JPH10256391A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the thickness of some local areas of an oxide film to be formed in a semiconductor device to any one in a one-time oxidation process by doping chlorine in the oxide film and making a heat treatment so that the concentration of fluorine in a conductor film formed on the oxide film may be different in some local areas. SOLUTION: On a semiconductor substrate 1, oxide films 4, 5 containing chlorine are formed. Then, a conductor film 8 which has a different fluorine concentration in some local areas is formed on the oxide films 4, 5 and then a heat treatment is conducted to control the thickness of the oxide films 4, 5 so that some local area may have different thickness form the other area. Dissociation energy of a Si-O bond is 622kJ/mol and that of a Si-Cl bond is 386kJ/mol. So, if chlorine is preliminarily doped in the oxide films 4, 5, fluorine implanted afterward cuts a Si-Cl bond and forms a Si-F bond easily. Therefore, the thickness of the oxide films can be increased good enough to control the thickness of some local areas of the films to any one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device characterized by a method for locally controlling the thickness of a gate oxide film in a MOS type semiconductor device. is there.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device, a process of growing a thin film on a semiconductor substrate for forming a wiring layer, an electrode, or an insulating layer is repeated.
In the OS type semiconductor device, in order to configure a plurality of MOSFETs having different functions in one chip, it is necessary to change the thickness of the gate oxide film for each MOSFET having a different function. The growth process is repeated.

For example, after a gate oxide film is formed by thermal oxidation, a conductor film serving as a gate electrode or the like is deposited, and then ion implantation is performed using the gate electrode formed by patterning only the conductor film in a predetermined region as a mask. To form source / drain regions.

[0004] Next, after a predetermined region is covered and the conductor film and the gate oxide film in the region where elements having different characteristics are to be formed are removed, thermal oxidation is newly performed. After forming a different gate oxide film, depositing a conductor film to be a gate electrode, etc., ion-implanting is performed using the patterned gate electrode as a mask to form source / drain regions. MOSFETs having different characteristics are provided.

In this case, although the controllability of the thickness of the gate oxide film is good, the step of forming the gate insulating film is performed twice and the step of forming the gate electrode cannot be shared. There is a problem that the number of steps increases and the throughput is low.

In another method, a gate oxide film is formed by thermal oxidation, a gate oxide film in a predetermined region is removed, and then the whole surface is thermally oxidized again to form a gate oxide film. The region is thermally oxidized twice to form a thick gate oxide film, and a thin gate oxide film is formed in other regions.

Next, a source / drain region is formed by depositing a conductive film serving as a gate electrode or the like over the entire surface and then performing ion implantation using the gate electrode formed by patterning as a mask to form a source / drain region. Are provided.

In this case, since the step of forming the gate electrode can be shared, the number of manufacturing steps is reduced, but the previously formed gate oxide film is exposed to an oxidizing atmosphere in the subsequent oxidation step. In addition, there is a problem that the controllability of the film thickness is poor, and the oxidation step remains twice.

In order to solve such a problem, by selectively implanting fluorine (F) or chlorine (Cl), the film thickness of the gate oxide film is locally changed in a single oxidation step. Since this is proposed (if necessary, see JP-A-4-206774), this conventional method for controlling the thickness of the gate oxide film will be described with reference to FIG.

Referring to FIG. 5A, first, a field oxide film 32 is formed on a p-type silicon substrate 31 by selective oxidation, and then gate oxide films 33 and 34 having a thickness of 20 nm are formed. 1x
An amorphous silicon film 35 having a thickness of 100 nm including 10 ²⁰ cm ⁻³ is deposited.

Next, a photoresist layer 36 is provided,
Of the region where the thickness of the gate oxide films 33 and 34 is to be increased.
The opening 37 is formed only through the opening 37, and the F
The projection range of ON 38 is amorphous silicon film 35 / g
4 F ions 38 so as to come to the interface of the gate oxide film 33.
1 × 10 at 0 keV energy¹³~ 2 × 10¹⁶cm ^-2
Is implanted at a dose of.

Next, after the photoresist layer 36 is removed, the amorphous silicon layer 35 is patterned to form the gate electrode 3.
After forming 9, 40, 90 in N ₂ atmosphere
By performing a heat treatment at 0 ° C. for 30 minutes, damage recovery from ion implantation and activation of P in the gate electrodes 39 and 40 are performed.

In this heat treatment, the thickness of the gate oxide film 33 in the region where the F ions 38 are selectively ion-implanted is increased by about 10%. Break the O bond to obtain Si-
It is considered that an F bond is formed, and the Si—F bond extends the Si—O structure and acts to relax the structure, thereby increasing the physical film thickness.

Next, referring to FIG. 5C, ion implantation is performed using the gate electrodes 39 and 40 as a mask to form n-type source / drain regions 41 and 4.
2 is formed, and a heat treatment is performed again to perform damage recovery by ion implantation, and a MOSF having a thick gate oxide film 33 is formed.
The ET and the MOSFET having the thin gate oxide film 34 are provided in one chip.

The implantation of F ions for controlling the film thickness is not limited to the interface between the amorphous silicon film 35 and the gate oxide film 33, but may be stopped in the amorphous silicon film 35. Something good
Further, Cl ions may be implanted instead of F ions.

[0016]

However, such a conventional method for controlling the thickness of an oxide film by selective implantation of F ions is as follows.
There is a problem that a sufficient change in film thickness cannot always be obtained.

According to the study by the present inventors, this
It is considered that since the dissociation energy of the -O bond is as large as 622 kJ / mol, the Si-O bond cannot be cut sufficiently even by implantation of F ions.

Therefore, an object of the present invention is to locally and arbitrarily control the thickness of an oxide film provided on a semiconductor device by only one oxidation step.

[0019]

FIG. 1 is an explanatory view of the principle configuration of the present invention, and FIG. 2 is an explanatory view of the operation of the present invention. Referring to FIG. 1 and FIG. Means for solving the problem in the invention will be described.

1 (a) and 1 (b) (1) In the present invention, in a method of manufacturing a semiconductor device, after providing oxide films 4 and 5 containing chlorine on a semiconductor substrate 1,
A conductive film 8 having a locally different fluorine concentration is provided on the oxide films 4 and 5, and heat treatment is performed to thereby form the oxide films 4 and 5.
Is characterized in that the film thickness is locally controlled.

As described above, the oxide films 4 and 5 are doped with chlorine, and the heat treatment is performed such that the fluorine concentration in the conductor film 8 provided thereon is locally different, so that the oxide films 4 and 5 are doped with chlorine. 5 can be easily controlled.

This is because the dissociation energy of the Si—O bond is 622 kJ / mol and the dissociation energy of the Si—Cl bond is 386 kJ / mol, so that the oxide films 4 and 5 are doped with Cl in advance. It is considered that the implanted F breaks the Si—Cl bond to form a Si—F bond, and the dissociation energy of the Si—Cl bond is low, so that the Si—F bond (dissociation energy: 5)
(91 kJ / mol), and the film thickness can be sufficiently increased.

FIG. 2 shows the dependence of the increase in the thickness of the oxide film 4 having a thickness of 7 nm formed by thermal oxidation in the oxidizing atmosphere 3 containing HCl on the Cl concentration in the oxide film 4 and the thickness thereof. is a diagram showing the concentration dependence of the ion-implanted F to the conductor films 8 formed a WSi film 7 having a thickness of 150nm on the amorphous silicon film 6 of the 50 nm, the heat treatment conditions are N ₂ atmosphere, 100
This was performed at 0 ° C. for 30 minutes.

As is apparent from the figure, when the Cl concentration in the oxide film 4 is 2 × 10 ¹¹ cm ⁻² , the conductor film 8
0.8 n when the concentration of F is 1 × 10 ¹⁵ cm ⁻²
When the concentrations of m and F are 1.5 × 10 ¹⁵ cm ⁻² ,
4 nm increase, and Cl in the oxide film 4
When the concentration is 3 × 10 ¹³ cm ⁻² , the concentration of F is 1 × 1
In the case of 0 ¹⁵ cm ^-2 , 1.1 nm and the concentration of F are 1.5
In the case of × 10 ¹⁵ cm ^-2 , an increase of 1.6 nm was observed.

In this case, when depositing the WSi film 7, since SiH ₄ and WF ₆ are used as source gases, a part of F decomposed from WF ₆ is doped into the WSi film, and its concentration is since the 1 × 10 ¹⁵ cm ^-2 order, the actual ion implantation amount minus only about 1 × 10 ¹⁵ cm ^-2 from F concentration in FIG.

As described above, by doping chlorine into the oxide films 4 and 5, when F ions are implanted by 0.5 × 10 ¹⁵ cm ⁻² , that is, when the F concentration is 1.5 × 10 ¹⁵ c
In the case of m ⁻² , the increase in film thickness is 20% (1.4 nm / 7 n
m) to 22.8 (1.6 nm / 7 nm), and as apparent from the trend extrapolation in the figure, it becomes possible to further increase the film thickness with an increase in the amount of F implantation.

(2) Further, according to the present invention, in the above (1), the chlorine concentration in the oxide films 4 and 5 is controlled by the chlorine concentration in the oxidizing atmosphere 3 containing chlorine in the step of forming the oxide films 4 and 5. It is characterized by doing.

As described above, by doping chlorine into the oxide films 4 and 5 by thermal oxidation in the oxidizing atmosphere 3 containing chlorine such as hydrochloric acid (HCl) or dichloroethylene (DCE), the dissociation energy can be reduced. Uniform oxide films 4 and 5 containing many low Si—Cl bonds can be formed in one process.

(3) In the present invention, in the above (2), the chlorine concentration in the oxide films 4 and 5 may be 1 × 10 ¹¹ to 1 × 1.
0 ¹⁴ cm ^-2 .

As described above, when the Cl concentration is smaller than 1 × 10 ¹¹ cm ⁻² , the degree of increase in the thickness of the oxide films 4 and 5 due to the implanted fluorine ions 10 becomes small, and the Cl concentration becomes 1 × 10 ¹¹ cm ^−2. If it is larger than × 10 ¹⁴ cm ⁻² , the oxide film
Of 1 × 10 ¹¹ to 1 ×
A range of 10 ¹⁴ cm ^-2 is preferred.

(4) The present invention is characterized in that in any one of the above (1) to (3), the fluorine concentration in the conductor film 8 is controlled by ion implantation of fluorine ions 10.

As described above, the fluorine ions 10 are transferred to the oxide film 4,
5 can be locally controlled by selectively implanting it into a region where the film thickness is to be increased by using an ion implantation mask such as a photoresist mask 9 and the like. The step of removing the film becomes unnecessary.

(5) The present invention is characterized in that in any one of the above (1) to (4), the above-mentioned heat treatment is performed before patterning the conductive film 8.

As described above, since the heat treatment is performed before patterning the conductor film 8, the fluorine ions 10
The ion implantation conditions need not be precisely controlled so that the projection range of the fluorine ions 10 comes to the interface between the conductor film 8 and the oxide films 4 and 5 as in the related art.

(6) Further, according to the present invention, in any one of the above (1) to (5), the oxide films 4 and 5 are gate oxide films, and the conductive film 8 is patterned to form a gate electrode. Is formed.

By using the manufacturing method of the present invention for a MOS type semiconductor device, the thickness of the gate oxide film of each MOSFET in one chip can be arbitrarily set according to the required breakdown voltage or the applied gate voltage. Can be set to

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A manufacturing process according to an embodiment of the present invention will be described with reference to FIGS. First, after a pad oxide film (not shown) is formed on the surface of the p-type silicon substrate 11 by thermal oxidation, a SiN film (not shown) is deposited on the entire surface by a CVD method to form an element. Patterning is performed so that the portion deposited in the region remains, and then the SiN film is thermally oxidized using the oxidation-resistant mask to form a thick field oxide film 12 for element isolation.

[0038] Next, after removing the SiN film pattern and the pad oxide film, 1-2 volume% of HCl relative to O _2, for example, in an oxidizing atmosphere 13 containing HCl were mixed 1.6 volume%, 800 1050 ° C., for example, 1
3 to 10 nm in thickness by thermal oxidation at 050 ° C.
For example, at 7 nm, the Cl concentration is 1 × 10 ¹¹ to 1 × 10 ^14.
cm ⁻² , for example, 2 × 10 ¹¹ cm ⁻² gate oxide film 1
4, 15 are formed.

In this case, if the Cl concentration is less than 1 × 10 ¹¹ cm ⁻² , the degree of increase in the film thickness due to the implanted F ions is small, and if the Cl concentration is more than 1 × 10 ¹⁴ cm ⁻² , The quality of the gate oxide films 14 and 15 is degraded.

Next, as shown in FIG. 3B, a thickness of 10 to 100 n is formed on the entire surface by the CVD method.
After depositing an amorphous silicon film 16 having a thickness of, for example, 50 nm, a WSi film 17 having a thickness of 100 to 200, for example, 150 nm is deposited by a CVD method using SiH ₄ and WF ₆ as source gases.

In this case, a part of the amorphous silicon film 16 and the WSi film 17 are inevitably doped with F decomposed from WF ₆ by about 1 × 10 ¹⁵ cm ⁻² .

Referring to FIG. 3C, an opening 19 is provided in the photoresist layer 18 in order to increase the thickness of the gate oxide film 14 in a region where a DRAM (Dynamic Random Access Memory) is formed. One F ion 20 is supplied through this opening 19.
0 to 30 keV, for example, 2 at an energy of 20 keV
Ion implantation is performed at a dose of 10 ¹⁵ cm ^-2 .

Next, after removing the photoresist layer 18, the photoresist layer 18 is removed at 800 to 1000 ° C., for example, 850 in an N ₂ atmosphere.
By performing heat treatment at 10 ° C. for 10 to 120 minutes, for example, 20 minutes, F ions diffuse in the solid phase into the gate oxide film 14 to cut Si—Cl bonds in the gate oxide film 14 to form S ions.
By forming the i-F bond, the thickness of the gate oxide film 14 in the formation region of the DRAM becomes 10 nm.

In this case, since a part of the amorphous silicon film 16 and the WSi film 17 are doped with about 1 × 10 ¹⁵ cm ⁻² of F, the thickness of the gate oxide film 15 in the microcomputer logic formation region is also about 1 nm. It increases to about 8 nm.

Referring to FIG. 4E, the amorphous silicon film 16 and the WSi film 17
Gate electrodes 21 and 22 by patterning
Is formed, As ions are implanted at an acceleration energy of 25 keV and a dose of 2 × 10 ¹⁵ cm ^{−2 using} the gate electrodes 21 and 22 and the field oxide film 12 as a mask. For 10 minutes to form low-resistance n-type source / drain regions 23 and 24.

As described above, the gate oxidation step and the gate electrode formation conductor film deposition step are performed once.
DRAM having a gate oxide film 14 having a thickness of about 10 nm
MOSFET and gate oxide film 1 about 8 nm thick
5 can be formed in one chip for microcomputer logic.

The embodiment of the present invention has been described above.
The implantation amount of F ions may be appropriately determined from FIG. 2 or the like according to the required increase in the film thickness. Further, as a method for introducing F, a diffusion method may be used instead of ion implantation. Good thing.

The oxidizing atmosphere containing Cl in the above embodiment is not limited to HCl + O ₂ , but may be HCl + O ₂ + Ar, and the Cl source is not limited to HCl. Chloroethylene (DCE) may be used, in which case the mixing ratio is O ₂ ,
0.5 to 1.0 with respect to O ₂ + Ar or O ₂ + H ₂ .
5% by volume is preferred.

Although the gate electrode in the above embodiment has a multilayer structure of an amorphous silicon film and a WSi film, it may have a single-layer structure, and the amorphous silicon film may be a polycrystalline silicon film. It may be replaced.

In the above description of the embodiment, two types of MOSFETs having different thicknesses of gate oxide films are described.
However, MOSFETs having three or more types of gate oxide films having different thicknesses may be formed, and the required breakdown voltage or the amount of F ions to be implanted in accordance with the applied voltage. Should be locally different.

Although the present invention has been described as a typical embodiment as a method for controlling the thickness of a gate oxide film in a MOS type semiconductor device, the present invention is not limited to the gate oxide film. It is not limited to the type semiconductor device.

Conventionally, it has been proposed to oxidize hydrochloric acid in order to reduce the interface state in the MOS structure. Although it is similar to the step of forming a gate oxide film of the present invention, the conventional hydrochloric acid oxidation is performed. Is a method adopted when a good-quality oxide film with few interface states cannot be obtained. In recent years, a good-quality and very thin gate oxide film of about 10 nm has been obtained with good reproducibility. This is not a necessary step, but is a technical idea that is essentially different from the oxidation step of the present invention.

[0053]

According to the present invention, a plurality of MOSFETs having different gate oxide film thicknesses in one chip can be formed by a single gate oxidation step and a single gate electrode deposition step.
Can be formed, which greatly contributes to improvement of the characteristics of the semiconductor device and improvement of the production yield.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is an explanatory diagram of the operation of the present invention.

FIG. 3 is an explanatory diagram of a manufacturing process partway through an embodiment of the present invention.

FIG. 4 is an explanatory diagram of a manufacturing process of the embodiment of the present invention after FIG. 3;

FIG. 5 is an explanatory diagram of a conventional method for controlling the thickness of a gate oxide film.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 element isolation insulating film 3 oxidizing atmosphere containing chlorine 4 oxide film 5 oxide film 6 amorphous silicon film 7 WSi film 8 conductor film 9 photoresist mask 10 fluorine ion 11 p-type silicon substrate 12 field oxide film 13 HCl Oxidation atmosphere containing 14 gate oxide film 15 gate oxide film 16 amorphous silicon film 17 WSi film 18 photoresist layer 19 opening 20 F ion 21 gate electrode 22 gate electrode 23 n-type source / drain region 24 n-type source / drain region 31 p-type silicon substrate 32 field oxide film 33 gate oxide film 34 gate oxide film 35 amorphous silicon film 36 photoresist layer 37 opening 38 F ion 39 gate electrode 40 gate electrode 41 n-type source / drain region 42 n-type Over vinegar drain region

Claims (6)

[Claims] After providing an oxide film containing chlorine on a semiconductor substrate, a conductor film having a locally different fluorine concentration is provided on the oxide film, and heat treatment is performed to reduce the thickness of the oxide film. A method for manufacturing a semiconductor device, comprising controlling locally. 2. The method according to claim 1, wherein the concentration of chlorine in the oxide film is controlled by the concentration of chlorine in an oxidizing atmosphere in the oxide film forming step. 3. The method according to claim 1, wherein the chlorine concentration in the oxide film is 1 × 10 ¹¹
3. The method for manufacturing a semiconductor device according to claim 2, wherein the pressure is set to about 1 * 10 ^{< 14} > cm ^<-2 >. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the concentration of fluorine in the conductor film is controlled by ion implantation of fluorine ions. 5. The method according to claim 1, wherein the conductive film is patterned before
The method of manufacturing a semiconductor device according to claim 1, wherein the heat treatment is performed. 6. The semiconductor according to claim 1, wherein said oxide film is a gate oxide film, and a gate electrode is formed by patterning said conductor film. Device manufacturing method.