JPH04350973A - Electrode structure of semiconductor element for high-temperature use and its manufacture - Google Patents

Abstract

PURPOSE:To provide the electrode structure, of a semiconductor element for high-temperature use, wherein the resistance value a metal to be used as an electrode for silicon by an SOI structure is not changed after a heat treatment in a high-temperature atmosphere and to provide its manufacturing method. CONSTITUTION:A semiconductor layer 12 is formed on a sapphire substrate 11 as an insulating substrate; an SOI structure is formed. An electrode which is composed sequentially of individual layers by titanium (Ti) 14 as a high- melting-point metal, titanium nitride (TiN) 15 as a high-melting-point metal nitride and platinum (Pt) 16 is formed on a contact part 12a in the semiconductor layer 12 on the sapphire substrate 11. Thereby, the electrode can be connected to the semiconductor layer 12 at low resistance thanks to the titanium 14. The electrode prevents that silicon in the semiconductor layer 12 is reacted with the platinum 16 formed on its upper layer and diffused into it thanks to the titanium nitride 15. Even when a heat treatment is executed in a high- temperature atmosphere, the electrode can maintain its low contact resistance.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an electrode structure of a semiconductor element used for detecting various physical quantities in a high-temperature atmosphere and a method for manufacturing the same. Can be used for pressure detectors.

0002

[Prior Art] Conventionally, high-temperature semiconductor devices, for example,
As a pressure detection element, so-called SOI (Silicon
On Insulator) structure. Unlike the diffusion gauge type structure, this structure does not have a PN junction, so no leakage current occurs in a high temperature atmosphere, making it possible to detect pressure in a high temperature atmosphere of 200° C. or higher. The above SOI structure includes one in which single crystal silicon or polycrystalline silicon is formed on a single crystal silicon substrate via an insulating layer, and the so-called SOS (in which single crystal silicon is grown in vapor phase on a single crystal sapphire substrate). Silico
On Sapphire).

0003

Problems to be Solved by the Invention In order to use the above-mentioned SOI structure pressure sensing element in a high temperature atmosphere, its housing must also be made of metal or the like with good high temperature durability. The pressure detection element is used by being bonded to the housing, and the bonding temperature at that time requires a high temperature. For example, in order to braze the above-mentioned SOS to a metal housing, a heat treatment of approximately 850° C. for 1 minute is required. Aluminum thread electrodes, which are currently widely used in IC chips in semiconductor manufacturing technology, cannot withstand such high-temperature heat treatment. Electrode materials other than the above-mentioned aluminum thread electrodes that have excellent high-temperature durability include platinum (Pt), gold (Au), and nickel (Ni). However, in the above-mentioned high-temperature atmosphere of approximately 850°C, all of the electrodes made of any of the three metals mentioned above react with silicon (Si), so the electrodes are in contact with silicon. There was a problem that resistance increased.

The present invention has been made to solve the above-mentioned problems, and its object is that platinum, gold, or nickel, which is a metal serving as a silicon electrode in an SOI structure, is, for example, approximately The purpose is to prevent reaction with silicon during heat treatment in an atmosphere of 850°C. Another object of the present invention is to provide an electrode structure for a high-temperature semiconductor element in which the resistance value of the metal at the contact portion with silicon does not change, and a method for manufacturing the same.

[0005]

[Means for Solving the Problems] The first feature of the structure of the invention for solving the above problems is that it is made of single-crystal silicon or polycrystalline silicon formed on an insulating substrate, and is capable of controlling various physical quantities in a high-temperature atmosphere. An electrode structure of a semiconductor element used for detection, comprising a refractory metal or a refractory metal silicide formed on a contact portion of the semiconductor element, and an electrode structure formed on the refractory metal or the refractory metal silicide. a high melting point metal nitride, platinum formed on the high melting point metal nitride,
It is characterized by being made of either gold or nickel.

The second feature is a method for manufacturing an electrode for a semiconductor element made of single crystal silicon or polycrystalline silicon formed on an insulating substrate and used for detecting various physical quantities in a high temperature atmosphere, comprising: A high melting point metal or a high melting point metal silicide is formed on the contact portion of the semiconductor element, a high melting point metal nitride is formed on the high melting point metal or the high melting point metal silicide, and the high melting point metal nitride is After the formation, the oxide on the surface of the high melting point metal nitride is removed, and any one of platinum, gold, or nickel is formed on the high melting point metal nitride.

A third feature is a method for manufacturing an electrode for a semiconductor element made of single crystal silicon or polycrystalline silicon formed on an insulating substrate and used for detecting various physical quantities in a high temperature atmosphere, comprising: A high melting point metal or a high melting point metal silicide is formed on the contact portion of the semiconductor element, a high melting point metal nitride is formed on the high melting point metal or the high melting point metal silicide, and a high melting point metal nitride is formed on the high melting point metal nitride. The method is characterized in that, after forming platinum on and microfabricating the platinum, the refractory metal or the refractory metal silicide and the refractory metal nitride are eroded using the platinum as an etching mask.

[0008]

[Operation and effect] The operation and effect of the first feature is as follows:
First, a high-melting point metal or a high-melting point metal silicide is formed on a contact portion of a semiconductor element made of single crystal silicon or polycrystalline silicon formed on an insulating substrate and used for detecting various physical quantities in a high-temperature atmosphere. ing. This allows the electrodes to maintain good ohmic contact and provide low-resistance connection. Further, a refractory metal nitride is formed on the refractory metal or the refractory metal silicide. Then, any one of platinum, gold, or nickel is formed on the high melting point metal nitride. When the high melting point metal nitride is heat-treated in a high-temperature atmosphere of about 850°C, the silicon reacts with any one of the platinum, gold, or nickel metals formed on the upper layer, and the metal nitride reacts with the metal. It becomes a barrier layer to prevent diffusion. Therefore,
The use of any one of platinum, gold, or nickel allows the contact resistance of the contact portion of the semiconductor element to be maintained at a low level.

[0009] As the action and effect of the second feature, the first
In addition to the functions and effects of the above characteristics, by removing the oxide on the surface of the high melting point metal nitride, the high melting point metal nitride and any one of platinum, gold, or nickel formed thereon can be removed. contact resistance can be reduced.

[0010] As the action and effect of the third feature, the first
Similar to the functions and effects of the characteristics, first, a high melting point metal or a high melting point metal silicide is made of single crystal silicon or polycrystalline silicon formed on an insulating substrate and is used to detect various physical quantities in a high temperature atmosphere. The contact portion of the semiconductor element is formed on the contact portion of the semiconductor element. This allows the electrodes to maintain good ohmic contact and provide low-resistance connection. Further, a refractory metal nitride is formed on the refractory metal or the refractory metal silicide. Then, platinum is formed on the high melting point metal nitride. The above high melting point metal nitride is
When heat treatment is performed in a high-temperature atmosphere of about 850° C., the silicon reacts with the platinum formed on top of the silicon and becomes a barrier layer for preventing diffusion into the metal. Therefore, the platinum can maintain a low contact resistance in the contact portion of a semiconductor element. Further, after the platinum is microfabricated, the platinum can be used as an etching mask to erode the refractory metal or the refractory metal silicide and the refractory metal nitride. That is, with this method of erosion, processes such as resist can be omitted, and highly accurate pattern formation can be realized by utilizing the corrosion resistance of platinum.

[0011]

EXAMPLES The present invention will be explained below based on specific examples. FIG. 1 is a longitudinal sectional view showing the electrode structure of a semiconductor pressure sensing element 10 constructed using the electrode structure of a high temperature semiconductor element according to the present invention. A semiconductor layer 12 made of single crystal silicon is formed on a sapphire substrate 11 made of single crystal sapphire, which is an insulating substrate, to form an SOI structure. An insulating layer 13 made of oxide or nitride is formed on the semiconductor layer 12 on the sapphire substrate 11 except on the contact portion 12a. Then, on the contact portion 12a of the semiconductor layer 12, titanium (Ti) 14, which is a high melting point metal, and titanium nitride (T
Electrodes made of layers of iN) 15 and platinum (Pt) 16 are formed. FIG. 2 is a longitudinal cross-sectional view of an electrode structure as a comparative example with respect to the electrode structure of FIG. Here, components having the same configuration are indicated by the same reference numerals. That is, the only difference in FIG. 2 from the configuration in FIG. 1 is that titanium nitride 15, which is a high melting point metal nitride, is not formed.

FIG. 3 shows the change in contact resistance (Ω) from immediately after film formation to after heat treatment [850° C. x 1 hour in a nitrogen gas (N2) atmosphere] in the electrode structure shown in FIGS. 1 and 2 above, as a function of contact width. The results of each measurement at 200 μm are shown. In FIG. 3, the change in contact resistance with respect to the electrode structure in FIG. 1 is shown by a solid line, and the change in contact resistance with respect to the electrode structure in FIG. 2 is shown by a dashed-dotted line. The contact resistances of the electrode structures shown in FIGS. 1 and 2 immediately after film formation are about 2.5Ω, which is approximately the same value. However, the contact resistance after the above heat treatment is approximately 0.95Ω in the electrode structure shown in FIG. 1, and approximately 420Ω in the electrode structure shown in FIG. 2, which is extremely large. In the electrode structure shown in FIG. 1, the titanium 14 allows good ohmic contact to be maintained at the contact portion 12a of the semiconductor layer 12, and a low-resistance connection is possible. In addition, in the electrode structure of FIG. 1, titanium nitride 15 can prevent silicon in semiconductor layer 12 from reacting with platinum 16 in the upper layer and diffusing. At this time, platinum 16 has inherent heat resistance, and as described above, its contact resistance does not increase, but on the contrary decreases. The reason for this is presumed to be that the above-described heat treatment progressed crystallization of platinum 16 and lowered its resistance.

Next, the steps in the method of manufacturing the electrode structure of a high-temperature semiconductor device according to the present invention will be explained in detail with reference to FIGS. 4 and 5. (Semiconductor layer formation process consisting of semiconductor strain gauge elements, etc.)
As shown in FIG. 4A, single crystal silicon grown in a vapor phase on a sapphire substrate 11 is microfabricated to form a semiconductor layer 12 comprising a semiconductor strain gauge element, etc., which will be described later. (Insulating layer formation and its microfabrication process) Next, FIG. 4(b)
As shown in FIG. 2, an insulating layer 13 is formed on the sapphire substrate 11 and the semiconductor layer 12 by CVD, sputtering, or the like. After this, the contact portion 1 in the semiconductor layer 12
Fine processing is performed on the insulating layer 13 such as the portion 2a by photolithography, and the insulating layer 13 above the contact portion 12a of the semiconductor layer 12 is removed. (Titanium layer forming step) Next, as shown in FIG. 4(c), titanium 14 is formed on the upper layer in the step of FIG. 4(b) by CVD, sputtering, etc. at about 400°C. (Titanium nitride layer forming step) Then, as shown in FIG. 4(d), titanium nitride 15 is further formed on the upper layer in the step of FIG. 4(c). This titanium nitride 15 is approximately 6
After forming the above titanium 14 using a direct forming method such as CVD or sputtering at 00°C, the surface of the titanium 14 is
There is a method of forming by nitriding at 0°C. The film thickness of the titanium nitride 15 needs to be 50 nm or more in order to reliably prevent diffusion of silicon in the semiconductor layer 12. (Surface oxide film removal step) Next, immediately before proceeding to the step shown in FIG. 5(e), the step shown in FIG.
d) The surface oxide film on the titanium nitride 15 formed in step 2 is removed. The surface oxide film on the titanium nitride 15 is formed by dry etching RIE (Reactive Io).
It can be removed by n Etching (reactive ion etching) or erosion. (Platinum layer forming step) Then, as shown in FIG. 5(e), platinum 16 is deposited on the upper layer of the titanium nitride 15 formed in the step of FIG. 4(d) above by sputtering, vapor deposition, etc. at about 300°C. Form. (Platinum layer microfabrication step) Next, as shown in FIG. 5(f), the platinum layer 16 formed in the step of FIG. 5(e) described above is
are finely processed by the above RIE or erosion so that they become electrodes of the semiconductor layer 12. (Titanium layer and titanium nitride layer etching process) and
As shown in FIG. 5G, titanium nitride 15 and titanium 14 are eroded and microfabricated using the platinum 16 microfabricated in the step of FIG. 5F described above as an etching mask. In this step, since the finely processed platinum 16 is used as an etching mask, not only is there no need to use a photoresist in the conventional erosion step, but the exposure step, development step, etc. can be omitted. In addition, since platinum 16, which has excellent chemical resistance, is used as an etching mask, it can be used as an etching mask.
A highly corrosive etching solution such as a mixed solution containing 3 parts O4 and 1 part hydrogen peroxide (H2O2) can be used.

FIG. 6 shows the semiconductor layer 12 according to the above embodiment.
1 is a vertical cross-sectional view of the main part of a high-temperature pressure sensor 100 configured using a semiconductor pressure sensing element (hereinafter referred to as sensing element) 10 in which electrodes made of layers of titanium 14, titanium nitride 15, and platinum 16 are formed. be. The cylindrical housing 30, which has a large diameter at the right end, has a mounting thread 30a formed on the outer periphery of the main body. Further, an element holder 31 having a cylindrical shape with one end closed is inserted through the left end opening and is tightly fixed by welding. The element holder 31 is made of Fe--Ni-- which has a small coefficient of thermal expansion.
The element holder 31 is made of Co alloy.
The inside forms a pressure introduction port. Further, an opening 31a is provided in the side wall of the pressure introduction port. Before the element holder 31 is welded and fixed to the housing 30, the sensing element 10 is firmly bonded and covered in advance by brazing inside the element holder 31 (in the upper part in FIG. 6) so as to close the opening 31a. Further, a thin recessed portion is provided in the sensing element 10 directly above the center of the opening portion 31a, and this is used as the pressure receiving diaphragm 21.

Next, details of the sensing element 10 are shown in FIG. Note that FIG. 7(a) is a plan view of the sensing element 10, and FIG. 7(b) is a longitudinal sectional view taken along line A-A in FIG. 7(a). As described above, the sensing element 10 is composed of the sapphire substrate 11, and has a pressure receiving diaphragm 21 formed by processing the sapphire substrate 11 into a concave shape and a thin wall. In addition, the pressure receiving diaphragm 2
1 is formed at one end of the rectangular parallelepiped sensing element 10 in its longitudinal direction. The other end of the sensing element 10 is configured as a lead extraction area. The detailed structure of this lead extraction area will be described later. Further, the sensing element 10 includes semiconductor strain gauge elements 22a and 2 made of a P-type single crystal silicon thin film doped with impurities by vapor phase growth of silicon on four locations on the surface of the sapphire substrate 11.
2b. These semiconductor strain gauge elements 22a
, 22b are the (100) plane, and the longitudinal direction of the semiconductor strain gauge elements 22a, 22b is the [110] direction of the (100) plane, which is the same as the longitudinal direction of the sensing element 10 in FIG. 7(a). It has become. Further, the semiconductor strain gauge elements 22a and 22b are connected to the pressure receiving diaphragm 21.
The semiconductor layer 12 is disposed directly above the peripheral edge of the sapphire substrate 11 and is connected to the semiconductor layer 12 made of a single-crystal silicon thin film formed on the sapphire substrate 11 as well. On the semiconductor layer 12 made of this single-crystal silicon thin film, electrodes made of the aforementioned titanium 14, titanium nitride 15, and platinum 16 layers are formed. This electrode is wired in parallel to the other end of the sensing element 10 that constitutes the above-mentioned lead extraction area, and a pad portion 25 is provided at the end of the wire. A surface protection film 26 for passivation is applied to the surface of the sensing element 10.

In FIG. 6, a lead extraction area is formed at the right end of the surface of the sensing element 10, and an IC chip 28 for signal processing to be bonded is adhesively fixed by a pad portion 25 and a wire line 27. There is. This IC chip 28 is composed of an amplifier circuit and a temperature compensation circuit, and is connected to the outside via a lead wire 29. Note that this temperature compensation circuit includes a pressure receiving diaphragm 2.
Semiconductor strain gauge element 2 that changes with temperature changes in 1
This is to compensate for the resistance value characteristics of 2a and 22b. Further, a cylindrical cover 32 is welded and fixed to the housing 30, and the housing element 10 is supported at its right end by a holder member 33 that is adhesively fixed to the cover 32 and the housing 30. Furthermore, the contact surface between the back surface of the sensing element 10 and the element holder 31 is shown in FIG.
As shown in FIG.
a, a metallized layer 18b such as molybdenum (Mo), and a metallized layer 18c such as nickel (Ni) are formed. The back surface of the sensing element 10 and the element holder 31 are bonded and fixed by a brazing layer 18d. It should be noted that a nickel plating layer 31a is also formed on the brazed portion of the element holder 31, making the bonding by brazing strong.

Next, the operation of the above configuration will be explained based on FIGS. 6 and 7. When the fluid pressure of the high temperature fluid acts on the pressure receiving diaphragm 21 provided in the sensing element 10, stress corresponding to the fluid pressure acts on the pressure receiving diaphragm 21. The pressure receiving diaphragm 21 is deformed, and an output signal corresponding to the deformation strain, that is, the applied stress value is emitted from the semiconductor strain gauge elements 22a and 22b. This output signal is transmitted to the titanium 14, titanium nitride 15, platinum 16 and their pad portions 25, which constitute the electrodes, and
The signal is input to the IC chip 28 via the wire line 27, and after amplification and temperature compensation are performed, it is taken out via the lead wire 29. Here, as the electrode of the sensing element 10, titanium 14, titanium nitride 15, and platinum 16 are sequentially formed on a single crystal silicon thin film.
Even if heat treatment is performed at 0° C. for 1 hour, the resistance of the sensing element 10 does not increase, but on the contrary decreases. In this way, since the resistance value of the sensing element 10 can be suppressed to a low value, variations in its output can be reduced. Further, by reducing the resistance value of the electrode portion of the sensing element 10, it is possible to reduce the decrease in output voltage due to a voltage drop in the electrode portion, and as a result, the output voltage of the high temperature pressure detector 100 can be increased. be able to.

Next, the semiconductor strain gauge elements 22a, 22
The principle of generating the output signal b will be explained with reference to FIG. FIG. 9 is a layout diagram of semiconductor strain gauge elements 22a and 22b in this example. A stress σt in the tangential direction of the pressure receiving diaphragm 21 acts on the semiconductor strain gauge element 22a with respect to this longitudinal direction, and a stress σr in the radial direction of the pressure receiving diaphragm 21 acts on the semiconductor strain gauge element 22a in a direction perpendicular to this longitudinal direction. work. On the other hand, semiconductor strain gauge element 2
2b is subjected to a stress σr in the longitudinal direction and a stress σt in a direction perpendicular to the longitudinal direction. Here, [1
10] direction, the piezoresistance coefficients πl and πs have πl
≒−πs
(However, πl is a longitudinal coefficient and πs is a lateral coefficient.) The semiconductor strain gauge elements 22a, 22
The rate of resistance change according to stress b is expressed as follows. Note that Ra and Rb are resistance values of the semiconductor strain gauge elements 22a and 22b, respectively. ΔRa/Ra=πlσr+πsσt≒πlσr−πlσ
t ΔRb/Rb=πlσt+πsσr≒πlσt−π
lσr In other words, the resistance changes of the semiconductor strain gauge elements 22a and 22b are in opposite directions, resulting in a total bridge circuit (not shown).
When configured, the balance of this total bridge circuit changes due to resistance changes of the semiconductor strain gauge elements 22a and 22b in response to applied stress. Since a constant current or constant voltage is applied to all bridge circuits, this resistance change is generated as a signal output. The output signal detected in this way, that is, the pressure signal, is amplified by the signal processing IC chip 28, temperature compensated, and taken out to the outside via the lead wire 29.

Although the high-temperature pressure detector 100 used to detect the pressure of high-temperature fluid has been described as an applied device according to this embodiment, other applied devices include a high-temperature acceleration detector, a high-temperature magnetic detector, etc. The present invention can also be applied to the electrode structures of these high-temperature semiconductor devices and their manufacturing methods. Further, as the electrode of this embodiment, each layer of titanium 14, titanium nitride 15, and platinum 16 is sequentially formed, but instead of titanium 14, a high melting point metal such as molybdenum, or a metal silicide such as TiSi2, MoSi2, etc. is used. You can also use objects. In place of titanium nitride 15, metal nitride such as zirconium nitride (ZrN) can be used, and in place of platinum 16, gold or nickel can be used. In the series of examples described above, SOS was used as the SOI structure of the high-temperature semiconductor element, but as an SOI structure other than this, single crystal silicon or polycrystalline silicon is used on a single crystal silicon substrate via an insulating layer. A structure in which polycrystalline silicon is formed on a metal substrate with an insulating layer interposed therebetween can be used.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the electrode structure of a sensing element constructed using the electrode structure of a high-temperature semiconductor device according to a specific embodiment of the present invention.

FIG. 2 is a longitudinal cross-sectional view of an electrode structure as a comparative example with respect to the electrode structure of FIG. 1;

FIG. 3 is an explanatory diagram showing a change in contact resistance in the electrode structure of FIGS. 1 and 2 from immediately after film formation to after heat treatment.

FIG. 4 is an explanatory diagram showing in detail a method for manufacturing the electrode structure of the sensing element according to the same example.

FIG. 5 is an explanatory diagram following FIG. 4 showing in detail the method for manufacturing the electrode structure of the sensing element according to the same example.

FIG. 6 is a longitudinal cross-sectional view showing the main structure of a high-temperature pressure detector constructed using the sensing element according to the same embodiment.

FIG. 7 is a detailed diagram showing a sensing element according to the same embodiment.

FIG. 8 is a partial vertical cross-sectional view showing a joined state of a sensing element and an element holder according to the same embodiment.

FIG. 9 is an explanatory diagram showing the arrangement of semiconductor strain gauge elements on the pressure receiving diaphragm of the sensing element according to the same example.

[Explanation of symbols]

10-Semiconductor pressure detection element (sensing element) 1
1-Sapphire substrate (insulating substrate) 12-semiconductor layer 12a-contact part 13-insulating layer
14-Titanium (high melting point metal) 15-Titanium nitride (high melting point metal nitride) 16-
Platinum 21-Pressure diaphragm 22a, 22b-
Semiconductor strain gauge element 25-pad portion 26-surface protection film
28-IC chip 30-housing 31-element holder
100-High temperature pressure detector

Claims (3)

[Claims] 1. An electrode structure of a semiconductor element made of single crystal silicon or polycrystalline silicon formed on an insulating substrate and used for detecting various physical quantities in a high temperature atmosphere, the electrode structure comprising: an electrode structure on a contact portion of the semiconductor element; a high melting point metal or a high melting point metal silicide formed; a high melting point metal nitride formed on the high melting point metal or the high melting point metal silicide;
1. An electrode structure for a high-temperature semiconductor device, characterized in that the electrode structure is made of one of platinum, gold, or nickel formed on the high-melting point metal nitride. 2. A method for manufacturing an electrode of a semiconductor element made of single crystal silicon or polycrystalline silicon formed on an insulating substrate and used for detecting various physical quantities in a high temperature atmosphere, comprising: a contact portion of the semiconductor element; A high melting point metal or a high melting point metal silicide is formed on the high melting point metal or the high melting point metal silicide, and after forming the high melting point metal nitride, the high melting point metal nitride is formed on the high melting point metal or the high melting point metal silicide. A method for manufacturing an electrode for a high-temperature semiconductor device, comprising removing oxides on the surface of a melting point metal nitride and forming any one of platinum, gold, or nickel on the high melting point metal nitride. 3. A method for manufacturing an electrode of a semiconductor element made of single crystal silicon or polycrystalline silicon formed on an insulating substrate and used for detecting various physical quantities in a high temperature atmosphere, comprising: a contact portion of the semiconductor element; forming a high melting point metal or a high melting point metal silicide thereon, forming a high melting point metal nitride on the high melting point metal or the high melting point metal silicide, and forming platinum on the high melting point metal nitride; A high-temperature semiconductor device characterized in that, after the platinum is microfabricated, the high melting point metal or the high melting point metal silicide and the high melting point metal nitride are eroded (wet etching) using the platinum as an etching mask. Method for manufacturing electrodes.