JP2009111093A - Manufacturing method of semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor substrate where a stable and uniform protective film is formed on a semiconductor surface by improving the treatment liquid. <P>SOLUTION: The manufacturing method of the semiconductor substrate includes a process of introducing the treatment liquid, containing a micro nano valve into a treatment tank, and a process of dipping the semiconductor substrate in the treatment liquid to form the protective film on the semiconductor substrate surface. The treatment liquid containing this micro nano valve is produced by a micro nano valve water producing device, provided to a semiconductor substrate treatment apparatus, prior to the treatment on the semiconductor substrate and is introduced into the treatment tank. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor substrate in which a protective film is formed on the surface of the semiconductor substrate, and more particularly to a method for manufacturing a semiconductor substrate using micro-nano bubbles.

  For example, a semiconductor substrate such as a silicon wafer is covered with a natural oxide film having a surface of about 1 nm by alkali cleaning such as SC-1 or SC-2. Such a natural oxide film serves to protect the surface of the semiconductor substrate from foreign matter and damage.

  However, in the process of manufacturing a semiconductor substrate, there are not a few processes in which the natural oxide film disappears from the wafer surface. One example is a polishing process for planarizing the surface of a semiconductor substrate. The surface of a semiconductor substrate without a natural oxide film is very active and easily adsorbs many contaminants and foreign substances.

  For this reason, for example, a process of supplying ozone water to the substrate surface during or immediately after the polishing process is introduced (Patent Document 1). In this step, ozone water becomes an oxidizing agent, so that the surface of the semiconductor substrate is quickly covered with an oxide film, and the surface of the semiconductor substrate is protected from contamination such as foreign matter.

However, the oxide film formed by supplying ozone water to the surface has a problem that the film quality is not stable and the film thickness becomes non-uniform, so that a sufficient wafer surface protection function cannot be achieved. Therefore, there has been a demand for a method for stably and uniformly oxidizing the surface of a semiconductor substrate that has become active due to the disappearance of the natural oxide film.
JP-A-11-307485

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a semiconductor substrate in which a stable and uniform protective film is formed on the surface of the semiconductor substrate.

  The method for manufacturing a semiconductor substrate of one embodiment of the present invention includes a step of introducing a treatment liquid containing micro-nano bubbles into a treatment tank, a step of immersing the semiconductor substrate in the treatment liquid, and forming a protective film on the surface of the semiconductor substrate It has the process to perform.

  Here, it is preferable that the gas in the micro / nano bubbles is ozone and the protective film is an oxide film.

  Here, it is desirable that the density of micro / nano bubbles in the treatment liquid is 1000 / ml or more.

  Here, the micro-nano bubbles are preferably micro-nano bubbles within one week after generation.

  Here, in the step of forming the oxide film, it is desirable to apply ultrasonic vibration to the treatment liquid.

  Here, it is preferable that the semiconductor substrate is a silicon wafer, and the treatment liquid is pure water containing micro-nano bubbles containing ozone.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the manufacturing method of the semiconductor substrate which forms a stable and uniform protective film on the semiconductor substrate surface.

  Embodiments of a method for manufacturing a semiconductor substrate according to the present invention will be described below with reference to the accompanying drawings. Here, a case where a silicon wafer (hereinafter also simply referred to as a wafer) is targeted as a semiconductor substrate will be described as an example. In the present specification, micro-nano bubbles are defined as bubbles having a diameter of 1 nm or more and less than 100 μm. And micro nano bubble water shall mean liquids, such as a pure water containing this micro nano bubble.

  The method of manufacturing a semiconductor substrate according to the present embodiment includes a step of introducing a treatment liquid containing micro / nano bubbles in which gas in the micro / nano bubbles is ozone into a treatment tank, and immersing the semiconductor substrate in the liquid, and the surface of the semiconductor substrate A step of forming an oxide film as a protective film.

  FIG. 1 is a schematic cross-sectional view of a semiconductor substrate processing apparatus used in the method of the present embodiment cut along a plane parallel to a wafer. The semiconductor substrate processing apparatus 10 mainly includes a processing tank 12, a lifter 14, a micro / nano bubble water generator 16, a micro / nano bubble water supply system 18, a process liquid supply system 20, and a process liquid discharge system 22.

  The processing tank 12 is a container for storing a processing liquid such as pure water, and is formed of, for example, quartz glass. And the upper surface of the processing tank 12 is open | released. Further, an outer tub 24 for storing a processing liquid overflowing from the processing tank 12 is provided at the upper peripheral edge of the processing tank 12. The processing liquid discharge system 22 is connected to the outer tank 24 and discharges the processing liquid.

  The lifter 14 includes three holding bars 28 each having a plurality of holding grooves. The holding grooves can hold a plurality of wafers 30 in an upright posture. The lifter 14 is provided with a lifter drive unit (not shown) having a servo motor, a timing belt, and the like. Then, by operating the lifter driving unit, the lifter 14 can be moved up and down, and the plurality of wafers 30 held by the lifter 14 are immersed in the processing tank 12 and the lifting position above the processing tank 10. It is possible to move between.

  The micro / nano bubble water supply system 18 is configured so that the micro / nano bubble water generated by the micro / nano bubble water generator 26 can be supplied to the treatment tank 12. In the present embodiment, ozone is used as the gas in the micro / nano bubbles. From the viewpoint of increasing the oxidation rate and increasing the oxide film thickness in the oxidation of the wafer surface, which will be described later, 100% ozone is desirable, but in addition to ozone, other gases such as air, oxygen, nitrogen, carbon dioxide Etc. may be contained.

  The effect is also great when the substrate to be processed is a silicon wafer on which a device manufacturing pattern has been created. The pattern size tends to shrink with the miniaturization of devices, but even with such narrow gaps, it is possible to form an oxide film uniformly due to the high wettability of micro-nano bubbles. .

  The micro-nano bubble water generator 16 is designed to generate micro-nano bubbles having a density of 1,000 to several million / ml using, for example, a swirling flow type micro-nano bubble generating mechanism.

  Next, a method for manufacturing the wafer 30 using the semiconductor substrate processing apparatus 12 will be described with reference to FIGS. In the present embodiment, the surface of the wafer 30 is oxidized by using pure water containing micro-nano bubbles whose gas in the micro-nano bubbles is ozone (hereinafter also referred to as ozone micro-nano bubble water) as a processing liquid.

  First, the oxide film on the surface of the semiconductor wafer is immersed in, for example, a diluted HF solution, washed with pure water, and spin-dried. A surface oxide film is formed on the wafer using the semiconductor substrate processing apparatus 10.

  Prior to the oxidation treatment, as shown in FIG. 2, pure water is supplied from the treatment liquid supply system 20 into the treatment tank 12 and overflowed from the upper end of the treatment tank 12.

  Next, as shown in FIG. 3, ozone micro / nano bubble water including ozone micro / nano bubbles 32 generated by the micro / nano bubble water generator 16 is introduced into the treatment tank 12 using the micro / nano bubble water supply system 18.

  Here, the production | generation of the ozone micro nano bubble water in the micro nano bubble water production | generation apparatus 16 is performed with the following method, for example. First, a mixture of pure water and ozone, which is a gas, is filled in a pump in the micro / nano bubble water generator 16. Thereafter, pure water containing ozone bubbles of the order of micrometers is generated by the pressure in the pump. The pure water containing the generated ozone bubbles is filled in a cylindrical stainless steel rotating body in the micro / nano bubble water generating device 16. By rotating this stainless steel tube, the micrometer order bubbles are sheared to produce nanometer order ozone micro-nano bubbles. By circulating water between the pump and the stainless steel rotating body in order, ozone micro-nano bubble water is generated.

  Next, as shown in FIG. 4, the lifter driving unit is operated, the lifter 14 is lowered, and the plurality of wafers 30 held by the lifter 14 are immersed in the processing bath 12. And the oxide film is formed in the wafer 30 surface by maintaining the state which immersed the wafer 30 in the processing tank 12. FIG.

  By performing the process of immersing the wafer in ozone micro / nano bubble water as in this embodiment, the wafer surface can be oxidized stably and uniformly. In addition, the thickness of the oxide film to be formed can be controlled.

  As described above, in the present embodiment, the reason why the wafer surface can be oxidized stably, uniformly and thickly is considered as follows. That is, the Si bond in the vicinity of the wafer surface is cut by the energy that is released when the micro / nano bubbles burst. Then, ozone in the ozone micro / nano bubbles dissolves in pure water, and ozone, which is an oxidizing agent, fills the cut Si bonds. And according to ozone micro nano bubble, it is possible to increase the oxygen content in a fixed pure water volume significantly compared with pure water or ozone water. Thus, the oxidizing power on the wafer surface is improved by the cutting of the Si bond and the high concentration of dissolved ozone. Therefore, it is possible to proceed with oxidation over the bonding state of the Si bond on the wafer surface, the non-uniformity of the terminal state, and the like. Therefore, it is possible to oxidize the wafer surface stably, uniformly and thickly as compared with the prior art.

  In the present embodiment, the ozone micro / nano bubble density of ozone micro / nano bubble water is desirably 1000 / ml or more. This is because, if the density is higher than this density, the effect of realizing stable, uniform and thick oxidation can be obtained sufficiently in practical use. Furthermore, it is desirable that the micro / nano bubble density of the micro / nano bubble water is 500,000 / ml or more. This is because, if the density is higher than this density, the effect of realizing stable, uniform and thick oxidation can be remarkably obtained.

  The ozone micro / nano bubble water is desirably ozone micro / nano bubble water within one week after the generation of the ozone micro / nano bubbles. Micro-nano bubbles can have positive and negative potentials depending on the generation method. By reversing this potential with that of silicon wafers, the surface tension of the processing solution on the wafer is reduced, that is, the wettability is improved. To do. Even if the surface of the silicon wafer is hydrophobic, the oxide film generation rate is increased by improving the wettability of the entire processing solution. This is because the potential of the ozone micro-nano bubbles decreases with time, but if the ozone micro-nano bubbles are within one week after the generation of the ozone micro-nano bubbles, the same effect is obtained immediately after the generation of the ozone micro-nano bubbles.

  In the step of forming the oxide film, it is desirable to apply ultrasonic vibration to the ozone micro / nano bubble water. This is because by applying ultrasonic vibration, the bursting of ozone micro-nano bubbles is promoted, and the oxidation ability of the wafer is improved.

  In the above description, after removing the oxide film on the wafer surface with dilute HF, ozone micro / nano bubble water treatment is performed to form an oxide film. In order to form a more stable and uniform oxide film, it is desirable to perform treatment with ozone micro / nano bubble water in the state where there is no oxide film on the wafer surface. However, for example, even if a natural oxide film formed by RCA cleaning or the like exists on the wafer surface, the Si bond under the natural oxide film can be cut by the energy of the micro / nano bubbles. Therefore, even when there is a natural oxide film, a stable, uniform and thick oxide film forming action can be obtained by ozone micro-nano bubble water. In particular, for example, by using ozone micro-nano bubble water as a rinsing process after RCA cleaning, a natural oxide film can be additionally oxidized to form a more stable, uniform and thick oxide film. In this case, the effect | action which suppresses the watermark (water glass) formation by nonuniform natural oxide film formation after RCA washing | cleaning is acquired. This is because the surface of the wafer is covered with a stable and uniform oxide film to increase the wettability of the surface, and the area where no oxide film exists on the wafer can be reduced. This is considered to be because the generation of watermarks can be suppressed.

  In the present embodiment, the case where the gas in the micro / nano bubbles is mainly ozone and the protective film formed on the semiconductor substrate is an oxide film has been described. However, the gas in the micro / nano bubbles does not necessarily have to be mainly ozone. For example, oxygen or air may be mainly used. In this case, the protective film that is also formed is an oxide film. Further, for example, the gas in the micro / nano bubble may be mainly nitrogen. In this case, the protective film is a nitride film. Further, for example, the gas in the micro / nano bubbles may be mainly carbon dioxide. In this case, the protective film is a carbonized film.

  The embodiments of the present invention have been described above with reference to specific examples. In the description of the embodiment, the description of the semiconductor substrate processing apparatus, the method for manufacturing the semiconductor substrate, etc., which is not directly necessary for the description of the present invention is omitted, but the required semiconductor substrate processing apparatus and semiconductor are described. Elements relating to the substrate manufacturing method and the like can be appropriately selected and used.

  For example, although a silicon wafer has been described as an example of a semiconductor substrate, the present invention is not necessarily limited to a silicon wafer, and can be applied to a wafer other than silicon, such as a GaAs wafer or an InP wafer, a semiconductor substrate, or the like.

  In addition, all methods of manufacturing a semiconductor substrate that include the elements of the present invention and whose design can be appropriately changed by those skilled in the art are included in the scope of the present invention.

Examples of the present invention will be described below.

(Example 1)
The oxide film on the wafer surface was completely removed by immersing a Φ200 mm Si (100) wafer in 1% dilute HF (dilute hydrofluoric acid or DHF) for 5 minutes. Thereafter, washing with pure water for 3 minutes and spin drying were performed.

Next, using the semiconductor substrate processing apparatus as shown in FIG. 1, the wafer was immersed in ozone nanobubble water as a processing solution to oxidize the wafer. As a micro nano bubble water production | generation apparatus, it produced | generated using the Kyowa machine establishment nano bubble production | generation apparatus BUVITAS (form: HYK-25). Ozone micro / nano bubble water generated by operating the micro / nano bubble water generator for 30 minutes with respect to 18 L of pure water was used as the treatment liquid. At this time, pure water containing ozone bubbles was filled in a stainless steel rotating body in the micro / nano bubble water generator, and the stainless steel rotating body was rotated at a rotation speed of 800 rpm. The flow rate of ozone gas sealed in pure water was 1 l (liter) / min. As a result of evaluating the particle size and density of the generated ozone micro / nano bubble water by the light refraction and scattering method, the bubble density was 2.2 to 7.2 × 10 ⁶ / ml, and the median value of the bubble particle size was 0. .623 to 0.632 μm, and peaks in the histogram were found in the vicinity of 0.1 μm, 0.3 μm, and 0.5 μm, respectively.

  Wafer processing was performed by changing the immersion time in ozone nanobubble water from 0 minutes to 100 minutes in increments of 10 minutes. For each wafer, the oxide film thickness at one wafer center position was measured using XPS (X-ray Photoelectron Spectroscopy). The results are shown in FIG.

  Moreover, about the wafer immersed for 50 minutes, the oxide film thickness of nine points in a wafer surface was measured by XPS, and the wafer surface variation of an oxide film thickness was evaluated. Standard deviation / average value was used as an index of variation. The results are shown in Table 1.

(Example 2)
The same treatment and evaluation as in Example 1 were performed, except that ultrasonic nanovibration of 50 KHz was applied to ozone nanobubble water as the treatment liquid. The results are shown in FIG.

(Comparative Example 1)
The same treatment and evaluation as in Example 1 were performed except that the treatment liquid was pure water only. The results are shown in FIG.

(Comparative Example 2)
The same treatment and evaluation as in Example 1 were performed except that the treatment liquid was 20 ppm ozone water. The results are shown in FIG.

  As is apparent from FIG. 5, when ozone micro-nano bubble water is used, the oxide film thickness increases as compared with pure water or ozone water. In particular, when ultrasonic vibration is applied, the increase is remarkable. Further, as apparent from Table 1, when ozone micro / nano bubble water is used, the in-wafer variation of the oxide film thickness is also reduced.

(Example 3)
A Φ200 mm Si (100) wafer was SC-1 cleaned. Next, using the semiconductor substrate processing apparatus as shown in FIG. 1, the wafer was immersed in ozone micro-nano bubble water as a processing solution, and a wafer rinsing process was performed to oxidize the wafer surface. Thereafter, the wafer surface was dried with a spin dryer. The micro-nano bubble generation device and the ozone micro-nano bubble water generation method are the same as in the first embodiment.

  In addition, the wafer process which changed the immersion time (rinsing time) in ozone micro nano bubble water from 1 minute to 10 minutes by 1 minute was performed. After drying each wafer, LPD (Light Point Defect) was evaluated on the wafer surface with a light scattering type particle counter. The evaluated LPD size is 120 nm or more. Later SEM observation revealed that most of the LPD was a watermark. The LPD measurement results are shown in FIG.

(Comparative Example 3)
The same treatment and evaluation as in Example 3 were performed except that the treatment liquid was pure water only. The results are shown in FIG.

  As is clear from FIG. 6, when ozone micro-nano bubble water is used, LPD (watermark) is reduced as compared with pure water.

  As mentioned above, the effect | action and effect of this invention were confirmed by the present Example.

The cross-sectional conceptual diagram of the semiconductor substrate processing apparatus of embodiment. Process drawing of the manufacturing method of the semiconductor substrate of an embodiment. Process drawing of the manufacturing method of the semiconductor substrate of an embodiment. Process drawing of the manufacturing method of the semiconductor substrate of an embodiment. The figure which shows the evaluation result of the oxide film thickness of an Example. The figure which shows the evaluation result of the number of LPD on Si substrate of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor substrate processing apparatus 12 Processing tank 14 Lifter 16 Micro nano bubble water production | generation apparatus 18 Micro nano bubble water supply system 20 Processing liquid supply system 22 Processing liquid discharge system 24 Outer tank 28 Holding rod 30 Wafer 32 Ozone micro nano bubble

Claims (6)

  A process for introducing a treatment liquid containing micro / nano bubbles into a treatment tank, and a process for immersing the semiconductor substrate in the treatment liquid to form a protective film on the surface of the semiconductor substrate. Method.   The method of manufacturing a semiconductor substrate according to claim 1, wherein the gas in the micro / nano bubbles is ozone, and the protective film is an oxide film.   The method for producing a semiconductor substrate according to claim 1 or 2, wherein the density of micro-nano bubbles in the treatment liquid is 1000 / ml or more.   4. The method of manufacturing a semiconductor substrate according to claim 1, wherein the micro-nano bubbles are micro-nano bubbles within one week after generation.   5. The method of manufacturing a semiconductor substrate according to claim 1, wherein, in the step of forming the protective film, ultrasonic vibration is applied to the treatment liquid. 6. The method of manufacturing a semiconductor substrate according to claim 1, wherein the semiconductor substrate is a silicon wafer, and the processing liquid is pure water containing micro / nano bubbles.

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