JP4161711B2 - Film forming method and film forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film forming method and a film forming apparatus, and more particularly to a film forming method and a film forming apparatus for forming a metal film by vapor-depositing a metal evaporated by heating on a substrate.
[0002]
[Prior art]
Conventionally, a film forming technique is important in manufacturing a semiconductor device, and in particular, a metal film is often formed by depositing a metal on a substrate such as a wafer for electrode formation, wiring formation, and the like. ing.
[0003]
As a film forming apparatus for depositing a metal film on a substrate, for example, an apparatus employing an electron beam gun (hereinafter referred to as “EB gun”) method is known (see, for example, Patent Document 1). This has the advantage that it can be applied to most metal materials, and has been widely used in recent years.
[0004]
As shown in FIG. 7, the film forming apparatus employing the EB gun method converges the thermoelectrons emitted from the filament 130 to generate an electron beam 110 and irradiates the electron beam 110 to form a metal for film formation. A metal material container 100 for melting the material, a substrate holder 300 for holding the substrate 200 for forming a metal film, and a chamber 400 for accommodating and arranging the substrate holder 300 and the metal material container 100. It is equipped with. The chamber 400 needs to be evacuated in order to prevent oxidation of a metal material or the like, and is provided with a vacuum drawing device such as a vacuum pump (not shown).
[0005]
In addition, an open / close shutter 500 is provided above the metal material container 100 and is closed in the initial melting state so that impurities that are likely to be generated at the initial melting time of the metal material do not adhere to the substrate. Opened and evaporated metal is deposited on the substrate. Reference numeral 120 denotes a crucible provided in the metal material container 100, 140 denotes a crystal oscillator sensor for measuring a film thickness, and 700 denotes a controller.
[0006]
With the above-described configuration, the metal material in the crucible 120 is irradiated with the electron beam 110 generated by passing a current through the filament 130 while being controlled by the control unit 700, and the metal material is heated to a temperature higher than the melting point temperature. It can be heated and melted and evaporated to form a deposited film on the substrate.
[0007]
Further, when the film forming operation is continued, it is necessary to replenish the metal material container 100 with a metal material. In this case as well, the chamber 400 is evacuated, and a new metal mass for replenishment is removed from the melting point temperature. It was heated to a high temperature and melted.
[0008]
[Patent Document 1]
JP 2001-332513 A
[Problems to be solved by the invention]
However, in the above-described film forming method and film forming apparatus, since the gas and impurities inside the metal material cannot be sufficiently removed, the following problems remain unsolved.
[0010]
That is, when the metal material evaporates, bumping may occur in which the metal material abnormally boils due to mixing of gas or impurities inside the metal material.
[0011]
When bumping occurs, coarsened evaporated particles are likely to be generated. When this occurs, several μm to several tens of μm of evaporated particles are formed together as metal spheres 600 on the substrate 200 to be formed as shown in FIG. Such metal spheres 600 cause irregularities on the film surface and cause various defects in later processes, such as wiring defects and insulation defects in ICs such as disconnection and short-circuiting, or a breakdown of the breakdown voltage or destruction of capacitors. There was a risk of inviting.
[0012]
From such a current situation, it is desired to provide a film forming apparatus and a film forming method capable of improving the yield by preventing the occurrence of bumping as much as possible. Is expensive and time consuming.
[0013]
An object of this invention is to provide the film-forming method and film-forming apparatus which can solve the said subject.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, the metal material is evaporated by heating, and the evaporated metal is deposited on the substrate to form the metal film . When vapor-depositing a metal, first, the metal material was heated for a predetermined time so as to maintain a temperature higher than the melting point temperature of the metal material, and then lowered to the melting point temperature to melt and evaporate the metal material .
[0017]
According to a second aspect of the present invention, in the film forming method of evaporating a metal material by heating and evaporating the evaporated metal on a substrate to form a metal film, the metal is deposited on the substrate when the metal is deposited. In a vacuum environment in which the vapor pressure temperature is lower than the melting point of the material under normal pressure, the metal material is first heated for a predetermined time at a temperature higher than the melting point temperature of the metal material, and then the metal material is cooled to the melting point temperature. It was decided to melt and evaporate.
[0019]
In this invention of Claim 3 , the metal material accommodating part which heat-melts a metal material, the board | substrate holding part holding the board | substrate for forming a metal film, the board | substrate holding part, and the said metal material accommodating part In a film forming apparatus comprising a chamber disposed and disposed, the metal material in the metal material container is first maintained at a temperature higher than the melting point temperature of the metal material, and then the temperature is lowered to the melting point temperature to melt evaporation. Configured to be possible.
[0021]
In this invention of Claim 4 , the metal material accommodating part which heat-melts a metal material, the board | substrate holding part holding the board | substrate for forming a metal film, the board | substrate holding part, and the said metal material accommodating part are comprised. In a film forming apparatus including a chamber that is housed and evacuated, and in a vacuum environment in which a vapor pressure temperature is lower than a melting point of the metal material under normal pressure, the metal in the metal material housing portion The material was first maintained at a temperature higher than the melting point temperature of the metal material, and then lowered to the melting point temperature so that it could be melted and evaporated.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to bumping that occurs during film formation, and thus coarse particles (metal spheres) that are generated during film formation by evaporating a metal material by heating and evaporating the evaporated metal onto a substrate to form a metal film. ) The metal material is melted in two stages as a film forming condition so that the gas and impurities inside the metal material causing the generation can be sufficiently removed when the metal material is melted.
[0024]
As a film forming apparatus, a metal material container that heats and melts a metal material, a substrate holder that holds a substrate for forming a metal film, and the substrate holder and the metal material container are accommodated. And a chamber.
[0025]
An open / close shutter is provided above the metal material container, and is closed in the initial melting state so that impurities that are likely to be generated at the initial melting stage of the metal material do not adhere to the substrate. Is deposited on the substrate.
[0026]
When a film forming process is performed using such a film forming apparatus, it is necessary to replenish the metal material at any timing after repeating the film forming operation. May cause bumping.
[0027]
Therefore, in the present invention, when the metal material is replenished, the metal material is melted in two stages.
[0028]
That is, when the metal material is replenished, after the metal material is replenished, the metal material is first heated for a predetermined time so as to maintain the melting temperature of the metal material, and then further heated to a high temperature to melt the metal material.
[0029]
By adopting this method, bumping during melting of the metal material can be prevented, and generation of metal spheres consisting of coarse particles due to bumping can also be prevented. Can be prevented.
[0030]
In addition, even during the film forming process performed by depositing metal on the substrate, bumping may occur when the metal material is melted.
[0031]
Therefore, when depositing a metal on the substrate, the metal material is first heated for a predetermined time so as to maintain a temperature higher than the melting point temperature of the metal material, and then cooled to the melting point temperature to melt and evaporate the metal material. I have to.
[0032]
By the way, as a more preferable form of the film forming apparatus, the chamber is configured to be evacuated, and the metal material container is provided with an electron beam gun capable of heating and melting the metal material by irradiating an electron beam. It can be. This is characterized in that a local high temperature can be obtained by focusing the electron beam, a high-purity thin film can be formed, and it can be applied to all materials including refractory metals.
[0033]
When the metal material is melted in two stages using the film forming apparatus described above, temperature management can be performed by focusing on the melting point and vapor pressure temperature of the metal material, and the occurrence of bumping can be prevented as much as possible. Reasonable material melting is possible, and stable film formation processing is possible.
[0034]
That is, when the metal material is replenished, after the metal material is replenished, the melting temperature of the metal material is first maintained in a vacuum environment in which the vapor pressure temperature is lower than the melting point of the metal material under normal pressure. Then, the metal material is melted by heating at a higher temperature.
[0035]
When melting a metal material containing gas or impurities, bumping is likely to occur at a high temperature. On the other hand, as is clear from the known vapor pressure tables of various physical properties, the vapor pressure temperature decreases as the vacuum becomes higher. Therefore, the evaporation of the metal material is started at least at the melting temperature of the metal material.
[0036]
Therefore, by creating a vacuum state that satisfies such conditions, the metal material can be melted and impurities and gases can be removed without unnecessarily high temperatures. Then, after sufficiently removing these impurities and gases that cause bumping, the metal material to be replenished can be sufficiently mixed with the existing metal material without further bumping by heating at a higher temperature. .
[0037]
As described above, based on the melting point of the metal material under normal pressure, first, in the first stage, a high vacuum environment is created as much as possible, and heating is performed to reach the melting point temperature in the vacuum environment, and bumping may occur. The metal material is melted at a low temperature to remove gas and impurities in the material while preventing bumping as much as possible, and then heated to a temperature higher than the previous melting point as the second stage. The metal material to be replenished and the existing metal material are sufficiently mixed. The heating power at this time may be set to a level that raises the temperature by about 1.5 times.
[0038]
By adopting such a method, bumping can be prevented and generation of metal spheres composed of coarse particles due to bumping can be prevented, so that it is possible to prevent metal spheres from being deposited on the substrate when the film forming operation is later performed. .
[0039]
Further, when depositing a metal on the substrate, first, heating is performed for a predetermined time at a temperature higher than the melting point of the metal material in a vacuum environment where the vapor pressure temperature is lower than the melting point of the metal material under normal pressure. Then, the temperature is lowered to the melting point temperature to melt and evaporate the metal material.
[0040]
In other words, the higher the vacuum environment is, the lower the vapor pressure temperature becomes, so that the metal material can be evaporated without raising the temperature and bumping can be prevented.
[0041]
Here, in order to melt the metal material more uniformly, first, heating is performed at a temperature higher than the melting point temperature of the metal material. Such a temperature is higher than the vapor pressure temperature in a high vacuum state, and the metal material can be melted and evaporated to remove impurities and gas from the metal material. However, as it is, when the opening / closing shutter is opened later to form a film on the substrate, film formation control is difficult and bumping may occur in the chamber. Therefore, as a second step, the temperature is once lowered to about the melting point. Then, the metal film is deposited on the substrate by opening the opening / closing shutter at a timing when the evaporation of the metal material is stabilized, and the film forming process proceeds.
[0042]
By the way, the above-described film formation method described separately for the replenishment of the metal material and the metal vapor deposition can also be executed in combination, and as a series of film formation processes, a useful film formation method capable of effectively suppressing bumping It can be
[0043]
That is, when replenishing the metal material, after replenishing the metal material in the metal material container, under a vacuum environment on condition that the vapor pressure temperature is lower than the melting point of the metal material under normal pressure, First, when the metal material is heated up to the melting point temperature, and then the metal material is heated and melted at a temperature higher than the melting point temperature to deposit the metal on the substrate, Heating is performed at a temperature higher than the melting point temperature of the metal material, and then heating is performed at the melting point temperature to melt.
[0044]
As described above, when a metal film is formed, a vacuum environment is created under the condition that the vapor pressure temperature is lower than the melting point of the metal material under normal pressure as the film formation condition. By controlling the temperature in two stages at the time of replenishing the metal material and at the time of film formation, the gas and impurities inside the metal material are sufficiently removed to prevent bumping, and the metal sphere is formed on the substrate. It is possible to perform a stable film formation process with the prevented quality, and to prevent the occurrence of defective products as much as possible to improve the yield.
[0045]
In addition, the degree of vacuum and temperature to be controlled can be easily set from the inherent melting point of the metal material and the vapor pressure table of various physical properties, and if the degree of vacuum is set based on the melting point, the temperature thereafter Since only control is required, the film forming conditions can be easily controlled, and the balance between the power required for evacuation and the power required for heating can be set satisfactorily without complicated calculations, and the energy efficiency is improved.
[0046]
Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings. Here, an electron beam (EB) gun system is adopted as the film forming method and the film forming apparatus.
[0047]
FIG. 1 is a schematic diagram of a film forming apparatus according to the present embodiment, FIG. 2 is a flowchart when a metal material is replenished in a film forming method using the film forming apparatus, FIG. 3 is a vapor pressure table of various physical properties, and FIG. FIG. 5 is a chart showing the film forming conditions when the metal material is replenished, FIG. 5 is a flowchart showing the film forming process, and FIG. 6 is a chart showing the film forming conditions during the film forming process.
[0048]
As shown in FIG. 1, a film forming apparatus A according to the present embodiment forms a metal film and a metal material container 3 that irradiates an electron beam 1 to heat and melt the metal material 2 for film formation. A substrate holding unit 5 for holding the substrate 4 for storing the substrate 4 and a chamber 6 capable of evacuating the substrate holding unit 5 and the metal material storage unit 3 are provided.
[0049]
The chamber 6 has a cylindrical shape and is connected to a vacuum pump (not shown). In addition, a crystal resonator sensor 61 is disposed at an upper position inside, and the metal material accommodating portion 3 is provided at a lower position in the center thereof. An open / close shutter 7 is disposed above the metal material housing 3.
[0050]
In addition, the metal material container 3 is provided with a crucible 30 for housing a metal material 2 required for film formation, such as gold, silver, and aluminum.
[0051]
The EB gun arranged for heating and evaporating the metal material 2 accommodated in a lump in the crucible 30 may have a known configuration, and is generated by passing an electric current through the filament 9 via the control unit 8. The thermoelectrons are collected by a beam former, and the thermoelectrons are extracted and accelerated by an anode plate and deflected in a loop shape using an electromagnet so that the metal material 2 in the crucible 30 can be irradiated.
[0052]
The substrate holding part 5 is provided on the upper part of the metal material accommodating part 3 at a position directly below the crystal oscillator sensor 61, and three substrate holding bodies 50 formed in a dome shape with a predetermined inclination at a predetermined angle. Each is arranged so as to be able to rotate and revolve at intervals. In addition, each substrate holder 50 is disposed such that the front surfaces thereof are at equal distances from the center line L passing through the center of the open / close shutter 7. Reference numeral 51 denotes a rotation axis of the substrate holder 5, and 52 denotes a rotation axis of each substrate holder 50. A plurality of substrate mounting holes 53 are arranged in the substrate holder 50 at predetermined intervals. The substrate 4 is inserted from the back side of the substrate holder 50 and can be mounted via the substrate pressing member 54. .
[0053]
When a metal film is formed on the substrate 4 using the film forming apparatus A having the above-described configuration, in the present embodiment, when the metal material 2 is replenished, first, the metal material 2 is first used in a vacuum environment at a predetermined atmospheric pressure. When the metal material 2 is heated and melted at a temperature higher than the melting point temperature while being heated to a melting point temperature under pressure, the metal 4 is deposited on the substrate 4 in a vacuum environment of the same predetermined pressure as described above. First, the metal material 2 is heated at a temperature higher than the melting point temperature, and then heated at the melting point temperature to be melted.
[0054]
That is, as shown in FIG. 2, when the metal material 2 is replenished, first, a lump of the metal material 2 is accommodated in the crucible 30 (step 1).
[0055]
Next, the inside of the chamber 6 is evacuated (step 2). The vacuum value at this time can be obtained from the known physical property value vapor pressure table shown in FIG. 3 and is set so that the vapor pressure temperature is lower than the melting point of the metal material 2 under normal pressure. For example, if the metal material 2 is Ag, the melting point under normal pressure is 1233, 8 (K), and in order to make the vapor pressure temperature lower than this melting point, it can be seen from the physical vapor pressure table. It can be seen that it may be evacuated to 10 ⁻¹ Pa or less.
[0056]
Then, the process proceeds to Step 3 where the material is melted in the first stage, and is heated to the melting point temperature of the metal material 2.
[0057]
That is, as described above, a high vacuum environment in which the vapor pressure temperature is lower than the melting point is created, and the metal material 2 is melted and evaporated at a lower temperature than before to prevent the occurrence of bumping as much as possible. The gas, impurities, etc. in the metal material 2 are effectively removed.
[0058]
Next, the process proceeds to Step 4 where the material is dissolved in the second stage, and the metal material 2 is further heated at a temperature higher than the melting point temperature. Generally, a power of 1.5 times (necessary amount of heat) may be used as a guide.
[0059]
Since the gas and impurities in the metal material 2 have already been removed and bumping is unlikely to occur even when heated in that state, naturally melting of the metal material 2 is prevented from occurring and melting is accelerated. Then, the replenished metal material 2 is uniformly melted with the existing metal material 2.
[0060]
Next, an inert gas N ₂ is introduced into the chamber 6 to remove impurities and the like in the chamber 6 while returning the inside of the chamber 6 to normal pressure (step 5), and the metal material replenishment process is completed.
[0061]
The film formation conditions when the metal material is replenished according to the above flow are as shown in FIG. 4, and the power output necessary for the first stage material dissolution (step 3) and the second stage material dissolution (step 4). Is preferably set as a program in the film forming apparatus A in advance so that the above can be executed.
[0062]
In addition, it has been experimentally found that the heating time (a to d) shown in FIG. 4 is more advantageous for suppressing bumping, but may be appropriately set in consideration of the efficiency of the film forming process.
[0063]
After the required number of substrates 4 are set on the substrate holder 50 of the substrate holder 5 described above, the film forming process is actually executed. In this case as well, a vacuum environment set to a predetermined atmospheric pressure as described above is created, Here, the metal material 2 is first heated at a temperature higher than the melting point temperature under normal pressure and then lowered to the melting point temperature to melt and evaporate the metal material 2.
[0064]
That is, as shown in FIG. 5, the chamber 6 is depressurized and evacuated while rotating and revolving the substrate holder 50 on which the substrate 4 is mounted (step 1). The vacuum value at this time can also be obtained from the known physical property value vapor pressure table shown in FIG. 3 and is set so that the vapor pressure temperature is lower than the melting point of the metal material 2 under normal pressure. .
[0065]
When the inside of the chamber 6 reaches a set vacuum value, the process proceeds to Step 2 where the material is melted in the first stage, and the metal material container 3 irradiates the metal material 2 with the electron beam 1 from the filament 9, and the metal material 2. It heats so that it may become higher than the said melting | fusing point temperature.
[0066]
In this temperature setting, in order to melt the metal material more uniformly, the metal material is first heated at a temperature higher than the melting point temperature of the metal material. In a high vacuum state as in this embodiment, the temperature is much higher than the vapor pressure temperature. The metal material can be melted and evaporated to remove impurities and gas from the metal material. However, as it is, when the opening / closing shutter 7 is later opened to form a film on the substrate 4, film formation control becomes difficult and bumping may occur in the chamber 6. The process proceeds to step 3 and, as the second stage, the metal material is evaporated in a state where the temperature is once lowered to about the melting point.
[0067]
Then, the opening / closing shutter 7 is opened at an appropriate timing after elapse of a predetermined time so that the impurities which are likely to be generated at the initial stage of melting of the metal material do not adhere to the substrate 4 after the predetermined time has elapsed and the evaporation is stabilized. While being monitored by the sensor 61, vapor deposition is performed on the substrate 4 up to a required metal film thickness (see FIG. 6), and a film forming process is executed (step 4). As a result, a metal film having a desired thickness is formed on a predetermined metal deposition region on all the substrates 4 held by the three rotating substrate holders 50. At this time, the occurrence of bumping is prevented as much as possible, and the generation of metal spheres due to bumping is also prevented, so that the film formation state is extremely good.
[0068]
Next, an inert gas N ₂ is introduced into the chamber 6 to remove impurities and the like in the chamber 6 while returning the inside of the chamber 6 to normal pressure (step 5), and the film forming process is terminated.
[0069]
The film formation conditions at the time of replenishing the metal material are as shown in FIG. 6, and again, the film formation apparatus A is necessary for the first stage material dissolution (step 2) and the second stage material dissolution (step 3). It is set in advance so that as much power output as possible can be executed.
[0070]
Also in this case, it has been experimentally found that the longer the heating time (a to d) shown in FIG. 6, the more advantageous for suppressing bumping. Can be set.
[0071]
In the film forming apparatus A in the embodiment described above, the power (necessary heat amount) for setting the melting point temperature under high vacuum can be calculated using a measuring instrument such as a radiation thermometer.
[0072]
Further, the film forming method has been described as being based on the electron beam gun method, but can also be applied to a method based on the heating vapor deposition method.
[0073]
Further, by using a thermometer such as the above-mentioned radiation thermometer as a monitor and adopting a configuration capable of automatic control so that this temperature is fed back to power control, an appropriate power condition can be obtained even if the metal material is changed. As a result, the completeness of the film forming apparatus A that can prevent bumping also increases.
[0074]
【The invention's effect】
According to the present invention, since gas and impurities inside the metal material can be sufficiently removed, bumping can be prevented, and generation of metal spheres composed of coarse particles due to bumping can also be prevented. The metal spheres can be prevented from being formed on the substrate, and the product yield can be improved.
[0075]
In addition, when film formation is performed in a vacuum environment where the vapor pressure temperature is lower than the melting point of the metal material under normal pressure, the degree of vacuum and temperature to be controlled are the melting point of the metal material under normal pressure and various physical property values. It can be easily set from the vapor pressure table, and if the degree of vacuum is set based on the melting point as a temperature reference, it is only necessary to control the temperature thereafter, so that the film formation conditions can be easily controlled, and the power and heating required for evacuation. Balance with the power required to improve energy efficiency.
[Brief description of the drawings]
FIG. 1 is a schematic view of a film forming apparatus according to an embodiment.
FIG. 2 is a flowchart when a metal material is replenished in a film forming method using the film forming apparatus.
FIG. 3 is a table showing various physical property values of vapor pressure.
FIG. 4 is a chart showing film forming conditions when a metal material is replenished.
FIG. 5 is a flowchart during film formation processing;
FIG. 6 is a chart showing film forming conditions during the film forming process.
FIG. 7 is a schematic view of a conventional film forming apparatus.
FIG. 8 is an explanatory diagram showing a state in which metal spheres are formed on a substrate.
[Explanation of symbols]
A film forming apparatus 1 EB gun 2 metal material 3 metal material container 4 substrate 5 substrate holder 6 chamber 7 opening / closing shutter

Claims (4)

In a film forming method of evaporating a metal material by heating and evaporating the evaporated metal on a substrate to form a metal film,
When depositing a metal on the substrate, the metal material is first heated for a predetermined time so as to maintain a temperature higher than the melting point temperature of the metal material, and then cooled to the melting point temperature to melt and evaporate the metal material. Film forming method. In a film forming method of evaporating a metal material by heating and evaporating the evaporated metal on a substrate to form a metal film,
When depositing a metal on the substrate, first, in a vacuum environment where the vapor pressure temperature is lower than the melting point of the metal material under normal pressure, first heated at a temperature higher than the melting point temperature of the metal material for a predetermined time, A film forming method in which the metal material is melted and evaporated by lowering to the melting point temperature. A metal material container that heats and melts the metal material; a substrate holder that holds a substrate for forming a metal film; and a chamber that houses and arranges the substrate holder and the metal material container. In the film forming apparatus,
The film forming apparatus, wherein the metal material in the metal material container is first maintained at a temperature higher than a melting point temperature of the metal material, and then lowered to the melting point temperature to be melted and evaporated. A metal material container that heats and melts a metal material, a substrate holder that holds a substrate for forming a metal film, and the substrate holder and the metal material container are accommodated and evacuated. In the film forming apparatus comprising the chamber,
Under a vacuum environment in which the vapor pressure temperature is lower than the melting point of the metal material under normal pressure, the metal material in the metal material container is first maintained at a temperature higher than the melting temperature of the metal material, A film-forming apparatus configured to be capable of melting and evaporating by dropping to a melting point temperature.

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