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CN-122003106-A - Manufacturing method for improving etching window of alumina passivation layer of gallium arsenide device

CN122003106ACN 122003106 ACN122003106 ACN 122003106ACN-122003106-A

Abstract

The invention relates to the technical field of gallium arsenide semiconductor device manufacture, in particular to a manufacturing method for improving an etching window of an alumina passivation layer of a gallium arsenide device, which comprises the following steps of reserving silicon nitride in a cutting channel area when a first passivation layer is opened by optimizing a process flow; after the second metal electrode and the Al 2 O 3 passivation layer are deposited, a two-step etching strategy is adopted, firstly, the mixed gas of SF 6 and O2 is used for removing the PAD and the Al 2 O 3 film in the cutting channel region, and then the mixed gas of SF 6 and Ar is used for removing the residual silicon nitride in the cutting channel region and thoroughly removing the Ti layer in the PAD region, so that the problems of wire bonding failure caused by the residual Ti in the PAD region and structural damage caused by etching through the cutting channel semiconductor layer are solved, the process window is widened, and the production efficiency and the product comprehensive yield are improved.

Inventors

  • HUANG GUANGWEI
  • ZHANG CHAOMIN
  • CHEN JIANXING
  • WU JING
  • CHEN CHAO

Assignees

  • 福建省福联集成电路有限公司

Dates

Publication Date
20260508
Application Date
20260206

Claims (9)

  1. 1. The manufacturing method for improving the etching window of the alumina passivation layer of the gallium arsenide device is characterized by comprising the following steps of: Sequentially forming ohmic contact metal and a first metal electrode on an epitaxial layer of a gallium arsenide substrate, and depositing a silicon nitride film as a first passivation layer; step 2, coating a first layer of photoresist, carrying out opening treatment on the first passivation layer, removing silicon nitride of the PAD area, reserving the silicon nitride of the cutting channel area, and removing residual photoresist after the opening treatment; Step 3, coating a second layer of photoresist, depositing a second metal electrode, and removing redundant metal and photoresist after deposition; Step 4, depositing an Al 2 O 3 film on the surface of the whole wafer to serve as a second passivation layer; step 5, coating a third layer of photoresist, exposing and developing the PAD area and the cutting channel area to form a graphical window; Step 6, adopting mixed gas of SF 6 and O 2 to carry out plasma etching to remove the Al 2 O 3 film on the surfaces of the PAD area and the cutting channel area; Step 7, adopting mixed gas of SF 6 and Ar to carry out plasma etching, removing residual silicon nitride in the cutting channel area, and thoroughly removing Ti on the top layer of the second metal electrode in the PAD area; and 8, removing the third layer of photoresist, and sequentially carrying out wafer thinning, back hole manufacturing, back gold deposition, dicing channel back gold etching and wafer dicing processes to finally finish device manufacturing.
  2. 2. The method for improving the etching window of the alumina passivation layer of the gallium arsenide device according to claim 1, wherein the step 2 is specifically to coat positive photoresist, align the PAD area by a mask plate for exposure and development, remove the silicon nitride of the PAD area by a reactive ion etching machine, reserve the silicon nitride of the dicing channel area, and then remove the residual photoresist.
  3. 3. The method for improving the etching window of the alumina passivation layer of the gallium arsenide device according to claim 2, wherein in the step 2, the coating rotation speed of the positive photoresist is 3000-5000rpm, the photoresist thickness is controlled to be 1.82 μm, 2.38% TMAH developer is adopted for developing after exposure, SF 6 gas is adopted for silicon nitride etching, and residual photoresist is removed through N-methylpyrrolidone NMP solution after etching.
  4. 4. The method for improving the etching window of the alumina passivation layer of the gallium arsenide device according to claim 1, wherein the step 3 is specifically that thick film positive photoresist is coated, an M2 pattern is formed through exposure and development, ti/Pt/Au/Ti multilayer metal is deposited in sequence, redundant metal and photoresist are removed through a lift-off process, and a patterned second metal electrode is reserved.
  5. 5. The method of claim 4, wherein in the step 3, the coating speed of the thick film positive photoresist is 1500-5000rpm, the photoresist thickness is 6 μm, the multi-layer metal deposition thickness is 30 a of Ti, 100 a of Pt, 16000 a of Au and 100 a of Ti, and the lift-off process is performed by soaking in NMP solution and assisted by ultrasonic or megasonic treatment.
  6. 6. The method for improving etching window of alumina passivation layer of gallium arsenide device according to claim 1, wherein step 4 comprises depositing Al 2 O 3 film as the second passivation layer on the surface of the whole wafer by atomic layer deposition; The atomic layer deposition parameters are that Trimethylaluminum (TMA) is used as a metal source precursor, deionized water H 2 O is used as an oxygen source precursor, the deposition temperature is 80-250 ℃, the TMA vapor pulse time is 0.05-0.1s, the first nitrogen purging time is 5-15s, the water vapor pulse time is 0.05-0.1s, and the second nitrogen purging time is 5-15s; the Al 2 O 3 film thickness was 25nm.
  7. 7. The method for improving the etching window of the aluminum oxide passivation layer of the gallium arsenide device according to claim 1, wherein in the step 6, the ratio of the mixed gas of SF 6 and O 2 is 10:1, the flow rate of SF 6 is 20-50sccm, the flow rate of O 2 is 1-5sccm, and the etching time is 30-50 seconds.
  8. 8. The method for improving etching window of alumina passivation layer of gallium arsenide device according to claim 1, wherein in step 7, the flow rate of SF 6 is 30-100sccm, the flow rate of Ar is 10-50sccm, and the etching time is 60-90 seconds.
  9. 9. The method for improving the etching window of the alumina passivation layer of the gallium arsenide device according to claim 1, wherein in the step 8, the wafer is thinned to 100 μm, and the wafer is etched after being cut by adopting a solution of ammonia water, hydrogen peroxide and water=1:1:50.

Description

Manufacturing method for improving etching window of alumina passivation layer of gallium arsenide device Technical Field The invention relates to the technical field of gallium arsenide semiconductor device manufacturing, in particular to a manufacturing method for improving an aluminum oxide passivation layer etching window of a gallium arsenide device. Background Gallium arsenide devices are widely applied to the fields of radio frequency communication, microwave power and the like because of excellent characteristics of high frequency, high speed, low power consumption and the like. In the gallium arsenide device manufacturing process, the etching window process of the passivation layer directly affects the bonding reliability and mechanical structure stability of the device. Referring to fig. 1-11, in the prior art, a passivation layer etching window manufacturing process of a gallium arsenide device includes the steps of firstly sequentially forming an epitaxial layer, ohmic contact metal and a first metal electrode on a gallium arsenide substrate, depositing silicon nitride as a first passivation layer, opening a PAD and a cutting channel region of the first passivation layer through photoetching and etching processes, then forming a second metal electrode, wherein the electrode comprises a bottom layer Ti/Pt/Au and a top layer Ti, depositing an Al 2O3 film as a second passivation layer through an Atomic Layer Deposition (ALD) process, opening a PAD and a cutting channel region of the second passivation layer through photoetching and etching processes again, and etching through an SF 6+O2 mixed gas plasma process, wherein the purposes of removing the Al 2O3 of the PAD region, the Al 2O3 of the top layer and the Al 2O3 of the cutting channel region are simultaneously achieved. However, the prior art suffers from the following significant drawbacks: The process window is extremely narrow, namely, the dry etching of Al 2O3 needs to meet two contradictory requirements simultaneously, namely, the Al 2O3 and Ti on the PAD are thoroughly removed, the GaAs/InGaP epitaxial layer of the cutting channel cannot be etched through, and the stable implementation is difficult in the same etching step; The etching stability is poor, the thickness of an Al 2O3 film is thin, the etching time is short, the tiny fluctuation of the state of a machine (gas flow and plasma uniformity) is easy to cause insufficient etching or excessive etching, the ALD deposition rate is slow, a control wafer cannot be frequently inserted in mass production to monitor the etching rate, and the process drift is difficult to correct; The bonding failure risk of PAD is high, namely, during conservative etching, a Ti layer (inert and easy to oxidize) remained on the surface of the PAD can lead to the failure of gold wire bonding to form good intermetallic compound (IMC), so that the bonding strength is weak, and the bonding is free from welding or non-sticking; The risk of cutting path damage is that SF 6+O2 plasma can rapidly etch through an epitaxial layer in a cutting path region when excessive etching is performed, and an ammonia water system solution etched after subsequent cutting can invade a corrosion substrate, so that abnormal cutting path appearance, reduced mechanical strength and even chip edge breakage are caused; The yield and the reliability are difficult to be achieved, and the process needs to be divided between the process of ensuring the wire bonding and the process of ensuring the cutting channel, so that potential variation exists in the yield and the reliability of different batches or different areas of the same wafer. Therefore, there is a need for a manufacturing method that can widen the process window, eliminate Ti residues and risk of dicing lane damage, and improve the production efficiency and product reliability. Disclosure of Invention The invention aims to overcome the defects in the prior art, and provides a manufacturing method for improving an etching window of an alumina passivation layer of a gallium arsenide device, which solves the problems of wire bonding failure caused by Ti residue in a PAD area and structural damage caused by etching through a semiconductor layer of a cutting channel simultaneously by optimizing process steps and etching strategies, widens the process window and improves the production efficiency and the comprehensive yield of products. The technical scheme of the invention is as follows: A manufacturing method for improving an etching window of an alumina passivation layer of a gallium arsenide device comprises the following steps: Sequentially forming ohmic contact metal and a first metal electrode on an epitaxial layer of a gallium arsenide substrate, and depositing a silicon nitride film as a first passivation layer; Step 2, coating a first layer of photoresist, carrying out opening treatment on the first passivation layer, removing silicon nitride of the PAD area, reserving the s