JPH05144734A - Vapor phase growth apparatus - Google Patents

Abstract

PURPOSE:To provide a vapor phase growth apparatus wherein a reaction product which is grown inside a reactor is cleaned easily and, in addition, a high- quality thin film can be formed by vapor phase grown. CONSTITUTION:A cylindrical shielding plate 20 is arranged and installed so as to be close to the inner wall surface of an upper-part reactor 6. A reaction product 9 which is grown inside a reactor 1 in a vapor phase growth operation is deposited on the shielding plate 20. The vapor phase growth operation is performed the definite number of times. After that, the shielding plate 20 is detached; the reaction product 9 is cleaned. Since the surface area of the shielding plate 20 is smaller than that of the upper-part reactor 6, an influence on a degassed growth film after a cleaning operation is small and a high-quality thin film can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth apparatus used for manufacturing, for example, a compound semiconductor having a hetero structure.

[0002]

2. Description of the Related Art A conventional vapor phase growth apparatus for producing a semiconductor or the like by vapor-depositing a thin film of a semiconductor or the like on a substrate is constructed, for example, as shown in FIG.

As shown in this figure, a conventional vapor phase growth apparatus comprises a substrate holder 3 for mounting a substrate 2 in a reaction furnace 1,
A rotation shaft 4 to which the substrate holder 3 is detachably supported and a rotation driving device (not shown) is connected, and a heater 5 for heating the substrate 2 and the substrate holder 3 are provided.

The reaction tube 1 comprises an upper reaction furnace 6 and a lower reaction furnace 7.
The upper flange 6a and the lower flange 7a of the upper reaction furnace 6 and the lower reaction furnace 7 are detachably adhered to each other via an O-ring 8. The inner wall surfaces of the upper flange 6a and the lower flange 7a are in contact with each other without steps.

A gas supply device (not shown) for supplying gas (raw material gas, carrier gas, etc.) into the reaction furnace 1 through a supply unit 6b is connected to the upper part of the upper reaction furnace 6, and the lower reaction furnace 7 is connected. An exhaust device (not shown) for adjusting the pressure in the reaction furnace 1 and exhausting unreacted gas is connected to the lower part of the exhaust gas via the exhaust port 7b.

The conventional vapor phase growth apparatus is constructed as described above, and the substrate 2 and the substrate holder 3 are heated to a predetermined temperature by heating by the heater 5, and are also driven by a rotary driving device (not shown) to rotate them at a predetermined temperature. And a source gas (for example, Si H ₂ Cl ₂ ) is supplied together with a carrier gas (for example, H ₂ ) into the reaction furnace 1 from a gas supply device (not shown) through the supply port 6a, and the gas is supplied onto the substrate 2. A compound semiconductor thin film is vapor-deposited.

By the way, during the above-described vapor phase growth, the inner wall surfaces of the upper reaction furnace 6 and the lower reaction furnace 7 are also heated to a high temperature, so that the reaction products are also formed on the inner wall surfaces of the upper reaction furnace 6 and the lower reaction furnace 7. 9 is deposited and becomes thicker as the number of times of growth increases. Then, when a part of the deposited reaction product 9 is separated and becomes dust and falls onto the substrate 2 during vapor phase growth, the film thickness becomes non-uniform or the composition of the grown film changes.

For this reason, after the upper reaction furnace 6 of the reaction furnace 1 has been vapor-deposited a certain number of times, the inner wall surface of the upper reaction furnace 6 which has been separated from the lower reaction furnace 7 and removed is washed to deposit the reaction product. After removing 9, it is necessary to connect the lower reaction furnace 7 again to degas the adsorbed gas.

When vapor phase growth is performed by increasing the temperature without degassing, oxygen other than the source gas, such as oxygen in the air, is taken into the reaction furnace 1 during the vapor phase growth, so that the composition of the grown film is increased. Will change. If the upper reaction furnace 6 is, for example, glass, there is a risk of damage during transportation and cleaning of the reaction product 9, and if the upper reaction furnace 6 is made of metal, it is heavy and difficult to handle. The reaction product 9 deposited on the inner wall surface of the furnace 6 may be diffused into the atmosphere, which is a safety problem.

Further, as shown in FIG. 9, the upper reaction furnace 6 and the lower reaction furnace 7 are separated before the start of the vapor phase growth and after the completion of the vapor phase growth, and the upper reaction furnace 6 is raised to carry in the substrate 2. Carry out. At this time, the reaction product 9 deposited in the vicinity of the lower flange 6a of the upper reaction furnace 6 peels off to become dust 9a,
It falls in the lower reaction furnace 7 and on the O-ring 8 arranged on the lower flange 7a.

Thus, the upper reaction furnace 6 and the lower reaction furnace 7
If the dust 9a falls on the O-ring 8 when the substrate 2 is carried in and carried out by separating the wafers, it causes a leak. And
When the upper flange 6a and the lower flange 7a of the upper reaction furnace 6 and the lower reaction furnace 7 are brought into close contact with each other through the O-ring 8, if there is a leak between the upper flange 6a and the lower flange 7a, the thin film during vapor phase growth may be formed. Incorporation of oxygen or the like in the air other than the source gas causes a problem such as an increase in the resistance of the growth film.

Further, when H ₂ is used as the carrier gas, there is a risk of explosion if there is a leak.

Further, in the conventional vapor phase growth apparatus, as shown in FIG. 10, for example, a counterbore portion 12a is formed in the substrate support 12 provided in the substrate holder 3, and the peripheral portion of the substrate 2 is formed in the counterbore portion 12a. There are some that are placed. The substrate support 12 is made of, for example, a material such as silicon, glass, or ceramics, and the hole 1 is formed inside the counterbore 12a.
3 is formed. Other configurations are the same as those of the conventional vapor phase growth apparatus shown in FIG.

The substrate support 12 is made of silicon, glass, ceramics or the like because it has a relatively low thermal conductivity. In other words, when a metal or the like having good thermal conductivity is used, the temperature of the peripheral portion of the substrate that comes into contact with the substrate support made of metal becomes extremely high,
This results in non-uniform temperature distribution in the substrate plane.

For the above reasons, since the substrate support 12 is made of silicon, glass, ceramics or the like, the counterbore 12a is generally processed by ultrasonic processing suitable for processing those materials. When ultrasonically machining the countersunk portion 12a, an abrasive material is put between the ultrasonic processing tool and the processing portion (the countersunk portion 12a) to be processed by ultrasonic vibration. Therefore, the abrasive material is first attached to the tip of the ultrasonic processing tool. Goes in.
For this reason, since the tip of the ultrasonic machining tool is inevitably rounded, the corner 12b of the counterbore 12a of the substrate support tool 12 that is machined by such an ultrasonic machining tool is also rounded. (See FIG. 11).

Then, the corner portion 12b of the countersunk portion 12a.
As shown in FIG. 11, one edge side (left side in the figure) of the substrate 2 which is rotating at a high speed is moved to the upper part of the counterbore portion 12a by placing the peripheral edge portion of the substrate 2 on the substrate. As a result, the in-plane temperature distribution of the substrate 2 changes (see FIG. 12). That is, since the left end of the substrate 2 is farther from the heater 5 than the right end, the substrate 2
The temperature at the left end is lower than that at the right end. As described above, when the in-plane temperature distribution of the substrate 2 changes, the oscillation wavelength of a semiconductor laser such as InGaA1P obtained by vapor phase growth does not become constant, and a desired oscillation wavelength cannot be obtained. there were.

[0017]

As described above, the conventional vapor phase growth apparatus has a problem that cleaning the reaction products deposited on the inner wall surface of the upper reaction furnace 6 is difficult.

Further, the dust 9a of the reaction product 9 deposited in the vicinity of the upper flange 6a is attached to the O-ring 8 which connects the upper flange 6a and the lower flange 7a in an airtight state when the upper reactor 6 and the lower reactor 7 are attached and detached. If adhered, there was a risk that a leak would occur.

Further, since the corner 12b of the counterbore 12a of the substrate support 12 on which the substrate 2 is placed is rounded during processing, when the substrate 2 and the substrate holder 3 rotate during vapor phase growth, the substrate is rotated by centrifugal force. There is a problem that the peripheral edge of No. 2 moves and tilts along the corner 12b, and the in-plane temperature distribution of the substrate 2 becomes non-uniform.

The present invention has been made for the purpose of solving the above-mentioned problems, and facilitates cleaning and removal of reaction products deposited in the reaction furnace, and a sealing means for connecting the divided surfaces of the reaction furnace in an airtight state. An object of the present invention is to provide a vapor phase growth apparatus capable of preventing the dust of the reaction product from falling down and keeping the in-plane temperature distribution of the substrate constant to obtain a high quality thin film.

[0021]

In order to solve the above-mentioned problems, in the invention described in claim 1, the substrate mounted on the substrate holder arranged in the reaction furnace is heated by the heating means, and In a vapor phase growth apparatus for supplying a raw material gas into the reaction furnace to perform vapor phase growth of a thin film on the substrate, a shield plate for depositing a reaction product growing in the reaction furnace during the vapor phase growth is provided in the reaction furnace. It is characterized in that it is arranged close to the inner wall surface.

According to the second aspect of the invention, the reactor is divisible into the first reactor constituent and the second reactor constituent, and the dividing surface is hermetically connected via the sealing means. A vapor phase for heating a substrate placed on a substrate holder arranged in the reaction furnace by a heating means, and supplying a source gas into the reaction furnace to vapor-deposit a thin film on the substrate. In the growth apparatus, at an end portion of the first reactor structure located upstream of the raw material gas in the flow direction in contact with the second reactor structure, and at an inner wall surface of the second reactor structure. It is characterized in that a shielding portion to be inserted along is formed.

According to the third aspect of the present invention, the substrate placed on the substrate supporting member arranged in the reaction furnace is heated by the heating means, and the source gas is supplied into the reaction furnace. In a vapor phase growth apparatus for vapor-depositing a thin film on the substrate, a counterbore portion for supporting a peripheral portion of the substrate is formed on the substrate supporting member, and a groove is formed at a corner portion of the counterbore portion where the peripheral portion of the substrate bottom surface contacts. Is formed.

[0024]

According to the first aspect of the present invention, the reaction product that grows during the vapor phase growth is deposited on the shield plate disposed in the vicinity of the inner wall surface of the reaction furnace. Cleaning can be performed easily and safely simply by removing the accumulated shielding plate.

Further, since the shielding plate is arranged in the reaction furnace, its surface area is smaller than that of the inner wall surface of the reaction furnace, so that the adsorbed amount of degas after cleaning becomes small, so that gas is released during vapor phase growth. A small amount and a high quality thin film can be obtained.

According to the second aspect of the invention, the vapor phase growth is performed by inserting the shield portion formed in the first reactor structure along the inner wall surface of the second reactor structure. At times, reaction products that grow near the dividing surface are deposited on the shielding portion, so that the first and second reaction furnace constituents are divided and the sealing means is provided to seal the dividing surface when the substrate is loaded or unloaded. Since the reaction products deposited near the dividing surface do not drop, leakage during vapor phase growth is prevented and a high quality thin film can be obtained.

According to the third aspect of the present invention, the groove is formed at the corner of the countersunk portion of the substrate support member where the lower portion of the peripheral edge of the substrate contacts, so that the peripheral edge of the bottom surface of the substrate closely contacts the countersink. Therefore, even if the substrate and the substrate supporting member are rotated at high speed during vapor phase growth, the peripheral edge of the substrate is reliably supported without being displaced or tilted, so that the temperature distribution in the substrate surface becomes uniform and a high quality thin film is obtained. be able to.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the illustrated embodiments. It should be noted that the same members as those of the related art will be described with the same reference numerals.

<First Embodiment> FIG. 1 is a schematic sectional view showing a vapor phase growth apparatus according to the first embodiment. As shown in this figure, the reaction furnace 1 is divided into an upper reaction furnace 6 and a lower reaction furnace 7. The upper flange 6a of the upper reaction furnace 6 and the lower flange 7a of the lower reaction furnace 7 have an O-ring 8 therebetween. It is attached in a detachable manner.

In the reaction furnace 1, a substrate holder 3 on which the substrate 2 is placed, a rotary shaft 4 to which the substrate holder 3 is detachably supported and a rotation driving device (not shown) is connected, the substrate 2 and A heater 5 for heating the substrate holder 3 is provided.

A gas supply device (not shown) for supplying gas (raw material gas, carrier gas, etc.) into the reaction furnace 1 through a supply port 6b is connected to the upper part of the upper reaction furnace 6, and the lower reaction furnace 7 is connected. An exhaust device (not shown) for adjusting the pressure in the reaction furnace 1 and exhausting unreacted gas is connected to the lower part of the exhaust gas via the exhaust port 7b.

Further, in the reaction furnace 6, a shielding plate 20 made of cylindrical quartz glass is arranged so as to be close to the inner wall surface (for example, at a distance of 0.01 to 0.3 mm). , Is supported on a support plate 21 fixed to the upper flange 6a by screwing or the like.

The vapor phase growth apparatus according to this embodiment is configured as described above, and the substrate 2 and the substrate holder 3 are heated to a predetermined temperature by heating the heater 5, and the rotation drive device (not shown) is rotated. The raw material gas (for example, Si H ₂ Cl ₂ ) is driven into the reactor 1 through a supply port 6b from a gas supply device (not shown).
Are supplied together with a carrier gas (for example, H ₂ ) to vapor-deposit a thin film of a compound semiconductor on the substrate 2.

At this time, since the shielding plate 20 disposed close to the inner wall surface of the upper reaction furnace 6 is also heated to a high temperature, the shielding plate 20 also grows in crystal and the reaction product is produced. 9 is deposited.

After the vapor phase growth as described above is performed a predetermined number of times, the upper flange 6a of the upper reaction furnace 6 and the lower flange 7a of the lower reaction furnace 7 are separated to raise the upper reaction furnace 6 and shield it. Remove the plate 10. The shielding plate 20 on which the reaction product 9 is deposited is washed in a container (not shown) containing a washing liquid, and then placed in the reaction furnace 6 again.

As described above, in this embodiment, the upper reaction furnace 6
The reaction product 9 may be deposited on the shield plate 20 disposed in the vicinity of the upper flange 6a of the above, and the shield plate 20 in the upper reaction furnace 6 may be periodically taken out and cleaned. Can be easily and safely cleaned, and since the shield plate 20 has a smaller surface area than the inner wall surface of the upper reaction furnace 6, the amount of degassed adsorbed after cleaning is small, so that vapor phase growth is possible. The amount of gas released at that time is reduced, and a high quality thin film can be obtained.

The shield plate 20 is arranged on the inner wall surface of the upper reaction furnace 6 with a gap of approximately 0.01 to 0.3 mm or less, but this gap is narrow (the inner wall surface of the upper reaction furnace 6). The surface roughness of 0.01 mm is the minimum), the less the amount of the reaction product 9 deposited on the inner wall surface of the upper reaction furnace 6, the more the effect of the previous source gas is changed even when the type of the source gas is changed. Can be made smaller.

Further, in the above-mentioned embodiment, the shielding plate 20 is made of quartz glass which emits little gas, but it is not limited to this and may be made of metal, ceramics or the like which emits little gas.

<Second Embodiment> FIG. 2 is a schematic sectional view showing a vapor phase growth apparatus according to the second embodiment. As shown in this figure, in this embodiment, the upper reactor (first reactor structure) is used.
The upper flange 6a of 6 has a cylindrical shielding portion 6c protruding downward. Other configurations are the same as those of the conventional vapor phase growth apparatus shown in FIG.

The shielding portion 6c is formed so as to be almost in contact with the inner wall surface of the lower flange 7a of the lower reaction furnace (second reactor constituent body) 7, and the lower flange 7 of the shielding portion 6c is formed.
A taper portion 6d is formed on the tip side in contact with the a side so that the insertion into the lower reaction furnace 7 can be smoothly performed, and the shield portion 6d is formed.
The tip side of c is made into an acute angle.

The vapor phase growth apparatus according to the present embodiment is constructed as described above, and vapor phase growth on the substrate 2 is carried out in the same manner as in the first embodiment, so it is omitted here.

During vapor phase growth on the substrate 2, the inner wall surfaces of the upper reaction furnace 6 and the lower reaction furnace 7 are also heated to a high temperature, so that crystal growth also occurs on the inner wall surface of the upper reaction furnace 6 and the reaction product 9 is deposited. To do. The reaction product 9 becomes thicker as the number of times of growth on the substrate 2 increases.

Then, with the reaction product 9 deposited on the inner wall surface of the upper reaction furnace 6, as shown in FIG. 3, the upper flange 6a of the upper reaction furnace 6 and the lower flange 7 of the lower reaction furnace 7 are connected.
a is separated, the upper reaction furnace 6 is raised, and the substrate 2 is loaded.
Carry out.

At this time, the upper flange 6a of the upper reaction furnace 6
Since the vicinity of the connecting portion of the lower flange 7a of the lower reaction furnace 7 is covered with the shielding portion 6b formed on the upper flange 6a, the reaction product 9 in this vicinity is deposited on the shielding portion 6b.
Further, since the lower flange 7a side of the tip of the shielding portion 6b is formed in an acute angle shape, the reaction product 9 is less likely to deposit on this portion.

Therefore, when the upper reaction furnace 6 is separated upward, the dust of the reaction product 9 deposited on the inner wall surface of the upper reaction furnace 6 and the shielding portion 6b hardly falls.

Therefore, when the upper flange 6a of the upper reaction furnace 6 and the lower flange 7a of the lower reaction furnace 7 are airtightly connected to each other through the O-ring 8 and vapor phase growth is performed, no oxygen leaks from the oxygen in the air. It is possible to obtain a high quality thin film without taking in the above.

Further, even when H ₂ is used as the carrier gas, the leak is eliminated, so that air (oxygen) is generated during vapor phase growth.
Are not captured and there is no danger of explosion.

The length of the shielding portion 6b is not particularly limited, but it is preferable that the length is as long as possible so long as it does not hinder the loading and unloading of the substrate 2.

FIG. 4 shows a shield portion 6 according to a modification of this embodiment.
2B is a cross-sectional view of the lower flange 7a, and in this embodiment, the same taper portion 7c is formed on the inner wall surface of the lower flange 7a of the lower reactor 7 in accordance with the inclination of the taper portion 6d of the shielding portion 6c.
Is provided. In this embodiment, the shielding portion 6c of the upper flange 6 can be inserted into the lower reaction furnace 7 more smoothly.

<Third Embodiment> FIG. 5 is a schematic sectional view showing a vapor phase growth apparatus according to the third embodiment, and FIG. 6 is an enlarged sectional view showing a main part thereof. In this embodiment, as shown in both figures,
Counterbore 12 of substrate support 12 provided in substrate holder 3
The groove 22 is formed along the corner 12b of the a, and the counterbore 12
The bottom surface of the peripheral edge of the substrate 2 is supported by a, and the substrate holder 3 and the substrate support 12 form a substrate support member 23. Other configurations are similar to those of the conventional vapor phase growth apparatus shown in FIG.

Corner 1 of counterbore 12a of substrate support 12
The groove 22 formed in 2b has, for example, a depth of 0.2 mm and a width of 1 mm, the bottom surface of the peripheral edge of the substrate 2 is placed on the groove 22, and the outer peripheral surface of the substrate 2 has a counterbore portion 12a. It is almost in contact with the inner wall surface.

The vapor phase growth apparatus according to the present embodiment is constructed as described above, and vapor phase growth on the substrate 2 is carried out in the same manner as in the first embodiment, so it is omitted here.

Even if the substrate 2 rotates at high speed during vapor phase growth, the corners 12b are not rounded due to the grooves 22 formed in the corners 12b of the counterbore 12a. Since the surface is in contact with the spot facing portion 12a with almost no gap, the substrate 2 is not tilted or displaced. Therefore, as shown in FIG. 7, since the in-plane temperature distribution of the substrate 2 becomes uniform and a good thin film can be obtained, the oscillation wavelength of a semiconductor laser such as InGaA1P obtained by vapor phase growth becomes uniform. Sexuality improves.

In this embodiment, the substrate holder 3 and the substrate supporting member 12 which are separately formed form the substrate supporting member 23, but the substrate holder 3 and the substrate supporting member 12 may be integrally formed. ..

[0055]

As described above in detail with reference to the embodiments, according to the first aspect of the present invention, the reaction is effected by the shield plate arranged in the vicinity of the inner wall surface of the reaction furnace. Cleaning and removal of reaction products growing in the furnace can be performed easily and safely, and since the shielding plate has a smaller surface area than the inner wall surface of the reaction furnace, less degassing occurs after cleaning. Therefore, a high quality thin film can be obtained.

Further, according to the invention described in claim 2, in the second reactor structure, the divided surfaces of the first reactor structure and the second reactor structure to be divided are covered. By forming the shield part to be inserted in the first reactor structure,
Since reaction products near the dividing surface are deposited on the shielding part, the first
The reaction product does not drop and adhere to the sealing means that seals the divided surfaces when the reaction furnace constituent body and the second reaction furnace constituent body are divided.

Therefore, since gas does not leak during vapor phase growth, gas other than the source gas is prevented from being taken in, and a high quality thin film can be obtained.

According to the third aspect of the present invention, since the groove is formed at the corner portion of the countersunk portion of the substrate supporting member which is in contact with the bottom surface of the peripheral edge portion of the substrate, the bottom surface of the peripheral edge portion of the substrate is at the corner of the counterbore portion. Since the substrate is stably supported without being tilted or displaced, the in-plane temperature distribution of the substrate becomes uniform and a high quality thin film can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a vapor phase growth apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a vapor phase growth apparatus according to a second embodiment of the present invention.

3 is a schematic cross-sectional view showing a state in which the reaction furnace of the vapor phase growth apparatus shown in FIG. 2 is divided.

FIG. 4 is a sectional view showing an essential part of a modified example of the vapor phase growth apparatus according to the second embodiment.

FIG. 5 is a schematic sectional view showing a vapor phase growth apparatus according to a third embodiment of the present invention.

6 is a cross-sectional view showing a main part of the vapor phase growth apparatus shown in FIG.

FIG. 7 is a diagram showing a temperature distribution in a substrate surface by a vapor phase growth apparatus according to a third embodiment of the present invention.

FIG. 8 is a schematic sectional view showing a conventional vapor phase growth apparatus.

9 is a schematic cross-sectional view showing a state in which the reaction furnace of the vapor phase growth apparatus shown in FIG. 8 is divided.

FIG. 10 is a schematic cross-sectional view showing a conventional vapor phase growth apparatus.

11 is an enlarged cross-sectional view showing a main part of the vapor phase growth apparatus shown in FIG.

12 is a diagram showing a temperature distribution in a substrate surface by the conventional vapor phase growth apparatus shown in FIG.

[Explanation of symbols]

 1 Reactor 2 Substrate 3 Substrate Holder 5 Heater 6 Upper Reactor (First Reactor Constituent) 6a Upper Flange 6c Shielding Plate 6d Tapered Part 7 Lower Reactor (Second Reactor Constituent) 7b Lower Flange 8 O Ring (seal means) 9 Reaction product 12 Substrate support 12a Counterbore 12b Corner 20 Shielding plate 22 Groove 23 Substrate support member

Claims (3)

[Claims] 1. A gas for heating a substrate placed on a substrate holder arranged in a reaction furnace by a heating means and supplying a source gas into the reaction furnace to vapor-deposit a thin film on the substrate. In the phase growth apparatus, a shield plate for depositing a reaction product that grows in the reaction furnace at the time of vapor phase growth is arranged close to the inner wall surface of the reaction furnace. 2. A reaction furnace, which is divisible into a first reactor structure and a second reactor structure, and whose dividing surface is hermetically connected via a sealing means, is provided in the reactor. In a vapor phase growth apparatus for heating a substrate placed on an established substrate holder by a heating means and supplying a source gas into the reaction furnace to vapor-deposit a thin film on the substrate, the flow of the source gas A shield part to be inserted along the inner wall surface of the second reactor structure at the end of the first reactor structure located upstream in the direction in contact with the second reactor structure. A vapor phase growth apparatus characterized in that 3. A substrate placed on a substrate supporting member arranged in a reaction furnace is heated by a heating means, and a source gas is supplied into the reaction furnace to vapor-deposit a thin film on the substrate. In the vapor phase growth apparatus, the substrate supporting member is provided with a countersunk portion for supporting the peripheral portion of the substrate, and a groove is formed at a corner portion of the countersunk portion which is in contact with the peripheral portion of the substrate bottom surface. Phase growth equipment.