JP2001267285A - Semiconductor device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method in which boron contamination or the like can be effectively suppressed in a simple and practical method. SOLUTION: This is a manufacturing method of a semiconductor device which is provided at least with a step of drying a semiconductor wafer. The drying is performed by a dryer which is installed with a boronless filter and a chemical filter made of an ion exchange resin. The drying is performed after the semiconductor wafer is treated by a liquid containing at least hydrofluoric acid and hydrogen peroxide solution. The drying is performed by using such an organic solution as isopropyl alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device having at least a step of drying a semiconductor wafer. INDUSTRIAL APPLICABILITY The present invention can be widely used as a technique for manufacturing various semiconductor devices, and is particularly preferably applicable as a technique for preventing boron contamination on a semiconductor wafer.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing technique of this type, it is important to suppress contamination of a semiconductor wafer, and various wafer cleaning techniques have been proposed.

By the way, a clean room has been used in the manufacturing process of various semiconductor devices. Conventionally, boron glass has been frequently used as a material for taking in air supplied to the clean room from the outside air and as a material for a silencing material of an air conditioner. Have been.

Further, a HEPA filter (High) used in a filter of an air conditioner or a clean room is used.
Efficiency Penetrate Air
Filter) and ULPA filter (Ultra)
Low Penetration Air Filt
As shown in Table 1, the components of the ULPA filter constituent material include B ₂ O ₃
% Is included.

[0005]

[Table 1]

[0006] BF produced by the reaction between such glass fiber and HF vapor used in a wet process.
₃ (see the following formula (1)) and boric acid vapor generated by reacting with water vapor (see the following formula (2)) are known as boron contamination sources.

[0007]

Embedded image B ₂ O ₃ + 6HF → 2BF ₃ (gas) + 3H ₂ O (1) B ₂ O ₃ + 6H ₂ O → 2B (OH) ₃ (gas) + 3H ₂ O (2)

In particular, according to the study of the present inventor, about 0.3
When air containing HF vapor of ppm (1/10 of the allowable concentration of the human body) is passed through the ULPA filter, the boron concentration is 250 times that of the case where outside air is passed.
Further, according to the study by the present inventors, even if the cleanliness (dust concentration) of the clean room is increased, there is no effect of reducing the boron concentration in the clean room, and boron in the air is almost trapped by the filter. There is nothing.

In a clean room, it can be said that boron contamination is more or less present due to the use of the ULPA filter or the like. In particular, in a full downflow type clean room, the pleated ULPA filter has an overwhelmingly large surface area compared to the exposed surface area of construction components such as floors, ceilings, walls, partitions, etc., so that there is more or less boron contamination. To do
Inevitable. Therefore, if the wafer to be processed is left in the clean room, borides such as BF ₃ and boric acid vapor contained in the air of the clean room adhere to the wafer and contaminate the wafer. As a result, in a diffusion step or a heat treatment process such as a CVD step, boron is diffused, and the carrier concentration in the diffusion layer or the CVD film fluctuates depending on the amount of boron diffusion due to contamination, thereby causing variations in device characteristics. I will invite you.

As a countermeasure against boron contamination caused by leaving a wafer in a clean room, a chemical filter (cation exchange resin) capable of trapping boron, HF
A chemical filter that removes the HF before passing through the ULPA filter has been developed and is commercially available.

Further, an HF-resistant filter (made of polypropylene or Teflon) made of a material which does not react with HF is also effective. However, as a basic measure for existing lines, it is necessary to review the entire line, and it is not practical to change the filter for the entire line in consideration of the suspension period and cost of the line. Therefore, reducing the amount of adhered boron by storing the wafer in a wafer case and keeping it out of direct contact with air in a clean room is a conventional boron contamination countermeasure. However, such a regulation of leaving a wafer cannot prevent boron contamination during processing in the apparatus or during wafer transfer. Therefore, an appropriate technique for removing boron attached to a wafer is desired.

[0012] Boron contamination generally occurs on a wafer after a diffusion process or a CVD process by SIMS or Spreadin.
It is evaluated by measuring an impurity profile using g Resistance. Boron contamination is a cleaning process such as an SC cleaning process (cleaning of a mixed solution of ammonia and hydrogen peroxide, followed by cleaning of a mixed solution of hydrochloric acid and hydrogen peroxide) which is widely used as a pre-process cleaning such as a diffusion process and a CVD process. It has been confirmed that this occurs significantly when the wafer is left behind. The present inventor conducted the following experiment in order to confirm the effect of boron contamination due to the standing on the subsequent diffusion step, CVD step, and the like. That is, the wafer after the SC cleaning is exposed to the air in the clean room to contaminate boron, and the wafer is subjected to an Sb diffusion process or reduced pressure poly-Si.
After the CVD process, the amount of boron contamination with respect to the wafer standing time after SC cleaning was examined using SIMS. Hereinafter, the results will be described.

Table 2 shows a flow of preparing an Sb diffusion sample. Table 3 shows a flow of preparing a poly-Si sample. For each sample, the standing time after the SC cleaning, which is the pretreatment, is varied between 0 and 120 minutes, and the dependence of boron contamination on the standing time is examined. As the Sb diffusion here, a two-zone diffusion method using Sb ₂ O ₃ as a solid source is used. This is based on SiO ₂ formed by a reaction between Sb ₂ O ₃ sublimated into a furnace and Si.
This is a diffusion technique in which Sb taken in is diffused into Si at a high temperature of about 1200 ° C., and the formed oxide film is removed by an HF solution after the diffusion. Therefore, SI
In the measurement of the concentration of boron by MS, only the concentration of boron diffused in Si is determined.

The poly-Si CVD film has a po
Gate material of ly-Si resistance element and MOS transistor
And in these cases, generally on a thermal oxide film
Is deposited on the substrate. Therefore, this decompression poly
In the measurement of boron contamination after the -Si CVD process,
As shown in the sample creation flow of Table 3, poly-S
i is deposited on the oxide film (see the third step of thermal oxidation in Table 3).
So that the _Two Of boron at Si / Si interface
The concentration was determined.

[0015]

[Table 2]

[0016]

[Table 3]

FIG. 2 shows the results of measuring the boron concentration by SIMS. Symbol I indicates the result of boron contamination evaluation of the Sb diffusion sample, and symbol II indicates the result of boron contamination evaluation of the poly-Si CVD sample. From this result, it can be seen that the amount of boron contamination increases in both the diffusion sample and the CVD sample depending on the time for which the wafer is left in the clean room after cleaning. Further, even in the sample where the standing time is zero minutes, a small amount of boron is detected, which indicates that the wafer is contaminated by boride in the clean room dissolved in the ammonia-hydrogen peroxide aqueous solution and the cleaning process. It is known that the contamination was caused by clean room air during the wafer transfer at the same time. Thus, even if the leaving of the wafer is minimized, boron contamination actually occurs, and it is understood that the technology for removing the attached boron is becoming more and more important.

Further, the present inventors have made the following specific studies. For example, the step of diffusing Sb used for forming the collector region of the bipolar transistor LSI is generally performed at a high temperature of about 1200 ° C., so that impurities adhering to the wafer surface diffuse deeply into the Si wafer together with the heat treatment. . Therefore, when the impurity profile after Sb diffusion is examined by SIMS measurement, boron having a higher diffusion coefficient than Sb diffuses deeply. Therefore, the amount of boron diffused into the silicon substrate due to boron contamination was evaluated by SIMS.

As shown in Table 4, five kinds of samples were examined. Table 4 shows the wafer No. 1 to 6. The following SC cleaning was performed as a diffusion pretreatment. _{NH 4 OH: H 2 O 2} : H 2 O = 1: 2: 7 mixture for 10 minutes _{HCl: H 2 O 2: H} 2 O = 1: 1: 8 mixture for 10 minutes after the washing P ^- The mold wafer was exposed to air in a clean room for 0 to 120 minutes (0 min., 60 m
in. , 120 min. Table 4)
As shown in FIG. 1 to 3.

After performing the same washing as described above, 12
The wafer left to stand for 0 minutes is treated with hydrofluoric acid (HF: H ₂ O).
= 100: 1) is converted to 30 nm in terms of a thermal oxide film.
An additional time is added for a considerable amount of etching, running water with pure water for 10 minutes, and a spin dryer (1000 rpm)
m, 3 min) and similarly exposed to the air of a clean room for 0 to 120 minutes (0 min., 3 min).
60 min. , 120 min. As shown in Table 4, wafer No. 4 to 6.

[0021]

[Table 4]

The above sample was subjected to S by a horizontal diffusion furnace.
Sb diffusion was performed at 1200 ° C. for 60 minutes in the b ₂ O ₃ gas phase, and the concentration of boron diffused into the silicon substrate was measured by SIMS. The results are shown in FIG. Symbol IV shows data on samples (wafer Nos. 4 to 6) to which a treatment with hydrofluoric acid (light etching) was added,
Reference numeral III indicates data on samples without the treatment with hydrofluoric acid (wafer Nos. 1 to 3).

As shown in FIG. 3, by performing the HF treatment, the boron contamination attached to the wafer surface can be removed (data III and IV in the case of zero leaving time).
(Comparison of data of No. 3) shows that remarkable contamination from the clean room air has occurred again after being left after the HF treatment (the data of code III and the code IV according to the time of leaving).
, In particular, the change in the data of the symbol IV).

FIG. 4 shows the result of similarly evaluating the amount of boron contamination when the drying time by a spin drier (1000 rpm) after the HF treatment was varied in the range of 3 to 15 minutes. Is a spin dryer drying time of 3 minutes). In the evaluation shown in FIG. 4, the wafer was not intentionally exposed to the air in the clean room. Nevertheless, as can be understood from FIG. 4, during the drying by the spin drier, the air in the clean room containing boron is taken into the spin drier and touches the wafer. Will increase.

As described above, the boron compound adhering to the wafer can be removed by the HF treatment. However, when the wafer is again exposed to the air in the clean room, boron contamination occurs. In particular, in the case of drying using a spin drier, boron contamination occurs. This is presumably because the air that has passed through the filter is supplied into the spin dryer, and boron contamination is also generated by boric acid vapor or the like from the filter, and the effect of removing boron contamination by the HF treatment is weakened.

[0026]

As described above, the prior art does not sufficiently solve the problem of boron contamination of wafers.

Accordingly, an object of the present invention is to provide a method of manufacturing a semiconductor device capable of effectively suppressing contamination, particularly, for example, boron contamination by a simple and practical method.

[0028]

A method of manufacturing a semiconductor device according to the present invention comprises, first, a method of manufacturing a semiconductor device comprising at least a step of drying a semiconductor wafer.
The drying is performed by a dryer equipped with a boron-less filter and a chemical filter made of an ion-exchange resin.

According to the present invention, since the boron-less filter is used, the contamination of boron from the filter is prevented, and the contamination by boron taken in from the air is suppressed by the chemical filter made of the ion exchange resin. Can be effectively suppressed.

The method of manufacturing a semiconductor device according to the present invention comprises, secondly, a method of manufacturing a semiconductor device comprising at least a step of drying a semiconductor wafer, wherein the drying is performed by removing hydrofluoric acid and aqueous hydrogen peroxide. Drying after treatment with a solution containing at least, and drying is performed using an organic solvent.

According to the present invention, the contamination such as boron can be effectively removed by the hydrofluoric acid-containing solution, and the organic solvent such as alcohol can be used for drying. Thus, the surface of the wafer is prevented from becoming hydrophobic, and the problem of watermark when an organic solvent such as alcohol is used can be solved.

Japanese Patent Application Laid-Open No. 4-177725 discloses a technique for oxidizing a wafer surface with an oxidizing agent such as aqueous hydrogen peroxide after cleaning with hydrofluoric acid. It is performed separately from water treatment, and
There is no description about drying using an organic solvent. Japanese Patent Application Laid-Open No. 8-264498 discloses a technique in which an oxide film is formed with a cleaning solution containing hydrogen peroxide and then rinsed with ultrapure water containing ozone and hydrofluoric acid. The cleaning with hydrofluoric acid and the treatment with aqueous hydrogen peroxide are separate, and drying using an organic solvent is not performed. In addition, Japanese Patent Application Laid-Open No. 5-029
Japanese Patent No. 292 discloses a technique of rinsing with pure water or water vapor after etching with hydrofluoric acid, and then etching the substrate after drying with hydrofluoric acid. As for the drying, only spin drying is disclosed. Japanese Patent Application Laid-Open No. Hei 5-343394 discloses a technique of performing thermal oxidation after etching with hydrofluoric acid, but here also does not describe a technique relating to the present invention with respect to drying in particular.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be further described below, and preferred specific examples will be described with reference to the drawings. Needless to say, the present invention is not limited to the illustrated embodiment.

In the invention in which the drying is carried out by a dryer equipped with a boron-less filter and a chemical filter made of an ion-exchange resin, the boron-less filter is a filter substantially free of boron, that is, a boron-free filter. Any filter can be used as long as it is not included. Generally, a filter using Teflon (registered trademark) or PTFE as a filter medium does not contain boron, and is generally called a boron-less filter. These filters have high resistance to hydrofluoric acid and can be preferably used. Chemical filters include anion filters, cation filters, and activated carbon filters.
As a boron removing effect, a filter made of a cation exchange resin has a remarkable effect, so that it can be particularly preferably used.

The mounting of the boronless filter and the chemical filter made of ion exchange resin on the dryer can be performed as follows. For example, by installing a chemical filter at the front stage to remove boron in the air and providing a boron-less filter at the rear stage at the air intake port of the dryer, it is possible to eliminate the emission of boron from a filter such as an ULPA filter. .

The drying in the present invention is drying after a cleaning treatment by wet treatment, and drying after a cleaning treatment including at least a step of treating with a solution containing hydrofluoric acid. It is a preferable embodiment that the solution containing at least contains hydrofluoric acid and aqueous hydrogen peroxide.

Drying is drying after treating a semiconductor wafer with a solution containing at least hydrofluoric acid and aqueous hydrogen peroxide. In the invention in which the drying is drying using an organic solvent, the organic solvent used is And isopropyl alcohol.

Next, preferred specific embodiments of the present invention will be described. In the following embodiments, for example, a diffusion step of Sb used for forming a collector region of a bipolar transistor LSI, or a poly-Si CVD for various semiconductor devices, which is used for the above-described examination of contamination, is described. The present invention can be suitably applied to a manufacturing example of a semiconductor device having a process and the like.

Embodiment 1 In this embodiment, a boronless filter is used as an air filter of a dryer. In this example, in particular, a boron-less filter and a chemical filter made of an ion exchange resin were used in combination as an air filter of a spin dryer. Here, a so-called boronless filter using Teflon or PTFE as a filter medium was used as the boronless filter. As the ion exchange resin, a chemical filter made of a cation exchange resin was used. As a mounting structure of the filter on the dryer, a chemical filter was installed at the front stage to remove boron in the air at the air intake port of the dryer, and a boron-less filter was provided at the rear stage to prevent the release of boron. .

In the present embodiment, the manufacturing method of the used sample and the handling thereof are the same as those shown in the above-described examination example, particularly the sample used for the evaluation of FIG. 4 described above and the handling thereof. .

According to this embodiment, since the spin dryer which does not release boron from the filter of the dryer itself and which can remove boron from clean room air by the chemical filter is used, boron contamination is suppressed. it can.

In this example, the wafer after the HF treatment was dried by the above-mentioned dryer to obtain a good effect of suppressing boron contamination. FIG. 1 shows the effect of wafer drying after HF treatment by a spin dryer in this example. The result shown in FIG. 1 is different from the evaluation of FIG. 4 showing the comparison only in the filter of the spin dryer, and dried using a spin dryer equipped with a combination of the boronless filter and the chemical filter according to this example. The only difference is that, as shown in FIG. 1, the level of boron contamination removed by the HF treatment is maintained regardless of the drying time.

As described above, according to the present embodiment, it is possible to leave the wafer in a clean room and remove boron contamination of the wafer generated during the process.

Embodiment 2 In this embodiment, the contamination of the wafer, such as boron contamination, is suppressed by improving the drying of the wafer after the HF treatment.

That is, as a technique for preventing the contamination source from being taken in from the dryer, a method of drying the wafer after the HF treatment and then the running water treatment with an organic solvent such as isopropyl alcohol can be considered.
Since the wafer after the HF treatment, for example, a silicon wafer, becomes hydrophobic, a watermark is easily formed.
There is a problem that an oxide film is formed on a wafer by oxygen dissolved in pure water.

In this example, based on the finding that it is effective to make the surface of a silicon wafer hydrophilic to avoid the above problems, a study was conducted based on this finding, and the wafer was constructed in the following configuration. Washing and drying were performed. That is, in this example, boron contamination was removed by a mixed solution of HF and H ₂ O ₂ , and a uniform oxide film was formed on the wafer surface by the oxidizing action of H ₂ O ₂ to form a hydrophilic surface. Thus, the watermark at the time of drying isopropyl alcohol is reduced.

In the present embodiment, specifically, wafer cleaning and drying are performed as follows. In the same manner as described above, the wafer to which boron was adhered by leaving it in a clean room was placed in a mixed solution of HF and H ₂ O ₂ (particularly,
After a treatment with ₂ O ₂ : H ₂ O = 1: 1: 8 mixed solution for 10 minutes, a running of pure water and drying of isopropyl alcohol for 10 minutes were performed (each of running of pure water and drying of isopropyl alcohol for 10 minutes). ). In the isopropyl alcohol drying, the wafer after the pure water running treatment is exposed to the vapor of isopropyl alcohol, and the alcohol is volatilized together with the water dissolved in the alcohol, whereby the drying is performed. No drying is required).

The sample subjected to the above processing was evaluated as described above.
In the same manner as in the _Two O_Three After gas phase diffusion of
Next, the amount of boron diffused into the silicon substrate by SIMS
Was evaluated. As a result, boron is diffused into the silicon substrate.
Dispersion is 5.0E9 atoms / cm^Two Met. Further
Watermark for drying isopropyl alcohol
Did not occur at all, and a hydrophilic surface was formed.

Thus, HF and H_Two O_Two Depending on the mixture of
Boron contamination adhering to the wafer surface
Isopropyl alcohol dry
Can prevent the formation of watermarks, which can be problematic in drying
Noh. HF and H _Two O_Two Treatment with a mixture of
In this case, an oxide film without boron contamination is formed.
Acts as a protective film on the surface of the wafer.
Immediately before the taxi growth process and CVD process,
At H_Two Do not perform high temperature treatment in a reducing atmosphere such as
Removing the oxide film by filing and then depositing the film
Completely prevents boron contamination at the interface between the wafer and the deposited film.
Is possible.

According to the present embodiment, it is possible to prevent the formation of a watermark which is a problem in drying an organic solvent such as isopropyl alcohol by making the wafer surface hydrophilic in addition to the effect of removing boron contamination. Becomes

[0051]

As described above, according to the method of manufacturing a semiconductor device of the present invention, contamination and contamination can be reduced by a simple and practical method.
In particular, an excellent effect that, for example, boron contamination can be effectively suppressed can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an effect of a first embodiment of the present invention.

FIG. 2 is a diagram showing a problem of the related art.

FIG. 3 is a diagram showing a problem of the related art.

FIG. 4 is a diagram showing a problem of the related art.

[Explanation of symbols]

I: Relationship between leaving time after cleaning and boron contamination (in case of impurity diffusion), II: Relationship between leaving time after cleaning and boron contamination (in case of CVD), III: Substrate after impurity diffusion Boron contamination (without hydrofluoric acid treatment), IV
-Boron contamination in the substrate after impurity diffusion (with hydrofluoric acid treatment).

Claims (6)

[Claims] 1. A method for manufacturing a semiconductor device, comprising at least a step of drying a semiconductor wafer, wherein the drying is performed by a dryer equipped with a boronless filter and a chemical filter made of an ion exchange resin. A method for manufacturing a semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the drying is drying after a cleaning process by a wet process. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the drying is a drying after a cleaning treatment including at least a treatment with a solution containing hydrofluoric acid. 4. The method for manufacturing a semiconductor device according to claim 3, wherein the solution containing hydrofluoric acid contains at least hydrofluoric acid and a hydrogen peroxide solution. 5. A method of manufacturing a semiconductor device comprising at least a step of drying a semiconductor wafer, wherein the drying is a treatment after treating the semiconductor wafer with a solution containing at least hydrofluoric acid and hydrogen peroxide solution, and The method of manufacturing a semiconductor device, wherein the drying is drying using an organic solvent. 6. The method according to claim 5, wherein the organic solvent is isopropyl alcohol.