JPS598341A - Semiconductor device - Google Patents

Abstract

PURPOSE:To acquire the semiconductor device of stable performance characteristics by obtaining a boundary condition of the physicochemical characteristics of a silicon nitride film prepared through a plasma CVD method. CONSTITUTION:The silicon nitride film is formed through the plasma CVD method at a temperature of 500 deg.C or less. I=Ioe<-alphat> is formed when the intensity of transmitted light is I, the intensity of incident light Io, the thickness of the silicon nitride film t and an optical absorption coefficient alpha, and a wavelength of I=0.1XIo is used as an optical absorption end when alpha is 10<4>/loge. A wavelength of the optical absorption end is made 235nm or less at that time. An infrared absorption coefficient based on a Si-H union is made 450cm<-1> or less in an infrared absorption spectrum close to 2,150cm<-1>. The silicon nitride film having such physical properties is used as the final protective film or inter-layer insulating film of the semiconductor device.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a semiconductor device having a silicon nitride film formed at a low temperature of 500° C. or lower, and more specifically to a semiconductor device that can maintain stable operating characteristics of the semiconductor device. This invention relates to a semiconductor device # having a highly reliable silicon nitride film.

[Technical background of the invention]

Conventionally, chemical vapor deposition (CVD) has been used as the final protective film or interlayer insulation film for semiconductor devices.
low-temperature oxide film (SiO3 film) and C
'Phosphorus-doped glass film by VD method (hereinafter VC refers to PS)
In addition to the plasma silicon nitride film (hereinafter referred to as P -SiN film) produced by the plasma C'VD method
) has been used. Of this 1%, q!
f, the P-8iN film UNa ion has a blocking effect on trifuts, a blocking effect on film defect density such as ste, bukano ledge (i.e., damage to steps), pinholes, non-hygroscopic property, dielectric strength voltage, etc. It is much superior to SiO□ films and PSG films, and also has the advantages of f:l'i, which is that it has high crack resistance because the internal force of the film is a compression stress. Conventionally, it has been used as a final protection element for a resin-sealed conductor device or as an interlayer insulating film between multilayer interconnections, contributing to improving the reliability of the semiconductor device.

However, as the use of p-8iN films expands, it has become clear that the use of p-5iN causes the following problems, and therefore further research is needed to investigate the characteristics of P-8iN from various aspects. It has become necessary to do so.

[Problems with back m technology]

At present, it has been reported that the following phenomenon occurs in a semiconductor device having a P-8iN film.

(i,) Si gate N-channel MO8 type semiconductor device c
'Variation of threshold voltage (vth) at c.

(ii) Field inversion in MOS diodes.

(iji) Channel depletion in AI gate N channel MO8+- transistor VC.

However, in the research reports that have been conducted on these phenomena, the correspondence between the phenomena and the physicochemical composition of p-siN and the boundary conditions are not necessarily clarified, so it is unclear what physicochemical properties it has. The problem of whether forming P-SiN of
If this problem is solved, it will be possible to clarify the boundary conditions such as the physicochemical properties and composition of P-SiN and the film formation conditions. is important.

[Purpose of the invention]

The purpose of this invention is to solve various unstable phenomena as mentioned above.
P-8iN with physicochemical properties that do not cause
An object of the present invention is to provide a semiconductor device including a film.

[Summary of the invention]

The inventors have determined that the optical weight of p-5iN is P-SiN
Focusing on the most accurate representation of the physicochemical composition of P
- By investigating the optical properties of SiN, we found the boundary conditions of the physicochemical properties of P-8-iN that do not cause the unstable phenomenon in the semiconductor device, and as a result, we found that [) 1 station (2
It was possible to obtain a ``1'' conductor device with a p-5iN film tray that is free from instability phenomena. That is, the semiconductor device according to the present invention has a P-3iN film having the optical characteristics described in claims 1 and 4, and the optical characteristics (4-), i.e., physical By forming the P-8iN film having the characteristic Jjl, it is possible to provide a highly reliable semiconductor device that does not cause the above-mentioned instability phenomenon.

[Embodiments of the invention]

Before detailed explanation of this invention, VC Figures 1 to 41\l
With reference to this, the facts underlying this invention and related experimental results will be explained.

Figure 1 shows MNStN (M
etal-Nitride-8emiconducto
FIG. 3 is a cross-sectional view of a diode made of nfc as shown below. First, AM, T company P
A P-type semiconductor substrate 1 is loaded into a LASMA-'11100 parallel plate plasma CVD apparatus, and
A P--SiN film 2 having a thickness of about 1000^ was formed on the substrate 1 using a reaction gas containing H3+N2). Next, AI is vapor-deposited on the entire surface, and the Al 'f
AI by photoetching and leaving a part of it
Electrode 6 was formed. After that, this diode driver 485
A sample was prepared by heat treatment in a N2 gas atmosphere at ℃ for 30 minutes. The sample is 15f by changing the reaction gas set W.
,! I! A similar type was manufactured, and the IV characteristics and C-V characteristics of each sample were investigated as follows.

Figure 2 is a diagram showing the IV characteristics (current-voltage characteristics) of the sample, in which the ordinate represents the logarithm of the current (10 de) and the abscissa represents the square root J of the electric field strength E. represents. , and the subscript #1 of each line in the same figure. tt2... represents the sample number.

6 Notice From FIG. 2, it can be seen that the carrier conduction mechanism in P-3iN under a high electric field follows Pool-Frenkel conduction. Furthermore, it has been found that the electrical conductivity for the same electric field strength varies by 9 to 10 orders of magnitude depending on the composition of the reaction gas. Therefore, from this fact, P -Si
It has become clear that the insulating properties of N are highly dependent on the composition of the reactive gas during the formation of P-8iN.

Figure 6 shows the electric field strength and F, 1at, Ba for each sample.
B shows the relationship between the variation amount ΔVFB of the nd voltage V, and ΔVFB is obtained from the C-v characteristics when an electric field is applied to each sample. Note that the C-v characteristics of each sample were measured after applying an electric field to each sample for 1 minute at room temperature.

Referring to Figure 6, it can be seen that the FB fluctuation of each sample increases by 2 as the applied electric field strength increases, and that the amount of VFB fluctuation differs for each sample. . If the FB fluctuation of such an MNS diode is Hado,
It can be concluded that there are few traps in the P-SiN film and the film defect density is also low.

Furthermore, referring to Figures 2 and 6, as the sample number increases, both the electrical conductivity and the film defect density decrease, while the electrical insulation increases as the sample number increases, and the larger the sample number, the higher the sample number. It can be seen that the P-SiN film is extremely stable against electric fields.

As mentioned above, due to the difference in the reaction gas composition, the obtained P
It became clear that the electrical properties of the -8iN film changed.1. In addition, although we were able to obtain a correspondence between the reactive gas composition and the electrical properties of p-5iN, we were unable to obtain a correspondence between the physicochemical structure and electrical properties of P-8iN and the reactive gas composition. , how is the physicochemical composition of p-5i
The question of whether desired electrical characteristics can be achieved by forming N cannot be solved only with the data shown in FIGS. 1 and 2.

Therefore, in order to understand the correspondence between the physicochemical structure, electrical properties, and reaction gas composition of UP-8iN, the present inventors measured the optical properties of P-3iN through the following experiment, and found that p- It was possible to obtain the correspondence between the chemical or physical structure of 5iN and its electrical properties, and the correspondence between the chemical or physical structure of P-8iN and film formation conditions. As a result, P
The boundary conditions for the physicochemical structure of -SiN were obtained, and a semiconductor device that does not cause instability phenomena was obtained.

A P-8iN film to be tested was formed on a transparent quartz plate with a thickness of 1M using the same parallel plate type plasma CVD apparatus as described above. There were 11 types of samples produced, and the number of each sample corresponded to the sample number of the MNS diode.

The P-8iN film of each sample contained a reactive gas with the same composition as above (i.e., SiH4 + NH3, N2 component gases,
The samples were formed under the same conditions as the MNS diode samples described above, using a sample in which the content ratio of each component gas was changed for each sample. The thickness of the P-SiN film of each sample was 10000X, which is 10 times that of the MNS diode.

The sample thus prepared was irradiated with light and the transmitted light was measured.

Figure 4 shows the transmitted light spectrum of each sample, in which the ordinate is the transmittance (%) and the abscissa is the wavelength (nm).
shows.

Here, the intensity of the transmitted light is calculated and the intensity of the incident light is kI. .

If the film thickness of the P-8iN film is ot, and α is the optical absorption coefficient, then
According to the Beer-Lamlert law, I=I between the above variables. The relational expression C-at holds true.

Therefore, in Figure 4, let α=10/log e and I
Defining the wavelength of -0,11o as the optical absorption edge and reading it, the optical absorption edge is 3 from sample #2 to sample #11.
547i! 772 to 227.5 nnl''! ! It was found that the optical absorption edge extends into the ultraviolet region even though it has excellent insulation properties and a low film defect density. According to a report by M-J, Rand et al., the optical absorption edge of a 513N4 film with a stoichiometric composition is 2.
2511m, sample #11 has a composition close to the stoichiometric composition of Si3N.

Therefore, a sample whose optical absorption edge is on the short wavelength side has a chemical composition close to the stoichiometric composition, and a sample whose optical absorption edge is on the long wavelength side has a chemical composition far from the stoichiometric composition. This means that it has a structure.

Therefore, in addition to 5i-N bonds, 5i-8
It is thought that excess Si existing in the form of I bonds is included, and charges are trapped there due to the unsaturation behavior of the localized unsaturated bonds, that is, dangling bonds, of this excess SiK. It is thought that the field reversal phenomenon and deterioration of insulation properties as described in (ii) above occur.
do.

The experimental results shown in Figure 4 allow us to estimate the influence of excess S1 dangling bonds in P-8IN, and establish a correspondence between the field reversal phenomenon and the physicochemical structure of the P-SiN film. However, the correspondence between the phenomenon (1) and the physicochemical structure of p-5iN must be clearly understood from another perspective.

According to R, B Fair's research, p-5rN contains 20 to 30 atomic carbon atoms in its composition, unlike silicon nitride (silicon nitride) formed by sintering, high-temperature carbon coating, etc.
It contains hydrogen in the bond form of fsi-H and N-H, and when thermionic electrons generated in the channel of the MO8 semiconductor device enter the P-SiN film, they combine with the hydrogen atoms and form P-SiN. - destabilizes the physicochemical structure and insulation properties of 8iN, resulting in the damage to the semiconductor device.

It is believed that this is due to a change in the amount of water. If we expand this further, we get the following.

In general, hydrogen in P -SiN compensates for the unpaired electrons of "-LPi-8i and N in the form of 5i-H and N -H bonds, so P
Even if -8iN has a composition far from its stoichiometric composition, the initial C-■ characteristic has a density of 1×
10/cd or less, which appears as a relatively small value.

However, when a high electric field is applied, dissociation of the <5l-n bond occurs as shown in the following equation, similar to that in low-temperature oxide films and wet oxide films, and it is thought that the unpaired electrons of Sl act as trap sites.

"I S 1- H""'% EE S'i +Hi Here, ESi is an S1 atom bonded to N or 81, and I (1 is an interstitial hydrogen atom, . is an unpaired electron.

In order to clarify the χ;
Experiments are required to be able to estimate the number of 5I-n bonds in P-8iN.

Therefore, the inventor conducted the following experiment to observe the number of bonds present in P-8iN medium 5i-I.
The sample used in this experiment was the same as the sample [1.] used in the experiment shown in Figure 4, and was produced under the following conditions.

That is, a P-8iN film with a thickness of 10,000 Å was formed on a transparent quartz plate with a thickness of 1M in an AIViT company's PLASMA-iI parallel plate plasma CVD apparatus using a reaction gas containing SII4, N113, and N2. was used as a sample. Other conditions &U1, growth temperature 360-370°C.

tj]","yOk117.500W, Taebo Jinyoung pressure Q2torr.

Si II 150 re/min. The sample type was Ullf1, and one set of reaction gases used to form the p-8iN film in each test f1 was the same as f' in test t1 using the MNS diode and VC in the experiment shown in FIG. The reaction gas composition was the same, and the conditions for forming 11!4 were also the same.

Therefore, the samples of this experiment, the samples of the experiment of FIG. 4, and the above-mentioned MNS diode all correspond to those with the same sample number, and those with the same phaseless number can be discussed under the same experimental conditions.

”2, the 11 divine specimens prepared as described in Section 2 were illuminated with light, and the infrared absorption spectrum of each sample was
, an absorption peak based on the 5i-H bond near 150 cm was determined.

Here, if ■ is the intensity of the transmitted light at the absorption peak, ■o is the intensity of the incident light, t is the film thickness, and α is the absorption coefficient, then Beer-1, Amhert's law exists between these variables. Therefore, the relational expression ■2■oc is established.

When the infrared absorption coefficient α corresponding to each absorption peak was determined based on the value of the observed absorption peak (■), the results shown in Table 1 were obtained.

Table 1 In Table 1, since the value of the infrared absorption coefficient α is proportional to the number of 5l-H bonds in P-SiN, it can be seen that the larger the sample number, the fewer the number of 51-H bonds. This means that the composition of the reaction gas during P-8iN formation is P'
It can be seen that this significantly influences the physicochemical structure of -3iN. When inspected in conjunction with the experimental results shown in Figures 2, 6, and 4, the smaller the number of 5i-H bonds in P-8iN, the better the insulating properties of P-8iN, and the better the semiconductor. It was found that the device had stable operating characteristics.

The present inventors conducted an experiment similar to the above for an interlayer insulating film, and found that the results showed that if the amount of VFB fluctuation after addition is ±IV or less, the semiconductor device It was determined that no instability would occur in the operating characteristics of the sword.

Furthermore, the final protective film exhibited sufficiently stable operating characteristics under the above conditions.

Among the above experimental results, when considering the results in Figures 2 and 3 together with the results in Figure 4 and Table 1, it is found that sample 7
There is a critical point between and test f49, and P greater than that critical point
It has been found that -SiN does not cause the above-mentioned instability in the semiconductor device.

Therefore, when we calculated the optical absorption edge and infrared absorption coefficient corresponding to this critical point, we found that the critical optical absorption edge is the optical absorption coefficient ki
o'/loge was 23572772, and the critical infrared absorption coefficient was 450 cn-1.

The parallel plate plasma CVD apparatus used for the above sample preparation is AMT's PLASMA-11 (fc type), but other equipment such as I) WS's GL-450 can also be used for critical optical absorption. There was no change in the fact that the edge was 235 nm and the critical infrared absorption coefficient was 45 Q o -1. For example, using GL-450, the growth temperature is 380°C.
.

RF 440-kHz 250 j) 7A, deposition pressure 1. Otorr.

Under the condition of a total gas amount of 1400 cc/rnin, the optical absorption edge is 235 horns or less than 2 horns for NH3/51f.
(4 ratio is 11 or more, and the infrared absorption coefficient is 450
c) It was x-1 or less when NH3/S i H4 was 11 to 12.

This departure F! A was obtained based on the results of various studies on P-8INK as described above, and this invention is directed to a semiconductor device having P-8iN having a temperature above the critical point as an interlayer insulating film or a final protective film. It provides:

In the following, embodiments of a semiconductor device having a P--SiN film according to the present invention will be described.

Example 1 In order to compare the operating characteristics of the semiconductor device of the present invention and a semiconductor device to which the present invention is applied, two-line semiconductor devices were fabricated and their operating characteristics were compared. (A1 game, which is commonly manufactured as a base for semiconductor devices used in experiments)
An N-channel MO8 enhancement type transistor is selected, and a P-3 transistor with an optical absorption edge λ of 23072772 is selected.
A first specimen to which the present invention was applied, which was coated on iN' as the final protective film, was fabricated, and a specimen to which the present invention was not applied, which was coated as the final protective film on the matrix, was fabricated. A second specimen was manufactured. 1.5 at a temperature of 150°C for these two types of specimens.
By applying an electric field strength of MV/cm, the threshold value (
@hre sho ldl e ye L) Temporal changes in V and h were observed.

The results are illustrated in FIG. 5, in which the ordinate is the threshold voltage th+the abscissa is the logarithm of the time (hour). In addition, the optical absorption edge λ8 of the curve C7 is 364
The curve shows the vth change of the second specimen to which the present invention is not applied, which has a P-SiN film of n7n, and the curve indicates the optical absorption edge λ8.
Figure 2 shows the vth changes and changes of a specimen of the present invention having a P-8iN film with a diameter of 23υ2m.

As is clear from this figure, vth in the second specimen to which the present invention was not applied decreased rapidly within a relatively short time (48 hours) after the start of bias application, and then gradually increased. Therefore, the electrical properties of the second specimen are clearly unstable.

On the contrary, vth in the first specimen to which the present invention is applied
does not show any fluctuations, and therefore it can be seen that according to the present invention, a semiconductor device with stable operating characteristics without vth fluctuations can be obtained.

Example 2 AI gate N of the same type as that used in Example 1 above
Enhancement of channel MO8) A type 1 transistor is used as the base of the specimen, and the infrared absorption coefficient α is 820.
A first specimen to which the present invention is not applied was fabricated with on-1 P-3iN as the final protective film, and a final protective film of ( A second specimen to which the present invention was applied was fabricated, and these two types of specimens were coated with
An electric field of M'V/cm was applied to observe all temporal changes in the threshold voltages of both specimens.

FIG. 6 illustrates the results. In the figure, a curve C shows a change in Vth of a specimen to which the present invention is not applied, and a straight line L2 shows a change in Vth of a specimen to which the present invention is applied. As is clear from this diagram, in the specimen to which the present invention is applied, V
While th does not vary at all, vth varies significantly in the specimens to which the present invention is not applied, and it is thus seen that the semiconductor device of the present invention can obtain extremely stable operating characteristics.

Example 3 MNO8 structure (Metal-
Nitride-Oxide-8erniconduc
The fluctuation of the flat band voltage VFB was investigated using a semiconductor device as a specimen. The optical absorption edge λ8 of the test specimen to which the present invention is applied is 230.
72772 P-3iN was deposited as an interlayer insulating film, and the optical absorption edge λ8 was 3541i in a specimen to which J was not applied.
m of P-SiN was deposited as an interlayer insulating film.

Then, for these two types of specimens, 1
Electric fields of various strengths were applied for minutes, and fluctuations in the flat band voltage FB were determined from the C-■ characteristics at that time. 7th
The figure shows the results, and the ordinate is vFB
(volt), the abscissa is the applied electric field strength E (MV/
cm), curve C3 shows the vFB change of the specimen to which the invention was applied, and curve C4 shows the vFB change of the specimen to which the present invention was applied.

As can be seen from the figure, in the specimen to which the present invention is applied, there is almost no variation in VFB, whereas in the specimen to which the present invention is not applied, vFB fluctuates significantly.

Therefore, it has been revealed that according to the present invention, a semiconductor device without fluctuation in VFR can be obtained.

Example 4 A semiconductor device with the same MNO8 structure as in Example 3 was used as a test sample, and an interlayer insulating film of this semiconductor device was coated with P-8iN' having an infrared absorption coefficient α of 25 Q ctn. A specimen to which the invention was applied was used, and a specimen to which the invention was not applied was one in which P-SiN with an infrared absorption coefficient α of 820 nn-'' was deposited as an interlayer insulating film of the semiconductor device. Electric fields of various strengths were applied to two types of specimens for 1 minute at a temperature of 200°C, and the C
-■Characteristic 7: Fluctuations in flat band voltages VI and I3 were determined from l).

Figure 8 illustrates the results, and the ordinate is yF
B (V O1t ), the abscissa is the electric field strength E (MV/
Curve C5 is ■FB change of the specimen to which the present invention is applied;
Curve C6 shows the vFB change of the specimen to which the present invention was not applied.

As can be seen from the figure, in the specimen to which the present invention is applied,
n's strange! In contrast to almost no Ilb, vFB fluctuates significantly in the specimen to which the present invention was not applied. Therefore, it is clear that according to the present invention, it is possible to produce a semiconductor device with stable operating characteristics as long as tL.

〔Effect of the invention〕

As described above, according to the present invention, the boundary conditions, that is, the critical point, of the physicochemical properties of P-SiN for obtaining a semiconductor device with stable operating characteristics are made clear, and
According to the present invention, a semiconductor device with stable operating characteristics can be provided.

In the above embodiments, only a MOS type semiconductor device is shown as an embodiment of the semiconductor device according to the present invention, but it is clear that the present invention can be realized as a semiconductor device of other types such as a bipolar type.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the MOS diode used in the experiments that form the basis of the present invention, and Figure 2 is the I-V diagram of the diode in Figure 1.
Figure 6 is a flat band voltage characteristic diagram obtained from the C-■ characteristics of the diode in Figure 1. Figure 4 is a diagram showing transmitted light spectra for plasma nitride silicon films of various compositions. Figure 5 is a diagram showing the characteristics. 7 and 6 are diagrams comparing changes in threshold voltage of a semiconductor device according to the present invention and changes in threshold voltage of a semiconductor device not according to the present invention, and FIG.
1 and 8 are diagrams comparing and showing changes in the flat band voltage Vl''H of the semiconductor device of the present invention and changes in the flat band voltage VFB of a semiconductor device not related to the present invention.1 ... P-type semiconductor substrate, 2... plasma silicon nitride film, 6... A1 electrode. Fig. 1. Fig. 2 f (x ton W valley) Fig. 3 Withdrawal plastic beak climbing lg ear impression force Time (hrs) (He'ia xeu exactly 1 degree 150°C) Figure 6 0 10 10' to5104

Claims (1)

[Claims] A semiconductor device having a silicon nitride film formed at a temperature of 1500° C. or lower, wherein the silicon nitride film has physical properties such that the optical absorption coefficient of transmitted light is low. A semiconductor device characterized by: 2. The semiconductor device according to claim 1, which has a silicon nitride film as a final protective film. 6. The semiconductor device according to claim 1, comprising a silicon nitride film as an interlayer insulating film. A semiconductor device having a silicon nitride film formed at a temperature of 4500° C. or lower, the silicon nitride film having a temperature of 2,15° C.
0CIl+-”@5j in the near infrared absorption spectrum
A semiconductor device characterized by having physical properties such that an infrared absorption coefficient is 45Qnn-' or less based on a -H bond. 5. The semiconductor f4/device fijt according to claim 4, which has a silicon nitride film as a final protective film. 6. The semiconductor device according to claim 4, comprising a silicon nitride film as an interlayer insulating film.