JP2001332509A - Ion implantation apparatus and thin film semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion implantation apparatus capable of restraining particles from being implanted into a sample and a thin film semiconductor device improved in productivity and excellent in switching characteristics. SOLUTION: This ion implantation apparatus generates ions by exciting a prescribed material in plasma, and an ion beam is made to impinge on the sample so as to implant ions into it. The material is mainly composed of B2H6, and moreover the ion implantation apparatus is equipped with a dilute gas feed means for diluting B2H6 gas with other gases so as to set the concentration of B2H6 at a range from 1 to 40% and supplying the dilute B2H6 to a plasma chamber, and a gas flow rate selection means for selecting the flow rate of the diluent gas at a range from 5 to 40sccm so as to control the number of particles generated in the chamber under conditions such that the degree of vacuum of the chamber is kept at 2×10-4 Torr or above. A thin film semiconductor device is manufactured by the use of the ion implantation device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion chamber having a plasma chamber in which a predetermined substance is excited in a plasma to generate ions, and a processing chamber in which an ion beam collides with a sample to implant the substance into the sample. The present invention relates to an implanter and a thin-film semiconductor device manufactured using the ion implanter.

[0002]

2. Description of the Related Art In recent years, an active matrix type liquid crystal display device in which polycrystalline silicon (hereinafter, referred to as polysilicon) or amorphous silicon (hereinafter, referred to as amorphous silicon) uses a thin film transistor (hereinafter, also referred to as TFT). It has been widely used. Among them, polysilicon has higher mobility than amorphous silicon and can form a circuit on a glass substrate required to be formed at 600 ° C. or lower. Its application is prosperous.

For example, polysilicon has begun to be applied as a pixel switching element, which is a display section of a liquid crystal display device, and has been applied to a driving circuit mainly composed of CMOS transistors for operating the pixel switching element. Applications are also being studied.

[0004]

In the manufacture of a polysilicon TFT, there are several steps of impurity implantation using an ion implantation apparatus. When particles generated in these injection processes or attached to the inner wall are taken into the device, they cause deterioration of characteristics and wiring defects, resulting in defective bright spots, defective spots, and defective lines of the completed liquid crystal display device. And so on. For this reason, the yield may be deteriorated, and the productivity may be significantly reduced.

[0005] Such a defect caused by the ion implantation apparatus has been known only when the polysilicon TFT is used for the liquid crystal display device. In addition, an ion implantation apparatus in which an ion beam is generated in a line is not conventionally used for producing a liquid crystal display element, and the above defect is a phenomenon that has been observed for the first time.

As described above, in an ion implantation apparatus in which an ion beam is generated in a line, ions are generated in a plasma chamber, and the ions are injected into a sample. The particles consist of powder (powder) particles generated as a result of a chemical reaction in the gas phase during the plasma reaction, and flake particles that are once formed into a film and deposited on the inner wall of the device and then peeled off. There is. Since the ion density of the linear beam ion implanter is very high, the generated particles are charged and injected into the sample. In particular, when B ₂ H ₆ (diborane) gas was used, the phenomenon was remarkable.

The present invention has been made to solve the above problems, and a first object of the present invention is to provide an ion implantation apparatus capable of suppressing particles injected into a sample at a low level.

A second object of the present invention is to provide a thin-film semiconductor device which improves productivity and has excellent switching characteristics.

[0009]

SUMMARY OF THE INVENTION The present invention has a plasma chamber in which a predetermined substance is excited in a plasma to generate ions, and a processing chamber in which an ion beam collides with a sample to implant ions into the sample. In the ion implantation apparatus, B ₂ H ₆ gas is mainly used as a predetermined substance, and the B ₂ H ₆ gas is any one of H ₂ , N ₂ , Ar, Ne, Kr, F ₂ , O ₂ or A diluting gas supply means for diluting with a plurality of types of gases and selecting a concentration of B ₂ H ₆ gas from a range of 1 to 40% and supplying the diluted gas to a plasma chamber; Gas flow rate selection means capable of selecting the flow rate of the diluent gas from a range of 5 to 40 sccm on condition that the pressure is maintained at 2 × 10 ⁻⁴ Torr or more, and controlling the number of particles generated in the chamber. , And it is characterized in that there was example.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings.

In general, an ion implantation apparatus includes an ion source system,
It consists of elements such as a drawing and acceleration system, a sample system and a vacuum system. FIG. 1 is a schematic configuration diagram of an ion implantation apparatus according to the present invention. The ion implantation apparatus 1 includes a plasma chamber 2 as an ion source system, an extraction electrode 7, a suppression electrode 8, and a ground electrode 9 constituting an extraction and acceleration system. And beam line carbons 10 a and 10 b constituting a sample system, and a fixed Faraday 11. This ion implantation apparatus is called a hollow cathode type, and for convenience of explanation, the accommodation space of each component other than the plasma chamber 2 is referred to as a processing chamber 6.

Here, the plasma chamber 2 has three high-frequency coils (only one is shown in the figure), also called an antenna.
Is used to create ions of gaseous substances using air discharge. A plasma electrode 4 having a large number of openings formed in rows and a plurality of rows is provided at a portion facing the high-frequency coil 3, and the plasma electrode 4 serves as a partition between the plasma chamber 2 and the processing chamber 6. I have. The plasma chamber 2 may be covered with a permanent magnet to increase the plasma density. In the interior of the plasma chamber 2, for example, an upper shutter 5a as an opening area variable means capable of changing the number of opening rows so as to change the opening area of the plasma electrode 4 into a plurality of types by driving with an air cylinder. And a lower shutter 5b.

The extraction electrode 7 is arranged outside the plasma electrode 4 and extracts ions in the plasma chamber 2. The suppression electrode 8 is a countercurrent of secondary electrons generated by being hit against the surface of the glass substrate 12 as a sample. The ground electrode 9 accelerates ions by interaction with the extraction electrode 7. The beam line carbons 10a and 10b protect the beam line, and the fixed Faraday 11 measures the beam current. FIG. 2 is a schematic configuration diagram of a main part of the ion implantation apparatus shown in FIG. 1. In the figure, the same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Here, the ion beam 2 extracted from the plasma chamber 2 and further accelerated
0 is hit against the glass substrate 12 reciprocally driven in the arrow X direction by the vacuum transfer robot 22. In addition, a load lock chamber 21 for holding the glass substrate on standby is provided outside the processing chamber 6 on the opposite side of the plasma chamber 2. A turbo pump 2 as a vacuum system to maintain
3 and a dry pump 24 connected thereto.

A gas introduction path for the plasma chamber 2
And B_TwoH₆Mainly gas, this B _TwoH₆Gas to H_Two,
N_Two, Ar, Ne, Kr, F_Two, O_TwoAny one of
Diluted with one or more types of gas, and B_TwoH₆Gas
Select the concentration from the range of 1 to 40% to plasma chamber 2.
The dilution gas supply means 31 for supplying the plasma
The degree of vacuum of the chamber composed of the science room 6 is 2 × 10^-FourTorr
The flow rate of the dilution gas should be
Generated in the chamber from a range of 5-40 sccm
Externally select a value that minimizes the number of particles
And a gas flow rate selecting means 32 capable of performing the following.

An example of a method of generating an ion beam in the ion implantation apparatus configured as described above will be described below.

The diluting gas supply means 31 dilutes the B ₂ H ₆ gas with any one or more of H ₂ , N ₂ , Ar, Ne, Kr, F ₂ , and O ₂ , and adjusts the concentration. 20% B ₂ H ₆ gas is introduced into the plasma chamber 2. At this time, the partial pressure in the chamber is set to 2 × 1 by the gas flow rate selecting means 32.
The gas flow rate is selected to a value determined by experiments in advance so as to be 0 ^-4 Torr or less. Also, 13.56M is applied to each of the three high-frequency coils 3 by a high-frequency power supply not shown.
A power of 50 Hz is applied to generate induction plasma to decompose the raw material gas into ion species. In this state, a voltage of 3 kV is supplied to the extraction electrode 7 to extract ion species. Further, a voltage of 77 kV is applied between the extraction electrode 7 and the ground electrode 9.
Is applied to accelerate the ions. At this time, a negative voltage is applied to the suppression electrode 8. For example, a voltage of -4 kV is applied to prevent the secondary electrons generated on the glass substrate 12 as a sample from flying.

In this manner, a linear beam is formed, and ions are implanted into the glass substrate 12. The capacity of the plasma chamber 2 according to this embodiment is about 105 L, and the total capacity including the chamber is about 1800 L. The number of generated particles was examined each time ions were implanted into the glass substrate 12 using this ion implantation apparatus. As a result, data on various parameter dependence of the particles shown in FIG. 3 was obtained.

[0018] The degree of vacuum chamber by the lower vacuum system of FIG. 3 as 40sccm the flow rate of the diluent gas while maintaining the 1 × 10 ^-4 or more states, the concentration of B ₂ H ₆ gas 10
%, 20%, 30%, and 40%, the number of particles having a particle size of 1 μm or less is approximately 70,2.
This indicates that the number was 30,500,530. The hatched portions in the figure represent "small" particles divided into large, medium, and small according to the particle size, and the white frame portion represents particles combining "large" and "medium". As is clear from these relationships, the lower the concentration of the B ₂ H ₆ gas, the lower the number of particles. Therefore, B ₂
The concentration of the H ₆ gas is generally in the range of 1 to 40%, and the concentration can be selected so as to minimize the number of generated particles in consideration of other conditions such as productivity.

On the other hand, in the upper part of FIG. 3, B ₂ is maintained while maintaining the degree of vacuum of the chamber at 1 × 10 ^-4 or more by a vacuum system.
Assuming that the concentration of H ₆ gas is 40%, the gas flow rate is 20 scc.
m, 40 sccm, and 60 sccm, the number of particles having a particle size of 1 μm or less is approximately 16
0,520,820. Therefore, it can be seen that the number of particles decreases as the flow rate of the dilution gas decreases. Therefore, the flow rate of the diluent gas can be selected from the commonly used range of 5 to 40 sccm so as to minimize the number of particles generated in the chamber.

Thus, the dilution gas supply means 31 is provided with B ₂ H ₆
The main component is a gas, and this B ₂ H ₆ gas is H ₂ , N ₂ , Ar, N
e, Kr, F ₂ , or O ₂ , when diluted with any one or more of gases and selecting the concentration of B ₂ H ₆ gas from the range of 1 to 40% and supplying it to the plasma chamber 2 , The degree of vacuum in the chamber is set to 2 × 10
^-4 Torr or higher, the flow rate of the diluent gas is selected from the range of 5 to 40 sccm to minimize the number of generated particles from the outside, so that the particles injected into the sample can be lowered. Can be suppressed.

Further, by using the ion implantation apparatus shown in this embodiment, it is possible to obtain a thin-film semiconductor device having improved productivity and excellent switching characteristics.

Further, by manufacturing a liquid crystal display device using this thin-film semiconductor device, it is possible to obtain a device which hardly causes a defective bright spot, a defective dark spot, a defective wire and the like.

The ion implantation apparatus for suppressing the generation of particles has been described above. A method of manufacturing a thin film transistor using this ion implantation apparatus will be described with reference to FIG.
This will be described below with reference to FIGS.

First, as shown in FIG. 4A, a silicon oxide film 102 and amorphous silicon 103 are formed on a non-alkali glass substrate 101 by a CVD method. Subsequently, annealing is performed in N ₂ (nitrogen) gas to reduce the amount of H (hydrogen) in the amorphous silicon 103.
Next, as shown in FIG. 4B, B (boron) in B ₂ Hx + (boron hydride) was 1 × 1 using an ion implantation apparatus.
Amorphous silicon 103 at a dose of 0 ¹² / cm ²
Inject into This B (boron) changes the threshold value Vth of the n-channel and p-channel TFTs so that the CMOS circuit can operate. Next, as shown in FIG. 4C, the amorphous silicon 103 is instantaneously melted using an excimer laser ELA to grow the polysilicon layer 104. Next, the polysilicon layer 104 is formed by CDE (Chem
4D, the island 104n of the polysilicon layer for the n-type TFT and the island 104p of the polysilicon layer for the p-type TFT are formed as shown in FIG. 4D.

Next, as shown in FIG.
A gate oxide film 105 is deposited on the entire surface by using a (Chemical Vapor Deposition) method. Subsequently, as shown in FIG. 5B, after forming a metal film on the entire surface by sputtering, the metal film is patterned by RIE (Reactive Ion Etching) to thereby form the gate electrode 108.
n, 108p are formed. Further, after applying a resist 109, the n-type T is applied by PEP (PhotoEngraving Process).
Cover the entire top of the FT. Then, B (boron) in B ₂ Hx + (boron hydride) is converted into, for example, a dose of 5 × 1.
By implanting at 0 ¹⁴ / cm ^{2 at} an acceleration voltage of 80 keV, the island 104p of the polysilicon layer is doped at a high concentration using the gate electrode 108p as a mask. As a result,
A high concentration conductive layer is formed on both sides of the active layer 145 below the gate electrode 108p. After that, resist 10
9 is removed by an ashing method.

Next, as shown in FIG. 5C, PHx +
P (phosphorus) in (phosphorus hydride) is converted into, for example, a dose of 2
By implanting at × 10 ¹³ / cm ^{2 at} an acceleration voltage of 80 keV, the island 104n of the polysilicon layer is doped at a low concentration using the gate electrode 108n as a mask. As a result, a low concentration conductive layer 141 is formed on both sides of the active layer 144 below the gate electrode 108n.

Next, as shown in FIG.
And apply PEP to the entire top of the p-type TFT region, and
Part of the n-type TFT region is covered. Then Ion Do
P (phosphorus) in PHx + (phosphorus hydride) by the ping method
Is, for example, 5 × 10 ¹⁴/ Cm^Two, Acceleration voltage 8
Inject at 0 keV. In this case, PHx +
PH)_Three(Phosphine) gas is used. That
Thereafter, the resist is stripped. At this time, the high concentration of the n channel
Conductive layers 142 and 143 and active layer 144 under the gate electrode.
A low concentration n-type layer 141 is formed between them. This low concentration
The layer 141 lowers the electric field near the drain end to reduce the leakage current.
It has the role of lowering the flow and preventing TFT deterioration. Then the example
For example, N_Two1 hour at 600 ° C in a (nitrogen) gas atmosphere
Annealing is performed. This is done by ion doping.
This is for activating the entered impurities.

Next, as shown in FIG.
An SiO ₂ (oxide film) layer is formed to a thickness of, for example, 400 nm by a D (plasma enhanced CVD) method. Further, FIG.
As shown in (c), a hole 110a is formed in the oxide film at the source and drain contact portions by the PEP method. In this case, the portions other than the source and drain contact portions are covered with a photoresist, and, for example, an ammonium fluoride solution is used as an etching solution. Then, after removing the photoresist with a stripper, as shown in FIG. 6D, a signal line 111 is formed by embedding a metal film in the contact hole. In this case, Mo, A
Films are formed in the order of l and Mo. The film thickness is 50 nm, 400
nm and 50 nm. Thereafter, a wiring is formed through a PEP and an etching process, and finally a CM as shown in FIG.
The OS transistor is completed.

In the above embodiment, a case has been described in which a CMOS transistor is formed as a thin-film semiconductor device. However, it goes without saying that a MOS transistor can be formed in exactly the same manner.

Thus, it is possible to provide a thin-film semiconductor device having high productivity and excellent switching characteristics by using the ion implantation apparatus in which the generation of particles is suppressed.

[0031]

As is apparent from the above description, according to the present invention, it is possible to provide an ion implantation apparatus capable of suppressing particles injected into a sample at a low level.

According to another aspect of the present invention, a thin-film semiconductor device having improved productivity and excellent switching characteristics can be obtained by using this ion implantation apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an ion implantation apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram of a main part of the ion implantation apparatus shown in FIG.

FIG. 3 is a characteristic diagram showing various parameter dependencies of particles that change according to the operation of the ion implantation apparatus shown in FIG. 1;

FIG. 4 is a sectional view showing a manufacturing process of the thin-film semiconductor device formed using the ion implantation apparatus shown in FIG.

FIG. 5 is a sectional view showing a manufacturing process of the thin-film semiconductor device formed using the ion implantation apparatus shown in FIG.

FIG. 6 is a sectional view showing a manufacturing process of the thin-film semiconductor device formed by using the ion implantation apparatus shown in FIG.

FIG. 7 is a sectional view of a completed thin film semiconductor device formed using the ion implantation apparatus shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion implantation apparatus 2 Plasma chamber 3 High frequency coil 4 Plasma electrode 5a Upper shutter 5b Lower shutter 6 Processing chamber 7 Extraction electrode 8 Suppression electrode 9 Ground electrode 12 Glass substrate 23 Turbo pump 24 Dry pump 31 Diluent gas supply means 32 Gas flow rate selection means Reference Signs List 101 glass substrate 102 silicon oxide film 105 gate oxide film 108p, 108n gate electrode 111 signal line 141 low concentration conductive layer 142, 143 high concentration conductive layer 144, 145 active layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01L 21/336 H01L 29/78 616L F-term (Reference) 5C034 CC01 CC19 5F110 AA26 BB02 BB04 CC02 DD02 DD13 EE44 FF29 GG02 GG13 GG32 GG44 GG52 HJ01 HJ04 HJ12 HJ13 HJ23 HL03 HL04 HL12 HM15 NN03 NN23 NN35 PP03 PP32 PP35 QQ05 QQ11

Claims (5)

[Claims] 1. An ion implantation apparatus having a plasma chamber for exciting a predetermined substance in plasma to generate ions, and a processing chamber for colliding an ion beam with a sample to implant the ions into the sample. mainly of B ₂ H ₆ gas as the predetermined material, the B ₂
The H ₆ gas is diluted with one or more of H ₂ , N ₂ , Ar, Ne, Kr, F ₂ and O ₂ gas, and the concentration of the B ₂ H ₆ gas is 1 to 40. % And a diluent gas supply means for supplying the diluent gas to the plasma chamber and supplying the diluent gas to the plasma chamber under the condition that the degree of vacuum of the plasma chamber and the processing chamber is maintained at 2 × 10 ⁻⁴ Torr or more. A gas flow rate selection means capable of selecting a flow rate of 5 to 40 sccm from the range and controlling the number of particles generated in the chamber. 2. The partial pressure of the B ₂ H ₆ gas is set to 5 × 10 ⁻⁵ Torr.
The ion implantation apparatus according to claim 1, further comprising a vacuum system capable of controlling the temperature to r or less. 3. The ion implantation apparatus according to claim 1, wherein said plasma chamber and said processing chamber are separated by a plasma electrode having an opening for extracting ions. 4. The apparatus according to claim 1, wherein said opening comprises an opening area variable means capable of changing the number of ions in a range of 1 × 10 ^{11 to} 5 × 10 ¹⁵ / cm ^2. An ion implanter according to any one of the preceding claims. 5. A thin film semiconductor device manufactured by using the ion implantation apparatus according to claim 1.