JPH04320357A - Wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE:To suppress production of dust particle by employing such insulating film as the additive contained therein exists only in the form of compound of silicon or oxygen in the vicinity of the surface of the insulating film and setting the minimum milling dimensions of elements mounted on a wiring board lower than a predetermined value. CONSTITUTION:Such insulating film is employed as the additives contained therein exist only in the form of a compound of silicon or oxygen at least in the vicinity of the surface of the film or the concentration of the additive on the surface of the insulating film is equal to or lower than that at other parts in the film. Furthermore, minimum milling dimensions of elements mounted on a wiring board are set smaller than 0.8mum. At first, a BPSG film is formed and subjected to heat treatment for fluidisation. It is then processed in hydrogen environment in order to stabilize the characteristics or enhance the reliability, followed by oxidization process.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board suitable for forming fine conductor wiring patterns and a method of manufacturing the same.

0002

2. Description of the Related Art As the density of semiconductor integrated circuits and wiring boards increases, there is an increasing demand for miniaturization and higher density of wiring used for interconnection of semiconductor elements and wiring boards therefor. It is well known that one of the biggest challenges in forming a high-density wiring board with multiple layers of wiring is how to overcome the negative effects of the height difference that increases as the wiring is stacked. There is. For example, Journal of the Electrochemical Society, Vol. 135, No. 10, pp. 2557-2562 (19
Published in 1988) (J. Electrochem. So
c. Vol. 135 No. 10, p2557-
p. 2562 (1988) describes that a SiO2 film made of a high-density aluminum alloy (hereinafter referred to as Al) was formed by absorbing the underlying level difference and forming a SiO2 film with a flat surface by a bias sputtering method using a planar magnetron cathode. Techniques for forming layer wiring are described. These are intended to form a protective insulating film at a temperature sufficiently lower than the melting point of Al.

On the other hand, the wiring conductor layer is made of metal silicide (
When the material is made of a material with a higher melting point such as silicide (hereinafter referred to as silicide), a higher temperature can be used to form or stabilize an insulating film covering the material. However, in order to reduce the influence on device characteristics, it is desirable that the heat treatment temperature be as low as possible.

A typical insulating film that is formed at a relatively high temperature and is widely used is glass containing phosphorus (P) and boron (B) as additives.
Phospho-Silicate Glass. BPSG (hereinafter referred to as BPSG) is known and is widely used as a protective film for elements having a flattening effect and wiring made of metal silicide (referred to as silicide), polycrystalline Si, or the like. In general, a film is formed by chemical vapor deposition (hereinafter referred to as CVD) on integrated circuit elements or wiring while adding P or B, and then heat-treated in the range of 850 to 950°C to cause the film to flow. The surface becomes flat.

In addition to P and B, germanium (Ge
), arsenic (As), etc., are believed to further reduce the temperature required for fluidization. Furthermore, in order to improve and stabilize the characteristics of the element, heat treatment may be performed in an atmosphere containing hydrogen (hereinafter referred to as hydrogen atmosphere). This is because this heat treatment in a hydrogen atmosphere improves the electrical characteristics of a layer of a Si compound containing nitrogen, such as a SiN film, and wiring made of a high melting point material used in the element. Further, connection holes are formed at necessary locations on the surface of the substrate to connect elements and wiring or wiring to wiring.

[0006]

[Problems to be Solved by the Invention] However, it is difficult to use an etchant containing hydrofluoric acid to form contact holes in the BPSG film formed by the above-mentioned conventional technique, or to remove the upper wiring layer after forming the contact holes. It was found that when light etching is performed with a solution containing hydrofluoric acid as a pretreatment for forming a substrate, irregularly shaped particles remain as foreign matter on the substrate surface. This foreign object is P
The occurrence situation changes not only depending on the concentration of B but also on the concentration of B. Generally, as the B concentration increases, foreign particles tend to become larger. Moreover, this foreign material remains in various shapes depending on the method of cleaning and drying the substrate after etching. When using a drying method that mainly dries the substrate by rotating it, such as a conventional rotary dryer for substrates, the foreign matter is generally small. Further, since foreign substances are generally very fine and thin, it is difficult to observe foreign substances by distinguishing them from the interference color of the BPSG film itself using an optical microscope using a white light source. Even when the degree of occurrence of foreign matter is quite severe, in most cases it is only visible as uneven color and is determined to be a variation in etch depth, and the occurrence of foreign matter is not necessarily known. Furthermore, since the wiring and connection holes in conventional wiring boards were not so small, the presence of these foreign substances did not immediately lead to the occurrence of defects.

However, in recent years, as substrates have become larger and it has become known that rotating substrates tends to attract foreign matter in the air, heating, steam, or Drying methods using gas are increasingly used. When this type of drying method is used, foreign particles tend to grow in size, sometimes so large that they can be observed even with a normal optical microscope. As processing dimensions become finer, the presence of these foreign substances causes peeling of wiring and poor electrical continuity (mainly due to increased connection resistance and variation), and their presence cannot be ignored. In addition, it has been found that some of these foreign substances float inside the etching liquid or cleaning liquid tank and adhere to other substrates during etching or cleaning, causing defects.

[0008] If the foreign matter generated in this way is stored for a long time in an atmosphere containing moisture, it will gradually react and become an oxide. In such a state, it appears that the foreign matter has disappeared, but in reality, the foreign matter adheres to the membrane surface as a thin layer that is thought to have been formed by reacting with moisture in the air, and the remaining foreign matter appears to have disappeared. Because of this, it was found that providing a wiring metal layer on top of this would cause corrosion, which would reduce the reliability of the wiring. Like this,
As wiring becomes finer, foreign particles generated when etching conventional BPSG films are becoming a major cause of defects, and solving this problem is thought to become more important in the future.

The inventors have discovered that although this foreign material is not soluble in water or a solution containing hydrofluoric acid, it can be dissolved by selecting an appropriate etchant. For example, foreign substances generated when a BPSG film is etched are dissolved in nitric acid or aqueous ammonia. Therefore, foreign matter generated during formation of the connecting hole can be removed by cleaning the membrane surface using these liquids. However, the surfaces of the substrate and lower layer wiring exposed at the bottom of the hole may react with these liquids and change in quality, resulting in deterioration of electrical connection characteristics with upper layer wiring to be formed later. Therefore, it is desirable to perform light etching again using a solution containing hydrofluoric acid, but foreign matter will be generated again. When devices become smaller and their connection holes become smaller, this becomes a problem.

Note that if annealing in a hydrogen atmosphere is not performed, P will not be reduced, and therefore no foreign matter will be generated due to the hydrofluoric acid etchant.
Using an analytical method, it was found that a layer containing a high concentration of oxidized or combined P was present on the surface. If such a layer containing a high concentration of P exists, there is a high possibility that the wiring layer formed thereon will corrode or the adhesiveness will deteriorate.

In addition to P, germanium (Ge) and arsenic (
It was confirmed that almost the same phenomenon occurs when at least one of As), antimony (Sb), molybdenum (Mo), and tungsten (W) is included.

An object of the present invention is to provide a wiring board having an insulating film containing the above-mentioned additives, in which generation of foreign matter during etching of the insulating film is suppressed, and a method for manufacturing the same.

[0013]

[Means for solving the problem] The above purpose is to
At least one substance selected from the group consisting of As, Sb, Mo, and W (hereinafter, the selected substance will be referred to as an additive)
In a wiring board on which at least a portion of an insulating film containing a
(denoted as ) or as a compound with oxygen, or an insulating film is used in which the concentration of the additive on the surface of the insulating film containing the additive is equal to or lower than the concentration in other parts of the film. This is achieved by a wiring board in which the minimum processing dimensions of elements included in the wiring board are 0.8 μm or less. Note that the vicinity of the film surface mentioned above refers to a solution containing hydrogen fluoride (hereinafter referred to as "hydrogen fluoride-containing solution") used for pretreatment of depositing a wiring layer to be formed thereon.
Refers to the same depth from the film surface that is etched using hydrofluoric acid (denoted as hydrofluoric acid). Usually, it is in the range of 10-50 nm in many cases. In recent years, this depth tends to become shallower in highly integrated circuits. The additive is characterized in that it is in a combined state at least near the surface of the insulating film before the wiring layer is formed. In a deeper part, it is more stable for the manufacturing process if the additive is in a combined state, but it may be in an uncombined state.

Furthermore, the above object includes the steps of forming an insulating film containing the additive used in a wiring board, heat-treating the board in a reducing atmosphere, and then oxidizing the board. This is achieved by a method of manufacturing a wiring board having the following method.

[0015]

[Function] It has been generally believed that the excess P in Si oxide films (SiO2 films) exists as oxides such as P2O5, except for those that are solidly dissolved in the film (bonded directly with Si). . However, the inventors have discovered that this idea is not necessarily correct.

As active elements and wiring become finer in wiring boards including semiconductor integrated circuit elements, etc., heat treatment in an atmosphere containing hydrogen is required after forming the BPSG film in order to stabilize the characteristics and improve reliability. It has become necessary to do so. In particular, some elements (including active elements and wiring) may contain nitrogen-containing compounds, such as Si nitride (silicon nitride film; SiN).
), Si nitride oxide (oxynitride)
This is because when these nitrogen-containing compounds are used, heat treatment of a thin film made of these nitrogen-containing compounds in an atmosphere containing hydrogen improves electrical insulation and reduces leakage current. However, on the other hand, the inventors found that some of the P in the BPSG film subjected to such heat treatment was reduced to an unstable substance substantially equivalent to P (hereinafter referred to as non-oxidized P). I found out that things are changing. Furthermore, in the case of films to which other additives were added, they were found to be reduced to a non-oxidized state and remain on the film surface during etching.

[0017] Such a BPSG film was coated with a hydrogen fluoride aqueous solution (
Hereinafter referred to as hydrofluoric acid. When etching with a solution containing (usually supplied as a 50% aqueous solution), an etch residue is generated on the film surface or a thin layer with a high concentration of P is formed. These residues or layers with high P concentration on the surface are
It was also found that the reliability of wiring boards was significantly impaired. As described above, in the present invention, substantially all of the additives such as P contained in the insulating film exist as compounds with Si, oxygen, etc., and the film does not contain P in the non-oxidized state. It is characterized by the presence of In addition, the concentration of additives near the surface of such BPSG films and films containing other additives is
It is characterized by a concentration lower than that of other parts inside the membrane. Furthermore, it is a feature of the present invention to provide an apparatus that realizes such a BPSG film and has a processing function that allows manufacturing of wiring boards with a high yield rate and with high efficiency. It has been found that in addition to P as described in detail above, when the additive is Ge, As, Sb, or Mo, almost the same change in chemical state is exhibited, and the problem can be solved by the method of the present invention. Regarding the conditions of the oxidation treatment, the higher the oxygen concentration, the longer the oxidation treatment time, and the higher the temperature, the deeper the effect of oxidizing the additives. Generally, if the oxygen concentration is 5% or more, the treatment temperature is 430° C. or more, and the time is 20 minutes or more, it is possible to oxidize the additives contained within a depth of about 20 nm.

However, some of the bonded additives may be converted into a non-oxidized state by further performing heat treatment in a hydrogen atmosphere after the formation of the predetermined wiring; however, on the surface of such a film, Compared to the interior, the concentration of additives is reduced.

If the additive is present as a compound in the insulating film, the additive compound in the film will be eluted into the solution during etching with a hydrofluoric acid solution, so that it will be deposited on the substrate surface as foreign matter. It does not accumulate in By using such a film, it is now possible to manufacture wiring boards containing wiring and semiconductor integrated circuits with a minimum processing size of 0.8 μm or less, with almost no decrease in the yield rate, which previously had a strong tendency to decrease. It becomes possible to do so.

[0020] As a typical example, a BPSG film will be explained. This is because P is the most widely used material added to insulating films and has a high concentration, so the effects of the present invention are large.

[0021] Chemical vapor deposition method (hereinafter referred to as CVD method)
Until now, there have been no detailed analysis results regarding the state of B and P in the BPSG film immediately after it is formed. BPSG
As mentioned above, the film is unstable and has no flattening effect when it is just formed, so high-temperature heat treatment for fluidization is generally performed at an appropriate stage in the wiring board manufacturing process. . This heat treatment atmosphere may be a reducing (atmosphere mainly containing hydrogen; referred to as a hydrogen atmosphere), an oxidizing atmosphere, or an inert gas atmosphere. However, it has been found that heat treatment in an oxidizing atmosphere generally leads to deterioration of the characteristics of integrated circuit elements in the wiring board, such as an increase in interface states and leakage current. It has been found that this is mainly due to the deterioration of the electrical characteristics of the SiN film and high melting point material wiring layer used in the device. This deterioration of the silicon nitride film causes, for example, deterioration of transistor characteristics, deterioration of storage characteristics of nonvolatile memory elements, deterioration of charge retention characteristics of capacitors used in memory elements, and even an increase in leakage current of adjacent high-melting point material wiring. happens. Therefore, it is necessary to use a reducing atmosphere as the heat treatment atmosphere for fluidization, or to perform heat treatment in a reducing atmosphere again after the heat treatment for fluidization. Generally, a temperature of 600°C or higher is used. However, as mentioned above, when heat treatment is performed at a relatively high temperature in such a reducing atmosphere, some of the P in the BPSG film becomes non-oxidized P, except for that bonded to the base material Si. It becomes slightly soluble in water and hydrofluoric acid. When the surface of such a film is etched using a hydrofluoric acid-based etchant, foreign matter mainly composed of non-oxidized P or a layer with a high concentration of P is formed on the film surface. However, this layer has heretofore been hardly recognized as a foreign substance. This is because these foreign substances are so small or thin that they can hardly be detected by observation using a microscope using a normal white light source. In contrast, when the inventors observed using a monochromatic light source, they found that foreign matter could be easily observed even at the same magnification. Also, B
It has also been found that the generation of such foreign substances can be suppressed by setting the P concentration in the PSG film to 4 mol% or less. Generally S
This coincides with the phenomenon that the concentration of P that can be dissolved in iO2 is 4 mol%. However, P below 4 mol%
It is difficult to cause fluidization in a BPSG film containing .

On the other hand, in the present invention, even if the films contain the same P and B, at least in the vicinity of the surface of the insulating film, P is substantially completely converted into an oxide or hydroxide in the film. Even if an etching treatment using a hydrofluoric acid solution is performed as a pre-treatment for forming the wiring metal layer in order to distribute the wiring metal layer, no foreign matter is generated. An example of one method for producing such a film is shown in FIG. In the figure, first of all, BP
Form an SG film. Next, heat treatment is performed for fluidization. Thirdly, atmospheric heat treatment in a hydrogen atmosphere is performed to stabilize characteristics or increase reliability. Fourth, oxidation treatment, which is a feature of the present invention, is performed. The processing conditions include performing an oxidation treatment equivalent to heat-treating the film in an oxidizing atmosphere at a temperature of 700°C or lower, preferably 650°C or lower, to oxidize unstable P in the BPSG film. I end up. As the oxidizing heat treatment atmosphere, a gas having an oxygen concentration of at least 1% or more, preferably 20% or more is used. The heat treatment temperature is 40
It was confirmed that a temperature of 0°C or higher is at least effective, and a temperature of 430°C or higher is particularly desirable. By performing such heat treatment at a relatively low temperature, non-oxidized P is oxidized and continues to exist in the film in a stable state. Even when etched with an etchant such as hydrofluoric acid, no foreign matter is generated. A layer with high P concentration is not formed on the film surface. Note that it is desirable that the heat treatment temperature be as low as possible. If the heat treatment temperature in an oxidizing atmosphere becomes high, as in the case of heat treatment for fluidization, the characteristics of the element will deteriorate, reducing the effect of the heat treatment in a reducing atmosphere. On the other hand, if the temperature is below 650°C, such characteristic deterioration becomes negligible, and if the temperature is lowered to 400 to 450°C, almost no characteristic deterioration is observed. Similarly, the same effect can be obtained by using a treatment that corresponds to an oxidizing atmosphere at substantially 400° C., such as performing oxidizing plasma treatment while heating the substrate. Another effective method is to heat the substrate to about 300° C. and irradiate it with ozone or, if necessary, ultraviolet light. Further, instead of oxygen or ozone, plasma of a gas containing oxygen may be used.

The difference in the chemical state of oxidized and non-oxidized P is determined not only by the presence or absence of foreign matter during etching, but also by, for example, XPS analysis (X ray probe spectroscopy).
This can be determined by using a method such as oscopy. According to the inventors' analysis, taking a BPSG film as an example, when a film mainly containing oxidized P is irradiated with X-rays, the energy of the secondary electrons generated is 135, 187, and 192.
A peak is observed near eV (when the energy of secondary electrons of Si is calibrated as 103.4 eV). However, in the case of an oxidized P film, the peak at 187 and 192 eV is extremely weak or overlaps with the B peak, so it may be difficult to detect. However, the energy of secondary electrons generated from a film containing non-oxidized P is approximately 130.1
A rather strong peak of 87 eV appears. The peak at 187 eV from a film mainly containing P in an oxidized state is weak, and the peak at 187 eV from a film mainly containing P in a non-oxidized state is relatively strong. Furthermore, P in a substantially oxidized state is detected on the surface of a BPSG film that has just been formed or a film that has been fluidized in an oxidizing atmosphere or an inert gas atmosphere. In addition, P is no longer detected by the XPS method on the surface of the BPSG film that has been subjected to high-temperature hydrogen annealing, but when the surface of this film is etched with a hydrofluoric acid solution, the surface contains non-oxidized P as the main component. A layer containing a high concentration of foreign matter or non-oxidized P comes to exist.

On the other hand, in the BPSG film of the present invention, P is not detected on the surface, or even if it is detected, the concentration is not higher than the concentration inside the film. The characteristics of the elements included in the wiring board are improved by heat treatment in a high-temperature hydrogen atmosphere, and the non-oxidized P generated at that time is converted into an oxidized state by the subsequent low-temperature oxidation treatment, so the characteristics of the elements are improved. It is possible to achieve both improvement and suppression of the adverse effects of non-oxidized P. Furthermore, since the concentration of additives on the surface of the BPSG film is reduced by heat treatment in a hydrogen atmosphere, the reliability of the wiring layer formed thereon can also be improved.

As described above, according to the present invention, BP
It becomes possible to realize a wiring board without causing deterioration of the flow characteristics of the SG film or the characteristics of elements in the wiring board, and without the presence of foreign matter or a high concentration layer of P on the surface. Through such heat treatment,
Changes in the oxidized/non-oxidized chemical state of the additive are substantially the same for the other additives described in the present invention. However, since the concentrations of other additives are lower than P, there is no noticeable effect. However, when elements and interconnections made of high-melting point materials become extremely fine, they cannot be ignored. Furthermore, if after such heat treatment and oxidation treatment in a hydrogen atmosphere, the equipment is taken out and etched with a solution containing hydrofluoric acid using another equipment, not only will the process be complicated, but the Adhesion of foreign matter may also cause a decrease in the yield rate in wiring board manufacturing. Therefore, we have developed a device that can perform the above oxidation treatment and etching treatment in the same device. As a result, not only the process was simplified, but also the decrease in the yield rate due to foreign matter was suppressed.

In the manufacture of wiring boards, when the board is a semiconductor substrate containing integrated circuit elements, the treatment for cleaning the exposed substrate surface after forming connection holes is a treatment mainly based on a chemical reaction, such as hydrofluoric acid. In most cases, it is unavoidable to use a light etch using a liquid or steam containing This is because if plasma or ion treatment is used, the crystallinity of the substrate material exposed at the bottom of the contact hole may be reduced, or contamination may occur due to redeposition phenomenon accompanying plasma processing. In order to avoid such problems, it is necessary to increase the chemical reactivity as much as possible even when using plasma treatment and to suppress damage and contamination caused by plasma energy. However, in treatments based on chemical reactions, the selectivity of the reaction is high, so substances in the film that do not react under the treatment conditions accumulate on the surface. Therefore, the result is similar to that of light etching using a liquid or steam containing hydrofluoric acid. The effects of foreign particles that have not reacted or been removed by subsequent cleaning on elements and wiring become more serious as they become finer.

On the other hand, in the wiring board and its manufacturing method of the present invention, since the additives in the film have the property of being dissolved in the etchant and subsequent cleaning solution (water), the additives that occur in the conventional insulating film are No such problems will occur. This problem is especially serious in BPSG films, and the effects of the present invention are also significant.

[0028]

[Examples] The present invention will be explained in detail below with reference to Examples.

(Embodiment 1) An example in which the present invention is applied to an ultraviolet erasable nonvolatile memory integrated circuit (hereinafter referred to as LSI) will be explained. In addition, ultraviolet erasable nonvolatile memory (hereinafter referred to as E
PROM) is described in, for example, the Institute of Electronics, Information and Communication Engineers Technical Research Report Paper No. SSDM-11. The B concentration is 4 mol% as a protective film for this element.
, by depositing a BPSG film with a P concentration of 6 mol%,
A heat treatment was performed in a nitrogen atmosphere to fluidize the BPSG film and flatten the film surface. Next, in order to make the information storage characteristics of the device sufficiently good, heat treatment was performed at 900° C. in a hydrogen atmosphere. This reduces the leakage current of SiN films or oxynitride films (films containing Si oxide and nitride) used in substrate MOS (semiconductor elements consisting of metal/oxide/Si layers). This is because electrical characteristics can be improved.

[0030] In such a substrate, connection holes between elements and wiring are further formed, and as a pre-treatment for forming a wiring conductor layer,
When the substrate surface is etched with a buffered etch solution of hydrofluoric acid: ammonium fluoride solution = 1:20 (volume ratio; both are 50% aqueous solutions), foreign matter will be generated on the element surface after washing with water and drying. The etching amount is approximately 20 nm in terms of the BPSG film.

As a countermeasure to this problem, in the present invention, after hydrogen annealing, oxidation treatment was performed again in a gas atmosphere containing 20% oxygen using the heat treatment temperature as a parameter. Processing time is 30 minutes. The study results are shown in Figure 2. As a guideline for EPROM characteristics, the change over time of the threshold voltage Vth on the write side after 10 years when the number of rewrites is small (hereinafter referred to as precycle characteristics), and the
Time-dependent change in threshold voltage on the erase side after 0 years (hereinafter referred to as 100
,000 cycle characteristics) (hereinafter referred to as memory window). The memory window requires 0.35V or more. In the same figure, 9
In the case where the electrodes are only formed by hydrogen annealing at 00° C., the pre-cycle characteristics are represented by a curve 21, and the 100,000 cycle characteristics are represented by a curve 21'. Similarly, the curves when 800° C. oxidation heat treatment is performed after hydrogen annealing are shown as 22 and 22', respectively. In addition, curve 23 shows the characteristics when oxidation heat treatment is performed at 650°C.
and 23'. Note that the characteristics when the oxidation heat treatment was performed at 450°C almost matched curves 21 and 21'. First, if oxidation heat treatment is performed at 800° C., the memory window after 10 years will be negative. In other words, the characteristics are severely deteriorated and cannot be used. When the oxidation heat treatment was performed at 650°C, the memory window was improved to 0.3V. However, it does not meet the above specification of 0.35V. When the oxidation heat treatment temperature is 450℃, the memory window is 0.4V.
is almost the same as that without oxidation heat treatment,
Almost no characteristic deterioration was observed.

It should be noted that no foreign matter was observed due to the buffer etchant in any of the oxidation heat treatments.

(Example 2) Similar to Example 1, EPRO
The present invention was applied to M. In the present invention, after hydrogen annealing, the substrate was inserted into a barrel-shaped oxygen plasma asher, and discharged for 30 minutes at an oxygen pressure of 1 Torr and a high frequency power of 500 W. The oxygen plasma asher is described, for example, in Journal of the Electrochemical Society, Vol. 137, No. 4, pp. 1212-1218. Incidentally, under these discharge conditions, polymeric resin such as photoresist is etched at a rate of about 500 nm/min. Further, the substrate temperature reaches 350° C. or higher within a few minutes after the start of discharge. When the substrate was exposed to oxygen plasma at a temperature of 350° C. or higher in this way, no foreign matter was observed even when etching was performed using the buffer etchant described in Example 1. However, the plasma treatment described in this example is extremely harsh compared to the conditions used for general resist removal and is highly likely to cause deterioration of device characteristics, so it is less effective than the method of Example 1.

(Example 3) The present invention was applied to a DRAM (Dyna
An example of application to mic RandomAccess Memory) will be described. A DRAM memory cell generally has a capacitor that stores signal charges and a readout function.
It consists of a MOS transistor used for write control. In order to reduce the memory cell area and not reduce the amount of signal charge stored, it is necessary to use a material with a high dielectric constant as the capacitor insulating film and to make the film thickness as thin as possible. For example, in a 4 Mb DRAM, a two-layer film of SiO2/SiN film is used as a capacitor insulating film. The reason for using the SiN film is that the SiN film has a high dielectric constant. First, on the surface of the lower electrode of the capacitor,
A 0 nm SiN film was formed. The dielectric constant of the SiN film is 8 or more. However, since the SiN film has a large leakage current,
To prevent this, the surface is oxidized to a thickness of approximately 3 nm.
A film was formed. As a result, a capacitor insulating film with a high dielectric constant and low leakage current was realized. However, by oxidizing the surface of the SiN film and converting it to SiO2, which has a low dielectric constant, the effective dielectric constant of the film was reduced to 5. In future DRAMs, it will be necessary to reduce the amount of oxidation of the SiN film as much as possible.

Therefore, in the present invention, the thickness of the oxide film on the surface of the SiN film is reduced to 1.5 nm.

The leakage current of the capacitor increased due to the decrease in the SiO2 film thickness. P on the surface after memory cell formation
A BPSG film containing 6 mol % of B and 10 mol % of B was formed and heat-treated at 900° C. for 10 minutes in a hydrogen atmosphere. As a result, the leakage current was reduced to the same level as when the oxide film thickness on the surface of the SiN film was 3 nm, and the effective dielectric constant was improved to 6 or more. Further, after forming the connection hole, heat treatment was performed at 430° C. for 30 minutes in a nitrogen atmosphere containing 20% oxygen. Through the above treatment, the electrical characteristics of the elements and high melting point material wiring provided in the BPSG film were improved. Furthermore, since the P concentration on the surface of the BPSG film was reduced, the problem of reduced reliability such as corrosion of the wiring made of metal containing aluminum formed thereon was also improved.

(Embodiment 4) This will be explained using FIG. 3. Figure (a) shows a wiring board structure formed using a conventional manufacturing method. In the figure, BP with a B concentration of 7 mol% and a P concentration of 7 mol% is deposited on the surface of a Si substrate 31 having steps.
SG film 32 was formed to a thickness of about 500 nm, and heated at 850° C. for 30 minutes.
It was heat-treated in a mixed gas atmosphere of oxygen and nitrogen to make it fluid. Then, heat treatment was performed at 800° C. for 30 minutes in a pure hydrogen atmosphere. On top of that, the thickness is 0.5μm, and the width and spacing are both 0.5μm.
When forming the wiring 34 made of AlSi alloy with a length of 2 m, hydrofluoric acid:
The BPSG film 32 was etched for 30 seconds using a 1:10 diluted solution, washed with water, and dried. Foreign matter 33 was generated by this etching. After that, A by a known sputtering method.
An lSi alloy film was formed to a thickness of 0.5 μm, and predetermined wirings 34 were formed using known lithography and etching techniques. Then, as a protective film, 0.0% was deposited by chemical vapor deposition.
A 5 μm thick SiO2 film was formed.

However, in this wiring board 31,
As a result of applying a voltage of 5V between adjacent wirings 34 and measuring the withstand voltage, a leakage current of about 0.1 μA was observed. A wiring having such leakage current characteristics cannot be applied to, for example, a 4 megabit DRAM. It is considered that the insulation between adjacent wirings deteriorated due to adsorption of moisture to the foreign matter 33 or the like.

On the other hand, as shown in the same figure (b),
Before performing the pretreatment for forming the wiring metal film, the BPSG film 36 was heat-treated at 400° C. for 30 minutes in a nitrogen atmosphere containing 30% oxygen as the method of the present invention. After that, the wiring board was manufactured through the same steps as the conventional method. the result,
Leakage current between adjacent wires has been reduced to less than 1/100 of the conventional level, and has been improved to a non-problematic level.

(Embodiment 4) A manufacturing apparatus for oxidizing a wiring board according to the present invention will be described with reference to FIG. In the figure, an oxidizing chamber 41 is provided with an inlet 43 for introducing an oxidizing gas or a gas containing ozone, and an exhaust port 45 thereof. A heat source 47 for heating the wiring board 49 and a stand 48 for supporting and moving the wiring board 49 are provided therein. Although an example of an infrared lamp is shown in FIG. 4 as the heat source 47, if a sheath heater is used, it may be included inside the stand 48. Furthermore, the heat source 47 may be provided outside the oxidation chamber 41 through a transparent window. stand 4
8, a plate-shaped one is shown in the same figure, but it may be of any type as long as it can support and move the wiring board 49. heat source 47
shall have the ability to heat the substrate 49 to 400° C. or higher. However, when ozone or plasma is used as the oxidizing gas, the capacity may be lower. A BPSG film (not shown) on the surface of the substrate 49 in this oxidation chamber 41
After performing the oxidation treatment, the substrate 49 is placed in the etch chamber 4 to be connected.
2. The etch chamber 42 has an inlet hole 44 for introducing an etching gas or steam, and furthermore, a drying gas, and an exhaust hole 4 thereof.
6. The substrate 49 transferred to the etching chamber 42 is exposed to hydrofluoric acid vapor for a predetermined time to etch the surface of the BPSG film (not shown). Then, if necessary,
After treatment such as exposure to water vapor for cleaning, dry air or nitrogen is introduced, and if necessary, the substrate is heated (heat source not shown) to dry it. Although FIG. 4 shows the case where steam is used as the etching means, the etch chamber 42
Conventional wet chemical etching may be performed by providing a mechanism (not shown) for etching using a hydrofluoric acid solution inside. Furthermore, although only the oxidation chamber and the etch chamber are shown in this embodiment, a chamber for forming a wiring metal layer or the like may be added in addition to these two processing chambers.

Furthermore, although heat treatment in an oxidizing atmosphere is shown as the oxidation treatment in this embodiment, it goes without saying that a method of exposing to oxygen-containing plasma in a reduced pressure atmosphere may also be used. In this case, the oxidation chamber 41 will be equipped with a mechanism (not shown) for plasma generation and introduction. As a plasma generation method, known high frequency discharge (50 kHz or higher) or microwave discharge (2.45 GHz) may be used.

[0042] In the case of a conventional method that does not use such an apparatus, the time required for transporting the substrate is equal to or longer than that for oxidation treatment or etching. Further, during transportation, a large number of foreign substances adhere to the surface of the substrate due to friction between the substrate and the transportation case. Generally, when the substrate is a Si wafer with a diameter of 4 inches, it is said that the number of foreign particles attached to the wafer during one transport is 50 or more pieces/wafer. It is also said that about 10 foreign objects adhere to each insertion/removal from the device. By using the device of the present invention, adhesion of foreign matter due to transportation could be almost completely prevented. It was also possible to reduce the adhesion of foreign matter by half due to insertion/removal from the device.

[0043]

[Effects of the Invention] In the present invention, P contained in the insulating film,
By using a film in which Ge, As, Sb, Mo, W, etc. are substantially all oxidized, there is an effect of preventing a decrease in the yield rate in the wiring board manufacturing process and deterioration of characteristics after manufacturing. In addition, the heat treatment in an oxidizing atmosphere or the equivalent plasma treatment used as a method for forming such a film corresponds to sufficiently low temperature heat treatment conditions, so that the characteristics of the memory LSI etc. will not deteriorate. .

Application of the present invention is not necessarily necessary in cases where the above-mentioned additives do not cause problems such as peeling off because the wiring is not very fine, or in cases where deterioration of element characteristics due to foreign substances or foreign substances is unlikely to occur. . However, the effects of the present invention cannot be ignored when the processing dimensions of elements and wiring are miniaturized to 0.8 μm or less. In addition, although P was mainly described in the above embodiments, Ge, A
Attempts have also been made to further lower the fluidization temperature by adding s, Sb, Mo, W, etc. However, Ge
, As, etc., are unstable and are preferably stabilized by the treatment of the present invention. Further, lowering the surface concentration is also effective for improving the reliability of the wiring layer thereon. In particular, if Sb is added in an unstable, non-oxidized state at a high concentration on the surface of an insulating film, it will react with moisture entering from the outside in the long term, causing corrosion of the aluminum alloy wiring above it. There is. The present invention is also effective in preventing such defects.

Furthermore, by using the apparatus having the oxidation treatment mechanism and the etching treatment mechanism shown in Example 4, the defective rate can be significantly reduced compared to using the conventional apparatus.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a method for manufacturing a substrate having a BPSG film according to the present invention.

FIG. 2 is a diagram showing changes in EPROM characteristics in Example 1.

FIG. 3 is a cross-sectional view of a conventional wiring board (a) and a wiring board (b) according to the present invention.

FIG. 4 is a schematic cross-sectional view of a manufacturing apparatus used for oxidizing a wiring board according to the present invention.

[Explanation of symbols]

21, 22, 23... Pre-cycle characteristics, 21', 22'
, 23'...100,000 cycle characteristics, 31...substrate, 32...BPSG film, 33...foreign matter, 34...wiring, 35...
Protective film, 41... Oxidation chamber, 42... Etching chamber, 43, 44...
Inlet, 45, 46... Exhaust port, 47... Heat source, 48... Unit,
49...Substrate.

Claims (10)

[Claims] [Claim 1] Phosphorus, germanium, arsenic, antimony,
In a wiring board on which an insulating film containing at least one kind of additive selected from the group consisting of molybdenum and tungsten is deposited, at least in part, the additive contained in the insulating film is at least near the surface of the insulating film. A wiring board characterized in that an insulating film that is substantially entirely present as a compound with silicon or oxygen is used, and the minimum processing dimension of an element included in the wiring board is 0.8 μm or less. . 2. The wiring board according to claim 1, wherein the substrate includes a semiconductor integrated circuit, and an active element or a passive element in the semiconductor integrated circuit contains a compound containing nitrogen. [Claim 3] Phosphorus, germanium, arsenic,
a step of forming an insulating film containing at least one kind of additive selected from the group consisting of antimony, molybdenum, and tungsten; a step of heat-treating the substrate in a reducing atmosphere; and a step of oxidizing the substrate. A method for manufacturing a wiring board, comprising: 4. The oxidation treatment is performed at a temperature of 400°C or higher and 650°C.
4. The method of manufacturing a wiring board according to claim 3, wherein the heat treatment is carried out in the following temperature range and the atmosphere is a gas atmosphere containing oxygen at a concentration of 1% or more. 5. The oxidation treatment is performed at a temperature of 300°C or higher,
4. The method of manufacturing a wiring board according to claim 3, further comprising a process of irradiating with a gas containing 1% or more of ozone. 6. The heat treatment is performed at a temperature of 300°C or higher for 1
4. The method of manufacturing a wiring board according to claim 3, further comprising a process of irradiating plasma using a gas containing % or more of oxygen. 7. The oxidation treatment is performed at a temperature of 300°C or higher,
4. The method of manufacturing a wiring board according to claim 3, further comprising a process of irradiating a gas containing ozone and ultraviolet light. 8. The method for manufacturing a wiring board according to claim 3, further comprising the step of heat-treating the substrate in a second reducing atmosphere after the oxidation treatment step. 9. The method according to claim 3, further comprising the steps of forming an opening in the insulating film and forming a metal wiring layer on the insulating film after the oxidation treatment step. A method for manufacturing a wiring board according to any one of the above. 10. After the heat treatment in the second reducing atmosphere, the method further comprises the steps of: forming an opening in the insulating film; and forming a metal wiring layer on the insulating film. The method for manufacturing a wiring board according to claim 8.