JP3161007B2 - Method for manufacturing mirror wafer with InP single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The invention according to this application is based on InP
The present invention relates to a single crystal mirror-finished wafer and a method for manufacturing the same, particularly, a surface film such as an oxide film or an organic contaminant film formed on the wafer surface after polishing and removing a processing damage layer on the wafer surface with an abrasive or a chemical polishing liquid. The present invention relates to a mirror-finished InP single crystal wafer having only an etched-off portion and a method of manufacturing the same.

[0002]

2. Description of the Related Art An InP single crystal is cut into an ingot to form a wafer, and then polished with a polishing agent or a chemical polishing liquid to remove a processing damage layer during the cutting, thereby obtaining a mirror-finished wafer. Various polishing agents and chemical polishing liquids used for polishing the processing damage layer are known.
al of Material Science 10
(1975) p. 321-p. 329, such as "bromomethanol" in which bromine is dissolved in methanol. In this way, the surface of the mirror-finished mirror-finished wafer has a layer different from a bulk or the like in which components such as an abrasive remain or are oxidized after polishing or organic substances are attached. (The layer present on the mirror wafer after such mirror processing is referred to as “surface film” in this specification).

If a mirror surface wafer having such a surface film is used as it is in a process such as MOCVD or ion implantation for device fabrication, poor growth or poor characteristics will occur.

For this reason, conventionally, after removing the surface film by etching, it has been used in a process such as MOCVD.

[0005] The removal of this surface film is conventionally performed by using an InP surface film.
Was performed by etching. That's it
Such conventional techniques include, for example, Appl. P
hys. 55 (4), 15 February 198
4 p. 1139-p. At 1148, etch
H as a liquid_TwoO_Two, HF or H_TwoSO_Four: H _Two
O_Two: H_TwoAn etching solution having a composition of O = 3: 1: 1, B
r_Two: CH_ThreeEtching solution having a composition of OH = 1: 100
Is disclosed. In addition, for example, J.I. Va
c. Sci. Technol. B4 (2), Mar / A
pr 1986 p. 536-p. At 538, W.M.
Lee et al., With an etchant for InP wafer for MBE
And H_TwoSO_Four: H_TwoO_Two: H_TwoO = 5: 1: 1 set
Etching solution or 0.3% bromethanol
Disclosed is a chilling solution.

When these conventional etching solutions are used, the wafer surface after mirror polishing by polishing is several μm.
It is removed by etching with a thickness of 〜10 μm.

As a conventional method not using etching, cleaning with alcohol, ketone, pure water or the like is performed. Such conventional techniques include:
For example, a pure water ultrasonic cleaning method, an isopropyl alcohol ultrasonic cleaning method, or, under a state of applying an ultrasonic wave, a step of cleaning with tricrene, a step of cleaning with acetone, and a step of cleaning with ethanol, A method for cleaning an InP mirror surface wafer is known.

[0008]

However, in such a technique using a conventional etching solution, not only the InP surface film but also the InP itself is etched, and uneven etching or dislocations are formed on the mirror surface wafer surface. Unevenness occurs due to different etching speeds of the substrate.

Further, since the wafer surface is etched with a large thickness of several μm to several tens of μm, there is a problem that the flatness after the etching removal is considerably worse than before the etching.

In addition, the conventional method not using etching has a problem that the surface film cannot be completely removed after the mirror surface is cleaned.

The invention according to the present application solves the above-mentioned problems of the technique using the conventional etching solution and the mirror processing of the InP single crystal wafer by the conventional method without etching. Provided is an InP single crystal mirror-finished wafer, which is a mirror-finished wafer from which only a surface film has been completely removed, wherein the thickness of a newly formed surface layer after etching treatment is 1 nm or less, and a method of manufacturing the same. The purpose is to do.

[0012]

Means for Solving the Problems The inventor of the present invention has conducted intensive studies in order to solve such a conventional problem. As a result, the technique using a conventional etching solution has a problem in addition to the InP surface film.
The present inventors have found a method of removing a surface film that cannot be removed without etching InP itself without etching the InP itself, and have accomplished the invention according to the present application.

That is, the I produced by the present invention
The nP single crystal wafer is an InP single crystal wafer in which a processing damage layer on the wafer surface is polished and removed with an abrasive or a chemical polishing liquid, and the surface film on the wafer surface formed by polishing with the abrasive or the chemical polishing liquid is sulfuric acid. And the thickness of a newly formed surface layer after the etching removal is set to 1 nm or less.

The sulfuric acid used in the present invention is not particularly limited in concentration, but is usually concentrated sulfuric acid in order to speed up the removal of the surface film sufficiently or to completely remove the surface film. Is preferred.

Further, the surface film on the wafer surface formed by polishing with an abrasive or a chemical polishing solution is removed by etching with sulfuric acid, and after the etching removal, the thickness of the newly formed surface layer is reduced to 1 nm or less. This is because it is known that if the thickness of this surface layer is 1 nm or less, there is no adverse effect on the subsequent device fabrication process. That is, when the thickness of this surface layer is 1 nm or more, InP
It is known that when a mirror-finished wafer is used for processes such as MOCVD and ion implantation, there is a high possibility that poor growth or poor characteristics will occur.

Further, in this specification, when an abrasive or a chemical polishing liquid is used to polish and remove a processing damage layer of a wafer, an oxide film or an organic contaminant film on the wafer surface formed by the abrasive or the chemical polishing liquid is removed. Is referred to as a "surface film", and the surface of the substrate having the surface film is etched or the like, and a newly formed film is referred to as a "surface layer" to be distinguished from the "surface film". The thickness of the surface layer is a value measured by an ellipsometer.

Further, such a surface layer is caused by a natural oxide film formed by oxygen or the like in the atmosphere when removing the surface film on the wafer surface by etching with sulfuric acid and then removing sulfuric acid with pure water or the like. It is thought to occur as Such a surface layer is formed in the same manner when the etching solution is removed by a conventional technique using an etching solution, or when the etching solution is removed with pure water or the like after the etching removal.

According to the first aspect of the present invention, after a processing damage layer on a wafer surface is polished and removed with an abrasive or a chemical polishing liquid, the surface film on the wafer surface formed by polishing with the abrasive or the chemical polishing liquid is treated with sulfuric acid. And the thickness of a newly formed surface layer after the etching removal is set to 1 nm or less.

When the surface film on the wafer surface formed by polishing with a polishing agent or a chemical polishing solution is removed by etching with sulfuric acid, the processing damage layer on the wafer surface is polished and removed with the polishing agent or the chemical polishing solution. InP
What is necessary is just to immerse the single crystal wafer in a sulfuric acid solution. There is no particular limitation on the temperature of the sulfuric acid solution. It may be used at normal temperature, or may be used by heating as needed.

The time of such immersion may vary depending on the temperature and concentration of the sulfuric acid solution and the polishing or chemical polishing liquid when the processing damage layer on the wafer surface is polished and removed by the polishing agent or chemical polishing liquid. When concentrated sulfuric acid is used at room temperature, the surface film can be completely removed in about 2 minutes, although it depends on the state of the surface film on the wafer surface formed by the above method.

The method of immersing the mirrored InP wafer in a sulfuric acid solution may be simply immersion, stirring the sulfuric acid solution, or applying ultrasonic vibration to the sulfuric acid solution. .

[0022]

As a result of the study of the present invention, it has been found that sulfuric acid dissolves the InP oxide film but hardly dissolves InP itself.

On the other hand, other mineral acids such as hydrochloric acid and nitric acid
Both the oxide film of InP and the InP itself are dissolved.

As described above, the present invention is achieved based on the difference in reactivity between sulfuric acid and InP and an oxide film.

A surface film such as an oxide film or an organic contaminant film formed by polishing with an abrasive or a chemical polishing solution of an InP single crystal wafer in which a processing damage layer on the wafer surface is polished and removed with an abrasive or a chemical polishing solution is removed. For example, an oxide film such as indium oxide, an organic contaminant film, or the like is used.

These oxide films and organic contaminant films are easily dissolved in the presence of sulfuric acid. For this reason, when an InP single crystal wafer from which the processing damage layer on the wafer surface has been polished and removed with an abrasive or a chemical polishing liquid is immersed in a sulfuric acid solution, the surface film on the wafer surface formed by polishing with the abrasive or the chemical polishing liquid Only are selectively etched away.

FIGS. 1 to 3 are schematic sectional views of an InP single crystal mirror surface wafer for explaining the invention according to this application.

Referring to FIG. 1, FIG. 1 shows an example of a wafer obtained by removing a processing damage layer on a wafer surface with an abrasive or a chemical polishing liquid.
The mirror surface wafer 1 before etching of the nP single crystal mirror surface wafer is shown, and the boundary line of the surface film 2 is shown by a dashed line. The thickness of the surface film 2 is usually about 2 nm to 5 nm.

Referring to FIG. 2, FIG. 2 shows wafer 3 after the surface film has been etched by a conventional technique using an etching solution.
Is removed by etching with a considerably large thickness. In FIG. 2, the boundary line of the newly formed surface layer 6 after the surface film is removed by etching using a conventional technique using an etching solution is indicated by a one-dot chain line. The thickness of the surface layer 6 is usually about 1 nm.

The etching solution used in the prior art is
In general, since the etching solution is a diffusion-controlled etching solution, edges are easily etched, and irregularities due to uneven etching and dislocations are easily etched after the etching process.

Referring to FIG. 3, FIG. 3 shows mirror-finished wafer 7 after the etching process of the invention according to the present application, and only surface film 9 is removed from mirror-finished wafer 7.
Therefore, the InP itself is not etched as compared with the case where the etching process is performed by the conventional technique using an etching solution, so that the flatness of the surface of the mirror surface wafer 7 is deteriorated after the etching process as in the conventional technique. Does not occur. In FIG. 3, after the surface film is removed by etching with sulfuric acid according to the invention of this application,
The boundary line of the newly formed surface layer 8 is indicated by a dashed line. The thickness of the surface layer 8 is about 8 to 9 degrees. Therefore, according to the invention according to this application, the thickness of the newly formed surface layer after the surface film is removed by etching, the thickness is newly formed after the surface film is removed by etching using the conventional etching solution. The mirror surface wafer having a thickness equal to the thickness of the surface layer and having the surface film etched away by the invention according to the present application can be used without adversely affecting the subsequent device fabrication process.

Moreover, in the invention according to this application, In
Since only the surface film is removed without etching P itself, the decrease in flatness is significantly reduced by a technique using a conventional etching solution, as compared with a mirror-surface wafer whose surface film has been removed by etching. That is, according to the invention of this application, a mirror-finished wafer having a flatness with a good degree of identification can be formed before and after the etching process.

In the conventional technique using an etching solution, the InP itself is etched in addition to the surface film on the surface of the InP single crystal wafer. Therefore, as shown in FIG. Had to be placed in. That is, in the technology using the conventional etching solution,
If the wafer is supported by the wafer support and immersed in an etching solution, the contact portion between the support and the wafer is likely to be etched. Therefore, there is a problem that uneven etching occurs after the etching removal.

Therefore, in the conventional technique using an etching solution, it is necessary to etch the mirror-finished InP single crystal wafer one by one.

In the invention according to this application, since InP itself is not etched by sulfuric acid, nonuniform etching does not occur even if the wafer is supported by a wafer support or the like and immersed in a sulfuric acid solution. Therefore, the wafers are supported by a wafer support table or the like, and, for example, by arranging the wafers vertically in a sulfuric acid solution, a plurality of wafers are simultaneously immersed in the sulfuric acid solution, and the surface films of those wafers are simultaneously removed. can do.

As described above, even if a plurality of wafers are supported by a support or the like and immersed in a sulfuric acid solution, the InP itself of the wafers is not etched. Non-uniformity such as uneven etching does not occur in the crystal mirror surface wafer. As described above, simultaneous processing of a plurality of wafers becomes possible, so that the cost for the step of etching and removing the surface film can be reduced.

[0037]

FIG. 5 is a schematic structural view showing an apparatus for explaining the manufacturing method of the invention according to the present application. The etching bath 12 contains 98% concentrated sulfuric acid as the processing liquid 13. In the embodiment according to the present invention, a plurality of (n = 5) In
The P mirror surface wafer 15 was immersed in the treatment liquid 13 at room temperature for 10 minutes to remove the surface film by etching. After the etching removal, the treatment liquid 13 was removed (rinsed) with pure water to produce an InP mirror-finished wafer.

As Comparative Example 1, a plurality of (n = 5) mirror-surfaced InP wafers were immersed in trichlene for 5 minutes in the same manner as in the example, using the same etching bath 12 and holding jig 14 as in the example. After immersion in acetone for 5 minutes,
It was immersed in ethanol for 5 minutes. The InP mirror-polished wafer was washed (rinsed) with pure water to prepare an InP mirror-polished wafer.

As Comparative Example 2, a plurality of (n = 5) mirror-finished InP wafers were immersed in pure water using the same etching tank 12 and holding jig 14 as in the example, in the same manner as in the example. Ultrasonic vibration was applied for 15 minutes. The InP mirror-polished wafer was washed (rinsed) with pure water to prepare an InP mirror-polished wafer.

As Comparative Example 3, a plurality of (n = 5) mirror surface wafers of 99.9 were prepared using the same etching tank 12 and holding jig 14 as in the example in the same manner as the example.
After immersion in the isopropyl alcohol solution, ultrasonic vibration was applied for 15 minutes. The InP mirror-polished wafer was washed (rinsed) with pure water to prepare an InP mirror-polished wafer.

As Comparative Example 4, a mirror-finished wafer was placed horizontally in an etching solution and removed by etching using the conventional method shown in FIG. A conventional 0.3% volume ratio bromomethanol was used as an etchant, and the wafer surface was etched to a thickness of 5 μm. After the etching removal, the bromomethanol was removed (rinsed) with pure water to produce an InP mirror-finished wafer.

The surface layers of these mirror-finished wafers were measured with an ellipsometer. Table 1 shows the measurement results of the thickness of the surface film before each treatment and the thickness of the surface layer after each treatment. Also,
The change in flatness of the mirror surface wafer before and after each treatment was measured.

TTV (Tot) which is an index of flatness
al Thickness Variation)
The thickness of the entire surface of the wafer was measured after the wafer was chucked except for the periphery of 3 mm, and the difference between the maximum value and the minimum value was measured. Table 1 shows the results.

[0044]

[Table 1]

As is clear from the results shown in Table 1, the thickness of the newly formed surface layer after the etching removal in this embodiment and Comparative Example 4 is 1 nm or less. On the other hand, the mirror surface wafer processed by the conventional method without etching has a thickness of about 2 nm newly formed after the processing as apparent from Comparative Examples 1 to 3, and the surface film Has not been completely removed.

Further, as is clear from the results in Table 1, in Example and Comparative Examples 1 to 3, ΔTTV, which is a change in TTV before and after the treatment, did not change to 0 μm, but in Comparative Example 4, ΔTTV Is 2 μm. That is, in Comparative Example 4, InP itself was etched, and the flatness was deteriorated.

[0047]

In the invention according to the present application, since only the surface film is removed without etching the InP itself, the flatness of the wafer surface is reduced before and after the etching removal as compared with the conventional technique using an etching solution. And the mirror surface wafer having a flatness with a good degree of identification substantially before etching can be obtained.

In the invention according to this application, the surface film on the surface of the mirror-polished InP single crystal wafer formed by polishing with an abrasive or a chemical polishing liquid can be completely removed similarly to the conventional technique using an etching liquid. After the etching removal, the thickness of the newly formed surface layer can be reduced to 1 nm or less.

Therefore, the In of the invention according to this application
When using the P single crystal mirror-finished wafer, it can be used as it is in a subsequent device working process without performing an etching process by a conventional technique using an etching solution.

In the invention according to the present application, a plurality of wafers can be processed at the same time, so that a large number of wafers can be processed at one time, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a surface film of a mirror-polished InP single crystal wafer before etching of a mirror-polished InP single crystal wafer from which a processing damage layer on the wafer surface has been removed by an abrasive or a chemical polishing liquid.

FIG. 2 is a cross-sectional view schematically showing a surface layer on a mirror-finished wafer surface of an InP single-crystal mirror-polished wafer after a surface film is etched by a conventional technique using an etching solution.

FIG. 3 is a cross-sectional view schematically showing a surface layer on the surface of an InP single crystal mirror-finished wafer after etching a surface film according to the present invention.

FIG. 4 is a cross-sectional view schematically showing a conventional etching method.

FIG. 5 is a partial cross-sectional view schematically showing a specific example of an apparatus for explaining a method for manufacturing an InP single crystal mirror-finished wafer according to the present invention.

[Explanation of symbols]

 1, 3, 7, 10, 15 InP single crystal mirror-finished wafer 2 Surface film 4, 9 Surface film removed by etching 5 InP itself is removed by etching 6, 8 Surface layer 11 Etching solution 12 Etching bath 13 Treatment solution 14 Holding jig

Claims (1)

(57) [Claims] After a processing damage layer on a wafer surface is polished and removed with an abrasive or a chemical polishing liquid, a surface film on the wafer surface formed by polishing with the abrasive or the chemical polishing liquid is etched and removed using sulfuric acid. After the etching removal, the thickness of the newly formed surface layer is 1 n
m or less, and a method for producing a mirror-polished InP single crystal wafer.