JPH06140377A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To keep cleaned crystal surface more stably and clean for a longer time by removing residual impurities on crystal surface with a liquid surface treating agent as pretreatment for film-forming process and then by washing the crystal with pure water substantially not forming oxides and storing the crystal in pure water. CONSTITUTION:A liquid state surface treating agent 27 such as pure water, hydrofluoric acid-based, sulfuric acid-based, hydrochlolic acid-based, hydrogen peroxide-based, ammonia-basd or their combinations are preselected depending on the contents of treatment, adjusted and stored in a treating vessel 21 in advance. Then, residual impurities, oxide films and organic pollutants on crystal surface are removed. Then, valves 22 and 26 are opened, pure water with dissolved oxygen concentration of less than 300ppb is introduced to the treating vessel 21, the surface treating agent 27 is replaced with pure water, and the surface of silicone crystal substrate 28 is washed with pure water having the dissolved oxygen concentration of lower than 300ppb. After the washing, it is stored in pure water having the dissolved oxygen concentration of lower than 300 ppb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device.

[0002]

2. Description of the Related Art The cleaning of a crystal surface in a semiconductor device manufacturing process has a great influence on the quality of the obtained semiconductor device. Taking the case of a silicon crystal surface as an example, residual impurities such as a natural oxide film, organic contaminants, and heavy metals present on the surface impede the growth of high-quality Si epitaxial crystals at low temperatures, or cause thin film gate oxide films. , Which makes it difficult to control with high precision, or acts as a process impeding factor or a device performance deteriorating factor such as an increase in series resistance or deterioration of rectification characteristics in the production of a metal ohmic contact. Therefore, it is essential to form a clean crystal surface free of residual impurities such as oxide films, organic substances, and heavy metals.

The cleaning treatment of the silicon crystal surface is as follows:
In order to remove organic substances and natural oxide films, a method of heating at a high temperature of about 800 to 1000 ° C in vacuum after performing organic cleaning or acid cleaning is widely used. While this method is reliable, it is not easy to keep stable as the cleaned surface becomes very active. On the other hand, if it is limited to oxide film removal, dry etching using a chemical reaction can be applied, but since heavy metals cannot be removed sufficiently,
The combined use of wet pretreatment is essential. As a typical example of the above-mentioned technique, there is a removal of an oxide film on the crystal surface by cleaning with hydrofluoric acid (HF) and a subsequent hydrogen termination (hydrogen termination) of the outermost surface silicon. It has been reported that the silicon crystal surface cleaned by this method is not oxidized thereafter in the atmosphere for several hours. However, in the normal semiconductor device manufacturing process, it is necessary to perform rinsing with pure water after HF cleaning, and it is known that the dissolved oxygen concentration in this pure water affects the oxidation of the silicon crystal surface. Has been.

By the way, the oxide film thickness on the crystal and the surface composition of carbon, oxygen, etc. are determined by XPS (X-ray photoelectron Spectral).
More detailed evaluation can be performed by using roscopy). FIG. 25 shows the XPS measurement result of a general silicon substrate surface. This spectrum is shown as Si oxide film and Si
When the signal intensity obtained from the substrate crystal is separated, the Si oxide film thickness on the Si substrate crystal is required to be about 0.8 nm. Further, using the same sample, as shown in FIG. 26, it is possible to evaluate the surface composition of Si, oxygen, carbon, etc. from the XPS results measured by changing the energy region. , 39.58%, 46.37% and 14.05% of carbon are found respectively.

Using the XPS evaluation as described above, the HF
After cleaning, when the oxide film thickness and surface composition of the silicon substrate crystal surface rinsed with pure water with a dissolved oxygen concentration of about several ppm, which was generally used, were examined, an oxide film of about several angstroms was found immediately after the rinse. In addition, it can be seen that organic matter pollution is also occurring. Although these are almost no problem for semiconductor devices with 1 μm rule, they are becoming more and more negative as design rules become finer and more highly integrated. Further, the above-described oxidation of the silicon crystal progresses with the elapse of the rinse time. From the above, in order to improve the performance of the semiconductor device, the surface of the silicon crystal or the like can be cleaned more, and
There is a demand for a processing method capable of maintaining the clean state.

On the other hand, the treatment liquid containing hydrofluoric acid is also used for the flattening treatment of the silicon substrate. For example, silicon
The (111) substrate surface is treated with a pH-adjusted buffered hydrofluoric acid (hereinafter referred to as BHF) solution, treated with hydrofluoric acid, and then boiled in pure water. Flattening is realized. Also, silicon (1
Regarding the (00) substrate surface, it is reported that the treatment with a BHF solution (pH = 5.3) gives the flattest surface.

However, in the above-described flattening treatment, for example, in the BHF solution treatment, pure water rinsing is not performed thereafter, and in the hydrofluoric acid treatment, pure water rinsing must be performed at a high temperature. However, there was a problem in terms of safety and stabilization of the manufacturing process. Therefore, there is a demand for a processing technique capable of easily and safely flattening the surface of a silicon substrate.

Here, a recent 0.1 μm rule CMOS
Then, the thickness of the gate oxide film is several nm, and the EEPR
The tunnel oxide film of the OM is also required to be extremely thin, about 7 to 10 nm. In such a thin oxide film, the unevenness on the silicon surface is transmitted similarly to the unevenness after the oxide film is formed. The MOS gate breakdown voltage depends on the roughness of the silicon surface, and the higher the surface flatness, the more uniform the gate breakdown voltage. Also, EEPRO
Regarding the reliability of M, it is recognized that the flattening of the tunnel oxide film relaxes the electric field concentration and improves the electric field breakdown voltage. Therefore, there is a strong demand for a safe and simple planarization technique on the surface of the silicon substrate at the atomic level.

[0009]

As described above, although the crystal surface cleaning technology typified by the silicon surface has been vigorously studied, the conventional cleaning technology does not provide sufficient cleanliness. With the emergence of technological areas that would become clear, it was difficult to maintain the cleaned surface in that state, as seen in the increase in the oxide film on the crystal surface after cleaning and the adsorption of carbon and oxygen. . These impede favorable crystal growth on the crystal surface, and therefore, it is desired to solve the above-mentioned problems in obtaining a higher performance semiconductor device.

On the other hand, in the conventional flattening technique for a silicon substrate, there are problems in safety and stability.
There is a demand for a safe and simple flattening technique on the surface of a silicon substrate at the atomic level.

The present invention has been made in order to solve such a problem, and makes it possible to further clean the crystal surface, and to keep the cleaned crystal surface more stably for a long time. It is an object of the present invention to provide a method for manufacturing a semiconductor device capable of achieving the above, and another object of the present invention is to flatten the surface of a silicon substrate at the atomic level.
It is an object of the present invention to provide a method for manufacturing a semiconductor device, which is safe and easy to carry out.

[0012]

A first method for manufacturing a semiconductor device according to the present invention is a method for manufacturing a semiconductor device, including a film forming step of forming a crystal film, a metal film, an insulating film, etc. on a crystal. As a pretreatment of the film forming step, a step of removing residual impurities on the crystal surface with a liquid surface treatment agent, and a crystal after removing the residual impurities are washed with pure water that does not substantially form an oxide. And a step of storing in the pure water. A second method for manufacturing a semiconductor device is a method for manufacturing a semiconductor device, which includes a film forming step of forming a crystal film, a metal film, an insulating film, etc. on a silicon crystal. A step of hydrogen-terminating the silicon crystal surface, and a step of planarizing the silicon crystal surface by washing the hydrogen-terminated silicon crystal with pure water that does not substantially form an oxide. It has a feature.

[0013]

In the first method for manufacturing a semiconductor device according to the present invention, pure water that does not substantially form an oxide after removing residual impurities on the crystal surface with a liquid surface treatment agent containing hydrofluoric acid, Specifically, the rinse cleaning is performed with pure water having a dissolved oxygen concentration of 300 ppb or less. Here, the surface oxidation of crystals in pure water can be suppressed to such an extent that oxidation does not occur if the dissolved oxygen concentration in pure water is extremely low such as 300 ppb or less. Moreover, the adhesion of surface contaminants such as carbon and oxygen can be suppressed. Therefore, the clean crystal surface after the surface treatment can be retained even after the rinse cleaning with pure water. Since this state hardly depends on the immersion time in pure water, the crystal after surface treatment and rinse cleaning is preserved in pure water with a dissolved oxygen concentration of 300 ppb or less after rinsing and cleaning. Can be held for a long time. Note that Si
Compared to the (100) plane, the Si (111) plane has a higher tolerance for dissolved oxygen and is effective even at about 1 ppm or less.

The pure water having a dissolved oxygen concentration of 300 ppb or less also contributes to the flattening of the silicon crystal surface. That is, although the surface of the silicon crystal surface-treated with the treatment liquid containing hydrofluoric acid or the like is terminated with hydrogen, the smoothness is not sufficient. A simple schematic diagram of the surface of the silicon crystal in this state is shown in FIG. As shown in the figure, the surface of the silicon crystal 1 has microroughness such as steps 2 and facets 3. FIG. 2 shows a state of silicon atoms terminated with hydrogen by hydrofluoric acid treatment or the like. The bonding force 14 between the silicon atoms 12 bonded to the hydrogen 11 and the internal silicon atoms 13 is weaker than the bonding force 15 between the silicon atoms in the solid. On the other hand, in pure water, OH ⁻ groups 16 are present at 10 ⁻⁷ mol / l, and these OH ⁻ groups 16 are the weakened silicon-silicon bonds 14 described above.
Has the effect of etching the silicon atoms 12 on the outermost surface. However, if the dissolved oxygen concentration in pure water is high (for example, about 5 ppm), the silicon atom 1
2, particularly the portion of step 2 in FIG. 1 is oxidized, and the effect of the OH ⁻ group 16 cannot be fully brought out.

On the other hand, when pure water having a dissolved oxygen concentration of 300 ppb or less is used, the oxidation of the crystal surface is suppressed as described above, so that the above-mentioned etching effect of the OH ^- group is sufficiently exerted. It becomes possible. Since the etching with the OH ⁻ group mainly occurs in the step 2 in FIG. 1, the surface of the silicon crystal can be planarized even by the pure water rinsing process at about room temperature.

That is, in the conventional pure water rinse containing a high concentration of dissolved oxygen, the interaction between the silicon crystal surface and pure water, which has been hindered by the formation of the oxide film, is such that the dissolved oxygen concentration is 300 ppb or less. It is possible to reliably generate it by using pure pure water. As a result, the surface of the crystal can be flattened by the pure water etching the silicon crystal. For example, in the case of the center line average roughness _Ra (DIN 4768, JIS B 0601) which is a measure of smoothness, according to the flattening treatment of the present invention, the dissolved oxygen concentration is 300 ppb or less in pure water. R just by processing
A value of _a = 0.1 nm or less can be achieved in the region of 100 × 100 nm ² or more. In this way, flattening at the device size is possible, and at the same time, the crystal surface can be highly cleaned by suppressing the formation of an oxide film and the adhesion of surface contaminants such as oxygen and carbon. It is possible to realize crystal growth and improvement of electrical characteristics of the interface,
It is possible to obtain a semiconductor device with higher performance. It should be noted that the Si (111) plane has a higher tolerance for dissolved oxygen than the Si (100) plane, and is effective even at about 1 ppm or less.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

First, an embodiment of the first semiconductor device manufacturing method according to the present invention will be described with reference to FIGS.

FIG. 3 is a diagram schematically showing the structure of a crystal surface pretreatment apparatus according to one embodiment, to which the method for manufacturing a semiconductor device of the present invention is applied. In the figure, 21 is a processing container having a drain pipe 23 in which a valve 22 is inserted in its lower part, and this processing container 21 is made of quartz or PFA.
It is made of a low elution material such as Teflon resin such as PVDF and PVDF. The processing container 21 is sealed by a lid 24 made of the same material, and an inlet pipe 25 for pure water or the like is connected to the lid 24. A valve 26 is inserted in the pure water introduction pipe 25.

In the processing container 21, a liquid surface treatment agent 27 selected in advance according to the processing content, such as pure water, hydrofluoric acid type, sulfuric acid type, hydrochloric acid type, hydrogen peroxide type, ammonia type,
Alternatively, a product prepared by combining them is housed in advance, and an object to be processed, for example, a silicon crystal substrate 28 is put therein, and first, residual impurities on the crystal surface, for example, an oxide film and organic contaminants are removed. Next, the bubbles 22 and 26 are opened, pure water having a dissolved oxygen concentration of 300 ppb or less is introduced into the processing container 21, and the surface treatment agent 27 is replaced with pure water.
The surface of the silicon crystal substrate 28 is washed with pure water having a dissolved oxygen concentration of 300 ppb or less.

After the cleaning with pure water, a film forming process for forming a crystal film, a metal film, an insulating film, etc., for example, MBE, CV
Until the crystal growth process by D, LPE, etc., the metal film formation process by metal deposition, etc.
Is stored in pure water with a dissolved oxygen concentration of 300 ppb or less.

By performing the pretreatment as described above, formation of an oxide film on the surface of the silicon crystal substrate 28 and adhesion of organic contaminants can be prevented, and the electrical properties of the semiconductor device are significantly improved. be able to. Further, it is preferable to replace the surface treatment agent 27 with pure water in a state where the surface of the silicon crystal substrate 28 is in contact with any of these liquids, that is, not exposed to the atmosphere or the like.
If the surface of the silicon crystal substrate 28 is exposed to the atmosphere or the like during the processing, there is a possibility that organic contaminants may be attached.

A 6-inch p-Si having a specific resistance of 25 to 50 Ω · cm was prepared according to the procedure described above using the crystal pretreatment apparatus having the above-mentioned structure.
A (100) substrate was pretreated. As the treatment liquid, a 2% HF aqueous solution and, as an example of pure water in the present invention, pure water having a dissolved oxygen concentration of 30 ppb or less was used. FIG. 4 shows the result of measuring the oxide film thickness formed on the silicon crystal substrate 27 by XPS as a relationship with the elapsed time in pure water. In addition, FIG. 4 shows the dissolved oxygen concentration as a comparison with the present invention.
The results of using 5 ppm of pure water and 1 ppm of dissolved oxygen concentration are also shown.

As is clear from FIG. 4, the dissolved oxygen concentration is
When pure water of 30 ppb or less is used, not only the oxide film is not formed after the normal rinse time (usually about 20 minutes), but the surface is not oxidized even after 5000 hours. . In contrast, the dissolved oxygen concentration is 5p
With pure water of pm or 1 ppm, an oxide film of a certain thickness is formed at the time when the normal rinse time has passed,
The thickness of the oxide film increases with time.

The effect of the ultra-low dissolved oxygen concentration of pure water,
That is, regarding the effect of suppressing the formation of the oxide film, almost the same effect was obtained up to a dissolved oxygen concentration of 300 ppb.
The effect was obtained at 1 ppm or less on the Si (111) plane. From these facts, surface oxidation in pure water has a dissolved oxygen concentration of 30%.
At 0 ppb or less, more specifically, at about 200 ppb, it can be seen that oxidation is suppressed so that the original clean state can be maintained even after storage for a long time.

Further, the silicon crystal substrate pretreated by the above-mentioned procedure and the silicon substrate treated with a 2% HF aqueous solution, exposed to air for 1 minute, and then rinsed with pure water having a dissolved oxygen concentration of 30 ppb or less. Using the crystal substrate, the amount of surface residual impurities (carbon, oxygen) was determined by XSP measurement. The results are shown in FIG.

No oxide film due to the Si--O bond was observed in both of the above-mentioned samples. However, as is clear from FIG. 5, the sample exposed to the atmosphere in the middle was continuously exposed without being exposed to the atmosphere.
The amount of oxygen and carbon bound in another form was about 20% higher than that of the sample subjected to HF treatment and pure water treatment. From this result, by rinsing the purified crystal surface after the HF treatment with pure water without exposing it to the atmosphere, hydrogen termination of the crystal surface by pure water is performed preferentially. I,
It is understood that carbon or oxygen in the atmosphere can be suppressed from adsorbing or binding to the crystal surface. Then, once the termination with hydrogen is performed, it is possible to further reduce the surface contamination due to carbon, oxygen and the like.

By manufacturing a device using the crystal substrate which has been subjected to the pretreatment as described above, it is possible to greatly improve the electrical properties thereof. As an example thereof, pretreatment based on the above-mentioned example, specifically, treatment with 2% HF aqueous solution, dissolved oxygen concentration DO, on a silicon crystal substrate continuously rinsed with pure water of 30 ppb or less, a metal After vapor deposition, the contact resistance was measured. Further, as a comparison with the present invention, a metal was vapor-deposited on a silicon crystal substrate treated in the same manner except that pure water having a dissolved oxygen concentration of about 8 ppm was used, and its contact resistance was measured. The results are shown in FIG. From Fig. 6, the dissolved oxygen concentration is about 8ppm.
It can be seen that the sample according to the present invention has a smaller contact resistance than the sample using pure water.

FIG. 7 shows a semiconductor device manufactured according to one embodiment of the present invention, showing the structure of an NPN type bipolar transistor (BJT). NPN shown in FIG.
As the pretreatment of the electrode forming process of the emitter E, the base B, or the collector C, which is the final manufacturing process of the type BJT, the pretreatment based on the above-mentioned embodiment and the dissolved oxygen concentration of about 8 ppm are performed.
Pretreatment with pure water was performed, and NPN bipolar transistors shown in FIG. 7 were produced using these pretreatment materials. These base current emitters
FIG. 8 shows the change with the base bias voltage V _EB . It can be seen that the base current of the sample pretreated by the method of the present invention has a smaller change due to the bias voltage. Further, the fluctuation of the current due to the change of the bias voltage is also reduced.

In FIG. 7, the electrode formation on the crystal of the bipolar transistor using diffusion is shown as an example, but in addition to such electrode formation, MBE, CVD, L on the substrate.
Similar effects can be obtained in pretreatments of various film forming steps, such as pretreatment of crystal growth on crystals in the manufacturing process of BJT, HBT, MOS-FET, etc. in which a transistor is formed by epitaxy growth of PE or the like.

FIG. 9 shows another configuration example of the pretreatment device to which the present invention is applied. In the crystal pretreatment apparatus shown in FIG. 9, the lid 24 is connected to the pure water introducing pipe 25 and the nitrogen introducing pipe 29. A valve 30 is inserted in the nitrogen introducing pipe 29.

In the above-mentioned pretreatment apparatus, similarly to the pretreatment apparatus shown in FIG. 3, first, the crystal to be treated 28 and the liquid surface treatment agent 27 are previously stored in the treatment container 21,
After a lapse of a predetermined time, residual impurities on the surface of the crystal 28 are removed. Next, the valve 30 is opened to introduce high-purity nitrogen from the nitrogen introducing pipe 29, and then the valves 22 and 26 are opened to introduce pure water. As described above, by supplying pure water with nitrogen introduced, pure water having a dissolved oxygen concentration of 300 ppb or less can be produced on the spot. The decrease in dissolved oxygen concentration can be explained by Henry's law. That is, by utilizing the fact that the dissolved oxygen concentration in the liquid depends on the oxygen partial pressure in the gas with which the liquid is in contact, the dissolved oxygen concentration in the processing container 21 can be reduced to 3 Torr or less by
It can be reduced to 300 ppb or less. Also, the processing container 2
By setting the oxygen concentration in nitrogen in 1 to 0.1 Torr or less, the dissolved oxygen concentration can be reduced to the order of 10 ppb. Therefore, by introducing nitrogen into the processing container 21, the concentration of dissolved oxygen in pure water necessary for the present invention can be achieved. Further, by introducing nitrogen, the dissolved oxygen concentration in the liquid surface treatment agent 27 can be reduced to 300 ppb or less.

FIG. 10 shows another structural example of the crystal pretreatment apparatus. In the pretreatment apparatus of the above embodiment, when the inflow rate of pure water into the processing container 21 is high, the escape rate of oxygen from the liquid may not be sufficiently secured, and the desired effect may not be obtained. It is possible. In this case, it is necessary to increase the contact area between nitrogen and pure water. For example, as shown in FIG. 10, nitrogen bubbling can be performed to intentionally increase the contact area between nitrogen and pure water. it can. This allows
It becomes possible to reduce the dissolved oxygen concentration.

In the above-mentioned embodiments, the case where nitrogen is used is shown. However, even if other gas such as argon, hydrogen, helium gas, etc. is used, the oxygen concentration in the gas is not more than the above concentration. If so, the same effect can be obtained.

FIG. 11 shows still another example of the structure of the crystal pretreatment apparatus. In the pretreatment apparatus of each of the embodiments described above, the dissolved oxygen concentration is reduced by supplying a gas having a low oxygen concentration such as nitrogen, but the atmosphere in contact with the surface treatment agent 27 or the surface of pure water is changed. The dissolved oxygen concentration can be reduced by reducing the pressure using the vacuum exhaust device 31. Also in this case, the desired dissolved oxygen concentration can be achieved by setting the oxygen concentration in the vacuum to 3 Torr or less.

Next, an embodiment of the second semiconductor device manufacturing method according to the present invention will be described with reference to FIGS.

FIG. 12 is a diagram schematically showing the structure of the surface flattening processing apparatus used in this embodiment. 12
The processing apparatus shown in FIG. 9 is similar to the crystal preprocessing apparatus shown in FIGS. 9 and 10 and has a processing container 42 having a drain pipe 41.
And a lid 45 to which the pure water introducing pipe 43 and the nitrogen introducing pipe 44 are connected.

Using the processing apparatus having the above-described structure, for example, the HF-based processing liquid 46 is stored in the processing container 42 in advance.
After immersing the silicon substrate 47 in the HF-based processing liquid 46 and allowing a predetermined time to terminate the surface of the silicon substrate 47 with hydrogen, the processing container 42 is purged with ultra-high-purity nitrogen from the nitrogen introducing pipe 44, and thereafter. By supplying pure water having a low dissolved oxygen concentration to, it is possible to rinse with pure water having a dissolved oxygen concentration of 300 ppb or less. As described above, the surface flattening treatment can be performed with the same device configuration and treatment procedure as the above-described surface cleaning treatment device. That is, by introducing nitrogen into the processing container, nitrogen bubbling into the processing liquid, and further reducing the pressure in the processing container, the rinse treatment is stably performed with pure water having a dissolved oxygen concentration of 300 ppb or less. be able to. The conditions such as the introduction amount of nitrogen and the pressure reduction in the processing container are the same as those in the surface cleaning process described above.

The surface of the silicon substrate was processed according to the above-described processing procedure. Specifically, about 2% with a 5% HF aqueous solution.
After the separation treatment, as an example of pure water in the present invention, rinsed with pure water at room temperature having a dissolved oxygen concentration of 30 ppb or less. Silicon (100) surface and (11
1) The measurement results (p deflection component) of the surface by FT-IR (Fourier transform infrared spectroscopy) method are shown in FIGS. 13 and 14, respectively.

Here, in the FT-IR measurement, the completely flat surfaces of silicon (100) and (111) which are hydrogen-terminated by the HF-based treatment liquid are observed to have absorptions of only Si-H ₂ and Si-H, respectively. . The other absorption peaks are due to the microroughness of the substrate surface (step 2 and facet 3 in FIG. 1) and mean surface roughness at the atomic level. These micro-roughnesses are Si-H, Si-H ₃ , and
In the (111) plane, absorption in the form of Si-H ₂ and Si-H ₃ is FT-IR.
Appears in the measurement results.

From FIG. 13, the silicon (10
It can be seen that the silicon (100) surface is rough due to the absorption of Si-H _{3 in} addition to Si-H _{2 on} the 0) surface. On the other hand, the surface absorption peak after rinsing with pure water keeping the dissolved oxygen concentration at 30 ppb or less shows that Si-H ₂ increases.
It can be seen that Si-H ₃ is decreasing. This means that the flatness of the silicon (100) surface is improved. Similar effects occur on the silicon (111) surface. From FIG. 14, it can be seen that immediately after the 5% HF treatment, there are absorption peaks of Si—H ₂ other than Si—H, and the surface of the silicon (111) is rough. On the other hand, the absorption peak of the surface after treatment with pure water that maintains the dissolved oxygen concentration below 30 ppb is Si-H
Is increased and Si-H ₂ is decreased. This means that the flatness of the silicon (111) surface is improved.

Further, FIG. 15 shows the standard deviation (RMS) of the dissolved oxygen concentration and the surface roughness when the silicon (100) substrate was treated with the HF-based solution and then rinsed with pure water in which the dissolved oxygen concentration was changed. Shows the relationship with. When the dissolved oxygen concentration in pure water is 300 ppb or less, more specifically 200 ppb or less,
It can be seen that oxidation of the silicon surface is suppressed and silicon etching occurs, resulting in improved surface flatness and a reduced RMS. Similar effects were also obtained on the silicon (111) surface.

Next, as an example of manufacturing a semiconductor device to which the above-mentioned processing method is applied, an example of manufacturing a 0.1 μm rule CMOS will be described. FIG. 16 shows the structure of the 0.1 μm rule NMOS manufactured in this example. First, a locos oxide film 52 was formed on a silicon (100) substrate 51. Then, after removing the oxide film on the surface corresponding to the film formation surface of the silicon (100) substrate 51 with an HF-based solution, the dissolved oxygen concentration is
A rinse treatment was performed with pure water of 30 ppb or less to form a silicon surface 51a having excellent flatness. This silicon surface 51
A gate oxide film 53 (thickness: 5 nm) was formed on a by wet or dry thermal oxidation. Continue to source 5
4, drain 55, gate electrode 56, source electrode 57,
The drain electrode 58 was formed.

FIG. 17 shows the relationship between the dissolved oxygen concentration and the gate breakdown voltage when the dissolved oxygen concentration in pure water in the pure water rinse is changed. It can be seen that the gate voltage is low in the region treated with pure water up to a dissolved oxygen concentration of about 5 ppm, and the gate voltage increases from a dissolved oxygen concentration of 300 ppb or less, more specifically about 200 ppb or less. 0.1 μm rule NMO
To obtain the gate voltage corresponding to the S semiconductor device,
It is necessary to treat with pure water having a dissolved oxygen concentration of 300 ppb or less, and it is preferable to treat with pure water having a dissolved oxygen concentration of 200 ppb or less in order to obtain a better gate voltage. Furthermore, it can be seen that the best gate voltage can be obtained for the semiconductor device of the 0.1 μm rule NMOS by treating with pure water having a dissolved oxygen concentration of 30 ppb or less. Also,
As already reported, when there is little unevenness (microroughness) such as terraces on the silicon surface due to flattening, when a voltage is applied to the NMOS gate, electric field concentration is relieved and the gate voltage can be made uniform. Therefore, it is expected that the device characteristics will be made uniform and the yield will be improved. This characteristic
Shown in (111) CMOS, in the case of (111), this effect appears at 1 ppm or less.

Further, normally, in the MOS structure, silicon (1
00) Substrates are often used. This is because Nit of (100) (the number of dangling bonds per unit area) is smaller than that of other plane orientations, which is advantageous in reliability against electric field stress. In the operating state of the MOS, hot electrons and hot holes exist in the gate oxide film. During this dive, the dangling bond breaks,
This leads to reduced reliability. At this time, silicon (10
(0) The presence of irregularities on the surface means that there are (111) plane orientations and the like in addition to the (100) plane.
0) Not a face. That is, since the (111) plane and the like have more Nit than the (100) plane, the number of dangling bonds is large on the (100) surface having more irregularities than the ideal (100) Nit, and the reliability is high. Sex decreases. Therefore, reliability can be enhanced by improving the flatness of the surface of the silicon substrate.

Next, another embodiment of the surface flattening treatment of the silicon crystal will be described.

First, similarly to the surface flattening treatment of the above-mentioned embodiment, a 6-inch p-Si (100) substrate having a specific resistance of 25 to 50 Ω · cm was dipped in a 1% HF aqueous solution to form an oxide film on the crystal surface. After removing the above, the treatment vessel was purged with ultra-high-purity nitrogen, and then pure water having an extremely low dissolved oxygen concentration was supplied to rinse with pure water having a dissolved oxygen concentration of about 5 ppb.

[0048] In this way, the surface roughness R _a of the silicon substrate was rinsed with pure water was measured for areas of 100 nm × 100 nm ^2. _Ra is the atmospheric AFM (Atomic Force M
It was calculated from the value of the measurement area of 100 nm × 100 nm ² measured by using the ICP. FIG. 18 shows R _a as a relationship with the rinse treatment time with pure water having a dissolved oxygen concentration of about 5 ppb.

From FIG. 18, R _a = 0.1 nm in the region corresponding to the device size of 100 nm × 100 nm ² by rinsing with pure water having a dissolved oxygen concentration of about 5 ppb.
It can be seen that the following planarization at the atomic level can be achieved. The flatness of the surface of the silicon crystal substrate depends on the treatment time with pure water, and in this embodiment, the purest surface is obtained by rinsing with pure water for about 30 minutes. That is, as the treatment time with pure water progresses, the flatness of the surface initially improves, and the flatness is highest for about 30 minutes to 1 hour from the start of the treatment, and thereafter, the flatness of the surface decreases with the passage of time. I understand that it will go. As described above, there is an optimum value for the flattening treatment time of the silicon crystal surface with pure water. Since this optimum time changes depending on the processing conditions such as the concentration of dissolved oxygen in pure water and the amount of pure water supplied,
It is preferable to empirically obtain the optimum value and perform the pure water rinse. Similar results were obtained for the silicon (111) surface.

Next, an example of manufacturing a 0.1 μm rule CMOS using the silicon substrate to which the above-mentioned processing is applied will be described. The structure and manufacturing process of the CMOS are the same as those of the above-described embodiment whose structure is shown in FIG. The treatment according to the above-mentioned embodiment, that is, the 1% HF treatment and the rinse with pure water having a dissolved oxygen concentration of about 5 ppb are performed by changing the treatment time with pure water variously, and using each treated silicon substrate, 0.1 μm A rule CMOS was manufactured. FIG. 19 shows the relationship between the gate breakdown voltage of each CMOS and the pure water rinse time.

It can be seen from FIG. 19 that the gate breakdown voltage increases with the processing time in response to changes in flatness, and shows the highest value when the silicon substrate having the highest flatness is used. Further, with respect to the substrate which was rinsed for more than the optimum processing time, the gate breakdown voltage decreased with the processing time. From this result, it is understood that the flatness of the surface of the silicon substrate greatly affects the gate breakdown voltage, and the optimum gate breakdown voltage can be obtained by using the silicon substrate having extremely high flatness.

It is expected that the flattening of the silicon surface brings about the uniformization of the gate voltage accompanying the relaxation of the electric field concentration, and also contributes to the uniformization of the device characteristics and the improvement of the yield. These effects can be obtained regardless of the orientation of the substrate and the structure of the semiconductor device such as NMOS and CMOS.

In each of the above-mentioned embodiments, an example in which the surface of the silicon substrate is hydrogen-terminated by the treatment with the HF-based solution has been described as a pre-process of the planarization treatment with pure water having a dissolved oxygen concentration of 300 ppb or less. Similar effects can be obtained even if hydrogen is terminated by irradiation with hydrogen radicals in a vacuum.

On the other hand, for example, when pure water having a low dissolved oxygen is used for cleaning after opening a part of the silicon oxide film, an etching action occurs although it is slight depending on the opening diameter. An example thereof will be described below.

FIG. 20 shows the surface of silicon (100) and (111) in pure water after removing the natural oxide film at the openings (500 μm × 500 μm) of the silicon oxide film (100 nm) with a hydrofluoric acid solution. The dependence of the etching amount on the dissolved oxygen concentration is shown. Figure 20
It can be seen from the results that the silicon (100) and (111) surfaces are etched in pure water having a dissolved oxygen concentration of 300 ppb or less and 1 ppm or less, respectively.

FIG. 21 shows that in pure water (concentration of dissolved oxygen, the scale of silicon oxide film (100 nm) is used as a parameter.
It shows the flow rate dependence of the silicon etching amount at 30 ppb). It can be seen from FIG. 21 that the silicon etching amount increases as the flow velocity is increased. It can also be seen that the silicon etching amount increases as the mask scale becomes smaller. For example, the flow velocity is 2 cm / sec, 5 μm
In the case of a pattern of × 5 μm, etching of ~ 4 nm occurs per hour.

FIG. 22 shows an etching cross-sectional shape of a pattern of 5 μm × 5 μm when washed with pure water at a flow rate of 2 cm / sec for 1 hour. In the figure, 61 is a silicon substrate, 62 is a silicon oxide film, 63 is an etching step, and 64 is the direction of pure water flow. A local deep etching groove 65, which is considered to be caused by stress, is formed at the edge portion of the silicon oxide film 62 and the exposed portion 61a of the silicon substrate 61, which is not preferable in terms of process and device structure. FIG. 23 shows the cross-sectional shape when the flow rate of pure water is 0.5 cm / sec under the above conditions. Since the etching amount was reduced to 1 nm, no local etching groove was formed and the surface flatness was improved.

As a method of reducing the etching amount of silicon, shortening the processing time can be considered, but in the actual process, cleaning for at least 15 minutes is necessary. From the tendency of Fig.21, in the future miniaturization LSI, when considering a pattern with a size of 1 μm or less, it is considered that a flow velocity of 0.5 cm / sec or less is indispensable in order to reduce the etching amount to 1 nm or less in 15 minutes. To be

FIG. 24 shows a processing device for satisfying the above processing conditions. As the material of the processing device 70, it is preferable to use Teflon-based or quartz. The ultra-high-purity nitrogen gas 71 is once stored inside the lid portion 72, and is thus made to uniformly flow out. Further, the nitrogen gas is also caused to flow out to the outer peripheral portion 72a of the lid portion 72 to prevent the atmospheric air from entering the inside of the processing device 70. Since the atmosphere in the processing apparatus 70 is filled with nitrogen gas, when 5 ppb of ultrapure water is supplied from the ultrapure water inlet 73, the dissolved oxygen concentration in the ultrapure water in the processing tank 74 is set to 10 ppb or less. It can be held, and the oxidation of the surface of the silicon substrate 75 can be completely suppressed. The flow rate of ultrapure water can be controlled by the amount of water supplied at the ultrapure water inlet 73. In this processing device 70,
When a silicon substrate having a pattern of 5 μm × 5 μm level or less is washed, the silicon surface is not oxidized and etching can be controlled to 1 nm or less (1 hour treatment).

[0060]

As described above, according to the first manufacturing method of the present invention, it is possible to suppress the growth of the surface oxide film, and at the same time, the crystal surface exists in a form different from that of the oxide film. It is possible to simultaneously reduce the pollution caused by the adsorbed or chemically adsorbed oxygen, carbon and the like. in this way,
By obtaining a clean crystal surface, crystal growth and electrical characteristics of the interface can be improved, so that a high-performance semiconductor device can be obtained with good reproducibility.

According to the second manufacturing method of the present invention,
Since it is possible to easily and safely obtain an atomically flattened silicon surface, it is possible to stabilize the manufacturing process of semiconductor devices, etc., and it is possible to obtain higher performance semiconductor devices with good reproducibility. Becomes

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a state of a silicon substrate surface after being treated with an HF-based solution.

FIG. 2 is a diagram schematically showing the state of the surface of a silicon substrate that has been hydrogen-terminated with an HF-based solution.

FIG. 3 is a diagram schematically showing a configuration of a crystal surface pretreatment device used in one example of the present invention.

FIG. 4 is a diagram showing a relationship between an oxide film thickness of a silicon substrate rinsed with pure water and a holding time in pure water in an example of the present invention in comparison with a conventional example.

FIG. 5 is a diagram showing XSP measurement results of surface residues on a silicon substrate rinsed with pure water according to an example of the present invention.

FIG. 6 is a diagram showing pretreatment dependency of contact resistance of a metal film produced in an example of the present invention.

FIG. 7 is a diagram showing a configuration of a bipolar transistor manufactured in an example of the present invention.

FIG. 8 is a diagram showing a pretreatment dependency of a change of a base current according to an emitter-base bias voltage in a bipolar transistor according to an embodiment of the present invention.

FIG. 9 is a diagram schematically showing a configuration of a crystal pretreatment apparatus according to another embodiment of the present invention.

10 is a diagram showing a modification of the crystal pretreatment apparatus shown in FIG.

FIG. 11 is a diagram schematically showing the structure of a crystal pretreatment apparatus according to still another embodiment of the present invention.

FIG. 12 is a diagram schematically showing a configuration of a processing apparatus used in another example of the present invention.

FIG. 13: Silicon (100) treated according to an embodiment of the invention
It is a figure which respectively shows the FT-IR measurement result after HF processing and the pure water processing of the surface.

FIG. 14: Silicon (111) treated according to an embodiment of the present invention
It is a figure which respectively shows the FT-IR measurement result after HF processing and the pure water processing of the surface.

FIG. 15 is a diagram showing standard deviations of surface roughness of a silicon substrate when rinsed with pure water having various dissolved oxygen concentrations.

FIG. 16 is a diagram showing a configuration of an NMOS manufactured in an example of the present invention.

FIG. 17 is a diagram showing the relationship between the concentration of dissolved oxygen in pure water and the gate breakdown voltage of the NMOS manufactured in the example of the present invention.

FIG. 18 is a diagram showing a relationship between R _{a on the} surface of _a silicon substrate and a pure water rinsing time in an example of the present invention.

FIG. 19 is a diagram showing a relationship between a gate breakdown voltage of an NMOS manufactured in an example of the present invention and a pure water rinse time.

FIG. 20 is a diagram showing a dissolved oxygen concentration dependency of an etching amount of a silicon surface, (a) showing a result of a silicon (100) surface, and (b) showing a result of a silicon (111) surface. .

FIG. 21 is a diagram showing a flow rate dependence of a silicon etching amount in pure water when a mask scale of a silicon oxide film is used as a parameter.

FIG. 22 is a diagram showing an etching cross-sectional shape when cleaning is performed at a pure water flow rate of 2 cm / sec.

FIG. 23 is a diagram showing an etching cross-sectional shape when cleaning is performed at a pure water flow rate of 0.5 cm / sec.

FIG. 24 is a diagram showing a configuration example of a processing device to which the present invention has been applied.

FIG. 25 is a diagram showing an example of an XPS measurement result on the surface of a silicon substrate.

FIG. 26 is a diagram showing an example of an XPS measurement result of a silicon substrate surface for measuring the residual impurity concentration on the crystal surface.

[Explanation of symbols]

 21, 42 ... Processing container 23, 41 ... Drain pipe 24, 45 ... Lid 25, 43 ... Pure water introduction pipe 27, 46 ... Liquid surface treatment agent 28, 47 ... Silicon crystal substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Mochizuki No. 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Incorporated Toshiba Research and Development Center

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor device including a film forming step of forming a crystal film, a metal film, an insulating film, etc. on a crystal, wherein residual impurities on the crystal surface are liquefied as a pretreatment of the film forming step. It has a step of removing with a surface treatment agent and a step of washing the crystal after removing the residual impurities with pure water that does not substantially form an oxide and storing the crystal in the pure water. Of manufacturing a semiconductor device. 2. A method for manufacturing a semiconductor device including a film forming step of forming a crystal film, a metal film, an insulating film, etc. on a silicon crystal, wherein the silicon crystal surface is hydrogen-terminated as a pretreatment of the film forming step. And a step of flattening the surface of the silicon crystal by washing the hydrogen-terminated silicon crystal with pure water that does not substantially form an oxide. Method.