KR20080021790A - Method for manufacturing simox wafer and simox wafer manufactured by such method - Google Patents

Abstract

A SIMOX wafer manufacturing method includes a step of implanting oxygen ions into a silicon wafer; a step of cleaning the oxygen ion implanted silicon wafer; and a step of forming an embedded oxide film inside the silicon wafer by performing heat treatment to the cleaned silicon wafer. The method further includes a step of etching a SiO2 film formed on the silicon wafer surface by dipping the silicon wafer in a hydrofluoric acid solution, after the oxygen ions are implanted into the silicon wafer and prior to cleaning the silicon wafer. An etching rate of the hydrofluoric acid solution to the SiO2 film in the etching process is 150-3,000(Š/min). ® KIPO & WIPO 2008

Description

FIELD OF THE INVENTION AND METHOD FOR MANUFACTURING SIMOX WAFER AND SIMOX WAFER MANUFACTURED BY SUCH METHOD

According to the present invention, a buried oxide film is formed in a region of a predetermined depth from a wafer surface by injecting oxygen ions into a silicon wafer and then heat-treating, and then a SIMOX (Separation by Implanted Oxygen) having a silicon on insulator (SOI) layer formed on the wafer surface. A method for manufacturing a wafer.

In the manufacturing process of a conventional SIMOX wafer, it is known that particles attached at the time of oxygen ion implantation become nuclei for defect formation by a subsequent annealing treatment, and the particles need to be removed before the annealing treatment. As a method of removing the particles, generally a washing method using a mixture of ammonia water, hydrogen peroxide and pure water (hereinafter referred to as SC-1 washing liquid), a washing method using a mixture of sulfuric acid, hydrogen peroxide and pure water, and ozone water And a washing method using a hydrofluoric acid aqueous solution having a concentration of 0.2 to 2% by weight, a washing method combining these washing methods, and the like. However, even when the wafer was cleaned by the above cleaning method, the particle removal rate on the surface of the wafer was about 80% at maximum, and it was thought that there was a limit to reduction of the defect of the wafer because the wafer proceeded to the annealing process with the particles remaining. In addition, the said particle removal rate is calculated | required by measuring the number of particle | grains of particle size (particle diameter) 0.20 micrometer or more before and after each washing | cleaning using SurfScan6420 (surface inspection apparatus of the KLA-Tencor company of USA).

On the other hand, during the process of injecting oxygen ions into a silicon wafer, a jet cleaning for jetting water flow applied with ultrasonic waves, cleaning with SC-1 cleaning liquid, or cleaning using a mixed solution of hydrochloric acid, hydrogen peroxide and pure water ( See, for example, Patent Document 1). This semiconductor manufacturing method comprises a step of forming a surface oxide film on a silicon wafer in advance before implantation of oxygen ions, and removing the surface oxide film using an aqueous solution of difluoric acid during the implantation process of oxygen ions.

In the semiconductor manufacturing method configured as described above, since the wafer is cleaned during the oxygen ion implantation step to remove particles, the shielding area by the particles of the wafer can be reduced during the subsequent implantation of oxygen ions, thereby eliminating the current path defects of the buried oxide film. Can be reduced. In addition, since oxygen ions are implanted into the wafer while the surface oxide film is formed on the wafer in advance, and the surface oxide film is removed using an aqueous solution of fluoric acid during the oxygen ion implantation process on the wafer, particles adhering to the surface of the surface oxide film It is removed together with the oxide film to effectively reduce particles on the wafer surface.

However, in the method for manufacturing a semiconductor disclosed in the above-mentioned conventional patent document 1, the concentration of the aqueous solution of hexafluoric acid is low and the etching rate of the surface oxide film is low. Therefore, although the surface oxide film can be removed, it is difficult to remove all the particles that are firmly chemically bonded through silicon and oxygen at the time of oxygen ion implantation, and there is a problem that only about 80% can be removed by this method. When SIMOX wafers are manufactured in this state, deep defects (defects observed after immersion for 30 minutes in a 50% by weight hydrofluoric acid solution at a temperature of 23 ° C.) that penetrate the SOI layer adversely affect the electrical properties of the wafer. There was a problem that still exists.

Patent Document 1: Japanese Patent Application Laid-Open No. 8-78647 (claims 1 to 5, paragraph (0019), paragraph (0024), FIG. 5)

Disclosure of the Invention

Problems to be Solved by the Invention

SUMMARY OF THE INVENTION An object of the present invention is a method for manufacturing a SIMOX wafer capable of efficiently removing particles adhered upon oxygen ion implantation and reducing deep defects penetrating through the SOI layer in a SIMOX structure, and a SIMOX manufactured by the method. It is to provide a wafer.

Means to solve the problem

One embodiment of the method for manufacturing a SIMOX wafer of the present invention includes a step of injecting oxygen ions into a silicon wafer, a step of cleaning a silicon wafer in which oxygen ions have been implanted, and a heat treatment of the cleaned silicon wafer. It is an improvement of the manufacturing method of a SIMOX wafer including the process of forming a buried oxide film.

The characteristic configuration further includes a step of etching the SiO ₂ film formed on the surface of the silicon wafer by immersing the silicon wafer in an aqueous hydrofluoric acid solution after injecting oxygen ions into the silicon wafer and before cleaning the silicon wafer. having a removal rate of the SiO ₂ film of a hydrofluoric acid aqueous solution at the time of treatment is 150~3000 (Å / min).

According to one embodiment of the SIMOX wafer manufacturing method of the present invention, since the silicon wafer is immersed in an aqueous hydrofluoric acid solution having an etching rate of 150 to 3000 Pa / min for the SiO ₂ film on the wafer surface, the surface of the silicon wafer can be etched at high speed. At this time, since the etching rate with respect to silicon dioxide is high, the strong bond of the particle containing the bond of silicon and oxygen in large quantities is also cut | disconnected. As a result, particles can be almost completely removed from the silicon wafer surface.

In one embodiment of the SIMOX wafer manufacturing method of the present invention, oxygen ion implantation into a silicon wafer is divided into a plurality of times, and the silicon wafer is immediately after any one of these oxygen ion implantation steps or immediately after two or more implantation steps. May be immersed in an aqueous hydrofluoric acid solution.

In this case, when the surface treatment of the wafer is performed by immersion in an aqueous hydrofluoric acid solution immediately after one injection step of the oxygen ion implantation step, for example, immediately after the first oxygen ion implantation, fewer particles remain on the wafer surface before the next oxygen ion implantation. As a result, the shielding effect of oxygen ion implantation by particles is reduced, so that deep defects penetrating the SOI layer on the wafer surface subjected to the SIMOX heat treatment process (soaked in a hydrofluoric acid solution having a concentration of 50% by weight at a temperature of 23 ° C. for 30 minutes) Can be reduced afterwards.

Moreover, in one aspect of the manufacturing method of the SIMOX wafer of this invention, the temperature of hydrofluoric acid aqueous solution is 40 degreeC or less more than the freezing point of this hydrofluoric acid aqueous solution 12, and the immersion time of a silicon wafer in hydrofluoric acid aqueous solution may be for 10 to 600 second. have.

Furthermore, in one embodiment of the method for producing a SIMOX wafer of the present invention, the etching rate of the hydrofluoric acid aqueous solution 12 with respect to the SiO ₂ film is called R (Å / min), and the silicon wafer 11 is immersed in the hydrofluoric acid aqueous solution 12. When the time is referred to as H (seconds), the immersion time may be set such that H≥ (1500 / R) (seconds).

In one embodiment of the method for producing a SIMOX wafer of the present invention, a surfactant may be added to the hydrofluoric acid aqueous solution.

In this case, when the silicon wafer is pulled up from the hydrofluoric acid solution to which the surfactant is added, since the surfactant acts as a protective film on the wafer surface, particles can be prevented from reattaching to the wafer surface. At this time, even if the wafer is rinsed with pure water, moisture removal is good.

One aspect of the manufacturing method of the SIMOX wafer of this invention is manufactured by the manufacturing method of the SIMOX wafer of this invention, and was made to immerse for 30 minutes in the deep defect (50-% by weight concentration of hydrofluoric acid at the temperature of 23 degreeC) penetrating a SOI layer. Number of defects observed later) 0.05 / cm ² Is less than

According to one embodiment of the SIMOX wafer of the present invention, the particles remaining on the wafer surface before the oxygen ion implantation are reduced by being manufactured by the method of manufacturing the SIMOX wafer of the present invention. Therefore, since the shielding effect of oxygen ion implantation by particles is reduced, the number of deep defects penetrating through the SOI layer (defects observed after soaking in a hydrofluoric acid solution having a concentration of 50% by weight at a temperature of 23 ° C. for 30 minutes) is very small. .

Effects of the Invention

According to the present invention, after injecting oxygen ions into a silicon wafer and before cleaning the silicon wafer, the silicon wafer is immersed in an aqueous hydrofluoric acid solution to etch the SiO ₂ film formed on the surface of the silicon wafer. Since the etching rate for the SiO ₂ film is 150 to 3000 Pa / min, the surface of the silicon wafer is etched at high speed. At this time, since the etching rate with respect to silicon dioxide is high, the strong bond of the particle containing the bond of silicon and oxygen in large quantities is also cut | disconnected. As a result, particles can be almost completely removed from the silicon wafer surface.

In addition, the oxygen injection into the silicon wafer is divided into a plurality of times, and the silicon wafer is immersed in the hydrofluoric acid solution immediately after any one of these oxygen ion implantation steps or immediately after each two or more implantation steps, before the next oxygen ion implantation. Particles remaining on the surface can be reduced. Therefore, the shielding effect of oxygen ion implantation by a particle becomes small. As a result, the number of deep defects (defects observed after soaking in a hydrofluoric acid solution having a concentration of 50% by weight for 30 minutes at a temperature of 23 ° C.) in the SOI layer can be reduced in the wafer subjected to the SIMOX treatment process.

When surfactant is added to the hydrofluoric acid solution, the surfactant acts as a protective film on the wafer surface when the silicon wafer is pulled up from the hydrofluoric acid solution to which the surfactant is added. As a result, particles can be prevented from re-adhering to the wafer surface, and water removal after rinsing with pure water of the wafer at this time is good.

Furthermore, the SIMOX wafer manufactured by the above method has a number of deep defects (defects observed after immersion for 30 minutes in a 50% by weight hydrofluoric acid solution at a temperature of 23 ° C. at a temperature of 23 ° C.) of 0.05 pieces / cm ^2. It becomes very small as follows.

FIG. 1 is a view showing an etching treatment step using an aqueous hydrofluoric acid solution having an etching rate of 150 to 3000 Pa / min and a rinsing step using pure water.

2 is a block diagram including an oxygen ion implantation process and a cleaning process of the silicon wafer of this embodiment.

3A is a view showing the particle removal rate of Examples 1-12.

3B is a view showing particle removal rates of Comparative Examples 1 to 13. FIG.

3C is a view showing particle removal rates of Comparative Examples 14 to 26. FIG.

4A is a view showing the particle removal rate of Comparative Examples 27-39.

4B is a view showing particle removal rates of Comparative Examples 40 to 52. FIG.

FIG. 5 is a view showing the number of deep defects (defects observed after immersion in an aqueous solution of hydrofluoric acid at a concentration of 50% by weight for 30 minutes at a temperature of 23 ° C.) at an SOI layer of Examples and Comparative Examples.

<Description of the code>

11... Silicon wafer,

12... Hydrofluoric acid

EMBODIMENT OF THE INVENTION Next, the best form for implementing this invention is demonstrated with reference to drawings.

As shown in FIG. 1 and FIG. 2, the method for manufacturing a SIMOX wafer includes a step of implanting oxygen ions into the silicon wafer 11, a process of cleaning the wafer 11 into which oxygen ions have been implanted, And heat-treating the wafer 11 to form a buried oxide film in the wafer 11.

In this embodiment, oxygen ion implantation is performed in three steps.

As the cleaning method of the wafer 11, a cleaning method using an SC-1 cleaning solution, a cleaning method using a mixture of sulfuric acid, hydrogen peroxide and pure water, a cleaning method using a mixture of hydrochloric acid, hydrogen peroxide and pure water, ozone water and a concentration of 0.2 to The washing | cleaning method using 2 weight% hydrofluoric acid aqueous solution, the washing | cleaning method which combined these washing | cleaning methods, or the washing | cleaning method which combined these washing | cleaning methods and megasonic washing | cleaning, etc. are mentioned. Here, megasonic washing | cleaning is washing | cleaning which irradiates the to-be-cleaned object in the liquid with the ultra-sonic wave of 0.8-10 MHz.

The silicon ingot pulled up by the Czochralski method is cleaned by the first cleaning process after slicing and polishing the surface (FIG. 2). The cleaned wafer 11 is implanted with the first oxygen ion (first oxygen ion implantation step). The implantation of oxygen ions is performed at a dose of 5 × 10 ¹⁶ to 2 × 10 ¹⁷ atoms / cm ² of oxygen ions while the wafer 11 is heated to 300 to 500 ° C.

Subsequently, before cleaning the wafer 11, the wafer 11 is immersed in the hydrofluoric acid aqueous solution 12 to etch the SiO ₂ film formed on the surface of the wafer 11 (FIGS. 1 and 2).

Removal rate on the SiO ₂ film of the aqueous solution of hydrofluoric acid 12 during this etching treatment is 150~3000Å / min, preferably 500~1000Å / min, and more preferably from 500~600Å / min. The concentration of hydrofluoric acid solution for achieving an etching rate of 150 to 3000 Pa / min is 2.5 to 50% by weight at 23 ° C, and the concentration of hydrofluoric acid solution for achieving an etching rate of 500 to 1000 Pa / min is 10 to 20 at 23 ° C. The concentration of hydrofluoric acid solution to achieve an etching rate of 500 to 600 Pa / min is 10 to 12% by weight at 23 ° C.

Since the surface of the wafer 11 is etched at a high speed by the etching process, the firm bonding of particles including a large amount of silicon and oxygen bonding together with the natural oxide film on the surface of the wafer 11 is also cut. That is, the chemical bonds of particles firmly bonded through silicon and oxygen at the time of oxygen ion implantation are also cut.

Specifically, it is considered that the chemical bond of oxygen and particles includes not only one bond but also many bonds to one particle. In order to cleave these bonds, HF or HF ₂ ⁻ must meet with Si—O bonds, and the probability of this encounter becomes rate.

In order to cleave a large number of bonds in a physically narrow gap, in hydrofluoric acid solution with an etching rate of less than 150 μs / min for SiO ₂ film, HF or HF ₂ ⁻ is encountered and consumed with Si-O before reaching the deep inner part. It is difficult to reach deep inside.

However, in hydrofluoric acid solution having an etching rate of 150 to 3000 mW / min for SiO ₂ film, even if HF or HF ₂ ⁻ reaches deep inside the gap, HF or HF ₂ ⁻ remains and thus all of the many bonds present in the narrow gap It is thought to be able to cut. As a result, the particles can be almost completely removed from the wafer 11 surface.

The reason why the wafer is limited to the method of immersing the wafer in the hydrofluoric acid solution is described below, rather than the method of spraying the hydrofluoric acid solution on the surface of the rotating wafer. In the method of injecting an aqueous hydrofluoric acid solution onto the surface of the rotating wafer, the surface of the wafer becomes hydrophobic after the natural oxide film on the surface of the wafer is dissolved, so that the hydrofluoric acid aqueous solution does not become affinity with the wafer surface (pure salt). Thus, traces of dry solidification as the droplets roll are left on the wafer surface, which is detected as particles or the wafer surface becomes unevenly roughened, resulting in an undesirable state of the wafer surface. Therefore, in this embodiment, the method of immersing a wafer in hydrofluoric acid aqueous solution is applied.

In addition, in the case where the treatment with the SC-1 cleaning liquid was performed instead of the wafer surface treatment immersed in the hydrofluoric acid solution having an etching rate of 150 to 3000 Pa / min for the SiO ₂ film, the SC-1 cleaning liquid was treated with silicon and silicon dioxide (SiO ₂ ). The etching rate is limited to about 20 μs / minute. Even if the etching time is increased by increasing the processing time, a large number of floating point particles that cannot be removed remain and cause defects in the wafer.

Here, the floating point particle refers to a particle remaining at the same position before and after the second cleaning process.

The temperature of the said hydrofluoric acid aqueous solution 12 is 40 degrees C or less exceeding the freezing point of this hydrofluoric acid aqueous solution, Preferably it is 20-25 degreeC. The immersion time of the wafer 11 in the hydrofluoric acid solution 12 is for 10 to 600 seconds, preferably for 30 to 100 seconds.

Here, when the etching rate of the aqueous solution of hydrofluoric acid 12 to the SiO ₂ film is less than 150 GPa / min, the etching rate of the surface of the wafer 11 is slow, so that the strong bonding of particles containing a large amount of silicon and oxygen bonding cannot be cut. . In other words, it is not possible to cut chemical bonds of particles that are firmly bound through silicon and oxygen at the time of oxygen ion implantation. In addition, the surface roughness of the wafer 11 deteriorates when it exceeds 3000 kPa / min. Thus, the etching rate of the SiO ₂ film of a hydrofluoric acid aqueous solution (12) in the range of 150~3000Å / min.

In addition, an etching process cannot be performed at the temperature of the hydrofluoric acid aqueous solution 12 below the freezing point of hydrofluoric acid aqueous solution. When it exceeds 40 degreeC, mist will generate | occur | produce from hydrofluoric acid aqueous solution, it will become difficult to handle, and surface roughness will worsen. Therefore, the temperature of the hydrofluoric acid aqueous solution 12 is made into the range exceeding the freezing point of this hydrofluoric acid aqueous solution and 40 degrees C or less.

Furthermore, when the immersion time of the wafer 11 in the hydrofluoric acid aqueous solution 12 is less than 10 seconds, the immersion time is excessively short, so that the strong bonds of the particles containing a large amount of silicon and oxygen bonds cannot be cut. In other words, it is not possible to cut chemical bonds of particles that are firmly bound through silicon and oxygen at the time of oxygen ion implantation. If it exceeds 600 seconds, surface roughness will worsen. Therefore, the immersion time of the wafer 11 in the hydrofluoric acid aqueous solution 12 is made into the range for 10 to 600 second.

Also, considered the etching rate of the hydrofluoric acid aqueous solution 12 with respect to the SiO ₂ formed on the wafer 11 surface R (Å / minute) as, and a hydrofluoric acid aqueous solution dipping time to the 12 of the wafer 11, H (s) At this time, it is preferable to set the immersion time such that H? (1500 / R) (second). Thereby, the immersion time of the optimum wafer 11 based on the etching rate of the hydrofluoric acid aqueous solution 12 can be calculated | required quickly.

Moreover, it is preferable to add surfactant to the said hydrofluoric acid aqueous solution 12. When surfactant is added to the hydrofluoric acid aqueous solution 12, since the surfactant acts as a protective film on the surface of the wafer 11, particles can be prevented from reattaching to the surface of the wafer 11. In addition, when the wafer 11 is rinsed with pure water, moisture removal is good.

As said surfactant, an ionic surfactant, a nonionic surfactant, etc. are mentioned. The addition amount of surfactant is 0.1-10 weight%, Preferably it is 0.3-1 weight%.

If the added amount of the surfactant is less than 0.1% by weight, it does not function as a protective film on the surface of the wafer 11, but when it exceeds 10% by weight, salting out occurs to prevent etching. Therefore, the addition amount of surfactant is made into 0.1 to 10 weight% of range.

Next, the wafer 11 is immersed in a rinse bath 13 in which the pure water 14 is stored, rinsed, and then pulled up (raised) and dried (FIG. 1). This rinse tank 13 is provided with the tank main body 13a which stores the pure water 14, and the pure water 14 which overflowed from the tank main body 13a provided in the upper outer peripheral edge of this tank main body 13a. It has the overflow tank 13b which receives. In addition, a supply pipe 13c for supplying pure water 14 to the tank main body 13a is connected to the lower portion of the tank main body 13a, and pure water 14 accumulated in the overflow tank 13b is provided on the lower surface of the overflow tank 13b. A discharge pipe 13d for discharging) is connected.

Further, the wafer 11 is subjected to SIMOX heat treatment through a second oxygen ion implantation process, a third cleaning process, a third oxygen ion implantation process, and a fourth cleaning process (FIG. 2).

The implantation of oxygen ions in the second oxygen ion implantation step is performed at a dose of 5 × 10 ¹⁶ to 2 × 10 ¹⁷ atoms / cm ² of oxygen ions while the wafer is held at 300 to 500 ° C. The implantation of oxygen ions in the third oxygen ion implantation step is performed at a dose of 1 × 10 ^{15 to} 1 × 10 ¹⁷ atoms / cm ² of oxygen ions while keeping the wafer at room temperature.

In this embodiment, the oxygen ion implantation of the silicon wafer is divided into three times, but the oxygen ion implantation of the silicon wafer may be one time, or may be divided into two or four or more times.

In the present embodiment, the silicon wafer is immersed in the hydrofluoric acid solution immediately after the first oxygen ion implantation, but immediately after the second or third oxygen ion implantation, or immediately after each two oxygen implantation of one to three times, or three times. Immediately after each oxygen ion implantation, the silicon wafer may be immersed in an aqueous hydrofluoric acid solution.

SIMOX wafers thus prepared have fewer particles remaining on the wafer surface prior to oxygen ion implantation, thereby reducing the shielding effect of oxygen ion implantation by the particles. Thus, deep defects penetrating the SOI layer (concentration at a temperature of 23 ° C. at 50% by weight) Of defects observed after soaking in aqueous hydrofluoric acid solution (12) for 30 minutes at 0.05 pieces / cm ² It becomes very small as follows.

Next, the Example of this invention is described in detail with a comparative example.

(Examples 1-3)

As shown in Fig. 2, silicon ingots having a diameter of 200 mm pulled up by the Czochralski method were sliced, polished and cleaned (first cleaning step), and then oxygen ion implantation was performed in three portions.

As shown in Fig. 1 and Fig. 2, immediately after the first oxygen ion implantation, the etching rate of these wafers 11 with respect to the SiO ₂ film on the surface of the wafers 11 was 600 Pa / min (concentration of aqueous hydrofluoric acid: 10 wt%). As an example, the solution was immersed in a hydrofluoric acid solution 12 having a temperature of 23 ° C. for 60 seconds. Subsequently, these wafers 11 were immersed in the rinse bath 13 in which the pure water 14 overflowed, and dried for 3 minutes.

Next, these wafers 11 were cleaned by a single sheet spin method. In detail, the surface of the wafer 11 was rotated one by one, sprayed with a concentration of 15 ppm of ozone water for 20 seconds, and then washed with a hydrofluoric acid solution having a concentration of 0.5% by weight for 10 seconds. After these washings were repeated three times (second washing step), the wafer was dried.

Furthermore, SIMOX heat treatment was performed on these wafers 11 through a 2nd oxygen ion implantation process, a 3rd cleaning process, a 3rd oxygen ion implantation process, and a 4th cleaning process. These wafers were set as Examples 1-3.

(Examples 4 to 6)

Immediately after the first oxygen ion implantation, these wafers were etched with respect to the SiO ₂ film on the wafer surface at 700 Pa / min (concentration of aqueous hydrofluoric acid: 50% by weight), and one weight of nonionic surfactant was added to the aqueous hydrofluoric acid having a temperature of 5 ° C. It was immersed in the added liquid for 30 seconds and etched. These wafers were further immersed for 5 minutes in a rinse bath overflowing with pure water. Except the above conditions, three SIMOX wafers were produced by the same method as Examples 1-3. These wafers were set as Examples 4-6.

(Examples 7-9)

Immediately after the first oxygen ion implantation, these wafers were etched by immersion for 300 seconds in a hydrofluoric acid solution having a temperature of 15 DEG C with an etching rate of 400 Pa / min (concentration of aqueous hydrofluoric acid: 25 wt%) for the SiO ₂ film on the wafer surface. These wafers were further immersed in a rinse bath overflowing with pure water for 1 minute. Except the above conditions, three SIMOX wafers were produced by the same method as Examples 1-3. These wafers were set as Examples 7-9.

(Examples 10-12)

Immediately after the first oxygen ion implantation, these wafers were etched with respect to the SiO ₂ film on the wafer surface at 350 Pa / min (concentration of aqueous hydrofluoric acid: 2% by weight) and 3% by weight of an ionic surfactant in an aqueous solution of hydrofluoric acid having a temperature of 35 ° C. It was immersed in the added liquid for 500 seconds and etched. These wafers were immersed in a rinse bath overflowing with pure water for 1 minute and dried. These wafers were further immersed in an SC-1 cleaning liquid (NH ₄ OH: H ₂ O ₂ : H ₂ O = 0.5: 1: 10) at 80 ° C. for 5 minutes and washed. Except the above conditions, three SIMOX wafers were produced by the same method as Examples 1-3. These wafers were set as Examples 10-12.

(Comparative Examples 1 to 13)

After the silicon ingot having a diameter of 200 mm pulled up by the Czochralski method was sliced and polished and cleaned (first cleaning step), oxygen ion implantation was performed in three portions.

Immediately after the first oxygen ion implantation, these wafers were immersed in an SC-1 cleaning liquid (NH ₄ OH: H ₂ O ₂ : H ₂ O = 0.5: 1: 10) at 80 ° C. for 10 minutes and washed (second cleaning). Step).

Next, these wafers were subjected to SIMOX heat treatment through a second oxygen ion implantation step, a third cleaning step, a third oxygen ion implantation step, and a fourth cleaning step. These wafers were made into Comparative Examples 1-13.

(Comparative Examples 14-26)

After the silicon ingot having a diameter of 200 mm pulled up by the Czochralski method was sliced and polished and cleaned (first cleaning step), oxygen ion implantation was performed in three portions.

Immediately after the first oxygen ion implantation, these wafers were cleaned by a single sheet spin method. Specifically, the wafer was rotated one by one, sprayed with a concentration of 15 ppm of ozone water for 20 seconds, and then washed with a hydrofluoric acid solution having a concentration of 0.5% by weight for 10 seconds. After these washings were repeated three times (second washing step), the wafer was dried.

Next, these wafers were subjected to SIMOX heat treatment through a second oxygen ion implantation step, a third cleaning step, a third oxygen ion implantation step, and a fourth cleaning step. These wafers were referred to as Comparative Examples 14 to 26.

(Comparative Examples 27-39)

Immediately after the first oxygen ion implantation, these wafers were etched by immersion for 30 seconds in a hydrofluoric acid solution having a temperature of 23 ° C. for 30 seconds / min (concentration of hydrofluoric acid solution: 0.5% by weight) for the SiO ₂ film on the wafer surface. . A SIMOX wafer was produced in the same manner as in Example 1 except these conditions. These wafers were set as Comparative Examples 27-39.

(Comparative Examples 40-52)

Was treated by immersing 30 seconds in the hydrofluoric acid aqueous solution temperature is 23 ℃ as etching: a first oxygen ion these wafer immediately after the injection etch rate is 120Å / min (2.0% by weight concentration of the hydrofluoric acid aqueous solution) to the SiO ₂ film on the wafer surface. A SIMOX wafer was produced in the same manner as in Example 1 except these conditions. These wafers were set as Comparative Examples 40-52.

(Comparative exam 1 and evaluation)

The removal rate of the floating point particle before and behind the 2nd cleaning process of the silicon wafer of Examples 1-12 and Comparative Examples 1-52 was measured.

The removal rate of this floating point particle was computed by the following method. First, the number of particles of 0.20 μm or more in particle size (particle size 粒 徑) before and after the second cleaning process was measured using SurfScan6420 (a surface inspection apparatus manufactured by KLA-Tencor, USA). Next, the ratio which divided the number of particles of 0.20 micrometer or more of particle size after a 2nd washing process by the number of particles of 0.20 micrometer or more of particle size before a 2nd washing process was represented by the percentage, and it was set as the removal rate of a floating point particle. The results are shown in Figs. 3A to 3C and Figs. 4A and 4B.

As can be seen from Figs. 3A to 3C and Figs. 4A and 4B, in Comparative Examples 1 to 52, the removal rate of the floating point particles is low as 45 to 85%, whereas in Examples 1 to 12, The removal rate was very high, 88-100%. This reason is considered to be because the removal rate of the floating point particle of the Example became very high by injecting oxygen ions in three portions and reducing the particles immediately before the second oxygen ion implantation. In addition, since the oxygen ion implantation of the third time is low temperature, it is considered that even if some particles are brought in, it will not become a defect nucleus. In addition, since particles having a long residence time on the wafer surface with respect to the implantation time become defect nuclei, particles present during the first and second oxygen ion implantation tend to become defect nuclei, but the second and third oxygen ion implantation Particles that exist only in time are considered to be difficult to become defective nuclei.

(Comparative Exam 2 and Evaluation)

The number of deep defects penetrating through the SOI layer of the silicon wafer subjected to the first to third oxygen ion implantation steps and the SIMOX heat treatment step of Examples 1, 4, 7 and 10, Comparative Examples 3 to 6, and Comparative Examples 16 to 19 was determined. It was measured.

The number of defects was determined by immersing the wafer in a 50% by weight hydrofluoric acid solution at 23 ° C. for 30 minutes to reveal defects in the SOI layer (presentation). It measured by observing with an optical microscope. The results are shown in FIG.

As can be seen from FIG. 5, in Comparative Examples 3 to 6 and Comparative Examples 16 to 19, the number of deep defects penetrating through the SOI layer was 17 to 26, whereas in Examples 1, 4, 7 and 10, the SOI layer was used. the number of deep dog 0-5, that SIMOX wafer having a diameter of 200mm of a defect extending through the opening of 0.016 / cm ² It became very small as follows.

According to the manufacturing method of the SIMOX wafer of the present invention, since the strong bond of particles containing a large amount of silicon and oxygen bonds can also be cut, the particles can be removed almost completely efficiently from the silicon wafer surface. Thus, it is possible to manufacture SIMOX wafers with very few defects.

Claims (6)

Implanting oxygen ions into the silicon wafer, Cleaning the silicon wafer implanted with the oxygen ions; Forming a buried oxide film in the silicon wafer by heat-treating the cleaned silicon wafer, And etching the SiO ₂ film formed on the surface of the silicon wafer by immersing the silicon wafer in an aqueous hydrofluoric acid solution after injecting oxygen ions into the silicon wafer and before cleaning the silicon wafer. Method of producing a SIMOX wafer, characterized in that the etching rate for the SiO ₂ film of a hydrofluoric acid aqueous solution at the time of the etching processing of 150~3000 (Å / min). 2. The SIMOX according to claim 1, wherein oxygen ion implantation into a silicon wafer is divided into a plurality of times, and the silicon wafer is immersed in a hydrofluoric acid solution immediately after any one of these oxygen ion implantation steps or immediately after two or more implantation steps. Wafer manufacturing method. The temperature of the hydrofluoric acid aqueous solution is more than the freezing point of this hydrofluoric acid solution, and is 40 degrees C or less, The manufacturing method of the SIMOX wafer whose immersion time of the silicon wafer in the said hydrofluoric acid aqueous solution is for 10 to 600 second. Claim 1 or claim 2, when the hydrofluoric acid as the etching rate R (Å / minute) of an aqueous solution for a SiO ₂ film, and the dipping time of the aqueous solution of hydrofluoric acid to the silicon wafer la H (seconds), H≥ ( And the immersion time is set to be 1500 / R) (seconds). The method of manufacturing a SIMOX wafer according to claim 1, wherein a surfactant is added to the hydrofluoric acid aqueous solution. Is prepared by the method described in claim 1, the number of deep defects penetrating through the SOI layer defects are observed after immersion for 30 min hydrofluoric acid aqueous solution having a concentration of 50% by weight at a temperature of 23 ℃ 0.05 pieces / cm ² SIMOX wafer which is below.

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