damage.For example, the resist that is mainly used is carbonized, and under the implantation conditions, a stubborn residue that cannot be removed by normal means is created, causing particles. or even damage the device. Further, dopant ions have good directionality, and therefore can be diffused downwardly but cannot be diffused laterally. This indicates that, for example, when forming an element with a grooved structure that has been proposed in recent years, it is impossible to perform the necessary injection of dopants into the side surfaces of the groove. Furthermore, with the current level of equipment, an accelerating voltage of several tens of KeV is required to stably extract the ion beam, and as a result,
Another problem is that the implantation becomes deep, making it difficult to form a shallow diffusion layer of several hundred angstroms. This method inevitably makes the device large and complicated, resulting in many failures and high costs.

As another method, a plasma doping method has been proposed (Japanese Patent Laid-Open No. 138921/1983). This involves creating plasma containing dopants and implanting it into a semiconductor substrate using an ion sheath or an extraction electrode, and can be said to be a method of lowering the acceleration voltage of the ion implantation method. However, damage to the semiconductor surface layer due to direct contact of the substrate with plasma cannot be avoided. Also, lateral diffusion is not possible. Another similar example is one in which DC discharge is used for plasma generation, gaseous PH3, Bz Hb is used as a plasma source, and phosphorus (P) or boron (B) is doped. (For example, the magazine "Surface Treatment Research" Volume 2, No. 1, 19
(September 1983, P, 147-153) In this case, it has been shown that doping is not simply caused by ions being accelerated and implanted by an ion sheath. However, one possible reason for this is an increase in temperature of the surface layer due to ion bombardment.In other words, this is thought to suggest damage caused by direct contact of the substrate surface with plasma. Moreover, if the place to be doped with -C is exposed to the plasma, the structure of the plasma chamber Tht that has entered the plasma by sputtering etc.
It also has the disadvantage that it can also be doped at the same time.

[Means and effects for solving the problems] The present invention provides a method for manufacturing a semiconductor device that solves the above-mentioned problems. In a method for manufacturing a semiconductor device that forms a P-type or N-type semiconductor, a substance containing the impurity is provided in a layer with a predetermined thickness on the surface of a substrate of the semiconductor, and plasma of a predetermined gas is irradiated from above the layer. , the impurity contained in the layer is implanted into the substrate by irradiation with the plasma to form a P-type or N-type semiconductor corresponding to the impurity.

〔Example〕

The attached drawings are diagrams for explaining a method for manufacturing a semiconductor device according to the present invention. A feature of the present invention is that a layer of a predetermined thickness is formed on a semiconductor using a substance containing a dopant that acts as a P-type or N-type semiconductor, and plasma of a predetermined gas is irradiated from above this layer to form a layer containing a dopant that acts as a P-type or N-type semiconductor. It is characterized by injecting dopants into the semiconductor to form a P-type or N-type semiconductor. In this method, as will be described later, since the plasma does not come into direct contact with the semiconductor surface, damage to the surface can be completely prevented.

This process will be explained below.

(a) is an N-type silicon (S) with a surface resistance of 200Ω/hole.
i) Shows the substrate.

In (b), a commercially available polyboron film (PBF) (manufactured by Tokyo Ohka Kogyo) containing 1% boron (B) is coated on a Si substrate to a predetermined thickness, heated in air to about 70°C, and then This shows the step of skipping the PBF layer and forming a PBF layer with a thickness of about 1,500 layers.

(c) is the step of irradiating nitrogen (N2) gas plasma generated by microwaves with a frequency of 2.45 GHz and a power of 1.5 KW at 250 CC/min for 5 minutes in a vacuum container with a vacuum degree of 0.3 Torr. , boron (B) in the PBF layer is doped into the semiconductor by N2 gas plasma.

(d) shows that after the boron implantation (B doping) is performed in (c), the PBF layer is coated with HF solution or H,SO4+H! O
□This is the stage of separating fjJ using wet means such as a solution, and PB
When the F layer is removed, a B-doped layer is formed on the semiconductor surface and P
form a type semiconductor.

(e) shows the final annealing step for 8-layer activation, which is carried out in an Nt gas atmosphere at 1000° C. for about 30 minutes. However, this step is not necessarily necessary, and the B layer is activated to some extent.

After such a step, the surface resistance of the semiconductor was measured and found to be P-type and 3Ω/min, indicating that it was doped with boron. This method avoids temperature rise due to electron collision, and since the surface of the workpiece does not come into direct contact with the plasma, damage to the substrate can also be avoided.
Since it was in a state of 00Ω/gate, selective doping (selective diffusion) is also possible using this.

In the above example, a layer containing boron is applied to the semiconductor surface and P
Although an N-type semiconductor was obtained, an N-type semiconductor can be obtained by applying a layer containing phosphorus (P) or arsenic (As) and performing similar steps.

Additionally, since this method implants the dopant inside the layer into the semiconductor surface, there is no damage to the crystal alignment compared to the conventional method of implanting dopants into the surface.

This is because it is not directly attacked by charged particles of several tens of keys.

[Efficacy of invention]

As explained above, according to the present invention, when implanting an impurity to form a P-type semiconductor or an N-type semiconductor, a layer containing the impurity is provided and plasma is irradiated from above to implant the impurity into the semiconductor. As a result, damage to the semiconductor surface can be avoided, and the number of manufacturing steps and costs can be reduced.

[Brief explanation of the drawing]

The accompanying drawings are diagrams illustrating a method for manufacturing a semiconductor device according to the present invention. (Explanation of symbols) PBF...Polyboron film, Si...Silicon substrate. Patent distributor Fujitsu Limited Patent application agent

Claims (1)

[Claims] 1. In a method for manufacturing a semiconductor device in which an impurity is implanted into a semiconductor to form a P-type or N-type semiconductor corresponding to the impurity, a substance containing the impurity is provided in a layer to a predetermined thickness on the surface of the semiconductor substrate. , irradiating plasma of a predetermined gas from above the layer, introducing the impurity contained in the layer into the substrate by irradiating the plasma, and forming a P-type or N-type semiconductor corresponding to the impurity. A method of manufacturing a semiconductor device, characterized in that: