JP2004055694A - Manufacturing method for semiconductor substrate including insulated silicon single crystal layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an SIMOX substrate, having a silicon single-crystal layer that has no stripe patterns and has uniform film thickness, and to provide a manufacturing method of an SIMOX substrate that facilitates management of the thickness in the silicon single-crystal layer. <P>SOLUTION: The single crystal silicon substrate is heated to 500 °C for ion-implanting oxygen ions, under the conditions of the acceleration energy of 50 - 245 keV and the dosage amount of 1×10<SP>16</SP>- 2×10<SP>18</SP>cm<SP>-2</SP>. As a result, an embedded damage layer is formed at a position of a specific depth on a silicon substrate. Then, the substrate is cooled to 300 °C or lower, and the oxygen ions are implanted under the conditions of 50 - 245 keV and 2×10<SP>15</SP>cm<SP>-2</SP>- 1×10<SP>17</SP>cm<SP>-2</SP>. As a result, an amorphous layer is formed. Then, the substrate is annealed at approximately 900 °C. As a result, the amorphous layer becomes a polycrystalline or a single crystal having defects. Additionally, a continuous embedded oxide film is formed by annealing at least at 1,100 °C. The thickness of the silicon single crystal the SIMOX substrate becomes 200 nm or smaller. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing an SOI substrate, and more particularly, to a method for manufacturing a low-dose SIMOX (Separation by IMplanted Oxygen) substrate.
[0002]
[Prior art]
The low-dose SIMOX substrate initially had a problem with the quality of the buried oxide film, such as the insulating property. However, by implanting oxygen ions into the single crystal silicon substrate, performing an annealing process of performing a high-temperature heat treatment in an inert gas atmosphere to form a buried oxide film, and then performing an oxidation process in a high-temperature oxygen atmosphere, the buried oxide film is formed. Has become possible (Japanese Patent No. 3036619), which has opened the way to practical use.
However, this technique has a problem that the density of dislocations generated from the interface between the silicon single crystal layer on the surface and the buried oxide film is high. Since the dislocation density decreases rapidly from the interface to the surface of the silicon single crystal layer, when the thickness of the silicon single crystal layer is large, the influence on the device manufactured using this SIMOX substrate is very small. It was not a practical problem.
However, with the recent progress of thinning of a silicon single crystal layer, the density of dislocations penetrating from the interface to the surface has been increased, which has been a practical problem.
On the other hand, a low-dose SIMOX manufacturing method has been developed in which the buried oxide film is efficiently strengthened and the dislocation density of the silicon single crystal layer is significantly reduced (US Pat. Nos. 5,930,643, 6,259,137 B1, and 6,090,689). No. 62222253B1, No. 6043166 and No. 6204546B1).
[0003]
[Problems to be solved by the invention]
However, even in this new low-dose SIMOX manufacturing method, there are three problems that are not clearly solved in aspects other than the quality of the buried oxide film and the dislocation density. The first problem is a stripe pattern (non-uniformity of the silicon single crystal layer due to uneven dose) observed on the surface of the silicon single crystal layer, and the second problem is the thickness of the silicon single crystal layer mainly observed on the outer periphery of the SIMOX substrate. Abnormality (non-uniform silicon single crystal layer due to uneven wafer temperature during ion implantation). The third problem is low process reproducibility in SIMOX substrate manufacturing.
The first problem, the stripe pattern, is due to the fact that the ion beam area of the ion implanter is smaller than the area of the silicon substrate to be implanted. In order to uniformly implant ions over the entire surface of the silicon substrate, a method of relatively scanning the ion beam and the silicon substrate is usually used, but it is difficult to achieve completely uniform implantation. In particular, when the number of scans is small, a stripe pattern is generated in the scan direction.
The second problem, the abnormal film thickness, is mainly due to the fact that the film thickness is sensitive to the substrate temperature during ion implantation (details will be described later). By optimizing the heating method of the ion implanter and the substrate holder structure, the temperature distribution in the substrate during ion implantation can be made substantially uniform, but the substrate support of the oxygen ion implanter usually holds the substrate edge partially. Since the heat escapes from the holding portion, the substrate temperature of the holding portion is locally lowered. In this case, a film thickness abnormality occurs in the region around the holding portion.
The third problem, poor process reproducibility, is due to the use of conditions with large process variations.
Therefore, the present inventors have made intensive studies and have developed a process that can minimize the above-mentioned problems caused by the ion implanter and has small fluctuations. As a result, a method for manufacturing a low-dose SIMOX substrate having no stripe pattern, good film thickness uniformity, and good reproducibility was established.
[0004]
[Object of the invention]
An object of the present invention is to provide a method of manufacturing a SIMOX substrate that forms a silicon single crystal layer having no stripe pattern and a uniform film thickness.
It is another object of the present invention to provide a method for manufacturing a SIMOX substrate that facilitates control of the thickness of a silicon single crystal layer.
[0005]
[Means for Solving the Problems]
The dose in the ion implantation process directly affects the quality of the manufactured SIMOX. Therefore, it is known that the unevenness of the dose amount in the substrate surface is important from the viewpoint of the in-plane uniformity of the manufactured SIMOX.
On the other hand, in an oxygen ion implantation apparatus for manufacturing a large-diameter SIMOX wafer, a beam scan type is generally adopted. In addition, development of high ion current has been generally promoted in a SIMOX production oxygen implanter with a goal of high throughput due to cost problems.
The above-mentioned improved low dose SIMOX manufacturing method (U.S. Pat. It is characterized in that after implanting a dose of oxygen ions, the substrate temperature is lowered to further implant a lower dose of oxygen ions. However, the uniform implantation of the small dose in the latter half of the whole substrate means that the number of scans is reduced in the case of the high ion current scanning method. There is a problem that the uniformity of the thickness of the silicon single crystal layer is deteriorated and a stripe pattern is generated in the beam scanning direction.
In addition, the substrate temperature during the implantation of oxygen ions in SIMOX production is generally adjusted by heating with, for example, a lamp heater. However, in the peripheral portion where the substrate is held by heat conduction, heat is dissipated from the holding portion due to heat conduction, so that there has been a problem that the uniformity is deteriorated due to a decrease in temperature.
The inventors studied the dose and the substrate temperature and obtained the following findings. FIG. 1 shows the relationship between the dose in the second ion implantation step and the thickness of the silicon single crystal layer, and its substrate temperature dependence. Here, the substrate temperature is a set value when heating the substrate while performing temperature adjustment by PID control or the like before starting ion implantation. Ion implantation was started after confirming that the temperature was sufficiently stabilized after starting the substrate heating. At the set temperature of 0 ° C., the substrate temperature immediately before the actual ion implantation is room temperature. The substrate temperature at the time of ion implantation is considered to have risen due to heating by an oxygen ion beam, but it is generally difficult to measure accurately in a vacuum.
From this figure, the dependency of the thickness of the silicon single crystal layer on the dose is larger when the dose in the second ion implantation step is 2 × 10 ¹⁵ cm ⁻² or more than when the dose is less than 2 × 10 ¹⁵ cm ⁻² . Is smaller. This small village of dose in the wafer surface at a dose of each object in this step, the dose amount is 2 × ¹⁰ 15 ^{cm -2} or higher, than in the case of less than 2 × ¹⁰ 15 ^{cm -2} This indicates that the thickness of the silicon single crystal layer tends to be large and uneven.
Further, the small unevenness in the substrate temperature in this step is more pronounced as a silicon single crystal layer thickness unevenness when the dose amount is 2 × 10 ¹⁵ cm ⁻² or more than when the dose amount is less than 2 × 10 ¹⁵ cm ^−2. (See the difference between the film thicknesses at 0 ° C., 100 ° C., and 150 ° C. in FIG. 1; the film thickness in the figure is a relative value.)
On the other hand, in the above-mentioned US Pat. Nos. 5,930,643 and 6,259,137 B1, the dose in the second ion implantation step is set to about 1 × 10 ¹⁴ cm ⁻² or more and about 1 × 10 ¹⁶ cm ⁻² or less. Preferably, the thickness is about 3 × 10 ¹⁴ cm ⁻² or more and about 2 × 10 ¹⁵ cm ⁻² or less. In U.S. Pat. Nos. 6,090,689 and 6,222,253 B1, in the claims, the dose of the second ion implantation step is set to about 1 × 10 ¹⁴ cm ⁻² or more and about 1 × 10 ¹⁶ cm ⁻² or less. The analysis result of Rutherford Backscattered Spectroscopy (RBS) Spectrum is also cited in the text, and the dose in the second ion implantation step is most preferably between 1 × 10 ¹⁵ cm ⁻² and 2 × 10 ¹⁵ cm ^−2. We conclude that it is close to the optimal value. Also, US Pat. Nos. 6,043,166 and 6,204,546 B1 state that the dose in the second ion implantation step is about 1 × 10 ¹⁴ cm ⁻² or more and about 2 × 10 ¹⁵ cm ⁻² or less.
However, as described above, the present inventors have improved the aforementioned low-dose SIMOX manufacturing method (U.S. Pat. The cause of the non-uniformity of the silicon single crystal layer and the stripe in the above-mentioned is examined. The non-uniformity of the silicon single crystal layer and the stripe are insufficient when the dose amount in the second ion implantation step is less than 2 × 10 ¹⁵ cm ^−2. What we have learned is what is happening.
Therefore, the invention according to claim 1 provides a first ion implantation step of heating a semiconductor single crystal substrate to implant ions of oxygen, and cooling the substrate temperature to 300 ° C. or less after the first ion implantation step. A second ion implantation step of forming an amorphous layer by performing ion implantation, a step of annealing the amorphous layer into a polycrystal or a single crystal having defects, and a step of annealing the polycrystal or the single crystal having defects. Forming a continuous oxide film at a position where the SIMOX substrate is located. In the second ion implantation step, the dose is increased from the surface of the single crystal substrate with energy of 50 to 245 keV. This is a method for manufacturing a SIMOX substrate in which oxygen ions are implanted under the conditions of 2 × 10 ¹⁵ cm ⁻² to 1 × 10 ¹⁷ cm ⁻² .
[0006]
According to a second aspect of the present invention, in the first ion implantation step, oxygen ions are implanted under the conditions of an acceleration energy of 50 to 245 keV and an ion implantation amount of 1 × 10 ¹⁶ to 2 × 10 ¹⁸ cm ^−2. 3. A method for manufacturing a SIMOX substrate according to (1).
[Action]
According to the first aspect of the present invention, first, the buried damage layer is formed at a predetermined depth position in the single crystal substrate by the first ion implantation. Next, an amorphous layer is formed by second ion implantation. Next, the amorphous layer is oxidized (annealed; for example, at 800 to 1200 ° C.) to form a continuous buried oxide layer or an intermediate structure layer for producing the buried oxide layer. Further, annealing (for example, 1100 ° C. to 1420 ° C .: the melting point of silicon) makes the intermediate structure layer a continuous buried oxide layer. That is, a series of annealing can be performed continuously.
In the second ion implantation, oxygen ions are implanted from the surface of the single crystal substrate with energy of 50 to 245 keV and a dose of 2 × 10 ¹⁵ cm ⁻² to 1 × 10 ¹⁷ cm ^−2. I do. As a result, a SIMOX substrate having a buried oxide layer formed at a predetermined depth from the surface is manufactured. Thereby, the problem of the stripe pattern can be solved without increasing the dislocation density, and a SIMOX substrate having a silicon single crystal layer with a uniform film thickness can be obtained. In addition, this manufacturing method has a wide dose amount in SIMOX manufacturing and a wide substrate temperature margin at the time of oxygen implantation, and is excellent in reproducibility. Further, when the dose amount of oxygen ions exceeds 1 × 10 ¹⁷ cm ⁻² , the condition is close to the first ion implantation condition, and cost merit cannot be achieved.
According to the second aspect of the present invention, in the first ion implantation step, oxygen ions are implanted at an acceleration energy of 50 to 245 keV and an implantation amount of 1 × 10 ¹⁶ to 2 × 10 ¹⁸ cm ⁻² .
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
First, a semiconductor single crystal substrate 10 having a predetermined thickness is prepared. On this substrate, an epitaxial single crystal layer of silicon, silicon germanium, or the like may be grown. The thickness, diameter and the like of the substrate do not matter, and the surface may be a bare single crystal layer or may be oxidized.
Next, oxygen ions are implanted at a predetermined depth position in the single crystal substrate 10 by first ion implantation. (A) shows this state. By heating (for example, 480 to 650 ° C.) the single crystal substrate 10 during the first ion implantation, the buried damage layer containing a large amount of buried Si damage clusters and vacancies of interstitial Si and Si atoms is formed. 11 is formed. In the first ion implantation step, when the thickness of the silicon single crystal of the SIMOX substrate to be completed is set to 200 nm or less, oxygen ions usually have an acceleration energy of 50 to 245 keV and an implantation amount of 1 × 10 ¹⁶ to 2 × 10 ¹⁸ cm ⁻² . inject. In the figure, reference numeral 12 denotes a portion to be a silicon single crystal layer. It is technically possible to add a step of thinning after completion of SIMOX to a silicon single crystal that has been made thicker than desired by implanting with energy higher than 245 keV, but most silicon single crystals are thinned after completion of SIMOX. This is not cost effective. Note that a known ion implantation apparatus is used.
Next, the amorphous layer 13 is formed by second ion implantation. When the first and second implantations are performed by oxygen ion implantation of the same energy, the amorphous layer 13 has a predetermined thickness adjacent to and above the buried damage layer 11 formed in the first ion implantation step. It is formed. Specifically, after the first ion implantation, the single-crystal silicon substrate 10 is cooled to 300 ° C. or lower, and implantation is performed from the surface of the single-crystal silicon substrate 10 at an energy of 50 to 245 keV. The implantation amount of oxygen ions is 2 × 10 ¹⁵ to 1 × 10 ¹⁷ cm ⁻² . A known ion implantation apparatus is used. (B) shows this state.
Next, since the amorphous layer 13 is thermally unstable, annealing at a relatively low temperature (for example, 800 to 1200 ° C.) easily converts the amorphous layer 13 into a polycrystalline layer or an intermediate layer 14 containing a single crystal containing many defects. Changes to The implanted oxygen ions start forming a continuous buried oxide film 11 by this annealing. (C) shows this state. Known annealing apparatuses and annealing conditions are used. Note that these changes also proceed during the temperature rise from room temperature in the high-temperature annealing described below.
Further, the single-crystal substrate 10 is annealed in an oxygen atmosphere at a higher temperature than the low-temperature annealing (for example, at a temperature of 1100 ° C. or higher and lower than the melting point of silicon), so that oxygen is diffused from the atmosphere through the intermediate structure layer 14 to be embedded. The thickness of the oxide film is increased, and the intermediate layer is oxidized from the side of the buried oxide film 11 to finally become an integrated continuous buried oxide layer 11. (D) shows this state. A known apparatus and a known oxidation condition are used. The oxidation conditions are usually determined in view of the cost in view of the thickness of the SIMOX silicon single crystal layer to be completed.
[0008]
Hereinafter, experimental examples will be described.
"Silicon wafer 1"
A normal p-type mirror surface wafer was used. In each step, a known ion implantation apparatus and annealing apparatus were used. The same conditions apply to wafers 2 and 3. The other steps are the same as those known in the aforementioned U.S. Patent.
First implantation step: 163 keV, preheat heating setting: 380 ° C., oxygen ions are implanted under the conditions of 2.76E17 / cm ² .
Second injection step: After once cooling to room temperature after the first injection step,
Oxygen ions are implanted under the conditions of 163 keV, preheat heating setting: 120 ° C., and 3.00E15 / cm ² .
Annealing step: The following inspection was performed on a SIMOX substrate manufactured at 1320 ° C. for 15 hours or more in an oxygen atmosphere.
Stripe (visible under fluorescent light): not confirmed.
Silicon single crystal film thickness measurement (121-point spectral ellipsometry in 300 mm wafer plane):
Average film thickness: 607.7 A (angstrom), film thickness Range (maximum value-minimum value): 34.0 A (angstrom),
Secco defect density: 2E1 cm ⁻²
"Silicon wafer 2"
First implantation step: 163 keV, preheat heating setting: 380 ° C., oxygen ions are implanted under the conditions of 2.76E17 / cm ² .
Second implantation step: Oxygen ions are implanted under the conditions of once cooling to room temperature after the first implantation, 163 keV, preheat heating setting: 120 ° C., 4.00E15 / cm ² .
Annealing step: The following inspection was performed on a SIMOX substrate manufactured at 1320 ° C. for 15 hours or more in an oxygen atmosphere.
Stripe (visual observation under a fluorescent lamp): not confirmed Measurement of silicon single crystal film thickness (measurement of 121 points in a 300 mm wafer plane by spectral ellipsometry):
Film thickness average value: 622.2 A (angstrom), film thickness Range (maximum value-minimum value): 34.0 A (angstrom),
"Comparative example (silicon wafer 3)"
First implantation step: 163 keV, preheat heating setting: 380 ° C., oxygen ions are implanted under the conditions of 2.76E17 / cm ² .
Second injection: once cooled to room temperature after the first injection,
Oxygen ions are implanted under the conditions of 163 keV, preheat heating setting: 120 ° C. and 1.50E15 / cm ² .
Monitor board measured temperature: about 178 ° C
Annealing step: The following inspection was performed on a SIMOX substrate manufactured at 1320 ° C. for 15 hours or more in an oxygen atmosphere.
Stripe (visual observation under a fluorescent lamp): Yes Silicon single crystal film thickness measurement (spectroscopic ellipsometry at 121 points in a 300 mm wafer plane): Average film thickness: 509.5 A, Film thickness Range (maximum value-minimum value): 226.7 A
Secco defect density (typical value): 1E1 to 1E5 cm ⁻²
[0009]
【effect】
According to the present invention, the problem of the stripe pattern is solved without increasing the dislocation density in the silicon single crystal layer, and a SIMOX substrate having a silicon single crystal layer having a uniform film thickness can be obtained.
[Brief description of the drawings]
FIG. 1 shows experimental data on the relationship between the dose and the thickness of a silicon single crystal layer in a second implantation step, which is the basis of the present invention, and its substrate temperature dependence.
FIG. 2 is a flow sheet showing a method for manufacturing a SIMOX substrate according to one embodiment of the present invention.
[Explanation of symbols]
10 single crystal substrate,
11 embedded damage layer,
13 amorphous layer,
14 Middle layer.

Claims (2)

A first ion implantation step of heating the single crystal substrate to implant oxygen ions;
A second ion implantation step of forming an amorphous layer by ion implantation performed after cooling the temperature of the single crystal substrate to 300 ° C. or lower after the first ion implantation step;
A step of annealing the amorphous layer into a polycrystal or a single crystal having defects,
Forming a continuous oxide film at a position where the polycrystal or the single crystal having a defect is located by further annealing.
In the second ion implantation step, oxygen ions are implanted from the surface of the single crystal substrate with an energy of 50 to 245 keV and an ion implantation amount of 2 × 10 ¹⁵ cm ⁻² to 1 × 10 ¹⁷ cm ^−2. Of manufacturing a SIMOX substrate. In the first ion implantation step, a method of manufacturing a SIMOX substrate in which oxygen ions are implanted under conditions of an acceleration energy of 50 to 245 keV and an ion implantation amount of 1 × 10 ¹⁶ to 2 × 10 ¹⁸ cm ⁻² .

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