JPS6191901A - Thin film protection layer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a thin film protection M, and more particularly to a thin film protection layer in a thermal head or the like.

Prior Art The thermal head of a thermal printer, which has been used as an output method for facsimiles, computer terminals, word processors, recorders, etc., is basically a substrate made of porcelain or the like, as shown in Figure 1. 2 is provided with a glaze (glass) layer 3 for heat storage, a resistance heating element layer 4 is formed on its surface, and lead layers 5 and 6 for conducting electricity are provided on both ends thereof.
In addition, as the top layer, in order to prevent wear and damage of the heating element layer 4 and lead layer 5.6 due to sliding contact with the thermal paper,
A protective layer 7 is provided. Usability, lead layer 5.6
If current is applied during this period, the resistive heating element layer 4 generates heat, and this heat is applied to the thermal paper via the protective layer 7, thereby forming a thermal symbol.

It has high hardness and can be used as a protective layer for thermal heads.
It is required to have excellent abrasion resistance and heat resistance, and as a result, to be able to fully perform its functions against long-term sliding contact with thermal paper and long-term heat generation.

Conventionally, amorphous or polycrystalline phosphorus/boron compounds, su/
゛・Boron-silicon compounds, or boron-silicon compounds (JP-A-56-12051.2), or silicon nitride, tantalum oxide, silicon carbide, etc. (JP-A-55-1)
No. 11680) have been proposed, but they are not fully satisfactory. The present invention particularly relates to improvements in wear-resistant protective layers using amorphous phosphorus-boron-silicon compounds.

The phosphorus-boron-silicon compound that Mizude Hato proposed earlier contains 0 to 0 phosphorus to 1 boron in terms of atomic ratio.
．． 5, and contains silicon in an amount less than twice that of boron. This compound is thought to have better wear resistance and heat resistance than other conventional protective films. However, according to research conducted by the present inventors, it has been found that cracks are likely to occur due to thermal shock caused by pulsed energization of the heating element layer.

OBJECTS OF THE INVENTION The object of the present invention is to provide a film protective layer with high crack resistance. The present invention is particularly suitable for severe thermal and mechanical
The purpose of the present invention is to provide a thin film protective layer with high heat resistance and abrasion resistance that can be used under abrasive conditions.

SUMMARY OF THE INVENTION The present invention provides boron, which has a phosphorus content of 0 to 0.5 and a silicon content of more than 2 times and less than 7 times (preferably up to 5) to 1 boron, expressed in atomic ratio. A thin protective layer made of phosphorus-silicon compound.

The thin film protective layer of the present invention has excellent heat resistance, excellent abrasion resistance, and excellent crack resistance.

The only major difference between the protective layer of the present invention and the boron/phosphorus/silicon protective layer described in JP-A-56-120512 is the silicon content. However, the same publication states that if the silicon content is greater than 2, the protective layer properties deteriorate and it cannot be used. According to the examples in the same publication, cracks occur in boron-silicon compounds when the ratio of silicon to boron is 2 or more (sample E), and in boron-phosphorus-silicon compounds, when the ratio of silicon to boron is 2 or more On the contrary, the conductivity becomes high and leaks occur (Sample N), and on the other hand, cracks occur (Sample M), indicating a marked lack of stability.

However, according to the present invention, this is not the case;
A protective layer with excellent heat resistance and abrasion resistance could be provided.

Another advantage of the present invention is that since the amount of silicon can be increased compared to conventional methods, the amount of expensive boron used can be reduced.

The thin film protective layer of the present invention is usually amorphous, and in some cases polycrystalline. Also, the layer thickness is 11
It is formed as a protective layer on the underlying device to a particle size of ~10 μm.

To form such a thin film protective layer of the present invention on a predetermined underlying device such as a thermal head, vapor phase epitaxy (CVD) or sputtering may generally be used. A preferred method is vapor phase growth.

It has already been mentioned that the protective layer of the present invention is made of a boron-phosphorus-silicon compound, and the atomic ratio thereof is 1-20 to 0.5:2.1 to 7 (preferably 21 to 5). When the atomic ratio of phosphorus exceeds 0.5, the protective layer becomes brittle and causes cracks. On the other hand, if the amount of silicon is less than 2, cracks may occur due to thermal stress. Generally, the higher the amount of silicon, the higher the toughness and the higher the crack resistance. As the amount of silicon increases, the hardness tends to decrease and the amount of wear increases, but since the hardness is still much greater than the minimum hardness required for thermal transfer, no problems arise from this aspect. If the atomic ratio of silicon exceeds 7 times, a problem of current leakage occurs.

Note that it is usually not necessary to include other additive elements in a thin protective film having such a composition, but in some cases, if necessary, Ge, Sn, etc. may be added in an amount of 1% by weight or less.
Pb, AI, Zr, Nb, etc. may be included.

When manufacturing the thin film protective layer of the present invention by vapor phase epitaxy (CVD), diporan (fj2H6) is used as a volatile substance.
), boron trichloride (BCI, ) etc. as a boron source, phosphine (PH,), phosphorus trichloride ()'C13)
Etc. Sort 1-. , also shi'y y (5iH4)
, silicon tetrachloride (S+C14), etc. may be used as the silicon source. Note that when other additive elements are further included in the thin film protective layer, corresponding chlorides, hydrides, etc. may be used as the source. On the other hand, the flow rate ratio of the substances generated by these companies can be easily determined through experiments depending on the predetermined thin film composition. The carrier gas used is H2.
, He, Ar, etc. can be used. The flow rate ratio, total flow rate, etc. of the carrier gas can also be determined through experiments as described above, and conditions depending on the composition may be used as appropriate.

In addition, what is necessary is just to generally make reaction temperature about 400-1300 degreeC.

On the other hand, when sputtering is used, for example, raw material powders are mixed and compression molded in accordance with the composition of the thin film protective layer, and using the powder as a target, 5 m To
It is best to perform R and F sputtering according to a conventional method, such as performing R and F sputtering under Condition 1 of about rr.

In this way, the thin film protective layer of the present invention is formed on a predetermined underlying device such as a thermal head by vapor phase growth or sputtering.

The thin film protective layer formed in this way has high wear resistance and significantly improves the life of the device to which it is applied, compared to a composition that does not contain silicon.

In particular, when used as a protective layer for a thermal head, K exhibits good protective layer performance even under harsh conditions of long-term use, and prevents deterioration of the resistance value of the heating resistor layer due to long-term use of the thermal head. The deterioration of the characteristics of the thermal head is significantly reduced, and the life of the thermal head is extended.

In this case, one typical example of constructing a thermal head using the thin film protective layer of the present invention will be described as follows.

In other words, referring to FIG. 1, the substrate 2
For this purpose, ceramics such as alumina may be used. Furthermore, the glaze layer 3 provided on the substrate 2 may be formed from ordinary glass. Note that the glaze layer 3 is provided over almost the entire area on the substrate as in the usual case, and its thickness may be 15 to 200 μm. It may be formed by a screen printing method, a dipping method, or the like.

On the other hand, a heat generating resistor IP44 is arranged on the glaze layer 3. The heating resistor layer 4 may be a thin film formed by various methods, but from the viewpoint of its characteristics,
Preferably, it is a silicon polycrystalline thin film formed according to a known chemical vapor deposition method. In addition, in this case, impurities such as P, As, and B are present in the silicon polycrystalline lIr film.
It may be included to the extent of z-view% or less. The resistance may be approximately 2×10−′−5×10−50·α. Furthermore, only one heating resistor layer 4 may be provided on the substrate in a predetermined shape, but usually, it is separated into many pieces and provided in a predetermined arrangement, for example, in the form of a thousand rows of spiers. Generally, the thickness is 0.1 to 5μ+11.

A pair of lead layers 5.6 are connected to the heating resistor layer 4 having a predetermined shape and a predetermined arrangement. The lead layer may be formed as a thin film from various high melting point metals according to various methods.
Alternatively, it is preferable to use an alloy of these, or a silicide of these. In this case, the lead layer may be located below the heating resistor layer, but it is usually preferable that the lead layer be stacked above the heat generating resistor layer. Also, its thickness is generally 1l.
L is about 5 to 2 μm.

Then, over almost the entire upper surface of such a laminate,
As the top layer, a thin film protective layer 7 of the invention is provided.

Above, we have described in detail one typical example of configuring a thermal head using the thin film protective layer of the present invention. It goes without saying that various embodiments are possible, such as providing a convex region on the substrate 2 or making the region corresponding to the heat generating portion on the substrate 2 convex. Moreover, the thin film protective layer can be formed into a multilayer structure of two or more layers, and the composition of each layer can be changed.

As mentioned above, the thin film protective layer of the present invention has high abrasion resistance and heat resistance, and by taking advantage of these characteristics, it exhibits extremely good characteristics as a protective layer for various devices and has a long service life. shall be. For example, by taking advantage of its abrasion resistance, it can be used as protection 1 for a semiconductor photodetection head that is used in sliding contact with a transparent recording paper.

The inventor conducted various experiments to confirm the effects of the present invention. An example is shown below.

EXPERIMENTAL EXAMPLE A thermal head as shown in FIG. 1 was constructed to confirm the effects of the present invention.

First, as the substrate 2, alumina having a size of 300×300 and a thickness of 2 m was used, and a glaze layer 3 having a thickness of 80 μm was formed on the negative side thereof. A long time ago, according to the chemical vapor deposition method, using silane and diborane as the source and H2 as the carrier,
A 1 μm thick polycrystalline silicon film containing 1 wt% of B was coated at 850° C. and etched with a gap of 30 μm using the Yoshin etching method.
A heating resistor layer 4 made of silicon and having a width of 00 μm in a thousand rows was formed. Thereafter, a W thin film with a thickness of 15 μm was deposited, and a window of 100×200 μm was formed in the center on each of the strip-shaped heating resistor layers 4 by photolithography. , a W lead layer 5.6 was formed.

Next, on the base of the thermal head 1 thus formed, a thin film protective layer according to the present invention or for comparison was formed to a thickness of 1 μm over the entire surface. H2 as carrier 2O8CM
, He was flowed at a flow rate of 1105C, and 5XB was used as the source.
2H6/H2 sooscCM, 25% PH gate/horse 1
oosccM, 20% SiH4/H6 400~2
A protective film having a silicon ratio varying widely was formed under normal pressure and 700° C. by flowing at a flow rate of 0,008 CCM. These conditions are conditions for producing a BjPolSix film. When the micro-Vickers hardness and toughness (Kic) corresponding to crack strength of the thin film-retaining film thus produced were measured, the results shown in FIG. 2 were obtained.

It can be seen from the figure that the hardness decreases as the silicon content increases. However, since the hardness sufficient to withstand abrasion by paper in a thermal head should be 500 to 9/1 m2 or more, the present invention, which can ensure a hardness of 1200 to 9/1 m2 or more, is sufficient. On the other hand, with regard to toughness, it is understood that the more silicon there is, the better; however, if the silicon content is more than 7 times as large as the boron content, it is not preferable because the electrical conductivity increases and leakage occurs.

Next, we changed the content of phosphorus and silicon to improve the retention Q%.
When we manufactured a thermal head and tested its crack resistance, we obtained the results shown in the table. However, the test was conducted using the following method. In other words, the dot density of the heating element was M8 class. (approximately 8 lines/1 m), and cracks were observed after running for 30 m.The pulse period was 10
1rL seconds, pulse printing time is 0.5rrL seconds, thermal and rad power consumption is 10mA with logic5■±■, printing power peak is 8-15A0 running line density is 17/-, data transfer rate is iMHz/second. Ta. Note that the compositions in the following table are relative values when 1j is set to 1.

As shown in Table 1, according to the present invention, the crack resistance is good.
An excellent protective film was provided.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the thermal head structure, and fp
, 2 is a graph showing the characteristics of the protective film of the present invention. Figure 2 BPASIX →X

Claims (1)

[Claims] 1. In atomic ratio, the phosphorus content is 0 to 0.5 per 1 boron.
, a thin film protective layer made of a boron-phosphorus-silicon compound containing more than 2 times as much silicon and less than 7 times as much silicon. 2. The thin film protective layer according to item 1 above, wherein the silicon content is 2.1 to 5 to 1 boron. 3. The thin film protective layer according to item 1 above, which is for a thermal head.