JP3119988B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining a gate insulating film used for a thin film device such as an insulating gate type field effect transistor at a low temperature of 650.degree. C. or less, and an insulating film thus obtained. .

[0002]

2. Description of the Related Art Conventionally, in a thin film device such as a thin film type insulated gate field effect transistor (TFT), after forming crystalline silicon, this surface is 900-1100.
By performing thermal oxidation at a high temperature of ° C., silicon oxide having good characteristics has been manufactured and used as a gate insulating film.

The characteristics of such a thermal oxide film are summarized in that the interface state density is extremely low and that it can be formed with a uniform thickness on the surface of crystalline silicon. That is, the former provides good on / off characteristics and long-term reliability for bias / temperature, and the latter reduces short circuits between the gate electrode and the semiconductor region (active layer) at the edge of the island-like semiconductor region. As a result, the yield was improved.

[0004]

However, when such a thermal oxide film is used, a material that can withstand high temperatures must be selected as a substrate material. In this regard, an inexpensive glass material (non-alkali glass such as Corning 7059) could not be used, and this was disadvantageous in that the cost increased particularly when a large-area substrate was used. In recent years, technology for forming a TFT on an alkali-free glass substrate is under development. However, in such technology, a thermal oxide film cannot be used. The gate insulating film has been formed by chemical or chemical vapor deposition.

However, the characteristics of the silicon oxide film formed by such means are inferior to those of the thermal oxide film. That is, the interface state density is generally large,
Further, there has always been a danger that alkali ions such as sodium may enter during film formation. In addition, since step coverage (step coverage) was not so good, short-circuiting between the gate electrode and the active layer at the edge of the island-shaped semiconductor region occurred frequently. For this reason, it has been extremely difficult to obtain one that satisfies all of the characteristics, reliability, and yield.

The present invention addresses at least one of these problems.
It was made to solve one. That is, in the present invention, a method for producing a silicon oxide film having good step coverage is provided.
Provided is a silicon oxide film having resistance to alkali ions and other undesirable impurities, and a method for producing the same.

[0007]

According to a first aspect of the present invention, as a gate insulating film, a mixed gas containing an organic silane having an ethoxy group, oxygen, and hydrogen chloride or a hydrocarbon containing chlorine is used as a material gas. It is characterized by using a film mainly containing silicon oxide obtained by a plasma CVD method. A second aspect of the present invention is a plasma CVD method using, as a material gas, a mixed gas containing an organic silane having an ethoxy group, oxygen, and a fluorine-containing gas (for example, NF ₃ or C ₂ F ₆ ) as a gate insulating film. Characterized by using a film containing silicon oxide as a main component obtained by the method described above.

Here, the organic silane having an ethoxy group includes the chemical formula Si (OC ₂ H ₅ ) ₄ (tetraethoxy silane, hereinafter referred to as TEOS), Si ₂ O (OC
_{2 H 5) 6, Si 3} O 2 (OC 2 H 5) 8, Si 4 O 3
Substances represented by (OC ₂ H ₅ ) ₁₀ and Si ₅ O ₄ (OC ₂ H ₅ ) ₁₂ are preferable. Such an organic silane material,
Since the migration time on the substrate surface is long and the silicon oxide film is formed by the decomposition on the surface, a coating film having good step coverage to the concave portion and excellent step coverage can be obtained.

The hydrocarbon containing chlorine includes the chemical formulas C ₂ HCl ₃ (trichloroethylene), C ₂ H ₃ Cl
Substances represented by ₃ (trichloroethane) and CH ₂ Cl ₂ (dichloromethane) are preferred. Such a chlorine-containing gas is mainly decomposed in the gas phase, combines with an alkali element such as sodium present in the film formation atmosphere, separates from the substrate, and promotes the desorption of the alkali element from the silicon oxide film. I do. Some of the chlorine atoms remain in the silicon oxide film, which functions as a barrier against alkali elements that subsequently enter from the outside. As a result, the reliability of the TFT can be improved. The concentration of the hydrocarbon containing chlorine is preferably 0.01 to 1% of the whole. 1%
Addition of the above concentrations adversely affects the properties.

In the insulating coating containing silicon oxide as a main component obtained by the above method, a halogen element (for example, fluorine or chlorine) is used as an impurity element in the secondary ion mass spectrometry at 1 × 10 ^{17 to} 5 ×. 10 ²⁰ cm was detected, while carbon was at a concentration of 5 × 10 ¹⁹ cm ⁻³ or less. In particular, to lower the interface state density, the concentration of carbon should be 1 × 10 ¹⁸ cm.
It is desired to be ^-3 or less. In order to reduce the concentration of carbon, the substrate temperature during film formation should be 200 ° C. or higher, preferably 3 ° C.
The temperature may be set to 00 ° C. or higher.

Further, in the insulating film formed in this manner, a large number of dangling bonds tend to be deposited in the early stage of the formation, and therefore, a semiconductor as a base material (preferably one containing silicon as a main component) is prepared in advance. The film is preferably exposed to a plasma atmosphere containing oxygen. As a result, the interface state density is reduced, the fluctuation of the flat band voltage in the bias / temperature test is reduced, and the reliability is improved. In this case, even more effects can be obtained by mixing a material containing hydrogen chloride or chlorine such as trichloroethylene, trichloroethane, or dichloromethane in addition to oxygen.

On the other hand, after forming an insulating film containing silicon oxide as a main component by the above-described method, a heat treatment at 200 to 650 ° C. can also reduce the fluctuation of the flat band voltage. In this case, it is preferable to perform the treatment in an atmosphere having no oxygen such as argon or nitrogen. Fluctuation of flat band voltage is especially 450 ° C
The heat treatment markedly reduced the temperature and saturated at 600 ° C. or higher.

A second aspect of the present invention is to expose an island-shaped non-single-crystal semiconductor region containing silicon as a main component to a plasma atmosphere containing oxygen and hydrogen chloride or a hydrocarbon containing chlorine, and then to form the non-single-crystal semiconductor region. It is characterized in that a film whose main component is silicon oxide is formed by a plasma CVD method using organic silane having an ethoxy group and oxygen as materials so as to cover the region.

In this case, hydrocarbons containing hydrogen chloride or chlorine are mainly accumulated in the chamber during the plasma treatment, and the hydrocarbon containing hydrogen chloride or chlorine is used in the first invention when the silicon oxide is subsequently formed. Has the same effect as mixing. The improvement in reliability by the plasma processing is the same as described above. Further, good results were obtained when the concentrations of chlorine and carbon in the obtained silicon oxide film were set to the same values as in the first invention. Further, when a heat treatment is performed at 200 to 650 ° C., preferably 450 to 600 ° C. after the formation of the film containing silicon oxide as a main component, better results are obtained.

The plasma CV used in the present invention
The D apparatus is a commonly used parallel plate type (that is, 1 type).
(A structure in which a set of plate-shaped electrodes are opposed to each other in a chamber and a sample substrate is disposed on one or both electrodes) or a positive column type as shown in the embodiment.

The latter has two advantages over the former.
That is, first, in the former, the amount of the substrate that can be processed at one time is determined by the area of the electrode, while in the latter, the amount is determined by the discharge volume. Second, the former has a large plasma damage on the substrate surface, whereas the latter has a very small potential gradient, so that the plasma damage is extremely small, and the uniformity is good, so that the TFT characteristics and yield are adversely affected. Is less affected.

It is required that the chamber of the plasma CVD apparatus used for film formation be sufficiently cleaned to reduce alkali elements such as sodium. To clean the chamber, plasma may be generated after introducing chlorine, hydrogen chloride, or a hydrocarbon containing chlorine as described above and oxygen into the chamber. In this case, if the inside of the chamber is heated to 150 ° C. or more, preferably 300 ° C. or more, a further effect can be obtained.

[0018]

EXAMPLE In this example, a method of forming a silicon oxide film as a gate insulating film on an island-shaped non-single-crystal semiconductor film of silicon by a positive column type plasma CVD method, and the obtained silicon oxide film Mainly relates to electrical characteristics. The used plasma CVD apparatus has a vertical section (cross section shown in FIG. 1) and a horizontal section (top view shown in FIG. 1) as shown in FIG. The positive column method is characterized in that a substrate is arranged in a positive column region in a plasma discharge to form a coating.

The power for generating the plasma is RF power 10
2 and 103. A radio wave represented by 13.56 MHz is generally used as a frequency. The power supplied from the two power supplies is adjusted by the phase shifter 104 and the matching boxes 105 and 106 so that the state of the plasma is optimized.
The power supplied from the RF power source is disposed in parallel inside the chamber 101, reaches a pair of electrodes 107 and 108 protected by the electrode covers 112 and 113, and discharge occurs between the electrodes. A substrate is set between the electrodes 107 and 108. The substrate 111 is placed in a container 109 to improve mass productivity, and set on both sides of the sample holder 110 in the container. The feature is that the substrate is disposed horizontally between the electrodes. Substrate is infrared lamp 1
14 and maintained at a suitable temperature. Although not shown in the figure, this device is also provided with an exhaust device and a gas supply device.

First, the film forming conditions and the characteristics of the obtained film will be described. The substrate temperature was 300 ° C. In the chamber, oxygen was supplied at 300 SCCM and TEOS at 15 S
CSC and trichloroethylene (hereinafter referred to as TCE) were introduced into 2 SCCM. RF power is 75W, total pressure is 5P
a. After film formation, annealing was performed at 350 ° C. for 35 minutes in a hydrogen atmosphere.

FIG. 3 shows the results of a dielectric breakdown test of a 1000-nm-thick silicon oxide film formed on a high-resistance silicon wafer using this apparatus. A 1 mmφ aluminum electrode was formed on the silicon oxide film, and the voltage-current relationship was plotted. FIG. 3C shows a film formed without performing any special treatment on the substrate and having a low withstand voltage. However, after setting the substrate in the chamber, the substrate temperature was set to 300 ° C., oxygen was supplied at 400 SCCM, TCE was flown at 0 to 5 SCCM, and the substrate was exposed to a plasma atmosphere at a total pressure of 5 Pa and an RF power of 150 W for 10 minutes (in this step, gas phase reaction was performed). After that, a film was not formed.) After that, when a silicon oxide film was successively deposited, a silicon oxide film having a good withstand voltage was obtained as shown in FIG. However, TCE during silicon oxide film formation
When the flow rate was increased to 4 SCCM or more, for example, 5 SCCM, a film having a low withstand voltage was obtained as shown in FIG. 3B. From this result, it became clear that there was an optimum value for the concentration of TCE.

FIG. 4A shows one of the reliability tests.
Flat band voltage (V
Variation of _{FB) (ΔV FB)} and shows the relation between the substrate pretreatment. In the bias / temperature test, the sample
After applying a voltage of 17 V for 1 hour, the CV characteristics were measured at room temperature. Further, after applying a voltage of −17 V at 150 ° C. for 1 hour, the CV characteristics were measured at room temperature.
The difference of V _FB in each measurement was evaluated as ΔV _FB .

In the sample not subjected to the pretreatment (in FIG. 4A, indicated by (a)), ΔV _FB showed a relatively large value around 5 V. However, the pretreatment improved it. (B) and (c) of FIG.
Are shown below. Sample (b) (c) Substrate temperature 300 ° C. 300 ° C. TCE / oxygen 0/400 0.5 / 400 RF power 150 W 150 W Processing time 10 minutes 10 minutes From FIG. 4, by performing the pre-processing of the substrate using TCE It was confirmed that further improvement was observed.

A similar improvement can be obtained by performing annealing after film formation. Annealing was performed at 300 to 570 ° C. for 1 hour in an argon atmosphere at 1 atm. FIG. 4B shows the relationship between the annealing temperature and ΔV _FB . Especially 450
A decrease in ΔV _FB is observed at a temperature lower than or equal to ° C., and it tends to approach a constant value as the temperature approaches 600 ° C. From this, it was clarified that annealing after film formation contributes to improvement in reliability.

Using the results obtained from the above experiments, T
FT was produced. The process is shown in FIG. First, an underlying silicon oxide film 202 having a thickness of 2000 に was formed on a substrate (Corning 7059) 201 by a positive column plasma CVD method using TEOS, oxygen, and TCE as raw materials.
The apparatus used is the same as that shown in FIG. The main conditions are as follows. Substrate temperature: 300 ° C Total pressure: 5 Pa Gas TEOS: 15 SCCM Oxygen: 300 SCC
M TCE: 2SCCM RF power: 75W

Thereafter, an amorphous silicon film having a thickness of 500 nm was deposited by a plasma CVD method, and this was patterned to form an island-shaped silicon region 203. Further, by leaving the substrate in a nitrogen atmosphere at 400 ° C. for 30 minutes, hydrogen was removed. And FIG.
As shown in (A), laser annealing was performed to crystallize. The laser used was a KrF excimer laser (wavelength 248 nm, pulse width 20 nsec).
The energy density was 200 to 350 mJ / cm ² .
Further, at the time of laser irradiation, the substrate temperature is set to 300 to 500.
° C, for example 450 ° C.

Then, as shown in FIG. 2B, a 1000-nm-thick silicon oxide film 204 as a gate insulating film is covered with TEOS, oxygen, T
It was formed by a positive column plasma CVD method using CE as a raw material. Prior to the film formation, a pretreatment of the substrate was performed. The apparatus used is the same as that shown in FIG. The main conditions for preprocessing are shown below. Substrate temperature: 300 ° C. Total pressure: 5 Pa gas Oxygen: 400 SCCM TCE: 0.5 SCCM RF power 150 W Processing time 10 minutes Subsequently, a film was formed. The main film forming conditions are as follows. After the film formation, an argon atmosphere at 550.degree.
Time annealing was performed. Substrate temperature: 300 ° C Total pressure: 5 Pa Gas TEOS: 15 SCCM Oxygen: 300 SC
CM TCE: 2SCCM RF power: 75W

Next, an aluminum film doped with 2% of silicon was deposited at 6000.degree., And this was patterned to form a gate electrode 205. FIG. Then, as shown in FIG. 2C, impurity ions (phosphorus or boron) were introduced in a self-aligned manner by a plasma doping method using the gate electrode 205 as a mask, thereby forming impurity regions 206 and 207.
The region where no impurity is formed is the channel forming region 20.
It becomes 8. Since doping is performed through the gate insulating film, an accelerating voltage of 80 kV for phosphorus and 65 kV for boron is required. Further, the dose amount was suitably 1 × 10 ¹⁵ to 4 × 10 ¹⁵ cm ⁻² .

Then, as shown in FIG. 2D, the impurity was activated again by the laser annealing method. KrF excimer laser (wavelength 24)
8 nm and a pulse width of 20 nsec). The energy density was 200 to 350 mJ / cm ² . During laser irradiation, the substrate temperature may be kept at 300 to 500 ° C. After the laser irradiation, annealing was performed at 350 ° C. for 35 minutes in a hydrogen atmosphere at a partial pressure of 0.1 to 1 atm.

Next, a 5000-nm-thick silicon oxide film 209 was deposited as an interlayer insulator. The silicon oxide film 209 is made of TE
Positive column type plasma C using OS, oxygen and TCE as raw materials
It was formed by the VD method. The apparatus used is the same as that shown in FIG. The main film forming conditions are as follows. Substrate temperature: 300 ° C Total pressure: 5 Pa Gas TEOS: 30 SCCM Oxygen: 300 SC
CM RF power: 100W

Then, a contact hole 2 is formed in the interlayer insulator.
10 and 211 were formed, and electrodes 212 and 213 were formed on the source and drain of the TFT using aluminum. Titanium or titanium nitride may be used instead of aluminum. Thus, the TFT was completed. The yield of the obtained TFT was remarkably improved because the step coverage of the gate insulating film was improved and the reliability of the gate insulating film was improved.

[0032]

As described above, the silicon oxide film obtained by the present invention has sufficiently high reliability as a gate insulating film. And not only reliability,
It became clear that it also contributed to the improvement of the yield. Further, in particular, the positive column type plasma C as shown in the embodiment is used.
By using the VD device, mass productivity can be improved. As described above, the present invention is an industrially useful invention.

[Brief description of the drawings]

FIG. 1 shows a conceptual diagram of a positive column type CVD apparatus used in Examples.

FIG. 2 shows a manufacturing process of a TFT in an example.

FIG. 3 shows a breakdown voltage characteristic of an insulating film obtained in an example.

FIG. 4 shows ΔV _{FB of} an insulating film obtained in an example.
Show characteristics.

[Explanation of symbols]

 101 ... chamber 102, 103 ... RF power supply 104 ... phase shifter 105, 106 ... matching box 107, 108 ... electrode 109 ... container 110 ... substrate holder 111 ... substrate 112, 113: Electrode holder 114, 115: Heater (infrared lamp)

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroshi Uehara 398 Hase, Atsugi-shi, Kanagawa Prefecture Examiner at Semiconductor Energy Laboratory Co., Ltd. Ritsuru Ikebuchi (56) References JP-A-3-289140 (JP, A) JP-A-4-36679 (JP, A) JP-A-4-165679 (JP, A) JP-A-6-37315 (JP, A) JP-A-6-124889 (JP, A) JP-A-4-110471 (JP, A A) JP-A-5-267480 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/316 H01L 21/336 H01L 29/786

Claims (7)

(57) [Claims] A first step of forming an island-shaped semiconductor region containing silicon as a main component; and a second step of exposing the semiconductor region to a plasma atmosphere containing oxygen and a hydrocarbon containing chlorine or chlorine. And a third step of forming a film containing silicon oxide as a main component on the semiconductor region by generating plasma on the semiconductor region in a mixed atmosphere containing organic silane and oxygen. A method for manufacturing a semiconductor device, comprising: 2. The method according to claim 2, wherein the silicon oxide is mainly
The membrane to be separated is salt at a concentration of 1 × 10 ^{17 to} 5 × 10 ²⁰ cm ^-3.
Containing carbon at a concentration of 5 × 10 ¹⁹ cm ⁻³ or less.
A method for manufacturing a semiconductor device. 3. The method of claim 1 or 2, organic silane
It has an ethoxy group and has the chemical formula Si (OC ₂ H ₅ ) ₄ , Si
₂ O (OC ₂ H ₅ ) ₆ , Si ₃ O ₂ (OC ₂ H ₅ ) ₈ ,
Si ₄ O ₃ (OC ₂ H ₅ ) ₁₀ , Si ₅ O ₄ (OC
₂ H ₅ ) A method for manufacturing a semiconductor device, which is any of the substances represented by ₁₂ . 4. A claim 1,
The chlorine containing hydrocarbon of the second step has the chemical formula C ₂ HCl
_{3. A} method for manufacturing a semiconductor device, which is one of substances represented by C ₂ H ₃ Cl and CH ₂ Cl ₂ . 5. The method according to claim 1, wherein:
Hydrogen chloride of the third step or chemical formula C ₂ HCl ₃ , C
_A method for manufacturing a semiconductor device, comprising a substance represented by ₂ H ₃ Cl or CH ₂ Cl ₂ . 6. The method according to claim 1, wherein:
After the third step, a film mainly containing the silicon oxide 2
The method for manufacturing a semiconductor device, characterized in that it comprises a fourth step of heat treatment at from 00 to 650 ° C.. 7. The method according to claim 1, wherein
After the third step, the film containing silicon oxide as a main component is
A method for manufacturing a semiconductor device, comprising a fourth step of performing a heat treatment at 50 to 600 ° C.