JP2000357665A - Method of forming insulation region in semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive method of manufacturing an insulation layer having higher insulation characteristic within a semiconductor substrate with a reduced number of processes. SOLUTION: A mask pattern 14 is formed on a semiconductor substrate 11, and oxygen ions 15 are implanted from the upper side of the substrate. The oxygen ions 16b implanted directly into the substrate reaches deep region of substrate, and oxygen ions 16a implanted via the mask pattern are located in the region near the substrate surface. After the ion implantation, the heat treatment is executed to form a silicon dioxide film as the insulation layer. A single-crystal silicon region at the upper part of the oxygen ions 16b becomes a circuit element region, and the desired circuits are formed in the following processes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an insulating region in a semiconductor substrate, and more particularly to a method for implanting oxygen ions into a semiconductor substrate and oxidizing a part of the semiconductor substrate by heat treatment to form an insulating region. On how to do that.

[0002]

2. Description of the Related Art In order to form various circuit elements on a semiconductor substrate and operate them normally, it is important that each element is electrically separated. If the element separation is not sufficient, an electrical influence is exerted between the elements, causing a malfunction. Conventionally, various configurations have been proposed as means for element isolation. For example, LOCOS (Local Oxidation S
Silicon) method, SIMOX (Separation by Implanted Oxyg)
en) method, trench isolation method and the like have been proposed. The LOCOS method, which is an oxide film separation, requires 0.7 to 2 between each element.
The elements are separated by surrounding them in an island shape by a method of separating with a thick silicon oxide film of μm. It is suitable for high-speed operation because the degree of integration can be increased and the junction capacitance can be reduced. The trench isolation method is a means for forming a trench in a substrate and burying an insulator in the trench to perform element isolation. SIMOX is one of the single crystal separation methods.
One known method is to implant oxygen ions or the like into a silicon substrate to form a silicon oxide film layer inside the substrate. According to this method, an insulating layer is formed in a silicon substrate, and a single crystal silicon layer forming a circuit element is formed thereon. So-called SOI (Silicon on Insulator)
A structure is formed. The SIMOX method does not perform element isolation by itself, but is used to provide an insulating region below a region forming a circuit element, and complete element isolation by providing a LOCOS method or the like.

[0003]

In order to achieve complete element isolation, any of the above-mentioned methods is not enough, and it is necessary to combine them. For example, SI
An isolation region is provided below the circuit formation region by the MOX method,
Further, it is necessary to perform lateral isolation of the element by a LOCOS method or a trench isolation method. By providing such an insulating region, element isolation can be performed by surrounding the circuit element. However, an element isolation method that combines the SIMOX method and another isolation method requires an extremely large number of processes, and as a result, a large amount of time is required for substrate processing, which results in an increase in manufacturing cost. The present invention has been made to solve such a problem, and it is possible to realize the above-described separation method at one time.

[0004]

According to the present invention, a mask pattern for separating a circuit element region and a circuit isolation region is formed on a semiconductor substrate, and then oxygen ions are implanted. After oxygen ions are implanted into the substrate, the entire substrate is heat-treated. As a result, the oxygen ions combine with the substrate single crystal to form an oxide region. This oxide region acts as an insulating region.

[0005]

1 to 5 show a process for implementing the invention and have been simplified for ease of understanding.
First, as shown in FIG. 1, a silicon substrate 11 is provided. Although another substrate can be used, a case where a single crystal silicon substrate is used will be described below. A silicon oxide film of about 100 A is formed on the upper surface of the silicon substrate 11 (not shown), and a mask layer 12 serving as a mask pattern for ion implantation performed later is formed thereon. This mask layer 12 is made of polysilicon, SiO ₂ , Si ₃ N ₄ or the like.
For example, it is deposited to a thickness of about 3000 ° by CVD (Chemical Vapor Deposition). This mask layer 12
During ion implantation, it plays a role in controlling the implantation of ions into the substrate, and its thickness is an important factor in particular.
In order to form a mask pattern, a photoresist layer 13 is formed on the mask layer 12 by a well-known photolithography method. Next, as shown in FIG. 2, by performing an etching process on the mask layer 12, the mask layer 12 is removed according to the mask pattern.
A mask pattern layer 14 is formed. Once the mask pattern layer 14 has been formed, the photoresist layer 13 is removed. FIG. 3 is a cross-sectional view showing the implantation position of oxygen ions in the semiconductor substrate when oxygen ions are implanted.
When the mask pattern layer 14 is formed on the semiconductor substrate 11, oxygen ions 15 are implanted. Oxygen ions are implanted into the semiconductor substrate by a well-known method called ion implantation. The depth at which the oxygen ions are implanted corresponds to the acceleration energy of the ions. In this embodiment, the ion implantation is performed at 100 KeV. The amount of ions to be implanted is defined by the dose amount.
This was performed at × 10 ¹⁷ ions / cm ² . A small circle 16 in the semiconductor substrate in FIG. 3 indicates the position of the implanted oxygen ion. As can be understood from FIG. 3, the oxygen ions 16a implanted through the mask pattern layer 14 are concentrated on a shallow portion near the surface of the semiconductor substrate 11. This is because the energy of oxygen ions is absorbed by the mask pattern layer 14. On the other hand, the oxygen ions directly implanted into the semiconductor substrate 11 are implanted deeper than the ions implanted through the mask pattern layer 14. The oxygen ion 16b in FIG. 3 shows the state. Oxygen ion 16a
Is determined by the acceleration energy of oxygen ions and the thickness of the mask pattern layer 14, and the oxygen ions 16b
Is determined by the acceleration energy of oxygen ions. Therefore, first, when the depth of the circuit element region constituting the circuit element, that is, the depth of the oxygen ion 16b is determined, the acceleration energy of the oxygen ion is determined. When the acceleration energy of oxygen ions is determined, the thickness of the mask pattern layer necessary for implanting oxygen ions into the shallow portion of the substrate surface is determined. The amount of oxygen ions to be implanted in the substrate is determined by the dose. According to the above procedure, it becomes possible to implant oxygen ions at a predetermined position at a predetermined density. In the above description, the oxygen ions are implanted vertically from above the semiconductor substrate.
In order to adjust the density of the oxygen ions of a and 16b, the ion implantation angle may be changed to perform the ion implantation concentrated on the transition regions 17a and 17b. By performing ion implantation at an angle, the oxygen ion density in the transition regions 17a and 17b can be averaged. When the oxygen ion implantation step is completed, the mask pattern (polysilicon) layer 14 is removed as shown in FIG. The mask pattern layer 14 is removed by wet etching or a combination of wet etching and dry etching. The semiconductor substrate from which the mask pattern layer has been removed is then subjected to a heat treatment. About 130 degrees Celsius
By annealing in a 0 degree argon atmosphere for about 7 hours, oxygen ions and single crystal silicon are chemically bonded to form silicon dioxide. FIG. 5 shows that a silicon dioxide layer 18 as an insulating layer is formed in a semiconductor substrate as a result of heat treatment.
Is formed. The portion where the insulating layer is formed in the deep part of the substrate becomes the circuit element region 19, and a process for forming a predetermined circuit element is performed in the next step. Also,
The portion where the insulating layer is formed on the substrate surface is the circuit isolation region 2
Functions as 0. In FIG. 5, the circuit isolation region 20 is formed wide in the horizontal direction, but is actually formed narrow to improve the element density.

[0006]

As described above, by selectively implanting oxygen ions into a semiconductor substrate and performing heat treatment, the process for element isolation can be greatly simplified, so that an inexpensive semiconductor device can be manufactured. Can be manufactured. Further, since a region where a circuit element is formed can be surrounded by an insulating region, a semiconductor device using the present invention has less current leakage and has an effect of reducing power consumption. further,
When a CMOS device is formed by using the present invention, occurrence of a so-called latch-up phenomenon can be suppressed.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view of one embodiment of the present invention, showing a stage in which a photoresist layer 13 is provided.

FIG. 2 is a process sectional view of one embodiment of the present invention, showing a stage in which a mask pattern layer 14 is provided.

FIG. 3 is a process sectional view of one embodiment of the present invention, showing a step of implanting oxygen ions into a semiconductor substrate.

FIG. 4 is a process cross-sectional view of one embodiment of the present invention, showing a stage after removing a mask pattern layer after oxygen ion implantation.

FIG. 5 is a process cross-sectional view of one embodiment of the present invention, showing a stage where an insulating layer is formed by heat treatment.

[Explanation of symbols]

Reference Signs List 11 semiconductor substrate 12 mask layer 13 photoresist layer 14 mask / pattern layer 15 oxygen ion 16 oxygen ion implanted into substrate 16a oxygen ion implanted through mask / pattern layer 16b oxygen ion implanted directly into semiconductor substrate 17a, 17b Transition region of oxygen ions 18 Silicon dioxide layer 19 Circuit element region 20 Circuit isolation region

Claims (8)

[Claims] A step of forming a mask pattern on the semiconductor substrate; a step of implanting oxygen ions from above the semiconductor substrate; and a step of subjecting the semiconductor substrate implanted with oxygen ions to a heat treatment. Forming an oxide layer on the semiconductor substrate. 2. The method of claim 1, further comprising providing a silicon substrate. 3. The semiconductor substrate according to claim 1, wherein the step of implanting oxygen ions further comprises the step of implanting oxygen ions at a predetermined angle with respect to an axis perpendicular to an upper surface of the semiconductor substrate. A method of forming an insulating region therein. 4. The step of forming the mask pattern,
The method of claim 1 including forming a mask pattern with polysilicon. 5. The method according to claim 1, wherein said oxygen ions are implanted at an acceleration energy of 100 KeV and a dose of 1 × 10 ¹⁷ ions /
The method of claim 1, further comprising implanting the oxygen ions in cm ² . 6. A method for preparing a silicon substrate, forming a polysilicon layer on the silicon substrate, forming a photoresist pattern on the polysilicon layer,
Forming a mask pattern by removing a part of a polysilicon layer, implanting oxygen ions from above the semiconductor substrate, and heat-treating the semiconductor substrate implanted with oxygen ions to form the semiconductor substrate. Forming an oxide layer therein. A method for forming an insulating region in a semiconductor substrate, the method comprising: 7. The semiconductor substrate according to claim 6, wherein the step of implanting oxygen ions further comprises the step of implanting oxygen ions at a predetermined angle with respect to an axis perpendicular to an upper surface of the semiconductor substrate. A method of forming an insulating region therein. 8. The step of implanting oxygen ions comprises the steps of: accelerating energy of 100 KeV and a dose of 1 × 10 ¹⁷ ions /
7. The method of claim 6, further comprising implanting the oxygen ions in cm < ² >.