JP3195422B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having an insulating film used for a highly integrated memory and a method of manufacturing the same.

[0002]

2. Description of the Related Art A halogen element such as fluorine and chlorine is ion-implanted into a polycrystalline Si electrode or a Si substrate, and the halogen element is moved to the interface between the insulating film and the Si substrate by thermal diffusion, so that X-ray irradiation and charge injection can be performed. The accompanying suppression of the increase of interface states and the deterioration of mobility
EE, Transactions on Nuclear
Science (IEEE TRANSACTIONS ON NUCLEAR SCIENCE)
36, No. 6, pp. 2116 (1989). There is an optimum value for the amount of halogen for minimizing deterioration, and it varies depending on the heat treatment conditions of the entire process. That is, the amount of the halogen deviates from the optimum value due to a slight change in the heat treatment conditions, and when the halogen is excessively supplied, the deterioration rate becomes higher than that of a device into which no halogen is introduced. Therefore, in the method of controlling the amount introduced into the insulating film by thermal diffusion by introducing an amount equal to or more than the optimum value,
The amount of halogen entering the insulating film fluctuates depending on the process conditions after halogen introduction, and it is difficult to obtain stable characteristics.

[0003] It is also known that a halogen element is introduced into the interface between the insulating film and the Si substrate by adding a halogen gas when the insulating film is formed by oxidizing the Si substrate, and NF ₃ , TCA (trichloroethane), H
Cl, Cl _{2 and the} like are used. TCA is C
And hinder the effect of reducing the interface mismatch by the halogen. In a conventional report on the amount of halogen introduced, halogen is introduced in an amount equal to or more than that necessary for alleviating the interface mismatch.

An example of introducing nitrogen into an insulating film is NH 4
There is a method due oxynitride by thermal nitridation or N ₂ O by _3, accompanied by the same way the charge injection in the case of the halogen element, that the degradation of the increase and the mobility of the interface state is suppressed, Extended Abstracts Of 22
nd Conference on Solid State Devices and Materials (EXTENDED ABSTRA
CTS OF THE 22NDCONFERENCE ON SOLID STATE DEVICE
S AND MATERIALS), page 1155 (1990). As described above, there is an example in which fluorine, nitrogen, and the like are solely introduced into an insulating film, but there is no report in which two or more elements such as fluorine, chlorine, and nitrogen are controlled and introduced.

On the other hand, from the viewpoint of the electrical characteristics of the device, there is a problem that a gate insulating film having a thickness of 10 nm or less is deteriorated by a high electric field stress. For example, in a batch erase flash memory (EEPROM), a high electric field (-
(About 10 MV / cm) is applied to the control gate electrode to erase information accumulated in the floating gate electrode. For this reason, the insulating film deteriorates during repeated writing and erasing of information,
There is a problem that a leak current in a low electric field (about −5 MV / cm) increases and the charge retention characteristics deteriorate. The cause of the low electric field leakage current is considered to be due to the trap level in the bulk insulating film (IEE, Electron Device,
Letters (IEEE ELECTRON DEVICE LETTERS), Vol. 12, No. 11, p. 632 (1991)).

[0006]

The above-mentioned prior art has a problem that a high electric field stress causes a deterioration phenomenon of an insulating film. The generation of trap levels in the bulk insulating film and at the insulating film / Si interface is caused by the Si
From the volume expansion in the SiO _2, or Si and by the occurrence of local stress at the time of wafer cooling due to a difference in expansion coefficient between the SiO _2, in the film stress in a high electric field stress is applied is acting It is considered that the bond at the interface is broken and a trap level is generated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor device having an insulating film capable of maintaining stable characteristics even when process conditions change after the formation of the insulating film and preventing deterioration due to high electric field stress, and a method of manufacturing the same. Is to do.

[0008]

To achieve SUMMARY OF to the above objects, a semiconductor device of the present invention, where the main component is SiO ₂
In the desired insulating film, its constituent elements silicon and oxygen
If, further containing two or more elements other than hydrogen,
The sum of the concentrations of the other elements is 5 × 10 ^{18 to} 5 × 10 ²¹ cm
^-3 range. This substrate has an insulated gate
Type field effect transistor is provided, this insulated gate type
The field effect transistor is provided on the gate insulating film
A floating gate electrode and an interlayer insulating film interposed on the floating gate electrode
Having a control gate electrode provided as, the insulating film,
This interlayer insulating film is formed or this control gate
A side wall insulating film of the electrode and the floating gate electrode is formed. It is preferable that the two or more types of other elements have different atomic radii and / or valences. For example, one kind of a group VII element and one kind of a group III element, a group IV element, and a group V element can be used. Further, at least two kinds of elements from the group consisting of nitrogen, fluorine and chlorine can be used.

[0009] Formation of the insulating film, by oxidizing the silicon, when silicon oxide, exposing the silicon to an atmosphere compound containing at least the other element is present, further,
It can be formed by exposing silicon to an atmosphere in which a compound containing at least a second other element different from the other element used here exists. This other element and the second other element
The sum of elemental concentrations in the range of 5 × 10 ^{18 to} 5 × 10 ²¹ cm ^-3
I do. If this compound is a compound containing two kinds of other elements such as nitrogen trifluoride, two kinds of other elements can be introduced into the insulating film by using only that compound. As the compound, when the other element is halogen, chlorine, fluorine, chlorine trifluoride, nitrogen trifluoride, argon fluoride, or the like is used. When the other element is nitrogen, one compound is used. Nitrogen oxide, nitrous oxide, ammonia and the like are used. In the step of exposing the silicon to an atmosphere in which these compounds are present, the residual water content is 1 ppb.
It is preferable to be performed in the following atmosphere.

[0010]

In the MOS device performing the [action] X-ray irradiation and a charge injection from the interface state density is typically ¹⁰ 10 eV ~ ¹ cm ~ ² level, the X-ray intensity, depending on the injected charge amount 10 ¹² 10 ¹⁴
It reaches the level of eV ~ ¹ cm ~ ² . This interface state is Si
This is caused by the charge being captured by the stressed bond at the interface between O ₂ and Si. Therefore, by introducing elements other than Si, hydrogen, and oxygen, such as nitrogen, fluorine, and chlorine, to the interface to alleviate the stress, the amount of interface states generated can be reduced.

For example, when the thickness of the gate insulating film is reduced to 7.4 nm, the leakage current at a low electric field (−6 MV / cm) after application of a high electric field (−14 MV / cm) is 10 to ¹⁰ μm.
It increases from A / cm ² to 10 to ⁷ A / cm ² . This is due to the stressed bond existing in the Si oxide film or the Si bond.
It can be interpreted that a trap level is generated by trapping electric charge by a weak bond such as -H (3.1 eV), and that the electric charge flows through this level to increase a low electric field leakage current.

Accordingly, Si—F (5.6 eV) and Si—C having a large binding energy are present at the interface or in the bulk oxide film.
By controlling and introducing an element that forms 1 (3.7 eV) and Si—N (4.6 eV) in an amount necessary for stress relaxation, the high electric field stress resistance is improved. that time,
In order for the characteristics of the gate insulating film not to be changed even by the change of the heat treatment condition, an amount (5 × 10 ^{18 to} 5 × 1) necessary to reduce the mismatch of the coupling between the gate insulating film and the Si substrate.
0 ²¹ cm ³ ) is to be added. As a result, since there is no excess other element as in the case where ions are implanted into a portion other than the oxide film, for example, a Si substrate or a polycrystalline Si electrode, there is no diffusion of these other elements due to a high-temperature process, and An interface structure that is stable against heat treatment after the formation of the Si film is formed.

Further, F having one bond penetrates into an interface strain that cannot be repaired by N having three bonds, and a strong bond can be formed. That is, the effect of stress relaxation by introducing another element is further enhanced by introducing two or more kinds of other elements having different atomic radii and valences from Si and oxygen.

[0014]

Embodiments of the present invention will be described with reference to the drawings. Embodiment 1 This embodiment is an example of a semiconductor device having an insulating film into which nitrogen, fluorine, and chlorine are introduced. FIG. 1 shows a cross-sectional view of a memory cell of the semiconductor device of this embodiment. This memory cell is created as follows. A p-type Si substrate 1 on which an element isolation oxide film 2 is formed and the Si surface to be oxidized is exposed is introduced as a sample into a hermetically closed furnace so as not to be entrained in the atmosphere, and the sample is kept at a temperature at which oxidation does not proceed. Ar gas having a reduced water content of 40 ppt was flowed through the purifier at a flow rate of 1 liter / min. 1) Switching to oxygen gas having a reduced water content of 100 ppt,
At a flow rate of 2 liters / minute, the residual gas in the furnace was sufficiently replaced over 1 hour, and then A containing 10 ppb chlorine trifluoride was used.
While mixing the r gas at a flow rate of 1 liter / min, the above p
The temperature of the mold Si substrate 1 was raised, kept at 800 ° C. for 30 minutes, and returned to room temperature. 2) After that, switch to nitrous oxide (N ₂ O) gas and
Oxynitridation was performed at 50 ° C. for 30 seconds. 3) Further, an oxygen gas of 2 liter / min with a reduced water content is flowed to 100 ppt, and the residual gas in the furnace is sufficiently replaced for 1 hour, and then A containing 10 ppb of chlorine trifluoride is used.
The temperature was increased in an atmosphere in which r gas was mixed at a rate of 1 liter / minute, and the temperature was maintained at 800 ° C. for 30 minutes to form a gate oxide film 4 having a thickness of 6 nm.

On the gate oxide film 4, 540 ° C. using disilane and phosphine by a low pressure chemical vapor deposition method.
Then, 200 nm of polycrystalline Si containing phosphorus was deposited, and then heated at 900 ° C. for 20 minutes in an Ar atmosphere. This polycrystalline Si forms the floating gate electrode 5. Thereafter, the surface was oxidized to form an interlayer insulating film 6, the control gate electrode 7 was formed in the same manner as the formation of the floating gate electrode 5, and after patterning these, the surface and the side wall were oxidized. Next, an N-type source region 8 and an N-type drain region 9 are formed by ion implantation, and the insulating film 10 and the electrode 3 are formed by a usual method.
And a memory cell as shown in FIG. 1 was created. FIG. 2 shows the variation of the transfer coefficient β due to the rewriting operation of the memory cell.
Shown in In this example, a total of 5 × 10 ²⁰ cm ³ of fluorine, chlorine and nitrogen was added, and the deterioration of β was significantly suppressed as compared with the case where no addition was made. Further, the number of rewriting times in collective erasure type EEPROM including the memory cell was improved to 10 ⁶ times from 10 ⁴ times.

This improvement in the number of rewrites can be understood from the fact that the low electric field leakage current of the MOS capacitor having the gate insulating film formed by the same process as the above embodiment is improved. That is, as shown in FIG. 3, a low electric field (−6 MV) after a high electric field (−14 MV / cm) stress of a MOS capacitor having an insulating film into which fluorine, chlorine and nitrogen are introduced.
/ Cm) is 10 to ⁸ A / cm ² (Fig. 3
(B)), which is an order of magnitude improvement from 10 to ⁷ A / cm ² (FIG. 3A) in the case of a MOS capacitor having a normal thermally oxidized Si film. Note that a similar memory cell could be made when NH ₃ gas was used instead of N ₂ O gas in the step of forming the gate oxide film 4 and the heating time in an oxygen gas atmosphere was extended.

Embodiment 2 This embodiment is an example of a semiconductor device having an insulating film into which nitrogen and chlorine are introduced. The cross-sectional view of the memory cell of the semiconductor device of this embodiment is the same as that of the first embodiment shown in FIG. After the Si substrate 1 on which the element isolation oxide film 2 is formed is thermally oxidized to form a gate oxide film 4 having a thickness of 10 nm, disilane and phosphine are deposited on the gate oxide film 4 by a low pressure chemical vapor deposition method. Polycrystalline Si containing phosphorus at 540 ° C
Was deposited at 200 ° C. in an Ar atmosphere at 900 ° C.
Heated for 0 minutes. This polycrystalline Si forms the floating gate electrode 5. After cleaning the polycrystalline Si surface with HF solution,
The sample is introduced into a closed furnace so as not to be trapped by the atmosphere, and the sample is kept at a temperature at which oxidation does not proceed.
t) Reduce the amount of water to 1) Fully replace with 100% nitric oxide.
After cleaning for minutes, the temperature was returned to room temperature. 2) An atmosphere in which oxygen gas with a reduced water content of 50 ppt is flown at 1 liter / minute and the residual gas in the furnace is sufficiently replaced over 1 hour, and then oxygen gas containing 5 ppb of chlorine is mixed at 1 liter / minute. The temperature of the sample was raised in
By maintaining the temperature at 0 ° C. for 180 minutes, an interlayer oxide film 6 having a thickness of 20 nm was formed.

A control gate electrode 7 made of phosphorus-doped polycrystalline Si was formed on the interlayer insulating film 6, and the memory cell shown in FIG.
In this embodiment, the total of nitrogen and chlorine is 5 × 10 ²⁰ cm to ³
And the tunnel current of the memory device having this insulating film is 1 compared with the case where the above element is not added.
It was an order of magnitude smaller. As a result, the batch erase type EEPRO
The charge retention time at M was improved from 10 to 40 years. The improvement effect in the present example could be achieved by reducing the amount of water in the atmosphere during the treatment with nitric oxide and chlorine to 100 ppt.

Embodiment 3 This embodiment is an example of a semiconductor device in which nitrogen, fluorine and chlorine are introduced into a side wall insulating film constituting a side wall of a memory cell. FIG. 1 is a sectional view of a memory cell of the semiconductor device of this embodiment.
This is the same as Example 1 shown in FIG. After thermally oxidizing the Si substrate 1 on which the element isolation oxide film 2 is formed to form a gate oxide film 4 having a thickness of 10 nm, disilane and phosphine are deposited on the gate oxide film 4 by a low pressure chemical vapor deposition method. Then, 200 nm of polycrystalline Si containing phosphorus was deposited at 540 ° C., and then heated at 900 ° C. for 20 minutes in an Ar atmosphere.
This polycrystalline Si forms the floating gate electrode 5. After cleaning the surface of the polycrystalline Si with an HF solution, the polycrystalline silicon film is thermally oxidized to form an interlayer insulating film 6, and a control gate electrode 7 made of polycrystalline Si doped with phosphorus is formed on the interlayer insulating film 6. Was formed. Thereafter, the control gate electrode 7, the interlayer insulating film 6, and the floating gate electrode 5 were patterned by dry etching.

Subsequently, the wafer is placed in an oxidizing atmosphere at 800 ° C.
To form a SiO ₂ film and heated at 850 ° C. for 2 minutes in NH ₃ diluted to 2% with argon. In addition, 1
The substrate was heated to 1000 ° C. in oxygen gas containing 0 ppb of ClF ₃ to form a 50-nm sidewall insulating film and an insulating film on the control gate electrode 7.

In this embodiment, nitrogen, fluorine and chlorine are added in a total of 5 × 10 ²⁰ cm ³ , and the tunnel current of the memory device having this side wall insulating film is smaller than that in the case where the above element is not added. Was an order of magnitude smaller. As a result, the charge retention time in the batch erase type EEPROM is 1
It improved from 0 to 40 years. Embodiment 4 This embodiment is an example of a semiconductor device having an insulating film into which nitrogen, fluorine and chlorine are introduced. FIG. 5 shows a cross-sectional view of the capacitor of the semiconductor device of this embodiment. This capacitor is made as follows. A p-type Si substrate 11 in which an element isolation oxide film 12 is formed and an oxidized Si surface is exposed is introduced into a furnace body sealed so as not to be entrapped in the atmosphere, and the sample is kept at a temperature at which oxidation does not proceed. Ar gas with a reduced water content of 50 ppt was flowed through the purifier at a flow rate of 1 liter / min. 1) Switching to oxygen gas with a reduced water content of 100 ppt,
At a flow rate of 2 liters / minute, the residual gas in the furnace was sufficiently replaced over 1 hour, and then A containing 10 ppb chlorine trifluoride was used.
While mixing the r gas at a flow rate of 1 liter / min, the above p
The temperature of the mold Si substrate 11 was raised, kept at 800 ° C. for 30 minutes, and returned to room temperature. 2) After that, the gas was switched to N ₂ O gas and oxynitridation was performed at 1050 ° C. for 30 seconds.

3) Further, an oxygen gas whose water content is suppressed to 50 ppt is flowed at 2 liters / minute, and the residual gas in the furnace is sufficiently replaced for 1 hour, and then Ar gas containing 5 ppb chlorine trifluoride is added to the furnace. By raising the temperature in an atmosphere mixed at a rate of 1 liter / minute and maintaining the temperature at 800 ° C. for 30 minutes, a film thickness of 6 n
m gate oxide film 13 was formed. On the gate oxide film 13, polycrystalline Si containing phosphorus was deposited in a thickness of 200 nm at 540 ° C. using disilane and phosphine by low pressure chemical vapor deposition, and then heated at 900 ° C. for 20 minutes in an Ar atmosphere. . Thereafter, the gate electrode 14 was processed to produce a capacitor as shown in FIG.

In this capacitor, the amount of halogen to be introduced is changed by adjusting the flow rate of chlorine trifluoride.
The amount of generation of interface states after applying a constant current stress of A / cm ² for 100 seconds was determined from CV characteristics. FIG. 4 shows the results. The amount of the introduced element is 5 × 10 ^{18 to} 5 × 10 ²¹
By setting cm- ³ , the amount of generation of interface states can be significantly reduced. FIG. 4 shows the results when only nitrogen was introduced into the silicon oxide film by ammonia thermal nitridation. It can be seen that in the case of using only nitrogen, the amount of interface states generated is larger than in the case of introducing together with fluorine and chlorine.

As described above, the addition of elements such as nitrogen and halogen not only causes thermal oxidation of single-crystal Si on the substrate but also adds polycrystalline S
The same effect is obtained for the i film. The improvement effect of the above-described element introduction on single crystal Si is achieved not only when the plane orientation is (100) but also when the plane orientation is (111) and (110). Further, as described above, the same effect can be achieved by adding elements such as nitrogen and halogen by reducing the amount of water in an atmosphere containing a nitrogen compound or a halogen compound to 1 ppb or less.

[0025]

As described above, in the semiconductor device of the present invention, the insulating film contains 5 × 10 ^{18 to} 5 × 10 ²¹ cm to ³ of two or more elements other than Si, oxygen and hydrogen.
The mismatch at the interface between the semiconductor film or the semiconductor substrate and the insulating film and the mismatch in the bulk insulating film can be reduced, and a stable film can be supplied even by heat treatment. Accordingly, an increase in interface state due to high electric field stress can be suppressed, and a leak current can be reduced, so that a high-performance device having high rewrite reliability and excellent charge retention characteristics can be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a memory cell according to Examples 1, 2, and 3 of the present invention.

FIG. 2 is a view showing the effect of nitrogen, fluorine and chlorine treatment in Example 1.

FIG. 3 is a diagram showing the effect of nitrogen, fluorine and chlorine treatment in Example 1.

FIG. 4 is a diagram showing the effect of adding two types of elements in Example 4.

FIG. 5 is a sectional view of a capacitor according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 P-type Si substrate 2, 12 Element isolation oxide film 3 Electrode 4 Gate oxide film 5 Floating gate electrode 6 Interlayer insulating film 7 Control gate electrode 8 Source region 9 Drain region 10 Insulating film 13 Gate oxide film 14 Gate electrode

Continuation of the front page (56) References JP-A-5-206453 (JP, A) JP-A-4-268730 (JP, A) JP-A-5-74762 (JP, A) JP-A-5-217931 (JP) , A) JP-A-2-42725 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/316 H01L 21/8247 H01L 29/788 H01L 29/792

Claims (6)

(57) [Claims] 1. A semiconductor device having a semiconductor element provided on a substrate, wherein a main component of a desired insulating film is SiO ₂ , and the constituent elements of the insulating film other than silicon and oxygen, and hydrogen And the sum of the concentrations of the other elements is 5 × 10 ^{18 to} 5 × 10 ²¹ c
m ^-3 , wherein the semiconductor element has an insulated gate electric field having a floating gate electrode provided on the gate insulating film and a control gate electrode provided on the floating gate electrode via an interlayer insulating film. A semiconductor device, which is an effect transistor, wherein the insulating film forms the interlayer insulating film. 2. A semiconductor device having a semiconductor element provided on a substrate, wherein a main component of a desired insulating film is SiO ₂ , and the constituent elements of the insulating film are silicon and oxygen and other than hydrogen. And the sum of the concentrations of the other elements is 5 × 10 ^{18 to} 5 × 10 ²¹ c
m ^-3 , wherein the semiconductor element has an insulated gate electric field having a floating gate electrode provided on the gate insulating film and a control gate electrode provided on the floating gate electrode via an interlayer insulating film. A semiconductor device, which is an effect transistor, wherein the insulating film forms a sidewall insulating film of the control gate electrode and the floating gate electrode. 3. The semiconductor device according to claim 1, wherein said two or more kinds of other elements are at least two kinds of elements selected from the group consisting of nitrogen, fluorine and chlorine. Semiconductor device. 4. A method for manufacturing a semiconductor device, comprising the step of oxidizing silicon and forming an insulating film made of silicon oxide, wherein the silicon is replaced with at least an element other than Si, oxygen and hydrogen. Exposing the silicon to an atmosphere in which a compound containing at least a second other element other than Si, oxygen and hydrogen and different from the other elements is present. The film contains the constituent elements silicon and oxygen, the other element and the second other element, and the sum of the concentrations of the other element and the second other element is 5
A method for manufacturing a semiconductor device, wherein the range is from × 10 ^{18 to} 5 × 10 ²¹ cm ⁻³ . 5. The method of manufacturing a semiconductor device according to claim 4, wherein the compound containing at least the other element or the compound containing at least the second other element is chlorine trifluoride or chlorine. A method for manufacturing a semiconductor device, comprising: 6. The method for manufacturing a semiconductor device according to claim 4, wherein the atmosphere containing the compound containing at least the other element and the second other element has a residual moisture content of 1 p.
A method for manufacturing a semiconductor device, wherein the atmosphere is at most pb or less.