JPS61288431A - Manufacture of insulating layer - Google Patents

Abstract

PURPOSE:To contrive improvement both in the characteristics and in the yield rate of the semiconductor device such as IC, LSI and the like by a method wherein ammonia or nitride a=gas is ionized by projecting a pulse-like laser beam on ammonia or nitride gas, and it is reacted with a semiconductor substrate, thereby enabling to form an Si nitride film of high quality. CONSTITUTION:After the Si substrate 1 to be processed is washed by performing a nitride acid boiling and a hydrofluoric acid treatment and the substrate is cleaned up, the substrate is set on the susceptor 9 of a nitriding device. After a reaction pipe 11 is evacuated by operating the vacuum pump having a pipeline connected to an exhaust hole 14, high purity NH3 gas is introduced from an introducing hole 13. Then, a current is applied to a heater 10, the Si substrate 1 is heated up through the susceptor 9, and it is mainained at the temperature of 800 deg.C. Also, a DC power source 12 is turned ON, and a negative electric field is added to the Si substrate 1. An argon- fluoric excimer laser 18 is made to irradiate as laser power in the above-mentioned state, and a focus is set at the height of approximately 5mm on the substrate 1 by adjusting a focusing lens for the purpose of placing the Si substrate 1 within the range of distance of the length of diffusion when NH3 is ionized. An Si3N4 film of approximately 100Angstrom in thickness can be formed by performing a treatment for 10min in the above-mentioned state.

Description

[Detailed Description of the Invention] [Summary] A method for manufacturing an insulating layer made of a nitride film, which ionizes ammonia or nitrogen gas by irradiating it with a pulsed laser beam, and causes the ionized gas to react with a semiconductor substrate.

[Industrial application field]

The present invention relates to a method for manufacturing an insulating layer in which a nitride film is grown on a semiconductor substrate using active ions ionized by multiphoton absorption.

2. Description of the Related Art Along with advances in information processing devices that can quickly process large amounts of information, the capacity of semiconductor devices has been increased by miniaturizing unit elements, and LSI and VLSI have been put into practical use.

Here, semiconductor materials include single semiconductors represented by silicon (Si) and compound semiconductors represented by gallium arsenide (GaAs), but the materials currently most commonly used and used to form the above-mentioned LSIs and VLSIs. is a Si semiconductor.

Integration is achieved by miniaturizing patterns and increasing the number of layers, but insulation between unit elements and layer insulation include silicon dioxide (Si02), an oxide of Si, silicon nitride (Si3Ng), a nitride, etc. This is done using phosphosilicate glass (abbreviated as PSG), which is made by adding phosphorus (P) to 5i02.

Here, the Si02 layer can be formed by heat-treating the Si substrate in the atmosphere, which is relatively easy, but it is not easy to form a high-quality nitride film.

The present invention relates to a method of manufacturing a silicon nitride film of high quality at a relatively low temperature using a multiphoton absorption method.

[Conventional technology]

Methods for growing an insulating layer made of Si3N4 on a Si substrate include a method of chemically coating Si3N4 on the Si substrate and a method of growing it directly from the Si substrate.

That is, chemical vapor deposition method (Chemical Vapor Deposition method)
porDeposit ion (abbreviated as CVa method)
In this method, the St substrate to be processed is placed on a susceptor installed in the device, and while the Si substrate is heated to approximately 900°C, monosilane (SiH4) and ammonia (NH3) gas are supplied into the device. By pyrolysis with
An insulating layer made of i3N4 is formed.

SiH4+4/3 NH co →1/3 Si3
N 4 +4 H2... (1) However, in this method, the interface is not clean compared to the method of growing Si3 N 4 by directly nitriding the Si substrate in a nitrogen-containing gas atmosphere, and the interface between the Si substrate and the Since it is crystallographically discontinuous with the nitride film and highly pure Si3N4 is difficult to form, ion migration and carrier traps are likely to occur.

Therefore, in order to improve the quality of the insulating layer, it is preferable to form a Si3N4 layer by direct nitriding of the Si substrate.

Note that the lower the heat treatment temperature, the fewer thermally induced defects occur.
In addition, since the occurrence of warping can be suppressed, it is necessary to carry out the reaction at as low a temperature as possible.

FIG. 2 shows the configuration of an apparatus using a conventional plasma generation method.

That is, the Si substrate 1 is a susceptor 2 made of carbon or the like.
It is placed on top of a reaction tube 3 made of transparent quartz or the like, and is heated by a heater 4 from the surrounding area.

The reaction tube 3 also has a reaction gas inlet 5 and an outlet 6, and the outlet 6 is connected to an exhaust system (not shown).

Further, a high frequency coil 7 is provided between the inlet 5 and the heater 4.

In order to grow Si3N4 on a Si substrate in such an apparatus, N2 or a gaseous nitrogen compound such as NH3 is introduced into the reaction tube 3 through the inlet 5, exhausted through the outlet 6, and then
The atmospheric pressure is 0.1 torr, and the Si substrate 1 is heated to 800 to 10 torr.
The high frequency power supply 8 was operated with the temperature heated to 400°C.
By applying a high frequency current of KHz to 13.56 MHz to the high frequency coil 7, a reactive gas such as NH3 is turned into plasma, and the generated ammonia ions, such as Nut.
A Si3N4 film is formed at a relatively low temperature by reacting NH2'' +NH+ with the Si substrate 1.

However, when such a plasma generation method is used, ions in the plasma collide with the wall of the reaction tube 3, and the oxygen (02), carbon (C), and water (
There is a problem that impurities such as [20] and the tube wall itself are also sputtered, and these are incorporated into the Si3N4 film as impurities.

[Problem that the invention seeks to solve]

As explained above, S is produced at relatively low temperatures by the direct nitriding method.
When forming an insulating layer made of Si3N4 on an i-substrate, it is necessary to reduce impurities introduced by conventional plasma generation methods.

[Means for solving problems]

The problem mentioned above is that the semiconductor substrate to be processed is placed inside a reaction tube equipped with a reaction gas inlet and an exhaust port connected to an exhaust system, and placed on top of a susceptor that also serves as a lower electrode! ! The susceptor is placed so as to face an upper electrode provided outside the reaction tube, and the susceptor is connected in a circuit to the negative electrode of a DC power source, and a reaction gas consisting of either ammonia or nitrogen is supplied into the reaction tube. The insulating layer is characterized in that a laser beam is irradiated into the reaction chamber while the susceptor is heated to ionize the reaction gas, and the ions are transferred to the semiconductor substrate by an electric field and caused to react, thereby growing a nitride. This problem can be solved by changing the manufacturing method.

[Effect]

The present invention irradiates a reactive gas such as N2 or NH3 with a high-power laser beam, ionizes the molecules of the reactive gas by multiphoton absorption, and transfers the active ions to a Si substrate heated by an external electric field. , which causes a reaction to grow a nitride film.

In contrast to the conventional ionization of reactive gases, which was performed by applying a high-frequency electric field to form plasma, the present invention ionizes the reaction gas by multiphoton absorption, and the ions are ionized by an electric field.
By transferring to a Si substrate, the number of effective collisions is increased, thereby growing a high quality nitride film that does not contain impurities.If the substrate to be processed is Si, a Si3N4 layer is grown; When SiOz 1i is provided on the surface, an insulating layer made of St nitrogen oxide, for example 5iON, can be grown.

In order to perform ionization through multiphoton absorption, the laser beam must be powerful, and for this purpose, pulsed laser light is more suitable than continuous wave light.

Now, assuming that the reaction gas is NH3, the ionization reaction due to multiphoton absorption is shown as follows.

NH3-”NH3”+e=(2)N
H3-” NH2” + H+e = (3)N)1
3 →NH” + [2+e −=−(4) 1st
The figure shows the configuration of a nitriding apparatus for carrying out the present invention.
The i-substrate 1 is placed on a susceptor 9 made of carbon or the like and which also serves as a lower electrode, and the heater 1 provided below the susceptor 9.
It is heated by 0.

Further, the susceptor 9 is connected to the negative electrode of a DC power source 12 through a reaction tube 11.

The reaction tube 11 has an inlet 13 and an outlet 14 for the reaction gas, and the outlet 14 is connected to the exhaust system, and is also provided with a laser beam entrance window 15 and a reflector 16, and a susceptor 9. On the outside of the reflection tube 11, facing the
7 is provided and connected to the positive electrode of the DC power supply 12.

Further, a laser light source 18 and a condensing lens 19 are provided on a straight line connecting the entrance window 15 and the reflecting mirror 16.
6, the light is focused directly above the Si substrate 1 to excite the reactive gas, causing multiphoton absorption to cause ionization.

Since the ions of the reaction gas thus produced have a positive charge, they collide with the negatively charged Si substrate 1 and the nitriding reaction proceeds.

〔Example〕

The Si substrate 1 to be processed is prepared using boiling nitric acid (INO3) and hydrofluoric acid (
After cleaning and cleaning the substrate by HF) treatment, the first
Set it on the susceptor 9 of the nitriding apparatus whose configuration is shown in the figure,
After operating the vacuum pump connected to the discharge port 14 to evacuate the inside of the reaction tube 11 to about 5 XIP' Pa, high-purity NH3 gas was introduced from the introduction port 13 and the pressure was maintained at IPa.

Next, the heater 10 was energized to heat the Si substrate 1 through the susceptor 9, and the temperature was maintained at soo''c.

Further, the DC power supply 12 is turned on to apply a negative electric field to the Si substrate 1.

In this state, argon/fluorine excimer laser (wavelength 19
3nm) 200mJ/pulse with 1B as the laser power.

Irradiation was performed at a pulse repetition rate of 100 Hz, and the condenser lens 19 was adjusted to focus on the height of about 5 mm above the Si substrate 1.

This is because the Si substrate 1 is placed within the distance range of the diffusion length when NH3 is ionized.

In other words, at a position beyond the diffusion length, ions and electrons recombine, and the nitriding rate sharply decreases.

By processing for 10 minutes under these conditions, the thickness of
We were able to make 000 Si3N4 films.

In order to confirm the performance of the nitride film made in this way, M
When the breakdown voltage of the gate insulating film of an IS transistor was measured, it was found to be 15 MV/cm, which is about 10 MV/cm for a film formed using a conventional plasma nitriding system.
It was confirmed that the quality was higher than that of the previous one.

Although the above embodiment describes a method for nitriding a Si substrate from which the oxide film on the surface has been removed, the process is similar when nitriding a Si substrate with an oxide film as a substrate to be processed, and a high-quality insulating layer can be created. Can be done.

〔Effect of the invention〕

As explained above, by carrying out the present invention, it is possible to form a high quality Si nitride film, thereby making it possible to improve the characteristics and yield of semiconductor devices such as ICs and LSIs.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a nitriding apparatus using ionization by multiphoton absorption, and FIG. 2 is a block diagram of a plasma nitriding apparatus. In the figure, 1 is a Si substrate, 2 and 9 are susceptors, and 3.
11 is a reaction tube, 4 and 10 are heaters, 5.13
is an inlet, 6.14 is an outlet, 7 is a high frequency coil, 15 is an entrance window, 16 is a reflector,
17 is an upper electrode, 18 is a laser light source, 19 is a condensing lens, and 20 is a laser beam.

Claims (1)

[Claims] The reaction gas inlet (13) and the outlet connected to the exhaust system (
A semiconductor substrate to be processed is placed on a susceptor (9) which is provided in a reaction tube (11) which also serves as a lower electrode, and an upper electrode (14) is provided outside the reaction tube (11). 1
7), the susceptor (9) is connected in a circuit to the negative electrode of the DC power source (12), a reaction gas consisting of either ammonia or nitrogen is supplied to the reaction tube (11), and the susceptor (9) 9) is heated and irradiated with a laser beam into the reaction tube (11) to ionize the reaction gas, and the ions are transferred to the semiconductor substrate by an electric field and caused to react, thereby growing a nitride. A method for manufacturing an insulating layer.