JPH01134935A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To produce the material of passivation film in high ultraviolet ray transmissivity and humidity resistance by a method wherein growing temperature, growing gas pressure, supply power and high-frequency bias are specified by the diverging magnetic field type electronic cyclotron plasma vapor growing process. CONSTITUTION:A silicon nitride film used as a passivation film of erasing and writing ROM is formed. At this time, the silicon nitride film is formed meeting specific requirements by the divergence magnetic field type electronic cyclotron plasma vapor growing process. The specific requirements comprise growing temperature of room temperature at 150 deg.C, growing gas pressure of 7X10<-3>-1X10<-4>Torr, power supply power of 100W-1.0kW, high-frequency bias of 0-500W. This plasma vapor growing apparatus is composed of a plasma producing chamber 11 and a plasma reaction chamber 12. The growing gas is SiH4-N2 or Si2H6-N2. Through these procedures, the material of passivation film in high ultraviolet ray transmissivity and humidity resistance can be produced.

Description

[Detailed Description of the Invention] [Summary] At a film thickness of 1.5 ttm, the refractive index (refraction
1ndex) is extremely close to 2.0, and ultraviolet light (λ=2
Silicon nitride (S) with a transmittance of 50% or more
Regarding the method of manufacturing iN) film, we aim to provide a passivation film material with excellent ultraviolet transmittance and strong moisture resistance.
In forming the silicon nitride film to be used as the passivation film of M, a divergent magnetic field type electron cyclotron plasma vapor phase epitaxy is used, the growth temperature is room temperature to 150°C, and the growth gas pressure is 7xto-3 to Ixl0-4Torr.
, a method for manufacturing a semiconductor device characterized in that the power source power is selected to be 100 W to 1.0 KW, and the high frequency bias is selected to be 0 to 500-.

[Industrial application field]

The present invention is a one-time EFROM (OEPROM),
The refractive index used as the final passivation film (also called cover film) of EPROM
The present invention relates to a method for manufacturing a silicon nitride (SiN) film with a UV (λ=2536.5) transmittance of 50% or more and an ultraviolet light (λ=2536.5) extremely close to 2.0.

[Conventional technology]

In order to ensure the functionality and reliability of semiconductor integrated circuits, the final passivation film has been an SiN film formed using radio frequency (RF) plasma chemical vapor deposition (CVD). Recently, OEPROM.

Plasma 5iON films, which have excellent ultraviolet transmittance, have come to be used in EPROMs and the like.

[Problem that the invention seeks to solve]

SiN films made using the RF plasma CVD method have a problem in film quality that the film has a high defect density.

Furthermore, RF plasma SiN, which has a large internal stress and can cause significant damage to the underlying wiring material, is not suitable for EOP (
4.1eV) is small but has excellent moisture resistance, and 5iON made using the same method has an E rating. Although P is large, there is a problem that moisture resistance is poor. This is shown below as Table I.

Table ■ In principle, the mean free path and ion sheath of RF plasma itself will no longer be able to completely cover the submicron region, which will result in a film with many defects during film formation.

Therefore, an object of the present invention is to provide a material for a passivation film that has low stress, low hydrogen concentration, excellent ultraviolet transmittance, and strong moisture resistance.

[Means for solving problems]

The above problem arises when forming a silicon nitride film used as a passivation film for an erasable and writable ROM using a divergent magnetic field type electron cyclotron plasma vapor phase epitaxy, with a growth temperature ranging from room temperature to 150°C and a growth gas pressure of 7°C. X
l0-'~I Xl0-4 Torr, power supply is 100
Xiong~1. The problem is solved by a semiconductor device manufacturing method characterized in that the high frequency bias is selected to be 0 to 500W.

[Effect]

The above method forms SiN with superior film quality at low temperatures (even below 100°C) compared to thermal CVD, and has low hydrogen concentration, low stress, wide optical bandgap, and excellent moisture resistance. A SiN film is formed.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to illustrated embodiments.

In the method of the present invention, a divergent magnetic field type electron cyclotron resonance (ECR) is used to excite gas species, and SiN
This method forms a thin film. The gas system and growth conditions used at that time are shown in Table 3.

Table ■ To keep the growth temperature low as mentioned above, an electrostatic chuck is used to cool down the heat generated by the plasma.

In addition to SSi34N, Si, H6-
N2. SiH4NH3, Si2Hb NH3, SiH
4N2 NH3 or 5izlli Nt NH
Use 3.

For the growth of 5iON film, SiH4Nz NzO, Si
H4N20 or 5in4Nz 1lho NH3
use.

Conditions such that the microwave angular frequency ω1 and the electron cyclotron angular frequency ω2 match ω1=ω2−・−・・−・・−(1) ω2　eB/
m e; charge B; magnetic flux density m; electron mass, i.e., ECR (electron cyclotron resonance) plasma is formed in a magnetic field (875 Gauss) that satisfies the ECR conditions, and the plasma is drawn out along the divergent magnetic field.CVD (
SiN lpJ formation). This ECR plasma is
Compared to conventional plasma (r, f,), the molecular activity (
The decomposition, excitation, and ionization rates) are extremely excellent, and a variety of process and material developments can be considered using Cv0 technology alone. In this ECR plasma, a large amount of circularly moving descendant energetic electrons interact with the divergent magnetic field and are accelerated in the divergent direction of the magnetic field. Since the sample stage surface and the plasma generation chamber are electrically insulated, the electrons accelerated toward the sample generate a bipolar magnetic field that accelerates the ions and decelerates the electrons to satisfy the neutralization conditions. and reach an equilibrium state. In such a state, electrons and ions are in the same accelerated state in the direction of the divergent magnetic field, so the following relational expression holds true.

If the force acting on the ion is Fl, the force acting on the electron is F2, and their masses are M and m, then P l/M = F 2 /m −−−−−−−−−
----(2) Furthermore, if the electric field in the plasma flow is E, the above F3 and F2 are expressed as follows.

F+= eE ・−・−1−−−−−−−−−−−
--- (3) Fz = -g dB/dZ-eE---
−−(4) u ; Gtl moment If the circular kinetic energy of an electron is U, then μ = U/B−・・−−−−−−−・・−・・−・・
(5) Calculating the electric field E in the plasma flow from the relational expressions (2), (3), and (4), E = (-ω6 1 dB/dz)/eBo(1+m
/M) -------=- (6) Also, if the potential is φ, E=-dφ/dz -・-・～・-(7) (6), (7
) from the formula. The ion energy provided by this method is given by the product of the circular kinetic energy of the electrons in the plasma generation chamber and the reduction rate of the magnetic field, and the electrons lose that amount of energy. As mentioned above, the plasma formed by ECR (electron cyclotron resonance) has a lower gas pressure (I x 10-S~7 x 10-
” high-density plasma can be obtained even in the region of
In CR plasma, the floating potential is as low as several tens of square meters, so damage caused by charged particle impact is thought to be rather small. R on the front
The results of comparing F and ECR plasma diagnosis are shown.

Table ■ ECR plasma CVD equipment used in this experiment (SEE-1
; ZEUS) is shown in Figure 1. This ECR-C
The VD device includes a plasma generation chamber 11 and a plasma reaction chamber 12. A microwave with a frequency of 2.45 Gllz generated by a microwave oscillator 13 is introduced into the ECR plasma generation chamber 11 through a rectangular waveguide 14. A magnetic coil 15 is arranged around the plasma generation chamber 11,
ECR conditions are satisfied within the plasma generation chamber 11. In addition, the exhaust configuration is such that the plasma generation chamber and plasma reaction chamber are connected to a turbo molecular compound pump (TlM, P,) 16 (
Displacement: 1800 Q/5ee), Mechanical booster pump CM, B, P,) 17 (Roots pump)
It is a system that exhausts the air. In FIG. 1, 18 is a plasma shutter, 19 is a sample, 20 is a heater, 21 is a rotary pump (R, P,), and 22 is a matching device.

Show box.

The source gas system used to form the SiN film was SiH4-
Nz, N2 gas is introduced into the plasma generation chamber, SiH4 (
99,99%) gas was introduced into the plasma reaction chamber. The substrate temperature and growth pressure during growth were approximately 150°C, respectively.
It was 1 x to 3 torr. (A plus of the conventional method?
CVD method; Gas system used: SiH4-'N2, SiH
4-NH3-)b, growth temperature 415°C, growth pressure 1.0
torr) experimental parameters are source gas ratio (SiH
4/ Nz-〇, 1~i, o>, microwave power (100~100OW), substrate self-bias (400
kHz, O~300W'').

No special substrate heating was performed. Below, basic SiN
We will discuss film properties (physical properties, chemical properties), basic electrical properties, and cover film properties of FETs.

FIG. 2 shows the relationship between the growth rate of the ECR-SiN film and the total gas flow rate. The microwave power during growth was 400W.

Growth pressure is 0. It was I Pa. The growth rate of the SiN film increases significantly as the flow rate of the source gas increases.

This is because the plasma density is more than one order of magnitude higher than that of conventional RF plasma (and the saturated ion current is more than two orders of magnitude higher, and the ionization rate is more than four orders of magnitude better than that of conventional RF plasma, so it depends greatly on the source gas flow rate. It is thought that the result shows that.The thing to note here is that E
Since CR plasma is very sensitive to pressure, the greatest care must be taken with respect to the pressure during growth.

(SiN formed using conventional plasma CVD method)
The growth rate of the film varies depending on the frequency used, but ・200
In the case of kHz, z, it is 70 nm/min, and in the case of 50 ktlz, it is about 20 nm/min. ) Although it is difficult to directly compare the ECR plasma CVD method with other plasma CVD methods, it can be said that it is far superior to other plasma CVD methods in terms of reaction efficiency, etc.

FIG. 3 shows the results of investigating the relationship between internal stress, refractive index, etching rate, growth rate, and microwave power during growth of a SiN film formed by ECR plasma CVD. In this case, two types of source gas systems are used to form the SiN film. There are two types: a case where SiHa is used as the Si source gas and a case where Si2H6 is used. It can be seen that each characteristic greatly depends on the microwave power during film formation. The internal stress of the SiN film tends to decrease as the microwave power increases. This is also seen when Si2H6 is used as the Si source gas. The refractive index also depends on the microwave power, and results have been obtained that the stability of the refractive index is better when Si2H6 is used as the Si source gas.Usually, SiH4 and Si2H
When comparing the decomposition efficiency of b, Si2Hb has a higher
Since it is superior to Ha, it is thought that the difference in the reaction system will be reflected in the refractive index, but the opposite result was obtained regarding the refractive index.

There is almost no difference in the etching rate (we believe that there is almost no difference in film quality (chemical resistance, etc.) depending on the source gas. The growth rate reflects the difference in the decomposition efficiency of the S1 source gas; It was confirmed that the use of 5i2116 was superior to the use of SiH4.

Figure 4 - ECR Plas? CVD method (SiH, -N2 system)
The infrared absorption spectrum of the SiN film formed using the above is shown.

Figure 5 shows ECR-5i film formed from SiJ, -Nz system.
The infrared absorption spectrum of the N film is shown.

This is a comparison using two types of gas systems.
It can be seen that the hydrogen concentration in the film is lower when the Si2Hb-Nz system is used than when the -Nz system is used.

Also, as the microwave power increases, 2
The absorption peak of the 5i-H bond near 100 cm-' is also no longer observed. On the other hand, the absorption peak of the N--H bond is in the increasing direction, and it is considered that a large amount of NH3 is generated during the plasma reaction and incorporated into the film.

Focusing on the 5iN-N bond, the absorption peak increases to 850 cm -'89 as the microwave power increases during film formation.
It can be seen that there is a chemical shift to 0 cm −'.

(Thermal CVD-3iN SiN absorption peak; 890
cm −') Next, the results of the annealing characteristics are shown. FIG. 6 shows the results of annealing characteristics of a SiN film formed by the conventional plasma CVD method. (Growth conditions; 200kHz) 7th
The figure shows the annealing characteristics of a SiN film formed by the ECR plasma CVD method. Comparing the two, the ECR-3iN film shows almost no change between before and after annealing, whereas the S film formed using the conventional plasma CVD method
In the iN film, N-H is slightly bonded to 5i-Si.
It is observed that the groups are reduced after annealing. This result shows that the SiN film formed by the ECR plasma CVD method is thermally stable. Although it is qualitative, the hydrogen concentration in the SiN film is a maximum of 3
' (from the Si-H peak, see Figures 4 and 5), and the hydrogen concentration of the SiN film formed by the conventional plasma CVD method was IXIO"cm-'. From this, It can be confirmed that the SiN film formed by the ECR-CVD method has a very low hydrogen concentration.

Furthermore, in order to deeply investigate the bonding state of the ECR-3iN film, Electron 5 pectroscopy for
The results of chemical analysis (ESCA) are shown in FIG. The following can be inferred from the results of this waveform separation process. Assuming that the bonding state of the thermal nitride film is stoichiometric, the Si 2P spectrum is 102.6 eV or 1
There are two ways to interpret the value as 01.8 eV, but if we consider the former value, we can think of the following. Si3N,
If we write '5i44' to represent the state in which all four directions of Si's bonds are bonded to N, then Si3 is 101,7 e
V and Six are thought to be 100.8 eV, but since there are also 0 and H, in reality there are N in three directions and O and H in one direction.
It is thought that there exists Si in which these are bonded. They have peak positions different from those of Si3 above. From these facts, the binding state of St is 4
The state in which three of the directional bonds are bonded to N is around 80%, and it is presumed that Si, which is less bonded to N, is mixed in with this.

FIGS. 9 to 11 show the measurement results of the ultraviolet transmission spectrum of the SiN film formed by the ECR plasma CVD method.

As shown in FIGS. 9 to 11, it can be seen that the growth greatly depends on the source gas ratio (SiH4/Nz) during growth and the microwave power during growth. This means that the composition ratio of the SiN film is controlled by the ECR plasma CVD method, and it was confirmed that depending on the control, a film having transmission characteristics comparable to thermal CVD-5iN could be formed. (In the conventional plasma CVD method, ECR-
In the CVD method, it is difficult to control changes in the composition ratio. ) Regarding the moisture resistance of the ECR-3iN film, in an experiment after the MOSFET was processed at room temperature, it was confirmed that moisture etc. were prevented from entering from the top of the cover film after the 168H humidification test, and the protection effect of the underlying layer was confirmed. There was almost no variation in vth due to damage, damage, or poor moisture resistance.

〔Effect of the invention〕

As described above, according to the present invention, ECR-SiN has R, F
.

This far exceeds the properties of plasma CVD SiN or 5iON, and stabilizes the properties of OEPROM and EPROM. Conventional R, F, and plasma 5iONs are not moisture resistant and require the use of expensive ceramic packages. On the other hand, R, P, and plasma SiN had excellent moisture resistance, but had poor optical properties and had poor EFR.
It could not be used for OM. However, ECR-3iO
N or ECR-SiN has not only excellent optical properties (also excellent moisture resistance), so it is possible to use it to provide EFROM in a plastic package that is 1/10 to 1150 times cheaper than a ceramic package. Thus, the ECR-SiN of the present invention,
ECR-5iON stabilizes the characteristics of EI'ROM, etc., and this stabilization improves yield and shortens memory erase time.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a magnetic field-destructive type ECR plasma CVD system, Figure 2 is a diagram showing the relationship between the growth rate of the ECR-SiN film and the total flow rate of source gas, and Figure 3 is a diagram showing the relationship between the growth rate of the ECR-SiN film and the total flow rate of the source gas. Diagram of dependence on wave power (stress, refractive index, etching rate, growth rate); Figure 4 is a diagram of infrared absorption spectrum of ECR-SiN film formed from 5iL-Nz system; Figure 5 is a diagram of Si2H6 -ECR-3i formed from Nz system
Figure 6 shows the infrared absorption spectrum of the N film, Figure 6 shows the annealing characteristics of the plasma CVD-3iN film formed using a frequency of 200k), Figure 7 shows the EC
A diagram of the annealing characteristics of the SiN film formed using the R plasma CVD method. Figure 8 is a diagram of the ESC 80% results of the ECR-SiN film. Figures 9, 10, and 11 are the results of the ECR-3iN film. (7) U
It is a figure of a V light spectrum. In FIG. 1, 11 is a plasma generation chamber, 12 is a plasma reaction chamber, 13 is a microwave oscillator, 14 is a waveguide, 15 is a magnetic coil, 16 is T, M, P, 17 is M, B, P , 18 is a plasma shutter, 19 is a sample, 20 is a heater, 21 is R, P, 22 is a matching box. Patent applicant Fujitsu Limited

Claims (3)

[Claims] (1) In forming the silicon nitride film used as the passivation film of the erasable and writable ROM, the growth temperature was room temperature to 150°C and the growth gas pressure was 7°C using the divergent magnetic field type electron cyclotron plasma vapor phase epitaxy.
×10^-^3 to 1 × 10^-^4 Torr, power supply power is 100W to 1.0KW, high frequency bias is 0 to 500
A method for manufacturing a semiconductor device, characterized in that W is selected. (2) The growth gas is SiH_4-N_2 or S
i_2H_6-N_2, SiH_4-NH_3 or Si_2H_6-NH_3 or SiH_4-N_2
The method according to claim 1, wherein NH_3 or Si_2H_6-N_2-NH_3. (3) SiH_4-N_2-N_2O, SiH_4-N
_2O or SiH_4-N_2-N_2O-NH_3
The method according to claim 1, wherein a SiON film is formed using as a growth gas.